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Mixed thermo-elastohydrodynamic cam-tappet power loss in low-speed emission cycles

Mixed thermo-elastohydrodynamic cam-tappet power loss in low-speed emission cycles
Mixed thermo-elastohydrodynamic cam-tappet power loss in low-speed emission cycles
The key driving forces in engine development are fuel efficiency and emission levels. These aspects are particularly poignant under vehicle idling or low crawling motions in typical city driving. Under these conditions the parasitic frictional losses are exacerbated and the emission levels are especially high. A key engine sub-system is the valve train system. Although it accounts for only 2-3% of the overall engine losses, it is the highest loaded conjunction in the engine, thus limiting the opportunity for lowering the lubricant bulk viscosity. The paper presents detailed tribology of cam-tappet contact, subjected to a mixed thermo-elastohydrodynamic regime of lubrication. In particular, the frictional behaviour of the conjunction is investigated under the stringent North American emission testing city cycle. Such a comprehensive approach has not hitherto been reported in literature. The predictions show good conformance with vehicle frictional assessments in industry. It further demonstrates that under the aforementioned cycle, highest power losses occur which are mainly as the result of lubricant film viscous shear at low sliding speeds and below the lubricant limiting Eyring shear stress.
cam–tappet contact, mixed thermo-elastohydrodynamics, frictional power loss, low-speed city cycle
1468-0874
Chong, W.W.F.
ddfcee50-9898-41be-b32c-b1b9932a1748
Teodorescu, M.
10e22073-39f7-41c3-b2b7-2886c2d976f6
Rahnejat, H.
f5b9b13a-dc42-4fde-a98d-4e0c48bb19ab
Chong, W.W.F.
ddfcee50-9898-41be-b32c-b1b9932a1748
Teodorescu, M.
10e22073-39f7-41c3-b2b7-2886c2d976f6
Rahnejat, H.
f5b9b13a-dc42-4fde-a98d-4e0c48bb19ab

Chong, W.W.F., Teodorescu, M. and Rahnejat, H. (2012) Mixed thermo-elastohydrodynamic cam-tappet power loss in low-speed emission cycles. International Journal of Engine Research. (doi:10.1177/1468087412461631).

Record type: Article

Abstract

The key driving forces in engine development are fuel efficiency and emission levels. These aspects are particularly poignant under vehicle idling or low crawling motions in typical city driving. Under these conditions the parasitic frictional losses are exacerbated and the emission levels are especially high. A key engine sub-system is the valve train system. Although it accounts for only 2-3% of the overall engine losses, it is the highest loaded conjunction in the engine, thus limiting the opportunity for lowering the lubricant bulk viscosity. The paper presents detailed tribology of cam-tappet contact, subjected to a mixed thermo-elastohydrodynamic regime of lubrication. In particular, the frictional behaviour of the conjunction is investigated under the stringent North American emission testing city cycle. Such a comprehensive approach has not hitherto been reported in literature. The predictions show good conformance with vehicle frictional assessments in industry. It further demonstrates that under the aforementioned cycle, highest power losses occur which are mainly as the result of lubricant film viscous shear at low sliding speeds and below the lubricant limiting Eyring shear stress.

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More information

e-pub ahead of print date: 18 October 2012
Keywords: cam–tappet contact, mixed thermo-elastohydrodynamics, frictional power loss, low-speed city cycle
Organisations: nCATS Group

Identifiers

Local EPrints ID: 353123
URI: https://eprints.soton.ac.uk/id/eprint/353123
ISSN: 1468-0874
PURE UUID: 51a5b331-3f22-4519-8fed-f87f3bb6caab

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Date deposited: 03 Jun 2013 09:10
Last modified: 19 Jul 2019 21:35

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