Masaaki Kubo

Internal flow analysis of nozzles for DI diesel engines using a cavitation model

Abstract A three-dimensional viscous flow analysis method using a cavitation model was applied to run internal flow calculations for the fuel injector nozzles of direct-injection diesel engines. It is especially notable that this method made it possible to examine and clarify the mechanism producing an asymmetrical spray from the valve covered orifice type nozzle under a small lift condition with an eccentric needle position. The calculated results for cavitation were compared with experimental data obtained by using a transparent model scaled up fivefold, and good qualitative agreement was seen between the two sets of data.

Improvement of prediction accuracy for torque converter performance: One-dimensional flow theory reflecting the stator blade geometry

Abstract Specific fuel consumption is a key word these days, and the torque converter can play an important role in improving it. This makes it essential to improve the accuracy of methods for predicting torque converter performance. In this work, the accuracy of performance predictions ws improved by replacing the flow angle and total pressure loss in the angular momentum theory with corresponding values obtained by analyzing the flow around the stator using a general flow analysis code. A quick and highly accurate prediction of torque converter performance is made possible with this method.

Three Way Catalyst Modeling for HEV After Treatment System Design

System simulation tools are effective in examining complex systems such as those of a hybrid electric vehicle (HEV). However, since most system issues originate in physical phenomena, it is necessary to reproduce the physical phenomena involved in order to resolve the issues. One problem that occurs especially in HEVs is that stopping and restarting the engine frequently can cause emission performance to deteriorate. To resolve this issue, the phenomena that occur in the catalyst must be reproduced accurately. Based on this reasoning, we have developed an exhaust system simulation tool that takes into account catalyst reactions and have experimentally used the tool in an effort to resolve the issue of HEV emission performance. This paper describes the newly developed simulation tool and the application results obtained.

Knocking Prediction by Using Zero-Dimensional Engine Cycle Simulation with Chemical Kinetic Model

A zero-dimensional engine cycle simulation has been developed by implementing chemical kinetics as the auto-ignition model into the two-zone combustion chamber model. A mixed chemical reaction mechanism of the primary reference fuels is used. Experimental data have been carefully investigated to obtain correlation between calculated auto-ignition of the end-gas and actual knock intensity. The result shows that a combination of time of auto-ignition occurrence and heat release by auto-ignition can explain knock intensity. This correlation has been applied to the simulation so that it can predict knock occurrence including knock intensity. A number of calculations have been done under various engine parameters including compression ratio, intake temperature, octane rating and equivalence ratio. The results show that fair levels of agreements are obtained between calculated trace knock spark advance sensitivity and experimental trends.

Validation of Predicted Characteristics of Swirl Nozzles Using a 3-dimensional CFD Technique.

A new technique was applied to the swirl nozzles of direct-injection gasoline engines with the aim of predicting their characteristics with higher accuracy. This new technique is based on 3-dimensional Computational Fluid Dynamics (CFD) using a volume of fluid (VOF) model. A new technique using particle image velocimetry (PIV) was also developed to measure the spray at the exit of the nozzle holes in order to obtain experimental data for validation. This technique made it possible to ascertain the cavity factor, which affects atomization characteristics. The calculated results showed relatively good agreement with the measured results. A conventional method, known as Tanasawas equation, was also compared with the measured results and shown to be accurate.

DEVELOPMENT OF A VIRTUAL ENGINE FOR COMBUSTION CONCEPT DESIGNS

A virtual engine has been developed that has the potential to contribute significantly to reducing the development lead time and development costs of automotive engines.