Flow Boundary

Flow boundary for ambient temperature and pressure

  • Library:
  • Powertrain Blockset / Propulsion / Combustion Engine Components / Fundamental Flow

Description

The Flow Boundary block implements a flow boundary that typically represents ambient temperature and pressure. Engine models require flow boundaries at the intake inlet and exhaust outlet. In dynamic engine models, flow-modifying components (for example, flow restriction, turbines, and compressors) connect to control volumes and flow boundaries.

You can specify these block configurations:

  • Constant pressure and temperature

  • Externally input pressure and temperature

The Flow Boundary block outputs pressure, temperature, and specific enthalpy:

h=cpT

The block models the mass fractions as dry air, resulting in these mass fractions:

  • yN2 = 0.767

  • yO2 = .233

The equation uses these variables.

T

Temperature

h

Specific enthalpy

cp

Specific heat at constant pressure

yN2

Nitrogen mass fraction

yO2

Oxygen mass fraction

Power Accounting

For the power accounting, the block implements these equations.

Bus Signal DescriptionEquations

PwrInfo

PwrTrnsfrd — Power transferred between blocks

  • Positive signals indicate flow into block

  • Negative signals indicate flow out of block

PwrBndrFlw

Heat flow rate to flow restriction

qorf

PwrNotTrnsfrd — Power crossing the block boundary, but not transferred

  • Positive signals indicate an input

  • Negative signals indicate a loss

PwrEnv

Heat flow rate to environment

-qorf

PwrStored — Stored energy rate of change

  • Positive signals indicate an increase

  • Negative signals indicate a decrease

Not used

Ports

Input

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External input pressure, P, in Pa.

Dependencies

To create this port, select External input for the Pressure and temperature source parameter.

External input temperature, T, in K.

Dependencies

To create this port, select External input for the Pressure and temperature source parameter.

Output

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Bus signal containing these block calculations.

SignalDescriptionUnits

BndryPrs

Boundary pressure

Pa

BndryTemp

Boundary temperature

K

BndryEnth

Boundary specific enthalpy

J/kg

PwrInfoPwrTrnsfrdPwrBndryFlw

Heat flow rate to flow restriction

W
PwrNotTrnsfrdPwrEnv

Heat flow rate to environment

W
PwrStored

Not used

Bus containing the flow boundary:

  • Prs — Pressure, P, in Pa

  • Temp — Temperature, T, in K

  • Enth — Specific enthalpy, h, in J/kg

  • MassFrac — Mass fractions, dimensionless.

    Specifically, a bus with these mass fractions:

    • O2MassFrac — Oxygen

    • N2MassFrac — Nitrogen

    • UnbrndFuelMassFrac — Unburned fuel

    • CO2MassFrac — Carbon dioxide

    • H2OMassFrac — Water

    • COMassFrac — Carbon monoxide

    • NOMassFrac — Nitric oxide

    • NO2MassFrac — Nitrogen dioxide

    • NOxMassFrac — Nitric oxide and nitrogen dioxide

    • PmMassFrac — Particulate matter

    • AirMassFrac — Air

    • BrndGasMassFrac — Burned gas

Parameters

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Block Options

Pressure and temperature source.

Dependencies

The table summarizes the parameter and port dependencies.

ValueEnables ParametersCreates Ports
Constant

Pressure, Pcnst

Temperature, Tcnst

None
External inputNone

Prs

Temp

Select color for block icon:

  • Cold for blue

  • Hot for red

Constant pressure, P, in Pa.

Dependencies

To enable this parameter, select Constant for the Pressure and temperature source parameter.

Constant temperature, T, in K.

Dependencies

To enable this parameter, select Constant for the Pressure and temperature source parameter.

Specific heat at constant pressure, in J/(kg·K).

References

[1] Heywood, John B. Internal Combustion Engine Fundamentals. New York: McGraw-Hill, 1988.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Introduced in R2017a