Noise Analysis Of Medium-power Silent Type Diesel Generator Set And Optimization Of Its Acoustic Enclosure

Diesel engine generator sets are widely used as backup power equipment. However, noise pollution becomes serious since high noise is produced during the sets’ operation. It is necessary to develop silent diesel generator set via improving sound insulation performance for the acoustic enclosure. Base on the KV275 silent type diesel generator set, noise measurement and numerical simulation are conducted to opitimize the acoustic enclosure, aming at improving the competitiveness of products. The primary contents are as follows:First of all, numerical simulations are conducted to understand the sound transmission loss of the single plate and double plate, by the application of auto matching layer(AML) technology and boundary element method(BEM). The numerical results are in good agreement with the theoretical datas. It may be concluded that the numerical method is feasible.Then, surface sound pressure and near-field sound pressure of the KV275 silent type diesel generaor set are measured before and after the application of acoustic enclosure. Sound pressure contours for the generator set and sound transmission loss of the acoustic enclosure are determined via experimental data. It is noted that the main sources of noise in the generator set are: cooling water tank, exhaust fan and exhaust pipes, and the noise leakage occurs mainly on the top opening, bottom opening and ventilation shutters of the acoustic enclosure. The noise level is obvious at 250 Hz, 500 Hz, 630 Hz and 1000 Hz, respectively.After that, based on the CAE software, such as Hypermesh, ANSYS and Virtual.lab, the vibro-acoustic coupling analysis is performed by combining the FEM and indirect boundary element method(IBEM). The sound pressure contours and sound field information of diesel generator set are figured out under the ideal sound source excitation. Compared with the near-field sound pressure experimental results, the numerical results are well consistent. By using the established numerical model, the effects of sound absorbing material and vent structure of the acoustic enclosure are studied. In terms of sound transmission loss, the sond impendance parameters for the sound absorbing material are determined and the vent structure for the enclosure is improved. It is resulted that the sound transmission loss is increased 2.3dB.Finally, in order to guarantee the ventilation and cooling performance for the revised acoustic enclosure, the flow fields inside of acoustic enclosure before and after the improvement are numerically simulated by using Flunet software and computational fluid dynamics(CFD). The numerical analysis indicates that the improved acoustic enclosure can meet the requirement of ventilation and cooling.