Numerical Simulation Of Thermoacoustic Coupling Characteristics Of Helmholtz Pulse Combustor

As a combustion method with high combustion efficiency and heat transfer coefficient,high combustion intensity,low pollutant emission,and simple mechanism of combustion,pulse combustion has a very good development space under the current energy form.The reason why the pulse combustion has many advantages is that its internal combustion is oscillating combustion.The direct cause of os cillating combustion is the combination of heat and sound,ie,thermo-acoustic coupling.Due to the thermo-acoustic coupling,the operating parameters of the pulse combustor’s combustion chamber will change periodically.In this paper,according to the oscillation phenomenon in the combustion process,combing the combustion theory and the acoustic theory,the combustion model and the acoustic model of the two-dimensional pulse burner are simulated to obtain the thermo-acoustic coupling characteristics of the pulsation burner,and the different structures and working conditions are determined.Thermoacoustic coupling effect.The Rayleigh criterion and vortex theory show that the position coupling inside the burner can be determined by analyzing the distribution of vorticity and the reaction heat release rate.The analysis of pressure and reaction heat release rate over time can determine that the heat and sound are coupling in the time domain.The comparative analysis found that when the number of nozzles chan ged from single to dual,the operating parameters were characterized by a significant decrease in pressure amplitude,a reduction in the main peak,and a decrease in the reflow intensity.This is due to the difference in the structure between the two resul ting in different coupling conditions.Since the supply of heat during the lean times or the extraction of heat during condensation suppresses the vibration,it is indicated that the increase in the number of nozzles makes the heat at the moment of combust ion uninterrupted and the heat at the time of return is thinner.When other structures change,they will also bring about thermo-acoustic coupling changes.The increase of the combustion chamber diameter affects the maximum degree of expansion and compression.The length of tail pipe affects the frequency of oscillation.Structural changes lead to changes in the phase or amplitude between heat and sound,with different effects.The influence of different operating conditions on thermo-acoustic coupling is also different.With the increase of power,the frequency increases,the peak value rises first and then decreases,and the reflux intensity also rises first and then decreases.With the increase of the equivalence ratio,the main frequency is basically unchanged,and the main peak increases first and then decreases.The amplitude of the pressure increases first and then decreases gradually;with the increase of the ratio,the main frequency remains basically unchanged,and the main peak decreases first and then rises rapidly.Changes in these physical characteristics reveal that the thermo-acoustic coupling is constrained by environmental conditions.In summary,the pulsating combustion thermo-acoustic coupling can be adjusted through reasonable pulsating burner design and operating conditions,and further achieve higher combustion efficiency,longer service life,reduced noise,and improved operating environment purpose.