Although increasing the fan speed can increase the fan air volume approximately linearly, it is necessary to change the fan drive equipment and its foundation, and the requirements for the dust, water and impeller balance accuracy of the fan are higher, which cannot be achieved without a large amount of investment. Changing the number of impeller blades does not cause changes in the main structural dimensions of the fan, which has less impact on the total pressure of the fan, the fan speed does not increase, and the retrofit cycle is shorter, saving investment in transformation. The disadvantage is that the operating efficiency of the fan changes, increasing the energy consumption, but by matching the blade angle, the power loss can be reduced.
According to the Eck fan theory, a centrifugal fan cannot be mathematically determined to determine its optimum number of blades, as in an axial fan. Therefore, when designing a blade flow path, the number of blades is determined by ensuring that the airflow flows reasonably, so that the airflow is not Separation occurs or eddy currents are less generated. The optimum number of blades for a centrifugal impeller can only be determined by experimentation. According to Stodora's inference and its test, changing the actual geometric width of the blade flow path will cause a considerable change in the angle of the relative velocity of the airflow and the absolute velocity. The velocity triangle at the partial filling and the full flow of the blade is not at the rotational speed. In the case of change, reducing the blade pitch, that is, increasing the number of blades, will cause the relative speed w3 to increase, resulting in a significant increase in the radial velocity 2m. According to the theoretical flow calculation formula of the fan v=c2mPd2b2, the impeller diameter d2 and the impeller width b2 are known. When the circumferential speed u2 is constant, the increase of c2m will increase the theoretical flow of the fan proportionally.
Reform practice and its effect In early 1999, our factory commissioned Shenyang Blower Factory to increase the number of blades for a fan impeller used. From the original design, 18 blades were increased to 20 blades, the blade shape was unchanged, and the boost was not Change, the spindle power increased from 1042kW to 1132kW, in line with the requirements of this transformation. It was installed on the unit in May 1999 and started to run after the overhaul in July. The operation was in good condition. Before and after the operation, we made a comprehensive measurement of the fan volume. Before the transformation (in June 1999), the average gas volume was 4780915m3/h, and after the transformation (November 1999), the average gas volume was 5811516m3/h. Excluding the effect of resistance changes after purification and modification, the fan volume is increased by about 5000-7000 m3/h. Centrifugal fans can significantly increase the amount of air supplied by increasing the number of impeller blades, and can greatly save the transformation funds. The optimum number of blades for the impeller can only be determined experimentally. Not every fan can increase the amount of air by increasing the number of impeller blades. Increasing the number of impeller blades will increase the impact loss, decrease the boost voltage, and reduce the fan efficiency. Therefore, it is not appropriate to increase the number of blades by 132.d1 to increase the number of blades. The spindle power increases and the bearing load increases accordingly. The strength of the sliding bearing must be redesigned during design. Check that the operation must be controlled at rated speed.
. Digital/Mechanical control with Rotation.
*. Food grade Aluminum plated for inner chamber
*. 1-60 minutes timer setting,TEMP. setting 65-200℃
*. Rotation function for cooking, and rolling cage.
*. Dual mesh basket for two different favor one time.
*. Non-stick coating for 5.5L basket with detachable handle*. High speed hot air circulation, to make food even & crispier.
*. Transparent visible window to see cooking process.
*. With overheat protection, free oil to cook health food.
*. Plug:UL/VDE/BS Optional, exposed length 1M
*. Certificate: GS CE EMC LVD ROHS LFGB ETL FDA
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