Low-emission center staged combustion chamber based on subcritical / supercritical kerosene mixed combustion

Abstract

The invention discloses a low-emission center staged combustion chamber based on subcritical / supercritical kerosene mixed combustion, and relates to the technical field of aero-engines, the key part of the low-emission center staged combustion chamber is composed of a pre-combustion stage, a main combustion stage and an oil supply support, and the pre-combustion stage comprises a first-stage axial swirler, a second-stage axial swirler, a convergent-divergent spray pipe, a divergent spray pipe, a centrifugal spray nozzle and a direct-injection spray nozzle; the main combustion stage comprises a three-stage radial swirler, a four-stage axial swirler, a coaxial nozzle, a combustion chamber head shell and a boss. The system is characterized in that the main combustion stage is closed under the slow working condition of an engine, and supercritical kerosene is combusted in the pre-combustion stage; according to the combustion organization mode that subcritical kerosene is combusted in the pre-combustion stage and supercritical kerosene is combusted in the main combustion stage under the full-power working condition of the engine, a high-efficiency combustion mode with high temperature rise and low pollutant emission is achieved, and excellent lean oil ignition performance is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of aviation engines, in particular to a low-emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion. Background Art

[0002] The center-staged combustion chamber is a partitioned and graded combustion chamber. The common configuration is that the flame tube head is coaxially nested with the pre-combustion stage and the main combustion stage. The pre-combustion stage can be opened separately when the engine is in the slow-running state, and plays a role in flame stabilization when the main combustion stage is working; while the main combustion stage works when the aircraft engine is running at high power, the combustion area of ​​the pre-combustion stage will interact with the main combustion stage flame, which can improve the combustion efficiency. The characteristic of the center-staged combustion chamber is that it broadens the stable working range of the combustion chamber, can stably burn in a high oil-gas ratio environment, and reduces the emission of pollutants such as NOx, meeting the future design requirements for high temperature rise of military aircraft engines / low pollution of civil aircraft engines.

[0003] With the development goal of "two highs and one wide" for future aircraft engines, aircraft will operate in the high-speed domain of 3.5-5Ma. At this time, the total temperature of the air will be very high, and the working efficiency of traditional compressors will be reduced at high temperatures. In response to this situation, the concept of "air pre-cooling" was proposed. This cooling method uses the fuel carried by the aircraft itself as a cooling medium to cool the air flowing through the compressor. While improving the working efficiency of the compressor, it also brings this part of the heat into the combustion chamber, making the temperature rise at the combustion chamber outlet higher, while meeting the design requirements for high temperature rise of military aircraft engines. Therefore, using supercritical kerosene as fuel is the future development trend of aircraft engines. Summary of the invention

[0004] The purpose of the present invention is to provide a low-emission central staged combustion chamber based on sub / supercritical kerosene mixed combustion, which can take into account high combustion efficiency, flame stability, low pollutant emissions, and the needs of air precooling-fuel supercritical injection during future aircraft hypersonic flight.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a low-emission center-staged combustion chamber based on sub- / supercritical kerosene mixed combustion, characterized in that it includes a combustion chamber head, which is composed of a pre-combustion stage, a main combustion stage and an oil supply bracket. The pre-combustion stage includes a pre-combustion stage central column, and the pre-combustion stage central column is coaxially sleeved with a convergent nozzle outside. The convergent nozzle is from left to right: a contraction section with an inclination of 45° on the left side, a straight section in the middle and a waist section on the right side. A first-level axial swirler is sandwiched between the left end of the straight section in the middle of the convergent nozzle and the pre-combustion stage central column. The annular area surrounded by the pre-combustion stage central column and the convergent nozzle is the first air inlet; similarly, a gradually expanding nozzle is coaxially sleeved outside the convergent nozzle, the rightmost side of the gradually expanding nozzle is an expansion section, and the middle part is a straight section. A second-level axial swirler is installed between the leftmost side of the gradually expanding nozzle and the contraction section of the convergent nozzle, and the annular area surrounded by the gradually expanding nozzle and the convergent nozzle is the second air inlet. The above-mentioned main combustion stage includes a main combustion stage main ring, which is an annular structure with a cross-section that is approximately circular on the left side and square on the upper right side. A boss is coaxially provided on the upper right part of the main combustion stage main ring, and the boss is an annular structure with a cross-section that is approximately L-shaped. A three-stage radial swirler is sandwiched between the right side of the main combustion stage main ring and the lower left side of the boss, and the zigzag area surrounded by the main combustion stage main ring and the boss is the third air inlet; similarly, a combustion chamber head shell is coaxially provided on the outside of the boss, and the cross-section of the combustion chamber head shell is a right-angled trapezoid, wherein the left side of the combustion chamber head shell is parallel to the axial direction and the right side is an expansion section, a four-stage axial swirler is installed between the inner side of the combustion chamber head shell and the outer side of the boss, and the annular area surrounded by the combustion chamber head shell and the boss is the fourth air inlet. The above-mentioned oil supply bracket includes a first oil supply pipeline for the pre-combustion stage, a second oil supply pipeline for the pre-combustion stage and a main combustion stage oil supply pipeline. The lower ends of the first oil supply pipeline for the pre-combustion stage and the second oil supply pipeline for the pre-combustion stage respectively lead to the central column of the pre-combustion stage, and the main combustion stage oil supply pipeline is connected to the main ring of the main combustion stage after turning to the right; the first oil supply pipeline for the pre-combustion stage, the second oil supply pipeline for the pre-combustion stage and the main combustion stage oil supply pipeline are forked at the top of the oil supply bracket, and a threaded interface is provided at the top thereof.

[0006] Furthermore, the main combustion stage is coaxially sleeved outside the pre-combustion stage, and together they form the combustion chamber head. Furthermore, the aircraft engine has two operating conditions: slow and full power. When in the slow operating condition, the main combustion stage is closed and the pre-combustion stage injects supercritical kerosene; when in the full power operating condition, the pre-combustion stage injects subcritical kerosene and the main combustion stage injects supercritical kerosene.

[0007] Furthermore, six centrifugal nozzles are symmetrically installed along the axis of symmetry inside the right side of the pre-combustion stage central column, and the side surfaces of the centrifugal nozzles are connected to the first oil supply pipeline of the pre-combustion stage through a capillary, and the first oil supply pipeline of the pre-combustion stage is coaxial with the central column of the pre-combustion stage; twelve direct-injection nozzles are opened on the circumference of the outer side of the central column of the pre-combustion stage, and an oil dividing ring is arranged inside the central column of the pre-combustion stage, and the oil dividing ring is an annular structure with an internal hollow and communicated with the bottom of the above-mentioned direct-injection nozzle, and the oil dividing ring is coaxial with the first oil supply pipeline of the pre-combustion stage and is sleeved on the outside of the first oil supply pipeline of the pre-combustion stage, and the second oil supply pipeline of the pre-combustion stage is connected to one side of the oil dividing ring after entering the central column of the pre-combustion stage.

[0008] Furthermore, the right side surface of the main ring of the main combustion stage shrinks inward to form a two-layer platform and twelve pairs of coaxial nozzles are installed therein. The coaxial nozzle is divided into an outer cavity and an inner cavity. An oil dividing ring is also provided inside the main ring of the main combustion stage. The oil dividing ring is an internally hollow annular structure, one end of which is connected to the inner cavity of the coaxial nozzle, and the other end extends to the outside of the main ring of the main combustion stage and leads to the main combustion stage oil supply pipeline; a coaxial nozzle air inlet gap is provided on the upper surface of the main ring of the main combustion stage to connect the third air inlet duct with the outer cavity of the coaxial nozzle.

[0009] Furthermore, the cross section of the left half of the boss is a long strip parallel to the axis of symmetry, and the right half is provided with impact holes, impact cavities and air film holes from left to right, the impact holes are connected to the inner wall of the boss on the left side and lead to the impact cavity on the right side, and the impact cavity is provided with air film holes and leads to the right surface of the boss. Furthermore, the upper right corner of the boss is a protruding acute angle.

[0010] Furthermore, a gas collecting cavity is provided between the gradually diverging nozzle and the main ring of the main combustion stage, the gas collecting cavity is narrow and long and extends to the inside of the gradually diverging nozzle, and a plurality of gas film holes are opened on the inner wall of the gas collecting cavity near the gradually diverging nozzle. Furthermore, the spacing between the gas film holes is five times the diameter of the gas film holes, and the opening direction of the gas film holes is parallel to the axis of the symmetry axis.

[0011] Furthermore, the first and second stage cyclone blades adopt a rotation direction combination of +45° / -45° (clockwise facing the flow direction is positive), and the first and second stage swirl numbers are 0.78 and 0.88 respectively, which are strong swirl types; the third and fourth stage cyclone blades adopt a rotation direction combination of +45° / +60°, and the third and fourth stage swirl numbers are 0.36 and 0.60 respectively, which are weak swirl types.

[0012] Furthermore, a flame tube is sleeved on the outside of the combustion chamber head, the flame tube has a plurality of mixing holes and the left end of the flame tube is stuck in the slot on the combustion chamber head shell, the flame tube is sleeved on the outside of the central staged combustion chamber shell and forms a ring combustion chamber with it in three dimensions, a diffuser is provided on the left end of the central staged combustion chamber shell, the diffuser penetrates the central staged combustion chamber shell to the right and extends to the inside thereof, and the left side of the diffuser is an air intake composed of a first-stage compressor, a second-stage compressor, and a first-stage precooler. Furthermore, a high-energy spark plug is installed from the outside of the central staged combustion chamber shell, and the high-energy spark plug penetrates the central staged combustion chamber shell and the flame tube respectively until it extends to the vicinity of the combustion chamber head.

[0013] Furthermore, a compressor bleed air duct is provided between the second-stage compressor and the diffuser, and the compressor bleed air duct leads to the turbine for turbine cooling; the turbine is located at the right side outlet of the central staged combustion chamber casing, and the drive shaft on the turbine is connected to the generator through a gear set.

[0014] Furthermore, the present invention also includes a fuel tank, in which an outlet pipeline leads to an oil pump, and a pipeline at the outlet of the oil pump is bifurcated into a subcritical kerosene pipeline and a supercritical kerosene pipeline, and a subcritical kerosene pipeline stop valve and a supercritical kerosene pipeline stop valve are respectively provided thereon, wherein the subcritical kerosene pipeline directly extends into the central staged combustion chamber shell, and is connected to the first pre-combustion stage oil supply pipeline through a threaded interface; and the supercritical kerosene pipeline leads to the inlet of the first-stage precooler, and the first-stage precooler outlet is connected to the three-way valve through a pipeline, and the outlet pipeline on the left side of the three-way valve passes through the electric heating pipe, passes through the central staged combustion chamber shell and is connected to the second pre-combustion stage oil supply pipeline through a threaded interface; the right side of the three-way valve is connected to the compressor bleed air precooler through a pipeline, and the compressor bleed air precooler is placed in the compressor bleed air pipe inlet, and the compressor bleed air precooler outlet is connected to the threaded interface at the top of the main combustion stage oil supply pipeline through a pipeline.

[0015] Compared with the prior art, the low-emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion provided by the present invention has the following beneficial effects:

[0016] 1. For the central staged combustion chamber under full power conditions, an innovative combustion organization mode of pre-combustion stage combustion of subcritical kerosene and main combustion stage combustion of supercritical kerosene is adopted, which utilizes the advantages of high temperature rise, low pollution emission, uniform distribution of combustion chamber outlet temperature and high combustion efficiency brought by supercritical kerosene combustion. A small amount of subcritical kerosene burned in the pre-combustion stage can interact with the main combustion stage flame, thereby achieving a flame stabilization effect, which makes the combustion chamber have better lean oil ignition performance than pure supercritical combustion.

[0017] Second, for the slow-running condition of the center-stage combustion chamber, the innovative combustion organization mode of the main combustion stage not working and the pre-combustion stage burning supercritical kerosene is adopted. The gradual expansion nozzle pressure expansion, the direct-injection nozzle spraying perpendicular to the airflow direction of the first inlet, the first and second swirler blades rotating in opposite directions and other methods are used together to strengthen the supercritical kerosene mixing and ensure the flame stability, overcoming the shortcoming of the poor flame stability performance of the combustion chamber under supercritical combustion. The characteristics of supercritical kerosene combustion with high combustion efficiency and low pollution emissions are used to reduce the unburned hydrocarbon emissions of aircraft under slow-running conditions such as takeoff and landing, and reduce the pollution to the air around the airport, so as to meet the increasingly stringent pollutant emission regulations of the civil aviation industry.

[0018] 3. Under the condition of low kerosene mass flow rate in slow running condition, the present invention innovatively adopts a two-stage heating method, which first uses the first-stage precooler to exchange the waste heat generated in the working process of the compressor to heat the kerosene to the transcritical temperature, and then uses the electric heating tube to further accurately control the temperature of the kerosene to the supercritical temperature. This method helps to reduce the time that the kerosene stays at the supercritical temperature and avoids heating the kerosene to too high a temperature, thereby suppressing the shortcoming that supercritical kerosene is easy to coke at high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a cross-sectional schematic diagram of the combustion chamber head in the present invention;

[0020] Figure 2 For the present invention Figure 1 A schematic diagram of the enlarged cross section of the middle part A;

[0021] Figure 3 For the present invention Figure 1 The enlarged cross-sectional diagram of the middle B part;

[0022] Figure 4 It is a cross-sectional schematic diagram of the central staged combustion chamber in the present invention;

[0023] Figure 5 It is a schematic diagram of the overall structure of the present invention;

[0024] Figure 6 This is a working principle diagram of specific embodiment 1 of the present invention;

[0025] Figure 7 This is a working principle diagram of specific embodiment 2 of the present invention;

[0026] Figure 8 The figure is a relationship diagram between the fuel-air flow rate and the ignition result of the comparative example 1 of the present invention;

[0027] Fig. 9 The figure is a relationship diagram between the oil-gas ratio and the ignition result of the comparative example 1 of the present invention;

[0028] Fig.10The figure is a relationship diagram between the oil-gas ratio and the ignition result of the comparative example 2 of the present invention;

[0029] Fig.11 The figure is a relationship diagram between the oil-gas ratio and the ignition result of the specific embodiment 1 of the present invention;

[0030] Fig.12 This is a graph showing the relationship between the oil-gas ratio and the ignition result in the specific embodiment 2 of the present invention;

[0031] In the figure: 1. combustion chamber head; 11. centrifugal nozzle; 12. direct nozzle; 13. coaxial nozzle; 14. slot; 15. oil supply bracket; 16. first oil supply pipeline of pre-combustion stage; 17. second oil supply pipeline of pre-combustion stage; 18. oil supply pipeline of main combustion stage; 19. oil distribution ring; 2. pre-combustion stage; 21. first axial swirler; 22. second axial swirler; 23. convergent nozzle; 24. divergent nozzle; 25. center column of pre-combustion stage; 26. first air inlet; 27. second air inlet; 28. gas collecting cavity; 29. ​​air film hole; 3. main combustion stage; 31. third radial swirler; 32. fourth axial swirler; 33. third air inlet; 34. fourth air inlet; 35. main ring of main combustion stage; 36. boss; 37. impact hole; 38. impact cavity ;39. Combustion chamber head shell;41. Diffuser;42. Subcritical kerosene pipeline;43. Supercritical kerosene pipeline;44. Coaxial nozzle bleed air slit;45. Threaded interface;46. Flame tube;47. Mixing hole;48. Center-staged combustion chamber shell;49. High-energy spark plug;51. First-stage compressor;52. Second-stage compressor;53. First-stage precooler;54. Fuel tank;55. Compressor bleed air precooler;56. Electric heating pipe;57. Generator;58. Oil pump;59. Three-way valve;61. Turbine;62. Compressor bleed air pipe;63. Subcritical kerosene pipeline stop valve;64. Supercritical kerosene pipeline stop valve;a. Pre-combustion stage flame existence area;b. Main combustion stage flame existence area;c. Main combustion stage and pre-combustion stage flame interaction area. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In the description of the invention, it should be noted that the terms "inside", "outside", "up", "down", "left", "right", "horizontal", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the invention.

[0034] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, it can be connected through a pipeline, or it can be an electrical connection; it can be directly connected, it can be indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] Please refer to Figure 1 A low-emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion, characterized in that it includes a combustion chamber head 1, which is composed of a pre-combustion stage 2, a main combustion stage 3 and an oil supply bracket 15. The pre-combustion stage 2 includes a pre-combustion stage center column 25, and a convergent-divergent nozzle 23 is coaxially sleeved on the outside of the pre-combustion stage center column 25. The convergent-divergent nozzle 23 is composed of: a contraction section with an inclination of 45° on the left side, a straight section in the middle and a waist section on the right side, and a first-level axial swirler 21 is sandwiched between the left end of the straight section in the middle of the convergent-divergent nozzle 23 and the pre-combustion stage center column 25. The annular area surrounded by the pre-combustion stage center column 25 and the convergent-divergent nozzle 23 is the first air inlet duct 26; similarly, a gradually divergent nozzle 24 is coaxially sleeved on the outside of the convergent-divergent nozzle 23, and the rightmost side of the gradually divergent nozzle 24 is an expansion section and the middle part is a straight section. A second-level axial swirler 22 is installed between the leftmost side of the gradually divergent nozzle 24 and the contraction section of the convergent-divergent nozzle 23, and the annular area surrounded by the gradually divergent nozzle 24 and the convergent-divergent nozzle 23 is the second air inlet duct 27.

[0036] The above-mentioned main combustion stage 2 includes a main combustion stage main ring 35, which is an annular structure with an approximately circular left side and a square upper right side. A boss 36 is coaxially arranged on the upper right part of the main combustion stage main ring 35, and the boss 36 is an annular structure with an approximately L-shaped cross section. A three-stage radial swirler 31 is sandwiched between the right side of the main combustion stage main ring 35 and the lower left side of the boss 36, and the zigzag area surrounded by the main combustion stage main ring 35 and the boss 36 is the third air inlet 33; similarly, a combustion chamber head shell 39 is coaxially arranged outside the boss 36, and the cross-section of the combustion chamber head shell 29 is a right-angled trapezoid, wherein the left side of the combustion chamber head shell 39 is parallel to the axial direction, and the right side is an expansion section, and a four-stage axial swirler 32 is installed between the inner side of the combustion chamber head shell 39 and the outer side of the boss 36, and the annular area surrounded by the combustion chamber head shell 39 and the boss 36 is the fourth air inlet 34.

[0037] The above-mentioned oil supply bracket 15 includes a first pre-combustion stage oil supply pipeline 16, a second pre-combustion stage oil supply pipeline 17 and a main combustion stage oil supply pipeline 18. The lower ends of the first pre-combustion stage oil supply pipeline 16 and the second pre-combustion stage oil supply pipeline 17 lead to the pre-combustion stage center column 25 respectively, and the main combustion stage oil supply pipeline 18 is connected to the main combustion stage main ring 35 after turning to the right; the first pre-combustion stage oil supply pipeline 16, the second pre-combustion stage oil supply pipeline 17 and the main combustion stage oil supply pipeline 18 are forked at the top of the oil supply bracket 15, and a threaded interface 45 is provided at the top thereof.

[0038] Furthermore, the main combustion stage 3 is coaxially sleeved outside the pre-combustion stage 2. Furthermore, the aircraft engine has two operating conditions, idling and full power. When in the idling condition, the main combustion stage 3 is closed and the pre-combustion stage 2 injects supercritical kerosene; when in the full power condition, the pre-combustion stage 2 injects subcritical kerosene and the main combustion stage 3 injects supercritical kerosene.

[0039] Please refer to Figure 2 Six centrifugal nozzles 11 are symmetrically installed along the axis of symmetry inside the right side of the pre-combustion stage central column 25, and the side of the centrifugal nozzle 11 is connected to the first oil supply pipeline 16 of the pre-combustion stage through a capillary, and the first oil supply pipeline 16 of the pre-combustion stage is coaxial with the pre-combustion stage central column 25; twelve direct-injection nozzles 12 are arranged on the outer circumference of the pre-combustion stage central column 25, and an oil separator 19 is arranged inside the pre-combustion stage central column 25. The oil separator 19 is an annular structure with an internal hollow and is connected to the bottom of the above-mentioned direct-injection nozzle 12, and the oil separator 19 is coaxial with the first oil supply pipeline 16 of the pre-combustion stage and is sleeved on the outside of the first oil supply pipeline 16 of the pre-combustion stage, and the second oil supply pipeline 17 of the pre-combustion stage is connected to one side of the oil separator 19 after entering the pre-combustion stage central column 25.

[0040] Please refer to Figure 3The right side surface of the main combustion stage main ring 35 shrinks inward to form a two-layer platform and twelve pairs of coaxial nozzles 13 are installed therein. The coaxial nozzles 13 are divided into an outer cavity and an inner cavity. An oil dividing ring 19 is also arranged inside the main combustion stage main ring 35. The oil dividing ring 19 is an internally hollow annular structure, one end of which is connected to the inner cavity of the coaxial nozzle 13, and the other end extends to the outside of the main combustion stage main ring 35 and leads to the main combustion stage oil supply pipeline 18; a coaxial nozzle air inlet slit 44 is arranged on the upper surface of the main combustion stage main ring 35 to connect the third air inlet duct 33 with the outer cavity of the coaxial nozzle 13.

[0041] Furthermore, the cross section of the left half of the boss 36 is a long strip parallel to the axis of symmetry, and the right half is provided with an impact hole 37, an impact cavity 38 and an air film hole 29 from left to right. The left side of the impact hole 37 is connected to the inner wall of the boss 36 and the right side leads to the impact cavity 38. The impact cavity 38 is provided with an air film hole 29 and leads to the right surface of the boss 36. Furthermore, the upper right corner of the boss 36 is a protruding acute angle, which helps to reduce the flow resistance, construct a reflow zone for flame stabilization on the right side surface of the boss 36, and deflect the airflow in the fourth air inlet 34 to make it flow upward.

[0042] Furthermore, a gas collecting cavity 28 is provided between the gradually diverging nozzle 24 and the main ring 35 of the main combustion stage. The gas collecting cavity 28 is long and narrow and extends to the inside of the gradually diverging nozzle 24, and a plurality of gas film holes 29 are opened on the inner wall of the gas collecting cavity 28 on the side close to the gradually diverging nozzle 24. Furthermore, the spacing between the gas film holes 29 is five times the diameter thereof, and the opening direction of the gas film holes 29 is parallel to the axis of the symmetry axis.

[0043] Furthermore, the blades of the first-stage axial cyclone 21 and the second-stage axial cyclone 22 adopt a rotation direction combination of +45° / -45° (clockwise facing the flow direction is positive), and the first and second-stage swirl numbers are 0.78 and 0.88 respectively, which belong to the strong swirl type; the blades of the third-stage radial cyclone 31 and the fourth-stage axial cyclone 32 adopt a rotation direction combination of +45° / +60°, and the third and fourth-stage swirl numbers are 0.36 and 0.60 respectively, which belong to the weak swirl type.

[0044] Please refer to Figure 4The outer side of the combustion chamber head 1 is covered with a flame tube 46, which has a plurality of mixing holes 47 and the left end of the flame tube 46 is stuck in the slot 14 on the combustion chamber head shell 39. The outer side of the flame tube 46 is covered with a central staged combustion chamber shell 48 and forms a ring combustion chamber with it in three dimensions. The left end of the central staged combustion chamber shell 48 is provided with a diffuser 41, which penetrates the central staged combustion chamber shell 48 to the right and extends to the inside thereof. The left side of the diffuser is an air intake composed of a first-stage compressor 51, a second-stage compressor 62, and a first-stage precooler 53. Furthermore, a high-energy spark plug 49 is installed from the outside of the central staged combustion chamber shell 48. The high-energy spark plug 49 penetrates the central staged combustion chamber shell 48 and the flame tube 46 respectively until it extends to the vicinity of the combustion chamber head 1. The function of the high-energy spark plug 49 is to ignite the combustion chamber.

[0045] Furthermore, a compressor air bleed duct 62 is provided between the second-stage compressor 52 and the diffuser 41, and the compressor air bleed duct 62 leads to the turbine 61 for cooling the turbine; the turbine 61 is located at the right side outlet of the central staged combustion chamber casing 48, and the drive shaft on the turbine 61 is connected to the generator 57 through a gear set.

[0046] Please refer to Figure 5 The pipeline from the oil tank 54 leads to the oil pump 58, and the pipeline at the outlet of the oil pump 58 is bifurcated into a subcritical kerosene pipeline 42 and a supercritical kerosene pipeline 43, and a subcritical kerosene pipeline stop valve 63 and a supercritical kerosene pipeline stop valve 64 are respectively provided thereon, wherein the subcritical kerosene pipeline 42 directly extends into the central staged combustion chamber shell 48, and is connected to the first fuel supply pipeline 16 of the pre-combustion stage through a threaded interface 45; and the supercritical kerosene pipeline 43 leads to the inlet of the first precooler 53, the first precooler The outlet of the device 53 is connected to the three-way valve 59 through a pipeline. The outlet pipeline on the left side of the three-way valve 59 passes through the electric heating pipe 56, penetrates the central staged combustion chamber shell 48 and is connected to the second oil supply pipeline 17 of the pre-combustion stage through the threaded interface 45; the right side of the three-way valve 59 is connected to the compressor bleed air precooler 55 through a pipeline. The compressor bleed air precooler 55 is placed in the inlet of the compressor bleed air pipe 62, and the outlet of the compressor bleed air precooler 55 is connected to the threaded interface 45 at the top of the main combustion stage oil supply pipeline 18 through a pipeline.

[0047] The centrifugal nozzle 11 is opened on the right side of the pre-combustion stage center column 25, and the direct-injection nozzle 12 is opened circumferentially because the centrifugal nozzle 11 sprays subcritical kerosene, which will first form a conical liquid film after being ejected from the nozzle, and then break into kerosene particles of different sizes under the combined action of wind and viscosity. Since larger kerosene droplets have higher momentum and the speed of subcritical kerosene mixing and combustion is slower, the length of the pre-combustion stage flame existence area a is larger, which can enhance the interaction between the main combustion stage and the pre-combustion stage flame under the full speed state of the engine; the direct-injection nozzle 12 sprays supercritical kerosene, which has the characteristic of fast mixing. It can be quickly mixed with air by being injected vertically into the lateral air flow of the first air inlet duct 26, which is beneficial to the subsequent high-temperature rise-low-pollution combustion.

[0048] The reason for designing the divergent nozzle 23 on the outer surface of the first air inlet 26 is that when the engine is operating at full power (see specific embodiment 1 for details), when the pre-combustion stage 2 sprays subcritical kerosene, the divergent nozzle 23 between the first-stage axial swirler 21 and the second-stage axial swirler 22 promotes the breakup of the liquid film sprayed from the centrifugal nozzle 11, and helps the kerosene splashing to cause secondary atomization. At the same time, the suction effect of the airflow at the outlet of the first-stage axial swirler and the second-stage axial swirler accelerates the fuel atomization and mixing process, which is beneficial to the ignition process.

[0049] The reason for designing the gradually diverging nozzle 24 on the outer surface of the second air inlet 27 is that when the air intake speed is subsonic, the gradually diverging nozzle 24 can act as a diffuser, further reducing the air flow speed and increasing the air flow pressure. When the engine is in the slow-running condition (see specific embodiment 2 for details), when only the pre-combustion stage 2 is working, the gradually diverging nozzle 24 can provide a local low-flow-rate, oil-rich environment, so that the fuel sprayed from the pre-combustion stage 2 burns at the nozzle of the gradually diverging nozzle 24, which is beneficial to improving the engine ignition performance and flame stability.

[0050] The oil distribution ring 19 can be regarded as an annular pipeline, which serves as an extension of the second oil supply pipeline 17 of the pre-combustion stage (the main combustion stage oil supply pipeline 18), adjusts the oil supply pressure, and is connected to the direct-injection nozzle 12 (coaxial nozzle 13) at one end to supply oil evenly to each nozzle, ensuring that the injection pressure at the outlet of each nozzle is basically consistent with the kerosene mass flow rate.

[0051] The reason why the main combustion stage 3 uses the coaxial nozzle 13 to spray fuel into the flame tube is that the mass flow rate of the fuel sprayed by the main combustion stage 3 is more than one order of magnitude higher than that of the pre-combustion stage 3, so the problem of large flow rate injection and mixing must be considered. The coaxial nozzle 13 injects supercritical kerosene in the inner cavity and air in the outer cavity to enhance mixing. In addition, the nozzle diameter of the coaxial nozzle 13 is larger than that of the straight nozzle 12, and a larger kerosene mass flow rate can be achieved at the same injection pressure to meet the requirements of the large kerosene mass flow rate of the main combustion stage 3.

[0052] The function of the coaxial nozzle air intake slit 44 is to draw a small amount of air from the third air inlet duct 33 to supply air to the coaxial nozzle 13 .

[0053] The reason why the third air inlet duct 33 is designed in a zigzag shape is to make the airflow perpendicular to the injection direction of the coaxial nozzle 13; in addition, the reason why the three-stage radial swirler 31 adopts a radial swirler instead of an axial swirler is the same as above. The zigzag third air inlet duct 33 is used to construct an airflow perpendicular to the injection direction of the coaxial nozzle 13, thereby enhancing the mixing effect of supercritical kerosene and air.

[0054] The reason for opening the air film hole 29 on the divergent nozzle 24 is that under slow-running conditions, the supercritical kerosene injected by the pre-combustion stage 2 is mixed with air and burns at the outlet of the divergent nozzle 24. Therefore, a small amount of gas is introduced from the combustion chamber head 1 to cool the inner wall of the divergent nozzle 24, thereby reducing its surface temperature and increasing its service life. The reason why the boss 36 requires impact-air film cooling is that the right side of the boss 36 can be regarded as a blunt body. Under full-power conditions of the engine, a recirculation zone will be formed on the right side of the boss 36. At that time, the kerosene injected by the main combustion stage 3 will burn in the recirculation zone, which may cause the right surface temperature of the boss 36 to be too high, resulting in melting or ablation. Therefore, an air flow is used from the impact hole 37 to enter the inner surface of the purge impact chamber 38 to remove heat and cool the inside of the boss 36. In addition, the air flow in the impact chamber 38 is discharged from the air film hole 29 on the right surface of the boss 36, which helps to push the above-mentioned recirculation zone away from the boss 36 and slow down the ablation effect on the outer surface of the boss 36.

[0055] Working principle of oil supply pipeline:

[0056] ① Under full power condition: the stop valve 63 of the subcritical kerosene pipeline is open, the stop valve 64 of the supercritical kerosene pipeline is open, and the three-way valve 59 is in the right-open state. Under the action of the oil pump 58, the room-temperature kerosene is pumped out from the oil tank, and then the kerosene is pumped into the subcritical kerosene pipeline 42 and the supercritical kerosene pipeline 43 respectively. Affected by the different cross-sectional areas of the pipelines and the nozzles, the ratio of the kerosene mass flow rate in the subcritical kerosene pipeline 42 and the supercritical kerosene pipeline 43 is about 1:10. The room-temperature kerosene in the subcritical kerosene pipeline 42 enters the first oil supply pipeline 16 of the pre-combustion stage, and is supplied by the central column 25 of the pre-combustion stage. The kerosene in the supercritical kerosene pipeline 43 first enters the first-stage precooler 53 to exchange heat with the compressed air compressed by the first-stage compressor 51. The kerosene is first heated to a subcritical state of about 240-280°C, and then passes through the three-way valve 59 to enter the compressor bleed air precooler 55 to exchange heat with the compressor bleed air pipe 62, so that the kerosene is further heated to a supercritical state, and finally enters the main combustion stage oil supply pipeline 18 and is ejected by the coaxial nozzle 13.

[0057] ② Under the slow-speed working condition: the stop valve 63 of the subcritical kerosene pipeline is closed, the stop valve 64 of the supercritical kerosene pipeline is opened, the three-way valve 59 is in the left-open state, and the electric heating pipe 56 is powered on. Under the action of the oil pump 58, the room-temperature kerosene is pumped out from the oil tank. Because the stop valve 63 of the subcritical kerosene pipeline is in the closed state, the kerosene can only enter the supercritical kerosene pipeline 43. Due to the influence of the cross-section of the pipeline and the direct-injection nozzle 12, the mass flow rate of kerosene in the pipeline under the slow-speed working condition is much lower than that under the full-power working condition mentioned above, which also makes the kerosene in the supercritical kerosene pipeline 43 heated to a higher temperature when it is pumped into the first-stage precooler 53, about 350°C, and then enters the electric heating pipe 56 through the three-way valve 59 to be electrically heated to a supercritical temperature of 380°C, and the error is controlled within ±2°C. Finally, the kerosene enters the second oil supply pipeline 17 of the pre-combustion stage and is sprayed out by the direct-injection nozzle 12. The function of the generator 57 is to supply power to the avionics equipment on the aircraft and to allocate part of the electrical energy for heating kerosene under slow vehicle conditions.

[0058] The electric heating tube 56 is a hollow pipe bent into a spiral shape and made of high-temperature alloy steel. Both ends of the steel tube are connected to an AC power supply with a rated voltage of 220V and a power of 5kW. The fuel flowing through the high-temperature alloy steel tube is heated by its own resistance (about 2Ω). The temperature of the inlet and outlet of the electric heating tube 56 is monitored by a thermocouple, and precise temperature control is achieved by changing the current applied to the electric heating tube 56.

[0059] The first-stage precooler 53 is arranged between the first-stage compressor 51 and the second-stage compressor 52, which can convert the adiabatic compression into a process close to isothermal compression, thereby improving the efficiency of the compressor unit. At the same time, by exchanging heat with kerosene, this part of the heat is brought into the combustion chamber, thereby realizing a high temperature rise in the combustion chamber. The function of the compressor bleed pipe 62 is to lead out part of the compressed air for cooling the turbine 61. The compressor bleed air precooler 55 is installed at the inlet of the compressor bleed pipe 62. While further heating the kerosene to the supercritical temperature, it also reduces the temperature of the compressed air in the compressor bleed pipe 62, thereby enhancing the cooling effect on the turbine 61.

[0060] Whether in full power or slow-running conditions, the supercritical kerosene pipeline 43 adopts a two-stage heating method, which can reduce the time that kerosene stays at supercritical temperature and slow down the coking effect of kerosene at high temperature. The reason why the second-stage heating under slow-running conditions adopts electric heating is that the mass flow rate of the oil supply under slow-running conditions is small. If the kerosene directly enters the compressor bleed air precooler 55 for heating, it may be heated to a temperature above 400°C, and there is a risk of coking and clogging the pipeline; while electric heating can accurately control the temperature at which the kerosene is heated to avoid coking and clogging the pipeline. In addition, under slow-running conditions, the kerosene has been heated to a higher temperature during the first-stage heating, and the temperature increment required for the second-stage heating is small, and it does not consume too much electricity.

[0061] It is worth noting that compressors, oil pumps, turbines and engines are commonly used equipment and belong to existing mature technologies. Their working principles and specific structures will not be described in detail here.

[0062] The technical effects of the present invention are described below through specific embodiments and comparative examples. Specific embodiment 1:

[0064] This case is used to test the "full power" condition of the central staged combustion chamber, that is, the pre-combustion stage 2 injects / burns subcritical kerosene and the main combustion stage 3 injects / burns supercritical kerosene.

[0065] The experimental equipment includes a combustion chamber head 1, a high-energy spark plug 49; and a 30° circle cut in the annular combustion chamber composed of a flame tube 46 and a central staged combustion chamber shell 48 as the combustion chamber shell used for the experiment. The two cross-sections of the combustion chamber are sealed with quartz glass to observe the ignition and flameout conditions in the laboratory.

[0066] The air used in the experiment is provided by the compressor unit, and the air mass flow rate is between 50-600g / s. The temperature of the air entering the combustion chamber is controlled by the electric heater in the range of 700-750K (about 427-477 degrees Celsius). Table 1 shows the air flow distribution scheme in each area of ​​the combustion chamber and in each inlet duct of the combustion chamber head 1. It is worth mentioning that the values ​​in this table are calculated based on the ideal gas assumption that the gas flow rate is proportional to the cross-sectional area of ​​the flow channel, and are not actual values. The gas distribution of each part may be affected by factors such as the actual gas flow rate, temperature, turbulence, etc., but the data in this table can be used as a reference for calculating the local oil-gas ratio in the combustion chamber.

[0067] Table 1 Air flow distribution of each part

[0068]

[0069] The fuel supply parameters are: the main combustion stage uses aviation kerosene with an oil temperature of 380°C, the pre-combustion stage uses aviation kerosene at room temperature, and the kerosene mass flow distribution of the pre-combustion stage is 10% of the main combustion stage. When the total kerosene flow rate is increased to 3.6g / s, that is, when the kerosene flow rate of the main combustion stage 3 is increased to 3.2g / s, the oil pressure in the coaxial nozzle 13 of the main combustion stage 3 reaches the critical pressure of 2.4MPa, which is a supercritical injection; at low kerosene flow rate, it is a subcritical injection, and the main combustion stage 3 coaxial nozzle 13 sprays kerosene vapor with a temperature of 380°C, rather than supercritical kerosene. Specific embodiment 2:

[0071] This case is used to test the "slow-speed" condition of the center-staged combustion chamber, that is, the pre-combustion stage 2 injects / burns supercritical kerosene and the main combustion stage 3 is not working.

[0072] The pre-combustion stage uses aviation kerosene with an oil temperature of 380°C, and the kerosene mass flow rate in the pre-combustion stage 2 is the same as the pre-combustion stage kerosene mass flow rate in Example 1. According to the measured data, when the kerosene flow rate of the pre-combustion stage 2 is increased to 0.34g / s, the oil pressure reaches the critical pressure of 2.4MPa, which is a supercritical injection. The rest is completely the same as in Specific Example 1.

[0073] Comparative Example 1:

[0074] On the basis of Specific Example 1, both the pre-combustion stage and the main combustion stage use aviation kerosene with an oil temperature of 380°C, and the kerosene mass flow distribution of the pre-combustion stage is 10% of that of the main combustion stage. At a small flow rate, the kerosene does not reach the supercritical pressure and is gaseous injection; when the kerosene flow rate is increased to 3.6g / s, the oil pressure reaches the critical pressure of 2.4MPa, which is supercritical injection. The rest of the parts are completely the same as Specific Example 1.

[0075] Comparative Example 2:

[0076] On the basis of Specific Example 1, both the pre-combustion stage and the main combustion stage use subcritical aviation kerosene with an oil temperature of 100°C. The kerosene mass flow distribution of the pre-combustion stage is 10% of that of the main combustion stage, and the rest is completely identical to Specific Example 1.

[0077] The following tests were conducted on the performance of four groups of central staged combustion chambers of Examples 1-2 and Comparative Examples 1-2:

[0078] (1) Lean oil ignition limit determination

[0079] The lean-fuel ignition limit is an important parameter for measuring the performance of the combustion chamber. Generally speaking, the smaller the oil-gas ratio that can achieve stable ignition during ignition, the better the combustion chamber performance, and the safer the aircraft will be in the event of an emergency such as an engine shutdown in mid-air.

[0080] The experimental method is to keep the gas volume unchanged, gradually modify the mass flow rate of the fuel, and use the dichotomy method to find the lean ignition boundary of the combustion chamber. When the experimental conditions are close to the lean ignition boundary, there are three types of experimental results: (a) the first type of ignition failure, such as no fire core formation or failure of fire core propagation; (b) the second type of ignition failure, in which the flame is successfully ignited but fails to burn steadily after a period of time, and the flame is blown out, which can also be called a transition state; (c) ignition success, in which the flame is successfully ignited and maintains burning for more than ten seconds. The above three ignition results are represented by inverted triangles, half-solid circles and solid circles, respectively, and are recorded in combination with the corresponding air and fuel mass flow rates. Figure 8-12 middle.

[0081] Comparative Example 1: Figure 8As shown, the left side of the dotted line is a subcritical injection. At a lower air flow rate, the kerosene flow rate required for ignition is also less. At this time, due to the low injection pressure, the injected kerosene is in a subcritical state (gaseous state). At this time, a pseudo-rich oil limit is formed in the combustion chamber, and the oil-gas ratio range for successful ignition in the combustion chamber becomes narrower. As the kerosene flow rate increases, the pseudo-rich oil limit is gradually improved and disappears, and the ignition performance of the combustion chamber becomes better as the kerosene flow rate increases. The right side of the dotted line is a supercritical injection. When the kerosene mass flow rate is further increased, when the injection pressure reaches the supercritical state, after increasing the kerosene flow rate, the corresponding air volume when the ignition is successful does not increase further as expected. This shows that after using supercritical kerosene, the lean oil ignition boundary of the combustion chamber becomes narrower, that is, the lean oil ignition performance becomes worse.

[0082] In order to study the relationship between the oil-gas ratio and the ignition condition in comparative example 1, the oil-gas ratio is equal to the kerosene mass flow rate diagram divided by the combustion chamber inlet air mass flow rate under the condition. Figure 8 After swapping the horizontal and vertical coordinates, we get Fig. 9 The slope is the oil-gas ratio. When the kerosene mass flow rate is less than 3.6g / s under subcritical conditions, the lean oil ignition boundary oil-gas ratio is in the range of 0.009 to 0.01; while for the three groups whose injection flow rate reaches supercritical pressure, the lean oil ignition boundary oil-gas ratio is around 0.018. There are two possible reasons for the poor ignition performance of kerosene under full supercritical conditions: first, when kerosene reaches supercritical pressure and is ejected, the injection pressure is greater and the relative velocity between the jet and the ambient airflow is higher, which is equivalent to creating a local high velocity zone near the nozzle outlet, which is not conducive to flame stability; second, the atomization injection process of traditional subcritical kerosene is non-steady-state, in which the distribution of kerosene concentration and kerosene atomized particle size with time and space is uneven. When a spark discharge moment happens to match the moment when the kerosene concentration near the ignition position is high during ignition, it is easy to form an initial fire nucleus, which increases the ignition success rate. Under supercritical conditions, the mixing speed of the ejected kerosene and air is several orders of magnitude higher than the subcritical. Therefore, the supercritical atomization injection process can be approximated as steady-state. In addition, the concentration distribution is more uniform, so it is difficult to match the moment when the kerosene concentration is high during spark discharge, thereby reducing the ignition success rate.

[0083] Comparative Example 2: From Fig.10It can be seen that the oil-gas ratio at the lean oil ignition boundary of Control Example 2 is greater than 0.01 under any working condition. Comparing Control Example 2 with Control Example 1, under the subcritical working condition where the kerosene mass flow rate is less than 3.6 grams per second, the oil-gas ratio at the lean oil ignition boundary of Control Example 1 is slightly lower than that of Control Example 2. This is because increasing the kerosene temperature can widen the lean oil ignition oil-gas ratio. However, when the kerosene mass flow rate is less than 3.6 grams per second, the oil-gas ratio at the lean oil ignition boundary of Control Example 2 is significantly lower than that of Control Example 1 at supercritical injection pressure and temperature. This proves that supercritical combustion will make the lean oil ignition performance of the combustion chamber worse than subcritical combustion, eliminating the interference with the ignition performance of the combustion chamber caused by the excessively fast air flow velocity in the combustion chamber under large air flow.

[0084] Specific Example 1: Compared with Control Example 1, the "pseudo-rich limit" is greatly weakened at a lower air flow rate. This is because under this operating condition, the pre-combustion stage sprays liquid kerosene at room temperature, while the main combustion stage does not reach the supercritical injection pressure and sprays gaseous kerosene vapor. The liquid kerosene injected by the pre-combustion stage has a slower crushing-mixing process and has a higher momentum, and will burn at a position farther away from the nozzle, which helps to weaken the "pseudo-rich limit" at low flow rates.

[0085] In addition, the ignition performance under supercritical conditions with kerosene mass flow rate above 3.6g / s has also been improved. Fig.11 It is shown that the ignition oil-gas ratio under supercritical conditions is still maintained at about 0.01, compared with the control example 1 ( Fig. 9 ), a fuel-gas ratio of 0.02 can achieve stable ignition under supercritical conditions. This shows that the combustion organization mode of burning subcritical kerosene in the pre-combustion stage and supercritical kerosene in the main combustion stage can solve the problem that pure supercritical combustion will cause the poor ignition performance of the combustion chamber.

[0086] Specific embodiment 2: Compared with specific embodiment 1, the lean oil ignition of the combustion chamber in specific embodiment 2 is lower, only about 0.001. Fig.12 . It is worth noting that the oil-gas ratio here refers to the overall oil-gas ratio in the combustion chamber, not the local oil-gas ratio near the pre-combustion stage. The air intake of the pre-combustion stage is about 1 / 15 of the air intake of the main combustion stage. Based on this calculation, the local oil-gas ratio near the pre-combustion stage is about 0.04-0.05, which belongs to oil-rich combustion. In addition, when the mass flow rate of the injected kerosene is higher than 0.34g / s, the injection pressure reaches 2.4MPa, which belongs to supercritical injection. At this time, the total oil-gas ratio that can achieve stable ignition is still maintained at about 0.001, or even slightly increased. This shows that under the joint action of flame stabilization measures such as the gradually expanding nozzle and the + / - direction strong swirl type swirler, the ignition performance of the pre-combustion stage combustion supercritical kerosene has not decreased, which further proves that the shortcoming of poor oil-poor ignition performance of the combustion chamber under pure supercritical conditions has been solved.

[0087] (2) Combustion efficiency measurement

[0088] The XGF-404 flue gas analyzer is used to measure the content of CO, NO, NOx and unburned hydrocarbons in the exhaust gas, and the measurement results are converted into the pollutant emission index (EI) according to the CAEP6 standard, which is the ratio of the mass of a certain gaseous pollutant produced by combustion to the mass of the fuel consumed. Taking carbon monoxide as an example, the calculation method of its EI value is as follows:

[0089]

[0090] Where, P5 is the mole number of carbon monoxide measured by the instrument; M CO 、M C 、M H are the molar masses of carbon monoxide, carbon, and hydrogen respectively.

[0091] Similarly, the NO, NOx and unburned hydrocarbon content can also be calculated according to the above formula.

[0092] There are two ways to measure combustion efficiency. One is to calculate the ratio of actual heat release to theoretical heat release, and the other is to infer from combustion products. Here we use the method of inferring from combustion products, and the specific formula is as follows:

[0093]

[0094] Where, EI CO EI is the emission index of carbon monoxide (g / kg); CxHy is the emission index of unburned hydrocarbons (g / kg); H C is the calorific value of the fuel (J / kg).

[0095] In the experiment, considering that the oil-to-gas ratio will affect the exhaust pollutant emission index and combustion efficiency, the oil-to-gas ratio is controlled in the range of 0.020-0.022. This is because within this range, the kerosene in Example 1, Example 2 and Control Example 1 can reach the supercritical injection pressure and can burn stably.

[0096] Table 2 Combustion chamber tail gas pollutant emission index and combustion efficiency

[0097]

[0098]

[0099] Comparing Example 1 / Example 2 / Control Example 1 with Control Example 2, the combustion efficiency and pollutant emission index under the condition of complete or partial supercritical combustion are better than those under the condition of pure subcritical combustion.

[0100] Analyzing Example 1 and Control Example 1, on the basis of the main combustion stage burning supercritical kerosene, the pre-combustion stage using subcritical kerosene as fuel has higher combustion efficiency and lower pollutant emission index compared with supercritical kerosene. This may be because the chemical reaction rate of subcritical kerosene during combustion is lower than that of supercritical kerosene, which will lead to a longer flame length in the pre-combustion zone when the pre-combustion stage burns supercritical kerosene, strengthen the interaction between the flame of the pre-combustion stage and the flame of the main combustion stage, improve the combustion efficiency and thus reduce the pollutant emission. Comparing Example 1 with Example 2, the combustion efficiency of only turning on the pre-combustion stage in the engine slow state is higher than the combustion efficiency of the pre-combustion stage and the main combustion stage working at the same time in the engine full power state. This is because the oxygen during the combustion of the pre-combustion stage is only provided by the first-stage axial swirler 21 and the second-stage axial swirler 22. In order to achieve the purpose of flame stability, a local oil-rich environment close to the chemically appropriate ratio is provided for the pre-combustion stage during design, and the combustion efficiency is higher in the oil-rich state. However, the higher flame temperature during oil-rich combustion will promote the formation of nitric oxide, so the nitric oxide emission index in Example 2 is slightly higher than that in Example 1, which is inevitable in pursuit of flame stability performance.

[0101] In summary, the present invention utilizes the advantages of high temperature rise, low pollution emission, uniform temperature distribution at the combustion chamber outlet and high combustion efficiency brought by supercritical kerosene combustion by closing the main combustion stage and burning supercritical kerosene in the pre-combustion stage when the engine is in an idling state; and the combustion organization mode of the pre-combustion stage burning subcritical kerosene and the main combustion stage burning supercritical kerosene in the full power state of the engine, and overcomes the disadvantage that pure supercritical combustion will deteriorate the lean oil ignition performance of the combustion chamber.

[0102] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion, characterized in that: include: The invention comprises a combustion chamber head (1), wherein the combustion chamber head (1) is composed of a pre-combustion stage (2), a main combustion stage (3) and an oil supply bracket (15). The pre-combustion stage (2) comprises a pre-combustion stage central column (25), and a convergent-divergent nozzle (23) is coaxially sleeved on the outside of the pre-combustion stage central column (25). The convergent-divergent nozzle (23) comprises, from left to right: a contraction section with a slope of 45° on the left side, a straight section in the middle, and a waist section on the right side. A first-stage axial swirler (21) is sandwiched between the left end of the straight section in the middle of the convergent-divergent nozzle (23) and the pre-combustion stage central column (25). The pre-combustion stage central column (25) and the convergent-divergent nozzle (23) are ) is the first air inlet duct (26); similarly, a gradually diverging nozzle (24) is coaxially sleeved outside the convergent-diverging nozzle (23), the rightmost portion of the gradually diverging nozzle (24) is an expansion section, the middle portion is a straight section, a secondary axial swirler (22) is installed between the leftmost portion of the gradually diverging nozzle (24) and the contraction section of the convergent-diverging nozzle (23), and the annular area enclosed between the gradually diverging nozzle (24) and the convergent-diverging nozzle (23) is the second air inlet duct (27). The main combustion stage (2) comprises a main combustion stage main ring (35), the main combustion stage main ring (35) is an annular structure with a left side approximately circular and an upper right side square, a boss (36) is coaxially arranged at the upper right part of the main combustion stage main ring (35), the boss (36) is an annular structure with a cross section approximately L-shaped, a third-stage radial swirler (31) is sandwiched between the right side of the main combustion stage main ring (35) and the lower left side of the boss (36), and the zigzag area enclosed by the main combustion stage main ring (35) and the boss (36) is the third combustion stage. air duct (33); similarly, a combustion chamber head shell (39) is coaxially arranged outside the boss (36), and the cross-section of the combustion chamber head shell (29) is a right-angled trapezoid, wherein the left side of the combustion chamber head shell (39) is parallel to the axial direction and the right side is an expansion section, and a four-stage axial swirler (32) is installed between the inner side of the combustion chamber head shell (39) and the outer side of the boss (36), and the annular area enclosed by the combustion chamber head shell (39) and the boss (36) is the fourth air inlet duct (34). The oil supply bracket (15) includes a first pre-combustion stage oil supply pipeline (16), a second pre-combustion stage oil supply pipeline (17) and a main combustion stage oil supply pipeline (18). The lower ends of the first pre-combustion stage oil supply pipeline (16) and the second pre-combustion stage oil supply pipeline (17) lead to the pre-combustion stage center column (25) respectively, and the main combustion stage oil supply pipeline (18) is connected to the main combustion stage main ring (35) after turning to the right; the first pre-combustion stage oil supply pipeline (16), the second pre-combustion stage oil supply pipeline (17) and the main combustion stage oil supply pipeline (18) are forked at the top of the oil supply bracket (15), and a threaded interface (45) is provided at the top thereof. The main combustion stage (3) is coaxially sleeved on the outside of the pre-combustion stage (2); when in an idle condition, the main combustion stage (3) is closed and the pre-combustion stage (2) sprays supercritical kerosene; when in a full power condition, the pre-combustion stage (2) sprays subcritical kerosene and the main combustion stage (3) sprays supercritical kerosene.

2. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion according to claim 1, characterized in that: Six centrifugal nozzles (11) are symmetrically installed along the axis of symmetry inside the right side of the pre-combustion stage central column (25), and the side of the centrifugal nozzle (11) is connected to the first oil supply pipeline (16) of the pre-combustion stage through a capillary tube, and the first oil supply pipeline (16) of the pre-combustion stage is coaxial with the pre-combustion stage central column (25); twelve direct-injection nozzles (12) are arranged on the outer circumference of the pre-combustion stage central column (25), and an oil separator ring (19) is arranged inside the pre-combustion stage central column (25), and the oil separator ring (19) is an annular structure with a hollow interior and communicates with the bottom of the direct-injection nozzle (12), and the oil separator ring (19) is coaxial with the first oil supply pipeline (16) of the pre-combustion stage and is sleeved on the outside of the first oil supply pipeline (16) of the pre-combustion stage, and the second oil supply pipeline (17) of the pre-combustion stage is connected to one side of the oil separator ring (19) after entering the pre-combustion stage central column (25).

3. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion according to claim 1, characterized in that: The right side surface of the main combustion stage main ring (35) shrinks inward to form a two-layer platform and twelve pairs of coaxial nozzles (13) are installed therein. The coaxial nozzles (13) are divided into an outer cavity and an inner cavity. An oil separator ring (19) is also arranged inside the main combustion stage main ring (35). The oil separator ring (19) is an internally hollow annular structure, one end of which is connected to the inner cavity of the coaxial nozzle (13), and the other end extends to the outside of the main combustion stage main ring (35) and leads to the main combustion stage oil supply pipeline (18); a coaxial nozzle air inlet slit (44) is provided on the upper surface of the main combustion stage main ring (35) to connect the third air inlet duct (33) with the outer cavity of the coaxial nozzle (13).

4. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion according to claim 1, characterized in that: The cross section of the left half of the boss (36) is in the shape of a long strip parallel to the axis of symmetry, and the right half is provided with an impact hole (37), an impact cavity (38) and an air film hole (29) from left to right. The left side of the impact hole (37) is connected to the inner wall of the boss (36) and the right side leads to the impact cavity (38). The impact cavity (38) is provided with an air film hole (29) and leads to the right surface of the boss (36). Furthermore, the upper right corner of the boss (36) is a protruding acute angle.

5. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion according to claim 1, characterized in that: A gas collecting cavity (28) is provided between the gradually diverging nozzle (24) and the main ring (35) of the main combustion stage. The gas collecting cavity (28) is narrow and long and extends into the gradually diverging nozzle (24). A plurality of gas film holes (29) are provided on the inner wall of the gas collecting cavity (28) on the side close to the gradually diverging nozzle (24). Furthermore, the spacing between the gas film holes (29) is five times the diameter of the gas film holes, and the opening direction of the gas film holes (29) is parallel to the axis of the symmetry axis.

6. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion according to claim 1, characterized in that: The outer side of the combustion chamber head is covered with a flame tube (46), the flame tube (46) is provided with a plurality of mixing holes (47) and the left end of the flame tube (46) is stuck in the slot (14) on the combustion chamber head shell (39), the outer side of the flame tube (46) is covered with a central staged combustion chamber shell (48) and three-dimensionally forms an annular combustion chamber with it, the left end of the central staged combustion chamber shell (48) is provided with a diffuser (41), the diffuser (41) penetrates the central staged combustion chamber shell (48) to the right and extends to the inside thereof, the left side of the diffuser (41) is an intake duct composed of a first-stage compressor (51), a second-stage compressor (52) and a first-stage precooler (53). Furthermore, a high-energy spark plug (49) is installed from the outside of the central staged combustion chamber shell (48), the high-energy spark plug (49) respectively penetrates the central staged combustion chamber shell (48) and the flame tube (46) until it extends to the vicinity of the combustion chamber head (1).

7. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion according to claim 6, characterized in that: A compressor bleed pipe (62) is provided between the two-stage compressor (52) and the diffuser (41), and the compressor bleed pipe (62) leads to a turbine for cooling the turbine (61); the turbine (61) is located at the right outlet of the central staged combustion chamber casing (48), and a transmission shaft on the turbine (61) is connected to a generator (57) through a gear set.

8. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion according to claims 1-7, characterized in that: The pipeline leading out of the oil tank (54) leads to an oil pump (58), and the pipeline at the outlet of the oil pump (58) is bifurcated into a subcritical kerosene pipeline (42) and a supercritical kerosene pipeline (43), and a subcritical kerosene pipeline stop valve (63) and a supercritical kerosene pipeline stop valve (64) are respectively provided thereon, wherein the subcritical kerosene pipeline (42) directly extends into the central staged combustion chamber shell (48) and is connected to the first pre-combustion stage first oil supply pipeline (16) through a threaded interface (45); and the supercritical kerosene pipeline (43) leads to the inlet of a primary precooler (53), and the primary precooler (5 3) The outlet is connected to the three-way valve (59) through a pipeline. The outlet pipeline on the left side of the three-way valve (59) passes through the electric heating pipe (56), penetrates the central stage combustion chamber shell (48) and is connected to the second oil supply pipeline (17) of the pre-combustion stage through a threaded interface (45); the right side of the three-way valve (59) is connected to the compressor bleed air precooler (55) through a pipeline. The compressor bleed air precooler (55) is placed in the inlet of the compressor bleed air pipe (62). The outlet of the compressor bleed air precooler (55) is connected to the threaded interface (45) at the top of the main combustion stage oil supply pipeline (18) through a pipeline.

9. A low emission central staged combustion chamber based on sub- / supercritical kerosene mixed combustion according to claim 1, characterized in that: The blades of the first-stage axial swirler (21) and the second-stage axial swirler (22) adopt a rotation direction combination of +45° / -45°, and the first and second-stage swirl numbers are 0.78 and 0.88 respectively, which belong to the strong swirl type; the blades of the third-stage radial swirler (31) and the fourth-stage axial swirler (32) adopt a rotation direction combination of +45° / +60°, and the third and fourth-stage swirl numbers are 0.36 and 0.60 respectively, which belong to the weak swirl type.

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