Liquid and vapor fuel distributions in a small-bore high-speed direct-injection diesel engine

An optically-accessible single cylinder small-bore HSDI diesel engine equipped with a Bosch common-rail injection system is used to study the effects of multiple injection. High-speed video is used to study the injector and spray behavior. Laser-induced exciplex fluorescence is used to obtain simultaneous liquid and vapor fuel distributions within the combustion chamber, with tetradecane-TMPD-naphthalene as the base fuel-dopant combination. Significant liquid impingement is seen in the single main injection case, while evidence of liquid impingement is seen only in the first stage of the multiple injection case. No appreciable liquid impingement is seen for the second stage of the multiple injection case. Vapor is seen throughout the jet cross-section regardless of the injection parameters. The majority of the vapor is confined to the bowl region in the single injection case while evidence of vapor is seen outside of the bowl for the multiple injection case.