活塞内冷油腔振荡流动与传热的瞬态分析方法

A Transient Analysis Approach of the Oscillating Flow and Instantaneous Heat Transfer Processes of the Piston Cooling Gallery

为了分析活塞内冷油腔中机油流动与传热特性,基于相对位移法,提出了一种把内冷油腔看作刚体,采用边界条件随曲轴转角变化的内冷油腔振荡流动与传热的仿真方法。采用该方法建立了内冷油腔振荡流动与传热的计算流体力学模型,计算分析了不同转速下机油流动与传热过程,并与采用其他仿真方法的计算结果进行了对比分析。研究结果表明,在相同发动机转速下,内冷油腔各壁而的瞬时面积平均换热系数有较大的差异,其出现峰谷值的数值与峰谷值对应的曲轴角度都有所差异。在不同的转速下,各壁面的瞬时换热系数呈现出相似的规律,随着发动机转速的增加,瞬时换热系数增加。通过计算分析对比表明,采用本方法减少了计算工作量且具有较高的计算精度。

In order to obtain stable characteristics of oil flow and heat transfer of the cooling gallery with an efficient way, a transient analysis approach of oil oscillating flow and heat transfer process was proposed. By using a relative displacement method, the cooling gallery was treated as rigid body, and the boundary conditions changed with crank angle that was instead of the unchanged conditions. A computational fluid dynamics simulation model was established by the approach. The processes of the oil flow and heat transfer inside piston cooling gallery was calculated with the model under different engine speeds. The numerical result was compared with other simulation methods and a set of test data. It was found that, the averaged heat transfer coefficient of each wall regions of the cooling gallery have great differences for a giving engine speed. The values and the moment of peaks and valleys of the heat transfer coefficient curves are different. For different engine speed,instantaneous heat transfer coefficient of all regions shows a similar rule, and it will increase with an increasing engine speed. Numerical results showed that the simulation model was established with the approach resulting a much less calculation amount and a better accuracy.