RCAIDE.Library.Methods.Powertrain.Converters.Expansion_Nozzle.compute_expansion_nozzle_performance

compute_expansion_nozzle_performance#

compute_expansion_nozzle_performance(expansion_nozzle, conditions)[source]#

Computes the thermodynamic performance of an expansion nozzle in a propulsion system.

Parameters:

  • expansion_nozzle (RCAIDE.Library.Components.Converters.Expansion_Nozzle) –

    Expansion nozzle component with the following attributes:
    • tagstr

      Identifier for the nozzle

    • working_fluidData

      Working fluid properties object

    • pressure_ratiofloat

      Pressure ratio across the nozzle

    • polytropic_efficiencyfloat

      Polytropic efficiency of the expansion process

  • conditions (RCAIDE.Framework.Mission.Common.Conditions) –

    Flight conditions with:
    • freestreamData

      Freestream properties - isentropic_expansion_factor : numpy.ndarray

      Ratio of specific heats (gamma)

      • specific_heat_at_constant_pressurenumpy.ndarray

        Specific heat at constant pressure [J/(kg·K)]

      • pressurenumpy.ndarray

        Freestream pressure [Pa]

      • stagnation_pressurenumpy.ndarray

        Freestream stagnation pressure [Pa]

      • stagnation_temperaturenumpy.ndarray

        Freestream stagnation temperature [K]

      • specific_gas_constantnumpy.ndarray

        Specific gas constant [J/(kg·K)]

      • mach_numbernumpy.ndarray

        Freestream Mach number

    • energyData
      Energy conditions
      • convertersdict

        Converter energy conditions indexed by tag

Returns:

Results are stored in conditions.energy.converters[expansion_nozzle.tag].outputs:
  • stagnation_temperaturenumpy.ndarray

    Stagnation temperature at nozzle exit [K]

  • stagnation_pressurenumpy.ndarray

    Stagnation pressure at nozzle exit [Pa]

  • stagnation_enthalpynumpy.ndarray

    Stagnation enthalpy at nozzle exit [J/kg]

  • mach_numbernumpy.ndarray

    Mach number at nozzle exit

  • static_temperaturenumpy.ndarray

    Static temperature at nozzle exit [K]

  • static_enthalpynumpy.ndarray

    Static enthalpy at nozzle exit [J/kg]

  • velocitynumpy.ndarray

    Exit velocity [m/s]

  • static_pressurenumpy.ndarray

    Static pressure at nozzle exit [Pa]

  • area_rationumpy.ndarray

    Exit to freestream area ratio

Return type:

None

Notes

This function computes the thermodynamic properties at the expansion nozzle exit based on the inlet conditions and nozzle characteristics. It calculates the exit velocity, pressure, temperature, and other properties for both subsonic and supersonic flow regimes.

The computation follows these steps:

  1. Extract freestream and inlet conditions

  2. Compute working fluid properties (gamma, Cp)

  3. Calculate stagnation conditions at exit using pressure ratio

  4. Compute exit Mach number based on pressure ratio

  5. Handle subsonic (M < 1.0) and supersonic (M ≥ 1.0) cases separately

  6. Calculate static conditions (temperature, pressure) at exit

  7. Compute exit velocity from energy conservation

  8. Calculate area ratio between freestream and nozzle exit

  9. Store all results in the conditions data structure

Major Assumptions

  • Constant polytropic efficiency and pressure ratio

  • If pressures make the Mach number go negative, these values are corrected

Theory For subsonic flow (M < 1.0), the exit pressure equals the ambient pressure, and the Mach number is calculated from the pressure ratio. For supersonic flow (M ≥ 1.0), the nozzle is choked, and the exit pressure is calculated from the Mach number.

The exit velocity is calculated from the conservation of energy:

\[u_{out} = \sqrt{2(h_{t,out} - h_{out})}\]

where h_{t,out} is the exit stagnation enthalpy and h_{out} is the exit static enthalpy.

References

[1] Cantwell, B., “AA283 Course Notes”, Stanford University https://web.stanford.edu/~cantwell/AA283_Course_Material/AA283_Course_Notes/

See also

RCAIDE.Library.Methods.Gas_Dynamics.fm_id