Page 383 - Understanding Automotive Electronics

2735 | CH 11 Page 370 Tuesday, March 10, 1998 1:30 PM

11 FUTURE AUTOMOTIVE ELECTRONIC SYSTEMS

the future, variable valve timing will provide significant improvement in
volumetric efficiency by reducing the constraints on valve timing.
Variable intake components offer great potential for engine performance
improvement. However, these components must be controlled by the engine’s
digital control system. A control system for optimal use of a variable intake
system is currently under development and is, of course, equally as important as
the components themselves. In addition, there is an increasing trend to apply
modern control theory (i.e., adaptive learning systems) to automotive engine
control.
Perhaps in the more distant future, technological improvements can be
expected in the following areas:
1. Variable compression
2. Swirl control
3. Fuel atomization
Compression ratio directly affects the thermal efficiency and, hence,
performance of the engine. It also affects knocking. A variable compression
ratio has the potential for significant performance improvement when suitably
controlled. The thermal efficiency of an engine is increased with increased
compression ratio. However, excessively high compression ratio can lead to
knocking. In a variable compression ratio engine the maximum compression
ratio must be limited to prevent excessive knock. The development of actuator
mechanisms and control strategies for variable compression are important
future research areas.
Swirl is a term used to describe the motion of intake gases as they enter
the combustion chamber. Swirl influences combustion speed and, thereby,
thermal efficiency. Swirl control can theoretically be achieved by using a
variable intake system. There is research currently being done in this area.
Efficient combustion of all of the energy that is available in the fuel is
influenced by fuel atomization. When fuel is mixed with air, the droplets
should be sized such that air and gasoline molecules can readily be combined.
The atomization of fuel to optimally-sized droplets is influenced by the fuel
injector configuration. Research into new fuel injectors that can provide
improved fuel atomization is underway. Also being researched is the use of
ultrasonics to increase atomization after injection has occurred.
Control Based on Cylinder Pressure Measurements
One of the more interesting new control concepts currently under
investigation is based on cylinder pressure measurements. Cylinder pressure
developed during the power stroke has long been recognized as the most
fundamental variable that can be monitored to determine the operating state of
the engine. Cylinder pressure measurements provide real-time combustion
process feedback that can be used for control of engine variables of individual
cylinders.

370 UNDERSTANDING AUTOMOTIVE ELECTRONICS