a b s t r a c tThe influence of EIVC (early inlet valve closure) on emissions, fuel economy and exhaust gas temperature of a turbocharged, 4 cylinder common rail direct injection diesel engine has been investigated and compared with the influence of deactivating two cylinders. IVC (inlet valve closing) timings were set at up to 60 CA (crank angle) degrees earlier than the production setting of 37 ABDC for the engine. At the earliest timing, effective compression ratio was reduced from 15.2:1 to 13.7:1. The effects on emissions were significant only for EIVC settings at least 40 CA degrees earlier than the production setting, and were sensitive to engine load. At 2 bar BMEP (brake mean effective pressure) and fixed levels of NO x , soot emissions were reduced but CO (carbon monoxide) and HC (hydrocarbon) increased unless fuel rail pressure was reduced. With increasing load, soot reduction diminished and was negligible at 6 bar BMEP; CO and HC emissions deteriorated further. At all conditions, EIVC raised exhaust gas temperature by >50 C; the effect on fuel economy was negligible or a fuel economy penalty. Comparisons indicate cylinder deactivation is the more effective strategy for reducing engine-out emissions of HC and CO and raising exhaust gas temperature under light load operating conditions.

The potential benefits and limitations of deactivating two of four cylinders by cam switching to disable the intake and exhaust valve lift were investigated experimentally on a turbocharged four-cylinder common-rail direct-injection diesel engine. When running on two firing cylinders, at light engine loads (a brake mean effective pressure of 2 bar, based on four-cylinder operation), the brake specific fuel consumption at given engine-out nitrogen oxide levels is comparable with or marginally better than when the engine is running on four cylinders. Cylinder deactivation allowed higher fuel rail pressures to be used to reduce the soot emissions while maintaining the advantages of lower carbon monoxide emissions and lower hydrocarbon emissions. At engine loads with a brake mean effective pressure of up to 3 bar on four cylinders, cylinder deactivation lowered the carbon monoxide and hydrocarbon emissions and raised the exhaust gas temperature by around 120 °C but, at higher loads, the fuel economy deteriorated and the soot and nitrogen oxide emissions increased markedly. The benefits of cylinder deactivation are therefore limited to light-load operating conditions, where the fuel economy is improved, the hydrocarbon and carbon monoxide emissions are reduced and the exhaust gas temperature is raised.

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Morphology plays an important role in determining behaviour and impact of soot nanoparticles, including effect on human health, atmospheric optical properties, contribution to engine wear, and role in marine ecology. However, its nanoscopic size has limited the ability to directly measure useful morphological parameters such as surface area and effective volume. Recently, 3D morphology characterization of soot nanoparticles via electron tomography has been the subject of several introductory studies. So-called '3D-TEM' has been posited as an improvement over traditional 2D-TEM characterization due to the elimination of the error-inducing information gap that exists between 3-dimensional soot structures and 2-dimensional TEM projections. Little follow-up work has been performed due to difficulties with developing methodologies into robust high-throughput techniques. Recent work by the authors has exhibited significant improvements in efficiency, though as yet due consideration has not been given to assessing fidelity of the technique. This is vital to confirm significant and tangible improvements in soot-characterization accuracy that will establish 3D-TEM as a legitimate tool. Synthetic ground-truth data was developed to closely mimic real soot structures and the 3D-TEM volume-reconstruction process. A variety of procedures were tested to assess the magnitude and nuances of deviations from ground-truth values. Results showed average Z-elongation due to the 'missing-wedge' at 3.5% for the previously developed optimized procedure. Mean deviations from ground-truth in volume and surface area were 2.0% and -0.1% respectively. Results indicate highly accurate 3D-reconstruction can be achieved with an optimized procedure that can bridge the gap to permit highthroughput 3D morphology characterization of soot.

Factors determining the success or failure of combustion initiation using a glow plug have been investigated through experimental work on a single cylinder, common rail diesel engine with a geometric compression ratio of 15.5, and a quiescent combustion bomb with optical access. A glow plug was required to avoid engine misfires when bulk gas temperature at the start of injection was less than 413°C. The distance between the glow plug and the spray edge, glow plug temperature and bulk gas temperature were important factors in meeting two requirements for successful ignition: a minimum local temperature of 413°C, and a minimum air/fuel vapour equivalence ratio of 0.15-0.35.