| With the rapid development of our industrialization and urbanization,the environmental problem of water resources is becoming increasingly prominent,among which water black deodorization is particularly serious.Oxygen-enriched aeration is one of the common physical methods to repair black and smelly water bodies.Its high efficiency and green characteristics can effectively improve the oxygen solubility of water bodies and the rate of pollutant degradation by aerobic microorganisms.Micro-nano bubbles show unique technical advantages compared with traditional aeration because of their large specific surface area and high mass transfer efficiency.In addition,micro nano bubbles have good application prospects in mineral flotation,Marine drag reduction and medical diagnostic carrier.At present,the generation technology of micro and nano bubbles has made great progress,but the existing micro and nano bubble generation devices still have many shortcomings,such as complex structure,high failure rate,small shear force of water flow at the intake position,large energy loss of gas supply and the limitations of traditional circular outlet applications.In view of the research progress of the principle of jet flow and the shortcomings of the existing devices,a method of generating micro-nano bubbles in the aeration device with built-in wing is proposed.Firstly,the unique physical and chemical properties of micro-nano bubbles and the research status of micro-nano bubble generating device are introduced,and the formation mechanism of bubbles,diffusion and influencing factors of gas liquid transfer are summarized.At the same time,the relevant theoretical basis of airfoil structure and flow is studied.After considering Reynolds number,lift force and drag coefficient,E423 airfoil is selected.The theoretical basis of the design of the device is given,that is,the shear force of the high-speed water flow should be greater than the shear force required by the broken air flow to form microbubbles,and the theoretical bubble diameter is obtained.The main structure of the design is the aeration device with rectangular flow channel,double airfoil blade and capillary intake pipe.The double airfoil blade is arranged in the vertical height direction,and the trailing edge is kept horizontal although the string length is different.The stainless steel capillary intake pipe shall be embedded into the upper surface of the upper and lower airfoil blades respectively,and the embedding depth shall be horizontal with the surface.This article adopts a combination of theoretical analysis,numerical simulation solution,and experimental verification method for the design and optimization of the device structure.Solid Works software is used for three-dimensional modeling of the designed device structure,and numerical simulation research and preliminary experimental verification are conducted.The simulation results show that the upper surface of the airfoil blade exhibits high shear and high negative pressure,A large vacuum degree can be generated on the upper surface to ensure sufficient air intake is sheared by high-speed water flow to form micro nano bubbles;A large pressure gradient is generated from the leading edge to the trailing edge of the blade,and flow separation occurs near the trailing edge of the blade,forming vortices that facilitate gas suction;Simultaneously extracting the pressure distribution values at various positions on the upper surface,the position with the smallest pressure is the embedded position of the stainless steel capillary intake pipe.Experimental verification is conducted on the influence of different opening positions on the intake volume on the upper surface,and the gas-water ratio of the system is measured.The experimental results verify the rationality of the installation design and the reliability of the numerical simulation results,and provide a basis and direction for subsequent structural and system optimization.Subsequently,the structure of device was optimized by numerical simulation,and the expansion angles of the runner inlet were was 30 °,45 °,and 60 °,respectively,and the results showed that the flow characteristics were better when the diffuser angle was 30 °.The characteristic position method is used to study the horizontal arrangement structure of double blades,and the results show that the shear airflow effect of double blade staggered arrangement is better.The influence of the angle attack on the flow of the double lobe in the flow field is studied,and the results show that it should be less than 2 °.The gap between the chord and the inner wall of the runner was studied,and the results showed that the distance between the inlet pipe wall and the inner wall of the runner should be greater.The results show that the appropriated movement of the double blades to the inlet direction in the horizontal direction can effectively enhance the shear effect on the water flow.Changing the round inlet pipe into a narrow one can make the pressure and velocity distribution on the upper surface more uniform.At the same time,in order to adapt to the main body of the narrow inlet and flow channel,the traditional centrifugal pump structure is changed into a single-stage double suction narrow one,and the influence of the inlet pipe shape and the number of blades on the flow characteristics is studied.The MRF method is used for numerical solution and quantitative analysis of the pump performance under different factors,The simulation results confirm the feasibility of the structural design,and the performance is optimal when the gradually expanding inlet pipe and the number of blades is 6.Finally,the designed jet bubble generator was used to aerate ultra-pure water,artificial sewage and solutions of different p H values,and the influence of different properties of solutions on the bubble particle size distribution was studied.The results show that the surfactant can effectively reduce the surface tension,and the bubble diameter of the solution with surfactant is smaller than that of the ultra-pure water.The microbubbles generated by the aeration of ultra-pure water can still exist stably for several hours.The larger the p H value of the solution is more conducive to the formation of micro-nano bubbles;In addition,the aeration device is also applied in the black and smelly water restoration project to observe the practical application effect. |
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