Influence of fuel properties on engine characteristics and tribology parameters

U radu se razmatra korištenje mineralnog dizelskog goriva, čistog biodizelskog goriva, te njegovih mješavina i utjecaj svojstava goriva na značajke motora s ciljem smanjenja štetnih emisija. Za eksperimente je korišten autobusni dizelov motor, te čisto biodizelsko gorivo proizvedeno iz repičina ulja i nekoliko njegovih mješavina s mineralnim dizelskim gorivom. Gustoća, viskoznost, površinska napetost i brzina zvuka ispitivanih goriva određivane su eksperimentalno i vrijednosti su uspoređivane s istima od mineralnog dizelskog goriva. Dobivene rezultate smo upotrijebili za analizu najvažnijih značajki motora i triboloških parametara.This paper deals with the mineral diesel, neat biodiesel and their blends and it discusses the influence of fuel properties on the engine characteristics with the aim to reduce harmful emissions. The considered engine is a bus diesel engine. The considered fuels are neat biodiesel from rapeseed oil and some of its blends with mineral diesel. The density, viscosity, surface tension, and sound velocity of tested fuels are determined experimentally and compared to those of mineral diesel. The obtained results are used to analyze the most important engine characteristics and tribology parameters

INFLUENCE OF VARIOUS MESH TYPES ON CAVITATION PHENOMENA IN THE INJECTION NOZZLE

Isparivost dizelskog goriva u otvoru mlaznice u velikoj mjeri utječe na značajke ubrizgavanja i formiranja mlaza. U radu se analizira utjecaj različitih tipova mreže na procese kavitacije. Budućid da je CPU (Centralna Procesorska Jedinica) vremena često dugačka, u analizi su korišteni parcijalni modeli. Numeričku analizu izvodili smo za dvije vrste tekućina, dizel (D2) i biodizel (B100), koristeći računski program FIRE za dinamiku fluida (CFD). Rezultati su uspoređivani za razne tipove mreže za obje vrste goriva i pokazuju da veće razlike u tlaku uzrokuju veću kavitaciju u otvoru sapnice brizgaljke te ističu važnost strukture i gustoće mreže.The evaporation of diesel fuel in the injection nozzle influences the injection characteristics and spray formation process significantly. In the presented paper the influence of various type of mesh on the cavitation phenomena is analysed. Since CPU (central processing unit) times are often high, partial models are used for the analysis. The numerical analysis is made for two types of fluid, diesel (D2) and biodiesel (B100), using computation fluid dynamic (CFD) program FIRE. The results are compared for various meshes and both types of fuel. The results show that higher pressure differences yield more cavitation in the injector nozzle holes and point out the importance of the structure of the mesh and its density

The Influence Of Biofuel Mixtures on Flow Phenomena in Diesel Engine Injectors

Vbrizgavanje curka goriva spada na področje dvofaznih tokov, ki obravnava karakteristike curka goriva v odvisnosti od fizikalnih lastnosti, s poudarkom na vbrizgavanju različnih goriv, pod različnimi delovnimi pogoji. Poleg ocene kvalitete tvorbe zmesi je raziskovanje karakteristik curka goriva pomembno tudi za oceno izkoriščenosti zraka v zgorevalni komori in zaradi morebitnega nezaželenega stika goriva s stenami zgorevalne komore. Obstoječi fizikalno-matematični modeli lahko v splošnem relativno natančno popišejo razmere dvofaznega toka. V samih podmodelih so prisotne empirične konstante (vplivni parametri), s pomočjo katerih se uravnavajo karakteristike vbrizganega curka in ki so v osnovi odvisne od lastnosti samega vbrizgalnega sistema, predvsem od geometrije vbrizgalne šobe. V okviru naloge bo vpeljan model, ki bo omogočal obravnavanje karakteristik različnih biogoriv, razmer v šobi in posledice vpliva karakteristik na razvoj, obliko in strukturo curka, kjer bo omogočeno natančnejše analiziranje dvofaznih tokov. Model bo zajemal prenosne enačbe za številsko gostoto parnih mehurčkov, z upoštevanjem fizikalnih procesov nastajanja in izginjanja posameznih mehurčkov, pri različnih oblikah kavitacijskih tokov, hkrati pa bo omogočal še raziskavo vpliva med kapljicami goriva ter obravnavo sil trka z vpeljavo velikostne porazdelitve kapljic goriva. Naloga je razdeljena na eksperimentalni in numerični del. V eksperimentalnem delu so določene in analizirane fizikalne lastnosti uporabljenih goriv, karakteristike procesa vbrizgavanja, s pomočjo hitre kamere pa je bil posnet razvoj curka goriva. V numeričnem delu je prikazan osnovni poenostavljeni fizikalno-matematični model. V disertaciji je pokazano, da je mogoče s spremembo fizikalno-matematičnega modela, ob upoštevanju fizikalnih lastnosti goriva, delovnega režima in karakteristik procesa vbrizgavanja, določiti konstante, ki pri izračunu uravnavajo karakteristike curka goriva. S pomočjo ustreznih izrazov je tako mogoče izraziti empirične vrednosti parametrov in vnaprej napovedati probleme, ki bi se lahko pojavili v dizelskih motorjih z uporabo biogoriv.Fuel spray investigations belong to the field of the two-phase flows witch presents the study of physical fuel property dependent spray characteristics. The research will be focused on different type of fuels under different operating conditions. The investigation of spray development as contributing factor in mixture formation is also very important for the study of processes in internal combustion engine. Existing physical-mathematical model for two phase flows generally gives good results. Several empirical constants are present in sub models and they have significant influence on spray development. They are usually depended on injection system and the geometry of injection nozzle. The improvement of physical-mathematical model including the most influential factors with in the momentum equation for spray development, will enable efficient analysis of spray characteristics of alternative fuels. The model will also include the equations for bubble density and the equation for cavitation occurrence. The parts of equation representing the spray development, formation of bubbles and cavitation will be modelled with the adaptation of knowledge of other authors, where the modified model will be able to predict the spray development more accurately. The work contains both experimental and numerical part. Physical properties of the fuels, characteristics of the fuel injection process and high-speed recordings are described and analysed in the experimental part. The simplified physical-mathematical models is presented in the numerical part. The dissertation shows, that the improvement of standard mathematical model for spray development considering the physical fuel properties, the operating conditions and the injection characteristics enables determination of empirical constants. Additionally the physical-mathematical model can be included. By using of appropriate expressions, the empirical parameters values can be determined and enable predictions of potential problems which could appear in diesel engines during operation with biofuels

Selective glucose oxidation to glucaric acid using bimetallic catalysts : lattice expansion or electronic structure effect

Our study presents a comprehensive approach for the selective oxidation of glucose to glucaric acid (GA) by heterogeneous catalysis. We have synthesized and characterized Au/ZrO2, AuCu/ZrO2 and AuPt/ZrO2 catalysts using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and oxygen pulse chemisorption (OPS) techniques. Combining experimental observations with in-depth density functional theory (DFT) studies, we found that bimetallic catalysts form alloys, which exhibit different characteristics than monometallic counterparts for the given reaction. We performed batch reactions, varying temperature and oxygen pressure, and used the data to construct a predictive microkinetic model. As it turned out, AuPt/ZrO2 showed the highest selectivity, yielding 32 % of GA at 100 °C and 30 barg O2. Our results provide valuable insights for the developing of efficient catalysts and point out the bottlenecks for the oxidation of glucose to GA

Genome-wide association analyses identify new risk variants and the genetic architecture of amyotrophic lateral sclerosis.

To elucidate the genetic architecture of amyotrophic lateral sclerosis (ALS) and find associated loci, we assembled a custom imputation reference panel from whole-genome-sequenced patients with ALS and matched controls (n = 1,861). Through imputation and mixed-model association analysis in 12,577 cases and 23,475 controls, combined with 2,579 cases and 2,767 controls in an independent replication cohort, we fine-mapped a new risk locus on chromosome 21 and identified C21orf2 as a gene associated with ALS risk. In addition, we identified MOBP and SCFD1 as new associated risk loci. We established evidence of ALS being a complex genetic trait with a polygenic architecture. Furthermore, we estimated the SNP-based heritability at 8.5%, with a distinct and important role for low-frequency variants (frequency 1-10%). This study motivates the interrogation of larger samples with full genome coverage to identify rare causal variants that underpin ALS risk

Genome-wide association analyses identify new risk variants and the genetic architecture of amyotrophic lateral sclerosis

To elucidate the genetic architecture of amyotrophic lateral sclerosis (ALS) and find associated loci, we assembled a custom imputation reference panel from whole-genome-sequenced patients with ALS and matched controls (n = 1,861). Through imputation and mixed-model association analysis in 12,577 cases and 23,475 controls, combined with 2,579 cases and 2,767 controls in an independent replication cohort, we fine-mapped a new risk locus on chromosome 21 and identified C21orf2 as a gene associated with ALS risk. In addition, we identified MOBP and SCFD1 as new associated risk loci. We established evidence of ALS being a complex genetic trait with a polygenic architecture. Furthermore, we estimated the SNP-based heritability at 8.5%, with a distinct and important role for low-frequency variants (frequency 1–10%). This study motivates the interrogation of larger samples with full genome coverage to identify rare causal variants that underpin ALS risk