0
Research Papers: Forced Convection

Analysis of the Heat Transfer Driving Parameters in Tight Rotor Blade Tip Clearances

[+] Author and Article Information
Sergio Lavagnoli

Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Chaussée de Waterloo 72,
Rhode Saint Genèse 1640, Belgium
e-mail: lavagnoli@vki.ac.be
Mem. ASME

Cis De Maesschalck

Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Chaussée de Waterloo 72,
Rhode Saint Genèse 1640, Belgium
e-mail: demaess@vki.ac.be

Guillermo Paniagua

Associate Professor
of Mechanical Engineering
Purdue University,
Zucrow Laboratories,
500 Allison Road,
West Lafayette, IN 47907
e-mail: gpaniagua@me.com
Mem. ASME

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 24, 2014; final manuscript received July 1, 2015; published online August 18, 2015. Assoc. Editor: Jim A. Liburdy.

J. Heat Transfer 138(1), 011705 (Aug 18, 2015) (10 pages) Paper No: HT-14-1637; doi: 10.1115/1.4031131 History: Received September 24, 2014; Revised July 01, 2015

Turbine rotor tips and casings are vulnerable to mechanical failures due to the extreme thermal loads they undergo during engine service. In addition to the heat flux variations during the engine transient operation, periodic unsteadiness occurs at every rotor passage, with amplitude dependent on the tip gap. The development of appropriate predictive tools and cooling schemes requires the precise understanding of the heat transfer mechanisms. The present paper analyses the nature of the overtip flow in transonic turbine rotors running at tight clearances and explores a methodology to determine the relevant flow parameters that model the heat transfer. Steady-state three-dimensional Reynolds-averaged Navier–Stokes (RANS) calculations were performed to simulate engine-like conditions considering two rotor tip gaps, 0.1% and 1%, of the blade span. At tight tip clearance, the adiabatic wall temperature is no longer independent of the solid thermal boundary conditions. The adiabatic wall temperature predicted with the linear Newton's cooling law was observed to rise to unphysical levels in certain regions within the rotor tip gap, resulting in unreliable convective heat transfer coefficients (HTCs). This paper investigates different approaches to estimate the relevant flow parameters that drive the heat transfer. A novel four-coefficient nonlinear cooling law is proposed to model the effects of temperature-dependent gas properties and of the heat transfer history. The four-parameter correlation provided reliable estimates of the convective heat transfer descriptors for the 1% tip clearance case, but failed to model the tip heat transfer of the 0.1% tip gap rotor. The present study allows experimentalists to retrieve information on the gap flow temperature and convective HTC based on the use of wall heat flux measurements. The use of nonlinear cooling laws is sought to improve the evaluation of the rotor heat transfer data while enhancing the understanding of tight-clearance overtip flows.

FIGURES IN THIS ARTICLE
<>
Copyright © 2016 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

Wall heat transfer in function of the wall temperature ratio for different HTC laws

Grahic Jump Location
Fig. 2

Error in HTC and Taw using the linear Newton's cooling law (n = −0.25)

Grahic Jump Location
Fig. 3

Blade mesh (a), detail of the tip gap mesh (b), and shroud mesh (c)

Grahic Jump Location
Fig. 4

Comparison of numerical predictions of isentropic Mach number and Nusselt number distributions with experimental data from Ref. [29]

Grahic Jump Location
Fig. 5

Chordwise tip heat transfer variations in function of the grid density

Grahic Jump Location
Fig. 6

Rotor blade tip heat transfer (a), adiabatic heat transfer parameters calculated using the conventional linear approach (b) and (c), and relative total flow temperature in the midgap (d). Rotor tip gap t/H = 1.0%.

Grahic Jump Location
Fig. 7

Rotor blade tip heat transfer (a), adiabatic heat transfer parameters calculated using the conventional linear approach (b) and (c), and relative total flow temperature in the midgap (d). Rotor tip gap t/H = 0.1%.

Grahic Jump Location
Fig. 8

Estimation of the tip adiabatic convective heat transfer coefficient, tip adiabatic wall temperature, and exponent n using Eq. (3) for the rotor tip gap t/H = 1.0%

Grahic Jump Location
Fig. 9

Estimation of the tip adiabatic convective heat transfer coefficient, tip adiabatic wall temperature, and exponent n using Eq. (3) for the rotor tip gap t/H = 0.1%

Grahic Jump Location
Fig. 10

The effect of the thermal boundary conditions on the overtip aerothermodynamics: contours of midgap relative total flow temperature with streamlines for the two tip clearances calculated at low (TR = 0.35) and large (TR = 0.95) wall-to-gas temperature ratios

Grahic Jump Location
Fig. 11

The effect of the thermal boundary conditions on the overtip aerothermodynamics: dependency of tip heat transfer and midgap relative total flow temperature on wall-to-gas temperature ratio

Grahic Jump Location
Fig. 12

Estimation of the adiabatic convective heat transfer coefficient and adiabatic wall temperature on the tip surface using Eq. (5) for the 1.0% tip clearance

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In