Modeling of Unsteady Multiphase Flow in the Intake Manifold of Spark Ignition Engines

Experimental studies show that spark ignition engines under unsteady operation are subject to a temporary equivalence ratio excursion. This phenomenon can lead to lean misfiring and/or high pollution levels.

In this paper, we propose a model that describes this phenomenon by an unsteady annular dispersed flow with two components, air and fuel (film and droplets).

The results show that the modeling reproduces well the equivalence ratio excursions in transient operation, as well as response times comparable to those observed experimentaly. Besides, and although they have a small response time, the droplet population can play a great part into the equivalence ratio excursions. Furthermore, the model analyses the influence of some parameters such as:

• the droplet deposition rate,
• the air temperature,
• the initial droplet diameter,
• etc.