Research On The Gap Sealing Characteristics Of Positive Pressure Respiratory Protective Devices

Since the emergence of the COVID-19,about 260 million people worldwide have been infected with the virus,and more than 5 million people have died.Up till now,the virus continues to spread and poses a serious threat to people’s lives.People’s infection of COVID-19 is often caused by equipment protection failure.Aiming at this phenomenon,this paper takes positive pressure respiratory protection device as the research object,especially in the respiratory cavity formed by the respiratory mask and face.Through the process of gas inflow and outflow,we explore the forming conditions of positive pressure in the respiratory cavity and the main factors affecting the pressure change.At the same time,the change of the gas flow state will affect the convection heat exchange efficiency of the airflow,resulting in the heat cannot be released and affecting the thermal comfort of the user.The characteristics of changes in the respiratory cavity environment were studied by the combination of theoretical modeling,numerical simulation and experiment,which was verified by comparison with the experiment at the same time,to ensure the safety and comfort of the device.First,the relevant parameters that affect the pressure change in the breathing cavity and perform modeling,and establish a breathing model under moderate labor intensity and establish a gas leakage model of the breathing cavity based on actual working conditions,and obtain the relationship between the size of the sealing gap and the pressure drop.The curve provides a theoretical basis for the subsequent flow field simulation of the device.Secondly,the finite element analysis software Fluent is used to study the pressure characteristics in the breathing cavity,simplify the facial contours to establish a simple model flow field,and simulate the two working conditions with or without respiratory disturbance.When the air intake does not change,the exploration is The pressure changes in the breathing cavity under different sizes of the sealing gaps,and then using different sizes and numbers of air intake holes as research variables,observe the pressure changes under different sealing gap sizes,through quantitative analysis,find out the main factors that affect the pressure change in the respiratory cavity and the law of change,and at the same time,combine the retention of carbon dioxide in the respiratory cavity to find the comprehensive optimal parameter range.Then,the temperature field changes are analyzed without changing the model,and the comprehensive optimal structural parameters are determined by combining the pressure changes and the carbon dioxide retention amount.Based on these parameters,the modified flow field model is established after the facial contour is added,to explore the effects of different environmental temperatures and air supply volumes on the thermal comfort of the human body.Finally,the positive pressure respiratory protection device was manufactured and a data acquisition platform was built for human wearing experiments to test the pressure and temperature in the respiratory cavity.The obtained experimental curve was compared with the simulation results to verify the safety and thermal comfort of the positive pressure protective device,which laid a foundation for the performance optimization of the protective device.