Research On Technology And Application Of Turbine Flow Measurement Based On Novel Optical Fiber Sensor

With the advantages of high precision,good repeatability,small volume,light weight,less processing parts and high reliability,turbine flowmeters are widely used in the flow measurement of scientific researches and defense technologies.The traditional turbine flowmeters adopt electromagnetic detector,which can be easily interfered in the strong electromagnetic environment;in addition,the electromagnetic detector causes an additional electromagnetic resistance influencing the rotation of turbine rotor.Therefore,in some measuring environments with special requirements,such as strong electromagnetic,high temperature and high pressure,the traditional electromagnetic turbine flowmeter cannot meet the measurement requirements.What's more,with the demand for measuring the wide range flow measurement,the range ratio of turbine flowmeters is urgently to be improved.Accordingly,taking the turbine flowmeters as the research object,a new type of optical fiber turbine flow sensor is proposed based on the advantages of optical fiber sensor,including resistance of high temperature and high pressure,immunity of electromagnetic interference,and remote measurement.To solve the above problems,following aspects are studied:Firstly,a type of double circle coaxial(DCC)optical fiber sensor is proposed and designed.Based on the selection and design of optical fiber probe,a type of DCC optical fiber sensor is proposed.The principles and advantages of the flowmeter are discussed,which is characterized by fast response,ability of withstanding high temperature and pressure,immunity of electromagnetic interference,and remote measurement.After that,the working principle of the DCC optical fiber sensor is described.Furtherly,it is studied that the model of the optical fiber intensity distribution field and modulation characteristics.And then,the size of the optical fiber probe is designed.The static characteristics of the fiber sensor is calculated,including measurement range,sensitivity,linearity and so on.The nonlinear correction method of LS-SVM is studied.After designing high pressure resistant seal installation of the optical fiber probe,four different size groups of fiber optic turbine flow sensor are developed.Secondly,a method of improving the range ratio is studied for optical fiber turbine flowmeter.By establishing the theoretical mathematical model and numerical simulation of the turbine flowmeter,the results show that the electromagnetic resistance torque of the electromagnetic turbine flowmeter has a great influence on the rotation of the turbine in the low flow rate.It is demonstrated theoretically that the optical fiber detection method can remove the electromagnetic resistance.Then,the output characteristics of the turbine flowmeter are analyzed.Since the calibration range of the turbine flowmeter only consists of the linear region,the nonlinear region about 1/3 of the output range is available.Thus,a piecewise linearization method is proposed to extend the non-linear region in order to increase the range ratio.Therefore,the nonlinear range of the turbine flowmeter is processed by a piecewise linear method based on the calculation result of the mathematical model,which lays a theoretical foundation for the verification experiment of the optical fiber turbine flowmeter.Thirdly,verification experiments are performed for fiber turbine flowmeters in laboratory flow measurement.The post-processing circuit of the fiber optical flow sensor is designed.The time domain and frequency domain methods of frequency measurement of turbine rotation are and discussed.The frequency domain FFT method is selected as the main flow detection algorithm.Thus,a computer system for flow online measurement based on LabVIEW is developed independently.Taking the DN20 turbine flowmeter as the test object,the accuracy and reliability of the fiber turbine flowmeter were verified step by step through four different flow measurement experiments.The experimental results show that the range ratio of the fiber turbine flowmeter increased nearly 3 times comparing with the electromagnetic turbine flowmeter.The experimental results show that the proposed DCC fiber turbine flowmeter is effective and reliable,which improves the range ratio and is immune to electromagnetic interference.Finally,the intelligent optical fiber turbine flowmeter is studied based on DSP,as well as its application.The intelligent optical fiber turbine flowmeter based on DSP is designed from two aspects,including hardware system and software algorithm.Taking the intelligent distributed control system of scramjet engine as the application background,the framework of distributed control system is designed.Afterward,the sensor monitoring system is analyzed.Aiming at the need of fuel flow on-line monitoring,the fuel supply cycling system is studied for scramjet engine.Then,the change mechanism of fuel properties in active cooling pipeline is studied.Based on the above study,a fuel flow online monitoring method is proposed,namely,the fiber turbine flowmeter measures the high-temperature pipeline outlet fuel flow in real time,combined with the density neural network soft measurement model to realize on-line monitoring of fuel mass flow rate.Three kinds of density neural network soft-sensing models are studied,in which the RNN soft-sensing model is proved the best.This method provides a new measurement path for on-line monitoring of scramjet engine fuel flow,which has a certain engineering application value.