A design method for a composite impeller of a centrifugal pump

Abstract

The present invention discloses a design method for a composite impeller of a centrifugal pump. The composite impeller consists of two parts: a twisted blade and a cylindrical blade. The twisted blade is adopted at the inlet part of the impeller to reduce the turbulence and impact loss at the inlet of the centrifugal pump and improve the efficiency of the pump. The cylindrical blade is adopted at the outlet part of the blade, so that other parameters of the impeller change less except the impeller diameter during the cutting process, thereby ensuring the similarity between the external characteristic curve of the pump after cutting and the external characteristic curve of the original pump, and realizing precise cutting of the impeller outer diameter. Compared with the traditional centrifugal pump impeller cutting method, the time cost and trial-and-error cost of cutting are greatly shortened, which is beneficial to reducing the production cost of enterprises.

Description

Technical field:

[0001] The invention relates to a design method for a centrifugal pump composite blade, and in particular to a design method for a centrifugal pump composite blade that can achieve precise cutting of a centrifugal pump impeller and ensure similar centrifugal pump performance before and after blade cutting. Background technology:

[0002] As an important general-purpose machine, centrifugal pumps are widely used, in high demand, and users have various needs for pumps. Therefore, in order to meet the needs of different users, it is necessary to expand the working range of the pump and realize the standardized and serialized production of the pump. However, the design and development cycle of the pump is long, and it is difficult to develop an excellent hydraulic model. In order to reduce the time and economic costs brought by redesign and mold opening, the expansion of the working range of the centrifugal pump in the actual production process is often achieved by cutting the outer diameter of the pump impeller. However, in the design process of centrifugal pump blades, in order to make the blade shape more consistent with the movement law of the fluid in the impeller and reduce turbulence and impact losses, the blades are often designed as twisted blades. For such impellers with twisted blades, cutting not only changes the outer diameter of the impeller, but also causes changes in parameters such as the outlet placement angle of the blade and the line shape of the blade outlet section. This makes it difficult to use the cutting law to predict the head and efficiency of the centrifugal pump after cutting, and it is impossible to achieve accurate cutting of the impeller. Therefore, the cutting of traditional centrifugal pump impellers is often carried out through multiple trial cuttings, and then the cutting amount of the impeller is determined by experimental verification. This greatly increases the experimental cost and time cost of impeller cutting. At the same time, the substantial change in outlet parameters caused by excessive cutting may also lead to problems such as deterioration of the energy performance and efficiency of the pump and failure to meet actual engineering needs. Summary of the invention:

[0003] The purpose of this patent is to solve the problem that the centrifugal pump impeller cannot be accurately cut. The composite blade design method proposed in this patent is characterized in that a twisted blade design method is used at the impeller inlet and a cylindrical blade design method is used at the outlet. This design method combines the advantages of twisted blades and cylindrical blades. The blades designed by this composite blade design method are basically the same as the original centrifugal pump in terms of blade outlet linearity and outlet placement angle after cutting. Therefore, the impeller designed by this method can achieve accurate cutting of the impeller while ensuring the performance of the centrifugal pump. Compared with the traditional centrifugal pump impeller cutting method, it greatly shortens the cutting time cost and trial and error cost, which is beneficial to reducing the production cost of the enterprise. The technical implementation plan of the patent of this invention is as follows:

[0004] Blade Angle The calculation formula is as follows:

[0005]

[0006]

[0007]

[0008]

[0009] Where:

[0010] z—number of blades;

[0011] n s —Specific speed;

[0012] k 1 —Correction factor.

[0013] When designing the blades, the blades at the inlet of the impeller are designed as twisted blades, and the blades at the outlet of the impeller are designed as cylindrical blades. The calculation formula is as follows:

[0014]

[0015]

[0016]

[0017]

[0018] Where:

[0019] β 2 —Blade outlet placement angle, degrees;

[0020] n s — Impeller specific speed;

[0021] —The wrap angle corresponding to the cylindrical blade, degrees.

[0022] According to the calculation results, we can Making an approximate rounding can help reduce the design workload.

[0023] The wrap angle corresponding to the twisted blade The determination formula is as follows:

[0024]

[0025] Where:

[0026] —The wrap angle corresponding to the composite blade, degrees;

[0027] —The wrap angle corresponding to the cylindrical blade, degrees.

[0028] The beneficial effects of the present invention are:

[0029] The composite blade design method proposed in this patent can achieve precise cutting of the impeller while ensuring the performance of the centrifugal pump, which not only shortens the time cost and trial-and-error cost of impeller cutting, but also ensures that the pump performance of the impeller after cutting is similar to that of the original pump. Description of the drawings:

[0030] Figure 1 A plane projection diagram of a blade according to an embodiment of the present invention;

[0031] 1- Cylindrical blade, 2- Twisted blade. Specific implementation method:

[0032] Design requirements, design flow Q = 12m 3 / h, design head H = 20m, rated speed n = 6000r / min, specific speed n s =133.

[0033] Blade Angle

[0034]

[0035] Substitute z = 6, k 1 =0.956,

[0036] have to

[0037] Cylindrical blade corresponding to the wrap angle

[0038]

[0039] Bring in n s =133,β 2 =30°,

[0040] After rounding, we get

[0041] That is, the wrap angle corresponding to the cylindrical blade is 20°.

[0042] The above is an explanation of the present invention with reference to specific embodiments, but the present invention is not limited to the specific embodiments, and also includes other embodiments or variations within the scope of the present invention.

Claims

1. A design method for composite blades of a centrifugal pump. It is characterized in that The front half of the composite blade is a twisted blade, and the rear half is a cylindrical blade. The wrap angle of the composite blade is determined by the impeller specific speed and the number of blades. The choice is determined according to the following formula: Where: z—number of blades; n s —Specific speed; k 1 —Correction factor.

2. A method for designing composite blades for a centrifugal pump according to claim 1, It is characterized in that The wrap angle of the cylindrical blade The calculation formula is: Where: β 2 —Blade outlet placement angle, degrees; n s — Specific speed; —The wrap angle corresponding to the cylindrical blade, degrees.

3. A method for designing composite blades for a centrifugal pump according to claim 2, It is characterized in that The wrap angle corresponding to the twisted blade The determination formula is as follows: Where: —The wrap angle corresponding to the composite blade, degrees; —The wrap angle corresponding to the cylindrical blade, degrees.

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