The design trend for light duty diesel engines is towards lower compression ratio and higher turbocharger boost. This can enable higher specific power and lower pollutant emissions to be achieved, but raises concerns that cold start operation might be adversely affected. This is investigated and quantified through the study of a modern light duty diesel engine at two compression ratios and temperatures down to -20ºC. Key indicators of cold start performance are the magnitude and cycle-to-cycle variation of indicated mean effective pressure. Initial studies were carried out at 300 rpm, a speed representative of post-first-fire conditions. Studies were then conducted at higher engine speeds representative of cold idle. The utility of different injection strategies, timings and quantities is investigated when varying test temperature and engine speed through a range of values encountered during the cold start phase of engine operation. The importance of the glow plug as a cold start aid is also investigated by varying its operating temperature and protrusion into the combustion chamber. The indicated mean effective pressure was used to assess the effects of varying input parameters, and gross heat release rate information is used to identify the phenomena responsible for desirable or undesirable characteristics. Reduction in compression ratio led to no deterioration of initial start performance from speeds just above cranking, provided an appropriate injection strategy was chosen. Higher indicated mean effective pressure was possible at low speeds using low compression ratio due to reduced losses and more complete combustion. Cycle-to-cycle variability in indicated mean effective pressure increased markedly for both compression ratios at engine speeds representative of cold idle, especially when test temperature was reduced. Stability reduction was more severe at low compression ratio. Multiple pilot injections at high compression ratio cold idle resulted in better cycle-to-cycle stability. Analysis of heat release profiles suggested that additional pilots assisted fuel mixing, a conclusion supported by a computational fluid dynamics model. Multiple pilots created a more homogeneous fuel distribution through the bowl at time of main injection. Multiple pilots could not stabilise operation at low compression ratio. Improvement in cold idle at low compression ratio was achieved by increasing glow plug temperature, which significantly increased the rate of fuel preparation. This increased the initial rate of heat release and resulted in significantly less variation in the heat release rate profiles. Small changes in glow plug protrusion rapidly degraded cold idle performance, indicating the importance of correct design.

Partially-premixed Charge Compression Ignition (PCCI) combustion is defined by increased levels of premixed charge whilst retaining control over combustion through injection timing. An experimental investigation has been carried out on a current generation DI diesel engine, equipped with High Pressure Common Rail (HPCR) fuel injection equipment and an external Exhaust Gas Recirculation (EGR) system. The aims of the investigation were to determine the constraints imposed on operating a PCCI combustion strategy with the aim of simultaneously reducing engine-out net soot and NOx emissions. The work was carried out at fully-warm steady-state conditions at engine speeds of 1500 rpm and 1800 rpm, predominantly using a single injection strategy. With a single injection the Start of Injection (SOI), fuel rail pressure, and rate of EGR have been examined with a view to realising PCCI combustion. Timing ranges of -20º to +3ºATDC, rail pressures of 500-1200 bar, and EGR rates of 0-60% have been investigated. The responses looked at have been engine-out soot, NOx, HC, and CO emissions, fuel consumption, and combustion noise. It is shown that variation of the parameters has allowed PCCI combustion to be achieved in a restricted operating region, offering improvement in the NOx-soot trade-off. This region is limited on the available test engine by oxygen availability due to the specifications of the turbocharger and EGR systems. Engine speeds up to 2000 rpm (at 2.5 bar BMEP), and loads of 4.4 bar gross IMEP (at 1500 rpm) have been found to be the limits, beyond which soot and CO emissions rise excessively. It is shown that enhancing the mixing time and intensity are both desirable in achieving PCCI combustion. The net soot reduction mechanism exploited with PCCI combustion strategies is reducing soot formation to outweigh the reduction in oxidation. Enhancing the mixing intensity by increasing injection pressure is highly effective at reducing soot output, but at the expense of brake specific fuel consumption. Increasing the mixing time can also be effective in reducing soot output, but careful parameter selection is required to avoid excessive soot output. Retarded or highly advanced injection timings are shown to reduce net soot output, but both have associated trade-offs and penalties. Retarding combustion is effective at lowering soot and NOx emissions with low associated noise, but a fuel economy penalty is paid. Advanced combustion phasing can result in large peak rates of increase of pressure, which have been shown to correlate well with combustion noise. Overall soot reductions of up to 97% were achieved, but with associated penalties. One of the most acceptable reductions of ~90% came at the cost of a 6% increase in fuel consumption, highlighting that improvements in emissions are achievable with PCCI strategies with acceptable trade-offs.

No description available.

An experimental investigation of post-start cold idling behaviour has been carried out on a modern single-cylinder HPCR DI light duty diesel engine with a low compression ratio of 15.5:1 at temperatures between 10 and -20°C. The trend toward lower compression ratios from more common values of around 22:1 a few years ago has resulted in lower compression pressures and temperatures, which negatively affects cold idle operation. Improvements in cycle-by-cycle stability of indicated work output through fuel injection strategy and glow plug temperature changes have been explored. This is important to improve NVH and the consumer’s perception of vehicle quality. The key effects on heat release characteristics have been identified and the associated impact on stability discussed. High speed imaging of ignition in a combustion bomb has been used to aid interpretation of engine results. Up to four pilot injections placed in advance of the main have been used. Shorter separation between pilots and pilot-to-main improves stability independent of the number of pilot injections and extends the range of main injection timings to meet target stability of 10% or lower at -20°C. Increasing the number of pilot injections was effective in stabilising combustion at all investigated soak temperatures at fuelling levels producing indicated work required to match friction and ancillary demands. Stability can be susceptible to deterioration at moderate soak temperatures because fuelling demand is relatively low. If a high number of pilot injections are to be avoided to reduce potential wear, then increasing main injection quantity is an effective method to stabilise combustion for a lower pilot number strategy but any increase above target load has to be harnessed by additional ancillary devices. Very high glow plug temperatures of up to 1200°C were examined using a smaller diameter tip ceramic type design. Stable combustion cannot be achieved through higher glow plug temperatures alone. A temperature of 1000°C, which can be achieved using a low voltage metallic type, is adequate to stabilise combustion when combined with a triple-pilot strategy at sub-zero temperatures. The best stability is achieved using 1200°C, which can only be achieved using a more expensive ceramic type, in combination with a triple-pilot strategy producing the desirable target of ~5% or below; the effects are not mutually exclusive. At high glow plug temperatures and using three or four pilot injections, stability improved with warmer soak temperatures. At -5°C, stability was relatively poor when one or two pilots were used irrespective of glow plug temperature. A high premixed contribution to main combustion is associated with improved stability. Minimum threshold values are necessary to stabilise combustion: ~25 J/° at -20°C, ~20 J/° at -5°C and only ~10 J/° at 10°C. A higher number of pilot injections raises pilot induced combustion and improves mixture distribution. These effects subsequently increase the premixed combustion and help sustain a strong main development with less variability. This benefit is maximised when using hotter glow plug temperatures raising IMEPg magnitude and reducing variation.

Increases in air pollution, especially the particulate component, are associated with increased cardiovascular mortality, possibly through increases in thrombogenic mechanisms. The research presented in this thesis addresses the hypothesis that diesel exhaust particulates (DEP) increase thrombogenicity by impairing the release of tissue plasminogen activator (t-PA) from vascular endothelial cells, thus inhibiting the endogenous fibrinolytic mechanisms that promote thrombus breakdown. The initial aims of this work were to develop an in vivo model of thrombosis, to determine whether exposure to DEP did alter clotting. Initial attempts to develop the Folts’ model (which stimulates thrombus formation via arterial stenosis and mechanical injury), first in male C57/Bl6 mice and later in male Wistar rats, were unsuccessful. An alternative approach, using ferric chloride (FeCl3) to induce chemical injury to the rat carotid artery was found to produce reliable and reproducible thrombotic occlusion: this model was used for all subsequent experiments. The effects of DEP on thrombus formation were assessed in vivo by applying the FeCl3 model. DEP were administered via intratracheal instillation or tail vein injection 2, 6 or 24 hours prior to induction of thrombosis. The effects of DEP were compared with vehicle and suitable controls: carbon black (a clean carbon nanoparticle); quartz (a large non-carbon particle that causes well-characterised pulmonary inflammation). The time to thrombotic occlusion was significantly reduced 6h after intra-pulmonary instillation of DEP (0.5ml of a 1mg/ml suspension). In contrast, instillation of carbon black or quartz had no significant effect on thrombosis, despite causing greater pulmonary (increased neutrophils and levels of interleukin-6, tumour necrosis factor-α and C-reactive protein in bronchoalveolar lavage fluid) and systemic (C-reactive protein in plasma) inflammation than DEP. Direct administration of DEP (0.5mg/kg) to the blood stream resulted in an acute (2 hours after injection) increase in time to thrombotic occlusion in the absence of pulmonary inflammation. A similar (but less pronounced) effect was observed following administration of carbon black (0.5mg/kg). These data suggest that the DEP-mediated increase in thrombosis is independent of pulmonary and systemic inflammation. The mechanisms involved were addressed by measuring platelet-monocyte interactions (flow cytometry) and markers of the endogenous fibrinolytic system (ELISA). Exposure (either instillation of injection) to DEP significantly increased platelet-monocyte aggregation. Carbon black and quartz produced no such effect (but did increase platelet-platelet aggregation). t-PA antigen and activity were reduced, whilst PAI-1 and fibrinogen were increased, following either instillation or injection of DEP. The final aim was to develop a suitable dispersant for use in cell culture to determine whether DEP alter the expression (real-time polymerase chain reaction; rtPCR) and generation (enzyme-linked immunosorbent assay; ELISA) of t-PA and plasminogen activator inhibitor (PAI-1). Cell culture medium containing bovine serum albumin (0.5mg/ml; BSA) provided the best combination for DEP dispersal and maintenance of small particle size (<200nM), without detrimental effects on human umbilical endothelial cells (HUVECs). Exposure (6 and 24 hours) of HUVECs to DEP resulted in reduced basal and thrombin stimulated t-PA and PAI-1 expression. This was mirrored by reduced detection of t-PA and PAI-1 in culture medium. In conclusion, these investigations confirm that exposure to DEP is capable of increasing the rate of thrombus formation and that this is, in part, mediated by an alteration in the endogenous fibrinolytic system. These changes did not appear to be secondary to pulmonary or systemic inflammation. Whilst cell culture experiments suggested DEP could directly alter endogenous fibrinolytic activity in endothelial cells, there was no evidence from these experiments of DEP translocation into the systemic circulation. Thus, this work suggests that DEP is capable of increasing thrombus formation in vivo via several mechanisms. Similar changes may account for the increased thrombus formation in humans exposed to diesel exhaust in air pollution.

El biodiesel es un combustible preparado en base a aceites vegetales, grasas animales, o desperdicios de aceites los cuales se hacen reaccionar con metanol o etanol para convertir las grasas triglicéridos en metil o etil ésteres vía transesterificación. Las características de este combustible lo hacen apropiado para funcionar en motores de ignición por compresión. En la actualidad el biodiesel se plantea como una alternativa o un complemento al diesel para los vehículos pesados, siendo entonces necesario establecer políticas para su producción y utilización en bases a los efectos que pueda tener en los vehículos. La presente investigación tiene como objetivo determinar el efecto de la utilización de distintas mezclas de biodiesel sobre las emisiones de vehículos pesados. Para llevar a cabo la investigación se realizaron mediciones de los niveles de contaminantes críticos: hidrocarburos (HC), óxidos de nitrógeno (NOX), monóxido de carbono (CO), material particulado (MP) y dióxido de carbono (CO2). Estas se efectuaron sobre 2 tipos de camiones (con norma y sin norma de emisiones); con 2 tipos de biodiesel (raps y aceite refrito) y 2 porcentajes de biodiesel en la mezcla (5%, y 10%). Los ensayos se realizaron siguiendo la fase rural y la fase urbana del ciclo transiente de conducción europeo FIGE-ETC, sobre un dinamómetro de chasis para vehículos pesados. Para los dos camiones y los dos tipos de biodiesel, las emisiones de NOX aumentaron entre 4% y 5%, para una mezcla al 10% de biodiesel, siendo este aumento mayor para el biodiesel de aceite refrito. Así mismo, en todos los casos el material particulado presentó reducciones entre un 20% y un 50%. CO presentó reducciones sólo para el camión con norma Euro II, mientras que para el camión sin norma no presentó tendencias definidas. Tanto NOX como MP y CO se comportaron de forma similar a lo reportado en la literatura, mientras que HC ni CO2 mostraron tendencias de cambio en sus emisiones. En conclusión, es posible utilizar una mezcla de diesel hasta con 10% de biodiesel, teniendo únicamente efectos negativos en las emisiones de NOX, las cuales pueden ser tratadas modificando el tiempo de inyección; con efectos positivos en las emisiones de material particulado y en algunos casos en las emisiones de CO; y sin efectos importantes en el resto de los contaminantes.

No description available.

The research reported in the thesis addresses questions of how engine fuel consumption and carbon dioxide emissions are can be reduced through improvements in thermal management, lubricant design, and energy recovery. The investigations are based on simulation studies using computational models and sub-models developed or revised during the work, and results provided by complementary experimental studies carried out by collaborating investigators. The brake thermal efficiency of the internal combustion engines (ICE) used in cars and light duty commercial vehicles is reduced by frictional losses. These losses vary with engine design, lubricant formulation and thermal state. They are most significant when the engine is running cold or partially warm. Over the New European Drive Cycle (NEDC), engine friction losses raise vehicle fuel consumption by several percentage points. A version of the computational model, PROMETS, has been developed and applied in studies of thermal behaviour, friction and engine lubricant to investigate the performance of a 2.0l, I4 GTDI spark ignition engine and in particular, how these influence fuel consumption over the NEDC. Core parts of PROMETS include a physics-based, empirically calibrated friction model, a cycle averaged description of gas-to-structure heat transfer and a lumped capacity description of thermal behaviour of the engine block and cylinder head. In the thesis, revisions to the description of friction and interactions between friction, local thermal conditions and lubricant are reported. It is shown that the bulk temperature of coolant rather than oil has the stronger influence on friction at the piston-liner interface, whilst bulk oil temperature more strongly influences friction in crankshaft bearings and other lower engine components. However, local oil film temperatures have a direct influence on local friction contribution. To account for this, local values of oil temperature and viscosity are used in describing local friction contributions. Implementation required an oil system model to be developed; an iterative model of the frictional dissipation within the main bearings, and a prediction of piston cooling jet heat transfer coefficients have been added to the oil circuit. Simulations of a range of scenarios and design changes are presented and analysed in the thesis. The size of the fuel savings that could potentially be made through improved thermal management has been demonstrated to be 4.5% for the engine being simulated. Model results show that of the friction contributing surfaces, the piston group is responsible for the highest levels of friction, and also exhibits the largest absolute reduction in friction as the temperature of the engine rises. The relatively low warm-up rate of the lower engine structure gives a correspondingly slow reduction in friction in crankshaft bearings from their cold start values. Measures to accelerate this reduction by raising oil temperature have limited effect unless the strong thermal links between the oil and the surrounding metal are broken. When additional heating is applied to the engine oil, only around 30% is retained to raise the oil temperature due to these thermal links.

Despite being hailed as a green fuel, emissions from diesel engines including particulate matter (PM10 and PM 2.5) have been implicated in a range of adverse human health effects from lung and bladder cancers to premature mortality. In this study diesel engine exhaust emissions were collected from a light duty direct injection diesel engine on a standard test bed. Engine conditions of speed and load were altered to provide a set of total emission samples from over the engine's operating range. Diesel emission samples collected were fractionated on a silica column into aliphatic, aromatic, and polar groups of compounds, which were tested for their genotoxicity in the chromosome aberration assay in Chinese hamster ovary CHO-KI cells both with and without metabolic activation (rat liver S9 fraction). The aliphatic fractions did not exhibit cytotoxicity up to the maximum concentration assayed, and one emission sample (3000 rpm speed and 5 Nm load) assayed for effect on chromosome aberrations was not clastogenic (up to 600 pg/ml). The aromatic fractions of all engine emission samples assayed and of the fuel were not clastogenic, but did show high levels of cytotoxicity at relatively low doses, raising concern that any genotoxic effect was masked by the toxicity of certain chemicals within the fraction. Further fractionation, using 1 PLC, was therefore performed which separated the aromatics into various ring sizes. Assay of the ring fractions showed evidence of increasing clastogenicity with increasing ring size, with the -1+ -ring fractions of both the fuel and one emission sample clearly clastogenic when assayed with metabolic activation (evidence of the presence of indirect-acting genotoxic compounds within both samples). The final fractions to be assayed, the polar fractions, were clastogenic when assayed both with and without metabolic activation. All seven fractions from emission samples collected over a range of speed and load conditions caused highly significant increases in chromosome aberrations at concentrations as low as 20 μg/ml. An engine running for less than 30 minutes at 1000 rpm speed and 55 Nm load (urban driving conditions for a heavily laden vehicle) would emit 148 mg of polar group compounds for every litre of fuel consumed. Polar compounds have been shown to be a highly mutagenic fraction of air particulate samples, and as diesel emissions contribute up to 80 % of the particulate matter in urban air in some areas, diesel emissions and the polar compounds in particular are of real concern to human health. 3

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / The use of fuels (from crude oil) in vehicles is responsible for one of the biggest environmental challenges; SO2 emission. As a result most countries regulate their sulfur emissions, with the goal of getting to the use of 10 ppm sulfur fuels. These stringent fuel sulfur content requirements have resulted in intensive research being directed at alternative desulfurization technologies which will ensure the treatment of fuels to acceptable sulfur levels. Extractive desulfurization using ionic liquids (IL) may be considered as one of the most promising of these technologies and is the subject of the study presented in this work. This study served two major purposes: (1) to investigate the capacity as well as key parameters which affect the extraction efficiency of the IL; 1-butyl-3-methylimidazolium octylsulfate as a solvent for deep extractive desulfurization of real Fluid Catalytic Cracking Unit (FCCU) diesel fuel samples collected from a typical South African Refinery, (2) to study/find suitable solvents for the regeneration of sulfur-loaded 1-butyl-3-methylimidazolium octylsulfate and the efficiency and effectiveness of the regenerated IL in the desulfurization of diesel fuel. 1-butyl-3-methylimidazolium octylsulfate was selected due to its properties i.e. good extractive ability for S-compounds and insolubility in fuel oils. A 22.1% sulfur removal was achieved in the desulfurization of FCCU feed stream diesel fuel, while 96% sulfur removal was achieved for FCCU product stream diesel fuel. These results show that the IL is more effective in the selective removal of sulfur (S) from FCCU diesel product than from FCCU feed stream, suggesting that fuel sulfur content and stream composition affects the extraction efficiency and effectiveness of the IL. Based on thermodynamic considerations, hexane was selected as the most suitable solvent for the re-extraction of sulfur from spent IL. Regenerated IL was used for desulfurization of diesel and achieved highest sulfur removal of 95% and the IL was regenerated up to four times without appreciable decrease in efficiency. The results obtained herein show that ILs are effective in the desulfurization of real diesel oil samples when the sulfur concentration is not very high. Further studies on the recoverability of ILs as well as their environmental impact need to be done to support findings in this study. / GR2016