【摘要】 以两级增压柴油机为研究机型,采用GT-Power构建其一维热力学仿真模型,对比模拟研究了柴油机采用两级增压(two stage turbocharger,TST)和可变两级增压(regulated two stage turbocharger,RTST)的变海拔(0km、2km、4km)工作特性。模拟结果表明:针对发动机外特性,不同两级增压系统高压级压比随海拔升高而增加。相比TST增压系统,高原环境下(2km、4km),RTST增压系统能够保证更高的进气流量及空燃比,抑制柴油机高原限扭,同时降低有效燃油消耗率。随着海拔升高,TST及RTST涡前温度及传热能均出现不同程度的升高;但RTST涡前温度及传热能升高幅度相对较低。低海拔(2km)下,NO_x比排放随海拔升高呈增加的趋势。高海拔(4km)下,可变截面涡轮增压器(variable geometry turbocharger,VGT)开度减小及推迟主喷定时,进气流量及空燃比增加。随着VGT开度增加及主喷定时推迟,涡前温度升高。传热能随VGT开度增加先减小后升高,随主喷定时推迟而减小。NO_x比排放随VGT开度的增加而减小,随主喷定时的推迟减小幅度较小。较早的喷油定时(-7°～-4°)协同合理的VGT开度(0.3～0.5)有利于减小有效燃油消耗率(BSFC)与NO_x比排放的折中关系。更多还原

【Abstract】 Based on an 1D thermodynamics model set up with the GT-power,the comparative simulation study on the performance of a diesel engine equipped respectively with a two-stage turbocharger(TST)system and a regulated two-stage turbocharger(RTST)system at different altitudes(0 km,2 km and 4 km)was carried out to achieve high efficiency and low emissions of diesel engines in a plateau environment.The results show that,at full load,the high stage boosting rates of both two-stage turbocharger systems increase with the altitude.Compared with TST,RTST guarantees higher intake air flow and air/fuel ratio(AFR)at the plateau of 2 km and 4 km,thus having less restrain in torque and reducing the brake specific fuel consumption(BSFC).The temperature before turbocharger and heat transfer energy of TST and RTST increase similarly with the altitude,but those of RTST increase less.At the low altitude of 2 km,the specific emissions of NO_x increase with the altitude.At the altitude of 4 km,when the opening of the variable geometry turbocharger(VGT)decreases and the start of main injection(SOI)delays,both the intake air flow and AFR increase.With the increase of the VGT opening and the delay of SOI,the temperature before turbocharger rises.The heat transfer energy decreases first and then increases with the increase in the VGT opening,and decreases with the delay of SOI.NO_x specific emissions decrease with the increase in the VGT opening,and decrease slightly with the delay of SOI.Earlier SOI(-7° to -4° in crank angle after the top dead center)coordinated with reasonable VGT opening(0.3～0.5)is beneficial to reducing the trade-off between BSFC and NO_x specific emissions.更多还原