Table of Contents


    • Surface treatment – effect on spring parts in the automotive industry

      pg(s) 3-4

      In modern automotive engineering, a particular car is composed of various parts that are manufactured using a wide variety of materials and technologies and that meet the high demands of modern customers and environmental norms. In the production process of a specific article for assembling cars, a problem with springs of a certain type is found. During the planned production, assembled products began to show the same defect. The mounted springs fall spontaneously. An analysis of the possible causes was made. A visual examination was made which showed a lack of plasticity, a change in geometry and raised doubts about the thermal surface treatment. Based on the results of the performed measurements and analysis, the possible causes of the problems during production were recognized. Several conditions could have caused this:
      – Two different tools were available at the manufacturer, respectively two different technologies for the production of the springs;
      – The manufacturer used two different sub-suppliers for surface treatment;
      – insufficient corrosion protection;
      The results of the measurements show that despite the geometric deviations of the dimensions, the springs lose their function due to lack or improper surface treatment.

    • Analysis of planetary gear trains applied in vehicles

      pg(s) 5-8

      The paper presents a theoretical analysis in the field of the application of planetary gear trains in vehicles. The following main areas have been considered: design features of planetary gear trains, specific aspects of the application use of planetary gears in vehicles and possibilities of increasing the efficiency coefficient of these drives. An analysis of the option for investigating these gear sets has been implemented as well. Special attention is dedicated to the options of minimizing energy consumption, taking into account the relevant limitations and operating conditions of planetary gear trains. Conclusions have been deduces. Ideas for future scientific work are presented

    • Computational fluid dynamics (CFD) analysis of the divergent part of the Formula Student car restrictor

      pg(s) 9-13

      The FSAE competition is a student engineering competition that involves designing, constructing, and building a small racing car. Students from different universities compete on auto-moto sports tracks. The competition’s judges are eminent experts in marketing, automotive engineering, and racing car engineering. In class IC, engines are used as power units. One of the main limitations is that all intake air must pass through a diameter of 20 mm. One of the main challenges facing student competitors is solving this problem, and the convergent-divergent jet is one of the possible solutions to the problem. In this paper, CFD simulations were used to examine the influence of the divergent part of the restrictor on the total mass flow at the nozzle exit. A diagram of the dependence of the mass flow on the half-angle of the divergent part was obtained. For the CFD simulation, ANSYS Fluent was used, which proved to be very good for examining the mentioned influence.


    • Road freight risks in supply chains

      pg(s) 14-17

      Supply chains (SC) are becoming increasingly important for the global society. The spatial and temporal connections in them are carried out through the transport vehicles and through the infrastructure. Land transport accounts for more than fifty percent of the transport of goods in Europe. Its condition is a measure of the resistance of SC. The transport sector is high-risk. Identifying, analyzing, developing a program, controlling, and anticipating the risks of freight transport is a prerequisite for the successful development of SC.

    • Cordon counting in the territory of the city of Bitola

      pg(s) 18-20

      The collection and analysis of transport data is of great importance for traffic engineers, who use that data to perceive existing problems and offer solutions. Depending on the type of data and the meaning available, there are different methods and equipment. Data collection can be done on sections, intersections, entire cities, hourly, daily, weekly, monthly and annually. For the city of Bitola, data collection was carried out for cars, buses and heavy goods vehicles in the peak hour according to the directions of movement, i.e. cordon counting, by setting up checkpoints with personnel on those roads that intersect with the cordon line. In this case, the vehicles in transit are important to us and we grouped them into two groups, cargo transit and individual traffic.

    • Forecasting the occurrence of risks and the dynamics of their development in navigation

      pg(s) 21-24

      Analysis of claims incoming over the past years and the industry data on losses in supply chains allows to identify the most common risks and pay attention to the necessary measures to protect cargo during transportation.
      Sometimes it is difficult to establish the relationships between a specific event and business, then logisticians use a probabilistic approach.
      They predict how events can develop in the future. Each outcome is calculated and assessed as a separate risk.


    • The prospects for the use of hydrogen as a fuel in maritime transport

      pg(s) 25-27

      In diesel engines, the fuel mixture consisting of liquefied gas and hydrogen is prepared, and a process corresponding to the gasdiesel cycle is implemented, where methanol or diesel fuel are used as an explosive fuel, as a result of which the self-ignition delay period is reduced, and the fuel combustion duration during active combustion is reduced as well. That is, the limits of the working mixture combustion are expanded (hybrid combustion), the mixture formation process is improved, and the cycle carried out in the engine is closer to the Otto cycle, which improves the environmental and efficient indicators of diesel engine compared to the gas-diesel engine, where diesel fuel is used as an explosive fuel, which makes it possible for diesel engine to run: only on liquefied gas; only on hydrogen, only on a diesel fuel or on a combination of different fuel mixtures.

    • Energy analysis of main and auxiliary steam turbine from coal fired power plant

      pg(s) 28-31

      This paper presents an energy analysis of main and auxiliary steam turbines from conventional coal fired power plant. Main turbine is composed of three cylinders connected to the same shaft which drives an electric generator, while auxiliary steam turbine is used for the boiler feedwater pump drive. The whole analyzed main steam turbine produces mechanical power equal to 312.34 MW, while in an ideal situation, it can produce mechanical power equal to 347.28 MW. The highest part of the mechanical power in the main turbine is produced in the low pressure cylinder. Auxiliary steam turbine in exploitation develops mechanical power equal to 6768.94 kW, while in an ideal situation it can develop 8029.03 kW. Whole main turbine energy efficiency is equal to almost 90% what is in the expected range for such high power turbines. The auxiliary steam turbine has an energy efficiency equal to 84.31%, which is almost 6% lower in comparison to the main turbine. Energy flows delivered to the last two feedwater heaters (HPH2 and HPH3) in the condensate/feedwater heating system are notably higher in comparison to energy flows delivered to any other condensate/feedwater heater.