An ultrasonic sound speed sensor for measuring exhaust gas recirculation levels

Abstract

Exhaust gas recirculation (EGR) has been used for years to improve the performance of internal combustion engines. This paper shows that acoustic methods can be used to measure EGR. Theory is presented which shows that measurements of the speed of sound can be used to measure the amount of EGR in the intake manifold. In particular, a new method called the discrete acoustic wave and phase detection (DAWPD) method can be used to measure EGR levels with a fast-response time. Experimental results show that a DAWPD sensor can be used to measure EGR levels with adequate accuracy (± 1.3 per cent EGR) at steady state. Transient measurements were not possible owing to engine limitations. The sensor's performance was limited by the ultrasonic transducers used. It is postulated that sensor performance could be improved with smaller and temperature-independent non-resonant transducers.