Practical research of the angle of thermodynamic losses when indicating pressure in the cylinder diesel engine

Vrlo važan literaturni izvor pri proučavanju radnih procesa u cilindrima motora, decenijama unazad, predstavlja članak Güntera Hohenberga 'Definition und Eigenschaften des termodinamischen Verlust-winkels von Kolbenmaschinen', objavljen 1976. godine u časopisu Automobil industrie, izdanje 4. Ovim člankom je teoretski i praktično (eksperimentalno) obrađena tema određivanja ugla termodinamičkih gubitaka na krivoj pritiska bez sagorevanja izmerenoj u cilindru motora. Posebna vrednost Hohenbergovih istraživanja je u eksperimentalnim rezultatima dobijenim osrednjavanjem izmerenih podataka na većem broju različitih motora. Pokazalo se da su ti eksperimentalni rezultati i te kako upotrebljivi za brzo, ali dosta tačno, određivanje ugla termodinamičkih gubitaka na krivoj pritiska bez sagorevanja,kod bilo kog motora. Dijagrami koje je predložio Hohenberg su od koristi i danas, bilo da se primenjuju direktno ili služe za poređenje sa rezultatima neke od savremenijih računskih metoda zasnovanih na termodinamičkoj analizi procesa u cilindru motora. Međutim, teoretski prilaz Hohenberga datom problemu kroz jednačine koje je postavio, daje dosta dobru predstavu o najuticajnijim faktorima na veličinu ugla termodinamičkih gubitaka, ali u sebi ima i dosta grešaka i grubih aproksimacija. Dobrim i lošim stranama ovog vrlo važnog literaturnog izvora kroz poređenje sa jednom od savremenih termodinamičkih metoda vezanim za problematiku određivanja ugla termodinamičkih gubitaka, posvećen je ovaj rad.Very important literary source for the study of work processes in the engine cylinders, for decades, has been an article by Günter Hohenberg 'Definition und Eigenschaften des termodinamischen Verlust-winkels von Kolbenmaschinen', published in 1976 in the magazine Automobil Industrie, Edition 4. This article theoretically and practically (experimentally) deals with the topic of determining the angle of thermodynamic losses on the pressure curve without combustion measured in the engine cylinder. The special value of this research is in the experimental results obtained by averaging the measured data on a large number of different engines. It has been shown that these experimental results are useful for a quick, but quite accurate, determining of the angle of thermodynamic losses on the pressure curve without combustion, with any engine. Diagrams proposed by Hohenberg are used today, whether they are applied directly or used for comparison with the results of some of the more modern computational methods based on thermodynamic analysis of the processes in the engine cylinder. However, the theoretical approach by Hohenberg to the given problem through the equations he set, gives a pretty good idea of the most influential factors on the size of the angle of thermodynamic losses, but it has a lot of mistakes and rough approximations. This work is dedicated to the good and bad sides of this very important literature source through a comparison with one of the modern thermodynamic methods related to the issue of determining the angle of thermodynamic losses

Influence of disturbances in the process of fuel injection on the working processes in the cylinder diesel engine

Neujednačenost radnih procesa u cilindrima dizel-motora se može desiti iz više razloga. Dva najuticajnija faktora na ovu pojavu, a koji se odnose na poremećaje u procesu ubrizgavanja goriva, su: poremećaji u pogledu trenutnog položaja (ugla obrtanja) kolenastog vratila kada započinje ubrizgavanje goriva u nekom od cilindara, tzv. ugao predubrizgavanja, i poremećaji u količini goriva koja se isporučuje pojedinim cilindrima tokom jednog radnog ciklusa, tzv. ciklusna količina goriva. Navedeni poremećaji su daleko izraženiji kod klasičnih, mehaničkih sistema za ubrizgavanje goriva (pumpa visokog pritiska, pumpa-brizgač, itd.), i vrlo često se ne mogu preduprediti pri vanmotorskim ispitivanjima i podešavanjima sistema ubrizgavanja goriva. Simulacija opisanih poremaćaja u realnim uslovima rada dizel-motora, i proširivanje saznanja o njihovom pojedinačnom i zajedničkom uticaju na radne procese u cilindrima, nije nimalo jednostavna. Međutim, danas postoje komercijalni programi koji imaju ugrađene module zasnovane na proverenim jednačinama termodinamike, teorije sagorevanja i teorije strujanja, koje omogućavaju da se ova simulacija izvrši primenom računara. Jedan od takvih programa je program BOOST AVL. Rezultati simulacija dobijeni primenom ovog i sličnih programa mogu biti i pouzdaniji od simulacija u realnim uslovima rada motora, pošto je kod mehaničkih sistema ubrizgavanja goriva, vrlo teško kvantifikovati stepen poremećaja koji se želi simulirati. Dobijeni rezultati mogu biti iskorišćeni za razvijanje metoda identifikacije uticaja opisanih poremećaja na srednji indikatorski pritisak svakog cilindra, pa i celog motora, tačniju procenu mehaničkih gubitaka (stepena mehaničke korisnosti), itd.Unevenness of working processes in diesel engine cylinders can happen for several reasons. The two most influential factors to this phenomenon, which are related to disturbances in the fuel injection process are: disturbances in terms of the current position (rotation angle) of the crankshaft when the fuel injection in one of the cylinders starts, so-called pre-injection angle, and disturbances in the quantity of fuel that is supplied to individual cylinders during one work cycle, the so-called cycle amounts of fuel. These disturbances are more prominent in classical, mechanical fuel injection systems (high-pressure pump, pump-injector, etc.), and very often can not be prevented during the out engine testing and the fuel injection system adjustments. The simulation of disturbances described under real operating conditions of diesel engines, and expanding the knowledge of their individual and joined impact on the working processes in cylinders, is not at all simple. However, today there are commercial software which have built-in modules based on the proven equations of thermodynamics, combustion theory and the theory of flow, which makes it possible to carry out these simulations by using a computer. One such software is AVL BOOST. The simulation results obtained using this and similar software can be more reliable than simulations in real conditions of the engine, because in the mechanical fuel injection system it is very difficult to quantify the degree of the disturbance which is to be simulated. The given results can be used to develop methods of identifying the impact of described disturbances on the mean indicated pressure of each cylinder, as well as the entire engine, a more accurate assessment of mechanical losses (degree of mechanical utility), etc

Practical research of the angle of thermodynamic losses when indicating pressure in the cylinder diesel engine

Vrlo važan literaturni izvor pri proučavanju radnih procesa u cilindrima motora, decenijama unazad, predstavlja članak Güntera Hohenberga 'Definition und Eigenschaften des termodinamischen Verlust-winkels von Kolbenmaschinen', objavljen 1976. godine u časopisu Automobil industrie, izdanje 4. Ovim člankom je teoretski i praktično (eksperimentalno) obrađena tema određivanja ugla termodinamičkih gubitaka na krivoj pritiska bez sagorevanja izmerenoj u cilindru motora. Posebna vrednost Hohenbergovih istraživanja je u eksperimentalnim rezultatima dobijenim osrednjavanjem izmerenih podataka na većem broju različitih motora. Pokazalo se da su ti eksperimentalni rezultati i te kako upotrebljivi za brzo, ali dosta tačno, određivanje ugla termodinamičkih gubitaka na krivoj pritiska bez sagorevanja,kod bilo kog motora. Dijagrami koje je predložio Hohenberg su od koristi i danas, bilo da se primenjuju direktno ili služe za poređenje sa rezultatima neke od savremenijih računskih metoda zasnovanih na termodinamičkoj analizi procesa u cilindru motora. Međutim, teoretski prilaz Hohenberga datom problemu kroz jednačine koje je postavio, daje dosta dobru predstavu o najuticajnijim faktorima na veličinu ugla termodinamičkih gubitaka, ali u sebi ima i dosta grešaka i grubih aproksimacija. Dobrim i lošim stranama ovog vrlo važnog literaturnog izvora kroz poređenje sa jednom od savremenih termodinamičkih metoda vezanim za problematiku određivanja ugla termodinamičkih gubitaka, posvećen je ovaj rad.Very important literary source for the study of work processes in the engine cylinders, for decades, has been an article by Günter Hohenberg 'Definition und Eigenschaften des termodinamischen Verlust-winkels von Kolbenmaschinen', published in 1976 in the magazine Automobil Industrie, Edition 4. This article theoretically and practically (experimentally) deals with the topic of determining the angle of thermodynamic losses on the pressure curve without combustion measured in the engine cylinder. The special value of this research is in the experimental results obtained by averaging the measured data on a large number of different engines. It has been shown that these experimental results are useful for a quick, but quite accurate, determining of the angle of thermodynamic losses on the pressure curve without combustion, with any engine. Diagrams proposed by Hohenberg are used today, whether they are applied directly or used for comparison with the results of some of the more modern computational methods based on thermodynamic analysis of the processes in the engine cylinder. However, the theoretical approach by Hohenberg to the given problem through the equations he set, gives a pretty good idea of the most influential factors on the size of the angle of thermodynamic losses, but it has a lot of mistakes and rough approximations. This work is dedicated to the good and bad sides of this very important literature source through a comparison with one of the modern thermodynamic methods related to the issue of determining the angle of thermodynamic losses

Measurement of maintenance excellence

U održavanju je potrebno imati kvalificirane i obučene zaposlenike kako za uporabu suvremene opreme za održavanje, za defektažu i izvođenje radova održavanja tako i za primjenu suvremenih zahtijeva organizacije i menadžmenta. Zbog toga je potrebno redizajnirati procese održavanja na širi način od "klasičnog", koje se bazira na terotehnološkom konceptu. Uređenje održavanja treba se ostvarivati na istim suvremenim principima na kojima se zasniva postizanje poslovne izvrsnosti sustava u cjelini. To ujedno uključuje i poslovnu filozofiju koju čine procesni pristup projektiranja i rada, integrirani sustav menadžmenta baziran na primjeni određenih standarda (kvaliteta, životna sredina, sigurnost na radu i dr.) i elementima poslovne izvrsnosti. Izvrsnost održavanja predstavlja okvir za izazovan kritički osvrt na cjelovitost i produktivnost svakog poslovnog procesa ili projekta. Kroz izvrsnost održavanja, organizacija nastoji osigurati visoku kvalitetu procesa koji podržava kontinuirani napredak u funkciji održavanja i usmjerava se na različita područja kao što su strategije, zaposleni, informacije, rad i ostali poslovni aspekti održavanja.It is necessary for maintenance to have qualified and trained staff, capable of using modern equipment for maintenance, defect inspection and maintenance work, able of applying modern requirements of organization and management. Therefore, it is necessary to redesign the maintenance processes in a more extensive way than the classical, which is based on the terotechnological concept. Maintenance organization should be achieved at the same modern principles as the business excellence system of a company as a whole. This also includes a business philosophy that consists of the process approach to the design and operations of a company, an integrated management system based on the application of certain standards (quality, environment, safety at work, etc.) and elements of business excellence of a company. Maintenance excellence is a framework for a challenging and critical review of the integrity and productivity of any business process or project. Through maintenance excellence, any company seeks to provide a high quality process that supports continuous improvement focusing on various areas such as strategy, employees, information, work and other business aspects of maintenance

Bucket-wheel excavator gearbox failure analysis and reliability assessment

This paper presents the analysis of failure causes and reliability assessment executed for the gearbox of the bucket-wheel excavator SRs 470.20/3 “TAKRAF” (produced by “Lauhhammer”, Germany), which is engaged in overburden excavation at the surface mine ’Kostolac’ (in Serbia). In order to determine during which phase the error was made (during the design process, production or exploitation), failure analyses and assessments of reliability have been performed for gearbox elements through the use of Pareto analysis, FTA - Fault Tree Analysis, reliability allocation and failure intensity. For the calculation of reliability allocation and failure intensity an adequate program package was developed. Through the use of the above mentioned procedures data necessary for the identification of most important elements for the analysis regarding the maintenance process and failure prevention measures have been collected

Repair of shaft and ventilation ring vanes damages of the generator of the hydroelectric generating set at the hydro power plant

Hydro power plant ’Pirot’, which was built in 1990, is an accumulation-derivative power plant, which consists of 2 above-ground vertical hydroelectric generating sets that contain Francis turbines with nominal power of 41,5 MW, manufactured in Czech Republic, a tunnel and a sunken pipeline with overall length of 2.030 m and diameter that ranges from 3.000 to 3.500 mm. Pipeline, made of 22 mm thick pipes, has been designed and built without anchor blocks at curvatures, which is a rarity elsewhere. Maximum pressure of 2.5 MPa occurs in front of the turbine cover. This paper contains the analysis of the state of the generator shaft on which the mechanical damages were detected, as well as the analysis of the state of vanes of the upper and lower ventilation ring designed for air cooling of the generator rotor where corrosion, erosion and, most of all, cavitation damages were detected, based on results of nondestructive testing (visual testing, penetrant testing, ultrasonic testing). Procedures for the rehabilitation of damaged components without disassembling them were defined. The execution of these procedures helped in saving approximately 100.000 €. Taking into account the period of time necessary to perform complete disassembling of components, as well as the period of time needed to perform reassembling, which is directly linked with the amount of energy the hydroelectric generating set A2 would produce during that period, the overall save would mount up to approximately 500.000 €

THE FREQUENCY OF USING SCREEN-BASED MEDIA AMONG CHILDREN AND ADOLESCENTS AND ITS IMPACT ON HEALTH-RELATED BEHAVIORS

Screen-based media are becoming an increasingly important part of life for today’s children and adolescents. That is why our purpose was to review the literature published within the past 10 years regarding the use and impact of TV, video game, and computer /Internet on youth health outcomes including how they affect their psychosocial outcomes and physical well-being. Systematic literature search for and analysis of a variety of media used by children and adolescents from a public health perspective was done. Literature was reviewed from May to July 2014. Children and adolescents spend a great deal of time using screen-based media. This high overall electronic media use was associated with poorer behavior and health status. A large part of this younger generation’s social and emotional development is occurring while on the Internet and on cell phones. Screen-based media use was mutually associated, and the plural use of these media had stronger associations with unhealthy lifestyles and subjective health complaints. Various physical complaints, like obesity, backache and headache, neck-shoulder pain, and sleep disorders were also found significant. Children and adolescents are consumers, but also they are producers of social media. Public health professionals and society as a whole should increase health education on screen-based media consumption, by stimulating reasonable use and teaching youth to be critical. Parents can be most helpful if they understand the core issues and have strategies for dealing with them