Study On Gas Mass Weighing Device For Rossini Calorific Value Metering System

At present,the Rossini gas calorific value measurement method is the most accurate gas calorific value measurement method,in which the accurate weighing of gas mass is one of the key technologies.In this paper,an accurate gas mass weighing device has been designed.Before and after gas calorific value measurement,the gas mass that has been burned can be weighed by the device automatically and accurately,and it ensures the accuracy of the gas calorific value measurement.In order to achieve interference-free measurement,it is necessary to realize the automation of the gas mass weighing process and accurately analyze the factors affecting the mass weighing of gas.The theoretical analysis and experimental research are carried out for the gas mass weighing device and the matching control unit,and the uncertainty of various influencing factors of gas mass weighing is analyzed.The main research contents of the paper are as follows:(1)The overall scheme of gas mass weighing device was designed.Combined with the design indicators,the composition module of the device was analyzed,the mechanical structure of the automatic weighing device and the automatic ejection device was designed in detail,other relevant parts of the device were analyzed and calculated,and they were selected and processed according to the accuracy requirements of each part finally.(2)A set of automatic gas mass weighing device was developed.The control scheme of automatic ejection device for gas storage container and the required hardware circuit were designed.A lower computer composed of STM32microcontroller was set up.The upper computer software was written based on LabVIEW software platform.The LabVIEW software realized the accurate movement of the three-axis gantry platform,the accurate on-off of the proximity switch and the real-time signal acquisition of the pressure sensor.(3)Factors affecting accuracy during gas mass weighing were analyzed in detail.First of all,the volume of the gas storage container was calibrated by the gas standard method,and the volume of the gas storage container is 264.43cm~3,uncertainty was0.053%.The effect on the volume was 0.057%when the internal air pressure was0.75MPa.Changes in air density due to fluctuations in air temperature,relative humidity and atmospheric pressure have a greater impact on gas weighing.In this paper,the maximum influence of air density on the uncertainty of buoyancy measurement is 0.036%under experimental conditions.Through experimental measurements,the relative error of mass measurement caused by air buoyancy fluctuation is-0.026%～0.026%,after eliminating the effects of air buoyancy using the double-ball comparative weighing method,the extended uncertainty measured by the mass weighing device is u_c=0.511mg.