| Pipeline transportation,together with railway,aviation,highway and water transportation,is known as the five major transportation industries,forming a material transportation network of the world.Among them,oil,natural gas and other strategic resources rely heavily on pipelines for long-distance transportation.But pipeline accidents occur frequently due to pipeline aging,external damage and other factors.Pipeline monitoring has become a powerful means to ensure the normal operation of pipelines.However,with the increase of pipeline transportation mileage year by year,the t raditional pipeline monitoring technology is difficult to achieve real-time monitoring without blind time and blind area.The difficulty of distributed full-time pipeline monitoring is increasing,and the safe operation of pipeline is facing severe challenges.In this thesis,the theoretical and experimental research of pipeline flow rate measurement and leakage monitoring is carried out to meet the needs of distributed full-time on-line pipeline condition monitoring.In this paper,a monitoring method of pipeline operation state is proposed,which combines fiber distributed acoustic sensing technology with fluid structure coupling effect of pipeline.A single fiber is used to realize non-invasive monitoring of flow rate and leakage of long-distance pipeline,which has a good application prospect in ensuring the safe operation of long-distance pipeline network.The main contents are as follows:（1）Based on the flow rate measurement model of flow induced vibration effect and optical fiber distributed acoustic sensor system,the theoretical model of pipeline flow rate and leakage monitoring is established.The relationship between flow rate and pipe wall pressure is simulated and analyzed by FLUENT software.The correctness of the model is verified,and the feasibility of non-invasive flow rate measurement method is demonstrated.Meanwhile,the theoretical derivation of pipeline leakage monitoring is carried out,the prediction model of pipeline leakage diameter is constructed.What is more,the leakage positioning method is systematically studied,and the influence of sensor unit layout on leakage positioning accuracy is expounded.（2）The research on pipeline leakage monitoring based on fiber distributed acoustic sensor technology is carried out.The pipeline leakage monitoring system is built.The response characteristics and location methods of the pipeline leakage diameter are studied systematically.The results show that the leakage diameter prediction and leakage location could be achieved by monitoring the leakage vibration signal,and the leakage diameter prediction in the range of 2.5mm-9.8mm could be achieved by calculating the time domain statistical characteristics of 25 mm PVC pipes.Also,by monitoring the transmission characteristics of the leakage vibration wave along the pipeline,the centimeter level leakage location is realized,and the positioning error is only 0.45%.（3）Based on the flow induced vibratio,the non-invasive and distributed flow rate measurement of pipeline is carried out,and the response characteristics of single pipe and long-distance pipeline under different flow rate conditions are systematically studied.The non-invasive flow rate measurement method was explored in the flow rate range of 0-3.6 m/s,employing single PVC pipe.The results show that the non-invasive measurement of flow rate could be realized by monitoring the characteristics of flow induced vibration signal.The sensitivity of flow rate measurement is 0.03998 rad/(m·s-1)at 3.6 m/s,and the measurement error is stable within 10%.The results of single pipe section are extended to the flow rtae measurement of long-distance pipeline,and the experiments are carried out in laboratory（25m long PVC pipeline）and field test（20m long steel pipe）.The experimental results show that the method has the ability of distributed pipeline flow rate measurement,and the T-test results show that it has good spatial consistency. |
