Subject of study. We aim at the problem that the conventional pipeline leakage detection methods cannot meet the needs of oil and gas pipeline leakage detection at the present stage, combined with the application analysis of optical fiber pressure sensing in oil and gas pipeline detection. Method. A fiber Bragg grating pressure sensing system integrating a diaphragm and an L-shaped cantilever beam as a sensitive structure is designed for pressure change monitoring of an oil and gas pipeline in this paper. First, the sensitivity, temperature self-compensation effect, and static and dynamic characteristics of the sensor are analyzed theoretically. Combined with the negative pressure wave model, the pipeline leakage detection experimental system is constructed. Second, the data is denoised by the wavelet analysis method, and then the inflection point of the negative pressure wave is judged. Finally, the leakage point is located according to the data processing results. Main results. The experimental results show that the error between the theoretical pressure sensitivity of a fiber Bragg grating pressure sensor and the pressure sensitivity of static finite element analysis is 4.7%, and the first-order modal natural frequency is 3290.9 Hz. In the range of 0–2 MPa, the pressure sensitivity of the sensor is 1185.621 pm/MPa. The average leakage location error of the model is 8.5%. Practical significance. Practice has proved that the fiber Bragg grating pressure sensing technology has many advantages, such as high sensitivity, high reliability, and easy networking. The system can be effectively applied to the field of oil and gas pipeline leakage detection engineering.
Accurate calculation of water content is of great significance for mastering the production capacity, channeling, and water flooding of oil wells. This article proposes an optimized empirical wavelet transform (EWT) and frequency wavenumber spectrum (FK) analysis based method for measuring water content, which addresses the issue of noise interference affecting the measurement of sound velocity and resulting in high uncertainty in water content measurement. The experimental results show that compared with WT, EMD-WT, and CEEMDAN-WT denoising methods, this method exhibits excellent capabilities in both noise filtering and maintaining the original signal waveform. The final measured curve of the relationship between sound velocity and water content has a fitting degree of 94.36%, which is superior to other methods.
Transient temperature measurement technology with fast response, harsh measurement environment, and high technical challenges has attracted research interest in the field of temperature measurement. Based on the differential equation of heat conduction at the interface of an optical fiber, the dynamic-response-time formula of the optical fiber was derived and the transient thermal response simulation of the optical fiber was conducted. Fast-response fiber Bragg grating (FR-FBG) temperature sensors were designed and manufactured by femtosecond-fabricated FBGs with diameters of 80 and 125 μm. The average response times of the 80 and 125 μm-FR-FBG temperature sensors were 33.2 and 65.3 ms, and the errors between the data and theoretical values were 9.89% and 7.44%, respectively. From explosion experiments, it is concluded that the femtosecond grating can be applied to the monitoring of rapid temperature response during explosion, and the response time is related to the diameter of the grating.
A compact temperature sensor based on a simple nonadiabatic microfiber loop is demonstrated experimentally using nonadiabatic microfiber loop. High sensitivity within a large temperature range can be obtained utilizing a microfiber with 20mm length.
The anti-electromagnetic interference performance of Fiber Bragg Grating (FBG) is a potential advantage in explosive measurement with electromagnetic pulses. Firstly, this paper verified the high strain rate performance of FBG in dynamic measurement by Split Hopkinson Pressure Bar (SHPB). Then, a concrete explosion-proof model was designed and built. Various types of acceleration sensors and strain gauges were arranged on inner wall of the model to measure acceleration and strain during explosion. The experimental results showed that response curves of FBG acceleration sensor and electrical acceleration sensor are similar, and the response curves of various FBG strain gauges are consistent, which proved the feasibility of FBG sensing technology in explosion measurement. Finally, by analyzing propagation of blast wave, this paper put forward some suggestions of health monitoring for explosion-proof engineering structure.
Abstract In this paper the working principle and application status of distributed optical fiber temperature sensor, amplified spontaneous Raman scattering phenomenon and its time-domain characteristics are analyzed. A new measuring principle based on amplified spontaneous Raman scattering light pulse signal temperature effect is presented, and is applied to distributed optical fiber sensor systems. Noise inevitably exists in data collected by distributed optical fiber temperature sensing systems. According to the needs of high-temperature oil well testing, distributed high temperature single-mode fiber sensors and detection equipment are designed, and gives two-dimensional data of oil well temperature testing. Because of the weak Raman backwards scattered signal and serious noise disturbance, multi-resolution wavelet analysis and reconstruction method are adopted for the denoising of testing signal.
The principle and characteristic of a photoelectric sensor have been introduced, and the advantage of the sensor used in civil engineering measuring has also been presented. As the results of the experiments, the sensor has high stability and precision, good repeatability and long-term behaviors, which is suited to monitor the displacement in civil engineering, and can meet the requirement of huge project both in signal measuring precision and scope.
A high-sensitivity optical fiber relative humidity (RH) sensing probe with the ability of temperature calibration is proposed and experimentally demonstrated. It consists of a simple Fabry-Perot interferometer constructed by coating a layer of thin polyimide (PI) film on the end face of single-mode fiber and an upstream fiber Bragg grating (FBG). PI is one of the organic polymer humidity-sensitive materials with good comprehensive properties. The cascaded FBG is used for temperature calibration and elimination of the temperature cross-sensitivity in the process of measuring RH. Experimental results show that this sensing probe can realize simultaneous measurement of temperature and RH. The RH response sensitivity reaches up to 986.25 pm/%RH. This sensing probe with the advantages of simple structure, compact size, high sensitivity, easy packaging, and dual-parameter measurement has an extensive application prospect.
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