Research On Vapor Compensation Algorithm And Echo Signal Processing Of Guided Wave Radar

With the development of modern industrial production,monitoring instruments have become more and more popular,which,at the same time,increases the demand for higher accuracy and reliability.As a new type liquid level measurement device,the Guided Wave Radar(GWR)are widely used as a result of its high accuracy and reliability,bringing itself broad market prospects.Following the Fukushima nuclear accident,National Nuclear Safety Administration(NNSA)issued a series of guidance documents that set higher requirements for monitoring equipment at nuclear power plant in many aspects such as liquid level,temperature and pressure in order to obtain critical information about the spent fuel pools after the accident.GWR can be used to monitor the level of spent fuel pool.Therefore,it’s very important to improve the accuracy and reliability of GWR in complicated and harsh environment.In some extreme conditions with high temperature,high pressure,and high saturated vapor,the dielectric constant of vapor increases and cannot be ignored.The propagation of electromagnetic wave slows down,causing large measurement error.GWR suitable for this situation is introduced by some foreign manufactures,but the specific algorithm has not been disclosedBased on the theoretical analysis and the simulated experiments,This thesis studied the vapor compensation algorithm of GWR and tested its efficiency experimentally under the simulated condition of high temperature,high pressure and high saturated vapor.The main research work of the thesis is as follows:(1)Research on echo signal processing.Echo signal processing is directly related to the measurement accuracy of GWR.In the preprocessing of echo signal,in order to eliminate the high-frequency noise of the signal and reduce its distortion,the filter parameter is optimized through experimental comparison and analysis.In the calibration of liquid level,in order to improve the measurement accuracy in the nonlinear zone,the calibration method is improved by referring to the first-order Lagrange Interpolation Polynomial(LIP)and the least square method.In the post-processing of calculation results,the median filter and the first-order low-pass filter are used to smooth the output of GWR.(2)Research on vapor compensation algorithm.Based on Time Domain Reflectometry principle(TDR),this thesis analyzed under simulated vapor condition the cause of the measuring error and the echo signal of GWR,proposed the flow of vapor compensation algorithm based on reference echo signal,which is generated by setting a reference reflection point on the probe.Designed simulated vapor condition experiment to verified and improved the vapor compensation algorithm.Conducted regular condition experiment and simulated vapor condition experiment,the experiment result showed that by using the vapor compensation algorithm under simulated vapor condition,the GWR’s measurement error can be reduced from 70%to 2%,confirming that the vapor compensation algorithm can effectively improve GWR’s measurement accuracy under simulated vapor condition.