Study On Hydraulic Characteristics Of Submersible Propeller In Biological Sewage Treatment Process

Submersible propeller,an important sewage treatment equipment,which is widely used in biological wastewater treatment process.It is also the third energy consuming equipment besides fan and pump in this process.Its main function is to prevent the deposition of sludge in the sewage treatment pool,so that the activated sludge and sewage fully contact with biochemical reactions.Push effect of the Submersible propeller directly related to the quality of the effluent standards.At this stage,the researches on submersible propeller only include power,thrust and rotational speed.However,no research has been done on the mapping relationship between submersible propeller speed and impeller diameter.In particular,the lack of pool type and submersible propeller matching problem directly affects the selection of submersible propeller.Therefore,it is of great significance to study the hydraulic characteristics of the Submersible propeller.The specific research contents and achievements of this paper are as follows:1.The grid model combining polyhedron grid with prismatic grid was constructed.Based on the standard k-? turbulence model,the steady state numerical simulation of the submersible propeller was carried outand verified by the flow field test,and the numerical simulation method of the submersible flow impeller was obtained.2.Reference to national standards,this paper proposes using STAR-CCM + threshold function to obtain the equivalent volume,based on the operating power in the annular pool and the square pool,submersible propeller(two blades)under different speed conditions were simulated,and found that the operating power of the annular pool and the square pool decreases first and then increases with the increase of the speed.3.Based on annular pool and square pool,the influence of impeller diameter on its hydraulic performance was compared under same power condition.The results show that the push-flow effect of the submersible propeller in the annular pool increases with the increase of the impeller diameter.However,the push-flow effect of the submersible propeller in the square pool increases and then decreases with the increase of the impeller diameter.4.The calculation formula of the push flow efficiency of the submersible propeller was derived.Based on the formula and the flow field in the pool,the reasons for the different effect of the push flow in different pools were analyzed.The optimal placement of the submersible propeller in the square pool was determined.5.In the annular pool and the square pool,the three-blade submersible propeller under different speed conditions were studied.It is found that in the annular pool,with the increase of speed,the operating power of the submersible propeller first decreased and then increased.the higher the speed of the impeller in the square pool,the greater the operating power.6.The same power of two-blade submersible propeller and three-blade submersible propeller were compared and found that in the annular pool when the impeller diameter in the range of 1.1m~3.1m,there is little difference in the push-flow effect between twoblade submersible propeller and three-blade submersible propeller.In a square pool,when the impeller diameter is small,the three-blade submersible propeller has better push-flow effect.When the impeller diameter is large,the two-blade submersible propeller has better push-flow effect.