| In the modern medical field,the powder atomizer is a medical device used in the treatment of respiratory diseases.It can produce uniform powder fog(aerosol)and directly reach the affected area through the patient's breathing.At present,the structure of the compressed atomizer is simple,powder is added at one time,and air flow can not be adjusted which results in that the concentration of powder is not adjustable,and the existing device has no on-line detection function.So that it can not effectively change the dose according to the requirements of the dose and adjust the concentration of powder,so the treatment effect is not ideal,and even makes patients with discomfort.Therefore,it is of great theoretical and practical value to study the application of powder aerosol particle concentration detection sensor and its application in powder atomizer.This paper combined with the current charge method to measure the concentration of gas particles with high sensitivity,simple structure and so on.The electrostatic sensor based on non-contact structure detecting the concentration of gas particles does not interfere with the flow field,only respond to the flow of particles,but the detection signal is weak and susceptible to interference.So the paper developed a ring-type electrostatic induction sensor which is applicable to dechect solid phase concentration parameter in powder aerosol.It can be used in the atomizer to detect the concentration of the powder in real time.And the instrument can change amount of powder and airflow rate to improve reliability and curative effect.So it has great application prospect.The main research work and results include:Firstly,this paper researches the method of detecting parameters in gas-solid two phase flow based on ectrostatic induction.The ring electrode is chosen as the structure of the electrostatic induction sensor,It calculats and analyzese and the mathematical model of the uniform dispersion flow of the ring electrostatic induction sensor.It analyzes the factors affecting dynamic inspection with powder concentration of aerosol particles based on mathematical model.Secondly,it designs the structure of sensor based on the principle of electrostatic induction sensor.And it conducts the 3D finite element simulation model in COMSOL MULTIPHYSICS.It carries out the simulation of single factor analysis with different radius of PVC insulation tube,length and thickness of induced electrode,length and radius of shield.The simulation results show that the sensor has lager senstivity with lager length and thickness of induced electrode,smaller radius of PVC insulation tube,larger length and radius of shield.And it prefers the structure parameters of the sensor.Electrode axial length and radial thickness were taken 5mm and 3mm,PVC insulated tube radius of 10 mm is better,and the wall is 0.5mm.Thirdly,the paper designs the signal processing circuit of good anti-interference ability for ring-type electrostatic induction sensor.It also designs a concentration test device.The device uses LABVIEW as main control software and it realizes the function of sampling,computing and recording for the signal of ring-type electrostatic induction sensor by the data acquisition card.Establishing multivariate linear regression equation based on rate of flow,signal root mean square,skewness and kurtosis by performance test and data analysis.The relative error ia between-4.4% and 4.8% when the flow rate is between 5 L/min and 17L/min.So it meets the requirements of ±10% of the detection accuracy.Lastly,this paper carrys out application experiment for ring-type electrostatic induction sensor in atomizer.It performs experimental analysis for optimals atomizing time,performance of flow regulation and performance of concentration regulation.The result shows that the optimal atomizing time is 6s after atoming starts;when the relative error is less than 5%,the flow adjustment time is within 5 ~ 10s;the relative error of detecting concentration and standard deployment of concentration is below ±5.8%.It can meet the design requirement. |
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