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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.

A direct-injection natural gas (DING) engine was modified for optical access to allow the use of laser diagnostic techniques to measure species concentrations and temperatures within the cylinder. The injection and mixing processes were examined using planar laser-induced fluorescence (PLIF) of acetone-seeded natural gas to obtain qualitative maps of the fuel/air ratio. Initial acetone PLIF images were acquired in a quiescent combustion chamber with the piston locked in a position corresponding to 90° BTDC. A series of single shot images acquired in 0.1 ms intervals was used to measure the progression of one of the fuel jets across the cylinder. Cylinder pressures as high as 2 MPa were used to match the in-cylinder density during injection in a firing engine. Subsequent images were acquired in a motoring engine at 600 rpm with injections starting at 30, 20, and 15° BTDC in 0.5 crank angle degree increments.

This paper describes work from an investigation using a Phase/Doppler Particle Analyzer to characterize a throttle body injection system. Spray data are presented from two injectors, a ball type and a pintle type. Tests were performed on externally mounted injectors spraying continuously and under pulsed injection conditions. Further experiments were performed with these injectors mounted in the throttle body to obtain spray data at the throttle body exit under simulated engine operating conditions. Steady injection data from externally mounted injectors show that the pintle injector has better symmetry and spray atomization quality (including a 50 per cent reduction in peak mean drop size) than the ball nozzle. External pulsed tests indicate a severe degradation in spray atomization quality under the idle condition, while increasing the time the injector is open during an injection cycle provides a spray whose time averaged behavior approaches steady injection characteristics.