Experimental study on precise thrust control of hydrogen peroxide and polyethylene hybrid rocket motors

This paper presents a closed-loop thrust control method for laboratory-scale hydrogen peroxide and polyethylene hybrid rocket motors. In this paper, the thrust is used as the feedback signal, and the oxidant flow adjustment is achieved by variable area cavitating venturi. The hot test based on thrust closed-loop control was carried out. The closed-loop control significantly improves the thrust control accuracy as demonstrated by the hot test with constant thrust. To obtain thrust closed-loop control parameters and improve control accuracy, a nonlinear increment proportional-integral-derivative algorithm is proposed. With the help of valve test parameters and thermodynamic calculation results, the method can directly obtain the control parameters of the thrust closed-loop control, which avoids the need for a large number of ground hot tests to debug the control parameters, and greatly reduces the test cost. For the purpose of improving thrust control accuracy, a linear variable area cavitating venturi was selected as the flow regulator and hydrogen peroxide and polyethylene were used as the propellant, which made the thrust approximately proportional to the flow rate. The experimental results show that the target thrust values of three stages in the test process are 400 N, 600 N and 400 N, the actual average thrust values are 399.8 N, 599.8 N and 400.8 N respectively, and the average thrust control accuracy is better than 0.5%.