Experimental and numerical investigation of an 8-cm valveless pulsejet

This paper investigates the performance of a small scale pulsejet whose overall length is approximately 8 cm, the smallest pulsejet ever reported to the author's knowledge. Gas dynamics, acoustics and chemical kinetics were modeled to gain an understanding of various physical phenomena affecting pulsejet operation, scalability, and efficiency. Numerical simulations were performed utilizing CFX to model 3-D compressible vicious flow in the pulsejet using the integrated Westbrook-Dryer single step combustion model. The simulation results were validated with experimental data and provide physical insight into the pulsejet operation. The pulsejet was run in valveless mode on hydrogen fuel with either a forward-facing inlet or a pair of rearward-facing inlets. Pressure, temperature, thrust, and frequency were measured as a function of valveless inlet and exit lengths and different geometries. As expected, the rearward-facing inlet produced considerably more net thrust, although still not very efficient, with a TSFC of 0.02 kg/N-h. The operating frequency was found to scale with inlet length to the negative 0.22 power, in addition to the inverse of the overall length for valved pulsejet.