In order to protect gas turbine blades from hot gases exiting the combustor, several intricate external and internal cooling concepts are employed. High pressure stage gas turbine blades feature serpentine passages where rib turbulators are installed to enhance heat transfer between the relatively colder air bled off from the compressor and the hot internal walls. Most of the prior studies have been restricted to Reynolds number of 90000 and several studies have been carried out to determine geometrically optimized parameters for achieving high levels of heat transfer in this range of Reynolds number. However, for land-based power generation gas turbines, the Reynolds numbers are significantly high and vary between 105 and 106. Present study is targeted towards these high Reynolds numbers where traditional rib turbulator shapes and prescribed optimum geometrical parameters have been investigated experimentally. A steady-state liquid crystal thermography technique is employed for measurement of detailed heat transfer coefficient. Five different rib configurations, viz., 45 deg., V-shaped, inverse V-shaped, W-shaped and M-shaped have been investigated for Reynolds numbers ranging from 150,000 to 400,000. The ribs were installed on two opposite walls of a straight duct with aspect ratio of unity. For very high Reynolds numbers, the heat transfer enhancement levels for different rib shapes varied between 1.3 and 1.7 and the thermal hydraulic performance was found to be less than unity. / Master of Science / Gas turbine blades operate in hot gases exiting from combustor. The temperature of the hot gas is much higher than the melting point of blades material. To protect gas turbine blades several intricate external and internal cooling technique have been applied. Inside the blades, impingement cooling, rib turbulators cooling and pin fins cooling technique are applied in the leading edge, central body and trailing edge, respectively. At the central body serpentine passage was manufactured where rib turbulators are installed to enhance heat transfer between the relatively colder air bled off from the compressor and the hot internal walls. This is attributed to the colder air’s boundary layer is tripped by the rib turbulators enhance the flow turbulence. All the previous works are based on lower Reynolds number (under 90000) which always happens in aircraft gas turbine engine. In land based gas turbine the Reynolds numbers of cooling air are significantly high and vary between 10⁵ and 10⁶ . Present study is targeted towards these high Reynolds numbers where traditional rib turbulator shapes and prescribed optimum geometrical parameters have been investigated experimentally. Five different rib configurations, viz., 45 deg., V-shaped, inverse V-shaped, W-shaped and M-shaped have been investigated for Reynolds numbers ranging from 150,000 to 400,000. For very high Reynolds numbers, the heat transfer enhancement levels for different rib shapes varied between 1.3 and 1.7 and the thermal hydraulic performance was found to be less than unity. It’s a caution to turbine hot gas path designers, particularly for the cases where rib designs for aircrafts are used in land based power generationgas turbines
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/81859 |
| Date | 18 January 2018 |
| Creators | Zhang, Mingyang |
| Contributors | Mechanical Engineering, Ekkad, Srinath V., Qiao, Rui, Pitchumani, Ranga |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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