Numerical studies of a marine diesel engine intake silencer are conducted to evaluate its performance, and effects of the silencer on the turbocharger compressor performance are also discussed. The results show that the duct acoustic mode method can be used in the silencer transmission loss prediction, and the predicted noise reduction and main frequency range agree with the measurements fairly well. However, it is found that the silencer compromises the compressor performance by shortening its operating range. It is found that the static pressure on the compressor blade surface is decreased, thus the compressor total-to-total pressure ratio and isentropic efficiency are reduced. Pressure fluctuations at compressor rotor and stator inlets enhanced when a silencer is installed, which means the trend of pressure spectrum in the rotor and stator passage is changed. Compared with the results of a compressor in natural aspiration, it is found that the silencer can significantly reduce high-frequency noise. In particular, it is quite effective in tonal noise reduction. In addition, the compressor inlet noise spectrum indicates that noise radiation characteristics are different with a silencer installed.
Estimation of the Laser Frequency Noise Spectrum by Continuous Dynamical Decoupling
