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CFD study of non-premixed swirling burners: Effect of turbulence models 被引量:1
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作者 Erfan Khodabandeh Hesam Moghadasi +4 位作者 Mohsen Saffari Pour Mikael Ersson Par G.Jonsson Marc A.Rosen Alireza Rahbari 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2020年第4期1029-1038,共10页
This research investigates a numerical simulation of swirling turbulent non-premixed combustion.The effects on the combustion characteristics are examined with three turbulence models:namely as the Reynolds stress mod... This research investigates a numerical simulation of swirling turbulent non-premixed combustion.The effects on the combustion characteristics are examined with three turbulence models:namely as the Reynolds stress model,spectral turbulence analysis and Re-Normalization Group.In addition,the P-1 and discrete ordinate(DO)models are used to simulate the radiative heat transfer in this model.The governing equations associated with the required boundary conditions are solved using the numerical model.The accuracy of this model is validated with the published experimental data and the comparison elucidates that there is a reasonable agreement between the obtained values from this model and the corresponding experimental quantities.Among different models proposed in this research,the Reynolds stress model with the Probability Density Function(PDF)approach is more accurate(nearly up to 50%)than other turbulent models for a swirling flow field.Regarding the effect of radiative heat transfer model,it is observed that the discrete ordinate model is more precise than the P-1 model in anticipating the experimental behavior.This model is able to simulate the subcritical nature of the isothermal flow as well as the size and shape of the internal recirculation induced by the swirl due to combustion. 展开更多
关键词 Computational Fluid Dynamics(CFD) Turbulent combustion non-premixed flames Large eddy simulations Radiative heat transfer model Modeling validation
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Combining flamelet-generated manifold and machine learning models in simulation of a non-premixed diffusion flame
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作者 Kaimeng Li Pourya Rahnama +1 位作者 Ricardo Novella Bart Somers 《Energy and AI》 2023年第4期173-188,共16页
Flamelet Generated Manifold(FGM)is an example of a chemistry tabulation or a flamelet method that is under attention because of its accuracy and speed in predicting combustion characteristics.However,the main problem ... Flamelet Generated Manifold(FGM)is an example of a chemistry tabulation or a flamelet method that is under attention because of its accuracy and speed in predicting combustion characteristics.However,the main problem in applying the model is a large amount of memory required.One way to solve this problem is to apply machine learning(ML)to replace the stored tabulated data.Four different machine learning methods,including two Artificial Neural Networks(ANNs),a Random Forest(RF),and a Gradient Boosted Trees(GBT),are trained,validated,and compared in terms of various performance measures.The progress variable source term and transport properties are replaced with the ML models.Particular attention was paid to the progress variable source term due to its high gradient and wide range of its value in the control variables space.Data preprocessing is shown to play an essential role in improving the performance of the models.Two ensemble models,namely RF and GBT,exhibit high training efficiency and acceptable accuracy.On the other hand,the ANN models have lower training errors and take longer to train.The four models are then combined with a one-dimensional combustion code to simulate a counterflow non-premixed diffusion flame in engine-relevant conditions.The predictions of the ML-FGM models are compared with detailed chemical simulations and the original FGM model for key combustion properties and representative species profiles. 展开更多
关键词 Flamelet models Tabulated chemistry models Computational fluid dynamics Machine learning non-premixed diffusion flame
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Non-premixed turbulent combustion modeling based on the filtered turbulent flamelet equation
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作者 Jian Zhang LiPo Wang YuQing Guo 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS CSCD 2020年第4期119-124,共6页
In turbulent combustion simulations, the flow structure at the unresolved scale level needs to be reasonably modeled. Following the idea of turbulent flamelet equation for the non-premixed flame case, which was derive... In turbulent combustion simulations, the flow structure at the unresolved scale level needs to be reasonably modeled. Following the idea of turbulent flamelet equation for the non-premixed flame case, which was derived based on the filtered governing equations(L. Wang, Combust. Flame 175, 259(2017)), the scalar dissipation term for tabulation can be directly computed from the resolved flowing quantities, instead of solving species transport equations. Therefore, the challenging source term closure for the scalar dissipation or any assumed probability density functions can be avoided;meanwhile the chemical sources are closed by scaling relations. The general principles are discussed in the context of large eddy simulation with case validation. The new model predictions of the bluff-body flame show sufficiently improved results, compared with these from the classic progress-variable approach. 展开更多
关键词 TURBULENT combustion modeling TURBULENT FLAMELET EQUATION large EDDY simulation non-premixed flame
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Nonlinear Dynamic Characteristics of Turbulent Non-Premixed Acoustically Perturbed Swirling Flames
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作者 ZHOU Hao TAO Chengfei +1 位作者 MENG Sheng CEN Kefa 《Journal of Thermal Science》 SCIE EI CAS CSCD 2022年第3期882-894,共13页
The main objective of this article was to experimentally investigate the dynamic response of diffusion flame under acoustic excitation in a laboratory-scale burner.Two parametric variations of the burner,the burner in... The main objective of this article was to experimentally investigate the dynamic response of diffusion flame under acoustic excitation in a laboratory-scale burner.Two parametric variations of the burner,the burner inlet length and variation of the airflow rate,were studied.Experimental results were analyzed through nonlinear time series analysis and several resonance characteristics were obtained.Results indicate that the flame-acoustic resonance only appears under certain frequencies together with the fuel tube vibration.Resonance characteristics of the combustion chamber and air inlet in the non-premixed burner indicate quasi-periodic or limit cycle oscillations,respectively.Flame-acoustic resonance would trigger the frequency and amplitude mode-transition in burners.Moreover,the intermittency of flame heat release was observed under variation of inlet length and airflow rate in the burner;the 445 mm case shows more frequency peaks and fluctuations than the 245 mm one.Four typical flame forms were examined during the flame-acoustic resonance conditions,evolves from wrinkled flames to diverged flames,then evolves to reattached flames and finally to blow-off flames.This study proposed the practical application of nonlinear time-series analysis method as a detection tool for flame-acoustic resonance in laboratory non-premixed burners,which could contribute to the detection and prevention of potential thermoacoustic instabilities or resonance structure failures of industrial boilers.Finally,this study demonstrates an alternative to conventional linear tool for the characterization of nonlinear acoustic resonance in industrial boilers. 展开更多
关键词 flame-acoustic resonance non-linear time series analysis non-premixed burners intermittency dynamic characteristics
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Investigation on C_(2)H_(4)-Air combustion mode in a non-premixed rotating detonation combustor
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作者 Shengbing Zhou Hu Ma +2 位作者 Yuan Ma Changsheng Zhou Ning Hu 《Propulsion and Power Research》 SCIE 2022年第1期85-96,共12页
Based on the working characteristics of the rotating detonation combustor,the combustion mode of C_(2)H_(4)-Air under non-premixed injection conditions is experimentally studied in this paper.By changing the equivalen... Based on the working characteristics of the rotating detonation combustor,the combustion mode of C_(2)H_(4)-Air under non-premixed injection conditions is experimentally studied in this paper.By changing the equivalence ratio,we observed the acoustic deflagration mode,fast deflagration mode,stable detonation mode,and weak detonation mode in the combustor.The velocity and pressure of the shock wave increase gradually as the equivalence ratio increases from 0.6 to 1.8.The stable detonation region appears near the stoichiometric ratio and the velocity of the detonation wave is relatively stable.When the equivalence ratio of the mixture is larger than 1.32,the stable detonation wave will suddenly extinguish,forming a weak detonation mode until the end of the combustor operation.The combustion mode of weak detonation is greatly affected by the fuel injection pressure ratio,and the release rate of energy is the main reason for the formation of deflagration mode or detonation mode. 展开更多
关键词 Rotating detonation combustor Detonation wave DEFLAGRATION non-premixed injection C2H4
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Inhibition Effects of CH_(4)/CH_(3)OH on Dimethyl Ether Cool Flames
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作者 ZHOU Xun ZHANG Rui +1 位作者 YANG Shenghua LIU Dong 《Journal of Thermal Science》 SCIE EI CAS CSCD 2023年第6期2284-2296,共13页
CH_(4)/DME mixtures can be used for engines and gas turbines,and have already been studied for many years.However,DME has a strong cool flame phenomenon,which will greatly influence the ignition and combustion charact... CH_(4)/DME mixtures can be used for engines and gas turbines,and have already been studied for many years.However,DME has a strong cool flame phenomenon,which will greatly influence the ignition and combustion characteristics of following hot flames.Therefore,the cool flame characteristics of CH_(4)/DME mixture are very important for their utilization.Recently,the inhibition effect of CH_(4)on DME cool flames has been discovered,but the mechanisms of the inhibition effects lack further verification and research.In this study,the inhibition effects were investigated via both experiments and simulations.In order to validate the inhibition effects,a comparison fuel of CH_(3)OH/DME was also used in this study.The extinction limits,flame temperatures and combustion products of the cool flames of the CH_(4)/DME and CH_(3)OH/DME mixtures were measured using a counterflow burner,and the reaction paths and heat release rate were derived from the HPMech-v3.3.The results indicate that CH_(4)and CH_(3)OH will both inhibit the cool flame of DME via competing with DME for OH and O radicals,and CH_(3)OH has stronger inhibition effects than CH_(4),because it is more competitive and produces more CH2O,which inhibits the oxidation of DME.The HPMech-v3.3 closely agrees with the experimental data,but still needs to be improved. 展开更多
关键词 cool flame dimethyl ether METHANE METHANOL non-premixed counterflow flame
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Numerical Investigation of Effect of Porosity and Fuel Inlet Velocity on Diffusion Filtration Combustion 被引量:2
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作者 TAROKH Ali LAVRENTEV Artem MANSOURI Abraham 《Journal of Thermal Science》 SCIE EI CAS CSCD 2021年第4期1278-1288,共11页
Methane-air diffusion filtration combustion in a radiative round-jet burner was numerically investigated in this work.The purpose of this study was focused on the effects of porous media porosity and gas velocity on t... Methane-air diffusion filtration combustion in a radiative round-jet burner was numerically investigated in this work.The purpose of this study was focused on the effects of porous media porosity and gas velocity on temperature distribution and CO and NO_(x)emissions.Reduced chemical kinetics was used where air and methane were assumed to be at their stoichiometric ratio,while thermo-physical properties were varied per the solid matrix porosity variation.Combustion characteristics were evaluated based on conduction and radiation as the two primary heat transfer modes within the solid matrix.Numerical simulations were carried out based on a packed bed with 3 mm alumina pellets.Results show that combustion temperature increases while the temperature gradient decreases with the increase in porosity,yielding higher NO_(x),and lower CO emissions.Furthermore,the combustion temperature is the lowest and most uniformly distributed with 1 m/s and 3 m/s gas velocities,wherewith 3 m/s gas velocity,combustion occurs outside of the porous zone.The corresponding NO_(x)and CO emissions are the lowest with 1 m/s gas velocity and increase with the increase in gas velocity from 1 m/s to 10m/s. 展开更多
关键词 non-premixed diffusion filtration combustion methane-air combustion porous media numerical simulation
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