Optical study of HCCI Combustion using NVO and an SI Stratified Charge
Optical study of HCCI Combustion using NVO and an SI Stratified Charge
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DOI：
10.4271/2007-24-0012
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发表时间：
2007-09
期刊：
影响因子：
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通讯作者：
Andreas Berntsson;I. Denbratt
中科院分区：
文献类型：
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作者：
Andreas Berntsson;I. Denbratt
在发动机试验中研究了SI分层进气与HCCI燃烧相结合对燃烧相位、放热率和排放的影响，以确定将HCCI燃烧的操作范围扩展到较低负荷的方法。在实验中，光学单缸发动机配备有压电向外打开的喷射器，并且以负气门重叠（NVO）和低升程、短持续时间、凸轮轴轮廓操作，用于通过增加废气再循环（EGR）来启动HCCI燃烧，从而保持足够的热能以达到自燃温度。进行了两个系列的实验与全析因设计，以研究如何测试的参数（在先导喷射和主喷射，分层喷射定时和火花辅助的燃料喷射量）影响燃烧。在光学研究中，从Nd：YAG激光器的四次谐波光（266 nm）被用来诱导荧光（LIF），从3-戊酮添加作为燃料示踪剂，分析气缸内的燃料蒸气的浓度和分布。此外，三次谐波光（355 nm）被用来研究在气缸中的甲醛的浓度和分布，OH自由基的化学发光信号被用来定位火焰前锋。结果表明，SI分层进气的喷油和点火时刻是影响HCCI燃烧相位的主要参数。发现使用SI分层进气及其喷射正时对NOx排放有显著影响。结果表明，采用SI分层进气可通过提前燃烧相位，将HCCI燃烧的工作范围扩展到低负荷。此外，NVO与SI分层充气结合使用提供了一种有用、灵活的控制HCCI燃烧的方法。
The effects of using an SI stratified charge in combination with HCCI combustion on combustion phasing, rate of heat release and emissions were investigated in engine experiments to identify ways to extend the operational range of HCCI combustion to lower loads. In the experiments an optical single-cylinder engine equipped with a piezo electric outward-opening injector and operated with negative valve overlap (NVO) and low lift, short duration, camshaft profiles, was used to initiate HCCI combustion by increasing the exhaust gas recirculation (EGR) and thus retaining sufficient thermal energy to reach auto-ignition temperatures. Two series of experiments with full factorial designs were performed, to investigate how the tested parameters (amounts of fuel injected in pilot injections and main injections, stratification injection timing and spark-assistance) influenced the combustion. In the optical study fourth harmonic light (266 nm) from a Nd:YAG laser was used to induce fluorescence (LIF), from 3-pentanone added as a fuel tracer, to analyze the concentration and distribution of fuel vapor within the cylinder. In addition third harmonic light (355 nm) was used to study the concentration and distribution of formaldehyde in the cylinder, and chemiluminescence signals from OH radicals were used to locate the flame front. It was found that the injection and ignition timing of the SI stratified charge were the main parameters influencing the HCCI combustion phasing. The NOX emissions were found to be significantly affected by the use of a SI stratified charge, and its injection timing. The results show that use of an SI stratified charge can extend the operational range of HCCI combustion to lower loads by advancing combustion phasing. In addition, use of NVO in combination with an SI stratified charge provides a useful, flexible means to control HCCI combustion.