Correlation of Cavitating Centrifugal Pumps

1984 ◽  
Vol 106 (2) ◽  
pp. 141-146 ◽  
Author(s):  
V. J. Zika
Keyword(s):  
Narrow Band ◽  
Centrifugal Pumps ◽  
Cavitation Process ◽  
New Methods ◽  
Thermodynamic Effect ◽  
Variable Nature ◽  
Test Points ◽  
Actual Test

The foreknowledge of the minimum NPSH (“net positive suction head”) required for a cavitation-free performance of centrifugal pumps is important for a safe and sound operation of these machines. The required NPSH varies from pump to pump, from fluid to fluid, and from temperature to temperature of the pumped fluid. This is known as the thermodynamic effect. The methods currently used for the correlation and analysis of this condition are not always reliable because of the multi-variable nature of the cavitation process. In this paper, two new methods are proposed which lead to more consistent correlations of the required minimum NPSH; thus they can also be used for more dependable predictions of the net positive suction head for any pump, fluid and temperature. The predictions by the two methods do not coincide, but outline a narrow band of probability, within which the actual test points are invariably located.

New Estimation Methods for the Steel Weight of European Inland Dry Bulk Ships

2015 ◽  
Vol 31 (02) ◽  
pp. 79-87
Author(s):  
Robert G. Hekkenberg ◽  
Hans Hopman
Keyword(s):  
Narrow Band ◽  
Estimation Methods ◽  
Weight Estimation ◽  
New Methods ◽  
Steel Weight ◽  
Phd Thesis

There are hardly any methods available for the estimation of the steel weight of inland ships in the earliest design stages. The few weight estimation methods that are available are out of date, limited to a narrow band of main dimensions and not sensitive enough to be used for innovative designs. In this article, which summarizes key results from the PhD thesis of Hekkenberg (2013), new methods are derived for the estimation of the steel weight of inland dry bulk ships. The estimation methods that are presented are derived from large systematic series of computer generated ship designs that comply with Lloyds Register's rules regarding their structure and with the European rules for freeboard. The structure and weight of these designs are validated by a comparison of modeled scantlings with the scantlings of midship sections of existing ships. Further validation is done by a comparison of the modeled overall steel weight with the steel weight of actual ships and the weight estimates of existing methods. The designs are used to derive two types of estimation methods: the first is a set of simple formulas that are valid for inland ships with common sizes and L/B ratios and the second is a more complex set of formulas that allows estimation of the steel weight of inland ships with draughts ranging from 1.5 to 4.5 m, lengths of 40–185 m, beams of 5–25 m, and L/B ratios of 4–20.

The Effects of Fluid Properties on Cavitation in Centrifugal Pumps

1965 ◽  
Vol 87 (3) ◽  
pp. 309-318 ◽  
Author(s):  
W. A. Spraker
Keyword(s):  
Cold Water ◽  
Fuel Oil ◽  
Centrifugal Pumps ◽  
Hydrocarbon Mixtures ◽  
Volume Percentage ◽  
Cavitation Process ◽  
Pure Fluids ◽  
Two Fluids ◽  
Fluid Properties ◽  
The Difference

An analytical model of the cavitation process in a pump is developed assuming that the flow is adiabatic, frictionless, steady, and irrotational. A relationship is developed relating the volume percentage of the fluid vaporized during the cavitation process to the “thermal cavitation parameter.” Two assumptions are then introduced concerning the cavitation process in a pump pumping fluids of different cavitation characteristics. Using these assumptions, a relationship is derived indicating that the difference in net positive suction head (NPSH) of a given pump handling two fluids is a function of the difference of the reciprocals of the thermal cavitation parameter for the two fluids and of the volume percentage of the fluid vaporized. This relationship is compared with data describing the cavitation characteristics of six pumps handling four pure fluids. The change in NPSH for all of the pumps and fluids, using the cold-water NPSH as a reference, is found to correlate as a function of the reciprocal of the thermal cavitation parameter with an accuracy of ±1 ft in NPSH. Experimental and analytical methods for determining the cavitation characteristics of pumps handling petroleum-based hydrocarbon mixtures are then described. Cavitation data for two pumps handling gasoline, fuel oil, and crude oil are presented. The data correlation for pure fluids is extended to include cavitation data for petroleum-based hydrocarbon mixtures. It is found that mixtures exhibit an additional decrement in NPSH over that for pure fluids having the same value of the thermal cavitation parameter. This additional decrement is found to be temperature dependent.

Cavitation and NPSH Requirements of Various Liquids

1959 ◽  
Vol 81 (2) ◽  
pp. 167-174 ◽  
Author(s):  
Victor Salemann
Keyword(s):  
Direct Measurement ◽  
Cold Water ◽  
Test Results ◽  
Centrifugal Pumps ◽  
Pump Performance ◽  
Cavitation Process

Test results on the net positive suction head, NPSH, requirements for centrifugal pumps handling water up to 420 F, some hydrocarbons, and Freon-11 are presented. Satisfactory pump performance was observed with net positive suction heads less than those required by the pump on cold water. A direct measurement of NPSH was attempted and is reported. The cavitation process is discussed and a correlation and method of prediction for all liquids is proposed.

Numerical Simulation Study of the Impellers of the Centrifugal Pump Based on Different Turbulence Models

2013 ◽  
Vol 423-426 ◽  
pp. 2049-2053 ◽  
Author(s):  
Ao Hui Guo ◽  
Yong Zhong Zeng ◽  
Xiao Bing Liu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Centrifugal Pump ◽  
Simulation Study ◽  
Turbulence Models ◽  
Centrifugal Pumps ◽  
Ansys Software ◽  
Sst Model ◽  
Simulation Results ◽  
Actual Test

The Computational Fluid (CFD) technology has been successfully used in the numerical simulation of the turbulent flow of centrifugal pump.In this article , we carry on the experiment by using uses ANSYS software,based on the standard k-ε model, SST model and BSL model , to get the the flow field of the numerical simulationof the impeller .We found that the simulation results and the actual results are different under different turbulence models. Then we can draw out the Q-η curve and compare it with the actual test data.Compared with other turbulence models, The SST model is more suitable for the models of centrifugal pumps in the article.Furthermore,we list the pressure contours and velocity vectors for pumps discussed in the paper under the optimal model.The process can provide a theoretical reference for the optimization and further study of the centrifugal pump in the future.

Optimal Design of Cylindrical Helical Torsional Spring Including Fatigue Reliability

2013 ◽  
Vol 395-396 ◽  
pp. 862-865
Author(s):  
Shi Jian Zhao ◽  
Wei Min Cui ◽  
Wei Tian
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Optimal Design ◽  
New Method ◽  
Fatigue Reliability ◽  
Torsion Spring ◽  
New Methods ◽  
Traditional Design ◽  
Torsional Spring ◽  
Test Points

To get a way of calculating the reliability of fatigue life of torsion spring, the paper discussed the optimal design of fatigue reliability for cylindrical helical torsional spring with Monte-Carlo method, and tried to build a new method to analyze the fatigue reliability of cylindrical helical torsional spring. The new method could test different values of parameters of a spring, and it could calculate the fatigue reliability of the spring in every parameter value with about 100 thousand test points with Monte-Carlo method, which can be set to get a better result, and it gave the comparison and selection to designers finally. The method was run with the software-MATLAB. The paper gave an example at last, and it compared the new methods results with ones of traditional design and discussed the differences.

Statistical analysis of classification

1966 ◽  
Vol 24 ◽  
pp. 188-189
Author(s):  
T. J. Deeming
Keyword(s):  
Multivariate Analysis ◽  
Statistical Analysis ◽  
Classification Scheme ◽  
Analytical Procedure ◽  
Narrow Band ◽  
Scientific Research ◽  
Maximum Amount ◽  
Amount Of Information

If we make a set of measurements, such as narrow-band or multicolour photo-electric measurements, which are designed to improve a scheme of classification, and in particular if they are designed to extend the number of dimensions of classification, i.e. the number of classification parameters, then some important problems of analytical procedure arise. First, it is important not to reproduce the errors of the classification scheme which we are trying to improve. Second, when trying to extend the number of dimensions of classification we have little or nothing with which to test the validity of the new parameters.Problems similar to these have occurred in other areas of scientific research (notably psychology and education) and the branch of Statistics called Multivariate Analysis has been developed to deal with them. The techniques of this subject are largely unknown to astronomers, but, if carefully applied, they should at the very least ensure that the astronomer gets the maximum amount of information out of his data and does not waste his time looking for information which is not there. More optimistically, these techniques are potentially capable of indicating the number of classification parameters necessary and giving specific formulas for computing them, as well as pinpointing those particular measurements which are most crucial for determining the classification parameters.

Photo-electric Hβ and uvby photometry

1966 ◽  
Vol 24 ◽  
pp. 170-180
Author(s):  
D. L. Crawford
Keyword(s):  
Narrow Band ◽  
Line Strength ◽  
Interference Filter ◽  
B Stars ◽  
Relative Line ◽  
The Mean ◽  
F Stars ◽  
Two Parameters ◽  
Filter Photometry ◽  
The Continuum

Early in the 1950's Strömgren (1, 2, 3, 4, 5) introduced medium to narrow-band interference filter photometry at the McDonald Observatory. He used six interference filters to obtain two parameters of astrophysical interest. These parameters he calledlandc, for line and continuum hydrogen absorption. The first measured empirically the absorption line strength of Hβby means of a filter of half width 35Å centered on Hβand compared to the mean of two filters situated in the continuum near Hβ. The second index measured empirically the Balmer discontinuity by means of a filter situated below the Balmer discontinuity and two above it. He showed that these two indices could accurately predict the spectral type and luminosity of both B stars and A and F stars. He later derived (6) an indexmfrom the same filters. This index was a measure of the relative line blanketing near 4100Å compared to two filters above 4500Å. These three indices confirmed earlier work by many people, including Lindblad and Becker. References to this earlier work and to the systems discussed today can be found in Strömgren's article inBasic Astronomical Data(7).

Southern Hemisphere Seti Survey: Five Years of Project Meta II

1997 ◽  
Vol 161 ◽  
pp. 611-621
Author(s):  
Guillermo A. Lemarchand ◽  
Fernando R. Colomb ◽  
E. Eduardo Hurrell ◽  
Juan Carlos Olalde
Keyword(s):  
Southern Hemisphere ◽  
Scattering Theory ◽  
Galactic Plane ◽  
Narrow Band ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Inertial Frames ◽  
Interstellar Scattering ◽  
Extraterrestrial Origin ◽  
Spectral Channels

AbstractProject META II, a full sky survey for artificial narrow-band signals, has been conducted from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomía (IAR). The search was performed near the 1420 Mhz line of neutral hydrogen, using a 8.4 million channels Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earths rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 2 × 1013spectral channels analyzed, 29 extra-statistical narrow-band events were found, exceeding the average threshold of 1.7 × 10−23Wm−2. The strongest signals that survive culling for terrestrial interference lie in or near the galactic plane. A description of the project META II observing scheme and results is made as well as the possible interpretation of the results using the Cordes-Lazio-Sagan model based in interstellar scattering theory.

Replication of Wet Objects and Cells

1974 ◽  
Vol 32 ◽  
pp. 102-103
Author(s):  
S. Basu ◽  
D. F. Parsons
Keyword(s):  
Water Vapor Pressure ◽  
High Vacuum ◽  
Polystyrene Latex ◽  
Vacuum System ◽  
Saturated Water Vapor ◽  
Replication Method ◽  
New Methods ◽  
Saturated Water ◽  
Water Vapors ◽  
Intermediate Chamber

We are approaching the invasiveness of cancer cells from the studies of their wet surface morphology which should distinguish them from their normal counterparts. In this report attempts have been made to provide physical basis and background work to a wet replication method with a differentially pumped hydration chamber (Fig. 1) (1,2), to apply this knowledge for obtaining replica of some specimens of known features (e.g. polystyrene latex) and finally to realize more specific problems and to improvize new methods and instrumentation for their rectification. In principle, the evaporant molecules penetrate through a pair of apertures (250, 350μ), through water vapors and is, then, deposited on the specimen. An intermediate chamber between the apertures is pumped independently of the high vacuum system. The size of the apertures is sufficiently small so that full saturated water vapor pressure is maintained near the specimen.

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