Sensor Research On Oil Tank Level Sensor Based On Fiber F-P Interference

In the petrochemical industry,the liquid level measurement of oil storage tanks is of great significance.At present,oil production and processing are inseparable from the storage of crude oil in oil storage tanks,and the liquid level of stored crude oil needs to be monitored by sensors in real time.With the development of optical fiber sensing technology,people have designed a variety of optical fiber sensors to realize liquid level measurement.Among them,Fabry-Perot(F-P)interferometric optical fiber liquid level sensor has been widely used in oil tank liquid level measurement because of its large measurement range.In paper,the oil tank level sensor based on optical fiber F-P interference is studied,and its main research contents are summarized as follows:(1)Based on the research background and significance of this paper,we introduce the demand of the current society for liquid level measurement of oil storage tanks.According to this demand,we introduce the research status of several common liquid level sensors,then we analyzed the advantages and disadvantages of different sensors.Finally,we analyze the research status of several grating and interferometric optical fiber liquid level sensors.(2)Based on the principle of multi-beam interference,we introduce the sensing theory of single F-P cavity and double F-P cavity.Next,we analyzed the sensitization principle of vernier effect in detail,and discussed the law of spectral shift direction in vernier effect.Finally,we introduce the spectrum analysis method of optical fiber sensor and the working mechanism of optical fiber liquid level sensor.(3)Based on the sensing principle of single F-P cavity,we designed and fabricated single F-P sensing structure based on air cavity and single F-P sensing structure based on polymer.Then,we studied the pressure and temperature response characteristics of these two structures through experiments.The experimental results show that the air cavity structure is sensitive to the change of external pressure and insensitive to the change of external temperature.In contrast,the structure of glue cavity is insensitive to the change of external pressure,but sensitive to the change of external temperature.(4)We designed an optical fiber F-P interferometric sensor based on the vernier effect,and analyzed the pressure and temperature sensing characteristics of the sensor through experiments.The experimental results show that the pressure sensitivity and temperature sensitivity of the optical fiber sensor are 25.52 nm/Mpa and 14.5 nm/℃.Next,according to the temperature characteristics of FBG,we theoretically analyze the method of two-parameter differential measurement of fiber F-P interferometric sensor.Finally,we explore the liquid level response characteristics of this type of sensor.(5)According to the enhanced vernier effect theory and related experiments,we designed an F-P interferometric optical fiber sensor which can measure the oil tank level.The experimental results show that the maximum pressure sensitivity of the sensor is-358.45nm/Mpa in the pressure range of 0 to 0.2 Mpa,and the linearity is above 0.99.In the temperature range from 30 ℃ to 56 ℃,its temperature sensitivity is 2 nm/℃,and its linearity is 0.994.In the liquid level range from 0 to 1.8 m,its liquid level sensitivity is 3.4 pm/mm,and its linearity is 0.989.Finally,according to the temperature characteristic theory of FBG,we analyze the method of distinguishing the liquid level and temperature of the sensor.