On the Effect of Transient In-Plane Dynamics of the Compression Ring Upon Its Tribological Performance

Abstract

Energy losses in an internal combustion engine are either thermal or parasitic. The latter are the mechanical inefficiencies, chiefly as the result of generated friction. Nearly half of these losses are attributed to the piston–cylinder system. During idle and at low engine speeds, friction is the major contributor to the overall engine losses. In particular, the rather small top compression ring accounts for a disproportionate share. Therefore, detailed understanding of compression ring tribology/dynamics (referred to as tribodynamics) is essential. Moreover, the ring’s primary sealing function may be breached by its elastodynamic behavior. The reported analyses in literature do not account for the transient nature of ring elastodynamics, as an essential feature of ring–bore tribology. The transient in-plane dynamics of incomplete rings are introduced in the analysis and verified using a finite element analysis (FEA) model, in order to address this shortcoming. The methodology is then coupled with the tribological analysis of the top compression ring. Comparison is made with experimental measurements which show the validity of the proposed method. The radial in-plane elastodynamic response of the ring improves the accuracy of the frictional power loss calculations.

Effect of cylinder de-activation on the tribological performance of compression ring conjunction

“…A study including these features was carried out by Baker et al 9,10 The generated contact pressures are also insufficient to cause any localised contact deflection as shown by Bolander et al 20 and Mishra et al 21 Therefore, the lubricant film shape is a function of its instantaneous gap and the ring axial profile, h s as…”

“…Therefore, the compression ring should conform well to the cylinder bore, thus resulting in increased friction. Baker et al 9,10 showed that compression ring elastodynamic modal behaviour and conformance to the bore surface results in a disproportionate share of parasitic losses from such a small contact conjunction.…”

A hydrodynamic flow analysis for optimal positioning of surface textures

“…Haddad and Tian [19] showed the validity of a one-dimensional analysis in such a case for rings with large length-to-width ratio; in excess of 30. In practice, the compression ring is subjected to in-radial plane modal behaviour and out-of-plane twist and bending [20][21][22]. Furthermore, in this analysis, the bore is considered to be a right circular cylinder, which is not the case in practice due to its out-of-roundness and cylinder block thermo-elastic distortion [23].…”

On the Transient Three-Dimensional Tribodynamics of Internal Combustion Engine Top Compression Ring

“…The degrees of freedom employed for the in-plane case are the radial and tangential deflections, w and v [24,25], as GTP-16-1220 S. Theodossiades opposed to the out-of-plane deflection and ring twist. Further information on the in-plane ring dynamics can be found in Baker et al [24,25]. Additionally, whilst a finite element analysis is useful for validating the dynamics of the proposed methodology, the inclusion of a tribological model into the FEA would result in very long computation times.…”

“…The ring dynamic response for both the in-plane [24,25] and out-of-plane cases includes a forcing term, which incorporates any excitation applied to the relevant ring plane. This force profile is extracted from the tribological analysis post calculation of the external and internal forces acting upon the ring, as shown in Figure 3 for the ring's cross-section.…”