Impulse force-measurement system
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ORIGINAL ARTICLE
Impulse force-measurement system Y. Wang1
· Z. Jiang1
Received: 6 May 2019 / Revised: 10 June 2020 / Accepted: 7 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Shock tunnels are important ground test facilities that can generate high-enthalpy flow. Flight velocity at a high Mach number can be simulated for aerodynamic testing of chemically reacting flows. However, the application of these tunnels is limited due to the only milliseconds-long test duration, especially for aerodynamic force measurement using traditional strain gauge balances. This study presents an impulse force-measurement system, which was used for a large-scale test model to measure its drag in a high-enthalpy shock tunnel with an approximately 3–7-ms test time. Force tests were conducted for a cone in the JF-10 high-enthalpy shock tunnel in the Institute of Mechanics, Chinese Academy of Sciences. An integrated design of the impulse force-measurement system was proposed for load measurement over a short duration, for which a recommended design criterion is that the measurement period be a minimum of twice the period corresponding to the lowest natural frequency of the measurement system. The current measurement technique breaks the limitations of the application of the conventional strain gauge balance. As an integrated measuring system, the impulse force-measurement system expands the structural design concept of strain gauge balances. The impulse force-measurement system performed well in the present tests. The test results show differences from the numerical simulations and some data obtained in a conventional wind tunnel. A preliminary analysis was performed on the real gas effects on the aerodynamic force. Keywords Shock tunnel · High enthalpy · Aerodynamic force measurement · Strain gauge balance
1 Introduction In hypersonic aircraft design, the ground test is very important in providing aerodynamic data support. As an impulse facility, a shock tunnel can create very high-speed flow at very high temperature and pressure. Compared with the conventional hypersonic wind tunnel, the high-enthalpy hypersonic flow simulated in a shock tunnel is closer to real flight conditions. However, in force tests in the shock tunnel, because of the instantaneous flowfield and the short test time [1–4] (generally 500 µs–20 ms), mechanical vibration of the model–balance–support occurs and cannot be damped over the short duration. The inertial forces lead to low-frequency vibrations of the model, and its motion cannot be addressed by digital filtering. This implies restrictions on the model’s Communicated by F. Seiler.
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Y. Wang [email protected] State Key Laboratory of High Temperature Gas Dynamics (LHD), Institute of Mechanics, Chinese Academy of Sciences (CAS), Beijing 100190, China
size and mass because its natural frequencies are inversely proportional to its length scale. Regarding the measurement system, the lowest frequency of 1 kHz is required for the test time of typically 5 ms to ob
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