Applications Of Ultrasonic Technique In Parameter Measurement Of Complex Fluid

Fluid widely exists in industrial processes such as chemical industry,energy industry,and so on.Accurate parameter measurement of fluid is critical for modeling,prediction,control and design of process systems.Although the parameter measurement of complex fluid is of great importance,the problem of parameter measurement has not been well-solved yet due to the complex and changeable flow characteristics.Because of various merits like strong adaptability,wide measuring range,no moving parts,etc.,ultrasonic technique provides an effective approach and shows good application potential for parameter measurement of complex fluid.Ultrasonic technique has become one of the research focuses of the fluid measurement field in recent years.This dissertation studies the applications of ultrasonic technique in parameter measurement of complex fluid(gas flow and gas-liquid two-phase flow),which can provide new ideas for solving the current parameter measurement problems of complex fluid.The main innovation points and contributions are listed as follows:1.To overcome the problem that the conventional time of flight(TOF)measurement methods only use limited information of the ultrasonic signal and may not work effectively to meet the increasing industrial requirement,a new model-based TOF measurement method is proposed by introducing the model-fitting technique and the optimization method.In the proposed method,the multi-pulse excitation mode of the ultrasonic transducer is used to obtain higher-energy/SNR ultrasonic signal.First,zero-phase filter and independent component analysis with reference method are introduced for signal preprocessing.Then the mathematical model of the detected ultrasonic signal is established.Model-fitting of the detected signal is implemented by an improved steepest decent method to obtain the optimal TOF estimation.Finally,gas flowrate is calculated on the basis of the TOF measurements.TOF and gas flowrate measurement experiments were carried out and the experimental results verify the feasibility and effectiveness of the proposed method.For gas flowrate ranges from 5m3/h to 50m3/h,the maximum relative error and repeatability of gas flowrate measurement are 3.27%and 1.99%,respectively.For gas flowrate ranges from 50m3/h to 500m3/h,the maximum relative error and repeatability of gas flowrate measurement are 1.43%and 0.51%,respectively.2.To overcome the problem that most of the current multi-path gas flowmeters can not avoid the negative influences resulted from the non-uniform velocity field and the internal disturbance of dynamic fluid,a new hybrid dual-path ultrasonic flowrate sensor is developed by combining the transmission "Z" mode and the reflection "V"mode.In the new hybrid sensor,the "Z" mode transducer pair and the "V" mode transducer pair are constructed on two different planes,which enables ultrasonic signals to propagate through two different velocity profiles,so more information concerning the flow velocity distribution and the dynamic characteristics offluid can be obtained.Meanwhile,research on seeking signal filtering and optimization strategy which is suitable for the hybrid sensor is also carried out based on the previous model-based idea.A new model-based TOF measurement method is proposed by introducing the Butterworth bandpass filter and the hybrid Gauss-Newton structured BFGS algorithm.With the hybrid sensor and the TOF measurement method,a new model-based hybrid ultrasonic gas flowmeter prototype is developed.Dynamic gas flowrate measurement experiments were carried out.Results show that the development of the hybrid ultrasonic sensor is successful and the new hybrid flowrate sensor has better measurement performance than those of the single-mode sensors.For the common flowrate ranges from 50m3/h to 500 m3/h,the maximum relative error and the repeatability of gas flowrate measurement without calibration are 1.80%and 0.38%,respectively.3.To overcome the drawback of capacitively coupled electrical resistance tomography(CCERT)in measuring gas-liquid two-phase stratified flow,ultrasonic technique is introduced to gas-liquid two-phase flow CCERT measurement system.Based on the ultrasonic technique,a measurement model of the phase interface of gas-liquid two-phase stratified flow is established and the influence of transducer installation angle on measurement is investigated to choose a suitable angle.A new contactless fused sensor which combines ultrasonic technique and CCERT is developed.The accurate position information of phase interphase obtained by ultrasonic technique is used to compensate for the missing interphase information in the CCERT image of gas-liquid two-phase stratified flow,which can improve the accuracy of the phase distribution imaging and the consequent flow monitor and parameter measurement.Static measurement experiments of typical flow regimes of gas-liquid two-phase flow(stratified flow,annular flow,slug flow and bubble flow)were carried out and the effectiveness of using ultrasonic technique to improve the measurement performance of gas-liquid two-phase flow CCERT system is verified,by comparing the reconstructed images and void fraction measurement results obtained before and after introducing ultrasonic technique.For gas flowrate measurement problem,this dissertation seeks new solutions from two aspects of ultrasonic gas flowmeters:signal processing and sensor design.On the one hand,new model-based TOF measurement methods are proposed by introducing the model-fitting technique and optimization methods,to improve the measurement accuracy and stability of TOF and gas flowrate.On the other hand,by combining the advantages of two different acoustic path arrangement modes(the "Z"mode and the "V" mode),a new hybrid sensor structure for ultrasonic flowmeters is proposed,offering a new approach of overcoming the negative influences of non-uniform flow velocity field and internal fluid disturbance.Besides,as an extention research,ultrasonic technique is introduced to the current CCERT system for parameter measurement of gas-liquid two-phase flow.By developing the phase interphase measurement model of the two-phase stratified flow with ultrasonic technique,the missing information of CCERT system in measuring stratified flow is compensated and the parameter measurement accuracy of the whole system is improved.