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By paralleling the network resistance formed by artificially adjusting the air leakage, the operating point of the tested wind turbine can be moved along its own characteristic curve, so that different working condition parameters can be obtained. The two parallel modes are used to change the operating parameters of another fan by adjusting the opening of a vertical gate. However, it should be pointed out that the use of different parallel methods causes different changes in the operating conditions of the fan. When the fans are connected in parallel, the operating point of the tested fan is shifted to the right along the wind pressure curve of the standby fan gate, until the normal ventilation condition is stopped; when the network is connected in parallel, the working condition changes exactly the opposite. By combining two parallel modes, a wide range of fan operating parameters can be measured. Since it is not necessary to adjust the vertical gate or the anti-damper of the tested fan, it can avoid causing a distorted flow field in its air passage. As long as there is a certain linear length between the fan inlet and the branching elbow (4B6B, the site can generally be satisfied), it can provide the uniform flow field conditions required for measuring the section and the fan inlet.
Estimation of the influence of mine air volume The parallel adjustment of operating parameters can solve the problem of generating a distorted flow field in the test, and create conditions for the performance of the mine without stopping production. However, regardless of the parallel mode test, the downhole air volume will change, and the degree of influence of the method on the downhole air volume should be analyzed. The fan is connected in parallel with the two vertical gates. The downhole air volume has a maximum value of Qmax, which is greater than the normal ventilation air volume of the mine (QM (the air volume when a single fan works on the network); the network parallel standby fan is fully open, and the downhole air volume has a minimum value Qmin. , less than QM.
The relative change amount of the mine air volume |q| is |q|=Qmax(Qmin)-QMQM100%. The size of |q| varies depending on the characteristics of the mine network and the characteristics of the wind turbine. To ensure the safety of underground ventilation, it must be controlled within a reasonable range. Before the test, we should make an estimate of |q|, which can use computer to simulate the resistance characteristics of the mine network and the wind pressure characteristics of the wind turbine. The Qmax, Qmin and QM are solved according to the above correlation formula. The specific method is not described in this paper. Although the simulation results are approximate, it is necessary to guide the adoption of appropriate testing measures.
The measured results and analysis The author cooperated with the Yubei Mining Bureau to conduct a non-stop production field test on a mine south wind shaft ventilator by parallel method. Two G4-73No18 fans were installed in the wind shaft, and the operating air volume was 2200 m3/min. The measuring section is selected between the vertical gate and the fan inlet, 4B from the branching turn, 15B from the fan inlet, 9 full pressure pipes and 4 static pressure pipes are arranged, and the dynamic pressure and static pressure of the section are measured by the velocity field method. Calculate the air volume of the fan and the full pressure of the unit.
During the test, the fan vertical gate is fully opened, and the opening degree of the standby fan is gradually adjusted. The two parallel methods are combined to adjust the working condition parameters. The pressure gauge readings were stable during the measurement, indicating that the test section airflow was stable and the pressure did not fluctuate irregularly. During the period, a wind surveyor was set up to monitor the wind flow changes. Before the test, the relative change of the downhole volume was calculated by computer simulation |q| up to 18%, the wind gauge measured by the wind meter was 15%, but the time was not long (about 10min), and the underground production was not affected. Comparing the measured curve with the manufacturer's product sample curve, the two are very close. The data of each measuring point agree well with the fitting curve, and the variation law is consistent with the sample curve. The measured results show that the parallel operation method is used to adjust the working condition, and the distortion flow field is not caused in the inlet duct of the fan. The test data is stable and reliable. The internal flow field of the fan is not disturbed during the test, and the characteristic curve of the survey reflects its actual running performance.
The flow field in the air duct when the on-site centrifugal fan is tested under the production conditions by the traditional method is analyzed. It shows that the standby fan is used for the ground short-circuit air intake test, or the vertical gate is used to adjust the working condition, resulting in a distorted flow field in the inlet air duct. The test data is distorted, and the internal flow field of the impeller is disturbed, so that the performance of the fan is changed, and the test result cannot truly reflect the running characteristics. The test is carried out by parallel connection of the fan and the parallel connection of the network. The standby fan vertical gate is used as the condition adjustment device of the tested fan, which does not interfere with the flow field in the front air duct of the tested fan, and improves the accuracy of the test result. Testing in parallel mode will cause changes in the air volume of the mine. Before the test, the relative variation of the air volume can be estimated by computer simulation |q| for reference when formulating the test plan. The field test proved that the parallel test proposed in this paper provides a more accurate and feasible method for the performance test of the centrifugal fan under the production conditions.
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