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Temperature variation and heat transfer phenomena in the intake port of a spark ignition engine with port injection play a significant role in the mixture preparation process, especially during the warm up period. Cold temperatures in the intake port result in a large amount of liquid-fuel film. Since the liquid-fuel film responds at a slower speed than the gas-phase flow during transient operations, the liquid-fuel film acts as a fuel sink (or source) and can degrade the vehicle's driveability, fuel economy, and emissions control. In this work, a one-dimensional, unsteady, multicomponent, multiphase flow model has been developed to study the mixture formation process in the intake port for a modern, multipoint-fuel-injection, gasoline engine. The droplet, liquid film and gas-phase mixture temperature variations and the effects of charge air, initial fuel and port wall temperatures involved in generating the air-fuel mixture are examined.

Most of the current fuel supply specifications, including the key parameters in the transient fuel control strategies, are experimentally determined since the complexity of multiphase fuel flow behavior inside the intake manifold is still not quantitatively understood. Optimizing these specifications, especially the parameters in transient fueling systems, is a key issue in improving fuel efficiency and reducing exhaust emissions. In this paper, a model of fuel spray, wall-film flow and wall-film vaporization has been developed to gain a better understanding of the multiphase fuel-flow behavior within the intake manifold which may help to determine the fuel supply specifications in a multi-point injection system.

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.