شبيه سازي عددي توليد و انتشار اكسيد نيتروژن ﴿NO﴾ با استفاده از شبكه بدون سازمان

چكيده انگليسي :

Numerical simulation of NO formation emission using unstructured mesh Farid Khaleghi f khaleghi@aut ac ir Isfahan university of Technology October2009Degree M Sc language FarsiSupervisor Dr Mohsen Davazdah Emami mohsen@cc iut ac irAbstractAll combustion processes lead to formation of the unwanted nitrogen oxides NOx NOxrepresent a family of seven compounds NO N2O2 NO2 N2O4 N2O N2O3 and N2O5 These species are among the most important air pollutants During the last decades manyefforts have been performed to reduce the formation and emission of these species Unfortunately all the available measures to alleviate the formation and emission of NOxinhibit the combustion efficiency Among all of the above mentioned oxides of Nitrogen NO contributes about 95 of the cumulative Nitrogen oxides Therefore accurateestimation of nitrogen oxide in combustion phenomena is an important factor in designingthe combustion chambers The purpose of this study is to address this issue It starts with acomprehensive survey on different physical mechanisms of formation and emission ofNOx including thermal NO prompt NO intermediate NO2 fuel NO and reburn NO Then the effect of different parameters such as temperature residence time the size and designof furnace combustion chamber pressure mixture and mass transport on the formation andemission of nitrogen oxides is assessed Different techniques for the reduction of nitrogenoxide formation emission that comprises of pollution prevention methods Less Excess Air LEA Burners Out Of Service BOOS Over Fire Air OFA Low NOx Burner LNB Flue Gas Recirculation FGR air staging fuel staging use of oxygen instead of air forcombustion injection of water or stream and reduction of preheated air and add ontechnologies Selective Non Catalytic reduction SNCR Selective Catalytic reduction SCR adsorption and absorption is introduced Next a complete study on themathematical models of the thermal NO and prompt NO mechanisms is done and differentproposed formulas for calculating NO sources due to these mechanisms is presented Theeffect of the turbulence on the NOx formation emission mechanisms is examined anddifferent ways for including turbulence chemistry interaction using assumed ProbabilityDensity Function PDF containing Equilibrium Model EQM Steady Laminar FlameletModel SLFM and Unsteady Laminar Flamelet Model ULFM is explained Then thecombustion problem for three Non premixed diffusion flame containing CO CH4 and H2flames is solved using fluent code and the results are compared with experimental data Finally a post processing code is developed to solve the transport equation of NO Thiscode is written in C and is able to handle unstructured mesh The code uses fluentcombustion results including mass fractions temperature mixture fraction variancemixture fraction and scalar dissipation rate to calculate NO mass fraction The turbulence chemistry interaction is taken into account via steady laminar flamelet model and severalsub models for calculating NO sources is presented The validity of NO models andcorrectness of the program have been assessed by simulating aforementioned diffusionflames and comparing the results with available experimental data The results are givenboth by considering turbulence chemistry interaction and without it It is concluded thatthe turbulence chemistry interaction has a profound effect on the accuracy of predictions

خالقي، فريد

شبيه سازي عددي توليد و انتشار اكسيد نيتروژن ﴿NO﴾ با استفاده از شبكه بدون سازمان

روش فليملت آرام پايدار , اندر كنش شيمي- توربولانس