Title of Invention	FLOW DISTRIBUTION DEVICE
Abstract	1. An improved flow-distribution device adaptable to a gas turbine combined cycle system, the system comprising a turbine (3) oriented one of a vertically or horizontally which emits exhaust gas; a heat recovery steam generator (5) for receiving the exhaust gas; the device comprising a transition duct (4) disposed between the turbine (3) and the steam generator (5), wherein the transition duct (4) is configured to have a contour comprising at least two steps utilizing composite angles (6,7) extending along the flow pattern of the exhaust gas, and in that a momentum transformation grid (9) is disposed across the width of the transition duct (4), the momentum transformation grid comprising a plurality of flat plates (8) rigidly connected to a rectangular steel frame (10), having orientations and pitches selected to effect a multifold reduction in gas momentum in the flow direction altering the flow pattern thereby achieving an uniform flow distribution.

Title of Invention

FLOW DISTRIBUTION DEVICE

Abstract

1. An improved flow-distribution device adaptable to a gas turbine combined cycle system, the system comprising a turbine (3) oriented one of a vertically or horizontally which emits exhaust gas; a heat recovery steam generator (5) for receiving the exhaust gas; the device comprising a transition duct (4) disposed between the turbine (3) and the steam generator (5), wherein the transition duct (4) is configured to have a contour comprising at least two steps utilizing composite angles (6,7) extending along the flow pattern of the exhaust gas, and in that a momentum transformation grid (9) is disposed across the width of the transition duct (4), the momentum transformation grid comprising a plurality of flat plates (8) rigidly connected to a rectangular steel frame (10), having orientations and pitches selected to effect a multifold reduction in gas momentum in the flow direction altering the flow pattern thereby achieving an uniform flow distribution.

Full Text	FIELD OF INVENTION The invention generally relates to a flow-distribution method and apparatus adaptable in systems involving geometrical in the flow area. More particularly, the present invention relates to an improved flow-distribution device in a heat recovery steam generator connected to a gas turbine. BACKGROUND OF THE INVENTION A heat recovery steam generator extracting heat from gases emanating from various sources including gas turbine or Gas turbine based combined cycle system comprises: a. Gas Turbine component - air Compressor, Combustor, Turbine Generators, Fuel Injection and Pollutant Control System, Lubrication and Cooling system b. Heat Recovery Steam Generator for receiving the exhaust of the Gas Turbine Component and transition ducting for connecting the two components of the system. The exhausts from Gas turbine entering the heat recovery system are at a state of high turbulence and swirl with highly non-uniform flow characteristics. Heat recovery system is designed to have optimum pressure drop on the gas side to reduce compressor load of the gas turbine to improve its heat rate. Large ducts with wide cross section heat transfer surfaces are employed to reduce the flue gas velocities to levels providing good heat transfer for the pressure drop. The outlet of gas turbine employs a velocity in region of 40-60 m/s. If the same velocity range were adopted in Heat recovery system, it would increase the load on Gas Turbine compressor. Therefore a transition is adopted to join the exhaust of the gas turbine to that recovery system reducing the gas velocities to levels optimum for heat recovery and pressure drop on the Gas turbine exhaust side. The exhaust gases undergo huge reduction in their velocity in the transition duct whose angle of divergence with respect to the horizontal is normally kept more than 15° - the threshold level which will not allow separation and consequent back flow of gases. One of the major reasons for adopting such steep transition is of economic criteria of cost of ducting and space availability. The symmetry required for smooth transition is also not practicable on account of standard exhaust configuration of Gas Turbine. The conventional solution is to employ flow control by plates with holes to induce pressure drop to normalize flow. The drawback of the above flow control that they are expensive and tend to have penalty on gas side pressure drop. There are other methods of improving flow distribution with use of gas removal line having an inlet end in the diverging wall of the transition ducting and use of flue gases re-injection (natural or assisted) at the point of separation. The disadvantage of such system is practical ducting problems associated with natural re-injection and extra continuous power consumed in assisted case re- injection. There is also a limitation on preference of divergence angle upto 60° calling for more space for the footprint of Heat Recovery System. Accordingly, an object of the present invention is to provide an improved flow- modification device, which improves the flow distribution inside the transition duct. Another object of the present invention is to provide an improved flow- modification device, which positively eliminates the re-circulating eddy formation in the asymmetrical ducts. A further object of the present invention is to provide an improved flow- modification device, which reduces heat transfer surfaces requirement on account of improved flow distribution. Yet another object of the present invention is to provide an improved flow- modification device, which substantially reduce the back flow of gas because of better flow distribution at the entry of the heat recovery system. A still further object of the present invention is to provide an improved flow- modification device, which uses unsymmetrical ducting in place of expensive smooth transition with reduced divergence ducting. Additional objects and features of the invention will be more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 - schematically shows a conventional gas turbine combined cycle system having a heat recovery steam generator. Fig. 2 - a schematic view of a conventional transition duct particularly showing the gas flow pattern inside the duct. Fig. 3 - shows an improved flow-modification device in accordance with the present invention. Fig. 4 - shows a momentum transformation grid of the improved flow- modification device according to the present invention. SUMMARY OF THE INVENTION Accordingly there is provided an improved flow-modification device adaptable to a gas turbine combined cycle system, the system comprising a turbine oriented one of a vertically or horizontally which emits exhaust gas; a heat recovery steam generator for receiving the exhaust gas; the device comprising a transition duct disposed between the turbine and the steam generator. The transition duct is configured to have a contour comprising at least two steps utilizing composite angles extending along the flow-pattern of the exhaust gas. That a momentum transformation grid is disposed across the width of the transition duct, the momentum transformation grid comprising a plurality of flat plates rigidly connected to a rectangular steel frame, having orientations and pitches selected to effect a multifold reduction in gas momentum in the flow direction including altering the flow pattern thereby achieving an uniform flow distribution. The invention adopts a Momentum Transformation Grid consisting of plates arranged in particular fashion placed across the duct width so as to modulate the flow area and therefore modifying the area available for the flow. The variation of flow area along with arrangement of plates in the duct improves the flow distribution inside the duct. The invention also identifies the most optimum location at the ducting for improving flow distribution. The standard shape of transition duct is replaced with composite angle ducting in the Flow Modifying Device locating the point of inflexion exactly at the eye of recirculation and select the ducting angles close to the flow pattern existing in the asymmetrical ducting thereby positively eliminating the re-circulating eddy formation. The modus of supporting Momentum Transformation Grid is using rectangular frame of plates on which the component plates are welded on to and is hung from top beam of supporting structures. The invention comprises of suitable combination of flow area and composite angles to improve the flow distribution as explained in detailed description of invention. It reduces footprint requirement of Heat Recovery System. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION. Referring to the drawings, and in particular to Fig. 1, a conventional gas turbine- HRSG system is shown generally designated as 9. The system comprises a generator 1, a compressor 2, and a gas turbine 3, connected in series. The turbine 3 has an inlet 3a and an outlet 3b. The exhaust from the gas turbine 3 passes through a transition duct 4 and into an inlet of a heat recovery steam generator 5. The HRSG 5 comprises a super heater 5a, and a boiler bank 5b downstream from the super heater 5a. The transition duct 4 is required because the turbine outlet 3b is smaller than the inlet of the HRSG 5. The transition duct 4 is asymmetrical, having a horizontal bottom wall 4a, an upwardly slanting, diverging upper wall 4b, an inlet 4c, and an outlet 4d. Such a typical configuration allows for hazard-free connection between the turbine 3 and the HRSG 5 without requiring the turbine 3 to be elevated, as would be necessary if the transition duct 4 diverged in a symmetrical fashion. As shown in fig - 3, the present invention provides an improved flow- modification device in which the transition duct (4) is configured to have a contour comprising at least two steps utilizing composite angles (6,7) which extend along the flow-pattern of the exhaust gas thereby positively prevent recirculation of the gas. A momentum transformation grid (9) as separately shown in fig - 4is disposed across the width of the transition duct (4) so as to modulate the flow area and therefore modifying the area available for the flow. Thus, a variation of flow area by utilizing the momentum transformation grid (9) improves the flow distribution inside the duct (4). The momentum transformation grid (9) comprises a plurality of flat plates (8) having orientations and pitches selected in registration with the system features including the physical parameters of the exhaust gas in order to reduce momentum of gases in flow direction and suitably altering the flow pattern for uniform flow distribution. A rectangular steel frame (10) accommodating said plurality of flat plates (8) being rigidly connected thereupon. The advantage of the invention lies in retrofitting the Momentum Transformation Grid in the existing Heat Recovery System due to ease with which the Grid can be brought into the duct through the access manhole and site welded at the desired location. The other benefits associated with Flow Modifying device are that the improved flow distribution enhances heat transfer of the sections downstream and also improves combustion and flame characteristic of the heating system. This results in more uniform temperature profile at the outlet of the duct burner resulting optimum material selection of heat transfer section downstream. This further results in economic benefits desired from employing correct heat transfer surface area (savings on account of material costs) and resulting continuous saving from improved generation on account of operation near predicted regime on account of optimum. A significant reduction in heat Recovery Steam Generator length contributes immensely to savings in plot plan and ducting and structural requirement. It is also cost effective as the savings comes from reduced ducting requirement in the high temperature zone of the system. The overall weight of the system is brought down resulting in more economic arrangement. WE CLAIM 1. An improved flow-distribution device adaptable to a gas turbine combined cycle system, the system comprising a turbine (3) oriented one of a vertically or horizontally which emits exhaust gas; a heat recovery steam generator (5) for receiving the exhaust gas; the device comprising a transition duct (4) disposed between the turbine (3) and the steam generator (5), wherein the transition duct (4) is configured to have a contour comprising at least two steps utilizing composite angles (6,7) extending along the flow pattern of the exhaust gas, and in that a momentum transformation grid (9) is disposed across the width of the transition duct (4), the momentum transformation grid comprising a plurality of flat plates (8) rigidly connected to a rectangular steel frame (10), having orientations and pitches selected to effect a multifold reduction in gas momentum in the flow direction altering the flow pattern thereby achieving an uniform flow distribution. 2. The device as claimed in claim 1, wherein the transition duct (4) is asymmetrical and eliminates the re-circulating eddy formation. 3. The device as claimed in claim 1, wherein the momentum transformation grid (9) can be retrofitted in the existing transition duct (4). 4. An improved flow-distribution device adaptable to a gas turbine combined cycle system, as substantially herein described and illustrated with reference to the accompanying drawings. 1. An improved flow-distribution device adaptable to a gas turbine combined cycle system, the system comprising a turbine (3) oriented one of a vertically or horizontally which emits exhaust gas; a heat recovery steam generator (5) for receiving the exhaust gas; the device comprising a transition duct (4) disposed between the turbine (3) and the steam generator (5), wherein the transition duct (4) is configured to have a contour comprising at least two steps utilizing composite angles (6,7) extending along the flow pattern of the exhaust gas, and in that a momentum transformation grid (9) is disposed across the width of the transition duct (4), the momentum transformation grid comprising a plurality of flat plates (8) rigidly connected to a rectangular steel frame (10), having orientations and pitches selected to effect a multifold reduction in gas momentum in the flow direction altering the flow pattern thereby achieving an uniform flow distribution.

Full Text

FIELD OF INVENTION
The invention generally relates to a flow-distribution method and apparatus
adaptable in systems involving geometrical in the flow area. More particularly,
the present invention relates to an improved flow-distribution device in a heat
recovery steam generator connected to a gas turbine.
BACKGROUND OF THE INVENTION
A heat recovery steam generator extracting heat from gases emanating from
various sources including gas turbine or Gas turbine based combined cycle
system comprises:
a. Gas Turbine component - air Compressor, Combustor, Turbine Generators,
Fuel Injection and Pollutant Control System, Lubrication and Cooling system
b. Heat Recovery Steam Generator for receiving the exhaust of the Gas Turbine
Component and transition ducting for connecting the two components of the
system.
The exhausts from Gas turbine entering the heat recovery system are at a state
of high turbulence and swirl with highly non-uniform flow characteristics. Heat
recovery system is designed to have optimum pressure drop on the gas side to
reduce compressor load of the gas turbine to improve its heat rate. Large ducts
with wide cross section heat transfer surfaces are employed to reduce the flue
gas velocities to levels providing good heat transfer for the pressure drop. The
outlet of gas turbine employs a velocity in region of 40-60 m/s. If the same
velocity range were adopted in Heat recovery system, it would increase the load
on Gas Turbine compressor. Therefore a transition is adopted to join the
exhaust of the gas turbine to that recovery system reducing the gas velocities to
levels optimum for heat recovery and pressure drop on the Gas turbine exhaust
side.

The exhaust gases undergo huge reduction in their velocity in the transition duct
whose angle of divergence with respect to the horizontal is normally kept more
than 15° - the threshold level which will not allow separation and consequent
back flow of gases.
One of the major reasons for adopting such steep transition is of economic
criteria of cost of ducting and space availability. The symmetry required for
smooth transition is also not practicable on account of standard exhaust
configuration of Gas Turbine.
The conventional solution is to employ flow control by plates with holes to induce
pressure drop to normalize flow.
The drawback of the above flow control that they are expensive and tend to
have penalty on gas side pressure drop.
There are other methods of improving flow distribution with use of gas removal
line having an inlet end in the diverging wall of the transition ducting and use of
flue gases re-injection (natural or assisted) at the point of separation.
The disadvantage of such system is practical ducting problems associated with
natural re-injection and extra continuous power consumed in assisted case re-
injection. There is also a limitation on preference of divergence angle upto 60°
calling for more space for the footprint of Heat Recovery System.
Accordingly, an object of the present invention is to provide an improved flow-
modification device, which improves the flow distribution inside the transition
duct.
Another object of the present invention is to provide an improved flow-
modification device, which positively eliminates the re-circulating eddy formation
in the asymmetrical ducts.
A further object of the present invention is to provide an improved flow-
modification device, which reduces heat transfer surfaces requirement on
account of improved flow distribution.

Yet another object of the present invention is to provide an improved flow-
modification device, which substantially reduce the back flow of gas because of
better flow distribution at the entry of the heat recovery system.
A still further object of the present invention is to provide an improved flow-
modification device, which uses unsymmetrical ducting in place of expensive
smooth transition with reduced divergence ducting.
Additional objects and features of the invention will be more readily apparent
from the following detailed description when taken in conjunction with the
accompanying drawings, in which:
Fig. 1 - schematically shows a conventional gas turbine combined cycle system
having a heat recovery steam generator.
Fig. 2 - a schematic view of a conventional transition duct particularly showing
the gas flow pattern inside the duct.
Fig. 3 - shows an improved flow-modification device in accordance with the
present invention.
Fig. 4 - shows a momentum transformation grid of the improved flow-
modification device according to the present invention.

SUMMARY OF THE INVENTION
Accordingly there is provided an improved flow-modification device adaptable to
a gas turbine combined cycle system, the system comprising a turbine oriented
one of a vertically or horizontally which emits exhaust gas; a heat recovery
steam generator for receiving the exhaust gas; the device comprising a transition
duct disposed between the turbine and the steam generator. The transition duct
is configured to have a contour comprising at least two steps utilizing composite
angles extending along the flow-pattern of the exhaust gas.
That a momentum transformation grid is disposed across the width of the
transition duct, the momentum transformation grid comprising a plurality of flat
plates rigidly connected to a rectangular steel frame, having orientations and
pitches selected to effect a multifold reduction in gas momentum in the flow
direction including altering the flow pattern thereby achieving an uniform flow
distribution.
The invention adopts a Momentum Transformation Grid consisting of plates
arranged in particular fashion placed across the duct width so as to modulate the
flow area and therefore modifying the area available for the flow. The variation
of flow area along with arrangement of plates in the duct improves the flow
distribution inside the duct. The invention also identifies the most optimum
location at the ducting for improving flow distribution.
The standard shape of transition duct is replaced with composite angle ducting in
the Flow Modifying Device locating the point of inflexion exactly at the eye of
recirculation and select the ducting angles close to the flow pattern existing in
the asymmetrical ducting thereby positively eliminating the re-circulating eddy
formation.
The modus of supporting Momentum Transformation Grid is using rectangular
frame of plates on which the component plates are welded on to and is hung
from top beam of supporting structures.

The invention comprises of suitable combination of flow area and composite
angles to improve the flow distribution as explained in detailed description of
invention.
It reduces footprint requirement of Heat Recovery System.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
PRESENT INVENTION.
Referring to the drawings, and in particular to Fig. 1, a conventional gas turbine-
HRSG system is shown generally designated as 9. The system comprises a
generator 1, a compressor 2, and a gas turbine 3, connected in series. The
turbine 3 has an inlet 3a and an outlet 3b. The exhaust from the gas turbine 3
passes through a transition duct 4 and into an inlet of a heat recovery steam
generator 5. The HRSG 5 comprises a super heater 5a, and a boiler bank 5b
downstream from the super heater 5a. The transition duct 4 is required because
the turbine outlet 3b is smaller than the inlet of the HRSG 5. The transition duct
4 is asymmetrical, having a horizontal bottom wall 4a, an upwardly slanting,
diverging upper wall 4b, an inlet 4c, and an outlet 4d. Such a typical
configuration allows for hazard-free connection between the turbine 3 and the
HRSG 5 without requiring the turbine 3 to be elevated, as would be necessary if
the transition duct 4 diverged in a symmetrical fashion.
As shown in fig - 3, the present invention provides an improved flow-
modification device in which the transition duct (4) is configured to have a
contour comprising at least two steps utilizing composite angles (6,7) which
extend along the flow-pattern of the exhaust gas thereby positively prevent
recirculation of the gas. A momentum transformation grid (9) as separately
shown in fig - 4is disposed across the width of the transition duct (4) so as to
modulate the flow area and therefore modifying the area available for the flow.
Thus, a variation of flow area by utilizing the momentum transformation grid (9)

improves the flow distribution inside the duct (4). The momentum transformation
grid (9) comprises a plurality of flat plates (8) having orientations and pitches
selected in registration with the system features including the physical
parameters of the exhaust gas in order to reduce momentum of gases in flow
direction and suitably altering the flow pattern for uniform flow distribution. A
rectangular steel frame (10) accommodating said plurality of flat plates (8) being
rigidly connected thereupon. The advantage of the invention lies in retrofitting
the Momentum Transformation Grid in the existing Heat Recovery System due to
ease with which the Grid can be brought into the duct through the access
manhole and site welded at the desired location.
The other benefits associated with Flow Modifying device are that the improved
flow distribution enhances heat transfer of the sections downstream and also
improves combustion and flame characteristic of the heating system. This results
in more uniform temperature profile at the outlet of the duct burner resulting
optimum material selection of heat transfer section downstream. This further
results in economic benefits desired from employing correct heat transfer surface
area (savings on account of material costs) and resulting continuous saving from
improved generation on account of operation near predicted regime on account
of optimum.
A significant reduction in heat Recovery Steam Generator length contributes
immensely to savings in plot plan and ducting and structural requirement. It is
also cost effective as the savings comes from reduced ducting requirement in the
high temperature zone of the system. The overall weight of the system is
brought down resulting in more economic arrangement.

WE CLAIM
1. An improved flow-distribution device adaptable to a gas turbine combined
cycle system, the system comprising a turbine (3) oriented one of a vertically
or horizontally which emits exhaust gas; a heat recovery steam generator (5)
for receiving the exhaust gas; the device comprising a transition duct (4)
disposed between the turbine (3) and the steam generator (5), wherein the
transition duct (4) is configured to have a contour comprising at least two
steps utilizing composite angles (6,7) extending along the flow pattern of the
exhaust gas, and in that a momentum transformation grid (9) is disposed
across the width of the transition duct (4), the momentum transformation
grid comprising a plurality of flat plates (8) rigidly connected to a rectangular
steel frame (10), having orientations and pitches selected to effect a multifold
reduction in gas momentum in the flow direction altering the flow pattern
thereby achieving an uniform flow distribution.
2. The device as claimed in claim 1, wherein the transition duct (4) is
asymmetrical and eliminates the re-circulating eddy formation.
3. The device as claimed in claim 1, wherein the momentum transformation grid
(9) can be retrofitted in the existing transition duct (4).
4. An improved flow-distribution device adaptable to a gas turbine combined
cycle system, as substantially herein described and illustrated with reference
to the accompanying drawings.

1. An improved flow-distribution device adaptable to a gas turbine combined
cycle system, the system comprising a turbine (3) oriented one of a vertically
or horizontally which emits exhaust gas; a heat recovery steam generator (5)
for receiving the exhaust gas; the device comprising a transition duct (4)
disposed between the turbine (3) and the steam generator (5), wherein the
transition duct (4) is configured to have a contour comprising at least two
steps utilizing composite angles (6,7) extending along the flow pattern of the
exhaust gas, and in that a momentum transformation grid (9) is disposed
across the width of the transition duct (4), the momentum transformation
grid comprising a plurality of flat plates (8) rigidly connected to a rectangular
steel frame (10), having orientations and pitches selected to effect a multifold
reduction in gas momentum in the flow direction altering the flow pattern
thereby achieving an uniform flow distribution.

Documents:

00203-kol-2005-abstract.pdf

00203-kol-2005-claims.pdf

00203-kol-2005-correspondence-1.1.pdf

00203-kol-2005-correspondence.pdf

00203-kol-2005-description(complete).pdf

00203-kol-2005-drawings.pdf

00203-kol-2005-form-1.pdf

00203-kol-2005-form-18.pdf

00203-kol-2005-form-2.pdf

00203-kol-2005-form-3.pdf

203-KOL-2005-FORM-27-1.pdf

203-KOL-2005-FORM-27.pdf

203-kol-2005-granted-abstract.pdf

203-kol-2005-granted-claims.pdf

203-kol-2005-granted-correspondence.pdf

203-kol-2005-granted-description (complete).pdf

203-kol-2005-granted-drawings.pdf

203-kol-2005-granted-examination report.pdf

203-kol-2005-granted-form 1.pdf

203-kol-2005-granted-form 18.pdf

203-kol-2005-granted-form 2.pdf

203-kol-2005-granted-form 3.pdf

203-kol-2005-granted-gpa.pdf

203-kol-2005-granted-reply to examination report.pdf

203-kol-2005-granted-specification.pdf

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Patent Number

227270

Indian Patent Application Number

203/KOL/2005

PG Journal Number

02/2009

Publication Date

09-Jan-2009

Grant Date

05-Jan-2009

Date of Filing

22-Mar-2005

Name of Patentee

BHARAT HEAVY ELECTRICALS LIMITED

Applicant Address

PLOT NO. 9/1,DJ BLOCK 3rd FLOOR,KARUNAMOYEE,SALT LAKE CITY, KOLKATA

Inventors:

#	Inventor's Name	Inventor's Address
1	PERIAKARUPPAN ASHOKKUMAR	HIGH PRESSURE BOILER PLANT,TRICHY,TAMIL NADU 620 014
2	VAITHIALINGAM SIVAKUMAR	HIGH PRESSURE BOILER PLANT,TRICHY,TAMIL NADU 620 014
3	MUKUNDARAJAN LAKSHMINARASIMHAN	HIGH PRESSURE BOILER PLANT,TRICHY,TAMIL NADU 620 014
4	VAITHINATHAN DHANDAYUTHAM	HIGH PRESSURE BOILER PLANT,TRICHY,TAMIL NADU 620 014

PCT International Classification Number

F15D 5/04

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA