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This study measures transient torque, smoke opacity and pumping-losses derived from in-cylinder pressure, as a function of Variable Geometry Turbocharger (VGT) vane position (derived through Engine Control Unit, ECU). Tests were conducted using a typical passenger car/light duty truck application turbo-charged common-rail diesel engine, of 14 configuration. The aim was to seek potential improvements in engine pumping-losses (and thus fuel economy) during full-load transients and at low engine speeds, due to opening of VGT vanes. The objective was to record engine performance (e.g. engine transient-torque, smoke opacity, fuel-demand, engine pressure-ratio etc.), under full-load operation, and at engine speeds of 900-1600 rpm. The effects of “slow” and “fast” transient manoeuvres were established (in a transient test facility) by performing four different acceleration rates (i.e. 2s, 5s, 10s and 20s).

This study measures, during various transients of speed and load, in-cylinder-, intake-/exhaust- (manifold) pressures and engine torque. The tests were conducted on a typical high power-density, passenger car powertrain (common-rail diesel engine, of in-line 4-cylinder configuration equipped with a Variable Geometry Turbocharger). The objective was to quantify the deterioration (relative to a steady-steady condition) in transient Specific Fuel Consumption (SFC) that may occur during lagged-boost closed-loop control and thus propose an engine control strategy that minimises the transient SFC deterioration. The results, from transient characterisation and the analysis method applied in this study, indicate that transient SFC can deteriorate up to 30% (function of load transient) and is primarily caused by excessive engine pumping-loss.

Measurements are presented of droplet characteristics and air velocity in the cylinder of a 0.36 litre four valve engine, equipped with an sohc VTEC-E valve train and port injection. The results show that injection at crank angles, θinj(s), when the inlet valve is open results in most of the liquid volume flux being in the form of droplets with Sauter mean diameter between 20 and 30 mm which strikes the sleeve up to about 2.5 cm below the exhaust valves, thus generating a locally rich cloud there. The amount of liquid phase gasoline passing through the plane 16 mm below the spark plug gap increases with θinj(s) up to 50 CA after intake TDC and this, together with the crank angle of droplet arrival and vapour generation, controls stratification of the gaseous fuel phase. The optimum injection time is when the fuel-rich cloud is generated so that the tumble vortex convects it to the spark plug at the time of ignition.