The ignition sparks provided by the conventional spark plug (CSP) do not always ensure a fast and complete combustion of the hydrocarbon–air mixture. For this reason, we offer a new type of spark plug with two simultaneous discharges generated by a pulsed high voltage–power supply. First, we present results concerning geometrical and electrical characteristics of plasmas produced in air and in engine combustion chamber. A more important volume of plasma is highlighted. The larger surface of interaction of plasma with the air-to-fuel mixture promotes the initiation of a greater number of chemical reactions thus increases the rate of propagation of the combustion. In addition, for long pulse durations the energy delivered by the double spark plug (DSP) to the discharge is 20% higher, as compared to a CSP. The current rise rate is more important for the DSP, which allows better ionization of the mixture. Afterwards, we present a study of two four-strokes engines ignited by this DSP, one powered with gasoline and the second one with propane. The pressure into the cylinder, measured as a function of the crankshaft angle, allowed to compute the IMEP , COV IMEP , and PPP , for both tested engines. In the case of the gasoline engine, when the ignition and flame development conditions are difficult—a high ignition angle was considered—the DSP can offer an almost 3.5 times better operation stability (considering the coefficient of variation of the indicated mean effective pressure as main indicator) and a faster development of the combustion flame (defined by the means of the pressure peak position). A study was also performed as a function of the equivalence ratio for the propane-powered engine, which confirmed the results regarding the DSP performances obtained with the first engine. In addition, this study highlighted that for very lean mixtures, the DSP can provide a better stability in operation ( COV IMEP , COV PPP ) is assured even for equivalence ratios in the range of 0.65, where the use of CSPs involves misfires and very high engine vibrations.

中文翻译：

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评估双火花塞提高内燃机性能的效率：压力测量和等离子体研究

传统火花塞 (CSP) 提供的点火火花并不总能确保碳氢化合物 - 空气混合物的快速和完全燃烧。出于这个原因，我们提供了一种新型火花塞，它具有由脉冲高压电源产生的两次同时放电。首先，我们展示了关于空气和发动机燃烧室中产生的等离子体的几何和电学特性的结果。突出显示了更重要的血浆体积。等离子体与空气-燃料混合物相互作用的较大表面促进了更多化学反应的开始，从而增加了燃烧的传播速率。此外，对于长脉冲持续时间，双火花塞 (DSP) 提供给放电的能量比 CSP 高 20%。电流上升速率对于 DSP 更为重要，它可以更好地电离混合物。之后，我们对由该 DSP 点燃的两个四冲程发动机进行了研究，一个用汽油驱动，另一个用丙烷驱动。进入气缸的压力作为曲轴角度的函数测量，允许计算两个测试发动机的 IMEP 、COV IMEP 和 PPP 。在汽油发动机的情况下，当点火和火焰发展条件困难时——考虑高点火角——DSP 可以提供几乎 3.5 倍的运行稳定性（考虑到指示平均有效压力的变异系数作为主要因素）指示器）和燃烧火焰的更快发展（由压力峰值位置定义）。还根据丙烷动力发动机的当量比进行了一项研究，这证实了第一台发动机获得的 DSP 性能的结果。此外，这项研究强调，对于非常稀薄的混合物，即使当量比在 0.65 范围内时，DSP 也可以提供更好的运行稳定性（COV IMEP、COV PPP），其中 CSP 的使用涉及失火和非常高的发动机振动。