抄録
This study clarified the influence of high temperature gas jet on combustion enhancement effect for lean mixture in the plasma jet ignition by the use of combustion bomb. The hot gas jet was generated by the plasma and was ejected after the plasma jet finished injecting. The combustion chamber had a cylindrical shape with 80 mm of diameter and 40 mm of thickness and its volume was about 201 cm3, and the igniter was attached to the bottom of combustion chamber. The igniter was composed by central electrode, orifice and cavity. Tests were carried out with propane-air mixture at equivalence ratio of 0.6 and cavity depth, orifice diameter and discharge energy were varied. The hot gas jet was visualized by schlieren method in the absence of combustion, and combustion development processes were also visualized and the combustion pressure was measured. The voltage throughout electrical discharge and the plasma luminescence was also measured. The electrical discharge began early and the intense luminescence was emitted from plasma jet as the supplied energy increased. The electrical discharge and light emission durations were not so influenced by igniter configuration. The initial flame kernel and hot gas jet were similarly developed. For small diameter orifice and large volume cavity, flame propagation was enhanced and combustion duration was shortened, because the hot gas jet velocity increased. Because the discharging duration was very short as compared with combustion period, the hot gas jet was more effective against the combustion enhancement than the plasma generated by electrical discharge.
