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In this paper we analyze the cycle-to-cycle variations of peak pressure pmax and peak pressure angle αpmax in a four-cylinder spark ignition engine. We examine the experimental time series of pmax and αpmax for three different spark advance angles. Using standard statistical techniques such as return maps and histograms we show that depending on the spark advance angle, there are significant...
The analytical solutions of displacements and stresses for an eigenstrain problem in a composite bi-layered coaxial cylinder are presented in this article. The inner cylinder is assumed to undergo a dynamic, spatially varying eigenstrain. The spatial distribution of the eigenstrian is taken to be a quadratic polynomial with arbitrary coefficients along the radial direction. Furthermore, the eigenstrain...
A method for investigation of the dynamical couplings between the manipulator links is presented in this paper. The method is based on quasi velocities introduced originally by Hurtado (2004) and on a diagonalized Poincaré form of the Hamel representation described by Sovinsky et al. (2005). Some observations and a heuristic algorithm are proposed to determine the dynamical couplings between the rigid...
The constitutive laws are obtained for the linear micropolar thermopiezoelectric/piezomagnetic continuum with two relaxation times. A positive decreasing dissipative pyroelectric/pyromagnetic function is introduced and a uniqueness theorem is proved. The equation of motions and the boundary condition are obtained from a Hamilton’s type variational principle. Extended Hamilton’s principle is given.
We consider slow steady flows of Navier–Stokes-like fluids with pressure dependent viscosities between rotating infinite parallel plates with Navier slip boundary conditions. We derive exact solutions which correspond to flows in orthogonal and torsional rheometers, and investigate the effect of the slip coefficient and the material parameters on the solutions. We find that even when inertial effects...
The influence of preliminary repeated mechanical thermal treatment on the strength of turbine disks has been studied. The analytical description in terms of a generalized synthetic theory has been carried out. The agreement between calculated and experimental data makes possible the use of the obtained results on an industrial scale.
We investigate the impact of different boundary conditions on the flow field developing around a tilted rectangular cylinder with two different values of the aspect ratio (l/s=3 and 4). We are mainly interested in analyzing the changes in force coefficients and in the vortex shedding Strouhal number when the cylinder is placed at various distances from a bottom wall and different values of attack...
A matched-asymptotics approach is proposed to show the occurrence of two distinct characteristic length scales in the carbonation process. The separation of these scales arises due to the strong competition between reaction and diffusion effects. We show that for sufficiently large times τ the width of the carbonated region is proportional to , while the width of the reaction front...
In the present paper the dynamic solutions of two non-steady seepage problems are discussed. It is shown that the acceleration term in the equation of motion is important for a correct qualitative description of the flow.
A similarity analysis was performed to investigate the laminar boundary-layer flow in the presence of a transverse magnetic field over a down-pointing and spinning cone with mixed thermal boundary conditions. Boundary layer velocity and temperature profiles were determined numerically for various values of the magnetic and spin parameters and the Prandtl number. The spin of the cone compresses the...
The present paper is concerned with the study of radiation effects on the combined (forced-free) convection flow of an optically dense viscous incompressible fluid over a vertical surface embedded in a fluid saturated porous medium of variable porosity with heat generation or absorption. The effects of radiation heat transfer from a porous wall on convection flow are very important in high temperature...
The film forces in porous journal bearings are capable of sustaining self-exciting oscillations under certain operating conditions; if their amplitude becomes too large, it may endanger safe operation. Thus, there is a need to understand the dynamic characteristics of porous journal bearings identifying the dominant parameters. This paper aims to identify the journal stability threshold by using an...
Results of FEM simulations of fatigue crack growth under mixed mode loading are presented in this paper. At Czech Technical University in Prague (CTU) the program code which uses commercial software ABAQUS for fatigue crack simulations has been developed. The program works on basis of gradual crack extending. In simulation are considered small scale yielding conditions. Both classic criteria (J-integral,...
In this paper an analysis has been made to study heat and mass transfer in two-dimensional stagnation-point flow of an incompressible viscous fluid over a stretching vertical sheet in the presence of buoyancy force and thermal radiation. The similarity solution is used to transform the problem under consideration into a boundary value problem of nonlinear coupled ordinary differential equations containing...
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