2EASY5 Gas Dynamics Modeling- History EASY5 predecessor EASY4 resulted from a Boeing contract to model aircraft environmental control systems.Environmental control (EC) library models many aspects of compressible gas flowOther custom libraries for gas dynamics have been supplied to customers as a result of consulting contracts and ensuing development efforts.
3Major features include: Multispecies, variable composition gasesUser choice of equation of statesIdeal gasBuilt-in real gas: Lee-Kestler correlationUser-defined real gasBuilt-in or user-defined gas speciesCommon connection scheme for fluid-flow componentsComponent GroupsPipes: transient and steady momentumOrificesValvesHeat exchangersGas-cycle machinesNodes and volumesActuatorsBody DynamicsForces
4Major features continued: Choice of SI, English unitsConsideration of humidity effectsRigorous formulation of mass, energy and momentum balancesMolecular (vacuum) flow can be modeled
5Multispecies Gases Variable composition gas streams Composition modeled with species partial pressure statesfor a single-species gas, partial pressure = pressurefor invariant composition, treat multispecies gas as single species (air, for example)inlet partial pressure vector is usually a stateDensity, viscosity, thermal conductivity and thermochemical properties are functions of pressure, temperature and composition.
6Equation of States Ideal Gas Built-in Real Gas Lee-Kestler 3-Parameter Correlation for Thermodynamic PropertiesTable based deviations from ideal gas behaviorIndependent Variables: Tr=T/Tc, Pr=P/Pc, accentric factor wCompressibility (Z=P/rRT)Residual Enthalpy: Hr=(H-Hig)/RTcResidual Entropy: Sr=(S-Sig)/R0 < Tr < 4, 0 < Pr < 10Transport propertiesEquation based correlations for single or multispecies gasesTemperature, pressure and composition dependentUser supplies routines to calculate thermodynamic and transport propertiesEASY5 supplies critical properties
7Definition of Gas Species Eight gas species are built-in at present:Air, N2, O2, H2O, CO2, CO, SO2, H2User-defined species are easily includedUser supplies:critical propertiesspecific heat (as function of temperature)viscosity (as function of temperature)thermal conductivity (as function of temperature)
8Common Connection Scheme All fluid-flow components have the same ported input/output structureEnabled by implicit modeling, Radau54 integratorInlet PortExit PortTemperature (TR1)Pressure (PP1, vector)Kinetic energy (KR1)Temperature (TR2)Pressure (PP2, vector)Kinetic energy (KR2)Temperature (TF1)Mass flow (W1, vector)Kinetic energy (KF1)Temperature (TR2)Mass flow (W2, vector)Kinetic energy (KF2)
9Components and Groups Pipes Orifices Valves Discretized transient momentumSteady-momentum pipeOrificesFixed-diameter orificeVariable area orificeValvesCheck valveRelief valveButterfly/globe/gate valveFour way valveThree way valvesOne inlet, two exitsTwo inlets, one exit
10Components and Groups (continued) Valves (continued)Servo ValvePressure-regulating valve (with control logic)Heat exchangers (thermally connectable to HC, VC and EC heat exchangers)Gas PrimaryGas SecondaryGas-cycle machinesCompressorMotor/turbineMiscellaneousGas Properties (with units definition)Filter
11Components and Groups (continued) Nodes and VolumesNode with one inlet port, one exit portNode with four inlet ports, four exit portsVariable volumeActuatorsSingle-chambered actuatorDual-chambered actuatorKit components:Active actuator building blockPassive actuator building blockActuator end- piston external force inputActuator end- mass dynamics input
12Components and Groups (continued) Body Dynamics (same as HV library)Single moving mass with hard limits, frictionTwo masses with hard limits, frictionForces (same as HV library)Pressure force and/or volume for two chambersForce and/or volume from dimensions and pressuresViscous damping forcesSteady-state flow forcesSum of forcesTransient flow forcesSpring forceSolenoid forceSpring stop