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The paper addresses some aspects of an ongoing research on a commercial compact excavator. The interest is focused on the analysis and modelling of the whole hydraulic circuit that, beside a load sensing variable displacement pump, features a stack of nine proportional directional control valves modules of which seven are of the load sensing type. Loads being sensed are the boom swing, boom, stick and bucket, right and left track motors and work tools; instead, the blade and the turret swing users do not contribute to the load sensing signal. Of specific interest are the peculiarities that were observed in the stack. In fact, to develop an accurate AMESim modelling, the stack was dismantled and all modules analysed and represented in a CAD environment as 3D parts. The load sensing flow generation unit was replaced on the vehicle by another one whose analysis and modelling have been developed using available design and experimental data.

Scope of this work is to analyse potentials in terms of efficiency of two pump units belonging to two families: the first intervening on the maximum volume generated by variable volume chambers (e.g. a vane pump where eccentricity is varied), the second that changes the quantity of fluid being sucked or delivered (e.g. a gear pump with variable timing). In more detail the comparison will be established between a vane pump where displacement is varied through eccentricity and an internal gear pump of Gerotor type where flow rate is controlled through a rotating sector that alters the effective geometry of kidney ports. A detailed simulation of the two solutions brings to evidence the advantages of the first approach with respect to the second as confirmed by experimental investigations.

The paper presents geometric, kinematic and fluid-dynamic modelling of variable displacement vane pumps for low pressure applications in internal combustion engines lubrication. All these fundamental aspects are integrated in a simulation environment and form the core of a design tool leading to the assessment of performance, critical issues, related influences and possible solutions in a well grounded engineering support to decision.

In hydrostatic steering systems, occasionally, the need arises of exerting large forces as, for example, is the case in steering actuators of articulated dumpers (see Fig. 1) or in rudder actuation on ships. Consequently, linear motors with large bore diameters are required not to exceed system operational pressure limits. Such actuators, whose travel is dependent on the specific application, absorb a quite large flow rate (up to 400 L/min) to respond, within an appropriate time frame, to steering commands. The flow rate, generated by a properly sized feed unit, cannot in full be handled by the hydro-steering (see Fig. 2), as this, beside other aspects, would necessarily imply too large an orbital motor.

The paper presents experimental and theoretical investigations on a shaft mounted gerotor lubricating pump aimed at reducing radiated noise at high engine speed. Effects of noise generation identified as main sources are the fluid borne noise (FBN) that originates in unsteady flow and related pressure fluctuations and structure borne noise (SBN) as a result of pressure transients occurring internally, which cause vibrations of the pump case. To clarify the onset of large delivery pressure fluctuations detected at high pump speed (in excess of 4000 rpm), and validate simulation results (AMESim environment), experimental and theoretical studies have been performed.

The rapid and ever increasing development of microprocessor based controllers in a wide and diversified range of applications leads to consider their candidacy on spacecraft systems. Easy programmability, potentials for implementing the most complex logical control laws, and their “adaptivity” form the backbone of their many interesting features. In this perspective, the paper illustrates an application of adaptive control, within a closed air loop, for thermal conditioning of a typical biochemical experiment cell to be flown in space and addresses some aspects specific to the underlying control philosophy.

The present paper details an original investigation based on the attainment of performance predictions of a radiator panel that is in itself a subsystem of the Technology Demonstration Model, an advanced heat rejection device conceived, and built, by AERITALIA SpA under Contract to ESA (European Space Agency) Since at the time of writing this report experimental results we re not available, expected correlations and contrasts will form the object of future communications. In this perspective, the feasibility of simulating via computer assisted analysis the aforementioned subsystem is demonstrated; this being achieved by an accurate build-up of the mathematical model and subsequent development of appropriate software tools grounded on the finite element method.

A rigorous study of physical phenomena that characterize the energy transfer in a radiative panel, presents serious problems when, aiming at optimizing feasible design solutions, is oriented to the prognostic evaluation of the overall system performance. Different thermal interaction modes among constitutive components (i.e. headers, tubes, fins, honeycombs) and an intrinsically complex geometry make extremely cumbersome, if not impossible, to operate with a mathematical model featuring infinite degrees of freedom, as is the case for the real system. The need thus arises to build up a model possessing limited degrees of freedom, capable of approximately portraying, yet with specifiable accuracy, the bulk of physical phenomena that actually evolve in the heat rejection system. In the given frame this work elucidates how the objective may be attained by utilizing the finite element method and how it is also possible to deal with non-linearities stemming from existing boundary conditions.