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ENCYCLOPAEDIC

Refinement of Engine In-Cycle Losses of Parasitic and Errant Dynamic Nature

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Conformance
Ring Shape
Conjunctional Geometry

Top Compression Ring

 

Ring Tribology

Compression ring conjunction accounts for nearly 65-70% of piston/cylinder parasitic losses and these are caused by a) ring-bore conformability, b)ring dynamics or rigid-body motions (twist and flutter), c) the behaviour of the ring in global deformation (in plane and out of plane modes), d) lubrication regime and e) asperity interactions.

 

 

               

 

Current numerical analysis of piston compression ring tribology agrees with experiment of Furuhama and Sasaki under same conditions at Chevrolet.

 

 

 

Common out of plane mode shapes of the top ring are represented in this figure

 

 

 

 

3D representation of the ring out of plane mode shapes

 

     

 
Dynamics of Piston Rings
  
Piston rings are subjected to high loads and pressures that can be of mechanical, temperature, and tribological origin. A combination of stresses can affect the performance of the piston rings, in particular the top compression ring; mechanically this ring is subjected to complex motions comprising inertial dynamics relative to the piston within the confine of its seating groove, in-plane and out of plane modal behaviour, and twisting drag about the axis of the piston.  
 
                                      
 
The above figure shows top ring frequency modes used to assess the dynamic behaviour of the ring. A computer model to simulate these together with tribological studies are used to predict lubricant film thickness and friction during engine operation.