Effect of High Intensity Radiation on Soot Morphology within a Laminar Ethylene/Air Effect of High Intensity Radiation on Soot Morphology within a Laminar Ethylene/Air Diffusion Flame Diffusion Flame

1 1, 2 1, * 3, * 1 1, 4 5, 6 Cheng Wang1, Yue Wang1, 2, Shaun Chan1, *, Jeonghoon Lee3, *, Sanghoon Kook1, Evatt R. Hawkes1, 4 and Graham J. Nathan5, 6

1School of Mechanical and Manufacturing Engineering, UNSW Australia, NSW 2052, Australia

1School of Mechanical and Manufacturing Engineering, UNSW Australia, NSW 2052, Australia

2Shaanxi Aerospace Electro-Machinery and Environment Engineering Design Academy Co.,Ltd , Xi’an, 710100 ,China

3School of Mechanical Engineering, Korea University of Technology and Education, 1600 Choongjeol ro, Byeongcheonmyeon, Cheonan, South Korea

3School of Mechanical Engineering, Korea University of Technology and Education, 1600 Choongjeol ro, Byeongcheonmyeon, Cheonan, South Korea

4School of Photovoltaic and Renewable Energy Engineering, UNSW Australia, NSW 2052, Australia

5Centre for Energy Technology, The University of Adelaide, SA 5005, Australia

5Centre for Energy Technology, The University of Adelaide, SA 5005, Australia

6School of Mechanical Engineering, The University of Adelaide, SA 5005, Australia

INTRODUCTION

Soot-radiation interaction is a subject of great interest due to its potential use in hybrid solar-thermochemical processes[1]

. It is also commonly used in

INTRODUCTION

Soot-radiation interaction is a subject of great interest due to its potential use in hybrid solar-thermochemical processes[1]

. It is also commonly used in nanomaterial synthesis applications by material scientists

[2]. Recent studies observed distinct soot property changes when high-power single wavelength laser

was applied to flame [2] [3]

. The physics behind such changes, however, remain not well-understood. was applied to flame [2] [3]

. The physics behind such changes, however, remain not well-understood.

The aim of this project is to study the soot morphological changes when external irradiation is introduced into flame. In this study, the soot samples were The aim of this project is to study the soot morphological changes when external irradiation is introduced into flame. In this study, the soot samples were thermopheretically extracted at different heights above burner (HABs) from a laminar ethylene-air diffusion flame. The flame was irradiated by a focused, broadband solid-state plasma light source that was used to simulate concentrated solar irradiation. broadband solid-state plasma light source that was used to simulate concentrated solar irradiation.

EXPERIMENTAL DETAILS EXPERIMENTAL DETAILS

Layout Light source spectral distribution TEM images Image post-processing

No external irradiation With external irradiation

4 major components: 1.Wolfhard-Parker burner

Light source: Solid State Light Source (INT-30-04, THORLABS) Focused light intensity: 0.012 kW/cm

2

Typical TEM images acquired without (L) and with (R) external irradiation

• HAB: 40mm

• Box-counting to determine : Aggregation size 1.Wolfhard-Parker burner

2.Thermocouple with triggering and data acquisition system

3.Thermophoretic sampling system with 4-way solenoid valve controller 4.Solid-state plasma light source

Focused light intensity: 0.012 kW/cm2

UVA Output (315 — 400nm) : 0.6W

VIS Output (400 — 750nm) : 10.2W

NIR Output (750 — 1400nm) : 2.5W

IR Output (1400 — 3000nm) : 0.6W

• HAB: 40mm

• Radial position: near air/fuel intersection 1mm toward air slot • Exposure time: 100ms

• Magnification: 100K

• Pixel resolution: 1.02nm/pixel

Aggregation size

Radius of gyration

• Manually picking particles to assess : Primary particle diameter Number of particles per aggregate

RESULTS RESULTS Key parameter changes:

Other parameter changes Key parameter changes:

Soot volume fraction (fv) & Primary particle diameter (dp) Other parameter changes

HAB % of increase

20 975

% of increase in fv after irradiation

20 975

30 213

40 118

*Note: flame with or without irradiation is represented as (1) or (0)

DISCUSSION CONCLUSIONS [4] [4]

• Soot morphology changes were observed when an focused external light source (0.012kW/cm2 ) was applied to

laminar ethylene-air diffusion flame, specifically:

Changes in key parameters if only one mechanism is taking place Changes in key parameters at each region

◊ Soot volume fraction (fv) values at of the soot samples acquired were found to be have increased.

◊ Mean primary particle size (dp) values of the soot samples were measured to be larger.

◊ Mean radius of gyration (Rg) values of the soot samples were also observed to be higher. ◊ Mean radius of gyration (Rg) values of the soot samples were also observed to be higher.

• The dominant soot formation/growth mechanisms at the lower height above burner (between HAB20 and 30) were observed to have transformed from “nucleation and coalescence” into “surface growth and agglomeration” when external irradiation was introduced.

match the trend to determine the dominant mechanism at each stage

external irradiation was introduced.

ACKNOWLEDGEMENT ACKNOWLEDGEMENT

The authors wish to acknowledge the financial support of Australian Research Council (ARC) and UNSW • The authors wish to acknowledge the financial support of Australian Research Council (ARC) and UNSW Australia.

References: [1] Nathan, G.J., Battye, D.L., Ashman P.J. (2014), ‘Economic evaluation of a novel fuel-saver hybrid combining a solar receiver with a combustor for a solar power tower ’, Applied Energy, 113, 1235-1243. [2] Hu, L.G., Wang, S.M., Zhang, B.Z., Zeng, Y.W. (2006), ‘Structural changes in soot particles induced by diode laser irradiation’, Carbon, 44, 1725-1729. [2] Hu, L.G., Wang, S.M., Zhang, B.Z., Zeng, Y.W. (2006), ‘Structural changes in soot particles induced by diode laser irradiation’, Carbon, 44, 1725-1729. [3] Medwell, P.R., Nathan, G.J., Chan, Q.N.., Alwahabi, Z.T., Dally, B.B. (2011), ‘The influence on the soot distribution within a laminar flame of radiation at fluxes of relevance to concentrated solar radiation’, Combustion and Flame, 158, 1814-1824. [4] Tree, D.R., Svensson, K.I. (2007), ‘Soot processes in compression ignition engines’, Progress in Energy and Combustion Science, 33, 272-309.