Discussion on the errors and integration of the operation of the air blower

Test device This test adopts the export single nozzle air chamber type fan performance test device established according to AMCA210-74 standard. The device has passed the test and identification of Inner Mongolia Autonomous Region Product Quality Supervision and Inspection Institute organized by Inner Mongolia Science and Technology Commission. The test device is stable and reliable. The test accuracy is high.

This test uses the Q5 centrifugal fan as the object, and compares the error of the 15 kinds of speed flow, full pressure, shaft power and full pressure effect 11 ventilator performance and the experimental study of the Page 2 rate and the converted value. Extensive comparison. The full-pressure conversion error and the correction curve of the full-pressure performance conversion value and the measured value of the fan at different speeds are as shown in the figure. The two curves in the upper right corner are the full-pressure curve and 3000r after the measured value at low speed is converted to 3000r/min. The measured value curve under /min; the two curves in the lower left corner are the measured values ​​of the full-pressure curve and the measured value at low speed after the measured value is converted to low speed at 3000r/min.

It can be seen that the relative error of full-pressure conversion within the scope of this test does not exceed 5%; when the relative rotational speed difference is less than 20%, the error of similar conversion of the fan is small, less than 1%, within the system error range. If the error of the instrument test and the error of the data calculation are considered, it can be considered that the full-pressure performance conversion error of the fan in this speed range can be corrected, and the full-pressure performance after conversion can represent the full-pressure performance of the fan at the actual design speed. When the converted relative rotational speed difference is greater than 20%, the conversion error must be corrected. If the relative rotational speed difference is used as the abscissa and the total pressure relative error is the ordinate, a graph is drawn. As shown in the figure, the rotational speed ranges from 1000 to 2400 r/min, and the fitting and regression processing are performed, and the similarity given above is substituted. The conversion formula (2) can be used to obtain an error correction formula within a certain speed range.

The low-speed to high-speed full-pressure conversion error distribution curve verifies the empirical formula to see if it meets the actual situation. The method is to take a full-pressure measured value at a lower speed and use a formula to convert the full-pressure correction value at a higher speed to compare with the full-pressure measured value at this speed; then, at a higher speed The full-pressure measured value is converted to a full-pressure correction value at another lower speed using a formula, and compared with the full-pressure measured value at a lower speed. As a verification, the author only gives the results of the mutual conversion between 1000r/min and 2000r/min, the rotation speed conversion correction result and the test result.

The high-speed to low-speed full-pressure conversion error distribution curve can be visually seen. The measured value and the corrected conversion value basically agree well. Only the low-flow segment conversion value is slightly smaller than the measured value, while in the large flow segment. On the contrary, this is because the correction coefficient is the average value, while the actual low flow rate segment has a large relative error, and the large flow rate segment has a relatively small relative error. By verifying the comparison between the corrected value and the converted value in the range of 1000r/min to 3000r/min, it is found that the relative error between the corrected converted value and the measured value is less than 0.87% except for the single point, and the average relative error is less than 1.0%, which means that the correction formula is valid.

Conclusions (1) The test fan is a low-pressure small fan, the airflow speed is less than 20m/s, and the density of the fan outlet and inlet gas changes little. The change of gas density has been considered in the conversion process. It is found by calculation that the difference between Kpc and Kp is less than 0.005 at all speeds. It can be seen that the pressure ratio of the fan is very small. In this case, the conversion error of the flow can be neglected. (2) The shaft power of the fan has little relationship with the aerodynamic performance of the fan. In the process of similar conversion, only the calculation of the speed and density is involved, and the accuracy of the power test instrument is high. The wheel resistance loss is only related to the air density and speed. The impact on power is small, so the power conversion error is negligible within the allowable range of system error and test error.

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