Measurement of short-circuiting and its effect on the controlled autoignition or homogeneous charge compression ignition combustion in a two-stroke poppet valve engine
Measurement of short-circuiting and its effect on the controlled autoignition or homogeneous charge compression ignition combustion in a two-stroke poppet valve engine
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DOI：
10.1177/0954407011434252
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发表时间：
2012-02
期刊：
影响因子：
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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
四冲程火花点火发动机中的受控自动点火或均质充量压缩点火燃烧在过去十年中一直是广泛研究的主题。为了扩大汽车应用中可控自燃燃烧的负荷范围，在一台通过灵活可变气门驱动实现四冲程和二冲程工作的单缸提升阀发动机上对这些燃烧过程进行了系统的研究。由于短路是二冲程发动机运行的常见问题，因此有必要量化短路量。本文提出了一种测量二冲程发动机工作过程中短路率的新方法，并将其应用于研究短路对二冲程可控自燃或均质充量压燃工作过程的影响。循环分解的空气短路率是从使用Cameroon快速响应非色散红外分析仪对排气阀附近的二氧化碳浓度的瞬时测量得出的。研究发现，在λ = 1的闭环控制下，短路空气导致富油燃烧，从而导致高的一氧化碳和碳氢化合物排放。提出了一种基于实测短路率计算缸内空燃比的方法，用于更好地了解直喷四气门发动机二冲程工作时缸内燃烧和污染物生成过程。
Controlled autoignition or homogeneous charge compression ignition combustion in four-stroke spark ignition engines has been the subject of extensive research over the last decade. In order to extend the load range of controlled autoignition combustion for automotive applications, systematic research has been carried out on these combustion processes in a single-cylinder poppet valve engine that is capable of both four-stroke operation and two-stroke operation through flexible variable valve actuation. Since short-circuiting is a common issue for two-stroke engine operation, it is necessary to quantify the amount of short-circuiting. In this paper, a new method of measuring the short-circuiting rate during two-stroke engine operation is presented and applied to investigate the effect of short-circuiting on two-stroke controlled autoignition or homogeneous charge compression ignition operation. The cycle-resolved air short-circuiting rate is derived from instantaneous measurement of the carbon dioxide concentration near an exhaust valve using a Cambustion fast-response non-dispersive infrared analyser. It is found that the short-circuited air leads to fuel-rich combustion and hence high carbon monoxide and hydrocarbon emissions under closed-loop λ = 1 control. A method to calculate the in-cylinder air-to-fuel ratio based on the measured short-circuiting rate is presented and used to understand better the in-cylinder combustion and pollutant formation process during two-stroke operation of a direct-injection four-valve engine.