Assessment of an eccentric link in the connecting rod of a spark ignition engine intended for variable compression ratio operation

Malpress, Ray and Buttsworth, David (2010) Assessment of an eccentric link in the connecting rod of a spark ignition engine intended for variable compression ratio operation. In: 6th Australasian Congress on Applied Mechanics (ACAM 6), 12-15 Dec 2010, Perth, Western Australia.


Previous modelling and numerical simulation has determined that potential exists to improve the low load efficiency of spark ignition engines through the application of variable compression ratio (VCR) in conjunction with other engine control technology. A large proportion of the potential efficiency gains can be achieved using a stepped change in compression ratio. One mechanism that can achieve this is an eccentric bush (eccentric) operated in the big-end of the connecting-rod. The natural dynamics associated with the motion of the crankshaft and connecting rod can potentially move the eccentric in the required manner. The present work aims to identify whether this is a practical means to shift the position of the eccentric. Matlab simulations of the dynamic performance of the eccentric in
various simulated engine operating conditions have been performed. An experimental eccentric was also operated in a motored engine to: (1) assess its performance, and (2) compare with, and validate the modelling. Further comparisons with commercial dynamics analysis software tools are also presented. The results show that when operated within limited bounds of engine speed and oil
viscosity, the eccentric can be moved in the required manner by the dynamics of the engine component motion. For application as a practical mechanism, the eccentric suffers from a very high sensitivity to its bearing surfaces friction regimes. The mixed friction which results from low speed or high bearing loads prevents the required rotation of the eccentric. In a practical sense, the motion of
the eccentric does not provide the consistency over the operating range of an internal combustion engine to employ it as a VCR technology.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Additional Information: Copyright 2010 Engineers Australia. Permanent restricted access to published version due to publisher copyright policy.
Faculty/School / Institute/Centre: Historic - Faculty of Engineering and Surveying - Department of Mechanical and Mechatronic Engineering
Date Deposited: 27 Mar 2011 08:01
Last Modified: 28 Nov 2014 06:46
Uncontrolled Keywords: internal combustion engine; variable compression ratio; eccentric; connecting rod
Fields of Research : 09 Engineering > 0902 Automotive Engineering > 090299 Automotive Engineering not elsewhere classified
09 Engineering > 0913 Mechanical Engineering > 091304 Dynamics, Vibration and Vibration Control
01 Mathematical Sciences > 0102 Applied Mathematics > 010207 Theoretical and Applied Mechanics
Socio-Economic Objective: D Environment > 96 Environment > 9603 Climate and Climate Change > 960302 Climate Change Mitigation Strategies
E Expanding Knowledge > 97 Expanding Knowledge > 970109 Expanding Knowledge in Engineering

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