Experimental and theoretical investigation of thermoacoustic oscillations in natural gas metering stations

In natural gas flow metering and pressure regulation stations flowmeters, heat exchangers and control valves are usually connected in series. Especially in the case of two or more measuring bars sometimes at minor flow rates untypical pipe vibration together with flow metering faults are observed. Based on field investigations the dependencies between the pipe vibration level, the gas pulsation inside the pipe and the operating conditions of the heat exchanger are analysed. It turns out that with increasing heat flow rates into the natural gas the pulsation and hence the metering faults as well as the pipe vibrations are amplified. In order to understand the physical dependencies of this phenomenon besides experiment a theoretical study is performed. The origin of the vibration turns out to be a thermoacoustic instability. According to the Rayleigh criterion gas pulsations are amplified if heat is given to the gas at the moment of greatest condensation. Based on detailed theoretical investigations by means of the method of characteristics using a Rijke tube model the physical dependencies are analysed. Finally potential solutions to avoid this vibration problem at natural gas metering stations are introduced. (c) 2011 Elsevier Ltd. All rights reserved.