Simulation of Air Induction, Spray, and Combustion for a Commercial Single Cylinder Engine
(Accepted: 1Dec98)

This investigation models the intake, compression, and power stroke for a single cylinder commercial engine. The simulation includes a wide range of physics typical for internal combustion engines including air induction, fuel spray from a carburetor, an advanced spray model, formation of the fuel vapor, moving piston, moving intake valve, and combustion using a turbulence driven (i.e. Magnussen) combustion model.

Several simulations were run to check the sensitivity of results to several parameters. Results are compared to laboratory pressure traces in the intake manifold and engine cylinder for validation. Qualitative observations (fuel reaching the air filter and location of soot deposits) are also reproduced in the simulation results. Animations of the computational results show complicated 3D, time dependent behavior.

Cycle to cycle variations, especially at partial load, encourage the analyst to perform a multiple cycle analysis that was not done in this study due to excluding the exhaust valve and exhaust stroke. An alternative to the complexity of a multiple cycle study is to conduct a sensitivity study of engine performance for a single cycle to slightly different initial conditions of wallfilm and spray droplet sizes and the amount of leftover exhaust vapors from the previous cycle.

Here are web pointers to the two figures showing the comparison of CFD results with pressure traces (demonstration of validation).

Here are web pointers to a couple of animations showing sample results.