科研之友
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摘要
Electro-spraying is an effective technique to enhance combustion of liquid fuel in micro/small-scale. A new combustor using a stainless steel capillary tube with inner diameter of 0.9 mm was designed. Electro-spraying experiments using ethanol as fuel were carried out under single electric field and combined electric field, and the spraying angels in the spraying region were measured under stable cone-jet mode. The experimental results found that the spraying angel under the combined electric field was bigger than that under single electric field at the same flow rate of 1.6 mL/h. It can be inferred that the ring electrode can enhance the spraying process of ethanol. The space electric field during the electro-spraying process was established by the combination of the combined electrodes and space charges. Both the electrode parameters and space charges play great roles in the electric field distribution. According to the uniformly charged ring electric potential and field strength formula, the limited long and thin cylinder was regarded as a set of uniformly charged ring. Based on superposition theorem, the distribution of electric field strength in the spraying region was calculated using ellipse integral method and the relationship between Cartesian coordinates and polar coordinates. The electric field established by the space charges depends on the form of spraying region and the quantity of electric charge. The results show that the electric field strength was an axial symmetry and extremely nonuniform when using the ring electrode only. When keeping the voltage of nozzle as a constant, the electric field strength in the spraying region varies greatly along with increasing the electrode spacing and voltage of ring electrode. The electric field strength from the space charges was also an axial symmetry and extremely nonuiform, which cannot be ignored. Especially near to the steel mesh, the space charge dominated the whole electric field. The electric field strength under combined electrodes was enhanced greatly when comparing with that under single electrode. The selection of suitable electrode spacing and voltage is very important for the form of stable cone-jet mode. The present study can supply some guidelines for the design and operation of small-scale combustor.
