Benjamin A. Reid

An investigation of string cavitation in a true-scale fuel injector flow geometry at high pressure

String cavitation has been studied in an optical automotive size fuel injector with true-scale flow geometry at injection pressures of up to 2050 bar. The multihole nozzle geometry studied allowed observation of the hole-to-hole vortex interaction and, in particular, that of a bridging vortex in the sac region between the holes. A dependency on Reynolds number was observed in the formation of the visible, vapor filled vortex cores. Above a threshold Reynolds number, their formation and appearance during a 2 ms injection event was repeatable and independent of upstream pressure and cavitation number.

Optical Investigation on the Ability of a Cordierite Substrate Mixing Device to Combat Deposits in SCR Dosing Systems

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. A three-hole injector and a single-hole pressure-swirl injector were characterised in ambient and heated exhaust flow conditions. A metallic two-stage mixer and an uncoated cordierite ceramic substrate mixer were compared and demonstrated the ability of the substrate mixer to reduce deposit formation at higher dosing rates inside the mixer tube when used with the correct spray type. High-speed imaging revealed the ability of the substrate to absorb injected AdBlue spray at cooler exhaust temperatures. However, using the incorrect spray can lead to liquid saturation inside the substrate channels, which is detrimental due to the formation of deposits on the rear face of the substrate.

An Experimental Investigation into DEF Dosing Strategies for Heavy Duty Vehicle Applications

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Crankcase Sampling of PM from a Fired and Motored Compression Ignition Engine

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. A sequence of sampling equipment was used to characterise the emissions in the size range 5 nm - 19 μm; Cambustion DMS500 fast particulate spectrometer, TSI Scanning Mobility Particle Sizer (SMPS), TSI™ Condensation Particle Counter (CPC) and, TSI™ Aerodynamic Particle Sizer (APS). The combination of the two test engines and range of sampling equipment provided new information on the generation and behavior of aerodynamic particulate matter within an engine crankcase. Data is presented for the effect of controlled parameter changes on number distributions over the measured particle size range. A complex lognormal bimodal size distribution of sub micron accumulation mode particles was present in the crankcase of both engines at a low idle speed of 900rpm. At 1400rpm this complex distribution was not present. Increasing the engine load, on the fired engine, initially reduced the particle number concentration with a final significant increase in particle number concentration at 75% load. At 900 rpm 50% load there was a single strong peak at 32nm in the rocker cover however sampling from the push rod gallery and sump showed a strongly bimodal distribution with peaks at 32nm and 133nm. All other sampling data, from the fired engine, was consistent at each sampling location. The SMPS results, 15-665nm, on the motored engine showed location dependency, with the highest number concentration of particles present in the push rod gallery.