组合电极小型燃烧器的电学及雾化特性研究

Study on the Electrical and Spraying Characteristics of Small-scale Combustor With Combined Electrodes

组合电极对小型发电系统的关键设备小型燃烧器的效率和稳定性上有显著的改善作用。在荷电雾化燃烧中,燃烧效果很大程度上取决于雾化程度,而充电电场是决定静电雾化的关键因素。对毛细管喷嘴–环形电极–收集网格组合电极的电场进行了理论计算,利用静电场叠加原理,通过单喷嘴电极和单环形电极电场分布导出了不同环形电极位置的组合电极电场分布。通过实验采集了不同电极距下的雾化图像、测量了雾化产生的电流、雾化液滴速度和粒径。结果表明:组合电极轴向电场强度在喷嘴出口处最大,并且沿着z轴方向,总体呈下降趋势。随着环形电极位置从上向下移动,组合电极喷嘴出口处轴向电场强度大小逐渐增加,实验测得的乙醇荷质比相应增加。由此推论,在本研究范围内电场强度是影响荷质比的关键因素。综合考虑不同电极距对液滴粒径和速度的影响,认为当极距L_1=3.6mm或L_1=2.5mm时能实现较好的雾化及燃烧效果。研究结果对于合理设计小型燃烧器结构具有指导意义。

Combined electrodes have a significant effect on the efficiency and stability of small-scale combustion system which is key equipment of small-scale power system. The combustion performance depends on atomization degree and the electrospray depends on the electric field. The electric field intensity was calculated theoretically based on a small-scale combined electrodes combustion system consisting of a capillary, a ring electrode and a stainless steel grid. The electric field intensity distribution using combined electrodes was deduced by the electric fields of single nozzle electrode and single ring electrode based on the superposition principle of electric field. The photos of electrospray were taken and the current caused by the electrospray was measured. The droplet size and velocity were measured by phase doppler anemometer（PDA）. The results show that the axial electric field intensity with combined electrodes arrive its maximum value near to the nozzle outlet and gradually decrease along the z-axis direction. Both axial electric field intensity near to the nozzle outlet and specific charge increase along with moving the ring electrode from top to bottom. It can be inferred that electric field intensity is a key factor on the specific charge. Taking both the effect on droplet size and velocity into account, better spraying and combustion performance can be achieved under the conditions of the spacing L_1= 3.6mm or L_1= 2.5mm. The results may provide some help for designing a small-scale combustion system reasonably.