Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Measurement of regression rate in hybrid rocket using combustion chamber pressure
Submission Author:
Isabel Matos , SP
Co-Authors:
Isabel Matos, Leonardo Henrique Gouvêa, Pedro Lacava
Presenter: Isabel Matos
doi://10.26678/ABCM.ENCIT2022.CIT22-0061
Abstract
Hybrid rocket propulsion provides an attractive alternative to the conventional liquid or solid rockets. Compared to liquid bipropellants rockets, hybrids have less complexity and lower costs, due to less piping and valves. And compared to solid rockets, they have controllable thrust, shutoff and restart capability, and are safer, since the fuel is not reactive by itself and can be manufactured, transported, and handled safely, avoiding the explosiveness of the propellant. Despite its advantages, hybrid rocket propulsion has never attained mainstream adoption. A strong reason for that stems from its inherently low fuel regression rate, that limits its applications in relatively lower thrust levels rocket motors. The low thrust is a consequence of the difficulty in quickly mixing the fuel and oxidizer, which is characterized by a low rate of regression of the fuel grain. Therefore, the measurement of this parameter is of great importance in studies that aim solutions for this deficiency in hybrid rocket motors (HRM). Several studies evaluate the average regression rate over time, measuring the total mass of fuel before and after a burn (weight loss method). Measuring the instantaneous surface regression rate increases data reliability and substantially reduces the required number of developmental tests, since it is a more accurate description of the dependence of the solid-fuel regression rate on the oxidizer mass flux. As such, a large body of research has been dedicated to developing regression instrumentation. Some of the methods that have been used are resistance-based, ultrasonic pulse–echo and x-ray radiography. An alternative and least expensive method to measure instantaneous regression rate will be tested in this work. Using an existing laboratory scale test bench with high-density polyethylene (HDPE) and gaseous oxygen, the objective of this work is to develop an algorithm to determine the regression rate of a hybrid fuel by using its measured combustion chamber pressure. In this method, the choked flow condition at the nozzle throat of the hybrid rocket was used to obtain the mass of fuel burnt and in turn the regression rate. The results obtained will be compared with the results obtained with the weight loss method, using the same motor and the same fuel and oxidizer combination. In addition, it will be analysed if the O/F ratio obtained is in good agreement with those obtained using the weight loss method.
Keywords
Aerospace engineering, hybrid rocket, Propulsion, Regression Rate
