Blade tip design and tip leakage flows are crucial aspects for the development of modern aero-engines. The inevitable clearance between stationary and rotating parts in turbine stages generates high-enthalpy unsteady leakage flows that strongly reduce the engine efficiency and can cause thermally induced blade failures. An improved understanding of the tip flow physics is essential to refine the current design strategies and achieve increased turbine aerothermal performance. However, while past studies have mainly focused on conventional tip shapes (flat tip or squealer geometries), the open literature suffers from a shortage of experimental and numerical data on advanced blade tip configurations of unshrouded rotors. This work presents a complete numerical and experimental investigation on the unsteady flow field of a high-pressure turbine, adopting three different blade tip profiles. The aerothermal characteristics of two novel high-performance tip geometries, one with a fully contoured shape and the other presenting a multicavity squealer-like tip with partially open external rims, are compared against the baseline performance of a regular squealer geometry. The turbine stage is tested at engine-representative conditions in the high-speed turbine facility of the von Karman Institute. A rainbow rotor is mounted for simultaneous aerothermal testing of multiple blade tip geometries. On the rotor disk, the blades are arranged in sectors operating at two different clearance levels. A numerical campaign of full-stage simulations was also conducted on all the investigated tip designs to model the secondary flows development and identify the tip loss and heat transfer mechanisms. In the first part of this work, we describe the experimental setup, instrumentation, and data processing techniques used to measure the unsteady aerothermal field of multiple blade tip geometries using the rainbow rotor approach. We report the time-average and time-resolved static pressure and heat transfer measured on the shroud of the turbine rotor. The experimental data are compared against numerical predictions. These numerical results are then used in the second part of the paper to analyze the tip flow physics, model the tip loss mechanisms, and quantify the aero-thermal performance of each tip geometry.
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January 2019
Research-Article
Experimental and Numerical Investigation of Optimized Blade Tip Shapes—Part I: Turbine Rainbow Rotor Testing and Numerical Methods
Bogdan C. Cernat,
Bogdan C. Cernat
Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: cernat@vki.ac.be
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: cernat@vki.ac.be
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Marek Pátý,
Marek Pátý
Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: marek.paty@seznam.cz
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: marek.paty@seznam.cz
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Cis De Maesschalck,
Cis De Maesschalck
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: cis.demaesschalck@gmail.com
Rhode Saint Genèse 1640, Belgium
e-mail: cis.demaesschalck@gmail.com
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Sergio Lavagnoli
Sergio Lavagnoli
Assistant Professor
Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: lavagnoli@vki.ac.be
Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: lavagnoli@vki.ac.be
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Bogdan C. Cernat
Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: cernat@vki.ac.be
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: cernat@vki.ac.be
Marek Pátý
Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: marek.paty@seznam.cz
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: marek.paty@seznam.cz
Cis De Maesschalck
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: cis.demaesschalck@gmail.com
Rhode Saint Genèse 1640, Belgium
e-mail: cis.demaesschalck@gmail.com
Sergio Lavagnoli
Assistant Professor
Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: lavagnoli@vki.ac.be
Turbomachinery and Propulsion Department,
von Karman Institute for Fluid Dynamics,
Rhode Saint Genèse 1640, Belgium
e-mail: lavagnoli@vki.ac.be
1Corresponding author.
2Present address: CTU, Prague 166 36, Czech Republic.
3Present address: Rolls-Royce plc, Derby DE 21 7BB, UK.
Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 22, 2018; final manuscript received September 8, 2018; published online December 20, 2018. Editor: Kenneth Hall.
J. Turbomach. Jan 2019, 141(1): 011006 (13 pages)
Published Online: December 20, 2018
Article history
Received:
August 22, 2018
Revised:
September 8, 2018
Citation
Cernat, B. C., Pátý, M., De Maesschalck, C., and Lavagnoli, S. (December 20, 2018). "Experimental and Numerical Investigation of Optimized Blade Tip Shapes—Part I: Turbine Rainbow Rotor Testing and Numerical Methods." ASME. J. Turbomach. January 2019; 141(1): 011006. https://doi.org/10.1115/1.4041465
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