CN109186927B - injection low-total-pressure cold medium secondary throat diffuser - Google Patents
injection low-total-pressure cold medium secondary throat diffuser Download PDFInfo
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- CN109186927B CN109186927B CN201810937843.2A CN201810937843A CN109186927B CN 109186927 B CN109186927 B CN 109186927B CN 201810937843 A CN201810937843 A CN 201810937843A CN 109186927 B CN109186927 B CN 109186927B
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Abstract
The invention discloses an ejection low total pressure cold medium adjustable secondary throat diffuser, which is used at the downstream of a large hypersonic wind tunnel experiment section, can be self-adapted to a wider range of operation conditions by adjusting ejection gas quantity, simultaneously improves the diffusion capacity and reduces the work load of a rear-section ejector.
Description
Technical Field
The invention belongs to the field of supersonic speed wind tunnel diffusers of aerodynamic equipment, and particularly relates to injection low-total-pressure cold medium secondary throat diffusers.
Background
The supersonic speed secondary throat diffuser is arranged behind a wind tunnel test section, is subjected to diffusion to a certain degree, and then the supersonic speed secondary throat diffuser is subjected to pressure boosting and discharged through an ejector after being sprayed with water in steps.
The secondary throat diffuser for injecting the low total pressure cooling medium provided by the invention can generate layers of cold air films on the straight section of the secondary throat through the expansion of the low total pressure cooling medium, the diameter of the secondary throat is adjusted while the heat load is reduced, the diffusion performance is improved, the load capacity of an injector can be greatly reduced, the overall operation economy of the wind tunnel is improved, and the secondary throat diffuser has a good application prospect.
Disclosure of Invention
The invention aims to solve the technical problems that injection low-total-pressure cold medium secondary throat diffusers mainly realize the improvement of diffuser performance by adjusting the diameter length of a straight section of a secondary throat through groove injection low-total-pressure cold medium, and realize the cooling effect by taking off part of heat through cold medium air film isolation and shearing mixing.
The technical scheme includes that the ejection low-total-pressure cold medium secondary throat diffuser comprises a flow regulating valve, a groove, an ejection nozzle, a secondary throat compression section, a secondary throat straight section, a secondary throat expansion section, a cold medium and a gas compressor, wherein the groove is in a right-angled trapezoid shape in cross section and is arranged just in front of the secondary throat compression section, after the secondary throat is started, low-total-pressure gas passes through the flow regulating valve and the ejection nozzle through the gas compressor or a direct atmospheric environment to enable high-speed gas to be continuously ejected from the groove, the cold medium begins to diffuse in the secondary throat compression section and forms layers of gas films in the secondary throat straight section, incoming flow gas in a test section is subjected to speed reduction and pressurization through inclined shock waves of series at the secondary throat straight section with the gas films, and reaches high static pressure at the secondary throat expansion section and is ejected into a lower-stage exhaust flow passage through the diffuser.
The jet nozzle jets the cold medium flow at a high speed through the groove position to form a pneumatic diffuser with variable secondary throat straight section diameter; through optimization calculation, the position of the groove is taken in the position right in front of the compression section of the secondary throat, and the Mach number of a high-speed gas outlet ejected through the injection nozzle is 2.
A working method of a secondary throat diffuser for injecting a low total pressure cooling medium is characterized by comprising the following steps:
step 1: closing the injection spray pipe at the groove, injecting and sucking to the starting pressure of the wind tunnel, and starting a spray pipe heater of the wind tunnel equipment; meanwhile, opening an injection spray pipe at the groove, adjusting a flow valve, injecting a small amount of atmospheric cold medium to protect the wall surface of the secondary throat, waiting for hypersonic airflow sprayed by an upstream equipment spray pipe at the wind tunnel experimental section to pass through the model and reach full flow at the outlet of the spray pipe, and starting a diffuser of the secondary throat at supersonic speed;
step 2, after the secondary throat is started, adjusting a flow valve, closing an air inlet, and ejecting gas slightly higher than atmospheric pressures at a high speed by a compressor through an ejection nozzle, wherein in order to reduce cost and enlarge application, the total pressure of the gas ejected from the groove is not more than 2 atmospheric pressures, the total temperature is about 300K, the speed of an ejection device is kept at 2 Mach numbers, and the mass flow is about half of the mass flow at the inlet of a diffuser;
and 3, because the static pressure in the diffuser is very low, the high-speed and high-pressure gas at the groove begins to expand in front of the compression section of the secondary throat and forms layers of gas films by clinging to the wall surfaces of the compression section and the straight section of the secondary throat, the diameter length of the straight section of the secondary throat is reduced, and the thickness of the gas films can be controlled by the state parameters of the gas injected by the groove.
Compared with the prior art, the invention has the advantages that:
(1) the invention can adjust the diameter of the diffuser of the secondary throat under the condition of a fixed geometric structure, and effectively improves the diffusion capability of the secondary throat adopting the fixed geometric structure under the working conditions of high Mach number and low total pressure. The conventional diffuser adopts a secondary throat with a larger diameter to ensure the starting problem, and when the working condition of high Mach number is met, the diffusion effect is not ideal.
(2) The novel diffuser can effectively reduce the heat load of the secondary throat section, the temperature of the wall surface of the diffuser can be increased sharply even exceeds 2000K when the diffuser is subjected to deceleration pressurization by oblique shock waves, so that the material is difficult to bear, the cooling water jacket and the water spray columns are mainly used for spraying water to reduce the temperature at present, and the gas sprayed at the groove of the novel diffuser can take away considerable part of heat, so that the heat load of the secondary throat section is effectively reduced, and the cost of the cooling water jacket is reduced.
(3) The most important part of the invention is the low total pressure cooling medium airflow jetted from the groove, the total pressure of the air source is not more than 2 atmospheric pressures, the total temperature is about 300K, even the air source can be an unpowered air source close to the atmosphere, the air source can be realized by a common air compressor on the market, and the cost is lower.
Drawings
FIG. 1 is a structural diagram of injection low total pressure cold medium secondary throat diffusers, wherein 1 is a flow regulating valve, 2 is a groove, 3 is an injection nozzle, 4 is a secondary throat compression section, 5 is a secondary throat straight section, 6 is a secondary throat expansion section, 7 is a cold medium, 8 is a compressor, and 9 is a model;
FIG. 2 is a structural dimension diagram of a groove in a diffuser;
FIG. 3 is a velocity, temperature cloud plot for the diffuser of the present invention for the specific case of ;
FIG. 4 is a velocity, temperature cloud plot for the conventional diffuser for the specific case of ;
fig. 5 is a comparison of the diffuser wall pressure and temperature distribution of the present invention with a conventional diffuser.
Detailed Description
The invention is further illustrated in conjunction with the figures and the detailed description.
The invention relates to an ejection low-total-pressure cold medium secondary throat diffuser which comprises a flow control valve 1, a groove 2, an ejection nozzle 3, a secondary throat compression section 4, a secondary throat straight section 5, a secondary throat expansion section 6, a cold medium 7 and a gas compressor 8, wherein the section of the groove 2 is in a right-angled trapezoid shape and is arranged in front of the secondary throat compression section 4, after the secondary throat is started, the gas with low total pressure passes through the flow control valve 1 by the gas compressor 8 or a direct atmospheric environment, the high-speed gas is continuously ejected from the left side of the groove 2 by the ejection nozzle 3, the cold medium 7 starts to diffuse in the secondary throat compression section 4 and forms layers of gas films in the secondary throat straight section 5, the upstream gas is subjected to deceleration pressurization at the secondary throat straight section 5 with the gas films through series of oblique shock waves, and reaches high static pressure in the secondary throat expansion section 6, and is ejected into the atmosphere through an outlet.
A working method of a secondary throat diffuser for injecting a low total pressure cold medium comprises the following steps:
step 1: and closing the injection spray pipe at the groove 2, and injecting and sucking to the starting pressure of the wind tunnel. Starting a nozzle heater of the wind tunnel equipment; meanwhile, the injection spray pipe at the groove 2 is opened, the flow regulating valve 1 is regulated, and a small amount of atmospheric cold medium is injected to protect the wall surface of the secondary throat. Waiting for hypersonic airflow ejected by an upstream equipment spray pipe of the wind tunnel experimental section to pass through the model and reach full flow at the outlet of the spray pipe, and starting the secondary throat diffuser at supersonic speed;
step 2, after the secondary throat is started, the flow regulating valve 1 is regulated, the air inlet is closed, and the air compressor 8 ejects the gas slightly higher than atmospheric pressures at a high speed through the injection nozzle 3, in order to reduce the cost and expand the application, the total pressure of the gas ejected from the groove is not more than 2 atmospheric pressures, the total temperature is about 300K, the speed of the ejection device is kept at 2 Mach numbers, and the mass flow is about half of the mass flow at the diffuser inlet;
because the static pressure in the diffuser is very low, the high-speed, high-pressure gas of groove 2 begins to expand in the compression section 4 front of secondary throat, and form layers of air films in the wall of compression section 4 and straight section 5 of secondary throat of the secondary throat of close fitting, reduce the diametral length of the straight section of the secondary throat, the thickness of the air film can be controlled by the state parameter of the jet gas of groove, through simulating this diffuser to the high Mach number working condition, the diffusion capacity will be obviously promoted, to the low Mach number working condition, the diffusion capacity also has to promote definitely;
in the step 2, Ma is 7 and P istotalFor example, under the working condition of 4.9Mpa, the diffuser designed according to the traditional scheme can only raise the back pressure at the outlet to about 13 kpa; by using a novel diffuser, the geometric structure is unchanged, the total pressure of the gas sprayed at the groove is 1.15atm, the total temperature is 300K, the Mach number is 2, the mass flow is 115kg/s, and through numerical simulation, the outlet back pressure can be increased to 20kpa and the performance can be improved by 53.8% under the same condition; when the total pressure of the gas sprayed at the groove is 1.75atm and the mass flow is 173kg/s, the outlet back pressure can be increased to 23.5kpa through numerical simulation, and the performance is improved by 80%; with Ma being 6 and PtotalFor example, the diffuser can only be designed according to the traditional scheme under the working condition of 2.84MpaThe back pressure at the outlet is raised to about 23 kpa; with the novel diffuser, the total pressure of the jet gas at the groove is 1.75atm, the total temperature is 300K, the Mach number is 2, the mass flow is 173kg/s, the outlet backpressure can be increased to 31kpa through numerical simulation, and the performance is improved by 35%.
In the step 3, the low total pressure and high flow compressor is adopted, so that the low total pressure cooling medium with 2 atmospheric pressures and mass flow rate within 200kg/s can be obtained economically, and the economy is better.
Examples
The working conditions of the embodiment are as follows: ma ═ 7; simulating the total pressure of 4.91 Mpa; total temperature: 2017K;
for the traditional secondary throat diffuser, the groove 2 and the injection nozzle 3 are not included, the outlet backpressure of the diffuser can only reach 13kpa, and the lowest temperature of the wall surface of the diffuser also exceeds 1800K.
According to the low-total-pressure cold medium injection pressurization type secondary throat, the cross section of a groove is in a right-angled trapezoid shape, for the case, the cross section of the groove is 40mm in height, 300mm in bottom and 15 degrees in bevel angle, specifically referring to a groove structure diagram in the drawing, and the position of the groove 2 is located in the close front of a compression section of the secondary throat, specifically referring to a structure diagram of an injection diffuser in the drawing.
It is pointed out that the sectional shape and the position of the groove are fixed in the invention, but the size of the groove is adjustable, and the optimal size can be obtained by numerical simulation according to different working conditions.
S1, closing the injection device at the groove, starting the secondary throat with a back pressure of 1.2kpa, wherein the upstream airflow flows through the model and basically fills the whole diffuser, and the secondary throat is started normally;
s2, starting an injection device at the groove, and starting to inject compressed air at the left end of the groove, wherein the state parameters of the compressed air flow in the case are as follows: total pressure 1.15 atm; the total temperature is 300K; ma is 2; the mass flow rate is 115 kg/s;
s3, the static pressure in the diffuser is very low and basically less than several kilopascals, the static pressure of the gas injected in the groove is not high but still far greater than the pressure in the diffuser, so the gas starts to expand, and the injected gas has horizontal right initial speed and forms layers of gas films from the compression section of the secondary throat to the straight section of the secondary throat, so the radial length of the secondary throat is adjusted, the diffusion effect is improved, and part of heat of is taken away;
in the step S3, the final improved diffusion effect can reach 20kpa, which is 54% higher than the original effect, the wall temperature of the secondary throat near half length is less than 600K, which is reduced to third of the original effect, and the wall temperature of the rest part is also less than 1500K, so that the heat load of the secondary throat can be effectively reduced.
More importantly, through comprehensive calculation, due to the improvement of the diffusion performance, although the load of the ejector is increased by the introduced low-total-pressure airflow part, the final gas consumption of the rear-end ejector is still saved by 30% compared with that of the ejector before due to the reduction of the pressure increase ratio. This is a considerable economic saving for the operation of large wind tunnel installations.
The pressure-expanding effect, the speed Mach number diagram and the temperature of the low-total-pressure cold medium injection supercharged diffuser are compared in the attached drawings in detail with those of the conventional diffuser.
Claims (2)
- The cold medium secondary throat diffuser is characterized by comprising a flow regulating valve (1), a groove (2), an injection nozzle (3), a secondary throat compression section (4), a secondary throat straight section (5), a secondary throat expansion section (6), a cold medium (7) and a gas compressor (8), wherein the cross section of the groove (2) is in a right trapezoid shape and is arranged just in front of the secondary throat compression section (4);the cold medium (7) is injected at high speed through the injection nozzle (3) at the position of the groove (2) to form a pneumatic diffuser with the diameter of the straight section of the secondary throat being variable; through optimization calculation, the position of the groove (2) is taken in the position right in front of the secondary throat compression section (4), and the Mach number of a high-speed gas outlet ejected through the ejector nozzle (3) is 2.
- The working method of the injection low total pressure cold medium secondary throat diffuser is characterized by comprising a flow regulating valve (1), a groove (2), an injection nozzle (3), a secondary throat compression section (4), a secondary throat straight section (5), a secondary throat expansion section (6), a cold medium (7) and a gas compressor (8), wherein the section of the groove (2) is in a right trapezoid shape and is arranged in the immediate front of the secondary throat compression section (4);the working method comprises the following steps:step 1: closing the injection spray pipe (3) at the groove (2), injecting and sucking to the starting pressure of the wind tunnel, and starting a spray pipe heater of the wind tunnel equipment; meanwhile, an injection spray pipe (3) at the groove (2) is opened, the flow regulating valve (1) is injected with a small amount of large air-cooling medium (7) to protect the wall surface of the secondary throat, hypersonic airflow sprayed by an upstream equipment spray pipe at the wind tunnel experimental section passes through the model and reaches full flow at the outlet of the spray pipe, and a diffuser of the secondary throat is started at supersonic speed;step 2, after the secondary throat is started, adjusting a flow regulating valve (1), closing an air inlet, and ejecting gas slightly higher than atmospheric pressures at a high speed by a compressor (8) through an ejector nozzle (3), wherein the total pressure of the gas ejected at the groove (2) is not more than 2 atmospheric pressures, the total temperature is 300K, the speed is 2 Mach numbers, and the mass flow is half of the mass flow at the inlet of a diffuser;and 3, because the static pressure in the diffuser is very low, the high-speed and high-pressure gas at the groove (2) begins to expand in front of the secondary throat compression section (4) and is tightly attached to the wall surfaces of the secondary throat compression section (4) and the secondary throat straight section (5) to form an -layer gas film, the radial length of the secondary throat straight section is reduced, the thickness of the gas film can be controlled by the state parameters of the gas injected at the groove, and the high-Mach-number working condition and the low-Mach-number working condition of the diffuser are simulated.
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Families Citing this family (9)
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| CN111006841B (en) * | 2019-11-29 | 2022-07-05 | 中国航天空气动力技术研究院 | Wide-area air inlet pressure regulating system for hypersonic wind tunnel |
| CN111878252B (en) * | 2020-08-04 | 2021-05-28 | 南京航空航天大学 | Air inlet injection nozzle model and turbofan engine model |
| CN112098033A (en) * | 2020-08-04 | 2020-12-18 | 空气动力学国家重点实验室 | Central hypersonic speed wind tunnel diffuser |
| CN114518229A (en) * | 2020-11-20 | 2022-05-20 | 北京航天试验技术研究所 | Double-duct diffuser for supersonic free jet test of air-breathing engine |
| CN113049261B (en) * | 2021-03-08 | 2022-05-24 | 中国科学院力学研究所 | Direct connection experiment platform and method for measuring thrust of stamping engine |
| CN114279673B (en) * | 2021-12-29 | 2024-04-05 | 中国航天空气动力技术研究院 | Simulated arc wind tunnel diffuser structure with variable inlet area |
| CN114544136B (en) * | 2022-04-22 | 2022-08-19 | 中国航空工业集团公司沈阳飞机设计研究所 | Embedded surface pressure gradient measuring device |
| CN117588467B (en) * | 2023-11-22 | 2024-08-13 | 中国科学院力学研究所 | Backpressure generation system and method for wide-speed-domain stable flow field |
| CN118090126B (en) * | 2024-04-28 | 2024-06-21 | 中国空气动力研究与发展中心超高速空气动力研究所 | Blending cooling device for high-temperature wind tunnel combustion heater and design method thereof |
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| JPS59151000A (en) * | 1983-02-16 | 1984-08-29 | Mitsubishi Heavy Ind Ltd | Ejector |
| CN203688195U (en) * | 2013-12-19 | 2014-07-02 | 中国航天空气动力技术研究院 | Supersonic velocity diffusion device with active injection |
| CN106525434A (en) * | 2016-09-09 | 2017-03-22 | 西安航天动力试验技术研究所 | Injecting equipment for direct connection test of novel stamping engine and environment simulation system |
| CN108131336A (en) * | 2016-11-29 | 2018-06-08 | 北京航天试验技术研究所 | A kind of supersonic gas injector of the tangential tonifying Qi of mixing chamber |
| CN106838902B (en) * | 2016-12-12 | 2019-01-15 | 中国航天空气动力技术研究院 | A kind of supersonic speed combustion gas injector |
| CN107234010A (en) * | 2017-06-20 | 2017-10-10 | 大连理工大学 | From ejection circulation backflow supersonic cyclone separator and its separation method |
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Address after: No.443 Huangshan Road, Shushan District, Hefei City, Anhui Province 230022 Patentee after: University of Science and Technology of China Address before: 230026 Jinzhai Road, Baohe District, Hefei, Anhui Province, No. 96 Patentee before: University of Science and Technology of China |