TECHNIQUE TO DETECT AND CONTROL INITIATION OF SCUFFING IN AN ENGINE
Publication Date: 2015-Mar-24
The IP.com Prior Art Database
The present invention provides a technique to detect and control initiation of scuffing in an engine by observing friction and liner temperature during reciprocating movement of a piston in an engine. According to the technique described herein, the instantaneous friction force and the temperature at the liner surface are defined as the scuffing criteria. The proposed invention provides direct correlation between scuffing failure and the friction and temperature observed at the ring-liner interface. Further, friction and liner temperature are modified by controlling the coolant flow direction, topography of the liner surface and fueling to the cylinder.
The present invention relates generally to diesel engines and more particularly to a technique to detect and control initiation of scuffing in an engine.
Scuffing is a complex phenomenon accompanied by a sudden increase in friction and contact temperature. Frictional heating at ring-liner interface results in an increase in contact temperature. Friction and temperature are high at top ring reversal (TRR) in comparison to mid-stroke on a liner. Friction increases with the increasing severity at the interface. A significant increase in friction and the contact temperature at the TRR may lead to premature failure of the ring-liner interface. Scuffing is initiated due to lack of lubrication and increase in load and interface temperature at the piston ring-liner interface. Due to an increase in contact pressure, micro welds develop at the interface which drag material from both surfaces due to the sliding motion of the piston on the liner, leaving such material attached and producing an accelerated scuffing effect at areas of extensive contact.
Conventional techniques to overcome scuffing do not establishing a direct correlation between scuffing failure and the friction and the surface temperature observed at the ring-liner interface. Further, conventional techniques are unable to define criteria for detecting onset of scuffing in the piston ring-liner interface of a diesel engine.
It would be desirable to have a technique for detecting and controlling initiation of scuffing in an engine.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a flow diagram for determination of scuffing criteria.
Figure 2 depicts friction curve within a cycle.
Figure 3 depicts a liner temperature for scuffed and unscuffed conditions.
Figure 4 depicts friction coefficient plot for scuffing under different conditions.
Figure 5 depicts scuffing when reduction in liner surface roughness is beyond 30 %.
Figure 6 depicts linear lubrication and friction reduction through cooling and cylinder fuelling control.
Figure 7 depicts engine cooling and fueling control logic.
The present invention provides a technique to detect and control the initiation of scuffing in an engine by observing the friction and liner temperature during reciprocating movement of a piston in an engine. Further, scuffing is reduced by controlling oil film thickness.
Figure 1 depicts a flow diagram to determine the scuffing criteria. The flow diagram starts with the tribological modeling of severe operating conditions for piston ring-cylinder liner in a reciprocating rig. Visual inspection and sudden increase in friction and liner temperature are used for scuffing detection at the ring-liner interface. When scuffing is detected, such data is captured. Peak and root mean square (rms) friction, surface roughness and linear temperature are defined as scuffing threshold parameters.