Vibroacoustic Analysis and Optimisation of an Electric Refrigerant Scroll Compressor

In electrified vehicles, auxiliary units can be a dominant source of noise, one of which is the refrigerant scroll compressor. Compared to vehicles with combustion engines, e-vehicles re-quire larger refrigerant compressors, as in addition to the interior, the battery and the electric motors must be cooled. Various types of excitation in the compressor cause vibrations on the compressor surface and the emission of airborne noise. Fluid dynamic forces resulting from the cyclic compression principle act on flow-conducting components, while alternating forces caused by the imbalance of the eccentrically running compressor scroll or by torque fluctua-tions on the drive shaft are transmitted to the housing via the bearings. In order to identify the sound generation mechanisms in the compressor, the vibrations of the compressor surface were measured using a laser scanning vibrometer and the sound radiation was characterised using a sound intensity probe. This paper illustrates the relationship between vibrations and the sound radiation of a scroll compressor. The sound spectra of structure-borne and airborne noise are dominated by speed-dependent, tonal components. Vibration resonances caused by the excitation of the compressor's natural modes influence the amplitudes and radiation char-acteristics of the tonal components. To reduce sound radiation, a heavy-layer damping materi-al was applied to the compressor surface and its influence on the vibroacoustic behaviour of the compressor was investigated. The results provide valuable information for the development of suitable sound reduction measures for refrigerant compressors.