Heat Transfer in Diesel and Partially Premixed Combustion Engines; A Computational Fluid Dynamics Study

ABSTRACT

This article presents findings from a Computational Fluid Dynamics (CFD) study performed on the heat transfer characteristics of diesel and partially-premixed combustion (PPC) engines. The study is confined to the combustion bowl, where numerical simulations have been performed on a part of the engine cycle, namely the compression, combustion, and expansion phases. Three engine geometries were simulated and after validating the results with experimental data, parameter variations were carried out, in order to estimate their effects on the heat transfer, engine performance, and emission levels. The work was performed using a commercial CFD tool, with which only a part of the engine cylinder was modeled, the enclosure of one spray. The results highlight some important characteristic differences between the conventional diesel combustion and the low-temperature combustion scheme PPC. The reduced in-cylinder temperatures for the PPC case lead to a reduced production of NO_x and soot emissions, without compromising the engine performance, only a small penalty in the increased intake air pressure is found. The importance of an appropriate injection strategy was also highlighted, as the presence of a pilot injection during the compression stroke enhanced the temperature stratification in a PPC engine. This leads to reduced heat losses and improved engine efficiency. Finally, the shape of the combustion bowl was shown to have significant effects on both heat losses as well as emission levels.

Additional information

Notes on contributors

Helgi Fridriksson

Helgi Fridriksson received his Ph.D. in mechanical engineering from Lund University at the end of 2013, where he had performed research on compression ignited engines with CFD. Prior to his time as a Ph.D. student, he finished his M.Sc. degree at the same university and a B.Sc. degree at the University of Iceland. Being an employee at the division of heat transfer, at the university, his research has mainly been focused on the heat transfer process within diesel and PPC engines, using various CFD tools to calculate the fluid flow and heat transfer within the engine cylinder. Besides the research work, he has been actively involved in teaching at the undergraduate level, within the courses for thermodynamics, fluid mechanics and heat & mass transfer.

Bengt Sundén

Bengt Sundén received his M.Sc. in mechanical engineering 1973, Ph.D. in applied thermodynamics and fluid mechanics 1979, and became docent in applied thermodynamics and fluid mechanics in 1980, all from Chalmers University of Technology, Gothenburg, Sweden. He was appointed Professor of Heat Transfer at Lund University, Lund, Sweden, in 1992 and has served as Department Head of Energy Sciences, Lund University from 1995 to 2016. His research activities include compact heat exchangers, enhancement of heat transfer, gas turbine heat transfer, combustion-related heat transfer, CFD methods for laminar and turbulent fluid flow and heat transfer, liquid crystal thermography, micro-scale heat transfer, transport phenomena in fuel cells, computational modeling and analysis of multi-physics, and multi-scale phenomena for fuel cells. He established and was first editor-in-chief of IJHEX—International Journal of Heat Exchangers (R. T. Edwards, Inc., USA), 1999–2008, was an associate editor of ASME Journal of Heat Transfer, 2005–2008, and has been editor-in-chief of a book series, Developments in Heat Transfer (WIT Press, UK), since 1995. He has published more than 700 papers in journals (>300), books, and proceedings. He has edited 30 books and authored three textbooks. He has supervised more than 180 M.Sc. theses, 47 licentiate of engineering theses, and 45 Ph.D. theses. He is a fellow of the ASME, honorary professor of Xian Jiaotong University, China, a regional editor of Journal of Enhanced Heat Transfer since 2007, an associate editor of Heat Transfer Research since 2011, and an associate editor ASME Journal of Thermal Science, Engineering and Applications, 2010–2016. He was a recipient of the ASME Heat Transfer Memorial Award, 2011 and the ASME Heat Transfer Division 75^th Anniversary Medal in 2013. He received the Donald Q. Kern Award in 2016.

Martin Tunér

Martin Tunér has a Ph.D. in Combustion Physics and holds a position as Associate Professor at the Division of Combustion Engines at Lund University. He has published more than 50 peer-reviewed papers in research areas such as high efficiency engine combustion concepts, fuel effects, engine heat transfer, waste heat recovery and combustion modeling. He has been awarded a prize by The Royal Majesty King Carl XVI Gustaf for the research on emissions reducing FPGA circuits, the “Best Technical Contribution” at the ASME-ICE and recently “Excellent Teaching Practitioner” at Lund University.

Öivind Andersson

Öivind Andersson received his M.Sc. in Physics 1995 and his Ph.D. in Combustion Physics 2000, both at Lund University in Sweden. After this he worked for seven years at Volvo Car Corporation, Gothenburg, Sweden, developing combustion systems for diesel engines. In 2007 he joined the Combustion Engines group at the Department of Energy Sciences at Lund University as lecturer and became docent in 2010. He was appointed Professor of Combustion Engines at the same department in 2011. His research activities focus on the combustion process in diesel engines, especially on in-cylinder studies of soot formation and oxidation, but it also includes other aspects such as heat balance investigations and studies of fluid flow. He has published more than 50 peer-reviewed papers, has authored two book chapters and one textbook, and holds two patents.