An optical fiber balance for short-time wind tunnel force measurement of large-scale scramjet models

The scale of a scramjet has a profound impact on its combustion characteristics, and accurately replicating the integrated coupling dynamics between an aircraft and a scramjet in wind tunnel tests remains a significant challenge. To address the critical issues of natural frequency and sensitivity associated with wind tunnel force balances in large-scale model short-time force measurement tests, this paper presents a specialized three-component optical fiber balance designed for the precise short-term force measurement of large-scale models. Aerodynamic measurements are achieved by employing open cavity Fabry–Perot interferometers, which precisely measure the displacement of the floating frame of the balance. Through the integration of simulation optimization and experimental validation, the results demonstrate that the calibration accuracy of the designed balance exceeds 0.21%, maintaining high measurement precision even under conditions of high stiffness. Furthermore, under model loading conditions, the system exhibits a first-order vibration frequency of 31 Hz, allowing for six complete vibration cycles within the effective duration of a 200 ms pulse propulsion wind tunnel test, thereby satisfying the testing criteria. This research addresses a long-standing challenge in conducting large-scale model tests in wind tunnel environments, providing a critical technical solution that advances scramjet and hypersonic propulsion technologies.