A DC combustion chamber for adapting centrifugal compressors to small aircraft engines

Abstract

This invention relates to the field of aero-engine combustor design technology, and more particularly to a direct-flow combustor for a small aero-engine adapted to a centrifugal compressor. It includes an outer casing, an inner casing, and a flame tube. A centrifugal nozzle is located at the front end of the flame tube, a swirler is arranged circumferentially around the flame tube, and a flame tube mounting edge is located at the rear end of the flame tube. The swirler is mounted on the outer ring of the flame tube, fully utilizing the high-speed airflow after the diffuser to form a stable recirculation zone within the flame tube for ignition and flame stabilization. The centrifugal nozzle and heat shield design, matched with the large-scale stable recirculation zone downstream of the swirler, provide excellent ignition and quenching performance, enabling in-flight re-ignition. The flame tube employs film cooling technology, forming a full cooling film covering the flame tube for effective thermal protection.

Description

Technical Field

[0001] This invention relates to the field of aero-engine combustor design technology, and more particularly to a DC combustor for a small aero-engine adapted to a centrifugal compressor. Background Technology

[0002] In the design of small aero engines, efforts are made to shorten the length of the gas generator to reduce the number of rotor pivots and lighten the weight. To meet the overall engine parameter requirements, centrifugal compressors are used for the compressor, and deflector and recirculation combustion chambers are employed. Deflector combustion chambers use an oil slinger for fuel supply, which results in poor ignition performance, poor sealing performance, and a rotating hot spot at the outlet synchronized with the turbine rotor. Recirculation combustion chambers, due to their smaller head size, mostly use a single-vortex flame tube head combined with evaporator pipes for fuel supply, resulting in poor ignition performance, poor acceleration and deceleration performance, and the inability to achieve in-flight ignition, severely limiting the operational efficiency of the engine and its platform. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a DC combustor for small aero-engines adapted to centrifugal compressors. It adopts a single-stage vortex head combined with a single oil circuit centrifugal nozzle to improve the ignition performance of the small aero-engine combustor, enhance acceleration and deceleration characteristics, and overcome the technical difficulties of in-flight re-ignition in small aero-engines.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a DC combustion chamber for a small aero-engine adapted to a centrifugal compressor includes an outer casing, an inner casing and a flame tube, a centrifugal nozzle is provided at the front end of the flame tube, a swirler is provided around the flame tube, and a flame tube mounting edge is provided at the rear of the flame tube. The outer casing and inner casing constitute the main structure of the combustion chamber, providing the internal space of the combustion chamber. They are connected to the engine compressor and turbine to transmit axial force. The flame tube, together with the outer casing and inner casing, forms the internal airflow channel of the combustion chamber, which divides the incoming airflow into three paths: the outer ring airflow, the flame tube internal airflow, and the inner ring airflow, for organizing combustion and cooling.

[0005] Furthermore, the centrifugal nozzle is a single-oil-path centrifugal nozzle, whose main function is to allow fuel to enter the nozzle and, under pressure, enter the swirling chamber. Under the combined action of pressure and centrifugal force, the fuel is ejected from the nozzle, broken up and atomized, forming fine liquid that enters the flame tube and mixes with air for combustion. The swirler is a single-stage axial swirler, whose main function is to allow air to enter the flame tube through the swirler's air inlet. Under the action of viscosity and reverse pressure gradient, the air forms a reflux zone in the flame tube, which is used to organize combustion, achieve ignition, and stabilize the flame. The flame tube mounting edge is used to connect the flame tube and the turbine guide, achieving axial and circumferential positioning of the flame tube and transmitting axial force.

[0006] Furthermore, the centrifugal nozzle is a single-path centrifugal nozzle structure with an outer diameter of 10~11mm and a flow rate FN of 10~15.

[0007] Furthermore, the flame tube is formed by welding thin-walled plates. The flame tube is provided with cyclone mounting holes, a first mixing hole, a second mixing hole, cooling holes, and nozzle mounting holes. The cyclone mounting holes are evenly spaced in groups of 8-10 along the circumference of the flame tube, with a diameter of 35-37 mm. The cyclone is mounted on the flame tube through these mounting holes. The first mixing hole... The flame tube has 28-35 uniformly spaced holes with a diameter of 6.8-7.2 mm; the second mixing holes have 12-25 uniformly spaced holes with a diameter of 7.5-8.5 mm; the cooling holes have a diameter of 1.3-1.8 mm, a circumferential spacing angle of 4°-6°, and an axial spacing of 6-8 mm; the nozzle mounting holes have 8-12 uniformly spaced holes with a diameter of 11-13 mm, and the centrifugal nozzles are mounted on the flame tube through the nozzle mounting holes.

[0008] The first and second mixing holes are used to introduce inner and outer ring airflow into the flame tube, mix with the high-temperature gas, reduce the gas temperature, and meet the inlet temperature requirements of the turbine guide vane; the cooling holes are evenly distributed on the flame tube wall in a staggered manner, and the inner and outer ring airflow passes through the cooling holes to perform gas film cooling on the flame tube, protecting the flame tube so that its wall temperature is below the long-term allowable temperature of the material; the centrifugal nozzle and the cyclone separator are respectively provided.

[0009] The centrifugal nozzle is a single-oil-path centrifugal nozzle, and a heat insulation cover made of high-temperature alloy is installed on the outside of the centrifugal nozzle housing to prevent nozzle ablation; the cyclone is a single-stage axial cyclone, and the cyclone adopts a strong swirling design to form a large-scale recirculation zone in the flame tube to achieve ignition and flame stability.

[0010] The flame tube is provided with positioning holes and cooling holes on its mounting side.

[0011] The beneficial effects of this invention are as follows: The DC combustor for a small aero-engine adapted to a centrifugal compressor has a swirler installed on the outer ring of the flame tube, making full use of the high-speed airflow after the diffuser to form a stable recirculation zone within the flame tube for ignition and flame stabilization; it uses a centrifugal nozzle and a heat shield is designed to match the large-scale stable recirculation zone downstream of the swirler, resulting in good ignition and quenching performance and the ability to reignite in the air; the flame tube uses film cooling technology to form a full cooling film covering the flame tube, providing effective thermal protection. Attached Figure Description

[0012] Figure 1 This is a cross-sectional structural diagram of the present invention.

[0013] In the diagram: 1. Outer casing; 2. Inner casing; 3. Flame tube; 31. Cyclone mounting hole; 32. First mixing hole; 33. Second mixing hole; 34. Cooling hole; 35. Nozzle mounting hole; 4. Centrifugal nozzle; 5. Cyclone; 6. Flame tube mounting edge; 61. Positioning hole; 62. Cooling hole. Detailed Implementation

[0014] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0015] To achieve the above objectives, the present invention provides the following specific embodiments: Figure 1 As shown, the DC combustion chamber for a small aero-engine adapted to a centrifugal compressor is characterized by including an outer casing 1, an inner casing 2 and a flame tube 3. A centrifugal nozzle 4 is provided at the front end of the flame tube 3, a swirler 5 is provided around the flame tube 3, and a flame tube mounting edge 6 is provided at the rear of the flame tube 3. The outer casing 1 and the inner casing 2 constitute the main structure of the combustion chamber, providing the internal space of the combustion chamber. They are connected to the engine compressor and turbine to transmit axial force. The flame tube 3, together with the outer casing 1 and the inner casing 2, forms the internal airflow channel of the combustion chamber, which divides the incoming airflow into three paths: the outer ring airflow, the flame tube internal airflow, and the inner ring airflow, for organizing combustion and cooling.

[0016] Furthermore, the centrifugal nozzle 4 is a single-oil-path centrifugal nozzle. Its main function is to allow fuel to enter the nozzle and, under pressure, enter the swirling chamber. Under the combined action of pressure and centrifugal force, the fuel is ejected from the nozzle, broken up, and atomized into fine liquid particles, which then enter the flame tube to mix with air for combustion. The swirler 5 is a single-stage axial swirler. Its main function is to allow air to enter the flame tube through the swirler's inlet, creating a reflux zone within the flame tube under the influence of viscosity and a reverse pressure gradient. This zone is used to organize combustion, achieve ignition, and stabilize the flame. The flame tube mounting edge 6 connects the flame tube and the turbine guide, enabling axial and circumferential positioning of the flame tube and transmitting axial force. The flame tube mounting edge 6 is provided with positioning holes 61 and cooling holes 62.

[0017] Furthermore, the centrifugal nozzle 4 is a single-path centrifugal nozzle structure with an outer diameter of 10~11mm and a flow rate FN of 10~15.

[0018] Furthermore, the flame tube 3 is formed by welding thin-walled plates. The flame tube 3 is provided with cyclone mounting holes 31, first mixing holes 32, second mixing holes 33, cooling holes 34, and nozzle mounting holes 35. The cyclone mounting holes 31 are evenly arranged in 10 holes along the circumference of the flame tube 3, with a diameter of 36 mm. The cyclone 5 is mounted on the flame tube 3 through the cyclone mounting holes 31. The first mixing holes 32 are evenly arranged in 30 holes along the circumference of the flame tube 3, with a diameter of 7 mm. The second mixing holes 33 are evenly arranged in 20 holes along the circumference of the flame tube 3, with a diameter of 8 mm. The cooling holes 34 have a diameter of 1.5 mm, and the circumferential spacing angle of the cooling holes 34 on the flame tube 3 is 6°, and the axial spacing is 7 mm. The nozzle mounting holes 35 are evenly arranged in 10 holes along the circumference of the flame tube 3, with a diameter of 12 mm. The centrifugal nozzle 4 is mounted on the flame tube 3 through the nozzle mounting holes 35.

[0019] The first mixing hole 32 and the second mixing hole 33 are used to introduce the inner and outer ring airflow into the flame tube 3, mix with the high-temperature gas, reduce the gas temperature, and meet the inlet temperature requirements of the turbine guide vane; the cooling holes 34 are evenly distributed on the flame tube wall in a staggered manner, and the inner and outer ring airflows pass through the cooling holes 34 to perform gas film cooling on the flame tube, protecting the flame tube so that its wall temperature is below the long-term allowable temperature of the material; the centrifugal nozzle 4 and the cyclone separator 5 are respectively provided.

[0020] The centrifugal nozzle 4 is a single-oil-path centrifugal nozzle, and a heat insulation cover made of high-temperature alloy is installed on the outside of the centrifugal nozzle housing to prevent nozzle ablation; the cyclone separator 5 is a single-stage axial cyclone separator, and the cyclone separator 5 adopts a strong swirling design to form a large-scale recirculation zone in the flame tube 3 to achieve ignition and flame stability.

[0021] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A DC combustion chamber for a small aero-engine adapted to a centrifugal compressor, characterized in that, It includes an outer casing, an inner casing, and a flame tube. A centrifugal nozzle is provided at the front end of the flame tube, a cyclone separator is provided around the flame tube, and a flame tube mounting edge is provided at the rear end of the flame tube. The outer casing and inner casing constitute the main structure of the combustion chamber, providing the internal space of the combustion chamber. They are connected to the engine compressor and turbine to transmit axial force. The flame tube, together with the outer casing and inner casing, forms the internal airflow channel of the combustion chamber, which divides the incoming airflow into three paths: the outer ring airflow, the flame tube internal airflow, and the inner ring airflow, for organizing combustion and cooling.

2. The DC combustion chamber for a small aero-engine adapted to a centrifugal compressor as described in claim 1, characterized in that, The centrifugal nozzle is a single-oil-path centrifugal nozzle. Its main function is to allow fuel to enter the nozzle and, under pressure, enter the swirling chamber. Under the combined action of pressure and centrifugal force, the fuel is ejected from the nozzle, broken up and atomized into fine liquid, which then enters the flame tube to mix with air for combustion. The swirler is a single-stage axial swirler. Its main function is to allow air to enter the flame tube through the swirler's air inlet. Under the action of viscosity and reverse pressure gradient, the air forms a reflux zone in the flame tube, which is used to organize combustion, achieve ignition, and stabilize the flame. The flame tube mounting edge is used to connect the flame tube and the turbine guide, achieving axial and circumferential positioning of the flame tube and transmitting axial force.

3. The DC combustion chamber for a small aero-engine adapted to a centrifugal compressor as described in claim 1, characterized in that, The flame tube is formed by welding thin-walled plates. The flame tube is provided with cyclone mounting holes, a first mixing hole, a second mixing hole, cooling holes, and nozzle mounting holes. The cyclone mounting holes are evenly spaced at 8-10 locations along the circumference of the flame tube, with a diameter of 35-37 mm. The cyclone is mounted on the flame tube through these mounting holes. The first mixing holes are evenly spaced at 28-35 locations along the circumference of the flame tube, with a diameter of 6.8-7.2 mm. The second mixing holes are evenly spaced at 12-25 locations along the circumference of the flame tube, with a diameter of 7.5-8.5 mm. The cooling holes have a diameter of 1.3-1.8 mm, a circumferential spacing angle of 4°-6°, and an axial spacing of 6-8 mm. The nozzle mounting holes are evenly spaced at 8-12 locations along the circumference of the flame tube, with a diameter of 11-13 mm. Centrifugal nozzles are mounted on the flame tube through these mounting holes.

4. A DC combustion chamber for a small aero-engine adapted to a centrifugal compressor as described in claim 1, characterized in that, The centrifugal nozzle is a single-path centrifugal nozzle with an outer diameter of 10~11mm and a flow rate FN of 10~15.

5. A DC combustion chamber for a small aero-engine adapted to a centrifugal compressor as described in claim 1, characterized in that, The first and second mixing holes are used to introduce inner and outer ring airflow into the flame tube, mix with the high-temperature gas, reduce the gas temperature, and meet the inlet temperature requirements of the turbine guide vane; the cooling holes are evenly distributed on the flame tube wall in a staggered manner, and the inner and outer ring airflow passes through the cooling holes to perform gas film cooling on the flame tube, protecting the flame tube so that its wall temperature is below the long-term allowable temperature of the material; the centrifugal nozzle and the cyclone separator are respectively provided.

6. A DC combustion chamber for a small aero-engine adapted to a centrifugal compressor as described in claim 1, characterized in that, The centrifugal nozzle is a single-oil-path centrifugal nozzle, and a heat insulation cover made of high-temperature alloy is installed on the outside of the centrifugal nozzle housing to prevent nozzle ablation; the cyclone is a single-stage axial cyclone, and the cyclone adopts a strong swirling design to form a large-scale recirculation zone in the flame tube to achieve ignition and flame stability.

7. A DC combustion chamber for a small aero-engine adapted to a centrifugal compressor as described in any one of claims 1 to 6, characterized in that, The flame tube is provided with positioning holes and cooling holes on its mounting side.

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