Towards 60% fuel efficient engine


On Sunday, August 23, 2015, CCRC organized a seminar titled 'Towards 60% Fuel Efficient Engine' by Prof. Bengt Johansson. The semianr discussed in detail the potential that the internal combustion engine has for high fuel effeciency. Read more about the talk abstract and the bio of the speaker below.  


The internal combustion engine has great potential for high fuel efficiency. The ideal otto and diesel cycles can easily achieve more than 70% thermodynamic efficiency. The problems come when those cycles should be implemented in a real engine. Extreme peak pressure during the cycle will call for a very robust engine structure that in turn will increase friction and hence reduce mechanical efficiency. A very high compression ratio also increase the surface to volume ratio and promote heat losses, taking away much of the benefits from the theoretical cycle.

 The presentation will start with a standard SI engine and it’s efficiency as a function of load. Then a high compression ratio SI with be introduced and compared with the same engine operated in HCCI mode. The four efficiencies of SI as well as HCCI will be discussed and variations like HCCI with negative valve overlap and higher mean piston speed will be shown.

 A next step is the results with Partially Premixed Combustion. With PPC the indicated efficiency was shown to be up to 57%, thus 10% up from the best HCCI engine of 47%. However, to get the very high efficiency a high dilution level is needed. This is a challenge for the gas management system and hence gas exchange and mechanical efficiencies can suffer.

 The final part of the presentation is giving an engine concept that can enable the conditions for PPC combustion but with much improved gas exchange and mechanical efficiency. It enables an effective compression ratio in excess of 60:1 but with much less cylinder surface area. The concept also enables low friction and hence high mechanical efficiency. The basic concept will be explained and initial simulation results will be presented.


Bengt Johansson is Professor in Internal Combustion Engines at Lund University since 2001 and head of the combustion engine group since 2004. He is also director of the Centre of Competence Combustion Processes with a number of international industry partners since 2003. His group is among the leaders in low temperature combustion research and has published more than 250 papers within HCCI. He is also part time professor at TU Eindhoven, the Netherlands 2011-2015. He was chairman of the SAE Engine Combustion Committee 2012-2015 and since 2006 chair for the HCCI fuels collaborative task within the International Energy Agency, IEA.