Flame Structure And Stability Of Pulse Combustion Of Non-Premixed Propane In A Rijke Tube

Micro-burner is the core component of micro-electromechanical systems (MEMS) and the existing micro-burner are developed on continuous combustion.where the microscale effects,cause problems like combustion instability, incomplete combustion, low combustion efficiency and thermal efficiency, and high pollutant emissions. Pulse combustion has the advantages of high combustion efficiency, high combustion intensity, high heat transfer efficiency, and low emissions, which may be applied to overcome the existing problems of the existing micro-combustor. In this thesis, a micro-pulsating combustion technology concept was proposed and its feasibility was verified through experimental study.Since the current research efforts on the pulse combustors are on normal size, the operating characteristics of the small/micro size pulse combustors are lack of knowledge. In this work, some small/micro size quartz Rijke pulse combustors whose diameters were10-25mm were developed and tested under different operational conditions The acoustic signals and high-frequency flame images were collected, processed and analyzed to obtain some knowledge of the operation characteristics, stability and flame characteristics of the small/micro size Rijke-type pulse combustors.The main findings of this work includes:1,According to its operational frequency, the quartz pulse combustor with inner diameter of12mm and the combustion bed height of60mm can be operated in four regions: low frequency region, high frequency region, high harmonics region and turbulence region. Pulsating combustion in the first three regions can be continuous and stable while it was easy to be extinguished in the turbulence region. A frequency hopping phenomenon was observed in the pulse combustor and the occurring of the frequency hopping follows a pattern "low-frequency attenuation, high frequency enhancement and final frequency alternative". The high-temperature region in the Rijke tube focused on the pulsating flame’s position and there was a large axial temperature gradient.2, The operating stability maps were plotted for the above pulse combustor. The phase relationship between the non-premixed pulsating flame, gas velocity, and gas pressure in Rijke tube meets the requirements "Rayleigh criteria". Some special phenomenons including reverse flame spreading,"Flame Oscillation to Extinguish" and flame floating were observed for the small/micro pulse combustor in this work.3, The flames in the non-premixed Rijke tube was pulsating as a sine wave pattern and there was a linear relationship between flame fluctuation parameters and the flow rate of air/propane. It was also found that the increasing of the heat releasing height will results in the decreasing of the pulsation intensity of the burner. 4, A premixed micro-pulse combustion with frequencies of360.5Hz and996.4Hz has been achieved in a quartz tube with outer diameter of9.9mm and its energy density was up to500kW/m2.