RU2687545C1 - Low-emission combustion chamber and method of feeding fuel therein - Google Patents

Abstract

FIELD: machine building.SUBSTANCE: low-emission combustion chamber of gas turbine engine includes at least two fuel collectors: main and pilot, fuel redistribution valve, at least two burner devices, each of which is equipped with curved channel formed by two profiled shells. Inner surface of curvilinear channel is conjugated with central body of burner device, on which axial swirler and tubes of fuel supply to flow part of burner device from main fuel collector are installed. On external surface of curvilinear channel there arranged is levelling header for fuel supply through corresponding tubes from pilot collector to flow part of burner device, which is connected to the flame tube, having air supply holes, inside which a coaxial to it screen is located, consisting of a transverse annular part and a longitudinal cylindrical part. Screen and fire tube form air flow cavity. At the inlet of the flame tube coaxially to the burner device there is a silencer consisting of interconnected first and second annular volumes and an annular slot, one end of which extends into the inner volume of the flame tube, and the other end is connected to the first annular volume.EFFECT: invention is aimed at improvement of reliability of combustion chamber and increase in its service life at maintaining low level of nitrogen oxides emissions at modes close to maximum engine load, by means of reduction of pressure pulsations in combustion chamber and prevention of carbonization on output parts of burner devices.2 cl, 1 dwg

Description

The invention relates to the field of engine construction and can be used in gas turbine installations and engines with low levels of harmful emissions, in particular in low-emission combustion chambers operating on gaseous fuels.

It is known that low-emission combustion chambers of this type tend to initiate self-oscillations, which reduces their life and reliability, and to maintain combustion stability in low fuel gas consumption regimes it is necessary to supply some fuel with a worse mixing quality compared to the maximum power mixing quality. (Tim C. Lieuwen Unsteady Combustor Physics Cambridge University Press, August 27, 2012, 405 s). Usually, such a supply of a part of the fuel, which ensures a worse mixing quality, is provided by another burner with a separate fuel manifold or a special arrangement of fuel supply openings on it. When the maximum power mode is reached, the fuel supply to this fuel manifold either stops or decreases to a minimum, which causes the problem of fuel flow from one burner to another due to the lack of pressure in a separate collector and the difference in hydraulic resistance of the burner devices and the problem of coking cut burner device.

Known low-emission combustion chamber (US 7,284,378 B2, IPC F02C 9/26, publ. 10/23/2007), which consists of several modules of low-emission combustion, each of which consists of several burners, a flame tube, a transition branch pipe. Fleece to the burner device is carried out from several fuel collectors. In each burner device, except for the central burner device, there are two fuel supply channels: the main and pilot. The disadvantage of this combustion chamber is the mismatch of hydraulic resistances in the modules of low-emission combustion, leading to the overflow of combustion products between them, which necessitates blowing the fuel pilot channels with air. This purge hinders the transition from the operation mode with the participation of the pilot fuel and leads to the instability of combustion at the cut-off of the burner in its central recirculation zone.

Known combustion chamber (EP 3029376 A1, IPC F23R 3/00, publ. 06/08/2016), which used the Helmholtz muffler to suppress self-oscillations in the combustion chamber of a gas turbine engine. In this invention it is proposed to adjust the suppressed oscillation frequency by changing the resonant volume by making the Helmholtz resonator in the form of a piston in a cylinder. A change in the position of the piston ensures a change in the working volume of the resonator and thereby a change in its first natural frequency. The throat of the Helmholtz resonator is made in the form of a cylindrical tube. The disadvantage of this technical solution is that the design provides for the presence of moving parts of the system, which is in conditions of high temperatures, which can lead to the "biting" of parts of the cylinder and piston. This circumstance significantly reduces the reliability of the combustion chamber.

A known method of supplying fuel to the burner of the combustion chamber (EP 2631544 B1, IPC F23R 3/14, publ. 05/09/2018), in which the fuel is supplied near the recirculation zone, and air is mixed with it, which reduces the recirculation zone. This adversely affects the stability of the combustion chamber.

A known method of supplying fuel to the burner device of the combustion chamber with a short mixing time directly into the recirculation zone (US 6,363,724 B1, IPC F23R 3/28, publ. 04/02/2002). The disadvantage of this method is the occurrence of the flow of combustion products between the nozzles. This can lead to damage to the elements of the design of the fuel manifold and gas injectors, which reduces the reliability of the design.

A burner device is known (US 2,970,772 IPC F23D 11/38, publ. 07.02.1961), in which a high concentration of fuel is blown off from the surface of the central body with a thin film of air to solve the problem of carbon formation. However, this leads to a decrease in the stability of combustion due to excessive depletion of the air-fuel mixture in the recirculation zone.

The technical result of the invention is to improve the reliability of the combustion chamber and increase its service life while maintaining low emissions of nitrogen oxides at modes close to the maximum engine load, by reducing pressure pulsations in the combustion chamber and preventing carbon formation on the output parts of the burner.

This technical result is achieved by a low-emission combustion chamber of a gas turbine engine containing at least two fuel manifolds: main and pilot, a valve for redistributing fuel, at least two burner devices, each of which is equipped with a curvilinear channel with the ability to rotate the flow through 90 degrees formed by two shaped shells, at the entrance of which an annular shell is installed with air holes in the burner device located normally to its surface and, the inner surface of the curvilinear channel is associated with the central body of the burner device, on which an axial swirler is installed with a twist of flow of 35-50 degrees and fuel supply pipes to the flow part of the burner device from the main fuel collector, and on the outer surface of the curvilinear channel there is a leveling collector for fuel supply through the corresponding tubes from the pilot manifold to the flow part of the burner device, which is connected to the flame tube having an opening The air inlet, inside of which the screen consisting of the transverse annular part and the longitudinal cylindrical part is located coaxially with it, has a transitional nozzle with uniformly spaced around the circumference of the air supply holes for mixing, and the screen and the heat pipe form a flow cavity for air, and at the inlet of the flame tube coaxially with the burner device there is a silencer consisting of communicating first and second annular volumes and an annular gap, one end of which goes into the internal volume of the flame tube, and the other end is connected to the first annular volume.

The technical result is also achieved by the method of supplying gaseous fuel in the combustion chamber, including fuel injection into the air stream supplied to the burner through the main fuel manifold and pilot fuel manifold, the fuel being injected from the latter through tubes with the ratio of tube length to its hydraulic hole diameter more than 10, while these tubes are directed to the central body so that the fuel jets hit the central body of the burner, and the distance from the central body Before the jet of fuel escapes from the tubes, it does not exceed two hydraulic diameters of the hole, and fuel is injected into the air stream from the main fuel manifold downstream from the fuel supply to the air stream from the pilot manifold, which is turned off during the main modes of operation of the combustion chamber.

The essence of the invention is illustrated in the drawing, which shows a schematic diagram of low-emission combustion chamber.

The combustion chamber contains a primary fuel manifold 1 and a pilot fuel manifold 2, a fuel redistribution valve 3 connecting the fuel system of the engine with a pilot fuel manifold, two burners 4, each of which is connected to a flame tube 5, inside which is located coaxially with it a screen 6, consisting of a transverse annular part and a longitudinal cylindrical part, on the flame tube are openings 7 for air supply, the screen and the flame tube form a flow cavity for air 8. At the exit of the flame tube a transition nozzle 9 is installed, on which holes 10 for supplying air for mixing are uniformly placed around the circumference. At the inlet of the flame tube, a silencer is arranged coaxially with the burner device, including the first 11 and second 12 ring volumes connected by channel 13 and the ring slit 14, one end of which goes into the internal volume of the flame tube and the other end is connected to the first ring volume 11. Burning The device is equipped with a curvilinear channel 15, which provides the rotation of the flow by 90 degrees, formed by two profiled shells. At the entrance of the curved channel is installed an annular shell 16 with holes for supplying air to the burner, located normally to its surface. The inner surface of the curved channel is associated with the central body of the burner 17, on which axial swirler 18 is installed with a flow swirl from 35 to 50 degrees and a tube 19 for supplying fuel to the flow part of the burner from the main fuel manifold. A leveling manifold 20 is placed on the outer surface of the curvilinear channel of the burner, to which fuel is fed from pilot fuel manifold 2, fuel is supplied from equalizing manifold 20 through pipes 21, by increasing the length of the tube to its hydraulic bore diameter more than 10, which are directed to the central body 17. that the jets of fuel hit him, and the distance from the central body 17 to the exit of the jets of fuel from the tubes 21 does not exceed two hydraulic diameters of its opening.

The method of supplying fuel to the combustion chamber is as follows. Air is fed into the combustion chamber from a compressor or other source of compressed air. One part of the air enters the transition pipe 9 through the openings 10, and the other part enters the burner 4 through the openings 16. The gaseous fuel is also supplied to the burner through the main fuel manifold 1 and pilot fuel manifold 2. The fuel enters the main fuel collector 1 from the fuel system of the engine directly, and in the pilot fuel manifold 2 - through the valve of fuel redistribution 3. Through this valve, they regulate the share of pilot fuel consumption depending on the mode of operation Engine s: With a reduced engine load, the pilot fuel manifold 2 receives a large proportion of fuel compared to the engine overload conditions. The small distance of the fuel supply point through the tubes 21 from the central body of the burner 17 prevents the fuel from mixing with air and ensures the creation of a thin fuel film on the central body, and accordingly, a high concentration of fuel at the output end of the central body. This reduces the mixing of fuel with air and increases the stability of combustion at low power modes. At maximum operation mode of the gas turbine engine, the supply of fuel to the pilot fuel manifold 2 is completely stopped. When the fuel supply to the pilot fuel manifold 2 is turned off by closing the fuel redistribution valve 3, the hydraulic resistances of the burners 4 of the combustion chamber are not equal and the air flows out of the compressor through the pilot fuel manifold 2. As the air does not contain combustion products, this prevents soot deposition in the pilot fuel manifold 2 . The flow of fuel into the air stream from the main fuel manifold 1 through the tube 19 is carried out downstream from the place of fuel supply in the air flow through the tube 21 from the pilot fuel manifold. In the place of the main fuel supply through the tubes 19 to the air flow in the burner device, the fuel is mixed with air. Due to the axial swirler 18, a high mixing quality is ensured, which leads to a low level of nitrogen oxides emission, however, in this mode of combustion, a positive feedback occurs between the mixing process and pressure pulsations in the combustion chamber. The presence of positive feedback leads to the excitation of self-oscillations in the combustion chamber, which are damped by silencers installed at the inlets of the flame tubes 5. At the cut of the burner 4, the air-fuel mixture burns to form high-temperature combustion products. Protection of the flame tube 5 from high-temperature products of combustion is carried out by the screen 6. The screen is cooled from the products of combustion by shock cooling of the screen with air entering through the holes 7.

Thus, in the inventive combustion chamber, due to its design features, the reliability of operation is increased due to the damping of pressure fluctuations in the combustion chamber and the prevention of the flow of combustion products through the pilot fuel manifold pipeline. Also, this design allows you to protect the fuel injectors from clogging with carbon deposits and to prevent the combustion products from flowing into them when the fuel supply to the nozzles is switched off through the pilot fuel manifold or when fuel consumption in them is significantly reduced. The proposed method of supplying fuel in the combustion chamber provides an improvement in the stabilization of combustion due to a significant decrease in mixing the fuel supplied from the tubes with the air flow to the cut-off of the burner, including the creation of a thin fuel film.

Claims (2)

1. Low-emission combustion chamber of a gas turbine engine, containing at least two fuel manifolds: main and pilot, fuel redistribution valve, at least two burner devices, each of which is equipped with a curvilinear channel with the ability to rotate the flow through 90 degrees formed by two shaped shells at the inlet which is installed an annular shell with holes for supplying air to the burner device, located normally to its surface, and the inner surface is curved channel is connected to the central body of the burner device, on which an axial swirler is installed with a twist of flow of 35-50 degrees and fuel supply pipes to the flow part of the burner device from the main fuel manifold, and an equalizing collector is placed on the outer surface of the curvilinear channel tubes from the pilot manifold to the flow part of the burner device, which is connected to a flame tube having air inlets, which are coaxially inside there is a screen with it, consisting of a transverse annular part and a longitudinal cylindrical part, at the exit of the flame tube there is a transitional nozzle with uniformly spaced around the circumference of the air supply holes for mixing, the screen and the flame tube forming a flow cavity for air, and at the inlet of the flame tube coaxially with the burner, there is a silencer consisting of interconnecting first and second annular volumes and an annular gap, one end of which goes into the internal volume of the flame tube and the other end The tip is connected to the first annular volume. 2. The method of supplying gaseous fuel in the combustion chamber according to claim 1, comprising fuel injection into the stream of air supplied to the burner through the main fuel manifold and pilot fuel manifold, the fuel being injected from the latter through tubes with a ratio of tube length to its hydraulic bore diameter of more than 10, while these tubes are directed to the central body so that the jet of fuel hits the central body of the burner, and the distance from the central body to the exit of the jet of fuel from tubes do not exceed two hydraulic diameters of the hole, and fuel is injected into the air stream from the main fuel manifold downstream from the fuel supply to the air stream from the pilot manifold, which is turned off in the main modes of operation of the combustion chamber.

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