Thrust chamber dynamics and propulsive performance of single-tube pulse detonation engines

The modeling and simulation of the thrust chamber dynamics in an airbreathing pulse detonation engine (PDE) are conducted. The system under consideration includes a supersonic inlet, an air manifold, a valve, a single-tube combustor, and a convergent-divergent nozzle. The analysis accommodates the full conservation equations in two-dimensional coordinates and employs a chemical reaction scheme with a single-progress variable calibrated for a stoichiometric hydrogen/air mixture. The combustion and flow dynamics involved in typical PDE operations are carefully examined. In addition, a flowpath-based performance prediction model is established to estimate the theoretical limit of the engine propulsive performance. Various performance loss mechanisms, including the refilling process, nozzle flow expansion and divergence, and internal flow process are identified and quantified. The internal flow loss, which mainly arises from the shock waves within the chamber, was found to play a dominant role in degrading the PDE performance. The effects of engine operating parameters and nozzle configurations on the system dynamics are also studied in depth. Results indicate the existence of an optimum operating frequency for maximizing the performance margin. For a given cycle period and purge time, the performance increases with decreasing valve-closed time in most cases. On the other hand, a larger purge time decreases the specific thrust but increases the specific impulse for a given cycle period and valve-closed time. The nozzle throat area affects both the flow expansion process and chamber dynamics, thereby exerting a much more significant influence than the other nozzle geometrical parameters.