# Experimental study of emulsion dispersed phase temperature under radiant heating using 2clif method

Thomas Naudin, Dominique Tarlet, Raffaela Calabria, Patrizio Massoli,
Jérôme Bellettre

► To cite this version:

Thomas Naudin, Dominique Tarlet, Raffaela Calabria, Patrizio Massoli, Jérôme Bellettre. Experimental study of emulsion dispersed phase temperature under radiant heating using 2clif method. 12th Mediterranean Combustion Symposium, Jan 2023, Luxor, Egypt. hal-03977589

HAL Id: hal-03977589

https://hal.science/hal-03977589

Submitted on 7 Feb 2023

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# EXPERIMENTAL STUDY OF EMULSION DISPersed PHASE TEMPERATURE UNDER RADIANT HEATING USING 2CLIF METHOD

NAUDIN Thomas(1,2), TARLET Dominique(1), CALABRIA Raffaela (2), MASSOLI Patrizio (2) & BELLETTRE Jérôme (1*)

## INTRODUCTION

Micro-explosion of W/O emulsions droplets can help to achieve combustion with **high efficiency** while **reducing pollutants emissions**

* Micro-explosion is the fragmentation of a drop in a **cloud of fine secondary droplets** due to water phase-change

* This phenomenon depends on **different parameters** such as the composition of the emulsion, the temporal evolution of the granulometry (coalescence) and the type of heat flux

* First step of the study showed that **coalescence promotes micro-explosion occurrence**

* Internal convective motion has been observed. Temperature field measurement within the two phases are under investigation

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

<figure><img src="image_3.png" /><figcaption>(a) Optimized micro-explosion (cloud of fine secondary droplets) (b) non-optimized micro-explosion (puffing)</figcaption></figure>

## FIRST STEPS OF THE INVESTIGATION

### Experimental Setup (1C LIF)

**Objectives:**

* Visualization of the dispersed (water) phase **motion** during the heating of the droplet

* Measuring the **impact of coalescence on micro-explosion rate**

Photron SA-X2 Camera

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

Single droplet heating apparatus

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

**Post treatment :**

* Positions and size of water droplets are measured during sampling time

* The Data are feeding a **PTV algorithm** that computes droplet trajectories and velocities

<figure><img src="image_6.png" /></figure>

### Results

* **A dimensionless indicator** is used to quantify the intensity of the motion

$$I = \frac{1}{f_z} \frac{\| \vec{v}_i \|}{\bar{D}_i}$$

* $\vec{v}_i$: identified droplet velocity

* $\bar{D}_i$: identified droplet diameter

* $f_z$: acquisition frequency

* For **small values of I** (weak convective motion with high coalescence rate), **ME is obtained**

* For higher values of I (**strong motion** of the water droplets), **ME never happens and coalescence is inhibited**

* Fine emulsions undergo strong internal motion, **which inhibits coalescence**

* Internal motion is observed even with the heat source located **at the top of the droplet**

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

Incident IR heating

<figure><img src="image_8.png" /></figure>

## TEMPERATURE MEASUREMENTS WITHIN THE WATER PHASE

### calibration 2C LIF in test cell

**Temperature measurement** within water is made possible by the **Ratiometric 2C LIF method** :

* Since fluorescence is a function of the temperature, it can be computed from the intensity of the image :

$$I f_{\lambda} = \int_{\lambda-\Delta\lambda}^{\lambda+\Delta\lambda} K_{opt} K_{spect} C I_{o} v_{meas} e^{s\lambda/T} d\lambda$$

With :
* $K_{opt}$ the optical path cste
* $K_{spect}$ dye properties resulting cste
* C the dye concentration
* $I_o$ the incident laser intensity
* $v_{meas}$ the measurement volume

* In that case, **ratio of two collection wavelengths** is used in order to be free from the **dependency on others parameters** (such as $v_{meas}$)

* Several dyes such as Fluorescein, Rhodamine B and Rhodamine 6G are tested

* Rhodamine 6G showed best response (**monotonous** with **variation interval large enough**)

<figure><img src="image_9.png" /></figure>

### Temperature of dispersed water microdroplets

* Dispersed water droplets **temperature evolution** has been made possible by the use of LIF2C technique

* The droplets undergo **temperature cycles** (heated when close to the heat source and cooled while moving further)

* Current limitations on the reliability of measurements for temperatures > 100°C due to calibration setup

* Next steps of the investigation : calibration for temperatures > 100°C

* Temperature measurements in the continuous phase

<figure><img src="image_10.png" /></figure>

temporal evolution of a water droplet during an ascending phase

<figure><img src="image_11.png" /></figure>