MATHEMATICAL MODEL AND EXPERIMENTAL RESULTS FOR HYBRID ROCKET ENGINE, TYPES OF INJECTORS, SCRATCHES DESIGN, THRUST CONTROL

摘要

The purpose of this paper is to build a theoretical model for the hybrid rocket engine/motor, to validate it usingexperimental results while also presenting novel techniques to increase its performance such as: swirl injectors andscratches. The work approaches the main problems of the hybrid motor: the scalability, the stability/controllability ofthe operating parameters. At first, we focus on theoretical models for hybrid rocket motor and a comparison with ourown results obtained in tests performed at Electromecanica Ploiesti. Experimental results are presented together withresults from a numerical algorithm based on the computation model. The paper presents thoroughly the input data ofthe model, which allows reproducing easily the results obtained. In the experiments we used NOX as oxidizer andPVC as fuel with a cylindrical geometry of the fuel grain and combustion port. Besides the conical injectors usedinitially for which we present the experimental thrust curves we also propose the usage of a swirl injector thatpromises increases in performance by as much as 35%. Also, we present a simplified mathematical model that showsthe basic steps for the design of a swirl injector related to the scale of the motor. Next, we show introduce thevolumetric specific impulse as a constraint for the swirl injector design. As a novel technique, we show the influenceof "geometrical scratches" on the inner walls of the combustion port and the relation between their sizes and theperformance of the hybrid rocket motor