• MACHINES

    EXPERIMENTAL SIMULATION OF COMMON RAIL ELECTROMAGNETIC INJECTORS WEARING

    Machines. Technologies. Materials., Vol. 12 (2018), Issue 5, pg(s) 208-211

    At the time of exploitation, the geometrical position of the control valve changes as a result of wearing, which leads to a change of residual electromagnetic gap stroke and force of control valve spring. The following study measures the hydraulic characteristic changes, based only on common rail injector increased stroke of control valve and residual electromagnetic gap. The results show that the increasing of control valve stroke and residual electromagnetic gap increase the fuel flow rate and return fuel flow. Increased fuel flow rate and return fuel flow are presented with short injector signal time and lower levels of working pressure. The increasing is lower with longer injector signal time and high level of working pressure. The follow-up results are practically significant by common rail electromagnetic injector diagnosing and repairing.

  • MACHINES

    NATURALLY ASPIRATED GASOLINE ENGINE UPGRADE WITH TURBOCHARGER – NUMERICAL INVESTIGATION OF CHANGE IN OPERATING PARAMETERS

    Machines. Technologies. Materials., Vol. 12 (2018), Issue 5, pg(s) 204-207

    Numerical investigation of naturally aspirated gasoline engine main operating parameters and engine upgrade with a turbocharger is presented in this paper. Analysis is performed by using numerical 0D (zero-dimensional) simulation model. Turbocharging process with a selected turbocharger increases engine maximum torque for 62.58 % and also increases maximum engine effective power for 58.82 %. One of the main reasons of turbocharging process usage is reduction of engine brake specific fuel consumption. The highest decrease in brake specific fuel consumption for a turbocharged engine, in comparison with naturally aspirated one, is obtained at 4000 rpm and amounts 8.83 g/kWh (from 239.01 g/kWh for naturally aspirated engine to 230.18 g/kWh for a turbocharged engine). Turbocharging process brings several useful benefits to the analyzed gasoline engine, which is also a valid conclusion for internal combustion engines in general.

  • MACHINES

    THEORETICAL AND EXPERIMENTAL RESEARCH OF AUTOMATIC BALANCING DEVICE

    Machines. Technologies. Materials., Vol. 12 (2018), Issue 5, pg(s) 200-203

    The article deals with the process of wave forming on the surface of a liquid in a chamber of a liquid auto-balancing device partially filled with a liquid for rotors with a vertical axis of rotation under non-stationary modes of the system’s motion. In non-stationary processes, the possible wave formation causes a dynamic instability in the operation of the machine and the increase of vibrations under certain operating modes. In the article the problem for the case when the rotor is installed in elastic supports is solved, the joint movements of the rotor – liquid system are considered and their stability is investigated.

  • MACHINES

    MECHANICAL DESIGN AND FINITE ELEMENT ANALYSIS OF A 3 UNIT CUBESAT STRUCTURE

    Machines. Technologies. Materials., Vol. 12 (2018), Issue 5, pg(s) 193-196

    The aim of this study is to design a 3 Unit CubeSat structure performing finite element analysis under static, dynamic and thermal loads. The main idea of this process is to construct a 3U CubeSat main frame that can structurally endure launching process and space environment. To accomplish the task, a 3U CubeSat structure is designed and standard loads that a 3 unit CubeSat structure has to endure are obtained. After the selection of a suitable material, modal analysis, quasi-static launch analysis and thermal stress analysis coupled with heat transfer analysis are accomplished in Abaqus environment. Finally, the results are evaluatedand endurance level of the
    design is determined.

  • MACHINES

    ANALYTICAL AND FINITE ELEMENT IN-PLANE VIBRATION ANALYSIS OF A GANTRY CRANE

    Machines. Technologies. Materials., Vol. 12 (2018), Issue 4, pg(s) 157-159

    Every object in nature has an infinite number of vibration frequency and amplitude as called “Natural Vibration Frequency”. Developing computer capacities allow calculating of natural frequencies and shapes of complex structures more accurate and understandable. In this study, a dual-trolley (2×400 tons) heavy-duty overhead gantry crane that can carry loads up to 800 tons was analysed by mathematical and finite element methods. The mathematical method is based on Euler-Bernoulli transverse vibration approach. On the other hand, finite element method is one of the most common numerical methods that can solve many engineering problems in a range from solid mechanics to acoustic. The generated solid model was analysed by the finite element method with the help of ANSYS Workbench 14.5 which is a commonly used analysis program. The obtained values of natural frequencies at mathematical calculations and finite element analysis were compared and presented.

  • MACHINES

    THE INFLUENCE OF THE TOOTH PROFILE SHAPE ON THE STRESS-STRAIN STATE IN THE GEAR

    Machines. Technologies. Materials., Vol. 12 (2018), Issue 4, pg(s) 153-156

    The shape of the tooth profile affects the stress-strain state in the gear. In the case of a fatigue failure the stress state is a decisive criterion for the lifetime of the gear. The shape of the tooth flank affects the magnitude of the contact pressure in the contact of the meshing teeth. The consequence of which are surface cracks and pitting. The shape of the tooth root influences the magnitude of the root stress, which, when limit is exceeded, leads to root cracks and teeth breakage. Many different types of gearing are known, but in the practice most widely used is the involute one. Other types of gearing become interesting especially when polymer materials are being used. If the gears are injection molded the type of gearing does not affect the cost of the tool. In the case of metal gears, standardized tools for involute gearing make the use of other special types of gearing economically unjustified. Our research is focused on the S-gears, which got their name from the S-shaped path of contact. The paper presents the research of how the defining parameters of S-gears impact the stress-strain state in the gear. This was done using a numerical model which simulates gear meshing. The stress state of two different types of S-gears was compared with the stress state in an involute gear of the same dimensions (same module, number of teeth and width). It was found that with a proper choice of gearing type we can improve the load bearing capability of the gear pair. With use of our numerical model we have also analyzed the impact of the tip relief on the stress state. The numerical model was validated for the case of meshing steel involute gears, where we can compare the results of the model with the results according the ISO 6336 calculation. A good match between the results of the model and results according the standard was obtained. After validation the same numerical model was used for the calculation of the stress-strain state in S-gears. This was calculated then for metal and polymer (POM/PA) gear pairs.

  • MACHINES

    HEAT PUMP HEATING SYSTEM OPTIMISATION

    Machines. Technologies. Materials., Vol. 12 (2018), Issue 4, pg(s) 149-152

    The goal of this paper is to minimalize the gap between the heat pump’s compressor COP and the system COPs. A water-water heat pump was installed in a family house without piped floor heating, with 13 radiators, together with a 300 litres thermal storage and 200 litres hot water storage tank. Some measurements are published, taken before and after the system optimisation. The measured compressor COP is compared with theoretical data published by the device producer. The results show that the power consumption was decreased by 15 percent after the system optimisation. The influence of the equithermal curve settings and the power of the submersible pump are analysed and the results are presented. The seasonal COP (SCOP) for Bratislava area is calculated. for the system under consideration.