The Component Steam Turbine
With the Steam Turbine component, electricity generation by the energetic devaluation of a steam flow is simulated.
Component Template
The Steam Turbine.e-ctpl component template is located in the Steam Supply Component template library folder.
Integration Into a Scheme
Input Data
In the Steam turbine Input data form (see following figure), the Nominal electrical power and either the Nominal conversion ratio or the Nominal driving power or the Nominal steam mass flow must be entered in order to determine the ratio of the nominal electrical to thermal capacity.
You can select the input size under Design parameters depending on the Design of energy conversion:
The thermal output corresponds to the difference between the incoming and outgoing enthalpy flow.
The partial load behavior can be specified in the drop-down menu under Design of energy conversion and stored with a characteristic curve.
The inlet and outlet states are determined in the upstream and downstream State determination components.
Output Data
In the Output data (see following figure) you will find the usual information.
In addition, the Isentropic efficiency \( \eta_{isentropic}\) is calculated, which describes the ratio of the actual thermal power to the ideal thermal power. Ideal means here the isentropic relaxation of the turbine (efficiency = 1).
If an efficiency greater than 1 is calculated, the warning appears:
The isentropic efficiency exceeds 1. Please check the plausibility of the in- and outlet steam states.
The isentropic efficiency is calculated as ratio of actual to ideal specific enthalpy difference \(h\) (see following equation). The ideal outlet state is determined by the real outlet temperature \(T_{outlet}\) and the same specific entropy as at the inlet \(s_{inlet}\) (isentrop = no change in entropy).
\( \eta_{isentropic} =\frac{h_{inlet} – h_{outlet,real}}{h_{outlet} -h_{outlet, ideal}} \),
\( h_{outlet, ideal} = h(T_{outlet},s_{inlet})\)Multistage Steam Turbines
Multi-stage steam turbines are formed from a combination of individual turbine components. In this way, every variation (with reheating, side removal, etc.) can be modeled. The following figure shows a two-stage steam turbine with sidestream, modeled from the components Steam_turbine and Valve-separator.
In the input form of the valve, the Steam withdrawal can be limited to a range (see following figure), so that the branched steam quantity can also be included in the optimization as a degree of freedom. Depending on the steam demand in the rest of the system, the operating mode of the turbine can be optimized.
Steam Turbine With Reheating
In combination with the Heat Transfer components, turbines with reheat can be modeled as shown in the following figure.
The transferable heat quantity can be limited in the component Intermediate Superheating (i.e., reheating, created from the component template Heat_Release_To_Steam). Whether the energy required for this is generated by cooling another steam flow, flue gas heat recovery, or by additional firing of a steam boiler, can be individually adapted for each project.
Fixing numerical problems (error message 8327)
For very unfavorable thermodynamic steam conditions, the material value functions may not converge for numerical reasons. This causes that the variable ideal exit enthalpy, which is needed for the calculation of the isentropic efficiency, cannot be calculated. In this case, the simulation ends with an error message (see the following figure).
The error message 8327 is displayed in the Simulator window:
The property model function geth_from_ps did not converge after 50 iterations. The last valid value is used for enthalpy.
In the example in the following figure, the incorrect calculation is located in block 481.
Click on the blue link of the block number. More detailed information about the faulty block will appear on the right side of the Simulator window (see the following figure). Such a link is only active immediately after an executed simulation.
Use a different formulation in the model, which may be more favorable for your steam condition. To do this, activate the Alternative property model calculation option in the component’s form under the Notes and tooltip → Developer options tabs.
