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为了计算微小型发动机的热负荷,提出了对其气缸体进行热分析的方法。通过理论计算确定热边界条件,建立三维有限元模型对温度场进行数值计算;利用热成像和红外技术测量气缸温度场,以试验数据和计算数值之差为依据反推得到准确的温度场,并在此基础上计算气缸热变形。以排气量为0.33cm3的微小型发动机为例计算其热负荷,分析结果表明:排气窗口使得气缸温度场和热变形发生非轴对称性突变;由于高转速的强冷却效果,11000r/min时温度和变形达到最大值;高速冷却气流和大的散热面积与容积之比提供了良好的冷却效果,同时也降低了热效率。
In order to calculate the thermal load of a miniature engine, a method of thermal analysis of its cylinder block is proposed. The thermal boundary conditions are determined theoretically and the three-dimensional finite element model is established to calculate the temperature field. The temperature field of the cylinder is measured by thermography and infrared technology. The accurate temperature field is deduced based on the difference between the experimental data and the calculated value. Based on this calculation of cylinder thermal deformation. Taking the miniature engine with displacement of 0.33cm3 as an example, the thermal load is calculated. The analysis results show that the exhaust window causes a non-axisymmetric mutation in the temperature field and the thermal deformation of the cylinder. Due to the strong cooling effect of high speed, 11000r / min The maximum temperature and deformation are reached; the high cooling air flow rate and the large heat sink area-to-volume ratio provide good cooling while also reducing thermal efficiency.