冷启动过程中柴油机气缸盖热机耦合应力及低周疲劳寿命计算分析
发布时间：2018-08-06 14:39
【摘要】：为了研究柴油机冷启动过程中气缸盖的温度应力变化情况,通过数值仿真手段,计算在不同环境温度、额定工况工作情况下气缸盖温度和应力状态及寿命,比较分析启动过程中温度、应力随时间的变化过程。首次发现启动过程中温度-时间和应力-时间变化曲线峰值,对不同环境温度下、稳态计算和瞬态计算的气缸盖寿命进行对比,最后提出对冷却液温度优化的方案。主要研究内容和结论如下：(1)柴油机三维有限元模型建立和边界条件获取,进行流固耦合数值仿真计算,并将缸盖温度场计算结果与试验进行对比分析。结果表明,两者误差都在5%以内,该数值计算模型满足工程应用的要求。(2) 不同环境温度下稳态的气缸盖温度、应力和低周疲劳寿命计算,发现环境温度对于稳态工作下的温度、应力和寿命影响不大。(3) 不同环境温度下气缸盖温度-时间变化瞬态计算。发现启动过程中某些区域温度-时间变化曲线出现峰值,随着环境温度升高,峰值逐渐降低甚至消失。(4) 不同环境温度下气缸盖应力-时间变化和寿命的准稳态计算。发现启动过程中某些区域应力-时间变化曲线出现峰值,该峰值随着环境温度的升高而降低。低温启动准稳态计算的寿命要比稳态计算的寿命更低。(5)提出一种优化方案,在-25℃环境下将冷却液初始温度设置为0℃,结果表明其相应区域温度峰值和应力峰值都有明显降低,优化作用明显。
[Abstract]:In order to study the variation of temperature stress of cylinder head during cold start of diesel engine, the temperature, stress state and life of cylinder head under different ambient temperature and rated working condition were calculated by numerical simulation. The variation of temperature and stress with time during start-up is compared and analyzed. The peak values of temperature-time and stress-time curves during start-up are found for the first time. The life of cylinder head calculated by steady state calculation and transient calculation at different ambient temperatures is compared. Finally, the optimization scheme of coolant temperature is put forward. The main research contents and conclusions are as follows: (1) the three-dimensional finite element model and boundary conditions of diesel engine are established, the fluid-solid coupling numerical simulation is carried out, and the calculated results of cylinder head temperature field are compared with the experimental results. The results show that the error of both is less than 5%, and the numerical model can meet the requirements of engineering application. (2) the calculation of cylinder head temperature, stress and low cycle fatigue life at different ambient temperature shows that the ambient temperature is the temperature under steady operation. (3) transient calculation of temperature-time variation of cylinder head under different ambient temperature. It is found that there is a peak value of temperature time variation curve in some regions during start-up, and the peak value decreases or even disappears with the increase of ambient temperature. (4) Quasi-steady state calculation of stress-time variation and lifetime of cylinder head under different ambient temperature. It is found that there is a peak value of stress-time variation curve in some regions during start-up, which decreases with the increase of ambient temperature. The life of low-temperature start-up quasi steady state calculation is lower than that of steady state calculation. (5) an optimized scheme is proposed, in which the initial temperature of the coolant is set to 0 鈩，
本文编号：2168049
[Abstract]:In order to study the variation of temperature stress of cylinder head during cold start of diesel engine, the temperature, stress state and life of cylinder head under different ambient temperature and rated working condition were calculated by numerical simulation. The variation of temperature and stress with time during start-up is compared and analyzed. The peak values of temperature-time and stress-time curves during start-up are found for the first time. The life of cylinder head calculated by steady state calculation and transient calculation at different ambient temperatures is compared. Finally, the optimization scheme of coolant temperature is put forward. The main research contents and conclusions are as follows: (1) the three-dimensional finite element model and boundary conditions of diesel engine are established, the fluid-solid coupling numerical simulation is carried out, and the calculated results of cylinder head temperature field are compared with the experimental results. The results show that the error of both is less than 5%, and the numerical model can meet the requirements of engineering application. (2) the calculation of cylinder head temperature, stress and low cycle fatigue life at different ambient temperature shows that the ambient temperature is the temperature under steady operation. (3) transient calculation of temperature-time variation of cylinder head under different ambient temperature. It is found that there is a peak value of temperature time variation curve in some regions during start-up, and the peak value decreases or even disappears with the increase of ambient temperature. (4) Quasi-steady state calculation of stress-time variation and lifetime of cylinder head under different ambient temperature. It is found that there is a peak value of stress-time variation curve in some regions during start-up, which decreases with the increase of ambient temperature. The life of low-temperature start-up quasi steady state calculation is lower than that of steady state calculation. (5) an optimized scheme is proposed, in which the initial temperature of the coolant is set to 0 鈩，
本文编号：2168049
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