A Possible Strategy for the Performance Enhancement of Turbine Blade Internal Cooling With Inclined Ribs

ABSTRACT

Ribbing the internal passages of turbine blades with 45 deg inclined ribs is a common practice to achieve a good compromise between high heat transfer coefficients and not too large pressure drop penalties. Literature studies demonstrated that, for channels having a large aspect ratio, the effect of the secondary vortices induced by angled ribs is reduced and the heat transfer performance is degraded. In order to enhance the performance, a possible strategy consists in introducing one or more longitudinal ribs (intersecting ribs) aligned to the main direction of flow. The intersecting ribs cut the ribbed channel into separate sub-channels and markedly affect the secondary flows with consequent increases in heat transfer performance. Experiments were performed for a rectangular channel with a large aspect ratio (equal to five) and 45 deg inclined ribs, regularly spaced on one of the principal walls of the channel. The effect of one and two intersecting ribs on friction and heat transfer characteristics has been investigated. The ribbed surface of the channel has been electrically heated to provide a uniform heat flux condition over each inter-rib region. The convective fluid was air. Heat transfer experiments have been conducted by using the liquid crystal thermography. Results obtained for the ribbed channel without intersecting rib and with one/two intersecting ribs are compared in terms of dimensionless groups.

Additional information

Notes on contributors

Luca Baggetta

Luca Baggetta is a Ph.D. student in Engineering of Turbomachinery, Energy, Environment and Transportation Systems at the University of Genoa, Italy. Before beginning his Ph.D., he graduated in Mechanical Engineering at the University of Genoa, Italy. His research interests concern the heat transfer effects in gas turbines, including film and internal cooling of gas turbine blades and hot streaks propagation inside turbine cascades.

Francesca Satta

Francesca Satta is an associate professor of Aeronautical Propulsion and Fluid Machinery at the University of Genoa, Italy. She received the Mechanical Engineering degree with honors in 2005 and obtained her Ph.D. in Fluid Machinery Engineering in 2009. Her research activity is focused on the improvement of gas turbine component performance, with particular attention paid to the aeronautical application. She is currently investigating the aero-thermal unsteady flow-field in axial turbines, film cooling in the high pressure turbine endwalls, and heat transfer in ribbed channels for blade internal cooling applications.

Giovanni Tanda

Giovanni Tanda is a full professor of Engineering Thermodynamics and Heat Transfer at the University of Genoa, Italy. He received his degree in Mechanical Engineering from the University of Genoa, Italy and a Ph.D. from the City University, London, UK. He is author of more than one hundred research pap-ers published in peer-reviewed journals or presented at international conferences. His current areas of research include experimental heat transfer, with reference to electronic equipment cooling and cooling technology of gas turbine blades.