Heat transfer and thermo-mechanical behavior of the domestic heater atmospheric burner

Rad izlaže realizovanu 3D CFD simulaciju faze paljenja gasnog gorionika sa ciljem određivanja maksimalne temperaturske razlike koja u njemu izaziva maksimalne termičke napone. Proces je nestacionaran. Simulacije je realizovana za minimalnu snagu jer je taj slučaj kritičan.This paper presents performed 3D CFD simulation of burner start-up and finding the maximal temperature difference through mantle thickness which induces maximal thermal stress. The process is unsteady, beginning from the mantle room temperature and ending with its steady state condition. The behavior of burner is simulated for minimal thermal power, i.e., for critical conditions from the mantle temperature standpoint

Influence of combustion instabilities on the heater appliance with atmospheric gas burner and their elimination by cross flow of air

This paper presents results of experimental investigation on elimination of combustion oscillations caused by new low pollution burner which was integrated in a gas heater. The method is known as a passive method, based on introducing the air in the combustion chamber. Since efficiency of the passive method is highly dependent of the way the air is injected, several different methods were investigated and compared. The paper also presents effects on pollution characteristics during its operation in the unstable regime

Influence of combustion instabilities on the heater appliance with atmospheric gas burner and their elimination by cross flow of air

This paper presents results of experimental investigation on elimination of combustion oscillations caused by new low pollution burner which was integrated in a gas heater. The method is known as a passive method, based on introducing the air in the combustion chamber. Since efficiency of the passive method is highly dependent of the way the air is injected, several different methods were investigated and compared. The paper also presents effects on pollution characteristics during its operation in the unstable regime

Increasing the speed of computational fluid dynamics procedure for minimization the nitrogen oxide polution from the premixed atmospheric gas burner

This article presents innovative method for increasing the speed of procedure which includes complex computational fluid dynamic calculations for finding the distance between flame openings of atmospheric gas burner that lead to minimal NO pollution. The method is based on standard features included in commercial computational fluid dynamic software and shortens computer working time roughly seven times in this particular case

Two-dimensional numerical analysis of active flow control by steady blowing along foil suction side by different urans turbulence models

The effects of active separation control by steady blowing jets were investigated numerically on three different examples: subsonic flow past Aerospatiale A airfoil at 13 degrees angle-of-attack, transonic flow past NACA 0012 airfoil at 4 degrees angle-of attack, and transonic flow in linear compressor/turbine cascade. Performed analyses are two-dimensional, flow is turbulent (or transitional) while fluid is viscous and compressible. Jets are positioned along the suction sides of the foils, the first one being located just upstream of the separation point, and modeled by source terms added to flow equations. Several different jet diameters and intensities are investigated. As the choice of turbulence model affects the final solution of Reynolds equations, turbulence is modeled by four different models: Spalart-Allmaras, realizable k-epsilon, k-omega SST, and gamma-Re-theta, and a comparison of obtained results is performed. Goals of the study include definition of an adequate numerical setting that enables sufficiently correct simulation of the problems in question as well as evaluation of the possible increase in aerodynamic performances. Lift coefficients, lift-to-drag ratios or relative pressure differences are improved for all controlled cases

Influence of selected turbulence model on the optimization of a class-shape transformation parameterized airfoil

An airfoil was parameterized using the class-shape transformation technique and then optimized via genetic algorithm. The aerodynamic characteristics of the airfoil were obtained with the use of a CFD software. The automated numerical technique was validated using available experimental data and then the optimization procedure was repeated for few different turbulence models. The obtained optimized airfoils were then compared in order to gain some insight on the influence of the different turbulence models on the optimization result

Computational analysis of helicopter main rotor blades in ground effect

Numerička analiza izolovanog, reprezentativnog glavnog rotora helikoptera izvršena je u komercijalnom softverskom paketu ANSYS FLUENT 16.2. Generalno, strujna slika oko rotora je nestacionarna, trodimenzionalna, složena i vrtložna. Takve simulacije zahtevaju značajne proračunske resurse. Uticaj zemlje, koji poboljšava aerodinamičke performanse rotora, predstavlja dodatni izazov pri numeričkom modeliranju. U ovom radu strujno polje je izračunato Navije-Stoksovim jednačinama osrednjenim Rejnoldsovom statistikom (RANS). Rotaciono kretanje uzeto je u obzir primenom dva različita pristupa: 'Frame of reference' i 'Sliding mesh'. Izvršeno je poređenje dobijenih rezultata sa vrednostima jednostavnijih modela kao što su model zasnovan na zakonima održanja (MT) i kombinovani model segmenta lopatice (BEMT). Rezultati su predstavljenu u obliku kontura pritiska, brzine i vrtložnosti kao i vrednostima aerodinamičkih koeficijenata..Numerical investigation of an isolated representative helicopter main rotor has been performed in ANSYS FLUENT 16.2. In general, flow field around the rotor is unsteady, three-dimensional, complex and vortical. Such a simulation requires substantial computational resources. Ground effect, which improves the aerodynamic performances of the rotor, represents an additional challenge to numerical modeling. In this study, flow field is computed by Unsteady Reynolds Averaged Navier- Stokes (URANS) equations. Both Frame of reference and Sliding mesh approaches were employed to model the rotor rotation. Obtained results are compared to results obtained by simpler, sufficiently reliable models such as Momentum Theory (MT) and Blade Element Momentum Theory (BEMT). Presented results include fluid flow visualizations in the form of pressure, velocity and vorticity contours and the values of aerodynamic coefficients

Potentials for usage of significantly reduced chemical mechanisms in numerical modeling of combustion processes

Rezultati numeričkih modeliranja prezentovani u ovom radu, deo su istraživanja laboratorije za sagorevanje Mašinskog fakulteta u Beogradu, sprovedenog u okviru FP6 projekta 'FlexHEAT', koji su zajedno realizovale institucije iz šest evropskih zemalja a koji je finansiran od strane Evropske unije (www.flexheat.uni-erlangen.de). U radu su prezentovani uporedni rezultati numeričkih proračuna kojima se simulira sagorevanje goriva na bazi metana (prirodni gas, srpski gas, biogas i sl), a koji su dobijeni korišćenjem eksperimentalno proverenog, kompletnog hemijskog mehanizma GRI 3.0 koji čini 325 hemijskih reakcija i odgovarajućeg veoma redukovanog hemijskog mehanizama, koga čine 2 hemijske reakcije (od kojih je jedna povratna) razvijenog na bazi dvostepenog C.K. Westbrook & F.L. Dryer (WD) modela. Rezultati su dobijeni upotrebom programskog paketa 'ChemKin' i determinišu oblast i mogućnost primene ovako značajno redukovanih hemijskih mehanizama u CFD proračunima, u situacijama kada kompleksnost samog strujanja sa hemijskim reakcijama kroz složene geometrije gorionika i peći ne dozvoljava upotrebu složenijih hemijskih mehanizama.The paper presents comparison of the results obtained in numerical research conducted, with the aim to simulate combustion of methane-based fuels like natural gas, Serbian gas, biogas, etc. Presented results were obtained using experimentally verified, full chemical mechanism GRI 3.0, with 325 chemical reactions, and using selected, very reduced chemical mechanism, with only two chemical reactions, based on two-step C.K. Westbrook & F.L. Dryer (WD) model. 'ChemKin' software was used for all numerical simulations of chemical kinetics and 'Fluent' for CFD analysis. The goal was to determine possibilities and application fields of this very reduced chemical mechanism in CFD calculations, especially in cases when flows with chemical reactions through complex geometry of burners and furnaces, disable usage of full mechanisms

Potentials for usage of significantly reduced chemical mechanisms in numerical modeling of combustion processes

Rezultati numeričkih modeliranja prezentovani u ovom radu, deo su istraživanja laboratorije za sagorevanje Mašinskog fakulteta u Beogradu, sprovedenog u okviru FP6 projekta 'FlexHEAT', koji su zajedno realizovale institucije iz šest evropskih zemalja a koji je finansiran od strane Evropske unije (www.flexheat.uni-erlangen.de). U radu su prezentovani uporedni rezultati numeričkih proračuna kojima se simulira sagorevanje goriva na bazi metana (prirodni gas, srpski gas, biogas i sl), a koji su dobijeni korišćenjem eksperimentalno proverenog, kompletnog hemijskog mehanizma GRI 3.0 koji čini 325 hemijskih reakcija i odgovarajućeg veoma redukovanog hemijskog mehanizama, koga čine 2 hemijske reakcije (od kojih je jedna povratna) razvijenog na bazi dvostepenog C.K. Westbrook & F.L. Dryer (WD) modela. Rezultati su dobijeni upotrebom programskog paketa 'ChemKin' i determinišu oblast i mogućnost primene ovako značajno redukovanih hemijskih mehanizama u CFD proračunima, u situacijama kada kompleksnost samog strujanja sa hemijskim reakcijama kroz složene geometrije gorionika i peći ne dozvoljava upotrebu složenijih hemijskih mehanizama.The paper presents comparison of the results obtained in numerical research conducted, with the aim to simulate combustion of methane-based fuels like natural gas, Serbian gas, biogas, etc. Presented results were obtained using experimentally verified, full chemical mechanism GRI 3.0, with 325 chemical reactions, and using selected, very reduced chemical mechanism, with only two chemical reactions, based on two-step C.K. Westbrook & F.L. Dryer (WD) model. 'ChemKin' software was used for all numerical simulations of chemical kinetics and 'Fluent' for CFD analysis. The goal was to determine possibilities and application fields of this very reduced chemical mechanism in CFD calculations, especially in cases when flows with chemical reactions through complex geometry of burners and furnaces, disable usage of full mechanisms

Numerical analysis of lean premixed combustor fueled by propane-hydrogen mixture

A numerical investigation of combustion of propane-hydrogen mixture in a swirl premixed micro gas turbine combustor is presented. The effects of hydrogen addition into propane on temperature distribution in the combustor, reaction rates of propane and hydrogen and NO, emissions for different equivalence ratios and swirl numbers are given. The propane-hydrogen mixture of 90/10% by volume was assumed. The numerical results and measurements of NO emissions for pure propane are compared. Excellent agreements are found for all equivalence ratios and swirl numbers, except for the highest swirl number (1.13). It is found that the addition of hydrogen into propane increases NO, emission. On the other hand, the increase of swirl number and the decrease of equivalence ratio decrease the NO, emissions