PULSED DETONATION ENGINE PROCESSES: EXPERIMENTS AND SIMULATIONS

Abstract

Computational and experimental investigations of a pulsed detonation engine (PDE) operating in a cycle using ethylene/air mixtures are reported. Simulations are performed for two geometry configurations, namely, an ideal tube PDE with a smooth wall fueled with premixed C₂H₄/O₂ and a benchmark tube PDE with internal geometry and a valveless air supply fueled with C₂H₄. Performance estimates of fuel-specific impulse (I_spf) of an ideal tube PDE, obtained using a two-step reduced mechanism for a C₂H₄/O₂ mixture, are in good agreement with existing test measurements from the literature. Realistic simulations of all processes of the PDE cycle (fill, deflagration-to-detonation transition (DDT), detonation propagation, blowdown, and purge) of a benchmark tube PDE yielded important insights into continuous cycle operation. Experimental measurements include DDT visualizations and dynamic pressure measurements. Comparisons of experimental and computational visualizations show good agreement in cycle process timescales. However, run-up distance is underpredicted, indicating a need to improve the flame propagation mechanism. The predicted decrease in the fuel-specific impulse (I_spf) for the benchmark tube when compared to the I _spf of an ideal tube may be attributed to nonuniformities in the mixture composition, the pressure drop resulting from internal geometry, and backflow in the benchmark tube due to a compression wave propagating into the upstream geometry.

Keywords:

• Deflagration to Detonation Transition (DDT)
• Detonations, Pulsed Detonation Engine (PDE)
• PDE cycle processes

The authors wish to acknowledge the technical discussions with Dr. J. Shepherd of the California Institute of Technology and Dr. K. Kailasanath of Naval Research Laboratories. Ideal tube data, provided by K. Hinckley of Stanford University, is sincerely acknowledged. The authors acknowledge technical help with the experimental setup provided by Dr. A. Rasheed and E. Cornell of General Electric Global Research. Computational support provided by I. Schild of General Electric Global Research and Dr. S. Palaniswamy of Metacomp Technologies, Inc. is sincerely appreciated.