| 摘要 |
<PICT:0351584/III/1> In a device for withdrawing and estimating the dust in a sample of dust-laden gas flowing through a conduit, the sampling nozzle itself is used as a pilot tube for determining the fluid pressure conditions both within the conduit and within the nozzle itself. The nozzle 15 which faces the gas current in the conduit 5 communicates through a cock 16 with a dust extractor 18 and suction fan 20. Small tubes 21, 23 are fitted on the inside and outside respectively of the nozzle and have openings 26, 27 at right-angles to the gas current. Manometers C, A'have one limb open to the atmosphere and the [other limb connected to tubes 21, 23 respectively,] while manometer B is connected across the tubes 21, 23. Manometer C indicates the static pressure in the conduit. When cock 16 is closed the nozzle 15 and tube 23 convey both the static pressure and the impact pressure of the gas to manometer A, while B registers the impact pressure alone. When cock 16 is opened to withdraw a sample the suction is regulated until manometers A, C give the same reading. The gas velocity meters A, C give the same reading. The gas velocity in the nozzle is then the same as that in the conduit and the amount of dust passing through the latter is readily calculated from the test of the sample withdrawn. |
