Improvement Of Combustion Efficiency Using A Baffle Plate For A Lt/Gox Hybrid Rocket Motor

In this study, we developed a high-performance, high-thrust hybrid rocket motor using low-melting-point thermoplastic (LT) fuel and a baffle plate compared to conventional hybrid rocket motors using a low regression rate fuel such as hydroxyl terminal polybutadiene (HTPB). LT fuel has excellent mechanical and adhesive properties, as well as a high regression rate compared to conventional hybrid rocket fuel. Static firing tests lasting 10 s using the LT fuel and gaseous oxygen (GOX) were conducted to investigate the influence of different geometric-shaped baffle plates on the characteristic velocity. Tests with baffle plates with two or more holes improved the characteristic velocities and bottom chamber pressures compared to tests without the baffle plate. In the test using a baffle plate with two rows of holes, no improvement in the characteristic velocity was confirmed. This was because the oxidizer and fuel passed through different holes and did not mix. The characteristic velocity using a baffle plate having three holes was similar to 10% higher than without the baffle plate, because the fuel and the oxidizer passed through a common hole and the combustion gas stayed at the top of the baffle plate. In all the experiments, the fuel regression rate was higher than the conventional value, as the back end of the fuel was regressed by the baffle plate and unburned fuel was discharged. These results suggested that when two more baffle plates are set, or an after-combustion chamber is provided on the downstream side, the characteristic velocity is improved.