实验流体力学

contents

2022, 36(1)

Abstract(257) PDF(49)

Abstract:

2022, 36(1): 1-2.

Abstract(1583) HTML (208) PDF(107)

Abstract:

Digital intelligent technology research of large wind tunnel equipment

LIAO Daxiong, SUN Yunqiang, WU Jingyi, PENG Lei

2022, 36(1): 1-10. doi: 10.11729/syltlx20210072

Abstract(1980) HTML (295) PDF(150)

Abstract:
Digital intelligent technology is an important content and development direction of the large-scale wind tunnel equipment design, construction and operation. This paper briefly summarizes the research status of the digital technology, network technology and intelligent technology in the design and construction of the large-scale wind tunnel, analyzes the problems of the digital multidisciplinary collaborative design, data analysis and management, data processing and management, data interaction and fusion, intelligent manufacturing and assembly, health management, intelligent robot and other digital intelligent technology problems and development trends, and puts forward a series of design ideas to build the digital intelligent wind tunnel system.

Prediction of the combustion instability based on the thermos-acoustic decoupling method

GAO Yupeng, LI Junjie, LIU Wei, LI Jingxuan

2022, 36(1): 11-18. doi: 10.11729/syltlx20210078

Abstract(1680) HTML (224) PDF(77)

Abstract:
Large air heaters are prone to combustion instability, so that the heater cannot work at the expected operating conditions, even leading to failures. Because it is difficult to ob-tain accurate parameters inside the engine combustion chamber through experiments, numerical simulation is an important means to predict the unstable combustion process. In this paper, by decoupling the combustion-acoustic system inside the combustion chamber, the flame response to the acoustic disturbance and the acoustic system response to the heat source disturbance are calculated separately. The combustion response under the acoustic disturbance is characterized as the flame transfer function. Finally, the most unstable modal frequency in combustion chamber can be obtained. The results show that the modal frequency of the envisaged air heater is 1389.9 Hz and is stable in the acoustic mode. The prediction results match the test results, proving that the method has good prediction ability.

Key technology for mechanical design in large-scale cryogenic wind tunnel

LAI Huan, ZHU Changjiang, CHEN Wanhua, LIAO Daxiong, SUN Dewen

2022, 36(1): 19-26. doi: 10.11729/syltlx20210040

Abstract(2244) HTML (326) PDF(137)

Abstract:
The high range of the Reynolds number is a core requirement for the aircraft model testing in the wind tunnel, and the feasible engineering way for broadening it is reducing the total temperature of the fluid. Therefore the cryogenic wind tunnel is needed. The mechanical circuit system is the core function facility of the cryogenic wind tunnel with special characteristics as complex structure, high integrated functions, and cyclical loading bearer. By contrasting the design of the overseas the cryogenic wind tunnel and the domestic cryogenic technology, the key technologies for the cryogenic wind tunnel mechanical circuit system design are discussed in this article, such as cryogenic materials, thermal stress and deformation control, wide temperature range and heavy load transmission mechanism, liquid nitrogen spray valves and model transposing for cryogenic testing. The core indicators, technical difficulties and research approaches of each aforementioned key technology are expounded, respectively. Finally, some proposals are offered for the cryogenic wind tunnel mechanical design.

Aerodynamic and aero-acoustic design of continuous transonic wind tunnel compressor

LONG Bingxiang, LIU Zongzheng, CHEN Zhenhua, CHEN Jiming, LEI Pengfei

2022, 36(1): 27-36. doi: 10.11729/syltlx20210079

Abstract(1445) HTML (330) PDF(64)

Abstract:
The continuous transonic wind tunnel, which is generally a closed-circuit variable-density wind tunnel, is an excellent platform for aerodynamic mechanism research and advanced aero vehicles development. A cost-effective and stable continuous transonic wind tunnel requires its driver, usually a multistage axial-flow compressor, to have wide operating range with high adiabatic efficiency and sufficient surge margin. On the other hand, the good test section flow quality requires the outlet and inlet aero-acoustic noise of the compressor lower than 140 dB. Developing a multi-stage axial-flow compressor with high adiabatic efficiency, sufficient surge margin and low noise level working under extra-wide operating conditions faces many challenges. Thus, the effectiveness of the variable geometry method, including variable rotor blade and variable stator vanes, the choice of design point and its corresponding load coefficient and flow coefficient, and the choice of meridional type and the basic principles related to low-noise axial-flow compressor design, were analyzed for the purpose of providing some guidance for designing such a compressor. For compressors with the reaction degree higher than 0.5, the variable rotor blade is more effective. For compressors with the reaction degree lower than 0.5, the variable stator vanes method is more effective than variable rotor blade method. For wind tunnels with operating range from Ma=0.2–1.6, the design point of the compressor should be around Ma=1.4 and its corresponding loading coefficient and flow coefficient are about 0.6 and 0.25 respectively. The constant tip radius meridional type has advantages in aerodynamic performance improvement. Larger rotor-stator spacing and appropriate rotor/stator number ratio are effective in suppressing the compressor noise emission.

Key technology for model access system in cryogenic wind tunnel

CHEN Jianbing, LIU Bolin, CHEN Wanhua, LIAO Daxiong, LAI Huan

2022, 36(1): 37-43. doi: 10.11729/syltlx20210140

Abstract(1748) HTML (293) PDF(55)

Abstract:
The model access system is an important part of the cryogenic wind tunnel, and it is the core system to realize low temperature model replacement. The model access system of the cryogenic wind tunnel has the characteristics of complex structure, large scale, high functional integration and high requirements for environmental conditions. By contrasting overseas the design of the model access system of the cryogenic wind tunnel and introducing the domestic current situation of related technologies, the key technologies of the design for the model access system of the cryogenic wind tunnel are discussed in this article, such as the large volume and low dew point air drying system, temperature regulating system with a wide temperature range, large-tonnage and high precision model cart, large lock door, moisture emission control in dry space, etc.. The technical difficulties and research approaches of each aforementioned key technology are expounded, respectively. Finally, some proposals are offered for the design of the model access system of the cryogenic wind tunnel.

Design and construction progress of AVIC Φ1.0 m hypersonic wind tunnel

GAO Liangjie, XIN Yanan, YUAN Ye, LI Qiang, QIAN Zhansen

2022, 36(1): 44-51. doi: 10.11729/syltlx20210105

Abstract(1932) HTML (451) PDF(134)

Abstract:
The 1 m hypersonic wind tunnel for the AVIC （FL-64） is the newly built blow down free jet type large-diameter conventional hypersonic wind tunnel in China. It adopts the blowing type operation mode, at the same time, considering the test requirements of low dynamic pressure, a vacuum exhaust system is also equipped. The overall performance, key component design, flow field calibration and preliminary standard model test results of the FL-64 wind tunnel are presented in detail. The performance of the wind tunnel are as follows: the range of Mach number: 4.0 – 8.0; the total pressure range of the settling chamber: 0.1 – 8.0 MPa; the total temperature range of the settling chamber: 300 – 900 K; the unit Reynolds number range: 3.3×10⁶ – 4.6×10⁷ m^–1; the effective operating time is not less than 30 s. The FL-64 wind tunnel combined the FL-60 trisonic （Subsonic, Transonic, Supersonic） wind tunnel forming the high and low Mach number range, this can cover the wide-speed range aircraft test with a Mach number of 0.3 – 8.0. Especially the duplication capability of the total enthalpy of Mach number 4.0 can match the real flight conditions. Overall, the successful completion of the FL-64 wind tunnel provide an effective test platform for the development of nation’s high Mach number aircraft.

Researches on a large natural moveable icing wind tunnel and test methods

ZHU Dongyu, FENG Qiang, Han Xiaotao, Yang Ximing, Cui Xiaochun, Yuan Li

2022, 36(1): 52-61. doi: 10.11729/syltlx20210100

Abstract(1723) HTML (316) PDF(90)

Abstract:
An open circuit natural icing wind tunnel sucking cold air from the outside in winter provides affordable icing wind tunnel test methods for full scale models and aircrafts. Information of natural icing wind tunnels is summarized, and test capabilities on large scale wings, propellers, and aircrafts are analyzed. The propeller and aircraft icing test methods were researched in Harbin using a single module natural icing wind tunnel, and ice accretion and shedding on the propeller are documented and analyzed, test results of which have a certain reference value for propeller and aircraft icing researches. A seasonal, moveable and assembled icing wind tunnel concept is presented which can take the advantage of cold winter climate, and allows a similar period from November to March to conduct icing tests compared with the outdoor icing test facility in Winnipeg, Canada. Researches provide references for the construction of national large scale natural icing test facilities and development of test methods.

Characteristics and key technology analysis of large continuous transonic wind tunnel

CHEN Zhenhua, LIU Zongzheng, CHEN Jiming, GUO Shouchun, YAN Xiqiang, PEI Haitao

2022, 36(1): 62-68. doi: 10.11729/syltlx20210092

Abstract(1691) HTML (200) PDF(74)

Abstract:
The large scale continuous transonic wind tunnel has several main features, such as the large-size test section, high wind tunnel performance specifics, large scale wind tunnel system, multi-function wind tunnel operation. It has the test capabilities of accurate simulation of the aircraft shape, aero-elastic evaluation and integrated body/propulsion design. This paper briefly introduces the overall design of the large continuous transonic wind tunnel, and special focus is put on the preliminary research results of key technologies such as the realization of world-class flow quality and the development of the large axial compressor and its driving system.

Flow characteristics experiment of plate-fin heat exchanger in wind tunnel

ZHAO Bo, CHEN Zhenhua, LI Weimin, CHEN Jiming, ZHU Bo, WEN Qian

2022, 36(1): 69-76. doi: 10.11729/syltlx20210081

Abstract(1531) HTML (214) PDF(48)

Abstract:
The flow characteristics of a plate-fin heat exchanger in the wind tunnel were studied. Firstly, the turbulence characteristics and pressure loss of the plate-fin heat exchanger and the finned oval tube heat exchanger were compared, and then the turbulence developments downstream of the heat exchanger under different inflow wind speeds and spoiler angle conditions were studied by experiments. Finally, the impacts of typical structures on the flow disturbance downstream of the heat exchanger were obtained. The results show that the plate-fin heat exchanger has less disturbance to the air flow and much smaller pressure loss under the same heat transfer condition than the finned oval tube heat exchanger. The plate-fin heat exchanger has good rectifying effect, and the flow disturbance, which has little relation with the incoming flow conditions, is mainly determined by its own structures. The disturbance of the large thickness structures in the heat exchanger propagates long distances, and a proper rectifier scheme is needed to reduce the disturbance.

The development and key technologies of 2.0 m high energy shock tunnel

ZHU Hao, BI Zhixian, CHEN Xing, GONG Jian, JIANG Bo, ZHANG Bingbing, JIANG Hainan, LI Chen, WU Jian, SONG Keqing, SHEN Junmou, SUN Riming

2022, 36(1): 77-88. doi: 10.11729/syltlx20210090

Abstract(1555) HTML (191) PDF(86)

Abstract:
The Φ2.0 m high energy pulsed tunnel （FD–21） of CAAA is a free piston shock tunnel, which expands the test capability of CAAA. This paper mainly introduces the develop-ment process and key technologies of the FD–21 tunnel. Many key aerodynamic problems are settled independently. And the aerodynamic design is completed by the reverse design method. Based on these efforts, the engineering technical difficulties such as piston launch, piston stop, full floating support have been gradually overcome during the construction of the FD–21 tunnel. The successful development of the FD–21 tunnel marks the mastery of the free piston driving techno-logy, reduces the gap between China and some foreign countries, and improves the hypersonic research level in China greatly.

Study on the parameter optimization of air-drying system in large continuous transonic wind tunnel

PEI Haitao, CHEN Jiming, CHEN Zhenhua, CHEN Qin, WANG Pan

2022, 36(1): 89-95. doi: 10.11729/syltlx20210091

Abstract(1231) HTML (100) PDF(28)

Abstract:
In the transonic wind tunnel, the flow of wet air can turn into non-isentropic flow due to water vapor condensation in the test section, followed by the formation of condensation wave, seriously destroying the uniformity of the flow field and the accuracy of the test data. Therefore, the air should be dried ahead of test to ensure its moisture content less than 1.5 g/kg. The circulation drying system is an economical and efficient air-drying way in the large continuous transonic wind tunnel. In this paper, a rotary and cooling dehumidification drying system is designed for the wind tunnel, and an air-drying calculation model based on the assumption of uniform mixing is proposed and validated by experiment. According to the proposed model, the optimized parameters of the air-drying system are obtained. The results show that the model can effectively estimate the change of the average moisture content in the tunnel, and the deviation from the test is within 8.3% when the number of cycles is more than 2; the maximum cooling load of the front and rear heat exchanger can be reduced by about 41.9% and 27.8% respectively in this system by making full use of the dehumidification capacity of the first four cycles and the selected rotary dehumidifier.

Vacuum mode debugging and flow field performance calibration of large-scale hypersonic wind tunnel

MA Lichuan, SHI Yunjun, HUANG Bingxiu, SUN Yongtang, YAN Shuo

2022, 36(1): 96-102. doi: 10.11729/syltlx20210152

Abstract(1497) HTML (140) PDF(74)

Abstract:
With the continuous increase of the flight altitude of advanced aircraft in the future, the requirements for wind tunnel test simulation ability are constantly increasing, such as the lower vacuum running ability. The conventional multistage ejection system can no longer fully meet the operation requirements. In order to improve the height simulation range of the wind tunnel test, CAAA designed a vacuum exhaust branch based on the original equipment of its newly built Ф1.2 m hypersonic wind tunnel to realize the pressure vacuum mode operation of the wind tunnel. The wind tunnel system debugging and testing results show that after the wind tunnel capacity is improved, each subsystem works normally and the system performance reaches the design target, and the hypersonic flow field condition at the altitude above 40 km with Mach number 5–8 is realized. The flow field index in the uniform area of the test section meets the relevant requirements of the aerodynamic test of the National military standard GJB 4399-2002. It provides a test platform for the study of aerodynamic characteristics of aircraft and complex hypersonic flow at high altitude.

2022 Vol. 36, No. 1