Study On Stability Characteristics And Electrical Properties Of Small Scale Jet Diffusion Flame Of Ethanol

With the development of micro machining technology, great progress had beenmade on micro devices with various functions, and the demand for high energydensity micro power systems is increasing. The micro scale combustion systemsstudied currently was considered as viable alternatives to batteries due to the tens oftimes higher energy density of typical hydrocarbon fuels compared with the mostadvanced batteries. Micro scale combustion is the core of the micro power system,and, it will encounter problems such as large surface/volume ratio, increasing heatloss and flame dying out easily compared with large scale combustion.Tiny nozzles of different diameter and materials were used as the burnernozzles. Liquid ethanol was applied as fuel, burning in a confined space establishedby transparent glass, as well as DC and AC electric field established by DC/AC highvoltage power supplies and copper electrodes. The flame structure, flame temperature,combustion stability characteristics and electrical characteristics of ethanolsmall-scale jet diffusion flames were studied.The results indicated that there were four conditions of the jet flow flames in thestatic air, namely the quenching flames, stable combustion flames, quasi-oscillatoryflames, and oscillatory flames. AC electric field had a significant influence on flamepeak temperatures, which reached1391.72K with1.2mL/h of volumetric flow rate ofethanol. The upper combustion limits were significantly reduced with DC electricfield in confined space, while upper combustion limits were increased with ACelectric field, which increased from1.45mL/h to1.85mL/h. In the experimentalresearch scope, thermal quenching was the main factor of flame quenching, and themain reason of the transition from stable flames to oscillatory flames was fuelincomplete combustion. The voltage-current characteristics of the flame could bedivided into three regions with DC electric field, namely the sub-saturation region,saturation region and super-saturation region. The practical heat of combustion was7.4W with1.2mL/h of volumetric flow rate of ethanol, and the ultimate power ofDC/AC electric field was0.26W. So the power of electric field was negligible compared with the heat of combustion.The results of this paper discussed the stabilization mechanism of small scale jetdiffusion flame of ethanol, which can be used to improve the stability of micro scalecombustion. The electrical properties of flame was studied in this paper, whichindicated that appropriate condition of electric field could increase the flame peaktemperatures and enlarge the range of stable combustion.