Performance analysis of blade angle of submersible agitator
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Abstract:
Submersible agitator,also known as submersible propeller,is widely used in the sewage treatment plant process.Recently,the use of CFD software is used to simulate the flow field changes in the stirred tank,more clearly provides us with theoretical support.It is the emergence of this numerical simulation technology that the research of submersible agitators has entered a new stage.Therefore,researchers from the design parameters of the submersible mixer,installation position,speed adjustment,and other aspects,to not only improve the mixing effect of the submersible mixer,but also achieve the purpose of effective energy saving. Up to now,the installation scheme of submersible agitators has been studied more or less.However,how the blade angle of the submersible agitator affects the flow field has not been studied.Therefore,based on the previous research,the influence of blade angle on the performance of submersible agitators is simulated.The change of impeller blade setting angle is realized by rotating the corresponding angle around the y-axis in turbogrid.The y-axis rotates 2°in the positive direction (clockwise),that is,the blade setting angle is adjusted to -2°(clockwise is negative,counterclockwise is positive),and so on.The purpose is to study the flow characteristics in the stirred tank with different blade placement angles (-4°,-2°,0°,2° and 4°),to provide a reference for selecting the appropriate blade placement angle according to the mixing requirements and energysaving effect. To study the influence of different blade angles (-4°,-2°,0°,2° and 4°) on the flow field in the stirred tank,the numerical simulation of the submerged agitator with different blade angles is carried out,and the flow field is analyzed by CFD-Post software.According to the results of numerical simulation,it is concluded that:(1) The velocity field in the mixing tank is axisymmetric concerning the submersible agitator.The flow is pushed forward along the center of the submersible agitator.When the central jet moves to the other side of the tank wall,the flow diffuses around.The area of velocity distribution cloud diagram in the mixing tank to achieve effective mixing becomes larger and larger with the increase of blade angle,which indicates that the mixing effect of submersible agitator becomes better and better when the blade angle increases from -4° to 4°.(2) The pressure distribution characteristics of the impeller pressure surface are almost the same under different blade placement angles,that is,the high-pressure area is mainly concentrated in the inlet area of the impeller,and the negative pressure area is concentrated in the area near the blade flange and impeller outlet.The pressure on the blade working surface increases with the increase of blade placement angle,that is,the area of the highpressure area increases continuously.At the same time,the shaft power and thrust of the submersible agitator are increasing with the increase of blade angle.(3) Compared with the mixing effect,the effective mixing ratio and effective unit energy consumption of submersible agitators increase with the increase of blade angle.When the blade angle is -4°,the effective unit energy consumption of the submersible mixer is the minimum,and the effective mixing area in the mixing tank is only about half,and a part of low-speed zone or even dead zone will appear in the flow field,which affects the mixing effect.When the blade angle is increased to 4°,the mixing area of the submersible mixer is about 70% (the mixing effect of the submersible mixer has been improved in practical engineering application).Most of the fluid in the flow field has been stirred,which meets the design requirements,and the stirring effect is good.(4) Finally,to prove the accuracy of the numerical simulation results of submersible agitator,the experimental verification is carried out when the blade setting angle is 0°and the error between the numerical simulation and experimental verification is less than 5%,which proves the accuracy of the numerical simulation results.It shows that the research on the blade setting angle of the submersible agitator is feasible and provides a reference for the future research of submersible agitator certain reference. [WTHZ]Conclusions[WTBZ] (1) With the increase of blade angle,the effective mixing area of velocity distribution nephogram in the mixing tank is increasingly larger,and the mixing performance of submersible agitator is improved.(2) When the blade angle increases from -4° to 4°,the shaft power and thrust of submersible agitator motor increase continuously.At the same time,with the increase of blade angle,the corresponding effective mixing ratio and effective unit energy consumption are also increasing.(3) The accuracy and rationality of the numerical simulation results are verified by experiments,which provides certain reference for the future research of submersible agitator.
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