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Numerical Propulsion System Simulation Consortium

NPSS™ Thermodynamic Property Package

User Guide

Software Release: NPSSTM_2.4.1 Doc. #: NPSSTM–Thermo

Doc Revision: 2 Revision Date: June 21, 2012

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Doc. #: NPSSTM Thermo Guide

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Table of Contents PREFACE ............................................................................................................. 3

1 ALLFUEL ...................................................................................................... 4

1.1 ALLFUELFLOWSTATION ............................................................................. 4

1.2 ALLFUELFUELSTATION .............................................................................. 9

2 CEA (CHEMICAL EQUILIBRIUM WITH APPLICATIONS)......................... 12

2.1 CEAFLOWSTATION ................................................................................. 12

2.2 CEAFUELSTATION .................................................................................. 18

3 FLUID PROPERTY TABLES ...................................................................... 21

3.1 FPTFLOWSTATION ................................................................................. 21

4 GASTBL ...................................................................................................... 25

4.1 GASTAB ............................................................................................... 25

4.2 GASEQL ............................................................................................... 26

4.3 GASEQL2 ............................................................................................. 26

4.4 GASTBLFLOWSTATION ............................................................................ 27

4.5 GASTBLFUELSTATION ............................................................................. 31

5 JANAF ......................................................................................................... 35

5.1 JANAFFLOWSTATION ............................................................................... 35

5.2 JANAFFUELSTATION ................................................................................ 40


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List of Tables Table 1-1: allFuelFlowStation Supported Parameters ........................................... 7

Table 1-2: allFuelFlowStation Supported Functions.............................................. 9

Table 1-3: allFuelFuelStation Supported Parameters ......................................... 10

Table 1-4: allFuelFuelStation Supported Functions ............................................ 11

Table 2-1: CEAFlowStation Supported Parameters ............................................ 15

Table 2-2: CEAFlowStation Supported Functions ............................................... 17

Table 2-3: CEAFuelStation Supported Parameters ............................................ 20

Table 2-4: CEAFuelStation Supported Functions ............................................... 20

Table 3-1: FPT Supported Parameters ............................................................... 23

Table 3-2: FPT Supported Functions .................................................................. 24

Table 4-1: GASTAB Correlation Range .............................................................. 26

Table 4-2: GASEQL Correlation Range .............................................................. 26

Table 4-3: GASEQL2 Correlation Range ............................................................ 27

Table 4-4: GasTblFlowStation Supported Parameters ........................................ 29

Table 4-5: GasTblFlowStation Supported Functions........................................... 30

Table 4-6: GasTbl FuelStation Subset Options for switchGasTblOpt ................. 31

Table 4-7: Argument List for init Function ........................................................... 32

Table 4-8: GasTblFuelStation Supported Parameters ........................................ 33

Table 4-9: GasTblFuelStation Supported Functions ........................................... 34

Table 5-1: JanafFlowStation Supported Parameters .......................................... 37

Table 5-2: JanafFlowStation Supported Functions ............................................. 39

Table 5-3: JanafFuelStation Supported Parameters ........................................... 40

Table 5-4: JanafFuelStation Supported Functions .............................................. 40


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Preface This document is a user guide for the thermal dynamic property packages and is intended to be used in

conjunction with the NPSS User Guide Reference Sheets.

Calculations involving fluid properties require a thermodynamics package that models the fluid. NPSS

offers the user the ability to choose the thermodynamics package to be used.


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1 allFuel The allFuel thermo package defines the thermodynamic state of a gaseous mixture composed of air, water

vapor, and a variety of fuels.

1.1 allFuelFlowStation

The thermo package must be set before any FlowStation objects can be created. If the thermo package is

already set to “allFuel”, then it does not need to be set again before creating an allFuel FlowStation.

// Specify allFuel thermo package

setThermoPackage("allFuel");

// Create FlowStation(s)

FlowStation fs;

FlowStation fs2;

The allFuel thermo consists of seven switch-selectable models with a common interface. Allowed values

for fuel type in allFuel are "JP", "OLJP", "H2", "GAS", "CH4", "WBH2" and "UNIV".

// Set the flow station fuel type

fs.switchFuelType = “JP”;

Note: only "JP" and "CH4" are recommended for use.

"JP" is designed to produce properties for the combustion products of fuel, water and air, where the fuel H-

C atom ratio is 2:1. This model applies a 1962 atmosphere (with 0.03% CO2). This is a GE current

standard.

allFuel is a simple (fast) "burned properties only" thermo package. It does not keep track of the Cp, SG,

rho, etc. properties of unburned fuels. Therefore, it does not need to distinguish between JP4, JP7, JP8,

AvGas, Kerosene, etc.. The 2:1 H-C ratio value is close for all of these JP fuels.

"OLJP" stands for OLD JP and has an H-C ratio of 2:1 but with a 1945 Keenan and Keyes air composition

with no CO2 (used to match models from the 1950's to the 1990's).

"H2" stands for pure hydrogen gas with the 1962 atmosphere air composition.

"GAS" is a methane model with the 1945 Keenan and Keyes air composition. This is no longer the GE

standard.

"CH4" is the current methane model with the 1962 atmosphere air composition and is a GE standard.

"WBH2" is a pure hydrogen fuel with pure oxygen rather than air as the working fluid.

"UNIV" is a more complex option to address arbitrary fuel composition of H-C-O-N-A atoms with the

1962 atmosphere air composition. It can not be used without additional information and guidance.

Although there is a default Lower Heating Value (LHV), this parameter can vary dramatically (even for

fuels with the same H-C atom ratio) and thus should be input by the user. LHV has become problematic

and has been removed from FlowStations; it is currently only found in FuelStations.

Note: the zero enthalpy datum is at zero degrees Rankine/Kelvin (Keenan and Keyes base).


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It is to be noted that there is a single instance of the allFuel library, and hence common allFuel information

is shared across all the FlowStation objects. The above switchFuelType is an example of a common input.

The following examples demonstrate some of the functionality of the allFuel FlowStation. A complete list

of attributes and functions supported by allFuel FlowStation appear at the end of this section.

Dissociation flag can be set to be "ON" or "OFF."

// Set dissociation flag

fs.Dissociated = “ON”;

Constituents of the FlowStation have to be set prior to calculating the total conditions.

// Set fuel-to-air ratio

fs.FAR = 0.04;

// Set water-to-air ratio (specific humidity)

fs.WAR = 0.01;

Flow rate for a FlowStation can be set as follows.

// Set total flow rate, lbm/s

fs.W = 50.;

The total conditions at a station are set by any of the following functions.

// Define total properties of the FlowStation using

// one of the functions below

// setTotalTP(Tt, Pt); // based on input temperature and pressure

// setTotalSP(s, Pt); // based on input entropy and pressure

// setTotal_hS(ht, s); // based on input entropy and entropy

// setTotal_hP(ht, Pt); // based on input enthalpy and pressure

// set total state of fluid based on temperature and pressure

fs.setTotalTP(1000,50);

// set total state of fluid based on enthalpy and pressure

fs.setTotal_hP(135,30);

// Copy FlowStation flow, composition and total properties

fs2.copyFlow("fs");

// Combine two FlowStations: flow, composition, ht and Tt are

// calculated, while Pt is carried over from the 1st FlowStation

fs.add("fs2");

Once the flow rate and total conditions have been set, the static condition can be calculated by setting any

one of the following: area (A), static enthalpy (hs), static pressure (Ps), static temperature (Ts), Velocity

(V), or Mach number (MN).

// Set Mach number. This will set the flow static conditions.

fs.MN = 0.5;

// Set duct area. This will set the flow static conditions.

fs.A = 200.;

Note that the last static property input sets the static conditions. The example above sets the Mach number

and then sets cross-sectional area. Because area is set last, the static conditions will be based on area, and

the resulting Mach number will be calculated.


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Users will typically start the fluid flow using the FlowStart element. Therefore, they will use the FlowStart

element to set the temperature, pressure, flow rate, and water-to-air ratio. See the FlowStart element

description for additional information.

// Instantiate a FlowStart element

Element FlowStart AirStart {

// Set temperature, pressure, flow rate, and WAR

Tt = 520;

Pt = 14.7;

W = 50.;

WAR = 0.01;

}

The burn function is required in order to combine the fuel and air streams and burn the resulting mixture.

An allFuel FuelStation is required as an input argument.

// Create FuelStation

FuelStation fus;

// Set fuel station flow

fus.Wfuel = 5.;

// Burn FuelStation fuel in the FlowStation

// (use default fuel station settings)

// (use ideal efficiency for the purpose of the example)

fs.burn("fus",1);


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Table 1-1: allFuelFlowStation Supported Parameters

Name Units I/O Description A in2 I/O Physical cross sectional area. Can be used

to set static conditions.

Aphy in2 I/O Physical cross sectional area. Can be used


AphyDes in2 I Design physical cross sectional area. Can be

used to set static conditions.

Cd I Discharge coefficient

Cps Btu/(lbm*R) O Cp based on static conditions

Cpt Btu/(lbm*R) O Cp based on total conditions

Cvs Btu/(lbm*R) O Cv based on static conditions

Cvt Btu/(lbm*R) O Cv based on total conditions

Description O FlowStation description

Dissociated I Indicates whether the fluid is dissociated or

not. Allowed values are ON (default) and

OFF.

FAR Lbm/lbm I Fuel-to-air ratio (Wf/Wa)

FARst lbm/lbm O Stoichiometric Fuel to Air Ratio

fracAir O Fraction of the flow that is air

fracBurned O Fraction of the flow that is burned fuel

relative to the overall gas flow

fracUnburn O Fraction of the flow that is unburned fuel


gams O Gamma (specific heat ratio) based on static

conditions

gamt O Gamma (specific heat ratio) based on total

conditions

hs Btu/lbm I/O Enthalpy based on static conditions. Can be


ht Btu/lbm O Enthalpy based on total conditions

iDescription I

Imp lbf O Impulse

ks Btu/(sec*ft*R) O Conductivity based on static conditions

kt Btu/(sec*ft*R) O Conductivity based on total conditions

MN I/O Mach number. Can be used to set static

conditions.

MNdes I Design Mach number. Can be used to set

static conditions.

mus lbm/(ft*sec) O Viscosity based on total conditions

mut lbm/(ft*sec) O Viscosity based on total conditions

Prs O Prandtl number based on static conditions

Prt O Prandtl number based on total conditions

Ps psia O Static pressure

Pt psia O Total pressure

reconstitute I Determines if frozen or equilibrium

conditions are desired. Allow values are

EQUIL (default) or FROZEN.

rhos lbm/ft3 O Density based on static conditions

rhot lbm/ft3 O Density based on total conditions

Rs Btu/(lbm*R) O Gas constant based on static conditions

Rt Btu/(lbm*R) O Gas constant based on total conditions

s Btu/(lbm*R) O Entropy

superOrSub I Determines if the subsonic or supersonic

static conditions are desired. Allowed

values are SUBSONIC (default) and SUPERSONIC.

swirl rad I Swirl angle (relative to axial)

switchChokedMethod I Indicates the method used to determine the


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Name Units I/O Description statics when the flowstation is choked.

Allowed values are INVERT (default) and HOLD.

INVERT will decrease the area and determine

supersonic solution. HOLD will set the

static conditions to the choked value.

switchDes I Indicates if the flowstation is in design or

off-design mode

switchFuelType I Indicates the type of fuel to be used.

Allowed values are JP (default), OLJP, H2,

GAS, CH4, WBH2 and UNIV (see Section 1.1 for

details).

Ts R I/O Static temperature. Can be used to set

static conditions.

Tt R O Total temperature

us Btu/lbm O Internal energy based on static conditions

ut Btu/lbm O Internal energy based on total conditions

V ft/sec I/O Flow velocity. Can be used to set static

conditions.

W lbm/sec I Total Weight flow

Wa lbm/sec O Air flow

WAR lbm/lbm I Water-to-air ratio

Wc lbm/sec O Corrected weight flow. W*sqrt(theta)/delta

Wf lbm/sec O Fuel flow

Wh lbm/sec O Water flow

Wp O Referred weight flow (flow parameter).

W*sqrt(T)/P


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Table 1-2: allFuelFlowStation Supported Functions

Name Return

Type Arguments Description

add void stationName Add in a secondary flow station

of the same type. Conserve mass

and energy but not momentum.

Pressure is not updated

burn void fuelStation, eff Add in a fuel flow station of

the same type, conserve mass

and energy but not momentum;

burn fuel at given efficiency

copyFlow void stationName Copy primary variables from

another station in the same

object scope to this one

copyFlowRemote void stationName Copy primary variables from

another station anywhere in the

model to this one

copyFlowSatic void stationName Copy primary and static

variables from another station

in the same object scope to this

one

copyFlowStaticRemote void stationName Copy primary and static

variables from another station

anywhere in the model to this

one

getExergy real Tt, Pt Returns (dh – T*ds) at different

Tt and Pt

getIdealWork real Pt Returns (dh) at different Pt and

constant entropy

getIdealEnthalpy real s Returns (htIdeal) at different

entropy and constant Pt

getStationType string Returns FlowStation type (e.g.

“allFuelFlowStation”)

setStaticPs void Ps Determine static conditions

based on total conditions and

static pressure

setTotal_hP void h, P Set total conditions based on

enthalpy and pressure

setTotal_hS void h, s Set total conditions based on

enthalpy and entropy

setTotalSP void s, Pt Set total conditions based on

entropy and total pressure

setTotalTP void Tt, Pt Set total conditions based on

total temperature and total

pressure

setTotalTsPsMN void Ts, Ps, MN Set total conditions based on

the input static temperature,

pressure, and Mach number

1.2 allFuelFuelStation

The thermo package must be set before any FuelStation objects can be created. If the thermo package is

already set to “allFuel”, then it does not need to be set again before creating an allFuel FuelStation.

// Specify allFuel thermo package


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setThermoPackage("allFuel");

// Create fuel station

FuelStation fus;


This function is actually a FlowStation function, but it is presented gain here because it requires a

FuelStation as an input argument. Remember that the fuel type is set in the FlowStation, not the

FuelStation.

// Set the flow station fuel type

fs.switchFuelType = “JP”;

// Set the flow station flow rate

fs.W = 100.;

// Set the fuel station flow rate

fus.Wfuel = 5.;

// Override the default lower heating value

fus.LHV = 18200;

// Override the default fuel enthalpy

fus.hFuel = 20.;



fs.burn("fus",1);

Users will typically start the fuel flow using the FuelStart element, which automatically sets the fuel

parameters using the init function. See the FuelStart element description for additional information.

// Instantiate a FuelStart element and set fuel parameters

Element FuelStart FusEng{

LHV_in = 18500;

hFuel = 20;

Wfuel = 5;

}

Table 1-3: allFuelFuelStation Supported Parameters

Name Units I/O Description CHRatio O Carbon to Hydrogen mass ratio for fuel

FARst lbm/lbm O Stoichiometric fuel to air ratio

HCRatio O Hydrogen to Carbon mass ratio for fuel

HCRmolar O Hydrogen to Carbon molar ratio for fuel

hFuel Btu/lbm I Specific enthalpy

hRefFuel Btu/lbm I Specific enthalpy at the reference condition

LHV Btu/lbm I Fuel lower heating value

TrefFuel R I Reference temperature for the defined LHV

Wfuel lbm/sec I Weight flow


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Table 1-4: allFuelFuelStation Supported Functions

Name Return Type Arguments Description

copyFlow void stationName

Copy fuel properties (hRefFuel,

hFuel, Pfuel, TrefFuel, Tfuel,

and Wfuel) from another station

to this one

Init void dummyFuelType,

LHVin, Tstor, Pstor,

hstor, Tref, href,

Carbon, Hydrogen,

Nitrogen2, Oxygen

Initializes the FuelStation


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2 CEA (Chemical Equilibrium with Applications) CEA is a program which calculates chemical equilibrium composition from any set of reactants and

determines thermodynamic and transport properties for that composition.

CEA allows users to specify mixtures made up of any species. The possible reactants and products are

defined in the file thermo.inp. The reactants are defined in terms of the atomic ratios of their components.

When performing thermodynamic calculations (and solving for equilibrium), CEA will add all the reactants

together to determine the atomic ratio of the mix. It will then determine the mixture composition and

thermodynamic properties based on minimizing the product’s Gibbs free energy.

CEA will also calculate the transport properties of a mixture. The transport properties can be based on

frozen or equilibrium mixture compositions. For frozen properties, the assumption is made that the mixture

composition does not change as the derivatives are calculated (derivatives are used to obtain the values for

Cp, conductivity and Prandtl number). For equilibrium results, the assumption is made that the products do

change as the derivatives are calculated.

CEA allows users to specify a Mach number at which the static composition will be determined, different

from the actual static conditions. This allows users to simulate frozen flow through a nozzle expansion

process. Setting the composition Mach number at 0 is equivalent to fixing the mixture composition at the

stagnation conditions, upstream of the throat. Setting the Mach number to 1.0 is equivalent to freezing the

flow composition at the throat.

CEA allows users to remove reactants from a flow. This is equivalent to a product precipitating out of the

flow. An example of this would be water forming in a flow and precipitating out.

Normally CEA calculates the full equilibrium solution of given reactants. However, it may be desirable to

simulate incomplete reactions for such things as combustion inefficiencies. This is allowed by specifying

inert versions of the reactants. These inert reactants are thermodynamically the same as the true reactants.

The difference is they are not allowed to react with the rest of the flow. For example, the standard

thermo.inp file released with CEA contains an inert version of JP7. This JP7 does not combust with

oxygen; however, it can break down into inert versions of C2H4 and C8H10 that can not react with

anything else, unless additional inert species are added to the thermo.inp file.

For more technical information on CEA (including history and links to various technical reports concerning

CEA and its predecessors), see the website:

http://www.grc.nasa.gov/WWW/CEAWeb/ceaHome.htm

2.1 CEAFlowStation

To use CEA, the files thermo.inp and trans.inp must be in the include path. These are the default files that

define the thermodynamic and transport properties for the possible reactants and products. A complete list

of reactants can be found in the file thermo.inp, which is typically located in the NPSS “InterpIncludes”

directory.

The amount of time it takes CEA to converge is proportional the size of the thermo.inp file. NPSS is

released with two thermo input files, thermo.small and thermo.inp. The file thermo.small contains the

compounds associated with the combustion of a hydrocarbon fuel and air. The file thermo.inp contains a

large set of different compounds. If users wish to optimize CEA runs for speed, they should specify the

thermo.small file or create a new thermo file that is representative of the compounds that are pertinent to

the problem at hand.

http://www.grc.nasa.gov/WWW/CEAWeb/ceaHome.htm


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The CEA package itself is invoked using the setThermoPackage command.

// Specify CEA thermo package and allowable reactants

setThermoPackage("CEA", "thermo.inp", "trans.inp", "Air", "H2O", "JP_7",

"O2", "N2" );

// Create FlowStation

FlowStation fs;

The first argument sets the thermo package to "CEA", the second argument specifies the thermo property

file to use, the third argument specifies the transport property file to use, and the fourth argument is the first

reactant. Up to ten reactants can be specified. When running aircraft engine problems, the first reactant

should be air, and the second reactant should be water ("H2O"). This is because the elements that start the

flow will make this assumption when defining the air and humidity. When defining the fuel, the fuelType

variable in the FuelStart element must be set equal to one of the reactants listed above. The fuel enthalpy is

determined based on the heat of formation of the reactants. With these two changes – the

setThermoPackage and the fuel being defined correctly in the FuelStart – a standard NPSS model that was

running with a different thermo package should run with CEA.

Constituents of the flowstation have to be set prior to calculating the total conditions. Water-to-air ratio

can be set as follows.


fs.WAR = 0.01;



fs.W = 50.;

The total conditions at a station are set by any of the following setTotalxx functions.









Once the flow rate and total conditions have been set, the static condition can be calculated by setting any

of the following: area (A), static enthalpy (hs), static pressure (Ps), static temperature (Ts), Velocity (V), or

Mach number (MN).


fs.MN = 0.5;


fs.A = 200.;


and then sets cross-sectional area. Because area is set last, the static conditions will be based on area, and


To see the CEA output conditions set the switchPrint option to TRUE for that FlowStation. When this is

done, NPSS will produce CEA output files for the FlowStation. These files are <flowstationname>.ceaout


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and <flowstationname>.ceaoutStatic. The first file is the thermodynamic properties at the total conditions.

The second file is the thermodynamic properties at the static conditions (if they are calculated). IT IS

IMPORTANT THAT THESE FILES BE CHECKED PERIODICALLY TO ENSURE THE

THERMODYNAMIC CALCULATIONS ARE BEING PERFORMED CORRECTLY!

// Save flow station output conditions to the files fs.ceaout

// and fs.ceaoutStatic (if statics are calculated)

fs.setOption(“switchPrint”, “TRUE”);

// set the total state of the fluid using total temp and pressure

fs.setTotalTP(600., 30.);

// set the static state of the fluid using known static pressure

fs.Ps = 24.;

For CEA to calculate transport properties (specific heat, viscosity, thermal conductivity, etc.), the

FlowStation option variable switchTransport must be set to either EQUIL or FROZEN (default is NONE).

It is recommended that switchTransport be set only for FlowStations that require the retrieval of transport

properties and not for all FlowStations in the model.

// Enable the flow station to calculate transport properties

// at equilibrium

fs.setOption(“switchTransport”, “EQUIL”);

// set the fluid state using temperature and pressure


// save the thermal conductivity as ktIn

real ktIn = fs.kt;

Simulating frozen composition flow is a two-step process. First, the user sets the reconstitute option to

FROZEN. Then, the user specifies the desired Mach number. The following example will freeze the flow

at the total conditions:

// Set the flow conditions to FROZEN

fs.setOption(“reconstitute”, “FROZEN”);

// Set the frozen Mach number

fs.MNfroz = 0.;

The function addNonEq(string comp, real W) adds flow rate W amount of compound type comp to the

flow. When this is done, equilibrium is not recalculated. The thermodynamics are based on the previous

mix plus the new compound. Note: comp must be defined as a reactant in the setThermoPackage

command. Also, since equilibrium is not redone, comp must be available as a product.

// Add 3 lbm/s of H2O to the flow

// Do not recalculate equilibrium

fs.addNonEq("H2O", 3.);

The function addEq(string comp, real W) adds flow rate W amount of compound type comp to the flow.

When this is done, equilibrium is recalculated. As such, the final amount of compound comp may be

different than the initial amount plus W as more/less may form as the solution rebalances. Constant

temperature is assumed. Note: comp must be defined as a reactant in the setThermoPackage command.

// Add 5 lbm/s of H2O to the flow

// Recalculate equilibrium

fs.addEq("H2O", 5.);


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Note that in the examples above, water is added to the total flow at a specified flow rate. Using the

addNonEq or addEq functions to add water to the air flow is not technically the same as setting water-to-air

ratio (WAR) directly. The addNonEq and addEq functions increase the total flow rate by the specified

amount; whereas setting WAR will not change the total flow rate, just the fraction of water in the total

flow. Both methods will affect the reactant flow fractions, Wreac1 (air) and Wreac2 (H2O), but the

addNonEq and addEq functions will not automatically calculate WAR.

The function subtractNonEq(string comp, real W) subtracts flow rate W amount of compound type comp

from the flow. When this is done, equilibrium is not recalculated; the thermodynamics are based on the

previous mix minus the compound. Note, comp must be defined as a reactant in the setThermoPackage

command.

// Subtract 3 lbm/s of H2O from the flow

// Do not recalculate equilibrium

fs.subtractNonEq("H2O", 3.);

The function subtractEq(string comp, real W) subtracts flow rate W amount of compound type comp from

the flow. When this is done, equilibrium is recalculated. As such, the final amount of compound comp

may be different than the initial amount minus W as more/less may form as the solution rebalances.

Constant temperature is assumed. Note, comp must be defined as a reactant in the setThermoPackage

command.

// Subtract 5 lbm/s of H2O from the flow

// Recalculate equilibrium

fs.subtractEq("H2O", 5.);

The function setComp(string comp) sets the composition of the flow to be pure comp. Note: comp must be

defined as a reactant in the setThermoPackage command. The example below also sets the flow rate and

state of the fluid using the setTotalTP(real Tt, real Pt) function.

// Set the composition of the flow to pure oxygen

fs.setComp("O2");

// Set flow rate

fs.W = 10.;

// Set the state of the fluid at 600 R, and 30 psia


Table 2-1: CEAFlowStation Supported Parameters





AphyDes in2 I Design physical cross sectional area. Can

be used to set static conditions.

B O Beta used for water hammer


Cm O C minus used for water hammer





FAR O Fuel-to-air ratio (Wf/Wa)


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Name Units I/O Description gams O Gamma (specific heat ratio) based on static

conditions


conditions

hs Btu/lbm O Enthalpy based on static conditions. Can be


ht Btu/lbm O Enthalpy based on total conditions.

iDescription I

inertBurnReac1 I Percentage of reactant 1 to be moved to

reactant 10 (inerted) during a burn






















conditions.


static conditions.

MNfroz I Mach number used to freeze the flow



MW O Molecular weight

Ps psia I/O Static pressure. Can be used to set static

conditions.


reac1 O Name of reac1 (Air)

reac2 O Name of reac2 (H2O)

reac3 O Name of reac3 (empty)

















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Name Units I/O Description swirl rad I Swirl angle (relative to axial)

switchDes I Indicates if the flowstation is in design or

off-design mode

switchPrint I When set to TRUE, NPSS will produce standard

CEA output files: .ceaout for the total

conditions, .ceaoutStatic for the static

conditions. Allowed values are FALSE

(default) and TRUE.

switchTransport I Determines if the transport properties are

calculated (i.e. Cp, k, mu). Allowed values

are NONE (default), EQUIL, and FROZEN

Ts R O Static temperature. Can be used to set

static conditions.





conditions.








W*sqrt(T)/P

Wreac1 O Fraction of the flow that is Wreac1 (Air)

Wreac2 O Fraction of the flow that is Wreac2 (H2O)

Wreac3 O Fraction of the flow that is Wreac3








Table 2-2: CEAFlowStation Supported Functions

Name Return Type Arguments Description add void stationName Add in a secondary flow station

of the same type. Conserve mass

and energy but not momentum.

Pressure is not updated

addNonEq void comp, W Adds W amount of compound type

comp to the flow. Equilibrium is

not recalculated. See Usage

Notes above for further

description.

addEq void comp, W Adds W amount of compound type

comp to the flow. Equilibrium is

recalculated. See Usage Notes

above for further description.

burn void fuelStation,

eff

Add in a fuel flow station of the

same type, conserve mass and

energy but not momentum; burn

fuel, but efficiency is NOT USED.


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Name Return Type Arguments Description copyFlow void stationName Copy primary variables from




another station anywhere in the

model to this one

copyFlowSatic void stationName Copy primary and static variables

from another station in the same


copyFlowStaticRemote void stationName Copy primary and static variables

from another station anywhere in

the model to this one

setComp void comp Sets the composition of the flow

to be pure comp. See Usage Notes

above for further description.

setStaticPs void Ps Determine static conditions based

on total conditions and static

pressure





setTotal_hsPsV void hs, Ps, V Set total conditions based on the

input static enthalpy, pressure,

and velocity





pressure

setTotalTsPsMN void Ts, Ps, MN Set total conditions based on the

input static temperature,


subtractNonEq void comp, W Subtracts W amount of compound

type comp from the flow.

Equilibrium is not recalculated.

See Usage Notes above for further

description.

subtractEq void comp, W Subtracts W amount of compound

type comp from the flow.

Equilibrium is recalculated. See

Usage Notes above for further

description.

2.2 CEAFuelStation

As with the CEA FlowStation, the thermo package must be set before any FuelStation objects can be

created. If the thermo package is already set to “CEA” and the fuel you wish to use is among the allowed

reactants, then the thermo package does not need to be set again before creating a CEA FuelStation.

// Specify CEA thermo package, use JP_7 as the fuel

setThermoPackage("CEA", "thermo.inp", "trans.inp", "Air", "H2O", "JP_7");

// Create FuelStation(s)

FuelStation fus;

Up to ten reactants can be specified. When running aircraft engine problems, the first reactant should be

air, and the second reactant should be water. This is because the elements that start the flow will make this


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assumption when defining the air and humidity. The fluid used for the fuel is typically specified as the

third reactant, after air and water.

For the CEA FuelStation the only pertinent inputs are the fuel type and heat of formation. These values are

used to initialize the fuel by means of the FuelStation function init(string fuelType, real LHV, real Tfuel,

real Pfuel, real hFuel, real TrefFuel, real hRefFuel, real Carbon, real Hydrogen, real Nitrogen2, real

Oxygen). No other inputs will have any thermodynamic effect. (Pfuel and Tfuel are used for display only,

and the other values are for other NPSS thermo packages.) The fuelType is the fuel to be burned, and it

must correspond to a reactant as defined in the CEA setThermoPackage command. The parameter hFuel is

the heat of formation of the fuel at the desired fuel temperature. When switching between CEA and the

other packages, expect to make very large changes in the hFuel value.

// Set fuel type and heat of formation using the init function

fus.init(“JP_7”, 0., 0., 0., -200., 0., 0., 0., 0., 0., 0.);

// heat of formation can also be set directly in the fuel station

fus.hFuel = -200.;

// Define fuel flow of the FuelStation

fus.Wfuel = 5.;


// In CEA, efficiency argument is ignored

fs.burn("fus",1);

Users typically do not have to call the FuelStation init function directly because the FuelStation conditions

are set in the FuelStart element as fuelType and hFuel. The FuelStart element will automatically initialize

the FuelStation using fuelType and hFuel. See the FuelStart element description for additional information.



fuelType = “JP_7”;

hFuel = -200.;

Wfuel = 5;

}

If users wish to inert any of the fuel to simulate incomplete combustion, then the variable

inertBurnReac<number> is set equal to the fraction of the fuel the users wish to render inert in the

FlowStation where combustion occurs. The value of <number> must correspond to the reactant number of

the fuel that is to be rendered inert. In most cases, this will be three, since the first two reactants default to

air and water. When using this option, the tenth reactant in the setThermoPackage command must

correspond to the inert version of the fuel. NPSS will then use the tenth slot to manage the inert reactant.

// Specify CEA thermo package, use JP_7 as the fuel

// Set the tenth reactant as the inert fuel

setThermoPackage("CEA", "thermo.inp", "trans.inp", "Air", "H2O", "JP_7",

"", "", "", "", "", "", "Inert_JP_7" );


FlowStation fs;

// Set the fraction of fuel to be inert

fs.inertBurnReac3 = 0.02; // corresponds to 3rd reactant, JP_7

For the standard Burner element, the FlowStation where combustion occurs is Fl_Ocomb. Users would

directly set the inertBurn<number> parameter for Fl_Ocomb in the Burner element. When using CEA,

this method is used instead of setting the burner efficiency value. For example, if burner efficiency is 98%,

users would set the FlowStation inertBurnReac<number> value to 0.02.

// Set the burner combustion flow station inert fuel fraction

BrnPri.Fl_Ocomb.inertBurnReac3 = 0.02; // corresponds to 3rd


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// reactant, JP_7

Table 2-3: CEAFuelStation Supported Parameters

Name Units I/O Description CHRatio O Carbon to Hydrogen mass ratio for fuel. Not

used.

HCRatio O Hydrogen to Carbon mass ratio for fuel. Not

used.

hFuel Btu/lbm I Heat of formation

hRefFuel Btu/lbm O Specific enthalpy at the reference condition.

Not used.

kFuel O INTERNAL USE ONLY

LHV Btu/lbm O Fuel lower heating value. Not used.

Pfuel psia O Fuel pressure. Not used.

Tfuel R O Fuel temperature. Not used.

TrefFuel R O Fuel reference temperature. Not used.


Table 2-4: CEAFuelStation Supported Functions






to this one

Init void fuelType, LHV,

Tstor, PStor, hFuel,

Tref, href, Carbon,

Hydrogen, Nitrogen2,

Oxygen

Only fuelType and hFuel are

used by the init function.


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3 Fluid Property Tables The Fluid Property Tables (FPT) FlowStation was developed to allow users to model thermodynamic

properties for fluids not in the standard packages. Users supply the fluid’s thermodynamic properties via

an “.fpt” file. When the variable comp is set, the FPT FlowStation reads in this file, creates a FluidData

object for the fluid specified, and uses the data supplied to access the correct values for the fluid being

modeled. The fluid data can be in the form of NPSS Tables or functions that return a value of type real.

The functions can be algorithms, expressions, or constants. Table references in the following text refer to

both Tables and functions.

3.1 FPTFlowStation

Setting the composition of the fluid causes the appropriate FluidData object to be either selected or created.

Therefore, users must set the composition before setting any other parameters.

// Specify FPT thermo package

setThermoPackage("FPT");


FlowStation fs;

// Set the FlowStation composition

fs.comp = “air”; // The file air.fpt must exist

To set the state of a fluid in NPSS, users call the FlowStation setTotalxx functions. These functions set the

other state variables (i.e., setTotalTP uses the input values for Tt and Pt to calculate ht, and s). To

accommodate these functions there is a set of special .fpt Tables. They are h_s, h_T, s_h, s_T, T_h, and

T_s; where h_s would be ht= f(s,Pt) and so on.

// Set values for newly declared reals TtIn and PtIn

real TtIn = 600; // Rankine

real PtIn = 20; // psia

// Set the FlowStation state using total temperature and

// total pressure

fs.setTotalTP(TtIn, PtIn);

// Set flow rate

fs.W = 50.;

// Save the FlowStation enthalpy value

real htIn = fs.ht;


element to set the temperature, pressure, flow rate, and composition. See the FlowStart element description

for additional information.



// Set temperature, pressure, flow rate, and composition

Tt = 520;

Pt = 14.7;

W = 50.;

Fl_O.comp = “air”;

}


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The .fpt files have the following format (reference the air.fpt file below for examples):

- The file name is the name of the fluid with an .fpt extension (i.e., air.fpt)

- The file must be written in NPSS syntax.

- The description is a string containing information on the fluid being modeled.

- The indeps array is a list of the default parameters to be used for the fluid’s tables and/or

functions.

- The independents for the special Table calls have to be defined in the xxIndeps arrays.

- The table/function names should not include the t suffix (i.e., the table name for Cpt is Cp.)

- The tables/functions that return enthalpy, entropy or temperature must be named h_s (enthalpy as

a function of entropy), h_T, s_h, s_T, T_h, and T_s.

// Sample .fpt file (air.fpt)

description = "Air tables. Derived from …. ";

indeps = {"Tt","Pt"}; // thermodynamic property = f(Tt,Pt)

hsIndeps = {"s","Pt"}; // Table containing ht = f(s,Pt)

hTindeps = {"Tt","Pt"}; // Table containing ht = f(Tt,Pt)

shIndeps = {"ht","Pt"}; // Table containing s = f(ht,Pt)

sTindeps = {"Tt","Pt"}; // Table containing s = f(Tt,Pt)

ThIndeps = {"ht","Pt"}; // Table containing Tt = f(ht,Pt)

TsIndeps = {"s","Pt"}; // Table containing Tt = f(s,Pt)

// Constant Pressure Specific Heat as a function of temperature // and

pressure

Table Cp (real Tt, real Pt) {

Tt = 455.67 {

Pt = {3, 23.85, 44.7, 65.55, 86.4, 107.25, 128.1,

148.95, 169.8, 190.65, 211.5, 232.35, 253.2, 274.05, 294.9, 315.75,

336.6, 357.45, 378.3, 399.15, 420}

Cp = {0.23976, 0.23976, 0.23976, 0.23976, 0.23976,

0.23976, 0.23976, 0.23976, 0.23976, 0.23976, 0.23976, 0.23976, 0.23976,

0.23976, 0.23976, 0.23976, 0.23976, 0.23976, 0.23976, 0.23976, 0.23976}

}

Tt = 535.87 {

…

…

interp = "linear"; // interpolation method

extrap = "lagrange2"; // extrapolation method

printExtrap = 0; // do not print extrapolation warning

} // end Cp table

// Entropy as a function of temperature and pressure

Table s_T (real Tt, real Pt) {

…

…

} // end s_T table

// Gas constant as a function of temperature and pressure

real R (real Tt, real Pt) {

return 0.0685604; // Returns a constant value for R

}

…

…

The tables listed contain all the parameters and functions supported by the FPT thermo package. The

actual parameters and functions available for a specific fluid depend on what data is supplied by users in


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the .fpt file. Due to a problem in the internal setStatic function, the current version of FPT does not support

statics.

Table 3-1: FPT Supported Parameters

Name Units I/O Description A in2 I/O Cross sectional area. Statics not currently

supported in FPT.

Ades in2 I Design cross sectional area. Statics not

currently supported in FPT.


comp I Composition of fluid (must be same as name of

.fpt file)

Cpt Btu/(lbm*R) O Total constant pressure specific heat

Cpt_eq Btu/(lbm*R) O Total constant pressure specific heat –

equilibrium flow

Cpt_fz Btu/(lbm*R) O Total Constant Pressure Specific Heat –

Frozen flow

Cvt Btu/(lbm*R) O Total constant volume specific heat

Cvt_eq Btu/(lbm*R) O Total constant volume specific heat –

equilibrium flow

Cvt_fz Btu/(lbm*R) O Total Constant Volume Specific Heat – Frozen

flow

description I String describing the fluid being modeled

FAR lbm/lbm I/O Fuel-to-Air Ratio



conditions


imp lbf O Impulse


kt_eq Btu/(sec*ft*R) O Conductivity based on total conditions –

equilibrium flow

kt_fz Btu/(sec*ft*R) O Conductivity based on total conditions –

frozen flow

MN I/O Mach number. Statics not currently supported

in FPT.

MNdes I Design Mach number. Statics not currently

supported in FPT.





PtSat psia O Total saturation pressure

Rt Btu/(lbm*R) O Total gas constant

rhot lbm/ft3 O Total density

rhoPtSatL lbm/ft3 O Total saturated liquid density

rhoPtSatV lbm/ft3 O Total saturated vapor density


swirl rad O Swirl angle


TtSat R O Total saturation temperature


W lbm/sec I Total mass flow


Wc lbm/sec O Corrected air flow



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Name Units I/O Description Wh lbm/sec O Water flow


x O Quality (vapor mass / total mass)

Zt O Total compressibility

Table 3-2: FPT Supported Functions

Name Return

Type Arguments Description

add void stationName Adds the flow from stationName to the

FlowStation

addComposition void stationName Adds the composition of stationName to

the FlowStation

copyFlow void stationName Copies s, Tt, Pt, ht, W, FAR, WAR

values from StationName to the

FlowStation

copyFlowRemote void stationName

(incl. Path)

Performs a copyFlow from a remote

FlowStation to the FlowStation

getExergy real Tt, Pt Returns Exergy

getStationType string Returns the FlowStation type

setTotal_hP void ht, Pt Sets s and Tt based on ht and Pt

setTotalSP void s, Pt Sets ht and Tt based on s and Pt

setTotalTP void Tt, Pt Sets ht and s based on Tt and Pt

totalCompAll string Returns the composition based on total

conditions


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4 GasTbl GasTbl thermo package incorporates three property tables (GASTAB, GASEQL, and GASEQL2) for

defining the thermodynamic state of a gaseous mixture composed of air, water vapor, and a JP-class

hydrocarbon fuel.

4.1 GASTAB

GASTAB is a non-dissociated gas property table developed in the 1970s when cycle temperatures were

relatively modest. Properties for dry air and water vapor are similar to those defined by the widely used

Keenan & Keyes Steam Tables. Air is assumed to be composed of 21% oxygen and 79% atmospheric

nitrogen, by volume. The term atmospheric nitrogen indicates that the molecular weight of nitrogen has

been adjusted to account for the presence of minor species such as Argon and carbon dioxide. Atmospheric

N2 has a molecular weight of 28.16 as compared to 28.013 for pure N2. Gas mixture calculations assume

complete combustion, with no dissociation, and allow for only the major reaction products (CO2, H2O, N2,

and O2). The amount of each constituent in the reacted flow can be derived from a simple molar balance of

the following chemical equation-

22222yx N3.76424

yxOH

2

yxCON3.7642O

4

yxHC

and is a function of the fuel hydrocarbon ratio, fuel-to-air ratio, and specific humidity only. The

hydrocarbon jet fuel is defined as C1H1.906349, which approximates ASTM-A-1. Recalling that the molecular

weights of hydrogen and carbon equal 1.00794 and 12.0107, respectively, the molar and mass based fuel

hydrocarbon ratios are:

906349.1molar x

yHCR

15998.00107.12

00794.1906349.1

HCR

Once the gas constituency is known, the properties can be estimated by a simple mole weighted average of

the individual constituent properties, which are a function of temperature only.

GASTAB was commonly used for all thermodynamic property calculations prior to 1995 and is used in

many current cycle and component analysis models. Properties below 2000 R provide sufficient accuracy

for most gas turbine energy exchange calculations. Since GASTAB does not account for dissociation, it

should be used with caution when the temperature exceeds 2000 R. The range for the property values

being calculated is summarized as follows:


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Table 4-1: GASTAB Correlation Range

Parameter Range Notes

Gas Temperature (R) 300 T 4500 GASTAB does not account for

dissociation which occurs when

the gas temperature exceeds 2000

R. GASTAB should be used with caution in this high temperature

regime.

Gas Pressure (psia) N/A GASTAB properties are

independent of pressure.

Fuel/Air Ratio 0 f/a 0.068362 Analysis is limited to lean

mixtures.

Specific Humidity 0 0.02 GASTAB will extrapolate humidity

effects when sh > 0.02.

4.2 GASEQL

GASEQL incorporates expanded gas property tables relative to GASTAB. GASEQL matches GASTAB

below 2000oR temperature. Above 2000

oR, gas dissociation effects are modeled using the USAF TR85-13

equilibrium deck (using fuel HCR=0.16) and are compatible with NASA 1906-8 thermo-chemical data (per

AS681 requirement). The range for the property values being calculated is summarized as follows:

Table 4-2: GASEQL Correlation Range


Gas Temperature (R) 300 T 4500

Gas Pressure (psia) 1.47 P 735

Fuel/Air Ratio 0 f/a 0.068362 Analysis is limited to lean

mixtures.

Specific Humidity 0 0.02 GASEQL will extrapolate humidity


4.3 GASEQL2

GASEQL2 was developed to estimate the properties of a dissociated gas mixture at full equilibrium. Air is

assumed to be composed of 78.0840% N2, 20.9476% O2, 0.9340% Ar, 0.0314% CO2, and 0.0030% Ne, by

volume. The fuel is ASTM-A-1 hydrocarbon jet fuel (C1H1.9185) which has a mass-based hydrocarbon ratio

equal to:

1610.00107.12

00794.19185.1

HCR

Gas properties were estimated using an equilibrium computer model developed in 1985 by the Arnold

Engineering Development Center (AEDC) under contract to the U.S. Air Force. Non-dissociated gas

properties below 2000 R are very similar to those estimated by GASTAB. Above 2000 R the gas

constituents are limited to the eleven most common; N2, H2O, O2, CO2, Ar, Ne, H, O, OH, NO, and CO,

with the presence and amount of each constituent determined by a full equilibrium chemical analysis which

considers temperature, pressure, fuel-to-air ratio, and specific humidity. The AEDC equilibrium model,

commonly referred to as AEDC-TR-85-13, has been used by several U.S. gas turbine manufacturers to

establish their proprietary gas tables. As a result, gas properties estimated by GASEQL2 are very similar to

dissociated gas properties currently used throughout the U.S. industry.


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The range for the property values being calculated is summarized as follows:

Table 4-3: GASEQL2 Correlation Range


Gas Temperature (R) 300 T 4500

Gas Pressure (psia) 1.47 P 735

Fuel/Air Ratio 0 f/a 0.068362 Analysis is limited to lean mixtures.

Specific Humidity 0 0.02 GASEQL2 will extrapolate humidity


4.4 GasTblFlowStation


already set to “GasTbl”, then it does not need to be set again before creating a GasTbl FlowStation.

// Specify GasTbl thermo package

setThermoPackage("GasTbl");


FlowStation fs;

FlowStation fs2;

The following examples demonstrate some of the functionality of the GasTbl FlowStation. A complete list

of attributes and functions supported by GasTbl FlowStation appear at the end of this section.

// Define gas flow of the FlowStation

fs.W = 100;








// Print values to command window

cout << fs.Tt << endl;

cout << fs.Pt << endl;

cout << fs.ht << endl;

cout << fs.S << endl;

cout << endl;

// Define static properties of the FlowStation

// by setting one of the properties: MN, A, V, Ts, Ps, hs

fs.MN = 0.5;

cout << fs.MN << endl;

cout << fs.A << endl;

cout << fs.V << endl;

cout << fs.Ts << endl;

cout << fs.Ps << endl;

cout << endl;

// Copy FlowStation flow, composition and total properties

fs2.copyFlow("fs");


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cout << fs2.W << endl;

cout << fs2.Tt << endl;

cout << fs2.Pt << endl;

cout << endl;

// Combine two FlowStations: flow, composition, ht and Tt are

// calculated, while Pt is carried over from the 1st FlowStation

fs.add("fs2");

cout << fs.W << endl;


cout << fs.Pt << endl;

cout << endl;

// Create FuelStation

FuelStation fus;


fus.Wfuel = 5;


// (use default fuel station settings)


fs.burn("fus",1);


cout << fs.FAR << endl;



cout << endl;

Note that currently setting WAR of GasTbl FlowStation resets FAR to 0. While in the future this behavior

may be changed, for the time being, it is important to note that the original FAR value must be stored

before setting WAR and then must be reset after WAR has been assigned.

// Define water-air ratio of the FlowStation

// (assume no flow and enthalpy change for the purpose of the

// example)

real FARsave = fs.FAR;

fs.WAR = 0.0002;

fs.FAR = FARsave;

cout << fs.FARsave << endl;


cout << fs.WAR << endl;


element to set the temperature, pressure, flow rate, and water-to-air ratio. See the FlowStart element

description for additional information.




Tt = 520;

Pt = 14.7;

W = 50.;

WAR = 0.01;

}


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Table 4-4: GasTblFlowStation Supported Parameters

Name Units I/O Description A in2 I/O Physical cross sectional area. Can be used to

set static conditions.

Ades * in2 I Design physical cross sectional area. Can be


Ae * in2 O Effective area [A * Cd * cos( swirl )]






FAR lbm/lbm I Fuel-to-air ratio (Wf/Wa)


fracAir * O Fraction of the flow that is air

fracBurned * O Fraction of the flow that is burned fuel relative

to the overall gas flow

fracUnburn * O Fraction of the flow that is unburned fuel



conditions


conditions

hs Btu/lbm I/O Enthalpy based on static conditions. Can be used



iDescription I




conditions.

MNdes I Design Mach number. Can be used to set static

conditions.













switchDes I Indicates if the flowstation is in design or off-

design mode

Ts R I/O Static temperature. Can be used to set static

conditions.





conditions.






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Name Units I/O Description Wf lbm/sec O Fuel flow



W*sqrt(T)/P

Table 4-5: GasTblFlowStation Supported Functions

Name Return Type Arguments Description add void stationName Add in a secondary flow

station of the same type.

Conserve mass and energy but

not momentum. Pressure is not

updated

burn * void fuelStation, eff Add in a fuel flow station of








another station anywhere in



variables from another

station in the same object

scope to this one



station anywhere in the model

to this one

setStaticPs * void Ps Determine static conditions


static pressure

setTotal_hP * void h, P Set total conditions based on


setTotal_hS * void h, s Set total conditions based on


setTotal_hsPsV * void hs, Ps, V Set total conditions based on

the input static enthalpy,

pressure, and velocity

setTotalSP * void s, Pt Set total conditions based on


setTotalTP * void Tt, Pt Set total conditions based on


pressure

setTotalTsPsMN * void Ts, Ps, MN Set total conditions based on



*: defined or overwritten in GasTbl thermo package


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4.5 GasTblFuelStation As with the GasTbl FlowStation, the thermo package must be set before any FuelStation objects can be

created. If the thermo package is already set to “GasTbl”, then it does not need to be set again before

creating a GasTbl FuelStation.

// Specify GasTbl thermo package

setThermoPackage("GasTbl");


FuelStation fus;

The GasTbl thermo package supports several subsets of properties that are selected by setting

switchGasTblOpt switch of any FuelStation. The internal variable is global, so regardless of which

FuelStation switch is set,- the option will be reset for all of them. The switchGasTblOpt variable is

associated with the FuelStation instead of the FlowStation is because it may affect how fuel properties are

initialized. The following options may be displayed as allowed settings for the switchGasTblOpt switch,

but only some of them are supported in the GasTbl version provided with the NPSS Consortium release.

(The other ones are defined for P&W internal use.)

// Select thermo package subset

fus.switchGasTblOpt = “GASTAB”;

The summary of switchGasTblOpt options is shown below. Note that the GASEQL_GASTAB and

GASEQL2_GASTAB options were created for execution speed benefit when FlowStation has FAR=0.

Table 4-6: GasTbl FuelStation Subset Options for switchGasTblOpt

Option Notes GASTAB Use GASTAB subset of properties (default)

GASTABBM Disabled in NPSS Consortium release

GASTABBM_MF Disabled in NPSS Consortium release

GASEQL Use GASEQL subset of properties

GASEQL_GASTAB Use GASEQL if FAR>0 and GASTAB otherwise

GASEQL2 Use GASEQL2 subset of properties

GASEQL2_GASTAB Use GASEQL2 if FAR>0 and GASTAB otherwise

GASEQL3SN Disabled in NPSS Consortium release

GASEQL3SN_GASTAB Disabled in NPSS Consortium release

The FuelStation init function is used to define fuel properties that will be used during burning of fuel in the

FlowStation burn function. The complete argument list of init function is shown below:


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Table 4-7: Argument List for init Function

Argument Type Description fuelType string Not used in GasTbl

LHV real Sets LHV (if input is 0, 18400 is used)

Tfuel real Not used in GasTbl

Pfuel real Not used in GasTbl

hFuel real Used to set dhFuel relative to hRefFuel

TrefFuel real Temperature at which LHV is defined

hRefFuel real Used to set dhFuel relative to hRefFuel

Carbon real Not used in GasTbl

Hydrogen real Not used in GasTbl

Nitrogen2 real Not used in GasTbl

Oxygen real Not used in GasTbl

It should be noted that absolute values of hFuel and hRefFuel are irrelevant for GasTbl thermo package

since fuel properties are not handled as part of it (for example, note that hRefFuel value is not tied to

TrefFuel value). The only purpose of hFuel and hRefFuel variables is to define the extra fuel energy

relative to LHV that

is available for burning during the burn function call. Thus, it is a good practice to set hRefFuel=0 and

treat hFuel as dhFuel.

Also, note that if the init function is never called, the default LHV value is 18513, which is different than

the case when the init function is called with LHV=0 (in which case 18400 value is used).

Finally, it should be emphasized that regardless of Carbon and Hydrogen inputs in the init function, the

resulting HCRatio is 0.16 for all switchGasTblOpt options that are supported in the GasTbl version

provided with the NPSS Consortium release (GASTAB, GASEQL, GASEQL_GASTAB, GASEQL2,

GASEQL2_GASTAB).

// Initialize fuel properties

real LHV = 18400;

real Tref = 518.67;

real dhFuel = 10;

fus.init("", LHV, 0, 0, dhFuel, Tref, 0, 0, 0, 0, 0);


cout << fus.LHV << endl;

cout << fus.TrefFuel << endl;

cout << fus.hRefFuel << endl;

cout << fus.hFuel << endl;

cout << fus.HCRatio << endl;

cout << endl;

It should be noted that since HCRatio is constant for all switchGasTblOpt options that are supported in the

GasTbl version provided with the NPSS Consortium release, the use of the init function is not even

necessary.

All the relevant variables: LHV, TrefFuel, hFuel [dhFuel] can be set directly in the FuelStation.

// Set fuel properties directly, bypassing the init() function

fus.LHV = 18500;

fus.TrefFuel = 77 "F";

fus.hFuel = 20;


cout << fus.LHV << endl;


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cout << fus.TrefFuel << endl;

cout << fus.hRefFuel << endl;

cout << fus.hFuel << endl;

cout << fus.HCRatio << endl;

cout << endl;

Users typically do not have to call the FuelStation init function directly because the FuelStation conditions

are set in the FuelStart element. See the FuelStart element description for further information.



LHV_in = 18500;

Tref = 537;

hFuel = 20;

Wfuel = 5;

}


This function is actually a GasTbl FlowStation function, but is presented here again because it requires a

GasTbl FuelStation as an input argument.


fus.Wfuel = 5;



fs.burn("fus",1);





cout << endl;

Table 4-8: GasTblFuelStation Supported Parameters


FARst lbm/lbm O Stoichiometric fuel to air ratio


HCRmolar O Hydrogen to Carbon molar ratio for fuel

hFuel Btu/lbm I Specific enthalpy

hRefFuel Btu/lbm I Specific enthalpy at the reference condition


switchGasTblOpt I Flag that determines which set of GasTbl

routines to use. Options are GASTAB, GASEQL,

and GASEQL2.

TrefFuel R I Reference temperature for the defined LHV



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Table 4-9: GasTblFuelStation Supported Functions






to this one

init void dummyFuelType,

LHVin, Tstor, PStor,

hstor, Tref, href,

Carbon, Hydrogen,

Nitrogen2, Oxygen

Only LHVin is used by the

init() function. See the

descriptions for the GasTbl

thermo package.

*: defined or overwritten in GasTbl thermo package


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5 Janaf Janaf is a program which calculates chemical equilibrium product concentrations made up of the following

seventeen reactants: H2O, CO2, O2, N2, AR, CH4O, NH3, H2, O,H,CO,OH,NO,N,CH4,C2H4,C10H8.

The Janaf thermodynamic package determines the equilibrium solution of mixtures typical for air

combusted with a hydrocarbon fuel. It is similar to CEA in that it solves for composition based on

minimization of Gibb’s free energy. But unlike CEA it does not have an unlimited number of products.

The product list has been cut down to those typically seen in hydrocarbon combustion. Cutting the product

list down enables the problem formulation to be simplified; reducing run time. Janaf models run much

quicker than CEA models!

Janaf allows the user to freeze the composition of the flow. When this is done, the static composition at a

given location is not recalculated. Instead, the upstream conditions are used.

Janaf does solve for fuel rich mixtures. The species C2H4 and C10H8 are used to represent unburned fuel.

5.1 JanafFlowStation


already set to “Janaf”, then it does not need to be set again before creating a Janaf FlowStation.

// Specify Janaf thermo package

setThermoPackage("Janaf" );

// Create FlowStation

FlowStation fs;

With these two changes, the setThermoPackage and the fuel being defined correctly in the FuelStart, a

standard NPSS model that was running with a different thermo package should run with Janaf.

The FlowStation function setJanafComposition allows the user to set the fraction for each of the seventeen

possible reactants.

setJanafComposition( real q_h2o,

real q_co2,

real q_o2,

real q_n2,

real q_ar,

real q_ch4o,

real q_nh3,

real q_h2,

real q_o,

real q_h,

real q_co,

real q_oh,

real q_no,

real q_n,

real q_ch4,

real q_c2h4,

real q_c10h8 );

If the user wishes to set the flow composition to something other than the default, he/she would enter the

fractions of each constituent so that the total adds up to 1.0. The example below shows how to use the


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setJanafComposition function. The default values have been used for this example. However, if the user

wishes to use the default settings, then this function does not need to be used.

// Set the flow station composition.

// The default values have been used for this example.

fs.setJanafComposition( 0.0, // H2O

0.000484, // CO2

0.231416, // O2

0.7555184, // N2

0.012916, // AR

0.0, // CH4O

0.0, // NH3

0.0, // H2

0.0, // O

0.0, // H

0.0, // CO

0.0, // OH

0.0, // NO

0.0, // N

0.0, // CH4

0.0, // CH4O

0.0); // C10H8

Attributes of the FlowStation have to be set prior to calculating the total conditions. Water-to-air (WAR)

ratio can be set as follows. Note that setting WAR will update the FlowStation composition accordingly.


fs.WAR = 0.01;



fs.W = 50.;

The total conditions at a station are set by any of the following setTotalxx functions.









Once the flow rate and total conditions have been set, the static condition can be calculated by setting either

of the following: area (A), static enthalpy (hs), static pressure (Ps), static temperature (Ts), Velocity (V), or

Mach number (MN).


fs.MN = 0.5;


fs.A = 200.;


and then sets cross-sectional area. Because area is set last, the static conditions will be based on area and



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The FlowStation function totalCompAll() returns a string that shows the total conditions (Tt, ht, and Pt) and

composition solution of the flow.

// Print the flow station total conditions

// and composition to the command window

cout << “fs total composition = “ << fs.totalCompAll() << endl;

The FlowStation function staticCompAll() returns a string that shows the static conditions and composition

solution of the flow.

// Print the flow station total conditions

// and composition to the command window

cout << “fs static composition = “ << fs.staticCompAll() << endl;

The user will typically start the fluid flow using the FlowStart element. Therefore, he/she will use the

FlowStart element to set the temperature, pressure, flow rate, and water-to-air ratio. See the FlowStart

element description for additional information.




Tt = 520;

Pt = 14.7;

W = 50.;

WAR = 0.01;

}

Table 5-1: JanafFlowStation Supported Parameters





AphyDes in2 I Design physical cross sectional area. Can

be used to set static conditions.






description O FlowStation description

Dissociated I Indicates whether the fluid is dissociated

or not. Allowed values are ON (default)

and OFF.

FAR lbm/lbm I Fuel-to-air ratio (Wf/Wa)


fracAir O Fraction of the flow that is air

fracBurned O Fraction of the flow that is burned fuel


fracUnburn O Fraction of the flow that is unburned fuel



conditions


conditions

hs Btu/lbm I/O Enthalpy based on static conditions. Can


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Name Units I/O Description be used to set static conditions.


iDescription I

imp lbf O Impulse




conditions.


static conditions.

mus lbm/(ft*sec) O Viscosity based on static conditions



Pratio I Ratio of total pressure used to determine

static comp when staticComp is set to TOTAL













staticComp I Allowed values are TOTAL (default), STATIC,

and SEPARATE

superOrSub I Determines if the subsonic or supersonic

static conditions are desired. Allowed

values are SUBSONIC (default) and

SUPERSONIC.


switchChokedMethod I Indicates the method used to determine the

statics when the flowstation is choked.

Allowed values are INVERT (default) and

HOLD. INVERT will decrease the area and

determine supersonic solution. HOLD will

set the static conditions to the choked

value.

switchDes I Indicates if the flowstation is in design

or off-design mode

switchFuelRich I Allowed values are OFF (default) and ON

Tratio I Ratio of total temperature used to

determine static comp when staticComp is

set to TOTAL

Ts R I/O Static temperature. Can be used to set

static conditions.





conditions.







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Name Units I/O Description Wh lbm/sec O Water flow


W*sqrt(T)/P

Table 5-2: JanafFlowStation Supported Functions

Name Return Type Arguments Description add void stationName Add in a secondary flow

station of the same type.

Conserve mass and energy but

not momentum. Pressure is not

updated

burn void fuelStation, eff Add in a fuel flow station of








another station anywhere in




station in the same object

scope to this one



station anywhere in the model

to this one

getStationType string Returns FlowStation type

(e.g. “JanafFlowStation”)

setStaticPs void Ps Determine static conditions


static pressure









pressure

setTotalTsPsMN void Ts, Ps, MN Set total conditions based on



staticCompAll string Returns the static flow

conditions and composition

totalCompAll string Returns the total flow

conditions and composition


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5.2 JanafFuelStation

As with the Janaf FlowStation, the thermo package must be set before any FuelStation objects can be

created. If the thermo package is already set to Janaf, then the thermo package does not need to be set

again before creating a Janaf FuelStation.

// Specify Janaf thermo package

setThermoPackage("Janaf” );


FuelStation fus;

For the Janaf FuelStation the only pertinent inputs are hFuel, Carbon, Hydrogen, Nitorgen2, Oxygen, and

LHV. The hFuel is the enthalpy of the fuel itself. The values of Carbon, Hydrogen, Nitorgen2, and

Oxygen are the weight ratios of the specific atoms in the fuel.

The user will typically start the fuel flow using the FuelStart element, which automatically sets the fuel

parameters using the init function. When defining the fuel, weight ratios of the fuel’s Carbon, Hydrogen,

and Nitrogen must be defined. See the FuelStart element description for additional information.



LHV_in = 18300;

Wfuel = 5;

}

Table 5-3: JanafFuelStation Supported Parameters



hFuel Btu/lbm O Heat of formation

hRefFuel Btu/lbm O Specific enthalpy at the reference condition

kFuel O INTERNAL USE ONLY


Pfuel psia O Fuel pressure

Tfuel R O Fuel temperature

TrefFuel R O Fuel reference temperature.


Table 5-4: JanafFuelStation Supported Functions

Name Return Type Arguments Description compAll string Returns the fuel composition

copyFlow void stationName Copy fuel properties (hRefFuel,



to this one

init void fuelType, LHV,

Tstor, PStor, hFuel,

Tref, href, Carbon,

Hydrogen, Nitrogen2,

Oxygen

Initialize the FuelStation


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Appendix: Revision Page

Rev Date Description of Change

– 07/2010 Initial release of this document. (NPSS Thermodynamic Property Package User Guide)

C1 09/2011 CRs incorporated for release of NPSS 2.4: CR311 (two new arguments -- trans.inp and thermo.inp files -- added to setThermoPackage() function when specifying CEA thermodynamic property package, 2.1, 2.2), CR326 (added further description

of the allFuelFlowStation fuel types, 1.1), CR293 (corrected several attribute names from uppercase to lowercase – Gams to gams,

Hs to hs, Mus to mus, Us to us, S to s, Kt to kt, Rhos to rhos, Swirl to swirl, Table 1-1 and Table 4-1)


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NPSSTM Software © Copyright 2003. The U.S. Government, as Represented by the Administrator of the National

Aeronautics and Space Administration (NASA);

NPSSTM Software © Copyright 2008, 2009, 2010, 2011. The Ohio Aerospace Institute, on behalf of the

NPSSTM

Consortium. All rights reserved. Includes content licensed from the U.S. Government, National Aeronautics and

Space Administration under United States Copyright Registration Numbers V3503D364 and V3482D344.

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