Development of a Liquid Flow Meter for Aerospace Instrumentation

This paper deals with the analysis, design, manu-facturing, testing and evaluation a turbine flow meter to measure liquid propellant flow in launching rockets. Axial turbine flow-meters exhibit superior performance when used with low kinematic viscosity fluids. Under subsonic turbulent flow conditions these instruments show a highly linear behavior with very good repeatability without any additional compensation (neither hardware nor software) and they also exhibit a low pressure drop at maximum liquid flow. A 10 liter/s @ 1 bar pressure drop flow-meter designed to be used with MMH and NTO liquid propellants is exposed. Starting from the turbine's motion equations, the relative incidence of active and parasitic torques is analyzed, both in stationary and transient flow conditions. The dependence of the instrument's proportionality factor (K-factor: pulses per liter) related to the properties of the flowing fluid and turbine dynamics is evaluated in both aforesaid situations. The instrument has been assembled and successfully tested. The paper includes some abridged benchmark results.