Bilge Kutlay Hanlı
Gökçem Gökmen
Poppet valves are mechanisms which are widely used in industrial processes such as controlling the flow of milk or isolating sterile air, but they are well-known as a component of internal combustion engines. In engines, they are used to control the timing and the amount of gas or vapor flow into an engine. They mainly consist of a cam, a follower, a rocker arm, and valves.
In the internal combustion engines, the cam and follower system is used to control the opening and closing of the inlet and exhaust valves. The cam rotates around a shaft, the follower converts this motion into translation and manages to open or close the valves. The shape of the cam profile affects the position of the follower during rotation, and so, different shaped cams are used for different purposes. Also, different types of followers are used.
Pear, circular, and heart shaped cams are commonly used in combustion engines. Pear shaped cams are used on the shafts of the car. During the first half of the motion, the follower stays motionless, and it goes up and down for the rest. Circular cams maintain a smooth motion and used in steam engines. In heart shaped cams, the follower goes up and down with a uniform velocity.
Experimental Setup
A poppet valve mechanism mainly consists of a cam, a follower, a rocker arm, and valvesfor the maintainability of the system.
Shaft: The shaft transmits the circular motion created by the engine to the cams of the system. Our shaft is made of Aluminum with the radius of 20mm.
Circular, pear shaped and heart shaped cam: The cam is responsible to convert the circular motion to translational motion. Moreover, each cam profile creates different position, velocity and acceleration values for the valve. Our cams are made of Plexiglas, produced by laser cutting machine. The dimensions are shown in the drafts.
Follower: The follower makes the translational motion in the upward and downward directions. Our followers are made of wooden with the radius of 20mm.
Rocker arm: Rocker arm’s duty is to transmit the motion created by the follower on the cam to the follower carrying the valve. The rocker arm is also Plexiglas produced by laser cutting machine.