Research On The Performance Of Air Purifier Filters

PM2.5 has attracted extensive attention from countries all over the world due to its great harm to the human respiratory tract and its difficulty in removal.PM2.5 pollutants in the outdoor atmosphere can enter the indoor environment in various ways,and the use of filter air purifiers has become an effective measure to remove indoor PM2.5 and maintain indoor air quality.Based on the basic principle of filtering particulate matter by the filter screen,this thesis analyzes the influence of the relevant parameters of the filter fiber on the filtration efficiency and filtration resistance of the air purifier through a microscopic analysis,and explores the key technology to improve the purification efficiency of the filter air purifier.The main research contents of this thesis are as follows:Filtration of particulate matter by fibers is a very complex process.By simplifying the whole filtration process and using the isolated cylinder theory,the influencing factors of the filtration efficiency of the filter screen are analyzed,and the expressions of the total efficiency and pressure drop of the filter screen are given.Filtration efficiency and filtration resistance are two contradictory quantities,and one parameter cannot be used to measure the performance of the filter.Therefore,this thesis proposes the concept of filter quality factor.The quality factor can be used to characterize the performance of the filter screen.The filter screen is formed by stacking filamentous fibers.This thesis analyzes from a microscopic point of view,and establishes a single-fiber cylinder model according to the isolated cylinder theory.The effects of inlet flow rate,particle diameter,filter filling rate and fiber diameter on the filtration pressure drop,filtration efficiency and quality factor of the single-fiber filter screen were simulated.When the inlet air velocity of the filter screen is 2m/s,the quality factor of the filter screen is the largest;When the particle diameter is less than 5μm,the particle filtration efficiency increases rapidly with the increase of the particle diameter.When the particle diameter is greater than 5 μm,the larger the particle diameter increases,the smaller the improvement of the particle filtration efficiency;as the filling rate of the filter screen increases,the filtration pressure drop and filtration efficiency of the filter screen increase.When the filter screen filling rate is 10%,the quality factor of the filter screen is the largest;When the fiber diameter is 10μm,the quality factor of the filter screen is the largest.The variation laws of filter pressure drop and filtration efficiency of three kinds of fibers with elliptical,triangular and rectangular sections under different structural parameters are analyzed,such as the long short axis ratio of elliptical section fiber,the vertex angle degree of triangular section fiber and the length width ratio of rectangular section fiber.At the same time,the variation laws of filter pressure drop and filtration efficiency of different shape fibers under different inclination angles are analyzed.The larger the ratio of long axis to short axis of oval section,the greater the pressure drop of filter screen,the greater the filtration efficiency of particulate matter and the smaller the quality factor;When the inclination angle of oval section is 90°,the filtration efficiency is the highest and the quality factor of filter screen is the largest;When the top angle of triangular section is 60°,the quality factor of filter screen is the largest;When the inclination angle of the triangle is 60°,the quality factor of the filter screen is the largest;When the inclination angle of rectangular fiber is 45°,the quality factor of filter screen is the largest;When the aspect ratio of rectangular fiber is 1,that is,the quality factor of square fiber is the largest.Using the three-dimensional multi fiber model,the variation laws of filter screen pressure drop and filtration efficiency are analyzed when the filter screen is arranged in sequence,cross arrangement and vertical arrangement.The pressure drop difference of the filter screen under the three arrangement modes is very small,and increases with the increase of inlet wind speed and filter screen filling rate;The cross arranged filter screen has the maximum quality factor when the filter screen filling rate is 10%;Among the three permutations,the cross permutation has the highest filtering efficiency and the sequential permutation has the lowest efficiency,It is suggested that the fibers should be arranged in a cross arrangement.