Single-step turbine cooling

In order to make a preliminary assessment of the importance of turbine cooling in cycle analysis, the real gas calculations of a simple open uncooled cycle, carried out in Chapter 3 for various pressure ratios and combustion temperatures, are now repeated with single step turbine cooling, i.e. including cooling of the first turbine row, the stationary nozzle guide vanes. 

Fig. 5.2 shows that for the single-step cooled CBT plant at a given combustion temperature, the overall efficiency of the cooled gas turbine efficiency increases with pressure ratio initially but, compared with an uncooled cycle, reaches a maximum at a lower optimum pressure ratio. Fig. 5.3 shows that for a given pressure ratio the efficiency generally increases with the combustion temperature even though the required cooling fraction increases. 

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