Investigations of Heat Transfer and Fluid Flow in the Pocket Region of a Gas Turbine Engine and Cooling of a Turbine Blade

Research output: ThesisDoctoral Thesis (compilation)

Abstract

In the present work, heat transfer within gas turbine applications are investigated both
experimentally and numerically. The main content concerns heat transfer and fluid
flow over the pocket region and cooling of a turbine blade.
A pocket cavity is generated at the junction part of the low pressure turbine (LPT) and
the outlet guide vane (OGV) in the rear part of a gas turbine engine. The heat transfer
distribution and fluid flow over the pocket cavity have significant effects on the
incoming flow of the OGV placed downstream. These pocket cavities are built with
different radii to find out improved heat transfer distributions and flow patterns. The
effects of a pocket cavity on heat transfer and flow characteristics on the endwall with
a symmetric vane are also investigated. The relative location between the pocket
cavity and the symmetric vane is varied. In addition, the effect of incoming flow
attack angle of the pocket cavity upstream of an OGV is investigated numerically.
Liquid Crystal Thermography (LCT) is employed to measure the heat transfer of the
tested surfaces. The results show that the smaller fillet radius provides a higher heat
transfer peak value with a stronger recirculating flow inside the pocket cavity. When a
pocket cavity is placed upstream of the symmetric vane, the high heat transfer areas
around the symmetric vane are decreased. The attack angles of the incoming flow over
the pocket cavity affect the forming of horseshoe vortices in leading edge of the vane
and then affect the heat transfer distribution.
Rib turbulators are widely employed in internal cooling passages of a turbine blade.
Firstly, truncated ribs with various truncation types and arrangements are considered.
Secondly, perforated ribs with differently shaped penetration holes and perforation
ratios are investigated. LCT is employed to measure surface temperature and derive
heat transfer coefficients over the ribbed surfaces in the tested channels. The turbulent
flow details are presented by numerical calculations with an established turbulence
model, i.e., the k-ω SST model. From the results, the truncated ribs can reduce the
pressure loss penalty without reducing the heat transfer enhancement. By changing the
configurations to staggered arrangements, the heat transfer can be further enhanced
associated with a moderate pressure drop. By using perforated ribs, the low heat
transfer regions downstream of the rib rows are greatly improved.
Endwall film cooling is a significant cooling method to protect the endwall region
where the flow structures are complex due to horseshoe vortices and generated
secondary flows. This study firstly concentrates on film cooling holes arranged
upstream of the leading edge of a turbine vane. Several arrangements are designed
aiming at improving the coolant coverage. Based on the calculated results, the film
cooling holes upstream the leading edge have cooling effects on both the vane
surfaces and the endwall. A case with two rows of compound angle holes in staggered
arrangement shows relatively high overall averaged cooling effectiveness independent
of the blowing ratios. Then full-scale endwall film cooling is also investigated in this
study. The film holes arrangements are designed based on the pressure coefficient
distribution, streamline distribution and heat transfer distribution on the endwall. With
compound angle holes, the design based on the pressure distribution forces the flows
to the suction side, which creates benefits for cooling the vane surfaces. The design
based on the streamline distribution has more uniform coolant coverage on the
endwall. The design based on the heat transfer distributions has relatively large
coolant coverage and is effective in removing the high temperature region.
Keywords: pocket cavity, symmetric vane, Liquid Crystal Thermography, truncated
ribs, staggered arrangement, perforated ribs, secondary flows, endwall film cooling,
leading edge, turbine vane, coolant coverage

Details

Authors
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Engineering and Technology

Keywords

  • pocket cavity, symmetric vane, Liquid Crystal Thermography, truncated ribs, staggered arrangement, perforated ribs, secondary flows, endwall film cooling, leading edge, turbine vane, coolant coverage
Original languageEnglish
Supervisors/Assistant supervisor
Place of PublicationISRN: LUTMDN/TMHP-19/1144-SE
EditionISSN: 0282-1990
Publisher
  • Department of Energy Sciences, Lund University
Print ISBNs978-91-7895-038-6
Electronic ISBNs978-91-7895-039-3
Publication statusPublished - 2019 Mar 18
Publication categoryResearch

Bibliographic note

Defence details Date: 2019-05-17 Time: 10:15 Place: Lecture Hall M:E, M-Building, Ole Römers väg 1, Lund University, Faculty of Engineering LTH External reviewer(s) Name: Laumert, Björn Title: Professor Affiliation: KTH Royal Institute of Technology, Sweden ---

Total downloads

No data available

Related research output

View all (10)