Study On The Influence Of Acoustic Waves On Combustion Flame Characteristics

Combustion will affect the sound wave to a certain extent,and sound will also affect the stability of combustion.The flame characteristics of the burning substance in the sound field will inevitably change under the action of sound wave,which is worth studying.In the first part of this paper,firstly,the propagation characteristics of sound wave in air medium and the change of medium pressure under the action of sound wave are analyzed theoretically.Secondly,the combustion characteristics of candles and solid particles are analyzed from the nature of combustion.It is found that candle is a typical air-type diffusion flame.In the diffusion flame,the heat release rate is limited by the combustion reaction rate.When sound wave acts on the air-type diffusion flame,the thermal release process of the flame itself is coupled with sound wave,resulting in a large pressure fluctuation around the flame,affecting the diffusion process and mixing process.Pressure fluctuation affects the reaction rate of combustion mixture,which can change the flame area,and the flame height is also related to the pressure.For a general diffusion flame,the hot zone is concentrated in the outer flame.The larger the hot zone is,the higher the combustion efficiency of the flame is.Therefore,the characteristics of combustion flame affected by acoustic wave can be studied by studying the changes of flame area,height and radius under the action of acoustic wave.In the second part of the paper,the related algorithms of flame image processing are given,including image transformation,image enhancement,image segmentation and so on.Firstly,the idea and basic process of image processing are given.The image is treated as a set of image cables in the plane by spatial domain processing method,and then the corresponding processing is carried out directly.The method of processing the flicker of flame image in this study is proposed.Based on weighted average denoising method,the problem of duplication of flame image can be eliminated as far as possible,and the noise in flame image can be removed.Based on this,the k-cluster method is used to segment the image,and the segmentation effect is ideal.At last,the definition of flame geometric characteristic parameters is given,which is the basis of extracting flame characteristic parameters in experiments.The last part of this paper is the experimental study of combustion characteristics under acoustic wave.A combustion experimental platform is built and relevant experiments are carried out.Flame combustion characteristic images were recorded by camera under different frequency and sound pressure levels.Flame characteristic parameters were extracted.The variation of flame characteristic parameters with sound frequency and sound pressure level was obtained.In addition,the variation of flame characteristics and burning characteristics of solid aromatic rods under different acoustic parameters was studied.It is found that when the coupling of sound wave and heat release rate increases the reaction rate of flame,the area of hot zone of flame increases.It is also known from experiments that with the increase of sound pressure level,the area of hot zone of flame increases.This shows that sound pressure affects the pressure around the flame,which increases the diffusion rate of flame and the combustion efficiency.The total area increased.Therefore,the effect of acoustic wave makes the heat release rate of flame chan ge,which increases the reaction rate,so acoustic wave can promote the combustion efficiency of flame.The data and results in this paper can provide reference for further study of combustion mechanism under acoustic excitation.