Characteristic Analysis And Experimental Research Of Two-dimensional Dual Piston Flowmeter

As a kind of common flowmeter,the positive displacement flowmeter has high measurement accuracy,and the external factors such as the installation conditions and the viscosity of the measured fluid have little influence on the measurement accuracy.The positive displacement flowmeter can be used for accurate measurement of high viscosity liquid(such as hydraulic oil,etc.),which makes it have considerable application value in the industrial field.Although the positive displacement flowmeter has the above advantages,it can't measure the high frequency flow.In this paper,two-dimensional dual piston flowmeter is studied.The most remarkable feature of the flowmeter is that the internal piston can not only move axially,but also rotate circumferentially.Because there are two degrees of freedom in the moving parts,the structure of the moving parts can be designed more compact and lighter,which makes such flowmeter possible to measure high frequency flow signals.The main research contents of this article are as follows:1.The mathematical model of pressure loss and internal leakage flow of the twodimensional dual piston flowmeter under constant flow was established,and the pressure loss formula and the value of leakage formula were solved by iteration.The pressure loss includes the pressure loss of the orifice and the pressure loss caused by the movement of the moving parts.The pressure loss of the latter was obtained through the dynamic analysis of the moving parts.Internal leakage includes internal leakage at the side of the piston and internal leakage at the piston rod.After solving the mathematical model iteratively,it was found that the pressure loss will increase with the increase of the measured flow rate,and the proportion of the orifice loss will increase.In addition,the leakage flow will increase with the increase of the measured flow,but the leakage at the piston is always the most important leakage;2.For the phenomenon of the churning of moving parts in the measurement process.First of all,the fitting formula of the torque value is obtained by the fluid simulation.After that,on the basis of simulation,a bench was built to measure the torque value of churning.Finally,the fitting formula is optimized by experimental data and applied to the calculation of pressure loss;3.In view of the unique structure of the piston in the two-dimensional dual piston flowmeter,the internal leakage of the piston side was analyzed through the fluid simulation to verify the feasibility of the internal leakage calculation formula proposed in this paper;4.In order to verify the applicability of the theoretical formula,the pressure loss and flow coefficient of the two-dimensional dual piston flowmeter under constant flow rate were measured by experiment,and the experimental data were compared with the theoretical calculation value.The comparison results showed that the theoretical calculation value of pressure loss can match the experimental data well when the measured flow is less than 10 L / min,when the measured flow is greater than 10 L / min,the experimental data will be greater than the theoretical calculation value,and the gap will increase with the increase of the measured flow,but the maximum error within the measurement range will not exceed 20%.In addition,the flow coefficient obtained by theoretical calculation is larger than the ideal flow coefficient,which is closer to the experimental data.The relative error can be reduced by about 80% by using the flow coefficient measurement calculated by theoretical calculation;5.On the basis of the theoretical model under constant flow rate,the mathematical model of the two-dimensional dual piston flowmeter under unsteady flow rate was proposed,and the differential equations were established.Then,the Runge-Kutta method was used to solve the differential equations.The results showed that the rotation speed of the single model can't reflect the measured flow signal correctly,but the rotation speed of the dual model can reflect the measured flow more correctly.The theoretical response frequency of the dual two-dimensional piston flowmeter can reach 400 Hz with the amplitude attenuation to-3d B as the standard.