Ing. Petr Kočárník, Ph.D.

ELEKTRON I is the reactive platform for education of aerodynamics and evaluation of electronics, measurement and control algorithms on flying systems with high dynamics.

Computational study of pressure and energy losses in the control valve of the steam turbine is carried out. The impact of misalignment of a valve cone toward the valve chamber while changing the width of a parting rib in the chamber is assessed. The impact of the dimensions of the valve chamber on losses is examined. An optimal solution to misalignment of a valve cone, dimensions of the valve chamber and the width of a parting rib is established.

The paper deals with alternatives of minimization of the loss coefficient in the fully open valve. The basic shape of the investigated flow channel was based on the valve with spherical chamber and with long diffuser at the outlet behind the valve seat. Shape and size of the output diffuser, shape of valve plug and seat or degree of valve opening was constant in assessing of influence of the walls shape to the loss coefficient. Within the research there was considered various configurations of the relative positions of the inlet and outlet duct or modifications of the chamber shape and its connection to the inlet duct.

This paper provides a rather complex mathematical description of dynamic, thermodynamic and aerodynamic processes in a piston compressor actuated by an asynchronous motor. The model respects the influence of inertia of movable mechanical parts of the compressor, thermodynamic changes in the cylinder and pressure vessel, influence of heat transfer between the gas and walls and influence of aerodynamic losses and gas inertia in the inlet and discharge piping. The paper provides an example of a simulation of combined systems and their mutual dependencies in the Matlab-Simulink environment.

This paper provides a rather complex mathematical description of dynamic, thermodynamic and aerodynamic processes in a piston compressor actuated by an asynchronous motor. The model respects the influence of inertia of movable mechanical parts of the compressor, thermodynamic changes in the cylinder and pressure vessel, influence of heat transfer between the gas and walls and influence of aerodynamic losses and gas inertia in the inlet and discharge piping. The paper provides an example of a simulation of combined systems and their mutual dependencies in the Matlab-Simulink environment.

The document deals with the research of flow in the cross-over channel of the high-pressure stage with partial admission of first stage. In the opening part there is a description of the experimental model and the method of measuring flow fields with high velocity gradient using the stereo PIV principle. The second part describes the design of the model inlet part. The third chapter deals with measuring in the cross-over channel outlet slot with no influence of the stator blade cascade of the following stage. The stator blade cascade feedback is described in the fourth part. During all the measurements we observe the influence of the shaft revolution on the flow field at the cross-over channel outlet.

This paper analyses the effects of fluid on the dynamics of bodies immersed in a liquid and exerting linear oscillatory motion with small amplitude of oscillation. The effects are reflected by the pressure force corresponding to the acceleration or by what is called the 'fictitious mass'. The expressions for the above values have been derived under the assumption that the terms in the equation of motion of the fluid being subject to viscosity and convective acceleration can be disregarded. The result is a Laplace's differential equation of the pressure function the boundary conditions of which are defined by the motion of the body in question. In addition, the paper shows practical applications of the solution of the pressure field in the immediate vicinity of specific oscillating elements of hydraulic systems.

The following report focuses on studying the possibility of modifying the steam turbine wheel chamber, which converts the flow of the turbine degree with partial admission into the following degree with full admission. Previous studies of the original chamber demonstrated that the uniform distribution of outlet flow parameters cannot be achieved by modifying the meridian shape of the duct. In order to decrease the non-uniformity of the magnitude and direction of velocity at the outlet, it is necessary to modify the chamber by inserting rectifying walls, which supply the flow including partial admission of the tangential component of velocity. The fundamental idea of the modification was verified on a simple experimental variation with two inserted thin rectifying partitions. The experiment proved the application of rectified flow in the tangential direction is capable of significantly reducing the shortcomings of the original wheel chamber solution.

The report focuses on numerical flow simulation for an untraditionally interpreted steam turbine wheel chamber, i.e. inside the flow duct, which transfers the flow between the turbine degree with partial admission into the following degree with full admission. Previous research demonstrated that the standard wheel chamber with a simple concept of structure is not capable of entirely eliminating the effect partial admission has on the distribution uniformity of flow parameters on the inlet of the following degree with full admission, which is adversely demonstrated on the turbine efficiency. The fundamental idea to make modifications was firstly verified during an experiment by easily modifying the shape of the standard duct walls and subsequently an entirely new flow duct shape was designed and verified in the CFD program. The results confirm that the newly arranged duct practically eliminates the distribution uniformity of flow parameters

The contribution deals with optimization of flow duct shape in wheel chamber in steam turbine. Unconventional shaped duct minimizes non-uniformity of admission of subsequent blade cascade. There are compared basic integral parameters of two variant of optimized duct with parameters of standard arranged wheel chamber.

The contribution deals with mathematical description of dynamic and thermodynamic processes in cobined systems and their sumulation in Matlab-Simuling program.

This paper discusses the dynamic system solution with three degree of freedom consist a weightless cable thrown over two fixed side pulleys and the third, free pulley moving along the rope. The cable is stretched with weights attached to its ends and the weight of the free pulley causes the cable dip. Passive resistance on the pulleys stops them from moving. The mathematical description uses a system of differential equations combined with complex kinematic relationships and a description of the passive resistances. The set of equations is converted to a format suitable for numerical solution and a simulation model is created in the Matlab -Simulink program.