1,721,020 research outputs found
Utilizzo del codice MULTALL nel progetto preliminare di turbine radiali con cassa a spirale priva di palette distributrici
No full textPreliminary design of radial turbomachines is supported by “single-channel” CFD models, ideal for design concepts comparison. Unfortunately, these models do not suit non-periodic domain calculations like those of turbines with vaneless spiral casings. A new approach that makes such domains periodic was implemented in the open-source code MULTALL and validated against non-periodic-domain results of state-of-the-art commercial codes
PRELIMINARY HYDRAULIC PERFORMANCE MODEL FOR THE OPEN REV EVO PUMP
No full textThis brief technical note deals with a preliminary empirical model aimed at describing the hydraulic performance of a partial emission pump operating in the around of its own best efficiency point. In particular, the high-speed pump design internally named as OpenREV EVO is considered. Such design is the more recent evolution of the partial emission pump prototypes conceived to pressurise the fuel and oxidiser of a rocket engine to be installed in a European lunar lander, being developing by NAMMO UK under ESA funding. The aim of the technical note is to report the equations suggested as base for a mathematical model of the pump hydraulic performance.
To this purpose, the experimental data acquired by T4i were made dimensionless and approximated by polynomial curve fitting. The polynomials describing the dimensionless performance were finally rearranged to obtain dimensional equations of the pump pressure rise and hydraulic efficiency as a function of the pump mass flow rate, impeller rotational speed, and mass density of the working fluid. The results show the dimensional maps of the 45mm diameter OpenREV EVO prototype in the operation with the fuel and the oxidiser, as obtained using the presented equations, superimposed to the 50%, 100% and 117% nominal operation point requirements
Selection of the pump type for the propellants of the high-performance engine of a European lunar lander
No full textHYDRAULIC PERFORMANCE MODEL FOR THE OPEN REV EVO PUMP
No full textThis technical note presents the empirical model describing the hydraulic performance of the high-speed pump design internally named as OpenREV EVO. The latter is the more recent evolution of the partial emission pump prototypes conceived to pressurise the fuel and oxidiser of a rocket engine to be installed in a European lunar lander, being developing by NAMMO UK under ESA funding. The aim of the technical note is to update and extend to the entire pump operation range the equations suggested in a previous note as base for a mathematical model of the pump hydraulic performance in operation around its best efficiency point.
To this purpose, additional experimental data acquired by T4i for pump operation up to the maximum flow rate were included in the data set used to define an appropriate polynomial curves fitting model of the dimensionless pump performance parameters. The revised model incorporates corrections accounting for the effects of the Reynolds number in order to obtain as output reliable values of the pump pressure rise and hydraulic efficiency as a function of the pump mass flow rate, impeller rotational speed, and molecular properties of the working fluid. The model was used to build the dimensional maps of the 45mm diameter OpenREV EVO prototype in operation with the fuel and the oxidiser. To further exploit the capabilities of the model, the performance maps expected by the OpenRev EVO prototype if manufactured with a 40mm diameter impeller are presented as well
DESIGN OF FORWARD-INCLINED BLADES FOR A 0.5 HUB-TO-TIP RATIO TUBE-AXIAL FAN
No full textThe paper deals with the design of forward-inclined blades, where “forward-inclination” is intended as the design-dependent amount of forward sweep to be incorporated in non-free-vortex blades to restore a quasi-2D flow behaviour within the rotor passages. The aim of the work is to assess the effectiveness of this design modification in a 0.5 hub-to-tip ratio fan with radially stacked blades that induce a roughly constant-swirl velocity at the rotor exit. To this end, the original blade has been modified by incorporation of a forward sweep amount that translates into a forward-inclined design, defined in accordance with a method suggested by the authors. The forward-inclined design demonstrated experimentally to improve pressure rise and efficiency of the original fan in the whole operation range with ca 10% gain at design operation
EFFECT OF SOLIDITY AND ASPECT RATIO ON THE AERODYNAMIC PERFORMANCE OF AXIAL-FLOW FANS WITH 0.2 HUB-TO-TIP RATIO
No full textAspect ratio and solidity play complementary roles in the aerodynamic design of axial fan rotor blades. Few studies have experimented the effect of the aspect ratio of rotor blades on the performance of low-speed axial fans or on its interaction with blade solidity in terms of fan aerodynamic performance. This study examined the selection of the solidity and blade aspect ratio in the preliminary design of low-pressure industrial fans with minimized hub-to-tip ratios. The aim of this study was to make available to the fan community experimental data that allow determination of the optimal aspect ratio as a function of the blade solidity. Various aspects of the performance of 16 prototypes of a 315-mm-diameter propeller fan were compared. The industrial fan prototypes all had a hub-to-tip ratio of 0.2 and were derived from four baseline designs conceived to ideally achieve the same best efficiency operation with different values of the aspect ratio. In addition, the prototypes' assemblies were conceived to allow operation with different blade counts, i.e., with different rotor solidities at a fixed blade aspect ratio. The aerodynamic performance of the fans, measured in accordance with the ISO- 5801 standard, was evaluated to assess the sensitivity and trends of the fan pressure and efficiency with respect to the blade aspect ratio and solidity. The measured effects of the aspect ratio and solidity are discussed on the basis of data available in the literature. The results of the experimental analysis were used to formulate general guidelines for the preliminary design of propeller fans with minimized hub-to-tip ratios
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
- …
