1,720,961 research outputs found
Cross-Flow Fan Design Guidelines for Multi-Objective Performance Optimization
No full textMore than one century has passed since Mortier's first cross-flow fan patent in 1891, but the design is still based on empirical considerations and on the re-adaptation of previously developed configurations. The complexity of the flow field inside the machine is the main reason for the lack of an established design procedure, because the characteristics of the eccentric vortex that forms within the impeller are deeply influenced by the geometry of the impeller and also of the casing. In this paper, the objectives that should be pursued in the design procedure are discussed and defined, and guidelines for cross-flow fan design are determined through the analysis of an experimental database of fan performance and efficiencies, which is obtained by the systematic variation of the most important geometric parameters of the casing in combination with different impellers
An Experimental Investigation of the Flow Field Pattern within the Impeller of a Cross-Flow Fan
No full textCross-flow fan performance is strongly influenced by the geometry of the casing, as the latter, in turn, affects the position and the strength of the eccentric vortex that characterizes the operation of this category of fans. The paper presents a systematic experimental investigation of the flow field within the impeller at different throttling conditions and for different geometries of the fan casing. Both pressures and velocities are measured using a three-dimensional five-hole probe that is inserted in the flow. This study helps determine the relationship between the design parameters of the casing and the flow field pattern, and it is part of an extensive work, by the same research group, aimed at establishing a general theory on cross-flow fan operation and at outlining the design guidelines for this particular type of turbomachine
THE INFLUENCE OF SEPARATION, INCLINATION AND SWIRL ON SINGLE AND COUPLED JET FANS INSTALLATION EFFICIENCY
No full textExperimental tests have been carried out in order to acquire knowledge about the interaction between jet fans and the resulting secondary flow in tunnels with standard circular A.N.A.S. (Italian Road Board) cross section. During the experiment programme, model jet fans are hug with different distances between jet axes, tunnel roof and pitch angles. The resulting tunnel flow, with develops along the tunnel, is studied using a five hole probe and the effectiveness of the impulse fan is determined. In the test series the velocity distribution at the nozzle exit has been changed and the difference of the swirl has been evaluated. The aerodynamic characteristics of the single and couple jet fans as well as the probable onset of recirculation are reported as a function of the effects of eccentricity and pitch angle
Experimental investigation of interaction of jet fans mounted in series
No full textA road tunnel ventilation system should be objectively grated taking into account both the installation efficiency of individual fans and the interaction between adjacent fans and consecutive fan sets. This can be a reason for reduced of installation efficiency penalties and excessively high installation prices.
A comprehensive series of tests were carried out on a 1/10 scale model of a vehicle tunnel in order to investigate the effects of tunnel velocity, jet swirl, jet momentum, inclination and distances between jet axes and tunnel roof. To determine the effect on installation efficiency and on the interactions between fans mounted in series.
Recommendations have been derived for the design and operation on the longitudinal ventilation system
Experimental Study on the Longitudinal Ventilation System
No full textIn longitudinal ventilation road tunnel systems the booster fans are mounted close to the tunnel roof. Since velocities of the flow are high, the friction losses on the walls are an important elements in these types of application.
Tests have been carried out to determine the effectiveness of the impulsive fan. The actual impulse force delivered has been measured on a tunnel model with standard ANAS (Italian Road Board) cross section.
During the research the distance of the jet axis from the wall and the tunnel velocity have been varied.
In the final test series the velocity distribution at the nozzle exit has been changed and the influence of the jet swirl has been evaluated
Uno Studio Sperimentale sulla Ventilazione Longitudinale nelle Gallerie
No full textCome influiscono sull'induzione le componenti assiale e trasversale della velocità del getto e la posizione del ventilatore rispetto alla sagoma della galleri
Sull’utilizzo della norma UNI 10531 su metodi di prova e condizioni di accettazione di ventilatori industriali - Prima parte
No full textAnalisi Sperimentale e Numerica di un Ventilatore a Deflusso Trasversale
No full textIn questo lavoro si presentano i risultati sperimentali e teorici ottenuti per un ventilatore a deflusso trasversale, allo scopo di verificare le attuali capacità della fluidodinamica numerica nella previsione dl campo di moto, e quindi delle prestazioni, di questa tipologia di macchine.
L'analisi sperimentale è stata condotta su macchine di geometria diversa utilizzando un impianto di prova del tipo con camera alla mandata, realizzato secondo la normativa UNI 10531. Su una delle geometrie sperimentate è stata effettuata l'analisi numerica per mezzo del codice termofluidodinamico STAR della Computational Dynamics. Il fluido è stato supposto sia aviscoso che viscoso per quest'ultimo caso, sono stati provati diversi modelli di turbolenza con varie combinazioni di condizioni al contorno. Per superare le difficoltà numeriche incontrate nella simulazione a rotore fermo, ma con la presenza delle forze centrifughe e di Coriolis, è stata sfruttata la capacità del codice di realizzare un'effettiva rotazione della girante. Con quest'ultima opzione è stata ottenuta, per un ampio campo di portate attorno a quella di progetto, una buona concordanza tra dati sperimentali e risultati numerici
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
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