Gas turbine engine combustion chamber

Abstract

A combustion chamber of a gas turbine engine comprises a divergent duct, a hot chamber with a system of ports, support brackets, a streamlined inner and outer housing, injection nozzles, glow plugs, and a convergent duct at the exit from the chamber, wherein part of the airflow flows over the outside of the hot chamber and part of the airflow is fed via ports in the front wall of the chamber into an inner cavity and is mixed with fuel fed in via ports in the front wall of the hot chamber, the fuel spray cone angle is 30-90°, the total area of the ports in the front wall is selected so as to maintain a reducing medium in the hot chamber, the equivalence ratio is 3-6, and the area of ports provided in the lateral walls is selected so that as gas moves through the hot chamber, an influx of air ensures complete burn-up of the fuel prior to the exit into the convergent duct proportionally to the axial length of the hot chamber. Upon exit from the hot chamber, the medium must have a 25-50% excess of oxidizer. Upon exit of the combustion products into the convergent duct, the excess of oxidizer is 2-5%. The invention makes it possible to increase combustion efficiency, reduce the dimensions of the combustion chamber, and isolate the wall of the chamber from the combustion zone, thus extending the lifespan of the combustion chamber.

Description

[0001] Combustion chamber of a gas turbine engine

[0002] The invention relates to combustion chambers of turbojet engines. Its application is most effective in low-power fan turbojet twin-circuit engines.

[0003] Currently, due to the development of low-thrust turbojet engines, there is a need to design specialized combustion chambers for them. The main requirements for such chambers are: compact design, low production cost, acceptable efficiency, sufficiently long service life and low content of toxic substances in combustion products such as carbon monoxide, nitrogen oxides, unburned hydrocarbons and soot.

[0004] The most widely used today are annular combustion chambers with two working zones: a combustion zone and a zone of mixing combustion products with excess air (patent RU 2 670 858 C1, patent RU 2 243 448 C2, patent RU 2 515 909 C2). These chambers, as a rule, contain a combustion tube with holes, a diffuser for supplying air to the chamber, fuel injection nozzles into the combustion tube, a streamlined contour of the combustion chamber and an outlet pipe. Reduction of emission toxicity patent - RU2670858C1 and RU2515909C2, increase in the thermal cycling resource of the combustion tube patent RU2243448C2, is achieved by introducing special design elements and improving the geometry of the combustion chamber.

[0005] The disadvantages of existing designs are: the location of the nozzles directly in the combustion chamber, which leads to their unstable operation and low service life due to poor protection from the thermal radiation of the fuel combustion torch; high frontal resistance of the combustion chamber or combustion tube design, which improves the mixing of fuel with the oxidizer, but negatively affects the efficiency of the combustion chamber; passing the full volume of air flow through the combustion chamber / tube leads to increased pressure losses, unstable combustion of the torch with a high oxidizer content.

[0006] The design of the combustion chamber of a turbojet engine is known (patent RU 2 151 343 C1) adopted as a close analogue. The combustion chamber contains a plurality of aeromechanical fuel injectors installed in the bottom of this combustion chamber, connecting the forward parts of two annular walls. The fuel injectors are located in two concentric rows around the axis of symmetry and in pairs in longitudinal planes passing through the axis of symmetry. The fuel injectors of two rows are located at a strictly equal distance from the outlet of this combustion chamber and have axes directed towards this outlet. The corresponding distribution of primary openings, dilution openings and air flow rates allows to reduce emissions of nitrogen oxides into the atmosphere. A large number of injectors allows to distribute the uniformly sprayed fuel throughout the volume of the combustion chamber.

[0007] The disadvantage of this design is the location of the nozzles in the combustion chamber in close proximity to the fuel combustion flame and, as a consequence, their relatively short service life.

[0008] The purpose of this invention is to develop a simple combustion chamber design for a low-thrust gas turbine dual-circuit engine with stable combustion of the fuel flame in various engine operating modes, low content of toxic substances in combustion products and a long service life of the chamber design.

[0009] The stated objectives are achieved by: partially bypassing the air flow from the outside of the combustion chamber to cool the walls of the combustion chamber and the combustion chamber from the outside, placing fuel injectors outside the combustion chamber with the supply of atomized fuel to the combustion chamber through special openings in its frontal / frontal part, using glow plugs to ignite the fuel-air mixture, setting the required amount of oxidizer along the length of the combustion chamber by the total area of ​​openings in its frontal and side surfaces.

[0010] It is advisable to use nozzles with a spray cone in the range from 30 to 90° to achieve the set goals. The total area of ​​the holes in the frontal part of the combustion chamber should be taken such that the excess fuel coefficient lies in the range from 3 to 6 times, depending on the heat resistance of the materials used in the combustion chamber design. The area of ​​the holes in the side walls of the combustion chamber is selected so that as the gas moves in the combustion chamber, the air inflow ensures the afterburning of the fuel to the outlet in the confuser proportional to the axial length of the combustion chamber. At the outlet of the combustion chamber, the medium should have an excess of oxidizer of 25-50%.If it is necessary to sacrifice the efficiency of the thermodynamic process and the working life of the combustion chamber in favor of the compactness of the design, the ratio of the total area of ​​the holes in the side walls to the total area of ​​the side surface of the combustion chamber is taken to be higher up to the strength limits of the design, and the excess of oxidizer at the outlet of the combustion chamber is taken to be minimal, if possible close to 25%. At the outlet of the combustion products to the confuser, the excess oxidizer coefficient should lie in the range from 2 to 5 units. Smaller values ​​of excess oxidizer are preferable in compact designs, larger ones in designs with a priority working life.

[0011] The essence of the invention is explained by the drawing. Fig. 1 shows a typical general view of the combustion chamber of a low-power dual-circuit turbojet engine with a thrust from 1000 to 5000 N. Position (1) marks the position of the fuel injectors; the total number of injectors must be at least 3 pcs. Position (2) marks the glow plugs; their total number must also be at least 3 pcs. Position (3) is a streamlined combustion chamber wall on the inside of the chamber. Position (4) is a confuser in which the flow of combustion products is mixed with cooling air flowing around the combustion chamber from the outside. Position (5) is a diffuser for supplying air to the combustion chamber. Position (6) is a heat-resistant internal contour of the combustion chamber insulating the engine shaft. Position (7) and (8) of the half-body of the frontal / frontal part of the combustion chamber; in the half-body (8) there are holes for the fuel sprayed by the nozzles; they are coaxial with the nozzles.Positions (9) and (10) respectively mark the inner and outer side walls of the combustion chamber, in which openings are made for feeding the oxidizer into the combustion zone. Position (11) marks the support brackets of the combustion chamber.

[0012] Thus, the proposed design allows to increase the working life of the combustion chamber, create conditions for stable combustion of the fuel torch under fairly wide operating conditions and minimize the content of toxic substances in combustion products. The sum of the design solutions allows to make the combustion chamber in the most compact arrangement.

Claims

4 Invention formula The combustion chamber of a gas turbine two-circuit engine, containing an air supply diffuser, a combustion chamber of an original design with holes for distributed air supply to the fuel combustion zone, support brackets for fastening the combustion chamber, an inner and outer casing with streamlined walls on the side of air and combustion products movement, nozzles with a solid spray profile, glow plugs, a confuser for accelerating combustion products at the chamber outlet, while the cooling air flow flows around the annular combustion chamber from its outer part, part of the air flow is supplied through holes in the front wall of the combustion chamber into its internal cavity where it mixes with fuel sprayed by the nozzles and supplied through special holes in the front wall of the combustion chamber, the cone of fuel spray by the nozzles is in the range from 30 to 90 degrees, the diameter of the holes for feeding fuel to the combustion chamber is selected in such a way,To prevent the sprayed fuel from getting onto the front wall of the combustion chamber, the number of holes in the front wall is selected so that during fuel combustion a reducing environment is maintained in the combustion chamber due to the excess fuel, the excess fuel coefficient is in the range from 3 to 6 units, the area of ​​the holes in the side walls of the combustion chamber is calculated so that as the combustion products and fuel residues move in the internal cavity of the combustion chamber, the air flow through the holes ensures the afterburning of the fuel mixture to the outlet of the flow from the combustion chamber to the confuser in proportion to the axial length of the combustion chamber, at the outlet the environment should be acidic with an excess of oxidizer in the flow of combustion products from 25% to 50%, at the outlet of the combustion products to the confuser, the combustion products must contain an excess amount of oxidizer, the excess oxidizer coefficient at the outlet to the confuser must be maintained in the range from 2 to 5 units.

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