Ultrasonic Transit-time Gas Flowmeter for Automotive Applications: A Monitoring Tool for Exhaust Emission Control

Motivated by continuously decreasing automotive exhaust emission limits, car manufacturers are motivated to develop a measurement system that can determine the mass emission of all exhaust gas components with high time resolution. This work focuses on the analysis, optimization, simulation, and the performance testing of one main component of such a measurement system - a new ultrasonic transit-time gas flowmeter for dynamically measuring the exhaust gas mass flow. This flowmeter, used in combination with fast gas analyzer benches, facilitates the optimization and monitoring of the combustion process, the performance of the catalytic converter, and the exhaust gas train. The most important issues are to deal with a wide gas temperature range and a high pulse repetition frequency. This work, which is intended for researchers and engineers who work in the field of gas flow measurement, demonstrates that ultrasonic flow meters can be used efficiently in the exhaust gas train of automotive combustion engines, and, thus, in many other other applications, where ultrasound based flowmeter measurements in high-temperature gas flows with fast pulsations have been out of the question.