Novel Comprehensive Technique for Hybrid Rocket Experimental Ballistic Data Reconstruction

Abstract

A novel internal ballistics technique for determining the time-resolved spatially averaged regression rate of the solid-fuel grain in a hybrid rocket engine is presented. This technique makes use of the measurements of the oxidizer mass flow rate and the pressure levels in both the motor prechamber and postchamber, and it allows estimation of the combustion efficiency evolution over the burning time as well. A one-dimensional steady-state model, which takes into account the variation of the gas mixture thermodynamic properties along the fuel grain port, is adopted to predict thermofluid-dynamic parameters across the combustion chamber as a function of the regression rate and pressure. Two experimental test cases, both realized on a laboratory-scale rocket (one of which shows the typical features of the axial-injection motor burning oxygen with pure fuel, and the other the different behavior ensuing from a radial injection and fuel loaded with aluminum particles), are successfully analyzed, revealing the capability of this technique to reconstruct the fundamental aspects of the internal ballistics in substantially different conditions.