1,721,034 research outputs found
Testing the performance of an innovative high speed external gear pump as a reliable hydraulic power unit for automotive robotized transmissions
No full textIn this paper the performance of an innovative, high speed, external gear pump have been measured and verified in order to evaluate its potential application as a reliable and efficient power unit for automotive, electro-hydraulic actuated, robotized transmissions. More in detail, this particular type of volumetric machine is built with two suction and two delivery ports and is specifically designed for extremely challenging operating conditions, mainly in terms of both rotational speed and delivery pressure. First of all, the most important hydraulic and mechanical performance parameters have been measured and analyzed, over a wide range of rotational speeds, spanning between 400 and 7000 rpm, and for two different operating temperatures, respectively equal to 40 and 60 °C. In this case, with the aim to increase the consistency of the experimental measurements, two external gear pumps, with exactly the same design geometry and features, have been tested and compared, also with available data coming from the pump manufacturer. All the experimental measurements have been performed with the help of a test bench, equipped with a double Cardan joint and an overdrive, specifically tailored for running the pump at high rotational speed and applying a delivery pressure of about 45 bar, very near to a typical actuation value of a high-performance automotive robotized transmission. At the end of this experimental work, it is possible to conclude that the high speed external gear pump here tested and analyzed can be considered a reliable and effective alternative hydraulic power unit for high-performance, automotive, robotized transmissions
A combined numerical approach for the thermal analysis of a piston water pump
Full text linkThe paper proposes a numerical model for the investigation of a piston water pump under different operating conditions. In particular, the lubricating system is analysed and modelled. The study accounts for the lubrication and friction phenomena, heat transfer, multiphase fluid approach and motion simulation. A computational thermo fluid dynamics approach has been adopted to develop a numerical tool able to simulate the behaviour of the oil during the machine working phases. The CFD approach simulates the moving metal components by means of moving meshes techniques; the friction phenomenon is estimated on the basis of formulations available in literature. The numerical model evaluates the heat transfer between moving metal parts and oil during the operating phases of the system. Furthermore, the heat transfer between oil and environment is calculated, accounting for conduction through the metal crankcase walls. A multiphase fluid approach is used for the simulation of the oil and air mixing during the crank rotation. The heat transfer coefficient predicted by the CFD approach are employed in a lumped and distributed numerical model; the reliability and accuracy of the proposed numerical approach is addressed and validated against experimental results. Experimental data have been collected by means of a thermographic camera and thermocouples. Finally, the tool's predictive capabilities are addressed by simulating different working conditions
Experimental Investigation of the Suction Capabilities of an Innovative High Speed External Gear Pump for Electro-Hydraulic Actuated Automotive Transmissions
No full textTo achieve the goal of more electric aircrafts current research investigates the frontline capabilities of electro-hydrostatic actuators (EHA) as substitutionfor conventional hydraulic flight control systems. Due to durability limita-tions, EHAs are to date only utilized as backup. In this paper the design ofEHAs and the impact of the challenging working condition on the healthstatus are presented. A longevity test bench, as well as developed test profileto cover real world operation are explained. Lastly, measurements of load-holding modes are analyzed in detail and insight about run-ins, temperaturedependencies and wear-related efficiency losses are gained
Cavitation analysis through CFD in industrial pumps: A review
Full text linkCavitation is one of the most detrimental fluid-dynamic anomalies that occur to turbomachines. It mainly
affects machines characterized by high rotation speeds and clear distinctions between low and high pressure
zones, where cavitation first appears. During the years, starting from the well known Rayleigh formulation for
the formation of bubbles in a liquid medium, many models have been proposed to analyse the phenomenon.
Spanning from higher simplifications to more detailed formulations, the range of applications of these models
is wide and led to different quality results, where a clear methodology is not fully established when regarding
specific sectors, for example the industrial pumps. Restricting the application field to few, specific kinds of
pumps, i.e centrifugal, axial flow pumps, external gear and mixed flow pumps, this article analyses the main
literature sources in order to give an overall view to the Computational Fluid Dynamic applications of the
different cavitation models and their applications to industrial pumps.Cavitation is one of the most detrimental fluid-dynamic anomalies that occur to turbomachines. It mainly affects machines characterized by high rotation speeds and clear distinctions between low and high pressure zones, where cavitation first appears. During the years, starting from the well known Rayleigh formulation for the formation of bubbles in a liquid medium, many models have been proposed to analyse the phenomenon. Spanning from higher simplifications to more detailed formulations, the range of applications of these models is wide and led to different quality results, where a clear methodology is not fully established when regarding specific sectors, for example the industrial pumps. Restricting the application field to few, specific kinds of pumps, i.e centrifugal, axial flow pumps, external gear and mixed flow pumps, this article analyses the main literature sources in order to give an overall view to the Computational Fluid Dynamic applications of the different cavitation models and their applications to industrial pumps
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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