Simulation of rubber grommets and correlation with test at low frequencies

Residential air conditioning units include several sources which can lead to vibrational and noise issues. The most important structure-borne source is the compressor which controls both the vibration and noise in certain frequency ranges. Compressors are commonly mounted on three or four relatively stiff rubber grommets which partially isolate the basepan from the compressor motion while also ensuring that the compressor does not move so much that the copper refrigerant lines are compromised over time. In this work, the grommets are simulated using the finite element method and results are correlated to measurement results after some adjustment. It is demonstrated that the natural frequencies of the compressor plus isolators are very sensitive to the hyperelastic properties and boundary conditions.