非稳态温度场有限元分析及其在船用柴油机上的应用

用有限元素法计算非稳态温度场已有若干年的历史,但初始精度还有待提高。本文从截断误差和截断误差传播的角度分析了计算总误差,并提出了误差累积模式。根据分析可知,在中小步长时减小本步截断误差和误差增长因子对减小计算总误差是有效的,而在大步长时减小误差增长因子比减小本步截断误差更有效。本文选用G2格式编写了轴对称及平面非稳态溫度场电子计算机程序,对K150E柴油机缸盖进行了起动工况温度场计算,与实测结果相比吻合程度较好。

THE FINITE ELEMENT ANALYSIS OF UNSTEADY STATE TEMPERATURE FIELD AND ITS APPLICATION TO MARINE DIESEL ENGINE

Although the tinite element method has been used to solve unsteady state heat conduction problems for a long time, its initial short-time accuracy is still to be further improved.For computation the truncation error of scheme and accumulation of truncation error are analyzed. Through investigation we recognize that in order to decrease calculation error, it is desirable to decrease truncation error and error amplification factor in small and medium step sizes. But for the case of large time step size, it is more desirable to decrease error amplification factor than to decrease truncation error.Three node Galerkin scheme (abbreviated as G2 scheme) has smaller truncation error and smaller error amplification factor. G2 scheme is superior to other schemes investigation in wide range of time step sizes. So we choose G2 scheme for the development of a computer program for an axissymetric and plane unsteady state temperature field.This program has been used for the calculation of the unsteady temperature field of K150E engine cylinder. We suppose that the heat transfer coefficients at every part of the combustion chamber rise according to the same rule.In order to verify the accuracy of the finite element method, the wall temperature of K150E cylinder head at starting time is measured. The calculated temperature field agrees well with the experimental values.