Title of Invention

"AN APPARATUS AND A METHOD FOR FEEDING AIR IN SUPERCHARGED PISTON ENGINE"

Abstract

An arrangement for feeding air in a supercharged piston engine (1), which air feeding arrangement comprises at least a supercharging device (4) arranged for feeding air to more than one cylinder (3), an air chamber (2) being in connection with the supercharging device (4), and a channel arrangement (5) leading from the air chamber to each cylinder (3) of the piston engine, characterised in that a resonator system (6) is arranged in connection with the air chamber for attenuating pressure pulsation in the air chamber (2).

Full Text

The present invention relates to an -apparatus and a method for feeding air in a supercharged piston engine. The invention relates to an arrangement for feeding air in a supercharged piston engine, which air feeding arrangement comprises at least a supercharging device arranged for feeding air to more than one cylinder, an air chamber being in connection with the supercharging device, and a channel arrangement leading from the air chamber to each cylinder of the piston engine. The invention also relates to a method of operating a supercharged piston engine, in which method combustion air is fed by means of a supercharging device at a pressure higher than ambient pressure into an air chamber in connection with the supercharging device, and air is led from the air chamber to cylinders being in connection with the air chamber through channel arrangements between the cylinders and the air chamber. It is known that pressure vibrations take place in intake channels of piston engines and various solutions for damping intake noise have been disclosed. In publication DE 19641715 there is shown a resonator connected in parallel with an inlet air channel. The resonator is provided with a connection tube having variable length and diameter. In this kind of solution a starting point is to attenuate noise emitted from the intake channel to the environment. However, this fails to handle possible pressure pulsations in the engine itself. On the other hand, various resonator arrangements in connection with naturally aspirated engines for enhancing gas admission into the cylinder or combustion chamber have been suggested, eg. US 5572966. In contrast to naturally aspirated engines, in supercharged engines it is possible to select the boost pressure. Thus, a desired amount of gas mixture on average may be fed into the cylinders, but unevenness of charge of the cylinders still remains as a problem due to pressure pulsations. Additionally, in supercharged multi-cylinder piston engines some problematic operating disturbances, e.g. the so-called pumping phenomenon, have been noticed. In the pumping phenomenon pressure pulsation moves the operating point of the supercharger repeatedly over to the surging area. In certain types of engines valves operate in groups, causing strong pulsation in the air chamber, impeding the operation of the supercharger and so adversely affecting the operation of the engine. Moreover, the pulsation of pressure in the air chamber has an adverse effect on the filling of the cylinders. That is because the pressure level in the vicinity of each inlet valve fluctuates, and the amount of air remaining in the cylinder is ruled by the local pressure level when the inlet valve closes. The local pressure level may vary considerably, specifically in supercharged engines. It is found that specifically in supercharged engines applying the so called Miller-process, the valve timing, specifically when closing the inlet valve in the cycle prior to bottom dead centre, and also on simultaneous opening of valves, aggravates the above mentioned pumping phenomena. It is an aim of the present invention to provide an arrangement for feeding air into a piston engine and a method of operating a supercharged piston engine, with which it is possible to advance the known art and minimise the above and preferably other shortcomings of the prior art. It is a specific intention of the invention to provide an arrangement suitable for feeding air into a piston engine applying the so-called Miller-process and a method of operating such a piston engine. The present invention provides an arrangement for feeding air in a supercharged piston engine according to claim 1 and a method of operating a supercharged piston engine 11. Preferred or optional features of the invention are defined in the dependent claims. The arrangement for feeding air in a supercharged piston engine according to the invention comprises at least a supercharging device arranged for feeding air to more than one cylinder, an air chamber in connection with the supercharging device, and a channel arrangement leading from the air chamber to each cylinder of the piston engine. According to the invention a resonator system is arranged in connection with the air chamber for attenuating pressure pulsation in the air chamber. Advantageously the resonator system is arranged mainly to attenuate pressure pulsation, which appear at the third harmonics of the rotational speed of the engine or frequencies below that. The resonator system may be formed by use of a resonator chamber, which opens into the air chamber of the engine. Preferably the supercharging device is connected to a first end of the air chamber and the resonator system is arranged to operate substantially on the opposite end, i.e. a second end, to the first end of the air chamber. This way the effect of the resonator system according to the invention is optimal. According to an embodiment of the invention the resonator system may be formed of one or several elements each defining an elongated space, which are arranged to open into the air chamber. The air chamber is arranged to have a certain cross-sectional area perpendicular to a direction of successive cylinders, which in this connection means an average area. The average cross sectional area may be obtained by dividing the total volume of the air chamber by its total length. It is noticed that, in practice, it is advantageous as a whole that the cross sectional area of the space of the resonator system is below 50 %, but advantageously below about 30%, of the cross-sectional area of the air chamber. The resonator system provides advantages relating to its construction and production if it is arranged in connection with constructions of an engine block and/or an air chamber. The resonator system may also comprise a mechanical oscillator as well as an actuator system for moving the oscillator. In the method according to the invention in connection with a supercharged piston engine, combustion air is fed by means of a supercharging device to a pressure higher than ambient pressure into an air chamber in connection with the supercharging device, and air is led from the air chamber to cylinders in connection with the air chamber through channel arrangements between the cylinders and the air chamber. A pressure pulsation is generated in the air chamber, which pulsation is half-wavelength shifted from a pulsation in the air chamber at the third harmonics of the rotational speed of the engine or at frequencies below that. Advantageously but not necessarily, the pressure pulsation is formed mainly at the opposite end to the coupling location of the supercharging device in the air chamber. The resonator system may be controlled to be adjusting according to the rotational speed of the engine. If so, at each respective speed, the resonator system is controlled to attenuate substantially that pressure pulsation which appears at the third harmonics of the rotational speed of the engine or frequencies below that, so it always operates optimally. Advantageously the engine is arranged to be operated according to the so-called Miller-process and the supercharging device operates using the energy of exhaust gases of the engine. The invention will be further described, by way of example only, with reference to the accompanying drawings, in which • Figure 1 shows schematically an embodiment of a supercharged piston engine according to the invention, • Figure 2 shows schematically another embodiment of a supercharged piston engine according to the invention, and • Figure 3 shows schematically an third embodiment of a supercharged piston engine according to the invention. Figure 1 shows a supercharged piston engine 1. The engine is a so called V-engine. For clarity, only components relevant for describing the invention have been shown in the figure. The engine includes at least supercharging devices 4, which have been arranged to feed air for the cylinders 3. The superchargers are connected to an air chamber 2, from which the air is led to each cylinder through a channel arrangement 5 including at least one channel for each cylinder. It is possible to arrange desired devices, such as a cooler, between the supercharging devices and air chamber, however none are shown for clarity reasons. The air chamber extends in the direction of the cylinder line. Supercharger 4 feeds air into the air chamber and the pressurised air is distributed therefrom to each cylinder 3. The length of the air chamber is such that air may be fed to each cylinder 3 through a shortish channel 5 leading from the air chamber to each cylinder. A resonator system 6 is arranged in connection with the air chamber 2 for attenuating pressure pulsation in the air chamber. With the arrangement according to the invention it is possible to ensure appropriate operation, particularly of turbo-charged engines, in all circumstances. As can be seen from the figure 1, the supercharging device 4 is connected to a first end 2' of the elongated air chamber 2. The resonator system 6 is provided in order to operate substantially on the opposite end 2" to the first end 2' of the air chamber 2. The figure shows how the resonator system 6 is formed using one or several members having an elongated space, like tubes 8, 8', which members have been arranged to open into the air chamber. The air chamber forms a space which is directly in communication with the supercharging device 4. The space is arranged to have a certain cross-sectional area perpendicular to line of successive cylinders, which in this connection means average cross-sectional area. The average cross-sectional area may be defined by dividing the total volume of the air chamber by its total length. Theoretically, with a view to attenuating pulsation, it would be optimal if the vibrating air mass of the resonator system 6 corresponded to the air mass in the air chamber 2. That would result in an arrangement in which the space of the resonator system would have a cross sectional area 50% of the cross sectional area of the air chamber. However, in practice it has been discovered that it is advantageous in respect of operation as a whole, if the cross-sectional area of the resonator system is about 30% of the cross- sectional area of the air chamber. Thus an adequate attenuation is accomplished yet without substantially impairing the flow of combustion air for the engine. An engine arrangement dimensioned by these principles operates so that combustion air for the engine is fed by means of supercharging device 4 into an air chamber 2 in connection with the supercharging device to a pressure higher than ambient air pressure. From the air chamber 2 the air is led to cylinders 3 in connection with the air chamber through channel arrangements 5 connecting each cylinder with the air chamber. By means of the resonator system 6, a pressure pulsation is formed in the air chamber. The pulsation is half-wavelength shifted from a pulsation in the air chamber having a frequency at or below the third harmonics of the rotational speed of the engine. For example, for an engine rotating mainly at a speed of 1500 revolutions per minute (rpm), the frequency of the third harmonics is about 75 kHz. In the engine according to figure 1, the compensating pressure pulsation is realised mainly at the opposite end 2" to the coupling location of the supercharging device in the air chamber. The dimensioning of such a resonator tube 8 takes place simplistically using the equation (Equation Removed) in which / stands for the tuning frequency, C for speed of sound in the medium in question and L for the operational length of the resonator. This kind of resonator tube 8, 8' may be realised also by providing several tubes within each other. In that case, each tube being closed at one end, an inner tube 8' is fitted inside the outer tube 8, so that its open end faces the closed end of the outer tube 8. In this manner it is possible to provide a system having shorter external dimensions while the operational length remains substantially the same. With this method is possible to achieve a considerable effect, specifically on a pulsation which affects the operation of a supercharger, especially a turbocharger. In figure 1 the supercharger is connected to an exhaust gas channel 7 and it is operated by the energy of exhaust gases. The arrangement according to the invention is specifically advantageous for an engine or in connection with a method, which is arranged to operate so that the inlet valves of the engine are closed before the bottom dead centre position of the piston during the operating cycle of the engine. In figure 1 there is shown also an embodiment of the resonator system 6, in which it operates as an active resonator system or in which its operation is controllable. A mechanical oscillator is provided in connection with the air chamber 2, such as a movable membrane 11 or the like, as well as an actuator system 12 for moving it. In this kind of solution the phase of the pulsation of the device is arranged to be shifted by one half-wavelength from the oscillation prevailing in the air chamber. This may be accomplished, for example, by means of a control unit controlling the movement of the actuator system 12 based on measurement of the pressure pulsation in the air chamber. The actuator system is in this case also connected to a separate engine control system 18, which may feed control information to the actuator system. This kind of resonator system may be arranged to be controlled to correspond the circumstances of the engine. The resonator system may for example be adjusted according to the rotational speed of the engine so that at each speed the resonator system is controlled to attenuate substantially the pressure pulsation which appears at the third harmonics of the rotational speed of the engine or frequencies below that. Figure 1 also shows another way of implementing an active resonator system 6, the operation of which may be actively controlled. A piston device 16 is at the other end of the tube 8, and an actuator 17 is arranged to move the piston device as shown by the arrow such that the operational length of the tube 8 is alterable. The actuator is further connected to a separate control system 18 of the engine, which transmits control information to the actuator as mentioned before. Figure 2 shows schematically another embodiment of supercharged piston engine according to the invention and in the figure, the reference numbers correspond to those of figure 1. The engine in the figure is an in-line engine and its operation, with respect of the invention, corresponds to the engine of figure 1. Figure 2 shows how the resonators of the resonator system 6 have been constructed as a part of the construction of the engine. The elongated space is at least partly formed by a wall 9 of the air chamber 2. For this purpose it is possible to use advantageously also the wall of the engine block 10, and the resonators may be constructed already at the casting stage of the engine block. Thus, below the air chamber in the figure 2, there is the engine block, which has not been shown for clarity reasons, but which the dotted line illustrates. With this procedure it is possible to provide a significant advantages, inter alia firmness of construction and saving of space. Figure 3 shows schematically a third embodiment of supercharged piston engine according to the invention and in the figure, the reference numbers correspond to those of figure 1. With respect to the invention, the operation of the engine of figure 3 corresponds that of figure 1. In figure 3, a resonator of the resonator system 6 is formed as a part of the construction of the engine. A partition wall 13 or the like is arranged inside the chamber 2, which partition wall separates from the air chamber a chamber 15 having a separate space. The partition wall 13 is advantageously arranged so that it makes the cross-sectional area of the air chamber decrease towards its second end 2". In this example, the wall 13 begins approximately halfway along the chamber 2. There is an elongated opening 14 provided in the partition wall, which opening may be formed as a pipe. The elongated opening connects the chamber 15 and the air chamber with each other. With this solution it is possible to provide both a favourable form of the air chamber in respect of flow, and also a pulsation attenuating resonator system located in connection with the air chamber, whereas no external additional space is required. This resonator system operates in a manner of a so-called Helmholtz-resonator: its tuning approximately complies with the equation (Equation Removed) in which/stands for the tuning frequency, C for the speed of sound in the medium in question, S for the diameter of opening 14, L for the length of opening 14 and Ffor the volume of chamber 15. Several embodiments have been described above and it is possible to apply them separately or combine them according to need in particular circumstances. Thus, it is clear that the technical solutions disclosed above are only exemplary, and the invention is not limited to the embodiment shown but several modifications of the invention are reasonable within the scope of the attached claims. We claim: 1. An appartus for feeding air in a supercharged piston engine (1), which air feeding arrangement comprises at least a supercharging device (4) for feeding air to more than one cylinder (3), an air chamber (2) being in connection with the supercharging device (4), and a channel arrangement (5) leading from the air chamber to each cylinder (3) of the piston engine, characterised in that a resonator system (6) is connection with the air chamber for attenuating pressure pulsation in the air chamber (2). - 2. An arrangement "as claimed in claim 1, in which the supercharging device is connected to a first end of the air chamber, wherein the resonator system (6) to operate on another end (2") opposite to the first end (2') of the air chamber. 3. An appartus as claimed in claim 1 or 2, wherein the resonator system , arranged td attenuate mainly pressure pulsation which appears at the third harmonics of the rotational speed of the engine or frequencies below that. 4. An appartusas claimed in claim 1, 2 or 3, wherein the resonator system (6) is formed of one or several elongated elements (8, 9, 10) which open into the air chamber (2). 5. An appartus as claimed in claim 4, in which the air chamber to have a certain cross sectional area perpendicular to a "direction of successive cylinders, wherein the cross sectional area of the space of the resonator system (6) is below 50 % of the cross sectional area of the air chamber (2). 6. An appartus as claimed in claim 5, characterised in that cross sectional area of the space of the resonator system (6) is below 30% of the cross sectional area of the air chamber (2). 7. An appartus as claimed in claim 1, 2 or 3, wherein the resonator system (6) is formed of a resonator chamber (15) which opens into the air chamber (2) of the engine. 8. An appartus as claimed in claim I, 2 or 3, wherein the resonator system (6) is formed of a mechanical oscillator, such as a suitably movable membrane or the like (11), as well as of an actuator system (12) provided for moving the oscillator. 9. An appartus as claimed in any preceding claim, wherein the resonator system is connection with constructions of an engine block (10) and/or the air chamber (2). 10. An appartus for feeding air as claimed in claim 1, 2 or 3, wherein the operation of the resonator system (6) is externally controllable. 11. A method of operating a supercharged piston engine (1), in which method combustion air is fed by means of a supercharging device (4) at a pressure higher than ambient pressure into an air chamber (2) in connection with the supercharging device, and air is led from the air chamber (2) to cylinders (3) in connection with the air chamber through channel arrangements (5) between the cylinders and the air chamber, wherein pressure pulsation is formed in the air chamber, which pulsation is half-wavelength shifted from a pulsation in the air chamber, which appears at the third harmonics of the rotational speed of the engine or frequencies below that. 12. A method as claimed in claim 11, wherein the engine operates according to the Miller-process and the supercharging device operates using the energy of the exhaust gases of the engine. 13. A method as claimed in claim 11, wherein the pressure pulsation is formed mainly at the end (2") of the air chamber opposite the coupling location of the supercharging device (4). 14. A method as claimed in claim 11. wherein the resonator system (6) is controlled in according with rotational speed of the engine, so that at each speed the resonator system is controlled to attenuate substantially that pressure pulsation which appears at the third harmonics of the rotational speed of the engine or frequencies below that 15. An appartus for feeding air in a supercharged piston engine substantially as herein described with reference to the accompanying drawings.

Documents:

1081-del-2001-abstract.pdf

1081-del-2001-claims.pdf

1081-del-2001-correspondence-others.pdf

1081-del-2001-correspondence-po.pdf

1081-del-2001-description (complete).pdf

1081-del-2001-drawings.pdf

1081-del-2001-form-1.pdf

1081-del-2001-form-18.pdf

1081-del-2001-form-2.pdf

1081-del-2001-form-3.pdf

1081-del-2001-form-5.pdf

1081-del-2001-gpa.pdf

1081-del-2001-petition-138.pdf