Cavitation Field Simulation And Experimental Exploration Reed Whistle

The acceleration development of industry making the composition of pollutants in wastewater increasing year by year. The traditional water treatment technology is powerless. In recent years, the domestic and foreign scholars have conducted in the laboratory using ultrasonic acoustic cavitation effect to degradation of different organic matter in waste water, sewage, and combination with the oxidation treatment and traditional technologies such as membrane method, has obtained the certain effect. But because of the design limit of acoustic cavitation reactor make it difficult to realize industrialization. Therefore, scholars will focus on the research of hydraulic cavitation. Hydraulic cavitation is based on the design of hydraulic device (such as geometric orifice, venturi tube, reed whistle, etc.) to change the liquid passageway, so that occurs cavitation when the liquid passageway through the mutations section of hydraulic device, and form high pressure jet when fluid flows through the mutational cross-section where the cavitation is shaped, the vacuole will flow with the liquid in the area of cavitation, which is formed a larger cavitation field in the flow field. Besides hydraulic cavitation device is simple, low energy consumption, large quantity, which is of advantage for large flow process in industrial application. Reed whistle as hydraulic cavitation generator has higher dual cavitation effect than ordinary hydraulic machinery cavitation. This paper’s mainly work as follows:(1) By the cavitation mechanism knowing that the cavitation phenomenon contains cavitation nascent, cavitation development and demise. And the cavitation nascent should satisfy two necessary conditions, there are micro vacuole and low pressure force field in the liquid. Reed whistle as cavitation generator also should satisfy the two necessary conditions. In this paper, through theoretical analysis and calculation finding that reed whistle satisfy the necessary conditions of cavitation nascent, so the reed whistle can occurs cavitation.(2) Using the computational fluid dynamics software Fluent of finite volume method to numerically simulate the cavitation intensity of reed whistle. Through two phase flow continuous equation, momentum equation and the second liquid phase volume fraction equation to solve the liquid’s gas holdup distribution, turbulent kinetic energy distribution, absolute pressure distribution and velocity distribution in the flow field, found that the reed whistle can happen cavitation phenomenon, and the strongest cavitation intensity in the reed wedge.(3) Experimental research work mainly to prove and support the numerical simulation from the perspective of qualitative.To deeper and more intuitively study the reed whistle cavitation, this paper collects the noise signal for the different working pressure, and processing the Fourier transform for the noise signal to get the spectrum diagram, the analysis found that when the inlet pressure is0.5MPa, the reed whistle occurs cavitation phenomenon, and become stronger with the increase of inlet pressure. Meanwhile using aluminum foil corrosion experiment method measure the reed whistle cavitation phenomenon, can clearly observe the reed whistle cavitation phenomenon. Through analysing and observing the experimental results obtain the similar result as the Fluent software simulation.(4) Using the Fluent software to simulate the impact of the reed whistle’s structural parameters (length of nozzle, entrance diameter) on the cavitation effect. Found that when the reed whistle’s size and thickness of nozzle is constant, the gas holdup and turbulent kinetic energy will increases and absolute pressure reduce with the decrease of the nozzle length in the cavitation flow field, it is helpful to the occurrence of cavitation, also can enhance cavitation intensity of cavitation flow field; Secondly,when the inlet pressure, reed whistle’s size and nozzle size are unchaged, inlet diameter reduce, reed whistle cavitation flow field produce larger gas holdup, turbulent kinetic energy, and lower pressure field, these conditions increase the cavitation effect of flow field, can provide a reference for the optimization design of cantilever type of reed whistle.