Tham khảo tài liệu 'advanced gas turbine cycles episode 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | SPECIFIC WORK kJ kg exhaust gas Fig. . Overall efficiency and specific work for CBT lcl plant with single-step cooling of NGVs with combustion temperature and pressure ratio as parameters after Ref. 5 Chapter 4 . rows of the first turbine stage and the stationary nozzle guide vanes of the second stage. As in the single-step cooling calculations described before film cooling was assumed and the Holland and Thake approach was followed to determine the cooling air required in each of these blade rows. From the combustion temperature Tcol and an assumed first stage pressure ratio 3 1 the mixed out gas temperature at exit from the first stage Tei was obtained and this was taken as the gas entry temperature for the second stage third blade row . The entry relative stagnation temperature for the first stage rotor the second turbine blade row was obtained by interpolation between TE1 and Tcot assuming 50 reaction in the first stage. The cooling air inlet temperature was taken as the compressor delivery temperature Tci T2 for all three rows. This would have led to the estimation of coolant flow in the second and third rows being somewhat more than needed as the cooling air could theoretically be tapped at a lower pressure and therefore lower cooling temperature . But in practice the pressure loss through the supply ducts and past the turbine disks can be substantial and compressor delivery pressure may have to be used anyway. The cooling fractions thus obtained for the three rows are shown in Fig. obviously the first row requires most cooling the fractions for the subsequent rows decrease and it is assumed that the fourth row requires no cooling. The cycle calculations for this multi-cooling then proceeded in a similar fashion to those for the single-step cooling calculations of Section full details are given in Ref. 2 . Chapter 5. Full calculations of plant efficiency 79 Fig. . Calculated coolant air fractions for three step cooling of first stage and second
