MEASUREMENT OF JET GAS-LIQUID INTERFACES IN CONFINED SPACES BASED ON ULTRASONIC SCATTERING

In aircraft and rocket engines, acoustic oscillations, flow perturbations, and heat release rate fluctuations interact in a nonlinear manner to stimulate the combustion instability. Currently, optical methods are commonly used in academia to quantify flow fluctuations, but face challenges in practical applications when the optical access is limited. Therefore, in this study, ultrasonic scattering measurements are developed to detect jet gas-liquid interfaces in confined spaces using the ultrasonic scattering. The fluctuations of water jet gas-liquid interface under natural perturbations are accurately captured using ultrasonic measuring instruments and verified by a high-speed camera at room temperature. For images taken by the camera, the jet gas-liquid interfaces are obtained by means of sub-pixel boundary extraction. Specifically, the extraction of pulsed scattered waves of ultrasonic signals is realized in a confined space, and the experimental results are consistent with the theoretical analysis. Furthermore, to measure gas-liquid interface fluctuations within the jet flow effectively, a database using a metal scatterer enables is established. Compared to high-speed camera measurements, this method not only offers appropriate accuracy (mean relative error of 2.64%, maximum measurement relative error of 10.53%, the average diameter of the jet is 2mm, and the ultrasonic measurement frequency is 50 kHz), but also a relatively high temporal resolution of 125 Hz is achieved. The proposed method provides a novel alternative to measure two-phase flow parameters when the optical access is unavailable.