This book consists of papers prepared for and presented at a NATO sponsored Advanced Study Institute which was held in Montechoro, Portugal during the period 16-27 April, 1990. This Institute was attended by approximately ninety delegates from fifteen countries and followed from a related Institute held in Vimeiro, Portugal in 1987 (see the book entitled "Instrumentation for Combustion and Flow in Engines", edited by D. F. G. Dur~o, J. H. Whitelaw and P. O. Witzel. The purposes of the first Institute related closely to instrumentation for use in gas-turbine combustors and the cylinders of internal-combustion engines. These topics were also addressed in the second Institute, though in a manner which was wider ranging and chosen to demonstrate and explain the development and application of measurement methods to combusting flows in general. The papers contained in this boo~ were selected to provide the reader with a comprehensive and up-to-date view of the variety of experimental techniques available to measure in combusting flows. Included are discussions of their range and applicability, potential accuracy and ease of use. Thus, the first paper provides a brief overview and the second an indication of those aspects of combustion which should influence the choice of flow property to be measured and the technique to be used.

Much has been said and written about the abilities of modern instrumentation to help solve problems of combustion in engines. In the main, however, the design and fabr ication of combustion chambers continues to be based on extrapolation of exper ience gained from use and rig tests, with little input from advanced techniques such as those based on optical diagnotics. At the same time, it has become increasingly difficult to design better combustion chambers without knowledge of the relevant flow processes. Thus, the future must involve improved understanding which, in turn, will require detailed measurements of velocity, temperature and concentration. The need to narrow the gap between current industrial practice and the acquisition and implementation of improved techniques motivated the organization of the Advanced Study Institute upon which this volume is based. This Institute on Instrumentation for Combustion and Flow in Engines was arranged to display the needs of industry and the possibilities made available by modern instrumentation and, at the same time, to make clear the relative advantages of optical and probe techniques. Held at Vimeiro during the period from 13 to 26 September, 1987, the Institute was attended by 120 participants and 16 invited lecturers.

A work on turbulent premixed combustion is important because of increased concern about the environmental impact of combustion and the search for new combustion concepts and technologies. An improved understanding of lean fuel turbulent premixed flames must play a central role in the fundamental science of these new concepts. Lean premixed flames have the potential to offer ultra-low emission levels, but they are notoriously susceptible to combustion oscillations. Thus, sophisticated control measures are inevitably required. The editors' intent is to set out the modeling aspects in the field of turbulent premixed combustion. Good progress has been made on this topic, and this cohesive volume contains contributions from international experts on various subtopics of the lean premixed flame problem.

The combustion of fossil fuels remains a key technology for the foreseeable future. It is therefore important that we understand the mechanisms of combustion and, in particular, the role of turbulence within this process. Combustion always takes place within a turbulent flow field for two reasons: turbulence increases the mixing process and enhances combustion, but at the same time combustion releases heat which generates flow instability through buoyancy, thus enhancing the transition to turbulence. The four chapters of this book present a thorough introduction to the field of turbulent combustion. After an overview of modeling approaches, the three remaining chapters consider the three distinct cases of premixed, non-premixed, and partially premixed combustion, respectively. This book will be of value to researchers and students of engineering and applied mathematics by demonstrating the current theories of turbulent combustion within a unified presentation of the field.