$A$	area
$a$	cross-section ratio
$K$	contraction pressure loss coefficient
$L$	excess air ratio
$P$	pressure
$Q$	heat
$r$	compression ratio
$T$	temperature
$\overline{W}$	power output
$x$	area allocation ratio
Greek symbol
$\beta$	pressure ratio
$\epsilon$	effectiveness
$\gamma$	ratio of specific heats
$\eta$	efficiency
$\lambda$	excessive air ratio
$\theta$	adiabatic temperature ratio
$\tau$	temperature ratio
${\displaystyle \psi }$	pressure drop
Subscripts
$c$	compressor
$cf$	combustor
$f$	working fuel
$g$	gas
$\max$	maximum
$opt$	optimal
$R$	regenerator
$t$	turbine
$0$	ambient
$1,2,3,\dots ,9$	state points in the cycle/sequence numbers
Abbreviations
BCC	bottom cycle compressor
MFR	mass flow rate
OCBC	open combined Brayton cycle
PDL	pressure drop loss
PO	power output
PR	pressure ratio
TCC	top cycle compressor
TE	thermal efficiency