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Selective catalytic reduction (SCR) has become the mainstream approach for removing heavy-duty (HD) diesel engine NOx emissions. Highly efficient SCR systems are a key enabling technology allowing engines to be calibrated for very high NOx output with a resultant gain in fuel consumption while still maintaining NOx emissions compliance. One key to the successful implementation of high efficiency SCR at elevated engine out NOx levels is the ability to introduce significantly more AdBlue into the exhaust flow while still ensuring complete ammonia production and avoiding the formation of deposits. This paper presents a body of experimental work conducted on an exhaust test bench using optical techniques including high-speed imaging and phase Doppler interferometry (PDI), applied under representative exhaust conditions to a HD diesel engine after-treatment system with optical access inside the mixer tube. Two different sprays were used to dose AdBlue onto the mixing device.

Crankcase emissions are a complex mixture of combustion products and aerosol generated from lubrication oil. The crankcase emissions contribute substantially to the total particulate matter (PM) emitted from an engine. Environment legislation demands that either the combustion and crankcase emissions are combined to give a total measurement, or the crankcase gases are re-circulated back into the engine. There is a lack of understanding regarding the physical processes that generate crankcase aerosols, with a paucity of information on the size/mass concentrations of particles present in the crankcase. In this study the particulate matter crankcase emissions were measured from a fired and motored 4-cylinder compression ignition engine at a range of speeds and crankcase locations.

The worldwide introduction of new emission standards and new, more encompassing, legislating cycles have led to a need to increase both a selective catalytic reduction (SCR) system’s capacity and conversion efficiency. To this end, it is important for an SCR system to operate to the extremes of its temperature range which in many systems is currently limited by the temperature at which diesel exhaust fluid (DEF) can easily decompose without the formation of deposits. This paper analyses a new system for low-temperature ammonia provision to the SCR reaction. Ammonia Creation and Conversion Technology (ACCT) uses pressure controlled thermal decomposition of DEF followed by re-formation to form a fluid with greater volatility and the same ammonia density as DEF conforming to ISO 22241. A dosing strategy can then be employed where any combination of DEF or ACCT solution can be used to provide ammonia as a reductant over the whole activity temperature range of a catalyst.

In recent years urea selective catalytic reduction (SCR) has become the principal method of NOx abatement within heavy duty (HD) diesel exhaust systems; however, with upcoming applications demanding NOx reduction efficiencies of above 96 % on engines producing upwards of 10 g·kWh−1 NOx, future diesel exhaust fluid (DEF) dosing systems will be required to operate stably at significantly increased dosing rates. Developing a dosing system capable of meeting the increased performance requirements demands an improved understanding of how DEF sprays interact with changing exhaust flows. This study has investigated four production systems representing a diverse range of dosing strategies in order to determine how performance is influenced by spray structure and identify promising strategies for further development. The construction of an optically accessible hot-air flow rig has enabled visualisation of DEF injection into flows representative of HD diesel exhaust conditions.