In this study, a micromachined hot film anemometer, placed on a pressure stable LTCC-substrate, is presented to measure the different injection quantities, needed in modern direct injection (DI) system for optimum performance. A bi-layer of Titanium (Ti) and Platinum (Pt) as advanced metallisation system for the thin film resistors is used due to a lower resistivity and a higher temperature coefficient of resistance (TCR) compared to Molybdenum (Mo), which was taken for the first tests. Especially the increase in TCR is recommended for thermal mass flow sensors, as the resulting signal height is linearly related to this material parameter. Therefore, the new technology steps, to fabricate the sensor elements, are given in the paper. The latest injection rate measurements, performed for the first time up to 90 MPa with a nozzle integrated mass flow sensor, yield a strong increase in sensor amplitude at higher rail pressures. After the closing of the nozzle, pressure waves, caused by the strong deceleration of the fuel column, are clearly detectable, demonstrating the quality of the sensor signals.
A robust hot film anemometer for injection quantity measurements
Ein robustes Heissfilm-Anemometer zur Bestimmung der Einspritzrate
2002
10 Seiten, 6 Bilder, 10 Quellen
Conference paper
English
A Robust Hot Film Anemometer for Injection Quantity Measurements
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