The cylinder head gasket with integrated combustion pressure sensors (CHGICPS) reported here targets advanced engine controls and in particular those based on the HCCI, PCCI, or LTC combustion principles, for gasoline, diesel, and alternative fuel engines. Due to the fiber optic combustion pressure sensor's (CPS) accuracy at low pressure during compression integrated into the CHGICPS, this device aims at in-cylinder prediction of mass air flow as well as in-cycle closed loop control of pilot fuel injection in a diesel engine. This paper reports on a replaceable CPS which allows installation and removal from the cylinder head gasket (CHG) without the need for removing the engine head. At the same time the distance layer thickness of CHGICPS is minimized to 2.5 mm and 3.4 mm, depending on the access ability and space constraints around coolant and lubrication ports in the engine.
The PressureSense Glow Plug combines a miniature cylinder pressure sensor with the automotive glow plug. The 1.7mm diameter fiber optic-based sensor is welded into the glow plug heater and the signal conditioner is encapsulated into a “smart connector” located on the top of the glow plug body. The sensor offers accuracy better than +/-2% of reading between 220 bar and 5 bar and +/-0.2 to +/-0.5 bar error for pressures below 5 bar. The performance of “dummy” as well as glowing and pressure sensing devices was evaluated on various engines and over a wide range of engine operating conditions.
A high-accuracy and low-cost cylinder pressure sensor reported in this paper compensates for all major temperature errors encountered in internal combustion engines. The auto-referencing technique maintains sensor calibration compensating for temperature effects on the sensor signal conditioner over the range of -40 to +135°C. In an inexpensive design sensor head materials and dimensions are optimized to compensate for the mid-term thermal errors associated with engine load changes over a temperature range of -40 and 300°C, resulting in the thermal coefficient of sensitivity as low as 0.005%/°C. A miniature, specially shaped diaphragm results in less than 0.5% error associated with rapidly changing combustion gas temperatures. Under non-combustion conditions the sensor offers +/-0.25 - 0.5% accuracy while under combustion conditions the accuracy is typically in the 1- 2% range.