Research On CFD Simulation And Denoise Of The Leaf Vacuum Integrated With Blowing And Inhaling

The leaf vacuum integrated with blowing and inhaling often works with high working noise, which brings side effects to user’s comfort and health. However researches on denoise of the leaf vacuum are rare, most companies rely on copying, experience and experiments during designing. This results in high cost but low efficiency. In this paper, the CFD(Computational Fluid Dynamics) simulation method would be integrated into the optimal design of leaf vacuum. Some parts and flow channel of leaf vacuum are optimized in order to reduce the working noise as well as improve aerodynamic performance.Firstly, five parameters-the inlet flowrate and static pressure during inhaling, the oulet flowrate during blowing as well as sound pressure in both conditions are selected to be optimized by analyzing the structure of leaf vacuum. Before the simulation model of leaf vacuum with both blowing and inhaling condition is made, some parts are simplified, the flow channel is extracted, proper meshing method and solving method are adopted. Then the static flow simulation of leaf vacuum is done. The irrational design of volute outlet due to vortexes leads to more flow losses and higher noise. What’s more, the plain tongue’s bad performance in flow diversion results in backflow around the tongue when blowing. The static flow simulation results offer guidance for structure optimization.Secondly, considering higher computational precision and computer property, the LES model and FW-H model are combined to calculate the noise in two working conditions. Since the rotational noise in the bands of base frequency and multiple frequency are obviously higher than other bands, the discrete noise counts the most in the aerodynamic noise of leaf vacuum.Again, measuring the five parameters above according to the aerodynamic and noise measurement standards, and analyzing the noise signal and vibration signal. The simulation model is verified by comparing the results of experiments and simulation.Finally, taking the number of blades, hub ratio and outlet angle as structure optimization objectives, and optimizing the impeller by using orthogonal experiment method. What’s more, the flow channel and volute tongue are optimized under the guidance of flow field simulation results. By adopting arc linking structure in volute outlet, rounded volute tongue and push-pull switching operation, the collision between air and wall is eased, the leakage is reduced and the aerodynamic performance is enhanced too. There’s a good balance between higher aerodynamic performance and lower noise when the radius of volute tongue equals 4.3mm. The leaf vacuum’s speed is reduced by 2000rpm according to the similarity law. In this way, the blowing noise is reduced significantly, the aerodynamic performance is improved, thus satisfying the optimization requirement.