Online Diagnosis And Correction Of Orifice Plate Flow Measurement Device Based On Flow Field Distortion

Orifice plate flow measurement device is widely used in industrial production, but two kinds of failures condition often occurs in actual use, they are inlet square edge bluntness and deposition in upstream, They cause the orifice discharge coefficient change, make the measurement values inaccurate. To solve the problems, this paper completed the orifice online fault diagnosis and correction work.The flow field changes when the fault condition compared with the normal. So the orifice Fluent simulation model is built and the Gambit meshing is optimized. Then backward steps of vortex has carried on the quantitative analysis on the downstream of the orifice plate, to determine stability of the vortex backflow region and the calculation data.By research method combining of Fluent simulation and real flow experiment, the differential pressure ratio factor and the diagnosis pressure points is defined, and the method of "distortion of flow field diagnosis in differential pressure" is put forward. The flow field of orifice in normal condition are compared with that of two kinds of common distortion flow field, including the vortex stability, diagnosis of pressure measuring point location selection, stability and resolution of the factor. It can be implemented to achieve the online judgement of the fault types, and calculate failure extent and correction flow measurement value through the factor.Through the analysis of vortex stability, optimal selection method of diagnosis pressure point is gives about different β value, diagnosis algorithms is verified through the real flow experiments, the accuracy of the algorithm is within 1.0%.In order to avoid particles sedimentation deposition in measurement, working condition of fluid contains solid particles, research on optimization of general DPM model, it is pointed out that the general model to improve the optimization through four measures, that is, from the gas phase velocity entry model, particles resistance model, particles wall collision model, particles by reasonable choice of each force. And related program through calling the Fluent macros, import custom UDF function module, embedded in Fluent software realizes the improvement.Optimization in the simulation, experiments have verified the accuracy of the optimization of DPM model is superior to general DPM model, compared with simulation of real flow experiment, proved that optimization is a success. Model optimization method, which is versatile to applies in liquid-solid two phase flow conditions.Finally, through the simulation calculation, the paper discusses several kinds of orifice plate structure improvement measures on orifice plate structure which have arc-shaped and slope shape transition zone, through comparative study it is concluded that the improved orifice discharge coefficient increases, the pressure loss reduces, and the possibility of wear and sedimentation reduces.