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In this study, the effects of fuel injection on in-cylinder flow under various injection conditions were investigated using particle image velocimetry measurements in a two-cylinder, direct-injection spark-ignition, optically accessible engine with a spray-guided injection system. Various injection timings and pressures were applied to intensify the turbulence of in-cylinder flow. Simple double-injection strategies were used to determine how multiple injections affect in-cylinder flow. The average flow speed, turbulent kinetic energy, and enhancement level were calculated to quantitatively analyze the effects of fuel injection. Fuel injection can supply additional momentum to a cylinder. However, at an early injection timing such as 300° before top dead center, in-cylinder flow development could be disturbed by fuel injection due to piston impingement and interactions between the spray and air.

An important challenge for modeling Direct-Injection Spark-Ignition (DISI) gasoline engines is understanding flash boiling spray. Flash boiling occurs when the ambient pressure is lower than the vapor pressure of the fuel and affects the spray structure and mixture formation process inside an engine. Gasoline is a multi-component fuel and the effects of each component on flash boiling are difficult to estimate. As a preliminary study to investigate the mixture formation process of the flash boiling spray, a single-component fuel was used to validate the flash breakup model. The flash breakup model was applied to KIVA 3V release2. Bubble growth in the drop was modelled by the Rayleigh-Plesset equation. When bubbles grow to satisfy the breakup criterion, breakup occurs and induces a smaller SMD for flash breakup cases. To investigate flash breakup modeling, simulations without the flash breakup model and with the flash breakup model was compared.

This paper describes the effects of diverse driving modes and vehicle component characteristics impact on fuel efficiency and emissions of light commercial vehicles. The AVL's vehicle and powertrain system level simulation tool (CRUISE) was adopted in this study. The main input data such as the fuel consumption & emission map were based on the experimental value and vehicle components characteristic data (full load characteristic curves, gear shifting position curves, torque conversion curve etc.) and basic specifications (gross weight, gear ratio, tire radius etc.) were used based on the database or suggested value. The test database for two diesel vehicles adopted whether prediction accuracy of simulation data were converged in acceptable range. These data had been acquired from the portable emission measurement system, the exhaust emission and operating conditions (engine speed, vehicle speed, pedal position etc.) were acquired at each time step.

This paper describes the effects of two stage combustion strategy on the engine performance and the exhaust emission characteristics in a compression ignition engine. The two-stage combustion strategy targets reduction of NOx emissions by decreasing oxygen concentration for second stage combustion. Thus, the first injection was provided in order to consume in-cylinder oxygen, rather than generate power. A multi-dimensional CFD code was utilized to predict engine performance and emission characteristics. For the accurate and efficient computational calculation of ignition and combustion characteristics of diesel fuel, the reduced n-heptane mechanism was used in this study. The calculation for two-stage combustion was performed after validating against the experimental result. The KH-RT breakup model and gas-jet model was applied for the prediction of spray behavior and characteristics. To calculate the ignition and combustion process, CHEMKIN II [1] code was used.

Sources of unburned hydrocarbon (UHC) emissions are examined for a highly dilute (10% oxygen concentration), moderately boosted (1.5 bar), low load (3.0 bar IMEP) operating condition in a single-cylinder, light-duty, optically accessible diesel engine undergoing partially-premixed low-temperature combustion (LTC). The evolution of the in-cylinder spatial distribution of UHC is observed throughout the combustion event through measurement of liquid fuel distributions via elastic light scattering, vapor and liquid fuel distributions via laser-induced fluorescence, and velocity fields via particle image velocimetry (PIV). The measurements are complemented by and contrasted with the predictions of multi-dimensional simulations employing a realistic, though reduced, chemical mechanism to describe the combustion process.