| Resumo : |
As the aerospace industry advances, safer, cheaper, and environmentally friendly rocket engines become more interesting, which takes us to the hybrid rocket motors. Despite all the advantages of these motors, there is still progress to be made. The main issue about it concerns mainly to its general low fuel regression rate, which results in low thrust. However, para?n presents regression rates over 3 times higher than classical hybrid fuels such as HTPB and is highly researched at the moment. Therefore, a hybrid rocket prototype to burn para?n-based fuels with gaseous oxygen has been developed. Beyond the motor, a test bench, and a control system, and a system to manufacture the fuel formulations were designed and built as well. For this purpose, ?rstly thermodynamics, regression rate, and a temporal studies have been performed to simulate the behavior of para?n fuel burning with gaseous oxygen. With those analyses, it was possible to determine the internal ballistics of the hybrid rocket motor. Next, the nozzle has been designed using a method of parabolic approximation. Moreover, the injector and an ori?ce plate have been designed using gas dynamics theory. Finally, structural analysis has been performed to calculate the minimum wall thickness needed all over the motor. Knowing the internal geometry and the minimum wall thickness of the motor, the lab-scale hybrid rocket has been designed in CAD format. On next step, some numerical simulations were performed to assist the project development, such as determining of the ori?ce diameter of the injectors, or to relate the di?erential pressure of the ori?ce plate measured during tests with the mass ?ow rate of gaseous oxygen, or to validate the design and the materials chosen for construction of the test bench. Finally, all the systems such as the test bench, control system, hybrid rocket motor components have been built. Then, the tests have been performed initially with para?n fuel, later a sequence of tests have been performed burning 2 other motors with para?n and 2 containing a mixture of 90% para?n and 10 % ethanol weight-related. Thrusts at around 70 N, Isp of 120 s and combustion e?ciency higher than 80 % have been obtained to an estimated oxidant to fuel ratio of around 0.5 to all the samples tested. The principal bene?t observed by adding ethanol to para?n is the increase in combustion e?ciency. |