Acoustic Emission Inspection Method And Experimental Study On Jacketed Structure Under Inner Leakage

Jacketed equipments are commonly adopted in chemical industry, which consisting of two pressure chambers, namely inner pipe and jacket. The inner pipe usually carry highly corrosive, high temperature(or cryogenic) medium and serve under high pressure. So it is always under the attack of environmental corrosion, wear, fatigue, aging, fracture, perforating and so on. Each of them can lead to the leakage of inner pipe fluid. Leakage of jacketed structure has very serious consequences, especially the inner leakage. If no effectively detection, it is difficult to figure out in time and which will cause huge economic loss and injury to the operators. So, corresponding research is highly claimed on acoustic inspection method and experiment vertification.The new method will help to make sure the safety of key jacketed equipment, also prolong service life.For the inner pipe leakage of jacketed structure, it belongs to finite space jet flow. This makes it more complex than free jet flow and has more noise sources. In this paper, under the industry requirement, acoustic source mechanism and characteristics are studied when leakage occurs in the inner pipe of a jacketed structure. Numerical simulation method is taken to respectively discuss the jet flow field distribution and noise field characteristics under free boundary and jacketed structure condition. From that, the influence is identified of inner pressure, orifice diameter and gap distance on leakage flow field and noise acoustic filed. On the basis of theoretical and numerical analysis, experimental system is set up in the lab and with which, testing experiments are carried out for two different annular substances, namely, air and water. Also, after analysis, experimental data reveals the relationship between acoustic parameters and inner pressure, orifice diameter and gap distance.The main contents are listed below:1. According to fluid dynamics theory and the analysis of free boundary flow field, theoretical analysis on the change of single phase flow field in annular space is carried out when inner pipe leakage occurs, also the distribution of jet flow field is identified. On the basis of the above, the same analysis is executed for the situation in which annular substance is substituted by water. Some key characteristics that influence the distribution of acoustic field are achieved, including the motion of water under air excitation, the growth and distribution of bubbles and the movement of bubbles, etc. After that, fluid forces formulas acting on the outer wall of the jacketed structure are advanced.2. According to the aerodynamic acoustics theory, on the basis of acoustic field analysis of single phase jet flow, that and its radiation characteristics under the situation of inner pipe leakage are studied to get the acoustic field distribution in the annular space. After that, the annular substance is replaced by water and the acoustic field distribution is achieved with the same method and steps. Also, acoustic sources types are identified.3. On the built simulation model, numerical simulation and analysis are carried out under the term that the circular space is filled with atmospheric air. The law of flow field distribution that changes along with different flow parameters is obtained, namely, orifice diameter, leakage pressure and jacket clearance. The result shows that leakage pressure decides the state of flow field. If the substance in jacket space is changed to water, the influence law is similar, while the absolute peak flow rate will rise under the same leakage condition.4. On the basis of flow field simulation, sound energy level distribution of leakage fluid is achieved with wideband noise simulation model. After that, sound sources are identified. Also, the law is summarized for sound field distribution changing with different parameters(orifice diameter, leakage pressure and jacket clearance).5. Experiment system is established for acoustic inspection on the inner pipe leakage of jacketed structure. Various testing are performed to gather data, including gas jeting into gas and into water. On the basis propagation analysis of noise in the experimental structure, the influence of jacket clearance, leakage pressure, leakage rate, orifice diameter, orifice number are discussed individually on the basis of data analysis.