Twentyfour years have gone by since the publication of K. Lohner and H. Muller's comprehen sive work "Gemischbildung und Verbrennung im Ottomotor" in 1967 [1.1]' Naturally, the field of mixture formation and combustion in the spark-ignition engine has wit nessed great technological advances and many new findings in the intervening years, so that the time seemed ripe for presenting a summary of recent research and developments. There fore, I gladly took up the suggestion of the editors of this series of books, Professor Dr. H. List and Professor Dr. A. Pischinger, to write a book summarizing the present state of the art. A center of activity of the Institute of Internal-Combustion Engines and Automotive Engineering at the Vienna Technical University, which I am heading, is the field of mixture formation -there fore, many new results that have been achieved in this area in collaboration with the respective industry have been included in this volume. The basic principles of combustion are discussed only to that extent which seemect necessary for an understanding of the effects of mixture formation. The focal point of this volume is the mixture formation in spark-ignition engines, covering both the theory and actual design of the mixture formation units and appropriate intake manifolds. Also, the related measurement technology is explained in this work.

Abstract : Dilute combustion is an effective way to increase part-load efficiencies in a Spark Ignition (SI) engine. However, dilute combustion leads to a slower combustion rate and longer burn durations, which results in higher heat transfer loss. To overcome this, some degree of charge flow enhancement exists in modern engines that improves combustion rate and shortens burn durations. This flow enhancement has an adverse effect on performance of the modern Transistorized Coil Ignition (TCI) system and hence presents a limitation on improving combustion rates. Additionally, dilute combustion has a detrimental effect on combustion stability, wherein a larger variation in engine cycle work is observed from cycle to cycle which degrades engine performance. Improving combustion stability under dilution poses a challenge for the modern single coil ignition system, which is where the motivation lies in this research. This research details the development and instrumentation of a Configurable Dual Coil Ignition (CDCI) system that is later tested on a single cylinder metal engine. The effectiveness of different ignition profiles developed with the CDCI system in extending the dilution limit while maintaining combustion performance and lower cycle-cycle variations, thereby improving fuel conversion efficiency, is investigated. Effects of dilution by excess air and internal (exhaust) residuals on the performance of these ignition profiles are investigated under different operating conditions. In-cylinder flow is enhanced by means of tumble planks installed in the intake port of the engine. The impact of enhanced in-cylinder flow on the capabilities of the developed ignition profiles is also investigated under different conditions. Moreover, effects of different spark plug gap sizes and orientations are also investigated. Although majority of the tests are done with Direct Injection (DI) gasoline, some tests are performed with Port Fuel Injection (PFI) methane to compare the effects of fuel delivery and charge preparation.