Fundamental Study on Wave Pheonomenon in the Exhaust Pipe of an Internal Combustion Engine

It is assumed that the back pressure of an engine increases due to the frictional resistance of the gas flow when the length of the exhaust pipe is increased. As a matter of fact, however, the values of the back pressure increase or decrease according to the increase of the pipe length. The cause of the change of the back pressure resulting from the length of the exhaust pipe is presumed to be a wave interference. However, it is very difficult to pinpoint the wave phenomenon in an actual firing engine. Therefore, an air model engine is used in the experiment so that the observation of only one arbitrary time is possible. The piston is devised so that it can be fixed at an arbitrary position and the cylinder volume is kept constant. Compressed air is introduced into the cylinder from the top of the cylinder head, and the exhaust valve is processed so that the valve opening time and the valve clearance can be changed from outside of the engine. By using this model engine, many interesting conclusions on the wave phenomenon are shown in this paper.