Heating and Regenerative Cooling Model for a Rotating Detonation Engine Designed for Upper Stage Performance

Abstract

Rotating detonation engines (RDE) have the potential to significantly advance the efficiency of chemical propulsion. They are approximately one order of magnitude shorter than constant pressure engines, a savings benefit that is especially important for upper stage engines. There are many challenges to advancing their technological readiness level, but one area this thesis attempts to help mitigate is the understanding of heat loads and the viability of regenerative jacket cooling. A one-dimensional, steady-state heat transfer and regenerative cooling model for the upper stage RL10A-3-3A (RL10) engine is developed in MATLAB. This model considers forced convection in the boundary layer between the combustion product gases and the hot-gas-side wall, conduction through the wall, and forced convection in the boundary layer between the hydrogen coolant and coolant-side wall. Variable gas and coolant transport properties are utilized to increase physical accuracy. The model also quantifies pressure drop through the cooling channels due to wall friction. This allows for overall heat flux, and consequently hot-gas-side and coolant-side wall temperatures to be predicted along the length of the engine. Properties of the coolant can also be predicted including the jacket outlet temperature and pressure. These cooling circuit final parameters, temperature rise and pressure drop, were matched to a more detailed, three-dimensional, transient RL10 system model developed by NASA, thereby anchoring this model. An RDE is designed to notionally meet the thrust level of RL10. Model design decisions are documented and explained, and a detailed comparison of the two engine geometries is made. The regenerative cooling model is adapted for the RDE considering such unique aspects as detonative heat flux and the centerbody/plug nozzle. Steady state heating and cooling analysis is performed on the RDE and the results are compared to RL10. Investigation into the effects of the RDE’s differing cooling jacket output conditions on the turbine are calculated and discussed. Appendix analyses consider more realistic detonative heat flux approximations according to recent RDE calorimetry studies and the effect of altering detonation chamber heat flux. Even with the conservative assumption of throat-level heat flux everywhere in the RDE’s annular combustion chamber, regenerative jacket cooling shows promise as a means of thermal survival. Wall temperatures are reasonable, coolant temperature rise is lower, and coolant pressure drop is lower. The reduced temperature rise presents the new challenge of correctly powering the turbine since the incoming coolant is less energized. Further studies should also look at channel optimization specific to the RDE to maximize cooling performance and ease of system integration.