Micromachined flow sensor for fuel injection

This paper presents the structure, operation principle, and fabrication process of a novel type of flow-velocity sensor. Like the well known classical Pitot (Prandtl) tube, it realizes flow velocity detection by measurement of the pressure difference between stagnant fluid pressure in front of the sensor and static pressure in the flow around the sensor. This difference results in a deflection of a diaphragm suspended boss, that serves as the counter electrode of an integrated capacitor which is directly exposed to the fluid to be measured. Experimental results in the wind tunnel and in the gasoline direct injection experimental set-up confirm the sensor's operation principle and show good time response.