Research On Flow Measurement Of Wet Gas Based On Fluctuating Pressure Measurement And Convection Characteristics Of Vortex Street

Wet gas(mist flow)is an important typical flow pattern in the field of industrial production.And the on-line measurement accuracy of its key parameters is of great significance to control process optimization,energy conservation and production safety assurance.Based on Carmen vortex street principle,the vortex flowmeter is widely used in petroleum,chemical,power and other industries due to its simple structure,wide range of measurement and stability.However,in the application in mist flow,it is difficult to achieve the accurate measurement of the internal flow field and the separated phase flow.In order to analyze the properties of the vortex street,the stability and convection characteristics of the vortex street flow field in mist flow are measured and studied in this paper.The main research contents are as follows:1.Design and optimization of silicon piezoresistive pressure sensor with microstructure and high frequency response.Through literature research,the wall pressure measurement method is introduced into the measurement of vortex street flow field.The silicon piezoresistive sensor is selected to design pressure sensor.Then the design and optimization of probe and processing circuit of pressure sensor are completed.Finally,the static calibration and dynamic testing of the pressure sensor are carried out.The calculation results show that the overall performance of the sensor reaches 0.25%FS.2.Design and optimization of vortex flow measurement system based on micro high frequency response pressure sensor.The vortex street measurement system is proposed based on the designed pressure sensor.The circumferential and axial measurement positions are optimized by theoretical analysis and experiment validation.The experiment is carried out on the mist flow apparatus to test the effect of the measurement system.The characteristics of the signal of each position are analyzed in time and frequency domains.According to the analysis of signal amplitude and signal-to-noise ratio,the optimal measurement position of wall pressure is validated.3.Stability analysis of vortex flow field based on non-linear recursive and correlation analysis.The characteristics of the vortex street flow field in mist flow are analyzed by non-linear recursive analysis method.Then the evolutionary of recurrent graphs under different conditions is displayed visually,which shows the stability variation of vortex street signal.The main factors causing the symmetry reduction of the vortex street are analyzed through the the correlation coefficient quantitatively.The results indicate that under the same working conditions,the vortex street stability is positively related with the gas pressure while negatively related with the liquid mass loading.4.Separated phase flow measurement of vortex street in mist flow based on correlation velocity measurement.The correlation coefficient and correlation velocity measurement of the vortex street signals under various working conditions are calculated.And the convection characteristics of the vortex street flow field in the mist flow are analyzed.Based on the experimental data under different working conditions and the results of the correlation calculation method,the prediction models of the separated phase flow in the vortex street of the mist flow are established.Finally,the prediction effect of the models are validated and analyzed,which indicates that the relative errors of gas phase and liquid phase parameters of the prediction models are both within ±5% respectively.