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Droplet vaporization models that are currently employed in simulating diesel engine sprays are based on a quasi-steady, low-pressure formulation. This formulation does not adequately represent many high-pressure effects, such as non-ideal gas behavior, solubility of gases into liquid, pressure dependence of liquid- and gas-phase thermophysical properties, and transient liquid transport in the droplet interior. More importantly, the quasi-steady assumption becomes increasingly questionable as the ambient pressure approaches and /or exceeds the fuel critical pressure. In the present study, a high-pressure, quasi-steady vaporization model is developed. Except for the quasi-steady assumption that is retained in the model, it incorporates all the other high-pressure effects.

For spark ignition engines, the fuel-air mixture preparation process is known to have a significant influence on engine performance, exhaust emissions and fuel economy. In this work, a one-dimensional, unsteady, multicomponent, multiphase flow model has been developed to study the mixture formation process in the intake manifold for a port-injected gasoline engine. The model consists of three major parts: a gas-phase model, a multicomponent droplet vaporization model and a liquid-film model. Three subsets of equations are solved by a hybrid Eulerian-Lagrangian, explicit-implicit scheme. The model not only quantitatively identifies the effects of each parameter on the final mixture but also shows the interactive influences of three phases of the mixture during the process. As a development and calibration tool, the model helps to understand the behavior of multiphase flow in the intake port, and can give guidelines toward achieving more efficient, clean and smooth engine operation.