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Research Papers: Multiphase Flows

On the Preliminary Design and Noncavitating Performance Prediction of Tapered Axial Inducers

[+] Author and Article Information
Luca d’Agostino

Department of Aerospace Engineering, University of Pisa, Via G. Caruso, 56100 Pisa, Italyluca.dagostino@ing.unipi.it

Lucio Torre

 Alta S.p.A., Via Gherardesca 5, 56121 Pisa, Italyl.torre@alta-space.com

Angelo Pasini

 Alta S.p.A., Via Gherardesca 5, 56121 Pisa, Italya.pasini@alta-space.com

Angelo Cervone

 Alta S.p.A., Via Gherardesca 5, 56121 Pisa, Italya.cervone@alta-space.com

J. Fluids Eng 130(11), 111303 (Sep 23, 2008) (8 pages) doi:10.1115/1.2979007 History: Received February 05, 2008; Revised July 10, 2008; Published September 23, 2008

A reduced order model for preliminary design and noncavitating performance prediction of tapered axial inducers is illustrated. In the incompressible, inviscid, irrotational flow approximation, the model expresses the 3D flow field in the blade channels by superposing a 2D cross-sectional vorticity correction to a fully guided axisymmetric flow with radially uniform axial velocity. Suitable redefinition of the diffusion factor for bladings with non-negligible radial flow allows for the control of the blade loading and the estimate of the boundary layer blockage at the specified design flow coefficient, providing a simple criterion for matching the hub profile to the axial variation of the blade pitch angle. Carter’s rule is employed to account for flow deviation at the inducer trailing edge. Mass continuity, angular momentum conservation, and Euler’s equation are used to derive a simple second order boundary value problem, whose numerical solution describes the far-field axisymmetric flow at the inducer discharge. A closed form approximate solution is also provided, which proved to yield equivalently accurate results in the prediction of the inducer performance. Finally, the noncavitating pumping characteristic is obtained by introducing suitably adapted correlations of pressure losses and flow deviation effects. The model has been verified to closely approximate the geometry and noncavitating performance of two space inducers tested in Alta’s Cavitating Pump Rotordynamic Test Facility, as well as the measured pumping characteristics of a number of tapered-hub inducers documented in the literature.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Inducer schematic and nomenclature

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Figure 2

Schematic of the 2D cross-sectional slip velocity correction in the inducer blade channels

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Figure 3

Velocity triangles

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Figure 4

Nomenclature for blade boundary layer (left) and linear cascade (right)

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Figure 5

Ratio of the momentum thickness θ∗ of the blade boundary layer to the chord c as a function of the diffusion factor D, for axial cascades with three different profiles (adapted from Brennen (4)).

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Figure 6

3D rendering of a four-bladed, tapered-hub, variable-pitch inducer designed according to the proposed model

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Figure 7

Comparison between the numerical solution (ODE) and the corresponding closed form approximation (MOD) for the noncavitating performance prediction of tapered inducers

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Figure 8

Comparison between the experimental noncavitating performance of the MK1 inducer (dark stars) and the predictions of the analytical model

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Figure 9

Comparison between the experimental noncavitating performance of the FAST2 inducer (white stars) and the prediction of the analytical model

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Figure 10

Comparison between the experimental noncavitating performance of the inducer A (dark stars) and the predictions of the analytical model

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Figure 11

Comparison between the experimental noncavitating performance of the inducer B (dark stars) and the predictions of the analytical model

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Figure 12

Comparison between the experimental noncavitating performance of the inducer C (dark stars) and the predictions of the analytical model

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Figure 13

Comparison between the experimental noncavitating performance of the inducer D (dark stars) and the predictions of the analytical model

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