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

摘要： 基于GT-Power软件建立某汽油机仿真模型并进行验证，设计新的进气门升程曲线，将原Otto循环模型改进为高压缩比Atkinson循环模型。改变传热模型的对流换热因子，计算分析了2 000 r/min、50%负荷、理论空燃比时，对流换热强度对Atkinson循环能量分配特性的影响。结果表明：在常规散热条件下，与Otto循环相比，Atkinson循环散热能量增加3.5%，但因其作功冲程相对较长，排气带走的能量大幅降低，故其指示热效率仍提高了2.9%；对流换热强度越弱，缸内传热速率越小，燃烧等容度更大，因此散热损失的能量越少，指示热效率越高；降低散热后节省的能量转化为指示功或被排气带走，在不同的对流换热强度下，Atkinson循环将节省能量转化为指示功的效率更高，比Otto循环高6%以上；降低对流换热强度有利于优化Atkinson循环的能量分配特性，进一步发挥Atkinson循环节能优势，同时改善动力性，但缸内热负荷有所增大。

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