The high flow rate of the small lift leads to a large friction loss of the axially flowing narrow-diameter discs, which results in low efficiency. At the same time, the input power of the low specific speed pump rises rapidly with the increase of flow rate. The ratio of the maximum shaft power to the design point power is much larger than the corresponding value of the general centrifugal pump, which makes it easy to overload the motor than the large flow and low head operating conditions. . In the medium-to-high specific speed centrifugal pump, in order to obtain a higher efficiency value and a smaller maximum shaft power, there are relatively abundant design experiences and design theories to ensure. However, the characteristics of the low specific speed pump determine that it is not easy to achieve these two better results. At present, the main design methods for low specific speed pumps include the flow design method, the no-overload design method, the optimized design method, and the composite impeller design method. Literature 1 has a more detailed discussion of the above method. This article proposes a brief review of various existing optimization design methods and mathematical models, and points out their advantages and disadvantages and improvements.

The so-called optimization refers to choosing a suitable solution from the possible solutions so that the pre-defined objectives can be optimized. The optimal design method is used to set a low specific speed pump for large multi-objective optimization design. The multi-objective optimization mathematical shuttle can be used to find a bow that makes tmnF p where 1 = 12, and the heart 7 is a variable dimension. Euclidean space righteousness illusion is the objective function =, is the equality constraint, the private inequality constraint can also be written. Design variables, especially the objective function 1. Factories, where, the constraints and postures are 0, which are the elements of the structural optimization mathematical model.

3 Optimized Design Method of Low Specific Speed ​​Centrifugal Pump 3.1 Speed ​​Coefficient Method Optimization The design speed coefficient method is a commonly used method in pump design, and is obtained through summarizing and counting the existing models. At present, there are batches of advanced hydraulic models that have been optimized, such as type 13 Jia 8 and segment pump models. The development and application of computer technology has brought convenience to the optimization design of the velocity coefficient method. People have established an excellent hydraulic model library that can absorb advanced models and store them in time to optimize various velocity coefficients. Following the current advanced level of pumps, the deficiency is It is difficult to design the performance of chestnuts beyond the current level.

3.2 Loss-Extreme Method Optimization Design The efficiency of how to lift the chestnut has always been an important lesson for water pump workers. While efficiency is closely linked to losses, the highest efficiency should correspond to the minimum loss. Therefore, the optimal design of the idea is naturally to establish a variety of losses and the relationship between the geometric shape of the pump, that is, 3 this study is based on the Jiangsu Provincial Fund for Applied Funds, 2000006 total loss for this optimization method is guaranteed The design of the operating point requirements of the lift Dan and flow through the different combinations of seven conditions, making the total loss, in order to obtain the minimum value, known as the depletion extremum method. This hall method is more mature and effective in the performance of centrifugal pumps. But it also has shortcomings. Because in theory, the calculation of each specific loss is difficult to estimate accurately; generation times. In addition to optimizing design variables in the actual optimization process. Other parameters need to be based on experience. This in turn increases the limitations of optimal design. In addition, the above formula only emphasizes the relationship between the loss and the relevant geometrical parameters, and neglects the influence of the centrifugal impeller performance such as the shape of the front and rear cover plates and the shape of the blade of the wide-impeller runner, and therefore has its limitations.

3.3 Anti-positive and negative criteria screening method Optimum design anti-positive and negative criteria screening method In the centrifugal impeller internal flow machine, the basis of the analysis of the establishment of a variety of optimization criteria for the state area of ​​small loss and control performance objective function, seek the pump structure parameters and the corresponding flow The various combinations of road shapes, and from which to choose the best solution. This method is based on the lack of loss extremum method to rely on qualitative analysis and empirical parameters, such as the calculation can not reflect the true effects of flow, so this method itself needs to be perfect, at present, the optimization design of low specific speed pump It is developing in two aspects, namely the special pump optimization idea and the comprehensive optimization idea.

Because the basic structure of the low specific speed pump has been developed quite well, the future major cities of the 5th city are designed for special conditions; pumps, such as special hydraulic design without overload design, increased flow design, etc. and special structures Materials and seals. Dedicated pump optimization is based on the concept of different conditions and design requirements for agricultural use. There are a large number of farms, and the impact of various parameters on the performance of the technical link 2, all kinds of hydraulic performance are contradictory and unifying.

therefore. An excellent and successful hydraulic design must be designed to meet the requirements of a sobbing design. The optimization design of the low specific speed centrifugal pump used in the research and development of this low specific speed pump is based on the objective of improving the chestnut efficiency. .

In the loss of low-speed chestnuts, hydraulic loss cannot be calculated at present. The volumetric efficiency decreases with the decrease of the specific rotation speed, and is more accurate than 0.9. Compared with the mechanical efficiency, the volumetric efficiency of the pump is not low, the lower the specific speed of the pump is, the smaller the loss is, and the disc friction loss is proportional to the impeller radius or The diameter of the 5th power, so a small increase in the radius of the impeller can also cause a rapid increase in disk loss. In order for the low specific speed pump to produce a higher head, the impeller diameter must be larger, which is the main reason for the low specific speed efficiency. In the case of other conditions unchanged, to minimize disk friction loss, that is to reduce the diameter of the impeller, and to minimize it is to improve the objective function of the low specific speed pump, which is the function of the geometric parameters of the impeller outlet geometry The relationship is the use of the 5 finite blade number correction formula and assumes that the impeller inlet has no pre-rotation, the base-wood equation of the vane pump is derived Q, the theoretical flow rate II, theoretical head displacement coefficient n speed P2 blade outlet opening angle force, degree In leaf The wide projection can be seen from the above formula. Under a given design impeller performance parameter design flow 0, design head, and speed, a certain reliable method is used to determine the hydraulic efficiency and volumetric efficiency at the design point. In 2, the sum will also become a constant. In this way, the impeller radius is a multivariate function of the geometric parameters of the impeller exit, such as the exit angle of the blade outlet, the outlet width of the impeller 62, the exit coefficient of the impeller outlet and the number of the blades 2, and so on. This function is the objective function. Hearts 624 and 2 are required 4 Optimized Design Models for Low Specific Speed ​​Centrifugal Pumps 4.1 Optimized Design Models for Impellers 4.1.1 Optimization Models to Improve Efficiency The methods of this model also consider the hydraulic losses in the pressurized water chamber, and therefore the The value is set as the limit. The flash is only used when the minimum value is 尬1 as the minimum value of the nail. Disk friction, minimum loss, impeller exit velocity, and adverse rate of mimMmmnmm.mn. However, if the impeller is too small, the impeller outlet will be used for phase-out and the service will be too large, which will increase the hydraulic loss in the impeller. Therefore, it is necessary to limit the hydraulic force. This method is used in Reference 46. However, the greater the number of design variables, the greater the size of the question and the more difficult it is to solve. Therefore, the number of design variables can be reduced to reduce the number of documents, and the literature 7 is sufficient to compare the two methods described in setup document 8.

4.1.2 The optimization model with the extreme value of the axis power is under certain conditions. The caller also wants to select the motor with the rated power as small as possible in order to reduce the cost of the unit and improve the working efficiency of the motor. At this time, the geometric parameters of the impeller should be determined to reduce the maximum shaft power of the pump as the basic goal, while taking into account the efficiency of the pump as much as possible, its design objective function is the impeller rotation angular velocity R impeller 10 diameter Tuen exclusion coefficient P impeller outlet placement The optimal solution for the mechanical damage of the angle V is to reduce the water power of the person to the minimum, the energy value, and then find the minimum value and 2 under the given conditions to optimize the disk friction loss and reduce the maximum shaft power. To the minimum.

At this time, the theoretical flow rate of the impeller is exactly equal to the theoretical flow rate at a given point in the design. The maximum water power is exactly equal to the given water power at the design point. This axial power characteristic is called the saturation characteristic, and this characteristic is exactly the same as the overloadless juice setting method. of. According to Bibliography 10, this method is an optimal design for an overloadless pump. Especially for overloaded design methods, it makes sense for agricultural and engineering pumps with variable operating conditions. 4.2 Optimal design of the impeller inlet The cavitation performance of the buccal pump is good or bad. It is also an important indicator to evaluate pump performance. The cavitation bubble generation conditions of the pump are mainly related to the geometry and structure of the impeller inlet. The above two types of optimization methods are to increase the efficiency value of the pump and reduce the maximum shaft power value of the pump. The geometric parameters of the impeller exit are mainly taken into consideration, and the geometric parameters of the inlet of the impeller are not taken into consideration. When considering the optimization of the pump, the inlet of the impeller is also optimized. Improving the cavitation performance of pumps The literature considers pump volumetric efficiency in terms of pump cavitation performance. The pair and the blade number 2 are design variables, and the objective function is to enter 4+ into 1 ancient. This method couples the 1st optimization and the exit optimization.

Overall optimization of chestnuts. Document 12 proposes an alternative point-by-point calculation method for controllable wrap angles, which is used to optimize the design of the inlet angle and wrap angle of centrifugal pump impeller blades. In fact, the impeller inlet and outlet 1 are also considered.

4.3 Optimization design of the volute model In the design of the pump, the volute pressure chamber serves as an important flow-through component of the pump, and the performance of the design of the pump is very influential. Document 13 uses the hydraulic loss as the objective function and the cross-sectional area as the seeking variable to establish an optimized mathematical model for the eighth section and all sections of the volute spiral volute. The objective function is to establish the spiral casing damage on the Rf 2 scale. Any one of the relationship between cross-sectional area, the author will be applied to the design of mixed flow pump volute, and achieved good results. However, because there are not many studies on the optimal design of the pump volute, the above method needs to be verified through a large number of calculations and experiments when it is applied to a low specific speed pump. When the low specific speed pump is designed with an optimized design method, Pay attention to whether or not the optimal value makes zero pay out. The head flow characteristic curve with the maximum value or the peak of the snake is the main reason for the unstable working condition of the pump. Some poorly designed low specific speed chestnuts are particularly prone to the snake peak curve. The hump of the characteristic curve is related to many factors and it is difficult to establish an objective function. However, it is possible to eliminate the geometric parameters of the worm gear 1 controlling the volute of the impeller from two aspects, so as to increase the inclination of the straight-line music enterprise; 2 to reduce the hydraulic loss of the chestnut in the small flow area, and to increase the pump at the dead point and Its nearby lift. In the optimization design method of the low specific speed centrifugal pump, the hump consideration is placed in the constraint condition.

Adding the flow rate design method is also a common method for designing low specific speed pumps. The article, 141 for a large number of sculpting practices for a 1.7 basis, based on T-impeller inlet-outlet relative violation ratio y-to-b volume ratio optimization, a method using an impeller with a gate speed relative to the flow rate within 7 metric system impellers, using an area ratio control impeller Match the pump body. The low specific speed pump designed by this method has achieved satisfactory results. This method raises the efficiency of one. It also brings about the possibility of making the head line more prone to hump and making the shaft work, the curve more steep, and running in the large flow + zone. I was asked that the 4.5-no-overload design method was optimized for the cheek-type 7 overload design method to design low ratios. In addition, the pump's alternate approach to optimization is to optimize the heart and 7 under the condition that no overload constraints are met. This method is also optimized 7 to ensure the matching of the impeller and the pump body. The advantage of this method is that there is no overload during the recording run, but compared to the excellent hydraulic model, the efficiency of the no-overload pump is low, which is mainly caused by the hydraulic efficiency.

So the numerical simulation of the internal flow of the impeller of the non-overload centrifugal pump improves its hydraulic efficiency. It is the main way to improve the efficiency of the pump. The impeller is fed into the small column of the design, indicating that the optimized juice design method can also be applied to the plant's short blades. In the design of the biasing pump, 5 the conclusion is that the method and the mathematical model of the optimal design of the inlet and outlet of the impeller are briefly reviewed, and the advantages and disadvantages are pointed out. At the same time, it also reviewed the optimization of the increased flow rate method and the seven overload method.

Because the internal flow conditions of the pump are not yet fully understood, hydraulic design is still based on a large number of empirical factors. Therefore, various successful optimization designs are often completed after repeated calculations and modifications. In order to shorten the product development cycle, people have said that in recent years, the computer has been selected to assist in the design of juice, so as to optimize the selection of rapid multi-projects. 0 The development of the design is also shifting from the detailed design of the parts to the design phase of the product's principle scheme = the introduction of a large number of mature commercial software for the calculation of the flow field inside the fluid machinery, making the low specific speed pump based on the calculation of the primary flow field. The optimization design will eventually be based on the calculation of the flow field, the use of the internal flow conditions of the pump, and the rapid development of the technology.

I Yuan Shouqi. Low Specific Speed ​​Centrifugal Pump Theory and Design . Beijing Mechanical Industry Press, 1997 2 Wang Shuyu et al. Optimization principle method and engineering application. Zhejiang University Press, 1991 3 edited by Shen Tianyao. Centrifugal impeller inflow theoretical basis. Zhejiang University Press, 1986 4 Wang Jianhua. Optimized Design of Centrifugal Pump Impeller with Low Specific Speed ​​. Water 5 Yan Jing. Again on the turn ratio turns against the optimal design of the impeller. Water, technology, 6 Wang Jianhua. Optimization Design of Centrifugal Pump Impeller Parameters . Drainage machine 1 Wang Chunlin. Low specific speed centrifugal slurry impeller optimization 8 Yan Jing et al. Depth for the low specific speed impeller parameter optimization model. Low specific speed centrifugal pump principle. Parameter optimization and painting. Chengdu Science and Technology Press, 1998 Wang Jianhua et al. No overloaded chestnut design. Jiang Han Petroleum Institute He Xijie. Optimization Design Method of Centrifugal Pump Impeller with Middle and Low Specific Speed ​​. Water chestnut technology, 199232932 12 Wang Jiangxiang. Optimization of impeller blade inlet angle and wrap angle of centrifugal pump 13 Qian Hanxin et al. Pump volute optimization design method. Water conservancy 14 Yuan Shouqi, Gao Liangrun. Centrifugal pump design. Drainage machine 15 Wang Leqin and so on. Low specific speed two-stage compound impeller high-speed centrifugal pump

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