Search Results

This paper reports the findings from an experimental investigation of the engine cooling jacket filling process for a medium duty off-highway diesel engine to characterise the physical processes that lead to the occurrence of trapped air. The motivation for the project was to provide knowledge and data to aid the development of a computational design tool capable of predicting the amount and location of trapped air in a cooling circuit following a fill event. To quantify the coolant filling process, a transparent replica of a section of the cylinder head cooling core was manufactured from acrylic to allow the application of optical diagnostic techniques. Experimentation has characterised the coolant filling process through the use of three optical techniques. These include the two established methods of High-Speed Imaging and Particle Image Velocimetry (PIV), as well as a novel approach developed for tracking the liquid-air interface during the fill event.

Particulate Matter (PM) emissions reduction is an imminent challenge for Direct Injection Spark Ignition (DISI) engine designers due to the introduction of Particulate Number (PN) standards in the proposed Euro 6 emissions legislation aimed at delivering the next phase of air quality improvements. An understanding of how the formation of combustion-derived nanoparticulates in engines is affected by the engine operating temperature is important for air quality improvement and will influence future engine design and control strategies. This investigation has examined the effect on combustion and PM formation when reducing the engine operating temperature to -7°C. A DISI single-cylinder optical research engine was modified to simulate a range of operating temperatures down to the proposed -7°C.

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.

Particulate number (PN) standards in the current ‘Euro 6’ European emissions standards pose a challenge for engine designers and calibrators during the warm-up phases of cold direct injection spark ignition (DISI) engines. To achieve catalyst light-off in the shortest time, engine strategies are often employed which inherently use more fuel to attain higher exhaust temperatures. This can lead to the generation of locally fuel-rich regions within the combustion chamber and the emission of particulates. This investigation analyses the combustion structures during the transient start-up phase of an optical DISI engine. High-speed, colour 9 kHz imaging was used to investigate five important operating points of an engine start-up strategy whilst simultaneously recording in-cylinder pressure.