1,721,035 research outputs found
Theoretical flow rate in crescent pumps
No full textIn this paper, a method for evaluating the kinematic flow rate of a crescent oil pump is presented. The procedure also allows calculating the angular derivatives of the delivery, suction and trapped volumes of the pump, which are the prerequisites for the simulation of the unit using a lumped parameters approach. The method is based on the knowledge of the length of the vector rays between the centres of the gears and the contact points. From the volume derivatives, an analytic expression of the pump displacement and of the kinematic flow ripple index is obtained. Moreover, the same formula can also be applied to external gear machines. Finally, in this study the influence of the number of teeth of the driving and driven gears has been assessed. The increase of the number of teeth of the inner gear is beneficial; both for the reduction of the flow ripple and for the increase of the displacement at equal overall pump size
Piloted Displacement Controls for ICE Lubricating Vane Pumps
No full textThe paper brings to evidence critical issues in the design of variable displacement vane pump controls for ICE lubrication. Tight packaging, high rotational speed and variable pressure setting are key aspects influencing the selection of pump geometric parameters as well as its displacement controls. A specific layout, where the pump displacement control is carried out by two linear actuators and a two-way pilot control valve, has been analysed. The paper focuses on the dimensioning of the front areas of the actuators considering two kinematic solutions, linear and rotational, for the external ring. Through a simulation model, validated by experimental tests, the influence of different pressure control strategies on the dimensioning has been investigate
On the Dynamics of Pressure Relief Valves with External Pilot for ICE Lubrication
No full textThe paper analyzes the influence on the stability of the remote pilot in pressure relief valves used for engine lubrication. Such valves are mainly used to discharge the excess flow generated by a fixed displacement pump, moreover they can also be used as pilot stage to control the displacement in the new generation of vane pumps. In the paper the transfer function that relates the pressure in the main gallery with the valve spool position is determined. It was found that, when the valve is provided with an external pilot, the interaction between the hydraulic inductance of the pilot pipe and the spool decreases by many times the mechanical frequency of the valve, leading to a reduction of the stability. The experimental procedure used to measure the frequency response of the valve is also described. The test rig was provided with a servovalve used to generate a sinusoidal excitation pressure with variable frequency. The valve frequency response was evaluated by means of two pressure transducers at the two ends of the pilot channel. Finally the influence on the stability of some geometric parameters is analyzed by means of a simulation model in the AMESim environment
Models for Flow Rate Simulation in Gear Pumps: A Review
Full text linkGear pumps represent the majority of the fixed displacement machines used for flow generation in fluid power systems. In this context, the paper presents a review of the different methodologies used in the last years for the simulation of the flow rates generated by gerotor, external gear and crescent pumps. As far as the lumped parameter models are concerned, different ways of selecting the control volumes into which the pump is split are analyzed and the main governing equations are presented. The principles and the applications of distributed models from 1D to 3D are reported. A specific section is dedicated to the methods for the evaluation of the necessary geometric quantities: analytic, numerical and Computer-Aided Design (CAD)-based. The more recent studies taking into account the influence on leakages of the interactions between the fluid and the mechanical parts are explained. Finally the models for the simulation of the fluid aeration are described. The review brings to evidence the increasing effort for improving the simulation models used for the design and the optimization of the gear machines
Passi nell'oleodinamica. Vol. 1-2
Full text link“Passi nell’Oleodinamica” testimonia un cammino di conoscenza molto esteso nel tempo che è iniziato nei primi anni ‘80 al Politecnico di Torino. Questa esperienza, che non ha mai subito pause e che tuttora è ricca di nuovi stimoli, è nata e si è formata nell’intento di riuscire a trasmettere ai tantissimi allievi ingegneri l’entusiasmo e la curiosità per una disciplina allora relativamente sconosciuta che ancora oggi non riceve quella attenzione che, per certo, meriterebbe.
Questo volume ha anche le sue peculiarità che il lettore attento potrà progressivamente porre in luce. Il contenuto è assai vasto ed in qualche modo testimonia un approccio metodologico originale. Ciò è frutto sia degli aspetti didattici sia delle molte e fruttuose collaborazioni di ricerca che, nel tempo, si sono sviluppate.
Sussiste l’auspicio che possa risultare di aiuto a quanti per studio o per professione avranno la passione e la volontà di servirsene. A coloro che lo faranno va il pensiero riconoscente e le scuse per le indubbie manchevolezze ed omissioni unitamente all’augurio sincero di un proficuo lavoro
Geometry assessment of variable displacement radial pumps
No full textThe paper brings to evidence the effect that geometry of the stator ring of variable displacement radial pumps bears on performance characteristics of these units. The type of motion of the stator ring (linear or rotational), the location of the centre of rotation, the porting plate integral with the casing or with the stator ring all have remarkable effects on the pump steady state and dynamic performance. At steady state, an influence exists on the attainable minimum displacement and on the deviation of discharge pressure from the desired setting when displacement is being controlled. In turn, dynamic performance is affected by changes in port plate timing as stator position and displacement undergo transitions. Specific attention is then committed to variable displacement vane pumps for internal combustion engines lubrication where an additional and foremost effect is investigated concerning the issues entailed by internal forces distribution on the stator ring that originate from incomplete chambers filling at high rotational pump speed
Computational Fluid Dynamics Analysis of Gerotor Lubricating Pumps at High-Speed: Geometric Features Influencing the Filling Capability
No full textThe paper presents an extensive analysis of the influence on the suction capacity of the main geometric parameters of gerotor lubricating pumps. The study was carried out using a computational fluid dynamics (CFD) model developed with the commercial software PumpLinx®. The model of a reference gerotor unit was validated experimentally in terms of delivered flow rate in different operating conditions, in open and closed circuit configuration. In the former case, different geometries of the inlet pipe were tested. In the latter, the influence of the suction pressure at constant speed was analyzed. After the model validation, several geometric features were changed to assess their influence on the volumetric efficiency in conditions of incomplete filling, such as the thickness and the diameter of the gears, the position of the inlet pipe with respect to the rotors (radial, axial, and tangential), and the shape of the port plate
Two-Sided Feed Analysis in Gerotor Pumps to Enhance Filling Performance
No full textIn the context of CO2 emissions reduction, internal combustion engines are being replaced by electric motors in many applications. In hydraulic fluid power, this transition requires gear pumps to operate at much higher speeds than traditional systems, increasing the risk of incomplete chamber filling. This issue leads to significantly increased noise levels. Supplying the variable volume chambers from both sides of the rotor is a well-known method to improve filling. This study examines various inlet port placements for dual-sided feeding using a validated CFD model of a gerotor pump. Two axial inlet positions, aligned with the shaft, and three radial positions are investigated. For radial feeding, the axial alignment of rotors relative to the housing space is evaluated, comparing symmetric and asymmetric configurations. Results indicate that axial feeding outperforms radial feeding, with optimal performance achieved when the duct is aligned with the variable volume chambers. For radial feeding, a perfectly symmetrical configuration is preferable, though slightly asymmetrical setups yield comparable performance. Conversely, highly asymmetrical designs, while superior to single-side feeding, fail to fully exploit the advantages of dual-side feeding. This research demonstrates that, under high-speed operating conditions, CFD-based optimization of the suction volume can significantly improve volumetric efficiency by several percentage points
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