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Electromagnetic valve (EMV) actuation system is a new technology for the improvement of fuel efficiency and the reduction of emissions in SI engines. It can provide more flexibility in valve event control compared to conventional variable valve actuation devices. However, a more powerful and efficient actuator design is needed for this technology to be applied in mass production engines. This paper presents the effects of design and operating parameters on the thermal, static and dynamic performances of the actuator. The finite element method (FEM) and computer simulation models are used in predicting the solenoid forces, dynamic characteristics and thermal characteristics of the actuator. Effect of design parameters and operating environment on the actuator performance were verified before making prototypes using the analytical models. To verify the accuracy of the simulation model, experimental study is also carried out on a prototype actuator.

The residual gas in SI engines is one of important factors on emission and performance such as combustion stability. With high residual gas fractions, flame speed and maximum combustion temperature are decreased and there are deeply related with combustion stability, especially at Idle and NOx emission at relatively high engine load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating parameters. A model for predicting the residual gas fraction has been formulated in this paper. The model accounts for the contribution due to the back flow of exhaust gas to the cylinder during valve overlap and it includes in-cylinder pressure prediction model during valve overlap. The model is derived from the one dimension flow process during overlap period and a simple ideal cycle model.

Mixture preparation is a key contributor to both the combustion and emissions in automotive gasoline engines. The air-fuel ratio near the spark plug may have an effect on combustion characteristics since it is related to early flame development. Therefore, cycle resolved measurements of equivalence ratio near the spark plug is particularly important for better understanding of its contribution on combustion and emissions. This paper describes how we determined the in-cylinder equivalence ratio from the measured hydrocarbon concentration near the spark plug using a Fast Response Flame Ionization Detector (FRFID). The procedures established were then applied to a limited range of engine operating conditions, and the cycle resolved equivalence ratio near the spark plug was determined from the measured hydrocarbon concentration.

The control of ignition timing in the homogenous charge compression ignition (HCCI) of n-heptane by port injection of reaction inhibitors were studied in a single cylinder engine. Four suppression additive including methanol, ethanol, iso-propanol, and methyl tert-butyl ether (MTBE) were used in the experiments. The inhibition effectiveness on HCCI combustion with various additives was compared under the same n-heptane equivalence ratio and total fuel equivalence ratio. The experimental results found that the suppression effectiveness increased in the order: MTBE

The air fuel ratio of current gasoline engine is mostly controlled by various air flow meters. When CVVT (Continuous Variable Valve Timing) device is applied to gasoline engine for higher engine performance, MAP (Manifold Absolute Pressure) sensor can not be applied anymore due to intake valve motion. Therefore HFM (Hot film airflow meter) is used for measuring the intake air flow instead of MAP sensor. Usually HFM has a little sensitivity in flow direction, therefore reverse flow from engine to air cleaner can not be measured. Also, HFM maker request enough straight duct length nearly 10 times of a duct diameter making a fully developed flow. But, most vehicles have no enough space to install such an intake system in engine room. Thus the inserted duct was applied to confirm the stable fully developed flow in air duct. The various duct configurations in front of HFM effect on the sensitivity of HFM.