The objective of this study was to investigate the influence of a water vapor injection into the intake port of a small compression ignition engine and analyze the effect of the collisions between the water particles and the injected fuel on combustion and exhaust emission performances. To simulate the water vapor by the ultrasonic humidifier in the numerical analysis, the water particles were introduced into the cylinder through an intake port during the intake process, and the amount was varied from 10% to 30% of the injected fuel mass per stroke. When the water vapor was injected into the intake port, the rich equivalence ratio region was distributed in the center of cylinder. In addition, the ISNO (indicated specific nitrogen oxide) values decreased up to 46% more than the values for the condition without the water-vapor-injection. However, the ISSoot (indicated specific soot) exhibited similar values in any conditions. For starts of energizing timing that were BTDC (before top dead center) 25 deg and 15 deg, the ISFC (indicated fuel consumption) values decreased with increased portions of water vapor. However, in the case of BTDC 05deg, the ignition delay was too long, which deteriorated combustion performance.
The objective of this study is to investigate the effect of multi-hole nozzle on the performance of small CRDI engine. Combustion and exhaust emission characteristics of engine were studied by using CFD simulation with ECFM-3Z combustion model. The conditions of simulation were varied with nozzle geometry, injection timing and injection quantity. In addition, the results were compared in terms of combustion pressure, rate of heat release, NOx and soot emissions. It was found that combustion pressure was increased when injection timing was advanced. The rate of heat release of 6 hole nozzle was higher than that of 12 hole nozzle since the quantity of fuel impinged at the bottom of piston rim was different under different injection timing conditions. In the case of NOx emission, 6 hole nozzle generated more NOx emission than 12 hole nozzle. On the other hand, in the case of soot emission, 12 hole nozzle showed higher value than 6 hole nozzle because injected fuel droplets from multi-hole nozzle were coalesced.
The objective of this study is to investigate the effect of the premixed ethanol ratio based on the same total heating value in-cylinder on the equivalence ratio distributions and the injected fuel droplet behavior in the cylinder of the RCCI engine. The spray simulation was conducted by dividing two-part. First, the spray validation simulations progressed to find the spray-influenced factor of the test injector. Next, the engine simulations were performed with the spray-influenced factor obtained from spray validation simulations to investigate the effect of the premixed ethanol ratio based on the same total heating value in-cylinder on the injected fuel atomization and the equivalence ratio distributions. The introduced total heating value was fixed at 595J based on the lower heating value of diesel 14mg. The heating value of the premixed ethanol ratio varied from 0% to 40% based on the same total heating value in-cylinder in steps of 10%. It was revealed that when the premixed ethanol ratio based on the same total heating value in-cylinder was increased, the spray tip penetration value was reduced from the time after 4deg of diesel injection start because of the short injection duration by the small amount of diesel fuel. The SMD value was also more enormous up to 32.58% with increasing the premixed ethanol ratio because of the low kinetic energy of the injected fuel by the short injection duration and the slow evaporation of the injected fuel by the low cylinder temperature.
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