Numerical modelling of combustion process of different generations of biofuels produced from plant-derived waste

U svrhu redukcije emisije ugljikovog dioksida, biogoriva se nameću kao alternativa konvencionalnim gorivima u transportnom sektoru. Biodizel je tip biogoriva dobiven iz otpada biljnog podrijetla. Radi zatvorenog ciklusa ugljikova dioksida, pokazala su pozitivan utjecaj na ukupne emisije ugljikova dioksida te imaju visoku korisnost oporabe otpada. Jedna od važnih prednosti biodizelskih goriva jest mogućnost miješanja s konvencionalnim dizelskim gorivom te njegova primjena u motorima s unutarnjim izgaranjem. Takve mješavine mogu se primjenjivati u motorima s unutarnjim izgaranjem uz minimalnu ili skoro nikakvu modifikaciju motora. Računalna dinamika fluida u kombinaciji s kemijskom kinetikom često se primjenjuje za analizu novih goriva, uključujući i biodizel. U ovom radu bit će dan kratki pregled i klasifikacija biogoriva, opisane fundamentalne jednadžbe računalne dinamike fluida te jednadžbe modeliranja izgaranje pomoću kemijskog mehanizma. Također, provedene su numeričke simulacije izgaranja nekoliko generacija biodizela unutar softvera za računalnu dinamiku fluida AVL-FIRE™. Simulacije su validirane usporedbom dobivenih podataka za izgaranje n-heptana, surogata dizelskog goriva, s eksperimentalnim podacima dobivenih od strane AVL GmbH Graz. Analizirana su četiri tipa biodizela dobivena iz sirovina različitog biljnog podrijetla. Gorivo je analizirano u četiri radne točke te u različitim udjelima mješavine dizelskog goriva i biodizela.In order to meet the reduction of carbon dioxide emissions, biofuels are imposed as an alternative to conventional fuels in the transport sector. Biofuel made from plant-derived waste, called biodiesel, has shown to positively impact total carbon dioxide emissions and have a positive environmental impact on waste recovery. One of the great advantages of biodiesel is its applicability in standard internal combustion engines when blended with conventional fuels. Such mixtures require very little or almost any additional modifications to the engines. Computational fluid dynamics combined with chemical kinetics is often employed to investigate combustion and auto-ignition properties of new fuels, including biofuels. This thesis will present a brief overview and generation classification of biofuels, describe the fundamental equations of computational fluid dynamics and the equations of modelling chemical kinetics using the chemical mechanism of fuel combustion. Additionally, numerical simulations of the combustion process of different generations of biodiesel were performed in the computational fluid dynamics software AVL-FIRE™. Simulations were verified by comparing the obtained simulation data for n-heptane, a substitute for diesel fuel, to experimental data provided by AVL GmbH Graz. Biodiesels made from four different plant-derived feedstocks were compared under four operating conditions in various diesel-biodiesel blends