Miniature Static-Dynamic Cylinder Pressure Sensor

It is proposed to develop a 2.2mm diameter fiber-optic based sensor that measures both static and dynamic components of the cylinder pressure up to 350 bars over the frequency range of 0Hz to 20 kHz, operates at tip temperatures up to 450oC, and has the service life up to 20 thousands hours or 5 Billion cycles. The miniature sensing head and signal conditioner enable sensor integration with a diesel fuel injector or packaging as a stand-alone device. Unlike the current Optrand"s dynamic cylinder pressure sensor that uses a recessed diaphragm and a heat shield the proposed sensor has a dual diaphragm design with a flush mounted external diaphragm resisting soot fouling while being subject to minimum thermal shock error. In addition to pressure the sensor measures its head and signal conditioner temperatures, in order to compensate for the diaphragm deflection and signal conditioner temperature dependences, necessary to reach +/-1% accuracy over the sensor head temperature range of -50oC to 450oC and signal conditioner temperature range of -50oC to 140oC. A high speed microcontroller performs real-time calculations and provides high speed and resolution analog and digital outputs enabling real time control of fuel injection.