Page 57 - Advanced Gas Turbine Cycles

34 Advanced gas turbine cycles

Along a compression line,
p/Tz = constant, where now z = [yrlpc/(y - l)],

and exit and entry temperatures are related by T2/Tl = rgh) = xc.
The analysis of Hawthorne and Davis [ 13 for irreversible ds cycles is developed using
the criteria of component irreversibility, firstly for the simple cycle and subsequently for
the recuperative cycle. In the main analyses, the isentropic efficiencies are used for the
turbomachinery components. Following certain significant relationships, alternative
expressions, involving polytropic efficiency and xc and xT, are given, without a detailed
derivation, in equations with p added to the number.

3.2.2.2. The irreversible simple cycle [CHT],
A closed cycle [CHTIl, with state points 1,2,3,4, is shown in the T,s diagram of
Fig. 3.7. The specific compressor work input is given by
wc = c,(TZ - Ti) = cp(TZs - Tl)/Vc = c,T~(x - l)/lc. (3.9)
The specific turbine work output is

WT = cp(T3 - r4) = rh.cp(T3 - T4s) = 7h.CpT311 - (l/x)], (3.10)
so that the net specific work is

T

S
Fig. 3.7. T,s diagram for irreversible closed simple cycle [CHTII.