Aerodynamic Noise Analysis And Optimization Design Of Nozzle Of Outer Blowing Device Of Guardrail

The guardrail board made by splicing plates with corrugated shapes,has excellent crash resistance and absorption performance,and is widely used on highways.However,during the production of guardrail boards by a steel pipe factory,the process of blowing out excess zinc particles on the surface of the guardrail board by the nozzle of the external blowing device will generate strong noise,which will seriously affect the physical and mental health of the workers in the workshop.Therefore,in view of this problem,this paper conducts a noise simulation analysis on the original model of the nozzle of the external blowing device,and on this basis the nozzle is optimally designed to reduce its noise to meet the requirements of the steel pipe plant.First,taking the original nozzle model as the research object,a calculation model is established.The standard k-ε turbulence model and large eddy simulation are used to perform steady-state calculation and transient calculation on the nozzle.Based on the steady-state calculation,the distribution of the noise sound pressure level of the nozzle and the surface of the guardrail plate is calculated when using the broadband noise source model without guardboard and with guardrail board;based on the transient calculation,the inside and outside of the nozzle without guardboard and guardrail board were analyzed.The changes of velocity,dynamic pressure and vorticity in the flow field,and then combined with the FW-H equation,the spatial directivity and spectral characteristics of the noise at each point of the nozzle with and without guardrail plates are analyzed.Finally,the circumferential vorticity distribution of the nozzle outlet is analyzed,and the main reason for the largest noise sound pressure level at the nozzle outlet is found,which provides a direction for the optimization of the noise reduction of the nozzle.Secondly,starting from the nozzle outlet,the structure is optimized.Taking the working condition of the guardrail board just entering the nozzle as the research object,blind slope treatment is performed on the inclined surface of the outlet of the nozzle core mold,and the influence of the hole shape,hole area and hole depth on the nozzle noise is explored.It is found that the nozzle noise of the cylindrical hole,10%opening area,and 3mm opening depth is the lowest,which is 28.4dB lower than the original guardrail board just entering the nozzle working condition,and the reduction is about 24.3%.Finally,based on the program of cylindrical holes,10%opening area,and 3mm opening depth,a physical model is established,and aerodynamic noise experiments are carried out in the outside blowing workshop,and the final optimized working conditions and the points where the original guardrail just enters the nozzle working conditions are analyzed.The spatial directivity and spectral characteristics of the noise are compared with the simulation under the same working conditions,which verifies the accuracy of the simulation and provides an important basis for further noise reduction analysis of the nozzle.