Development Of A Partially Premixed Combustion Model For A Diesel Engine Using Multiple Injection Strategies

In order to fulfil future emissions legislations, new combustion systems are to be investigated. One way of improving exhaust emissions is the application of multiple injection strategies and conventional or partially premixed combustion conditions to a Diesel engine. The application of numerical techniques as CFD supports and improves the quality of engine developments. Unfortunately, current spray and combustion models are not accurate enough to simulate multiple injection systems, being in this way a topic of research. The goal of this study was the development of a novel simulation method for the investigation of Diesel engines operated with multiple injection strategies and different combustion modes. The first part of this work focused in improving the spray modelling. The inform ation of 3D CFD simulations of the injector nozzle was introduced in the spray simulation as boundary conditions developing coupling subroutines for this issue. The atomisation modelling was also improved using validated presumed droplet size distributions. Moreover, to avoid the simulation of the injector nozzle for every investigated operating point, a novel interpolating tool was developed in order to create spray boundary conditions based on few 3D CFD simulations of the nozzle under certain initial and boundary conditions. The second part of this thesis dealt with the combustion modelling of Diesel engines. For this issue, a laminar flamelet approach called Representative Interactive Flamelet model (RIF) was selected and implemented. Afterwards, an extended combustion model based on RIF was developed in order to take into account multiple injection strategies. Finally, this new model was validated with a wide range of operating points: applying multiple injection strategies under conventional and partially premixed combustion conditions.

Phenomenology of Diesel Combustion and Modeling Diesel is the most efficient combustion engine today and it plays an important role in transport of goods and passengers on land and on high seas. The emissions must be controlled as stipulated by the society without sacrificing the legendary fuel economy of the diesel engines. These important drivers caused innovations in diesel engineering like re-entrant combustion chambers in the piston, lower swirl support and high pressure injection, in turn reducing the ignition delay and hence the nitric oxides. The limits on emissions are being continually reduced. The- fore, the required accuracy of the models to predict the emissions and efficiency of the engines is high. The phenomenological combustion models based on physical and chemical description of the processes in the engine are practical to describe diesel engine combustion and to carry out parametric studies. This is because the injection process, which can be relatively well predicted, has the dominant effect on mixture formation and subsequent course of combustion. The need for improving these models by incorporating new developments in engine designs is explained in Chapter 2. With “model based control programs” used in the Electronic Control Units of the engines, phenomenological models are assuming more importance now because the detailed CFD based models are too slow to be handled by the Electronic Control Units. Experimental work is necessary to develop the basic understanding of the pr- esses.

Volume 2 of the two-volume set Advanced direct injection combustion engine technologies and development investigates diesel DI combustion engines, which despite their commercial success are facing ever more stringent emission legislation worldwide. Direct injection diesel engines are generally more efficient and cleaner than indirect injection engines and as fuel prices continue to rise DI engines are expected to gain in popularity for automotive applications. Two exclusive sections examine light-duty and heavy-duty diesel engines. Fuel injection systems and after treatment systems for DI diesel engines are discussed. The final section addresses exhaust emission control strategies, including combustion diagnostics and modelling, drawing on reputable diesel combustion system research and development. Investigates how HSDI and DI engines can meet ever more stringent emission legislation Examines technologies for both light-duty and heavy-duty diesel engines Discusses exhaust emission control strategies, combustion diagnostics and modelling

Gasoline compression ignition concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multi-cylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies has been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection strategy to create a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from -91° to -324° ATDC, which is just after the exhaust valve closes for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 L diesel engine with a variable geometry turbocharger, high pressure common rail injection system, wide included angle injectors, and variable swirl actuation was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection GTP-15-1067, Dempsey 2 pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).

This book focuses on gasoline compression ignition (GCI) which offers the prospect of engines with high efficiency and low exhaust emissions at a lower cost. A GCI engine is a compression ignition (CI) engine which is run on gasoline-like fuels (even on low-octane gasoline), making it significantly easier to control particulates and NOx but with high efficiency. The state of the art development to make GCI combustion feasible on practical vehicles is highlighted, e.g., on overcoming problems on cold start, high-pressure rise rates at high loads, transients, and HC and CO emissions. This book will be a useful guide to those in academia and industry.

Advances in Oxygenated Fuels for Sustainable Development: Feedstocks and Precursors for Catalysts Synthesis provides a roadmap to the sustainable implementation of oxygenated fuels in internal combustion engines through sustainable production, smart distribution and effective utilization. Focusing on the sustainability of feedstocks, the book assesses availability, emissions impact and reduction potential, and biodiversity and land utilization impact. Existing technologies and supply chains are reviewed, and recommendations are provided on how to sustainably implement or update these technologies, including for rural communities. Furthermore, effective supply and distribution network designs are provided alongside methods for monitoring and assessing their sustainability, accounting for social, economic, environmental and ecological factors. This book guides readers through every aspect of the production and commercialization of sustainable oxygenated fuels for internal combustion engines and their implementation across the global transport industry. Provides multilevel perspectives on how to facilitate the sustainable production of oxygenated fuel and develop new indices for measuring the effectiveness and sustainability of implementation Recommends a framework and criteria for assessing the suitability, sustainability, and environmental benefits of oxygenated biofuels Describes the fuel properties of all oxygenated fuels and their performance in unmodified and enhanced CI and SI engines