The objective of the work presented was to develop a suite of sensors for use in high-temperature aerospace environments, including turbine engine monitoring, hypersonic vehicle skin friction measurements, and support ground and flight test operations. A fiber optic sensor platform was used to construct the sensor suite. Successful laboratory demonstrations include calibration of pressure sensors to 500psi at a gas temperature of 800°C. Additionally, pressure sensors were demonstrated at 800°C in combination with a high-speed (1.0MHz) fiber optic readout system enabling previously unobtainable dynamic measurements at high-temperatures. Temperature sensors have been field tested up to 1400°C and as low as -195°C. The key advancement that enabled the operation of these novel harsh environment sensors was a fiber optic packaging methodology that allowed the coupling of alumina and sapphire transducer components, optical fiber, and high-temperature alloy housing materials. The basic operation of the sensors and early experimental results are presented. Each of the sensors described here represent a quantifiable advancement in the state of the art in high-temperature physical sensors and will have a significant impact on the aerospace propulsion instrumentation industry.
The motivation for the reported research was to support NASA space nuclear power initiatives through the development of advanced fiber Bragg grating (FBG) sensors for the SAFE-100 non-nuclear core simulator. The purpose of the combined temperature and strain mapping was to obtain a correlation between power distribution and core shape within the simulator. In a nuclear reactor, core dimension affects local reactivity and therefore power distribution. 20 FBG temperature sensors were installed in the SAFE-100 thermal simulator at the NASA Marshal Space Flight Center in an interstitial location approximately 2.3mm in diameter. The simulator was heated during two separate experiments using graphite resistive heating elements. The first experiment reached a maximum temperature of approximately 800°C, while the second experiment reached 1150°C. A detailed profile of temperature vs. time and location within the simulator was generated. During a second test, highly distributed fiber Bragg grating strain sensors were arrayed about the circumference and along the length of the heated core region. The maximum temperature during this test was approximately 300°C. A radial and longitudinal strain distribution was obtained that correlated well with known power distribution. Work continues to increase the strain sensor operating temperature and sensor multiplexing to allow high-resolution mapping.
The objective of the work presented was to develop a suite of sensors for use in high-temperature aerospace environments, including turbine engine monitoring, hypersonic vehicle skin friction measurements, and support ground and flight test operations. A fiber optic sensor platform was used to construct the sensor suite. Successful laboratory demonstrations include calibration of a pressure sensor to 100psi at a gas temperature of 800°C, calibration of an accelerometer to 2.5g at a substrate temperature of 850°C. Temperature sensors have been field tested up to 1400°C, and a skin friction sensor designed for 870°C operation has been constructed. The key advancement that enabled the operation of these novel harsh environment sensors was a fiber optic packaging methodology that allowed the coupling of alumina and sapphire transducer components, optical fiber, and high-temperature alloy housing materials. The basic operation of the sensors and early experimental results are presented. Each of the sensors described here represent a quantifiable advancement in the state of the art in high-temperature physical sensors and will have a significant impact on the aerospace propulsion instrumentation industry.
Fiber optic measurement systems are on the cutting edge of instrumentation for many industries from military and government applications to commercial needs such as the automotive, aerospace, and power turbine industries. Measurement parameters including temperature, pressure, and strain can provide valuable information. Sensor mapping allows for larger scale monitoring capabilities and provide flexibility in sensing applications. A sensor and readout system is being developed to expand the capabilities of fiber optic sensing. Several iterations of multiplexed sensors have been tested using a high-resolution fiber optic coupled dual Michelson interferometer based-instrument that has the capability of reading gaps of 25μm to 6.5mm. This measurement range opened the opportunity to read several different sensors on the same fiber, i.e. the same channel. Sensor strings combining temperature and strain
extrinsic Fabry-Perot interferometric sensors were tested. These sensor strings produced were either serial multiplexed, parallel multiplexed, or a combination. This paper will discuss the capabilities of the sensors and instrumentation systems developed.
Luna Innovations is developing a high temperature sensor suite based on novel metal oxide transducers and patented fiber optic sensor technology. This suite will include pressure, temperature, acceleration, and skin friction sensors. Luna has demonstrated prototype ceramic fiber optic pressure sensors with a range of 2000 psig and +/- 0.1 psig absolute accuracy and 0.01 psig dynamic resolution. By applying advanced materials and packaging technologies, designs that will support pressure measurements up to 1400°C have been produced. Fiber optic temperature sensors have been tested up to 1100°C. A ceramic accelerometer has also been developed that will enable high-temperature vibration measurements. A shear stress sensor is in the early stages of development that is expected to reach 850°C. The high temperature sensor suite will provide previously unobtainable measurements in advanced air-breathing propulsion systems, as well as in high-temperature industrial applications.
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