Sound field analysis and simulation for fluid machines

Fluid machines, such as pumps, fans, and internal combustion engines, are widely used in duct systems for air-conditioning, cooling, ventilating, heat releasing, and dust collecting. Vibration and noise will be created when the fluid machine works with fans at various rotating speeds. Noise problems associated with fan installation are a concern in fluid machines. Methods to analyze the sound field and simulation of fan installation are, therefore, important for the design to reduce the noise output from fluid machines. The sound field is simulated by using the boundary element method (BEM), which is a numerical technique to reduce the boundary integral equations using the fundamental solution and Green’s transfer functions, for sound field analysis in this paper. For the sound field analysis, the geometry of the fluid machines (the axial fan and centrifugal fan) and the acoustic properties are modeled in Beasy software based on the boundary element method technology. The 1/1 octave frequency band from 63 Hz to 8 kHz ranges are selected on sound field analysis. The sound pressure of the fan and the motor in each octave band are calculated by the parameters of rotating speed, flow volume, horse power and number of blades used. The results show that there is a high level sound pressure inside the housing of the axial fan due to the sound source located there. The higher sound pressure level is observed on both the inlet and outlet. The results for the centrifugal fan are the higher the frequency, the heavier energy that is found to radiate around the sound source.