Projects per year
Abstract
Threedimensional unsteady computational fluid dynamics (CFD) is applied to the ingestion of fluid from a nonuniform mainstream annulus flow via a rimseal into a rotorstator wheelspace. The results provide understanding of the complex flow and information for the development of more efficient computational models and analytical 'orifice models'. The commercial CFD code CFX has been used to carry out unsteady RANS computations with an SST turbulence model. A scalar equation is employed to represent the seeded tracer gas that can be used in experiments to determine sealing effectiveness, and the variation of effectiveness with sealing flow rate is determined for a simple axial clearance seal and one combination of axial and rotational Reynolds numbers. The computational domain comprises one pitch in a row of stator vanes and rotor blades The rotating blade is accounted for by a sliding interface between the stationary and rotating sections of the model, located downstream of the seal clearance. The unsteady computations confirm that the magnitude of the peaktotrough pressure difference in the annulus is the principal driving mechanism for ingestion (or ingress) into the wheelspace. This pressure difference is used in orifice models to predict sealing effectiveness; its magnitude however depends on the locations in the annulus and the wheelspace that are chosen for its evaluation as well as the sealing flow rate. The CFD is used to investigate the appropriateness of the locations that are often used to determine the pressure difference. It is shown that maximum ingestion occurs when the static pressure peak produced by the vane combines with that produced by the blade, and that highly swirled ingrested flow could contact both the stator and rotor disk when little sealing flow is provided. The relationships between the unsteady simulations and simplified, more computationally efficient steady computations are also investigated. For the system considered here, ingress is found to be dictated principally by the pressure distribution caused by the vane. The effect of the rotating blade on the pressure distribution in the annulus is investigated by comparing the unsteady results with those for steady models that do not involve a blade. It is found that the presence of the blade increases the pressure asymmetry in the annulus. Although the pressure asymmetry predicted by unsteady and steady models have a similar magnitude, the sealing effectiveness is overpredicted considerably for the corresponding steady model. If a "thin seal" geometric approximation is used in the steady model, however, similar effectiveness results compared with the unsteady model may be obtained much more economically.
Original language  English 

Title of host publication  Proceedings of the ASME Turbo Expo, 2011 
Subtitle of host publication  Turbine Technical Conference and Exposition. Volume 5: Heat Transfer, Parts A and B 
Publisher  ASME 
Pages  767777 
Number of pages  11 
ISBN (Print)  9780791854655 
DOIs  
Publication status  Published  2011 
Event  ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011  Vancouver, Canada Duration: 5 Jun 2011 → 9 Jun 2011 
Conference
Conference  ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011 

Country  Canada 
City  Vancouver 
Period  5/06/11 → 9/06/11 
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Projects
 1 Finished

Measurement and Modelling of Ingress
Lock, G., Owen, M., Robinson, K. & Wilson, M.
Engineering and Physical Sciences Research Council
1/10/09 → 30/09/12
Project: Research council
Equipment

High Performance Computing (HPC) Facility
Steven Chapman (Manager)
University of BathFacility/equipment: Facility