Abstract:
Literature showed quite clearly that the efficiency of Air
to Fuel Ratio (AFR) control for Spark Ignition (SI)
Internal Combustion Engines (ICE) strongly depends on
its capacity to deal with the fuel-flow phenomena inside
intake manifolds.
Moreover, engine performances (such as power output,
specific fuel consumption, and exhaust gas emissions)
are directly related to the efficiency of the combustion
process, which, on its turn, can be affected substantially
by the air/fuel ratio variations related to the fuel-film
dynamics.
In this work a comprehensive model-based air/fuel ratio
control technique is proposed: this is based on a
dynamical model of the air dynamics inside inlet
manifolds and on the online identification of the fuel-film
parameters. Here the identification procedure is
illustrated in detail and validated basing on experimental
data regarding a single-cylinder engine. In order to
demonstrate the method validity, in fact, a single-cylinder
research engine (type AVL 5401) equipped with a port-
fuel injection system has been experimented using a
dynamic test bench.
The first-order model of Aquino has been used as a
basis to form the required algorithm for the identification
process. The required input variables are the amount of
fuel injected and that of the air inducted in the cylinder.
This latter value is not obtained (as usual) by a look-up
table stored in the ECU, but is calculated within each
engine cycle by a mathematical model of the air
dynamics developed by the same authors. The model
used is named Model Of Interconnected Capacities
(MOIC) and has been previously presented and
separately validated.
