$A$	Heat released rate by fuel ($\mathrm{W}$)
$B$	Heat transfer loss coefficient ($\mathrm{W}/\mathrm{K}$)
$C_p$	Specific heat at constant pressure ($\mathrm{J}/(\mathrm{mol}\cdot \mathrm{K})$)
$C_v$	Specific heat at constant volume ($\mathrm{J}/(\mathrm{mol}\cdot \mathrm{K})$)
$E$	Ecological function ($\mathrm{W}$)
$k$	Specific heat ratio
$\dot{m}$	Molar flow rate ($\mathrm{mol}/\mathrm{s}$)
$P$	Power output ($\mathrm{W}$)
$P_d$	Power density (${\mathrm{W}/\mathrm{m}}^3$)
$Q$	Quantity of heat transfer rate ($\mathrm{W}$)
$T$	Temperature ($\mathrm{K}$)
Greek symbol
$\gamma$	Compression ratio (-)
$\tau$	Temperature ratio (-)
$\eta$	Thermal efficiency (-)
${\eta }_e$	Expansion efficiency (-)
${\eta }_c$	Compression efficiency (-)
$\mu$	Friction coefficient ($\mathrm{kg}/\mathrm{s}$)
$\sigma$	Entropy generation rate ($\mathrm{W}/\mathrm{K}$)
Subscripts
$in$	Input
$leak$	Heat leak
$max$	Maximum value
$out$	Output
$\overline{P}$	Max power output condition
${\overline{P}}_d$	Max power density condition
$pq$	Influence of working fluid exhausting to environment
$q$	Influence of heat transfer loss
$\mu$	Influence of friction Loss
$\eta$	Max thermal efficiency condition
$0$	Environment
$1-4$,$2s$,$4s$	Cycle state points
Superscripts
—	Dimensionless