Measurement of Transient Flash Evaporation Flow in Liquefied Gas Propulsion Using Dual-Plane ECT

Abstract

In this paper, the transient flash evaporation flow in liquified gas propulsion (LGP) was measured using a dual-plane electrical capacitance tomography (ECT) sensor. The novelty mainly stems from a selection method for more accurate liquid holdup measurement, a constrained adaptive cross-correlation algorithm for more stable velocity, and compensation methods against the changes of temperature and pressure. By the selection method, inter-electrodes capacitances that contribute less to the flow measurement, are removed from each data frame and more accurate liquid holdup is derived via image reconstruction. The adaptive cross-correlation algorithm with a constraint on the correlation coefficient is adopted to alleviate the adverse effect of the fast changes of flow pattern on the velocity measurement. Then, the compensation methods are realized by correcting the deviations of phase density and permittivity caused by dramatic temperature and pressures changes. Simulations and experiments validated the effectiveness of the proposed methods to derive the mass flow rate of the two-phase flow via the measured liquid holdup, flow velocity and estimated phase density. It is shown that the remaining mass of propellant in the storage tank calculated from the mass flow rate is in good agreement with the measured reference by the electronic balance, where the average relative errors under different initial pressures are less than 10%. As the best of our knowledge, this is the first-time of transient flash evaporation flow measurement in a lab-built LGP device, which is promising to be applied for the effective online control to maximize the output impulse of LGP and estimate the remaining life of small spacecrafts.