1,721,007 research outputs found
Experimental Validation of a Reduced Order for Radial Turbopump Design
No full textThe paper illustrates the experimental validation of the reduced order model recently developed at Alta, Pisa (Italy), for the simultaneous and preliminary geometrical definition and non-cavitating performance prediction of centrifugal turbopumps. The proposed model has been employed to size and design the test machine, named VAMPIRE and equipped with a six-bladed radial impeller, a vaneless diffuser and a single-spiral volute. The pumping and suction performance of the machine have been determined in a series of tests in Alta’s Cavitating Pump Rotordynamic Test Facility (CPRTF). The measured pumping characteristic proved to be in excellent agreement with the model predictions, thus effectively validating the design model. In addition, the experimental determination of the pump’s cavitation characteristic is fully consistent with the expected suction performance of comparable machines, confirming the capability of the proposed model to generate hydrodynamically efficient turbopump designs
PulCheR – Pulsed Chemical Rocket with Green High Performance Propellants: First Year Project Overview
Full text linkPulCheR (Pulsed Chemical Rocket with Green High Performance Propellants) is a research project co-funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n°313271. The project officially started as of January 1st, 2013, and is mainly aimed at demonstrating the feasibility of a pulsed propulsion system in which the propellants are fed in the combustion chamber at low pressure and the thrust is generated by means of high frequency pulses, reproducing the defence mechanism of a notable insect: the bombardier beetle. The feasibility of this new propulsion concept will be investigated at breadboard level in both mono and bipropellant configurations through the design, realization and testing of a platform of the overall propulsion system including all its main components. As an added value, the new propulsion concept will be investigated using green propellants. The present paper aims at introducing the project, its structure, its main objectives and at presenting an overview of the activities performed in the first year of the project and its current status
Pumping and Suction Performance of a Whirling Inducer
Full text linkThe experimental characterization of the rotordynamic fluid forces acting on a whirling inducer and the analysis of their influence on its pumping and suction performance are presented and discussed as functions of the operational conditions. The paper illustrates the first application of the novel approach recently developed at Alta for the simultaneous measurement of the relevant experimental data, demonstrating its remarkable versatility and effectiveness
Experimental Characterization of the Rotordynamic Forces on Space Rocket Axial Inducers
No full textThe present paper illustrates the results of an experimental campaign conducted in the Cavitating Pump Rotordynamic Test Facility (CPRTF) at ALTA S.p.A. aimed at characterizing the rotordynamic forces acting on two different whirling tapered-hub, variable-pitch axial inducers. The forces acting on the impeller have been measured by means of a rotating dynamometer mounted just behind the inducer. The roles of the imposed whirl motion of the rotor, flow coefficient, cavitation number, and liquid temperature have been investigated. The destabilizing role of cavitation has been confirmed. The experimental results are consistent with previous experimental campaigns documented by the open literature, including the former data published by Caltech researchers. The observed dependence of the tangential and normal components of the rotordynamic force on the whirl-to-rotational speed ratio does not follow the quadratic functional behavior often assumed in the open literature. Rotordynamic forces of large amplitude and destabilizing nature especially occur in the presence of cavitation, potentially compromising the stability of the pump operation
Experimental Characterization of Rotordynamic Forces Acting on Space Turbopumps
Full text linkThe experimental characterization of the rotordynamic fluid forces acting on a whirling inducer and the analysis of their influence on its pumping and suction performance are presented and discussed as functions of the operational conditions. The paper illustrates the first application of the novel approach recently developed at Alta for the simultaneous measurement of the relevant experimental data, demonstrating its remarkable versatility and effectiveness
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
Stationary Propulsive Performance of a Green Monopropellant Demonstrator for the PulCheR Project
No full textIn the framework of the PulCheR project, an experimental test campaign on a 20 N monopropellant thruster prototype has been carried out with the aim of assessing the capability of a new Pt/Al2O3 catalytic system of effectively decomposing 98% concentration hydrogen peroxide and the attainable propulsive performance in steady state conditions. The catalysts have been able to decompose up to 1 liter of 98% H2O2 with very good efficiencies (ηc* > 95% and ηΔT ≥ 90%) and without any pellets breakage or catalytic degradation. The thrust profile has been particularly smooth and the experimental specific impulse measured at sea level with the matched conical nozzle has been 130 s that corresponds to an extrapolated vacuum specific impulse for a high expansion area ratio bell-contoured nozzle higher than 185 s. The present experimental results represent useful reference data for the future assessment of the propulsive performance of the new propulsion concept proposed in the PulCheR project
Rotordynamic Forces on a Three Bladed Inducer under Forced Whirl Motion Operating at Different Conditions
Full text linkThe paper illustrates the main results of an experimental campaign conducted in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at ALTA S.p.A., aimed at characterizing the rotordynamic forces acting on a whirling three-bladed, tapered-hub, variable-pitch inducer, named DAPROT3. The forces acting on the impeller have been measured by means of a rotating dynamometer mounted just behind the inducer. The roles of the imposed whirl motion of the rotor, flow coefficient, cavitation number and liquid temperature have been investigated. The results have been obtained by means of a recent experimental technique, consisting in measuring the continuous spectra of the rotordynamic forces as functions of the whirl excitation frequency. This technique allows for extrapolating valuable information from the experiments by more accurately and rapidly characterizing the spectral behavior of these forces than can be obtained from a limited number of point experiments conducted at constant whirl frequency. Therefore, it is useful to better capture the complexity of the rotordynamic forces and assess their consequences on the stability of axial inducers
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
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