University of Cambridge > Department of Engineering > Whittle Lab > Graham Pullan

Turbine "Real Geometry"

Hub leakage An overlapping stator-rotor hub seal showing streamlines and passive scalar (purple) from the disk space below the main annulus line, from [3].

Until recently, the aerodynamic design of turbomachines has assumed a smooth, clean annulus line. In the actual machine, there are many gaps, steps and leakage paths. These features come under the broad heading of "real geometry". What is surprising is the very large impact that real geometry has on the aerodynamic efficiency of the machine. For example, blades are often manufactured with their own section of hub and casing endwall - when these blades are assembled into a ring, there will be steps and gaps between adjacent blades and this can result in a loss of 1% of efficiency from each endwall, [1]. Of course, resolving all such geometry in CFD can be challenging and so, for routine design calculations, we would like to develop and use modelling where appropriate, [2].

Publications

[1] Reid, K. and Denton, J.D. and Pullan, G. and Curtis, E.M. and Longley, J.P. (2007) The interaction of turbine inter-platform leakage flow with the mainstream flow. ASME Transactions, Journal of Turbomachinery, 129 (2). pp. 303-310.

[2] Rosic, B. and Denton, J.D. and Pullan, G. (2006) The importance of shroud leakage modelling in multistage turbine flow calculations. Transactions of ASME, Journal of Turbomachinery, 128 (4). pp. 699-707.

[3] Reid, K. and Denton, J.D. and Pullan, G. and Curtis, E.M. and Longley, J.P. (2006) The effect of stator-rotor hub sealing flow on the mainstream aerodynamics of a turbine. In: 2006 Proceedings of ASME Turbo Expo: Power for Land, Sea and Air. ASME, Barcelona, Spain.

[4] Reid, K. and Denton, J.D. and Pullan, G. and Curtis, E.M. and Longley, J.P. (2006) Reducing the performance penalty due to turbine inter-platform gaps. In: 2006 Proceedings of ASME Turbo Expo: Power for Land, Sea and Air. ASME, Barcelona, Spain.

Other Research at the Whittle Laboratory