In order to ensure the safe, efficient and low-noise operation of the Roots blower, this paper is based on a preliminary design of an air filter and muffler integrated device including an air filter and an air intake muffler. The FEM method and CFD method are used to numerically simulate its acoustic performance and aerodynamic performance. Taking the transmission loss and pressure loss at the inlet airflow velocity of 21m/s as the optimization goals, under the premise of without changing its external dimensions, the main internal structural parameters such as filter element thickness, insertion method of intubation, diameter of perforated pipe, and effective perforation length are optimized by orthogonal test design method. The sequence of structural factors that affect the overall performance of the air filter and muffler integrated device is obtained, and the optimal combination of main structural parameters is determined. Based on the optimal model obtained by the orthogonal test, the design of the length of the intubation of the air filter and muffler integrated device is optimized to obtain the best combination plan. The results show that the structural parameters are optimized through orthogonal tests, the overall performance of the air filter and muffler integrated device after optimization is significantly improved, the amount of overall noise reduction is increased by 18% , and the pressure loss is reduced by 20% on average compared with the original model.
In order to solve the problem of low heat transfer performance of helical tube under the condition of one-sided heating, twisted tapes in helical tube were built, and the enhanced heat transfer characteristics of the helical tube with twisted tapes were studied through numerical simulation. The result shows: The twisted tapes cause the gas in the helical tube to generate swirling flows in different directions, and divide the gas in the helical tube into different regions, and each region generates a vortex. The twisted tapes increase the gas friction coefficient and Nusselt number in the helical tube, and the helical tube with double twisted tapes has the largest gas friction coefficient and Nusselt number corresponding to the same Re number. Under low Re number, the performance evaluation criteria of the helical tube with double twisted tape are higher than that of the single twisted tape, but when the Re number is greater than 14,500, the performance evaluation criteria of the helical tube with single twisted tape is higher. After the twisted tapes were built in, the gas temperature in the helical tube rises. At low Re number, the gas temperature rise in the helical tube with double twisted tape is the highest. When the Re number is greater than 18500, the gas temperature rise in the helical tube with single twisted tape is the highest.
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