Study on the Key Parameters of Flow Element for Particle Samplers

In view of the deficiency of flow orifice flow element commonly used in particle samplers, we began to develop an orifice flow element with a small gas flow range. The inlet Reynolds number of the corresponding flow element in this flow range does not exceed two thousand, basically belonging to the laminar flow state, which has exceeded the application range of the differential pressure flow element specified by the existing various standards. In order to ensure the flow performance of the newly designed orifice, it is necessary to give the maximum allowable deviation of the three key parameters of orifice thickness E, throttle orifice thickness e and pressure extraction position. Computational fluid dynamics simulation was used to determine the maximum allowable deviation of the parametric machining of the above geometric dimensions. For two kinds of microflow orifice plates with different flow rates, the recommended thickness of the microflow orifice plate and the recommended thickness of the throttle orifice, and the corresponding maximum allowable geometric deviation were obtained. The upper and lower reaches used D-D/2 pressure, the accuracy of the upstream pressure position was
$\pm 0.1\mathrm{D}$
, and the accuracy of the downstream pressure position was
$\pm 0.05\mathrm{D}$
. Based on this key dimension, the linearity of the outflow coefficient and the processing consistency of the designed laminar flow orifice are better than 1.5 per cent.