Contents of Journal of Mechanical Engineering 59, 2 (2008) 




PŮST, L.: Interaction of vibrating system and energy source              61

RUDOLF VON ROHR, P., PRÍKOPSKÝ, K., ROTHENFLUH, T.: Flames 
in supercritical water and their applications                            91

ŠTIAVNICKÝ, M., KOMPIŠ, V., KAUKIČ, M.: Modelling of composites 
reinforced by micro/nanoparticles using dipoles                         105

Abstracts


Interaction of vibrating system and energy source

LADISLAV PŮST

Majority of publications on mechanical vibrations are based on the assumption that the external excitation is produced by an ideal source of power with prescribed frequency. But in reality, the excitation sources are non-ideal with limited power, limited inertia and their frequency fluctuates according to the instantaneous state of oscillating system. The paper presents an overview of systems and results gained during the several dozens of years on this interaction problem. The most characteristic properties of systems excited by source of limited power and limited inertia are variation of revolution, distortion of harmonic motion, instability and non-uniform passage through resonance zone.

Flames in supercritical water and their applications

PHILIPP RUDOLF VON ROHR, KAROL PRÍKOPSKÝ, TOBIAS ROTHENFLUH

Hydrothermal flames were firstly reported in the process of supercritical water oxidation (SCWO). The work at the ETH Zurich successfully investigated the possibility of a controlled use of hydrothermal flames to improve the process performance. Different reactor concepts were used to study continuous diffusion flames in supercritical water. In these experiments, water-methanol mixtures were used as fuel stream and oxygen as oxidizer. The ignition of the flame was achieved by heating up the reactants to auto-ignition temperatures. The concept of a transpiring-wall reactor and the hydrothermal flame as internal heat source showed a good performance in decomposition of artificial wastewater streams with salt contents up to 3 wt.%. Axial flame temperature measurements and chemiluminescence imaging were conducted to characterize the flame at various conditions in a reactor with optical access. The possibility of sustaining stable hydrothermal flames in supercritical water is a key feature for a novel drilling method.


Modelling of composites reinforced by micro/nanoparticles using dipoles

MÁRIO ŠTIAVNICKÝ, VLADIMÍR KOMPIŠ, MICHAL KAUKIČ

Composite materials reinforced by stiff particles possess higher stiffness, strength, better wear resistance and superior thermal and electrical properties. Special models are presented based on singular and hyper-singular source functions for modelling composites reinforced with micro/nanoparticles. In global, the model of each particle is represented with triple dipole which is describing the interaction effect of the rigid particle with the matrix. The intensities of the dipole are evaluated on detailed model from boundary conditions. The displacement, stress and strain fields are described by combination of Kelvin's solution and dipole functions acting in infinite domain with singularity outside of the domain. The governing equation is automatically satisfied by these functions so it is only necessary to fulfil the boundary conditions. Using such functions, also problems can be solved in which the stiffness of the particles is much higher than the stiffness of the matrix and its one or two dimensions are much smaller than the others, i.e. in the situations when the FEM and BEM models do not work well.