2. When dealing with energy conversion and considering ideal (isentropic) operation and the working fluid is air,
the following assumptions are valid:
Power Cycles
Single species consideration -- fuel mass flow rate is ignored and its impact on the properties of the working
fluid
Basic equations hold (continuity, momentum and energy equations)
Specific heat is constant
Power Cycle Components/Processes
Single species consideration
Basic equations hold (continuity, momentum and energy equations)
Specific heat is constant
Compressible Flow
Single species consideration
Basic equations hold (continuity, momentum and energy equations)
Specific heat is constant
Thermodynamic and Transport Properties
Single species consideration
Ideal gas approach is used (pv=RT)
Specific heat is not constant
Coefficients describing thermodynamic and transport properties were obtained from the NASA Glenn Research
Center at Lewis Field in Cleveland, OH -- such coefficients conform with the standard reference temperature of
298.15 K (77 F) and the JANAF Tables
Engineering Assumptions
3. Basic Conservation Equations
Continuity Equation
m = ρvA [kg/s]
Momentum Equation
F = (vm + pA)out - in [N]
Energy Equation
Q - W = ((h + v2/2 + gh)m)out - in [kW]
Basic Engineering Equations
4. Ideal Gas State Equation
pv = RT [kJ/kg]
Perfect Gas
cp = constant [kJ/kg*K]
Kappa
χ = cp/cv [/]
For air: χ = 1.4 [/], R = 0.2867 [kJ/kg*K] and
cp = 1.004 [kJ/kg*K]
Basic Engineering Equations
8. Combustion is ideal, complete with no heat loss and at
stoichiometric conditions.
Also,
Flame Temperature [K]
hreactants = hproducts [kJ/kg]
Power Cycle Components/Processes
Engineering Equations
10. Specific Enthalpy vs Temperature
-20,000
-10,000
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
500 800 1,100 1,400 1,700 2,000 2,300 2,600 2,900 3,200 3,500 3,800 4,100 4,400 4,700 5,000
C(S) H2 S(S) N2 O2 H2O(L) CH4 CO2 H2O SO2
SpecificEnthalpy[kJ/kg]
Temperature [K]
Power Cycle Components/Processes
Engineering Equations
11. Combustion h – T Diagram
SpecificEnthalpy--h[kJ/kg]
Temperature -- T [K]
Reactants
Products
TflameTreference
Power Cycle Components/Processes
Engineering Equations