A corrugated pre-film nozzle for primary fuel injection in a low-pollution combustor

Abstract

The present invention relates to a corrugated pre-filming nozzle for primary fuel injection in a low-pollution combustor, belonging to the field of aero-engine combustion. A corrugated structure is added to a traditional pre-filming plate with a smooth surface. The corrugated structure has two configurations. One configuration is a corrugated structure uniformly distributed along the central axis of the annular pre-filming nozzle. The pre-filming plate with this configuration can promote the breakup of the liquid film, resulting in a decrease in the droplet size generated behind the pre-filming plate. The other configuration is a corrugated structure uniformly distributed along the circumferential direction of the annular pre-filming nozzle. The pre-filming plate with this structure can enhance the transverse unstable fluctuations on the liquid film surface, increasing the number of liquid bands generated by the breakup of the liquid film, shortening the spacing between the liquid bands, and making the droplets formed by further breakup of the liquid bands more uniformly distributed in the circumferential direction. The present invention can be applied to the low-pollution combustor of civil aero-engines and has good prospects for engineering applications.

Description

Technical Field

[0001] The present invention belongs to the field of aeroengine combustion, and particularly relates to a corrugated prefilm nozzle for primary fuel injection in a low-pollution combustor. Background Art

[0002] At present, the pollutants emitted by civil aeroengines into the atmosphere are increasing, and the air pollution is becoming increasingly serious. In order to control the impact of aircraft engine emissions on the environment, the pollution emission requirements of civil aircraft combustors need to meet the International Civil Aviation Organization (ICAO) CAEP standards, and the requirements for NOx emissions are becoming increasingly strict. At present, in civil aeroengine combustors, rich-burn / quick-quench / lean-burn technology, lean-premixed pre-vaporization and other low-pollution combustion technologies are often used to reduce NOx emissions of aeroengines. These low-pollution combustion technologies all require uniform mixing of fuel and air, and the degree of mixing of fuel and oxidizer determines the combustion stability, combustion efficiency and pollutant emissions. As one of the important components in aeroengine combustors, the nozzle shoulders this important task. As a kind of air atomizing nozzle, the prefilm nozzle has a relatively simple atomization process. The fuel first forms a liquid film through the prefilm channel, and the oil film is subjected to the shearing action of high-speed airflows on both sides to form unstable disturbances on the surface. These disturbances further cause the liquid film to fluctuate, and the liquid film fluctuations will increase with the propagation amplitude and lead to liquid film breakup to achieve atomization. Compared with centrifugal nozzles, the prefilm nozzle has better atomization effect under low operating conditions, can improve the combustion efficiency of the combustor, and greatly reduce the emissions of pollutants such as NOx and smoke. It can be applied to low-pollution aeroengine combustors and has good engineering application prospects.

[0003] In the prior art, the surface of the prefilm plate of the prefilm nozzle is a flat surface, and the oil film on the plate only forms unstable disturbances under the shearing action of high-speed airflows and the turbulence pulsation of the oil film itself, and gradually becomes unstable, thus breaking and atomizing. The fluctuation of the liquid film on the prefilm plate is greatly affected by the fuel flow rate. When the fuel flow rate is large, the fluctuation degree of the liquid film on the prefilm plate is weak, which will further affect the generation and breakup of the liquid band behind the prefilm plate, and the atomization quality will decrease under the condition of low air flow velocity. Summary of the Invention

[0004] In view of the above deficiencies of the prior art, the present invention provides a corrugated prefilm nozzle for primary fuel injection in a low-pollution combustor. A corrugated structure is added to the surface of a conventional prefilm plate with a smooth surface. The corrugated structure has two configurations. One configuration is a corrugated structure evenly distributed along the central axis of the corrugated prefilm nozzle. The corrugated prefilm plate with this configuration can promote the breakup of the liquid film, resulting in a decrease in the droplet size generated behind the corrugated prefilm plate. The other configuration is a corrugated structure evenly distributed along the circumferential direction of the corrugated prefilm nozzle. The corrugated prefilm plate with this structure can enhance the transverse unstable fluctuations on the liquid film surface, increasing the number of liquid bands generated by the breakup of the liquid film, shortening the spacing between the liquid bands, and making the droplets formed by the further breakup of the liquid bands more evenly distributed in the circumferential direction.

[0005] The technical solution proposed by the present invention to solve the above technical problems is as follows:

[0006] A corrugated prefilm nozzle for primary fuel injection in a low-pollution combustor, comprising a primary swirler, a secondary swirler and a tertiary swirler arranged inside it. It is characterized in that the primary swirler is a radial / axial swirler, and the secondary swirler and the tertiary swirler are axial swirlers. The installation direction of the blades of the primary swirler is opposite to that of the secondary swirler. The opposite aerodynamic effects are more conducive to improving the fuel atomization quality of the corrugated prefilm nozzle. The secondary swirler and the tertiary swirler are installed with the same or opposite rotation directions. Inside the wall surface between the primary swirler and the secondary swirler, there is a corrugated prefilm nozzle. The corrugated prefilm nozzle sequentially includes an injection rod, an oil collecting chamber, a fuel inner channel and a corrugated prefilm plate along the fuel flow direction.

[0007] Furthermore, the surface of the corrugated prefilm plate is provided with a corrugated structure. The corrugated prefilm plate has a total of two configurations, namely Configuration A and Configuration B. The corrugations in Configuration A are evenly distributed along the central axis of the corrugated prefilm nozzle. The corrugated prefilm plate with this configuration can promote the breakup of the liquid film, resulting in a decrease in the droplet size generated behind the corrugated prefilm plate. The corrugations in Configuration B are evenly distributed along the circumferential direction of the corrugated prefilm nozzle, and the corrugations extend to the trailing edge of the corrugated prefilm plate. The corrugated prefilm plate with this configuration enhances the transverse unstable fluctuations on the liquid film surface, increasing the number of liquid bands generated by the breakup of the liquid film, shortening the spacing between the liquid bands, and making the droplets formed by the further breakup of the liquid bands more evenly distributed in the circumferential direction.

[0008] Furthermore, the corrugated structure of the corrugated prefilm plate in Configuration A includes sine waves and triangular waves. The cross-section in the central axis direction of the corrugated prefilm plate in Configuration A is defined as the reference cross-section. The highest point of the corrugation on the reference cross-section is defined as the wave crest, and the lowest point of the corrugation is defined as the wave trough. The shortest straight-line distance between two adjacent wave crests is defined as the wavelength λ, and the vertical distance between an adjacent wave crest and wave trough is defined as the peak-to-peak value h.

[0009] Furthermore, define the starting position of the corrugation on the reference section as the starting point p1. The starting point p1 is the crest of the corrugation. Define the termination position of the corrugation as the termination point p2, and define the distance between the starting point p1 and the termination point p2 along the central axis direction of the corrugated prefilm nozzle as the length l of the corrugated prefilm plate. For the sine wave structure, the starting point p1 has a smooth transition tangent to the fuel inner channel wall surface, which is beneficial to the flow of fuel on the corrugated prefilm plate. The termination point p2 is the trough of the corrugation. For the sine wave structure, the termination point p2 has a smooth transition tangent to the trailing edge of the corrugated prefilm plate. The termination point p2 being the trough of the corrugation can effectively reduce the thickness of the trailing edge of the corrugated prefilm plate, effectively improve the situation of oil droplet accumulation caused by the entrainment of oil droplets in the recirculation zone behind the trailing edge, and further improve the atomization effect of the corrugated prefilm nozzle.

[0010] Furthermore, the number of crests and troughs of the corrugation are n1 and n2 respectively. The number of crests and troughs is equal, ranging from 4 to 10, and the number varies according to different working conditions. The wavelength λ of the corrugation is related to the number of crests and troughs and changes with the number of crests and troughs. The specific relationship is λ = l / n1. By changing the number of crests n1 and the peak-to-peak value h of the corrugated prefilm plate, the disturbance on the liquid film on the corrugated prefilm plate is enhanced, the amplitude of the liquid film fluctuation continuously increases, the fragmentation of the liquid film is promoted, and the droplet size generated behind the corrugated prefilm plate is reduced.

[0011] Furthermore, the corrugated structure of the corrugated prefilm plate of configuration B includes shapes such as sine waves and triangular waves. The corrugated structure is periodically distributed along the circumferential direction. The central angle corresponding to a single corrugated structure is α, where 1.5° ≤ α ≤ 20° and α is a positive divisor of 360°. The number of corrugations on the entire corrugated prefilm plate is n3, and n3 is related to the central angle α corresponding to a single corrugated structure and changes with the size of α. The specific relationship is n3 = 360° / α. By changing the number of corrugations n3 on the corrugated prefilm plate, the lateral unstable fluctuation on the liquid film surface is enhanced, the number of liquid bands generated by the fragmentation of the liquid film increases, the droplet size generated behind the corrugated prefilm plate is reduced, the distance between the liquid bands is shortened, and the droplets further fragmented from the liquid bands are more evenly distributed in the circumferential direction. This corrugated prefilm nozzle avoids the phenomenon of fuel concentration behind the primary nozzle, improves the temperature distribution, and thus effectively reduces the generation amount of primary NOx.

[0012] The beneficial effects of the present invention compared with the prior art are as follows:

[0013] Adding a corrugated structure to a traditional prefilm plate with a smooth surface, there are two configurations for the corrugated structure. One configuration is a corrugated structure evenly distributed along the central axis of the corrugated prefilm nozzle. The corrugated prefilm plate with this configuration can promote the breakup of the liquid film, reducing the droplet size generated behind the corrugated prefilm plate. The other configuration is a corrugated structure evenly distributed along the circumferential direction of the corrugated prefilm nozzle. The corrugated prefilm plate with this structure can enhance the lateral unstable fluctuations on the liquid film surface, increasing the number of liquid bands generated by the breakup of the liquid film, shortening the spacing between the liquid bands, and making the droplets formed by the further breakup of the liquid bands more evenly distributed in the circumferential direction. The corrugated prefilm plates with both configurations can more effectively promote the liquid film atomization process of the corrugated prefilm nozzle, making the droplet size generated behind the corrugated prefilm plate smaller and more evenly distributed, thereby improving the combustion efficiency under low operating conditions of the combustion chamber and greatly reducing the emissions of pollutants such as NOx and smoke. In the future, it can be applied to low-pollution combustion chambers of civil aviation engines and has good engineering application prospects. Description of the Drawings

[0014] Figure 1 Cross-sectional view of the head of a low-pollution combustion chamber with a corrugated prefilm nozzle in the present invention;

[0015] Figure 2 Corrugated prefilm plates of configurations A and B in the corrugated prefilm nozzle for primary fuel injection in the low-pollution combustion chamber of the present invention;

[0016] Figure 3 Schematic diagram of a typical type of the corrugated prefilm plate of configuration A in the corrugated prefilm nozzle for primary fuel injection in the low-pollution combustion chamber of the present invention;

[0017] Figure 4 Schematic diagram of a typical type of the corrugated prefilm plate of configuration B in the corrugated prefilm nozzle for primary fuel injection in the low-pollution combustion chamber of the present invention;

[0018] Figure 5 Structural schematic diagram of the corrugated prefilm plate of configuration A in the corrugated prefilm nozzle for primary fuel injection in the low-pollution combustion chamber of the present invention;

[0019] Figure 6 Structural schematic diagram of the corrugated prefilm plate of configuration B in the corrugated prefilm nozzle for primary fuel injection in the low-pollution combustion chamber of the present invention;

[0020] Wherein: 1 - tertiary swirler, 2 - secondary swirler, 3 - corrugated prefilm nozzle, 4 - primary swirler, 5 - fuel injection rod, 6 - oil collecting chamber, 7 - fuel inner channel, 8 - corrugated prefilm plate. Detailed Embodiment

[0021] To make the objectives and effects of the present invention clearer and more definite, the present invention will be further described in detail below with reference to the accompanying drawings. It should be noted that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] As Figure 1 shown, it is a schematic diagram of the low-pollution combustor head structure with the corrugated pre-filming nozzle 3 of the present invention, including a primary swirler 4, and a secondary swirler 2 and a tertiary swirler 1 arranged inside it. The primary swirler 4 is equipped with radial / axial swirling vanes, which are evenly distributed along the circumferential direction of the primary swirler 4. Axial swirling vanes are installed on the secondary swirler 2 and the tertiary swirler 1, and the secondary swirler 2 and the tertiary swirler 1 are installed in the same / opposite swirling direction.

[0023] Inside the wall between the primary swirler 4 and the secondary swirler 2, there is a corrugated pre-filming nozzle 3. The corrugated pre-filming nozzle 3 sequentially includes an injection rod 5, an oil collecting cavity 6, a fuel inner channel 7, and a corrugated pre-filming plate 8 along the fuel flow direction.

[0024] The present invention is provided with a corrugated structure on the surface of the corrugated pre-filming plate 8. As Figure 2 shown, there are two configurations, A and B, for the corrugated pre-filming plate 8. As Figure 3 shown, the corrugations of configuration A are evenly distributed along the central axis direction of the corrugated pre-filming nozzle 3, including waveform structures such as sine waves and triangular waves. As Figure 4 shown, the corrugations of configuration B are evenly distributed along the circumferential direction of the corrugated pre-filming nozzle 3, and the corrugations extend to the trailing edge of the corrugated pre-filming plate 8, including shapes such as sine waves and triangular waves.

[0025] As Figure 5 shown, the cross-section in the central axis direction of the corrugated pre-filming plate 8 of configuration A is defined as the reference cross-section. The highest point of the corrugation on the reference cross-section is defined as the wave crest, and the lowest point of the corrugation is defined as the wave trough. The shortest straight-line distance between two adjacent wave crests is defined as the wavelength λ, and the vertical distance between an adjacent wave crest and wave trough is defined as the peak-to-peak value h. The starting position of the corrugation on the reference cross-section is defined as the starting point p1. The starting point p1 is the wave crest of the corrugation, the termination position of the corrugation is defined as the termination point p2, the termination point p2 is the wave trough of the corrugation, and the distance between the starting point p1 and the termination point p2 along the central axis direction of the corrugated pre-filming nozzle 3 is defined as the length l of the corrugated pre-filming plate 8. The numbers of wave crests and wave troughs of the corrugation are n1 and n2 respectively. The wavelength λ of the corrugation is related to the numbers of wave crests and wave troughs and changes with the numbers of wave crests and wave troughs. The specific relationship is λ = l / n1. By changing the number of wave crests n1 and the peak-to-peak value h of the corrugated pre-filming nozzle 3, the disturbance of the liquid film on the corrugated pre-filming plate 8 is enhanced, the amplitude of the liquid film fluctuation is continuously increased, the breakup of the liquid film is promoted, and the droplet size generated behind the corrugated pre-filming plate 8 is reduced.

[0026] As Figure 6For the corrugated prefilm plate 8 in Configuration B as shown, the corrugated structure is periodically distributed in the circumferential direction, and the central angle corresponding to a single corrugated structure is α. The number of corrugations on the entire corrugated prefilm plate 8 is n3, and n3 is related to the central angle α corresponding to a single corrugated structure and changes with the size of α. The specific relationship is n3 = 360° / α. By changing the number of corrugations n3 on the corrugated prefilm plate 8, the lateral unstable fluctuations on the liquid film surface are enhanced, so that the number of liquid bands generated by the fragmentation of the liquid film increases, the droplet size generated after the corrugated prefilm plate 8 decreases, the distance between the liquid bands shortens, and the droplets further fragmented from the liquid bands are more evenly distributed in the circumferential direction. This corrugated prefilm nozzle 3 avoids the phenomenon of fuel concentration behind the primary nozzle, improves the temperature distribution, and thus effectively reduces the generation amount of primary NOx.

[0027] The working process of the present invention:

[0028] The primary fuel enters the oil collecting chamber 6 through the fuel injection rod 5. The oil collecting chamber 6 plays a buffering role to make the fuel flow more evenly in the circumferential direction. After being buffered by the oil collecting chamber 6, the fuel enters the fuel inner channel 7. The fuel flows out to the corrugated prefilm plate 8, and the fuel forms a uniform thin oil film on the corrugated prefilm plate 8 and is exposed to the high-speed air flow generated by the primary swirler 4. Due to the velocity difference between the liquid film and the rotating air flow, there is momentum exchange between the two fluids. The liquid film is subjected to the action of the air flow shear force, and unstable perturbations are formed on the surface. These perturbations further cause the liquid film to fluctuate, and the amplitude of the liquid film fluctuation will continuously increase with propagation, and finally the liquid film breaks to form droplets.

[0029] The corrugations on the surface of the corrugated prefilm plate 8 can further enhance the perturbations received by the liquid film on the corrugated prefilm plate 8. Among them, the corrugated structures uniformly distributed along the central axis direction of the corrugated prefilm nozzle 3 can enhance the unstable fluctuations of the liquid film along the flow direction on the corrugated prefilm plate 8, promote the fragmentation of the liquid film, and make the droplet size generated after the corrugated prefilm plate 8 decrease; while the corrugated structures uniformly distributed along the circumferential direction of the corrugated prefilm nozzle 3 can enhance the lateral unstable fluctuations on the liquid film surface, so that the number of liquid bands generated by the fragmentation of the liquid film increases, the distance between the liquid bands shortens, and the droplets further fragmented from the liquid bands are more evenly distributed in the circumferential direction.

[0030] By arranging corrugations of various configurations on the corrugated prefilm plate 8, the atomization effect of the corrugated prefilm nozzle 3 can be further improved, the combustion efficiency under low load conditions of the combustion chamber can be significantly increased, and the emissions of pollutants such as NOx and smoke can be greatly reduced.

[0031] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements can still be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A corrugated pre-film type nozzle for primary fuel injection in a low-pollution combustor, characterized in that, It includes a primary cyclone (4), and a secondary cyclone (2) and a tertiary cyclone (1) are arranged inside the primary cyclone (4); A corrugated pre-filming nozzle (3) is arranged inside the wall surface between the primary cyclone (4) and the secondary cyclone (2); The corrugated pre-filming nozzle (3) sequentially includes an injection rod (5), an oil collecting cavity (6), a fuel inner channel (7), and a corrugated pre-filming plate (8) along the fuel flow direction; Two different configurations of corrugated structures are provided on the surface of the corrugated pre-filming plate (8), namely Configuration A and Configuration B; In Configuration A, the corrugations are evenly distributed along the central axis of the corrugated pre-filming nozzle (3); In Configuration B, the corrugations are evenly distributed along the circumferential direction of the corrugated pre-filming nozzle (3), and the corrugations extend to the trailing edge of the corrugated pre-filming plate (8); The corrugated pre-filming plate (8) with Configuration A can promote the breakup of the liquid film, so that the droplet size generated after the corrugated pre-filming plate (8) is reduced; The corrugated pre-filming plate (8) with Configuration B can enhance the transverse unstable fluctuations on the liquid film surface, so that the number of liquid bands generated by the breakup of the liquid film increases, the spacing between the liquid bands is shortened, and the droplets formed by the further breakup of the liquid bands are more evenly distributed in the circumferential direction; In the corrugated pre-filming plate (8) with Configuration A, its corrugated structure includes the shapes of a sine wave (300) and a triangular wave (301); The number of wave crests and wave troughs of the corrugations are n1 and n2 respectively; The number of wave crests and wave troughs being equal is 4 - 10, and the number varies according to different working conditions; The wavelength λ of the corrugations is related to the number of wave crests and wave troughs and changes with the number of wave crests and wave troughs. The specific relationship is λ = l / n1 or λ = l / n2; In the corrugated pre-filming plate (8) with Configuration B, its corrugated structure includes the shapes of a sine wave (300) and a triangular wave (301); The corrugated structure is periodically distributed along the circumferential direction, and the central angle corresponding to a single corrugated structure is α, 1.5° ≤ α ≤ 20° and α is a positive divisor of 360°; The number of corrugations on the entire corrugated pre-filming plate (8) is n3, and n3 is related to the central angle α corresponding to a single corrugated structure and changes with the size of α. The specific relationship is n3 = 360° / α.

2. The corrugated pre-film nozzle for primary fuel injection in a low-pollution combustor according to claim 1, characterized in that, The working process of the corrugated pre-filming nozzle (3) is as follows: The main fuel enters the oil collecting cavity (6) through the injection rod (5), the fuel enters the fuel inner channel (7) after being buffered by the oil collecting cavity (6), the fuel flows out to the corrugated pre-filming plate (8), and the fuel forms a uniform thin oil film on the corrugated pre-filming plate (8) and is exposed to the high-speed air flow generated by the primary cyclone (4); Due to the velocity difference between the liquid film and the rotating air flow, there is momentum exchange between the two fluids, the liquid film is subjected to the action of the air flow shear force, and unstable disturbances are formed on the surface. These disturbances further cause the liquid film to fluctuate, and the amplitude of the liquid film fluctuation will continuously increase with propagation, and finally lead to the breakup of the liquid film to form droplets; The corrugations on the surface of the corrugated pre-filming plate (8) further enhance the disturbances received by the liquid film on the plate. Among them, Configuration A evenly distributed along the central axis direction of the corrugated pre-filming nozzle (3) enhances the unstable fluctuations of the liquid film along the flow direction on the corrugated pre-filming plate (8); The atomization effect of the corrugated prefilm nozzle (3) is improved by arranging corrugations with various configurations on the corrugated prefilm plate (8).

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