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This work addresses the problem of fatigue strength prediction of crankshaft fillet rolling processes to improve its accuracy. It is empirical to usually consider the effect of fillet rolling process on crankshaft fatigue performance. The fatigue performance of rolling process is mainly determined by induced compressive residual stresses, increased hardness and reduced roughness. Because the first two factors are difficult to measure the arc surface of fillet rolled cranks, it is difficult to predict the enhanced rate of crankshaft rolled performance to baseline unrolled’s. In this work a prediction method of fatigue strength for ductile cast iron crankshafts rolling process is presented. This method indirectly predicts the effect of the increased hardness on fatigue performance by the resonant bending fatigue test and modelling of crankshaft fillet rolling dynamic for the induced compressive residual stress.

This paper describes a simulation guided design methodology for developing direct injection combustion systems of gasoline engines. The first step is the optimization of engine gas flow. The intake port is optimized by CFD simulations to compromise the engine breathing capacity and its tumble flow. Secondly, the piston crown shapes and the injection system designs (injection pressure, hole number, hole size and orientations) are optimized based on dedicated CFD simulation results. Thirdly, different injection strategies are used at different engine operating conditions to achieve best engine performance, such as split injections being used at cold starting and catalyst heating period to realize stratified charge combustion for fast catalyst light-off, and a single injection being used to achieve homogeneous mixture combustion at almost all other operating conditions.

Engine exhaust systems need to undergo continuous modifications to meet increasingly stricter regulations. In the past, much of the design and engineering process to optimize various components of engine and emission systems has involved prototype testing. The complexity of modern systems and the resulting flow dynamics, and thermal and chemical mechanisms have increased the difficulty in assessing and optimizing system operation. Due to overall complexity and increased costs associated with these factors, modeling continues to be pursued as a method of obtaining valuable information supporting the design and development process associated with the exhaust emission system optimization. Insufficient kinetic mechanisms and the lack of adequate kinetics data are major sources of inaccuracies in catalytic converters modeling.

Automotive exhaust emission regulations are becoming progressively stricter due to increasing awareness of the hazardous effects of exhaust emissions. The main challenge to meet the regulations is to reduce the emissions during cold starts, because catalytic converters are ineffective until they reach a light-off temperature. It has been found that 50% to 80% of the regulated hydrocarbon and carbon monoxide emissions are emitted from the automotive tailpipe during the cold starts. Therefore, understanding the catalytic converter characteristics during the cold starts is important for the improvement of the cold start performances This paper describes a mathematical model that simulates transient performances of catalytic converters. The model considers the effect of heat transfer and catalyst chemical reactions as exhaust gases flow through the catalyst. The heat transfer model includes the heat loss by conduction and convection.

This paper investigates the effects of the variations of turbulence characteristics and initial flame kernel center position on the cyclic combustion variations by means of quasi-dimensional turbulent entrainment combustion model. The turbulence intensity and turbulence integral length scale at spark ignition time in the model are determined by maximizing the agreement between the predicted and measured results such as pressure diagrams, mass fraction burned etc. With different values of the turbulence intensity and turbulence integral length scale at spark ignition time, the calculation of the cyclic combustion variations for the engine is carried out. In addition, the prediction of the effect of different flame kernel center positions on the cyclic combustion variations is also studied. Finally, some conclusions are drawn out about the importance of turbulence and initial flame kernel center position on the cyclic combustion variations for spark-ignition engine.

This paper describes the use of a modified quasi-dimensional spark-ignition engine simulation code to predict the extent of cycle-to-cycle variations in combustion. The modifications primarily relate to the combustion model and include the following: 1. A flame kernel model was developed and implemented to avoid choosing the initial flame size and temperature arbitrarily. 2. Instead of the usual assumption of the flame being spherical, ellipsoidal flame shapes are permitted in the model when the gas velocity in the vicinity of the spark plug during kernel development is high. Changes in flame shape influence the flame front area and the interaction of the enflamed volume with the combustion chamber walls. 3. The flame center shifts due to convection by the gas flow in the cylinder. This influences the flame front area through the interaction between the enflamed volume and the combustion chamber walls. 4. Turbulence intensity is not uniform in cylinder, and varies cycle-to-cycle.

This paper uses a model which calculates the flame kernel formation and its early development in spark ignition engines to examine the causes of cycle-to-cycle combustion variations. The model takes into account the primary physical factors influencing flame development. The spark-generated flame kernel size and temperature required to initialize the computation are completely determined by the breakdown energy and the heat conduction from burned region to unburned region. In order to verify the model, the computation results are compared with high-speed Schlieren photography flame development data from an operating spark-ignition engine; they match remarkably well with each other at all test conditions. For the application of this model to the study of cycle-to-cycle variation of the early stage of combustion, additional input is required.

This paper studied the flame initiation and early development in a spark ignition engine by using the Schlieren technique and a high speed camera. Some effects of different engine operating conditions and different spark energy are discussed. It was discovered that at any engine operating condition there exists a minimum flame propagation velocity during the early stage, and that its value as well as the corresponding time and flame radius can be used as a criterion to determine whether the early flame propagation is easy or not. To study the effects of different spark energy a special spark ignition system was designed which was controlled by a microcomputer for producing different spark energy levels. Both experimental and theoretical results show that the augmentation of breakdown energy in spark duration makes the original flame size increase effectively, which results in speeding up the flame kernel formation and early development.