35 research outputs found

    Model predictions and experimental results for the rotordynamic characteristics of leakage flows in centrifugal pumps

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    The role played by fluid forces in determining the rotordynamic stability and characteristics of a centrifugal pump is gaining increasing attention. The present research investigates the contributions to the rotordynamic forces from the discharge-to-suction leakage flows between the front shroud of the rotating impeller and the stationary pump casing. An experiment was designed to measure the rotordynamic shroud forces due to simulated leakage flows for different parameters such as flowrate, shroud clearance, face seal clearance, and eccentricity. The functional dependence on the ratio of whirl frequency to rotating frequency (termed the whirl ratio) is very similar to that measured in experiments and similar to that predicted by the theoretical work of Childs [1]. Childs' bulk flow model yielded some unusual results including peaks in the rotordynamic forces at particular positive whirl ratios, a phenomenon which Childs tentatively described as a "resonance" of the leakage flow. This unexpected phenomenon developed at small positive whirl ratios when the inlet swirl velocity ratio exceeds about 0.5. Childs points out that a typical swirl velocity ratio at inlet (pump discharge) would be about 0.5 and may not, therefore, be large enough for the resonance to be manifest. To explore whether this effect occurs, an inlet guide vane was constructed which introduced a known amount of swirl into the flow upstream of the leakage flow inlet. A detailed comparison of model predictions with the present experimental program is presented. The experimental results showed no evidence of the "resonances," even at much larger swirl inlet velocities than explored by Childs

    Space Shuttle Main Engine: Part Number RS007001

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    Topics considered include: low-pressure oxidizer turbopump; low-pressure fuel turbopump; high-pressure oxidizer turbopump; high-pressure oxidizer turbopump turbine; high-pressure fuel turbopump; and SSME propellant flow schematic

    The Effect of Inlet Swirl on the Rotordynamic Shroud Forces in a Centrifugal Pump

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    The role played by fluid forces in determining the rotordynamic stability of a centrifugal pump is gaining increasing attention. The present research investigates the contributions to the rotordynamic forces from the discharge-to-suction leakage flows between the front shroud of the rotating impeller and the stationary pump casing. In particular, the dependency of the rotordynamic characteristics of leakage flows on the swirl at the inlet to the leakage path was examined. An inlet guide vane was designed for the experiment so that swirl could be introduced at the leakage flow inlet. The data demonstrate substantial rotordynamic effects and a destabilizing tangential force for small positive whirl ratios: this force decreased with increasing flow rate. The effect of swirl on the rotordynamic forces was found to be destabilizing

    Measurements for the rotordynamic shroud forces for centrifugal pumps

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    An experiment was designed to measure the rotordynamic shroud forces on a centrigual pump impeller. The measurements were doen for various whirl/impeller ratios and for different flow rates. A destabilising tangential force was measured for small positive whirl ratios and this force decreased with increasing flow rate

    Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Centrifugal Pumps

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    This paper reviews the current state of knowledge of rotordynamic forces caused by the discharge-to-suction leakage flows in centrifugal pumps. The indications that these flows could contribute significantly to the rotordynamics motivated the fabrication of an experiment in which measurements of rotordynamic forces would be made on simulated leakage flows in which the flow rate, clearance, eccentricity and other parameters would be exercised in order to understand the phenomena. Sample data is presented and demonstrates substantial rotordynamic effects which could be potentially destabilizing. The rotordynamic forces appear to be inversely propertional to the clearance and change significant with the flow rate

    Experimental Results for the Rotordynamic Characteristics of Leakage Flows in Centrifugal Pumps

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    In recent years, increasing attention has been give to fluid-structure interaction problems in turbomachines. The present research focuses on just one such fluid-structure interaction problem, namely, the role played by fluid forces in determining the rotordynamic stability and characteristics of a centrifugal pump. The emphasis of this study is to investigate the contributions to the rotordynamic forces from the discharge-to-suction leakage flows between the front shroud of the rotating impeller and the stationary pump casing. An experiment was designed to measure the rotordynamic shroud forces due to simulated leakage flows for different parameters such as flow rate, shroud clearance, face-seal clearance and eccentricity. The data demonstrate substantial rotordynamic effects and a destabilizing tangential force for small positive whirl frequency ratios; this force decreased with increasing flow rate. The rotordynamic forces appear to be inversely proportional to the clearance and change significantly with the flow rate. Two sets of data taken at different eccentricities yielded quite similar nondimensional rotordynamic forces indicating that the experiments lie within the linear regime of eccentricity

    Basic quasi-Hopf algebras over cyclic groups

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    Let mm a positive integer, not divisible by 2,3,5,7. We generalize the classification of basic quasi-Hopf algebras over cyclic groups of prime order given in \cite{EG3} to the case of cyclic groups of order mm. To this end, we introduce a family of non-semisimple radically graded quasi-Hopf algebras A(H,s)A(H,s), constructed as subalgebras of Hopf algebras twisted by a quasi-Hopf twist, which are not twist equivalent to Hopf algebras. Any basic quasi-Hopf algebra over a cyclic group of order mm is either semisimple, or is twist equivalent to a Hopf algebra or a quasi-Hopf algebra of type A(H,s)A(H,s).Comment: 32page

    Importance of foot and mouth disease vaccine purity in interpreting serological surveys

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    The aim of this study was to determine whether the degree of purity achieved in conventional vaccines against the foot and mouth disease virus in Argentina interferes with the interpretation of seroepidemiological surveys for confirming the absence of viral activity, which are performed to support the recognition of free zones practising vaccination. The evaluation of 168 vaccine series due to be marketed in Argentina (2006–2012) and subjected to official control testing in cattle, as well as repeated vaccination of cattle and other species using vaccines with high antigen concentrations, demonstrated that they did not induce antibodies to non-structural proteins (NSPs). The results show clearly that vaccines with satisfactory potency do not induce a response to NSPs, even by forcing the immune response through more concentrated doses with multiple valences and revaccination protocols at shorter intervals than in vaccination campaigns. These results confirm that the vaccines used in routine vaccination programmes have a degree of antigen purification consistent with the needs observed on the basis of sampling for serological surveillance. Moreover, serological surveys conducted in 2006–2011 by Argentina’s official Veterinary Services – the National Health and Agrifood Quality Service (SENASA) – on more than 23,000 sera per year from cattle included in the vaccination programme, in order to confirm the absence of virus circulation, revealed an average 0.05% of reactive results, consistent with the specificity of the tests. In conclusion, the vaccines produced by conventional methods and with proven potency that are available in Argentina are sufficiently purified to ensure that they do not interfere with the interpretation of sampling for serological surveillance performed to support the recognition of FMD-free zones practising vaccination.Fil: Smitsaart, E.. Biogénesis Bagó; ArgentinaFil: Espinosa, A. M.. Biogénesis Bagó; ArgentinaFil: Maradei, E. D.. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; ArgentinaFil: Cosentino, B.. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; ArgentinaFil: Guinzburg, M.. Biogénesis Bagó; ArgentinaFil: Maddoni, G.. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; ArgentinaFil: Cadennazzi, G.. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; ArgentinaFil: Bottini, R.. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; ArgentinaFil: Filippi, J.. Biogénesis Bagó; ArgentinaFil: Bergmann, Ingrid Evelyn. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ciencia y Tecnología "Dr. César Milstein". Fundación Pablo Cassará. Instituto de Ciencia y Tecnología ; Argentin

    Evaluation du logiciel "I-IDEAS"

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    Rotordynamic forces generated by discharge-to-suction leakage flows in centrifugal pumps

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    In recent years, increasing attention has been given to fluid-structure interaction problems in turbomachines. The present research focuses on just one such fluid-structure interaction problem, namely the role played by fluid forces in determining the rotordynamic stability and characteristics of a centrifugal pump. While the geometry of the impeller shroud/pump casing annulus varies considerably, previous studies indicate that the contributions from the leakage flow can be of the same order as the contributions from the nonuniform pressure acting on the impeller discharge. Thus, the emphasis of this study is to investigate the contributions to the rotordynamic forces from the discharge-to-suction leakage flows between the front shroud of the rotating impeller and the stationary pump casing. An experiment was designed to measure the rotordynamic shroud forces due to simulated leakage flows for different parameters such as flow rate, shroud clearance, face-seal clearance and eccentricity. The data demonstrates substantial rotordynamic effects and a destabilizing tangential force for small positive whirl ratios; this force decreased with increasing flow rate. The rotordynamic forces appear to be inversely proportional to the clearance and change significantly with the flow rate. Two sets of data taken at different eccentricities yielded quite similar nondimensional rotordynamic forces indicating that the experiments lie within the linear regime of eccentricity. Like earlier measurements of the total fluid induced rotordynamic forces on impellers [Chamieh et al. (1985), Jery et al. (1985), Adkins et al. (1988)], the forces measured in these experiments scaled with the square of the rotor speed. The functional dependence on the ratio of whirl frequency to rotating frequency (termed the whirl ratio) is very similar to that measured in experiments and similar to that predicted by the theoretical work of Childs. Childs' bulk flow model yielded some unusual results including peaks in the rotordynamic forces at particular positive whirl ratios, a phenomenon which Childs tentatively described as a "resonance" of the leakage flow. This unexpected phenomenon developed at small positive whirl ratios when the inlet swirl velocity ratio exceeded about 0.5. Childs points out that a typical swirl velocity ratio at inlet (pump discharge) would be about 0.5 and may not therefore be large enough for the resonance to be manifest. To explore whether this effect occurs, an inlet guide vane was constructed which introduced a known amount of swirl into the flow upstream of the leakage flow inlet. A detailed comparison of model predictions with the present experimental program is presented. The experimental results showed no evidence of the "resonances", even at much larger swirl inlet velocities than explored by Childs
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