We report on the increase in combustion efficiency of a ～250 cm~3 one-cylinder combustion engine under turbulent conditions and on the turbulent flame extinction limits, which were induced by a four-bladed fan (d = 61 mm). A maximum pressure of Δp_(max) ～ 5 bar is achieved for injected propene/1-butene fuel and a fan speed of 13600 rpm (fan start 500 ms before ignition). In case of premixed conditions, the ignition probability for propane/air fuels significantly decreases for fan velocities above 10 000 rpm (fan start 300 ms before ignition). 2D OH-LIF measurements indicate the strong wrinkling and breakup of the flame within the first millisecond after ignition. Additional PIV measurements in the same viewing plane reveal a steep increase of vorticity and number of vortices near the spark plug after start of the fan. The measurements distinctly visualize the pronounced effect of the turbulence on flame ignition and extinction in a model engine.
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