Droplet Combustion Characteristics of Biodiesel–Diesel Blends using High Speed Backlit and Schlieren Imaging

ABSTRACT

This work investigates the effect of blending biodiesel with diesel on the combustion of an isolated fuel droplet. Biodiesel blends substituting diesel oil in different concentrations on volumetric basis, in addition to neat diesel and biodiesel, were studied. High-speed Schlieren and backlighting imaging techniques have been used to track droplet combustion. The results showed that partial substitution of diesel oil by biodiesel at the test conditions led to increasing secondary atomization from the droplet, compared to neat diesel or biodiesel fuel droplets. This in turn enhances evaporation, mixing, and then combustion. Additionally, the results showed that biodiesel has a higher burning rate compared to diesel, and that increasing biodiesel in the blend increases the burning rate of the blend. Nucleation has also been traced to take place inside the droplets of the blends. Moreover, flame size (height and width) has been reduced by increasing biodiesel concentration in the blend.

Acknowledgments

The authors would like to thank each of: HCED (Iraq), EPSRC (United Kingdom), FAPEMIG and CNPq (Brazil) for their supports to each of the authors respectively.

Nomenclature

D	=	Droplet diameter, mm
K	=	Burning rate constant, mm2/s
H	=	Flame height, mm
t	=	Time, s
W	=	Flame width, mm

Subscripts
i	=	Instantaneous
0	=	Initial
total	=	Total time

Fuels
B100	=	Neat Biodiesel
BD07	=	93% Diesel + 7% Biodiesel
BD10	=	90% Diesel + 10% Biodiesel
BD20	=	80% Diesel + 20% Biodiesel
BD30	=	70% Diesel + 30% Biodiesel
D100	=	Neat Diesel

Additional information

Funding

The work is partly sponsored by the Newton Research Collaboration Programme of Royal Academy of Engineering.

Notes on contributors

Ahmad Muneer El-Deen Faik

Ahmad Muneer El-Deen Faik is a PhD student at the Combustion and Flow Diagnostics Research Group, Mechanical Engineering Department, the University of Sheffield, United Kingdom. He received his BSc and MSc in Mechanical Engineering from Al-Nahrain University, Iraq, in 2003 and 2006, respectively. Then he moved to Al-Mustansiryah University, Mechanical Engineering Department. And now he is working on high-speed focused imaging of the droplet dynamics during combustion.

Yang Zhang

Yang Zhang is Professor of Combustion and Energy in the Mechanical Engineering Department of the University of Sheffield. He received his BEng degree from Zhejiang University, China, and PhD in the Engineering Department of Cambridge University, where he then worked as a Research Associate and a Research Fellow at Darwin College at the same time. Afterward, he moved to the Manchester University Institute of Science and Technology before taking the Chair of Combustion and Energy in Sheffield. His laboratory specializes in combustion and advanced flow diagnostics using both conventional and in-house developed techniques. He is also the author of many publications in this field.

Sérgio de Morais Hanriot

Sergio Hanriot is Professor of the Post-Graduate Programme in Mechanical Engineering of the Pontifical Catholic University of Minas Gerais, Brazil. He received his PhD in Mechanical Engineering in the area of Thermal and Fluids in 2011. Part of the studies was done at the FIAT Research Centre (CRF) in Turin, Italy. His area of research emphasizes on internal combustion engines, pulsating flow, applied fluid dynamics, refrigeration, compressible flow, and waves. In an administrative position, the following positions were held: Chief and Coordinator of the Department of Mechanical Engineering, Vice-Director of the Polytechnic Institute of PUC-Minas, Pro-Rector of Logistics and Operations, Executive Director of the Mariana Resende Costa Foundation. He currently holds the position of Provost of Research and Post-Graduation Studies.