Numerical Simulation And Performance Analysis Of The Flow Field In High-speed Partial Emission Pump

The partial emission pump which is also named tangent pump is a kind of special type centrifugal pump for small-capacity and high-head.Compared with generally centrifugal pump,its head-discharge curve is flat,then it can attain to the result of changing flow but keep the constant pressure.Resolved super pressure problem at small discharge with generally centrifugal pump.So far,the design theory of the partial emission pump is not perfect,the low n_s partial emission pump of small-capacity and high-head has gained some successful experience.But the high building,extremely high building within city flow out in great quantities now,to the fire fight pump which has the strict request for the problem of super press,and the type choosing for new item of Chemistry industry and petroleum industry,the expanding to permit of old machine sets,all needing the partial emission pump which has big-capacity and high-head Characteristics.How to make the big-capacity and high-head partial emission pump also have a flat head-discharge curve,for this problem,a concrete big-capacity and high-head fire fight pump has taken as the object of study in the article,and has carried out the inner flow field research and the performance prediction.Firstly,through comparing the original design partial emission pump's predicted external performance with the experimental result,confirmed that it was feasible and accurate to simulate the partial emission pump's inner flow field and predict its performance by CFD technology.Secondly,in view of the fact that the original design pump's head-discharge curve dropped degree can't satisfy the design requirements,it has been carried on the analysis to its inner flow field,and discovered its main problems.Based on this,the structural style of the impeller and volute has been made multi-plan improvement,then the various improving models has been carried on the simulation computation.Based on the simulation computation result,there has discussed the impact of the structural style of the impeller and volute over the partial emission pump's performance.Study indicated:1) the rectangular spiral volute can enhance pump's head and efficiency obviously,and cause the head-discharge curve tending to be flat;2) the tilted blade impeller will reduce pump's head coefficient,increase the dropped degree of the head performance curve;3) the compound impeller can enhance pump's head, can cause pump's head-discharge curve becoming more flat.Finally,through comparing the best pump's predicted external performance with the experimental result,proved that the pump had been developed successfully,based on the big-capacity and high-head fire fight pump's success development,when design the big-capacity and high-head partial emission pump,it is not suitable to use the present general design method of the small-capacity partial emission pump,might refer to the followingconclusion:(1) When n_s=56 or so,the head coefficient can be selected more than 0.7;(2) Because the current capacity is big,the throat efflux coefficient should be selected less than 0.6;(3) It is quite appropriate to take Z=8's straight blade impeller to match rectangular spiral volute.The research work in the article not only expands the hydraulic design method of the partial emission pump,expands the partial emission pump's use scope and structural style,but also obtains the actual applying in the project,has brought the considerable economic value and social value.