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The influence of pressure on spherically propagating premixed turbulent flames was examined with experiments carried out using a constant volume fan-stirred combustion vessel. The effects of mixture strength and turbulence intensity on the propagation and quench of turbulent flames were studied for mixture pressures of 0.10 to 0.50 MPa. Two mechanisms of quench were observed and are discussed for lean and rich flames. Possible correlations of turbulent burning velocity were developed in terms of Lewis and turbulence Reynolds numbers.

EGR (Exhaust gas recirculation) can reduce the pumping loss and improve the thermal efficiency of spark ignition engines. The techniques for combustion enhancement under high EGR rate condition has been required for further improvement of the thermal efficiency. In order to develop the technique of combustion enhancement by turbulence, the influences of turbulence scale on combustion properties, such as probability of flame propagation, EGR limit of flame propagation, flame quenching and combustion duration were investigated under the condition of same turbulence intensity. Experiments were carried out for stoichiometric spherically propagating turbulent i-C8H18/Air/N2 flames using a constant volume vessel. It was clarified that all of these combustion properties were affected by the turbulence scale. The development of spherically propagating turbulent flame during flame propagation was affected by the turbulence scale.