噴射ノズル仕様および燃焼室形状がディーゼル機関におけるアフター噴射の黒煙低減効果に与える影響

Abstract

This study aims at improving understanding of the relation between smoke-reduction effect of post injection and design and operating conditions in small diesel engines. A series of experiments was conducted using a single-cylinder diesel engine under a fixed NOx emission condition to investigate the smoke reduction effect of post injection varying the number of injection nozzle orifice and piston bowl diameter, which would influence the interaction between main spray flames and post sprays. The results indicate that the larger number of nozzle orifice with smaller diameter reduces smoke emissions under late post injection conditions. Advanced post injection reduces smoke emissions for the smaller piston bowl diameter; while retarded post injection reduces smoke emissions for the larger piston bowl diameter. Explanations for these trends were attempted paying attention to the influence of the main spray flames on post sprays.

単気筒ディーゼル機関においてアフター噴射を採用し，メイン噴霧火炎とアフター噴霧の干渉の強さに関連の深い噴射ノズル仕様(噴孔径×数)，噴射圧力，燃焼室形状を変更した実験を行った．その結果にもとづき，アフター噴射の効果と設計条件との関係について考察を行った．