Study on the factors influencing air valve protection against water hammer with column separation and rejoinder

Abstract

Air valves are used to suppress negative water pressures in water transmission pipelines. They also play a key role during the water filling and drainage stages in pipeline systems. However, systematic guidelines for the selection of air valve parameters are lacking. In practical engineering applications, the selection is mainly based on personal experience. If the selected parameters are not appropriate, negative pressures can occur in a pipeline due to insufficient air inflow or destructive water hammer pressures with column separation and rejoinder, which are caused by rapid air discharge. Given the subjectivity of the selection of air valve parameters in engineering applications, this paper introduces the structure and working principle of two different types of air valves. Combined with engineering examples, the one-dimensional transient flow elastic model and the characteristic method are used to conduct numerical simulations in MATLAB to investigate the influences of the air valve type, the inlet and outlet orifice diameters, and the inflow and outflow discharge coefficients on protection against water hammer with column separation and rejoinder. The inflow and outflow coefficients of the anti-slam air valve have a slight influence on preventing water hammers with column separation and rejoinder. The research results provide a theoretical basis for the rational selection of air valves in practical engineering applications.

Contribution of Air Management to the Energy Efficiency of Water Pipelines

“…Of note, Equation ( 23) has the largest value of β of those reported in the review done by Lauchlan et al (2005) [10]. Figure 11 shows the v c versus √ sinθ curves obtained using Equations ( 22) and (23). The curves obtained from Equation ( 23) have a lower inclination than those obtained from Equation (22).…”

“…The curves obtained from Equation ( 23) have a lower inclination than those obtained from Equation (22). However, this is somewhat compensated by the larger β in Equation (23). Figure 11 also indicates typically adopted minimum slopes for water pipelines [10].…”

“…Recent research has focused on the influence of entrapped air during typical unsteady pipeline flows, such as filling [18,19] and draining [20,21] procedures, pump trip events [22], and valve manoeuvres [23]. Nevertheless, entrapped air can also be influential to system behaviour during relatively steady flows, which are usually prolonged and thus have even greater importance regarding energy consumption considerations [16,[24][25][26][27][28][29].…”

Exploring the Sensitivity of the Transient Response following Power Failure to Air Valve and Pipeline Characteristics

“…Research relating to air in pressurised pipelines can be categorised into three classes: experimental studies [16], combined experimental-numerical investigations [17], and purely numerical explorations [18]. Due to space limitations in controlled labs, experimental and experimental-numerical studies often focus on small-scale systems, which hinders their applicability to large-scale applications [19].…”

“…Certainly, numerical studies exploring the transient behaviour of large-scale pipelines influenced by the presence of air can be found in the literature. These studies include, for example, the works by Pozos et al (2010) [23], Ramezani and Karney (2017) [10], and Li et al (2022) [18]. The current paper is in this tradition and provides a comprehensive numerical analysis of the transient behaviour in a pressurised rising water pipeline with an air valve during a pump trip scenario.…”