Ignition behaviors of close dual-point laser breakdown spark ignition were investigated experimentally for methane/air mixtures at 0.1 and 1.0 MPa in a constant volume combustion vessel. Absorbed energy was measured from the difference between incident and transmitted laser rays using two joule meters as the ignition energy, and the behaviors of the initial flame kernel were observed with Schlieren photography using a high-speed video camera. First, the ignition behaviors of a single-point laser breakdown spark ignition were investigated. The results indicated that the effect of the focusing lens on the minimum ignition energy (MIE) was limited in terms of the absorbed energy. Although the MIE at 1.0 MPa was lower than that at 0.1 MPa near the stoichiometric equivalence relationship was reversed near the lean limit. For lean mixtures, local quenching of the initial flame kernel was clearly observed including third lobe region especially at 1.0 MPa. In the case of the close dual-point sparks for an equivalence ratio of 0.6, formation of a third lobe was suppressed. When the dual spark gap was large, two flame kernels were formed as observed in the case of the single spark. An optimal gap in which the absorbed energy was minimal for successful ignition existed depending on the pressure, although the magnitude of the associated energy was not so different from that in the case of the single spark. However, the growth rate of the initial flame kernel formed by the close dual sparks was considerably higher than that formed by the single spark, especially at 1.0 MPa. Enhancement of the flame kernel development due to the close dual spark was clearly observed.

在恒定体积的燃烧容器中，对甲烷/空气混合物在0.1和1.0 MPa下的密闭双点激光击穿火花点火点火行为进行了实验研究。使用两个焦耳计作为点火能量，从入射和透射激光之间的差异测量吸收的能量，并使用高速摄像机通过Schlieren摄影观察初始火焰核的行为。首先，研究了单点激光击穿火花点火的点火行为。结果表明，在吸收能量方面，聚焦透镜对最小点火能量（MIE）的作用受到限制。尽管在1.0 MPa时的MIE低于在0.1 MPa时的MIE，但在稀薄极限附近，化学计量当量关系逆转。对于稀薄混合物，清楚地观察到初始火焰核的局部淬火，包括第三波瓣区域，尤其是在1.0 MPa时。在当量比为0.6的闭合双点火花的情况下，抑制了第三凸角的形成。当双火花间隙较大时，如在单火花情况下观察到的那样，形成了两个火焰核。尽管压力的大小与单火花的情况相差不大，但存在一个最佳间隙，在该间隙中，成功点火所吸收的能量最小。然而，由紧密双火花形成的初始火焰核的生长速率明显高于由单火花形成的生长核的生长速率，特别是在1.0 MPa时。清楚地观察到由于紧密的双重火花而引起的火焰核发展的增强。