In internal combustion engines, particularly for spark ignition (SI ) engines, valve events and their timings have a major influence on the engine's overall efficiency and its exhaust emissions. Because the conventional SI engine has fixed timing and synchronization between the camshaft and crankshaft, a compromise results between 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 overall engine performance. To get full benefits from VVT, various types of mechanisms have been proposed and designed. Some of these mechanisms are in production and have shown significant benefits in improving engine performance. During the last two decades, remarkable developments have been seen in the field of VVT. This paper reviews the literature in the technology of intake and exhaust philosophies of VVT and their effects on the pressure-volume (PV ) cycle of the engine. A single-cylinder engine is simulated by the GT-Power software. The effects of different VVT philosophies from the simulations are analysed and compared to those of the literature reviewed.Keywords: variable valve timing ( VVT ), variable valve actuation ( VVA), valve overlap, exhaust gas recirculation (EGR) INTRODUCTIONResidual gas fraction ( RGF ) is controlled by the valve overlap and cannot be changed for various speeds and loads. The fixed-valve events of conventional cam-A major goal of engine manufacturers is to minimize specific fuel consumption and emissions from engines.controlled engines compromises the engine for better performance under all operating conditions. The inlet-valve One solution is by the independent actuation of the inlet and exhaust valves at any position of the piston, with timing is the most important parameter for optimizing the engine volumetric efficiency, whereas the exhaustno more need for a camshaft.A major disadvantage of conventional spark ignition valve timing controls the RGF, which reduces exhaust NO x emission. For the engine to operate efficiently and (SI ) engines results from the energy losses during the inhaling of the sub-atmospheric gases during the suction effectively over its entire operating range and conditions, the valve events should be able to vary with speed and stroke and the expelling of exhaust gases to the atmosphere during the exhaust stroke. These pumping losses depend load anywhere on the engine map. The present investigation undertakes the assessment of on the opening and closing position of the throttle valve. The losses are high when the throttle valve tends to close intake and exhaust philosophies for VVT. and are low at wide-open throttle. Thus, the pumping losses are inversely proportional with the engine load. Without a throttle valve, control of the air-fuel mixture 2 VALVE EVENTS OF CONVENTIONAL SI can be realized by variation of the intake valve-opening ENGINES period; therefore, variable valve timing ( VVT ) h...

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This paper emphasizes on the effects of different biodiesels and diesel on; heat release, ignition delay, endothermic and exothermic reactions, NOx, fuel injection pressure due to the fuel’s modulus of elasticity and cylinder pressure. Two 100% biodiesel and its blends of 20% with of low sulfur #2 diesel, and #2 diesel are tested on a single cylinder diesel engine under full load condition. Engine performance and emissions data is obtained for 100% and 20% biodiesels blends and #2 diesel. Testes were conducted at Engine Systems Development Centre, Inc. (ESDC) to evaluate the effects of biodiesel and its blends on the performance and emissions of a single-cylinder medium-speed diesel engine. The main objective of this work was to gain initial information and experience about biodiesel for railway application based on which biodiesel and its blends could be recommended for further investigation on actual locomotives.

The objective of this paper is to the study effects of Late Intake Valve Closing (LIVC), and how it affects the in-cylinder fluid flow for four stroke gasoline engines. Further investigation of LIVC has been performed with the help of an engine cycle simulation program (GT-Power). Study shows that LIVC is beneficial for reduction of pumping losses, which may reduce the break specific fuel consumption (BSFC) of the engine. In this paper, a simulation of LIVC was achieved by retarding the timing of the solenoid actuated intake valve.