Chemiluminescence Spectroscopic Analysis of Homogeneous Charge Compression Ignition Combustion Processes
LIU Hai-feng1, YAO Ming-fa1*, JIN Chao2, ZHANG Peng1, LI Zhe-ming1, ZHENG Zun-qing1
1. State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China 2. School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
Abstract：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·min-1 and inlet pressure at 0.1 MPa; controlling inlet temperature at 95 ℃ and 125 ℃, 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 °ATDC, the chemiluminescence intensity is higher under the SOI=-300°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.
Key words：Homogeneous charge compression ignition (HCCI);Chemiluminescence spectrum;Injection strategies;Intake temperature
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