低碳醇汽油发动机燃烧分析实验平台设计及教学应用

Design and teaching application of an experimental platform for combustion analysis of low-carbon alcohol gasoline engines

为探究低碳醇掺混汽油的醇基燃料在缸内具体的燃烧状态和燃烧过程,该文基于自然吸气式气道喷射汽油发动机搭建实验平台,并改进了燃烧分析功能。基于实验平台开展了3种燃料(92号汽油、甲醇比例85%的甲醇汽油、50%异丙醇掺混的92号汽油)的缸内燃烧实验,分析了醇基燃料燃烧状和在发动机中的燃烧性能。实验平台可完成动力性、经济性分析等测试项目,并可对缸压、放热率以及燃料自燃性质进行测量分析。

[Objective]New technologies and techniques have significantly affected the development of internal combustion engines,leading to continuous improvements in their performance indexes.Among these innovations,data acquisition and combustion analysis technologies have played an immeasurable role in promoting internal combustion engines.This paper aims to study the specific combustion state of low-carbon alcohol blended gasoline within the cylinder,as simulations alone do not fully capture the combustion process.The research focuses on enhancing the combustion analysis function of a traditional naturally aspirated injection gasoline engine.[Methods]To obtain experimental data such as pressure,exothermic rate,and combustion mass fraction,the combustion pressure in cylinder 1 of the gasoline engine was measured using a sophisticated pressure collection device.The crankshaft angle position was also encoded and processed.The collected pressure data underwent low-pass filtering and averaging.The exothermic characteristics of the combustion process in the cylinder of the internal combustion engine were analyzed using the instantaneous combustion pressure curves from several engine operating cycles collected,applying the first law of thermodynamics.This analysis served as a criterion for evaluating the combustion state of different fuels under various operating conditions and overall engine performance.Prior to starting the gasoline engine experiments,several safety checks were conducted.These included verifying the engine coolant and oil levels,inspecting for leaks in the high-pressure oil pipe,oil consumption meter inlet and outlet oil pipes,and the oil cap,and ensuring the pipeline connection is firm.It was also necessary to check whether the normal operation of the engine starter and the battery’s electrical connections.After confirming there were no abnormal states,the dynamometer cooling water was turned on,excitation was added,and the throttle opening and startup load at startup were set to 0.The engine was then started and warmed up for at least 15 min,maintaining the engine cooling water temperature within 80±5℃,the oil temperature within 95±5℃,and the intake air temperature within 30±2℃.[Results and Conclusions]The results of this study are the following:①The power of the gasoline engine showed a linear growth trend with increasing torque,and this enhancement rate increased with higher engine speeds.A higher percentage of methanol gasoline(M85)exhibited higher fuel consumption than 92 octane gasoline under the same working conditions owing to its lower heat density,with the highest fuel consumption being more than 50%that of 92 octane gasoline.②Isopropanol cylinder pressure at high rpm and lower loads is affected by the amount of fuel injected,which can be erratic at peaks,and the higher the rpm,the higher the demand for isopropanol fuel.③Combustion of a 50%isopropanol blended fuel intensified near 1°CA,whereas gasoline began to burn near 3°CA,with combustion lasting longer.