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In-cylinder air motion characteristics with variable valve lift in a spark ignition engine. Part 1 : Swirl flow

While Variable Valve Actuation is used increasingly in spark ignition engines to improve fuel economy and reduce CO2 emissions, the in-cylinder flow characteristics for reduced maximum valve lifts (MVL) were experimentally investigated in a four-valve optical Gasoline Direct Injection test engine by applying Particle Image Velocimetry. The results showed that a reduced MVL significantly enhanced the in-cylinder swirl motion, increased both the high-frequency fluctuating kinetic energy and the low-frequency fluctuating kinetic energy. The results of this internationally collaborative research have helped Tianjin Yiqi Auto Company (China) improve their engine fuel economy by 3-5% and emission reduction (Dr Hongmei Cheng).