Species Transport: Engine Manifold

Manifold of Engine (Species Transport) — ANSYS Fluent CFD Simulation

Description

This project presents a CFD simulation of air–fuel mixing in an engine manifold using the Species Transport model without chemical reactions. The manifold has two inlets — one supplying air, one supplying a multi-component fuel gas — and three outlets, of which only one is open while the other two are blocked (treated as walls). The goal is to study how the species mix as they travel through the manifold and to evaluate the pressure on the blocked surfaces. As the opening project of the Species Transport: Beginner CFD Training Package, it introduces the model in its simplest form — tracking and mixing multiple species without chemistry — establishing the foundation the dispersion and reacting-flow cases build on.

Methodology

The three-outlet manifold fluid domain is designed in Design Modeler and meshed in ANSYS Meshing with an unstructured grid of roughly 231,646 elements. A multi-species mixture is built from the Fluent database (N₂, O₂, CO₂, CO, H₂, CH₄, H₂O), and the energy equation is activated along with the inlet diffusion and diffusion energy source options. Species mass fractions are set at each inlet — air (N₂ 0.79, O₂ 0.21) and a multi-component fuel stream (CO, CH₄, CO₂, N₂, H₂). Mass-flow inlet boundary conditions are applied — air at 0.2335 kg/s and fuel at 0.0374 kg/s — with the blocked outlets modeled as walls. The k-ε Standard model with enhanced wall treatment is used, together with PISO pressure–velocity coupling. Crucially, the Species Transport model here tracks how the multiple gas species convect, diffuse, and mix without any combustion reaction.

Analysis

Post-processing examines the species distributions through the manifold, showing how the air and fuel streams mix as they travel toward the open outlet, and evaluates the outlet mixture mass flow rate (0.271 kg/s) and the pressure on the blocked outlet surfaces (771.45 Pa and 780.98 Pa). From these results you can assess the quality of the mixing and the loading on the closed surfaces. Species Transport without reactions is the foundation for mixing, intake, dilution, and ventilation analysis, and mastering multi-species mixtures and mass-fraction boundary conditions here prepares you for combustion, emissions, and any flow where gas composition matters. By the end of this project, you'll be able to build a multi-species mixture, set species mass-fraction inlet conditions, run a non-reacting Species Transport simulation, and interpret the concentration, mass-flow, and pressure results that characterize gas mixing in a manifold.