Homework - Flow Through an Exhaust Manifold


In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. For many engines, the exhaust manifold consists of individual headpipes for each cylinder, which then converge into one tube called the collector. Other objectives of exhaust manifold design are to reduce exhaust flow and decrease the back pressure of the engine. Due to the high temperature of the exhaust, the conjugate heat transfer problem between the exhaust gas and the solid material of the manifold is also important. In this simulation, we will model exhaust gas flowing through a steel exhaust manifold consisting of four inlet pipes and one collector pipe. The working fluid used in this simulation is air with constant properties, as temperature changes in the fluid are not significant and the property variations with temperature are assumed to be negligible.



The primary objective of this simulation example is to model flow and conjugate heat transfer in an exhaust manifold. We will also (1) understand the flow structure inside the manifold, and (2) learn the conservation of mass and energy in such a system.



Download the Mesh file needed for setting up the simulation and the associated Case & Data files from here. Follow the instructions below to set up this simulation in Ansys Fluent starting with the Mesh file. In case you face any issues setting up or running the simulation, refer to the corresponding initial and final Case and Data files.

Alternate video link.

Results and Discussion

Let us now analyze the simulation results and understand the physics of exhaust gas mixing in the exhaust manifold.