The objective of this study is to investigate the relationship
of performance of the captioned engine and its characteristics of
exhaust emission and conclusively to systematize the combustion
analysis of it. As a first step, the burning rate and other several
combustion characteristics values are obtained from the statistical
values from the pressure-cards of a number of cycles, and their
correlation with the IMEP, ISFC, ISNO, exhaust temperature and
cyclic variation of combustion are determined, being employed the
connection orifices and air fuel ratios as parameters. By deducing
from their results, the following new concept is obtained that it
should be introduced into the analysis of the combustion phenomena
of this type of engine, that is to renew the past concept of two
staged combustion system but this is three staged combustion
engine. And a guiding principle for further study of this type of
engine is established.
1. The first stage combustion at prechamber has the role of
igniting the lean mixture of main chamber and that of the ejection
of the jet flame for accelerating the combustion of main
chamber.
2. The second stage combustion occurs during the first-half
combustion period of main chamber by means of flame jetting
combustion. The flame jet involves a great amount of the mixture of
main chamber within a short period. An increase of this component
causes a significant increase in heat loss than thermal efficiency,
resulting in a worsening IMEP, ISFC, and furthermore an increase in
ISNO.
3. The third stage combustion occurs during the later-half
combustion period of the main chamber by means of the diffusive
propagating combustion. The flame jet, impinged on the surface of
the wall after the second stage combustion, is converted into small
swirls and turbulences, which accelerate the combustion of the
unburned mixture in the main chamber. When this component is
increased, IMEP and ISFC are improved without heat loss and ISNO
showing any significant increase.
4. The deeper investigation of each role of three stage
combustion mechanism should be emphasized. Thereby, the
optimization of each component of this type of engine will be
improved and the capability and ultimate limit of performance
characteristics of it will be defined.