# Quantitative Analysis of NH 2 * in Premixed Ammonia-Air Flames

Alka Karan, Guillaume Dayma, Christian Chauveau, Fabien Halter

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Alka Karan, Guillaume Dayma, Christian Chauveau, Fabien Halter. Quantitative Analysis of NH 2 * in Premixed Ammonia-Air Flames. 11th European Combustion Meeting (ECM 2023), Apr 2023, Rouen, France. . [hal-04085381](https://hal-04085381)

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Submitted on 28 Apr 2023

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# Quantitative Analysis of NH₂* in Premixed Ammonia-Air Flames

Alka KARAN¹,¹,², Guillaume DAYMA¹,¹,², Christian CHAUVEAU¹,², Fabien HALTER¹,¹

¹Université d'Orléans, Chateau de la Source, 45100 Orléans, France
²CNRS - ICARE, 1C Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France

The interest in studying ammonia flames arises from the need to curb carbon emissions and to solve the energy crisis arising from the depletion of fossil reserves.

## Why chemiluminescence?

* A cheap and non-intrusive diagnostic tool

* It provides various information on the combustion process, like assessing flame ratio and understanding flame topology.

## Why NH₂* chemiluminescence?

* NH₂* chemiluminescence is used to determine the position of the maximum HRR in premixed ammonia-air flames.

* The relative intensity of NH₂* can give information on NOx formation

<figure><img src="image_2.png" /></figure>

## Why quantitative analysis?

Possibility to have reference data for the chemiluminescent part of the species to model the total excited species.

## Procedure

* NH₂* chemiluminescence data at 632 nm for ambient conditions.

* Calibration to quantify the data.

<figure><img src="image_3.png" /><figcaption>Normalized NH₂* distribution along the flame for different φ</figcaption></figure>

## Calibration process

### Step 1: Optics Calibration

NH₂* filter response and camera response against a fixed light source

<figure><img src="image_4.png" /></figure>

### Step 2: Tungsten lamp calibration

* Irradiation data as a function of wavelength

* Filter and camera response against the tungsten lamp

<figure><img src="image_5.png" /></figure>

### Step 3: Converting intensity to concentration¹

$$ \frac{I_{\text{species,Abel}}}{I_c} = \frac{\frac{1}{4\pi} [\text{species}] N_A \eta_\lambda \tau_1 \Delta t_1}{\int_{\lambda_1}^{\lambda_2} \frac{S_c(\lambda)}{h\nu} \eta_\lambda d\lambda \tau_2 \Delta t_2} $$

### Step 4: Adapting to the configuration

* Irradiation values were provided at a distance of 50 cm

* Values adapted to fit the experimental set-up distance

## Results

* On moving from fresh gases towards burnt gases, NH₂* profiles for a low stretch can be plotted.

* It is seen that the thickness of NH₂* increases with the equivalence ratio.

* Preferential diffusion of lighter species towards the base of the flame is noted for leaner flames.

* Future work includes accommodating these species in any existing chemical kinetic schemes.

<figure><img src="image_6.png" /><figcaption>NH₂* concentrations for different φ plotted for minimum stretch values</figcaption></figure>

## Acknowledgement

Support from the CAPRYSSES project (ANR-11-LABX-006-01) funded by the PIA (Programme d'Investissement d'Avenir) is gratefully acknowledged.

ICARE-CNRS and Université d'Orléans are acknowledged as well.

## Reference

¹Y. Liu, J. Tan, M. Wan, L. Zhang, X. Yao, Quantitative measurement of OH* and CH* chemiluminescence in jet diffusion flames, ACS Omega, (2020), 15922-30

<figure><img src="image_7.png" /></figure>

Université d'ORLÉANS

cnrs

Orléans

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11th EUROPEAN COMBUSTION MEETING 2023