An experimental study was performed to provide the combustion and emission characteristics resulting from fuel-reactivity controlled compression ignition (RCCI) combustion mode utilizing dual-fuel approach in a light-duty, multi-cylinder diesel engine. In-cylinder fuel blending using port fuel injection of gasoline before intake valve opening (IVO) and early-cycle, direct injection of diesel fuel was used as the charge preparation and fuel blending strategy. In order to achieve the desired auto-ignition quality through the stratification of the fuel-air equivalence ratio (), blends of commercially available gasoline and diesel fuel were used. Engine experiments were performed at an engine speed of 2300rpm and an engine load of 4.3bar brake mean effective pressure (BMEP). It was found that significant reduction in both nitrogen oxide (NOx) and particulate matter (PM) was realized successfully through the RCCI combustion mode even without applying exhaust gas recirculation (EGR). However, high carbon monoxide (CO) and hydrocarbon (HC) emissions were observed. The low combustion gas temperature during the expansion and exhaust processes seemed to be the dominant source of high CO emissions in the RCCI combustion mode. The high HC emissions during the RCCI combustion mode could be due to the increased combustion quenching layer thickness as well as the -stratification at the periphery of the combustion chamber. The slightly higher brake thermal efficiency (BTE) of the RCCI combustion mode was observed than the other combustion modes, such as the conventional diesel combustion (CDC) mode, and single-fuel, premixed charge compression ignition (PCCI) combustion mode. The parametric study of the RCCI combustion mode revealed that the combustion phasing and/or the peak cylinder pressure rise rate of the RCCI combustion mode could be controlled by several physical parameters premixed ratio (rp), intake swirl intensity, and start of injection (SOI) timing of directly injected fuel unlike other low temperature combustion (LTC) strategies.

Low Temperature Combustion (LTC) is currently being researched as a way to reduce problematic emissions (i.e., NOx and PM) from compression-ignition engines while maintaining high fuel efficiency. One of the primary types of LTC is Premixed Compression Ignition (PCI), with some examples of PCI being homogeneous charge compression ignition (HCCI), premixed charge compression ignition (PCCI), reactivity controlled compression ignition (RCCI) and partially premixed combustion (PPC). These LTC strategies use early fuel injections to allow sufficient time for air/fuel mixing before combustion. By increasing the amount of air/fuel premixing, NOx and PM emissions can be lowered due to the reduced local and global equivalence ratios. The lean nature of PCI also maintains high thermal efficiency due to the reduced heat transfer losses from the reduced peak combustion temperatures. However, too much air/fuel premixing can lead to rapid energy release rates, limiting the operation space for PCI. To combat this problem, the combustion strategy of interest for the study, RCCI, uses fuel reactivity gradients to increase combustion duration (i.e., reduce the energy release rate) and phasing control, thereby increasing the engine operating space for PCI operation. Previous tests [1-7] have shown promising results for petroleum-based fuels with RCCI. Recent work at Oak Ridge National Laboratory (ORNL) has shown how blends of biofuels with petroleum fuels can improve RCCI combustion performance [8,9] The work sets out to examine biofuel performance over a wide engine operating space both at steady-state and transient operating conditions with RCCI combustion. It is hoped to demonstrate the capability and effects of using bio-derived fuels in place of conventional petroleum-derived fuels for advanced combustion strategies under real-world operating conditions. In RCCI operation, blends of biodiesel and ethanol fuels will be investigated to examine the fuel effects on the combustion event.

Abstract : Among the various alternative fuels, natural gas is considered as a leading candidate for heavy-duty applications due to its availability and applicability in conventional internal combustion diesel engines. Compared to their diesel counterparts natural gas fueled spark-ignited engines have a lower power density, reduced low-end torque capability, limited altitude performance, and ammonia emissions downstream of the three-way catalyst. The dual fuel diesel/natural gas engine does not suffer with the performance limitations of the spark-ignited concept due to the flexibility of switching between different fueling modes. Considerable research has already been conducted to understand the combustion behavior of dual fuel diesel/natural gas engines. As reported by most researchers, the major difficulty with dual fuel operation is the challenge of providing high levels of natural gas substitution, especially at low and medium loads. In this study extensive experimental and simulation studies were conducted to understand the combustion behavior of a heavy-duty diesel engine when operated with compressed natural gas (CNG) in a dual fuel regime. In one of the experimental studies, conducted on a 13 liter heavy-duty six cylinder diesel engine with a compression ratio of 16.7:1, it was found that at part loads high levels of CNG substitution could be achieved along with very low NOx and PM emissions by applying reactivity controlled compression ignition (RCCI) combustion. When compared to the diesel-only baseline, a 75% reduction in both NOx and PM emissions was observed at a 5 bar BMEP load point along with comparable fuel consumption values. Further experimental studies conducted on the 13 liter heavy-duty six cylinder diesel engine have shown that RCCI combustion targeting low NOx emissions becomes progressively difficult to control as the load is increased at a given speed or the speed is reduced at a given load. To overcome these challenges a number of simulation studies were conducted to quantify the in-cylinder conditions that are needed at high loads and low to medium engine speeds to effectively control low NOx RCCI combustion. A number of design parameters were analyzed in this study including exhaust gas recirculation (EGR) rate, CNG substitution, injection strategy, fuel injection pressure, fuel spray angle and compression ratio. The study revealed that lowering the compression ratio was very effective in controlling low NOx RCCI combustion. By lowering the base compression ratio by 4 points, to 12.7:1, a low NOx RCCI combustion was achieved at both 12 bar and 20 bar BMEP load points. The NOx emissions were reduced by 75% at 12 bar BMEP while fuel consumption was improved by 5.5%. For the 20 BMEP case, a 2% improvement in fuel consumption was achieved with an 87.5% reduction in NOx emissions. At both load points low PM emissions were observed with RCCI combustion. A low NOx RCCI combustion system has multiple advantages over other combustion approaches, these include; significantly lower NOx and PM emission which allows a reduction in aftertreatment cost and packaging requirements along with application of higher CNG substitution rates resulting in reduced CO2 emissions.

This book discusses all aspects of advanced engine technologies, and describes the role of alternative fuels and solution-based modeling studies in meeting the increasingly higher standards of the automotive industry. By promoting research into more efficient and environment-friendly combustion technologies, it helps enable researchers to develop higher-power engines with lower fuel consumption, emissions, and noise levels. Over the course of 12 chapters, it covers research in areas such as homogeneous charge compression ignition (HCCI) combustion and control strategies, the use of alternative fuels and additives in combination with new combustion technology and novel approaches to recover the pumping loss in the spark ignition engine. The book will serve as a valuable resource for academic researchers and professional automotive engineers alike.

Combustion Engineering, Second Edition maintains the same goal as the original: to present the fundamentals of combustion science with application to today's energy challenges. Using combustion applications to reinforce the fundamentals of combustion science, this text provides a uniquely accessible introduction to combustion for undergraduate stud

Biofuels such as ethanol, butanol, and biodiesel have more desirable physico-chemical properties than base petroleum fuels (diesel and gasoline), making them more suitable for use in internal combustion engines. The book begins with a comprehensive review of biofuels and their utilization processes and culminates in an analysis of biofuel quality and impact on engine performance and emissions characteristics, while discussing relevant engine types, combustion aspects and effect on greenhouse gases. It will facilitate scattered information on biofuels and its utilization has to be integrated as a single information source. The information provided in this book would help readers to update their basic knowledge in the area of "biofuels and its utilization in internal combustion engines and its impact Environment and Ecology". It will serve as a reference source for UG/PG/Ph.D. Doctoral Scholars for their projects / research works and can provide valuable information to Researchers from Academic Universities and Industries. Key Features: • Compiles exhaustive information of biofuels and their utilization in internal combustion engines. • Explains engine performance of biofuels • Studies impact of biofuels on greenhouse gases and ecology highlighting integrated bio-energy system. • Discusses fuel quality of different biofuels and their suitability for internal combustion engines. • Details effects of biofuels on combustion and emissions characteristics.