Basic Aspects of Gas Turbine Heat Transfer

Abstract

The use of gas turbines for power generation and electricity production in both single cycle and combined cycle plant operation is extensive and will continue to globally grow into the future. Due to its high power density and ability to convert gaseous and liquid fuel into mechanical work with very high thermodynamic efficiencies, significant efforts continue today to further increase both the power output and thermodynamic efficiencies of the gas turbine. In particular, the aerothermal design of gas turbine components has progressed at a rapid pace in the last decade with all gas turbine manufacturers, in order to achieve higher thermodynamic efficiencies. This has been achieved by using higher turbine inlet temperatures and pressures, advanced turbine aerodynamics and efficient cooling systems of turbine airofoils, and advanced high temperature alloys, metallic coatings, and ceramic thermal barrier coatings. In this chapter, issues related to the thermal design of gas turbine blades are highlighted and several heat transfer technologies are examined, such as convective cooling, impingement cooling, film cooling, and application of thermal barrier coatings. Typical methods for validating the thermal designs of gas turbine airofoils are also outlined.

Colour changing material for the estimation of flue gas radiation on the miniature gas turbine surface

“…26 The mode of heat transfer from the root to the tip of the blade is considered conduction, and the heat transfer from the blade surface to the air is due to convection and radiation. 5,27 The computational parameters have been furnished in Table 6.…”

“…4 Firstly, heat transfer to the blade occurs due to convection from the free stream hot gases. 5 The second heat transfer mechanism on both the external pressure and suction airfoil surfaces that must be taken into account is the radiation from the hot gases and the other surfaces. The radiation is considered to be diffuse.…”

“…The radiation is considered to be diffuse. 5 The contribution of convection and radiation has been equally shared. One side of the blade has been exposed to flue gases as these gases impinge on one surface of the blade, whereas the annulus air flows over the other side of the blade, thereby cooling the blade.…”

“…9 The radiation plays a secondary role in heat transfer between blade surface and hot gas in motion. 4,5 Around 70–80% of total radiation absorbed by the blade painted with TIP is emitted at different locations on the surface of the turbine blade. The amount of emitted radiation has been calculated based on the wavelength of the colour obtained, and the temperature detected during experimentation.…”

Numerical Investigation of a Radially Cooled Turbine Guide Vane Using Air and Steam as a Cooling Medium

“…This temperature is constrained by the turbine vanes and blades ability to withstand the arduous operating conditions. These components are pushed to the limit of what the materials can endure in modern gas turbines, withstanding temperatures exceeding 1700 °C [6,7]. Thus, sophisticated cooling techniques are required to ensure that the blades and vanes can function under the immense thermal loads [8,9].…”