管道流量和瓦斯浓度的检测技术的说明（A description of the detection techniques for pipe flow and gas concentration is presented）.docVIP

管道流量和瓦斯浓度的检测技术的说明（A description of the detection techniques for pipe flow and gas concentration is presented） Measurement of gas flow in pipeline 1 、 flow sensor technology selection The accurate measurement of the flow in the gas drainage pipeline is one of the important conditions for the accurate measurement and normal operation of the gas drainage system in the coal mine. At present, some domestic gas drainage pipeline flowmeter adopts vortex flow sensor, the advantage of vortex flow sensor is that the output is pulse frequency signal, less pressure loss, no rotating parts, simple structure. But the effect of vortex flow sensor by the detection principle, there are obvious shortcomings, especially in large diameter (whose diameter is larger than 250mm) and low velocity (5m/s) under the condition of full pipe vortex vortex flow signal from the sensor detecting element is very weak, simply can not detect the correct signal, resulting in vortex flow sensor in this case the measurement error is very large, some vortex flow sensor manufacturers to solve this problem, put forward the field stream diameter approach, by narrowing the scope of the flow rate increased to full pipe diameter of vortex flow sensor to correct measurement (5 m/s ~ 35 m/s), although this method can solve the measurement the problem of flow, but also raises another problem -- pressure loss, pressure loss of gas is very strict requirements of the drainage system, reducing flow this method is not good Selected. If the inserted vortex sensor is used to solve the measurement problem of big diameter and low flow rate, the measurement accuracy can not be reached. The technical requirements of the CDM project of this project will not be met. As everyone knows, compared with the full pipe type vortex flow sensor, sensor insertion type vortex had poor accuracy, and insertion type vortex sensor originally is the detection of the pipeline velocity, the sensing head usually insertion type vortex sensor plac