Power Generation in an Extraction Steam Turbine-Generator: Expansion Data Tab

Variable Definitions, Ranges and Default Values

The following table shows a brief description of the variables appearing in this tab. The table also displays their default values and their generally acceptable range. Note that due to how the variables are used in the modeling equations, the range of acceptable values may be further reduced; for more details, see Power Generation in a Steam Turbine-Generator: Modeling Assumptions & Constraints.

Variable	Default Value	Range

● Expansion The index of the selected expansion.	1	1-4
◙ Final Pressure (atm) The pressure at the end of the selected expansion.	1.0	Positive
● Final Temp. (^oC) The temperature at the end of the selected expansion.	100.0	Positive
● Final Specific Enthalpy (W) The specific enthalpy at the end of the selected expansion.	0.0	Positive
● Final Vapor (%) The quality of steam at the end of the selected expansion.	0.0	Positive
○ Mech. Losses (%) Mechanical losses between rotor and shaft for the selected expansion.	0.0	0-100
● Shaft Power (Per Unit) The power that is delivered to the shaft of each turbine unit from the selected expansion.	0.0	Positive
◙ Specific Heat Ratio The average specific heat ratio of steam for the selected expansion. Available only if the Analytical Isentropic Expansion Model is selected through the Oper. Conds Tab.	1.3	Positive
● Condensate-Free Isentropic Eff. (%) The condensate-free isentropic efficiency value for the selected expansion.	60.0	0-100
◙ Isentropic Efficiency (%) The isentropic efficiency value for the selected expansion.	60.0	0-100
● Output Stream The name of the output stream that is attached to the extraction/output port corresponding to the selected expansion.	<none>	Any Name
◙ a Parameter of condensate-free isentropic efficiency model.	-5.872	Any Number
◙ b Parameter of condensate-free isentropic efficiency model.	0.6464	Any Number
◙ c Parameter of condensate-free isentropic efficiency model.	-0.0184	Any Number
● Specific Inlet Enthalpy (W) The specific enthalpy of gas at the turbine inlet.	0.0	Positive
● Total Shaft Power (Per Unit) (W) The total power from all expansions that is delivered to the shaft of each turbine unit.	0.0	Positive
○ Power Type Indicates the power type that is used by the operation. Click on the list box to bring up a list of available power types in order to select one.	<Std Power>	Any Power Type
○ Power Generator Efficiency (%) The power generator’s efficiency of conversion of shaft power to electric power.	90.0	0-100
● Electric Power The electric power that is produced by the operation.	0.0	Positive

Symbol Key: ○ User-specified value (always input); ● Calculated value (always output); ◙ Sometimes input, sometimes output

Specification Choices / Comments

The following list describes the available specification choices in this tab; for more details on how these are implemented, see Power Generation in a Steam Turbine-Generator: Modeling Calculations.

•Isentropic Efficiency Options...

You can either set the isentropic efficiency of each expansion directly, or calculate it based on the condensate-free isentropic efficiency.

•Condensate-Free Isentropic Efficiency Options...

If the isentropic efficiency of each expansion is calculated based on condensate-free isentropic efficiency, you can either use the built-in quadratic curve or specify custom parameters for that curve in order to calculate the condensate-free isentropic efficiency of each expansion. The built-in curve is valid for steam and for power output in the range of 100 W - 1.5 MW. If you choose the custom curve, the model checks that the following additional constraints are satisfied with respect to the values of curve parameters a, b, and c:

a) a must be <=0.

b) If c=0, then b must be <>1.

c) If c<>0, then the discriminant of the quadratic curve must be >0.

•Specific Heat Ratio Options...

These options are available only if the Analytical Isentropic Expansion Model is selected through the Oper. Conds Tab. In that case, you can either set the specific heat ratio for each expansion, or let the program calculate its value by assuming ideal gas behavior.