Experimental Research On Current Rush To Interception Air-mass In Delivery Pipeline System

Long water-delivery pipeline project has features of large span and flow. Theproject technical measures should be taken at the time of put into operation.Butthese measures made pipelines vaey with undulating terrain greatly. Thus, in thesystem, air mission will be inevitably trapped near the raised segments and othercomponents of pipeline. Because it contains pumps, valves, water hammerprotection devices and other components in the system, when the accumulation ofair mass reaches a certain magnitude, some operating behaviors of the water systemsuch as pump start and stop, fast closing valves, etc. will cause the emergence of thephenomenon of current rush to interception air-mass., the water pressure resultedfrom this phenomenon could cause damage to the pipe, such as bursting or clashing.In this paper, experimental methods, based on experimental theoretical basis and thetheory of two-phase flow, are used to found the physical model, and thus analyzedand discussed the issue in-depth.Research on current rush to interception air-mass in delivery pipeline systemconsists of two stages associated with each other. The first is the stage in thepipeline filling with water; Another is called current impact stage. That is,continuous operation of the full-pipe flow pipeline was destroyed by the methods ofsudden shutdown of valves and occured water hammer. For water-filling stage, asthe pipeline was mainly in the status of gas-liquid two-phase non-full pipe flow, thetransform process of flow patterns is relatively complex, the changes of current rushto interception air-mass related to location, frequency and intensity of the waterpressure occurred at local position and these changes were random. in order toaccurately recording the detail data and analysis of abnormal pressure and variation,the experiment has taken the following means:1. a collection software of pressure byadjusting and setting the sampling frequency to meet the requirements of theexperiment;2. Reasonable and feasible experimental program were raised to studythe filling process at various working condition about45°single-segment and theseries-connection segments(45°and60°);3. There are mainly some ways to changeworking conditions, using drive or valve to change the flow of pipeline, adjustingthe process of changing flow, that is, continuously adjusting, phased-adjustment offlow changing and varing the time of changing flow etc. In order to provideconditions for subsequent analysis by combining digital data with the image, thevideos and data of two-phase flow pressure and flow state data in the experimentalsection of piping systems were shot and recorded,,.Experimental measurements inevitably produce deviations. Thus the experimental deviation analysis and data processing become very important. First,basic theory of deviation analysis and data processing was regarded as basis andcarried out a general introduction of window function, deviation analysis methodand data processing.. In order to apply the theory, deviation analysis and dataprocessing should binded Specific examples of experiments. Under the guaranteethat the data could reflect the true value, finally, pressure curves for each measuringpoint could be got by removing system deviation and random deviation as much aspossible.Finally, the final results of the current impact process and the water fillingprocess was processed by charts. When the experimental results were combined withthe experimental phenomena, the result could be analyzed. It can be found that forthe water-filling process with complexity and randomness, means of flow changing(adjust the drive/control valve) and the process of flow adjusting (continuouslychanging flow/stages change the flow) can not affect the trends and results of thepressure alone. When it need to analyze their impact on the process and results ofpressure changing, both of the factors above should be combined with the time offlow changing. In the current impact process, however, flow, air-mass volume,methods of flow changing, addition of experimental segement, slope of inclined pipeon the raised segment and synchronization phenomena of water hammer could eachhad influence on the experimental results relatively independent. Conclusions drawnfrom further analysis of the factors above will bring some theoretical andapplication value for actual water project.