LES Analysis of Equivalence Ratio Effect on Turbulent Premixed Characteristics of LPG Flame Front Propagation

Document Type : Original Article

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Department of Mechanical Power, Faculty of Engineering, Cairo University, Cairo, EGYPT

Abstract

Turbulent premixed characteristics of LPG are not restricted to change of laminar flame velocity with equivalence ratio. Sudden pressure rise resulting from the ignition of such flammable mixture, peak pressure attained and time required for such peak to be reached should be investigated and tabulated with the same level of attention for loss prevention requirements. The current work is devoted to numerically examine thermodynamic effects of equivalence ratio and the way it would have on overall characteristics of the evolved LPG flame. The model used incorporates Large Eddy Simulation (LES) technique for turbulent reacting flows. The model is validated against available published experimental data. The combustion chamber under study is of 0.00625 m3 volume with square cross section involving three consecutive baffle-plates and a box to generate high turbulence level. A good numerical representation of experimental initial and boundary conditions resulted in good agreement with experimental data for generated propagating flame and pressure-time history. It was concluded that pressure gradient exists inside the combustion chamber. Peak pressure increases with equivalence ratio until it reaches a maximum at a slightly rich mixture before dropping with further increase of fuel concentration. Same conditions apply to the time required to reach the peak pressure.

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