Multi-stage CCA heat exchange system for turbofan engine and working method of multi-stage CCA heat exchange system

Abstract

The multi-stage CCA heat exchange system for the turbofan engine comprises an outer duct, an air-air heat exchanger is installed on the air inlet side of the outer duct, an air-kerosene heat exchanger is installed on the air outlet side of the outer duct, and a heat exchange air cavity is installed on the outer side of the air-kerosene heat exchanger; an outlet of the air compressor is connected with an air inlet of the air-air heat exchanger, an air outlet of the air-air heat exchanger is connected with an air inlet of the heat exchange air cavity, and an air outlet of the heat exchange air cavity outputs cooling air used for cooling the high-pressure turbine. The defects in the prior art can be overcome, meanwhile, heat sinks of outer duct air and airborne fuel oil are utilized, bleed air flow from an outlet of the air compressor is cooled, the bleed air cold air temperature is reduced, the problem that turbine blades of a turbofan engine are difficult to cool is solved, and meanwhile it is guaranteed that flow resistance caused by a heat exchange system to each stream is below a limit value.

Description

Technical Field

[0001] The invention belongs to the field of aviation engines, and in particular to a multi-stage CCA heat exchange system for a turbofan engine and a working method thereof. Background Art

[0002] In the future, high-performance aircraft engines will have higher cycle parameters and higher efficiency, but this will also bring more prominent thermal protection and thermal control issues, as well as stricter energy efficiency requirements; on the one hand, key components such as hot end components require a suitable thermal environment, and on the other hand, energy needs to be allocated in a coordinated manner to ensure the overall performance of the engine. In order to ensure safe and reliable operation of the engine, there is cooling gas interaction between the main engine and the air system, which puts forward requirements for the cooling gas flow, temperature and pressure.

[0003] The heat sinks used in CCA technology include engine external air, aviation kerosene and ram air, etc. The heat is extracted from the cooling air drawn from the compressor through the above low-temperature working fluids, thereby improving the quality of the cooling air and helping to solve the thermal protection and thermal control problems of aircraft engines. The core component of CCA technology is the heat exchanger, which is divided into air-to-air heat exchanger and air-to-kerosene heat exchanger according to the cooling working fluid.

[0004] Air-to-air heat exchangers have the advantages of a wide range of working fluid sources and no need to carry additional coolant. However, air as a heat exchange medium itself has the disadvantages of low thermal capacity, low density, and a relatively low air-solid wall-air heat transfer coefficient, which makes the air-to-air heat exchanger prone to large pressure losses, insufficient structural compactness, and difficulty in working under high heat load environments, limiting its application in certain scenarios.

[0005] The air-kerosene heat exchanger has a compact structure, and the convective heat transfer coefficient of air-kerosene is generally 1 to 2 orders of magnitude larger than that of air-air. When aviation kerosene is used as a working fluid, the larger heat capacity requires a smaller working mass of the air-kerosene heat exchanger, thereby reducing resistance, and the higher heat transfer coefficient allows the air-kerosene heat exchanger to work under high heat load. However, as an organic working fluid, aviation kerosene may produce coking at high temperatures. The coking is deposited on the solid wall of the heat exchange unit, causing the solid wall thermal resistance to increase, and even blocking the pipeline, thereby affecting the heat exchange efficiency and safety of the air-kerosene heat exchanger. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a multi-stage CCA heat exchange system for a turbofan engine and a working method thereof, which can solve the shortcomings of the prior art and at the same time utilize the heat sink of the duct air and the onboard fuel to cool the bleed air flow from the compressor outlet, reduce the bleed air cooling air temperature, solve the problem of difficult cooling of the turbofan engine turbine blades, and at the same time ensure that the flow resistance caused by the heat exchange system to each flow is below the limit value.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0008] A multi-stage CCA heat exchange system for a turbofan engine comprises an outer duct, an air-to-air heat exchanger is installed on the air inlet side of the outer duct, an air-to-kerosene heat exchanger is installed on the air outlet side of the outer duct, a heat exchange air cavity is installed on the outer side of the air-to-kerosene heat exchanger, an outlet of a compressor is connected to an air inlet of the air-to-air heat exchanger, an air outlet of the air-to-air heat exchanger is connected to an air inlet of the heat exchange air cavity, and an air outlet of the heat exchange air cavity outputs cooling air for cooling a high-pressure turbine.

[0009] Preferably, the air-to-air heat exchanger uses the bypass air as the cold side working medium and the high temperature air at the compressor outlet as the hot side working medium.

[0010] Preferably, the air-kerosene heat exchanger uses aviation kerosene as the cold side working fluid, and uses the air at the hot side outlet of the air-air heat exchanger as the hot side working fluid.

[0011] Preferably, the heat exchange air cavity is made of heat conductive material.

[0012] Preferably, the air output from the outer duct enters the mixing chamber and is mixed with the air from the inner duct.

[0013] A working method of the multi-stage CCA heat exchange system for a turbofan engine comprises the following steps:

[0014] The high-temperature air at the compressor outlet enters the air-to-air heat exchanger and exchanges heat with the duct air to achieve initial cooling. The air at the hot side outlet of the air-to-air heat exchanger enters the heat exchange air cavity and exchanges heat with aviation kerosene through the air-to-kerosene heat exchanger to achieve secondary cooling. At the same time, through the heat conduction of the heat exchange air cavity, the duct air continues to cool the air in the heat exchange air cavity. The air that has undergone secondary cooling is used to cool the high-pressure turbine. The air output from the duct enters the mixing chamber and mixes with the inner duct air. The aviation kerosene output from the air-to-kerosene heat exchanger outlet enters the main combustion chamber.

[0015] The beneficial effect brought about by adopting the above technical scheme is that the present invention can realize the cascade utilization of energy according to the cooling demand of engine bleed air, efficiently utilize the onboard fuel heat sink, form a thermal management technology scheme suitable for advanced turbofan engines, and support the comprehensive performance research of future advanced aircraft engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the installation position of the heat exchange system of the present invention in the engine.

[0017] Figure 2 It is a structural diagram of the heat exchange system of the present invention.

[0018] In the figure: 1. Air inlet; 2. Fan; 3. Compressor; 4. Main combustion chamber; 5. High-pressure turbine; 6. Low-pressure turbine; 7. Mixing chamber; 8. Afterburner; 9. Tail nozzle; 10. CCA heat exchange system; 11. Bypass duct; 12. Heat exchange air cavity; 13. Air-to-air heat exchanger; 14. Air-to-kerosene heat exchanger. DETAILED DESCRIPTION

[0019] Reference Figure 1-2 The multi-stage CCA heat exchange system for a turbofan engine provided by the present invention includes an outer duct 11, an air-to-air heat exchanger 13 is installed on the air inlet side of the outer duct 11, an air-to-kerosene heat exchanger 14 is installed on the air outlet side of the outer duct 11, a heat exchange air cavity 12 is installed on the outer side of the air-to-kerosene heat exchanger 14, the outlet of the compressor 3 is connected to the air inlet of the air-to-air heat exchanger 13, the air outlet of the air-to-air heat exchanger 13 is connected to the air inlet of the heat exchange air cavity 12, and the air outlet of the heat exchange air cavity 12 outputs cooling air for cooling the high-pressure turbine 5.

[0020] This system connects the air-to-air heat exchanger 13 and the air-to-kerosene heat exchanger 14 in series, so that the same heat fluid exchanges heat in the tube of the air-to-air heat exchanger 13 and outside the tube of the air-to-kerosene heat exchanger 14. The air-to-air heat exchanger 13 uses the outer duct air as a heat sink to cool the high-pressure turbine bleed air cooling air. The outer duct air, which has absorbed heat and heated up, enters the mixing chamber 7 and mixes with the inner duct air. This component is intended to perform preliminary cooling of the cooling air, and at the same time, the pressure loss caused by the heat exchanger to the outer duct air and the cooling air is not too large. The high-pressure turbine bleed air cooling air cooled by the air-to-air heat exchanger 13 flows into the heat exchange air cavity 12. The shape of the heat exchange air cavity 12 has been optimized and designed. Its main function is to separate the outer duct air and the bleed air cooling air so that they do not mix. At the same time, through the heat conduction of the heat exchange air cavity 12, the outer duct air can also cool the bleed air cooling air to a certain extent. The air-kerosene heat exchanger 14 uses aviation kerosene as a heat sink to further cool the high-pressure turbine bleed air cooling air cooled by the air-air heat exchanger 13, while controlling the temperature rise of the aviation kerosene after absorbing heat not to exceed the temperature limit. The aviation kerosene after absorbing heat and heating is injected into the main combustion chamber 4 to participate in combustion. This component is intended to perform secondary cooling on the cooling air, thereby further reducing the temperature of the cooling air.

[0021] The above-mentioned multi-stage heat exchanger CCA heat exchange system can comprehensively utilize the duct air and aviation kerosene. In view of the large flow resistance on both sides of the air-to-air heat exchanger 13 and the strict temperature limit of aviation kerosene in the air-to-kerosene heat exchanger 14, aviation kerosene is used to share the heat load of the air-to-air heat exchanger and reduce the size of the air-to-air heat exchanger. This can reduce the additional resistance caused by the air-to-air heat exchanger 13 to the duct air and the bleed air cooling air, and use the duct air to share the heat load of the air-to-kerosene heat exchanger 14 to prevent the aviation kerosene from overheating and causing coking problems.

[0022] A working method of the multi-stage CCA heat exchange system for a turbofan engine comprises the following steps:

[0023] The high-temperature air at the outlet of the compressor 3 enters the air-to-air heat exchanger 13, exchanges heat with the air in the outer duct to achieve initial cooling, and the air at the hot side outlet of the air-to-air heat exchanger 13 enters the heat exchange air cavity 12, exchanges heat with the aviation kerosene through the air-to-kerosene heat exchanger 14 to achieve secondary cooling. At the same time, through the heat conduction of the heat exchange air cavity, the air in the outer duct continues to cool the air in the heat exchange air cavity, and the air after secondary cooling is used to cool the high-pressure turbine; the air output from the outer duct 11 enters the mixing chamber 7 to mix with the inner duct air, and the aviation kerosene output from the outlet of the air-to-kerosene heat exchanger 14 enters the main combustion chamber 4.

[0024] This system uses air-to-air heat exchanger 13 and air-to-kerosene heat exchanger 14 as core components. The air-to-air heat exchanger 13 uses the bypass air as the cold side working medium and the high-temperature air from the outlet of the compressor 3 as the hot side working medium. The low-temperature air from the bypass absorbs the heat of the high-temperature air, and the cooling quality of the compressor outlet bleed air after heat release and temperature reduction is initially improved. The air-to-kerosene heat exchanger 14 uses aviation kerosene as the cold side working medium and the air from the hot side outlet of the air-to-air heat exchanger 13 as the hot side working medium. The aviation kerosene heat exchanger absorbs the heat of the high-temperature air, and the cooling quality of the compressor outlet bleed air after heat release and temperature reduction is further improved, which can then be used to cool hot end components such as the high-pressure turbine.

[0025] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0026] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A multi-stage CCA heat exchange system for a turbofan engine, characterized in that: The invention comprises an outer duct (11), an air-to-air heat exchanger (13) is installed on the air inlet side of the outer duct (11), an air-to-kerosene heat exchanger (14) is installed on the air outlet side of the outer duct (11), a heat exchange air cavity (12) is installed on the outer side of the air-to-kerosene heat exchanger (14), an outlet of the compressor (3) is connected to the air inlet of the air-to-air heat exchanger (13), an outlet of the air-to-air heat exchanger (13) is connected to the air inlet of the heat exchange air cavity (12), and an outlet of the heat exchange air cavity (12) outputs cooling air for cooling the high-pressure turbine (5).

2. The multi-stage CCA heat exchange system for a turbofan engine according to claim 1, characterized in that: The air-to-air heat exchanger (13) uses the bypass air as the cold side working medium and the high-temperature air at the outlet of the compressor (3) as the hot side working medium.

3. The multi-stage CCA heat exchange system for a turbofan engine according to claim 1, characterized in that: The air-kerosene heat exchanger (14) uses aviation kerosene as a cold side working medium and uses air at a hot side outlet of the air-air heat exchanger (13) as a hot side working medium.

4. The multi-stage CCA heat exchange system for a turbofan engine according to claim 1, characterized in that: The heat exchange air cavity (12) is made of heat conductive material.

5. The multi-stage CCA heat exchange system for a turbofan engine according to claim 1, characterized in that: The air output from the outer duct (11) enters the mixing chamber (7) and mixes with the air in the inner duct.

6. A method for operating a multi-stage CCA heat exchange system for a turbofan engine according to any one of claims 1 to 5, characterized in that The following steps are involved: The high-temperature air at the outlet of the compressor (3) enters the air-to-air heat exchanger (13) and exchanges heat with the air in the outer duct to achieve initial cooling. The air at the hot side outlet of the air-to-air heat exchanger (13) enters the heat exchange air cavity (12) and exchanges heat with aviation kerosene through the air-to-kerosene heat exchanger (14) to achieve secondary cooling. At the same time, the air in the heat exchange air cavity is further cooled by the air in the outer duct through heat conduction in the heat exchange air cavity. The air after secondary cooling is used to cool the high-pressure turbine. The air output from the outer duct (11) enters the mixing chamber (7) and is mixed with the air in the inner duct. The aviation kerosene output from the outlet of the air-to-kerosene heat exchanger (14) enters the main combustion chamber (4).

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