Source code for RCAIDE.Library.Attributes.Propellants.Liquid_Natural_Gas
# RCAIDE/Library/Attributes/Propellants/Liquid_Natural_Gas.py
#
#
# Created: April 2026, S. Shekar, S. Sharma
# ----------------------------------------------------------------------------------------------------------------------
# Imports
# ----------------------------------------------------------------------------------------------------------------------
import RCAIDE
from .Propellant import Propellant
import os
import numpy as np
from scipy.interpolate import interp1d
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# Liquid_Natural_Gas Class
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[docs]
class Liquid_Natural_Gas(Propellant):
"""
A class representing Liquid Natural Gas (LNG) fuel properties and composition
for propulsion applications.
Attributes
----------
tag : str
Identifier for the propellant ('Liquid_Natural_Gas')
reactant : str
Oxidizer used for combustion ('O2')
density : float
Fuel density in kg/m³ (414.2)
specific_energy : float
Lower heating value (LHV) specific energy content in J/kg (48.632e6)
energy_density : float
Energy density in J/m³ (22200.0e6)
stoichiometric_fuel_air_ratio : float
Stoichiometric fuel-to-air ratio [-] (0, placeholder)
heat_of_vaporization : float
Heat of vaporization at standard conditions in J/kg (0, placeholder)
temperature : float
Temperature of fuel in K (0, placeholder)
pressure : float
Pressure of fuel in Pa (0, placeholder)
fuel_surrogate_S1 : dict
Mole fractions of fuel surrogate species [-]
kinetic_mechanism : str
Kinetic mechanism name for fuel surrogate combustion
oxidizer : str
Oxidizer species name
emission_indices : Data
Emission indices in kg/kg fuel
- Production : float
Upstream extraction and liquefaction CO2 (0.35)
- CO2 : float
Carbon dioxide (2.75)
- CO : float
Carbon monoxide (0.00100)
- H2O : float
Water vapor (2.20)
- SO2 : float
Sulfur dioxide (0.0)
- NOx : float
Nitrogen oxides (0.0126)
- Soot : float
Particulate matter (0.0)
global_warming_potential_100 : Data
100-year global warming potentials (CO2-equivalent per kg of species)
- CO2 : float
Carbon dioxide (1)
- H2O : float
Water vapor (0.06)
- CO : float
Carbon monoxide (1)
- SO2 : float
Sulfur dioxide (-226)
- NOx : float
Nitrogen oxides (52)
- Soot : float
Particulate matter (1166)
- Contrails : float
Contrail formation factor in kg CO2e/km (11)
materials_properties : dict
Interpolated thermophysical property data loaded from ``LNG_properties.res``
Notes
-----
LNG is a cryogenic fuel consisting primarily of methane with small amounts of
heavier hydrocarbons. It requires storage at approximately -162°C (-111 K) but
offers reduced carbon emissions compared to conventional jet fuels.
The ``specific_energy`` value uses the lower heating value (LHV) of LNG, which
excludes the latent heat of water condensation in combustion products.
**Definitions**
'Global Warming Potential (GWP-100)'
Relative measure of heat trapped in the atmosphere over 100 years compared
to an equivalent mass of CO2
'Energy Density'
Energy content per unit volume, dependent on cryogenic storage conditions
**Major Assumptions**
* Properties are for saturated liquid at atmospheric pressure
* Composition represents a typical LNG mixture
References
----------
[1] Lower and Higher Heating Values of Gas, Liquid, and Solid Fuels.
NPRE 470 course resource, University of Illinois Urbana-Champaign, 2018.
https://courses.grainger.illinois.edu/npre470/sp2018/web/Lower_and_Higher_Heating_Values_of_Gas_Liquid_and_Solid_Fuels.pdf
"""
def __defaults__(self):
"""Set default values for Liquid Natural Gas propellant properties.
Assumptions
-----------
* Density and energy properties correspond to saturated liquid LNG
at atmospheric pressure.
* Specific energy is based on the lower heating value (LHV) of LNG.
* GWP-100 values follow standard aviation emission indices.
* Placeholder values of 0 are assigned to fields that must be set
by the user or a higher-fidelity model before use.
Source
------
Lower Heating Value:
NPRE 470, University of Illinois Urbana-Champaign (2018).
https://courses.grainger.illinois.edu/npre470/sp2018/web/
Lower_and_Higher_Heating_Values_of_Gas_Liquid_and_Solid_Fuels.pdf
"""
self.tag = 'Liquid_Natural_Gas'
self.reactant = 'O2'
self.density = 414.2 # [kg/m^3] saturated liquid at ~111 K
self.specific_energy = 48.632e6 # [J/kg] lower heating value (LHV)
self.energy_density = 22200.0e6 # [J/m^3]
self.stoichiometric_fuel_air_ratio = 0 # [-] stoichiometric fuel-to-air ratio (placeholder)
self.heat_of_vaporization = 0 # [J/kg] heat of vaporization at standard conditions (placeholder)
self.temperature = 0 # [K] fuel temperature (placeholder)
self.pressure = 0 # [Pa] fuel pressure (placeholder)
self.fuel_surrogate_S1 = {} # [-] mole fractions of fuel surrogate species
self.kinetic_mechanism = '' # kinetic mechanism name for combustion model
self.oxidizer = '' # oxidizer species name
self.emission_indices.Production = 0.35 # kg/kg upstream extraction + liquefaction (GREET)
self.emission_indices.CO2 = 2.75 # kg/kg stoichiometric floor for CH4 (44/16); LNG blend ≈ 2.75–2.78
self.emission_indices.CO = 0.00100 # kg/kg ~1.0 g/kg, typical gas turbine at cruise
self.emission_indices.H2O = 2.20 # kg/kg
self.emission_indices.SO2 = 0.0 # kg/kg
self.emission_indices.NOx = 0.0126 # kg/kg
self.emission_indices.Soot = 0.0 # kg/kg
self.global_warming_potential_100.CO2 = 1 # [CO2e/kg] carbon dioxide
self.global_warming_potential_100.H2O = 0.06 # [CO2e/kg] water vapor
self.global_warming_potential_100.CO = 1 # [CO2e/kg] carbon monoxide
self.global_warming_potential_100.SO2 = -226 # [CO2e/kg] sulfur dioxide (cooling effect)
self.global_warming_potential_100.NOx = 52 # [CO2e/kg] nitrogen oxides
self.global_warming_potential_100.Soot = 1166 # [CO2e/kg] soot / black carbon
self.global_warming_potential_100.Contrails = 11 # [CO2e/km] contrail radiative forcing
self.materials_properties = self.cryogen_properties()
[docs]
def cryogen_properties(self, T, prop_name):
"""
Return an interpolated LNG thermophysical property value at a given temperature.
Parameters
----------
T : float or ndarray
Temperature(s) in Kelvin at which the property is requested.
prop_name : str
Name of the property column to retrieve from the LNG data file.
Valid keys include:
- ``"Temperature (K)"``
- ``"Pressure (MPa)"``
- ``"Density (kg/m3)"``
- ``"Volume (m3/kg)"``
- ``"Internal Energy (kJ/kg)"``
- ``"Enthalpy (kJ/kg)"``
- ``"Entropy (J/g*K)"``
- ``"Cv (J/g*K)"``
- ``"Cp (J/g*K)"``
- ``"Sound Spd. (m/s)"``
- ``"Joule-Thomson (K/MPa)"``
- ``"Viscosity (Pa*s)"``
- ``"Therm. Cond. (W/m*K)"``
- ``"Phase"``
Returns
-------
prop_value : float or ndarray
Interpolated property value(s) corresponding to the input temperature(s).
Notes
-----
* Property data is loaded from ``LNG_properties.res`` via
:func:`load_lng_properties`.
* Linear interpolation is applied between tabulated data points.
* Extrapolation outside the tabulated temperature range is not supported
(``fill_value=None``).
* The ``"Phase"`` column is categorical and is not suitable for
numerical interpolation.
See Also
--------
load_lng_properties
"""
data = load_lng_properties()
temps = np.array(data["Temperature (K)"], dtype=float)
props = np.array(data[prop_name], dtype=float)
interp = interp1d(temps, props, kind="linear", fill_value=None)
return interp(T)
[docs]
def load_lng_properties():
"""
Load liquid natural gas property data from the RES file.
Parameters
----------
None
Returns
-------
lng_data : dict
Raw liquid natural gas property data loaded from ``LNG_properties.res``.
Notes
-----
Assumes liquid natural gas is pure Methane and behaves as an ideal fluid for the stored properties.
Source
------
Internal RCAIDE resource file: ``LNG_properties.res``
See Also
--------
RCAIDE.load : Function used to load RES files
"""
ospath = os.path.abspath(__file__)
separator = os.path.sep
rel_path = os.path.dirname(ospath) + separator
return RCAIDE.load(rel_path+ 'LNG_properties.res')
