IMPACT OF OIL VISCOSITY ON FUNCTIONAL PARAMETERS OF JOURNAL BEARINGS IN INTERNAL COMBUSTION ENGINES

Klizni ležajevi na radilici motora s unutarnjim izgaranjem, a posebno na letećim rukavcima, jako su opterećeni elementi. Zbog toga je za njihovo pravilno funkcioniranje potrebno pažljivo definirati radne uvjete, gdje je kvaliteta ulja jedan od vrlo bitnih čimbenika. S aspekta rada kliznih ležajeva bitno je osigurati minimalnu promjenu vizkoziteta ulja u širokom radnom području motora. Izbor ulja s gledišta fizikalnih osobina, u prvom redu odgovarajućeg viskoznosti, ima važno mjesto u području smanjenja gubitaka kod kliznih ležajeva, odnosno povećanju učinkovitosti motora. U radu je obrađen utjecaj viskoznosti ulja za podmazivanje na radne uvjete kod letećeg rukavca jednog dizelovog motora s predtlačenjem namijenjenog za ugradnju u vozila. Analizirani su parametri: temperatura ulja u ležaju, promjena maksimalne vrijednosti srednjeg tlaka u ulju, minimalni nosivi sloj ulja i udio mješovitog trenja, a sve u funkciji viskoznosti ulja na ulazu u ležaj, pri različitim zazorima sklopa ležaj – rukavac. Prikazani rezultati su dobiveni korištenjem modela i vlastito razvijenih računskih programa za simulaciju uvjeta rada kliznih ležajeva uz eksperimentalnu potvrdu korištenog modela.The IC engine crnakshaft bearings, especially at the crankpin journals, are very loaded elements. For their proper functioning it is necessary to define carefully the working conditions, where the quality of oil is one of the most important factors. From the aspect of the working conditions of journal bearings it is important to ensure a minimum change in oil viscosity in a wide IC engine operating range. Selection of lubricating oil from the standpoint of physical characteristics, primarily the appropriate viscosity, has an important place in the area of reducing friction losses in journal bearings and increasing IC engine efficiency. This paper deals with the impact of lubricating oil viscosity on the working conditions of vehicle turbocharged diesel engine crankpin journals. Analyzed parameters are: an oil temperature in the bearing, a change of the maximum value of the average pressure in the oil, the minimum carrying oil layer and the share of mixed friction, all in the function of oil viscosity at the bearing inlet, with different clearances between bearing and crankpin journal. Results were obtained using the model and own developed software to simulate the working conditions of journal bearings with an experimental verification

PRELIMINARY SELECTION OF BASIC PARAMETERS OF DIFFERENT TORSIONAL VIBRATION DAMPERS INTENDED FOR USE IN MEDIUM-SPEED DIESEL ENGINES

In the development and application of highly dynamic mechanical systems, major problems can arise from usually unwanted accompanying processes, such as torsional vibrations. The internal combustion engine is a typical dynamic system with a high probability of fracture of a system part due to the effects of torsional vibrations. In engineering practice, the IC engine crankshaft fracture due to torsional vibrations is prevented by using additional devices that allow the transfer of critical vibration modes of the crankshaft out of the IC engine operating range, or devices damping the resulting twist angle amplitudes. This paper presents a possible approach to defining parameters of torsional oscillatory systems of IC engines needed for a preliminary selection of basic parameters of various types of torsional vibration dampers, such as the elastic damper, the balance weight damper and the dual mass flywheel. The proposed physical and mathematical models and methods of defining the input parameters were compared with experimental results

INFLUENCE OF INJECTOR ON CHARACTERISTICS OF FUEL DISPERSION IN DIESEL ENGINE

Proces izgaranja goriva u motorima s unutarnjim izgaranjem (SUI) najviše ovisi o pripravi gorive smjese i uvjetima u kojima se odvija miješanje. Proces miješanja goriva i zraka može se analizirati preko unesene energije gorivom i zrakom, u odnosu na potrebnu energiju za racionalno formiranje smjese gorivo-zrak. Za kvalitetu smjese gorivo-zrak, kod dizelskog motora, presudnu ulogu ima energija unesena gorivom, odnosno karakteristike raspršivanja goriva. Ove karakteristike se izražavaju uglavnom dometom mlaza, kutom širenja mlaza goriva i fizikalnom i kemijskom strukturom mlaza goriva po različitim presjecima. Fizikalna struktura mlaza goriva najčešće se izražava preko srednjeg Sauterovog promjera kapljica. Pristupi za izračunavanje ovih parametara su: -modeliranje i izračunavanje nekom od numeričkih metoda sa 2D ili 3D modelom, ovisno o okolnim uvjetima, ili -različiti poluempirijski izrazi za proračun nabrojanih parametara. Svaki pristup izračunavanju karakteristika mlaza goriva zahtijeva poznavanje tzv. „graničnih i početnih" uvjeta, koji su definirani izlazom goriva kroz mlaznicu brizgaljke. Na primjeru dometa mlaza goriva, u radu će se objasniti dosadašnji način uzimanja graničnih uvjeta na brizgaljke, uloga same brizgaljke na konkretnom primjeru, te novi pristup definiranju graničnih uvjeta.The combustion process in the IC engines predominantly depends on the air/fuel mixture preparation and conditions for its preparation. The process of air and fuel mixing can be analyzed through energy introduced with air and fuel in relation with necessary energy for rational formation of air/fuel mixture. The main role for the quality of the air/fuel mixture in diesel engines has energy introduced by the fuel, i.e. the characteristics of fuel injection process. These characteristics are mostly represented by: jet length, cone jet angle, physical and chemical structure of jet on different cross sections. The physical jet structure is generally described by average Sauter diameter of droplets. The approaches to calculate these parameters are as follows: - modeling and calculating by a numerical method in order to solve 2D and 3D models, depending on the ambient conditions, - using different semi-empirical models for calculatons of mentioned parameters. Each approach the fuel jet characteristics calculations requires knowledge of so-called “boundary and initial” conditions, which are defined by the exit of fuel flow from nozzle orifice. In this paper using an example of jet fuel length it will be explained the current way of taking the boundary conditions at the nozzle, the role of injector itself in this specific case, as well as a new approach in defining the boundary conditions

INFLUENCE OF ALTERNATIVE FUELS ON COMBUSTION INDICATORS WITH DIESEL ENGINES

Sažetak Svakodnevno smanjivanje prirodnih rezervi goriva fosilnog porijekla, kao i neprestani porast troškova njihove eksploatacije uvjetuje sve intenzivnija istraživanja o mogućim alternativnim izvorima energije koji bi s jedne strane smanjili ovisnost o uvozu skupe sirove nafte i njezinih proizvoda, a ujedno doprinijeli smanjenju emisije toksičnih tvari koje se oslobađaju njezinim izgaranjem. Kao rezultat takvog razmišljanja većina razvijenih industrijskih zemalja u Europi nastoji ispuniti prijedlog Europskog parlamenta i Vijeća za promicanje uporabe biogoriva, u kojem se predlaže postupna zamjena benzina i dizelskog goriva u iznosu od 5,75 % od njihovih ukupno prodanih količina s biogorivima, mjereno po njihovom energetskom sadržaju, do 2010. godine. U okviru ovog rada razmatrana je uporaba biogoriva u dizelovim motorima s unutarnjim izgaranjem namijenjenih za pogon motornih vozila i strojeva. Akcent je stavljen na proces izgaranja tzv. biodizel goriva, kao potpune zamjene klasičnom dizelskom gorivu, te njegovih mješavina s njim, gdje vrlo važnu ulogu ima početak, karakter oslobađanja topline i vrijeme trajanja procesa izgaranja. Prikazani su rezultati proračuna relevantnih parametara procesa izgaranja tako dobivenih goriva, kao i njihova usporedba s odgovarajućim parametrima izgaranja dizelskog goriva fosilnog porijekla. Rezultati provedenih proračuna su verificirani namjenskim ispitivanjima na konkretnom dizelovom motoru.Abstract Constant lowering of natural reserves of fossil fuels as well as continuous increasing of its exploitation costs influences more intensive researching in finding alternative energy recourses that are able to decrease an import dependent of expensive raw oil and its products from one side and give contribution to decreasing toxic emission as a product of combustion process. As result of this consideration majority of developed European countries endeavor to fulfill proposals of the European parliament and the Council for promotion bio fuels to substitute petroleum and diesel fuels with bio fuels in proportion of 5.75% of their total sold amount, measured by its energy content, by the year 2010. In the paper usage of bio fuels in IC diesel engines for mobile applications is considered. Accent is given on combustion processes of so called biodiesel fuel, as a full alternative for classical diesel fuel, as well as their blends, where important role has beginning, character of heat release and duration of combustion process. Calculation results of relevant combustion parameters for the used fuels and comparison with appropriate parameters of combustion processes with fossil origin based diesel fuel are presented. Verification of the calculation results where carried out through tests made on one diesel engine

INFLUENCE OF INJECTOR ON CHARACTERISTICS OF FUEL DISPERSION IN DIESEL ENGINE

Proces izgaranja goriva u motorima s unutarnjim izgaranjem (SUI) najviše ovisi o pripravi gorive smjese i uvjetima u kojima se odvija miješanje. Proces miješanja goriva i zraka može se analizirati preko unesene energije gorivom i zrakom, u odnosu na potrebnu energiju za racionalno formiranje smjese gorivo-zrak. Za kvalitetu smjese gorivo-zrak, kod dizelskog motora, presudnu ulogu ima energija unesena gorivom, odnosno karakteristike raspršivanja goriva. Ove karakteristike se izražavaju uglavnom dometom mlaza, kutom širenja mlaza goriva i fizikalnom i kemijskom strukturom mlaza goriva po različitim presjecima. Fizikalna struktura mlaza goriva najčešće se izražava preko srednjeg Sauterovog promjera kapljica. Pristupi za izračunavanje ovih parametara su: -modeliranje i izračunavanje nekom od numeričkih metoda sa 2D ili 3D modelom, ovisno o okolnim uvjetima, ili -različiti poluempirijski izrazi za proračun nabrojanih parametara. Svaki pristup izračunavanju karakteristika mlaza goriva zahtijeva poznavanje tzv. „graničnih i početnih" uvjeta, koji su definirani izlazom goriva kroz mlaznicu brizgaljke. Na primjeru dometa mlaza goriva, u radu će se objasniti dosadašnji način uzimanja graničnih uvjeta na brizgaljke, uloga same brizgaljke na konkretnom primjeru, te novi pristup definiranju graničnih uvjeta.The combustion process in the IC engines predominantly depends on the air/fuel mixture preparation and conditions for its preparation. The process of air and fuel mixing can be analyzed through energy introduced with air and fuel in relation with necessary energy for rational formation of air/fuel mixture. The main role for the quality of the air/fuel mixture in diesel engines has energy introduced by the fuel, i.e. the characteristics of fuel injection process. These characteristics are mostly represented by: jet length, cone jet angle, physical and chemical structure of jet on different cross sections. The physical jet structure is generally described by average Sauter diameter of droplets. The approaches to calculate these parameters are as follows: - modeling and calculating by a numerical method in order to solve 2D and 3D models, depending on the ambient conditions, - using different semi-empirical models for calculatons of mentioned parameters. Each approach the fuel jet characteristics calculations requires knowledge of so-called “boundary and initial” conditions, which are defined by the exit of fuel flow from nozzle orifice. In this paper using an example of jet fuel length it will be explained the current way of taking the boundary conditions at the nozzle, the role of injector itself in this specific case, as well as a new approach in defining the boundary conditions

Heat release characteristic in internal combustion engines with M-type fuel injection procedure

Opisivanje procesa izgaranja u motoru s unutarnjim izgaranjem (sui) obično se vrši putem takozvanih parametara izgaranja, kao što su: maksimalni tlak izgaranja, maksimalna temperatura ciklusa, kut početka izgaranja, kutni interval trajanja izgaranja, karakteristika oslobađanja topline, prirast ukupne količine razvijene topline, kutni interval pritajenog izgaranja, prijenos topline i slično. Zbog složenosti procesa izgaranja u motoru sui do danas još uvijek ne postoje modeli koji bi na efikasan i prije svega pouzdan način omogućili predviđanje karakteristike oslobađanja topline za vrlo široku paletu različitih tipova motora sui. Ciljano se istražuju fenomenološki, empirijski i CFD modeli za konkretne konstruktivne osobitosti motora i primijenjenog goriva. U okviru ovog rada predstavljen je način određivanja karakteristike oslobađanja topline putem aproksimativnih funkcija izgaranja na primjeru vrlo specifičnog načina pripreme smjese goriva i zraka, u dizelovom motoru sui, tzv. M-postupak ubrizgavanja goriva. Validacija primijenjenih aproksimativnih funkcija izvršena je preko eksperimentalnih rezultata ispitivanja na konkretnom motoru sui.The description of the combustion process in internal combustion engines is typically performed through so-called combustion parameters, such as: the maximum combustion pressure, maximum temperature of the cycle, crankshaft angle of the start of combustion, the angular interval of duration of combustion, the heat release characteristics, thee increment of the total amount of heat developed, the angular interval of combustion delay, the heat transfer etc. Due to the complexity of the combustion process in internal combustion engines to this day there are still no models that could efficiently and above all in a reliable way predict the heat release characteristics for a wide range of different types of IC engines. Phenomenological, empirical and CFD models for specific constructive characters of the engine and fuel applied are targeted explored. The paper presents a procedure for determining the heat release characteristics through approximate functions of combustion, using the example of a very specific way of preparing a mixture of fuel and air in the diesel engine, so-called M-procedure. The applied approximate function is validated through experimental test results on a specific IC engine

IMPROVEMENT OF ECOLOGICAL PERFORMANCE OF DIESEL ENGINES BY USING MIXTURES OF CONVENTIONAL FOSSIL FUELS AND BIODIESEL

Uporaba goriva iz obnovljivih izvora energije nije više stvar opredjeljenja pojedinaca da na lokalnoj razini osobnim primjerom doprinesu smanjenju emisije zagađujućih tvari iz ispuha cestovnih vozila, već sveobuhvatna strategija i temelj unapređenja i razvoja globalnog energetskog sektora i ciljani doprinos smanjenju zagađenja okoliša. Kako bi se podcrtao značaj takvih opredjeljenja, u okviru međunarodnih sporazuma jasno se navode ciljevi koji se žele postići u budućnosti. Međutim, pri postavljanju ciljeva u pogledu povećanja obujma korištenja biodizela, treba voditi računa o dostupnosti takvog goriva i o mogućnosti njegove primjene u postojećem voznom parku. Budući da su izvori sirovine i tehnologije za dobivanje biodizela još uvijek na takvoj razini da ne mogu pokriti potrebe cjelokupnog tržišta, a i vozni park je prvenstveno prilagođen za korištenje konvencionalnog fosilnog goriva, prijelazno rješenje je upravo korištenje mješavine ova dva goriva. U okviru ovog rada razmatrana je uporaba mješavine konvencionalnog fosilnog dizel goriva i biodizela u dizelovim motorima s unutarnjim izgaranjem (SUI) namijenjenih za putna vozila. Analizirani su trendovi promjene energetskih (snaga, moment, specifična potrošnja goriva) i ekoloških (emisija zagađujućih tvari) performansi dizelovih motora u ovisnosti o postotnom udjelu biodizela u mješavini goriva.The use of fuels from renewable energy sources is no longer a matter of individual commitment to reduce emissions contributing to air pollution from exhausts of road vehicles, but a matter of comprehensive strategy to improve the foundation and development of the global energy sector, and to provide a targeted contribution to the reduction of environmental pollution. Underlying the importance of this determination, the framework of international agreements clearly states certain objectives to be achieved in the future. However, when setting targets for increasing the scope of use of biodiesel, it is important to take into account the availability of such fuel, as well as the possibilities of its application in the existing vehicle fleet. Given the fact that sources of raw feedstock and the technology for obtaining biodiesel are still at the level that cannot cover the needs of the entire market, coupled with the fact that the existing vehicle fleet is primarily suited for the use of conventional fossil fuels, using a mixture of these two fuels can be an interim solution. This paper considers the use of fuel blends of conventional fossil diesel fuel and bio diesel in diesel-powered internal combustion engines designed for on-road applications. It analyzes the trends of energy performance (power; torque; specific fuel consumption) and environmental properties of diesel engines (emissions of polluting substances), depending on the percentage of bio diesel in fuel blends

INFLUENCE OF FUEL PROPERTIES ON ENERGY TRANSFORMATION IN FUEL INJECTION SYSTEM AT DIESEL ENGINES

Uporaba alternativnih goriva za pogon cestovnih vozila postaje sve rasprostranjenija u svim vidovima transporta od javnog prijevoza putnika, taksi vozila, do lakih dostavnih vozila namijenjenih za kretanje u urbanim sredinama. Pri tome se mora reći da najveću primjenu imaju ona alternativna goriva koja ne zahtijevaju konstrukcijske izmjene na motorima (posebno dizelovim motorima). Međutim, pri tome se mora voditi računa o izlaznim karakteristikama sustava za ubrizgavanje pri uporabi različitih goriva. Karakteristike ubrizgavanja (tlak i brzina goriva na izlazu iz otvora brizgaljke) kod dizelovih motora, zavise od karakterističnih parametara sustava ubrizgavanja i osobina goriva. Najvažniji karakteristični parametri sustava ubrizgavanja su obujam u sustavu ubrizgavanja, rastojanje između mjesta potiskivanja i mjesta ubrizgavanja goriva, mase pokretnih dijelova u sustavu ubrizgavanja, protočni presjeci u sustavu ubrizgavanja i karakteristike refleksije valova tlaka i brzine. Da bi se poboljšale karakteristike ubrizgavanja najveća pažnja se poklanja minimiziranju obujma u sustavu ubrizgavanja, posebno u brizgaljci. Na ovaj način dolazi do bržeg porasta tlaka (dp/dt), manjeg generiranja reflektiranih valova tlaka goriva i kvalitetnijih karakteristika ubrizgavanja, posebno na niskim režimima opterećenja (male količine ubrizganog goriva). S druge strane, smanjenje volumena u sustavu ubrizgavanja ima posljedicu smanjenja dimenzija (posebno protočnih kanala). Ovim se direktno utječe na transformaciju potencijalne energije goriva (izražene u vidu tlaka goriva) u kinetičku energiju goriva (izraženu u vidu brzine toka goriva). Svaka promjena potencijalne u kinetičku energiju u sustavu ubrizgavanja ima posljedicu porasta hidrauličkih gubitaka i pogoršanja karakteristika ubrizgavanja goriva. U kontekstu prethodno iznesenih činjenica, u radu je prikazana detaljna analiza transformacije potencijalne energije u kinetičku energiju goriva u slučaju uporabe različitih vrsti goriva (dizelsko gorivo, biodizelsko gorivo). Posebna pozornost će se posvetiti brizgaljci, gdje se odvija najveća transformacija energije, čega je posljedica i stvaranje najvećih gubitaka u sustavu ubrizgavanja.Use of the alternative fuels for propulsion of motor vehicles becomes widespread in all types of transport, from public transportation, taxi vehicles up to light duty vehicles intended for use in urban areas. The greatest application of alternative fuels is achieved in case of the minor reconstruction of engine construction (especially in case of diesel engine). However, a special attention should be dedicated to the characteristics of the fuel injection system in case of use of different fuels. The injection characteristics (fuel pressure and velocity at the exit from injector orifice) at diesel engines depend on characteristics of the fuel injection systems and fuel properties. The most important characteristics of the fuel injection system are the following: volumes in the fuel injection system, lengths between locations from fuel pushing to injection, mass of moving parts in the fuel injection system, cross section of fuel flows in the fuel injection system and characteristics of reflection of pressure and velocity waves. In order to improve the injection characteristics, the greatest attention is paid to minimize the volumes of the fuel injection system, especially in the injector. On this way, rapid increasing in pressure gradient (dp/dt), smaller generating reflected pressure waves of fuel and better characteristics were obtained, especially at low load regimes (at small amounts of injected fuel). On the other hand, reducing the volumes in the injection system has the effect of reducing the dimensions (especially the flow channels). This directly affects on the transformation of potential energy (fuel pressure) into kinetic energy (velocity of fuel flow). Any change from potential to kinetic energy in the fuel injection system results an increasing of hydraulic losses and deterioration of the fuel injection characteristics. In the context of the above mentioned facts, the paper presents a detailed analysis of the transformation from potential to kinetic energy of the fuel in the case of the usage of different types of fuel (diesel fuel, biodiesel fuel). A special attention will be dedicated to the injector, where the biggest energy transformation and energy losses in the fuel injection system are occurred

THE APPLICATION OF ALTERNATIVE FUELS FOR THE PURPOSE OF REDUCING ROAD VEHICLES’ POLLUTANT EMISSION

Sažetak Jedan od najutjecajnijih činilaca u procesu onečišćenja čovjekovog okoliša je cestovni prijevoz, tj. emisija zagađivača u ispušnim plinovima kod vozila. Posebno izražen problem visokih koncentracija zagađivača od cestovnih vozila je u urbanim sredinama gdje je prisutna velika koncentracija vozila, s vrlo različitim režimima vožnje. Na emisije zagađivača od vozila najveći utjecaj imaju: - tehničko-tehnološka rješenja koja se koriste na motorima s unutarnjim izgaranjem, što je direktno povezano s godinom proizvodnje motora i vozila, - tip motora, - vrsta i kvaliteta goriva, - koncentracija i prohodnost vozila u pojedinim zonama, - uvjeti (režimi) vožnje i drugo. U cilju dobivanja slike o utjecaju cestovnih vozila na emisiju zagađivača u radu je napravljena analiza emisije zagađivača na primjeru urbane sredine sa cca 100000 registriranih vozila, gdje je oko 60 % vozila s dizelovim motorom, te dosta nepovoljne starosne strukture. Dobiveni rezultati su uspoređeni sa sličnim rezultatima u zemljama Zapadne Europe. U radu je dat i prikaz suvremenih tehničkih dostignuća koja se koriste na vozilima koja koriste konvencionalna goriva u cilju zadovoljavanja europskih regulativa o emisiji zagađivača. Posebno su obrađena alternativna goriva, s naglaskom na ona goriva koja se danas uglavnom koriste. Prikazana su tehnička rješenja uporabe prirodnog plina, kao perspektivnog alternativnog goriva i njegov utjecaj na emisiju zagađivača.Abstract One of the most influential factors in the process of environmental pollution is road transport, i.e. emission of gaseous pollutants from road vehicles. An especially pronounced problem is the air pollution in urban areas, with a high concentration of road vehicles having very different driving regimes. The largest influence on pollutants emission of road vehicles is that of: - Technical and technological solutions used in internal combustion engines, which is directly connected with the given vehicle\u27s particular year of production, - Engine type, - Fuel type and quality, - Vehicles concentration and use in certain areas, - Driving regimes, etc. For the purpose of getting a complete image of influences of road vehicles on pollutants emission, we have analyzed pollutants emission in an urban area with 100,000 registered vehicles, 60 % of which had diesel engines, with quite unfavorable age structure. The results have been compared with similar results in the Western European countries. Also, a review of modern technical accomplishments used in conventionally fueled vehicles for satisfying the European environmental legislation has been done in this paper. A special attention has been paid to alternative fuels, with the emphasis on the presently used fuels. Technical solution for the utilization of natural gas, as a very promising alternative fuel, and its influence on pollutants emission, has also been presented

IMPACT OF PHYSICAL PROPERTIES OF DIESEL AND BIODIESEL MIXTURE ON CHARACTERISTICS OF FUEL SPRAYING

Uporaba alternativnih goriva u motorima s unutarnjim izgaranjem postaje sve atraktivnija, sa stajališta štednje energije, smanjenja emisije reguliranih zagađivača u ispušnim plinovima te smanjenja emisije CO2 u okoliš. Kod dizelovih motora, od alternativnih goriva, najviše se radi na uporabi biodizelskog goriva i njegovih mješavina s dizelskim gorivom. Također, nije zanemariva ni uporaba mješavina tekućih i plinovitih goriva (D2 i CNG). Uporaba biodizelskog goriva i njegovih mješavina s dizelskim gorivom u motorima, zbog različitih fizikalnih i kemijskih osobina, ima značajan utjecaj na procese u motoru, od pripreme smjese zrak-gorivo do procesa izgaranja (različito vrijeme pritajenog izgaranja, različita brzina oslobađanja topline, itd.). Za optimalan rad motora, u prvom redu procesa izgaranja, potrebno je poznavati sve utjecajne parametre, koji su posljedica uporabe novog goriva. U ovom radu je napravljena detaljna analiza utjecaja fizikalnih osobina biodizela i njegovih mješavina s dizelskim gorivom, na karakteristike mlaza raspršenog goriva koji ima dominantan utjecaj na proces miješanja goriva i zraka. Rezutati prikazani u ovom radu su kombinacija eksperimentalnih i računskih rezultata, dobivenih pomoću vlastito razvijenog računarskog programa.The use of alternative fuels in internal combustion engines is becoming increasingly attractive, both from the standpoint of energy saving as well as the reduction of emissions of regulated pollutants in the exhaust gases and the reduction of CO2 emissions into the environment. Regarding alternative fuels in diesel engines, most of the work is based on the use of biodiesel and their blends with diesel fuel. Also, the use of a mixture of liquid and gaseous fuels (D2 and CNG) is not negligible. The use of biodiesel and their blends with diesel fuel in the engines, due to variety of physical and chemical properties, has a significant influence on the processes in the engine, from the preparation of the air-fuel mixture to the combustion process (different combustion time, different heat release rate, etc.). For optimum engine performance, but primarily the combustion process, it is necessary to know all influential parameters, which are the result of the use of the new fuel. This paper presents a detailed analysis of the impact of physical properties of biodiesel and their blends with diesel fuel, on the characteristics of the atomized fuel spray which has a dominant influence on the mixing of fuel and air. The results presented in this paper are combination of experimental and computational results, obtained using a self developed computer program