Turbulent boundary layer separation induced by positive pressure gradient at a plane surface is investigated experimentally. Separation is delayed by means of a jet vortex generator in a form of small jets injected to the boundary layer through orifices distributed across the main flow. The effect of jets intensity on delay of separation is examined. Swirled and non-swirled jets have been used. The energy of the air supplying the generator required to delay boundary layer separation is in the former case up to 40% lower than in the latter one.

The paper discusses a way of choosing the design features (geometry, the rate of grinding and thrust) of ring-ball mills. Various methods of calculating the optimal rate of grinding have been compared. Basing on experimental investigations on the pilot-plant and industrial scale, the influence of the angular velocity and the thrust on the mill have been verified, and the interdependence between the rate of grinding and the thrust of the grinding elements have been explained.

The present-day methods of supervising the operational use of jet engines are based, among other things, on computerised procedures of monitoring and recording various failure modes, including the surge. This dangerous mode of operation of a turbojet engine occurs quite commonly while operating it. In some cases, it could result even in the engine destruction. What has been presented in this study is the way of applying a non-linear observer of a one-spool single-flow turbojet to generate a computer algorithm to detect the surging. An exemplary application of such an algorithm to monitor the surging that occurs in the K-15 engine has also been shown.

In the paper, the authors present the shakedown analysis of the plate structures pre-loaded beyond the elastoplastic range. Two cases of loading are considered, namely: the structure is subjected to the action of two independent sets ofloads with constant points of application or one parameter set of loads moves slowly according to an a priori described program. As a result, the safe loading boundary or the shakedown load parameter are calculated, respectively, by means of the finite element method (FEM). Three examples confirmed the effectiveness of the proposed algorithms of analysis.

The motion of a ring pack on a thin oil film covering a cylinder liner has been analysed. In contrast to the previous paper [8], which considered only hydrodynamic phenomena, in the present paper a mixed lubrication case is also taken into account. Equations describing the mixed lubrication problem based on the empirical mathematical model formulated in works of Patir, Cheng [5], [6] and Greenwood, Trip [2] have been combined and used in this paper. Results of numerical simulations of this phenomenon have been presented. The model of ring motion considered takes the following phenomena into account: hydrodynamic and contact forces, spring and gas forces and the local motion of each ring in piston grooves. Differences between the motion of the ring on a thick and thin oil film are analysed and discussed.

The paper presents the possibilities of neural network application in recognition of rotor blade faults. Computer calculated data of rotor response due to faults were used for neural network training. The rotor was modeled by elastic axes with distribution of Jumped masses. The rotor defects were simulated by changing aerodynamic, inertial or stiffness properties of one of the blades. Time results were subjected to spectral analysis for the purpose of neural networks training.

The work is devoted to a horizontal tank composed of cylindrical shell closed with ellipsoidal heads and supported at the ends. The tank is loaded with internal or external pressure. For the first load case, a strength condition was formulated, for the other one -the condition of stability of the structure. An optimization model was formulated, in which the mass of the tank subject to the strength and stability conditions was assumed as an objective function. Optimal proportions of geometric dimensions for a family of the tanks of various capacities provided with heads of various convexities were determined. The results were presented in the form of plots. A function was proposed that approximated the solution and could be useful for purposes of designing of the tanks.

The paper presents a method of choosing parameters of a mathematical model for simulation of a working cycle of compression-ignition engine on the basis of experimental measurements. In order to choose the parameters of the model, the Nelder-Mead method has been used. As a result of such an approach, a simplified mathematical model with very good numerical effectiveness can be used for simulation of the working cycle of the engine, while very good compatibility of numerical results and experimental measurements is ensured. Suitable algorithms and results of calculations are presented.

The paper presents a numerical model of car exhaust pollutant dispersion. The model can be used for estimation of the impact of pollutant emissions from road vehicles on the environment. The finite volume method has been used for model formulation. Equations obtained after discretisation are solved by using different methods like Runge-Kutta, Crank-Nicholson or decomposition methods. On the basis of the numerical simulation, conclusions are formulated about the numerical effectiveness of the integration methods used. In the paper, a problem of nitrogen oxides dispersion is formulated and solved, whereby chemical reactions are included in considerations. The model presented in the paper has been used for numerical calculations of car exhaust pollutant concentrations in a real car park. The last part of the paper presents some numerical results of calculations, which include emissions after cold start of engines.

The paper presents the results of tests on fatigue crack growth under bending in an elastic-plastic material. Specimens with rectangular sections and stress concentrator in the form of external one-sided sharp notch were used. The tests were performed under the stress ratios R = - I, - 0.5, O. The test results were described by the /'i ]-integral range and compared with the /'i K stress intensity factor range. It has been found that there is a good agreement between the test results and the empirical formula of fatigue crack growth rate, which includes the /'i ]-integral range.

The paper presents application of direct pseudospectral Chebyshev method for solving a commercial airplane trajectory optimization problem. This method employs Nth-degree Lagrange polynomial approximations for the state and control variables with the values of these variables at the Chebyshev-Gauss-Lobatto (CGL) points as the expansion coefficients. This process is converted to a nonlinear programming problem (NLP) with the state and control values at the CGL points as unknown NLP parameters. The kinetic model of flight is formulated, where it is assumed that an airplane is a particle and the motion takes place in the vertical plane. The method is implemented in Matlab using sequential quadratic programming algorithm (SQP) as an efficient solver. Sensitivity analyses are performed concerning the influence of the degree of discretization and the initial approximation on the solution. Three examples of optimized trajectories in presence of wind are shown.