The test device and the test process were studied with a 5 high specific speed centrifugal fan with a rotational speed of 1450 r/min. The test uses the same centrifugal fan, only the number of impeller blades is changed. In the range of the optimal flow channel equivalent expansion angle 813, the impellers with the number of blades 6, 6, 12, 16 are tested respectively. .

In the test, the flow rate is measured by a compensating micro-pressure gauge with a resolution of 0.1Pa and an accuracy of 0.5Pa. The static pressure is measured by a tilting micro-pressure gauge, one-stage accuracy; the measured power is a three-phase power meter, one-stage accuracy; and the noise measurement is ND2 type. Precision sonic meter with an error of 0.5dB(A).

In order to ensure the comparability of the data under the same conditions, the same set of precision measuring instruments and equipment are used to perform dynamic and static balance before the impellers of different vane number fans are installed; the collector outlet and the impeller front cover inlet are strictly controlled during the installation process. The gap formed by the space; the three-phase regulated power supply is used in the test process; the measurement is to read the test data uniformly after the working condition is stable, and the data of each working condition is finally confirmed after repeated review.

The data obtained from the data calculation and processing test is calculated and processed. The aerodynamic performance and noise test are carried out according to the national standard, and the ratio A is calculated according to the relevant standards of the industry. The dimensionless pressure coefficient p, the dimensionless flow coefficient Q, the dimensionless power The coefficient N, the efficiency and the ratio of the A-level LSA finishing are plotted as shown.

The test conclusion can be seen that in the range of the dimensionless flow coefficient Q=0.20.3, the efficiency is near the maximum value, and the ratio of the A sound level is near the lowest value, so it is concluded that the number of blades is between 616 pieces (corresponding flow) The test conclusions of the ball equivalent expansion angle 813) are as follows: (1) The dimensionless flow rate corresponding to the highest total pressure efficiency point of the four blade number fans is basically unchanged; (2) The ratio of the A sound level of the fan with different blades is the highest. The lowest value is reached near the efficiency point, and the change is small with the number of blades; (3) the relationship between the dimensionless pressure coefficient p, the dimensionless power coefficient N and the dimensionless flow coefficient Q increases with the number of blades. There is a significant increase. The relationship between the efficiency and the dimensionless flow coefficient Q is relatively small, and the highest efficiency point is 0.810.85. (4) The selection of the optimal number of blades of the fan is not a certain value, but a certain range.

Significance and application Due to the different blade number 5 centrifugal fan efficiency of more than 80%, both are better efficiency models. According to the number of blades tested, four kinds of practical model fans are obtained. The various parameters are shown in the following table.

Fan blade number ratio revolution ns (SI system / engineering) impeller runner equivalent expansion angle eq dimensionless flow coefficient Q dimensionless pressure coefficient p efficiency This method is used to change the performance of the fan to adapt to the pipe network, Since only the number of blades needs to be changed, the method is simple, the processing cost is low, the time is saved, and the practical application is facilitated.

This method provides a new idea for the serial design, system matching and transformation of the fan, which makes the design and application of the fan more selective.

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