No abstract

Hoppers are used in various fields of application, as for material transportation in food industry, mining, agricultural industry, transport industry etc. Mass flow rate at the hopper outlet nozzle is one of the significant parameters which is used to evaluate efficiency of the hopper. During the discharge process of hopper, different effects in bulk material behavior, as accumulation or bridging of particles, could occur, therefore decreasing efficiency of the hopper discharge rate. In this paper physical and numerical experiments of bulk flow through the hopper are performed and analyzed under applied vertical vibrations to the hopper construction. Vibrations are considered with different frequency and amplitude in experimental and numerical models. As the bulk material spherical glass particles are used in the experiments. The obtained results of the physical experiments are compared with the results of numerical simulations, therefore allowing to evaluate efficiency of numerical models used for analysis of the bulk material flow effects in the hopper system. The obtained experimental and numerical model results will be used for further analysis of a more complicated hopper model, where the bulk material segregation process at the outlet nozzle of the hopper system and dust dispersion in surrounding environment during the bulk material loading process will be taken in account.

The impact of granules which are of various form, size and densities against a vibrating prism is analyzed. The analysis is performed in a two-dimensional plane (2D), assuming that the prism perpendicular to the plane is symmetric with the given constant height. In the description of the interactions, classical mechanics are used to describe the impact of granules or granule flow against a moving obstacle (vibrating prism). The air viscosity is not taken into account and thereby the present work offers simplified analytical solutions for engineer calculations through a straight forward mathematical model. In the interaction of granules with the obstacle, the impulse restitution coefficient is applied in the normal direction. The no-slip rule or the dry friction coefficient for slip, respectively, is applied to the interaction in the tangential direction. The analysis uses the superposition principle for individual airflow and for each granule fraction. As a result, for a continuous environment, it is possible to divide the interaction by the center of mass of several layers in the region of motion. The results obtained show the distribution of fractional flows, taking into account that there is a suction zone just behind the prism. Despite the complicated interactions of the components of the environmental fractions, the developed analytical method allows analytical prediction and calculation of the separation motions. The equipment for the experiments is 3D printed, and the experiments were performed to measure the flow speed of the medium using a bottom open cone container.

In the Thesis a new method is developed for optimising the shape of mechanical elements by considering the interaction of these elements with a multiphase uncertainty environment whose approximation model achieves a significant number of degrees of freedom (DOF). The Thesis analyses the process of dust formation during the handling of granular material. Different experimental designs are used to derive metamodels and to analyse the segregation of granular material in the silo discharge depending on the oscillation frequency, amplitude, and geometrical characteristics of the silo.

The problem of lateral wear intensity for rails and wheels has not been resolved at the present, despite many studies in this area. This article aims to provide evidence of the influence of rail head profile after grinding on the lateral wear of interacting surfaces of rail and wheel in curves and straight sections of 1520 mm track for Latvian Railways. The article suggests the method of creation of asymmetric repair profiles for rail grinding taking into account the shape of wear for wheel profile. For this purpose, statistical data were collected on the most typical form of wear for wheel profiles of railcars on the Latvian Railway. Asymmetrical profiles for rail grinding have been developed and the basic primary grinding angles for straight and curved sections of the track have been defined by means of geometric modeling. As a result, the contact points of rolling surface of wheels were shifted to the centre of the curve. The difference in wheel radii reached 5.6 mm in one wheel pair, and the fitting of wheel pairs was improved by 4 times. At the final stage of the study, the corrective profiles for grinding the rail head were developed utilizing SolidWorks Simulation, taking into account the most typical wear of the wheel profile, which increased the contact areas and as a result reduced the stresses up to 18 % on the outer rail in the curve with a radius of 800 m. As a result, for the outer rail, part of the load shifts from the wear zone of the wheel flange to the root of the wheel flange. For safety reasons, the stability coefficient of a worn wheel profile for the Latvian Railways with a flange angle of 66.8º was calculated in accordance with the rolling mode along developed asymmetric rail profiles. The calculated wheel stability reserve against derailing has a significant reserve. As an alternative to grinding, it was proposed to reduce the tilting of the outer rail and increase the tilting of the inner rail in curves.