Research On Structure Of Liquid Turbine Flow Sensor With High-precision

The turbine flow sensor is widely used in industrial measurement field because it has many advantages of high precision, good repeatability and wide measuring range. Measurement accuracy of sensor has practical significance to improve production efficiency and the accuracy of metrology. The purpose of this paper is to improve the measurement precision of sensor by the changes of the velocity profile at the entrance of impeller.This paper deeply analyzes the mechanism which velocity profile at the entrance of impeller effects turbine flow sensor and the factors which has the influence on the change of the velocity distribution at blades of sensor, the thesis puts forward two kinds of methods that improve measurement accuracy of turbine flow sensor based on velocity profile. Firstly: optimization structure parameters of the sensor by analysis of turbine flow sensor mathematical model, in order to reduce the sensitivity of measurement precision to the changes of velocity profile. Secondly: the rectifier is used to accelerate the development of turbulent flow in the pipeline, in order to improve velocity profile at the entrance of sensor.This paper analyses the existing mathematical model of turbine flow sensor, and designs a kind of algorithm for optimization of structure, draw a conclusion: when tip radius of the blade rt is equal to 24.3mm, the linearity error of the sensors is the miniun; when tip radius of the blade rt is greater than(or less than) 24.3mm, the linearity error of the sensors will increase. The kind of optimization algorithm of sensor structure is verified by the CFD simulation and experiment. Finally this paper obtains the optimal scheme: tip radius of the blade rt is equal to 24.3mm, hub radius of the blade rh is12.5mm.According to velocity distribution at the entrance of sensor, this paper is based on the principle that the ratio of the average flow velocity of the torus and the average velocity of pipe is equal to each torus flow cross-section ratio, and designs a non-uniform porous distributed rectifier. Axial momentum number KU, the radial momentum number KV and symmetry number KA is used to assess internal flow field distribution of sensor through the rectifier. The rectifier can effectively improve velocity profile at the entrance of sensor and reduce linearity error of the sensor by the result of the experimental.In this paper, the experimental test of turbine flow sensor with DN10 mm and DN50 mm were carried out on the water flow standard facility and variable viscosity liquid flow standard facility, and the result of the experiment is compared and analyzed, the conclusion that the trend of coefficient of the sensor is affected by the viscosity of fluid is obtained, and qualitatively explain the existing problems in experimental data.