Af
Mass air to fuel ratio
Rw
Moisture content of fuel: mass water/mass fuel
Cpa
Specific heat air = 1.01, kJ/K (at constant pressure)
Rθa
Total thermal resistance of AHX from working gas to ambient, K/W
Cpc
Specific heat combustion gasses. (at constant pressure)
Rθc
Effective thermal resistance of the combustion process
Cpf
Specific heat of fuel, kJ/K (at constant pressure)
Rθh
Total thermal resistance of HHX from combustion gas to Stirling working gas, K/watt
Cpw
Specific heat steam = 1.93, kJ/K
Ta
Ambient temperature, Kelvin
Higher calorific value of fuel, kJ/kg
Tc
Temperature of the cold heat exchanger (AHX), Kelvin
Lh
Latent heat of evaporation of water = 2264 kJ/kg
Te
Entry temperature to the heat engine, Kelvin
Mass flow rate of air, kg/s
Tf
Ideal flame temperature, assuming no dissociation of component gasses
Mass flow rate of fuel, kg/s
Th
Temperature of the hot heat exchanger (HHX) in Kelvin
Mass flow rate of combustion gasses, kg/s
WSE
Work output from the engine, W
Mass flow rate of water, kg/s
Xs
Mass ratio of air to stoichiometric air flow
Heat available from combustion, watts
η
Efficiency: work out/heat in
QSE
Amount of heat supplied to the Stirling engine, W
ηSE
The new efficiency of the Stirling engine: work out/heat from combustion
r
Otto cycle compression ratio
γ
Ratio of specific heats at constant volume to constant pressure