Time resolved measurements of flow fields and heat release in pulse combustors

摘要

Pulsating combustion is a non-steady combustion process where quantities like pressure, temperature, velocity etc., oscillate periodically in time. The oscillations occur spontaneously due to interaction between pressure oscillations and heat release. Pulsating combustion offers advantages like high heat transfer and low emissions of NO(sub x) and CO and a potential of simple design. In this work detailed measurements in the combustion chamber were performed in order to get information about fundamental processes that control the combustion and the operating characteristics of a pulse combustor. An increased theoretical and experimental knowledge may provide possibilities to control the combustion process, and that knowledge can be transferred to a design tool for pulse combustors with very low levels of exhaust emissions and high combustion efficiency. An experimental investigation of flow fields and CH-radical fields in two different combustion chambers of different pulse combustors was performed. Results from measurements from an axisymmetric (square cross section) combustion chamber were compared to measurements from a 'flat' combustion chamber. The results indicate that the fluid dynamic mixing that takes place in the vortices created by the flame holder and the air to fuel ratio control the phase shift between the heat release and pressure. Therefore, it seems likely to achieve operation characteristic control by this means. The emission levels of NO(sub x) are not influenced so much by internal flue gas recirculation from the tail pipe as by the air to fuel ratio and short residence time at high temperatures. Measurements used to support the development of a simulation model indicate that it is possible to simulate the important features of the flow. 45 refs, 34 figs, 8 tabs