• Thermodynamic analysis of three-cylinder steam turbine from combined cycle power plant

    pg(s) 61-64

    The paper present thermodynamic analysis of three-cylinder steam turbine, which operates in a combined cycle power plant. It is performed analysis of each turbine cylinder and of entire steam turbine. Comparison of steam turbine cylinders shows that intermediate pressure cylinder develops the highest real power and has the highest efficiencies while low pressure cylinder has the highest ideal (isentropic) power, the highest loses and the lowest efficiencies – therefore, improvement potential of the low pressure cylinder is the highest. Entire observed steam turbine has an energy efficiency equal to 86.58 % and exergy efficiency equal to 89.26 %, what is lower in
    comparison to high power steam turbines from some conventional land-based steam power plants but also higher in comparison to low power marine steam turbines.

  • A fuzzy logic-based Anti-Lock Braking Systems

    pg(s) 58-60

    In today’s automobile industry, the need to adjust the speed of the vehicle and stabilize the wheels control is still a task due to road conditions and traffic. The Anti-lock Braking System (ABS) is a tool used in automobiles to prevent wheels from locking while brakes are pressed. The objective of this work is the maintenance of the wheel slip value to a desirable slip ratio as the vehicle model is simulated using a fuzzy logic controller. The analyses are made based on the slip ratio, angular velocity and stopping time.

  • Automated design of proposal for new construction knitting unit consisting of a needle bed, needles and CAM systems for flat knitting automatic machine

    pg(s) 20-22

    The work proposes a new design of a new kind of knitting unit consisting of a needle bed, needles and cam systems that allow selection in operation only with the needles on the needle bed without any other additional details, such as springing or stopping jack. The proposed construction is designed in accordance with the requirements of modern flat knitting machines with the possibility of individual needle selection. Because the structures are interdependent, the braiding systems are designed to work only with the new proposed needles and needle bed construction. The three new construction for needle, needle bed and cam systems are aligned with one another and allow the introduction of a new principle for electromechanical needle selection with a special electromechanical selector operating with negative selection, i.e. turns the needle off when is on. The choice is made by working with needles with three types of butts, short and long, onesidedly rounded, and long two-sidedly rounded, as well as with cam systems divided into two parts. This makes it possible to remove the additional details used in existing methods. Which would lead to a reduction in the depreciation of the machine and, consequently, to a lower maintenance cost. The designs are designed in Solid works environments, providing excellent exploration and dynamic visualization capabilities.

  • Investigation on single phase induction motor efficiency and starting capability enhancement by incorporating magnesium alloys rotors

    pg(s) 16-19

    There is an increasing interest in saving energy through improving single phase induction motors (SPIMs) efficiency due to recent environmental concerns and industrial trends. According to the latest efficiency standards the minimum efficiency that the SPIMs have to present is that of IE3 (premium efficiency). Aiming to meet this target, the researchers have focused on the implementation of new manufacturing techniques, the development of effective design methodologies and the incorporation of advanced but also low-cost materials. In the most cases, the SPIMs rotor is constructed of a high-conductivity material, such as the die-cast copper, which benefits the motor’s efficiency, but deteriorates its starting performance. Thus, the aim of this work is to investigate if the use of die-cast magnesium alloys, which present lower electrical conductivity and cost than the corresponding ones of copper, could lead to the development of topologies with enhanced efficiency and starting capability. To make this happen, the authors proceeded to several investigations regarding the rotor slot configuration and the selection of the proper windings turns ratio along with the run-capacitor value. The derived topologies satisfied all the set requirements and have been proven to be advantageous over the die-cast rotor SPIMs by considering several operational characteristics

  • Exergy analysis of steam condenser at various loads during the ambient temperature change

    pg(s) 12-15

    The paper presents an exergy analysis of steam condenser at three different loads and in the ambient temperature range between 5 °C and 20 °C. An increase in the condenser load and increase in the ambient temperature resulted with an increase in steam condenser exergy destruction (exergy power losses). At low load, condenser exergy destruction is for the order of magnitude lower if compared to middle and high condenser loads. Decrease of the condenser load and decrease of the ambient temperature resulted with an increase in condenser exergy efficiency. The highest steam condenser exergy efficiencies are obtained at the lowest observed ambient temperature of 5 °C and amounts 81.47 % at low condenser load, 76.10 % at middle condenser load and 74.54 % at high condenser load. From the exergy viewpoint, the optimal condenser operating regime is low load and the lowest possible ambient temperature.

  • On intensifying the research processes of regular motions transformation

    pg(s) 3-11

    The study is a review of the scientific and applied content of the research carried out over the years on the topic, both worldwide and by the authors. The research is structured in a way that presents the topic in its active development over the years, which substantially proves its permanent relevance. The development of the researches of the spatial transformation of motions, oriented towards the synthesis and analysis of spatial transmissions with innovative characteristics, at this stage and up to the present moment for Bulgaria are realized exclusively at the Institute of Mechanics at Bulgarian Academy of Sciences (BAS). The content of the researches carried out at the Bulgarian Academy of Sciences clearly determines their market orientation and, therefore, their place of development was in the “Centre of competence MIRACle – Mechatronics, Innovation, Robotics, Automation, Clean Technologies” at the Institute of Mechanics. The above said makes it inexplicable the decision of the former management of the institute, in the face of Prof. Vasil Kavardjikov (Director) and Assoc. Detelina Ignatova (Project Manager), to ignore this topic when designing a project for the creation of the Competence Centre.

  • INCREASING OF THE OPPORTUNITIES FOR A CLASS OF MACHINE TOOLS WITH DIGITAL PROGRAM CONTROL

    pg(s) 538-541

    In this paper the basic requirements for the modern machine tools with digital program control are formulated. The main directions of modernization of a class of machine tools are shown. The practical applications of the modernized machines are presented with the machining of parts with complex geometric shapes in different mechanical operations. The research held as well as the results obtained can be used in the practical study of machine tools with digital program control.

  • RESEARCH OF THE FACTORS DETERMINING THE SAFETY OF TRAIN MOVEMENT UNDER BRAKING – INTEROPERABILITY

    pg(s) 535-537

    Interoperability for newly adopted countries in the EU is key to trains safety. Calculating the braking force used by the Leaflet 544-1 of the UIC Leaflet [1] brake elements is important for safety when running trains in the braking mode.
    The researching of the facts shows that Regulation 58 [2] is harmonized with the contents of UIC Leaflet 544-1[1] and EU Regulation No 1302/2014 [3]. The test is to be used for the interoperability of the technical infrastructure in connection with Commission Regulation (EU) No 1299/2014 of 18 November 2014 [4] on technical specifications for interoperability with respect to the infrastructure subsystem of the railway system in the Union concerned.
    When designing the rail lines used braking calculation, made by easy way remain based on the friction of the pads on the wheel surface, but it is not related to the examples in the UIC Leaflet 544-1 [1].

  • ESTIMATION OF THE MATHEMATICAL MODEL OF THE DC MOTOR COUPLED WITH A REACTION WHEEL BASED ON THE GENETIC ALGORITHM

    pg(s) 532-534

    In this paper, it was proposed the experimental identification of the mathematical model of the DC motor, coupled with a reaction wheel. It was proposed to approximate the experimental curve with the mathematical model of order 2 inertia, identified by Genetic Algorithm. To estimate the mathematical model of the control object it was proposed to use the Genetic Algorithm method, the results obtained were compared with the Strejc methods and the results obtained using the Process Models module from System Identification Toolbox from MATLAB.

  • DESIGN OF SOLAR PHOTOVOLTAIC FOR ELECTRIC VEHICLES CHARGING UNIT

    pg(s) 522-531

    In this paper, we design and simulate a 20 kW solar on grid power charging unit for electric vehicles at Al-Hussein Bin Talal University (AHU)/Maan-Jordan by using a Bluesol 3.0, Sketch Up 2018 software.
    Two scenarios are considered; one where number of vehicles is five in the interval (8 am – 12 pm) & five vehicles in the interval (12 pm – 4 pm) and time of charge half of battery capacity four hours and the second scenarios where number of vehicles is eight in the interval (8 am – 12 pm) & eight vehicles in the interval (12 pm – 4 pm) and time of charge half of battery capacity four hours. We conclude that the system is efficient and very useful to the electric vehicles users in the university. In addition, the system is reducing the CO2 emissions annually from generating power by 28.4 tons of CO2.

  • AGRICULTURAL ROBOTS ON THE BASIS OF INDUSTRY 4.0

    pg(s) 509-521

    Agricultural labor is physically demanding, tedious and often carried out in unfavorable conditions, making it suitable for robotization. Due to climate change and the swift increase of the human populace on Earth, the hunger is becoming increasingly an issue (currently, around 2 billion people suffer from malnourishment). With the aim of maximal efficiency of the production of plant food, an accelerated introduction of robotics in the field of agriculture is required (Agriculture 4.0).