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One promising solution for increasing vehicle fuel economy, while still maintaining long-range driving capability, is the plug-in hybrid electric vehicle (PHEV). A PHEV is a hybrid electric vehicle (HEV) whose rechargeable energy source can be recharged from an external power source, making it a combination of an electric vehicle and a traditional hybrid vehicle. A PHEV is capable of operating as an electric vehicle until the battery is almost depleted, at which point the on-board internal combustion engine turns on, and generates power to meet the vehicle demands. When the vehicle is not in use, the battery can be recharged from an external energy source, once again allowing electric driving. A series of models is presented which simulate various powertrain architectures of PHEVs. To objectively evaluate the effect of powertrain architecture on fuel economy, the models were run according to the latest test procedures and all fuel economy values were utility factor weighted.

Hybrid powertrain technology, which combines an internal combustion engine and an electric motor as power sources, is penetrating auto markets as a practical approach for reducing vehicle fuel consumption and exhaust emissions. This paper describes the development of an integrated powertrain simulation technology for predicting the fuel economy and exhaust emissions of hybrid electric vehicles with high accuracy and computation speed. Primary paths of kinetic, electric, chemical and thermal energies and their management were modeled. The predicted exhaust emissions and temperatures of the coolant and lubrication oil agreed well with experimental data in various vehicle driving conditions. This simulation was used to study an air-fuel ratio control strategy for reducing NOx at engine restart and to examine an exhaust heat recovery method for reducing fuel consumption and exhaust emissions under cold start conditions.

Three-dimensional combustion simulation tools together with the Universal Coherent Flamelet Model (UCFM), a flame propagation model, have been applied to SI lean-burn combustion to study the influence of the equivalence ratio on the amount of unburned hydrocarbons (HCs). Unburned HCs from piston-cylinder crevices were taken into the consideration by using a calculation grid incorporating the actual crevice volume and shape and by applying an autoignition model to post-flame phenomena. The calculation results show the general tendencies for the total amount of unburned HCs and their distribution in the combustion chamber.

Combustion in engines involves very complicated phenomena (including flame propagation and knocking), which are strongly affected by engine speed, load and turbulence intensity in the combustion chamber. The aim of this study was to develop a flame propagation model and a knocking prediction technique applicable to various engine operating conditions, including engine speed and in-cylinder turbulence intensity. A flame propagation model (UCFM) has been developed that improved the Coherent Flamelet Model by considering flame growth both in terms of the turbulent flame kernel and laminar flame kernel. A knocking prediction model was developed by implementing the Livengood-Wu integral as the autoignition model. The combined model allows evaluation of both where and when autoignition occurs in a real shape combustion chamber. A comparison of the measured and calculated time for the occurrence of knocking shows good agreement for various operating conditions.

A transient knock prediction technique has been developed by coupling a zero-dimensional knocking simulation with chemical kinetics and a one-dimensional gas exchange engine model to study the occurrence of transient knock in SI engines. A mixed chemical reaction mechanism of the primary reference fuels was implemented in the two-zone combustion chamber model as the auto-ignition model of the end-gas. An empirical correlation between end-gas auto-ignition and knock intensity obtained through intensive analysis of experimental data has been applied to the knocking simulation with the aim of obtaining better prediction accuracy. The results of calculations made under various engine operating parameters show good agreement with experimental data for trace knock sensitivity to spark advance.

A new auto-ignition combustion model for performing multi-zone engine cycle simulations has been developed to investigate the characteristics of compression ignition combustion in gasoline engines. In this combustion model, the auto-ignition timing is predicted with a modified shell model and combustion speed is calculated with a three-region (burned, ignited and unburned) model. Engine cycle simulations performed with this model were used to analyze the effect of engine operating parameters, i.e., temperature and air-fuel distributions in the cylinder, on combustion characteristics. It was found that the air-fuel distribution in the cylinder has a large impact on combustion characteristics and knocking was prevented by creating a fuel-rich zone at the center of the cylinder under high load conditions. The fuel-rich zone works as an ignition source to ignite the surrounding fuel-lean zone. In this way, two-step combustion is accomplished through two separate auto-ignitions.

This paper describes the numerical and experimental approaches that were applied to study swirl injectors that are widely used in direct-injection gasoline engines. As the numerical approach, the fuel and air flow inside an injector was first analyzed by using a two-phase flow analysis method [VOF (Volume of Fluid) model]. A time-series analysis was made of the flow though the injector and also of the air cavity that forms at the nozzle and influences fuel atomization. The calculated results made clear the process from initial spray formation to liquid film formation. Spray droplet formation was then analyzed with the synthesized spheroid particle (SSP) method. As the experimental approach, in order to measure the cavity factor that represents the liquid film thickness, nozzle exit flow velocities were measured by particle image velocimetry (PIV).

This paper describes the relationship between the design parameters used to define the geometry of an automotive torque converter and the resultant efficiency in relation to the internal flow characteristics. Taking the turbine bias angle and the contraction ratio of the pump flow passage as specific examples, the effects of each design parameter on the internal flow characteristics and the occurrence of loss were analyzed. A three-dimensional viscous flow analysis code was used in the numerical computation procedure and a method developed independently by the authors was used in the loss analysis. The flow near the wall was visualized experimentally using a technique resembling the so-called oil film method. The visualized results showed good qualitative agreement with the numerical analysis results.