Optimisation of boosting strategy for controlled auto-ignition combustion in a four-valve camless gasoline direct injection engine running in two-stroke cycle
Optimisation of boosting strategy for controlled auto-ignition combustion in a four-valve camless gasoline direct injection engine running in two-stroke cycle
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DOI：
10.1177/1468087413519991
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发表时间：
2014-02
影响因子：
2.5
通讯作者：
Yan Zhang;Hua Zhao
中科院分区：
文献类型：
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作者：
Yan Zhang;Hua Zhao
由于它们能够同时降低燃料消耗和NOx排放，受控自动点火或均质充量压缩点火燃烧过程在过去十年中得到了广泛的研究，并在原型汽油发动机上被采用。尽管它们最初是在传统的二冲程进气道汽油发动机上实现的，但由于与具有进气道和排气道的传统二冲程发动机相关的固有问题，对二冲程发动机中的受控自燃燃烧进行的研究少得多。同时，发动机小型化已经被积极地研究和开发，作为通过使发动机在更高负荷和更有效的区域下运行以及通过减少气缸数量来提高车辆燃料经济性的有效手段。但是，目前四冲程汽油机的发动机小型化受到爆震燃烧和高峰气缸压力的限制。作为发动机小型化的替代途径，提出并研究了提升阀发动机增压二冲程循环。结果表明，在二冲程循环中的受控自燃燃烧可以容易地实现，并且它导致比火花点火燃烧显著减少一氧化碳和未燃碳氢化合物排放。在这项研究中，已进行了广泛的发动机实验，以确定最佳的增压最小的燃料消耗在单缸汽油直喷无凸轮发动机运行在二冲程循环。为了使空气短路率最小化，调整了进气门和排气门正时。将稀薄增压应用于发动机操作，发现其扩展受控自燃燃烧的范围，导致更高的燃烧和热效率以及显著降低的一氧化碳和碳氢化合物排放。通过循环分辨缸内测量和放热分析，燃烧和热效率的改善归因于改善的缸内混合气，优化的自燃和燃烧阶段。
Due to their ability to simultaneously reduce fuel consumption and NOx emissions, controlled autoignition or homogeneous charge compression ignition combustion processes have been extensively researched over the last decade and adopted on prototype gasoline engines. Despite the fact that they were initially achieved on conventional two-stroke ported gasoline engines, there have been much fewer studies carried out on controlled autoignition combustion in two-stroke engines because of the inherent problems associated with the conventional two-stroke engine with intake and exhaust ports. In the meantime, engine downsizing has been actively researched and developed as an effective means to improve the vehicle’s fuel economy by operating the engine at higher load and more efficient regions and by reducing the number of cylinders. But the aggressive engine downsizing of the current four-stroke gasoline engine is limited by the knocking combustion and high peak cylinder pressure. As an alternative approach to engine downsizing, the boosted two-stroke cycle in a poppet valve engine is proposed and researched. It has been shown that the controlled autoignition combustion in the two-stroke cycle could be readily achieved and it led to significant reduction in carbon monoxide and unburned hydrocarbon emissions than the spark ignition combustion. In this study, extensive engine experiments have been performed to determine the optimum boosting for minimum fuel consumption in a single-cylinder gasoline direct injection camless engine operating in the two-stroke cycle. In order to minimise the air short-circuiting rate, the intake and exhaust valve timings were adjusted. Lean boost was applied to the engine operation, which was found to extend the range of controlled autoignition combustion, result in higher combustion and thermal efficiencies and significantly lower carbon monoxide and hydrocarbon emissions. By means of the cycle-resolved in-cylinder measurements and heat release analysis, the improvement in combustion and thermal efficiencies was attributed to the improved in-cylinder mixture, optimised autoignition and combustion phases.