HYDRAULIC NOISE PREDICTION AND CONTROL METHODS

Abstract

Noise, Vibration and Harshness have always been a primary focus of research area in a customer centric product design. As these are the adverse effects of a working machine which mainly causes various inadmissible effects such as deterioration of working lifetime of the product, creating uncomfortable work environment or even worse might create prolonged health hazards. Fluid Borne noise (FBN), even though insignificant in terms of its magnitude, is believed to be a source of vibration and noise occurrence in various hydraulic machines and hydraulic systems. Recent trend is that hydraulics are used in agro-machinery due their high power density and better controllability. One of the disadvantages of such systems is believed to be excessive noise generated during operations at certain conditions. This work is intended to identify or predict such conditions. Since first layer of transmission of such noise is the fluid layer, focus is on FBN, pertaining to certain physical and thermal properties of the system considered. Chapter 2 gives an overview of noise and FBN position in noise significance and mathematical definitions considered in order to model the hydraulic systems in acoustic domain. Such definitions mainly include the wave propagation properties inside the passive hydraulic elements. Chapter 3 consists of the hybrid approach using computational fluid dynamics (CFD) techniques with Turbulent (k-omega) Shear Stress Transport model and computational acoustics (CA) with Broadband Noise Sources model in ANSYS Fluent (2021 R1) commercial software Chapter 4 consists of mathematical formulations to model the passive elements of the circuit such as rigid pipe, hose, accumulator, etc. in acoustic model Chapter 5 provides with results of numerical simulations of centrifugal pumps with contours of pressure, velocity and acoustic power level of the surfaces and zones of pump along with plots of efficiencies and heads varying with blade number, blade outlet angles and blade width. Also, the variation of pressure ripples and flow ripples are plotted against harmonics of the pump. The objective being to identify the best blade numbers and blade designs that give the best hydraulic efficiency for the same flow conditions.