108 research outputs found
A quasi-dimensional model of pre-chamber spark-ignition engines
No full textIncreasingly stringent pollutant and CO2 emission standards require the car manufacturers to investigate innovative solutions to further improve the fuel economy of their fleets. Among these techniques, an extremely lean combustion has a large potential to simultaneously reduce the NOx raw emissions and the fuel consumption of spark-ignition engines. Application of pre-chamber ignition systems is a promising solution to realize a favorable air/fuel mixture ignitability and an adequate combustion speed, even with very lean mixtures.
In this work, the combustion characteristics of an active pre-chamber system are experimentally investigated using a single-cylinder research engine. Conventional gasoline fuel is injected into the main chamber, while the pre-chamber is fed with compressed natural gas. In a first stage, an experimental campaign was carried out at various speeds, spark timings and air-fuel ratios. Global engine operating parameters as well as cylinder pressure traces, inside main combustion chamber and pre-chamber, were recorded and analyzed.
Based on the available experimental data, a phenomenological model of this unconventional combustion system with divided combustion chambers was developed and validated. The model was then implemented in a 1D code. The proposed numerical approach shows the ability to simulate the experimental data with good accuracy, using a fixed tuning constant set. The model demonstrates to correctly describe the behavior of a pre-chamber combustion system under different operating conditions and to capture the physics behind such an innovative combustion system concept
Regarding pathogenesis of middle ear cholesteatoma
No full textУ роботі автор дійшов висновку, що розвиток холестеатоми середнього вуха при хронічному
гнійному середньому отиті є результатом порушення нормальних процесів загоєння в кістковій рані.
Дотримуючись концепції Habermann, він вважає, що розвиток холестеатоми в середньому вусі
пов’язане з атипичним запальним розростанням вростаючого в середнє вухо епидермиса зовнішнього
слухового проходуThe author concludes in his work that cholesteatoma development in the middle ear at chronic otopyosis
media results from bony-wound reparation disorders. Following Habermann’s conception, the author suggests
that cholesteatoma development in the middle ear is linked to atypical inflammatory in-growth of the external
auditory canal epidermis into the middle ear cavity
Regarding pathogenesis of middle ear cholesteatoma
No full textУ роботі автор дійшов висновку, що розвиток холестеатоми середнього вуха при хронічному
гнійному середньому отиті є результатом порушення нормальних процесів загоєння в кістковій рані.
Дотримуючись концепції Habermann, він вважає, що розвиток холестеатоми в середньому вусі
пов’язане з атипичним запальним розростанням вростаючого в середнє вухо епидермиса зовнішнього
слухового проходуThe author concludes in his work that cholesteatoma development in the middle ear at chronic otopyosis
media results from bony-wound reparation disorders. Following Habermann’s conception, the author suggests
that cholesteatoma development in the middle ear is linked to atypical inflammatory in-growth of the external
auditory canal epidermis into the middle ear cavity
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