Air injection type cooling device for embedded high-temperature and high-speed motor of aero-engine

Abstract

The invention discloses an aero-engine embedded high-temperature high-speed motor air injection type cooling device which comprises a motor shell, a hole in the shape of a Laval nozzle is formed in the motor shell and comprises a contraction section and an expansion section, the inlet end of the contraction section is located on the inner wall of the motor shell, and the outlet end of the expansion section is located on the inner wall of the motor shell. The outlet end of the expansion section is located on the outer wall of the motor shell. The holes in the shape of the Laval nozzle are formed in the shell of the motor, air with huge flow generated in the operation process of an aero-engine is adopted as a cooling working medium, the high-temperature and high-pressure motor is cooled, the cooling effect is good, the structure is simple, no extra structure needs to be added, the performance of the engine cannot be affected, and the safety of an aircraft is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of more-electric aircraft and more-electric engines, and in particular to an air jet cooling device for an aircraft engine embedded high-temperature and high-speed motor. Background Art

[0002] In order to improve the performance of future aircraft in terms of safety, cleanliness and quietness, the aerospace design community has proposed the concept of "multi / all-electric aircraft". The main idea of ​​realizing the concept of multi-electric aircraft is to install the motor directly on the high-pressure shaft of the aircraft engine to eliminate the auxiliary gearbox between the aircraft engine shaft and the motor. Its advantages include significantly simplifying engine maintenance, reducing engine weight and overall size (removing the auxiliary gearbox, the engine mass can be reduced by 15-20%), increasing engine fuel efficiency, and realizing direct electric starting of the engine. The difficulty of installing the motor on the high-pressure shaft of the engine is the high temperature ambient temperature condition of the high-pressure shaft and the high degree of integration of the motor. Therefore, the cooling effect of the motor is particularly important.

[0003] There are many cooling methods for motors at present. According to the different cooling media, they can be divided into air cooling and liquid cooling; according to whether there is a phase change in the cooling material during the cooling process, it can be divided into air / liquid cooling without phase change and evaporative cooling with phase change. Air cooling can be divided into natural and forced convection cooling according to the different convection methods. The cooling effect of natural convection is general, but its structure is relatively simple; the cooling effect of forced convection is relatively good, but its disadvantage is that the method is more complicated and requires more parts. Liquid cooling is divided into oil cooling, water cooling and mixed solution according to the type of coolant. The oil cooling structure is diverse, such as directly immersing the motor in the oil cooling medium, setting oil cooling pipes on structures such as stators or motor housings, spraying cooling oil on the ends of motor windings, etc., but the coolant will affect the motor, such as causing corrosion. The principle of evaporative cooling is different from the above. It mainly uses the vaporization of liquid to absorb part of the heat. One advantage of evaporative cooling is that once the cooling structure is cleverly designed, the self-circulation of the coolant can be fully realized. However, due to the harsh conditions of the cooling structure, it is currently rarely used in ordinary motors. Based on the current development status of motor cooling technology, cooling methods used in conventional fields: such as ventilation, water, spray and oil injection cooling methods, do not need to be restricted by special environmental conditions, and some even require additional equipment, devices and additional loads. However, there are fewer studies on cooling methods for aviation motors, and the efforts are relatively weak. The main reason is that for aviation vehicles, every additional equipment will cause a decrease in safety and stability. Therefore, the above-mentioned cooling methods do not meet the cooling needs of aviation high-temperature and high-speed motors. It is urgent to develop new safe and effective cooling methods to meet the high temperature (300°C) working environment requirements of aircraft engines. Summary of the invention

[0004] Purpose of the invention: In view of the above shortcomings, the present invention provides an air jet cooling device for an aircraft engine embedded high-temperature and high-speed motor, which can effectively cool the high-temperature and high-speed motor while ensuring the safety of the engine.

[0005] Technical solution: To solve the above problems, the present invention adopts an air jet cooling device for an embedded high-temperature and high-speed motor of an aircraft engine, comprising a motor casing, wherein the motor casing is provided with an opening in the shape of a Laval nozzle, wherein the opening comprises a contraction section and an expansion section, wherein the inlet end of the contraction section is located on the inner wall of the motor casing, and the outlet end of the expansion section is located on the outer wall of the motor casing.

[0006] Furthermore, the axis of the opening is perpendicular to the plane where the inner wall of the motor casing is located.

[0007] Furthermore, the openings are symmetrically arranged on the motor casing.

[0008] Furthermore, the contraction angle of the contraction section is 45°, and the expansion angle of the expansion section is 8°.

[0009] Furthermore, the inlet radius is equal to the outlet radius.

[0010] Furthermore, the radii of the inlet and outlet ends are both 2.6 mm, the radius of the throat is 2 mm, the length of the contraction section along the axial direction is 1.6 mm, and the length of the expansion section along the axial direction is 8.4 mm.

[0011] Furthermore, it also includes a motor, which is installed in a motor casing. The gas inside the motor enters from the inlet end and is ejected from the outlet end after passing through the opening.

[0012] Furthermore, the outlet port is communicated with an internal passage of the engine.

[0013] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) by setting a Laval nozzle-shaped opening on the motor housing, a huge amount of air generated during the operation of the aircraft engine is used as a cooling medium to achieve cooling of the high-temperature and high-pressure motor. The cooling effect is good and the structure is simple. No additional structure is required, and the engine performance will not be affected, thereby ensuring the safety of the aircraft. (2) After the motor is cooled through the opening, the air is ejected through the nozzle and then continues to return to the inner duct, which has little effect on the overall thrust of the aircraft engine. The gas discharged from the outlet has a higher temperature after expansion and heat absorption. After the gas returns to the inner duct, the temperature of the combustion air in the combustion chamber is increased, which helps to improve combustion efficiency and save aviation kerosene. (3) The optimal size of the nozzle is obtained through cooling numerical simulation calculations, thereby ensuring a working environment below 300°C inside the high-temperature and high-speed motor, thereby ensuring the safe operation of the high-temperature and high-speed motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic cross-sectional view of the overall structure of the cooling device of the present invention;

[0015] Figure 2 A schematic diagram of the shape of the openings on the cooling device of the present invention;

[0016] Figure 3 It is a schematic diagram of the local structure of the opening of the motor casing of the present invention;

[0017] Figure 4 A schematic diagram of the optimal size of the opening of the cooling device of the present invention;

[0018] Figure 5 This is a schematic diagram of the overall structure of an aircraft engine;

[0019] Figure 6 It is the temperature contour cloud diagram under adiabatic expansion conditions when the outlet Mach number is 2 and the outlet pressure is 0.01MPa;

[0020] Figure 7 It is the temperature contour cloud diagram under non-adiabatic expansion conditions when the outlet Mach number is 2 and the outlet pressure is 0.01MPa;

[0021] Figure 8 The temperature change curves of the air in the opening under adiabatic and non-adiabatic conditions; Curve 1 is the temperature change under non-adiabatic conditions, and Curve 2 is the temperature change under adiabatic conditions;

[0022] Fig. 9 It is the velocity change curve of the air in the opening under adiabatic and non-adiabatic conditions; wherein, curve 1 is the velocity change under non-adiabatic conditions, and curve 2 is the velocity change under adiabatic conditions. DETAILED DESCRIPTION

[0023] like Figures 1 to 3 As shown, an air jet cooling device for an aircraft engine embedded high-temperature and high-speed motor in this embodiment includes a motor housing 5, and an opening 6 in the shape of a Laval nozzle is opened on the motor housing 5, and the cooling of the housing is realized by absorbing heat by expanding compressed air. The opening 6 includes a contraction section and an expansion section, and the inlet end 1 of the contraction section is located on the inner wall 4 of the motor housing, and the outlet end 2 of the expansion section is located on the outer wall 3 of the motor housing. The planes where the inner wall and the outer wall of the motor housing 5 are located are parallel to each other, and the axis of the opening 6 is perpendicular to the plane where the inner wall of the motor housing is located. Openings 6 are provided on both sides of the motor housing 5, and the two openings are arranged symmetrically. The motor 13 is installed in the motor housing 5, and the gas inside the motor enters from the inlet end 1 and is ejected from the outlet end 2 after passing through the opening 6. The heat inside the high-temperature and high-speed motor is transferred to the housing through heat conduction and convection heat exchange, and the heat of the external environment of the high-temperature and high-speed motor is transferred to the motor housing. Through the present invention, a dynamic balance of heat can be achieved at the housing to ensure that the ambient temperature inside the motor is lower than 300°C.

[0024] In order to achieve the best cooling effect, it is necessary to design the optimal size of the opening. Based on the principles of thermodynamics and the thermodynamic process of adiabatic expansion of gas, the transformation of enthalpy and kinetic energy of air after adiabatic expansion through the nozzle and the temperature change trend and law of the expanding gas are analyzed. Drawing on the characteristics of adiabatic expansion of air, the cooling effect of air under non-adiabatic conditions is analyzed, and then metal nozzle channels of different structural sizes are designed. The air expansion process and boundary heat transfer of the designed nozzle under non-adiabatic conditions are numerically simulated, and the state changes of air under non-adiabatic expansion and the cooling effect on the surrounding environment under non-adiabatic boundaries are analyzed and compared. The optimal length of the nozzle that can ensure the working temperature (≯300℃) is obtained at the expense of the mass flow rate at the inlet. Then, by changing the size of the inlet and outlet dimensions of the nozzle, different boundary heat flow conditions and pressure conditions, cooling simulation calculations are performed to obtain the optimal size of the Laval nozzle that can ensure the working temperature (≯300℃). The optimal size of the final design is that the contraction angle of the contraction section is 45°, the expansion angle of the expansion section is 8°, the radius of the inlet end 1 and the outlet end 2 are both 2.6mm, the throat radius is 2mm, the length of the contraction section along the axial direction is 1.6mm, and the length of the expansion section along the axial direction is 8.4mm. Figure 4 shown.

[0025] like Figure 5 As shown, the overall structure of the engine is provided with a fan 11, a low-pressure compressor 12, a motor 13, a high-pressure compressor 14, a combustion chamber 15, a high-pressure turbine 16, a low-pressure turbine 17, and a tail nozzle 18 from front to back. The motor 13 is installed at the front end of the high-pressure shaft inside the engine. The motor needs to meet the requirements of stable operation at an operating temperature of 300°C and a speed of 15183rpm. The outlet port 2 is connected to the engine inner channel. After the opening completes the cooling of the motor, the air is ejected through the nozzle and then continues to return to the inner channel, which has little effect on the overall thrust of the aircraft engine; and the gas discharged from the outlet port 2 has a higher temperature after expansion and heat absorption. After the gas returns to the inner channel, the temperature of the combustion air in the combustion chamber is increased, which helps to improve the combustion efficiency and save aviation kerosene.

[0026] To verify the effectiveness of the present invention, the gas temperature and velocity simulations were performed under adiabatic expansion and non-adiabatic expansion conditions, respectively. Adiabatic expansion occurs under an ideal adiabatic state, while the actual situation is generally non-adiabatic expansion. Figures 6 to 8 As shown, under adiabatic expansion conditions, the gas temperature at the motor outlet drops to 163K, and under non-adiabatic expansion conditions, the gas temperature at the motor outlet drops to 176K.

[0027] The following formula is introduced to calculate the theoretical value of the gas temperature after cooling:

[0028]

[0029] In the formula, c p is the specific heat capacity at constant pressure, J / (kg·K), k is the air adiabatic index, which is 1.4, and R is the gas constant, which is 8.314 J / (mol·K).

[0030] Substituting formula (1) into formula (2) yields formula (3):

[0031]

[0032] In the formula, c f is the flow rate of the gas (m / s), T0 is the stagnation temperature (K), and T is the temperature of the fluid (K).

[0033] When the stagnation temperature at the inlet is 300K and the outlet Mach number is 2, the nozzle outlet temperature T = 166K is obtained by substituting into formula (3), indicating that the numerical simulation results are consistent with the theoretical results. Under non-adiabatic conditions, the air expands and absorbs heat. After contacting the metal plate wall, convection heat transfer occurs, absorbing and taking away the heat of the metal plate, resulting in the air outlet temperature of 175K, and the metal plate wall temperature drops from 300K to 251K. This result shows that compressed air has a very good cooling effect under non-adiabatic conditions.

[0034] like Fig. 9 As shown, this embodiment also simulates and measures the outlet gas velocity. It can be seen from the figure that the outlet flow velocity of the compressed air during adiabatic expansion can reach about 525m / s, while the outlet velocity of the air during non-adiabatic expansion reaches about 500m / s, which speed will basically not affect the normal thrust of the engine.

[0035] The present invention achieves cooling of the high-temperature and high-pressure motor by arranging a Laval nozzle-shaped opening on the motor housing and adopting the air with a huge flow rate generated during the operation of the aircraft engine as a cooling medium. The cooling effect is good and the structure is simple. No additional structure is required, and the engine performance will not be affected, thereby ensuring the safety of the aircraft.

Claims

1. An air jet cooling device for an aircraft engine built-in high-temperature and high-speed motor, characterized in that: The invention comprises a motor housing (5), wherein the motor housing (5) is provided with an opening (6) in the shape of a Laval nozzle, wherein the opening (6) comprises a contraction section and an expansion section, wherein the inlet end (1) of the contraction section is located on the inner wall (4) of the motor housing, and the outlet end (2) of the expansion section is located on the outer wall (3) of the motor housing.

2. The aircraft engine built-in high-temperature and high-speed motor air jet cooling device according to claim 1, characterized in that: The axis of the opening (6) is perpendicular to the plane where the inner wall of the motor housing is located.

3. The aircraft engine built-in high-temperature and high-speed motor air jet cooling device according to claim 1, characterized in that: The openings (6) are symmetrically arranged on the motor housing (5).

4. The aircraft engine built-in high-temperature and high-speed motor air jet cooling device according to claim 1, characterized in that: The contraction angle of the contraction section is 45°, and the expansion angle of the expansion section is 8°.

5. The aircraft engine built-in high-temperature and high-speed motor air jet cooling device as claimed in claim 4, characterized in that: The radius of the inlet end (1) is equal to the radius of the outlet end (2).

6. The aircraft engine built-in high-temperature and high-speed motor air jet cooling device according to claim 5, characterized in that: The radii of the inlet end (1) and the outlet end (2) are both 2.6 mm, the radius of the throat is 2 mm, the length of the contraction section along the axial direction is 1.6 mm, and the length of the expansion section along the axial direction is 8.4 mm.

7. The aircraft engine built-in high-temperature and high-speed motor air jet cooling device according to claim 1, characterized in that: It also includes a motor, which is installed in a motor housing (5). Gas inside the motor enters from an inlet end (1) and is ejected from an outlet end (2) after passing through an opening (6).

8. The aircraft engine built-in high-temperature and high-speed motor air jet cooling device according to claim 1, characterized in that: The outlet end (2) is in communication with the inner duct of the engine.

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