How to improve the impeller of centrifugal fan

As an important type of fluid machinery, centrifugal fan is widely used in various sectors of the national economy. It is one of the main energy consuming machinery and an important research field of energy conservation and emission reduction. The research process shows that improving the design level of centrifugal fan impeller is the key to improving the efficiency of centrifugal fan and expanding its operating range. In this paper, from the two aspects of the design of centrifugal fan impeller and the use of boundary layer control technology to improve the performance of centrifugal fan impeller, the methods and ways to improve the performance of centrifugal fan proposed in recent years are summarized and analyzed.

How to improve the impeller of centrifugal fan

Centrifugal fan impeller of design method

How to design a centrifugal fan with high efficiency and simple technology has always been the main problem for researchers. The main way to solve this problem is to design high-efficiency impeller blades.

Impeller is the core pneumatic component of the fan. The flow inside the impeller directly determines the performance and efficiency of the whole machine. Therefore, scholars at home and abroad have done a lot of work to understand the real flow situation inside the impeller and improve the impeller design to improve the performance and efficiency of the impeller.

In order to design an efficient centrifugal impeller, researchers have studied the flow law of gas in the impeller from various angles, and sought the best impeller design method. One dimensional design method was first used. Through a large number of statistical data and theoretical analysis, the selection rules of aerodynamic and structural parameters of each key section of centrifugal fan were obtained. In the early stage of using the one-dimensional method, the key parameters of centrifugal impeller and volute can be determined simply by calculating the average speed of each key section of the fan, and the general blade profile adopts simple single arc forming. This method is very rough, the design of fan performance requires designers have very rich experience, sometimes can get good performance fan, but in most cases, the design of fan efficiency is low. 

In order to improve the design, researchers used the concept of flow section to design the meridian surface profile of the impeller cover. The impeller cover designed in this way is two or more segments of arc. Although the efficiency of the impeller designed by this method is slightly higher than that of the previous one, the fan wheel cover designed by this method is difficult to process and has high cost, so it is difficult to be used in large fans and large fans Non standard fan production. Another important aspect is to improve the design of the blade. The improvement methods for the two-dimensional blade are mainly the equal deceleration method and the equal expansion method, and the method that the relative velocity W in the given impeller is distributed along the average streamline M. From the point of view of loss, the equal deceleration method can reduce the flow loss and improve the efficiency of impeller when the relative velocity of air flow changes uniformly at the same rate in the flow process of impeller passage; the equal expansion method is proposed to avoid excessive expansion angle in local area. The distribution of the relative velocity W along the average streamline m in a given impeller is obtained by controlling the variation of the relative average velocity along the streamline M. the distribution of the blade profile along the radius can be obtained by a simple geometric relationship. Although the above method is simple, it also needs complex numerical calculation.

With the development of computational technology, the calculation of three-dimensional viscous flow field has made great progress. According to this, some researchers have proposed approximate model method. This method is to solve the problem that the amount of calculation is too large when the random optimization method is completely used in engineering. By applying the statistical method, this method proposes a method with small amount of calculation and can ensure the accuracy of design to a certain extent. In the application of approximate model method to aerodynamic optimization design of turbomachinery, researchers at home and abroad have done a lot of work, among which response surface method and artificial neural network method are mostly used. How to effectively apply the approximate model method to the optimization of multi-disciplinary and multi operating conditions, and cover a larger practical design space with less design parameters, is an important topic.

With the deepening of theoretical research and the continuous improvement of design methods, the research on reducing the aerodynamic loss of impeller, improving the aerodynamic performance of impeller, and improving the efficiency of centrifugal fan will be better applied in engineering practice.

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