Contents of Journal of Mechanical Engineering 55, 6 (2004) 


 

DZIANIK, F., VAVRO, K.: Calculation of the separation efficiency 
of cyclone apparatus                                                     315 

GUŽELA, Š., PECIAR, M., FEKETE, R.: Mixing of particulate 
materials – experimental input power estimation                          329

DOMANOVÁ, M., DZIANIK, F., JELEMENSKÝ, K.: 
Study of tangential velocity component in helical (swirling) 
annulus flow                                                             341 

VARCHOLA, M., KNÍŽAT, B., TÓTH, P., GOLHA, M.: Hydraulic design 
of a spiral pump respecting the course of characteristics and radial 
thrust on the rotor                                                      356

Abstracts



Calculation of the separation efficiency of cyclone apparatus

FRANTIŠEK DZIANIK, KAROL VAVRO

There are a few definitions for the calculation of the separation efficiency of cyclone apparatus. However, none of them is suitable for the expression of the separation efficiency at specific operating conditions of cyclones. The definition derived by Kelsall is the nearest one to achieve correct evaluation of the separation efficiency at such operating conditions of cyclones. A new definition of the separation efficiency was derived from Kelsall's definition by the implementation of additional term. This term considers possible variations of operating conditions of the cyclone apparatus so that at the same time calculated values of the separation efficiency are qualitatively comparable and they reflect the real status as exactly as possible. The separation efficiency was expressed by the relative underflow of the suspension and the relative underflow of the particles. Values of these distribution ratios were obtained by measuring at various operating conditions of the experimental hydrocyclone. Within a presentation of the results the comparison between the evaluation of the separation efficiency according to the new definition and according to Kelsall's definition was introduced. From presented results it follows that the separation efficiency evaluation by the new definition is more exact.

Mixing of particulate materials – experimental input power estimation

ŠTEFAN GUŽELA, MARIÁN PECIAR, ROMAN FEKETE

Granular materials are treated in various branches of industry where it is necessary to insure the moving objects (mixing elements) of various shapes through batch of granular materials. The force effects of the mixed material on the moving blade submerged in the granular material have been measured. Solution starts with limit equilibrium stresses of the granular material described by Mohr's circle. The experimental station in the shape of rectangular prism for determining the effective force vector, i.e. the horizontal and vertical components of force was used, which enables only uniform rectilinear motion of the blending elements. A semi-empirical correlation based on elementary soil mechanics theory is presented.

Study of tangential velocity component in helical (swirling) annulus flow

MARTINA DOMANOVÁ, FRANTIŠEK DZIANIK, KAROL JELEMENSKÝ

Increase in the transfer properties intensity at fluids flowing in the devices is reachable by various means. Swirling motion of the fluid around the equipment axis is ensured by entering the fluid through a tangential inlet into the annular gap of the vertical heat exchanger model. This type of the flow can be characterized as gradually decaying. The tangential component of velocity is responsible for the increase in swirl intensity in this case. The degree of swirl along the model length is properly described with non-dimensional criterion S – swirl intensity or swirl number, by Gupta et al. defined as the ratio of axial flux of swirl momentum and axial flux of axial momentum multiplied by equivalent dimension. Measurements of average values of the axial and tangential velocity components were realized with the laser, by the Laser Doppler Anemometry method. From the specified criterion relations for mean and local values of swirl intensity, obtained from measured data, the mean and local values of tangential velocity component along the gap width for the specific geometry and volume flow can be expressed.

Hydraulic design of a spiral pump respecting the course of characteristics and radial thrust on the rotor

MICHAL VARCHOLA, BRANISLAV KNÍŽAT, PETER TÓTH, MIROSLAV GOLHA

In the paper there is described the procedure and theoretical background of a pump hydraulic design. Designed geometry is a basis for the calculation of a possible pump characteristics and considers the losses in a pump.

In the paper there is mentioned the principle of the losses calculation in a pump, which is important for numerical solution of differential equations. The result of the calculation is the pump Q-Y characteristics. In the paper there is described the example of the calculation and its results are compared with measured ones. This paper deals with a theoretical computation of the radial thrust, which is induced by a non-uniformity of the static pressure and the velocity distribution at the impeller outlet area, and due to non-uniformity of the static pressure on the curved area of impeller shrouds. Paper shows the comparison of calculated and measured values of the single impeller with conventional spiral casing.