Long-life fiber optic pressure sensors for monitoring and control of gas machinery

摘要

Abstract: In a robust, durable, and low-cost design Optrand pressure sensors utilize the principle of light intensity changes, transmitted by two optical fibers, upon reflection from a specially shaped, metal diaphragm deflecting under the effect of pressure. The non-contact detection principle combined with the diaphragm design optimized for infinite fatigue life translates into a sensor with extraordinary lifetime. The sensor's signal conditioner contains one LED and one photodiode and is permanently attached to the fibers. The electronic circuitry provides the auto- referencing function compensating for the effects of fiber bending, fiber-to-optoelectronics coupling changes, sensor thermal drift, as well as temperature and aging effects of the LED and the photodiode. The results of several along- term test in two key gas machinery applications are reported here: continuous and intermittent monitoring of power and compressor cylinders. In the longest application to date, hundreds of combustion pressure sensors have demonstrated over 12,000 hours or 500-million pressure-cycle lifetime. Dynamic pressure sensors for compressor monitoring have already demonstrated the lifetime of 1 billion cycles and target 5 billions. In compressor applications the sensor demonstrate typical $POM 0.25 percent accuracy while combustion pressure sensor accuracy is typically $POM 1 percent. For almost two years tens of indicator valve- mounted combustion sensor have been monitored for calibration stability demonstrating better than $POM 0.1 percent performance over a 6-month period. !10