NDLI: Admissible Roughness in Gas Turbines

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Martin, N. Goodhand
Copyright Year	2015
Abstract	Roughness below a certain, admissible level will not increase an aerofoil’s skin friction and thus will not impact on engine performance. In this paper a simple model is developed that demonstrates how this admissible roughness height changes through the engine. The model is determined by combining existing analytical models and is backed up by computational validation where necessary. It is shown that, given a fixed inlet/exit stagnation temperature and pressure to a blade row, the admissible roughness height is only a weak function of chord Reynolds number and Mach number for typical gas turbine blades. The aerofoil geometry/duty is also shown to have little impact. This allows the model to give a general picture of where roughness matters, irrespective of the exact details of the flow conditions/blade geometries. The model shows that the admissible roughness height decreases as the stagnation pressure increases. The lowest admissible roughness level occurs at the high pressure end of the compressor at sea-level; the admissible roughness increases as the stagnation pressure drops towards the front of the compressor. Turbines are also most sensitive to roughness close to the combustor, but even there the admissible roughness will be around three times greater than at the rear of the compressor.
Sponsorship	International Gas Turbine Institute
File Format	PDF
ISBN	9780791856734
DOI	10.1115/GT2015-43326
Volume Number	Volume 5C: Heat Transfer
Conference Proceedings	ASME Turbo Expo 2015: Turbine Technical Conference and Exposition
Language	English
Publisher Date	2015-06-15
Publisher Place	Montreal, Quebec, Canada
Access Restriction	Subscribed
Subject Keyword	Temperature Seas Blades Reynolds number Airfoils Surface roughness Compressors Pressure Flow (dynamics) Engines Geometry High pressure (physics) Gas turbines Pressure drop Skin friction (fluid dynamics) Chords (trusses) Combustion chambers Turbines Mach number
Content Type	Text
Resource Type	Article

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