THERMAL PULSE COMBUSTION

This paper describes theoretical and experimental observations of comb ustion oscillations produced in a continuously mixed, jet-stirred comb ustion system. This work is distinct from other investigations of puls e combustion, because it is shown both theoretically and experimentall y that combustion oscillations can be produced wtih a steady supply of fuel and air, requiring no mechanical or aerodynamic valves. The theo ry is a direct extension of thermal theories of combustion in back-mix ed reactors, extended to include the unsteady behavior of the combusto r and tailpipe. Because of the demonstrated effect of heat transfer an the oscillations, the name thermal pulse combustion is chosen to desc ribe these oscillations. Effects of friction in the combustor tailpipe , heat loss from the combustion zone, and flaw rate, are investigated theoretically. Depending on operating parameters, oscillating combusti on, steady flames, or blow-out are all predicted. The effects of finit e mixing rate are investigated by specifying a mixing time. Results of the simulation are then favorably compared to laboratory observations of a combustor operating with parameters similar to those used in the numeric model. Laboratory observations confirm that large amplitude o scillations can be produced in a jet-mixed combustor with a steady sup ply of fuel and air. Laboratory observations show qualitative agreemen t with predictions, and reasonable quantitative agreement at select co nditions.