RU2395039C1 - Front device of annular combustion chamber of gas-turbine engine - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: front device of annular combustion chamber of gas-turbine engine of ground units of various purpose includes fuel atomisers and air tubes with an inlet on one end and two opposite side outlets on the other end, which are equally located in a circumferential direction. Fuel atomiser is inserted in each tube. Inlet of each tube is arranged in the channel between combustion chamber housing and flame tube and directed towards the inlet of combustion chamber. Outlets of adjacent air tubes face each other. On inner surface of flame tube there installed is annular header of convex profile, which has the wall section common with flame tube, and at least one row of holes equally located in a circumferential direction (the first group of holes) on the side facing the initial part of flame tube. Outlets of air tubes are arranged in header. Each fuel atomiser in zone of outlet holes of air tube is equipped with two sprayers with through channels directed towards outlet holes of the tube at an angle to atomiser axis.

EFFECT: obtaining high fuel combustion completeness, decreasing emission of hazardous matters, and eliminating smoking.

7 cl, 7 dwg

Description

The invention relates to a device for preparing a poor air-fuel mixture before burning in the combustion chambers of gas turbine engines (GTE), operating as part of ground-based gas turbine installations (GTU) for various purposes.

One of the most important tasks in the development of combustion chambers is to reduce the level of emissions of pollutants in the atmosphere. The main attention is paid to the reduction of nitrogen oxides (NO _x ), carbon monoxide (CO), unburned hydrocarbons (UHC) in combustion products and smoke reduction (soot formation). The emission of these substances is characteristic of any heat engine running on fossil fuels. When creating low-emission combustion chambers, the main problem is to achieve effective preliminary mixing of fuel with air and the organization of sustainable combustion of poor mixtures. For example, the generation of nitrogen oxides by the basic thermal mechanism of Zeldovich strongly depends on the temperature in the combustion zone T and when its value is less than 1730 K, it becomes practically insignificant. In this temperature range (T <1730 K), the nitrogen oxide emission index very weakly depends on the gas residence time in the combustion chamber.

One of the ways to reduce harmful emissions from aviation combustion chambers is to use chambers in which combustion takes place in two zones: auxiliary (pilot) and primary. In the first, the combustion of a rich air-fuel mixture is organized, in the second - poor. Zones can be located relative to each other in series or in parallel.

However, the use of the pilot zone, in which combustion occurs according to the diffusion mechanism, significantly increases the emission of nitrogen oxides. In the combustion chambers of aircraft engines, where the gas residence time is short (≈7 ms), it is not possible to get rid of the pilot, constantly operating diffusion combustion zone without affecting the stable ignition and combustion of the air-fuel mixture, as well as ensuring the completeness of its combustion.

For combustion chambers of ground-based gas turbines, the indicated problems with stabilization and completeness of combustion of a poor air-fuel mixture can be solved by increasing the volume of the combustion chamber and increasing the size of the flame stabilization zone in it, and reducing the flow rate of the mixture.

To ensure the reduction of the level of pollutant emissions in the combustion products of aircraft gas turbine engine chambers and ground gas turbine engines, the main problem is to achieve effective preliminary mixing of fuel with air before combustion (homogenization of the air-fuel mixture).

Known front-end device of the engine NK-8-2U (see Timofeev NI "Design and flight operation of the engine NK-8-2U", M., Engineering, 1978, p.144). The front device contains a number of structural elements. Each element consists of a nozzle and a nozzle of a conical shape with numerous holes supplying the air-fuel mixture to the combustion zone. Liquid fuel is fed through a central centrifugal nozzle to the nozzle cavity filled with a rotating air stream. Such a device allows for a more uniform distribution of fuel over the angle in comparison with the distribution created by the centrifugal nozzle, especially in low thrust modes. As a result of this, ignition of fuel is greatly facilitated, ignition of the combustion chamber, the range of its stable operation in the direction of poor air-fuel mixtures expands. However, this device provides only a partial, rather crude mixture of fuel and air and, when trying to intensify it by increasing the twist of the air flow in the nozzle, leads to a breakthrough of the flame inside the nozzle with its subsequent destruction.

The closest analogue to the same purpose as the claimed technical solution, namely the preliminary preparation of the air-fuel mixture for combustion, is the combustion chamber of a gas turbine engine described in US patent No. 4,275,564, (NKI 60/738, Jim. 30, 1981, " Front device of the annular combustion chamber, fuel nozzles and evaporators equally spaced around the circumference "). The evaporator consists of a central air tube, which ends with a transverse evaporation tube. Each nozzle is associated with the central air tube of the evaporator. The evaporator has one air inlet and two opposite outlets for the air-fuel mixture. The outputs of the channels of neighboring evaporators are facing towards each other. Due to this, in the combustion zone between the outlet openings of the evaporators, circumferential regions with the maximum intensity of turbulence are formed, in which the processes of mixing fuel droplets with air entering the cavity of the flame tube through the holes in its walls, as well as the processes of evaporation and combustion, occur simultaneously. This helps to ensure a stable and efficient combustion of fuel in the combustion chamber, especially at low pressures and air temperatures at the engine inlet. However, in evaporators of this design, air is used only for the purpose of transportation and equal distribution of fuel and its vapors to the outlet openings. A reduction in the emission of nitrogen oxides NO _x does not occur with such an organization of the combustion process, since the rich air-fuel mixture resulting from the evaporator tubes burns out in high-temperature diffusion flames located in separate regions of the combustion zone. The uneven angular distribution of fuel over the cross section of the annular combustion chamber does not allow to obtain a homogeneous lean air-fuel mixture. The presence of local zones of high turbulence and increased fuel concentration in the head of the chimney leads to circumferential combustion unevenness. For this reason, evaporators are subjected to uneven heating and provide only partial evaporation of fuel. In addition, it is known that the appearance of a flame in the zone of mixing of fuel with air prevents their mixing.

The basis of the invention is the solution to the problem of significantly reducing the emission of harmful substances (NO _x , CO, UHC, soot) in the combustion products by preparing a poor pre-mixed and partially vaporized (in the case of using liquid fuel instead of gaseous) air-fuel mixture for burning without compromising fuel economy engine and service life of its hot parts. The main problem here remains the achievement of effective preliminary mixing of fuel with air (homogenization of the air-fuel mixture). The combustion of a poor homogeneous finely dispersed air-fuel mixture (with a droplet size of 20 microns or less) in its characteristics approaches the combustion of a homogeneous mixture. Therefore, an additional task is set for liquid fuel - its fine atomization.

The problem is solved in that the proposed front-end device of the annular combustion chamber of a gas turbine engine contains fuel nozzles and air tubes equally spaced around the circumference with an inlet at one end and two opposite side outlets at the other end of the tube, with a fuel nozzle inserted into each tube and an entrance to each tube placed in the channel between the housing of the combustion chamber and the flame tube and is directed towards the entrance to the combustion chamber, and the exits from adjacent air tubes are facing towards pyr friend.

According to the invention, an annular convex profile collector is installed on the inner surface of the flame tube, having a wall portion common to the flame tube and at least one row of holes equally spaced around the circumference (first group of holes) on the side facing the initial part of the flame tube. The outlets from the air tubes are located in the manifold. Each fuel nozzle in the area of the outlet openings of the air tube is equipped with two nozzles with through channels directed towards the outlet of the tube obliquely to the axis of the nozzle.

The installation on the inner surface of the flame tube of the annular collector of a convex profile and the execution on its side facing the initial part of the flame tube, evenly spaced around the circumference of the holes, provides a uniform flow of uniformly mixed air-fuel mixture into the combustion zone. The jets flowing from the openings are directed to flame stabilization zones and to the spark plugs located close to them. This ensures reliable ignition and stable effective combustion of the air-fuel mixture. Placing the collector directly on the wall of the flame tube simplifies the cooling of the collector, primarily due to the absence of connections between the tubes and the collector, which are usually subject to overheating when the collector is located entirely inside the combustion zone. In addition, the specified location of the manifold facilitates the supply of additional air to the manifold.

The arrangement of the outlet openings of the air tubes in the annular manifold so that the exits from the adjacent tubes are facing each other intensifies the process of preliminary mixing of fuel with air due to the collision of the oncoming jets of the mixture, already partially mixed in and out of the air tube, increases uniformity air-fuel mixture.

Each fuel nozzle is equipped in the zone of the outlet openings of the air tube with two nozzles with through channels directed towards the outlet of the tube obliquely to the axis of the nozzle, fuel is supplied across the air stream. This ensures intensive mixing of gaseous fuel with air, and in the case of liquid fuel and its crushing into small droplets by the mechanism of "spraying liquid jets in a blowing air stream" and the "explosive" mechanism of "spraying fuel jets with an air stream in a confuser nozzle", which implemented, for example, in a simple pneumatic nozzle. Both processes, mixing and atomization, improve with increasing relative air velocity. For this reason, direct air inflow into the air tubes is most advantageous for crushing the fuel jets into small droplets and mixing them with air, since the speed of air flow past the fuel jets reaches its maximum value. This is ensured by the fact that the entrance to each air tube is placed in the channel between the housing of the combustion chamber and the flame tube and is directed towards the entrance to the combustion chamber.

The essential features of the invention may have the development and refinement:

- the annular portion of the flame tube wall common with the collector may be provided with circumferential openings to provide preparation for burning a poorer air-fuel mixture;

- inside the flame tube, on the outside of the annular collector, an additional collector can be installed with a gap, provided on the wall facing the initial part of the flame tube with holes (second group of holes) interconnected with similar holes of the internal collector (holes of the first group). In addition, each of the two sections of the wall of the flame tube between the collectors is provided with holes around the circumference. This allows the internal collector to be shielded from the effects of high-temperature combustion products, to approach the required composition of the poor air-fuel mixture in it, and to add the necessary amount of air to it.

- The holes on the wall of the additional manifold facing the initial part of the flame tube (holes of the second group) can be coaxial with similar holes in the internal collector (holes of the first group). This allows you to mix in the air-fuel mixture flowing from the internal manifold, an additional portion of air and prevent the passage of flame.

- The holes on the wall of the additional manifold facing the initial part of the flame tube (holes of the second group) can be offset relative to similar holes in the internal collector (holes of the first group). This provides a more uniform mixture of air flowing in the gap between the manifolds with the air-fuel mixture flowing from the internal manifold.

- The diameter and number of holes in the rows located on the wall facing the initial part of the flame tube (holes of the first group) can be different depending on the volume of that part of the primary combustion zone into which the prepared air-fuel mixture is supplied.

- There is a through channel at the end of the fuel nozzle located along the nozzle axis (axial nozzle), which prevents the formation of a stagnant zone at the end of the nozzle, where it is possible to heat the fuel, decompose it, coke formation, which can change the fuel consumption through the atomizer channels, and in case of using liquid fuel lead to the formation of vapors, which also affect the flow of fuel through the channels of the atomizer.

Thus, the task of the invention is solved. Effective pre-mixing of fuel with air has been achieved. The preparation of a poor pre-mixed and partially vaporized air-fuel mixture for combustion is carried out without affecting the fuel economy of the engine and the service life of its hot parts. Significantly reduced emissions of harmful substances (NO _x , CO, UHC, soot) in the products of fuel combustion.

The present invention is illustrated by the following detailed description of the front-end device of the annular combustion chamber of a gas turbine engine and its operation with reference to the illustrations presented in figures 1-7, where:

figure 1 shows a longitudinal section of a once-through combustion chamber;

figure 2 is a section aa in figure 1;

figure 3 - element I in figure 2;

figure 4 - section B - B in figure 2;

figure 5 is a longitudinal section of a counterflow combustion chamber;

in Fig.6-element II in Fig.5;

Fig.7 is a longitudinal section of a direct-flow annular combustion chamber with a manifold that contains three rows of holes (the rows may differ in the number and diameter of the holes).

The front-end device of the annular combustion chamber 1 of the gas turbine engine (Fig. 1) contains fuel nozzles 2 and air tubes 3 equally spaced around the circumference with an inlet 4 (Fig. 4) at one end and two opposite side outlets 5 (Fig. 2) at the other end of the tube 3. A fuel injector 2 is inserted into each tube 3. An inlet 4 into each tube 3 is placed in a channel 6 (Fig. 1) between the housing 7 of the combustion chamber 1 and the flame tube 8 and is directed towards the entrance 9 to the combustion chamber 1. Exits 5 ( figure 2, 3) from adjacent neighboring air tubes 3 facing each other . On the inner surface of the flame tube 8 is installed an annular collector 10 convex profile (figure 1). The collector 10 has a common wall section 11 with the flame tube 8 (FIGS. 2, 4) and at least one row of holes 12 equally spaced around the circumference (first group of holes) on the side facing the initial part of the flame tube 8. Exits 5 from air tubes 3 are placed in the manifold 10. Each fuel nozzle 2 in the area of the outlet openings 5 of the air tube 3 is equipped with two nozzles 13 (FIG. 3) with through channels 14. The channels 14 are directed towards the outlet 5 of the tube 3 inclined to the axis of the nozzle 2.

The annular portion 11 of the wall of the flame tube 8, common with the collector 10, may be provided with circumferential openings 15 (figure 2).

Inside the flame tube 8, on the outside of the annular collector 10, an additional collector 16 can be installed with a gap (Fig. 5). The collector 16 is provided on the wall facing the initial part of the flame tube with holes 17 (second group of holes) interconnected with similar holes 12 (holes of the first group) of the internal manifold 10. In addition, on each of the two sections of the wall of the flame tube 8 between the collectors 10 and 16, holes 18 can be made around the circumference (FIG. 6).

Holes 17 (openings of the second group) on the convex side of the additional manifold 16 facing the initial part of the flame tube 8 can be aligned with similar holes 12 (openings of the first group) of the internal collector 10 (Fig.6).

Holes 17 (holes of the second group) on the convex side of the additional manifold 16 facing the initial part of the flame tube can be offset relative to similar holes 12 (holes of the first group) of the internal collector 10 (not shown).

The diameter and number of holes 12 (holes of the first group) in separate rows located on the wall of the collector 10, facing the initial part of the flame tube 8, can be different (Fig.7).

At the end of the fuel nozzle 2 can be made through the channel 19 located along the axis of the nozzle (axial nozzle) (Fig.3, 6).

The front device of the annular combustion chamber operates as follows (figure 1). When working on gaseous fuels, the front-mounted device performs turbulent mixing of fuel with air in several stages: in air tubes 3 as a result of the introduction by nozzles of 2 separate jets of fuel into the blowing air stream, in the manifold 10, where partially mixed fuel-air jets interact with the medium filling a collector, with oppositely directed jets flowing from the outlet openings 5 of adjacent air tubes, and with additional jets of air from the openings 15 on a wall common to the flame tube collector. Partial mixing of fuel with air continues in the combustion zone itself until it ignites. The result is a homogeneous (homogeneous) mixture with a lower combustion temperature compared with the combustion temperature of the stoichiometric mixture. An additional external collector allows additional air portions to be mixed with an almost uniform air-fuel mixture and depleted to such an extent that ignition, flame stabilization and high completeness of fuel combustion are ensured.

When working on liquid fuel, the front-mounted device atomizes and subsequently mixes droplets of fuel with additional portions of air, and partially evaporates the droplets. As a result, the front-mounted device creates a homogeneous finely dispersed mixture, close in its properties to a homogeneous gas mixture.

The gas turbine compressor supplies air to the input 9 of the combustion chamber 1 (Fig. 1,5) and then to the channel 6 between the housing 7 of the combustion chamber 1 and the flame tube 8. From the channel 6, the air is directed to the inputs of 4 tubes 3 (Fig. 4) and through opposite side exits 5 at the end of each tube 3 (FIG. 3) are pumped into the manifold 10 (FIG. 2). From the manifold 10, air through holes 12 around the circumference is introduced into the initial part of the flame tube (Fig. 1). The fuel is fed through all nozzles 2 into the tubes 3. The fuel from each nozzle 2 is fed into the area of the outlet holes 5 of the tube 3 through the through channels 14 of the two nozzles 13 (Fig. 3). In the area of the outlet openings 5, the majority of the fuel jets are fed across the air stream flowing through the pipe 3 from the inlet 4, crushed into droplets (in the case of liquid fuel) and mixed with air. Possible additional fuel supply to the tube 3 from the end of the fuel nozzle 2 through the through channel 19 along the axis of the nozzle (Fig.3, 4). The acceleration of the air flow when passing through the holes 5 of the tube 3 splits large droplets into smaller ones, as well as a stream of fuel supplied along the axis of the hole 5. At the outlet of the holes 5 in the manifold 10, the fuel is further mixed with air. The jets of the air-fuel mixture from the opposite outputs 5 of the adjacent tubes 3 collide and mix inside the manifold 10 (figure 2). Through holes 15 in the annular wall portion of the flame tube 8, air from the channel 6 is supplied to the manifold 10 for additional mixing and depletion of the air-fuel mixture. From the manifold 10, a homogeneous air-fuel mixture is injected through holes 12 around the circumference into the initial part of the flame tube 8, where it is first ignited with an ignitor (for example, a spark plug 20), and then in the flame stabilization zones located in the initial part of the flame tube (Figs. 1, 5 ) The number of rows of holes 12 may be several (Fig.7). Rows may vary in number and diameter of holes.

For the option when an additional manifold 16 with holes 17 is installed with a gap inside the flame tube 8 from the outside of the collector 10, the air-fuel mixture flows from the collector 10 into the initial part of the flame tube 8 as follows (Figs. 5, 6). From the manifold 10, the air-fuel mixture through the openings 12 enters the gap between the walls of the manifolds 10 and 16. At the same time, air from the channel 6 is fed into the gap through the openings 18 in the wall of the flame tube 8, common with the collector 16, providing additional mixing and depletion of the mixture. From the gap between the walls of the manifolds 10 and 16, the air-fuel mixture is directed through the openings 17 in the manifold 16 to the initial part of the flame tube 8 according to one of two schemes. The air-fuel mixture is directed towards the initial part of the flame tube 8 through the holes 17 of the collector 16 coaxial with the similar holes 12 of the collector 10 or through the holes 17 of the collector 16, offset from the holes 12 of the internal collector 10.

The proposed front-mounted device provides efficient mixing of fuel with air, preparation of a poor homogeneous gas (homogeneous) or homogeneous finely dispersed air-fuel mixture for environmentally friendly and efficient combustion in the combustion chambers of gas turbine engines operating as part of ground-based gas turbines for various purposes.

Claims (7)

1. The front-end device of the annular combustion chamber of a gas turbine engine, containing fuel nozzles and air tubes equally spaced around the circumference with an inlet at one end and two opposite side outlets at the other end, with a fuel nozzle inserted into each tube, an entrance to each tube placed in a channel between the housing the combustion chamber and the flame tube and is directed towards the entrance to the combustion chamber, and the exits from adjacent air tubes face each other, characterized in that on the inner surface An annular convex profile collector having a wall section and at least one row of holes equally spaced around the circumference (the first group of holes) on the side facing the initial part of the flame tube is installed on the side of the flame tube, and the exits from the air tubes are located in a manifold, with each fuel nozzle in the area of the outlet openings of the air tube equipped with two nozzles with through channels directed towards the outlet of the tube obliquely to the axis of the nozzle. 2. The front device according to claim 1, characterized in that the annular portion of the wall of the flame tube, common with the collector, is provided with circumferential openings. 3. The front device according to claim 1, characterized in that an additional collector is provided with a gap inside the flame tube on the outer side of the annular collector, provided with holes (the second group of holes) interconnected with similar openings on the wall facing the initial part of the flame tube the collector (holes of the first group), in addition, holes are made between the collectors around the circumference of the collector in each of the two sections of the wall of the flame tube. 4. The front device according to claim 3, characterized in that the openings on the convex side of the additional manifold (openings of the second group) are aligned with similar openings of the internal collector (openings of the first group). 5. The front device according to claim 3, characterized in that the openings on the wall of the additional manifold facing the initial part of the flame tube (openings of the second group) are offset relative to similar openings of the internal collector (openings of the first group). 6. The front device according to claim 1, characterized in that the diameter and number of holes in the rows located on the wall facing the initial part of the flame tube (holes of the first group) is different. 7. The front device according to claim 1, characterized in that at the end of the fuel nozzle there is a through channel located along the axis of the nozzle (axial nozzle).

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