Large Eddy Simulation Of Turbulent Premixed Combustion

Burning is the oldest human technology;it has been used for more than a million years.At present,about 90%of our global energy support is provided by combustion,becoming a part of humans and their important and highly dependent;burning can benefit mankind,while burning can cause pollution on some occasions.In engineering practice,there is a great deal of existence,whether it is gas,solid or liquid.In the combustion process,pollutants such as carbon monoxide and nitrogen oxides will be produced more or less in the combustion products.Turbulent combustion often occurs in many fields,such as energy,aerospace and power fields.The actual combustion process is usually a turbulent combustion process.The addition of combustion makes the turbulent flow field more complicated.Premixed combustion can reduce the emissions of pollutants such as carbon monoxide and nitrogen oxides.Compared with the traditional combustion,premixed combustion has a better prospect.In this paper,aircraft combustion chamber to establish a three-dimensional model,the main combustion chamber premixed combustion combustion efficiency and pollutant emissions.OpenFOAM software was used to simulate the software.The numerical method of large eddy simulation?LES?was used.With the control variable method,the turbulence intensity and the inlet velocity were kept constant.By analyzing three different equivalence ratios,Combustion chamber temperature field,pressure field,and the variation of pollutant emissions.Secondly,by changing the total length of the combustion chamber,the influence of the size of the combustion chamber on pollutant emission is analyzed.Finally,the center of the combustion chamber was analyzed by the method of EMD decomposition,the flow velocity and the vertical velocity of the various modal situation,and compared.Got the following conclusion:?1?The pressure in the combustion chamber is directly related to the chemical reaction and the temperature in the combustion chamber.As the equivalence ratio increases,the temperature in the chamber also raise.At the same time,the pressure increases accordingly Is due to the mixture into the main combustion zone chemical reaction,leading to temperature,the rapid expansion of the air mass,making the combustion chamber pressure increases.?2?The effect of equivalence ratio on pollutant discharge:The increase of equivalence ratio makes the combustion reaction more intense,and the turbulent pulsation movement on the flame surface is also more active,which makes the mixing of the components in the combustion chamber more sufficient.By comparing the carbon dioxide concentrations at different equivalence ratios,it can be seen that as the equivalence ratio increases,the carbon dioxide concentration increases accordingly,and the equivalence ratio of the premixed fuel can be appropriately reduced to mitigate the environmental pollution.?3?Comparing the influence of the total length of the combustion chamber on pollutant discharge,we found that the length of the combustion chamber should not be too long.By comparing the total length of the combustion chamber with the length of 0.6m,0.8m and1.0m respectively,it can be found that the total length of 0.6m Room emissions of pollutants CO₂ less.?4?EMD decomposition of the center of the combustion chamber,we can find:the time scale increases with the modal increase,the flow velocity of the pulsation is increased,and found that the velocity of the point at this point after EMD decomposition The local intermittency of each mode is enhanced.And from the Hilbert spectrum,we can find that the frequency is mainly concentrated in the low-frequency part.The Hilbert's marginal spectrum reflects the relationship between the frequency and the energy in the turbulent combustion more faithfully than the Fourier spectrum.