Evaluating influence of CFD mesh on flow characteristics of pneumatic brake valve differential section

The selection of the nozzle diameter of the differential section of the trailer air brake valve is crucial for two-range operation of the system adopted by the designers. Using CFD tools, it is possible to determine the flow characteristics of the components with reference to the mode of operation and the valve switching times from tracking to accelerating function. Taking into account the shape of the working chambers of the differential section of the conceptual brake valve and the small effective flow area resulting from the nozzle diameter, assessment of the influence of the mesh on the flow characteristics was carried out. The use of different meshes can be a cause in the discrepancies between the results obtained. The selection of a suitable mesh can reduce computation time and provide flow characteristics comparable to the results determined on a laboratory bench. For different nozzle diameters, both in SolidWorks Flow Simulation and Ansys Fluent, the influence of variable mesh parameters — element shape and number of nodes, on the flow characteristics is compared. The influence of the mesh was assessed on the orthogonal mesh in SolidWorks and on the different types of mesh available in Fluent. Evaluation of the quality of all finite element mesh variants considered was carried out using basic statistical indicators. The determined flow characteristics will allow evaluation of the influence of the nozzle diameter on MFR (mass flow rate) of the differential section, resulting in the selection of a nozzle that meets the design and functional objectives. The selection of an appropriate finite element mesh will enable further extension of the model to include the main and auxiliary feeders, taking into account the movement of the elements (dynamic mesh), resulting in a complete numerical model of the valve, ensuring a reduction in the response time of the system to the operator’s excitation in relation to solutions available on the market.