DIESEL AND BIODIESEL MACRO-SPRAY CHARACTERISTICS

Sažetak Karakteristike ubrizgavanja i formiranja mlaza u prostoru izgaranja jedan su od najvažnijih čimbenika modernih dizelovih motora i imaju značajan utjecaj na efektivne parametre i emisije ispuha. U posljednjih nekoliko desetljeća, biodizelu se kao motornom gorivu sve više posvećuje posebna pažnja. Unatoč tome što ima slične fizičke osobine kao dizelsko gorivo, svejedno veća gustoća, viskoznost i površinski napon mogu ponekad prouzročiti anomalije u procesu ubrizgavanja, kao što su npr. dodir mlaza sa stijenkama komore izgaranja, loše miješanje sa zrakom (prevelike kapljice) i drugo. U radu su prikazani rezultati istraživanja fizičkih svojstava dizelskog i biodizelskog goriva glede karakteristika ubrizgavanja i mlaza goriva. Utjecaj fizičkih osobina goriva proučavan je uz pomoć fizičko-matematičkog modela, simuliranjem procesa ubrizgavanja u konvencionalnom sustavu. Model je bio razvijen na IEPOI - Inštitut za energetiko, procesno in okoljsko inženirstvo Fakulteta za strojništvo, Univerza v Mariboru, koda Bkin, provjeren eksperimentalno na uređaju i na motoru. U posebnom smo uređaju izmjerili makro karakteristike mlaza (domet, kut, oblik), dok je vremensko prodiranje mlaza u mirujući zrak praćeno visokobrzinskom kamerom (2500 snimaka/s). Uz pomoć 3D programa (AVL "Fire"), dopunjena za ova istraživanja na IEPOI, mogli smo pratiti procese u motoru i odrediti ostale parametre mlaza (promjer kapljice i njihovu distribuciju u aksijalnom prosjeku) u ovisnosti o vremenu i odrediti njihove integralne prosječne vrijednosti i usporediti ih s vrijednostima dobivenih eksperimentom. U radu su prikazani rezultati utjecaja fizičkih osobina goriva i radnih uvjeta na karakteristike ubrizgavanja i mlaza goriva.Abstract Characteristics of fuel injection and spray formation in the engine combustion chamber are most important factor of up-to-date diesel engines, influencing their effective performance parameters and exhaust emissions. During last few decades alternative automotive fuels, such as biodiesel have received salient attention. Even though it has similar physical properties as diesel fuel, higher density, viscosity and surface tension of biodiesel may have a dominant influence on the spray formation and sometimes cause spray anomalies - such as contact between fuel and combustion chamber, poor mixing with air (bigger fuel droplets) etc. Results of the investigation about the impact of the diesel and biodiesel fuel physical properties on the injection and spray characteristics are presented in the paper. Physical properties of both have been examined and used in the mathematical model of the conventional injection system. The model was derived in IEPO - Institute for Power, Process and Environmental Engineering Faculty of mechanical engineering, University Maribor, simulation code Bkin, and was verified by experiment carried out on the fuel injection system test bench and on the engine. In a special test chamber the macro-characteristics of the spray injected into motionless air at the atmospheric pressure and room temperature (spray penetration distance, angle, and spray shape) have been measured and spray images were recorded by the high-speed camera (2500 frames/s). Using 3D simulation program (AVL "Fire") and including for the purpose of these investigations a few new estimates, the injection process for both fuels have been simulated and compared with the results obtained by experiments. These results are presented and discussed in the paper

Intake system design procedure for engines with special requirements

Intake manifolds provide fresh air to internal combustion engines and have a major effect on their performance. Therefore, many investigations are related to their design in order to improve the charging efficiency and to achieve theuniform distribution of fresh air among the engine cylinders. This paper deals with the design procedure of a cheap multipoint injection intake system,adapted to a racing car engine. Some special demands had to be taken into consideration. The intake manifold must contain the imposed constraint for the airflow in the shape of a single circular restrictor placed between the throttle and the engine to limit its power. The flow and the pressure lossreduction in the engine intake region were investigated with computationalfluid dynamics software. Two different geometries of the intake manifold were taken into consideration. On the basis of the numerically obtained three-dimensional results, a mathematical model of the engine with a more appropriate intake was made in the engine simulation code in order to anticipate its characteristics. The intake system was designed, practically manufactured, and tested in the laboratory. The experimental results confirmednumerical predictions, justifying the simple and relatively quick design procedure for the intake system

Diesel and biodiesel fuel spray simulations

This paper deals with the investigation of the influential parameters of a mathematical spray breakup model using different fuels. Beside injection system measurements, fuel physical properties and injection process characteristics were measured, because they are necessary for the spray simulation input. For validation purposes, spray was injected into motionless air at atmospheric pressure and room temperature and filmed with a high-speed camera. Spray macrocharacteristics have been determined on the recorded images. Using the simulation program, the injection processes for diesel, biodiesel, and their 50% blend B50 have been simulated. Spray mathematical model parameters were tuned based on the experimentally gained results. Primary breakup model parameters showed the biggest impact on the spray characteristics and were therefore expressed using the fuel physical properties, the injection process characteristics, and the working regime parameters. Spray simulations into the combustion chamber were made in the end. All of these results are presented and discussed in this paper

Developing a racing car

V prispevku sta prikazani dve moznosti izboljšanja lastnosti dirkalnika Formula S. Eden najskladnejsih načinov za dvig moči motorja je spretno oblikovan dovod zraka v motor. Zato je v prvem delu prispevka predstavljen postopek optimalnega oblikovanja sesalnega sistema. Postopek optimiranja temelji na uporabi metod matematičnega programiranja in pomeni učinkovit način za povečanje moči motorja v najbolj zanimivem področju obratovanja motorja. V drugem delu prispevka je pozornost posvečena novim zamislim izdelave celotnega dirkalnika. Za dosego vrhunskih rezultatov je treba narediti več, kakor le slediti konkurenci. Analiza postavitev glavnih agregatov je pokazala, da bi k večji okretnosti in stabilnosti dirkalnika pripomoglo to, da bi bil motor postavljen ob voznikovi strani. Optimiran sesalni sistem pomeni zanesljiv korak naprej v borbi za povečanje dejanske moči dirkalnika, kar je lahko uporabno takoj. Zasnova z bočno postavitvijo motorja pa predstavlja povsem novo pot razvoja dirkalnikov Formula S, kar bo morda prineslo dolgoročne prednosti.This article presents two approaches for improving a Formula S racing car. Oneof the best ways to increase the enginećs power is to skillfully design theair- supply system of the engine. This is the reason why the first part of the paper is about the intake-manifold optimization procedure. The procedure relies on mathematical programming and offers a way to significantly increase the engine power in the most important engine regimes. In the second part of the paper, attention is focused on new concepts of building the racing car. Inorder to be the best it is necessary to do more than symply follow the competion. An analysis of the positions of the main components has shown that a racing car would be more agile and stable if the engine was to be mounted beside the driver. Optimizing the intake manifold represents one significant step forward in the struggle to increase the effective power of the car, whichbrings an immediate advantage. The new position concept, however, which also eliminates the differential drive, represents a completely new development in the design of the Formula S car that might bring us long-term benefits

A de novo variant in OTX2 in a lamb with otocephaly

Background:Otocephaly is a rare lethal malformation of the first branchial arch. While the knowledge on the causes of otocephaly in animals is limited, different syndromic forms in man are associated with variants of the PRRX1 and OT X2 genes.Case presentation:A stillborn male lamb of the Istrian Pramenka sheep breed showed several congenital crani-ofacial anomalies including microstomia, agnathia, aglossia, and synotia. In addition, the lamb had a cleft palate, a small opening in the ventral neck region, a cystic oesophagus and two hepatic cysts. The brain was normally developed despite the deformed shape of the head. Taken together the findings led to a diagnosis of otocephaly. Whole-genome sequencing was performed from DNA of the affected lamb and both parents revealing a heterozy-gous single nucleotide variant in the OT X2 gene (Chr7: 71478714G > A). The variant was absent in both parents and therefore due to a de novo mutation event. It was a nonsense variant, XM_015097088.2:c.265C > Twhich leads to an early premature stop codon and is predicted to truncate more than 70% of the OT X2 open reading frame (p.Arg89*).Conclusions:The genetic findings were consistent with the diagnosis of the otocephaly and provide strong evi-dence that the identified loss-of-function variant is pathogenic due to OT X2 haploinsufficiency. The benefits of trio-based whole-genome sequencing as an emerging tool in veterinary pathology to confirm diagnosis are highlighted