19-07-2011, 04:28 PM
ABSTRACT
A high-frequency electrical resonance-based ignition concept
is in development to replace conventional spark ignition
functionality for gasoline engines employing various types of
fuel injection methods. The concept provides the benefit of a
continuous discharge phase and the electrical power of the
discharge can also be adjusted to the needs of the combustion
conditions.
This concept employs an alternative method of generating
high voltages, using inductors and capacitors trimmed such
that the supplied energy steadily increases the output voltage.
This configuration is widely known as Tesla transformer and
has been engineered to operate in a modern gasoline engine
combustion environment. This development allows very high
break down voltages to be generated and the power into the
spark itself can be influenced. Several new innovations in the
areas of high frequency, high current, and high voltage
electrical contacts were required, as well as new
encapsulation methods and electronic controls to give good
performance as an automotive ignition source.
The circuit topology for the concept is called a capacitiveloaded,
quarter-wave transmission line and the resonating
structure is dominated by a dedicated high frequency spark
plug and a single wound coil. The electronic source which
supplies this passive structure underwent several iterations
before a preferred electronic solid state driver-amplifier
configuration was identified.
The new ignition system concept and the latest engine results
will be presented. The chosen design trade-offs will be
discussed.
INTRODUCTION
The ignition complex of problems is as old as the
development of reciprocating engines. The aim is to increase
the efficiency of the fuel conversion to mechanical work at
minimum environmental impact, hence lowest emissions at
any time and any power. This paper is presenting a new
evolution step of the conventional ignition system. It allows
shaping of the electrical properties of the spark to behave like
a classical arc, a corona-type discharge or even allows to
release heat without a spark. The duration of discharges is a
parameter of free choice.
The motivation of this development is the GDi stratified lean
injection work at Delphi; it opens the possibility to enhance
the combustion process in regards to lowering the fuel
consumption (CO2) and emissions, particularly if operated
under a broad speed load range. This new ignition system
could be one enabler for this combustion process.
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