Numerical Simulation And Experiment Research On The Averaging Pitot Tube Flow Sensor Of Separate Structure

The averaging pilot-tube flow sensor has been widely applied in themeasurement of large-diameter flow with the following advantages: simple structure,low manufacture cost, convenient dismounting (applicable for no-cutoff dismounting),simple maintenance, small loss of pressure, energy conservation, high accuracy andgood long-term operating stability. With the expansion of the project scale at present,the measurement pipe diameter of the the averaging pilot-tube flow sensor alsoincreases, and the accompanying problem lies in the difficulty of processing thetraditional overall averaging pilot-tube flow sensor. In this paper, study on thefollowing aspects was carried out through the conception of new-type averagingpilot-tube, CFD simulation and real flow experiment.The averaging pilot-tube flow sensor in Separate structure was proposed anddesigned, including front and rear independent pressure-tapping test rods, betweenwhich a guide plate was placed. The two test rods and the guide board wereassembled together through biding ring, forming the whole sensor.Five cross-section shapes were proposed on the basis of separate structure.Through CDF simulation, two-dimensional numerical simulation was carried out forthe five cross-section shapes. According to the simulation result analysis, thecross-section shapes with performance were selected for three-dimensional simulation,to test the consistent degree between the two-dimensional simulation andthree-dimensional simulation. Prototype processing and experimental test werecarried out for the scheme4and scheme5. It could be concluded from the simulationand experimental result that within5~30m/s flow velocity, when measuring the gasflow, the instrument coefficient of the averaging pilot-tube flow sensor of the separatestructure in scheme4was0.587, and the linearity was1.210%, while it was0.592and0.534%respectively in scheme5. Through flow field analysis of two-dimensional andthree-dimensional simulation, it has been discovered that the width and length of thevortex in the downstream of the averaging pilot-tube test rod have a relatively hugeinfluence on the linearity of the instrument coefficient of the sensor. The greater thewidth and length of the vortex is, the better the linearity of the instrument coefficientwill be. In this paper, the influence on the performance of the averaging pilot-tube flowsensor, when the pressure port of the total pressure and flow direction respectivelytransferred about3°,5°and7°to the left and right respectivelywas studied. Throughexperimental verification, when the pressure port of the total pressure and the flowdirection transferred to the left and right about3°,5°and7°respectively, theinstrument coefficient may deviate from the normal one for less than3%, while thelinearity error is smaller than2.5%when compared to the normal operation. It isconclude that the deflection installation has a small influence on the instrumentcoefficient of the averaging pilot-tube.