Optimization Of Sonic Nozzle Device And Technology Transformation

This paper mainly aims at the problem of the gas flow standard device of the sonic nozzle in the Beijing public utility Science Research Institute.For example,gas meter test data is not accurate,gas meter test data curve is not normal,the temperature difference between the sonic nozzle and the measured surface is larger,and the measured surface temperature of a complete detection process of large engineering problems.The laboratory environment and the gas flow standard device of the sonic nozzle were modified,and the performance was tested and studied.Results show:First,after the transformation of the device can continue to work,and has a self-test function,but also increased the type of instrument can be certified.Second,using the double timing clock pulse interpolation technology,to improve the accuracy of pulse counting.And the use of low-frequency detection technology,simultaneous acquisition of the pulse number of the flow meter and time,the minimum can be collected 0.001 Hz pulse frequency.Third,using the modular structure design,all the control signals are connected with the computer through the RS484-232 module or TCP/IP network interface,which can eliminate all kinds of interference from the computer.Fourthly,the expanded uncertainty of the whole standard device is 0.12%,which is only 50% of the expanded uncertainty of the standard device.The effect of the device and the system after the transformation is obvious.Fifth,the use of three precision of 1.0,the flow range of 5~100 m3/h,20~400 m3/h,32~650m3/h flow meter to carry out verification tests.After the transformation,the instrument coefficient value is not only lower than the coefficient value before the transformation,but also after the transformation of the instrument coefficient fluctuation is smaller,indicating that the system stability and measurement accuracy has been significantly improved.