Understanding soot formation using advanced optical diagnostics

Project Information

USFAOD

Grant agreement ID: 794156

DOI

10.3030/794156

Project closed

EC signature date 6 March 2018

Start date 1 September 2018

End date 18 May 2021

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 185 857,20

EU contribution

€ 185 857,20

Coordinated by

LUNDS UNIVERSITET
Sweden

Periodic Reporting for period 1 - USFAOD (Understanding soot formation using advanced optical diagnostics)

Reporting period: 2018-09-01 to 2020-08-31

Summary of the context and overall objectives of the project

1. What is the problem being addressed?
Soot is any black, blackish or brown aggregate, which mainly consists of carbon with a variety of bonding structures and are generated by incomplete combustion.
The present understanding on soot suffers from the following important shortcomings:
• Firstly, there is lack of sensitive and non-invasive measurements of the physical and chemical properties of soot under the wide range of combustion conditions. There is also a lack of techniques that can be applied on both molecules and particles.
• Secondly, there are significant deficiencies in the understanding of particle growth, chemical and physical evolution and oxidation under combustion conditions. At the microscopic level, the crucial step from the molecular weight growth of large species to form nascent soot particles (called the nucleation process/the nucleation zone) is still speculative.

2. Why is it important for society?
It is challenging to determine the detailed chemical and physical routes of the species leading to the first soot nucleus. However, any progress on the characterization in the soot inception zone will lead to reduce uncertainties on soot formation modelling and understand more deeply its formation. This project relies on a novel approach set on experimental investigations of the soot formation mechanism and soot characteristics. It is important to understand soot formation and soot properties that will be valuable for other research such as climate studies or health care system.

3. What are the overall objectives?
• The main methodological/technical objective is further development of online Raman spectroscopy combining with other techniques to measure abundances of molecular species (or soot precursors) in the aerosol phase.
• The core objective is to use optical diagnostics to improve knowledge on optical and structural properties of soot particles and to understand the formation of critical nucleus from the gas phase enabling the transition to the solid phase and the subsequent soot evolution in various combustion processes.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The work was conducted via 4 work packages (WPs).

WP1: Designing and building a combined LIF/Raman system for soot in condensed phase
In term of technological achievements, one ex-situ Raman spectrometer was built up connected to a Linkam heating stage. This heating device allows to heat sample in different environments from ambient temperature to 1200 oC. The Raman spectrometer can detect inelastic scattered photons and provide structural information of the samples as well as structural changes of the annealed samples. This compact equipment is very useful for annealing studies of soot and other materials in various conditions. WP 1 comprised 3 qualitative research studies on annealing, oxidation, and polarization that yielded 2 peer-reviewed papers and one manuscript underway. In addition, the Fellow delivered 3 conference presentations and supervised one Master student. In this WP, the Fellow exceeded the goal.

WP 2: Designing and building up in-situ Raman spectroscopy and in-situ LII to detect soot in the aerosol phase
WP 2 involved developing in-situ/online Raman spectroscopy combined LII to detect soot in the aerosol phase. The milestone of this WP was to construct an online Raman spectrometer for detecting aerosol soot produced by a mini-CAST soot generator. LII measurements on the mini-CAST soot were studied by another group member previously so it was not proceeded in this WP. The results were used for comparison and explanation. WP2 sought to continue the development of online Raman technique. In this, the Fellow achieved the milestone, one prepared manuscript, and one poster presentation.

WP 3: Investigation of soot formation processes of atmospheric premixed laminar flames
We collaborated with a research group in Naples (prof. A. Ciajolo), Italy, to propose a method for determining optical band gap for soot that was analyzed separately from organic carbon. Studies of optical band gaps of soot at increasing height above the burner was used to investigate soot evolution in flames. This result was published in the journal of Carbon, presented in the world carbon conference 2019, and in one seminar.
We also planned to apply the online Raman setup developed in WP2 to investigate soot formation in a premixed laminar flame at atmospheric condition in WP3. However, due to the Fellow’s parental leave and the Corona pandemic after that, the sampling probe equipment designed to extract soot from the flame was delayed. This influenced on the progress of this task.

WP 4: Investigation of soot formation processes of low pressure premixed laminar flames
This task was done in collaboration with the group of Dr. Pino at ISMO (France) as a secondment. Currently the manuscript is revised in the journal of Combustion and Flame. Online spontaneous Raman spectroscopy was applied across the soot inception zone to progress on the understanding of soot formation and evolution in a low pressure premixed laminar flame. Watching spectral differences of by-products along the blue to orange zone of the flame permitted to probe soot formation and its evolution. The online spectra, by avoiding structural modifications of the real soot structures, highlight the role of unsaturated carbon chains in chemical condensation scenario. In addition to the revised manuscript, the output also contains one oral and two poster presentations.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Impact on the researcher's career: The project provided a great opportunity for the Fellow in research and teaching career as the Fellow could continue developing the new technique (Online Raman spectroscopy) succeeded in the PhD work and preparing for a new research application (Raman lidar) in the near future. These values contribute to the recent Fellow’s promotion to Associate senior lecturer / assistant professor position at Lund University.

European policy objectives
Soot emissions in the atmosphere contribute to climate change and pollution. Therefore, the data on soot properties is useful for the climate modelling community. The USFAOD proposal is a multidisciplinary and interdisciplinary project as it is related to laser-based diagnostics, combustion, and material science. Overall, the aims of the project reach the goals 3, 4, 7, 9, 11, 12, 13, 14, and 15 of the 17 United Nations Sustainable Development Goals.

Potential users of the project results. We could reach various users, such as the Federation of the European sections of the Combustion Institute, the European Carbon Association, and the World Meteorological Organization, etc. The scientific output was used in teaching as well as in popular science fora towards pupils at elementary schools to graduate students. In addition, the results could be extremely interesting for the climate modeling groups, such as MERGE and IPCC (Intergovernmental Panel on Climate Change) at Lund University. After this project, the Fellow will seek for a collaboration with MERGE. By that the Fellow will broaden the network to other users such as IPCC, the Swedish Environmental Protection Agency (EPA), and the Swedish Meteorological and Hydrological Institute (abbreviated SMHI).

publication