Combined Numerical and Experimental Investigation of a Hobby-Scale Pulsejet

Abstract

The pulsejet, due to its simplicity, may be an ideal micro propulsion system, but has received very little attention since the mid 1950’s. Here, modern computational and experimental tools are used to investigate the operation of a hobby scale (50 cm overall length) pulsejet. Gas dynamics, acoustics and chemical kinetics are all involved and are studied to gain an understanding of the various physical phenomena affecting pulsejet operation, scaleability and efficiency. A Bailey Machining Service (BMS) hobby pulsejet is instrumented to obtain pressure, temperature, thrust, and frequency. CH * chemiluminescence is utilized to determine combustion time and high speed imaging of the reed valve operation is undertaken to determine the valve duty cycle. Laser Doppler Velocimetry (LDV) has been used to measure the instantaneous exhaust velocity in these unsteady combustion devices. Numerical simulations are performed utilizing CFX to model the 3-D compressible vicious flow in the pulsejet using the integrated Westbrook-Dryer single step combustion model. The turbulent flow and reaction rate are modeled with the ke model and the Eddy Dissipation Model (EDM), respectively. Simulation results provide physical insight into the pulsejet cycle; comparisons with experimental data obtained in this research are carried out. The traditional view of a pulsejet as a 1/4 wave tube operating on the Humphrey cycle is modified with to account for valve operation and finite chemical kinetics.