A Unified Correlation for Slip Factor in Centrifugal Impellers

Abstract

A method that unifies the trusted centrifugal impeller slip factor prediction methods of Busemann, Stodola, Stanitz, Wiesner, Eck, and Csanady in one equation is presented. The simple analytical method derives the slip velocity in terms of a single relative eddy (SRE) centered on the rotor axis instead of the usual multiple (one per blade passage) eddies. It proposes blade solidity (blade length divided by spacing at rotor exit) as the prime variable determining slip. Comparisons with the analytical solution of Busemann and with tried and trusted methods and measured data show that the SRE method is a feasible replacement for the well-known Wiesner prediction method: it is not a mere curve fit, but is based on a fluid dynamic model; it is inherently sensitive to impeller inner-to-outer radius ratio and does not need a separate calculation to find a critical radius ratio; and it contains a constant, F0, that may be adjusted for specifically constructed families of impellers to improve the accuracy of the prediction. Since many of the other factors that contribute to slip are also dependent on solidity, it is recommended that radial turbomachinery investigators and designers investigate the use of solidity to correlate slip factor.

Modified one-dimensional analysis and two-zone modelling for predicting the performance of radial compressors

“…As the relative flow leaving an impeller will not be perfectly guided by the blades even under ideal frictionless flow conditions, slip factor (SF) correlation that resulted from different models such as those of Stodola [21], Stanitz [22], Wiesner [23], Paeng and Chung [24], Backström [25] and with combination of Various losses including static enthalpy loss, total pressure loss, and total enthalpy loss are described in detail in related literatures [10]. The exit area of the gas leaving the impeller shall be corrected according to the slip, which results in the corrected angle β dc .…”

A new approach for optimum selection of a turbocharger using a genetic algorithm

“…In the later case a geometrical parameter L was defined as described by equation (20). Then a turbocharger with the closest geometry values to L was selected as the final optimum turbocharger.…”

Numerical Study of Slip Factor in Centrifugal Pumps and Study Factors Affecting its Performance

“…But there is a big mistake in " Fig.3"because most of the pumps not work only on its best efficiency point but also work on different H&Q Points thus we must show the effect of different discharge the effect of this in " Fig.4" at the design exit blade angle. Which show different methods of calculation slip factor [3], [3], [7] .In this study I used CFD to calculate slip factor at different flow rates and make curve fit between them to show the general trend and compare this trend with the other relations trends.…”

“…Thus we study it on the radial impeller . which is affected on the energy transfer between impeller and the fluid thus we should know this phenomenon at every point and study the factors effected on it I will study the important factor in this papersuchasdischarge ,exit blade angle (blade difference angle, number of blades.There are many models predict the slip factor in centrifugal pump such as X. Qiu [1], Wiesner [3]T. W. von Backstrom [3],stodla [7], , , M. Memardezfouli [4] , in the majority of this models study the effect of geometry of impeller only but in this study we notice the slip factor depend on geometry and flow characteristics but in the first I will show what is the slip phenomenon in some radial machines such as Pumps, Compressors, etc the actual amount of energy transfer to the fluid is less than the theoretical one .The blades do not guide the flow completely and fluid deviation occurs at exit of impeller and hence the liquid is discharged from the impeller at a mean relative angle  2 less than the blade exit angle  / 2 .Which results in less Cu 2 than the In this study CFD package which is in the last years get high accurate results compared it to Experimental or analatical data thus we can depend on this tool to save more of time and money but take care in the boundary condition and turbulence model and mesh type and number maintaining the integrity of the Specifications…”