Table of Contents

  • TRANSPORT TECHNICS. INVESTIGATION OF ELEMENTS. RELIABILITY

    • The position of the steering wheel when turning off the turn signals automatically

      pg(s) 3-6

      Turn signals are an important device on vehicles, with which we inform other participants about our intention when changing lanes, realigning, turning, overtaking, etc. The use of turn signals increases the safety of all road users. According to research conducted in the USA and Canada, one of the reasons why drivers do not use their turn signals is that they sometimes forget to turn off this device. In this work paper, special emphasis is placed on determining the position of the steering wheel at which the automatic turning off of the turn signal is activated when returning the steering wheel to the original “zero” position, as well as the position of the steering wheel when the automatic turning off of this device is not activated.

    • Analysis of main feedwater pump from steam power plant at three loads

      pg(s) 6-9

      This paper presents results of the Main Feedwater Pump (MFP) isentropic and exergy analyses at three power plant loads. Observed MFP is a constituent component of condensate/feedwater sub-system from conventional steam power plant. In real exploitation conditions, MFP uses mechanical power higher than 3000 kW, considering all observed power plant loads. Main isentropic and exergy parameters of the MFP at various plant loads show the same general trends (increase in power plant load simultaneously increases MFP losses and efficiencies and vice versa, from both isentropic and exergy viewpoints). Analyzed MFP has high isentropic and exergy efficiencies, considering all plant loads and ambient temperatures (at any plant load MFP isentropic efficiency is higher than 85%, while the lowest MFP exergy efficiency is equal to 89.24% at the lowest observed plant load and the highest observed ambient temperature). The change in isentropic and exergy efficiency of the MFP is small if all observed plant loads and ambient temperatures are taken into consideration.

    • Modern tendencies and challenges in the car industry- international and national aspect

      pg(s) 10-11

      In the world today, Germany could lose its status as a superpower in the automotive industry, and the German Association of the Automotive Industry considers excessive regulation, slow political decisions and the absence of a legal framework for issues such as artificial intelligence as key problems.
      From the year 2021, the list of Chinese companies has doubled. China develops electric motor cars and has taken the lead compared to Europe, especially in battery technologies, but also subsidizes their production. At the same time, China became the world’s largest car exporter in 2023 – it exported 4.91 million cars, which is an increase of 57.9% compared to the last year, becoming the world’s first country according to the number of exported cars.
      An additional problem for car manufacturers is created by the European Union’s plans to phase out vehicles with internal combustion engines by 2035. There is also a lack of access to the raw materials needed to manufacture batteries and the slow development of electric vehicle charging infrastructure. Nevertheless, during the year 2023, 254 thousand “Tesla” models were sold in Europe, making this car the best-selling car on the continent.
      From July 2024, every new car must have the most modern safety systems, having in mind that 20.400 people died on the roads of the European Union in 2023, according to unofficial data (that’s 1% less than in 2022). From July 7, new cars are obliged to have 10 additional safety systems, which will contribute to increasing safety and reducing the number of accidents.
      On the territory of Serbia, a license was issued to one company for test driving of automated vehicles, after tests and analysis conducted jointly by the Traffic Safety Agency and the CIAX laboratory of the Faculty of Mechanical Engineering in Belgrade. And from
      February this year in Serbia, the registration of those interested in state subsidies for the purchase of electric vehicles began and will continue until October. In Kragujevac, from 2024 “Stelantis” will start producing the new “Panda” hybrid. It was announced that it will be called “PANDINA”. And we look forward to its production.

    • Exploring Transient 2D Conduction: A Practical Guide Using Ansys Mechanical

      pg(s) 12-15

      The present research paper examines the thermal conduction transient through a 2D model analysis using the Ansys Mechanical software product. The study focuses on the importance of time in the heat conduction process and its influence on temperature stabilization in various materials and structures. Any process related to heat transfer requires some time to reach a stable heat conduction state. In various scientific and engineering fields such as thermal engineering, electricity generation, and electronics, understanding, controlling, and analysing transient conductivity can lead to more efficient operation of machines and mechanisms, reduction of energy costs, development of more resistant materials, optimization of conditioning systems, and creation of engineering simulations and models to predict thermal behaviour under different conditions. In addition, the present study can provide new knowledge in the educational field and serve as a basis for a new approach in teaching in the field of thermal engineering regarding the clarification of the conditions under which heat exchange processes occur and related changes.

    • Policy of shipbuilding development in Bulgaria in the second half of the 20th century. Successes and shortcomings

      pg(s) 16-19

      Regardless of the fact that all the prerequisites exist for the development of maritime business and shipbuilding in Bulgaria, a purposeful state maritime policy has not been implemented for a long time. Although there are registered beginnings of our shipbuilding already at the end of the 19th century, and the first serious orders were made during the Second World War, one can speak of a Bulgarian state policy of shipbuilding only in the 2 ½ of the 20th century. Until 1962, the development of the shipbuilding industry was at an average level for the capabilities of our country. In the following decades until the end of the socialist period, shipbuilding emerged as a sub-branch of machine-building of strategic importance for the entire industry, and the scale of its development was comparable to the scale of countries with developed shipbuilding. It is characteristic of the entire period that the majority of shipbuilding production is not created for internal needs, but is dictated by external orders, structural changes are constantly made in the management, there is a lack of continuity, and the construction of capacities for the construction of large-tonnage ships takes a very long time time is a debatable issue. Nevertheless, the development of the shipbuilding industry brings enormous positives to the country. During this period, Bulgaria was recognized as a maritime country; builds a production and technical base that is not small for the scale of our country; puts the work on a scientific basis and gives an opportunity for the appearance of a whole constellation of engineers, according to whose projects dozens and hundreds of ships that sail under the Bulgarian and foreign flags have been built.

  • TRANSPORT. SAFETY AND ECOLOGY. LOGISTICS AND MANAGEMENT

    • Passenger intensity prediction as a tool for effective management of regional rail transport

      pg(s) 20-23

      Regional rail transport is a key part of the transport process, and its importance is growing every year. Suburban rail forms the backbone of the regional transport system and is widely regarded as a sustainable form of mobility with societal benefits. On the other hand, the costs associated with operating rail transport are significant and it is essential to design cost-effective and efficient transport solutions. This paper takes a closer look at the prediction of passenger volumes and the associated options for effective management of regional rail transport when travel demand is known. A practical application is developed in the conditions of suburban rail transport in the vicinity of Ostrava in the Czech Republic. It analyses the available data on transport supply and travel demand of which passengers can be assigned to specific directions and time slots in relation to daily and weekly variations of travel demand. Based on the data provided, a model for assigning passengers with respect to public transport supply was proposed. The prediction is harmonised with local specific conditions. The results obtained were used to design a new operational concept for the suburban railway in the assessed area. On the basis of the data obtained, a modelled composition of vehicle units and frequency of services on individual sections was proposed. An appropriately set capacity of the vehicle units enables a significant reduction of operating costs and leads to an economical and efficient transport solution.

    • Specific features of cargo insurance

      pg(s) 24-27

      In any economic system, the transportation of goods is critical to the functioning of commerce and industry. In the world of international trade and transportation of goods, the risks associated with the transportation of goods are inevitable. Although technological logistics systems are developing at an extraordinary pace thus ensuring the efficiency and safety of transportation, factors such as natural disasters, technical problems, theft and damage can lead to serious losses for both carriers and cargo owners.

    • Risk Assessment and Functional Safety Management in Air Traffic Control and Automated Air Traffic Control

      pg(s) 28-33

      Risk assessment is a crucial aspect of functional safety. As many of the safety development methods define the development process and applicable procedures based on the required risk reduction (safety level or tolerable hazard rate). System development, including hardware and software development requires special measures to reduce the dangerous effects of random hardware failure as well as systematic developer-made errors that can lead to dangerous situations during operation. This set of measures is known as safety management.
      In air traffic management there are international and European legislation and industry-specific standards that mainly focus on software issues. Additionally, general functional safety standards offer more complex hardware and software solutions to achieve the desired level of safety for newly developed systems.
      This paper discusses on the risk assessment challenges posed by new, highly automated air traffic control systems. These systems rely on hardware and software components to perform safety-critical control functions without human intervention or human supervision. The paper identifies the relevant legislative entities and compares a domain-specific risk assessment method for air traffic control with widely used general risk assessment methods. An example Air Traffic Control function is analysed according to EUROCAE ED153 (“Guidelines for ANS
      Software Safety Assurance”), according to 2017/373/EU (“Commission Implementing Regulation laying down common requirements for providers of air traffic management/air navigation services and other air traffic management network functions and their oversight…”) and in comparison, according to general functional safety standard IEC 61508 (“Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems”).

    • Ecological audits and green office in road transport company

      pg(s) 34-36

      At the beginning of the third millennium, environmental audit acquired new and importance, especially for the sustainable development of business activities, including transport companies. The triple planetary crisis refers to the three main interlinked issues that humanity currently faces: climate change, pollution, and biodiversity loss. The research pays special attention to the development of the “green office” concept in the sustainable development of a transport company. The goal of the research is the inclusion in the environmental audit of economic indicators of a transport company that affect the country’s СО2 emissions. The subject of the research is environmental audit indicators. Based on a method of partial least squares structural equation modeling (PLS-SEM) approach additional criteria for the environmental audit of company are evaluated.

  • VEHICLE ENGINES. APPLICATION OF FUELS TYPES. EFFICIENCY

    • Improvement of environmental and ecinomic indicators in marine vechicls using various fuel additives

      pg(s) 37-38

      The paper will discuss and analyze the values of ecological and efficient indicators of standard fuels used in marine vehicles, and their negative impact on the surrounding environment. Reasons for the deterioration of environmental indicators, considering the processes that occur in the engine and the properties of the fuel. The paper also discusses environmental and economic indicators by using various fuel additives. Marine internal combustion engines’ most important operational characteristics are reliability, fuel efficiency and environment safety indicators, which depend on complex design and operational factors. One of the most important factors is the quality of diesel fuel. The physical and chemical properties of fuel affect the mixture formation and combustion processes in diesel cylinders, the completeness of the combustion of the fuel mixture, fuel efficiency, the content of harmful substances in engine exhaust gases, fuel supply equipment and cylinder parts – (piston group) and others. The most common way to ensure diesel fuel’s required properties is to bring multifunctional additives into practice. An overview of the most modern diesel fuel additives will be presented based on the results of the patent search, which ensures improved formation of the mixture and complete combustion of fuel, The article will also present information about the chemical composition of additives and the effectiveness of their mechanism of action. Dependence on ignitability and structure of air-fuel mixture is described in the paper. Foreign manufacturers of diesel fuel additives are indicated. Tests conducted on four-stroke high-speed diesel engines made it possible to determine that the use of an additive (“Nagro Boost”) provides a reduction in effective fuel consumption by 3-7% and does not increase harmful effects in the exhaust gases of internal combustion engines when the engine operates with load and screw characteristics. A conclusion is made about the perspectives of using these and other additives to increase the fuel efficiency and environmental friendliness of internal combustion engines.