Measurement of Travelling Shock Waves and Transient Velocities with a Farnboro Indicator

Extract

The Farnboro Indicator gives a large permanent pressure-time diagram with a linear time base and pressure scale. In its latest versions accurate diagrams can be taken over a wide pressure range. The major disadvantage is that it can only be used for cyclic repetitive processes such as those occurring in engines or specially designed machines. During the course of an investigation of pressure wave phenomena in an exhaust pipe of a high-pressure-charged two-stroke cycle engine model the Farnboro indicator was used to record shock waves travelling along the pipe and to measure the total head pressure downstream of a nozzle placed at the end of the pipe and hence to calculate the transient velocity. In this note some of the pressure records taken in the investigation are presented.