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The motivation of this paper is to describe the effects of variable valve timing (VVT) events on diesel engine performances. The paper describes an investigation into the effects of inlet and exhaust valve gas dynamics. In particular, effects on the pressure-volume cycle, and reverse flow through the intake and exhaust valves are studied. Computer simulation results show that VVT is much more useful for gasoline engines as compared with diesel engines for reducing the pumping losses. But, for diesel engines, VVT could be useful for the reduction of exhaust emissions such as NOx by using internal exhaust gas recirculation. The role of VVT in gasoline and diesel engines are described and compared.

In internal combustion engines, particularly for spark ignition (SI) engines, valve events and their timings put forth a major influence on the engine overall efficiency and its exhaust emissions. Because the conventional SI engine has fixed timing and synchronization between the camshaft and crankshaft, a compromise results among engine efficiency, performance, and its maximum power. By using variable valve timing (VVT) technology it is possible to control the valve lift, phase, and valve timing at any point on the engine map, with the result of enhancing the engine overall performance. To get full benefits from VVT, various types of mechanisms have been proposed and designed. Some of these mechanisms are in production and they have shown significant benefits for improving the engine performance. During the last two decades, remarkable developments have been seen in the field of VVT.

The cost of fuel control systems for small gas turbine engines is quite high and could be significantly reduced by simplifying the fuel metering system and bringing it under electronic control. Such an attempt has been made regarding the popular Bendix DP-F2 fuel control unit (FCU). Presently, the DP-F2 FCU is using a metering valve with a complex profile head, being moved in a calibrated orifice using double bellows operated by the compressor pressure. The differential pressure across the metering valve is controlled by a bypass valve fitted with a diaphragm which moves a shaped plunger inside a multi-orifice barrel. It is proposed to use a pressure balanced metering valve with a plunger moved in a slitted barrel by a stepper motor, which is changing the valve flow area according to the engine compressor pressure signal.

Typical fuel metering systems for small gas turbine engines consist of a metering valve and a bypass valve which is maintaining a constant differential pressure across the metering valve orifice. The metering valve is operated by the compressor pressure signal and the bypass valve acts automatically. It is proposed to bring both the metering and the bypass valves under the control of two digital linear actuators. The first one would move the metering plunger according to the compressor pressure and the second would move the bypass plunger in such a way, that the differential pressure across the metering orifice would be maintained constant only during steady state engine operation. During the engine transient processes, however, it would be increased or decreased as required, to speed up the change in the nozzle flow rate and consequently the engine dynamic response.

New regulations adopted by some North America states, to reduce pollution from vehicles, are forcing the auto-industry to introduce hybrid electric cars as a temporary solution, before the “clean” electric vehicles would become ready for consumer use. The FutureCar concept introduced by the USA government, in cooperation with the “Big Three” automotive manufacturers, is the first step to solve the future energy shortage and pollution problems associated with today's vehicles. The paper presents a proposal towards development of a low-cost, high efficiency and low emission mid-size car with an acceptable driveability. The choice of the IC engine, electric motor, drivetrain and control system are described. A demonstration project initiated in parallel should contribute to the validity of this proposal.

An attempt is made to develop solenoid operated injectors for diesel engines, to inject natural gas directly into the combustion chamber at high pressure. These new injectors have the size of conventional diesel injectors with small but powerful solenoids located in the former spring chamber, and the spring is moved to a location closer to the nozzle. To provide fast opening and closing of the nozzle, a multiobjective optimization method is used to select the design variables of the injector. The mathematical model used for optimization is developed with the help of experimental results obtained from the solenoid force measurements at transient conditions. The optimization results did show good dynamic performance of the injector, despite the use of a small size solenoid actuator.