Theoretical And Experimental Study On Gear Flowmeter

As a kind of volumetric flowmeter with high measure accuracy, gear flowmeter is widely used to measure the flow of high viscosity medium, such as fuel oil, resin and polyvinyl alcohol. Although the measurement of hydraulic system steady mean flow is reliable, the dynamic flow of the high pressure side of the system test results are not ideal. When the primary instrument is determined, The dynamic characteristics of flow meter is also affected by the secondary instrument。 This paper mainly studies the feasibility of volumetric flow meter used in high pressure hydraulic system dynamic flow test. Myself work was summarized in this paper as follows:Firstly, this paper designed a standard gauge supported for remote real-time monitoring based on the Modbus protocol. In the stage of experiment cost-effective and high speed (1T) MCU 12C5A60S2 is used as the control chip, precision frequency measurement is achieved by MCU PCA module (programmable counter array), voltage signal is simpled by MCU AD converter module with the resolution of 10 bit. A stable analog voltage signal is achieved by PWM module (pulse width modulation) of MCU accompanied by the interface circuit. Half duplex communication network is composed of RS-485 with the feature of differential signal negative logic. Flow meter data in the form of IEEE754 single precision floating-point standard will be transmitted to the host computer in the data-link layer of the OSI model based on Modbus standard protocol. PC monitoring system is programmed by the Kingview, supporting remote access, data overrun alarm, parameter setting and other functions. The gauge can directly show the experimental results.Secondly, improved the original test-bed. The platform was designed with PLC control inverter, the inverter control motor, motor drive gears, traffic signal to realize dynamic simulation. The experimental results show that the frequency of the dynamic signal which is measured by gear flow meter can reach 16.67 Hz, which is much more higher than ever before.Then, we build a comprehensive test-bed with a servo valve and a flowmeter. The test-bed is used to study on the dynamic characteristic of gear flowmeter. The test-bed not only calibrate the measuring accuracy of the flowmeter, but also test the dynamic characteristics of the flowmeter. The pressure displayed by gauge on the test-bed is the same with the numerical value gathered by data acquisition card, which verified that the pressure signal acquisition system is stable and reliable. Through the test-bed, a lot of valuable data are collected, which provide the basis for the next analysis and research.At last, we simulated the gear by FLUENT software. We obtained pressure and velocity vector distribution,pressure and velocity nephograms. Simulation results and experimental results are in good agreement, which verify the correctness of the experiment.