Publications

Origins and Structure of Spike-Type Rotating Stall

Authors:

Pullan, G., Young, A.M., Day, I.J., Greitzer, E.M. and Spakovszky, Z.S.

Publication:

J. Turbomach 137(5), 051007 (May 01, 2015) (11 pages)

DOI:

10.1115/1.4028494

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An experimental and computational study of tip clearance effects on a transonic turbine stage

This paper describes an experimental and computational investigation into the influence of tip clearance on the blade tip heat load of a high-pressure (HP) turbine stage. Experiments were performed in the Oxford Rotor facility which is a 11 stage, shroudless, transonic, high pressure turbine. The experiments were conducted at an engine representative Mach number and Reynolds number. Rotating frame instrumentation was used to capture both aerodynamic and heat flux data within the rotor blade row. Two rotor blade tip clearances were tested (1.5% and 1.0% of blade span). The experiments were compared with computational fluid dynamics (CFD) predictions made using a steady Reynolds-averaged Navier-Stokes (RANS) solver. The experiments and computational predictions were in good agreement. The blade tip heat transfer was observed to increase with reduced tip gap in both the CFD and the experiment. The augmentation of tip heat load at smaller clearances was found to be due to the ingestion of

Authors:

Adam J. Jackson, Andrew P. S. Wheeler, Roger W. Ainsworth

Publication:

International Journal of Heat and Fluid Flow

DOI:

10.1016/j.ijheatfluidflow.2015.09.001

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Radial Turbine Rotor Response to Inlet Pulsating Flows

The performance of automotive turbocharger turbines has long been realized to be quite different under pulsating flow conditions compared to that under the equivalent steady and quasi-steady conditions on which the conventional design concept is based. However, the mechanisms of this phenomenon are still intensively investigated nowadays. This paper presents an investigation of the response of a stand-alone rotor to inlet pulsating flow conditions by using a validated unsteady Reynolds-averaged Navier–Stokes solver (URANS). The effects of the frequency, the amplitude, and the temporal gradient of pulse waves on the instantaneous and cycle integrated performance of a radial turbine rotor in isolation were studied, decoupled from the upstream turbine volute. A numerical method was used to help gain the physical understanding of these effects. A validation of the numerical method against the experiments on a full configuration of the turbine was performed prior to the numerical tool being

Authors:

Teng Cao , Liping Xu , Mingyang Yang , Ricardo F. Martinez-Botas

Publication:

Journal of Turbomachinery

DOI:

https://doi.org/10.1115/1.4025948

The frequency response of acoustic doppler current profilers: Spatiotemporal response and implicatio

Authors:

Guion, R. and Young, A.

Publication:

IEEE Oceans

DOI:

10.1109/OCEANS.2014.7003057

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Unsteady Gust Response of Tidal Stream Turbines

This paper investigates the limitations of 2D linear unsteady aerofoil theory for modelling the unsteady gust response of tidal stream turbines. Accurate unsteady load prediction is required to determine turbine life. Current state of the art design codes in industry use a single model, based on Theodorsen’s theory, to predict the response to all types of gust. This paper shows that different types of gust require different types of model. Vortical gusts, such as due to turbulence and shear flows, should be modelled using a combination of Sears’ and Horlock’s theories. Pressure gusts, such as those caused by free surface waves, should be modelled using Loewy’s theory. The accuracy of these models is examined using numerical predictions. The range of gusts likely to occur at real tidal sites is also examined. In most likely situations, pressure gusts cause variations in loads which can be modelled quasi-steadily,but vortical gusts must be modelled using the combined Sears/Horlock theory

Authors:

Sequeira, C., and Miller, R.

Publication:

In proceedings of the OCEANS'14 MTS/IEEE conference, St. John's, Canada

A Low Order Model for Predicting Turbocharger Turbine Unsteady Performance

In this paper, a low order model for predicting performance of radial turbocharger turbines is presented. The model combines an unsteady quasi-three dimensional CFD method with multiple one-dimensional meanline impeller solvers. The new model preserves the critical volute geometry features, which is crucial for the accurate prediction of the wave dynamics and retains effects of the rotor inlet circumferential non-uniformity. It also still maintains the desirable properties of being easy to set up and fast to run.

Authors:

Teng Cao, Liping Xu

Publication:

ASME Turbo Expo 2014

DOI:

10.1115/GT2014-25913

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Tip-Leakage Losses in Subsonic and Transonic Blade Rows

n this paper the effect of blade-exit Mach number on unshrouded turbine tip-leakage flows is investigated. Previously published experimental data of a high-pressure turbine blade are used to validate a computational fluid dynamics (CFD) code, which is then used to study the tip-leakage flow at blade-exit Mach numbers from 0.6 to 1.4. Three-dimensional (3D) calculations are performed of a flat-tip and a cavity-tip blade. Two-dimensional calculations are also performed to show the effect of various squealer-tip geometries on an idealized tip flow. The results show that as the blade-exit Mach number is increased the tip-leakage flow becomes choked. Therefore the tip-leakage flow becomes independent of the pressure difference across the tip and hence the blade loading. Thus the effect of the tip-leakage flow on overall blade loss reduces at blade-exit Mach numbers greater than 1.0. The results suggest that for transonic blade rows it should be possible to raise blade loading within the tip

Authors:

Andrew P. S. Wheeler, Theodosios Korakianitis and Shashimal Banneheke

Publication:

Journal of Turbomachinery

DOI:

10.1115/1.4006424

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Loss Mechanisms in Tidal Stream Turbines

This paper explores the loss mechanisms critical to the operation of a tidal stream turbine. There is an upper limit to the amount of power that may be removed from a tidal stream. The designer may therefore aim to minimise the ratio of loss to useful power. Computational predictions were undertaken on a horizontal axis turbine. At design point, the total loss for this case was 69.2% of the useful power extracted. This may be broken down to different sources: rotor profile loss, structural loss, and wake mixing loss. Wake mixing loss is shown to dominate. It is shown that in addition to the ‘idealised’ radial variation of velocity through the wake there was also significant circumferential variation. This circumferential variation is responsible for ~one third of total wake mixing loss, while the remaining two thirds is due to radial variations. This result implies that wake mixing loss could be reduced by designing turbines which produce wakes with lower circumferential non-uniformity

Authors:

Sequeira, C., and Miller, R.

Aerodynamic Design of High End Wall Angle Turbine Stages—Part I: Methodology Development

Authors:

A. W. Cranstone; G. Pullan; E. M. Curtis; S. Bather

Publication:

J. Turbomach. 2013; 136(2):021006-021006-8.

DOI:

10.1115/1.4023905

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The Role of Dense Gas Dynamics on Organic Rankine Cycle Turbine Performance

In this paper, we investigate the real gas flows which occur within organic Rankine cycle (ORC) turbines. A new method for the design of nozzles operating with dense gases is discussed, and applied to the case of a high pressure ratio turbine vane. A Navier-Stokes method, which uses equations of states for a variety of working fluids typical of ORC turbines, is then applied to the turbine vanes to determine the vane performance. The results suggest that the choice of working fluid has a significant influence on the turbine efficiency.

Authors:

Andrew P. S. Wheeler, Jonathan Ong

Publication:

Journal of Engineering for Gas Turbines and Power

DOI:

10.1115/1.4024963

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