• Energy and exergy losses analysis of back-pressure steam turbine from CHP plant

    pg(s) 42-45

    In this paper is analyzed back-pressure steam turbine which operates in CHP (Combined Heat and Power) plant from the aspect of energy and exergy losses. Produced turbine power, used for electricity generator drive equals 62548.77 kW, while the turbine mechanical loss is 1934.50 kW. Exergy analysis of the turbine shows that cumulative exergy loss is composed of two losses – mechanical loss and steam exergy loss. Steam exergy loss is additional loss which takes into account the state of the ambient in which turbine operates (unlike energy analysis which is independent of the ambient state). Change in the ambient temperature resulted with a change in turbine exergy efficiency and exergy loss. Ambient temperature change for 10 °C resulted with change in turbine exergy efficiency for less than 0.5 % on average, while the change in the turbine exergy loss (for the same temperature change) equals 266.21 kW on average.

  • Analysis of sinking of GRP pipe string DN 1600

    pg(s) 15-21

    The aim of this research it was the installation of a discharge sea water pipeline DN 1600 of GRP (glass-reinforced plastic) material in Vlore Bay. The analysis of the sinking of the pipe string has been carried out by using CAESAR II software and considering different load cases. The calculation was carried out for static condition (sustained load) and transient condition (occasional load). In consideration were taken the allowable stress due to bending for pipe and allowable stress for joint subjected to freezing. From the calculation it was evident that the most critical effect on the GRP pipe has done by the position of Concentrated Force due to the presence of sledge (approx.. 2 tons), not disassembled from the string after moving in the position from the shore. In these cases, where the central crane has been maintained fixed or moved downward, the maximum bending stress on the pipe was 12.03 MPa. According to the verification carried out for pipe wall in the transient condition (occasional load) the stability was good and for the joint, was shown, in the worst scenario, a bending stress 158% of the allowable one. In this case it is possible to have the crack of the resin used for the freezing of the joint but not the failure of the system joint + pipe that can withstand without, failure, a stress 3 times greater than the allowable stress for pipe according to EN1796.

  • Efficiencies and losses comparison of three steam turbines – from conventional, nuclear and marine power plant

    pg(s) 10-14

    This paper presents an analysis and comparison of three steam turbines and its cylinders: from the conventional steam power plant, from nuclear power plant and from the marine propulsion plant. The best parameters for the comparison of whole turbines and its cylinders are: energy loss per unit of produced mechanical power, exergy destruction per unit of produced mechanical power, energy efficiency and exergy efficiency. Steam turbine from marine propulsion plant shows the worst performance, regardless if observing each cylinder or the whole turbine – it has the highest losses per unit of produced mechanical power and the lowest efficiencies (both energy and exergy). Such results can be explained by a fact that marine steam turbine must be much more dynamic in operation in comparison to other two turbines. Also, marine steam turbine analyzed in this paper did not possess steam reheating between the cylinders as the other two observed steam turbines, what has a dominant impact on the obtained results.

  • Synthesis of machine – tool racking using a genetic-morphological approach

    pg(s) 3-9

    A fundamentally new methodological approach to the creation of progressive machine-tool equipment is proposed when considering a material point as a carrier of genetic information in the synthesis of technical systems of the “object” type. The main attention is paid to the search for new technical solutions with the use of tangential clamping, which allows one movement to simultaneously clamp several cutting tools offset from the axis of rotation, for example, in the form of carbide non-regrowth inserts.

  • Comparative Analysis of Geometrical Characteristics of a Test Specimen for Testing the Tensile Strength Before and After Punch Sharpening

    pg(s) 344-347

    In the present article, a comparative analysis of the widths and thicknesses of a test specimen prepared by punching a hydraulic press before and after sharpening the guillotine blades is made. The types of characteristics of the punch are considered. The comparative analysis was performed by a non-destructive method using a 3D computed tomography.

  • Contribution to the implementation of software control for seeding plates

    pg(s) 340-343

    Seed plates of all seeding machines for widerow plants are powered by wheel of seeding machine and mechanical transmission. That has impact to volume and possibilitz of stearing.This paper show possibilities of using electromotor for power of seed plates as well as analysis possibylities acting stearing by electro system. In this paper are research measurement system and create stearing by programabil logic controller and shown idea for implementation steering of speed rotating of seed plates. That has aim to go about nominal seed space in row.

  • Dual-flow dissymmetrical low pressure steam turbine energy analysis – comparison of both turbine cylinders

    pg(s) 336-339

    In this paper is performed energy analysis of the dual-flow dissymmetrical low pressure steam turbine, which operates in a coalfired power plant. Based on the measured operating parameters during exploitation it is calculated and presented an ideal and real power, energy losses and energy efficiencies of a whole turbine and both of its cylinders. Right cylinder of the analyzed turbine develops higher real (polytropic) and ideal (isentropic) power in comparison to left turbine cylinder. The first steam extraction of each cylinder dictates cylinder power (both ideal and real). Right cylinder has a higher energy loss and energy efficiency in comparison to left cylinder – the difference in energy loss is notable (5735.74 kW in comparison to 5447.23 kW), while the difference in energy efficiency is low, almost negligible (92.371% in comparison to 92.357%). Percentage differences between observed turbine cylinders show that left cylinder has approximately 5% lower real (polytropic) as well as ideal (isentropic) power and simultaneously approximately 5% lower energy loss.

  • Comparison of the Precision of Dry Sieve Analysis versus Wet Sieve Analysis for Some Selected Natural Clay Varieties

    pg(s) 262-267

    Clay is a specific soil type that composed with relatively finer particles usually less than 0.002mm according to most of standard definitions including the behaviours of cohesive and the clay particles may have different sizes less than 0.002mm and most of occasions the clay bulk is contaminated with some more coarse particles such as sand and silt even though those particles are comprised in a same deposit or a same massive body. Most of clay varieties are frequently condign in the advanced technological uses. Therefore, the investigation of the particle sizes of some of clay and categorization are important tasks in the selection of a clay type for some particular technological application. The well known methods for the grain size analysis are the wet sieve analysis and dry sieve analysis in order for cohesive soils and non-cohesive soils as usual. In the existing study, there were anticipated to compare the accuracy of dry sieve analysis results with the wet sieve analysis results of three different selected clay verities in Sri Lanka. As the experiential works those clay samples were separately analyzed using a sieve range of 2mm- 0.037mm and pan (<0.037mm) using dry sieve method. Also those clay types were wet sieve analyzed with respect to the sieve size of 0.075mm. According to dry sieve analysis results the finer portions (<0.075mm) were obtained as ~17%, ~6% and ~16% from clay 1, clay 2 and clay 3. The results of wet sieve analysis showed ~60%, ~37% and ~72% of finer portions (<0.075mm) in clay 1, clay 2 and clay 3 while the average grain sizes (D50) of them were 0.25mm, 0.27mm and 0.19mm. When comparing of those results the minimum deviation between wet sieve analysis result and dry sieve analysis result was found from clay 2 which is having maximum average grain size (D50) while the maximum deviation was observing from clay 3 which is having minimum average grain size (D50).

  • The strenous state of the contact at the sliding – flip pairs

    pg(s) 258-261

    The exact determination of strain on the load application area, regards to changing material or shape is one of the main problems of the mini structure constructions, which it does not interfere with the classical methods of linear elasticity. The main purpose of this article is to demonstrate accomplishments in the knowledge of linear elasticity with different mathematical methods, in order to penetrate into the area or into the contact lining, taking into consideration the friction between the bodies in contact. The methods and hypotheses are related to the analysis of different classical half-plane problems in loads of different types of linear elasticity. This material shows a clear original solution of the strained state in the contact area including the surface lining; it serves as a solution to the various contact plan problems. The details and the elements of the vehicles are part of a broad field, which should be optimized considering different analytical solutions and using various computer programs. These solutions can be installed in their structure. Classical methods in the details apply only when the hypotheses on studied subjects are being met, such as Material Resistance studying the Rod. A detail with a length of ten times greater than the transverse dimension. That’s the reason why extreme problems or problems out of the different hypotheses are solved and proven in practice with the most creative and sophisticated methods. The solution given in this article is an important contribution to constructive calculations, which is also associated with other works carried out by me on the friction coefficient on the flip-flop slippery contact.

  • 3-phase motor speed regulator based on microcontroller and intelligent power driver controller

    pg(s) 226-229

    This paper describes the design and practical implementation of speed controller for 3-phase induction motor based on ATmega 2560 microcontroller. Based on the theoretical analysis of the induction motor, are defined the requirements that the controller should satisfy them. Then, based on the specificity of the selected controller, the operating mode of the ATmega 2560 controller is designed. The specificity of this solution is that the driver circuit, which is connected between the controller and the motor, is realized with an intelligent power controller. Finally, the results of the practical work of this motor controller are given.

  • Evolution of rolling bearing life rating through the standardization

    pg(s) 222-225

    The operational ability of a rolling bearing selected for a specific application is assessed based on service life. The basic formula for bearing rating life was established more than 70 years ago by A. Palmgren. The first standard presenting a basic mathematical model for rating life calculation was published in 1962 (ISO/R281). The content of this standard has been revised and the next version was published in 1977 (ISO 281-1). The novelty was the introduction of adjustment factors for reliability other than 90%. This standard was replaced by the ISO 281 standard in 1990, which introduced additional adjustment factors for special bearing properties and operating conditions. The latest version of the ISO 281 standard was published in 2007. This standard provides a procedure for calculating the modified service life by taking into account the additional impacts of lubrication condition, lubricant contamination and limit fatigue load. Furthermore, the document ISO/TS 16281 was published in 2008 introducing the influence of bearing internal clearance and misalignment in the rating life calculation. An overview of the development of a standardized formula for bearing rating life is given in this paper, on the example of deep groove ball bearing under radial operational loading.

  • Effect of Weight and Diameter Variables on Balance Process for Inertia Wheel Pendulum by Using Swing Up and PID Controller

    pg(s) 191-193

    Inertia wheel pendulum balance control is performed by using swing up and PID controller with different wheel weight and diameters. In the pendulum control, 3 different radius wheels and different weights are added to analyze whether the system remained balance position. In this process, the effect of weight and diameter variables on the swing time and PID coefficients of the pendulum was observed. With this observation, the effects of input variables in the real-time system were compared with calculations in the dynamic pendulum model.