**1. Introduction**

The aerothermal design of advanced gas turbines has progressed significantly in the last decade, primarily due to the requirement of increased turbine efficiencies and power. Performance increases are driven not only for reducing the consumption of fuel and the subsequent cost benefits, but also to reduce the emissions of CO<sup>2</sup> , which is a primary component for the increased global warming. Over the last decade, major gas turbine performance enhancements have been achieved by the use of higher turbine inlet temperatures and pressures, design of advanced turbine aerodynamics, through reductions in turbine cooling and leakage

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

air, and via the introduction of new high temperature alloys, metallic antioxidation coatings, and thermal barrier coatings. In today's energy market, there is wide range of gas turbines ranging from 1 to 500 MW and can operate with low and high calorific fuels. **Figure 1** shows the GT26 heavy duty gas turbine [1, 2].

**Figure 1.** Heavy duty gas turbine, GT26.

The operation of a gas turbine, which essentially consists of four major components; compressor, combustor, turbine, and the exhaust diffuser, is governed by the Brayton thermodynamic cycle. For simple power generation applications, a generator is normally coupled to the gas turbine, whereby the mechanical work generated by the turbine is converted to useful electrical energy. In today's energy market, most gas turbine-based power plants are operated in combined cycle operation mode. **Figure 2** shows a typical component layout of a combined cycle plant, whereby the gas turbine plant is coupled to a steam turbine plant via the heat recovery steam generator. Thermodynamically, the gas turbine operates in a Brayton cycle, whereas the steam turbine operates in a Rankine cycle. Due to this combination, **Figure 2** highlights that combined cycle efficiencies are significantly higher than that of a gas turbine in simple operation. There are many variations of the gas turbine combined cycle plant and the interdependency of the component efficiencies and plant operating conditions. An extensive overview of industrial gas turbine combined cycle plant is given in Ref. [1].

**Figure 2.** Basic combined cycle plant arrangement, adapted from Ref. [1].

The historical progress in increased combined cycle plant efficiencies was recently reviewed in Ref. [3] and is highlighted in **Figure 3**, which predicts a continuous growth in cycle efficiencies approaching 65% over the next decades. **Figure 3** also shows that a major part of the current growth in combined cycle efficiencies is attributed to improvements in gas turbine thermodynamic efficiencies, particularly with the H and J class gas turbines. A key driver for the latter has been the increased turbine inlet temperatures, and as shown in **Figure 4**, this has also resulted in the development of high-grade alloy, coatings, and very efficient airofoil cooling designs which can maintain the blade metal temperatures and structural integrity for long continuous operating periods. In this chapter, issues related to the thermal design of gas turbine blades are examined and the various cooling technologies are outlined. In addition, typical methods for validating the thermal designs of gas turbine airofoils are also outlined.

**Figure 3.** Performance evolution of combined cycle and single cycle gas turbine [3].

air, and via the introduction of new high temperature alloys, metallic antioxidation coatings, and thermal barrier coatings. In today's energy market, there is wide range of gas turbines ranging from 1 to 500 MW and can operate with low and high calorific fuels. **Figure 1** shows

The operation of a gas turbine, which essentially consists of four major components; compressor, combustor, turbine, and the exhaust diffuser, is governed by the Brayton thermodynamic cycle. For simple power generation applications, a generator is normally coupled to the gas turbine, whereby the mechanical work generated by the turbine is converted to useful electrical energy. In today's energy market, most gas turbine-based power plants are operated in combined cycle operation mode. **Figure 2** shows a typical component layout of a combined cycle plant, whereby the gas turbine plant is coupled to a steam turbine plant via the heat recovery steam generator. Thermodynamically, the gas turbine operates in a Brayton cycle, whereas the steam turbine operates in a Rankine cycle. Due to this combination, **Figure 2** highlights that combined cycle efficiencies are significantly higher than that of a gas turbine in simple operation. There are many variations of the gas turbine combined cycle plant and the interdependency of the component efficiencies and plant operating conditions. An extensive

overview of industrial gas turbine combined cycle plant is given in Ref. [1].

**Figure 2.** Basic combined cycle plant arrangement, adapted from Ref. [1].

the GT26 heavy duty gas turbine [1, 2].

112 Heat Exchangers– Design, Experiment and Simulation

**Figure 1.** Heavy duty gas turbine, GT26.

**Figure 4.** Evolution of gas turbine hot gas temperatures, materials, and cooling technology, adapted from Ref. [7].
