# EASY5® Gas Dynamics Library Preview 1 1.

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EASY5® Gas Dynamics Library Preview 1 1

EASY5 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 flow Other custom libraries for gas dynamics have been supplied to customers as a result of consulting contracts and ensuing development efforts.

Major features include:
Multispecies, variable composition gases User choice of equation of states Ideal gas Built-in real gas: Lee-Kestler correlation User-defined real gas Built-in or user-defined gas species Common connection scheme for fluid-flow components Component Groups Pipes: transient and steady momentum Orifices Valves Heat exchangers Gas-cycle machines Nodes and volumes Actuators Body Dynamics Forces

Major features continued:
Choice of SI, English units Consideration of humidity effects Rigorous formulation of mass, energy and momentum balances Molecular (vacuum) flow can be modeled

Multispecies Gases Variable composition gas streams
Composition modeled with species partial pressure states for a single-species gas, partial pressure = pressure for invariant composition, treat multispecies gas as single species (air, for example) inlet partial pressure vector is usually a state Density, viscosity, thermal conductivity and thermochemical properties are functions of pressure, temperature and composition.

Equation of States Ideal Gas Built-in Real Gas
Lee-Kestler 3-Parameter Correlation for Thermodynamic Properties Table based deviations from ideal gas behavior Independent Variables: Tr=T/Tc, Pr=P/Pc, accentric factor w Compressibility (Z=P/rRT) Residual Enthalpy: Hr=(H-Hig)/RTc Residual Entropy: Sr=(S-Sig)/R 0 < Tr < 4, 0 < Pr < 10 Transport properties Equation based correlations for single or multispecies gases Temperature, pressure and composition dependent User supplies routines to calculate thermodynamic and transport properties EASY5 supplies critical properties

Definition of Gas Species
Eight gas species are built-in at present: Air, N2, O2, H2O, CO2, CO, SO2, H2 User-defined species are easily included User supplies: critical properties specific heat (as function of temperature) viscosity (as function of temperature) thermal conductivity (as function of temperature)

Common Connection Scheme
All fluid-flow components have the same ported input/output structure Enabled by implicit modeling, Radau54 integrator Inlet Port Exit Port Temperature (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)

Components and Groups Pipes Orifices Valves
Discretized transient momentum Steady-momentum pipe Orifices Fixed-diameter orifice Variable area orifice Valves Check valve Relief valve Butterfly/globe/gate valve Four way valve Three way valves One inlet, two exits Two inlets, one exit

Components and Groups (continued)
Valves (continued) Servo Valve Pressure-regulating valve (with control logic) Heat exchangers (thermally connectable to HC, VC and EC heat exchangers) Gas Primary Gas Secondary Gas-cycle machines Compressor Motor/turbine Miscellaneous Gas Properties (with units definition) Filter

Components and Groups (continued)
Nodes and Volumes Node with one inlet port, one exit port Node with four inlet ports, four exit ports Variable volume Actuators Single-chambered actuator Dual-chambered actuator Kit components: Active actuator building block Passive actuator building block Actuator end- piston external force input Actuator end- mass dynamics input

Components and Groups (continued)
Body Dynamics (same as HV library) Single moving mass with hard limits, friction Two masses with hard limits, friction Forces (same as HV library) Pressure force and/or volume for two chambers Force and/or volume from dimensions and pressures Viscous damping forces Steady-state flow forces Sum of forces Transient flow forces Spring force Solenoid force Spring stop

Pneumatic Linear Positioning Model

Actuator Submodel

Pneumatic Linear Position: Output

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