This paper presents an overview of some specific gas turbine sensor needs to serve as a focal point for discussion of necessary sensor development to meet the needs of gas turbine engine manufacturers for `better, faster, and cheaper' testing. The need for high temperature dynamic pressure sensors, durable strain measurements, and wireless sensors is discussed.
In this paper, an overview on the use of optical fiber sensor in subsea and downhole oil well and related applications is presented, along with the impact of this technology in the oil industry. Focus will be placed on identifying the needs and requirements for various sensing applications.
Efficient and complete recovery of petroleum reserves from existing oil wells has proven difficult due to a lack of robust information that can monitor processes in the downhole environment. Commercially available sensors for measurement of pressure, temperature, and fluid flow exhibit lifetimes in the harsh downhole conditions, which are characterized by high pressure (up to 20 kpsi), temperatures up to 250 degree(s)C, and exposure to chemically reactive fluids. Development of robust sensors that deliver continuous, real- time data on reservoir performance and petroleum flow pathways will facilitate application of advanced recovery technologies, including horizontal and multi-lateral wells. We describe the development and fabrication of pressure, temperature, and flow sensors designed for the downhole environment, based on the Self-Calibrated Interferometric/Intensity-Based configuration, which combines the high sensitivity of interferometric sensors with the high-speed of intensity-based sensors. By splitting the output of a Fabry-Perot sensor into two channels with differing coherence, unwanted perturbations, such as source power fluctuations and variations in fiber loss, may be compensated. Results of laboratory tests of prototype sensors demonstrate excellent resolution and accuracy.
In this sensor, we demonstrate the developing and testing of fiber optic sensors intended to detect acoustic waves. The sensor is based on a novel design housing a thin silica diaphragm and a single mode fiber in an extrinsic Fabry- Perot interferometric structure. The designed sensor is tested for different applications including the detection of the partial discharges inside a power transformer. The test results indicate that the designed sensor can detect acoustic signals with high sensitivity at frequency as high as 200 kHz.
This report describes a fiber-optic rotation sensor particularly adapted to be placed adjacent a drill head to measure the orientation of a drill during or after drilling for minerals such as oil and gas.
A novel approach for health monitoring of civil infrastructural systems using electrical time domain reflectometry (ETDR) sensors has been established. In this paper, experimental characterization results obtained when a coaxial cable is used as an ETDR sensor to monitor cracks in reinforced concrete structures will be provided. The first part of the paper shows simulation of cracks due to high pressure on the sensor when it is embedded in concrete. The results show that as the pressure on the sensor increases, the ETDR technique was able to detect exactly the location on the sensor where the high pressure is applied. The technique is able to detect the crack location and magnitude of pressure to an application point in a harsh environment. Furthermore, the ETDR technique was able to distinctly detect the locations on the sensors when multiple compressive high-pressure forces were applied on the sensor within a spatial resolution of less than one inch. This multiple sensing ability confirms the ETDR sensing approach as a fully distributed sensing technique. The second part of the paper will show the simulated effect of high temperature on the sensor when embedded in concrete. The results show that the ETDR sensor is reliable and durable with significant increases in temperature variations.
Electric potential measurement (EPM) technology offers an attractive alternative to conventional nondestructive evaluation for monitoring crack growth in harsh environments. Where conventional NDE methods typically require localized human interaction, the EPM technique developed at Idaho National Engineering and Environmental Laboratory can be operated remotely and automatically. Once a crack-like defect is discovered via conventional means, EPM can be applied to monitor local crack size changes. This is of particular interest in situations where an identified structural defect is not immediately rejectable from a fitness-for-service viewpoint, but due to operational and environmental conditions may grow to an unsafe size with continuing operation. If the location is in a harsh environment where periodic monitoring by normal means is either too costly or not possible, a very expensive repairs may be immediately mandated. However, the proposed EPM methodology may offer a unique monitoring capability that would allow for continuing service.
We present that development of a whitelight interferometric spectrum based signal processing method for fiber optic absolute sensing. The signal processing method achieves an extremely high resolution over a large dynamic range. The signal processing techniques are demonstrated on a whitelight fiber optic sensor system which uses a broadband LED as its source, and an low finesse extrinsic Fabry-Perot cavity as its sensing element. The interferometric spectrum from the sensor is received and processed through a computer compatible spectrometer which used a grating to disperse the light and a CCD array to record the spectrum. The experimental results show that the system achieves absolute measurement with nanometer accuracy over a range of more than 16 micrometers .
Laser-based ultrasonic (LBU) measurement shows great promise for on-line monitoring of weld quality in tailor-welded blanks. Tailor-welded blanks are steel blanks made from plates of differing thicknesses and/or properties butt- welded together, they are used in automobile manufacturing to produce body, frame, and closure panels. LBU uses a pulsed laser to generate the ultrasound and a continuous wave laser interferometer to detect the ultrasound at the point of interrogation to perform ultrasonic inspection. LBU enables in-process measurements since there is no sensor contact or near-contact with the workpiece.
3D mapping has many applications including robot navigation, medical diagnosis and industrial inspection. However, many applications remain unfilled due to the large size and complex nature of typical 3D mapping systems. This paper describes a 3D mapping system being developed by the Photonics Laboratory at Virginia Polytechnic Institute which uses a fiber optic coupler as a fringe generator or grid projector. Several benefits are derived from this arrangement including small size, low cost, remote operation and survivability inside harsh environments. The system design and mathematical model are presented along with an estimation of the system depth resolution.
Fiber optic microphone is a new device developed on the basis of the new fiber optic technology for measuring distances. Very small in size microphone consists of glass and plastic without any metal. Microphone works very linear in wide frequency and dynamic range in very harsh environment like heavy magnetic, electric, RFI and radioactive fields where no one of known microphones can't work. Microphone may be successfully used in MRI system for audio connection between a patient in MRI equipment and medical personnel outside of it.
The design and testing of a gas cooled probe protector shell is described. Standard optical probes are limited to relatively low temperature and mild environmental conditions. By enclosing such probes in concentric air- cooled stainless steel tubes with a brazed sapphire window at the end, their operating limits can be greatly extended. Gas cooling eliminates the facility requirements and leak hazards of water-cooled probes. Low gas flow rates have been demonstrated to maintain a probe at less than 100 degree(s)C in a 600 degree(s)C quiescent environment.
An external-cavity tunable diode laser operating at near-IR region is used to detect acetylene with laser absorption spectroscopy. Quantitative measurement of gas concentration is obtained by applying low-frequency wavelength modulation to the tunable laser and by phase-sensitive-detection of the fundamental and second-harmonic signals using a lock-in amplifier. A single-sensor and a time-division multiplexed two-sensor system have been implemented and experimentally tested. The sensor systems use single path 25 mm absorption cells and have demonstrated sensitivity of 75 ppm for the single sensor system and 182 ppm for the multiplexed two- sensor system.
This paper concentrates on the performance stability of sapphire fiber thermometer probe and the development of an alumina fiber cladding durable under high temperature and of high transparency. Analysis was made on the performance stability of sapphire fiber probe under high temperature when using different kinds of protective tube. It is found that direct contacting of the fiber with protective tubes is the most important factor that result in performance deterioration and the dirtying of evaporating substance is another important factor. Then it is applicable to design a suitable protective tube to assure the performance stability.