Laboratory Research On Leakage Model In Pressure Pipelines

Based on similarity theory, an experimental model for leakage of gas and liquid pipelines was established in the laboratory, which was called Jiangsu Polytechnic University Oil-gas Storage and Transportation Safety Experimental Equipment. Similarity criteria and dimensionless equation were derived from dimensional analysis method, and the results of similarity dimensionless numbers validation showed that the model was consistent with similar requirements.To eliminate systematic errors in gas and liquid pipelines pressure transducers, it was calibrated before experiment, and then analyzed and calculated the systematic errors. By adjusting ball valves, controlled the work states of pipelines until it was steady, and then simulated different combinations of pipelines leakage through regulating various combinations of four leakage valves. Automatic sampling online system recorded the experimental data, exported online curves, detected leakage qualitatively and provided data for further quantitative analysis of leakage.According to the mechanism of negative pressure wave in the theory of surge, the principle of leakage detection and location in negative pressure wave and its reasons for the error were analyzed. The experimentation of urban gas pipelines was simulated in the laboratory gas pipelines. Using correlation analysis and MATLAB programming, the delayed number and sampling interval were solved, and then the leak locations in pipelines were positioned. The conclusion figured that this method was preferably positioning accuracy.Multi-scale decomposition and reconstruction of wavelet transform were utilized to filter the noise of negative pressure wave, which was brought by pipelines leakage. The relation between modulus maximum of wavelet transforms and signal singularity was analyzed, and the break point of pressure signal was detected accurately. Furthermore, this method verified the accuracy of leak detection and location. According to sampling theory, a new data acquisition module was programmed in Delphi language, moreover the sampling data indicated that the module increased the sampling frequency and achieved more satisfying effect.Applied state equation, isentropic equation, continuity equation and mechanical energy conservation equation in the theory of fluid mechanics, the mathematical expressions of small holes leakage in gas and liquid pipelines. Experimental data was analyzed, which came from designed experimentation of gas and liquid pipelines, and modified the flow coefficient. It proved that there was a linear relationship between pipeline leakage and main factors (pipeline pressure and leakage area).