Study On The Dust Standard Sample Of Testing And Evaluating Filtration Performance

From the 1930 s, in order to reduce the inhaled amount of dust particles of an internal combustion engine, the application of intake air filter device on the engine had gradually been promoted. Until 1940, SAE journal proposed to prepare a standard test dust to evaluate the performance of the air filter. Currently, the test dust used more at home and abroad mainly is ISO 12103 A2 fine dust or A4 coarse dust produced by the Arizona sand, and Chinese test dust is mainly dependent on American imports, expensive and long delivery. In recent years, as the global economy developing, Chinese auto industry has been rapid development, while stimulates the market demand of parts, and filter industry is one typical example. Filters are wearing parts, and should be changed regularly. Testing filter will need to use the standard test dust. Therefore, localization of the standard test dust is existing market potential, but also to promote the development of China’s auto industry.In this paper, firstly, referring the American A2 standard test dust, the North typical clay was raw material, and the experiment analyzed the feasibility of Chinese clay replacing Arizona sand to prepare standard test dust, through physical and chemical properties research of the clay loss on ignition, thermogravimetry, chemical composition, color difference, grindability, and morphology. Secondly, the mechanical impact mill, vortex mill and vibration mill of the three different grinding equipment were applied to process preprocessing clay, and through the analysis of grinding results, the best crushing equipment and crushing parameters were chosen to produce coarse, medium and fine powder of the three different particle size distribution. Then, regarding particle size distribution of the American A2 test dust as the goal, using the "Visual Basic for Applications" language writing fitting simulation software of particle size distribution, with the Excel powerful data processing capabilities, fitted out the best mixing ratio of three powder, through error analysis. By suitable mixer, according to the proportion for mixing uniformly, particle size distribution of the mixed material closest with the American A2 dust, minimum deviation was taken as objective to determine the best mixing time. Finally, comparison analysis for detecting air cleaner filter performance by the mixed dust and American A2 dust, confirmed the feasibility of mixed dust instead of American A2 dust.The results showed that:(1)Loss on ignition deviation of clay calcined 6h at 200℃ and American standard dust was about 1%. The chemical composition is within the requirements of the American dust, and the color difference of the both was the smallest. Morphologies of both were irregular shape. In summary, Chinese clay replacing the American sand to prepare standard dust was feasible.(2)By detecting the particle size distribution of the grinding sample, there was a find that mechanical impact mill and vortex mill could not reach the crushing requires at their most crushing capacity, and the fineness of the sample was too large compared with the American dust. However, Vibration mill would grind better over time, and final test showed that vibration mill could be used as a suitable grinding equipment, and sample of vibration mill grinding 30 min used as coarse dust, grinding 40 min as medium dust, grinding 60 min as fine dust would mix at a next step.(3)The appropriate language written in Excel’s "Visual Basic for Applications" could calculate the theoretical smallest difference between American dust and mixed dust, and the best mixed proportion of the sample is: medium dust: fine dust=0.22:0.78. By v-type mixer uniformly mixing materials by the best ratio fitted, the samples of mixing different times were detected and analyzed to determine the extent of uniform mixing. The results showed that the optimal mixing time was 50 min, most uniform mixed at the time, and the difference of particle size distribution with the American dust is smallest.(4)The difference detected of the initial arrestance, whole life arrestance, dust-holding capacity between both dust was respectively 0.26%, 0.5%, and 0.30%. The results showed that the error was within the range allowed by national standards, and homemade mixed dust replacing the American dust to detect air filter is feasible.