Abstract

This article addresses the problem that fluctuations in the torque of an internal combustion engine (ICE) lead to additional energy losses, as it causes fluctuations in the speed and kinetic energy of the car. These losses increase as the frequency of oscillations of the torque of the internal combustion engine approaches the frequency of free (natural oscillations) of the running gear of the car in the longitudinal direction. If there is an elastic connection between the traction force and the movement of the car, the movement of the latter can be represented as complex. At the same time, the portable movement is uniform, and the relative movement is oscillatory. This article presents the results of the study of these losses for cars with mechanical and combined electromechanical drive wheels. Analytical expressions are obtained, which allows to take into account additional energy losses including the tangential rigidity of the tire and the rigidity of the suspension in the longitudinal direction. When using a combined electromechanical drive of the drive wheels as well as in the case of a mechanical transmission of a car, the resonance is dangerous. But with the increase in the share of torque "em"k"sub"em"/sub""/em" on the wheel generated by the electric motor, the relative additional energy losses for the movement of the car are reduced.

Abstract

Granular flow is a complex process depending on a large set of parameters such as grain morphology, surface friction, flow geometry, stress field and cohesion (e.g. attractive interaction between grains). The latter arises from the presence of humidity, electrostatic charges and Van der Waals forces within the grains that lead, among other effects, to the appearance of surface flow fluctuations also called avalanches. Those surface fluctuations produce an intermittent granular flow and determine the processability of a powder in many application. In order to link the flow fluctuations and the cohesion between grains, we reproduced numerically with a DEM model the flow of cohesive granular materials in a 2D rotating drum. A simplified cohesive interaction between circular grains has been implemented and the granular flow has been analyzed through the flowing angle and the interface fluctuations. The numerical results are compared with experimental results obtained with GranuDrum instrument and a set of silicon carbide grains with different grain sizes and therefore different cohesiveness. The motivation behind this study is to determine to what extent a simplified model can reproduce a complex flow. The similarities between numerical and experimental results and also the discrepancies are discussed. This comparison gives a fundamental background to the cohesive index parameter measured with GranuDrum instrument from the interface fluctuations. Finally, we show that comparing the flow inside a rotating drum obtained numerically and experimentally is a practical way to calibrate a set of parameters before the simulation of a complex process.