For the air performance test of the traditional range hood, the test conditions of the standard GB/T 17713-2011 Appendix A clearly stipulates that the connection state of the tested sample machine and the measuring device is: "The external type range hood should be installed separately with the manufacturer. The transition cover for connecting the exhaust pipe (except for the cover valve such as the check valve), but it is not necessary to install the exhaust pipe. The test arrangement is shown in Figure 1. When the enterprise and the laboratory use GB/T 17713-2011 Appendix A In the performance test of the integrated stove bottom range hood in the test apparatus of Figure A1, the over-cover and flexible retractable exhaust duct of the integrated stove-type range hood are installed inside the appliance at the factory, so the measurement When the air volume is measured, the sampler and the measuring device must be connected through the exhaust pipe, and it is found that the length of the exhaust pipe and the difference of the exhaust route have a great influence on the air volume test result. In this regard, this paper adopts the experimental method to carry out the research. By comparing the results of the I test results of different connection forms, the causes of the differences in the test results are found out, and the necessary theoretical analysis is made, and then the unified test method is proposed.
In order to analyze the difference and ensure the comparability of the data under the same conditions, the test uses the same integrated stove and uses the same set of measuring equipment for testing. The connection between the tested sample and the measuring duct is shown in Figure 2, Figure 3 and Figure respectively. The three methods shown in Figure 4, the connection mode of Figure 2 is currently more common in the laboratory. The main reason is that because the integrated stove is relatively heavy, the testers in the daily monitoring often put the integrated stove directly on the ground for easy and convenient testing. The long retractable exhaust duct is connected with the measuring device, and the exhaust duct is composed of two nearly 90 degree elbows and a straight straight section, and the total length L of the external exhaust duct of the appliance is about 1.2 m. FIG. 3 is to place the integrated stove. On the sample support platform, the exhaust vent of the range hood and the connector for measuring the air duct are coaxially buttly connected horizontally through the exhaust duct, and the length of the external exhaust duct is L=1m and L=0.5m respectively. The connection mode of Fig. 4 is The outlet of the integrated cooker hood type range hood is directly connected to the connector of the measuring duct, and the external exhaust duct is completely compressed by the length L=0m.
The performance data under four different test conditions are shown in Figure 5. From the test results, it can be seen that the use of different connection forms has a great influence on the test results. The deviation distribution law is that when the exhaust pipe L=0, the air volume and efficiency test results are the largest, and the measurement results of the increase in the air volume and efficiency of the elbow are continuously reduced as the length L of the exhaust pipe increases. The difference between efficiency and air volume measurement results when L=0 (Fig. 4 connection mode) and L=1.2m (connection mode of Fig. 2) are 19.1% and 16.6%, respectively.
Analysis of the influencing factors of test differences and countermeasures At present, the wind turbine and wind chamber improved test equipment is usually used for the performance test of the wind turbine. The air chamber test device is equipped with an auxiliary induced draft fan, which can be used to overcome the partial resistance that cannot be overcome by the test fan itself, thus obtaining different statics. The amount of air that is depressed. However, in Figure A1 of Appendix A of GB/T 17713-2011, the outlet air duct measuring device does not have an auxiliary induced draft fan. It mainly relies on the pressure provided by the measured range hood itself to overcome the resistance of the test duct. Changes in resistance will have an impact on the test results. First of all, from the flow calculation formula of GB/T 17713 for analysis, GB/T 17713 is defined as the volume of gas delivered by the range hood per unit time when the static pressure is 0 Pa, for the traditional upper-row range hood The static pressure here means that the air flow finally leaves the air outlet section 2 of the hood casing (at the filter cover round hole), that is, the static pressure of the inlet section of the measuring device. If the area A2 of the filter housing round hole is equal to the area A4 of the section 4 of the inlet position of the measuring device inlet pipe D4, that is, the static pressure at the section 4. GB/T 17713 Figure A1 outlet air duct measuring device has only one measuring section, that is, measuring the cross section 6 of the static pressure Ps6 in the decompression cylinder. The static pressure of the outlet is not directly measured, but is calculated by Bernoulli equation. The static pressure at the section 2 is obtained by calculation, and the static pressure Ps2n is obtained by the formula (1).
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