A high temperature rise combustion chamber for small turbojet engines

Abstract

This invention discloses a high-temperature combustion chamber for small turbojet engines, comprising a diffuser, a casing, a combined air atomizing nozzle, and a flame tube. It addresses the problems in existing technologies where low fuel supply pressure and increased fuel flow in high-temperature combustion chambers of small turbojet engines lead to poor fuel atomization and low combustion efficiency, while a significant reduction in cooling air volume and increased cooling air temperature result in insufficient flame tube lifespan. This invention innovatively adopts a radial and axial fuel grading layout. The swirlers used to assist fuel atomization all employ oblique holes. The cooling holes on the flame tube innovatively adopt a spatial compound angle layout, with different sizes and hole spacings in different areas. This improves fuel atomization quality and efficient combustion under various operating conditions, extends flame tube lifespan, and simplifies the manufacturing process of the swirlers due to the oblique hole design.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of small turbine engine combustion chambers for high-speed unmanned aerial vehicles, in particular to a high-temperature-rise combustion chamber applied to a small supersonic turbine engine. BACKGROUND

[0002] With the increase of the oil-gas ratio, the fuel flow supplied to the combustion chamber gradually increases, in order that more fuel can be fully atomized and efficiently combusted, researchers will adopt the fuel in a staged manner and adopt the corresponding fuel atomization mode to realize fuel atomization. Therefore, the generated fuel center staged combustion chamber, radial staged combustion chamber or axial staged combustion chamber, compared with the radial staged and circumferential staged combustion chamber, respectively, the radial dimension and axial dimension of the combustion chamber are required to be larger, and they are more suitable for large engines; more researchers will adopt the center staged combustion chamber, and with the increase of the fuel flow, the air volume for auxiliary fuel atomization is also gradually increased, forming a head atomization device combined with multiple oil paths and multiple cyclone separators, which requires a larger radial dimension of the combustion chamber, so that it is difficult to apply to small high-temperature-rise combustion chambers. And in this configuration, most of the cyclone separators adopt vane type cyclone separators, and only a small amount of first-stage cyclone separators adopt round hole forms, which makes the structure of the multi-stage cyclone separator too complex.

[0003] With the increase of the oil-gas ratio of the high-temperature-rise combustion chamber, the combustion chamber inlet temperature is further increased, but the gas amount for cooling of the high-temperature-rise combustion chamber is greatly reduced, compared with the cooling air amount of the conventional combustion chamber, the cooling air amount of the high-temperature-rise combustion chamber is reduced by nearly 40%, which increases the thermal load of the flame tube wall surface, and researchers will adopt various advanced cooling methods (such as divergent cooling, impingement + divergent cooling) to improve the heat exchange efficiency of the cooling air, reduce the temperature and temperature gradient of the flame tube wall surface, and improve the service life of the flame tube. SUMMARY

[0004] The application aims to provide a high-temperature-rise combustion chamber applied to a small supersonic turbine engine.

[0005] The application achieves the above-mentioned purpose through the following technical solutions:

[0006] The application provides a high-temperature-rise combustion chamber applied to a small supersonic turbine engine, which comprises a sudden expansion diffuser, a casing, a combined air atomizing nozzle and a flame tube, the right end of the sudden expansion diffuser is connected with the left end of the casing, the combined air atomizing nozzle and the flame tube are located in the casing, and the combined air atomizing nozzle partially extends into the flame tube.

[0007] As the preferred embodiment of the present application, the combined air atomizing nozzle comprises a centrifugal nozzle, a main oil path, a direct jet nozzle, a primary swirler and a secondary swirler, the centrifugal nozzle, the primary swirler, the main oil path and the secondary swirler are sequentially combined and connected to form an integrated body, and the direct jet nozzle penetrates the casing and extends into the inner part of the flame tube; the primary swirler and the secondary swirler have three air passage channels, the first air passage channel is composed of 4-8 first air holes with a circular cross section; the second air passage channel is composed of 6-10 second air holes with a circular cross section; and the third air passage channel is composed of 8-20 third air holes with a circular cross section.

[0008] As the preferred embodiment of the present application, the main oil path comprises an oil inlet, an oil groove, an oil injection hole one and an oil channel, the fuel enters the oil groove through the oil inlet, and is injected into the oil channel through the four oil injection holes.

[0009] As the preferred embodiment of the present application, the air holes of the three air channels have respective space angles, the circumferential deflection angle of the air holes of the first air channel is opposite to that of the second air channel, and the diameters of all the air holes are between 4 mm and 7 mm.

[0010] As the preferred embodiment of the present application, the flame tube comprises a flame tube wall, a main combustion hole and a cooling hole, the main combustion hole and the cooling hole are arranged on the flame tube wall, and the cooling hole is arranged in the front and rear areas of the main combustion hole.

[0011] As the preferred embodiment of the present application, the third oil path extends into the inner part of the combustion chamber in the form of a direct jet nozzle, the end face of the direct jet nozzle is provided with an oil injection hole two, and the direct jet nozzle extends into the main combustion hole of the flame tube; in order to better realize the fuel atomization, the main combustion hole adopts a flanged hole structure.

[0012] As the preferred embodiment of the present application, the flange height of the flanged hole of the main combustion hole is between 0 mm and 4 mm, and the insertion depth of the nozzle is between 2 mm and 5 mm.

[0013] As the preferred embodiment of the present application, the number of the main combustion holes is 1 or 2 times the number of the direct jet nozzles.

[0014] As the preferred embodiment of the present application, the high-temperature area positions in front of and behind the main combustion hole, and the cooling hole on the flame tube wall have a space compound angle, which has a radial angle (25°-35°) and a circumferential angle (20°-40°), and the diameter is between 0.3 mm and 0.5 mm.

[0015] The present application has the following advantages:

[0016] (1) In the present application, the high-temperature rise combustion chamber adopts a combined overall layout mode of fuel radial staging + axial staging, realizes wide-range adjustment of fuel flow, and has lower size requirements for the combustion chamber compared with the traditional radial staging combustion chamber and axial staging combustion chamber, and is more suitable for small-size high-temperature rise combustion chambers.

[0017] (2) In this invention, the combined air atomizing nozzle of the high-temperature combustion chamber, the air swirl that assists in fuel atomization, and the swirl that constructs the head recirculation zone are all constructed through a circular air vent. Compared with the blade swirler, the structure is simple and the process is easy to form.

[0018] (3) The high-temperature combustion chamber axial staged scheme in this invention achieves fuel atomization and mixing with air through the main combustion hole jet, avoiding excessively high fuel-air ratio at the head, resulting in fuel-rich combustion and uneven combustion, which is conducive to achieving efficient combustion and reducing pollutants.

[0019] (4) In this invention, the flame tube wall of the high-temperature combustion chamber adopts composite divergent cooling holes, and the size and spatial angle of the cooling holes are different according to different positions, which is more conducive to reducing the flame tube wall temperature and temperature gradient. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall high-temperature combustion chamber of the present invention;

[0021] Figure 2 This is a layout diagram of the fuel nozzle of the present invention;

[0022] Figure 3 This is a schematic cross-sectional view of the combined air atomizing nozzle of the present invention.

[0023] Figure 4 This is a schematic diagram of the combined air atomizing nozzle of the present invention;

[0024] Figure 5 This is a schematic diagram of the flame tube cooling structure of the present invention;

[0025] Figure 6 This is a partially enlarged schematic diagram of the flame tube cooling structure of the present invention.

[0026] Figure 7 This is a schematic diagram of the three types of cooling holes in the flame tube cooling structure of the present invention.

[0027] Reference numerals: 1-Sudden diffuser, 2-Casing, 3-Combined air atomizing nozzle, 31-Centrifugal nozzle, 32-Main oil passage, 321-Oil inlet, 322-Oil trough, 323-Injection hole one, 324-Oil passage, 33-Direct injection nozzle, 331-Injection hole two, 34-First-stage cyclone separator, 341-First vent, 35-Second-stage cyclone separator, 351-Second vent, 352-Third vent, 4-Flame tube, 41-Flame tube wall, 42-Main combustion port, 43-Cooling hole, 431-Cooling hole one, 432-Cooling hole two, 433-Cooling hole three, a-Fuel oil, b-Air. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the implementation method of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0030] Combined with appendix Figures 1-7 This invention relates to a high-temperature combustion chamber for use in small supersonic turbine engines, such as... Figure 1 As shown, it includes a sudden diffuser 1, a housing 2, a combined air atomizing nozzle 3, and a flame tube 4. The right end of the sudden diffuser 1 is connected to the left end of the housing 2. The combined air atomizing nozzle 3 and the flame tube 4 are located inside the housing 2, and the combined air atomizing nozzle 3 partially extends into the flame tube 4.

[0031] like Figures 2-4 As shown, the combined air atomizing nozzle 3 includes a centrifugal nozzle 31, a main oil passage 32, a direct-fire nozzle 33, a first-stage cyclone separator 34, and a second-stage cyclone separator 35. The centrifugal nozzle 31, the first-stage cyclone separator 34, the main oil passage 32, and the second-stage cyclone separator 35 are sequentially combined and connected as a single unit. The direct-fire nozzle 33 penetrates the outer shell of the casing 2 and extends into the interior of the flame tube 4. The first-stage cyclone separator 34 and the second-stage cyclone separator 35 have three air passages. The first air passage consists of 4-8 first vent holes 341 with a circular cross-section. The second air passage consists of 6-10 second vent holes 351 with a circular cross-section. The third air passage consists of 8-20 third vent holes 352 with a circular cross-section.

[0032] The main oil passage 32 includes an oil inlet 321, an oil trough 322, an injection hole 323, and an oil channel 324. Fuel enters the oil trough 322 through the oil inlet 321 and is injected into the oil channel 324 through the four injection holes 323.

[0033] The combined air atomizing nozzle 3 adopts a combined overall layout of radial and axial fuel grading. Fuel is supplied to the combustion chamber flame tube 4 via three paths (the internal combustion chamber path and the external combustion chamber path are not described here). The radial fuel grading is divided into two fuel flow paths: the central path uses a centrifugal nozzle 31, and the main path 32 uses a pre-filming air atomizing nozzle. The axial fuel grading has only one path, using a direct-injection nozzle 33. The two radially graded fuel paths are integrated with the first-stage swirler 34 and the second-stage swirler 35 to form the combined air atomizing nozzle 3. The first fuel a is injected into the flame tube 4 through the centrifugal nozzle 31 at the center of the combined air atomizing nozzle 3; the fuel nozzle 31 can be fixed on the combustion chamber casing 2; the second fuel a enters the oil trough 322 through the oil inlet 321, and is rotated and injected into the oil passage 324 through the four oil injection holes 323 with a certain spatial angle, flows along the oil passage 324 and forms an oil film a at the end of the oil passage 324, and flows into the flame tube 4 with the air b; this part of the fuel is coaxially distributed with the centrifugal nozzle and is located outside the central fuel; the main fuel passage 32 can be integrated with the central centrifugal nozzle 31, or it can be connected to the fuel main pipe and supplied by the external fuel passage of the combustion chamber. The third fuel a, which is axially graded, is sprayed out through the injection hole 331 on the direct-injection nozzle 33. It is broken up by the jet air b of the main combustion hole 42 of the flame tube and mixed with it before entering the flame tube 4. The direct-injection nozzle 33 is fixed on the casing 2 and connected to the external oil circuit. It can also be integrated with other oil circuits. The number of holes in the main combustion hole 42 is 1 or 2 times the number of direct-injection nozzles 33 to ensure uniform fuel distribution.

[0034] like Figure 4 As shown, part of the air b from the outlet of the diffuser 1 enters the flame tube 4 through the first vent 341 of the first-stage cyclone separator 34; part of the air b enters the flame tube 4 through the second vent 351 of the second-stage cyclone separator 35. At the end of the oil passage 324, the two airflows b interact, helping the oil film a break into oil droplets, forming an oil-gas mixture that flows downstream and mixes with the air b passing through the third vent 352 before entering the flame tube 4 for combustion.

[0035] like Figures 5-7As shown, the flame tube 4 includes a flame tube wall 41, a main combustion port 42, and cooling ports 43. The main combustion port 42 and cooling ports 43 are disposed on the flame tube wall 41, with the cooling ports 43 located in the areas before and after the main combustion port 42. Multiple cooling ports 43 are arranged near the areas before and after the main combustion port 42. The diameter of the cooling ports 43 is between 0.3mm and 0.5mm. Three types of cooling ports 43 are simply listed: cooling port one 431, cooling port two 432, and cooling port three 433. The circumferential angle between cooling port one 431 and the flame tube wall 41 is 0°, the circumferential angle between cooling port two 432 and the flame tube wall 41 is 30°, and the circumferential angle between cooling port three 433 and the flame tube wall 41 is 21°. This structural design can improve the heat exchange efficiency of the cooling gas and ensure the temperature distribution and temperature gradient of the flame tube wall even when the gas volume is reduced.

[0036] Working principle:

[0037] When the small supersonic turbo engine transitions from ignition start-up to idle operation, the engine fuel supply system only supplies fuel to the centrifugal nozzle 31 fuel line of the high-temperature combustion chamber, and the fuel a flow rate gradually increases. At the same time, the air b flow rate entering the combustion chamber also gradually increases. A small amount of air b will generate swirling flow through the first vent 341 on the first-stage swirler 34. This swirling air b can play a secondary breaking role on the initially atomized fuel a, so that the fuel a in this path is well atomized, can achieve stable combustion, and is not easy to extinguish.

[0038] When a small supersonic turbocharged engine transitions from idle to cruising (medium operating condition), the engine's fuel supply system begins supplying fuel to the main fuel line 32. As the intake air volume (b) increases, the fuel flow rate (a) in this line gradually increases. Fuel a passes through the inlet 321 of the main fuel line 32, through the fuel groove 322 and the injection port 323, forming an oil film at the end of the fuel passage 324. Air b enters the three air passages of the swirlers 34 and 35, forming two swirling air streams (b) with opposite directions and different flow rates at the end of the fuel passage 324. The oil film becomes unstable and atomized under the action of the primary swirling air 34 and the secondary swirler air b (b), i.e., the pre-filming air atomizing nozzle begins to operate. This atomized fuel a is distributed in the coaxial outer region of the fuel a in the centrifugal nozzle 31, resulting in a uniform radial distribution of fuel a, which enables efficient combustion in the high-temperature combustion chamber.

[0039] When a small supersonic turbine engine transitions from cruise mode to design point mode (high-level mode), the engine's fuel supply system begins supplying fuel via a third fuel path. As the engine's intake air volume (b) increases, the flow rate of fuel (a) in this path gradually increases. This portion of fuel (a) is impacted by a high-speed air jet (b) passing through the main combustion port (42) of the flame tube 4, achieving rapid deformation, film breakage, and atomization of the fuel jet. After mixing with the air jet (b) through the main combustion port (42), it enters the flame tube 4 for combustion, i.e., the direct-injection nozzle (33) begins operation. A portion of this fuel (a) enters the recirculation zone of the main combustion zone, while the remainder burns after the main combustion port. This prevents an over-rich state of fuel (a) in the main combustion zone, achieving axial fuel distribution and efficient combustion.

[0040] In the high-temperature zone before and after the main combustion hole 42, the cooling hole 43 on the flame tube wall 41 has a spatial compound angle, with an axial and circumferential angle. This increases the heat exchange area between the cooling hole 43 and the flame tube wall 41, which helps to reduce the temperature of the flame tube wall 41. This cooling hole 43 has a circumferential deflection angle, which matches the swirling air b inside the flame tube 4, and further reduces the temperature of the wall 41 and the temperature gradient.

[0041] Such a small-sized high-temperature combustion chamber fuel atomization device has a simpler structure, higher reliability, and greater versatility, making it more suitable for small turbine engines with a wide airspace and speed range.

[0042] Although the present invention has been described herein with reference to illustrative embodiments, the above embodiments are merely preferred embodiments of the present invention, and the implementation of the present invention is not limited to the above embodiments. It should be understood that those skilled in the art can devise many other modifications and implementations, which will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A high-temperature combustion chamber for use in a small supersonic turbine engine, characterized in that: It includes a sudden expansion diffuser (1), a casing (2), a combined air atomizing nozzle (3), and a flame tube (4). The right end of the sudden expansion diffuser (1) is connected to the left end of the casing (2). The combined air atomizing nozzle (3) and the flame tube (4) are located inside the casing (2), and the combined air atomizing nozzle (3) extends partially into the flame tube (4). The combined air atomizing nozzle (3) adopts a combined overall layout of radial fuel grading + axial fuel grading; the radial fuel grading is divided into two fuel flow paths, of which the central oil path adopts a centrifugal nozzle (31) and the main oil path (32) adopts a pre-film air atomizing nozzle; the axial fuel grading has only one path, which adopts a direct injection nozzle (33). The combined air atomizing nozzle (3) includes a primary cyclone separator (34) and a secondary cyclone separator (35). The primary cyclone separator (34) and the secondary cyclone separator (35) have three air passages, and the vents of the three air passages each have their own spatial angle. The circumferential deflection angle of the first vent (341) of the first air passage is opposite to that of the second vent (351) of the second air passage. The diameter of all vents is between 4mm and 7mm. The main oil passage (32) includes an oil inlet (321), an oil trough (322), an injection hole (323), and an oil channel (324). Fuel enters the oil trough (322) through the oil inlet (321) and is injected through four injection holes. The oil hole (323) is rotated and sprayed into the oil passage (324); the flame tube (4) includes a flame tube wall (41), a main combustion hole (42), and a cooling hole (43), which are set on the flame tube wall (41); the third oil passage extends into the combustion chamber and adopts the structure of a direct-fire nozzle (33), with an oil injection hole (331) arranged on its end face. The direct-fire nozzle (33) is inserted into the main combustion hole (42) on the outer ring of the flame tube (4), and the main combustion hole (42) adopts a flanged hole structure; the flange height of the flanged hole is between 0-4mm, and the insertion depth of the direct-fire nozzle (33) is 2mm-5mm.

2. The high-temperature combustion chamber for a small supersonic turbine engine according to claim 1, characterized in that: The combined air atomizing nozzle (3) also includes a centrifugal nozzle (31), a main oil passage (32) and a direct-fire nozzle (33). The centrifugal nozzle (31), the first-stage cyclone separator (34), the main oil passage (32) and the second-stage cyclone separator (35) are sequentially combined and connected as a whole. The direct-fire nozzle (33) penetrates the outer shell of the casing (2) and extends into the interior of the flame tube (4). The first air passage consists of 4-8 first vent holes (341) with a circular cross-section. The second air passage consists of 6-10 second vent holes (351) with a circular cross-section. The third air passage consists of 8-20 third vent holes (352) with a circular cross-section.

3. A high-temperature combustion chamber for a small supersonic turbine engine according to claim 1 or 2, characterized in that: The number of main combustion holes (42) is 1 or 2 times the number of direct-fire nozzles (33).

4. The high-temperature combustion chamber for a small supersonic turbine engine according to claim 3, characterized in that: The cooling holes (43) are generally arranged in a composite divergent form. The diameter and spatial angle of the cooling holes (43) at different positions are different. Among them, at the high temperature zone before and after the main combustion hole (42), the diameter of the cooling holes (43) is between 0.3mm and 0.5mm, the radial angle between the cooling holes (43) and the flame tube wall (41) is between 25° and 35°, and the circumferential angle is between 20° and 40°.

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