Experimental Study On Impinging Streams-hydrodynamic Cavitation Reactors And Its Strengthening Effect

Cavitation is the phenomenon that gas nucleus' explosive growth,development and breakdown caused by the local low pressure in the liquid.High temperature,high pressure,violent hock wave,high speed jet and other extreme conditions induced by cavitation bubbles' breakdown can be used for developing and strengthening many processes.This technology has wide application prospect,therefore,it's important to design new efficient cavitation reactors.On the basis of conventional hydrodynamic cavitation reactor,two kinds of impinging stream-hydrodynamic cavitation reactors were designed.A jet formed when liquid flowed through the orifice,and then collided with the model of impinging streams.According to the different impact angles,frontal impinging stream-hydrodynamic cavitation reactor and oblique impinging stream-hydrodynamic cavitation reactor were designed.Compared with the traditional orifice cavitation device,cavitation bubbles were larger in the every process of regeneration after collapse in impinging stream-hydrodynamic cavitation reactors because of the existence of violent pressure fluctuation in the impinging stream that liquid as the continuous phase,therefore,the times of bubble collapse were increased,and cavitation was strengthened as the more OH released by the bubbles' collapse.The hydroxyl radical induced by hydrodynamic cavitation was measured by methylene blue as the catcher.To investigate the cavitation effect of impinging stream-hydrodynamic cavitation reactors and the basic law of the strengthening effect of cavitation,the following studies have been done in this paper.(1)The concentration of OH induced by frontal impinging stream-hydrodynamic cavitation reactor and oblique impinging stream-hydrodynamic cavitation reactor were both increased with the time.Contrast with orifice plate hydrodynamic cavitation,it was respectively increased 27.5%and 7.5%.(2)The concentration of OH induced by frontal impinging stream-hydrodynamic cavitation reactor and oblique impinging stream-hydrodynamic cavitation reactor were both increased with the liquid velocity through orifice of plates.Contrast with orifice plate hydrodynamic cavitation,it was respectively increased 37.2%and 17.7%.(3)The concentration of OH induced by frontal impinging stream-hydrodynamic cavitation reactor and oblique impinging stream-hydrodynamic cavitation reactor were both decreased with the decrease of impinging distance.The concentration of OH respectively increased 32.5%and 10.5%when the impinging distance reduced 50%.(4)Hydroxyl radical concentration of the impinging stream-hydrodynamic cavitation devices increased with the decrease of impinging distances.Hydroxyl radical concentration of cavitation increased firstly and then decreased.When the diameter of orifices was 1.5mm,hydroxyl radical of cavitation reached its maximum value.Contrast with orifice plate hydrodynamic cavitation,it was respectively increased 33.3%and 8.3%.(5)Comparative experiments of the three kinds of cavitation reactors showed that the rank of hydroxyl radical concentration was:frontal impinging stream-hydrodynamic cavitation reactor,oblique impinging stream-hydrodynamic cavitation reactor and hydrodynamic cavitation reactor.(6)Using the experimental data,Correlations of hydroxyl radical concentration C OH,dimensionless impinging distance(AL/d0 is the ratio of the impinging distance and the diameter of pipe)and dimensionless orifice flow rate(u/u0 is the ratio of the orifice flow rate and the pipe the flow rate)had been established.Calculation results agreed well with experimental results.