Investigation Of Acoustic Emission Characteristics Of Horizontal Air-liquid Pipe Flow

Two-phase flow is commonly encountered in oil and gas production and transportation industry.The flow regime of flow system in pipe affects the overall operation status and the safety of the whole pipeline directly and greatly.Thus it is of great importance to characterize varies flow regimes like stratified flow,bubble flow,slug flow and dispersed flow.Acoustic emission method is a passive,non-invasive technique and has been widely used in various industry fields.AE monitoring can be performed anywhere in the vicinity of AE sources.The AE technology can save operating cost for oil production process;also it can avoid dangerous operating accidentsIn this paper,the feasibility of Acoustic Emission(AE)technology to monitor of two phase flow has been investigated.Then the influence on AE signals under varies conditions such as the sensor installation location,the gas and liquid superficial velocity and the fluid medium property has been analyzed.Based on this,both time domain and frequency domain characteristics of AE signals under three different flow regimes including stratified flow,bubble flow and slug flow have been analyzed and then compared.Combined with the experimental synchronous videos,the original AE waveforms have been used as a basis for identifying the air–oil flow conditions.After that,a new flow pattern map has been given based on the AE technology.Besides the time-domain analysis method,the acoustic signal characteristics of liquid slug unit cell(including slug head,slug body and liquid film)in slug flow regime have been studied through the method of fast Fourier transform analysis and Wavelet Transform analysis.The results show that the combination of time domain and frequency domain analysis of the acoustic signal can judge the degree of turbulence as well as the degree of the activities of the internal air bubble in the two-phase flow system.In addition,the two-channel AE measurement has been used to obtain slug frequency and slug velocity A pair of capacitance probes have been applied during the test and are used for the measurement of slug velocity,which have been used to make comparison with the experimental results achieved by AE method.The results show that the two methods match well under high mix velocity.Also the Nicklin empirical correlation has been compared with slug velocity achieved by AE method and it shows that these two methods match well under low mix velocity.The research results can be used to support the real-time monitoring of oil and gas pipeline based on the acoustic emission technique.