Investigation On Hydrodynamic Cavitation And It's Application On Waste Water Disposal

Cavitation is a process of vapor bubble's generation, growth and breakdown because of the abrupt change of pressure inside the liquid. At the moment of bubble breakdown, instantaneous high temperature and pressure will be produced in the subminiature area around the bubble, and the violence shock wave and high speed jet flow will also be induced. At this extreme condition, it's easy for organics inside the bubble to be degradated. Compared to other cavitation methods, the hydrodynamic caviton has many advantages, such as simple reaction operator, less energy consumption, convenient operation, lower maintenance cost and readily scale up, so it is meaningful to inivestigate the regular pattern of hydrodynamic cavitation, and apply it on field waste water disposal.In this paper, the CFD software FLUENT is used to simulate the flow fields of cavitation in venturi, single hole orifice and multihole orifice. The influences of the operation parameters and structures on cavitation effect are investigated, and some conclusions are educed. The numerical simulations indicate that cavitation firstly happens at the point with the lowest pressure. The cavitation area and the low pressure space are one to one correspondence. The greater the cavitation intensity is, the further away from the zone with the lowest pipe diameter the cavtitation area is. The cavitation intensity increases with increasing the inlet pressure and decreasing the outlet pressure. For venture and single hole orifice, the cavitation effect will be enhanced by increasing the ratio of hole diamerter to pipe diameter, increasing the ratio of the length to the diameter of shrinking area, and scaling up the size of cavitation setup. For multihole orifice, the cavtition effect will be intensified by increasing the diameter of small hole and increasing the flow area. When the ratio of the thickness to the diameter of multiorifice is close to 3.5, the cavitation effect is better. As compared with other two different kinds of hydrodynamic cavitation equipment, multiorifice is more suitbale for violent chemical reaction which is needed for field waste water disposal.Experimental setup for field waste water disposal by using hydrodianamic cavitation effect is build up. Waster water treatmentment experiments have been done for 6 different kinds of multiorifice. They verify the useability of using hydrodynamic cavitation effect to dispose the field waste water. The influences of the operation parameters and structures on cavitation effect are tested. The experimental results confirm the conclusions abtained by numerical simulation.