Fuel Injector: 3-Phase Flow, Mixture Model

Fuel Injector, Three-Phase Flow (Mixture Model) — ANSYS Fluent CFD Simulation

Description

Welcome to the Fuel Injector Three-Phase Flow CFD Simulation module. This project introduces fuel injection systems — a critical component in automotive and aerospace engineering — using the Mixture multiphase model in ANSYS Fluent to simulate three-phase flow inside an injector. Where the earlier injector case handled two phases, this one adds a third: liquid fuel, air, and fuel vapor all interact within the high-pressure injector, and the Mixture model represents their phase interactions, slip velocities, and mass transfer. Three-phase injector modeling of this kind supports automotive engines, aerospace propulsion, and combustion engineering. Within the Multiphase Flow: Beginner CFD Training Package, this project introduces the Mixture model and steps up to three phases, building on the two-phase VOF injector case.

Methodology

The project uses a pre-configured fuel injector geometry representing a real-world injector, including its internal passages and nozzle design, with a mesh built to capture the phase coupling within the complex geometry. Realistic boundary conditions are defined: flow rates, pressures, and phase fractions at the fuel inlet and air intake, along with nozzle-outlet and ambient conditions for spray formation. The Mixture model is central to the setup — the slip-velocity and mass-transfer models are selected and configured for accurate liquid–gas–vapor interaction and fuel vaporization, and turbulence and cavitation effects are incorporated, since these govern the multiphase behavior in the injector. The case is solved as a steady-state simulation.

Analysis

Post-processing visualizes the phase distribution and velocity profiles through contours and vector plots that reveal how liquid fuel, air, and fuel vapor move through the injector and nozzle, with spray characteristics such as cone angle, droplet size distribution, and vapor concentration quantified in the near-nozzle region. From these results you can investigate how injection pressure affects spray atomization, how nozzle geometry influences the flow patterns, and how effectively fuel and air mix — identifying opportunities to optimize the injector design. These insights connect directly to improving engine efficiency, reducing emissions, and enhancing combustion stability through precise fuel delivery. By the end of this project, you'll be able to set up a three-phase injector simulation with the Mixture multiphase model, configure slip-velocity, mass-transfer, and cavitation effects, and interpret the phase-distribution, velocity, and spray results that characterize fuel injection.