Transient Phenomena Generated in Emptying Operations in Large-Scale Hydraulic Pipelines

Abstract

Air pockets generated during emptying operations in pressurized hydraulic systems cause significant pressure drops inside pipes. To avoid these sudden pressure changes, one of the most widely used methods involves the installation of air valves along the pipeline route. These elements allow air exchange between the exterior and the interior of the pipe, which alleviates the pressure drops produced and thus prevents possible breaks or failures in the structure of the installation. This study uses a mathematical model previously validated by the authors in smaller installations to simulate all hydraulic variables involved in emptying processes over time. The purpose of these simulations is the validation of the mathematical model in real large-scale installations, and to do this, the results obtained with the mathematical model are compared with actual measurements made by the partner company. The hydraulic system selected for the study is a pipeline with a nominal diameter of 400 mm and a total length of 1020 m. The results obtained from the mathematical model show great similarity with the experimental measurements, thus validating the model for emptying large pipes.

Different Experimental and Numerical Models to Analyse Emptying Processes in Pressurised Pipes with Trapped Air

“…• Mathematical models based on the rigid column model are a fundamental tool for understanding the physical evolution of several hydraulic and thermodynamic variables based on differential equations that can be manipulated by the user according to the hydraulic scenario that is to be studied. These models have been validated in different investigations, showing good agreement with experimental measurements, and, additionally, they have been applied in large-scale hydraulic scenarios [19,36]; • A 2D CFD model allows study of the emptying process of an irregular pipeline with an air valve. The presence of air valves facilitates the air admission process during the water drainage process and mitigates subatmospheric pressures.…”

“…The use of these models depends on different user-determined factors, such as (i) physical equations, (ii) level of detail of the information, (iii) use of computational resources, (iv) calibration process and (v) computational simulation time. For example, mathematical models have provided good numerical results for pressure oscillations and discharge water flow in emptying processes, which have also been used in large-scale pipelines through the manipulation or control of the associated physical terms that may be considered in the water and air phases [19,36]. However, these models present restrictions in their use, taking into account that some complex hydraulic and thermodynamic phenomena cannot be predicted in detail or must be assumed in these hydraulic events.…”

Determination of the Characteristics of the Electromechanical Equipment of the Micro Hydroelectric Power Plant at the Gueeni Site on the Kokoulo River

“…These speed variations are the cause of pressure variations (also called water hammer) which can be positive or negative. The excess pressure is determined by formula 16 [15]. [5] IJESRT is licensed under a Creative Commons Attribution 4.0 International License.…”

Developing water supply system in Szőgye

“…Figure 7 shows a diagram of transients generated during operation of the asynchronous pump of Well 15. the maximum, minimum and absolute values of the pressure change can be read from the diagram [10].…”