| Mechanical ventilation cooling towers are widely used in various industry fields due to their effective cooling effect,convenient loading and unloading,and small land occupation.At the same time,mechanical cooling towers will also be installed in large shopping malls,residential areas and other places as the refrigeration equipment;Due to the excessive aerodynamic noise generated during the operation of mechanical cooling towers,the demand for low-noise,high-performance mechanical ventilation cooling towers is increasing.In order to reduce the noise generated by the operation of the cooling tower,optimization analysis can be conducted by changing the blade parameters or geometric configuration of the cylinder.In order to conduct the active noise reduction of cooling towers,a parameter optimization model method is proposed to investigate the effect of the blade parameters on the aerodynamic noise of counterflow cooling towers.Then the acoustic analogy method is adopted to estimate the noise of the standard monitoring points,in this way to achieve the purpose for efficient simulation and optimization of counterflow cooling tower noise.The main content of this thesis is as following.The numerical modeling of the blades for the CFD(Computational Fluid Dynamics)simulation analysis of the cooling tower was conducted for the LC-36525 C type counterflow cooling tower.The blades are the key elements to generate noise during the operation of the cooling tower.First the software Vista AFD is adopted to integrate with Blade Gen for modeling the blades,which includes the refined design of the airfoil,installation angle,thickness,and leading and trailing edges.Based on the analyzing and comparing results from the various CFD simulation algorithms in the estimation of the aerodynamic noise of cooling towers,the broadband noise and acoustic analogy models are selected for simulation analysis of cooling tower aerodynamic noise.By comparing the results of aerodynamic noise from CFD simulation with those measured results for the LC-36525 C type counterflow cooling tower,the effectiveness of CFD numerical simulation model selection and the correctness of simulation results are verified.Combined with the broadband noise method,CFD simulation with RANS model,namely Reynold-Averaged Navier-Stokes(RANS),was adopted to analyze the aerodynamic performance of the cooling tower and analyze the sound power of the aerodynamic noise.Parameterized analysis was conducted on the aerodynamic performance of the cooling tower by changing five working cases: different positions of installed blades,different number of blades,blade installation angle,rotational speed,and leading edge curvature.Various parameters were selected to analyze their effect on the aerodynamic performance of the cooling tower.The parameters that have more important effect on the aerodynamic noise of the cooling tower were selected for subsequent analysis on the noise or sound pressure level noise at relevant measurement points for the cooling tower.Using a combination of large eddy simulation algorithm and acoustic analogy model,CFD simulation on the aerodynamic noise was conducted on the counterflow mechanical ventilation cooling tower.The distribution of aerodynamic noise at the relevant standard measurement points of the cooling tower in various frequency bands was analyzed.The variation in the sound pressure level and the noise spectrum of the monitoring points of the cooling tower under different blade positions,blade speeds,blade numbers,and other operating conditions were studied and analyzed.The sound pressure level of each measurement point was compared. |
