The Turbine simulates three types of multi-extraction port turbines. The first type is designed to produce a specific amount of shaft work (i.e. sets the throttle flow). The second type is a back pressure turbine, which processes all throttle steam, distributing the flow to the ports, and determines the amount of shaft work produced. The third type sets the throttle flow and shaft work given port flows.
If the Shaftwork Given is checked (True), a type 1 turbine is used. If the Steam Flow Given is checked, a type 2 turbine is used. If port flows are given, a type 3 turbine is used.
Multiport turbines are modeled as a series of single extraction turbines. All the flow goes through the first extraction stage. If there is excess flow the remainder is sent to the second extraction stage, if there is excess flow the flow is sent to the third extraction stage, if there is excess flow the flow is sent to the exhaust stage.

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Data Description

Equipment Properties

Data		Unit		Description
Set	Item	Type	Native	Description
Equipment Properties	SteamGiven			If checked (True) the throttle steam flow is used. If not checked (False) the shaftwork value is used.
	Pres1stExt	Pressure	psia	Pressure of the 1st extraction port.
	MaxFlow1stExt	Mass Flow	lbs/hr	Maximum flow in the 1st extraction port.
	MaxFlowEff1stExt	Fraction or Percent	Fraction	Port efficiency of the 1st extraction port at the maximum flow.
	MinFlow1stExt	Mass Flow	lbs/hr	Minimum flow in the 1st extraction port.
	MinFlowEff1stExt	Fraction or Percent	Fraction	Port efficiency of the 1st extraction port at the minimum flow.
	FlowGiven1stExt			Current flow in the 1st extraction port stream is to be used.
	Pres2ndExt	Pressure	psia	Pressure of the 2nd extraction port.
	MaxFlow2ndExt	Mass Flow	lbs/hr	Maximum flow in the 2nd extraction port.
	MaxFlowEff2ndExt	Fraction or Percent	Fraction	Port efficiency of the 2nd extraction port at the maximum flow.
	MinFlow2ndExt	Mass Flow	lbs/hr	Minimum flow in the 2nd extraction port.
	MinFlowEff2ndExt	Fraction or Percent	Fraction	Port efficiency of the 2nd extraction port at the minimum flow.
	FlowGiven2ndExt			Current flow in the 2nd extraction port stream is to be used.
	Pres3rdExt	Pressure	psia	Pressure of the 3rd extraction port.
	MaxFlow3rdExt	Mass Flow	lbs/hr	Maximum flow in the 3rd extraction port.
	MaxFlowEff3rdExt	Fraction or Percent	Fraction	Port efficiency of the 3rd extraction port at the maximum flow.
	MinFlow3rdExt	Mass Flow	lbs/hr	Minimum flow in the 3rd extraction port.
	MinFlowEff3rdExt	Fraction or Percent	Fraction	Port efficiency of the 3rd extraction port at the minimum flow.
	FlowGiven3rdExt			Current flow in the 3rd extraction port stream is to be used.
	Pres4thExt	Pressure	psia	Pressure of the 3rd extraction port.
	MaxFlow4thExt	Mass Flow	lbs/hr	Maximum flow in the 4th extraction port.
	MaxFlowEff4thExt	Fraction or Percent	Fraction	Port efficiency of the 4th extraction port at the maximum flow.
	MinFlow4thExt	Mass Flow	lbs/hr	Minimum flow in the 4th extraction port.
	MinFlowEff4thExt	Fraction or Percent	Fraction	Port efficiency of the 4th extraction port at the minimum flow.
	FlowGiven4thExt			Current flow in the 4th extraction port stream is to be used.
	PresExh	Pressure	psia	Pressure of the exhaust port.
	MaxFlowExh	Mass Flow	lbs/hr	Maximum flow in the exhaust port.
	MaxFlowEffExh	Fraction or Percent	Fraction	Port efficiency of the exhaust port at the maximum flow.
	MinFlowExh	Mass Flow	lbs/hr	Minimum flow in the exhaust port.
	MinFlowEffExh	Fraction or Percent	Fraction	Port efficiency of the exhaust port at the minimum flow.
	FlowGivenExh			Current flow in the exhaust port stream is to be used.

Equipment Properties

Example of using equipment

Method&Equations

Three types of turbines are modeled and are dependent Shaftwork, Steam Flow and port Flow Given settings.
If the Shaftwork is given, a type 1 turbine is used. If throttle steam flow is given, a type 2 turbine is used. If port flows are given, a type 3 turbine is used.
Both type 1 and type 2 turbines adjust port flows to either match the required shaftwork or the fixed throttle flow. For both types, ports that are given are not adjusted. Port flows are adjusted in order. The 1st extraction port is filled first, the 2nd extraction port is filled next and the 3rd extraction port is filled next with the remainder going to the exhaust port.
The type 1 turbine is iterative. The type 1 turbine model first sets each ungiven port to its minimum flow and calculates the power produced. If the power produced is less than the required shaftwork each ungiven port is set to its maximum flow and the maximum power is calculated.
If the required shaftwork is less than the minimum power or the required shaftwork is greater than the maximum power, the shaftwork is set to the minimum or maximum, an error is issued and the turbine aborts.
If the required shaftwork is between the maximum and minimum power the next guess for the throttle flow is made by a linear interpolation. The power at this new throttle flow is calculated and compared against the required shaftwork. If the required shaftwork is less than the calculated power the new throttle flow is set as the maximum and the procedure is repeated. If the required shaftwork is greater than the calculated power the new throttle flow is set as the minimum and the procedure is repeated.
This procedure is repeated until the calculated power and the required shaft work's relative error is less than 0.001.
The type 2 turbine is a straight through calculation. Each ungiven port is adjusted, in order, until the throttle flow is met. The resulting power is then calculated.
The type 3 turbine is also a straight through calculation. The throttle flow is calculated from the given port flows, making sure that each port is at least at its minimum flow, and the resulting power is calculated.
The calculated power is that produced by reversible, ideal expansion. Port enthalpies are calculated by:
hport = hthrottle - Eff * ( hthrottle - hisentropic )
where:
hport is the port enthalpy
hthrottle is the throttle enthalpy
Eff is the port efficiency
hisentropic is the enthalpy at the throttle entropy and the port pressure
The power produced by the port is calculated by:
Pport = Fport * ( hthrottle - hport )
where:
Pport is the power produced by the port
Fport is the port flow
The total power produced is the sum of the power produced by each port.