Household Ultrasonic Gas Meter System Design

Natural gas is a green,environmentally friendly and clean energy source,and its demand is constantly increasing in the 21 st century,the theme of protecting the environment.Then,accurate metering of natural gas is very important.With the development of technology,ultrasonic flowmeters have further improved the performance of measuring flow such as accuracy,stability and power consumption.Different types of ultrasonic flow meters have been used in commercial,industrial and domestic applications.Among them,the time difference method ultrasonic flowmeter has unique characteristics,such as high precision,no moving parts,and wide range ratio,which has become the most used ultrasonic flowmeter.As a new type of flowmeter,ultrasonic flowmeters are widely used in industrial metrology and commercial natural gas trade due to their unique advantages such as high precision,non-contact and low cost.In this paper,through the research and analysis of the design of the flow channel,a flow channel design with a linear velocity correction coefficient is proposed.The flow path is a rectangular flow path and is added to the fairing such that the flow fields in each rectangular flow path are in a laminar flow state.By establishing the force balance equation through the knowledge of fluid mechanics,it can be deduced that the ratio of the mean flow velocity to the average flow velocity is linear in the laminar flow.The maximum spacing and the minimum spacing between the segments are determined according to the conditions of the laminar flow and the conditions under which the acoustic waves are diffracted.Compared with the nonlinear relationship between the surface average flow velocity and the line average flow velocity of the conventional circular flow channel in the turbulent state,the flow field distribution of the multilayer rectangular flow channel is more uniform,and the measurement error can be made smaller.In this paper,the linearization correction coefficient of the error curve of the ultrasonic gas flowmeter is compared and analyzed by the fourth-order polynomial fitting algorithm and the least squares method and the genetic algorithm.Among them,the fourth-order polynomial algorithm and the least squares method and the genetic algorithm respectively use polynomials and exponential polynomials as objective functions.The results show that the accuracy of the quadratic polynomial algorithm is higher than that of the other two algorithms.It further shows that the curve fitting with the fourth-order polynomial algorithm can best approximate the measured data and improve the measurement accuracy.In addition,this paper introduces the method of measuring the acceptance,transmission circuit and measurement time of the ultrasonic flowmeter,and adopts the MSP430FR6043 chip of TI(Texas Instruments).The whole system consists of four parts: MCU,charge amplifier(AMP),analog switch(SW)and ultrasonic sensor(T).