1. EASY5®
Gas Dynamics
Library Preview 1 1

2. 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.

3. 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

4. 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

5. 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.

6. 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

7. 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)

8. 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)

9. 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

10. 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

11. 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

12. 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

13. Pneumatic Linear Positioning Model

14. Actuator Submodel

15. Pneumatic Linear Position: Output