Prediction and control of the vibration radiation noise of a multifunctional straw kneading machine shell

Multifunctional straw kneading machines experience significant issues, such as severe shell vibrations and considerable radiated noise during operation. To accurately predict and control the vibration and radiated noise of the machine shell during the design phase, a thorough analysis and calculation of the excitation sources were conducted. These sources include the pulsating pressure on the casing caused by the internal coupled flow field and the unbalanced dynamic force of the rotor system. A vibration response analysis of the kneading machine shell was carried out, and the results were utilized to determine acoustic boundary conditions. The acoustic transfer vector and modal acoustic transfer vector methods were applied to forecast the vibration radiation noise emitted from the shell numerically. The precision of this noise prediction model and methodology was confirmed through experimental noise measurements, and the influence of each excitation source on the vibration radiation noise of the shell is discussed. The panel acoustic contribution analysis approach was used to optimize the structural design of the kneading machine shell to effectively manage and reduce vibration and radiated noise. The results show that both the numerically predicted and experimentally measured sound pressure levels (SPLs) exhibit consistent trends, with the peak SPL frequencies closely aligned. The maximum discrepancy between the simulated and measured total SPL was 2.42 dB(A), validating the accuracy of the vibration radiation noise prediction model. Following structural modifications, significant reductions in the surface vibration velocity, radiation noise frequency band SPL, and total SPL of the machine shell were observed. The total sound pressure level at the measuring points in front of the pulley, the lower discharge outlet, and the upper discharge outlet are below the 90 dB(A) threshold specified by the national standard. The research findings offer valuable insights into the effective design and noise control of low-vibration radiation noise in similar machinery.