Modelica.Fluid.Machines

Information

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name	Description
SweptVolume	varying cylindric volume depending on the postition of the piston
Pump	Centrifugal pump with mechanical connector for the shaft
ControlledPump	Centrifugal pump with ideally controlled mass flow rate
PrescribedPump	Centrifugal pump with ideally controlled speed
BaseClasses	Base classes used in the Machines package (only of interest to build new component models)

Modelica.Fluid.Machines.SweptVolume

Information

Mixing volume with varying size. The size of the volume is given by:

• cross sectional piston area
• piston stroke given by the flange position s
• clearance (volume at flang position = 0)

Losses are neglected. The shaft power is completely converted into mechanical work on the fluid.

The flange position has to be equal or greater than zero. Otherwise the simulation stops. The force of the flange results from the pressure difference between medium and ambient pressure and the cross sectional piston area. For using the component, a top level instance of the ambient model with the inner attribute is needed.

The pressure at both fluid ports equals the medium pressure in the volume. No suction nor discharge valve is included in the model.

The thermal port is directly connected to the medium. The temperature of the thermal port equals the medium temperature. The heat capacity of the cylinder and the piston are not includes in the model.

Extends from Modelica.Fluid.Vessels.BaseClasses.PartialLumpedVessel (Lumped volume with a vector of fluid ports and replaceable heat transfer model).

Parameters

Type	Name	Default	Description
Area	pistonCrossArea		cross sectional area of pistion [m2]
Volume	clearance		remaining volume at zero piston stroke [m3]
replaceable package Medium		PartialMedium	Medium in the component
Volume	fluidVolume	V	Volume [m3]
Ports
Boolean	use_portsData	true	= false to neglect pressure loss and kinetic energy
VesselPortsData	portsData[nPorts]		Data of inlet/outlet ports
Assumptions
Dynamics
Dynamics	energyDynamics	system.energyDynamics	Formulation of energy balance
Dynamics	massDynamics	system.massDynamics	Formulation of mass balance
Heat transfer
Boolean	use_HeatTransfer	false	= true to use the HeatTransfer model
replaceable model HeatTransfer		IdealHeatTransfer	Wall heat transfer
Initialization
AbsolutePressure	p_start	system.p_start	Start value of pressure [Pa]
Boolean	use_T_start	true	= true, use T_start, otherwise h_start
Temperature	T_start	if use_T_start then system.T...	Start value of temperature [K]
SpecificEnthalpy	h_start	if use_T_start then Medium.s...	Start value of specific enthalpy [J/kg]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances
Advanced
Port properties
MassFlowRate	m_flow_small	system.m_flow_small	Regularization range at zero mass flow rate [kg/s]

Connectors

Type	Name	Description
VesselFluidPorts_b	ports[nPorts]	Fluid inlets and outlets
HeatPort_a	heatPort
Flange_b	flange	translation flange for piston

Modelica definition

model SweptVolume 
  "varying cylindric volume depending on the postition of the piston"
  import Modelica.Constants.pi;

  parameter SI.Area pistonCrossArea "cross sectional area of pistion";
  parameter SI.Volume clearance "remaining volume at zero piston stroke";

  SI.Volume V "fluid volume";

  // Mass and energy balance, ports
  extends Modelica.Fluid.Vessels.BaseClasses.PartialLumpedVessel(
    final fluidVolume = V,
    heatTransfer(surfaceAreas={pistonCrossArea+2*sqrt(pistonCrossArea*pi)*(flange.s+clearance/pistonCrossArea)}));

  Modelica.Mechanics.Translational.Interfaces.Flange_b flange 
    "translation flange for piston";

equation 
  assert(flange.s >= 0, "Piston stroke (given by flange.s) must not be smaller than zero!");

  // volume size
  V = clearance + flange.s * pistonCrossArea;

  0 = flange.f + (medium.p - system.p_ambient) * pistonCrossArea;

  // energy balances
  Wb_flow = medium.p * pistonCrossArea * (-der(flange.s));

  // definition of port pressures
  for i in 1:nPorts loop
    vessel_ps_static[i] = medium.p;
  end for;

end SweptVolume;

Modelica.Fluid.Machines.Pump

Information

This model describes a centrifugal pump (or a group of nParallel pumps) with a mechanical rotational connector for the shaft, to be used when the pump drive has to be modelled explicitly. In the case of nParallel pumps, the mechanical connector is relative to a single pump.

The model extends PartialPump

Extends from Modelica.Fluid.Machines.BaseClasses.PartialPump (Base model for centrifugal pumps).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Characteristics
Integer	nParallel	1	Number of pumps in parallel
replaceable function flowCharacteristic		PumpCharacteristics.baseFlow	Head vs. V_flow characteristic at nominal speed and density
AngularVelocity_rpm	N_nominal		Nominal rotational speed for flow characteristic [1/min]
Density	rho_nominal	Medium.density_pTX(Medium.p_...	Nominal fluid density for characteristic [kg/m3]
Boolean	use_powerCharacteristic	false	Use powerCharacteristic (vs. efficiencyCharacteristic)
replaceable function powerCharacteristic		PumpCharacteristics.quadrati...	Power consumption vs. V_flow at nominal speed and density
replaceable function efficiencyCharacteristic		PumpCharacteristics.constant...	Efficiency vs. V_flow at nominal speed and density
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Boolean	checkValve	false	= true to prevent reverse flow
Volume	V	0	Volume inside the pump [m3]
Dynamics
Dynamics	energyDynamics	Types.Dynamics.SteadyState	Formulation of energy balance
Dynamics	massDynamics	Types.Dynamics.SteadyState	Formulation of mass balance
Heat transfer
Boolean	use_HeatTransfer	false	= true to use a HeatTransfer model, e.g., for a housing
replaceable model HeatTransfer		IdealHeatTransfer	Wall heat transfer
Initialization
AbsolutePressure	p_a_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b_start	p_a_start	Guess value for outlet pressure [Pa]
MassFlowRate	m_flow_start	1	Guess value of m_flow = port_a.m_flow [kg/s]
Boolean	use_T_start	true	= true, use T_start, otherwise h_start
Temperature	T_start	if use_T_start then system.T...	Start value of temperature [K]
SpecificEnthalpy	h_start	if use_T_start then Medium.s...	Start value of specific enthalpy [J/kg]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances
Advanced
Diagnostics
Boolean	show_NPSHa	false	= true to compute Net Positive Suction Head available

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
HeatPort_a	heatPort
Flange_a	shaft

Modelica definition

model Pump "Centrifugal pump with mechanical connector for the shaft"
  extends Modelica.Fluid.Machines.BaseClasses.PartialPump;
  SI.Angle phi "Shaft angle";
  SI.AngularVelocity omega "Shaft angular velocity";
  Modelica.Mechanics.Rotational.Interfaces.Flange_a shaft;
equation 
  phi = shaft.phi;
  omega = der(phi);
  N = Modelica.SIunits.Conversions.to_rpm(omega);
  W_single = omega*shaft.tau;
end Pump;

Modelica.Fluid.Machines.ControlledPump

Information

This model describes a centrifugal pump (or a group of nParallel pumps) with ideally controlled mass flow rate or pressure.

Nominal values are used to predefine an exemplary pump characteristics and to define the operation of the pump. The input connectors m_flow_set or p_set can optionally be enabled to provide time varying set points.

Use this model if the pump characteristics is of secondary interest. The actual characteristics can be configured later on for the appropriate rotational speed N. Then the model can be replaced with a Pump with rotational shaft or with a PrescribedPump.

Extends from Modelica.Fluid.Machines.BaseClasses.PartialPump (Base model for centrifugal pumps).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
AbsolutePressure	p_a_nominal		Nominal inlet pressure for predefined pump characteristics [Pa]
AbsolutePressure	p_b_nominal		Nominal outlet pressure, fixed if not control_m_flow and not use_p_set [Pa]
MassFlowRate	m_flow_nominal		Nominal mass flow rate, fixed if control_m_flow and not use_m_flow_set [kg/s]
Boolean	control_m_flow	true	= false to control outlet pressure port_b.p instead of m_flow
Boolean	use_m_flow_set	false	= true to use input signal m_flow_set instead of m_flow_nominal
Boolean	use_p_set	false	= true to use input signal p_set instead of p_b_nominal
Characteristics
Integer	nParallel	1	Number of pumps in parallel
replaceable function flowCharacteristic		Modelica.Fluid.Machines.Base...	Head vs. V_flow characteristic at nominal speed and density
AngularVelocity_rpm	N_nominal	1500	Nominal rotational speed for flow characteristic [1/min]
Density	rho_nominal	Medium.density_pTX(Medium.p_...	Nominal fluid density for characteristic [kg/m3]
Boolean	use_powerCharacteristic	false	Use powerCharacteristic (vs. efficiencyCharacteristic)
replaceable function powerCharacteristic		PumpCharacteristics.quadrati...	Power consumption vs. V_flow at nominal speed and density
replaceable function efficiencyCharacteristic		PumpCharacteristics.constant...	Efficiency vs. V_flow at nominal speed and density
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Boolean	checkValve	false	= true to prevent reverse flow
Volume	V	0	Volume inside the pump [m3]
Dynamics
Dynamics	energyDynamics	Types.Dynamics.SteadyState	Formulation of energy balance
Dynamics	massDynamics	Types.Dynamics.SteadyState	Formulation of mass balance
Heat transfer
Boolean	use_HeatTransfer	false	= true to use a HeatTransfer model, e.g., for a housing
replaceable model HeatTransfer		IdealHeatTransfer	Wall heat transfer
Initialization
AbsolutePressure	p_a_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b_start	p_a_start	Guess value for outlet pressure [Pa]
MassFlowRate	m_flow_start	1	Guess value of m_flow = port_a.m_flow [kg/s]
Boolean	use_T_start	true	= true, use T_start, otherwise h_start
Temperature	T_start	if use_T_start then system.T...	Start value of temperature [K]
SpecificEnthalpy	h_start	if use_T_start then Medium.s...	Start value of specific enthalpy [J/kg]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances
Advanced
Diagnostics
Boolean	show_NPSHa	false	= true to compute Net Positive Suction Head available

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
HeatPort_a	heatPort
input RealInput	m_flow_set	Prescribed mass flow rate
input RealInput	p_set	Prescribed outlet pressure
Characteristics
replaceable function flowCharacteristic		Head vs. V_flow characteristic at nominal speed and density

Modelica definition

model ControlledPump 
  "Centrifugal pump with ideally controlled mass flow rate"
  import Modelica.SIunits.Conversions.NonSIunits.AngularVelocity_rpm;
  extends Modelica.Fluid.Machines.BaseClasses.PartialPump(
    N_nominal=1500,
    N(start=N_nominal),
    redeclare replaceable function flowCharacteristic =
        Modelica.Fluid.Machines.BaseClasses.PumpCharacteristics.quadraticFlow (
          V_flow_nominal={0, V_flow_op, 1.5*V_flow_op},
          head_nominal={2*head_op, head_op, 0}));

  // nominal values
  parameter Medium.AbsolutePressure p_a_nominal 
    "Nominal inlet pressure for predefined pump characteristics";
  parameter Medium.AbsolutePressure p_b_nominal 
    "Nominal outlet pressure, fixed if not control_m_flow and not use_p_set";
  parameter Medium.MassFlowRate m_flow_nominal 
    "Nominal mass flow rate, fixed if control_m_flow and not use_m_flow_set";

  // what to control
  parameter Boolean control_m_flow = true 
    "= false to control outlet pressure port_b.p instead of m_flow";
  parameter Boolean use_m_flow_set = false 
    "= true to use input signal m_flow_set instead of m_flow_nominal";
  parameter Boolean use_p_set = false 
    "= true to use input signal p_set instead of p_b_nominal";

  // exemplary characteristics
  final parameter SI.VolumeFlowRate V_flow_op = m_flow_nominal/rho_nominal 
    "operational volume flow rate according to nominal values";
  final parameter SI.Height head_op = (p_b_nominal-p_a_nominal)/(rho_nominal*g) 
    "operational pump head according to nominal values";

  Modelica.Blocks.Interfaces.RealInput m_flow_set if use_m_flow_set 
    "Prescribed mass flow rate";
  Modelica.Blocks.Interfaces.RealInput p_set if use_p_set 
    "Prescribed outlet pressure";

protected 
  Modelica.Blocks.Interfaces.RealInput m_flow_set_internal 
    "Needed to connect to conditional connector";
  Modelica.Blocks.Interfaces.RealInput p_set_internal 
    "Needed to connect to conditional connector";
equation 
  // Ideal control
  if control_m_flow then
    m_flow = m_flow_set_internal;
  else
    dp_pump = p_set_internal - port_a.p;
  end if;

  // Internal connector value when use_m_flow_set = false
  if not use_m_flow_set then
    m_flow_set_internal = m_flow_nominal;
  end if;
  if not use_p_set then
    p_set_internal = p_b_nominal;
  end if;
  connect(m_flow_set, m_flow_set_internal);
  connect(p_set, p_set_internal);

end ControlledPump;

Modelica.Fluid.Machines.PrescribedPump

Information

This model describes a centrifugal pump (or a group of nParallel pumps) with prescribed speed, either fixed or provided by an external signal.

The model extends PartialPump

If the N_in input connector is wired, it provides rotational speed of the pumps (rpm); otherwise, a constant rotational speed equal to n_const (which can be different from N_nominal) is assumed.

Extends from Modelica.Fluid.Machines.BaseClasses.PartialPump (Base model for centrifugal pumps).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Boolean	use_N_in	false	Get the rotational speed from the input connector
AngularVelocity_rpm	N_const	N_nominal	Constant rotational speed [1/min]
Characteristics
Integer	nParallel	1	Number of pumps in parallel
replaceable function flowCharacteristic		PumpCharacteristics.baseFlow	Head vs. V_flow characteristic at nominal speed and density
AngularVelocity_rpm	N_nominal		Nominal rotational speed for flow characteristic [1/min]
Density	rho_nominal	Medium.density_pTX(Medium.p_...	Nominal fluid density for characteristic [kg/m3]
Boolean	use_powerCharacteristic	false	Use powerCharacteristic (vs. efficiencyCharacteristic)
replaceable function powerCharacteristic		PumpCharacteristics.quadrati...	Power consumption vs. V_flow at nominal speed and density
replaceable function efficiencyCharacteristic		PumpCharacteristics.constant...	Efficiency vs. V_flow at nominal speed and density
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Boolean	checkValve	false	= true to prevent reverse flow
Volume	V	0	Volume inside the pump [m3]
Dynamics
Dynamics	energyDynamics	Types.Dynamics.SteadyState	Formulation of energy balance
Dynamics	massDynamics	Types.Dynamics.SteadyState	Formulation of mass balance
Heat transfer
Boolean	use_HeatTransfer	false	= true to use a HeatTransfer model, e.g., for a housing
replaceable model HeatTransfer		IdealHeatTransfer	Wall heat transfer
Initialization
AbsolutePressure	p_a_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b_start	p_a_start	Guess value for outlet pressure [Pa]
MassFlowRate	m_flow_start	1	Guess value of m_flow = port_a.m_flow [kg/s]
Boolean	use_T_start	true	= true, use T_start, otherwise h_start
Temperature	T_start	if use_T_start then system.T...	Start value of temperature [K]
SpecificEnthalpy	h_start	if use_T_start then Medium.s...	Start value of specific enthalpy [J/kg]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances
Advanced
Diagnostics
Boolean	show_NPSHa	false	= true to compute Net Positive Suction Head available

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
HeatPort_a	heatPort
input RealInput	N_in	Prescribed rotational speed [1/min]

Modelica definition

model PrescribedPump "Centrifugal pump with ideally controlled speed"
  extends Modelica.Fluid.Machines.BaseClasses.PartialPump;
  parameter Boolean use_N_in = false 
    "Get the rotational speed from the input connector";
  parameter Modelica.SIunits.Conversions.NonSIunits.AngularVelocity_rpm
    N_const =                                                                     N_nominal 
    "Constant rotational speed";
  Modelica.Blocks.Interfaces.RealInput N_in(unit="1/min") if use_N_in 
    "Prescribed rotational speed";

protected 
  Modelica.Blocks.Interfaces.RealInput N_in_internal(unit="1/min") 
    "Needed to connect to conditional connector";
equation 
  // Connect statement active only if use_p_in = true
  connect(N_in, N_in_internal);
  // Internal connector value when use_p_in = false
  if not use_N_in then
    N_in_internal = N_const;
  end if;
  // Set N with a lower limit to avoid singularities at zero speed
  N = max(N_in_internal,1e-3) "Rotational speed";

end PrescribedPump;