Valve Elements

Valve Element General Description

Flow Simulator has a range of control valves that can be used in Flow Network Modeling. They are as follows

  1. Generic Valve: This type of valve element is used to model valve types that are not supported directly.
  2. Angle Valve: Valve with its outlet opening oriented at right angles to its inlet opening.
  3. Ball-Valve: This valve type is form of quarter-turn valve which uses a hollow, perforated and pivoting ball to control flow through it
  4. Butterfly valve: Type of quarter turn valve. A quarter turn valve can open or close whenever the handle is turned 90 degrees (a quarter of a turn).
  5. Gate Valve: They are opened by lifting a barrier (gate) out of the path of the fluid.
  6. Globe Valve: These valve elements restrict the flow of fluid by altering the distance between a movable plug and a stationary seat.
  7. Sluice Valve: This valve element is operating like gate valves, a sluice valve operates in the either fully on or fully off position and is used to allow or stop, but not regulate, flow.
  8. Y Valve: This type of valve element can be used when the fluid flow required to be conveniently diverted. They are easily mounted to a bulkhead. The valves are operated by a simple 120° movement.
  9. Spring Operated Check Valve: these valve elements function in the same way as swing check valves, but they have a spring to stay closed when there is no flow in the correct direction. That means that as soon as fluid stops flowing through, the valve claps shut.
  10. Swing Check valve: A swing check valve is mounted with a disc that swings on a hinge or shaft. The disc swings off the seat to allow forward flow and when the flow is stopped, the disc swings back onto the seat to block reverse flow.

Quick Guide for Valve Element Model Creation in the GUI

All valve elements can be found under “Compressible Gas Elements” and “Incompressible Liquid Elements” – “Valves” section.

The geometric inputs, valve position, momentum losses and compressible gas corrections (if the flow equation type is compressible gas) are mandatory inputs. And inputs related to heat, additional momentum losses, rotation effects, and valve characteristics are required if these effects are desired to be included in the element calculations. Descriptions about each input is described below in “Valve Elements Inputs” section. The (valve) position is synonymous with 'Valve Opening' and should be specified in Percentage (0% = closed, 100% = fully open). The variation of valve loss coefficient with position is specified as a curve. The valve position is fixed for a Steady State simulation, unless some form of feedback controller is used. In that case valve position will be adjusted, dependent upon some other parameter in the network.

Valve Element Input Variables

Valve Element inputs.

Valve Element Input Variables
Index UI Name (.flo label) Description
1 Valve Type (VALVE_TYPE) The following Valve types are available.

0: Generic Valve (used to model valve types that are not supported directly)

1: Angle Valve

2: Ball Valve

3: Butterfly Valve

4: Gate Valve

5: Globe Valve

6: Sluice Valve

7: Y-Valve

8: Spring-Operated Check Valve

9: Swing Check Valve

2 Loss Curve ID (LOSS_CURVE) The following Valve types are available.

-1: User-Defined Loss Curve in Table #1

0: Auto-select best loss curve based on VALVE_TYPE

11: Angle Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.24

21: Ball Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.24

31: Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

32: Butterfly Valve K Curve B from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

33: Butterfly Valve K Curve C from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

41: Gate Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.22

51: Globe Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.24

61: Sluice Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.22

71: Y-Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.24

3 Type of Loss Coefficient (LOSS_MODE) Seven of loss coefficient input curve are supported:

0: Reverse Loss same with Forward Loss

1: Cv (Valve Flow Coefficient)

2: Av (Valve Area Coefficient)

3: Aeff (Effective Area)

4: Cd (Discharge Coefficient)

5: K (K-Loss)

6: Cg (Flow Factor)

4 Type of Compressible Gas Choking Correction Factor (GASFAC_MODE) Three types of compressible gas choking correction factor are supported:

0: Off

1: C1 (Gas Flow Factor)

2: XT (XT Factor)

3: Cf (Critical Flow Factor)

5 Cross-section dimension input method (CS_MODE) The following Cross-section dimension (area, diameter) input options are available in the valve element:

1: Circular with Area Specified

2: Circular with Diameter Specified (default)

3: Arbitrary Shape (needs Area and Hyd.Diam. input)

6 Pipe Cross-Section Area (AREA) Cross-section area of both the pipe and the valve
7 Pipe Diameter (DIAMETER) Diameter of both the pipe and the valve
8 Special Valve Characteristic (VALVE_CHAR) The following Special Valve Characteristics are available. Any Special Valve Characteristic can be used in conjunction with any Valve Type.

0: Standard Reversible Valve

1: Check Valve

2: Pressure Relief Valve

9 Compressible Gas Correction Factor Curve (GASFAC_CURVE) -1: User-Defined Gas Factor Curve in Table #2

0: Auto-select best gas factor curve based on VALVE_TYPE

11: Angle Valve C1 Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 7.20

21: Ball Valve C1 Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 7.20

31: Butterfly Valve C1 Curve (High) from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

32: Butterfly Valve C1 Curve (Low) from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

33: Butterfly Valve C1 Curve (Averaged) from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

51: Globe Valve C1 Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 7.20

10 Valve Position (VALVEPOS) Valve Position, All the built-in valve curves used % opening.
11 Portion of Ustrm Chamb. Dyn. Head Lost (DQ_IN) Inlet dynamic head loss. Refer General solver theory sections for more details about this input
12 Rotor Index (RPMSEL) Reference rotor index for user-supplied swirl.

Stationary (Database Value = 0.0)

Rotor 1 (Database Value = 1.0): Points to general data Shaft 1 Rotor Speed.

Rotor 2 (Database Value = 2.0): Points to general data Shaft 2 Rotor Speed

Rotor 3 (Database Value = 3.0): Points to general data Shaft 3 Rotor Speed

13 Radius (RAD) Radius (in). Radial distance between the orifice inlet center and the engine centerline.
Note: Do not use zero unless the orifice is not rotating.
14 Element Inlet Orientation: Tangential Angle (THETA) Angle between the element centerline at the entrance of the element and the reference direction.

If the element is rotating or directly connected to one or more rotating elements, the reference direction is defined as parallel to the engine centerline and the angle is the projected angle in the tangential direction. Otherwise, the reference direction is arbitrary but assumed to be the same as the reference direction for all other elements attached to the upstream chamber.

THETA for an element downstream of a plenum chamber has no impact on the solution except to set the default value of THETA_EX.

(See also THETA_EX)

15 Element Inlet Orientation: Radial Angle (PHI) Angle between the element centerline at the entrance of the element and the THETA direction. (spherical coordinate system).

PHI for an element downstream of a plenum chamber has no impact on the solution except to set the default value of PHI_EX.

(See also PHI_EX)

16

17

18

Exit K Loss:

Axial (K_EXIT_Z)

Tangential (K_EXIT_U)

Radial (K_EXIT_R)

Head loss factors in the Z, U, and R directions based on the spherical coordinate system of theta and phi. (Default value provides no loss).

Refer General solver theory sections for more details about this input

19 Element Exit Orientation: Tangential Angle (THETA_EX) Angle between the orifice exit centerline and the reference direction.

THETA_EX is an optional variable to be used if the orientation of the element exit differs from that of the element inlet.

The default value (THETA_EX = -999) will result in the assumption that THETA_EX = THETA.

Other values will be interpreted in the manner presented in the description of THETA.

20 Element Exit Orientation: Radial Angle (PHI_EX) Angle between the orifice exit centerline and the THETA_EX direction.

PHI_EX is an optional variable to be used if the orientation of the element exit differs from that of the element inlet.

The default (PHI_EX = -999) will result in the assumption that PHI_EX = PHI.

Other values will be interpreted in the manner presented in the description of PHI.

21 Heat Addition Mode (HEAT_MODE) Mode of heat transfer to/from the fluid in the element.

See Element Heat Addition for more information.

22 Heat Added (QIN) The value entered for QIN depends on the HEAT_MODE chosen.

See Element Heat Addition for more information.

23 Fluid Compressibility Mode (FLUID_MODE) The user can choose which solution algorithm to use.

1: Compressible Gas

2: Incompressible Liquid

24 Reynolds Number Correction Relation for K

(RE_CORR)

The user can choose which to adjust K (or Cp) based according to the following options.

0: Off

1: Using Miller’s Internal Flow Systems 1st Ed. Fig. 14.33 or 2nd Ed. Fig. 14.32. Note: This option is recommended to be used when the Reynold’s number dependence on K is not known and is specifically suitable for valves and orifice plates.

25 Relief Pressure Chamber (RELIEF_CHAM) Chamber where relief pressure comes from.

If VALVE_CHAR=2 and RELIEF_CHAM=0, then the valve’s source pressure is the relief pressure.

If VALVE_CHAR=2 and RELIEF_CHAM>0, then the chamber PS is the relief pressure.

If VALVE_CHAR=2 and RELIEF_CHAM<0, then the relief chamber ID is ABS(RELIEF_CHAM) and the chamber PT is the relief pressure.

36 Valve Position as Input Variable in Curve Definition (TBL1_VALVEPOS) Independent variable curve

Should be in ascending order

37 Loss Coefficient (Cv, Av, Aeff, Cd, K, or Cg) as Output Variable in Curve Definition (TBL1_LOSS) Dependent variable curve
38 Valve Position as Input Variable in Curve Definition (TBL2_VALVEPOS) Independent variable curve

Should be in ascending order

39 Compressible Gas Choking Correction Factor (C1, XT, or Cf) as Output Variable in Curve Definition (TBL2_GASFACTOR) Dependent variable curve

C1, XT, and Cf are all unitless

40 Relief Pressure as Input Variable in Curve Definition

(TBL3_PRESSURE)

Independent variable curve

Should be in ascending order

41 Valve Position as Output Variable in Curve Definition

(TBL3_VALVEPOS)

Dependent variable curve
42 Pressure Ratio as Input Variable in Curve Definition (TBL4_PR) Independent variable curve
Note: Should be in ascending order.

Pressure Ratio defined as Ptotal Source (which is at the user-defined downstream since for reversed flow losses) divided by Pstatic Sink (which is at the user-defined upstream for reversed flow losses).

43 Loss Coefficient (Cv, Av, Aeff, Cd, K, or Cg) as Output Variable in Curve Definition (TBL4_REVLOSS) Dependent variable curve
Note: Reversed loss is intended to be used with check valves and pressure relief valves. Therefore, reversed loss is related to pressure ratio instead of valve position.

Valve Element Theory

Mass Flow rate Calculation

The valve element routine simulates incompressible liquid or compressible gas flows. For incompressible liquid flows, we start by presenting the standard equation of a valve with its flow rate defined by the Cv coefficient.

Since the Flow Simulator’s valve element supports other loss coefficient types, we were able to use the above equation together with standard incompressible loss coefficient conversions to make relate one form of loss coefficient to the others.

After conversion, the standard flow function is applied using effective area as the main driving loss parameter.

Rearranging the mass continuity equation yields the following function f, which expresses exit Mach number in terms of inlet Mach number. Then f is inserted into the momentum equation and the momentum equation is rearranged into a residual function that must be driven to zero by changing inlet Mach number in order to reach a converged solution. Finally, Newton’s method is applied to solve for inlet Mach number. The method uses a relaxation parameter that is generally equal to one (no relaxation) but drops to 0.5 or lower if convergence is not reached with 20 iterations. Usually convergence is attained in 1 to 4 iterations.

Once we know inlet Mach number, the continuity equation is used to solve for mass flow rate, exit Mach number, and all other previously unresolved velocity, static temperature, and pressure quantities at inlet and exit stations.

Before calculating subsonic flow rate however, we first need to decide in flow is in the choked regime. For valves, choking happens more easily than ideal flow channels, and this is where the choking correction factor and the semi-empirical choking area formula come into use.

Next, we re-introduce the mass continuity equation and the momentum balance equation. However, this time we rearrange and solve for pressure ratio and we substitute inlet Mach number that corresponds to choked at the artificial choking throat area.

Additional Momentum Loss

For Additional Momentum loss, Reynolds Number correction, Portion of Upstream Dynamic Head loss, Exit K Loss refer Solver General theory section.

Valve Element Output Variables

Outputs in file with “res” extension. Output units controlled by user setting in “Output Control” panel.

Name Description Units ENG, SI

FLOW:

FLOW: %WREF & MASSFLOWRATE

Flow rates in %WREF and [PPS]or [kg/s] (None) & (PPS or kg/s)
VALVE_TYPE Type of the valve information -
VALVE_CHARACTERISTIC Valve characteristics information
  • STANDARD_VALVE
-
FLUID Flow equation information
  • Compressible Gas
  • Incompressible Liquid
-
VALVEPOS Valve position (% opening), copy of user input %
PIPE_DIAM Diameter of the pipe, copy of user input inch, m
PIPE_AREA Cross sectional Area of the pipe, copy of user input Inch2, m2
PIPE_PERIM Pipe perimeter, copy of user input inch, m
DQ_IN Inlet dynamic head loss (copy of input) inch, m
ELEMENT_THETA Tangential Angle

(Usually an echo of the user input but converted to radians.)

radians
ELEMENT_PHI Radial Angle

(Usually an echo of the user input but converted to radians.)

radians
REL_INLET_ANGLE It is a relative inlet angle calculated based on upstream chamber velocity Deg
INLET_MACH_NEEDED_FOR_CHOKING Mach number at chocked flow.

Used to determining whether flow is subsonic or choked

CALCULATED_RESTRICTION_AREA_AT_THROAT Calculated Area for Choked Conditions inch, m

Compressible Gas Correction Factors:

C1=

XT=

CF=

Compressible gas correction factors (unitless)
Gas Factor Information *Valve Compr. Gas Factor from …

Information about gas factor calculations

-
Loss Curve Information *Valve Loss Curve taken from

-1: User-Defined Loss Curve in Table #1

0: Auto-select best loss curve based on VALVE_TYPE

11: Angle Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.24

21: Ball Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.24

31: Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

32: Butterfly Valve K Curve B from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

33: Butterfly Valve K Curve C from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19 Butterfly Valve K Curve A from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.19

41: Gate Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.22

51: Globe Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.24

61: Sluice Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.22

71: Y-Valve K Curve from D.S. Miller’s Internal Flow Systems 2nd Ed. Fig. 14.24

-
KB_INPUT (unitless)
KC_INPUT (unitless)
CD_INPUT (unitless)
AEFF_INPUT Pipe Area * CD_INPUT Inch2, m2
CV_INPUT Valve Flow Coefficient
AV_INPUT Flow coefficient Inch2, m2
CG_INPUT
KB_RESULT (PTIN - PTEX) / (0.5D0 * (PTIN - PSIN) + 0.5D0 * (PTEX - PSEX)) (unitless)
KC_RESULT (PTIN - PTEX) / (PTIN - PSVC) (unitless)
CD_RESULT (unitless)
AEFF_RESULT Pipe Area * CD_ RESULT Inch2, m2
FLOW REGIME

Information about flow regime:

  • Subsonic
  • Supersonic
-
ELEMENT_RPM Rotational speed of the restriction, RPM = 0 for Stationary rev/min
RAD Radius in, m
ELEMENT_THETA_EXIT Tangential Angle

(Usually an echo of the user input but converted to radians.)

radians
ELEMENT_PHI_EXIT Radial Angle

(Usually an echo of the user input but converted to radians.)

radians
PTS Driving pressure relative to the rotational reference frame (i.e. rotor) at the transition inlet. psia, MPa
PSIN Static pressure relative to the rotational reference frame (i.e. rotor) at the transition inlet.

Limited by critical pressure ratio for supersonic flows when inlet area is smaller than exit area.

psia, MPa
PTEX Total pressure relative to the rotational reference frame (i.e. rotor) at the transition exit including supersonic effects. psia, MPa
PSEX Static pressure relative to the rotational reference frame (i.e. rotor) at the transition exit.

Limited by critical pressure ratio for supersonic flows.

psia, MPa
TTS Total temperature of fluid relative to the rotational reference frame (i.e. rotor) at the transition inlet. deg F, deg K
TSIN Static temperature of fluid relative to the rotational reference frame (i.e. rotor) at the transition inlet. deg F, deg K
TTEX Total temperature of fluid relative to the rotational reference frame (i.e. rotor) at the transition exit. deg F, deg K
TSEX Static temperature of fluid relative to the rotational reference frame (i.e. rotor) at the transition exit. deg F, deg K
QIN Heat input.

Positive values indicate heat added to the fluid; negative values indicate heat removed.

BTU/s, W
INVEL Velocity of fluid relative to the rotational reference frame (i.e. rotor) at the transition inlet. ft/s, m/s
INMN Mach number of fluid relative to the rotational reference frame (i.e. rotor) at the transition inlet. (unitless)
INREYN Reynolds number at the inlet. (unitless)
EXVEL Velocity of fluid relative to the rotational reference frame (i.e. rotor) at the transition exit. ft/s, m/s
EXMN Mach of fluid relative to the rotational reference frame (i.e. rotor) at the transition exit. (unitless)
EXREYN Reynolds number at the exit. (unitless)
PTVC Total Pressure at Vena Contracta psia, MPa
PSVC Static Pressure at Vena Contracta psia, MPa
TTVC Total Temperature at Vena Contracta deg F, K
TSVC Static Temperature at Vena Contracta deg F, K
VCVEL Vena Contracta Velocity ft/s, m/s
VCMN Vena Contracta Mach Number -
VABS Magnitude of the fluid total absolute velocity ft/s, m/s
VTAN_ABS Magnitude of the fluid absolute tangential velocity ft/s, m/s
VAXIAL Magnitude of the fluid axial velocity ft/s, m/s
VRAD Magnitude of the fluid radial velocity ft/s, m/s
THTA_ABS Fluid absolute tangential flow angle rad
VREL Magnitude of the fluid total velocity relative to the element ft/s, m/s
VTAN_REF Reference frame tangential velocity ft/s, m/s
VTAN_REL Magnitude of the fluid tangential velocity relative to the element ft/s, m/s
VNORM Magnitude of the fluid total velocity relative to the element ft/s, m/s
THTA_REL Fluid relative tangential flow angle rad
TTABS Absolute total temperature deg F, K
TTREL Relative total temperature deg F, K

References

1. Miller, D, Internal Flow Systems, Miller Innovations, 1990