Research On The Method Of Focusing The Little Single Gas Particle

Infectious disease is a kind of disease which can intersect between animals and animals,human and human and between humans and animals.In recent years,with the imbalance of natural conditions such as climate,unbalanced socio-economic development,the continuous expansion of human life,and the accelerating development of global integration,infectious diseases pose a more serious threat to humans: the outbreak of the SARS,bird flu and the Ebola virus in recent years have made real-time detection work of epidemics particularly important.The spread of aerosol state of infectious bacteria is a major mode of spread and infection,and can be rapidly transmitted through air,water and other media.Bioaerosols affect the human production activities,living environment and quality of life all the time.50% of the bioaerosols will remain on the lung wall after humans inhale them and harmful substances contained in it will have adverse affects on the human body.After a certain amount of aerosol enters the body,it can easily cause pneumonia,asthma,bronchitis,emphysema,or even lung cancer.Therefore,early identification,rapid diagnosis,reasonable prevention and control methods for aerosol status of infectious diseases are necessary.The pathogen detection method in the laboratory needs to be sampled on the spot first and then the sample is detected by means of microbiological detection.They are mainly divided into molecular biology methods,isolation-culture methods and serological methods.These three bioassay methods have high detection sensitivity,strong specificity and inherent biological detection advantages,but have certain drawbacks.First of all.Sampling work is time consuming and it is difficult to meet the needs of real-time detection of biological aerosols.Second,samples collected in complex environments will increase the difficulty of purification.Because the accuracy of laboratory pathogen detection technology depends on the quality of the collected samples,it is complicated.Sampling in the environment will reduce the accuracy of the test.Third,laboratory pathogen detection techniques need to be completed by professional scientific researches and it is difficult to use them widely.The single-particle based bioaerosol detection system is different from the conventional detection method in that the physical characteristics and biological activity of the measured particles can be instantaneously monitored without changing the physicochemical properties of the bioaerosol particles.The principle is that under the action of the fan power source,the sample is wrapped with monodisperse particles in a stable air flow and the light spot crossing one by one under the confinement of the chamber structure is passed through the characterization.The elastic scattering light of the physical properties of the marking particles and the endogenous fluorescence of the biological characteristics are used to determine whether the particles are biological particles.It has the advantage that it not only do not damaging the particle's activity but also has fast detection speed.It is portable as well.Therefore,scientific research workers in various countries have spent a lot of manpower and material resources to conduct research on this technology,so that the relevant technology continues to progress and equipment continues to improve.Due to technical and theoretical limitations,the technology has not yet formed a mature theoretical system,and the relevant experimental platform is relatively rough.As a result,there has ample room for this technology to development.Bioaerosol detection system based on single particle technology is mainly divided into three parts: optical path,circuit and gas path.This study mainly focuses on the gas path of the system.The gas path section mainly includes the nozzle,the chamber itself and the outlet needle.In this study,analogous to the hydrodynamic focusing structure of the flow cytometer,a sheath flow inlet is added to the original structure of the chamber and clean air is used to wrap the sample flow and change the nozzle shape and outlet needle length.Outlet flow rate(1.00L/min,2.00L/min,2.83L/min,5.00L/min,10.00L/min)and the flow rate(Vsample=9.0m/s,Vsheath=3.0m/s,Vsample=9.0m/s,Vsheath=4.5m/s,Vsample=9.0m/s,Vsheath=1.4m/s,Vsample=9.0m/s,Vsheath=0)are also arranged to achieve improving the purpose of confining sample flow in the chamber.The method of this research is to carry on the simulation experiment to the diffident experimental parameters of the design at first.Firstly,the solidworks software was used to draw the model structure diagrams of each experiment according to the experimental design.Then the ICEMCFD software was used to mesh the model structure diagrams.Then the finite element iteration calculation of the grid structure diagrams was performed using ANSYS Fluent14.5 software.Visually revealing the flow trajectory of the sample flow in each experimental chamber and then performing post-processing on the results of the iteration and finally verifying the prototype experiment based on the results of experiments.According to the results of the simulation experiment and the prototype experiment,the sample flow velocity is 9.0m/s,the sheath flow velocity is 1.4m/s,the flow rate is 2.83L/min,the round nozzle and the long outlet needle of the condition has the best focus effect.Prototype experiments demonstrate the effectiveness of the simulation experiments and the CV obtained is 11.67.The study has improved the confinement ability of the chamber structure on the sample flow warpped by the bioaerosol.It also improved the accuracy of the system detection and has important reference value for the optimization of the bioaerosol detection system based on the single particle principle.