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Title: Experimental investigation of flow and heat transfer in rotating cooling passages using porous metal foam promoters
Author: Abdulsattar, Firas
ISNI:       0000 0005 0290 1803
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2019
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This study presents an experimental investigation of rotating flows related to gas turbine blade cooling. It focuses on measuring the development of turbulent flow and heat transfer inside a cooling passage which consists of two straight square-sectioned ducts connected with a square-ended bend, using porous metal foam blocks as turbulent promoters. The cooling passages are either stationary, or in orthogonal rotation. This study aims to improve the understanding of the effects of using porous metal foam on flow and thermal development in rotating cooling passages and exploring the possibility of using porous media for gas turbine blade cooling. Particle image velocimetry (PIV) and Thermochromic liquid crystals (TLC) experiments have been performed to measure the flow and heat transfer characteristics, respectively. A set of 12 static pressure taps around the passage provide detailed picture of the pressure variation along both sides of the rotating passage. Aluminium porous foam blocks of an aspect ratio of 1.5 with 0.93 porosity and pore density per cm of 2, were attached to two opposite walls of the straight sections normal to the bend in a staggered manner. The ratio of blocks spacing to the duct's hydraulic diameter (D) is 1; whereas the block's height ratio (h/D) is 0.6. Water is used as the working fluid at Reynolds numbers of 16,000, 26,000 and 36,000 and rotation numbers of 0.32 and 0.64. The resulting tests have generated original knowledge and information which advances our understanding of the effects of porous metallic foams on the flow and thermal development in rotating cooling passages and also provides detailed data for CFD validation. The results generated by the PIV method show the serpentine manner of the flow both upstream and downstream of the bend region due to the presence of the porous blocks. Within the bend, in contrast to the case with a smooth upstream section, a single vortex dominates the flow. While rotation does not change the overall flow character, it does force more fluid through the blocks on the trailing (pressure) side of the duct. For both stationary and rotating conditions, the upstream section is long enough for the flow to become periodic over successive rib intervals, which produces very attractive data for CFD validation. The Nusselt number distribution is significantly affected by the presence of the porous blocks and the heat transfer levels are improved by about 17%. The local Nusselt number distribution shows that the influence of rotation is negligible compared to the effect of the porous blocks.
Supervisor: Iacovides, Hector ; Zhang, Shanying Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Square bend ; TLC ; PIV ; Porous media ; Gas turbine blade cooling ; Experimental investigation