Combined Numerical and Experimental Investigation of a 15-cm Valveless Pulsejet

Abstract

The pulsejet, due to its simplicity, may be an ideal micro propulsion system. In this paper, modern computational and experimental tools are used to investigate the operation of a 15-cm overall length valveless pulsejet. Gas dynamics, acoustics and chemical kinetics are studied to gain understanding of various physical phenomena affecting pulsejet operation, scalability, and efficiency. Pressure, temperature, thrust, and frequency are measured as a function of valveless inlet and exit lengths and different geometries. At this length scale, it is necessary to run the pulsejets on hydrogen fuel. 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 k-ε model and the Eddy Dissipation Model (EDM), respectively. Simulation results provide physical insight into the pulsejet cycle; comparisons with experimental data are discussed. Nomenclature DaDamköhler number, ratio of flow times to chemical times Pr t turbulent Prandtl number, ratio of turbulent kinematic viscosity to turbulent thermal diffusivity P k shear production of turbulence S E energy source t flow fluid timescale, k/ε t chem chemical time scale ν KI stoichiometric coefficient for reactant I in reaction K ν KI stoichiometric coefficient for product I in reaction K

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“…Valveless pulsejet combustor designs with no moving parts at larger scales have been known since the early 1900s. Recently, a 15-cm long, conventionally fabricated system has been reported [5,6], where various system measurements such as temperature, pressure, operation frequency and thrust measurements have been described. To our knowledge, there is no literature reporting on the design, and fabrication of such engines at smaller scales (i.e.…”