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Stabilizing piston speed with a layer of carbon nanotubes on the lateral surface of the piston

Iskra A., Babiak M., Kałużny J., Giersig M., Kempa K.

Journal of Polish CIMAC

2013

Vol. 8, no 1

7--14

The paper presents the possibility of stabilizing higher harmonics of piston speed generated by torsional vibrations of the shaft. As a result of torsional vibrations, the transient speed of the piston deviates from the values resulting from the known formulae describing geometrical dependences of the piston position versus the angle of rotation of the crankshaft [1]. This phenomenon causes the desired effect of damping torsional vibrations. As it is known, in larger engines of the cylinder diameter exceeding 120mm and the number of in-line cylinders greater than or equal to 6, structural damping is insufficient and it becomes necessary to use torsional vibration dampers. In article [2] attention was drawn to the effect of damping higher harmonics of the moment generated by the engine whose lateral surfaces are coated with layers of nanotubes, which was not however, the main subject of the article. This work presents a preliminary analysis and determinants of the efficiency of vibration damping due to the impact of nanotubes on the reduction of the amplitude of higher harmonics of the moment generated by the engine. In addition, the possible mechanism of the phenomenon of vibration damping by a layer of nanotubes is presented. However, one should emphasize that at this stage the authors do not close the debate concerning the mechanical properties of the structures based on carbon nanotubes (CNTs), but in fact, they open up such a discussion. Besides the confirmed properties of nanotubes, such as extremely high tensile strength of properly structured fiber formed by CNTs, there is very little data concerning the properties of chaotic structures in which nanotubes combine in larger structures adopting any directions. No less important is the base on which nanotubes are grown, and it can be very different. The authors of the paper have presented preliminary results of a positive impact of selected properties of CNTs on the vibrations of the crankshaft.

Comparing the resistance to motion of pistons coated with a layer of nanotubes with standard pistons

Iskra A., Babiak M., Kałużny J., Giersig M., Kempa K.

Journal of KONES

2012

Vol. 19, No. 2

227-233

The paper presents preliminary results of testing the resistance to motion of pistons coated with a layer of carbon nanotubes (CNTs). A significant part of this paper was devoted to the problems of putting a layer of nanotubes on the surface of an aluminum alloy. Obtaining a layer of nanotubes of a very narrow margin of tolerance was a difficult technological problem to overcome. A standard process of growing a layer of nanotubes leads to a corrosion damage of the side surface of pistons; therefore, new technologies were developed allowing for obtaining a permanent layer of nanotubes less than 5 microns thick. Pistons whose side surfaces were coated with a layer of nanotubes were mounted to an engine with an external drive, and then measurements of the moment of momentary resistance to motion were performed, which enables capturing these phases of the engine work cycles in which the layer of nanotubes gives the best results. At present, long-term research is being carried out in order to determine the degree of the risk of exfoliation of the layer of nanotubes under the conditions of large mechanical and thermal loads. The special nanotechnology method cold nanosphere lithography has been invested to control the structural properties sand growth of multiwalled carbon nanotubes. The preliminary analysis of dismantled pistons revealed that nanotubes layers were partially worn off at the peaks of micro roughness but in the valleys, the nanotubes accurately adhered to the piston lateral surface.