双向蒸汽流量的测量

Bidirectional Steam Flow Measurement

双向蒸汽质量流量测量是一项特殊的流量测量课题。双向孔板不切斜角,节流件两个端面均应符合国家标准中关于上游端面的规定,节流件的两个直角边均应符合国家标准中关于上游边缘的规定。通常采用2台差压变送器分别测量正反向差压,用1台压力变送器测量正向流正端取压口压力,并根据关系式计算反向流正端口取压口压力,几路信号送流量二次表判断流动方向和计算蒸汽质量流量。双向孔板流量计可按JJG640规程用几何法进行检定。另外,对于要求不高的测量点,也可用菱形截面阿牛巴均速管流量计测量。时差法超声流量计也具有双向流测量能力,可用导波板降低外夹式换能器安装处的温度,用于温度不高于400℃的蒸汽双向流测量。

Bidirectional steam flow measurement is a special flow measurement subject. According to the national standard, bevel is not cut in hi-directional orifice, both throttle ends should meet requirement of upstream end in China national standard, two right-angle sides should be consistent with requirement of upstream edge in China national standard. Positive and negative differential pressures are usually measured using two differential pressure transmitters. One pressure transmitter measures the pressure of positive pressure port for positive flow, and the negative pressure on the pressure port is calculated based on the formula. Several signals are submitted to secondary flow meter to define flow direction and calculate steam mass flow. The bidirectional orifice flow meter could be calibrated with geometry method according to the regulation of JJG640. Besides, diamond shaped section Annubar can be used to measure the point with low accuracy requirement. Transit time supersonic flow meter also has capability to measure bi-directional flow; guided-wave plate can be used to reduce temPerature at the installation site of clamp-on transducer and measure bi- directional stream flow with temperature of below 400℃.