RU2561754C1 - Ring combustion chamber of gas-turbine engine and its operation method - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: ring combustion chamber of gas-turbine engine has nozzles group located in same plane on the face wall of the combustion chamber, by at least two coaxial rings. In each ring the same and even number of the low-emission burners is installed. The internal ring burners are displaced in the circumferential direction relatively to the burners of the external ring by half-step. All burners are made as two-channel. The internal channels of the burners are used to supply pilot fuel in them only, and the external channels of the burners are used to supply the compressed air in them from the compressor and the main fuel with creation of the lean air-fuel mixture. The external channel of each burner contains input guide vanes, their walls has holes for the fuel supply in the air cross-flow, the blade swirler installed at the channel output, and permeable element with set porosity, installed between the input guide vanes and blade swirler. The flow swirling direction in the burners using the blade swirlers alternates by the opposite direction upon transition from one burner to the another adjacent burner within the same ring. Besides, each burner contains a ring fuel receiver installed above the input guide vanes. The internal channels of the burners of the internal and external rings are combined respectively to the internal and external headers of the pilot fuel. The ring fuel receivers of the burners of the internal and external rings are combined respectively to the internal and external headers of the main fuel. At the inputs of the pilot and main fuel mains one fuel flow regulator is installed. Upstream the inputs of the internal headers of the pilot and main fuel in the supply fuel mains one valve in each is installed.

EFFECT: invention reduces full pressure losses, increases operation reliability of the ring combustion chamber, range of stable burning of the lean air-fuel mixture, and uniformity of the temperature fields in the radial and circumferential directions upon decreasing of emission of nitrogen oxides and carbon oxides.

7 cl, 5 dwg

Description

The invention relates to combustion chambers (CS), which are mainly used in aircraft gas turbine engines (GTE) and stationary gas turbine units (GTU), and to methods for their operation.

For stable combustion of a fuel-air mixture (FA) in burners of such CSs, poorly streamlined bodies or scapular swirlers, or both at the same time, are usually used. In a ring type CS, swirling of the flow in the same direction in separate burners leads to the appearance of coaxial ring vortices, the maintenance of which is accompanied by a pressure loss due to friction against the walls of the flame tube. Therefore, such annular vortices should be considered parasitic. In addition to pressure loss, their existence reduces the intensity of the burner vortices and the combustion stability of the fuel assemblies, since the part of the flow belonging to the parasitic vortices does not participate in combustion.

It is also necessary to pay attention to the fact that if the same flow swirl direction is selected in all burners, the transfer of flame from the burners in which the fuel assemblies are forced to ignite from an external source to passive burners will be significantly hindered, since the difference in the flow velocities at the points of contact of local burner vortex will be maximum. This difference in flow rates can exceed the normal flame propagation velocity and lead to flame failure, accompanied by a deterioration of the temperature field in the combustion zone and at the outlet of the compressor station.

If the annular CS contains one ring of burners with the same flow swirl direction in them, then two coaxial parasitic annular vortices arise, rotating in different circumferential directions, with average diameters larger and smaller than the average diameter on which the burners are located. If the annular CS contains two coaxial rings of the burners, then three coaxial annular vortices arise, the circumferential directions of motion of which depend on the selected directions of the swirling flow in the burners.

In parallel with the issues of the stability of combustion of fuel assemblies, it is also necessary to solve the problem of reducing the emission of nitrogen oxides (NOx) and carbon monoxide (CO), which complicates the task of creating stably working low-emission CS.

Of no small importance when creating low-emission CS are the methods of their operation.

All these problems are usually only partially solved in well-known CS, therefore, require the use of new non-trivial technical solutions for a comprehensive solution to these problems.

Known annular KS aviation GTE or stationary gas turbine [1] (RF patent No. 2094705, CL F23R 3/18, 1997), which contains two rings of burners. The number of burners made by two-channel (with an internal channel - fuel and external - air) is selected according to a certain formula so that the combustion process becomes close to multi-torch. Moreover, the burners are combined into blocks of 4 burners, 2 burners from each ring. The fuel channels of the start-up burners are combined into a common start-up manifold, and the fuel channels of the other burners are combined into the main fuel collector.

The objective of the invention is to reduce the emission of nitrogen oxides.

The task is achieved by reducing the length of the combustion zone and the residence time of the fuel assemblies in the high temperature zone.

The disadvantage of the proposed CS is the diffusion combustion of fuel in the starting and main burners, characterized by a wide front and the highest possible combustion temperatures of the fuel assemblies and accompanied by significant emission of NOx.

The method of operation of this COP is as follows.

At the start-up and before the power plant reaches the low-gas mode, fuel is supplied through the pilot burners of the outer ring, which make up ¼ of the entire set of burners. In the vicinity of the small gas mode, fuel is also supplied through the other manned burners of the outer and inner rings, which operate until the power plant reaches its nominal mode.

The main disadvantage of the operation method of this compressor is the possibility of flame failure and the occurrence of a significant temperature field unevenness when the power plant starts and enters the idle mode due to the fact that fuel is supplied through a small number of pilot burners surrounded by a large number of pilot burners with “cold” air, to which no fuel is supplied.

The disadvantages of this COP are partially eliminated in the COP [2] (RF patent No. 2171432, class F23R 3/28, 2000) due to the fact that the front device has an optimal number of burners - 3 pieces per 100 cm ² transverse (mid-section) section of the flame tube.

As in KS [1] in KS [3] (RF patent No. 2083926, class F23R 3/16, 1997), a multi-burner front device is used that contains an annular row of main burners and a standby burner with a blade swirl in the center. Reducing the emission of nitrogen oxides is ensured by crushing the torch in a multi-burner front device into a number of smaller flares, as well as by reducing the length of the high-temperature zone and the residence time of the combustion products in the high-temperature zone. Kinetic combustion of pre-prepared fuel assemblies in the absence of high-temperature zones in the flare is ensured by a standby burner. Reliable heat transfer from the standby burner to the fuel assemblies of the main burners is achieved due to the fact that the flow swirl using the blades of the swirl of this burner and the flow swirl using the main blades of the inner annular cavity are directed towards each other. Therefore, the difference in the velocities of neighboring flows at the point of contact will be minimal, below the stall velocity of the flame.

Also known is a ring KS [4] (US patent No. 5490380, class F02C 7/26, 1996) with one ring of starting burners with swirling flow in all burners in one direction. In such a CS, as noted above, two coaxial annular parasitic vortices are formed, which is its drawback.

In [5] (Nagashima, T. et al (2005) Lessons Learnt from the Ultra-Micro Gas Turbine Development at the University of Tokyo. In Micro Gas Turbines (pp.14-1 - 14-58). Educational Notes RTO- EN-AVT-131, Paper 14. Neuilly-sur-Seine. France: RTO. Available from: http://www.rto.nato.int/abstracts. Asp.) A ring propane-based COP is proposed, with 8- mu microburners and investigated its thermodynamic and environmental characteristics. The inner diameter of the radial-blade swirl is 16 mm. Two-channel burners are used (the internal channel is fuel, and the external is air) with diffusion combustion of fuel.

To stabilize the combustion of fuel assemblies, air flow swirl is used, and to create a favorable velocity field in the combustion zone and a satisfactory temperature field at the outlet from the KS, the swirl of the flow in adjacent burners alternately changes in the opposite direction (either clockwise or counterclockwise). Moreover, the number of burners in each ring of such a COP should be even. It lacks ring parasitic vortices. Instead, periodic paired vortices are formed, generating radial fluxes alternately to the center and from the center of the CS, which leads to an increase in the stability of combustion of fuel assemblies and equalization of temperature fields in the radial direction at the outlet of the CS.

Known annular COP [6] (EPO patent No. 0378505, CL F23R 3/14, 1979), containing a set of burners located in one plane on the front wall of the COP, at least two rings. Moreover, the burners within the same ring have the same flow swirl direction, opposite to the flow swirl direction in the burners of the adjacent ring.

Known also adopted for the prototype ring KS [7] (RF patent No. 2062408, CL F23R 3/14, 1996), containing burners, the ends of which are located in the same plane. Burners form two coaxial rings. In each ring, the burners have the same flow swirl directions, but opposite to the flow swirl directions in the burners of the adjacent ring. Thanks to this twist, three coaxial annular vortices are formed: two parasitic vortices (external and internal) and one intermediate vortex. Moreover, the direction of the swirl of the external and internal spurious vortices coincides with the direction of the swirl of the flow in the burners of the outer ring. The direction of twist of the intermediate annular vortex in a given CS is always opposite to the direction of twist of the parasitic annular vortices.

Typically, fuel assemblies are ignited in 2 or 3 burners evenly spaced around the circumference of the outer ring, which creates a fuel ignition problem in the remaining burners of this ring and fuel assemblies in the burners of the inner ring. The formation of an intermediate vortex partially solves the problem of flame transfer from burner to burner. Moreover, the flame is transferred alternately from a burner belonging to one ring to an adjacent burner belonging to another ring, etc. Pilot burners, which are supplied with fuel, make up 5/6 of the entire set of burners.

The main disadvantages of such a COP are:

- increased pressure loss due to the occurrence of spurious eddies;

- the inappropriateness of creating an "intense transverse flow along the walls of the compressor station and in the center" for reliable transfer of flame from burner to burner, since pilot burners already "well surround manned burners" and make up 5/6 of the entire set of burners;

- reducing the reliability of the transfer of flame in the annular COP in the case when the pilot burners are separated by pilot burners, which do not supply fuel;

- a decrease in the thermal stress of the compressor, accompanied by a decrease in the completeness of combustion of the fuel and a partial loss of stability of the combustion of the fuel assemblies, due to an increase in the area of the front wall and the volume of the annular compressor, due to the alternate shift of each 2 burners outward or to the center in each ring.

The method of operation of this ring compressor [7], adopted as a prototype, is that the fuel is supplied when piloting the compressor and increasing its load up to (40-55)% through pilot burners, and in the interval (40-55)% - ( 65-80)% of the load, the fuel consumption does not change, and when the load increases above (65-80)%, manned burners are put into operation.

There is also known a method of operating an annular CS [8] (EPO patent No. 0401529, class F23R 3/46, 1990) with a set of pilot and manned burners located on the front wall of the chamber, in accordance with which, when starting and increasing the load to a predetermined the fuel supply is carried out through pilot burners, and with a subsequent increase in load, fuel is supplied through manned burners.

The main objectives of the invention are:

- reduction of pressure loss in the combustion zone of the fuel assembly;

- increase the reliability of the transfer of flame from burner to burner;

- increase the combustion stability of the “poor” fuel assemblies;

- increase the uniformity of the temperature field in the radial and circumferential directions at the exit of the annular CS;

- reduction of emissions of NOx and CO.

The implementation of the tasks is ensured by the following technical solutions.

An annular combustion chamber of a gas turbine engine containing a group of burners located in the same plane on the front wall of the combustion chamber by at least two coaxial rings, with the same and even number of low emission burners being installed within each ring, the burners of the inner ring are displaced in the circumferential direction relative to burners of the outer ring at their half-step, all burners are made of two-channel, and the internal channels of the burners serve to supply them only pilot fuel, and the external channels of relok - for supplying compressed air to them due to the compressor and the main fuel with the formation of a “poor” air-fuel mixture, the outer channel of each burner contains an inlet guide apparatus, in the walls of which there are holes for supplying fuel to the blowing air stream, a blade swirl mounted on the outlet of the channel, and a permeable element with a given porosity, installed between the input guide vane and the blade swirl, the direction of flow swirl in the burners with the help of blade swirls through reversed during the transition from one burner to another neighboring burner within each ring, each burner also contains an annular fuel receiver located above the inlet guide apparatus, the inner channels of the burners of the inner and outer rings are combined into the inner and outer pilot fuel collectors, respectively and the ring fuel receivers of the burners of the inner and outer rings are combined, respectively, in the inner and outer manifolds of the main fuel, at the entrance to the highways and density to the main fuel is set by one fuel flow regulator before entering into the internal reservoir and the pilot primary fuel in the supply fuel lines established by one valve.

It is preferred that a turbine axial-blade swirl with profiled blades is used as the blade swirl.

Preferably, the spinning of the blades of the axial-blade swirl is performed according to the law

where R and R _P - the current radius and radius of the blades of the swirler at the periphery, respectively;

φ and φ _P - the current twist angle and the twist angle of the blades of the swirler at the periphery, respectively;

n is an exponent taking values in the range: 0> n> -1.

It is preferable that a permeable element made on the basis of metal micron meshes is used as a permeable element.

Preferably, the average flow rate of the mixture in the micropores of the porous body of the permeable element in the nominal mode of operation of the combustion chamber is maintained in the range of 40-60 m / s by selecting the surface area of the permeable element.

A method of operating an annular combustion chamber of a gas turbine engine containing a group of burners located in the same plane on the front wall of the combustion chamber by at least two coaxial rings, namely, when starting and increasing the load to a predetermined value, fuel is supplied through a portion of the total burners, and when the load increases above a predetermined value, the remaining burners are brought into action by supplying fuel to them, while within each ring the same and even number of low emission x burners, the burners of the inner ring are displaced in a circumferential direction relative to the burners of the outer ring by half a step, all low-emission burners are made of two-channel, the internal channels of the burners serve to supply only pilot fuel to them, and the external channels of the burners to supply compressed air from them for the compressor and the main fuel with the formation of a “poor” air-fuel mixture, the outer channel of each burner contains an input guide apparatus, in the walls of which holes are made for supplying fuel for demolition The shear air flow, the axial-blade swirl installed at the outlet of the channel, and the permeable element installed between the inlet guide apparatus and the axial-blade swirl, the flow swirl direction in the burners with the help of the blade swirls alternates in the opposite when switching from one burner to another adjacent burner within each ring, each burner contains, in addition, an annular fuel receiver located above the inlet guide apparatus, internal channels of the burners internally th and outer rings are combined respectively in the inner and outer pilot fuel collectors, and the ring fuel receivers of burners of the inner and outer rings are combined respectively in the inner and outer main fuel manifold, one fuel flow regulator is installed at the inlet of the pilot and main fuel highways, in front of the inlets one valve is installed in the internal collectors of the pilot and main fuel in the fuel supply lines, when starting and increasing the load to the load, close to the load of the low gas mode (65-70% of the nominal load), the valves are closed, therefore, the main and pilot fuel is supplied only to the burners of the outer ring, when the load is close to the load of the low gas mode and the load increases to the load of the nominal mode, both the valves open and supply the main and pilot fuel also to the burners of the inner ring.

It is preferable that in the burners of the outer and inner rings the relative consumption of pilot fuel, defined as the ratio of the consumption of pilot fuel to the sum of the consumption of main and pilot fuel, is reduced with the help of fuel consumption regulators from the conditions for obtaining a minimum emission of nitrogen oxides, maintaining a given total consumption of main and pilot fuel and a given total coefficient of excess air while maintaining the combustion stability of the "poor" air-fuel mixture.

The device ring KS and the method of its operation are illustrated by the following figures.

Figure 1. The scheme of the ring CS GTD.

Figure 2. View of the annular COP along arrow A indicated in the image of figure 1.

Figure 3. The shape of the streamlines on the scan of the front wall of the flame tube formed during the operation of the annular CS according to experimental studies.

Figure 4. Diagram of a two-channel low-emission burner using a permeable element.

Figure 5. A scan of the lattice of an axial-blade turbine type swirl with profiled blades in section AA shown in the image of Fig. 4.

We give the rationale for the proposed technical solutions for the annular CS GTE.

1. Two-channel burners with diffusion combustion of pilot fuel supplied through the internal channel of the burner were used, due to excess oxygen in the “poor” fuel assembly supplied through the external channel of the burner, with the formation of a pilot torch (it is called a pilot torch in foreign literature).

If the “poor” fuel assemblies in neighboring burners are rotated in the same direction with the help of scapular swirlers, then the difference in speeds at the points of contact of the local vortices of the burners will be maximum. This difference in flow rates can exceed the normal flame propagation velocity and lead to flame failure, accompanied by a deterioration of the temperature field in the combustion zone and at the outlet of the compressor station. In order to reduce the difference in velocities at the points of contact of the local vortices of neighboring burners to zero, the flow swirling in adjacent burners in opposite directions was applied, which allows improving the conditions of heat transfer from one burner in which fuel assemblies are burned to another burner where fuel assemblies are not burning, followed by ignition of the fuel assembly in it. Such a swirl of flows in adjacent burners is similar to two gears that are meshed (see figure 2).

To ensure the regularity and closure of such a heat transfer process between the burners forming the ring, the number of burners in the ring must be even.

In the proposed annular CS there are no parasitic vortices, which reduces the pressure loss due to friction against the walls of the flame tube. Instead, periodic paired vortices are formed, generating radial fluxes alternately to the center and from the center of the CS, which contributes not only to the reliable transfer of heat and flame between the burners, but also the equalization of temperature fields, primarily in the radial direction (see Fig. 3). In addition, with such a swirl of the flow, the number of contacting burners capable of transferring heat to a burner where there is no combustion of fuel assemblies, instead of two, as in the known solutions [7], increases to three. That is, the reliability of heat and flame transfer between the burners and the reliability of the operation of the COP increase.

2. From the conditions for coordinating the operation of the compressor and the turbine engine, primarily in the start-up mode, as well as in transient modes, it follows that the coefficient of excess air increases significantly. The operation of the SC in these modes is accompanied by a significant “depletion” of fuel assemblies, deterioration in the quality of fuel assemblies and combustion stability, as well as a significant decrease in the completeness of fuel combustion and an increase in CO emission.

In this case, an effective means of combating CO emissions is to cut off the supply of the main and pilot fuel to the burners of the inner ring, which make up 50% of the total number of KS burners. Such a technical solution allows 2 times to “enrich” fuel assemblies in the burners of the outer ring, improve the quality of the mixture, increase the combustion stability of the “poor” fuel assemblies and the completeness of fuel combustion and, as a result, significantly reduce CO emissions.

To implement this technical solution, the internal channels of the burners of the inner and outer rings are combined respectively in the inner and outer manifolds of the pilot fuel, and the ring receivers of the burners of the inner and outer rings are combined in the inner and outer manifolds of the main fuel, respectively. In the main and pilot fuel supply lines, one valve is respectively installed in front of the internal manifolds of the main and pilot fuel. Closing the valves allows you to disable, if necessary, the supply of primary and pilot fuel to the burners of the inner ring.

It should also be noted that the combination of the internal and external channels of the burners into common fuel collectors makes it possible to simplify the supply and control systems of the main and pilot fuel of both rings and make the fuel supply systems in each ring independent of each other.

It must also be emphasized that turning off the inner ring of burners for this purpose is more expedient than turning off the outer ring of burners, since access to the burners of the outer ring when organizing ignition of the fuel assemblies is more convenient than access to the burners of the inner ring. Moreover, the problem of heat and flame transfer from burner to burner in each ring is solved with the same degree of reliability due to the application of flow swirling in neighboring burners in opposite directions.

3. It is known [9] (Lefebvre A. Processes in the combustion chamber of a gas turbine engine: Transl. From English. - M .: Mir, 1986. - 566 p.) And [10] (Kutysh II. Methods and devices for gas purification of power plants Uch. Textbook for universities. M: MGOF Znanie, 2012. 800 p., Ed. 2 nd, rev. And additional), that burning pre-prepared “poor” fuel assemblies can significantly reduce NOx emissions due to that the combustion process of the “poor” fuel assembly can be carried out at low adiabatic temperature. Therefore, in the two-channel burners of the annular gas-turbine engine, the previously prepared “poor” fuel assemblies are burned. Particular attention is paid to the quality of the “poor” fuel assemblies.

4. It is well known that the quality of the mixture, which is understood as the degree of homogeneity of the fuel concentration in the volume of the “poor” fuel assembly, significantly affects the emission of NOx. If the quality of the “poor” fuel assemblies is low, then local zones of “overpopulated” and more “enriched” fuel assemblies with a higher adiabatic combustion temperature and increased NOx emission arise. It is more difficult to obtain good quality of a “poor” fuel assembly than a good quality mixture of stoichiometric composition. Therefore, with a significant "depletion" of fuel assemblies, it is necessary to apply additional non-trivial technical solutions that contribute to improving its quality.

For this purpose, a permeable element (PE) is installed between the VNA and the axial-blade swirl (ALZ).

In the proposed burner, a two-stage preparation system for the “poor” fuel assembly is used: jet supply and mixing of the main fuel with a blowing air stream in the area of the inlet guide apparatus (BHA) (first stage) and additional mixing of the formed “poor” fuel assembly in the microchannels of the porous PE body in the second stage due to turbulent pulsations of speed, pressure, temperature and concentration of components. Moreover, such a two-stage mixing of components (air and fuel) is carried out before the supply of the “poor” fuel assembly to its burning area.

5. The results of experimental studies of permeable materials made on the basis of metal micron powders, fibers and nets [11] (Kutysh II, Kutysh AI New ceramic-metal filters for gas treatment of diesel engines and their hydraulic characteristics. "Conversion in mechanical engineering ". 2002, No. 4. P.32-37), [12] (Kutysh II, Kutysh DI Experimental studies of the resistance coefficients of permeable plates made on the basis of micron powders // Materials of the XVI International Conference on Computational Mechanics and owls Small applied software systems (VMSPSPS ′ 2009), May 25-31, 2009, Alushta, - M .: MAI-PRINT Publishing House, 2009. - P.473-475), [13] (Kutysh I.I. , Kutysh A.I., Kutysh DI The results of experimental studies of the resistance coefficients of packages of metal micron grids // Materials of the XVII International Conference on Computational Mechanics and Modern Applied Software Systems (VMSPSPS ′ 2011), May 25-31, 2011, Alushta , - M .: MAI-PRINT Publishing House, 2011. - P.579-580), [14] (Kutysh I.I., Kutysh D.I., Kutysh A.I. The results of experimental studies of the resistance coefficients of permeable cermet materials of various types and their comparison // Materials of the IX International Conference on Nonequilibrium Processes in Nozzles and Jets (NPNJ ′ 2012), May 25-31, 2012, Alushta, Moscow: MAI Publishing House , 2011. - P.54-57), showed that all types of permeable materials provide a high quality mixture of liquid or gaseous fuel and air, but permeable materials made on the basis of metal micron grids have a minimum hydraulic oprotivleniem and maximum strength. Moreover, the minimum loss of total pressure during the movement of the mixture in the micropores of the porous body of PE and satisfactory mixing of the components are achieved when the average flow rate of the mixture does not exceed 40-60 m / s.

These properties of permeable materials made on the basis of metal micron grids determine their advantages over other types of permeable materials when used in burners as PE for preliminary preparation of “poor” fuel assemblies.

Another important property of permeable materials is their compactness, which reduces the mixing path of components compared to their jet mixing.

6. Blade swirls are widely used in KS burners [15] (Shchukin VK, Khalatov AA Heat transfer, mass transfer and hydrodynamics of swirling flows in axisymmetric channels. - M .: Mashinostroenie, 1982, 200 p.). They create wide opportunities for the formation of velocity fields, differing in the degree of swirling of the flow and the nature of the change in rotational speed along the radius of the blades. In practice, swirlers with flat blades and swirls with blades in the form of curved plates with twist angles from 15 ° to 60 ° are used. However, gratings with such blades, especially with flat blades, cannot provide a continuous flow in the interscapular channel, which is associated with increased losses.

For example, figure 5 shows the turbine-type ALZ grille with profiled blades in an arbitrary section along the height of the blade. Such gratings provide an uninterrupted flow in the interscapular channel with minimal pressure losses, therefore, they are devoid of the above-mentioned disadvantages.

The geometric or design swirl angles in the outlet section of the ALZ are different from the flow swirl corner.

The difference between these angles depends on the number and chord of the blades in the ALZ and decreases with increasing these parameters.

The law of variation of the swirl angle of the flow along the radius of the blades of the ALZ is conveniently written as a dependence

where u is the rotational component of the flow velocity at the outlet of the ALZ at a radius R;

n is an exponent taking the values -1≤n≤3.

To implement the law (1) at the exit from the ALZ, its blades must have some dependence of the design twist angle on the radius φ = f (R). The simplest dependence is obtained from the assumption of a uniform distribution of axial velocities W _a along the height of the blades at the inlet and outlet of the ALZ

where R _P is the radius of the blade on the periphery of the flow part of the burner;

φ _P - constructive twist angle on a radius of R _P ;

φ is the constructive twist angle on the radius R.

Of interest is the swirl law, which provides an increasing swirl of the flow with increasing radius of the blades ALZ. At n = 0, the twist of the ALZ blades along their height is preserved. The maximum increasing spin of the ALZ blades by their height in accordance with the adopted spin law (2) is realized at n = -1. It follows that the exponent n has only negative values that are in the range

As shown by experimental studies, ALZ with such a law (2) and taking into account expression (3) provide stable combustion of the “poor” fuel assembly.

7. Experimental studies of the environmental characteristics of two-channel burners with diffusive pilot-fuel combustion have shown that NOx emission substantially depends on the relative consumption of pilot fuel. Moreover, the lower the relative consumption of pilot fuel, while maintaining the combustion stability of the “poor” fuel assemblies, the lower the NOx emission. In order to be able to change the relative consumption of pilot fuel while maintaining a predetermined sum of the expenses of the main and pilot fuel, the corresponding fuel consumption regulators are installed in the main and pilot fuel supply lines (see Fig. 1).

We give the justification of the proposed technical solutions for the method of operation of the annular combustion chamber of a gas turbine engine.

1. As already noted above in the start-up mode and in transitional modes when entering the low-gas mode with a load of 65-70% of the nominal load of the gas turbine engine, very high values of the excess air coefficient are realized, accompanied by a violation of the combustion stability of the “poor” fuel assembly, deterioration the quality of the mixture, a decrease in the completeness of fuel combustion and a significant emission of CO. To eliminate this drawback in the operation of the annular compressor station, the supply of the main and pilot fuel to one part of the burners is stopped by closing the corresponding valves and all fuel is sent to the other part of the burners. In this example, shown in figure 2, shut off half of the burners belonging to the inner ring of the COP. At the same time, the coefficient of excess air decreases by 2 times, which is accompanied by an increase in the combustion stability of the “poor” fuel assemblies, an increase in the adiabatic combustion temperature, an increase in the completeness of fuel combustion, and a decrease in CO emission.

2. If at all operating modes of the annular compressor station to provide control of the pilot and main fuel consumption using appropriate flow controllers, providing the minimum relative pilot fuel consumption while maintaining the specified total fuel consumption and the combustion stability of the “poor” fuel assemblies, then, as experimental studies show, can significantly reduce NOx emissions. The reason for the decrease in NOx emission is a decrease in the volume of the high-temperature zone of diffusion combustion of pilot fuel. A decrease in the consumption of pilot fuel and a corresponding increase in the consumption of the main fuel through the burner also leads to a certain “enrichment” of the “poor” fuel assembly and an increase in its combustion stability.

The proposed annular CS GTE, which implements the proposed method of its operation, is shown in the figures (Figs. 1-5).

On the front wall 3 of the flame tube 4 of the annular KS, two-channel burners 1 of the outer ring C1 and two-channel burners 2 of the inner ring C2 are installed, the ends of the burners of both rings are in the same vertical plane (see image in figure 1). The inner channels 18 of the burners 1 of the outer ring C1 and the inner channels 17 of the burners 2 of the inner ring C2 are combined respectively in the outer annular manifold of the pilot fuel 16 and in the inner annular manifold of the pilot fuel 15, at the input of which, for example, an electric valve is installed 11. The annular receivers 19 of the burners 1 of the outer ring C1 and the annular receivers 20 of the burners 2 of the inner ring C2 are combined respectively in the outer annular manifold of the main fuel 14 and in the inner ring a main fuel manifold 13, at the input of which, for example, an electric valve 12 is installed in the main fuel supply line 8. For example, the main fuel supply line 8 and the pilot fuel supply line 7 have regulators 5 and 6 for the main fuel 9 and pilot fuel 10, respectively .

The image shown in figure 2 shows the middle line E of the flame tube separating the outer and inner rings KS, and the arrangement of the burners A1 with clockwise swirl and burners A2 with counterclockwise swirl in the outer ring C1, as well as burners B1 with clockwise swirl and B2 burners with counterclockwise swirl in the inner ring C2. The burners of the outer ring are marked in gray, which supply the main and pilot fuel at all possible operating modes of the gas turbine engine. White colors indicate the burners of the inner ring, which supply the main and pilot fuel when the load becomes close to the load of small gas, which is approximately 65-70% of the nominal load.

The figure shown in figure 3 shows a scan of the front wall 3 of the flame tube 4, which shows the gas flow diagram obtained in an experimental study. The arrows show the direction of gas movement with the formation of periodic paired vortices rotating in opposite directions and covering two burners A1 and B1 with the same flow swirl or A2 and B2 also with the same flow swirl, but with rotation in the opposite direction. Moreover, one burner A1 or A2 in each vortex belongs to the outer ring, and the other B1 or B2, respectively, to the inner ring.

At the points of contact of neighboring vortices, the difference in the flow rates is zero, therefore, reliable heat and flame transfer from the burners A1 of the outer ring to the burners B2 of the inner ring or from the burners A2 of the outer ring to the burners B1 of the inner ring in regimes exceeding the low gas mode when the main and pilot fuel is supplied not only to the burners of the outer ring C1, but also to the burners of the inner ring C2.

It can be seen from the flow diagram (see the figure in FIG. 3) that each KS burner has three connections with neighboring burners, in which reliable heat and flame transfer is guaranteed, since the difference in the flow velocities at the points of contact of adjacent paired vortices is zero.

Figure 4 shows a diagram of a two-channel low-emission burner using PE.

In accordance with the diagram shown in figure 4, the burner contains an internal channel 10 and an external channel bounded by walls 5, 10 and 11, and an annular fuel receiver 2.

The inner channel ends with a hollow conical stabilizer with a peak directed upstream.

The external channel of the burner contains VNA 8 installed at the entrance to the external channel, turbine type ALZ 4 with profiled blades installed at the outlet of the external channel, and PE 3 with predetermined porosity values installed between VNA 8 and ALZ 4.

Figure 5 shows a scan of the lattice of ALZ profiles of a turbine type, made in accordance with the annular section A-A, which is specified in the image of figure 4.

The lattice is profiled so that a smooth, continuous increase in the flow velocity in the interscapular channel is provided from the entrance to the lattice to the exit from it.

The spinning of the blades according to their height is made in accordance with the law (2) taking into account the expression (3).

и $${\overrightarrow{W}}_a$$

скоростей W и W_a соответственно образуют конструктивный угол закрутки лопаток АЛЗ φ.At the exit from the profile grid, a velocity triangle is shown formed by the absolute flow velocity W and its axial W _a and circumferential u components, respectively. Vectors $$\overrightarrow{W}$$

and $${\overrightarrow{W}}_a$$

speeds W and W _a respectively form a constructive twist angle of the blades ALZ φ.

The work of the annular CS GTE and the implementation of the proposed method of its operation is as follows.

During the launch of the annular CS GTE (see figure 1) and when the load increases to a value corresponding to the idle mode, valves 11 and 12 are closed.

The main fuel 9 at a pressure higher than the pressure in the air stream 22, is supplied through the regulator 5 only to the outer annular collector of the main fuel 14. Next, the main fuel from the collector 14 enters the annular fuel receivers 19 of the burners 1 belonging to the outer ring C1 (see Fig. 2), and through the openings made in the walls of the VHA, in the form of a system of jets is fed into a carrying stream of compressed air 22 coming from the gas turbine compressor to the external channels of the burners 1.

Pilot fuel 10 at a pressure higher than the pressure in the air stream 22, through the regulator 6 is fed first to the outer annular manifold of the pilot fuel 16, and then to the inner channels of the burners 1 of the outer ring C1.

In individual burners (for example, in 2 or 3 burners) of the outer ring, the fuel assembly is ignited from an external source. In figure 2, the burners of the outer ring are indicated in gray.

When the main and pilot fuel is supplied only to the burners of the outer ring C1, reliable transfer of heat and flame from the burner to the burner is ensured due to the fact that at the contact point of periodic paired vortices rotating in mutually opposite directions: either clockwise or counterclockwise , the difference in flow rates is zero.

Upon reaching a load close to the load of small gas, both valves 11 and 12 are simultaneously opened. Then, the main fuel 9, under a pressure higher than the pressure in the air stream 22, also starts to enter the inner annular manifold of the main fuel 13, from which it then goes to all ring fuel receivers 20 burners 2 inner ring C2. Then the main fuel through the holes made in the walls of the VHA, in the form of a system of jets is fed into a carrying stream of compressed air 22, also coming from the gas turbine compressor to the external channels of the burners 2.

Pilot fuel 10 at a pressure higher than the pressure in the air stream 22 is first supplied to the inner annular manifold of the pilot fuel 15, and then to the internal channels of the burners 2 of the inner ring C2 (see FIGS. 1 and 2).

When the load exceeds the load of small gas and the main and pilot fuels are supplied to all burners, reliable transfer of heat and flame to the burners of the inner ring is ensured from the working burners of the outer ring due to the fact that at the contact point of the periodic pair of vortices rotating in mutually opposite directions, the difference flow rates is zero. Each paired vortex during the operation of the annular CS at a given load covers two burners belonging to both rings. Moreover, each individual burner is in contact by pair vortices with 3 adjacent burners, which increases the reliability of heat and flame transfer from burner to burner (see figure 3). The use of flow swirling in adjacent burners belonging to both rings of the annular KS leads to the formation of periodic paired vortices on the front wall of the annular KS (see the scan in figure 3), which help to equalize the temperature fields in the radial and circumferential directions both in the fuel combustion zone and at the exit of the ring COP.

The regulation of the pilot fuel consumption at all possible operating modes of the annular gas turbine engine with the aim of reducing NOx emissions while maintaining the stable combustion of the “poor” fuel assemblies is provided using the pilot fuel flow regulator 6.

Preliminary preparation of high-quality “poor” fuel assemblies is carried out in a burner (see FIG. 4) due to two-stage mixing of components (compressed air and main fuel). In accordance with the low-emission burner circuit shown in FIG. 4, pilot fuel 6 is supplied through the internal channel 10, and then into the reverse current zone 12, which is located behind the hollow cone stabilizer 5.

Compressed air 7 from the compressor enters only the outer channel of the burner. The main fuel comes from the annular fuel receiver 2 through the openings made in the walls of the BHA 1, in the form of a system of jets 8 into the blowing air stream 7. The “poor” fuel assembly formed in the jet stage is then additionally passed through the microchannels of the porous PE body, which is the second mixing stage components, where due to turbulent pulsations of speed, pressure, temperature and component concentrations, high concentration uniformity of the “poor” fuel assembly 9 is achieved, that is, the high quality of this mixture.

The surface area of PE 3 in order to reduce the total pressure loss of the “poor” fuel assembly 9, when moving it in the micropores of the porous body of PE 3, is chosen such (for example, in the form of two truncated cones) so that the value of the average flow rate of the mixture 9 at the nominal operating mode of the compressor is in the range of 40-60 m / s.

Sustainable diffusion combustion of pilot fuel in the standby flare due to excess oxygen of the “poor” fuel assembly 9 is achieved by creating a reverse current zone 12 behind the cone stabilizer 5 as if it were a poorly streamlined body when flowing around its “poor” fuel assembly 9, and stable kinetic combustion of the “poor” A fuel assembly 9 is provided by supplying heat from the standby torch and the organization of an additional zone of reverse currents 13 using ALZ 4.

You can note the following advantages of the proposed annular KS GTD (figure 1-5) and the proposed method of its operation compared with the annular KS and the method of operation of the prototype:

- reliable transfer of heat and flame between the burners when starting the annular compressor station and in all possible modes of its operation;

- reduced loss of total pressure during the movement of the mixture flow on the front wall of the flame tube KS;

- reduced emissions of nitrogen oxides and carbon monoxide;

- increased combustion stability of the “poor” fuel assemblies at all possible operating modes of the ring CS;

- an increase in the uniformity of the temperature field in the radial and circumferential directions in the combustion zone and at the exit of the annular CS.

These advantages are achieved using the technical solutions given and justified above.

It is important to emphasize that all the problems noted above in the proposed annular CS GTE are solved comprehensively. In the above analogues and prototype, these problems are solved either partially or not at all.

Claims (7)

1. An annular combustion chamber of a gas turbine engine containing a group of burners located in the same plane on the front wall of the combustion chamber by at least two coaxial rings, characterized in that the same and even number of low emission burners are installed within each ring, the burners of the inner ring are offset in the circumferential direction relative to the burners of the outer ring at their half-step, all burners are made of two-channel, and the internal channels of the burners serve to supply only pilot fuel to them, and burner channels - for supplying compressed air to them due to the compressor and the main fuel with the formation of a “poor” air-fuel mixture, the outer channel of each burner contains an inlet guide apparatus, in the walls of which holes are made for supplying fuel to the blowing air stream, the blade swirl, installed at the outlet of the channel, and a permeable element with a given porosity, installed between the input guide vane and the blade swirl, the direction of the flow swirl in the burners with the help of shoulder blades the vortexes alternates to the opposite during the transition from one burner to another neighboring burner within each ring, each burner contains, in addition, an annular fuel receiver located above the inlet guide apparatus, the internal channels of the burners of the inner and outer rings are combined, respectively, in the inner and outer collectors of the pilot fuel, and the ring fuel receivers of the burners of the inner and outer rings are combined respectively in the inner and outer manifolds of the main fuel at the inlet one pilot fuel flow regulator is installed in the pilot and main fuel lines, one valve is installed in front of the inlets of the pilot and main fuel in the fuel supply lines. 2. The chamber according to claim 1, characterized in that the turbine type axial-blade swirl with profiled blades is used as a blade swirl. 3. The chamber according to claim 2, characterized in that the spinning of the blades of the axial-blade swirl is performed according to the law
$$tg\varphi ={\left(\frac{R_P}{R}\right)}^{n}tg{\varphi }_P$$

where R and R _P - the current radius and radius of the blades of the swirler at the periphery, respectively;
φ and φ _P - the current twist angle and the twist angle of the blades of the swirler at the periphery, respectively;
n is an exponent taking values in the range: 0> n≥-1. 4. The camera according to claim 1, characterized in that as a permeable element using a permeable element made on the basis of metal micron grids. 5. The chamber according to claim 1 or 4, characterized in that the average flow rate of the mixture in the micropores of the porous body of the permeable element in the nominal mode of operation of the combustion chamber is maintained in the range of 40-60 m / s by selecting the surface area of the permeable element. 6. A method of operating an annular combustion chamber of a gas turbine engine containing a group of burners located in one plane on the front wall of the combustion chamber by at least two coaxial rings, which consists in the following: when starting up and increasing the load to a predetermined amount, fuel is supplied through a portion of the total number of burners, and when the load increases above a predetermined value, the remaining burners are brought into action by supplying fuel to them, characterized in that the same and even number is set within each ring low-emission burners, the burners of the inner ring are shifted in the circumferential direction relative to the burners of the outer ring by half a step, all low-emission burners are made of two-channel, the internal channels of the burners serve to supply only pilot fuel to them, and the external channels of the burners to supply compressed air from them for the compressor and the main fuel with the formation of a “poor” air-fuel mixture, the outer channel of each burner contains an input guide apparatus, in the walls of which holes are made for supply fuel into the blowing air stream, an axial-blade swirl installed at the outlet of the channel, and a permeable element installed between the inlet guide apparatus and the axial-blade swirl, the direction of flow swirl in the burners with the help of blade swirls alternates in the opposite when switching from one burner to another adjacent burner within each ring, each burner contains, in addition, an annular fuel receiver located above the inlet guide apparatus, internal channels of the mountains trees of the inner and outer rings are combined respectively in the inner and outer manifolds of the pilot fuel, and the ring fuel receivers of burners of the inner and outer rings are combined respectively in the inner and outer manifolds of the main fuel, one fuel flow regulator is installed at the inlet of the pilot and main fuel lines, before one valve is installed at the entrances to the internal collectors of the pilot and main fuel in the fuel supply lines, when starting and increasing the load and until the load is close to the load of the low-gas mode (65-70% of the rated load), the valves are closed, therefore, the main and pilot fuel is supplied only to the burners of the outer ring, when the load is close to the load of the low-gas mode, and the load increases to rated load, both valves open and supply the main and pilot fuel also to the burners of the inner ring. 7. The method according to claim 6, characterized in that in the burners of the outer and inner rings, the relative consumption of pilot fuel, defined as the ratio of the consumption of pilot fuel to the sum of the costs of the main and pilot fuel, is reduced with the help of fuel consumption regulators from the conditions for obtaining a minimum emission of nitrogen oxides while maintaining a given total consumption of the main and pilot fuel and a given total coefficient of excess air while maintaining the combustion stability of the “poor” air-fuel mixture.

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