Cooling performance investigation of a two-pass rib-roughened channel

Download
2015
Kavas, İsa
The performance of the modern aero-engines is highly dependent on the turbine inlet gas temperature. The higher temperature leads to more compact and efficient machines. Additionally, specific fuel consumption of the engine is decreased for the same thrust rating. However, the turbine inlet temperatures of the today’s engines are already beyond the material structural limits. Hence, the turbine section must be cooled down to acceptable levels. Various types of cooling methods are typically applied to the gas turbine blades like internal cooling, film cooling, impingement cooling etc. The internal cooling channels are embedded inside the turbine blades and often equipped by ribs in order to enhance the turbulence activities and heat transfer area. Cooling channels may form as a single pass or multi-pass channels depending on the design considerations. Current research focuses on vi experimentally and numerically investigating the thermal performance of a 2-pass channel. Especially the performance of U turn section and its effect on the second channel were studied. A rectangular cross section tunnel with two passage and a U-turn section that mimic the modern gas turbine cooling configurations was designed and manufactured. The ribs with square cross section are located on the bottom wall of both passages. The ambient air is sucked to the wind tunnel by using a blower. The bottom wall of the test section was heated by a foil heater which generates uniform heat flux. The wall surface temperature was obtained by means of optical thermography method (IR camera). The heat loss was computed assuming one-dimensional heat conduction through the wall. The experiments were conducted at three Reynolds number by changing the blower speed. Finally the Nusselt number was computed based on the heater power, surface temperature and the mainstream temperature. The results were compared with the smooth wall configuration. The current investigation aims to provide Nusselt numbers and deep understanding of the flow physics of the modern gas turbine cooling configuration both experimentally an numerically. The U-turn section and cooling passage interaction is investigated. The cooling effectiveness improvement by design is addressed at the end of the manuscript. Experimental results are compared with the numerical analysis to come up with a suitable turbulence model.

Suggestions

Aerothermodynamics of turbine blade trailing edge cooling
Tunçel, Tuğba; Kahveci, Harika Senem; Department of Aerospace Engineering (2018)
It is known that the thermal efficiency of gas turbines strongly depends on the turbine entry temperature of the working fluid. This has resulted in increased turbine working temperatures, and peak temperatures in advanced gas turbines have been well above maximum allowable metal temperatures for quite some time. For turbine blades to survive while operating beyond these material temperature limits, internal and external cooling techniques have been developed. Due to structural and aerodynamic restrictions,...
Surrogate model based system identification and control of gas turbine engines
Ekinci, Sinan; Yavrucuk, İlkay; Department of Aerospace Engineering (2019)
The focus of this thesis is on small low-cost turbojet engines where the fuel flow is provided by a gear-type fuel pump rather than a more traditional fuel metering unit. The incorporation of such type of fuel flow actuation devices introduces additional nonlinearities into the modeling and control of the small turbojet engines. As an alternative solution, this thesis presents and applies online/offline parameter estimation and adaptive control methods to such sub-class turbojet engines. For the simulation ...
Simulation of a non-premixed swirl burner
Solmaz, Mehmet Burak; Uzol, Oğuz; Uslu, Sıtkı; Department of Aerospace Engineering (2014)
Flame stabilizing in a gas turbine combustion chamber is one of the designing issues. Non-premixed swirling flames are commonly applied to aerial vehicles’ combustors due to their advantages in flame stabilizing and flame length shortening. However, swirling flows are very complex and hard to simulate even without reaction. Previous studies have showed that Large Eddy Simulation (LES) is able to predict swirling flow with a good degree of accuracy. On the other, it is quite expensive and is still far away f...
The Influence of cooling configuration and tip geometry on gas turbine blade tip leakage flow and heat transfer
Sakaoğlu, Sergen; Kahveci, Harika Senem; Department of Aerospace Engineering (2019)
In gas turbine engines, an increase in the thermal efficiency and power output can be ensured by increasing the turbine inlet temperature. This causes the high-pressure turbine (HPT) blades to be exposed to extremely high temperatures that requires the introduction of cooling flow in order to keep the temperatures within the allowable material limits and to reduce the high thermal loads on the blade. However, cooling flow introduced around the blade tip region affects the blade tip leakage flow and blade tip he...
NREL VI rotor blade: Numerical investigation and winglet design and optimization using CFD
Elfarra, Monier A.; Sezer Uzol, Nilay; Akmandor, I. Sinan (2014-01-01)
The main objectives of this study were to aerodynamically design and optimize a winglet for a wind turbine blade by using computational fluid dynamics (CFD) and to investigate its effect on the power production. For validation and as a baseline rotor, the National Renewable Energy Laboratory Phase VI wind turbine rotor blade is used. The Reynolds-averaged Navier-Stokes equations are solved, and k-ε Launder-Sharma turbulence model was used. The numerical results have shown a considerable agreement with the e...
Citation Formats
İ. Kavas, “Cooling performance investigation of a two-pass rib-roughened channel,” M.S. - Master of Science, Middle East Technical University, 2015.