No abstract

An optical sensor system extends gas temperature measurement capability in turbine engines beyond the present generation of thermocouple technology. The sensing element which consists of a thermally emissive insert embedded inside a sapphire lightguide is capable of operating above the melting point of nickel-based super alloys. The emissive insert generates an optical signal as a function of temperature. Continued development has led to an optically averaged system by combining the optical signals from four individual sensing elements at a single detector assembly. The size of the signal processor module has been reduced to overall dimensions of 2 x 4 x 0.7 inches.The durability of the optical probe design has been evaluated in an electric-utility operated gas turbine under the sponsorship of the Electric Power Research Institute. The temperature probe was installed between the first stage rotor and second stage nozzle on a General Electric MS7001B turbine. The combined length of the ceramic support tube and sensing element reached 1 .5 inches into the hot gas stream. A total of over 2000 hours has been accumulated at probe operation temperatures near 1600°F.An optically averaged sensor system was designed to replace the existing four thermocouple probes on the upper half of a GE F404 aircraft turbine engine. The system was ground tested for 250 hours as part of GE Aircraft Engines IR&D Optical Engine Program. Subsequently, two flight sensor systems were shipped for use on the FOCSI (Fiber Optic Control System Integration) Program. The optical harnesses, each with four optical probes, measure the exhaust gas temperature in a GE F404 engine.

An optical sensor system extends gas temperature measurement capability in turbine engines beyond the present generation of sensor hardware for production engines. The sensing element incorporates a thermally emissive insert to generate an optical signal proportional to the gas temperature at the tip of the probe. The use of a sapphire lightguide allows operation above the melting point of nickel based alloys. Sensor development for aircraft turbines has included flight hardware for use on the Fiber Optic Control System Integration (FOCSI) Program sponsored by NASA Lewis Research Center. The optical probe harness measured exhaust gas temperatures in a General Electric F404 engine. Signals from four probes were optically combined at a single detector assembly to determine the average gas temperature. A comparison of optical and thermocouple temperature measurements was conducted during a preflight engine test. The durability of the probe design has been evaluated in an electric-utility operated gas turbine under the sponsorship of the Electric Power Research Institute. The temperature probe was installed between the first stage rotor and second stage nozzle on a General Electric MS 7001B turbine at Houston Lighting and Power Company. Two probes have been used in the field test and they have a combined total of 4660 hours of operation near 1600°F and 330 starts.

A simple and inexpensive fluorescein detector is described that is capable of detecting a solution of approximately one part fluorescein to five million parts of water. The device can be constructed in a laboratory or workshop equipped with the minimum tools and instrumentation. As conceived, the device is used as a leak detector and is designed to activate a relay when an aqueous fluorescein solution exceeding a concentration of one part per five million flows through a quartz tube.

A fiber optic temperature sensor (FOTS) system consisting of an optical probe, a flexible fiber optic cable, and an electro-optic signal processor was fabricated to measure the gas temperature in a turbine engine. The optical probe contained an emissive source embedded in a sapphire lightguide coupled to a fiber-optic jumper cable and was retrofitted into an existing thermocouple probe housing. The flexible fiber optic cable was constructed with 200 micron core, polyimidecoated fiber and was ruggedized for an aircraft environment. The electro-optic signal processing unit was used to ratio the intensities of two wavelength intervals and provided an analog output value of the indicated temperature.Subsequently, this optical sensor system was installed on a NASA Dryden F-l5 Highly Integrated Digital Electronic Control (HIDEC) Aircraft Engine and several flight tests were conducted. Over the course of flight testing, the FOTS system's response was proportional to the average of the existing thermocouples sensing the changes in turbine engine thermal conditions.