International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

By applying a complex, exact and scientific approach, was performed the development, calculation and analysis of a complex pilot installation (bioenergetics system consisting of the following elements: greenhouse for early vegetation crops, digester and internal combustion engine powered by biogas). Using the factorial experiment, i.e. applying the matrix of influence, a complete optimization of the internal combustion engine was performed in function of the other elements of the installation. An analysis is also made from the aspect of the positive current EU regulations in the field of air pollution.

The driving factor is an important technical feature of dynamical loaded working machines. It is especially important to know its value for the working wheel speed reducer of the rotating excavators. In this paper is presented a concept for determining the driving factor of a concrete gearbox speed reducer. To calculate the value of the driving factor according to the specified concept, knowledge of the load regime and the carrying capacity of the gearbox is necessary. The load regime is known from the load function, which is given in the paper, and is determined on the basis of the experimental measurements carried out for this purpose. The carrying capacity of the speed reducer is calculated by theoretical analysis according to the established methodology in this paper, for the characteristic pairs of gears determined in this analysis. As the most important gear pair, from the aspect of determining the driving factor, the most loaded gear pair is taken, in which during the exploitation of the speed reducer the most interventions are made, compared to the other gear pairs of the gearbox.

This paper presents a model for determining the static load on movable spatial console lattice girder and the clamps which bounded the same one. The paper presents guidelines for theoretical determination of the static load using an appropriate software package and conducted modeling for this purpose. Also, the paper displays the methodology for experimental determining the static load by setting a model for the experimental measurement on the specific measuring points of the clams and the characteristic positions of the carrying console. The research is carried out on a concrete real object and the results are shown numerically and graphically, which enables carrying out an analysis of the load and deducing concreting conclusions about the research object.

Environmental pollution should be understood as a permanent process caused mostly by anthropogenic factors, that is man. The products of combustion from internal combustion engines are toxic and harmful effects on humans and the environment. This is one reason for research of biogas as an alternative fuel and its benefits for smaller amounts of harmful products in its combustion. For this purpose is reconstructed diesel engine that runs with a mixed fuel diesel- biogas where diesel fuel used for combustion and biogas propulsion engine combustion. Thus it is given the overall internal construction of this type of engine. There is calculated speed characteristics of the diesel engine and the reconstructed motor biogas. Thus these diagrammatic comparisons will indicate the nature of the changes in both engines.

This paper presents the directions for load and safety appreciation of carrying structures component elements and their application to a particular object respectively carrying structure of rotating excavator working wheel. Load and safety of the carrying structure and its component elements are estimated based on the calculation of load and safety factors. The estimated load is based on the calculated value of load factors, while the safety by comparison of the calculated safety factors to the values of recommended minimum safety factors obtained by examinations of such structures in practice. With these indicators we have a situation where we are providing the static strength control of the analyzed elements. The paper presents numerical values of the load and safety coefficients for the excavator SRs-630 working in the coalmine "Suvodol" Bitola, for all characteristic working regimes in its exploitation lifetime. The numerical values of load and safety coefficients relate to clamps of the working wheel carrying structure and the most loaded joint of this structure.

As a result of the conducted theoretical and experimental researches of the local state of strains at the most loaded intersection of the clamps on the working wheel’s carrying structure in a concrete rotating excavator, an array of results has been attained. This paper represents systematically by means of diagrams the results of such researches under normal and specific working regimes of the excavator.

The specific working regimes during the entire exploitation life of the excavator account for about 1 %, with the excavator working in specific cases while digging under unpredictable working conditions. The experimental magnitudes of the strains are obtained with conducted experimental measurement in compliance with the established methodology for this purpose. The theoretical magnitudes of the strains are derived using the established mathematical model of clamps and applied computer FEM analysis.

This paper presents an access to modeling riveted and welded truss-joints on carrying structure with spatial lattice girder design. The paper illustrates the real model (geometric model) of the most loaded truss-joint on specific carrying structure with its overall complexity. It also illustrates the mathematical model (FE model) of the truss-joint in two designs introducing simplicity, in order to analyze the truss-joint by using a computer and an appropriate software package. FE models (the finite element models) keep up all the characteristics of the geometrical model of the truss-joint, ushering in suitable methodology for this purpose. The need for modeling truss- joints imposes itself as a prior step to further local analysis of stress-deformed conditions of the joint-steel plate under the influence of outside loads. The parallel modeling of the same truss-joint in two constructive designs enables further comparative analysis of stress-deformed shape under same loads and summarize more appropriate constructive design of the truss-joint and emphasizes the need for its optimization.

The gearboxes (reducing gears) built in the rotating excavators used at surface coal mines, are exposed to dynamic loads which are frequently unpredictable (stochastic) given the exploitation conditions. These gearboxes are very frequently oversized by the manufacturer. Nevertheless, the possibility of impact loads due to unpredictable working resistances the excavators run up against, can reduce the safety of the gearbox, even to the extent of breakdown of some of the constituent elements in given period till the planned overhaul. This paper presents the methodology for assessing the safety (reliability) of most unreliable gear in specific gearbox, being ascertained by the maintenance experience of the gearbox. Concerning this gearbox, the load function has been established based on experimental investigations, being presented in this paper. Regarding the most unreliable gear, the carrying capacity function has been established by means of theoretical research being displayed in the comparative diagram together with the load function. This comparative diagram helps to infer the safety of the most unreliable gear in the gearbox, i.e. the safety of the gearbox as a whole. The loading on the gearbox is a variable course of the rotating moment with the driven shaft depending on the time span during the total exploitation life of the gearbox. The carrying capacity of the gearbox is equal to the permissible temporally constant rotating moment acting on the driven shaft within a time span encompassing a number of changes in the loading on the driving shaft. The presented methodology can be applied to investigate the safety of other similar gearboxes.

Geothermal energy, solar energy, industrial thermal effluents, etc. mainly offer low-temperature waters. Heating installation or system, originally developed for one of the alternative energy source. The problem of low-temperature heating of greenhouses is not characteristically only for direct application of geothermal energy but is connected to the problem of all the “alternative” energies use for that purpose. Calculations determine the losses of heat transfer, losses from the application of heat and benefit from the use of hot water. Calculated is necessary and permissible temperature of the floor, the recommended speed of the fluid and plan for layout of pipes in the ground of greenhouse.