HCCI燃烧过程化学发光光谱研究

在一台经改装单缸光学发动机机上,进行不同喷油策略和进气温度条件下均质压燃(HCCI)燃烧化学发光光谱实验研究。实验保证循环供油量一定,燃用正庚烷作为燃料,转速600 r.min-1,进气压力0.1MPa,控制2个不同的进气温度:95和125℃。化学发光光谱研究结果表明,低温反应阶段化学发光很弱,主要源于甲醛光谱;低温反应后期-负温度系数区-高温反应初始阶段主要发光来源还是甲醛光谱;高温反应阶段发光主要来源于CO—O*连续谱,同时在CO—O*连续谱上出现OH,HCO,CH,HCHO谱峰;高温反应后期化学发光明显减弱。与-30°ATDC喷油相比,-300°ATDC喷油时CO—O*连续谱发光强度更大,HCO和OH生成量更多,燃烧反应进行程度更深。较高进气温度下CO—O*连续谱发光强度更大,HCO和OH生成量更多。

Chemiluminescence spectroscopic analysis of homogeneous charge compression ignition combustion processes

To study the combustion reaction kinetics of homogeneous charge compression ignition (HCCI) under different port injection strategies and intake temperature conditions, the tests were carried out on a modified single-cylinder optical engine using chemiluminescence spectroscopic analysis. The experimental conditions are keeping the fuel mass constant; fueling the n-heptane; controlling speed at 600 r x min(-1) and inlet pressure at 0.1 MPa; controlling inlet temperature at 95 degrees C and 125 degrees C, respectively. The results of chemiluminescence spectrum show that the chemiluminescence is quite faint during low temperature heat release (LTHR), and these bands spectrum originates from formaldehyde (CH2O) chemiluminescence. During the phase of later LTHR-negative temperature coefficient (NTC)-early high temperature heat release (HTHR), these bands spectrum also originates from formaldehyde (CH2O) chemiluminescence. The CO--O* continuum is strong during HTHR, and radicals such as OH, HCO, CH and CH2O appear superimposed on this CO--O* continuum. After the HTHR, the chemiluminescence intensity is quite faint. In comparison to the start of injection (SOI) of -30 degrees ATDC, the chemiluminescence intensity is higher under the SOI = -300 degrees ATDC condition due to the more intense emissions of CO--O* continuum. And more radicals of HCO and OH are formed, which also indicates a more intense combustion reaction. Similarly, more intense CO--O* continuum and more radicals of HCO and OH are emitted under higher intake temperature case.