Effects of a Multi-flow Trim on the Flow Characteristic of a Control Valve

Control valves are essential components in energy systems, particularly in industrial pipeline systems, where they are used to regulate flow conditions according to customer requirements. Among the various components of a control valve, the trim plays a significant role by providing an additional flow arrangement for pressure drop, which can have different shapes depending on the design specifications. Traditionally, the performance of control valves has been assessed experimentally using global flow parameters such as pressure and flow rate. However, understanding the impact of trim geometric features on the internal flow properties of control valves has been a challenging task. This study numerically analysed the local flow characteristics around an equal travel Multi-Flow trim using a well-validated Computational Fluid Dynamics (CFD) model of the control valve. The critical flow measurements including flow rate, pressure drop, and flow coefficient Cv of individual flow paths for the Multi-Flow trim have been computed using the CFD model. The study considered five valve open percentages (20, 40, 60, 80, and 100%) and two inlet velocities (1 and 2 m/s) as simulated conditions. The quantitative analysis of simulated results revealed that the complex shapes of the trim strongly influenced the internal flow distributions, as the holes in each row have different radial positions and diameters. The local Cv of the Multi-Flow trim is also a function of the position and size of the individual holes. A 1-D numerical model has been developed for local Cv prediction, which can be used in further trim optimisation designs.