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Heat Transfer Investigations at the Over-Tip Casing of a High Pressure Turbine Stage – Development of Heat Transfer Correlations

van Duikeren, Bart (2008) Heat Transfer Investigations at the Over-Tip Casing of a High Pressure Turbine Stage – Development of Heat Transfer Correlations. DLR-Forschungsbericht. FB 2008-22, 156 S.

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Abstract

The development of gas turbines aims to an increase of power and efficiency accounting environmental and economical aspects. Meanwhile combustion temperatures reaches values far above of the acceptable material temperatures. Thus the thermal highly loaded components have to be cooled intensive. These parts includes besides the blades, the platform and the casing of the first stages. Up to now the aero-thermal loading of the over-tip casing above the rotor was investigated poorly. This report contributes to a better understanding of the major phenomena governing the heat flux in the over-tip casing region. Using a HP-turbine at different flow conditions, extended measurements were performed at DLR’s wind tunnel for rotating cascades, Göttingen, concerning the flow field above the rotor and close to the over-tip casing. The data collected include time-averaged as well as time-resolved values as i.e. static pressure at the over-tip casing, wall temperatures and calculated heat flux coefficients, hot-film measurements. Additionally the passage near the casing was investigated using probes (steady and unsteady ones). The sensors and inserts necessary to perform the measurements had to be developed and manufactured; the necessary procedures to evaluate the gained data had to be developed, too. From these investigations an extended data basis was generated and used to proceed in getting information about work process within the tip gap and about the heat flux into linear segments. The Nusselt correlation for a flat plate is investigated for it’s applicability at the over-tip casing. The correlation is enhanced with operating parameters to take the elevated heat transfer levels observed at off-design conditions into account. Additionally a tip leakage model is introduced to examine the difference between heat transfer in the passage and in the gap. Finally differences between time-resolved and pitchwise averaged input data with the flat plate correlation are discussed.

Item URL in elib:https://elib.dlr.de/56865/
Document Type:Monograph (DLR-Forschungsbericht)
Title:Heat Transfer Investigations at the Over-Tip Casing of a High Pressure Turbine Stage – Development of Heat Transfer Correlations
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
van Duikeren, BartUNSPECIFIEDUNSPECIFIED
Date:December 2008
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Number of Pages:156
Status:Published
Keywords:turbine, shroud, over-tip casing, rotating cascade, heat transfer, heat flux, hot-films, steady and unsteady measurements, array of thermocouples, correlation, Nusselt number, off-design
HGF - Research field:Energy
HGF - Program:Efficient Energy Conversion (old)
HGF - Program Themes:E VG - Combustion and Gas Turbine Technologies (old)
DLR - Research area:Energy
DLR - Program:E VG - Combustion and Gas Turbine Technologies
DLR - Research theme (Project):E - Gasturbine (old)
Location: Göttingen
Institutes and Institutions:Institute of Propulsion Technology > Turbine
Deposited By: Klein, Stephanie
Deposited On:12 Dec 2008
Last Modified:27 Apr 2009 15:36

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