A Fundamental Investigation On Electrospray Combustion--Investigation On Electrospray Of Fuel And Charged Two Phase Turbulent Jet Flow

Based on series fundamental experiments and theoretical analyses, the electro-spray of fuel and charged two-phase turbulent flow are studied systematically and comprehensively in this thesis, which established a research foundation for electro-spray combustion. The research involves charging mechanism, charging and atomization characteristics of fuel, flow field properties of electro-spray, theory of charged two-phase flow and numerical simulation. The research work is supported by national science foundation of China.1 .The differences of charging mechanism between fuel and conductive polar medium are analyzed on the basis of comparing conductivity, polarization and electrification. The basic principle of charged droplet's fission and electro-spray with different charging method are presented.2. An experimental system of electro-spray with two different charging methods - inducted by ring electrode and polarized by contacted needle electrode is established. An effective charging equipment for fuel is designed. Water and kerosene's characteristics of charging and atomization in the electro-spray are measured and analyzed. The action of electrostatic on the atomization of fuel is investigated.3. The jet flow field of electro-spray is detected accurately and analyzed by means of PIV (Particle Image Velocimetry) for the first time. The distributions of velocity vector, vorticity. turbulent kinetic energy and some other detailed flow information in the field are obtained. The influence of electric field on the flow field is discussed and gives a deep insight on it.4. The experimental results of elecro-spray indicate that fuel could be polarized to charge under strong electric field and form electro-spray. Compared with uncharged spray, the droplets' average diameter of atomization is decreased in evidence, the distribution of droplets" size becomes narrow and the amount of small size droplets increases. A "saddle" shape appears in the curve of relationship between SMD (Sauter Mean Diameter) and charging voltage, the droplets' size distribution fluctuates with the change of charging voltage. The influence of electric field on flow field is apparent. The distribution of velocity and turbulent energy, structure and size of vortex appear different changes with the increase of voltage of charging.5. A kind of two-equation turbulent model of charged fluid flow is constructed, in which the interaction between electric field and flow field is considered. Based on analyzing the properties of forces on the charged droplets in the spray, Pseudo-Fluid of charged droplets phase method is adopted to develop a kind of charged two-phase turbulent model. This model takes account of the interaction between charged droplets phase and electric field, the inter-phase action between droplets and gas, convection and diffusion of droplets' turbulent energy.6. The electric field induced by the ring electrode is calculated and a model of the electric field induced by charged droplets is presented. Applying IPSA (inter-phaseslip algorithm), the charged two-phase jet turbulent flow is simulated and the results show that this model could predict the charged two phase turbulent flow in some degree. The research enriches the theory of charged two-phase turbulent flow.