This book contains the papers of the Internal Combustion Engines: Performance fuel economy and emissions conference, in the IMechE bi-annual series, held on the 29th and 30th November 2011. The internal combustion engine is produced in tens of millions per year for applications as the power unit of choice in transport and other sectors. It continues to meet both needs and challenges through improvements and innovations in technology and advances from the latest research. These papers set out to meet the challenges of internal combustion engines, which are greater than ever. How can engineers reduce both CO2 emissions and the dependence on oil-derivate fossil fuels? How will they meet the future, more stringent constraints on gaseous and particulate material emissions as set by EU, North American and Japanese regulations? How will technology developments enhance performance and shape the next generation of designs? This conference looks closely at developments for personal transport applications, though many of the drivers of change apply to light and heavy duty, on and off highway, transport and other sectors. - Aimed at anyone with interests in the internal combustion engine and its challenges - The papers consider key questions relating to the internal combustion engine

This book is a printed edition of the Special Issue "Selective Catalytic Reduction of NO_x" that was published in Catalysts

Selective catalytic reduction (SCR) of NO[Subscript x] with urea/NH[Subscript 3] is a leading candidate to the impending more stringent emissions regulations for diesel engines. Currently, there is no consensus on the durability and the deactivation mechanisms associated with zeolite-based SCR catalysts, nor is there an established protocol for rapidly aging zeolite-based SCR catalysts that replicates the catalyst deactivation associated with field service. A 517 cc single-cylinder, naturally-aspirated direct injection (NA/DI) diesel engine is used to perform accelerated thermal aging on Fe-zeolite SCR catalysts. The engine is fitted with an exhaust aftertreatment system consisting of a DOC, a SCR catalyst and a DPF. Accelerated aging protocol established for the SCR catalyst utilizes high temperature exhaust gases during the active regeneration of the DPF. Accelerated aging is carried out at exhaust gas temperatures of 650, 750 and 850°C at the SCR inlet and at a gas hourly space velocity (GHSV) of approximately 40,000 h−1. The engine is maintained at 1500 rpm and supplemental fuel is injected upstream of the DOC to alter the temperature of the aftertreatment system. The aged Fe-zeolite SCR catalysts are evaluated for NO[Subscript x] performance in a bench-flow reactor and characterized by multiple surface characterization techniques for materials changes. The NO[Subscript x] performance of the front sections of the engine-aged catalysts is severely degraded. BET surface area measurements of the engine-aged catalyst indicate a severe reduction of catalyst surface area in the front sections of the catalysts aged at 750 and 850°C. However, the catalyst aged at 650°C has a catalyst surface area similar to that of a fresh catalyst; thereby ruling out reduction of catalyst surface area as the sole cause of the catalyst deactivation seen in the front sections of the engine-aged catalysts. The similar shape of the NO[Subscript x] conversion profiles observed with these catalyst sections even at different aging temperatures indicates some type of catalyst poisoning; however, the cause of catalyst degradation in these catalyst sections is not identified in this investigation. There is a good relationship between the NO[Subscript x] performance and catalyst aging temperature for the rear sections of the engine-aged catalysts - NO[Subscript x] performance decreases with increasing aging temperature. XRD patterns and NO oxidation experiments reveal evidence of zeolite dealumination in the engine-aged catalysts. BET surface area measurements show that catalyst surface area decreases with increasing aging temperature, which further supports the suggestion of zeolite dealumination as the cause of catalyst deactivation in the rear sections of the engine-aged catalysts. A comparison between the engine-aged and field-aged catalysts is conducted to assess the validity of the implemented accelerated thermal aging protocol in replicating the aging conditions observed in the field-aged catalyst. Bench-flow reactor evaluation is used to determine the NO[Subscript x] performance of the engine-aged and field-aged catalysts, and in depth surface studies are used to determine the deactivation mechanisms associated with each type of catalyst aging. SEM micrographs and BET surface area measurements of the aged catalysts show that the deactivation mechanism associated with catalyst aging is primarily physical damage to the zeolite washcoat for both the field-aged and engine-aged catalysts. Furthermore, X-ray diffraction and NO oxidation experiments identify zeolite dealumination as the underlying cause of the washcoat degradation. Finally, BFR evaluation shows that the NO[Subscript x] performance of the catalyst aged at 750°C for approximately 50 hours compares very well to that of the field-aged catalyst with a service life of 3 years. It is concluded that accelerated thermal aging on the engine bench is successful in bringing about similar catalyst changes to those seen with the field-aged catalyst.

Abstract : Abstract The heavy-duty diesel (HDD) engines use the diesel oxidation catalyst (DOC), catalyzed particulate filter (CPF) and urea injection based selective catalytic reduction (SCR) systems in sequential combination, to meet the US EPA 2010 PM and NOx emission standards. The SCR along with a NH3 slip control catalyst (AMOX) offer NOx reduction >90 % with NH3 slipHowever, there is a strong desire to further improve the NOx reduction performance of such systems, to meet the California Optional Low NOx Standard implemented since 2015. Integrating SCR functionality into a diesel particulate filter (DPF), by coating the SCR catalyst on the DPF, offers potential to reduce the system cost and packaging weight/ volume. It also provides opportunity to increases the SCR volume without affecting the overall packaging, to achieve NOx reduction efficiencies >95 %. xvii In this research, the NOx reduction and NH3 storage performance of a Cu-zeolite SCR and Cu-zeolite SCR catalyst on DPF (SCRF®) were experimentally investigated based on the engine experimental data at steady state conditions. The experimental data for the production-2013-SCR and the SCRF® were collected (with and without PM loading in the SCRF®) on a Cummins ISB 2013 engine, at varying inlet temperatures, space velocities, inlet NOx concentrations and NO2/NOx ratios, to evaluate the NOx reduction, NH3 storage and NH3 slip characteristics of the SCR catalyst. The SCRF® was loaded with 2 and 4 g/L of PM prior to the NOx reduction tests to study the effect of PM loading on the NOx reduction and NH3 storage performance of the SCRF®. The experimental setup and test procedures for evaluation of NOx reduction performance of the SCRF®, with and without PM loading in the SCRF® are described. The 1-D SCR model developed at MTU was calibrated to the engine experimental data obtained from the seven NOx reduction tests conducted with the production-2013-SCR. The performance of the 1-D SCR model was validated by comparing the simulation and experimental data for NO, NO2 and NH3 concentrations at the outlet of the SCR. The NO and NO2 concentrations were calibrated to ±20 ppm and NH3 was calibrated to ±20 ppm. The experimental results for the production-2013-SCR indicate that the NOx reduction of 80 - 85% can be achieved for the inlet temperatures below 250°C and above 450°C and NOx reduction of 90 - 95% can be achieved for the inlet temperatures between 300 - 350°C, at ammonia to NOx ratio (ANR) 1.0, while the NH3 slip out of the SCR wasConversely, the SCRF® showed 90 - 95 % NOx reduction at ANR of 1.0, while the NH3 slip out of the SCRF® was >50 ppm, with and without PM loading in the SCRF®, for the inlet temperature range of 200 - 450°C, space velocity in the range of 13 to 48 k/hr and inlet NO2/NOx in the range of 0.2 to 0.5. The NOx reduction in the SCRF® increases to >98 % at ANR 1.2. However, the NH3 slip out of the SCRF® increases significantly at ANR 1.2. xviii The effect of PM loading at 2 and 4 g/L on the NOx reduction performance of the SCRF® was negligible below 300°C. However, with PM loading in the SCRF®, the NOx reduction decreased by 3 - 5% when compared to the clean SCRF®, for inlet temperature >350°C. Experimental data were also collected by reference [1] to investigate the NO2 assisted PM oxidation in the SCRF® for the inlet temperature range of 260 - 370°C, with and without urea injection and thermal oxidation of PM in the SCRF® for the inlet temperature range of 500 - 600°C, without urea injection by reference [1]. The experimental data obtained from this study and [1] will be used to develop and calibrate the SCR-F model at Michigan Tech. The NH3 storage for the production-2013-SCR and the SCRF® (with and without PM loading) were determined from the steady state engine experimental data. The NH3 storage for the production-2013-SCR and the SCRF® (without PM loading) were within ±5 gmol/m3 of the substrate, with maximum NH3 storage of 75 - 80 gmol/m3 of the substrate, at the SCR/SCRF® inlet temperature of 200°C. The NH3 storage in the SCRF®, with 2 g/L PM loading, decreased by 30%, when compared to the NH3 storage in the SCRF®, without PM loading. The further increase in the PM loading in the SCRF®, from 2 to 4 g/L, had negligible effect on NH3 storage.

The selective catalytic reduction (SCR) of NOx with NH3 is considered to be the most promising technique for the efficient reduction of highly detrimental NOx (to N2) emitted from diesel engine vehicles. Amongst the various catalysts available for SCR, Fe- and Cu-zeolite catalysts are found to be highly stable and efficient towards maximum NOx reduction over a wide temperature range. Cu-zeolites are more active at low temperatures ( 350 oC) while Fe-zeolites are more active at high temperatures ( 400 oC). We carried out a comprehensive experimental and kinetic modeling study of key SCR reactions on Fe- and Cu-zeolite catalysts and present a detailed understanding of mass transfer limitations and kinetics and mechanistic aspects of various SCR reactions on these catalysts. Experiments carried out on monolith catalysts having different washcoat loadings, washcoat thicknesses and lengths indicate the presence of washcoat (or pore) diffusion limitations at intermediate to high temperature range in all the SCR reactions. A detailed analysis of the effect of temperature on the transitions between various controlling regimes (kinetic, washcoat diffusion and external mass transfer) is presented. Agreement in the differential kinetics studies of NO oxidation and standard SCR (NO + O2 + NH3) reactions indicates NO oxidation is the rate determining step for standard SCR. A detailed kinetic model capturing key features of all the SCR reactions is developed. This model accurately predicts the experimentally observed NOx conversions over a wide temperature range and different feed conditions. Finally, a systematic study of various SCR reactions is carried out on a combined system of Fe- and Cu-zeolite monolithic catalysts to determine if a high NOx conversion could be sustained over a wider temperature range than with individual Fe- and Cu-zeolite catalysts. Amongst various configurations, a dual-layer catalyst with a thin Fe-zeolite layer on top of a thick Cu-zeolite layer resulted in a very high NOx removal efficiency over a broad temperature range of practical interest. The kinetic model accurately captures the experimental data with a combined system of Fe- and Cu-zeolite catalysts and provides further insights into the catalyst arrangements for maximum NOx reduction efficiency.