掃気ポートからの間欠燃料噴射を用いた天然ガス2ストロークサイクル火花点火機関の性能

摘要

2ストロークサイクル機関は，ストローク数が少なrnいため比出力が大きく，また動弁機構を持たないためrn構造が単純で軽量であるという本質的な長所を有する．rnしかしながら，吸排気を同時に行う掃気行程において，rn燃料がシリンダからそのまま排気される「吹き抜け」rnを生じるため，熱効率および排気特性の悪化が問題とrnなっている．%Performance of a 2 stroke cycle engine fuelled with CNG (Compressed natural gas) using intermittent fuel injection from a scavenging port is investigated experimentally. The test engine is a 2 cylinder, 398 cm3, 2 stroke cycle spark ignition engine. Gaseous fuel injectors are attached at the cylinder block, and a CNG is injected into the scavenging passage through a fuel injection pipe. The fuel injection pressure is set at 0.255 MPa, and the fuel is injected intermittently during the scavenging process. The length and tip geometry of the fuel injection pipe are varied, and the effect on the engine performance is investigated. Using the scavenging port fuel injection, the BSFC is reduced by 25%, and the lean burn limit extends from λ=1.2 to 1.46, at the maximum. The peak of the NO_x emission shifts to leaner side, and the THC emission is reduced by 47% at the maximum. It is considered that the intermittent fuel injection from a scavenging port is effective to achieve stratified combustion and reduction in fuel short circuiting through the cylinder.