EXPERIMENTAL AND NUMERICAL ANALYSIS OF REACTIVE AND FLOW QUANTITIES ON DUAL FUEL BURNER

Optimizacija zgorevalnih naprav v smislu povečanja učinkovitosti in zmanjšanja obremenitve okolja s polutanti, je danes glavno vodilo pri raziskavi ter snovanju novih projektov povezanih z zgorevanjem. To je mogoče doseči s pomočjo točnih zasnov pomembnih komponent gorilnika ter kurišča, kar dodatno zajema pojave prenosa mase in toplote. V zadnjih nekaj letih je računalniška dinamika tekočin (CFD) postala popularna metoda za uporaben pristop k pridobivanju preliminarnih informacij in napovedovanju obnašanja komercialnih zgorevalnih zasnov. Vendar so pojavi, ki potekajo v gorilnikih zelo kompleksnirecirkulacija dimnih plinov, prenos energije, turbulentna kemijska kinetika in razmerje toka-kemijskih reakcij so v primeru vrtinčnih zgorevalnih naprav še ojačeni. Z omenjenega vidika je CFD analiza vrtinčnih ne-predmešanih reaktivnih tokov ena najpomembnejših in zahtevnih področij v moderni CFD. Za primerjavo so dokumentirani eksperimentalni podatki, ki predstavljajo uporabno informacijo za kontrolo in testiranje CFD. Za popis dinamike tekočin skupaj s prenosom toplote, je v literature mogoče najti različne matematične pristope. Glavni pristop uporablja turbulentne modele zgorevanja kar omogoča uporabo statističnih lastnosti skalarnega polja. Ti pristopi omogočajo v večini primerov podrobne informacije o tokovnem polju ter temperaturi vendar so pri napovedovanju koncentracij nižjih vrst manj natančni. Za kotlovske naprave je bila že predlagana nova metoda (Faravelli et al., 2001). Ta pristop (SFIRN) temelji na originalni zasnovi hibridne metode. Tokovna ter temperaturna polja niso pod vplivom nastanka NOx. Za opis nastanka toplote v CFD modeliranju je dovolj manjše število hitrih kemijskih reakcij. Spisek oziroma skupina idealnih reaktantov je definirana na osnovi rezultatov pridobljenih z numerično simulacijo. Ti reaktanti skupaj predstavljajo število enakih celic in se rešujejo s pomočjo zelo podrobne kemijske kinetike. Podrobne eksperimentalne meritve 1SF gorilnika predstavljajo pomemben testni primer z namenom potrditve numeričnega postopka, kar je mogoče kasneje razširiti na kompleksnejše primere. Realno kurilno napravo smo preučevali z uporabo računalniške dinamike tekočinpodrobneje s programskim paketom ANSYS CFX. V nalogi smo uporabili eksperimentalno dognane robne pogoje vhodnih parametrov ter nekaj parametrov drugih avtorjev. Za numerične simulacije so bili uporabljeni turbulentni modeli, modeli zgorevanja ter sevanja. Nadalje smo primerjali rezultate različnih izbranih modelov z eksperimentalnimi ter ugotavljali primernost le teh. Cilj modeliranja je bila izbira primernih modelov za uporabo numeričnega preizkušanja novih industrijskih gorilnikov, kar smo v primerjavi z eksperimentom okarakterizirali s tokovnim in temperaturnim poljem, hkrati pa z lokalno stopnjo izgorelosti (CO). Rezultati numeričnega modeliranja so bili povsod primerjani z eksperimentalnimi meritvami. Prikazan znanstveni pristop omogoča CFD analizo tokovnih lastnosti kot tudi reaktivnega toka že v fazi načrtovanja novih zasnov gorilnikov kar omogoča hitrejši in bolj zanesljiv razvoj novega izdelka.The optimization of combustion systems in terms of efficiency and reduction of pollutants is considered the main aim of combustion research projects. This result can be achieved through an accurate design of the significant burner parts and/or combustion chamber which also takes heat and mass transfer phenomena into account. In the last few years, computational fluid dynamics (CFD) has become popular and represents a useful approach for providing preliminary information and predicting economical combustion systems design. However the phenomena occurring in burners are highly complex with hot flue gas recirculation, energy exchanges and strong turbulence-chemistry and flow-reaction rate effects which are enhanced still further in the case of swirled combustors. For this reason, CFD analysis of swirling confined non-premixed reacting flows is one of the most important and challenging areas of modern CFD. The experimental data are well documented and they represent useful information for CFD testing. For describing the fluid dynamics and heat transfer in the case of combustion devices, different mathematical approaches can be found in the literature. The main approach uses turbulent combustion models, which enables use of the statistical properties of the scalar field. These approaches are capable of detailed information on flow and temperature fields in many cases, but their prediction of the concentration of the minor species is less accurate. A new way of dealing with this problem has already been proposed for boilers (Faravelli et al., 2001). This approach (SFIRN) is based on the original concept of the hybrid method. Flow and temperature fields are not influenced by the NOx chemistry. A few very rapid combustion reactions suffice to describe the heat generation in CFD computations. A network of ideal reactants is defined on the basis of the results obtained by the fluid dynamic simulation. These reactants, group together number of equivalent cells and are solved by taking a very detailed chemistry into consideration. The detailed experimental measurements of the 1SF burner represent a significant test-case in order to validate the capability of the procedure, which can be then more reliably extended to complex boilers. We studied practical combustion device wit help of Computational Fluid Dynamicsin detail with software package ANSYS CFX. As part of this work we used experimentally acquired boundary conditions and additionally some boundary conditions from other authors. As for numerical simulations, we used turbulent and combustion models as well as radiation model. Further we have compared results of different models used with our experimental analysis with goal of their suitability. Goal of the numerical modeling was the right choice of suitable models for practical numerical simulation of new industrial burnersthat was characterized with use of flow and temperature fields as well as local burnout rate (CO). The numerical results are always compared with experimental. As shown, science approach allows CFD analysis of flow properties as well as reactive already in design phase, what makes research and development of a new product quicker and reliable