A Comparison of Advanced Numerical Techniques to Model Transient Flow in Turbomachinery Blade Rows

Connell, Stuart; Braaten, Mark E.; Zori, Laith; Steed, Robin; Hutchinson, Brad; Cox, Graham D.

doi:10.1115/gt2011-45820

Cited by 24 publications

(10 citation statements)

References 5 publications

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“…In this case, the time coordinate is transformed, being a linear function of circumferential location, blade pitch and rotor angular velocity. This approach also does not corrupt accuracy [62]. The different location of variables in time can be rectified during post-processing.…”

Section: Specialised Turbomachinery Boundary Conditionsmentioning

confidence: 99%

Future Use of Large Eddy Simulation in Aero‐engines

Tyacke

Tucker

2015

Journal of Turbomachinery

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Computational fluid dynamics (CFD) has become a critical tool in the design of aero-engines. Increasing demand for higher efficiency, performance, and reduced emissions of noise and pollutants has focused attention on secondary flows, small scale internal flows, and flow interactions. In conjunction with low order correlations and experimental data, RANS (Reynolds-averaged Navier–Stokes) modeling has been used effectively for some time, particularly at high Reynolds numbers and at design conditions. However, the range of flows throughout an engine is vast, with most, in reality being inherently unsteady. There are many cases where RANS can perform poorly, particularly in zones characterized by strong streamline curvature, separation, transition, relaminarization, and heat transfer. The reliable use of RANS has also been limited by its strong dependence on turbulence model choice and related ad-hoc corrections. For complex flows, large-eddy simulation (LES) methods provide reliable solutions, largely independent of turbulence model choice, and at a relatively low cost for particular flows. LES can now be used to provide in depth knowledge of flow physics, for example, in areas such as transition and real wall roughness effects. This can be used to inform RANS and lower order modeling (LOM). For some flows, LES can now even be used for design. Existing literature is used to show the potential of LES for a range of flows in different zones of the engine. Based on flow taxonomy, best practices including RANS/LES zonalization, meshing requirements, and turbulent inflow conditions are introduced, leading to the proposal of a tentative expert system for industrial use. In this way, LES becomes a well controlled tool, suitable for design use and reduces the burden on the end user. The problem sizes tackled however have lagged behind potential computing power, hence future LES use at scale requires substantial progress in several key areas. Current and future solver technologies are thus examined and the potential current and future use of LES is considered.

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Section: Specialised Turbomachinery Boundary Conditionsmentioning

confidence: 99%

Future Use of Large Eddy Simulation in Aero‐engines

Tyacke

Tucker

2015

Journal of Turbomachinery

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“…Here the time transformation (TT) method is used. It belongs to a family of transient blade row methods known as "transformation methods" [17], which overcome the issue of unequal pitch in adjacent blade rows by transforming some quantity according to its own specific method.…”

Section: Figure 2 Photograph Of the Subject Stagementioning

confidence: 99%

Impeller-Diffuser Interaction in Centrifugal Compressors

Robinson

Casey

Hutchinson

et al. 2012

Volume 8: Turbomachinery, Parts A, B, and C

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This paper reports several CFD analyses of a centrifugal compressor stage with a vaned diffuser at high pressure ratio using different techniques to model the rotor-stator interaction. A conventional steady stage calculation with a mixing-plane type interface between the rotor and stator was used as a baseline. This simulation gave excellent agreement with the measured performance characteristics at design speed, demonstrating the ability of the particular steady simulation used to capture the essential features of the blockage interaction between the components. A full annulus simulation using a transient rotor-stator interaction (TRS) method was then used at the peak efficiency point to obtain a fully unsteady reference solution, and this predicted a small increase in peak efficiency. Finally, a computationally less expensive unsteady calculation using a Time Transformation (TT) method was carried out. This gave similar results to the fully transient calculation suggesting that this is an acceptable approach to estimate unsteady blade loading from the interaction. The impeller diffuser spacing was then reduced from 15 to 7% of the impeller tip radius using the more affordable TT approach. This identified an increase in efficiency of 1% and predicted unsteady pressure fluctuations in the impeller which were 116% higher with the closely spaced diffuser.

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“…The present TT implementation was applied to turbomachinery problems by Biesiger et al, 4 Connell et al 5 and Blumenthal et al, 6 amongst others. Alternative methods include a profile transformation, where the impeller exit and diffuser inflow profiles are scaled to account for unequal pitches.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Tonal Sound Pressure Level Distribution in the Vaned Diffuser of a Centrifugal Compressor

Banica¹,

Fischer²,

Feld³

et al. 2014

20th AIAA/CEAS Aeroacoustics Conference

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Numerical predictions of acoustic fields in vaned diffusers of radial compressors are often impractical due to excessive runtimes. Two methods are evaluated here that promise runtime reductions through appropriate simplifications: 1) An inlet gust (IG) method and 2) A time transformation (TT) method. Each is assessed by comparing diffuser static pressure fluctuation levels on various reference planes and on the diffuser walls with full model (FM) predictions. In addition, a suitable Ffowcs Williams-Hawkings formulation is used to extract the far field sound. In the present setup, TT reduces runtimes by a factor of up to 18 when compared to FM but the results are dependend on the number of modeled passages. The IG method cannot properly account for rotor-stator interaction and predicts qualitatively different near fields. In the far field, FM and IG agree well whereas TT shows larger discrepancies to the FM data.

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A Comparison of Advanced Numerical Techniques to Model Transient Flow in Turbomachinery Blade Rows

Cited by 24 publications

References 5 publications

Future Use of Large Eddy Simulation in Aero‐engines

Future Use of Large Eddy Simulation in Aero‐engines

Impeller-Diffuser Interaction in Centrifugal Compressors

Numerical Analysis of the Tonal Sound Pressure Level Distribution in the Vaned Diffuser of a Centrifugal Compressor

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