1,720,997 research outputs found
Influences of the operating conditions on the rotordynamic forces acting on a three-bladed inducer under forced whirl motion
No full textIn the present paper the results from an extensive experimental characterization of the rotordynamic forces acting on a whirling three-bladed, tapered-hub, variable-pitch inducer are presented. The campaign has been conducted in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at ALTA S.p.A.. The forces acting on the impeller have been measured by means of a rotating dynamometer mounted just behind the inducer. The roles of the rotor whirl motion, flowrate, cavitating condition and liquid temperature have been investigated. The analysis has been conducted by means of the classical rotordynamic approach together with a recent experimental technique, consisting in measuring the rotordynamic forces continuous behavior (spectra) as functions of the whirl excitation frequency. This technique allows for evaluating information from experiments more rapidly and accurately with regards to previous methods. Therefore, it is useful to better capture the complexity of the rotordynamic forces and assess their consequences on the stability of axial inducers
Test Bench for the Unsteady Characterization of a Pulsed Green Monopropellant Thruster
No full textPulCheR is a R&D project funded by the European Union Seventh Framework Programme with the main aim of demonstrating the feasibility of a new propulsion concept in which the propellants are fed in the combustion chamber at low pressure and the thrust is generated by means of high frequency pulses. The characterization of this type of thruster has required to carefully design the test bench in order to allow the right assessment of the thruster performance. The unsteady behavior of the thruster has been the main difficulty during the design and the choice of transducers. The most difficult measurement concerns the assessment of the mass injected at each pulse inside the thruster. Because of this, two distinct test benches have been designed and two approaches at measuring the mass injected have been considered. The present article focuses on the challenges concerning the design of the test bench for the characterization of the PulCheR monopropellant thruster
PulCheR-Pulsed Chemical Rocket with Green High Performance Propellants: Second Year Project Overview
No full textPulCheR (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 and is at its second year. 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 concept is under study and many activities have been already performed.
The PulCheR monopropellant thruster is already ready for being tested, whereas more
difficulties concern the application of PulCheR to the bipropellant configuration, even if the
selected propellants, HTP and propyne show very interesting performance. As an added
value, the new propulsion concept investigates green propellants. The present paper aims at
presenting the state of the art of the project after two years since the beginnin
Pulse Mode Operation of a 1 N 98% Hydrogen Peroxide Thruster
No full textThe present article reports the results of a test campaign performed on a 1 N
monopropellant thruster powered by 98% Hydrogen Peroxide in order to assess its
propulsive performance in pulse mode operation. The test campaign comprises firings at
different feeding pressures, duty cycles and catalytic bed temperatures. The catalytic bed
made of 0.4 mm diameter pellets of a-Al2O3 covered by Platinum proved to give fast and
repeatable propulsive performance with good decomposition efficiency
Propulsive Performance of a 1 N 98% Hydrogen Peroxide Thruster
No full textThe present article reports the results of a test campaign performed on a 1 N
monopropellant thruster powered by 98% Hydrogen Peroxide. The test campaign comprises
firings at different feeding pressures and catalytic bed temperatures. The catalytic bed made
of 0.4 mm diameter pellets of -Al2O3 covered by Platinum proved to give fast and
repeatable propulsive performance with good decomposition efficiency
A Light Unsaturated Hydrocarbon and Hydrogen Peroxide as Future Green Propellants for Bipropellant Thrusters
No full textIn the framework of the PulCheR project, an experimental test campaign on a 40 N bipropellant thruster prototype has been carried out with the aim of assessing the attainable propulsive performance in steady state conditions of 98% concentration hydrogen peroxide and propyne. The experimental specific impulse measured at sea level with the matched conical nozzle of the prototype has been 213 s that corresponds to an extrapolated vacuum specific impulse for a high expansion area ratio bell-contoured nozzle higher than 320 s. The light unsaturated hydrocarbon has been effectively ignited by the oxygen-rich hot gases produced by the catalytic decomposition of the hydrogen peroxide
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
Cavitating Pump Rotordynamic Test Facility at ALTA S.p.A.: Upgraded Capabilities of a Unique Test Rig
Full text linkThe paper illustrates the upgrades recently introduced in Alta’s Cavitating Pump Rotordynamic Test Facility in order to extend its experimental capabilities, with special reference to the addition of an auxiliary pump for testing of turbopump inducers over a wider range of flow coefficients, and the set-up of an original apparatus specifically designed for the characterization of the dynamic transfer matrices of cavitating inducers and turbopumps. Examples are presented of the improved capabilities of the facility
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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