Design and experiment of gear-shaped diesel offgas particulate filter based on resistance

Abstract: Micron wood fiber is a kind of porous biological materials that can be applied to filter PM emitted by diesel engine. In this paper in order to increase the filtration area and decrease filtration resistance, a wood fiber filter, of which the internal structure was hollow and external structure like gear was developed, the advantages of which were low price, less requirement for diesel quality and large adsorption capacity for PM. In these respects, the gear-shaped wood fiber filter was promising in developing countries where the sulphur content was high in diesel oil. This gear-shaped wood fiber filter can be installed in a detachable DPF case where the temperature inside can be controlled below 220℃ and after reaching the end of its estimated useful lifetime it can be replaced easily. First of all, the pressure loss and structural parameters model of the diesel particulate filter (DPF) based on resistance were built. Referring to the existing research and empirical formula, the filtration resistance of the gear-shaped filters can be expressed by theoretical formula about tooth height, nominal pressure angle and the filter thickness. By analyzing through software Matlab, the tooth height, filter thickness and nominal pressure angle can be obtained. Furthermore, the tooth thickness and the teeth number can be obtained by some mathematic formula about gear. Then the optimal size of the gear-shaped wood fiber filter was figured out by numerical calculation and analysis. Lastly, the resistance changes of the gear-shaped wood fiber filter with different structural parameters were analyzed by the engine bench. In the test, we developed 8 gear-shaped filters with different structure parameters according to the simulation results and set the speed and the load of the engine kept at 2 200 r/min and 50%. The test results showed that when the diameter and height of the DPF case was 140 and 150 mm respectively, the parameters of the filter, whose tooth thickness was 23.27 mm, tooth height 30 mm, nominal pressure angle 5°, filter thickness 7 mm, teeth number 8 were optimal. This filter had the lowest filtration resistance and increase rate of back pressure, the longest lifetime and the best structure stability. Meanwhile, some other filters whose structural parameters were in the optimal range of parameters also had better filtration performance than those of the rest. According to the test results, it can be known that when the parameters remained in the optimal range, the filtration performances were better and their differences were very small. Furthermore, their filtration efficiency was over 90% and the lifetime was about 90 hours. However, when the parameters were out optimal range, the filtration performances of the gear-shaped wood fiber filter get worse apparently, which definitely proves the reliability and the optimum of the structure parameters of the gear-shaped filter researched in this paper. Above all, the gear-shaped wood fiber filter researched here are low price, less requirement for diesel quality, low filtration resistance, high filtration efficiency, large adsorption capacity and easy to recycle after used. It can filter PM emitted by diesel engine efficiently by combining with temperature control device, which has a reference for environmental protection and purifying diesel exhaust.