An experimental investigation of the sensitivity of the ignition and combustion properties of a single-cylinder research engine to spark-assisted HCCI
An experimental investigation of the sensitivity of the ignition and combustion properties of a single-cylinder research engine to spark-assisted HCCI
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DOI：
10.1177/1468087411401286
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发表时间：
2011-08
影响因子：
2.5
通讯作者：
B. Zigler;B. Zigler;P. Keros;K. Helleberg;M. Fatouraie;D. Assanis;M. Wooldridge
中科院分区：
文献类型：
--
作者：
B. Zigler;B. Zigler;P. Keros;K. Helleberg;M. Fatouraie;D. Assanis;M. Wooldridge
火花辅助均质充量压缩点火（HCCI）燃烧可能是改善 HCCI 发动机运行的一种方法。在当前的研究中，在单缸光学研究型发动机中研究了火花辅助对点火和燃烧基本特性的影响。在该研究中，早期进气道燃油喷射和空气预热与吲哚燃料一起使用。研究了一系列空气预热（T in = 256–281 °C）、燃油/空气当量比（φ = 0.38–0.62）和火花辅助正时（上止点前 10°−90°）条件对最大缸内压力和正时、循环变异性、平均有效指示压力 (IMEP) 和放热率的影响。此外，高速成像还用于捕捉火花辅助和无辅助 HCCI 操作期间的活塞视图点火和燃烧事件。开发了方法并将其应用于成像序列，以量化火花辅助和无辅助 HCCI 操作期间形成的反应前沿的物理特性（例如自燃点的位置）和传播速率。成像数据显示，随着空气预热温度的升高，自燃点出现的频率不断增加。火花辅助的添加导致在所有条件下都形成反应前沿，并以 1.9 至 4.3 m/s 的平均速度从火花电极向外传播。成像数据表明火花辅助的效果是由于传播反应前沿对未燃烧气体的压缩加热，这也导致自燃位置更加一致。成像和发动机数据的比较表明，反应前沿的初始形成并不是重要的热释放源。虽然发动机数据显示，在所研究的边际 HCCI 工况下，火花辅助会影响定相、放热率、IMEP 和发动机稳定性，但结果还表明，火花辅助的温度范围很窄，与 HCCI 燃料/空气充气的固有热分层的影响相比，该温度范围的变化将非常显着。
Spark-assisted homogeneous charge compression ignition (HCCI) combustion may be a method to improve the operation of HCCI engines. In the current study, the impact of spark assist on the fundamental properties of ignition and combustion was investigated in a single cylinder, optically-accessible research engine. Early port fuel injection and air preheating were used with indolene fuel in the study. The effects of a range of air preheat (T in = 256–281 °C), fuel/air equivalence ratio (ϕ = 0.38–0.62) and spark assist timing (10°−90° before top dead centre) conditions on maximum in-cylinder pressure and timing, cycle variability, indicated mean effective pressure (IMEP) and heat release rate were investigated. Additionally, high-speed imaging was used to capture the piston-view ignition and combustion events during spark-assisted and unassisted HCCI operation. Methods were developed and applied to the imaging sequences to quantify the physical characteristics (e.g. location of autoignition sites) and the rate of propagation of the reaction fronts formed during spark-assisted and unassisted HCCI operation. The imaging data show that autoignition sites appear with increasing frequency as air preheat temperature is increased. The addition of spark assist led to the formation of reaction fronts at all conditions that propagated outward from the spark electrode at average speeds between 1.9 and 4.3 m/s. The imaging data indicate the effects of spark assist are due to compression heating of the unburned gases by the propagating reaction fronts which also leads to more consistent location of autoignition. Comparison of the imaging and engine data show the initial formation of the reaction fronts are not significant sources of heat release. While the engine data show that spark assist can affect phasing, heat release rate, IMEP and engine stability at the marginal HCCI operating conditions studied, the results also indicate spark assist has a narrow temperature range where the changes will be significant compared to the effects of the inherent thermal stratification of the HCCI fuel/air charge.