The motion of a ring pack an oil film covering the cylinder liner has been considered. In the paper, equations, a numerical method, algorithm of solution and results of numerical simulations of this phenomena have been presented. The model presented takes into account hydrodynamic, spring and gas forces acting on each ring. The cases of motion with full and partial wetting of ring land have been considered. The influence of engine rotational speed, ring land curvature, oil viscosity on individual rings radial motion and oil film thickness have been analysed. The results of the calculations have been presented in graphical form.

The effect of air humidity on transonic flow around an NACA0012 airfoil at flow conditions, characteristic for buffet phenomenon, was investigated experimentally. Airfoil angles of attack in the range from 6° up to 10° were used, whereas values of initial relative air humidity were kept constant at four values 12%, 40%, 60% and 80%. Reconstructed time depending airfoil pressure distributions, time histories of normal aerodynamic force coefficient C, as well values of C0 pulsation are shown on the basis of surface pressure measurements at various humidity levels. The influence of the air humidity on the buffet origin is presented.

The time period of a jet engines full acceleration (from idle run rotating speed to full thrust) is a very important operational parameter. Minimization of this period is an important problem to be solved during the design of the fuel supply and control system. There are many methods of acceleration process control, especially in the case of engines with complicated design configurations. This work presents the problem of acceleration of a simple, single spool turbine jet engine with a so-called stable geometry, in which only one input (control) signal exists - fuel flow rate. Two methods of acceleration control consisting of limitation of the maximum allowable temperature of working medium in front of and behind the turbine in transient states were analyzed. In order to avoid difficulties associated with the direct measurement of actual temperatures, the so-called nonlinear engine observer was applied. With the use of the computer simulation method it was proven that the control algorithm with the limited maximum temperature in front of the turbine makes it possible the shortening of the acceleration time period significantly in comparison with a similar algorithm, that realizes the limitation of temperature behind the turbine.

The paper presents a model of the sealing process in kinematic pairs of hydraulic cylinders with elastic seals and an analytical form of this model based on the results obtained by the author. The prepared model distinguishes rheological parameters, allowing one to determine the criteria of a correct course of the sealing process and to forecast the operating time for the seals. Exemplary test results and their analysis are presented, too. It results from the analysis that leakage efficiency through the seal is dependent on the sealing pressure determined by the parameter 8, and it is unstable in relation to this parameter. Basing on this fact, the author determined conditions of hydrodynamic convection of the sealing and elaborated an analytical model of the sealing process including roughness of the piston rod surface as well as the seal flexibility.

The relationships between the conditions that describe the shape of the flow and power consumption characteristics and the pump design and performance parameters are described. These relations concern: - flow characteristics (throttling curves) described with a fourth-order polynomial, - non-overloading power consumption characteristics of the pump. The pumps that have to exhibit such characteristics are these designed to operate in an arbitrary installation. These pumps must also be characterised by cavitation-free operation in the whole range of discharge variability. In the relations presented, the condition of cavitation-free operation is considered as well.

The paper presents the stability analysis of a sandwich plate of the shape of an isosceles trapezoid, subjected to unidirectional in-plane compression. The critical load value of the trapezoidal sandwich plate was obtained by a combination of the Galerkin orthogonalisation method and the proposed method of the coordinate system transformation. An influence of plate material and geometrical properties on the critical load level was analysed. The obtained results were verified in a numerical experiment conducted with the FEM ANSYS software package.

The study is devoted to a parametric analysis of the stability and load carrying capacity of prismatic segment shells built of rectangular sections of cylindrical shells and subjected to compression. Segment shells (columns) with a constant crosssectional area (weight) have been analysed and all the results obtained have been compared with the results obtained for the cylindrical shell with a radius R and a thickness c; First, an influence of geometrical parameters of the cross-section of single-layer isotropic shells has been analysed and such profiles have been sought for which the load carrying capacity is significantly higher than in the case of the cylindrical shell. Then, for a selected shape of the shell (apart from higher load carrying capacity, this choice could be influenced by other factors such as, e.g. easiness of manufacturing), an effect of the arrangement and thickness of orthotropic layers of the shell (laminate) on the stability and load carrying capacity has been investigated. The analysis has shown that one can design a segment shell made of the same orthotropic material and characterised by higher resistance to buckling and load carrying capacity than a single-layer cylindrical orthotropic shell. The results are depicted in the form of plots.

New model of the simulation of the airbag inflation process, taking into account the influence of the airbag environment on the folding process, have been proposed. Equations describing a new model and the used numerical schemes were presented. The differences of the airbag fabric skin motion during the folding process, obtained by the use of different process models (existing and proposed), have been presented on the simple geometry examples. From the analysis of obtained results one acknowledged that the proposed model should be used in all calculations of the airbag operation in non-typical situations, out-of position occupants, side airbags, particularly in the case of small distances between the closed airbag and the elements of the body of the protected person.

A method of determination of drive functions of slewing of a mobile crane's upper structure is presented in the paper. The purpose of their determination is to reduce load oscillations at the end of the motion. Drive functions for selected angles and durations of slewing have been calculated using a simple model of the crane and dynamic optimisation. Drive functions for intermediate angles have been determined by means of interpolation. Res ul ts of numerical simulations executed for the model of the crane are presented, taking into consideration flexibilities and damping in the cranes subsystems. Results obtained for drive functions determined using optimisation and interpolation algorithms are compared. An attempt to determine sensitivity of load positioning to selected operating parameters is also presented. Introduction of the notion of a positioning quality coefficient is proposed.