NDLI: Performance Evaluation of a Modified Cross Section Grooved Channel as Turbulence Promoter in Internal Cooling Channel of a Gas Turbine Blade

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Saha, Krishnendu Prabhudharwadkar, Deoras
Copyright Year	2015
Abstract	Internal cooling channel in gas turbine blades use ribs as turbulence promoter to increase local turbulence and improve heat transfer from hot wall to coolant air flowing through the internal cooling channels. The ribs protrude into the flow and result in a significant pressure drop of the coolant air. Indentations like grooves in the cooling channel wall can also be used as turbulence promoters to enhance local heat transfer and as they do not protrude into the mainstream flow, the pressure drop penalty could be much lesser than a conventional ribbed channel. A numerical study is conducted under stationary condition on a square cross section channel representing an internal cooling channel of a turbine airfoil. Some standard and modified cross sections of grooved channel are used as turbulence promoters with a goal to enhance heat transfer from the internal cooling channel wall with minimal pressure drop. The steady state solution is based on using the Reynolds Averaged Navier-Stokes (RANS) equation and k-omega-SST turbulence model. Numerical calculations are done at four Reynolds numbers (Re=15000, 30000, 68000 and 88000) based on fluid properties at the inlet of the internal cooling channel. The grooves are placed on two opposite sides of the square cross section channel and other two walls are smooth walls without any turbulence promoters. A hemispherical cross section continuous groove which is placed perpendicular to the mainstream flow direction is taken as baseline case and a teardrop shaped groove is used to compare the performance difference between the two groove cross section. A broken shaped angled groove configuration with the teardrop cross section groove is also investigated to find the relative performance improvement with the baseline case. Performance comparison with standard 90° rib geometry is done to understand the overall effectiveness of the grooved geometries with respect to common standard in gas turbine blade internal cooling. The straight teardrop cross section groove improves the heat transfer values compared to the hemispherical cross section groove by 8–12% and the broken angled teardrop groove case improves heat transfer by 11–14% compared to the hemispherical cross section groove case. The pressure drop produced by all the groove geometries is about the same. It is seen that the broken angled groove can produce the same heat transfer enhancement compared to a 90° ribbed channel but the pressure drop is more than 3 times lesser compared to the ribbed case. Considering the heat transfer and pressure drop, an increase in thermal performance factor of 37–41% is seen for the angled grooved case compared to the 90° ribbed geometry.
File Format	PDF
ISBN	9780791857502
DOI	10.1115/IMECE2015-51428
Volume Number	Volume 8B: Heat Transfer and Thermal Engineering
Conference Proceedings	ASME 2015 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2015-11-13
Publisher Place	Houston, Texas, USA
Access Restriction	Subscribed
Subject Keyword	Performance evaluation Turbulence Cooling Blades Reynolds number Airfoils Flow (dynamics) Steady state Geometry Cross section (physics) Fluids Gas turbines Pressure drop Reynolds-averaged navier–stokes equations Coolants Heat transfer Turbines
Content Type	Text
Resource Type	Article

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