Operational Transfer Path Analysis Method And Its Industrial Application

The noise generated by household appliances,vehicles,open space equipment and other machinery has created tremendous health hazards to residents.Therefore,identification and control of such mechanical noise has become an urgent task.Due to the complexity of mechanical structures and the coupling between components,the traditional transfer path analysis(TPA)method is difficult to be used directly to identify the excitation source and the noise and vibration transfer path of a system in practical applications.On the contrast,operational transfer path analysis(OTPA)is an efficient and convenient technique for identifying the noise sources and main transfer paths without the need to dismantle the structure of a testing system or to decouple the coupling parts.It also has the advantage that the working load of the system don’t need to be identified.This thesis aims to apply the OTPA technique in the noise source and transfer paths identification in two practical mechanical applications,i.e.,the outdoor unit of a heat pump water heaters and the cabin of a high-speed lift.It provides the basis for the vibration and noise control of the industrial product.In the first part of the thesis,the development and application of the OTPA method are systematically reviewed.The current research on noise and vibration control of outdoor units of heat pump water heater and that of high-speed lifts are reviewed and summarized.A singular value decomposition technique is used alongside the OTPA to reduce the influence of the signal crossover between different transfer paths.Then a simple and effective control method was adopted to reduce the target noise by 2.9dB(A).The second part of the thesis is devoted in the application of the OTPA method in two real industrial projects,(1)to identify the noise sources and main noise transfer paths of a water heater outdoor unit,and(2)to identify the noise source and transfer paths in the cabin of a high-speed lift.The OTPA results show that the noise at the observation point of the outdoor unit is mainly composed of the noise transmitted by the compressor,the refrigerant pipe and the liquid reservoir,and the air noise transmitted by the fan and the fan motor,which provides a basis for the subsequent noise control.In another application case,OTPA is firstly applied to identify the noise source and the major transfer paths of the cabin noise of a high-speed lift.The OTPA results show that the noise in the lift cabin is mainly caused by the structural vibration of the traction wheel and the guide boot system which transfer to the cabin walls to cause the sound radiation of the cabin wall.The analysis result provides an effective guidance for controlling the noise in the lift cabin.Finally,the main findings from this thesis work are summarized,a number of future research areas are identified and put forward.