Narrow Band Parameter Creation from Radis

A python implementation to obtain narrow band parameters for thermal radiation in gas mixtures using the Malkmus model for gaseous species in high temperature applications such as combustion chambers. Based on RADIS and the following reference,

Updated band model parameters for H2O, CO2, CH4 and CO radiation at high temperature, Philippe Rivière, Anouar Soufiani, 2012

The method works by least-squares fitting of the Malkmus equation to transmittances computed from line-by-line (LBL) spectra — generated here via RADIS — to find the parameters that minimize the error with respect to the LBL reference.

Outputs:

Parameter	Units
k	cm⁻¹ bar⁻¹
delta	cm⁻¹

Results are written to a ascii file with the following structure as in the paper

• First block (one row per wavenumber band): wavenumber k(T1) k(T2) ... k(Tn)
• Second block (one row per wavenumber band): wavenumber delta(T1) delta(T2) ... delta(Tn)

Input parameters

The following parameters must be specified inside the build_narrow_band() function. More detail in Radis docmentation:

Parameter	Description	Example
molecule	Target species in capital letters	'CO', 'CO2', 'H2O', 'CH4'
isotope	Isotopologue selection	'all'
databankPath	Spectroscopic database to use	'hitran', 'hitemp'
pressure	Total pressure (bar)	1.0
moleFraction	estimation of approximately how much of this specie will be present in the mixture	0.01
numberOfFittingPoints	Number of transmittance points used in the Malkmus fit (higher = more accurate)	20
delta_wn	Narrow band width (cm⁻¹)	25
wn_range	Array of band-center wavenumbers (cm⁻¹)	np.arange(2000, 2100, 25)
Tgas_range	Array of temperatures K	np.arange(200, 700, 50)
wavenumberStep	Spectral resolution for LBL calculation (cm⁻¹)	0.01
cutoff	Line strength cutoff threshold (cm⁻¹)	1e-27
broadeningMethod	Line profile: 'voigt', 'lorentzian', or 'gaussian'	'voigt'
truncation	Line wing truncation distance (cm⁻¹)	50

Note: averaged Lorentz half-widths (γ) are implemented for H2O, CO2, CH4, and CO. The code automatically switch between these, To use any other species, a custom gamma_* function must be added to utilities.py.

use

Radis is the only requierement,

pip install radis

from narrowBand import build_narrow_band
# Configure parameters inside build_narrow_band() then run:
build_narrow_band()