非同步气门正时对高速汽油机进气及燃烧过程的影响

Effect of Asynchronous Valve Timing on Intake and Combustion Process of a High Speed Gasoline Engine

结合某高速进气道喷射五气门汽油机,采用CFD技术和台架试验手段研究了同步与非同步气门正时对高速汽油机进气和燃烧过程的影响。CFD分析结果表明:非同步气门正时能够加强缸内气体流动,提高点火时刻的缸内湍动能,有利于火焰的快速传播,提高燃烧速率。试验结果表明:进气门2提前20°开启,比其他进气门开启时刻的扭矩提高了约3.1%,燃油消耗率降低了约4.2%;进气门2推迟20°开启燃油消耗率降低了约2.6%,发动机扭矩略微降低。非同步气门正时下,发动机HC和CO排放量均降低,进气门2提前20°开启由于缸内温度较高,NO_x排放量增加了约11.3%。进气门2推迟20°开启由于缸内进气量较低,NO_x排放量降低了约6.7%。

Based on a high-speed intake port injection gasoline engine, the effect of asynchronous valve timing on intake and combustion process of a high-speed engine was studied by using CFD simulation and engine test. The CFD calculation results show that asynchronous valves timing can strengthen in-cylinder gas rotational flow, increase gas turbulence kinetic energy at the ignition timing, which is beneficial to increase the flame propagation speed and heat release rate. The engine test results show that the second IVO advanced 20°（in relation to other intake valves open timing） can increase torque by 3. 1%, and decrease the fuel consumption by 4. 2 % ; the second IVO delayed 20° can decrease the fuel consumption by 2. 6 % and reduce the engine torque slightly. Both HC and CO emissions with asynchronous valves timing are reduced. For the second IVO advanced 20°, NOx emission is increased by 11.3% due to the higher in-cylinder temperature, while for the second IVO delayed 20° NOx emission is reduced by 6. 7% due to the lower intake mass.