Research Papers

Multall—An Open Source, Computational Fluid Dynamics Based, Turbomachinery Design System

[+] Author and Article Information
John D. Denton

Whittle Laboratory,
Cambridge University Engineering Department,
Cambridge CB3 ODY, UK
e-mail: jdd1@cam.ac.uk

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 11, 2017; final manuscript received August 24, 2017; published online September 26, 2017. Editor: Kenneth Hall.

J. Turbomach 139(12), 121001 (Sep 26, 2017) (12 pages) Paper No: TURBO-17-1085; doi: 10.1115/1.4037819 History: Received July 11, 2017; Revised August 24, 2017

Turbomachinery design systems are usually the jealously guarded property of large companies, and the author is not aware of any for which the source code is freely available. This paper is aimed providing a freely available system that can be used by individuals or small companies who do not have access to an in-house system. The design system is based on the three-dimensional (3D) computational fluid dynamics (CFD) solver Multall, which has been developed over many years. Multall can obtain solutions for individual blade rows or for multistage machines, and it can also perform quasi-3D (Q3D) blade-to-blade calculations on a prescribed stream surface and axisymmetric throughflow calculations. Multall is combined with a one-dimensional (1D) mean-line program, Meangen, which predicts the blading parameters on a mean stream surface and writes an input file for Stagen. Stagen is a blade geometry generation and manipulation program which generates and stacks the blading, combines it into stages, and writes an input file for Multall. The system can be used to design the main blade path of all types of turbomachines. Although it cannot design complex features such as shroud seals and individual cooling holes, these features can be modeled, and their effect on overall performance predicted. The system is intended to be as simple and easy to use as possible, and the solver is also very fast compared to most CFD codes. A great deal of user experience ensures that the overall performance is reasonably well predicted for a wide variety of machines. This paper describes the system in outline and gives an example of its use. The source codes are written in FORTRAN77 and are freely available for other users to try.

Copyright © 2017 by ASME
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Fig. 1

Effects of local restagger on an LP turbine blade

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Fig. 2

Blade thickness distributions obtained from Stagen

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Fig. 3

Root, mean and tip blade sections for a last-stage steam turbine rotor

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Fig. 4

Prediction of the stagnation point on a turbine blade

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Fig. 5

Solution for the staggered wedge test case

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Fig. 6

A 9 × 9 multigrid block composed of 9 × 3 × 3 blocks

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Fig. 7

Mixing plane treatment

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Fig. 8

Mixing plane with shock and expansion waves

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Fig. 9

Static pressure for potential flow across a mixing plane

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Fig. 10

The cells used for a Q3D calculation

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Fig. 11

Cells used for a throughflow calculation

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Fig. 12

(a) Comparison of streamlines from throughflow and full 3D calculations, (b) comparison of throughflow and 3D solutions in the last stage of the LP steam turbine, and (c) midspan surface pressure distribution calculated by the throughflow method

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Fig. 13

Computed trailing edge pressure distributions with and without a cusp

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Fig. 14

Grid for a cusp model at the trailing edge

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Fig. 15

Contours of relative velocity through a water pump

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Fig. 16

Compressor layout with contours of pitchwise averaged entropy

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Fig. 17

Mach number contours at midspan

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Fig. 18

Surface pressure distribution at midspan

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Fig. 19

Computed characteristic of the compressor




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