27-09-2014, 01:54 PM
Abstracts: The engines powering today’s vehicles whether they burn gasoline or diesel fuel rely on asystem of valves to admit fuel and air into the cylinder and the exhaust gases to escape aftercombustion. Cam has been an integral part of internal combustion engine from its invention. Camcontrols the breathing channels of the IC engines and hence maintains constant valve timing. Theproblem in using cam shafts is being major power wastage in accelerating and decelerating thecomponents of the valve train. Friction of camshafts, springs, cam belts etc., also robs us ofprecious power and worsens fuel economy not to mention contributing to wear and tear.In response to the needs of improved engines some mechanical or hydraulic devices havebeen designed to achieve some variable valve timing and to reduce the disadvantagesaccompanied with the usage of cams. Most four-stroke piston engines today employ one or morecamshafts operated poppet valves. The lobes on the camshafts operate cam followers which inturn open the poppet valves. A cam less (or, free valve engine) uses electromagnetic, hydraulic,or pneumatic actuators to open the poppet valves instead. Actuators can be used to both open andclose the valves, or an actuator opens the valve while a spring closes it.In this paper a new lift control strategy is proposed based on the hydraulic supplypressure and flow control. Though our project started with hydraulics, later we found thatPneumatic valve actuation is even more advantageous and hence proceeded with pneumatic.