This book focuses on developing strategies for ultra-lean combustion of natural gas and hydrogen, and contributes to the research on extending the lean flammability limit of hydrogen and air using a hot supersonic jet. The author addresses experimental methods, data analysis techniques, and results throughout each chapter and: Explains the fundamental mechanisms behind turbulent hot jet ignition using non-dimensional analysis Explores ignition characteristics by impinging hot jet and multiple jets in relation to better controllability and lean combustion Explores how different instability modes interact with the acoustic modes of the combustion chamber. This book provides a potential answer to some of the issues that arise from lean engine operation, such as poor ignition, engine misfire, cycle-to-cycle variability, combustion instability, reduction in efficiency, and an increase in unburned hydrocarbon emissions. This thesis was submitted to and approved by Purdue University.

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.

Developing clean, sustainable energy systems is a pre-eminent issue of our time. Most projections indicate that combustion-based energy conversion systems will continue to be the predominant approach for the majority of our energy usage. Unsteady combustor issues present the key challenge associated with the development of clean, high-efficiency combustion systems such as those used for power generation, heating or propulsion applications. This comprehensive study is unique, treating the subject in a systematic manner. Although this book focuses on unsteady combusting flows, it places particular emphasis on the system dynamics that occur at the intersection of the combustion, fluid mechanics and acoustic disciplines. Individuals with a background in fluid mechanics and combustion will find this book to be an incomparable study that synthesises these fields into a coherent understanding of the intrinsically unsteady processes in combustors.

This book presents methodologies for analysing large data sets produced by the direct numerical simulation (DNS) of turbulence and combustion. It describes the development of models that can be used to analyse large eddy simulations, and highlights both the most common techniques and newly emerging ones. The chapters, written by internationally respected experts, invite readers to consider DNS of turbulence and combustion from a formal, data-driven standpoint, rather than one led by experience and intuition. This perspective allows readers to recognise the shortcomings of existing models, with the ultimate goal of quantifying and reducing model-based uncertainty. In addition, recent advances in machine learning and statistical inferences offer new insights on the interpretation of DNS data. The book will especially benefit graduate-level students and researchers in mechanical and aerospace engineering, e.g. those with an interest in general fluid mechanics, applied mathematics, and the environmental and atmospheric sciences.

This graduate-level text incorporates these advances in a comprehensive treatment of the fundamental principles of combustion physics. The presentation emphasises analytical proficiency and physical insight, with the former achieved through complete, though abbreviated, derivations at different levels of rigor, and the latter through physical interpretations of analytical solutions, experimental observations, and computational simulations. Exercises are mostly derivative in nature in order to further strengthen the student's mastery of the theory. Implications of the fundamental knowledge gained herein on practical phenomena are discussed whenever appropriate. These distinguishing features provide a solid foundation for an academic program in combustion science and engineering.

This book highlights the theories and research progress in gaseous detonation research, and proposes a universal framework theory that overcomes the current research limitations. Gaseous detonation is an extremely fast type of combustion that propagates at supersonic speed in premixed combustible gas. Being self-sustaining and self-organizing with the unique nature of pressure gaining, gaseous detonation and its gas dynamics has been an interdisciplinary frontier for decades. The research of detonation enjoyed its early success from the development of the CJ theory and ZND modeling, but phenomenon is far from being understood quantitatively, and the development of theories to predict the three-dimensional cellular structure remains a formidable task, being essentially a problem in high-speed compressible reacting flow. This theory proposed by the authors’ research group breaks down the limitation of the one-dimensional steady flow hypothesis of the early theories, successfully correlating the propagation and initiation processes of gaseous detonation, and realizing the unified expression of the three-dimensional structure of cell detonation. The book and the proposed open framework is of high value for researchers in conventional applications such as coal mine explosions and chemical plant accidents, and state-of-the-art research fields such as supernova explosion, new aerospace propulsion engines, and detonation-driven hypersonic testing facilities. It is also a driving force for future research of detonation.

Turbulent Jets

Combustion in Piston Engines presents the technique of pressure diagnostics to measure the fuel consumption in an engine cylinder and to monitor the operation of micro-electronic systems for its control. It provides a recipe for bridging the gap between the hydrocarbon-fed combustion technology of automotive powerplants of today and electro-magnetic technologies of the future. The author proposes and introduces a model for the design of a MECC (micro-electronically controlled combustion) systems to modulate combustion in engine cylinders. This system yields significant reduction in the formation of pollutants and the consumption of fuel, so that, eventually, emissions using any clean hydrocarbon fuel will be acceptable and gas mileage could be doubled.