Abstract
High level of mechanical efficiency is exacted from internal-combustion engines. The reduction of friction losses of crankshaft main bearings can significantly contribute to the enhancement of this efficiency. For this purpose, an innovative design of a crankshaft is developed. The potential of computational modelling during the development of this innovative crank train is described in the article. The dynamics of the whole crank train is solved by using a multi-body system software, where flexible finite-element bodies along with hydrodynamic bearings are incorporated. Regarding the simulation results, attention is paid to the torsional vibration and its analysis, including concept design of a torsional damper, because a reduction of friction losses is associated with the improvement of torsional vibration in this case.
Highlights
IntroductionThe crank train generates alternating torque due to alternating combustion pressure in conjunction with the alternating effect of reciprocating parts inertia
Torsional vibration is common to internal-combustion engine crankshafts
Simulations focused only on this type of loading are often based on the so-called physical model of linear torsional vibration system, where all the rotating and the reciprocating parts are reduced to the crankshaft rotation axis, under the condition of potential energy and mean value of kinetic energy of the real system and the physical model [1, 2]
Summary
The crank train generates alternating torque due to alternating combustion pressure in conjunction with the alternating effect of reciprocating parts inertia This torque brings the elastic crankshaft in vibration about the axis of rotation. Simulations of crankshaft friction losses are validated by measurement of motored standard engine with deactivated main bearing number 2 and 4 under miscellaneous lubricating oil conditions but under the same conditions for both variants. Another advantage of the laser welded 3-main-bearing crankshaft is the lower mass – a reduction of slightly more than 12 % – even though this crankshaft is made of steel, while the standard one is a ductile iron casting. The state-of-the-art computational methods are employed in order to investigate behavior of the crank train under dynamic conditions
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