Research On Gas Flow-meter Based On Fluidic Principle

The fluidic flow-meter with feedback passages induces fluid vibration according to Coanda effect.The frequency of the vibration is proportional to the flow rate in a large flow range.It has a application prospect in household gas,water,medical fluid and other places of small flow measurement because of its characteristics of no mechanical moving parts,long service life,low lower limit in theory,high measurement accuracy and so on.At present,the study on fluidic flow-meter mainly concentrated on the construction of planar oscillator.However,the vibration plane was not in the pipe axis planar of fluidic oscillator.So that the flow pressure pulsation which generated in upstream pipe easily disturbed with the internal flow field of fluidic oscillator and reduced the measuring precision.In addition,the intelligence of traditional fluidic flow-meter was low and it was hard to calibrate.These problems seriously limited its application scope.In order to solve the above problems,a new flow-meter based on fluidic principle has been researched and studied.The research of the paper was as follows:(1)The mechanical modeling and simulation analysis.According to the Coanda effect,a new mechanical model of the fluidic oscillator has been established in the Solid Works.The mechanical model was imported to the Gambit,the fluid domain was extracted and the grid model was meshed.Then Grid model was imported to the FLUENT,in order to simulate the status of the flow field in fluidic oscillator.The points have been placed in the key position of fluidic oscillator to monitor the pressure of the key position under the same velocity and to determine the position of the sensor.At the same time,the oscillating frequency has been monitored under different flow velocity and the corresponding relationship between oscillation frequency and flow velocity was obtained.(2)The design of hardware and software system.The sensor signal was so weak that the meter was susceptible to disturbance and its measurement precision was reduced.In order to improve the precision of the fluidic flow-meter,the weak signalprocessing circuit has been put forward and designed.In addition,the key circuit,LCD display circuit,storage circuit,pulse output circuit and GSM wireless communication circuit have been designed according to the requirements of its application.The system software mainly includes frequency acquisition subprogram,flow calculation subprogram,pulse output subprogram,data storage subprogram,GSM wireless communication subprogram and key subprogram.(3)Experiment research.It has been researched and studied on the fluidic flow-meter by constructing experimental platform with the standard meter method.The error and repeatability has been calculated by a large of experimental data and the source of uncertainty has been analyzed.According to the data,it has been proved that the fluidic flow-meter has advantages of wide measurement range,high accuracy and so on.