Research On Optimization Design Method And The Key Technology Of The Axial-flow Pump Hydraulic Model

As we all know,the impeller of the axial-flow pump is the core and the most important flow part in the pump station.The design quality of that equipment directly determines the overall efficiency of the pump device and even the pumping station.With the increasing complex operational requirements,the pump design put forward higher design requirements.At present,there is no design optimization method can combine hydraulic design and structural design,so it can not get the optimized impeller meeting the complex operating conditions.Material savings and operating costs are considered as the most important factors in the background of reducing the energy consumption.In the process of pump design,the 2 indexes of impeller quality and operation efficiency are the most intuitionistic visual indexes,when considering reducing the design and manufacturing costs and operatingcosts.In addition to these two indicators,the designer also need to consider the performance curve shape,cavitation performance,structural strength and other indicators.A successful design of the axial-flow impeller should be able to meet these four indicators.In this paper,in order to improve the comprehensive performance of the axial pump impeller,do the overall optimization design research of the axial-flow impeller on multiple targets,multiple constraints and multi-disciplinary.Which can get the best performance impeller and can promote the domestic development of pump optimization design theory and methods.It has important academic value in saving energy and reducing axial-flow pump design and manufacturing cost.And also has practical engineering significance and important theoretical value in the large-scale pumping station renovation and hydraulic model design comparison at the same time.In this paper,the optimal design method and theory of axial-flow pump are systematically studied by means of theoretical analysis,numerical simulation,numerical optimization and model test.The main research work and research results are as follows:(1)For the four design parameters of the cascades dense degree,the airfoil placed angle,the airfoil thickness and the airfoil camber,the paper through design of experiment(DOE)to analyze sensitivity on the design conditions of hydraulic performance of axial-flow pump.From the sensitivity analysis,the airfoil placed angle has the most effect on the hydraulic performance of axial-flow pump,the next is the cascades dense degree,the third is airfoil camber,and the last is the airfoil thickness.In the process of optimization design of an axial-flow pump,the designer can choose and adjust design parameters reasonably according to the result of sensitivity analysis.(2)Introduced the optimization technology based on the the numerical simulation,and given the factor parametric modelling method on DOE analysis,and established the automatic optimization design platform of the axial-flow impeller.And on the platform,the automatic optimization design aiming to the design condition was carried out separately by the blade number,the hub/tip ratio and the blade attack angle.In the actual project of pump station,the number of impeller blades should be chosen according to the highest running head,the lowest running head and the distribution of the efficiency curve.When the often running head is lower than the design head,we can choose the less hub/tip ratio or choose the larger hub/tip ratio on the contrary.So the designer can according the actual running conditions of the pump station to choose the hub/tip ratio of the axial-flow impeller.(3)According to the function and design requirements of the guide vane,in the design process of the guide vane,3 performance evaluation indexes were put forward.The influence of 2 main design parameters,cascade density and outlet angle of the guide vane blade,on the hydraulic performance was analyzed.Then the automatic optimization design of the guide vane was studied.Finally,the performance of swept-angle of the guide vane blade also was analyzed.The hydraulic loss of the automatic optimized guide vane decreased by 40 cm;the kinetic energy recovery coefficient of the guide vane was increased from 41.54%to 85.74%,the optimized guide vane can recover more velocity circulation,and the velocity distribution of the guide vane outlet is improved,which also can reduce the hydraulic loss of outlet passage.Under the design condition,the head and efficiency increase first and then decrease with the increase of blade swept-angle.When the blade swept-angle forward to 16°,the efficiency of the axial-flow pump appears the maximum value.Under high flow rate,the hydraulic performance of axial-flow pump has no obvious change,but under the small flow rate,the hydraulic performance of forward sweept-angle blade is obviously higher than the backward ones.(4)This paper proposed a normalized weight method of objective function for multi-objective optimization design.And according to the running condition's operation time or importance of pumping station,the weight factor of each target can be calculated by hyper transfer matrix.Combined with actual engineering,it always proposes the running requirement of the maximum head,design head,average head and minimum head.Which can be changed into three working conditions of the design head,the maximum and the minimum head of the high efficiency area.According the three working conditions to do the muliti-conditions optimization design.The head of the optimized axial-flow pump reduce slightly at the small flow rate and the design flow rate,but increases at the large flow rate.The efficiency of design flow rate is slightly improved,and the efficiency of large flow rate and small flow rate increased by 7.4%and 2.6%respectively.The optimization effect of axial-flow pump is obvious:the efficiency curve is overall raised,the high efficiency area is widened,the comprehensive efficiency of pumping station is improved,the operation cost of pumping station is reduced.By model test verification,the efficiency of the optimized axial flow pump is higher,the range of high efficiency is obviously widened,and the cavitation performance has greatly improved.(5)Through the optimization of the Optimized Latin Square analysis method,the fluid-solid coupling calculation of 80 sample points of axial flow pump impeller in multiple working conditions was carried out.And then the sensitivity analysis of the calculation results was also carried out.According to the calculated hydraulic performance parameters and structural performance parameters of the impeller to build the approximate model.Finally,the multi-objective optimization algorithm is adopted to optimize the design of the approximate model.The maximum deformation under small flow is mostly affected by the maximum airfoil thickness of the hub side and less affected by other design variables.The maximum stress value under the small flow rate shows a tendency of first decrease and then increase along with the design variables.The second-order main effect with each design variable is very obvious.The blade mass is mainly affected by the cascade density and the airfoil thickness and almost independent of the airfoil placed angle and the airfoil camber.The fitting effect of the response surface approximation model is better than that of other approximation models.After multi-disciplinary optimization,the quality of single blade decreases from 0.947kg to 0.848kg,the rate of decline is 10.47%,while the design efficiency increases from 93.91%to 94.49%,the rate of increase is 0.61%,and the optimization effect is obvious.In addition,except that the maximum stress value error is slightly larger,the error between the approximate model of other response and the numerical simulation value is within 0.5%,which indicates that the approximate model has high accuracy and reliable analysis result.