Research On Gas-Solid Two-Phase Flow Parameters Measurement Based On Flow Pattern And Design Of Experimental Device

The pneumatic conveying powder is a typical gas-solid two-phase flow,which has the characteristics of various flow pattern,uneven temporal and spatial distribution of flow parameters,such as velocity and concentration,is currently recognized as the industry measuring problem.Because the instantaneous signal fluctuations of the pneumatic conveying powder flow parameters are too large,it was difficult to achieve closed-loop control.Flow regime is an important parameter of gas-solid two-phase flow,which has important influence on spatio-temporal distribution of velocity and concentration.A new type of two-way eight-plate array sensor structure was proposed,and a pulverized powder mass-flow testing system was designed based on the analysis of the characteristics of the slug flow pattern,which velocity and concentration distribution are measured simultaneously;the velocity distribution of gas-solid two-phase flow was studied for the case that the velocity distribution of solid particles is inconsistent in the process of pneumatic conveying.The main works of this thesis were as follows:(1)The signal output characteristics of the array sensor plate were analyzed,the slug pattern identification method was studied,and the mass flow model of slug flow was proposed based on the novel double-layer plate array sensor structure with annular sensing electrodes.(2)In order to solve the problem of low peak finding accuracy in correlation measurement,a velocity distribution algorithm based on cross correlation velocity theory was studied based on the structure characteristics of a novel double layers plate array sensor.(3)A speed calibration experiment device with different velocity distribution at different positions in the same section was designed.The device uses three frequency converters to control three motors separately,and three V-belts are respectively controlled by three motors.The three motors are driven at different speeds,passing parallel to the sensor pipe,and placing the measured solid model on three V-belts,thus simulating the approximate velocity distribution of the fluid.(4)The system detection circuit with DSP as CPU was designed based on the analysis of the mass flow and velocity profile detection system requirements of the slug flow.In order to meet the requirement of the system signal stability,the DDS signal generation circuit based on AD9833 was used as the excitation source.In order to improve the detection system The TMS320F28335 with main frequency up to 150MHz was adopted as the main controller of the lower computer.In order to satisfy the excitation demand of the new double-layer array plate sensor,the analog switch circuit based on MAX306 and MAX352 were designed to realize the excitation Gating of the plates and grounding of the other plates.(5)Based on the development platform of Lab VIEW,the programming of the host computer software was completed,including the digital filter algorithm,the fast Fourier transform algorithm,the interpolated sampling algorithm,the cross correlation velocity measurement algorithm,the density detection algorithm,the mass flow algorithm and the velocity distribution algorithm.(6)The velocity distribution and the mass flow parameters of the dense plug flow were measured under the laboratory conditions.