【摘要】：為了研究柴油機(jī)冷啟動(dòng)過程中氣缸蓋的溫度應(yīng)力變化情況,通過數(shù)值仿真手段,計(jì)算在不同環(huán)境溫度、額定工況工作情況下氣缸蓋溫度和應(yīng)力狀態(tài)及壽命,比較分析啟動(dòng)過程中溫度、應(yīng)力隨時(shí)間的變化過程。首次發(fā)現(xiàn)啟動(dòng)過程中溫度-時(shí)間和應(yīng)力-時(shí)間變化曲線峰值,對(duì)不同環(huán)境溫度下、穩(wěn)態(tài)計(jì)算和瞬態(tài)計(jì)算的氣缸蓋壽命進(jìn)行對(duì)比,最后提出對(duì)冷卻液溫度優(yōu)化的方案。主要研究內(nèi)容和結(jié)論如下：(1)柴油機(jī)三維有限元模型建立和邊界條件獲取,進(jìn)行流固耦合數(shù)值仿真計(jì)算,并將缸蓋溫度場計(jì)算結(jié)果與試驗(yàn)進(jìn)行對(duì)比分析。結(jié)果表明,兩者誤差都在5%以內(nèi),該數(shù)值計(jì)算模型滿足工程應(yīng)用的要求。(2) 不同環(huán)境溫度下穩(wěn)態(tài)的氣缸蓋溫度、應(yīng)力和低周疲勞壽命計(jì)算,發(fā)現(xiàn)環(huán)境溫度對(duì)于穩(wěn)態(tài)工作下的溫度、應(yīng)力和壽命影響不大。(3) 不同環(huán)境溫度下氣缸蓋溫度-時(shí)間變化瞬態(tài)計(jì)算。發(fā)現(xiàn)啟動(dòng)過程中某些區(qū)域溫度-時(shí)間變化曲線出現(xiàn)峰值,隨著環(huán)境溫度升高,峰值逐漸降低甚至消失。(4) 不同環(huán)境溫度下氣缸蓋應(yīng)力-時(shí)間變化和壽命的準(zhǔn)穩(wěn)態(tài)計(jì)算。發(fā)現(xiàn)啟動(dòng)過程中某些區(qū)域應(yīng)力-時(shí)間變化曲線出現(xiàn)峰值,該峰值隨著環(huán)境溫度的升高而降低。低溫啟動(dòng)準(zhǔn)穩(wěn)態(tài)計(jì)算的壽命要比穩(wěn)態(tài)計(jì)算的壽命更低。(5)提出一種優(yōu)化方案,在-25℃環(huán)境下將冷卻液初始溫度設(shè)置為0℃,結(jié)果表明其相應(yīng)區(qū)域溫度峰值和應(yīng)力峰值都有明顯降低,優(yōu)化作用明顯。
[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，

本文編號(hào)：2168049