$B$	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 ($\mathrm{J}/(\mathrm{mol}\cdot \mathrm{K})$)
$\overline{E}$	Dimensionless ecological function
$\overline{P}$	Dimensionless power output
${\overline{P}}_d$	Dimensionless power density
$Q$	Heat transfer rate ($\mathrm{W}$)
T	Temperature ($\mathrm{K}$)
Greek symbols
$\gamma$	Compression ratio (-)
$\eta$	Thermal efficiency (-)
$\mu$	Friction coefficient ($\mathrm{kg}/\mathrm{s}$)
$\sigma$	Entropy generation rate ($\mathrm{W}/\mathrm{K}$)
$\tau$	Temperature ratio (-)
Subscripts
${\overline{P}}_d$	Max power density condition
$0$	Environment
1 − 4,$2s$,$4s$	Cycle state points
Abbreviations
FL	Friction loss
HTL	Heat transfer loss
IIL	Internal irreversibility loss
MOO	Multi-objective optimization