|Alternative Title||Theories and Technologies for the Components-Uncoupled Suspension Balance of Hypersonic Aerodynamic Measurement|
|Place of Conferral||北京|
|Keyword||高超声速 大型激波风洞 气动力测量 大尺度模型 分立悬挂式|
The real-gas effect and development of engine-integrated aircraft are the two challenges for the advanced technologies study of space-aeronautics flight. The reaction scale and the coupling effects of airframe and engine remain unchanged when the test model is reduced in its size in the wind-tunnel tests. That is, the large-scale aircraft model is needed for the ground test of hypersonic flow, which could minimize the effects induced by unchanged scale of chemical reaction. The Long test-Duration Hypervelocity Detonation driven Shock Tunnel (JF12 flight condition-reproducing tunnel ) is the world’s largest shock tunnel which is capable of reproduce the true hypersonic flight simulation with Mach numbers from 5 to 9. The lengths of its aircraft model are up to 6m and JF12 shock tunnel provides an excellent platform for the aerodynamic measurements. However, aerodynamic force measurement for a large-scale aircraft model by traditional method is confronted with great challenges. Poor stiffness and large interference to flow field place great limits to the aerodynamic measurements for large scale models in impulse tunnel. Moreover, the integrated structure of balance causes inevitable interference among force components, which limits the further improvement of the accuracy. To develop aerodynamic measurement technologies in the JF12 shock tunnel, this study presents a novel method named as Components-Uncoupled Suspension Balance (CUS Balance). It has advantages of high stiffness, low interference to flow field and six-components discrete. Development of the theories and technologies, design of the novel balance and verification by experiments were conducted and the main innovations are listed as follow:
1. The investigation to present the aerodynamic measurement method of the novel balance. The theoretical solutions for the relationship of inner forces of rods and aerodynamics were obtained based on the static and dynamic equations. The solutions by solving the equilibrium equation of the three dimensional forces perform nice agreement with the results of experiment. The deviation between outer loads and the resultant forces was less than 2%. The multi-degree vibration equation was solved to obtain the dynamic solution, which laid a theoretical foundation for the dynamic force measurement in shock tunnel. The theoretical solution reveals that there is a one-to-one correspondence between the inner forces of the rods and the aerodynamics, that is, the matrix of coefficient has an exact theoretical solution. However, for the conventional balance, a mass of the calibration experiments should be conducted to obtain a proximate matrix of coefficients.
2. A low-interference layout of the rods and balances was discussed from the perspective of the generalized modal matrix. It contained a perpendicular combination that included two planes and a sting support, which performed a holistic design form of balance. Theory for stiffness adjustment was investigated to provide rapid and simple equations for the layout design. Results showed that 5-6 parameters could give influence on the stiffness of the draw-rod system and it’s easier to change the stiffness of the system. The requirements of the low-interference layout and stiffness were chosen as constraint conditions to discuss the influence rules of items, such as positons and number of the planes to arrange the rods, numbers of rods in each plane, forms of sting support. As a requirement of the dynamic theory for the aerodynamic measurements, a one-station measurement method of spatial geometric parameters was developed. It’s essential for the high-accuracy aerodynamic measurement. In addition, an axial balance with capacities of self-equilibrium of inner forces was developed and manufactured to solve the large deformation during the preloading of the system. The HB2 standard aerodynamic model was applied in an actual shock tunnel experiments. For all the six components, 3~6 periods of the signals could be obtained. Compared with data of the national military standard, the derivation of the measured axial coefficient was 2% and the repeatability precision was less than 1.8%. Further study focused on the experimental study on engine-integrated aircraft model. And it aimed at the performance of the novel method when applied for the full-scale X-51A model. High stiffness and high accuracy were proved by the aerodynamic measurement results.
3. The investigation on the interference induced by rods for the novel balance was conducted. The surface of the aircraft model was simplified as the infinite plate and the rods were simplified as semi-infinite cylinder. The typical flow fields were simulated by solving the three-dimensional Navier-Stokes equation. Further analysis focused on the magnitude of aerodynamics increment on the plate and the characters of the aerodynamic distribution on rods. Results showed that the interference induced by the single rod was less than 0.5% and the symmetrical arrangement of rods makes it lower than 0.05%. And the interference could be corrected.
4. Investigation on the modelling method of the impulse force during the start-up process of the shock tunnel was performed. The evolution process of the wave structures was obtained. The frequency properties were analyzed by setting up analytical form of force. Moreover, the modelling of the impulse force was conducted. The theoretical form of the “energy metric” was derived based on the forced vibration properties of the force measurement system. Several harmonic forces (generally 3~5) were selected to model the impulse force and they contained the similar excited energy with impulse forces. A discussion was also conducted for the rules to design the balance based on properties of the impulse forces.
|孟宝清. 高超声速分立悬挂式气动力测量理论与技术[D]. 北京. 中国科学院大学,2018.|
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