As a gas pressurization and transportation equipment, roots blower is widely used in coal, chemical, aquaculture, sewage treatment and other industries. In the case of positive pressure air supply, the aerodynamic noise radiated by the inlet part aggravates the environmental pollution, and at the same time, the imported air quality seriously affects the safe operation of the roots blower.
The design of high-performance air filter and intake fan silencer is an effective way to improve the air quality of roots blower inlet and reduce inlet noise. In order to ensure the safe, efficient and low-noise operation of the roots blower, a set of integrated filtration and silencing device was numerically simulated by the acoustic finite element method that is in good agreement with the experimental results, and the aerodynamic performance was numerically simulated by computational fluid dynamics method to obtain the transmission loss, pressure loss and flow field distribution characteristics, and the acoustic performance and aerodynamic performance of the integrated filtration and silencing device were comprehensively considered, and the main structural parameters were optimized and improved by orthogonal experimental design method. The main research contents and conclusions are as follows:
By comparing the numerical simulation results of the silencing performance of a single silencing element, a simple silencing element in series and the integrated filter and silencing device, it is proved that the integrated filter and silencing device has better broadband silencing effect and is more compact in structure. Then, the effects of structural parameters such as the presence or absence of filter element, the thickness of the filter element, the position of the filter element, the flow resistance of the filter element, the insertion mode of the inner insertion tube, the length of the effective perforated section, the diameter of the perforated pipe and the perforation rate on the silencing performance and resistance characteristics of the integrated filter and silencing device were analyzed. The filter element can greatly improve the overall noise reduction performance of the integrated filtration and silencing device, especially in the high-frequency noise range, but it also produces a large pressure loss;
With the increase of the thickness of the filter element, the transfer loss and pressure loss both increased. The influence of the filter element position on the transfer loss and pressure loss is small; With the increase of the flow resistance of the filter element, the transfer loss increases. The insertion of the inner cannula on both sides can improve the transmission loss when the pressure loss is not significant; The length of the effective perforation section has a significant effect on the transmission loss, and the length of the effective perforation section corresponds to different resonance frequencies, which has little effect on the pressure loss. When the diameter of the perforated pipe is the same as that of the outlet pipe, there is a higher transmission loss and a smaller increase in pressure loss. The perforation rate has little effect on the transmission loss and pressure loss of the integrated filtration and silencing device.
Taking the transmission loss and the pressure loss at the inlet airflow velocity of 21 m s as the optimization objectives, the orthogonal experimental design method was used to determine the optimal combination of four structural parameters, namely the thickness of the filter element, the insertion mode of the inner insertion tube, the length of the effective perforated section and the diameter of the perforated pipe, and the length of the inner cannula was improved based on the resulting optimization model, and the optimal combination scheme was obtained, and the performance of the integrated filtration and silencing device before and after optimization was compared by numerical analysis. The results show that the optimization not only improves the acoustic performance in the whole frequency band, but also optimizes the drag characteristics, and the overall acoustic reduction is increased by 18% and the pressure loss is reduced by 20% on average compared with the initial model, and the comprehensive performance is significantly improved.
Through the optimization of the design and structural parameters of the integrated filtration and silencing device, while ensuring the air quality of the inlet of the roots blower, the noise reduction effect is improved, the flow loss is reduced, and the comprehensive performance of the integrated filtration and silencing device is significantly improved, which can provide a reference for the design and optimization of the air intake and silencing system in the project.