Technique of Measuring Gas Stream Velocity by means of Electric Discharge

Abstract

A new measuring technique of gas stream velocity, based on the phenomena that the path of electric discharge moves downstream under influence of gas stream, has been developed. A probe, a thin conductive wire grounded by a resistor, is placed at a distance l downstream from electrodes. When the discharge path arrives at the probe, the probe voltage rises rapidly. By means of measuring the time interval τ, elapsing between the beginning of spark and the rising of probe voltage, the stream velocity w can be determined by the formula, w=kl/τ, where k is a constant, independent of distance l, intensity of turbulence, temperature and pressure of flowing gases. The value of k depends only on electrode spacing. Digital measurement of τ can be made easily. This technique can be applied to not only steady but pulsating flow such as suction flow of internal combustion engines.