A multi-stage cca heat exchange system for a turbofan engine and a method of operation thereof

Abstract

The application discloses a multi-stage CCA heat exchange system for a turbofan engine, comprising an outer channel, an air-air heat exchanger is installed on the air inlet side of the outer channel, an air-kerosene heat exchanger is installed on the air outlet side of the outer channel, a heat exchange air cavity is installed on the outer side of the air-kerosene heat exchanger, the outlet of the compressor is connected with the air inlet of the air-air heat exchanger, the air outlet of the air-air heat exchanger is connected with the air inlet of the heat exchange air cavity, and the air outlet of the heat exchange air cavity outputs cooling air used for cooling a high-pressure turbine. The application can improve the defects of the prior art, simultaneously utilizes the heat sink of the outer channel air and the airborne fuel, cools the bleed air flow from the outlet of the compressor, reduces the temperature of the bleed air cooling air, solves the problem of difficult cooling of the turbine blade of the turbofan engine, and ensures that the flow resistance caused by the heat exchange system to each flow is below the limit value.

Description

Technical Field

[0001] This invention belongs to the field of aero-engines, and in particular to a multi-stage CCA heat exchange system for turbofan engines and its working method. Background Technology

[0002] Future high-performance aero engines will have higher cycle parameters and higher efficiency, but this also brings more prominent thermal protection and thermal control issues, as well as more stringent requirements for energy efficiency. On the one hand, key components such as hot-end parts require a suitable thermal environment; on the other hand, energy needs to be allocated in a coordinated manner to ensure the overall performance of the engine. To ensure the safe and reliable operation of the engine, there is an interaction between the main engine and the air system with cooling gases, which places requirements on the flow rate, temperature, and pressure of the cooling gases.

[0003] CCA (Computed Cooling) technology uses heat sinks including engine bypass air, aviation kerosene, and ram air. It extracts heat from the cooling air drawn from the compressor using these cryogenic working fluids, thereby improving the quality of the cooling air and helping to solve thermal protection and control problems in aero engines. The core component of CCA technology is the heat exchanger, which is classified into air-to-air heat exchangers and air-to-kerosene heat exchangers based on the cooling medium.

[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 has disadvantages such as low heat capacity, low density, and relatively low heat transfer coefficient between air and solid wall and air. These disadvantages make air-to-air heat exchangers prone to large pressure losses, insufficient structural compactness, and difficulty in working under high heat load environments, thus limiting their application in certain scenarios.

[0005] Air-kerosene heat exchangers are compact in 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 the working fluid, its large heat capacity allows for a smaller working mass in the air-kerosene heat exchanger, thus reducing resistance. The higher heat transfer coefficient also allows the air-kerosene heat exchanger to operate under high heat loads. However, as an organic working fluid, aviation kerosene may coke at high temperatures. Coke deposits on the solid walls of the heat exchange unit, leading to increased changes in solid wall thermal resistance and even blockage of pipelines, 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 turbofan engines and its working method, which can overcome the shortcomings of the prior art. At the same time, it utilizes the heat sink of the bypass air and airborne fuel to cool the bleed air flow from the compressor outlet, reduce the temperature of the bleed air, solve the problem of difficult cooling of turbofan engine turbine blades, and ensure that the flow resistance caused by the heat exchange system to each flow is below the limit value.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows.

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

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

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

[0011] Preferably, the heat exchange chamber is made of a thermally conductive material.

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

[0013] A method for operating the above-mentioned multi-stage CCA heat exchange system for a turbofan engine includes the following steps:

[0014] The high-temperature air from the compressor outlet enters the air-to-air heat exchanger, where it exchanges heat with the bypass air for initial cooling. The air from the hot side outlet of the air-to-air heat exchanger enters the heat exchange chamber, where it exchanges heat with aviation kerosene through the air-to-kerosene heat exchanger for secondary cooling. Simultaneously, the bypass air further cools the air in the heat exchange chamber through heat conduction. The air that has undergone secondary cooling is used to cool the high-pressure turbine. The air output from the bypass enters the mixing chamber and mixes with the air from the inner duct. The aviation kerosene output from the air-to-kerosene heat exchanger enters the main combustion chamber.

[0015] The beneficial effects of adopting the above technical solution are as follows: the present invention can achieve energy cascade utilization to meet the cooling requirements of engine bleed air, efficiently utilize airborne fuel heat sink, form a thermal management technology solution suitable for advanced turbofan engines, and support the comprehensive performance research of future advanced aero engines. Attached Figure Description

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

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

[0018] In the diagram: 1. Intake duct; 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. Outer bypass duct; 12. Heat exchange chamber; 13. Air-to-air heat exchanger; 14. Air-to-kerosene heat exchanger. Detailed Implementation

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

[0020] This system connects an air-to-air heat exchanger 13 and an air-to-kerosene heat exchanger 14 in series, allowing the same hot fluid to exchange heat successively inside the tubes of the air-to-air heat exchanger 13 and outside the tubes of the air-to-kerosene heat exchanger 14. The air-to-air heat exchanger 13 uses bypass air as a heat sink to cool the high-pressure turbine bleed air. The heated bypass air then enters the mixing chamber 7 to mix with the inner bypass air. This component is designed to provide initial cooling of the cooling air, while minimizing pressure loss between the bypass air and the cooling air. The high-pressure turbine bleed air, cooled by the air-to-air heat exchanger 13, flows into the heat exchange chamber 12. The heat exchange chamber 12 has an optimized shape; its main function is to separate the bypass air from the bleed air, preventing mixing. Simultaneously, through the heat conduction of the heat exchange chamber 12, the bypass air also provides some cooling to the bleed air. The air-kerosene heat exchanger 14 uses aviation kerosene as a heat sink to further cool the high-pressure turbine bleed air cooled by the air-air heat exchanger 13. At the same time, it controls the temperature rise of the aviation kerosene after absorbing heat to not exceed the temperature limit. The aviation kerosene that has absorbed heat and risen in temperature is injected into the main combustion chamber 4 to participate in combustion. This component is designed to perform secondary cooling of the cooling air, thereby further reducing the temperature of the cooling air.

[0021] The aforementioned multi-stage heat exchanger CCA heat exchange system can comprehensively utilize both bypass air and aviation kerosene. Addressing the high flow resistance on both sides of the air-to-air heat exchanger 13 and the stringent temperature limits of aviation kerosene in the air-to-kerosene heat exchanger 14, the system utilizes aviation kerosene to share the heat load of the air-to-air heat exchanger, reducing the size of the air-to-air heat exchanger. This reduces the additional resistance caused by the bypass air and bleed air cooling air in the air-to-air heat exchanger 13, and utilizes the bypass air to share the heat load of the air-to-kerosene heat exchanger 14, preventing the aviation kerosene from overheating and coking.

[0022] A method for operating the above-mentioned multi-stage CCA heat exchange system for a turbofan engine includes the following steps:

[0023] The high-temperature air from the compressor 3 outlet enters the air-to-air heat exchanger 13, where it exchanges heat with the bypass air for initial cooling. The air from the hot side outlet of the air-to-air heat exchanger 13 enters the heat exchange chamber 12, where it exchanges heat with aviation kerosene through the air-to-kerosene heat exchanger 14 for secondary cooling. Simultaneously, the bypass air further cools the air in the heat exchange chamber through heat conduction. The air that has undergone secondary cooling is used to cool the high-pressure turbine. The air output from the bypass duct 11 enters the mixing chamber 7 and mixes with the inner bypass air. The aviation kerosene output from the air-to-kerosene heat exchanger 14 enters the main combustion chamber 4.

[0024] This system uses an air-to-air heat exchanger 13 and an air-to-kerosene heat exchanger 14 as its core components. The air-to-air heat exchanger 13 uses bypass air as the cold-side working fluid and high-temperature air from the compressor 3 outlet as the hot-side working fluid. The low-temperature bypass air absorbs heat from the high-temperature air, resulting in an initial improvement in the cooling quality of the compressor outlet bleed air after heat release and cooling. The air-to-kerosene heat exchanger 14 uses aviation kerosene as the cold-side working fluid and air from the hot-side outlet of the air-to-air heat exchanger 13 as the hot-side working fluid. The aviation kerosene absorbs heat from the high-temperature air, further improving the cooling quality of the compressor outlet bleed air after heat release and cooling. This air can then be used to cool hot-end components such as the high-pressure turbine.

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

[0026] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A multi-stage CCA heat exchange system for a turbofan engine, characterized in that: Includes an outer bypass duct (11), an air-to-air heat exchanger (13) is installed on the air inlet side of the outer bypass duct (11), an air-to-kerosene heat exchanger (14) is installed on the air outlet side of the outer bypass duct (11), a heat exchange chamber (12) is installed on the outside 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 outlet of the air-to-air heat exchanger (13) is connected to the air inlet of the heat exchange chamber (12), and the outlet of the heat exchange chamber (12) outputs cooling air for cooling the high-pressure turbine (5); The heat exchange chamber (12) is made of thermally conductive material and is covered by the outside of the air-kerosene heat exchanger (14) to form an independent annular cavity for the flow of induced air. The shape of the heat exchange chamber (12) is optimized to separate the outer bypass air from the induced draft cooling air so that they do not mix. At the same time, the outer bypass air cools the induced draft cooling air to a certain extent through the heat conduction of the heat exchange chamber (12). After the induced draft air is initially cooled by the air-air heat exchanger (13), it enters the heat exchange chamber (12) and is simultaneously cooled by the inner air-kerosene heat exchanger (14) and the outer bypass air is cooled by the wall of the heat exchange chamber (12).

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

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

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

5. A method for operating a multi-stage CCA heat exchange system for a turbofan engine as described in any one of claims 1-4, characterized in that... Includes the following steps: The high-temperature air from the compressor (3) outlet enters the air-to-air heat exchanger (13) and exchanges heat with the bypass air to achieve initial cooling. The air from the hot side outlet of the air-to-air heat exchanger (13) enters the heat exchange chamber (12) and exchanges heat with 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 chamber, the bypass air continues to cool the air in the heat exchange chamber. The air that has undergone secondary cooling is used to cool the high-pressure turbine. The air output from the bypass (11) enters the mixing chamber (7) and mixes with the inner bypass air. The aviation kerosene output from the air-to-kerosene heat exchanger (14) outlet enters the main combustion chamber (4).

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