Modeling and Simulation of Cavitation in Hydraulic Systems
In this work, a Lumped parameter approach for modeling cavitation and aeration in hydraulic systems is developed. The modeling approach is based on the homogeneous mixture one fluid model for cavitation and aeration and takes into account the effects of compressibility of both the liquid phase and gaseous phase, related to aeration and fluid vaporization. By using the homogeneous mixture theory, equations suitable for lumped parameter models are derived, including the orifice equation to describe flow through hydraulic connections, the constitutive relations, and the pressure built up equation for hydraulic chambers. The proposed model is aimed at overcoming the drawbacks associated with existing static models for cavitation which assume an equilibrium between the gaseous phase components and liquid phase, and introduce a dynamic model that accurately predicts the dynamics of fluid power systems by considering non-equilibrium effects in phase change. The dynamic model for cavitation and aeration is derived by observing the dynamics of individual cavitation bubble and developing suitable approximations to quantify the extent of cavitation in fluid power systems. Two cavitation models, namely the Asymptotic growth rate model and the Hybrid Rayleigh Plesset Equation model derived from approximations to the Rayleigh Plesset Equation are presented. The proposed equations are then used in this work to simulate a Gerotor pump and an External Gear Pump operating under cavitating conditions. Results obtained from simulations are validated experimentally for different operating conditions. Thorough comparisons made with the static cavitation model developed by LMS indicate a significant improvement in prediction of dynamics of the gear pump units with the aforementioned dynamic models.
Dabiri, Purdue University.
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