Visual test system for internal flow of aero-engine nozzle under multiple working conditions

Abstract

The invention discloses a visual test system for internal flow of an aero-engine nozzle under multiple working conditions. The system is composed of a fuel oil supply system, a fuel oil recovery system, a nitrogen supply system, an experiment section, an optical test system and a signal acquisition system. The fuel oil supply system comprises an oil tank, a filter, an oil pump, a mass flow meter, an electric heating pipe, a first temperature sensor and a first pressure sensor and is used for adjusting and monitoring the temperature and pressure of fuel oil. The fuel oil recovery system comprises a switch valve, a cooling tower, a liquid collector, a second temperature sensor and a second pressure sensor and is used for recovering fuel oil. The nitrogen supply system comprises a gas cylinder, a pressure reducing valve and a gas guiding pipe and is used for adjusting gas pressure. The experiment section comprises a replaceable transparent section, a fuel oil inlet section, a metal cavity and various sensors and is used for simulating different nozzle structures and internal flow characteristics thereof. The optical testing system adopts a rainbow schlieren imaging technology to capture and analyze flow images of fuel oil. The signal acquisition system works cooperatively with a computer through a synchronous controller, and collects state parameters such as temperature, pressure and flow of fuel oil and internal flow images in real time. According to the invention, under the working conditions of high temperature and high pressure, the flow form and state parameters of fuel oil in a complex nozzle geometric structure can be comprehensively researched, and reliable experimental data and theoretical basis are provided for design and performance optimization of aero-engine nozzles.

Description

Technical Field

[0001] The present invention relates to the research field of aviation system power technology, and in particular to a test system and a method for using the system for exploring the influence of injection pressure, fuel temperature, fuel flow rate and nozzle geometry on fuel nozzle state parameters and internal flow characteristics. Background Art

[0002] In the field of high-performance aircraft design, the handling of thermal protection issues is crucial. Cooling systems that use fuel with high specific heat capacity as heat sinks are considered to have broad prospects. Such systems can not only provide efficient active cooling capabilities, but the preheated fuel is also beneficial to improving combustion performance. In this context, active cooling technologies such as regenerative cooling technology, precooling cooling air technology, and skin heat exchange technology have been proposed one after another, aiming to achieve comprehensive protection of the hot end components of the aircraft while improving overall flight performance.

[0003] When this type of technology is used, the fuel temperature will rise, and the fuel pressure, density and other state parameters will inevitably change. Changes in fuel temperature and pressure may cause liquid fuel to enter a gas-liquid mixed state, a gaseous state or even a supercritical state. The change in the fuel phase has a significant impact on the flow state and spray effect of the fuel: on the one hand, the diffusion capacity of the fuel in the gaseous and supercritical states is greatly enhanced, and the mixing speed with the air is greatly increased, which is conducive to the injection and mixing of the fuel, thereby better serving the rapid and efficient combustion of the aircraft engine combustion chamber; on the other hand, when the phase state and flow of the fuel are unstable, it may lead to instability in the fuel flow and fuel spray field, and then lead to instability in the combustion process or even flameout.

[0004] Therefore, it is very important to develop an experimental device that can explore the phase characteristics and flow characteristics of fuel in the nozzle under high temperature and high pressure conditions. Such a device can deeply explore the internal flow characteristics of fuel under different injection parameters, clearly describe the phase state of fuel, establish the relationship between the internal flow characteristics of fuel and spray characteristics, and provide important experimental data and theoretical basis for optimizing nozzle design, optimizing spray performance, and improving the stability of fuel injection mixing and combustion. Accordingly, the present invention aims to provide an experimental device with a wide parameter range, visualization and high controllability, which is used to systematically study the internal flow characteristics of fuel under different geometric configurations, flow conditions and injection temperature and pressure. Summary of the invention

[0005] In order to better study the flow characteristics of fuel inside a nozzle under different states, the present invention provides an experimental device capable of performing visual measurement of the flow inside an aero-engine nozzle under multiple working conditions.

[0006] The technical solution adopted by the present invention is:

[0007] A visual test system for internal flow of an aero-engine nozzle under multiple working conditions comprises a fuel supply system, a fuel recovery system, a nitrogen supply system, an experimental section, an optical test system and a signal acquisition system.

[0008] The fuel supply system includes a fuel tank, a filter, an oil pump, a mass flow meter, an electric heating tube, a first temperature sensor, and a first pressure sensor; the fuel recovery system includes a first switch valve, a second switch valve, a second temperature sensor, a second pressure sensor, a check valve, a cooling tower, and a liquid collector; the nitrogen supply system includes a gas cylinder, a third switch valve, and a pressure reducing valve; the experimental section includes an air bleed pipe, a transparent section, a cover plate, a metal cavity, a fuel inlet section, a third pressure sensor, a third temperature sensor, a replaceable transparent section nozzle, and a replaceable inlet section; the optical test system includes a light source, a slit, a first convex lens, a second convex lens, a rainbow filter, a third convex lens, and a high-speed camera; the signal acquisition system includes a synchronous controller and a computer.

[0009] The fuel supply system is connected to the experimental section through an oil inlet pipeline, and the fuel is pumped into the experimental section by an oil pump. An electric heating pipe is provided on the oil inlet pipeline to control the fuel temperature; a mass flow meter is attached to the oil pump to collect flow information; a first temperature sensor and a first pressure sensor are attached to the electric heating pipe to transmit the fuel temperature and pressure parameters at the outlet of the heating pipe to the signal acquisition system.

[0010] The fuel recovery system is arranged between the fuel supply system and the experimental section, and is attached with a first switch valve and a second switch valve for regulating the flow of fuel to the experimental section or the liquid collector; a cooling tower is arranged in front of the liquid collector, which is used to cool the fuel that has not reached the target temperature and pressure and then enter the liquid collector for recovery; a second temperature sensor and a second pressure sensor are arranged on the oil circuit in front of the cooling tower to transmit the fuel temperature and pressure parameters to the signal acquisition system.

[0011] The nitrogen supply system inputs the nitrogen in the gas cylinder into the experimental section through the air duct; the gas cylinder is equipped with a pressure reducing valve to adjust the gas pressure.

[0012] The experimental section includes an air duct, a transparent section, a cover plate, a metal cavity, and a fuel inlet section, wherein the transparent section and the fuel inlet section can be replaced with components with different structural parameters respectively.

[0013] The optical testing system is a rainbow schlieren imaging system. The light source generates a light beam which passes through a slit, a first convex lens, an experimental section, a second convex lens, a rainbow filter, and a third convex lens in sequence and enters a high-speed camera. The captured image is collected by a signal acquisition terminal.

[0014] The data acquisition system stores the temperature, pressure, flow data and internal flow image of the fuel when the fuel is sprayed into the computer synchronously through the synchronizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0016] Figure 2 is a schematic diagram of a fuel supply system of the present invention;

[0017] Figure 3 is a schematic diagram of a fuel recovery system of the present invention;

[0018] Figure 4 is a schematic diagram of a nitrogen supply system of the present invention;

[0019] Figure 5 It is a schematic diagram of the experimental section of the present invention;

[0020] Figure 6 is a schematic diagram of an optical testing system of the present invention;

[0021] In the figure: 1. fuel supply system; 2. fuel recovery system; 3. nitrogen supply system; 4. experimental section; 5. optical test system; 6. signal acquisition system; 7. oil tank; 8. filter; 9. oil pump; 10. mass flow meter; 11. electric heating tube; 12. first temperature sensor; 13. first pressure sensor; 14. first switch valve; 15. second switch valve; 16. second temperature sensor; 17. second pressure sensor; 18. check valve; 19. cooling tower; 2 0. Liquid collector; 21. Gas cylinder; 22. Third switch valve; 23. Pressure reducing valve; 24. Air bleed pipe; 25. Transparent section; 26. Cover plate; 27. Metal cavity; 28. Fuel inlet section; 29. ​​Third pressure sensor; 30. Third temperature sensor; 31. Replaceable transparent section nozzle; 32. Replaceable inlet section; 33. Light source; 34. Slit; 35. First convex lens; 36. Second convex lens; 37. Rainbow filter; 38. Third convex lens; 39. High-speed camera. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0023] like Figure 1 As shown, a multi-operating-condition aircraft engine nozzle internal flow test system is characterized by comprising a fuel supply system 1, a fuel recovery system 2, a nitrogen supply system 3, a test section 4, an optical test system 5 and a signal acquisition system 6.

[0024] like Figure 2As shown, in the fuel supply system 1, the fuel in the oil tank 7 is transported to the electric heating pipe 11 by the oil pump 9 after passing through the filter 8. The electric heating pipe 11 is used to adjust the fuel temperature, and cooperates with the mass flow meter 10, the first temperature sensor 12, and the first pressure sensor 13 to ensure that the fuel enters the experimental section under the set temperature, pressure and flow conditions.

[0025] like Figure 3 As shown, in the fuel recovery system 2, the first switch valve 14 and the second switch valve 15 are used to adjust the fuel entering the fuel recovery system or the experimental section. A second temperature sensor 16 and a second pressure sensor 17 are provided before the check valve 18. When the fuel temperature and pressure do not reach the target, the fuel enters the cooling tower 19 for cooling and then enters the liquid collector 20 for recovery.

[0026] like Figure 4 As shown, in the nitrogen supply system 3, the gas cylinder 21 inputs nitrogen into the experimental section through the air duct 24, and the air duct is equipped with a pressure reducing valve 23 for adjusting the gas pressure.

[0027] like Figure 5 As shown, in the experimental section 4, the fuel enters the fuel inlet section 28 after passing through the metal cavity 27, and is mixed with the gas in the transparent section 25 and sprayed out. The third pressure sensor 29 and the third temperature sensor 30 measure the temperature and pressure of the fuel in the metal cavity before spraying. A replaceable transparent section nozzle 31 is also provided, and its structure is as follows Figure 5 (a) Air atomization configuration with replaceable transparent nozzle and Figure 5 (b) A replaceable transparent nozzle section of a direct injection configuration is provided. According to the experimental requirements, replaceable nozzles with different nozzle radii, nozzle lengths, and nozzle inlet convergence angles are provided. In addition, a replaceable fuel inlet section 32 is provided, and its structure is as follows: Figure 5 (c) Direct injection fuel inlet section configuration, Figure 5 (d) Single-channel centrifugal cyclone chamber configuration, Figure 5 (e) A replaceable fuel inlet section of a dual-path centrifugal swirl chamber configuration, wherein the replaceable inlet section is manufactured according to experimental requirements with respect to the length, radius, number of swirl holes thereon, radius of the swirl holes, and distance of the swirl holes from the center axis.

[0028] The transparent section 25, the replaceable transparent section nozzle 31, and the replaceable fuel inlet section 32 are made of quartz glass with good temperature resistance and a refractive index similar to that of the fuel. It is necessary to pay attention to annealing the light-transmitting surface to ensure its smoothness. The thickness of the glass wall is about 5mm. Through the matched processing of the cover plate 26 and the metal cavity 27, it is ensured that there is no leakage under the conditions of 420℃ and 3MPa of fuel.

[0029] like Figure 6As shown, in the optical test system 5, the light source 33 of the rainbow schlieren imaging system generates a light beam which passes through the slit 34, the first convex lens 35, the experimental section 4, the second convex lens 36, the rainbow filter 37, and the third convex lens 38 in sequence and then enters the high-speed camera 39, and all the above components are aligned horizontally. The slit 34 is a 3mm×100μm rectangular square hole, and its position is strictly determined at one focal length of the first convex lens 35. The hue range of the rainbow filter 37 from its center to both sides is 20° to 320°, which is used to convert the light deflection angle information of the experimental section fluid into color information, and its position is strictly determined at one focal length of the second convex lens 36; the third convex lens 38 is used to focus and magnify the image, and the image information is obtained by the high-speed camera 39, and the captured image is collected by the signal acquisition system 6.

[0030] The data acquisition system 6 is composed of a synchronous controller and a computer equipped with relevant data processing software. The synchronous controller is used to ensure that the temperature, pressure, and flow information of the fuel at the outlet of the heater, the inlet of the recovery oil circuit, and the fuel before injection in the experimental section in the experimental system are obtained at the same time, as well as the image taken by the color high-speed camera at this moment. The processing program in the computer can convert the Red (R), Green (G), and Blue (B) signals collected by the camera into hue (Hue), saturation (Saturation), and brightness (Value) signals, and the hue signal is settled into a light deflection angle signal through the program. The light deflection angle θ is calculated by the following formula:

[0031]

[0032] Where f is the focal length of the lens, and ΔD is the distance the light is deflected. The relationship between the lateral deflection angle θ and the refractive index of the light is calculated by the following formula:

[0033]

[0034] Where n is the local refractive index, n0 is the refractive index around the test medium, and η is the normalized refractive index. The color tone information in the image is analyzed through a computer program to obtain the refractive index distribution law of the fluid.

[0035] The electric heating tube 11 made of high temperature alloy can heat the fuel to 600°C, and the heating effect is adjusted by the heating current. During the heating process, the current passing through the electric heating tube 11 may exceed 100A, so you must pay attention to electrical safety when using it.

[0036] The method of using the multi-operating-condition aeroengine nozzle internal flow testing system of the present invention is as follows:

[0037] (1) After selecting the required transparent section 25 and fuel inlet section 28 according to the selected experimental content, the experimental section 4 is assembled.

[0038] (2) Connect the experimental system, adjust the opening of each valve, check the sealing of the oil and gas lines, and ensure that there is no leakage of fuel or nitrogen.

[0039] (3) Check the insulation condition of the electric heating tube 11 to ensure there is no leakage.

[0040] (4) Install the light source 33, slit 34, first convex lens 35, experimental section 4, second convex lens 36, rainbow filter 37, third convex lens 38, and high-speed camera 39, ensure that the light path is collimated, and that the slit 34 and rainbow filter 37 are installed at the focal point of the lens. Then, record the image without the fluid medium, record the hue information of the background image, and calibrate the rainbow schlieren system.

[0041] (5) Connect the synchronization controller and debug the synchronization controller delay to ensure that the temperature and pressure information and image information are recorded simultaneously.

[0042] (6) Close the switch valve 14 connected to the experimental section 4, open the switch valve 15 connected to the liquid collector 20, turn on the oil pump 9, and then adjust the current of the electric heating tube 11 to start fuel heating. At this time, the fuel flows to the liquid collector 20.

[0043] (7) When the fuel temperature basically reaches the experimental requirements, first open the switch valve 14 and then close the switch valve 15 to allow the fuel to flow to the experimental section, and wait until the fuel temperature and pressure in the experimental section are stable within the experimental requirements.

[0044] (8) The fuel injection pressure, temperature and flow rate information of the experimental section 4 are collected by the recording software of the data acquisition system 6, and the flow field image in the transparent section 25 and its outlet during the injection is recorded. The flow field refractive index information is extracted by the image processing program.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. The present invention is based on constant flow, which is closer to actual working conditions and can simulate the flow and phase change behavior of fuel under high temperature and high pressure conditions in actual aircraft engines. By precisely controlling the temperature and pressure of the fuel, the experimental system can innovatively reproduce special phenomena such as flash boiling and supercritical fuel spray that may occur during the injection process, and conveniently obtain the fuel state parameters that cause such phenomena.

[0047] Second, by using the rainbow schlieren imaging system, the present invention can intuitively capture the flow image of the phase change of the fuel in the complex nozzle geometry. The rainbow schlieren system can clearly and intuitively reflect the refractive index information of the fluid medium, which is helpful for obtaining the density information inside the flow field and distinguishing the phase state of the fluid medium.

[0048] 3. The design of the experimental section allows the replacement of different nozzle flow channel geometries while the overall structure remains basically unchanged. This design allows researchers to produce replacement test pieces with various geometric configurations and flow channel sizes relatively cheaply and quickly, and to quickly study the effects of nozzle geometry parameters such as nozzle configuration, nozzle hole length, hole diameter, swirl chamber angle, swirl hole parameters, etc. on the fuel injection process in the same experimental system.

[0049] Fourth, the present invention can simultaneously capture images of the internal flow of fuel and images of the spray field, and use a synchronizer to record the temperature, pressure and flow parameters of the fuel when the image is taken, so as to provide more accurate theoretical analysis data for the image information.

[0050] The specific implementation methods of the present invention are described in detail above in combination with the accompanying drawings and specific implementation processes, but the present invention is not limited to the above implementation methods. Technicians in this field can make various changes and optimizations to the above methods without departing from the principles of the present invention.

Claims

1. A visual test system for internal flow of an aircraft engine nozzle under multiple working conditions, characterized in that: The invention comprises a fuel supply system (1), a fuel recovery system (2), a nitrogen supply system (3), an experimental section (4), an optical test system (5) and a signal acquisition system (6).

2. The visual testing system for internal flow of aeroengine nozzles under multiple working conditions according to claim 1, characterized in that: The fuel supply system (1) is connected to the experimental section (4) via an oil inlet pipeline, and the fuel is pumped into the experimental section (4) by an oil pump (9). An electric heating pipe (11) is provided on the oil inlet pipeline to control the fuel temperature. The fuel is heated to 600° C. in the electric heating pipe (11) made of a high-temperature alloy, and the heating effect is achieved by adjusting the current of the electric heating pipe (11). A mass flow meter (10) is attached to the oil pump (9) to collect flow information. A first temperature sensor (12) and a first pressure sensor (13) are attached to the electric heating pipe (11) to transmit the fuel temperature and pressure parameters at the outlet of the heating pipe to a signal acquisition system (6).

3. The visual testing system for internal flow of aero-engine nozzles under multiple working conditions according to claim 1, characterized in that: The fuel recovery system (2) is arranged between the fuel supply system (1) and the experimental section (4), and is provided with a first switch valve (14) and a second switch valve (15) for regulating the flow of fuel to the experimental section (4) or the liquid collector (20); a cooling tower (19) is provided in front of the liquid collector (20) for cooling and recovering fuel that has not reached the target temperature and pressure; a second temperature sensor (16) and a second pressure sensor (17) are provided on the oil circuit in front of the cooling tower (19) for transmitting fuel temperature and pressure parameters to the signal acquisition system (6).

4. The visual testing system for internal flow of aero-engine nozzles under multiple working conditions according to claim 1, characterized in that: The nitrogen supply system (3) inputs the gas in the gas cylinder (21) into the experimental section (4) through the gas introduction pipe (24); the gas cylinder (21) is equipped with a pressure reducing valve (23) to adjust the gas pressure.

5. The visual testing system for internal flow of aero-engine nozzles under multiple working conditions according to claim 1, characterized in that: The transparent section (25) and the fuel inlet section (28) in the experimental section (4) are made of quartz glass with good temperature resistance and a refractive index close to that of the fuel. The structures of the transparent section (25) and the replaceable transparent section nozzle (31), the fuel inlet section (28) and the replaceable inlet section (32) can be made into different geometric configurations according to experimental requirements, so as to study the influence of different nozzle structures on the fuel injection process.

6. The visual testing system for internal flow of aero-engine nozzles under multiple working conditions according to claim 1, characterized in that: The optical testing system (5) is a rainbow schlieren imaging system, wherein a light source (33) generates a light beam which passes through a slit (34), a first convex lens (35), an experimental section (4), a second convex lens (36), a rainbow filter (37), a third convex lens (38) and a high-speed camera (39) in sequence, and the captured image is collected by a signal acquisition system (6).

7. The visual testing system for internal flow of aero-engine nozzles under multiple working conditions according to claim 1, characterized in that: The signal acquisition system (6) synchronously stores the temperature, pressure, flow data and internal flow images of the fuel during spraying into the computer through the synchronous controller.

8. The visual testing system for internal flow of aero-engine nozzles under multiple working conditions according to claim 1, characterized in that: The optical testing system (5) uses a rainbow filter (37) with a hue range of 20° to 320°, which is used to convert the light deflection angle information of the test section fluid into color information, and obtain the refractive index distribution law of the fluid through image processing analysis.

9. A method for using the multi-condition aircraft engine nozzle internal flow visualization test system according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) According to the selected experimental content, the required transparent section (25) and fuel inlet section (28) are selected and assembled to complete the experimental section (4). 2) Connect the experimental system, adjust the opening of each valve, check the sealing of the oil and gas circuits, and ensure that there is no leakage of fuel or nitrogen. 3) Check the insulation of the electric heating tube (11) to ensure there is no leakage. 4) Install the light source (33), the slit (34), the first convex lens (35), the experimental section (4), the second convex lens (36), the rainbow filter (37), and the high-speed camera (39) to complete the optical path debugging work. 5) Close the first switch valve (14), open the second switch valve (15), start the oil pump (9), adjust the current of the electric heating pipe (11) to start fuel heating, and the fuel flows to the liquid collector (20). 6) When the fuel temperature basically reaches the experimental requirement, the first switch valve (14) is opened first, and then the second switch valve (15) is closed, so that the fuel flows to the experimental section (4). 7) Start the optical test system (5) and the signal acquisition system (6) to collect experimental data and images.

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