| Valves as a kind of universal mechanical product are applied widely in every field, whose safety are always paid more attention. Leakage is the main failure style of valves, including exterior leakage and inner leakage. The exterior leakage can bring many accidents, not only affecting producting, but also causing harm to the entironment and losing much energy. The exterior leakage has been paid more attention, and the inspecting technology and method are also developed. The inner leakage is difficult to find when the valves are at work, but that will affect the safe running of valves and can cause accidents, such as polluting medium, firing and blasting, poisoning, which are all the results of inner leakage. Now for the inspection of inner leakage, there are no effective methods; it mostly depends on sense and experience, which lack scientific basis, so an effective inspection method for inner leakage is required. Gas inner leakage of valves is process of jet flow, with jet flow noise, which can be inspected by acoustic method. This paper researches the sounding principle and acoustic characteristic of gas inner leakage for valves based on gas inner leakage of valves. Theory analysis proves the existence of jet flow noise for gas inner leakage of valves, and the formula between quadrupole acoustic intensity and jet flow speed is obtained. By the method of numerical simulation, the characteristics of jet flow field and sound field of pin valves, gate valves and ball valves are researched and the influenceof the parameters such as inlet pressure and inner leakage clearance of valves on inner leakage jet flow field and sound field. Acoustic inspection experiment system is established, then inner leakage acoustic inspection experiments of pin valves, gate valves and ball valves are made; at last, the numerical simulation results are vertified. The researches of this paper provide a theory foundation for the application and development of valves gas inner leakage acoustic inspection technology, which have important theoretical significance and Practical value.The main contents include of this paper:1.The research of sounding principle and acoustic charicteristic of dynamic fluid sound source during the process of gas inner leakage of vales. By the theory of pneumatic acoustic, gas jet flow and eddy movement, theory analysis of sounding principle and acoustic charicteristic of dynamic fluid sound source during the process of gas inner leakageis made. And according to the real condition of gas inner leakage, jet flow noise source of gas inner leakage could be approximately replaced by quadrupole sound source.2.The establishment of flow parameter equation of jet flow noise intensity for gas inner leakage. The interaction between jet flow field and jet noise fieldis analysesed, according to the flow equation of gas jet flow and aerodynamic sound equations, the equation between jet flow speed and jet flow noise intensity of inner leakage is established.3. Numerical simulation and analysis of gas jet flow field at different inner leakage condition of pin valves, gate valves and ball valves. By CFD simulation software, with RNG k-εmodel and low Re k-εmodel at near boundary area, gas inner leakage jet flow fields of pin valves, gate valves and ball valves are simulated, and the distributing rule of inner leakage jet flow flied of three kind of valves at different inner leakage clearance and different inlet pressure.4. According the analysis of the result of numerical simulation for axis symmetry gas jet flow field, the distributing rule of jet flow speed is obtained. By the method of numerical fitting, distribution function of axis symmetry gas jet flow speed is determined. By analogous method, the distributing simulation functions of inner leakage jet flow speed of three kinds of valves at different condition are obtained.5. The establishment of numerical simulation method of valves inner leakage jet flow sound field. According to the aerodynamic sound equations of Lighthill and gas jet flow equation, jet flow sound field control equation of valves gas inner leakage is established considering the influence of jet flow speed. By the second-order precision weighted average implicit finite difference method, the jet flow sound field control equations of valves gas inner leakage are computed. With no reflection and absorption and all reflection boundary calculation boundary, meanwhile corresponding treatment to the corner of the area is applied to ensure that the area is closed. Initial source Gaussian quadrupole sound source is as a source of pressure pulsation.6. Numerical simulation and analysis of gas jet flow sound field at different inner leakage condition of pin valves, gate valves and ball valves. According to numerical simulations of valves gas inner leakage jet flow sound field, By MATLAB software numerical simulation programme is worked out to get numerical simulation results of the three kind valves at different inner leakage condition.7. Acoustic inspection experiment study of valves gas inner leakage. Simulate experiment equipment for acoustic inspection of valves gas inner leakage is established, then acoustic inspection experiment of gas inner leakage of pin valves, gate valves and ball valves are made. The results prove that jet flow noise exists during valves gas inner leakage, and the best inspection position of the three kinds of valvesis determined so as that and gained the influence rule of inner leakage clearance, inlet and outlet pressure on noise intensity and inner leakage speed. It is also confirmed that the obstruction phenomenon exists during gas inner leakage and the relationship between jet flow noise intensity of gas inner leakage and inner leakage rate at the state of obstruction of the three kinds of valves. 8. According to the theory analysis, numerical simulation and experiment result of gas inner leakage jet flow sound field, the formula between gas inner leakage rate and noise intensity is established, acoustic quantitative inspection of valves gas inner leakage is achieved.
|
PDF Full Text Request