Dynamic characteristics of bladder type attenuator for hydraulic systems

Flow ripples caused by the pump will lead to system failure or equipment damage. The bladder type attenuator is utilised to suppress flow ripples in piping systems, though its mathematic model has not been given out precisely. In this paper, the governing equations of the hollow cylindrical shell describing the bladder’s behaviour are studied. Considering the bladder’s viscoelastic materials, the constitutive function is obtained through DMA (Dynamic thermo-mechanical analysis) test and the WLF (Williams–Landel–Ferry) equation. Thus, the dynamic model of the attenuator can be written as an impedance expression, which consists of integral, fractional, constant, and differential components. Three experiments are carried out to validate the theoretical models. The static and dynamic models of the bladder are validated by experiments, indicating good agreement. The impedance model of the attenuator is validated by a hydraulic experiment assessed with the IL (insertion loss) index, showing high accuracy. All models proposed in this work are proven to be effective and accurate, and can be used to evaluate and optimise the bladder type attenuator theoretically.