关键词: 车辆工程, Atkinson循环, 对流换热, 低散热, 能量分配, 散热损失

Abstract: A gasoline engine simulation model was established based on GT-Power software and validated by experiment. The original Otto cycle model was modified to an Atkinson cycle model with a higher geometric compression ratio by designing a new valve lift curve. The heat convection factor of the heat transfer model was changed to calculate and analyze the effect of heat convection on the energy distribution characteristics of the Atkinson cycle under the condition of 2000 r/min, 50% load, and theoretical air fuel ratio. The results show that compared with the Otto cycle, the heat loss of the Atkinson cycle is increased by 3.5% under the normal heat rejection conditions, but the energy taken off by the exhaust gas is greatly reduced owing to the longer expansion stroke of the Atkinson cycle, so the indicated thermal efficiency of the Atkinson cycle is still increased by 2.9%. The weaker heat convection intensity leads to the lower heat transfer rate in the cylinder and the higher level of isochoric heat release, which resulting in the less heat loss and the higher indicated thermal efficiency. The energy saved after reducing heat dissipation is converted into the indicated work or taken off by exhaust, and under different convective heat transfer intensities, Atkinson cycle is more efficient in converting the saved energy into the indicated work, which is more than 6% higher than that of Otto cycle. It is beneficial to optimize the energy distribution characteristics of the Atkinson cycle, further exert the energy saving advantages of Atkinson cycle and improve the power performance by reducing the heat convection intensity. However, the heat load in the cylinder is increased.

Key words: vehicle engineering, Atkinson cycle, heat convection, low heat rejection, energy distribution, heat loss