Title of Invention

A METHOD OF OPERATING AN INTERNAL COMBUSTION ENGINE.

Abstract A method of operating an internal combustion engine (51) comprising at least one piston/cylinder (59,111) combination having a main cylinder (111), and an auxiliary cylinder in communication via a conduit (54), with said auxiliary cylinder and said conduit forming an auxiliary volume, said auxiliary cylinder including a variable position auxiliary piston (57), a fuel injection system (56) for supplying fuel into said auxiliary volume (52), a first control deice for said fuel injection system, a second control device (123) for varying said auxiliary cylinder volume and an ignition device (55) in communication with said auxiliary volume, which method includes the steps of: a. directing all of the air supplied to said engine into both the main cylinder volume (63) and into said auxiliary volume; b. directing all of the fuel into said auxiliary volume; c. initiating combustion of said fuel and air in said main cylinder volume; d. completing combustion of said fuel and air in said main cylinder volume, and e. changing the volume of said auxiliary cylinder to vary the compression ratio of said cylinder/piston combination; characterized in that f. said engine is a spark ignited internal combustion engine; and g. said fuel is directed into said auxiliary volume by mixing with air flowing in said conduit (54) to said auxiliary volume during part or all of the compression phase of said engine forming therein a combustible mixture of fuel and air substantially uniformly mixed prior to said initiation of combustion. h. said fuel is injected substantially only into said conduit (54) into said air flowing into said auxiliary cylinder.
Full Text HIGH EFFICIENCY ENGINE
WITH VARIABLE COMPRESSION RATIO AND CHARGE
(VCRC ENGINE)
Cross-Reference To Related Application
[001] This application references Provisional Application No.60/253.799
filed 11/29/00; of Ken Cowans; titled, "High efficiency engine with variable compression
ratio and charge; (VCRC engine)".
Field of the Invention
[002] This invention relates to internal combustion engines designed to
improve efficiency, improve power to weight ratios, and reduce emitted pollutants in a
configuration which is readily manufacturable. The invention is most applicable to
engines used in automotive applications.
Background of the Invention
[003] A major objective of the invention is to provide a prime mover
engine, i.e. a device to derive mechanical energy from the heat energy of a burning
fuel, with higher efficiency in a lighter weight and smaller configuration than has
heretofore been the case; particularly at power demands less than the engine's
maximum. The main use for the invention is for automobile power: For this application
efficiency at low engine torque at moderate speeds is of prime interest since most of
the time an automobile engine operates at approximately 10 % of its maximum power
output at moderate speeds-typically 1,500 to 3,000 rpm.
[004] The engineering terminology used in this specification follows
standard mechanical engineering practice. Three works have been used as
engineering reference. These are
Avallone and Baumeister, Ed., Marks' Standard Handbook for Mechanical
Engineers, Tenth Edition, McGraw-Hill, 1996: referred to as 'Marks'.
Ricardo, Harry R., The High Speed Internal Combustion Engine, Fourth
Edition, Blackie & Son, Ltd., 1967: referred to as 'Ricardo1.
Stephenson, R. Rhoada., Should We Have a New Engine?, Jet
Propulsion Laboratory, California Institute of Technology, 1975: referred
to as 'Stephenson'.
[005] Current automotive practice is usually to employ a spark-ignition
engine with an average thermal efficiency around 20 %; i.e. about 20 % of the thermal
energy of the fuel used is transferred to mechanical energy. Alternatively, a
compression-ignition engine, more commonly called a diesel engine, is used having a
somewhat higher efficiency at low output. The added efficiency of the diesel engine is,
in passenger car application, offset by the added weight of current diesel engines. A
typical passenger car using a diesel engine is no more efficient than a car of equal
performance using a spark engine. Comparisons of apparent mileage differences
between spark engines and diesel engines is obscured by the difference in energy
content of diesel fuel and gasoline. Diesel fuel has about 18% more energy for a given
volume, liter or gallon, than does gasoline: Thus an accurate comparison of a diesel
car that gave 40 mpg with a spark-engine driven car giving 32 mpg would show that the
two vehicles use almost exactly the same amount of energy. Even more exact
comparisons that consider performance of the two autos shows that the diesel-driven
car is most often less efficient than an equivalent spark-engined vehicle. Support for
this argument comes from the choice of Toyota and Honda in their choice of spark
engines for the Prius and Insight vehicles respectively. These two cars are designed to
provide the ultimate in fuel mileage using contemporary techniques.
[006] The discussion above begins to illustrate the problem of increasing
the efficiency of automobiles. It is not enough to increase maximum efficiency of the
prime mover; the efficiency at low power outputs and the weight of the engine are of
equal or greater importance. In order to accomplish this increase of system efficiency it
is necessary to reduce engine friction; increase engine power-to-weight, and focus on
increasing the efficiency of the detailed burning process in the engine. In today's
environment it is also necessary to ensure that the engine does not pollute the
environment. If the engine is not inherently clean any accessories added to remove
exhaust pollutants to the degree needed today can easily reduce efficiency directly and
the weight added for these accessories will detract from the vehicle's fuel mileage.
[007] Current proposals mostly fail to globally address the complexity of
this problem. Any solution that addresses internal combustion engine efficiency needs
to consider the basic combustion process itself. To obtain high efficiency at very low
power outputs a solution must address the problem of lean burning. Hydrocarbon fuels
do not burn rapidly enough for use in an automotive sized engine at fuel-air ratios under
around 50-60% of stoichiometric ratio. To obtain ultra-efficient burning at 10% of
maximum power output it is necessary to efficiently combine the fuel with air at fuel air
ratios around 15-20% of stoichiometric within the time it takes an engine to rotate 30-
35° at around 2,000 rpm or about 3 milliseconds. No matter what is done to a bulk air-
fuel mixture this has not proved feasible in workable systems.
[008] Diesel engines sidestep this problem by finely dividing the fuel and
spraying it into a hot air environment. The burning that results occurs around each
droplet at a fuel-air ratio almost exactly stoichiometric: Thus a mixture that is nominally
a bulk mixture of fuel and air at a low fuel-air ratio is really a mixture of micro-domains
of fuel and air at near stoichiometric ratio. The penalties inherent in this approach
include the high friction penalties attendant with the use of compression ratios around
20:1 needed for automotive-sized engines and the aforementioned added weight. This
illustrates that the solution must firmly address the problem of mechanical friction.
[009] Friction and its effect on the part-load efficiency is largely ignored in
contemporary proposed automotive prime mover solutions. The effect of friction is a
very complicated factor. Typical modern production automotive engines battle friction
by employing sophisticated valving and induction systems to ensure that maximum
bearing loads are encountered only at moderate and higher speeds, where journal
bearings can endure higher pressure loadings. This allows these same journal
bearings to be designed smaller and thus the bearings contribute less friction to
degrade the engine's performance.
[0010] The effect of friction is especially complicated when considered in
conjunction with compression ratio. A higher compression ratio in an internal
combustion engine inevitably results in concomitantly increased thermal efficiency.
This is unfortunately accompanied by an increase in friction because the added
compression ratio is inevitably attended by added friction from the larger bearings that
are needed to support the higher loads that go along with the higher compression ratio.
The friction loads are particularly influential to the engine when delivering low power at
moderate speed which is the normal duty for an automotive engine.
[0011] It is highly desirable to realize an engine that is notably lighter and
smaller for a given power output than conventional engines. It is well known that the
fuel consumed by a road vehicle is approximately proportional to the vehicle's weight.
Combining an increase in efficiency with lowered engine weight greatly increases the
fuel efficiency of a vehicle system. This is especially true when the effects of what is
called, in automotive technology, weight propagation are considered. This term
describes the effects of changing the weight of any component of a vehicle system.
Since the component must be carried by the vehicle system and the component's mass
must be stopped by the vehicle's brakes the inevitable effect of changing the weight of
any of the vehicle's components further entails a change in the weight of the vehicle by
about 70% of the initial weight change. Thus a reduction of engine weight of 100
pounds will result in a total weight reduction of about 170 pounds due to the effects of
weight propagation.

Internal Combustion Engine Pollutants
[0012] Another objective of the invention needed in today's environment is
to create a prime mover than burns fuel in a manner that is inherently clean; whose
combustion process inherently produces few contaminants associated with interna!
combustion engines. Such an engine will need fewer or smaller cleanup mechanisms
such as catalytic converters used with it to meet increasingly stringent requirements for
engines in public use.
[0013] Internal combustion engine pollutants are of two general kinds:
Oxides of nitrogen and unburned or partially unburned hydrocarbons (carbon monoxide
production in engines can be considered as resulting from partial burning of the carbon
in a hydrocarbon fuel). Diesel, or compression-ignition, engines produce particulates,
microscopically small pieces of carbon and other matter due to the nature of
combustion in compression-ignition engines. Well designed engines using
homogeneous mixtures of fuel and air such as are burned in typical spark-ignition
engines have little tendency to produce significant quantities of particulates.
[0014] Oxides of nitrogen are produced when oxygen and nitrogen are
heated together to very high temperatures (ca. 2,500°C and above) such as occurs in
burning fuel-air mixtures. Production of nitrogen oxides is intensified when burning fuel-
air mixtures are close to stoichiometric ratios. Production of oxides of nitrogen is
reduced in mixtures of burning fuel and air that have an excessive amount of either fuel
or air and are further reduced by burning the fuel-air mixture in conjunction with inert
gasses such as recycled exhaust products (EGR). Stephenson shows data from
Blumberg, P., and Kummer, J.T., "Predictions of NO Formation in Spark-Ignited
Engines-An Analysis of Methods of Control", Combustion Science and Technology, Vol.
4, pp 73-95. This showed that an engine produced vanishingly small amounts of
nitrogen oxides when fuel was burned in an atmosphere with 40% excess fuel or air in
surplus over stoichiometric proportions when a small amount of EGR was present.
These data are shown in graphical form in Figure 9.
[0015] Complete burning the fuel in an engine, with the consequence that
small quantities of unburned hydrocarbons or carbon monoxide result from the process,
is most thoroughly accomplished by burning with an excess of air over stoichiometric
proportions at elevated temperatures followed by oxidation in a catalytic convertor.
Thorough burning such lean mixtures, however, is not easily implemented. Uniformly
mixed lean mixtures burn too slowly to be useful in an engine designed to be used at
speeds of 1,000-6,000 rpm if the burning is initiated in the uniformly mixed air-fuel bulk
blend.
Efficiency in Internal Combustion Engines
[0016] The efficiency of an internal combustion engine is determined by
complicated relationships. In order to obtain an optimum efficiency it is necessary to
balance many individual factors. Each of these tends to counteract, in some way or
ways, the effects of the others. The main parameters that need to be considered in the
design are:
a. Basic thermal efficiency
b. Friction between internal parts that occurs as the engine runs
c. Non-linearities due to chemical interactions within the burning
fuel-air mixture.
d. Pressure drops that occur as air moves into the engine and
exhaust products are expelled from the engine.
1. Basic thermal efficiency
[0017] The efficiency of a prime mover is the percentage of heat energy
obtained from the fuel burning that is converted to useful mechanical energy. Indicated
thermal efficiency is a term used to describe the percentage of the energy obtained
from the fuel that is converted to mechanical energy within the engine even though
some of this energy may not be available outside the engine due to factors such as
friction within the engine and the energy used to run ancillary mechanisms needed for

engine operation. Brake thermal efficiency is the term used to describe efficiency of the
engine in terms of the percentage of heat energy of the fuel that is available outside the
engine as usable energy. Friction converts some of the basic mechanical energy
delivered from the engine process to heat before mechanical energy is transferred
outside the engine: The difference between indicated thermal efficiency and brake
thermal efficiency is thus that percentage of the heat energy used up in moving engine
parts against internal friction of the engine, in pressure drops undergone by gases
flowing within the engine and that energy needed to drive accessory mechanisms within
the engine essential to the engine's operation. This last category includes fuel pumps,
water pumps and valve gear.
2. Friction of the internal parts that occurs as engine parts move
[0018] As noted above, friction takes away from the net thermal efficiency
of the engine. Mechanical friction in an internal combustion engine mostly originates
from bearings supporting the crankshaft, rubbing of pistons on their cylinder walls and
friction in the valve mechanism. Bearing and piston friction is dependent on loads
within the engine. The loads will vary with the detailed design of the engine but are
always a function of the compression ratio of the engine: A higher compression ratio
results in larger bearing and piston loads. Marks, Section 8, shows that the size of
bearings and their relative friction power loading is proportional to the load or force
placed on the bearings. The data also show that journal bearings can support a load
that is proportional to the notational speed of the bearing shaft.
[0019] The use of a large compression ratio will increase the indicated
thermal efficiency of an engine. However, a rise in the compression ratio of an internal
combustion engine always gives rise to an increase in the friction of a real engine, as
opposed to the engine as a theoretical entity. This results in a decrease in the average
operating efficiency at compression ratios over about 8 to 1 in the case of spark ignited
engines used in vehicle transport. This is clearly shown in Ricardo; one of the basic
texts on internal combustion engines. The relationship that leads to this conclusion is
found in the fact that most of the usage of an engine for passenger road transport in
particular, and practically all prime movers in general, occurs at outputs far less than
the maximum that can be derived from the engine. Thus an engine that has a high
efficiency at full power with a compression ratio of 10 to 1 will be less efficient in overall
passenger car usage than a correctly designed engine having a compression ratio or 8
to 1 when both engines are operated at 30% of their maximum torque. This torque
level is typical for passenger transportation needs and also approximately
representative for many applications of prime movers. The reason for the higher
efficiency of the engine using an optimum compression ratio is that the bearings and
other load supporting members of the engine must be designed to be large enough to
withstand the highest pressure internal to the engine that the engine will endure. This
results in larger frictional losses in the engine using the higher compression ratio:
These larger frictional losses are more than offset by higher indicated thermal efficiency
at full torque demand but when the engine's usage on an overall basis is analyzed the
average efficiency of an engine with a compression ratio of about 8 to 1 will be more
efficient than that of an engine having a compression ratio of 10 to 1. The fact that the
engine is used delivering a typical torque of around 30% of maximum means that the
efficiency during this service is more important to average efficiency than the efficiency
of the engine delivered when the engine is used at full torque.
3. Non-linearities due to chemical interactions within the
burning fuel-air mixture
[0020] A high compression ratio also incurs some chemical losses. The
efficiency gains engendered by the use of higher compression ratios are obtained
because heat is extracted from the fuel at higher temperatures as the compression ratio
is raised: Any heat engine is more efficient as the temperature at which the heat is
added to the engine is raised relative to the temperature at which heat is rejected from
the engine. This comes from basic Carnot teachings. At temperatures above about
2000°C two effects, disassociation and non-linear specific heat, occur in the fuel-air
products of carbon dioxide and water vapor; the basic products of burning organic fuels.

The effect of these two phenomena is to reduce the useful amount of heat that can
produce energy in the engine. Thus as an engine is designed to use higher and higher
compression ratios, the deviation from theoretical efficiency increases so that the actual
efficiency becomes less because of the friction effects noted previously and also due to
the fact that effects of disassociation and variable specific heat counteract some of the
added efficiency gained from the higher compression ratio. Chemical losses are
counteracted by using lean mixtures within the engine; mixtures of fuel and air that
have excessive amounts of air.
4. Pressure drops that occur as air moves into the engine and
exhaust products are expelled from the engine.
[0021] As any gas passes through a tube or other like conduit a pressure
gradient in the gas is required to maintain the velocity of the gas through the conduit.
The same statement applies to gas passing through a port, or entrance, to the conduit
or exit from such passage: A loss of pressure and thus energy is encountered
wherever gas is transported at significant velocity. This energy must be supplied by the
engine and thus creates a loss of efficiency. As noted above in the section on friction
these pressure drops can be considered a form of mechanical friction.
Design Approaches for High Efficiency in Internal Combustion engines
[0022] Balancing the above parameters is not a simple task. The
optimum engine would have negligible friction, high compression ratio, low gas velocity
in all transfer passages and would burn the fuel in a lean mixture at practically all times.
The VCRC engine uses a unique approach to obtain an engine close to this ideal.
Summary of the Invention
[0023] The VCRC concept is based on a unique method of optimization
and minimization of the losses in an internal combustion prime mover in creating a

prime mover of the highest efficiency. Implementation of the concept details also
results in an internal combustion engine whose combustion inherently creates little
pollutants of unburned hydrocarbons, carbon monoxide or oxides of nitrogen.
System and Subsystems
[0024] Engines in accordance with the invention accomplish the above
objectives by increasing the compression ratio as the torque demanded of the engine is
decreased throughout the engine's throttling range. As the compression ratio is raised
the engine simultaneously provides for a leaner burning of the fuel ingested into the
engine using a method of separated charge combustion. The combination of higher
compression ratio together with leaner burning raises the efficiency of the engine in
situations during which torque demanded of the engine is less than maximum. Since
practically all applications of prime movers perform the bulk of their duties at these
lower torque values the overall efficiency of systems using the inventive approach is
equally increased.
[0025] This approach has many features but is characterized herein as
Variable Compression Ratio and Charge (VCRC). VCRC engines particularly allow
efficient throttling of two stroke cycle engines to be accomplished. This efficiency is
further enhanced by a subsystem of the invention applicable to two stroke engines.
With a unique arrangement of engine-driven blower and exhaust-driven turbo charger
even further increases of efficiency in two-stroke versions of the VCRC can be
achieved.
[0026] The VCRC engine accomplishes a reduction in both oxides of
nitrogen and unburned hydrocarbons by a method of burning in two phases. First the
fuel is burned in a uniformly mixed fuel-rich environment which includes some EGR.
This mode of burning minimizes the creation of oxides of nitrogen. The initial burning is
immediately followed by a completion of the burning process in an environment in
which
air is present in excessive quantities when compared with that amount needed to
completely burn the fuel.
[0027] Thus in the VCRC internal combustion engine the compression
ratio and the amount of fuel burned (the 'charge') during each firing cycle are
simultaneously varied in response to torque demanded of the engine. A decrease in
torque demand is accompanied by an increase in the engine's compression ratio and a
reduced fuel flow. The relationship of compression ratio and fuel supplied is varied in
such manner as to keep the peak pressure in the engine's combustion process nearly
constant level for all torque demands at a given speed. The relationship of the two
parameters of compression ratio and fuel-air ratio are also varied as speed of the
engine changes so as to raise the combustion peak pressure with an increase in engine
speed.
[0028] Engines in accordance with the invention also include
subsystems that enable the basic engine to perform with increased efficiency and allow
the design to be smaller and lighter than engines now in common usage.
[0029] The engine varies the compression ratio and mixture ratio
simultaneously by arranging the engine so as to have a combustion volume in two
chambers connected by a passageway. The volume of one of these chambers is
varied by a separate piston subsystem mechanism: Burning is initiated in this variable
volume chamber after it has been filled with a uniformly mixed fuel-air mixture. The rise
in pressure and temperature caused by the initial burning forces the fuel air mixture out
of the variable volume to mix with the remaining engine volume in which volume
burning is completed.
[0030] The variable volume combustion chamber is varied by a piston
mechanism arranged to be both reliable and easily controllable. A hydraulic snubber is
used in a preferred embodiment in conjunction with a piston designed to oscillate in a
reciprocating motion each engine cycle. By such design the piston remains reliably
lubricated in its cylinder during operation. The hydraulic snubber provides accurate and
easily implemented control of the piston's motion.
[0031] The VCRC engine's method of combustion offers other
advantages also. By separating the combustion into two phases; an initial combustion
of the bulk of fuel and air in an fuel over-rich environment followed by a completion of
combustion in a high temperature fuel-lean mixture, the problems of detonation are
almost entirely eliminated. Detonation, or knock as it is colloquially called, is an
explosion of the last 5% or less of the bulk fuel-air mixture. An overly rapid rise in
pressure brought about by the initial combustion of the fuel-air mixture creates a
pressure wave that compresses an isolated mixture of fuel and air and the
accompanying rise in temperature of this isolated mixture creates an explosive situation
wherein this mixture spontaneously combusts giving the resultant explosive increase in
pressure and noise. In the VCRC engine the 'end gas', as this isolated fuel air mixture
is called in internal combustion engine engineering, consists only of air. Thus the
concept of octane requirements for the fuel used are moved so far off the engine's
boundary limits as to be of essentially no import. The fuel for a VCRC engine can be
most any mixture of fuel oil, of a low octane number, and gasoline with a higher value.
The need for a high cetane number, necessary for smooth combustion in compression
ignition engines, is equally unimportant.
[0032] The VCRC engine is exemplified here as a two-cycle engine.
The invention is most suitable to the two-stroke configuration but is not limited to this: A
four stroke configuration based on the same principles could also be easily realized.
Some subsystems that are singularly adaptable to a two-cycle engine are also part of
the invention. These include a unique method of supplying air to the engine in a
manner that minimizes the losses associated with air transport.
[0033] The VCRC concept also includes a unique method of

combustion to extract energy from a burning fuel-air mixture at higher efficiency than is
now commercially possible in an internal combustion engine This method of burning
has the advantage of chemically combining air and fuel while creating fewer pollutants
than does current engine designs. The VCRC method separates the air and fuel-air
mixture in the engine into two divided volumes. Burning is initiated in the portion of the
air that contains substantially all of the fuel and only part of the air used to support the
combustion in a uniform mixture that is over-rich in excess fuel. The VCRC engine
could be designed to provide a uniform mixture that is excessively lean as well. A
perfect balance between fuel and air, called a stoichiometric ratio is avoided because
this ratio results in an excessive production of nitrogen oxides. The combustion
process is completed by combining the initial burned air and fuel with the remaining air.
The remaining air is present in the combustion chamber in more than sufficient
quantities to oxidize all the fuel in the chamber.
[0034] This method of combustion, used in conjunction with the variable
volume noted above allows lean fuel-air mixtures to be burned at elevated compression
ratios in an engine assembly that has low mechanical friction. This creates internal
engine efficiencies higher than previously thought possible.
Stratified Charge vs. Separated Charge
[0035] Stratified charge has long been used as a method to obtain lean
burning in a spark-ignition engine. There are various ramifications but most have a
single generic embodiment in common. A small volume separated from the main
combustion chamber is supplied with a charge of fuel and air that is rich in fuel. This
charge is fired with a spark and the flame from this ignites the charge in the remainder of
the combustion chamber which latter charge is much leaner. In this manner it is
possible to fire charges as lean as around 50-60% of stoichiometric. Combustion that
takes place only in the small separated volume is often used to support very low torque
values; around 10% of maximum. Between around 10% to around 40% the typical
stratified charge engine is unstable and needs other mechanisms to appropriately
throttle the engine. Stratified charge design also has some problems with efficiency as
well. Near the lean limit of the stratified charge approach there is trouble firing the
charge in the main combustion volume rapidly enough for operation. The slow burning
results in a loss of some of the heat energy of the charge and also results in incomplete
combustion as well.
[0036] The VCRC engine uses what can best be termed as 'separated
charge'. The entire amount of fuel to be burned is contained in a separate variable
volume together with around 60% or less of the air that is to be reduced by the
combustion process. In this manner the difficulties of stratified charge burning are not
present. The bulk of the fuel is burned at rapid velocity in the initial phase of
combustion. Then, when the mixture of unburned fuel and very hot exhaust products
mix with the remaining air the entire amount is at a temperature high enough to
complete the combustion process rapidly.
[0037] A system that could be called 'separated charge' has been
employed in versions of compression-ignition (Diesel) engine. Ricardo shows some
varieties of this. The 'pre-combustion chamber design' and the 'Comet Mark III' can
each be considered to utilize a combustion method that can be characterized as
'separated charge'. In these engine configurations fuel is injected into a volume
separated, by a short gas passage or passages, from the main cylinder volume. In this
volume about 50% of the total air used by the engine is reduced by burning of the
injected fuel in a manner that can be considered conventional compression-ignition
engine spray combustion. Subsequently the hot mixture of fuel and combustion
products are combined with the remaining air in the rest of the cylinder volume. The
process allows up to 90 % of the air to be burned (in the Comet Mark III) at full throttle
showing that the process can be used to burn fuel at any level of leanness as long as all
the fuel and some air are mixed in a fuel-rich burning amalgam in the initial phase of the
burning process.
Brief Description of the Drawings
[0038] A better understanding of the invention may be had be reference
to the accompanying specification, taken in conjunction with the following drawings in
which:
[0039] Figure 1 is a perspective view partially broken away of a two-
stroke engine using the invention in a scavenge phase of operation.
[0040] Figure 2 shows a schematic concept for a system that links
throttle control of the engine with compression ratio control and fuel injection regulation
with an override control to modify the relationship with engine speed.
[0041] Figure 3 shows, in block diagram form, an air supply
arrangement that reduces flow losses during part throttle operation without limiting the
power of the VCRC engine.
[0042] Figure 4 is a fragmentary view partially broken away of one
possible mechanical assembly that can be used to implement the control of
compression ratio conceptually depicted in Figure 2.
[0043] Figure 5 shows a view of the engine in Figure 1 during a
compression stroke.
[0044] Figure 6 shows the same engine during a combustion phase.
[0045] Figure 7 shows the same engine during an expansion stroke.
[0046] Figure 8 shows the same engine during an exhaust phase.
[0047] Figure 9 is a graph depicting the production of oxides of nitrogen
in a spark-ignited engine as a function of fuel-air ratio and exhaust gas recirculation.
[0048] Figure 10 is a graph showing the indicated mean effective
pressure (IMEP) of an internal spark-ignited engine with various compression ratios and
fuel-air ratios relative to stoichiometric ratio. The data in Figures 10, 11 and 12 follow
Ricardo, referenced above, and standard texts on mechanical engineering.
[0049] Figure 11 is a graph of the theoretical peak pressure in a spark
ignited engine at various compression ratios and fuel-air ratios relative to stoichiometric
ratio.
[0050] Figure 12 is a graph of indicated efficiency of a spark ignited
internal combustion engines with various combinations of compression ratio and fuel-air
ratios relative to stoichiometric ratio.
[0051] Figure 13 is a depiction of a mechanical schematic of a system
to implement the control interaction described in Figure 2.
[0052] Figure 14 is a fragmentary view partially broken away of one
possible mechanical assembly that can be used to implement the pumping and control
of fuel to a fuel injector to implement the control system conceptually depicted in Figure
2. It is a combination pump and regulating mechanism.
[0053] Figure 15 is a detail of the device shown in Figure 14.
[0054] Figure 16 is a cross sectional view of a four-cycle version of the
VCRC engine.
Detailed Description of the Invention
Construction of the engine
[0055] The construction of an engine in accordance with the invention
can be best understood by referring to Figure 1. A two-stroke engine 51 is fitted with a
combustion chamber 52 of variable volume. Gas within the engine can pass freely
between combustion chamber 52 and the cylinder volume 53 through a gas passage 54.
A spark plug 55 is located in communication with gas passage 54. An injection nozzle
56 is so situated as to spray fuel into the engine in gas passage 54. Injection nozzle 56
is located generally towards the end of gas passage 54 closest to cylinder volume 53
and spark plug 55 is located generally at the other end of passage 54 closest to variable
volume 52. The volume of combustion chamber 52 can be varied with the movement of
an auxiliary piston 57. Auxiliary piston 57 is moved so as to minimize the volume of
variable combustion chamber volume 52 in the absence of any other forces by the
action of a spring 58. Two-stroke engine 51 incorporates a power piston 59 which is
coupled via a connecting rod 60 to a crankshaft 61 in conventional engine fashion. The
crankshaft rotates as shown by the arrow 62 in Figure 1.
[0056] The type of engine illustrated in Figure 1 and the other drawings
is characterized as a loop-scavenged two-stroke engine. Other types of two-stroke
engines would serve equally as well as a basis to use the invention. As noted
previously, four-stroke engine designs could be used alternatively.
[0057] Intake port 109 is connected to a source of air in the VCRC
engine. An exhaust port 110 is connected to reject exhaust products away from the
engine. Exhaust port would be connected to an exhaust manifold in a multi-cylinder
engine and from thence would connect to catalytic converters, a turbine of a turbo-
charger or the like. Both intake and exhaust ports are opened and closed by movement
of power piston 59 in a cylinder 111.
[0058] Referring now to Figure 4 as well as Figure 1, a hydraulic
snubber 64 limits the travel of auxiliary piston 57. Hydraulic snubber 64 is comprised of
a hydraulic piston 65 mounted in a hydraulic regulating cylinder 66, which hydraulic
regulating cylinder is slidably mounted on a fixed hydraulic piston 67. Hydraulic cylinder
66 is moved to the correct position by force supplied by the controller of the engine
acting on a regulating lever 68. Implementation of this snubber function could be
accomplished with a number of mechanisms as will be appreciated by those skilled in
the art but a hydraulic mechanism such as that shown has the advantage of being
reliable and simple to implement. During operation in a single engine cycle auxiliary
piston 57 moves from one end of its travel, wherein volume 52 is nearly zero, to the
other end of its travel, limited by the placement of hydraulic snubber 64. Through this
cyclical motion the interface between auxiliary piston 57 and the cylinder wall enclosing
auxiliary piston remains lubricated during operation. If auxiliary piston 57 were to remain
motionless for a number of cycles the surface of cylinder 117 could lose any lubricant
film on it causing piston 57 to partially or completely stick and become motionless or
erratic in motion.
Control of the system
[0059] Figure 2 illustrates the basic concept of control of various
parameters by the Variable Compression Ratio and Charge or VCRC engine control
linkage system. This drawing shows a schematic representation of the manner in which
the three functions of compression ratio, fuel feed and engine speed are linked in the
VCRC control system. A throttle control wheel 77 is rotated counter-clockwise by the
operator of the engine to increase torque. This rotation actuates a throttle control
linkage 78 to rotate a compression ratio control wheel 79 which regulates the engine
compression ratio through operation of a mechanism such as that shown in Figure 4. As
control wheel 79 is rotated counter-clockwise under the action of throttle control wheel
77 and throttle linkage 78 the compression ratio of the engine is reduced. Control wheel
79 is linked, through a compression ratio linkage rod 80, an auxiliary linkage rod 81, a
speed adjustment linkage rod 82 and a fuel feed linkage rod 83 to a fuel feed control
wheel 84. As control wheel 84 rotates counter-clockwise more fuel is supplied to the
engine at each cycle. The maximum travel of the torque control system is limited by a
throttle stop 92. A specific mechanism for controlling compression ratio and fuel feed is
not indicated in Figure 2. A variety of mechanisms for providing the interrelated
functions may be used by those skilled in the art of engine design. The particular
method of controlling compression ratio in the invention is unique to the present
invention as has been discussed.
[0060] A speed adjustment slider 85 is used to compensate for the
beneficial effects of speed on the load-carrying abilities of journal bearings. As slider 85
moves to the right in Figure 2 the effect is that of lengthening the connection between
compression ratio control wheel 79 and fuel feed control wheel 84 with the result that
more fuel is fed to the cylinder for a given value of compression ratio or, looked at
another way, the torque for a given amount of fuel fed will be higher as speed increases
due to the fact that the compression ratio is higher. If torque demand is held constant,
as speed increases there will be somewhat less fuel supplied for each revolution and the
compression ratio will increase compared to the settings for the same torque at a lower
speed.
[0061] Correcting for speed with this system concept somewhat
counteracts the effects of friction: Friction increases as speed is raised due to the effects
of lubricant viscosity and velocity of gasses passing in and out of the engine as
described previously. The increase in inefficiency due to friction effects is partially offset
by the added thermal efficiency brought about by increased compression ratio and
leaner burning. The higher compression ratio can be better supported by the engine's
bearings because the load capability of journal bearings increases as the shaft rotational
speed is raised.
Operation of the engine
[0062] Referring again to Figure 1 and Figure 4: The VCRC engine at
idle uses only gas passage 54 for a combustion space. In this mode of VCRC operation
slide 65 is moved through operation of control rod 68 so that auxiliary piston 57
nominally cannot move from its position closing combustion chamber 56. In this position
auxiliary piston 57 closes off the volume in combustion chamber 56 so that the
combustion chamber volume is nominally zero. During idle the engine needs a small
amount of torque to run the engine's accessories and any other devices such as air
conditioners and power steering pumps. The amount of fuel needed to support the
energy required is fed in through injector nozzle 56 in a carefully timed manner. By
regulating the time that the fuel flow starts and stops a temporary boundary between fuel
rich and fuel absent air exists in air passage 54 during a compression stroke. The fuel
rich volume will be bounded by auxiliary piston 57 at one end and at a position in air
passage 54 at the other. Spark plug 55 is located at the end of air passage 54 near
auxiliary piston 57 so that the mixture will burn upon firing of the spark plug. During idle
throttle control is only present in the timing of the fuel injection: The compression ratio
during idle mode is substantially constant. Although auxiliary piston 57 is nominally
immobile during idle the compliance of all the parts in the assembly holding auxiliary
piston 57 against gas pressure within the engine's working volume will allow piston 57 to
undergo a small oscillatory motion that will keep the surface between piston 57 and
cylinder 117 lubricated.
[0063] The advantage of keeping variable volume 52 substantially zero
during idle has to do with heat transfer from the burning fuel. Operation of an engine in
transportation duty is typically from 25% and up. At this torque requirement movable
piston 57 will be far enough away from the wall at the end of its travel that the burning
within the variable volume combustion chamber will be substantially unquenched. At
torque requirements of 10-15% of maximum (typical of idle requirements) the piston
head and the wall would be so close together that flame burning within the chamber
would lose much of its heat to the walls since the percentage of heat lost from a
contained gas space is strongly a function of the space between the walls: The loss is
typically proportional to the inverse 2nd or 3rd power of the gap between the surrounding
walls. Thus the design of the VCRC engine allows for torque values in the idle range to
be burned only within transfer passage 54.
[0064] During operation of the engine a pressure is generated in
working volume 63 of the engine; which working volume includes the total of cylinder
volume 53, variable combustion chamber 52 volume, and the volume in gas passage
54. This generated pressure can force auxiliary piston 57 to move, thereby increasing
the volume of variable combustion volume 52. It would also be feasible to move
auxiliary piston 57 with actuators of different kinds such as hydraulic or electrical
mechanisms.
[0065] Lever 68 is connected to the throttle controller for the engine
system. Lever 68 is also connected to the fuel injection system. The connections
amongst the elements of throttle, lever 68 and fuel injection system is not shown in
Figure 1. One possible mechanical schematic that connects compression ratio control,
fuel feed control and speed interaction control is shown in Figure 13. The control
relationship of throttle, compression ratio, speed and fuel feed is described in Figure 2.
A movement of the control towards increased torque demand is accompanied by a
control for lowered compression ratio as well as for increased fuel flow. The simultaneity
of these three commands and the organization within which they are linked provides the
engine that uses the inventive concept with a potential for an efficiency of heat energy
conversion to mechanical work higher than has been reached before in those sizes of
prime mover used for transportation applications. This type of control mechanism could
be reduced to practice using many types of conventional devices.
[0066] The throttle mechanism slides the hydraulic cylinder 66 so as to
allow more or less movement of auxiliary piston 57 when pressure in the working volume
of the engine forces auxiliary piston 57 outward from the engine so as to enlarge
combustion chamber 52. The compression ratio of the engine is thus varied while the
engine is running with the use of this mechanism. At the same time that the
compression ratio of the engine is altered the connection from the throttle to the fuel
injection system operates to alter the amount of fuel injected. The relationship is as
follows: As the compression ratio is raised less fuel is supplied for each firing and vice
versa. In this manner the peak pressure in the engine's cycle is held approximately
constant at any given speed.
[0067] Operation of a two-stroke engine can be broken into four
repeating phases:
a. Scavenge (ref. Figure1.)
b. Compression (ref. Figure 5.)
c. Combustion (ref. Figure 6.)
d. Expansion.(ref. Figure 7.)
[0068] Figure 1 shows the VCRC engine in the scavenge phase.
During this phase both the exhaust and intake ports are opened. In the VCRC engine,
air without fuel is forced through the engine, entering the intake port and continuing out
the exhaust port in the general direction of the arrow 108. This air first expels exhaust
products from the engine and then introduces fresh air into the engine's working volume
63 which includes cylinder volume 53, gas passage 54 and variable volume 52.
Scavenging is not perfect and the scavenging phase ends with an amount of exhaust
products still remaining in working volume 63. The engine shown is generally
characterized as a loop scavenged engine. Air flow through the engine follows a looping
path as indicated by the arrow 108 in Figure 1 as air flow traverses through cylinder
volume 53. Any other type of two-cycle engine porting could equally be used but as the
loop scavenged type is the most common the present discussion will be focused on this
type of engine. Auxiliary piston 57 is in a position to reduce the volume of combustion
chamber 52 to a minimum during the bulk of the scavenge phase. Spring 58 forces
auxiliary piston to this position because the lack of pressure in cylinder volume 53 is at
its lowest point since the exhaust port is open to the atmosphere.
[0069] The scavenge phase lasts typically about 120° of crankshaft
operation. The phase starts, when power piston 59 opens intake port 109, typically
about 60° before power piston 59 is at its bottom dead center (BDC) position or, in other
words, 60° before power piston 59 is at the crankshaft position when power piston 59 is
at the position closest to crankshaft 61 as power piston 59 travels up and down in its
travel. The scavenge phase continues to about 60° after BDC. As can be seen from
study of Figure 1 the opening and closing of exhaust port 60 occurs symmetrically about
BDC in a loop scavenged engine
[0070] Figure 5 shows the VCRC engine in the compression phase.
During this phase power piston 59 compresses air in working volume 63, which includes
cylinder volume 53, transfer port 54 and variable combustion volume 52. The rising
pressure in working volume 63 forces auxiliary piston 57 to move against the force
exerted by spring 58 on auxiliary piston 57. Motion of auxiliary piston 57 can also be
effected by mechanisms driven by hydraulic, electric or other forces as may prove
desirable. This movement of auxiliary piston 57 increases the volume of variable
combustion chamber .52. Air moving from cylinder volume 53 through gas passage 54
to variable combustion chamber 52 passes by injection nozzle 56. During part or all of
the compression phase fuel is injected through injection nozzle 56 into the air stream
proceeding through gas passage 54.
[0071] As the compression phase continues hydraulic snubber port 112
(Figure 4) is covered by hydraulic piston 65. This action prevents further movement of
hydraulic piston 65 and thus movement of auxiliary piston 57. This position of auxiliary
piston 57 determines the minimum volume of working volume 63 of the VCRC engine in
the cycle under discussion and thus the compression ratio of this particular engine
revolution. The compression cycle continues until power piston 59 is at or near top dead
center (TDC) wherein power piston 59 is furthest from crankshaft 61.
[0072] Figure 6 illustrates the combustion or firing phase. A few
degrees before TDC, typically around 30 degrees or less, spark plug 55 fires and this
action ignites the fuel air mixture in the vicinity of spark plug 55. In about the next 10 to
30 degrees of travel by crankshaft 61 all the oxygen in the fuel-air mixture in variable
combustion chamber 52 and gas passage 54 will be consumed. This burning process
greatly expands the fuel air mixture such that the exhaust products of the initial burning
are forced to expand into cylinder volume 53. As is discussed elsewhere in this
disclosure the fuel air mixture involved in the initial burning is often rich in excess fuel.
The total mixture of air and fuel contained in working volume 63 is however lean in fuel
and contains more air and therefore oxygen than is needed to burn the fuel in working
volume 63. In the final time of the firing phase substantially all of the fuel in working
volume is combined with oxygen.
[0073] Figure 7 shows the expansion phase. After power piston 59 has
passed a few degrees after TDC the firing phase becomes the expansion phase as
working volume 63 expands the mixture of exhaust products and air within the engine. It
is during the expansion phase that power is derived from the engine. The expansion
phase of the VCRC engine is like the same phase of other engines in all details. The
phase continues from a few degrees after TDC until power piston 59 opens exhaust port
110. Throughout this phase mechanism 123 operates so as to maintain variable volume
52 at the maximum value that volume 52 experiences during that particular cycle.
[0074] Figure 8 shows the exhaust phase of operation. Power piston
59 travels away from TDC far enough so that exhaust port 110 opens. After this port
opens the exhaust gasses leave the engine working volume as indicated by arrow 161.
Just before power piston 59 opens exhaust port 110 the pressure in working volume 63
is typically from 2 to 6 times the pressure of the surrounding environment. As the
exhaust phase continues through about 10° to 20° of crankshaft travel the pressure in
working volume 63 is reduced to a level near the environment just outside the cylinder
volume. Throughout most of this operation auxiliary piston 57 remains forced against
spring 58 so that variable combustion volume 52 remains open to the volume
determined by position of hydraulic piston 65. At the end of the exhaust phase spring 58
forces auxiliary piston 57 to move towards a minimum volume . This pushes out
exhaust products from volume 52 and readies the engine to enter into the scavenging
phase and repeat the sequence. As noted, movement of auxiliary piston 57 could be
driven by other mechanisms, e.g. hydraulic or electrical actuators.
Four stroke engine operation
[0075] A schematic representation of a four-cycle engine is shown in
Figure 16. Instead of the intake port 109 and exhaust port 110 in the cylinder walls of
the engine their function is replaced by intake valve 157 with intake port 159 and
exhaust valve 156 with exhaust port 158. Operation of the four-stroke VCRC engine
would follow the two-stroke unit exactly as pertains to the compression, combustion and
expansion phases. The scavenge phase of the two-stroke engine is replaced by two
separate strokes of the four-stroke piston; an exhaust stroke as the piston travels from
around bottom dead center (BDC) to close to top dead center (TDC) with exhaust valve
156 open followed by an intake stroke as the piston retreats from TDC to BDC with
intake valve 157 open.
Mechanical schematic of control system
[0076] Figure 13 shows a mechanical schematic for reducing the
control system shown in Figure 2 to practice. It shows how a functioning system could
be built with elementary mechanical structures. The mechanisms shown are auxiliary
piston control mechanism 123 shown in Figure 4, a fuel pump and controller 135 shown
in Figure 14 and a combination gear coupler controller 162 combined with a servo motor
132 to correct for the effects of speed as noted in a previous section. Operation is
described in the following paragraphs.
[0077] Throttle control is effected by moving the input lever 128. This
would normally be connected, in a real system, to the foot throttle in an automobile.
Alternatively this could be driven by a servo motor in a subsystem of a so-called 'control-
by-wire' system.
[0078] Motion of lever 128 directly moves fuel control arm 150 which is
connected to the input lever 136 of fuel pump and fuel controller 135. Movement of
lever 136 moves a vented cylinder 154. Cylinder 154 surrounds a fuel pump piston 137
which is constrained to move in an oscillatory fashion within cylinder 155. Piston 137 is
driven to move back and forth under the influence of cam 138 which is connected to the
crankshaft 61 of engine 51 to rotate as indicated by an arrow 141. Compression spring
140 keeps a piston cam follower 139 in contact with cam 138 to help effect the
aforementioned oscillatory motion of piston 137. Fuel is supplied to the interior of
cylinder 154 through a tube 142 which is connected to a source of fuel which is
pressurized to a pressure adequate to supply fuel at the amount required by the
operation of engine 51.
[0079] As piston 137 moves towards cam 138 fuel is drawn into the
interior of cylinder 154 through cylinder port 143. As piston 137 reverses motion and
moves away from cam 138 fuel is driven back through tube 142 until the movement of
piston 137 covers port 143. Further motion of piston 137 drives fuel out of cylinder 154
through spring-loaded check valve 144, shown in expanded detail in Figure 15. The
spring of valve 144 is of a high enough force such that it requires a pressure
considerably higher that the pressure of the aforementioned pressurized fuel source in
order for the fuel in cylinder 154 to open valve 144 by lifting piston 145 enough to allow
fuel in cylinder 137 to escape though valve 144. After fuel passes through valve 144 it
travels through a tube 162 to the fuel injector nozzle 56 where the fuel is sprayed into
gas passage 54. Cam 138 and the connection of the cam drive connected to engine
crankshaft 61 is designed to effect the injection of fuel into gas passage 54 while air is
being transferred from engine cylinder volume 63 to variable combustion volume 52
during the compression phase of the engine as discussed before.
[0080] The position of cylinder 154 determines how much fuel is
supplied to injector nozzle 56. As throttle lever 128 is moved away from cam 138 fuel
port 143 is moved further from cam 138 as well. This places the position of fuel port 143
closer to the end of the travel away from cam 138 of piston 137, thus limiting the amount
of fuel within cylinder 154 that will be passed though valve 144 before piston 137
reverses movement in its oscillatory travel. In converse fashion, the closer that fuel port
143 is positioned towards cam 138 by lever 128 and fuel control arm 150 the more fuel
will be pumped by the motion of piston 137.
[0081] The moving of lever 128 influences the position of port 112 in
auxiliary piston controller 123 through the action of gear coupler 162. As fuel port 143 is
moved to limit fuel flow the auxiliary piston snubber port 112 (see Figure 4) is moved via
a rack 130, attached to lever 128, a gear 129, in contact with rack 130, a rack 131 and
an auxiliary piston control arm 151. Control arm 151 directly moves regulating lever 68
which is attached to slidable cylinder 64. Cylinder 64 operates in the auxiliary piston
controller 123 in a similar manner as does cylinder 154 in the fuel pump controller 135.
As cylinder 64 moves to position hydraulic port 112 away from auxiliary piston 57 the
movement of piston 57 can travel through a longer path as piston 57 is moved under
action of increasing gas pressure. Due to the nature of the coupling among racks 130
and 131 and gear 129, as cylinder 154 moves to increase fuel flow cylinder 64 moves to
increase the total travel of auxiliary piston 57 during each cycle. Thus as more fuel is
supplied to the engine the travel of auxiliary piston 57 increases and this latter action
increases the volume of variable volume combustion chamber 52, reducing the
compression ratio of the engine.
[0082] The position of the central pivot point 160 of gear129 will change
the relationship between amount of fuel supplied and the compression ratio of the
engine. As pivot point 160 moves away from fuel pump controller 135 a given amount
of fuel supplied to the engine will result in a lower compression ratio. A servo motor 132
suitably designed for the task is positioned as shown in Figure 13. A signal to servo
motor 132 will position pivot point 160 to effect a suitable balance between compression
ratio and fuel supplied. As speed increases pivot point 160 will be positioned closer to
fuel pump controller 135 so as to effect a higher compression ratio for a given amount of
fuel supplied for each engine cycle. This will increase efficiency as speed increases as
noted in the section on control of the system discussed previously.
[0083] The control system of Figure 13 responds to an input from

sliding motion induced from a throttle command to throttle lever 128. As this lever is
moved to the right in Figure 13 fuel flow is increased as the sliding motion of lever 128
induces a like motion to movable fuel injection control cylinder 133. This motion moves
the fuel valve port 134 to the right. Such motion allows an increase in the fuel supplied
to the engine during the cycle.
Air supply in two-stroke VCRC engine
[0084] A blower must be provided to any two-cycle engine because this
form of engine, unlike its four-stroke counterpart, does not function directly as an air
pump. As noted above in the discussion of the operation of a four-cycle VCRC engine,
the intake stroke and exhaust stroke function as an air pump to draw air from the
surrounding environment. In low cost versions of two-stroke engines this pumping
function is dealt with by the underside of the piston. Appropriate valving is used to
enable the underside of the power piston to pump air first from the outside environment
to the crankcase under the power piston and then to the working volume. This has the
advantage of simplicity and concomitant low cost but has little else to recommend it.
The air so pumped absorbs heat from the crankcase and the piston and also causes a
high oil consumption to take place.
[0085] There is a fundamental problem with supplying two-stroke
engines with air in an efficient manner. The two-stroke engine needs typically around
40% more air than a four-stroke engine of equivalent power to carry out a proper degree
of scavenging. Since the power needed to pump air through an engine varies as the
third power of the air volume pumped through an engine the limitation for the two-stroke
is severe. Ricardo illustrates that a two-stroke engine at full throttle will be as efficient as
a four stroke engine only at speeds less than about 50% of maximum rotational speed.
Since normal engine practice is to supply the same volume of air at full throttle as at part
throttle this is a severe limitation. The comparison at part throttle would be even worse.
The subsystem discussed below deals with this problem in a manner that severely
reduces the friction associated with air supply.
[0086] The VCRC engine in its simplest two-stroke form, could utilize a
blower driven directly by the crankshaft to provide the air needs of the engine. This
would have the disadvantage discussed above in that the power to force the large
amount of air through the engine would absorb an excess of the engine output A
refinement of the invention that directly addresses and minimizes losses of air and
exhaust gasses passing through passages into and out of the engine is to have the
engine driven blower provide only a portion of the air that the two-stroke engine requires.
The remainder of the air needed to oxidize the fuel burned under high torque demands
would be provided by an exhaust-driven turbo-blower as schematically depicted in
Figure 3. The advantage of this system is that, for most of the usage of the engine, the
engine driven blower supplies only a little more air than is needed to burn the fuel. The
losses associated with pressure drop are thus very small since the energy consumed by
such losses is proportional to the third power, or cube, of the flow rate of the air. Thus,
as the engine is designed to have the shaft-driven blower supply only half or less of the
maximum air flow, the losses at all torque demands below about half the maximum will
be one eighth or less of what a more conventionally designed engine would engender.
Power to drive the turbo-blower is derived from energy in the engine's exhaust that
would be otherwise wasted and thus does not subtract from the output of the engine.
This system would be equally useful in a conventional two-cycle engine because the air
losses in any two stroke create a loss of efficiency. In conjunction with the efficiency
enhancing factors present in the VCRC engine the added effect of the compound blower
system disclosed above results in potential prime mover efficiencies higher than have
heretofore been achieved.
[0087] Figure 3 shows the VCRC compound blower system in
schematic form. Two-stroke engine 51 drives an impeller 96 of a blower 94 through a
shaft 113. Blower 94 takes air in an intake port 95 and drives the air through an intake
passage 118 as indicated by arrow 101. As the air passes through impeller 96 it
undergoes a pressure rise due to the action of impeller 96. After the air leaves blower
94 it passes through a lightly sprung check valve 97 on its way to two stroke engine 51
through an intake manifold 119 connected to intake port 109.
[0088] As the engine is required to provide more torque the exhaust
driven blower 99 is forced to rotate faster because the exhaust has more energy due to
the increased fuei flow and excess exhaust energy resulting from the lessened
compression ratio thus imparting more drive to the turbo impeller 106. As impeller 106
of turbo blower 99 spins faster it will cause more air to be drawn through an intake port
103. The added pressure delivered by blower 99 will overcome the pressure at the
output of blower 94 at some level of exhaust velocity. This over-pressure will force open
a lightly sprung check valve 98 and allow flow from blower 99 to supply the engine as air
flows through turbo driven blower 99 through an intake port 121 as shown by arrow 102.
The same pressure in excess of that delivered by blower 94 will force check valve 97 to
close thereby effectively stopping flow from blower 94. The two modes of operation; one
in which blower 94 supplies all the air needed at low torques and the other in which
blower 99 is the only supply, will overlap during the transition from one mode to the
other. During this transition phase air will be supplied by both blowers in combining to
satisfy the engine's requirements.
[0089] Certain mechanical details are needed to make the system
operative. Exhaust flows from engine 51 to the exhaust driven turbine from exhaust
passage 110 as indicated by arrow 122. After leaving the turbine the exhaust leaves the
system through exhaust manifold 107 to mufflers, catalytic converters, etc. not shown.
Power is transmitted from the turbine 105 to blower 99 by means of a rotating shaft 104.
[0090] The system is made more effective if blowers 105, 99 and 94 are
of the centrifugal type, which is the usual case in automotive turbo-blowers. The
characteristics of this type of blower suit the system shown in Figure 3. When a
centrifugal blower operates against a very high impedance and there is little or no flow
through the blower very little power is needed to turn the impeller of the blower. This is
opposite to the characteristics of a blower of the axial type: The axial type of blower
requires a maximum of power under high head conditions and a minimum power
requirement under high flow-low pressure conditions.
[0091] While the engine is operating at low torque substantially all the
air is supplied by engine driven blower 94. Turbine 105 is being driven by exhaust
gases but blower 99 requires very little power to spin up to full speed. This results in a
turbo-blower that is ready for increased torque demand while blower 99 is not delivering
flow. Because of the low power demand impeller 100 is almost up to speed and ready,
with a small increase in speed, to deliver pressure higher than that of blower 94. Thus
there will be relatively little time delay or 'turbo lag' when an increase in flow is
demanded that will allow the engine to deliver increased torque.
[0092] During periods when torque demand is high and substantially all
the air needed by the engine is supplied by turbo-driven blower 99 check valve 97 is
forced substantially closed by the excess pressure induced in the intake system of the
engine by turbo-driven blower 99. Since centrifugal blowers, as noted above, need very
little power under conditions of low or zero throughput flow the drag on the engine will be
reduced.
[0093] The blower subsystem shown in Figure 3 is made even more
effective due to the characteristics of VCRC engine operation. As discussed previously,
high torque in the VCRC engine is delivered at lowered compression ratios: Exhaust
energy in an internal combustion piston engine is oppositely proportional to the
compression ratio of the engine. Thus the need for high energy in the turbo-blower,
when added torque is demanded, is accompanied by a large increase in exhaust energy
due to the lowered compression ratio in concert with added fuel flow. Ordinary internal
combustion engines using turbo-blowers can suffer so-called 'turbo lag1 or a perceptible
delay in turbo speed increase when an increase in torque demand is needed. This is
because the only energy increase in the conventional engine's exhaust is derived from
an increase in fuel flow.
Throttling a two-cycle spark-ignition engine
[0094] It is well recognized that the two-stroke type engine is potentially
much lighter and potentially more efficient than the more conventional four-stroke
engines. This is because there are two power strokes in the two-stroke engine for each
in the four-stroke variety. Thus the engine does not weigh much more than half as
much as a four-stroke equivalent engine. Since the engine produces twice as much
power while employing the same or fewer parts there is basically less friction in the two-
stroke engine.
[0095] There are two basic problems with the two stroke engine as an
efficient prime mover. The most basic is the throttling problem. Two-stroke spark
engines are most often regulated by restricting the input fuel-air mixture since they are
normally fed a bulk carbureted mixture of gasoline and air. The effect of this restricting
is only to retain exhaust products in the cylinder volume. Thus the efficiency is good at
full throttle, limited only by the air breathing problem discussed before. At part throttle,
however, the efficiency is much worse that the four-stroke equivalent. This is one of the
main factors that has limited the usage of spark-ignition two-stroke engines.
[0096] As may be derived from a consideration of the description of the
VCRC operation the throttling process is carried out in a manner that does not degrade
the efficiency of the engine process in any way. Indeed, the use of a variable volume
that participates in the throttling process and increases compression ratio as a
fundamental part of throttling makes the throttling process one that vastly enhances the
engine efficiency.
Estimate of VCRC efficiency
[0097] The following analysis is given to illustrate the potential of the
VCRC concept. It is quite simplified and many assumptions are made to more easily
show the basic concept. A more precise analysis actually shows an even better
efficiency, particularly at the higher levels of indicated mean effective pressure (IMEP)
[0098] Figure 10 shows the relationship of compression ratio of a spark-
ignited engine relative to the amount of fuel supplied to the air in the engine and the
IMEP produced by the engine. Figure 11 shows how the peak pressure created by the
same sort of engine varies with both compression ratio and ratio of fuel supplied. Figure
12 shows how basic indicated efficiency varies with compression ratio and amount of
fuel supplied relative to a stoichiometric ratio. The relationships shown in these three
Figures are all manipulated in the VCRC engine concept to produce the highest
efficiency in a light weight engine.
[0099] Figure 11 shows four datum points: Pertinent data for these
points from Figure 10 and 11 are given in the following table.
[00100] With a frictional MEP equivalent of about 15 psi, which is about the value a
two stroke engine with little drag provided by intake air would experience at a moderate
speed, the torque values of these points can be characterized as; 100%, 76%, 44% and
26% respectively. The indicated efficiencies of the engine at these datum points can be
seen on Figure 12 as 38%, 46% 56% and 60%. Factoring in the frictional pressure as a
mechanical efficiency by:
nm = (IMEP-Pt)/IMEP
where nm = mechanical efficiency
Pt = frictional pressure equivalent
and:
?oa = ?0 X ?m
where Hoa = overall efficiency
n0 = indicated thermal efficiency from Figure 12.
[00101]The efficiencies for each of the datum points is:
Point 124 @100% torque 35%
Point 125 @ 76% torque 41 %
Point 126 @ 44% torque 47%

Point 127 @ 26% torque 50%
[00102] The calculations are only approximate but contrast greatly with
an equivalent range of efficiencies for a conventional automobile engine from 28%
efficiency at 100% torque to about 20% efficiency at about 30% of full torque. The
VCRC engine is enough lighter than a conventional four-cycle engine in automobile
service to provide an automobile system weight about 80% to 85% as heavy as a
conventional system using a four-stroke engine. The overall fuel mileage is thus
calculated to be about 3 times as good as the conventional system considering that the
typical torque needed at average speeds is about 30%.
[00103] The VCRC concept can be reduced to mechanical practice with
many different conventional mechanisms employed to provide operation. Figure 1
shows the version that is chosen to describe the system. This and the other drawings
show one method for illustration purposes but many others could be used. The methods
of varying the compression ratio and regulating the fuel flow could readily be chosen
from many kinds of mechanical actuators to optimize various applications. The
mechanical system shown here to describe the operation of the concept is one of myriad
others that could be used.
[00104] A speed correction is also provided as another inventive feature.
The bearings in an internal combustion engine are inevitably of the journal type: The
load that can be supported by such bearings is proportional to their rotational speed. As
the engine rotational speed increases the throttle linkage adjusts so that a given torque
demand will result in a higher compression ratio at increased speed. Less fuel is
supplied to balance out the torque demand and the result is a better fuel economy for a
given level of power. This is discussed in the presentation of Figure 2 previously shown.
Comparison of VCRC efficiency with an existing engine
[00105] Ricardo shows some efficiencies of a compression-ignition

(Diesel) engine using a 'Comet Mark III' combustion chamber. The engine uses a
compression ratio of 15 to 1 which is the approximate ratio that a VCRC engine would
have at a torque level about 26% of maximum. It is possible to compare an equivalent
VCRC engine with the Ricardo example. Such comparison is slightly artificial. The
naturally aspirated Ricardo example has a maximum brake MEP of about 125 psi. A
VCRC engine optimally designed would utilize the capabilities of its turbo-blower and
have a maximum brake MEP around 170 psi and would thus be even more efficient in a
properly balanced design.
[00106] The Comet Mark III engine shown as the example in Ricardo has
an efficiency of about 31% at a torque level about 26% of its maximum. The Comet
Mark III engine shown would have a friction level, per Ricardo's discussion, of about 25
psi. A VCRC engine of the same size would have a friction level, per the same data
shown in Ricardo, of about 9.5 psi. The efficiency of the VCRC equivalent engine would
thus be about 43%, a gain of 12 percentage points or a factor of 1.38 greater efficiency.
This ratio would actually be higher than this; about 45% overall efficiency for a factor of
1.45 total better than the Comet Mark III, when the effects of a leaner fuel mixture in the
VCRC is taken into account.
[00107] A turbo charged VCRC engine equivalent would be about only
about 1/3 as heavy as the Comet Mark III compression-ignition engine shown since the
VCRC engine develops twice the power per revolution, being two-stroke instead of four-
stroke, and the maximum brake MEP of an optimized turbocharged VCRC is 170 psi vs.
125 in the Comet Mark III example shown in Ricardo. The difference between 45%
indicated efficiency as calculated for a direct comparison with the Ricardo data and the
50% calculated in the body of this specification arises from the difference in heat
transfer within the engine and the better balance that is attained with the advantages of
the turbo-charged VCRC engine. All compression-ignition engines must have a high
degree of turbulence induced within the engine in order to thoroughly mix the injected
spray with the superheated air during combustion since there is only about 10° of
crankshaft travel to effect such mixing in the compression-ignition engine. This
turbulence results in a large amount of heat transfer between the gases in a
compression-ignition engine and the walls surrounding the combustion chamber and
cylinder. Such heat transfer wastes some of the energy of the burning fuel. Spark-
ignition engines, such as the VCRC engine, have around 100° of crankshaft travel to mix
fuel and air and thus need less turbulence. Consequently spark-ignition engines incur
less wasteful heat transfer. The difference is about 10% of the total delivered efficiency.
[00108] Although various arrangements and modifications have been
discussed above, it will be appreciated that the invention is not limited thereto but
encompasses all forms and variations falling within the scope of the appended claims.
What is claimed is:
WE CLAIM:
1. A method of operating an internal combustion engine (51) comprising
at least one piston/cylinder (59, 111) combination having a main cylinder (111),
and an auxiliary cylinder in communication via a conduit (54), with said auxiliary
cylinder and said conduit forming an auxiliary volume, said auxiliary cylinder
including a variable position auxiliary piston (57), a fuel injection system (56) for
supplying fuel into said auxiliary volume (52), a first control device for said fuel
injection system, a second control device (123) for varying said auxiliary cylinder
volume and an ignition device (55) in communication with said auxiliary volume,
which method includes the steps of:
a. directing all of the air supplied to said engine into both the main
cylinder volume (63) and into said auxiliary volume;
b. directing all of the fuel into said auxiliary volume;
c. initiating combustion of said fuel and air in said main cylinder
volume;
d. completing combustion of said fuel and air in said main cylinder
volume, and
e. changing the volume of said auxiliary cylinder to vary the
compression ratio of said cylinder/piston combination;
characterized in that
f. said engine is a spark ignited internal combustion engine; and
g. said fuel is directed into said auxiliary volume by mixing with air
flowing in said conduit (54) to said auxiliary volume during part or
all of the compression phase of said engine forming therein a
combustible mixture of fuel and air substantially uniformly mixed
prior to said initiation of combustion.
h. said fuel is injected substantially only into said conduit (54) into
said air flowing into said auxiliary cylinder.
2. A method as claimed in claim 1 above, further including the step of
providing fuel and air to said auxiliary volume in a ratio of fuel to air that is at
least stoichiometric or richer in fuel.
3. A method as claimed in claim 2, in which said fuel and air is
provided to said auxiliary volume in a ratio of fuel to air that is at least 40% richer
in fuel than stoichiometric.
4. A method as claimed in any one of the preceding claims, further
including the step of changing fuel supply in accordance with the torque demand
placed on the cylinder/piston combination and changing the compression ratio in
inverse acccordance with said torque demand.
5. A method as claimed in any one of the preceding claims, wherein
the step of changing the size of said auxiliary cylinder volume comprises varying
said volume between a minimum and a desired value for each combustion
sequence.
6. A method as claimed in any one of the preceding claims, wherein
the step of changing the size of the auxiliary cylinder volume comprises varying
said volume between a minimum and a desired value for each combustion
sequence during that portion of the engine cycle when the engine is at minimum
pressure.
7. A method as claimed in any one of the preceding claims, wherein
the control of the size of the auxiliary cylinder volume varies in response to the
speed of said engine so as to change the compression ratio in accordance with the
speed of said engine.
8. A method as claimed in any one of the preceding claims, wherein
the internal combustion engine is a two-cycle engine.
9. A method as claimed in any one of claims 1 to 5, wherein the step
of changing the size of the auxiliary cylinder volume comprises varying said
volume between a minimum and a desired value for each combustion sequence
during that portion of the engine cycle when the engine is undergoing compression
and wherein said auxiliary cylinder volume is returned to minimum volume

during the time when said engine is at minimum pressure.
10. A method as claimed in any one of the preceding claims, wherein
said air supplied to said engine includes an amount of recirculated exhaust gas.
11. An internal combustion engine (51) comprising;
at least one piston/cylinder (59, 111) combination having a main cylinder
(111);
an auxiliary cylinder in communication via a conduit (54), with said
auxiliary cylinder and conduit forming an auxiliary volume, said auxiliary cylinder
being controllably variable in volume with an auxiliary piston (57) to vary the
compression ratio;
a fuel injection system (56) comprising a fuel injector for supplying fuel
into said auxiliary volume;
a first control device controlling a fuel supply to said fuel injector;
a second control device (123) for varying said auxiliary cylinder volume
and an ignition device (55) in communication with said auxiliary volume;
said second control device for said auxiliary piston is so designed as to
vary the maximum volume of said auxiliary cylinder during a particular engine
cycle in accordance with the amount of fuel required to deliver the torque
demanded of said internal combustion engine during said particular cycle;
characterized in that:-
a. said first control device is configured to inject fuel into said
auxiliary volume during part or all of the compression phase of
said engine to form therein a combustible mixture of fuel and air
substantially uniformly mixed prior to said initiation of
combustion;
b. said engine is a spark ignited internal combustion engine, and;
c. said injection system (56) is placed so as to inject fuel substantially
only into said conduit (54) into the air flowing into said auxiliary
cylinder.
12, An internal combustion engine as claimed in claim 11, wherein said second
control device coupled to said auxiliary piston controls compression ratio in
inverse accordance to the amount of fuel supplied by said first control device.
13. An internal combustion engine as claimed in claim 11 or 12, wherein
said second control device coupled to said auxiliary piston controls operates to
move said auxiliary piston substantially only during that time when pressure
within said engine is close to the minimum value encountered during the engine
cycle.
14. An internal combustion engine as claimed in any one of claims 11 to
13, wherein said second control device varies said volume between a minimum
and a desired volume for each combustion sequence.
15. An internal combustion engine as claimed in any one of claims 11 to
14, wherein said second control device varies the size of the auxiliary cylinder
volume in response to speed of said engine so as to change compression ratio in
accordance with speed of said engine.
16. An internal combustion engine as claimed in any one of claims 11 to
14, wherein said second control device varies the size of the auxiliary cylinder
volume in response to the amount of fuel/air mix transported to said auxiliary
cylinder during the compression stroke of the engine and returns the volume of
said auxiliary cylinder to a minimum while said engine is at minimum pressure.
17. An internal combustion engine as claimed in any one of claims 11 to
16, wherein said second control device is designed so as to exert a force on said
auxiliary piston biasing said piston so as to maintain said auxiliary cylinder
volume at a minimum when the pressure in said engine is at a minimum and said
second control device is configured to direct and limit cyclic movement of said
auxiliary piston under the action of said engine pressure.
18. An internal combustion engine as claimed in any one of claims 11 to
17, wherein said second control device includes a hydraulic snubbing device to
direct and limit cyclic movement of said auxiliary piston under the action of said
engine pressure, comprising:
a. a hydraulic piston (65) attached to said auxiliary piston constrained
tamove in simultaneous motion with said auxiliary piston,
b. a hydraulic control cylinder (66) closely fitted around said
hydraulic piston, said hydraulic control cylinder filled with a substantially
incompressible fluid,
c. a vent (112) allowing flow of said fluid in and out of said hydraulic
control cylinder,
d. an auxiliary valving mechanism (123, 68, 64) in said hydraulic
snubbing device directed to close said vent at various positions of said control
piston to prevent motion of said control piston beyond such motion as needed.
19. An internal combustion engine as claimed in claim 18, wherein said
valving mechanism consists of said vent being placed in the wall of said hydraulic
cylinder so positioned to interrupt flow of said liquid from said hydraulic cylinder
when said hydraulic piston covers said vent at the desired position of said
hydraulic piston, said hydraulic cylinder being movable by a mechanism designed
to position said hydraulic cylinder to control the snubbing of said hydraulic piston
so as to place said vent such that flow of said liquid through said vent is
substantially stopped by the outside diameter of said hydraulic piston when said
hydraulic piston is in the position at which snubbing is desired.
20. An internal combustion engine as claimed in claim 18 or 19, wherein
said valving mechanism includes a non-moving static hydraulic piston (67)
substantially the same diameter as said hydraulic cylinder (66) and mounted
coaxially with said hydraulic cylinder, said static hydraulic piston placed within
said hydraulic cylinder at the opposite end from said hydraulic piston, said
hydraulic cylinder being open at both ends and slidably mounted to move
coaxially with said static hydraulic piston and said hydraulic piston.
A method of operating an internal combustion engine (51) comprising at
least one piston/cylinder (59,111) combination having a main cylinder
(111), and an auxiliary cylinder in communication via a conduit (54),
with said auxiliary cylinder and said conduit forming an auxiliary
volume, said auxiliary cylinder including a variable position auxiliary
piston (57), a fuel injection system (56) for supplying fuel into said
auxiliary volume (52), a first control deice for said fuel injection system, a
second control device (123) for varying said auxiliary cylinder volume and
an ignition device (55) in communication with said auxiliary volume,
which method includes the steps of:
a. directing all of the air supplied to said engine into both the
main cylinder volume (63) and into said auxiliary volume;
b. directing all of the fuel into said auxiliary volume;
c. initiating combustion of said fuel and air in said main cylinder
volume;
d. completing combustion of said fuel and air in said main
cylinder volume, and
e. changing the volume of said auxiliary cylinder to vary the
compression ratio of said cylinder/piston combination;
characterized in that
f. said engine is a spark ignited internal combustion engine; and
g. said fuel is directed into said auxiliary volume by mixing with
air flowing in said conduit (54) to said auxiliary volume during
part or all of the compression phase of said engine forming
therein a combustible mixture of fuel and air substantially
uniformly mixed prior to said initiation of combustion.
h. said fuel is injected substantially only into said conduit (54) into
said air flowing into said auxiliary cylinder.

Documents:

623-KOLNP-2003-FORM 27 1.1.pdf

623-KOLNP-2003-FORM 27.pdf

623-kolnp-2003-granted-abstract.pdf

623-kolnp-2003-granted-claims.pdf

623-kolnp-2003-granted-correspondence.pdf

623-kolnp-2003-granted-description (complete).pdf

623-kolnp-2003-granted-drawings.pdf

623-kolnp-2003-granted-examination report.pdf

623-kolnp-2003-granted-form 1.pdf

623-kolnp-2003-granted-form 18.pdf

623-kolnp-2003-granted-form 2.pdf

623-kolnp-2003-granted-form 26.pdf

623-kolnp-2003-granted-form 3.pdf

623-kolnp-2003-granted-form 5.pdf

623-kolnp-2003-granted-reply to examination report.pdf

623-kolnp-2003-granted-specification.pdf


Patent Number 223881
Indian Patent Application Number 623/KOLNP/2003
PG Journal Number 39/2008
Publication Date 26-Sep-2008
Grant Date 23-Sep-2008
Date of Filing 14-May-2003
Name of Patentee M/s. COWANS KENNETH W,
Applicant Address 1213 EAST E1 MIRADOR DRIVE, FULLERTON, CA
Inventors:
# Inventor's Name Inventor's Address
1 M/s. COWANS KENNETH W, 1213 EAST E1 MIRADOR DRIVE, FULLERTON, CA 92835
PCT International Classification Number F02B 75/04
PCT International Application Number PCT/US01/44487
PCT International Filing date 2001-11-29
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/253,799 2000-11-29 U.S.A.