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This paper presents a multidimensional approach to the hydraulic components design by means of an open-source fluid dynamics code. A preliminary study of a basic geometry was carried out by simulating the efflux of an incompressible fluid through circular pipes. Both laminar and turbulent conditions were analyzed and the influence of the grid resolution and modeling settings were investigated. A qualitative description of the internal flow-field distribution, and a quantitative comparison of pressure and velocity profiles along the pipe axis were used to asses the multidimensional open-source code capabilities. Moreover the results were compared with the experimental measurements available in literature and with the theoretical trends which can be found in well-known literature fundamentals (Hagen-Poiseuille theory and Nikuradse interpolation). Further comparison was performed by using a commercial CFD code.

The effect of cavitation plays a fundamental role in the hydraulic components design and the capability of predicting its causes and characteristics is fundamental for the optimization of fluid systems. In this paper, a multidimensional CFD approach is used to analyze the cavitating phenomena typical of hydraulic components using water as operating fluid. An open source fluid-dynamics code is used and the original cavitation model (based on a barotropic equation of state and homogeneous equilibrium assumption) is extended in order to account also for gases dissolved in the liquid medium. The effect of air dissolution into liquid water is modeled by introducing the Henry law for the equilibrium condition, and the time dependence of solubility is calculated on a Bunsen Coefficient basis. Furthermore, a simplified approach to turbulence modeling for compressible flows is coupled to the cavitation model and implemented into the CFD code.

This paper deals with the analysis of the interaction between solid contamination and internal geometry in hydraulic conical and spherical poppet valves, performed through a non-dimensional, axis-symmetric CFD analysis of their internal flow. The information coming from the flow field solution is used to identify regions having higher probability to be impacted by particles dragged by the fluid, and to estimate the erosion potential of solid particles having different size. The value of the kinetic energy of particles approaching the walls of the geometric domain is used to estimate the amount of material potentially eroded by impacting particles, and to provide a potential correlation between ISO 4406 and NAS 1638 solid contamination level classification. The long-term target is a numerical estimation of service life in hydraulic components.

The paper deals with the simulation and the experimental verification of the dynamic behaviour of a linear actuator equipped with different configurations of mechanical cushion. A numerical model, developed and tailored to describe the influence of different modulation of the discharged flow-rate (and of the correspondent discharging orifice design) on the cushioning characteristics variation is firstly introduced. Then, with respect to the case of the cylindrical cushioning engagement, both the reliability and the limits of the numerical approach are highlighted through a numerical vs. experimental comparison, involving the piston velocity and the cylinder chambers pressure. After, with the aim of highlighting the effect of mechanical cushions design on a two effect linear actuator dynamic performances, the characteristics modulation of four alternative cushioning systems are determined and deeply analyzed.

In this paper some design aspects related to external gear pumps balancing surfaces are studied, and some useful guidelines for designing bearing blocks balancing surfaces are suggested. In order to study bearing blocks axial balance, a numerical procedure for the determination of the pressure distribution inside the clearance bounded by gears sides and bearing blocks internal surfaces is firstly presented and applied. After, the influence of bearing blocks geometry and pump operating conditions on the widening thrust is highlighted, considering both constant and variable lateral clearance heights. Then, the computations are performed to evaluate the widening thrust variation as a function of bearing blocks relative tilt with respect to gears lateral sides, and both positive and negative bearing blocks tilts are evidenced and discussed.

This paper studies the proportional directional control valves design influence on the energetic behavior of a mid-power compact excavator. In particular, with reference to the hydraulic circuit actuating the primary workgroup, in the paper the hydraulic power metering performed with the boom cylinder proportional control valve is studied, and some design solution useful in reducing both the hydraulic power dissipation, and the power absorption from the machinery prime mover are highlighted. The analysis, experimentally performed for different operating conditions, is carried out highlighting the influence of a metering configuration both on the supply pressure modulation and on the flow-rate supplied to the actuator.

This paper studies the influence of the discharge chamber geometrical parameters on the steady-state characteristics behavior of a conical seat valve having compensating profile. More in details, starting from the analysis of the experimental behavior of an actual valve showing inefficient characteristic curves, the metering openings leading to the transition from under to over compensation are individuated. Then, a 3D CFD steady-state, incompressible and isothermal analysis is involved, mainly to evidence the valve discharge coefficient and flow-forces variations with operating conditions. After, two alternative valve configurations, presenting a low pressure region designed to optimize the flow-forces compensation, are characterized through the 3D CFD analysis.

The paper investigates, by means of a 3D, steady-state, incompressible and isothermal CFD analysis, the influence of the notch shape and number on proportional directional control valves metering edge characteristics. The numerical activity is firstly performed for a sharp metering edge, considered as reference case. Then, different configurations of notched metering edges are considered, coming from the adoption of two notch geometrical shapes largely used in proportional directional control valves actual design, and from a symmetrical displacement of two, three and four notches on the spool periphery. For all the cases considered, the qualitative analysis of the internal flow field is performed in order to highlight the fluid efflux main characteristics.