Pressure Losses in Hydraulic Manifolds

Abstract

Hydraulic manifolds are used to realize compact circuit layout, but may introduce a high pressure drop in the system. Their design is in fact oriented more toward achieving minimum size and weight than to reducing pressure losses. This work studies the pressure losses in hydraulic manifolds using different methods: Computational Fluid Dynamic (CFD) analysis; semi-empirical formulation derived from the scientific literature, when available; and experimental characterization. The purpose is to obtain the pressure losses when the channels' connections within the manifold are not ascribable to the few classic cases studied in the literature, in particular for 90 • bends (elbows) with expansion/contraction and offset intersection of channels. Moreover, since CFD analysis is used to predict pressure losses, general considerations of the manifold design may be outlined and this will help the design process in the optimization of flow passages. The main results obtained show how CFD analysis overestimates the experimental results; nevertheless, the numerical analysis represents the correct trends of the pressure losses.

Pressure Losses in Multiple-Elbow Paths and in V-Bends of Hydraulic Manifolds

“…This can be a good approach if the bends or junctions are sufficiently far from one another, in a way that they do not influence each other, but it is unsuitable if they are not; since the manifold has a reduced size to meet the requirements of low weight and minimum space in fluid power applications, often bends are very near one another and their reciprocal influence has a strong effect on the total pressure losses. As well shown in [2,9,10] for the case of a double-elbow geometry, the two elbows can condition each another if the reciprocal distance is lower than 10 times the diameter of the channel, and the reciprocal influence is much stronger within a distance of five times the channel diameter. Moreover, within this distance, also the relative orientation of the two elbows plays a fundamental role in determining the pressure losses.…”

“…The authors in [1], for example, analyzed the energy dissipations for the hydraulic system of an agricultural tractor, highlighting how much the pressure losses in the valves critically affect efficiency. As also explained in [2], hydraulic systems, in particular for mobile applications such as off-road machines, have both to fit in the usually narrow spaces of the vehicles and to guarantee functionality with acceptable efficiency. The space is never enough to arrange all the many hydraulic subsystems that in these vehicles are responsible for the translation (hydrostatic transmission) of the vehicle, the steering, the braking, the movement of the vehicle equipment (arm, bucket, forks, agricultural equipment .…”

Energy Efficiency and Controllability of Fluid Power Systems

“…Zardin et al in [14,15] tackle the problem of estimating the pressure losses in the hydraulic manifolds present in almost all mobile hydraulic machines. The design of these manifolds present challenges related to the complex layout and the requirements of low cost and compactness.…”

“…These challenges make it quite difficult for the designers to minimize the pressure losses, which reflect in a lower energy efficiency of the hydraulic system. In [14], Zardin's research team first present their simulation of a CFD based simulation strategy, properly validated against experiments for single path manifold designs. In [14], they extend their approach for the case of multiple path manifolds.…”

“…New approaches for the analysis, modeling, and design of hydraulic and pneumatic components This book contains the successful invited submissions [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] to the Special Issue.…”