Ultrasonic Measurement of the Exhaust Gas Mass Flow and Temperature with High Temporal Resolution

The exhaust gas flow from the cylinders of piston engines is a complicated highly dynamic process. Flow velocity, pressure and temperature are fluctuating fast and markedly, especially during motor charge changes. A knowledge of these parameters is decisive for future motor developments with regard to reduced pollutant emissions. A method, based upon the ultrasonic time-of-flight technique, for the high temporal resolved measurement of the exhaust gas mass flow and the temperature has been developped. The research activities centered on the realization of high-temperature stable air borne ultrasonic sensors. At the present state of development, the sensors are applicable for exhaust gas temperatures up to 400ø C without water cooling and up to 600ø C with water cooling. It is intended to extent the temperature range up to 1000ø C. The sensors and the measurement method were tested at a motor test stand. The average values of exhaust gas flow and temperature were in good agreement with the values determined from fuel / air consumption. It was demonstrated that the technique can be used up to 6000 revolutions per minute.