Session: S03: SYMPOSIUM IN MEMORY OF PROFESSOR RICHARD J. GOLDSTEIN III

Paper Number: 142226

142226 - Film Cooling Study on Turbine Blade Endwall With Prof. Goldstein 

Abstract: 

Cooling designers are making continuous efforts to improve the accuracy of metal temperature predictions. Turbine blade endwall is one of the most difficult areas to accurately predict metal temperatures due to the complex secondary flows within the blade passages. Additionally, the increasing trend of TIT and decreasing pattern factor at the combustor outlet result in higher gas temperatures on the turbine blade endwall, which requires more accurate prediction of the metal temperatures on the endwall.
In an effort to better optimize endwall cooling, leakage flow injected between the stator and rotor sections of a turbine can be used as additional coolant sources to cool the blade passage endwall. The primary purpose of leakage flow is to seal the wheelspace gap between the stator and rotor sections which helps to prevent hot gases from entering and heating turbine components from within the wheelspace. Much literature was on the topic of ingestion and wheelspace flow. However, more recently, the leakage flow been considered as a film-cooling source for endwalls in an effort to further optimize the endwall cooling scheme. Gold Stein's group had led a number of excellent studies on film cooling, including the film cooling effect of blade endwall leakage flow. IHI Corporation asked Professor Goldstein to collaborate on the effect of swirling leakage flow on endwall film cooling and conducted a research project from 2011 to 2013.
Mass transfer measurements are performed on the endwall surface in a five-blade linear cascade to study the effect of swirled leakage flow on endwall film-cooling. A 45 inclined slot equipped with turning vanes upstream of the blades is used to model the leakage flow path between a stator and rotor section. The turning vanes are used to impart swirl on the leakage flow, which simulates the relative motion between the stator and rotor walls found in a rotating turbine. For a Reynolds number of 6 X 10^5, based on blade chord and cascade exit velocity, a parametric study was conducted for three turning vane angles and three leakage flow blowing ratios. The effects on both mass transfer coefficient and film-cooling effectiveness were determined by injecting naphthalene-free and naphthalene-saturated air through the leakage flow slot upstream of the blade row. Endwall film-cooling coverage was found to improve with increased leakage flow rates and with decreased swirl angles (zero swirl defined as leakage flow aligned with axial direction, positive swirl defined as leakage flow angled towards suction surface). Endwall mass transfer coefficients were found to increase with increased leakage flow rate. The leakage flow path was found to be strongly influenced by the endwall secondary flows for the low leakage flow rates. At high leakage flow rates, the swirl angle was the primary determinant for where the leakage flow traveled. For realistic leakage flow rates and swirl angles, leakage flow alone was found to do a poor job at providing coolant coverage on the endwall surface. The downstream portion and the pressure side of the endwall surface were found to be especially difficult to cool, so additional cooling sources, such as discrete film cooling holes, should be utilized to provide more complete coolant coverage.

Presenting Author: Chiyuki Nakamata IHI Corporation

Presenting Author Biography: Chiyuki Nakamata received her master's degree in physics from Ochanomizu University in 1993.
Nakamata started her career at IHI as a turbine cooling designer and research engineer. Nakamata has worked as a research engineer in the areas of heat transfer and cooling technology, and she received her doctor degree in mechanical engineering from Iwate University in 2007. During her 27 years of experience at IHI, she participated in Japanese technology development programs and engine development programs.
After 27 years of experience as an engineer, she moved to the civil aero-engine MRO business and is currently in charge of the civil aero-engine MRO business and operations at IHI.

Authors:

Chiyuki Nakamata IHI Corporation
Shu Fujimoto IHI Corporation
Kozo Nita IHI Corporation