Analysis and Discussion on the Related Characteristics of Axial Flow Local Fans

JBT-51 partial fan with air splitter. The splitter is mainly composed of a casing 1, an inner cylinder 2, a current collector 3 and a streamline cover 4; 5 and 6 are an impeller and a rear guide vane, respectively. In the figure, L1 is the length at which the tip end of the blade extends into the flow divider; L2 is the distance between the tip end of the blade and the end surface of the inner cylinder.

Selecting different L1 values ​​will result in different characteristic curves. When L1=9mm, the characteristic curve still has a hump, but the pressure difference between the highest point and the lowest point has decreased from the original 22mmH2O to 4mmH2O. When L1=13mm, the hump has disappeared. When L1=18mm, there is no significant difference between the characteristic curve and L1=13mm. If L1=23mm, the characteristic curve has no hump, but the curve has dropped significantly and the efficiency has also decreased. Therefore, it can be considered that the reasonable range of the L1 value in the fan splitter is 13mm-18mm, which is equivalent to 40%-50% of the axial projection of the chord length of the top surface of the blade.

The operation effect and parameter selection of the fan splitter can be measured on the fan with the splitter. When the windage of the ventilation network is small and the internal quantity is large, the characteristic curve of the fan operating point when the curve hump fan is not installed with the shunt B , XXL1=13mmD, L1=23mmXX The wind turbine characteristic curve after installing the diverter, the airflow in the annular passage (K) between the shunt casing and the inner cylinder is in the same direction as the main airflow, that is, the wind is supplied to the impeller.

At the optimum operating point, the annular passage does not enter the wind or the wind. If the wind flow continues to decrease and the wind resistance increases, then there is a flow back through the annular passage. Since this backflow is promptly led to the inlet end of the fan, the harmful phenomenon of the hump section of the characteristic curve is eliminated. In the air splitter, the characteristic curve of the fan at L1=18mm and the characteristic curve of the original fan. After the fan is installed with the splitter, the wind pressure, air volume and power increase slightly at the operating point 8 and the efficiency is relatively large. improve. The more optimized the structural size of the shunt, the better its effect. The technical transformation work practice and statistical data show that the main parameters of the diverter should be in the following range: when the impeller diameter is D, L1=(0.035-0.045)D, L2=(0.015-0.025)D, L3=(0.32-0.42) D, the maximum diameter of the shunt housing is D2 = (1.05-1.15) D, and the inner diameter of the shunt can be designed as D1 = (0.95 - 0.98) D.

The axial flow type local fan is a device that uses a large number of long-term operation; from the above analysis and experiment, it can be seen that the simple and feasible technical improvement measures can improve the mechanical characteristics of the operation and improve the efficiency of the equipment, thus not only enhancing the ventilation effect, Moreover, a large amount of electric energy is saved, and significant benefits are obtained at the project site.

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