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The demand for low noise level in vehicle cabin continues to rise lately. In particular, noise generated by eco-friendly cars such as hybrid and electric ones tends to become lower and lower. In this market environment, the noise contributions caused by HVAC systems are also increasing. Therefore, it becomes increasingly important to accurately predict noise generated by HVAC systems and analyze the noise sources and resolve the noise issue. In this study, direct acoustics prediction approach based on Lattice Boltzmann Method is applied to predict the flow-induced noise from HVAC systems including blower and ducts and find noise sources. In order to validate the simulation result, acoustics measurements are performed on HVAC systems in an anechoic room and the results are compared to each other. A new technique is applied to finding a noise source for a specific frequency and shows improved noise level through modifying the geometry related to noise sources detected by the simulation.

This paper investigated the characteristics of the magnetic field and the attractive magnetic force in a magnetic clutch of the automotive air conditioner. The magnetic force was calculated by using the finite element method, the principle of virtual work and the Maxwell stress tensor, and it was measured by experiment. Magnetic field is not affected by the pulley groove and the attractive magnetic force is also not significantly affected by the bearing because the total magnetic field in the airgap is not changed. The magnetic force increases rapidly as the airgap decreases. The bridges in the disk and the pulley decrease the magnetic force because they create the radial flux to saturation and reduce the effective axial magnetic flux in the airgap to the amount of the radial magnetic flux flowing in the bridges. Also the magnetic force is decreased proportionally as the increase of the cross-sectional area of bridge.