No description available.

No description available.

No description available.

CAI combustion and the factors affecting it were intensively investigated in a single cylinder, air-assisted gasoline direct injection engine. CAI was achieved by means of residual gas trapping by utilising low-lift short duration camshafts and early closing of the exhaust valves. The effects of EVC (Exhaust Valve Closure) and IVO (Inlet Valve opening) timings, spark timing, single and split injection timings, coolant temperature, compression ratio, cam lift and duration on exhaust emissions and CAI operation were investigated experimentally. Engine speed throughout the course of the experiments, was varied from 1200rpm to 2400rpm and the air/fuel ratio was altered from stoichiometric to the misfire limit. The results show that the EVC timing, compression ratio, cam lift and duration had significant influences on CAI combustion and emissions. Early EVC when combined with higher compression ratio and higher cam lift, enhance CAI combustion operation and stability. IVO timing had minor effect on CAI combustion while spark timing hardly affects CAI operation as soon as fully-developed CAI conditions were established. Coolant temperature was revealed to have substantial impact on CAI combustion when the coolant temperature was below 65C. The results also show the importance of injection timing. Early injection gave faster and more stable combustion, less HC and CO emissions, but more prone to knocking combustion and higher NOx emissions. Furthermore, CAI operation range could considerably be extended with injection during the recompression process. Late injection led to slower and unstable combustion, higher HC and CO emissions but lower combustion noise and NOx emissions. Split injection gave even further extension of CAI range in both stoichiometric and lean mixture operations. All the above clearly suggest, that optimising injection timing and using split injection is an effective way to control and extend CAI operation in a direct injection gasoline engine.

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No description available.

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

Conversion of biomass to energy does not contribute to the net increase of carbon dioxide in the environment, therefore the use of biomass waste as a clean and renewable fuel source is an attractive alternative to the use of fossil fuels. Biomass can be converted to energy via direct combustion or via thermo-chemical conversion to liquid or gas fuels. This study focuses on employing gasification technology to convert biomass waste to producer gas, which is then cleaned and fed as gaseous fuel into the gas turbine. Since the producer gases are usually low caloric values, the power plants performance under various operating conditions has not yet been proven. In this study, system performance calculations are conducted for a 5MWe and a 20MWe power plants using commercial software ThermoFlow. The power plants considered including simple gas turbine systems, steam turbine systems, combined cycle systems, and steam injection gas turbine systems (STIG) using the producer gas with low caloric values at approximately 30% and 15% of the natural gas heating value. The low caloric value fuels are shown to impose high back compressor pressure and increased power output due to increased fuel flow. Power augmentations under four different weather conditions are also calculated by employing gas turbine inlet fog cooling. Different capacity options for the heat recovery steam generator (HRSG) that provides the steam for STIG are analyzed.

by Kwan Hok-wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 67-69). / Abstracts in English and Chinese. / Acknowledgment --- p.i / Abstract --- p.ii / Chapter 1. --- INTRODUCTION / Chapter 1.1 --- Chemical speciation of cyanide --- p.1 / Chapter 1.2 --- Review of analytical techniques for cyanide determination --- p.3 / Chapter 1.3 --- Importance of sediment in the environment --- p.6 / Chapter 1.4 --- Characteristics of marine sediment --- p.6 / Chapter 1.5 --- Antropogenic sources of cyanide --- p.7 / Chapter 1.6 --- Research objective --- p.8 / Chapter 1.7 --- Brief description of the project --- p.9 / Chapter 2. --- INSTRUMENTATION AND THEORY / Chapter 2.1 --- Instrumentation for flow injection analysis system --- p.11 / Chapter 2.2 --- Basic principles of flow injection analysis --- p.21 / Chapter 2.3 --- Basic principles of amperometric detection --- p.24 / Chapter 3. --- EXPERIMENTAL / Chapter 3.1 --- Instrumentation --- p.25 / Chapter 3.2 --- Reagents --- p.32 / Chapter 3.3 --- Sample preparation --- p.34 / Chapter 4. --- RESULTS AND DISCUSSION / Chapter 4.1 --- Effect of bismuth on on-line precipitation of sulphide in FIA --- p.37 / Chapter 4.2 --- Calibration --- p.37 / Chapter 4.3 --- Effectiveness of the distillation conditions --- p.41 / Chapter 4.4 --- Comparisons of cyanide extraction methods for sediment analysis --- p.42 / Chapter 4.5 --- Effect of bismuth nitrate on cyanide recoveries --- p.45 / Chapter 4.6 --- Effect of bismuth nitrate on cyanide recoveries in the presence of sulphide --- p.48 / Chapter 4.7 --- Effect of bismuth nitrate on recoveries of total cyanide in the analysis of interlaboratory test samples --- p.55 / Chapter 4.8 --- Recoveries of complexed cyanide in the analysis of SETOC sample with sulphide interference --- p.57 / Chapter 4.9 --- Analysis of marine sediment samples --- p.58 / Chapter 4.10 --- Recovery tests and precision studies --- p.59 / Chapter 4.11 --- Interferences --- p.62 / Chapter 5. --- CONCLUSION --- p.66 / Chapter 6. --- REFERENCES --- p.67

The currently reported work involved fundamental study of auto-ignition under unusually high knock intensities in an optical spark ignition engine. The single cylinder research engine adopted included full bore overhead optical access capable of withstanding continuous peak in-cylinder pressure and knock intensity of up to 150 bar and 60 bar respectively. Heavy knock was deliberately induced under relatively low loads (5 bar IMEP) using inlet air heating up to 66 °C and a primary reference fuel blend of reduced octane rating (75 RON). High speed chemiluminescence natural light imaging was used together with simultaneous heat release analysis to evaluate the combustion events. The key out comes of this study could be listed as follow: • Proof and improved understanding of multi centred auto-ignition events under high KIs • Improved understanding of the potential pitfalls of over-fuelling for heavy knock suppression • Optical validation of 'natural' oil droplet release and on-off behaviour of knocking cycles Multiple centred auto-ignition events were regularly observed to lead in to violent knocking events, with knock intensities above 140 bar observed. The ability to directly image the events associated with such high magnitude of knock is believed to be a world first in a full bore optical engine. The multiple centred events were in good agreement with the developing detonation theory to be the key mechanism leading to heavy knock in modern downsized SI engines. The accompanying thermodynamic analysis indicated lack of relation between knock intensity and the remaining unburned mass fraction burned at the onset of the auto-ignition. Spatial analysis of the full series of images captured demonstrated random location of the first captured auto-ignition sites during developing auto-ignition events. Under such circumstances new flame kernels formed at these sites, with initial steady growth sometimes observed to suppress the growth of the earlier spark initiated main flame front prior to violent end gas auto-ignition. It was found that pre-ignition most commonly initiated in the area surrounding the exhaust valve head and resulted in a deflagration that caused the overall combustion phasing to be over advanced. In the cycles after heavy knock, droplets of what appeared to be lubricant were sometimes observed moving within the main charge and causing pre-ignition. These released lubricant droplets were found to survive within the combustion chamber for multiple cycles and were associated with a corresponding "on-off" knocking combustion pattern that has been so widely associated with super-knock in real downsized spark ignition engines. This research also concerned with improving understanding of the competing effects of latent heat of vaporization and auto-ignition delay times of different ethanol blended fuels during heaving knocking combustion. Under normal operation the engine was operated under port fuel injection with a stoichiometric air-fuel mixture. Additional excess fuel of varied blend was then introduced directly into the end-gas in short transient bursts. As the mass of excess fuel was progressively increased a trade-off was apparent, with knock intensity first increasing by up to 60% before lower unburned gas temperatures suppressed knock under extremely rich conditions (γ=0.66). This trade-off is not usually observed during conventional low intensity knock suppression via over-fuelling and has been associated with the reducing auto-ignition delay times outweighing the influence of charge cooling and ratio of specific heats. Ethanol had the highest latent heat of vaporization amongst the other fuels directly injected and was more effective to reduce knock intensity albeit still aggravating knock under slightly rich conditions. Overall, the results demonstrate the risks in employing excess fuel to suppress knock deep within a heavy knocking combustion regime (potentially including a Super-Knock regime).