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U. Schmid:
"A Robust Flow Sensor for High Pressure Automotive Applications";
Sensors and Actuators A: Physical, 97-98 (2002), 253 - 263.

In this paper, a micromachined mass flow sensor mounted on a high pressure stable substrate is presented to measure on board the different injection quantities needed in modern direct injection (DI) systems for optimum performance of the engine. To detect the injection end/begin as well as the injection rate as precisely and fast as possible, the sensor is completely integrated into the nozzle body close to the injection holes for the first time. The thermal measurement principle is chosen, as gasoline and diesel fuel quantities can be detected and therefore, the use of this present flow sensor is not restricted to one of these different types of combustion engines. The fabrication process of the molybdenum (Mo) thin film sensors on an LTC (low temperature co-fired) ceramic chip is described. Additionally, FEM simulations concerning the velocity profile in the injection nozzle are performed and the electrical heating power of the hot film anemometer at different overheat ratios is analytically calculated. Finally, the injection rate measurements up to 60 MPa (600 bar) with the nozzle-integrated thin film sensor are presented and their additional information compared to signals gained from an injection amount indicator (EMI), which is part of the high-pressure hydraulic test bench, are discussed.

http://dx.doi.org/10.1016/S0924-4247(01)00869-X