Multi-Channel Fiber-Optic Pressure Sensor System for Monitoring & Control of Reciprocating Engines
A fiber-optic combustion pressure system is described dedicated to monitoring and control of natural gas-fueled, large-bore, reciprocating engines. The system consists of a multi-channel interface/signal conditioning unit, fiber-optic sensors, and detachable fiber optic patch cables. A fibber optic combustion pressure sensor utilizes an optical fiber in front of a flexing diaphragm for optical reflection measurement of pressure-induced deflections. The sensor can cover pressure ranges up to 3,000 psi and can operate continuously at temperatures up to 300° C. A proprietary auto-referencing technique guarantees calibrated and drift-free operation as well a compensates for sensor and fiber link environmental and temperature effects. In addition, the auto-referencing technique provides diagnostics about sensor and opto-electronic interface health. At constant temperature, the present sensor system demonstrates a typical +/- 0.5% linearity, negligible hysteresis and overall accuracy of 1% of full scale. Large-bore natural gas-burning engine test results demonstrate excellent sensor performance against a considerable more expensive piezoelectric transducer. The results of two long-term endurance tests are reported obtained on high- and low-speed engines. After seven months of operation, equivalent to approximately 2,000 hours and 100 Million pressure cycles alll tested sensors have survived and function as expected.