Multi-physics for integrated analysis of flexible body dynamics with tribological conjunction in IC engines

Since the inception of internal combustion engine, there has been a continual strive to improve its efficiency and refinement. Until very recently, the developments in this regard have been largely based on an experiential basis, or backed by analytical investigations, confined to particular features of the engines. This has been due to lack of computational power, and analysis tools of an integrative nature. In recent years enhanced computing power has meant that complex models, chiefly based on multi-body dynamics could be developed, and further enhanced by the inclusion of component flexibility in the form of structural modes, obtained through finite element analysis. This approach has enabled study of dynamics/vibration response of engines in a more quantitative manner than hitherto possible. Structural integrity issues, as well as noise and vibration (refinement) can then be studied in an integrated manner. However, earlier models still lack sufficient detail to include, within the same analysis, issues related to efficiency, chiefly prediction of parasitic losses due to mechanical imbalance and friction. [Continues.

Elasto-multi-body dynamics of internal combustion engines with tribological conjunctions

Reduction of frictional losses and NVH (Noise, Vibration, and Harshness) refinement constitute the key customer-focussed aims in internal combustion engine development. Numerical predictive tools have progressively become an important part of achieving these aims. However, the interactions and sometimes the conflicting requirements of the aforementioned objectives call for the inclusion of many phenomena in realistic models of practical significance. These phenomena occur at varying physics of scale, from micro-scale tribological conjunctions to small scale vibrations and onto large scale inertial dynamics. At the same time, the inclusion of many disciplines for a cohesive analysis will be required, such as rigid body dynamics and elastodynamics, as well as tribology. While the inclusion of such a multi-disciplinary approach is deemed essential, the use of analytical rather than numerical models, as far as possible, would render realistic predictions within the usual tight industrial timescales. This article presents an experimentally validated model of the engine piston assembly, which is based on the multi-physics, multi-scale nature of the interacting components. Furthermore, it provides predictions of some current development trends in engines such as the high output power to weight ratio and offset crankshaft. The emphasis of this article is on the integration of the kinetic reactions arising from the tribological conjunction of the dynamics of engine subsystems, piston, and crankshaft

A multi-physics multi-scale approach in engine design analysis

Vibration behaviour of an internal combustion engine depends on rigid body inertial dynamics, structural modal characteristics of its elastic members, tribological behaviour of loadbearing contacts, and piston-cylinder interactions. Therefore, it is essential to use a multi-physics approach that addresses all these physical properties in a single integrative model as presented in this paper. This approach can be regarded as holistic and a good aid for detailed design. Particular attention is paid to the critical elements in the system, such as load-bearing conjunctions (crankshaft main bearings) and piston-cylinder wall interactions. Another important feature is the integrated analysis across the physics of motion from microscale fluid film formation to submillimetre structural deformations and onto large displacements of inertial members. In order to succeed in predictions within sensible industrial time scales, analytical methods have been used as far as possible rather than numerical approaches. Model predictions show good agreement with fired engine test data