Low temperature combustion strategies have demonstrated high thermal efficiency with low emissions of pollutants, including oxides of nitrogen and particulate matter. One such combustion strategy, called Reactivity Controlled Compression Ignition (RCCI), which involves the port injection of a low reactivity fuel such as gasoline, ethanol, or natural gas, and a direct injection of a high reactivity fuel, such as diesel, has demonstrated excellent control over the heat release event due to the introduction of in-cylinder stratification of equivalence ratio and reactivity. The RCCI strategy is inherently fuel flexible, however the direct injection strategy needs to be tailored to the combination of premixed and direct injected fuels. Experimental results demonstrate that, when comparing different premixed fuels, matching combustion phasing with premixed mass percentage or SOI timing is not sufficient to retain baseline efficiency and emissions results. If the bulk characteristics of the heat release event can be matched, however, then the efficiency and emissions can be maintained. A 0-D methodology for predicting the required fuel stratification for a desired heat release for kinetically-controlled stratified-charge combustion strategies is proposed and validated with 3-D reacting and non-reacting CFD simulations performed with KIVA3Vr2 in this work. Various heat release rate shapes, phasing, duration, and premixed and DI fuel chemistries are explored using this analysis. This methodology provides a means by which the combustion process of a stratified-charge, kinetically-controlled combustion strategy could be optimized for any fuel combination, assuming that the fuel chemistry is well characterized.

This book deals with novel advanced engine combustion technologies having potential of high fuel conversion efficiency along with ultralow NOx and particulate matter (PM) emissions. It offers insight into advanced combustion modes for efficient utilization of gasoline like fuels. Fundamentals of various advanced low temperature combustion (LTC) systems such as HCCI, PCCI, PPC and RCCI engines and their fuel quality requirements are also discussed. Detailed performance, combustion and emissions characteristics of futuristic engine technologies such as PPC and RCCI employing conventional as well as alternative fuels are analyzed and discussed. Special emphasis is placed on soot particle number emission characterization, high load limiting constraints, and fuel effects on combustion characteristics in LTC engines. For closed loop combustion control of LTC engines, sensors, actuators and control strategies are also discussed. The book should prove useful to a broad audience, including graduate students, researchers, and professionals Offers novel technologies for improved and efficient utilization of gasoline like fuels; Deals with most advanced and futuristic engine combustion modes such as PPC and RCCI; Comprehensible presentation of the performance, combustion and emissions characteristics of low temperature combustion (LTC) engines; Deals with closed loop combustion control of advanced LTC engines; State-of-the-art technology book that concisely summarizes the recent advancements in LTC technology. .

In this study, the combustion process in a dual-fuel, reactivity-controlled compression-ignition (RCCI) engine is investigated using a combination of optical diagnostics and chemical kinetics modeling to explain the role of equivalence ratio, temperature, and fuel reactivity stratification for heat-release rate control. An optically accessible engine is operated in the RCCI combustion mode using gasoline primary reference fuels (PRF). A well-mixed charge of iso-octane (PRF = 100) is created by injecting fuel into the engine cylinder during the intake stroke using a gasoline-type direct injector. Later in the cycle, n-heptane (PRF = 0) is delivered through a centrally mounted diesel-type common-rail injector. This injection strategy generates stratification in equivalence ratio, fuel blend, and temperature. The first part of this study uses a high-speed camera to image the injection events and record high-temperature combustion chemiluminescence. The chemiluminescence imaging showed that, at the operating condition studied in the present work, mixtures in the squish region ignite first, and the reaction zone proceeds inward toward the center of the combustion chamber. The second part of this study investigates the charge preparation of the RCCI strategy using planar laser-induced fluorescence (PLIF) of a fuel tracer under non-reacting conditions to quantify fuel concentration distributions prior to ignition. The fuel-tracer PLIF data show that the combustion event proceeds down gradients in the n-heptane distribution. The third part of the study uses chemical kinetics modeling over a range of mixtures spanning the distributions observed from the fuel-tracer fluorescence imaging to isolate the roles of temperature, equivalence ratio, and PRF number stratification. The simulations predict that PRF number stratification is the dominant factor controlling the ignition location and growth rate of the reaction zone. Equivalence ratio has a smaller, but still significant, influence. Temperature stratification had a negligible influence due to the NTC behavior of the PRF mixtures.

This book provides a comparative analysis of both diesel and gasoline engine particulates, and also of the emissions resulting from the use of alternative fuels. Written by respected experts, it offers comprehensive insights into motor vehicle particulates, their formation, composition, location, measurement, characterisation and toxicology. It also addresses exhaust-gas treatment and legal, measurement-related and technological advancements concerning emissions. The book will serve as a valuable resource for academic researchers and professional automotive engineers alike.

Premixed Compression Ignition (PCI) strategies are promising methods to achieve low engine out NOx and soot emissions and high efficiency. However, PCI strategies have failed to see widespread implementation due to difficulties controlling the heat release rate and lack of an adequate combustion phasing control mechanism. In this research, a dual fuel reactivity controlled compression ignition (RCCI) concept is proposed to address these issues. In the RCCI strategy, two fuels with different auto ignition characteristics are blended inside the combustion chamber. Combustion phasing is controlled by the relative ratios of these two fuels and the combustion duration is controlled by spatial stratification between the two fuels. The study has three primary sections. The first section highlights the development of the RCCI strategy using computational fluid dynamics (CFD) modeling. The second section uses CFD modeling and metal engine experiments to evaluate the performance and emissions characteristics of RCCI combustion. The metal engine experiments confirm that RCCI operation is possible over a wide range of conditions with near zero levels of NOx and soot emissions. Additionally, it is found that RCCI is able to achieve very high indicated efficiency (greater than 50%) by lowering heat transfer losses and improving the control over the combustion phasing and burn duration. The third section uses optical engine experiments to validate model predictions and provide a fundamental explanation for the processes controlling RCCI combustion. The results of the optical engine experiments clarify the mechanisms controlling the RCCI energy release. Chemiluminescence imaging shows that RCCI features a reaction zone that appears to grow by the appearance of small auto ignition pockets. The fuel tracer fluorescence imaging shows that the ignition locations correspond to the regions with the lowest primary reference fuel (PRF) number and highest equivalence ratio. The rate of reaction zone growth is then controlled by the level of stratification in equivalence ratio and PRF number. Kinetics modeling based on the fuel tracer fluorescence imaging shows that the PRF number has the largest effect on the rate of reaction zone growth.

Abstract : Premixed compression ignition (PCI) technologies offer high efficiency and low emissions but are usually confined by limited operation range as well as high pressure rise and heat release rate. In this work, a more recently developed PCI mode is explored where in-cylinder blending of two fuels with different auto-ignition characteristics (diesel and gasoline) is utilized to create reactivity stratification such that heat release rate and combustion timing can be controlled. This mode has been defined as Reactivity Controlled Compression Ignition (RCCI). As part of this thesis, the main aim is to study various parameters that can be used to control combustion phasing. Also, steady state mapping of the engine is done so as to explore the operating range for the current engine setup. Best efficiencies as well as highest loads are obtained for higher Premixed Ratio (PR) values and advanced Start of Injection (SOI) timings, where as lower PR fuel blends are needed to achieve low load limit. The analysis is also extended to transient RCCI operation for observing various dynamics involved and their effects on combustion phasing. As part of realizing full-load range operation, switching to conventional Spark-Ignition (SI) combustion mode is also carried out. Various dynamics involved in the switching process are captured. A cycle-by-cycle closed loop combustion controller is designed and implemented on the engine to achieve optimum combustion phasing during transient engine operation. To provide feedback of combustion parameters like engine load and combustion phasing to the closed loop controller, a real-time combustion feedback system is designed and implemented utilizing Field Programmable Gate Array (FPGA).

Reactivity controlled compression ignition (RCCI) is a dual fuel combustion method that relies on the significant difference in reactivity of the fuels involved. RCCI had a low performance at high engine speed due to its high tendency on knocking and high pressure rise rate. Therefore, this study investigates the effect of the fuel stratification on the RCCI combustion and its extended to the interaction of two low reactive fuels, gasoline and compressed natural gas (CNG), in the RCCI combustion system. The investigation was experimentally performed on a single cylinder engine and constant volume chamber. The stratification was created by varying injection timing in the engine by injecting CNG at 80° and 120° before top dead center (BTDC) and varying injection gap in the constant volume chamber with the gaps between two fuel injection timing were varied between 0 ms to 20 manuscript The results in the engine experiment show that proportions of gasoline and CNG and degree of stratification of CNG were found to be effective means of combustion control within certain limits of engine load and HC and CO emissions could be significantly reduced. While in constant volume chamber it has a significant effect on the combustion phasing. Stratified mixture produces shorter combustion duration while homogeneous mixture produces longer duration.