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Tests were carried out with the aim of studying the influence of the fuel-injection equipment (FIE) on gaseous and particulate-mass (PM) emissions when using water-in-fuel emulsion. The tests included different pump-nozzle combinations, a new slide-valve-type fuel injector, water-in-fuel emulsion and different fuel-sulphur contents. The NOx reduction is compared with the results of several other tests in large two-stroke engines using water emulsions. A NOx reduction of approximately 25% was obtained using a large pump-nozzle combination and 30% added water, without deterioration in the specific fuel oil consumption. The NOx behaviour is correlated to the injection intensity as well as to a water-amount effect. Fuel sulphur has a major influence on PM, as sulphates account for approximately 35% of the total PM when operating on ‘normal’ heavy fuel. A linear approximation estimates the ‘non-sulphur’ fuel PM at between 30 and 60 mg/Nm3, depending on the FIE system.

Due to increasing problems with corrosive wear in marine Diesel Engines, caused by sulphuric acid, it is necessary to understand the mechanism of corrosion. Based on experience with large marine diesel engine operation, a mechanism model is proposed and verified by comparison with practical experience. From operation of engines it is known that the corrosion problem is most severe where the lubrication of the liner is most unsatisfactory. Therefore, most effort is put into modelling the formation and transportation of acid in the lubricant film area. Results from modelling the risk of corrosion during different engine operation conditions are presented.

Tests were performed on a single-cylinder direct-injection (DI) research diesel engine to evaluate the influence of methanol fuel on net heat release. The test program examined the use of a small pilot injection of methanol and intake-air heating as a means of compression igniting (CI) the main methanol injection. Heat-release characteristics calculated from pressure-time data and engine observations were compared between methanol and no. 2 diesel fuel. It was found that using a small pilot approximately 20 deg CA BTDC and increasing the intake temperature to about 100 deg C gave very consistent ignition. Rate shaping of the main injection was necessary to avoid too fast initial combustion during the main injection. The maximum rate of premixed combustion was approximately half of normal diesel values, and the maximum rate of diffusion combustion was higher at low load but lower at high load for methanol.

A quasi-steady gas-jet model was applied to examine the spray penetration and deflection in swirling flow during the ignition-delay period in an open-chamber diesel engine timed to start combustion at top dead center. The input to the gas-jet model included measured values of ignition delay and mean fuel-injection velocity. Attempts were made to correlate measured fuel-consumption and soot-emissions data with mixing parameters based on calculated spray penetration and deflection. The engine parameters examined were piston-bowl geometry, compression ratio, speed, and overall air-fuel ratio. Four empirical correlations proposed in the literature were examined. The correlations, which were based on spray penetration and deflection in the swirl direction, represented overall degrees of fuel distribution in the combustion chamber and of utilization of the cylinder air.

Tests were performed on a single-cylinder direct-injection (DI) research diesel engine to investigate the influence of elevated combustion-chamber temperature on combustion performance. The test program examined the low-heat-rejection (LHR) approach by removing the coolant but without employing heat-insulated parts. Heat-release characteristics calculated from pressure-time histories were correlated with measured exhaust emissions. It was found that increasing temperature level decreases the ignition delay and consequently decreases the fraction of total fuel that burns in the premixed-combustion phase. Exhaust hydrocarbon, NOx and particulate emission were found generally to increase with increasing temperature. The premixed-combustion fraction is concluded not to be the main source of the increased emissions.

HC emissions and ignition delay were investigated in a research single-cylinder DI diesel engine. Correlations were made between the measurements and different air-fuel mixing parameters calculated from a gas-jet spray model and expressions from the literature. The change in ignition delay was caused by varying engine inlet conditions of pressure and temperature and by adding a special cetane improver to No. 2 diesel fuel. In order to be able to interpret the experimental results a zero-heat-transfer heat release model was used in evaluation of the engine pressure data. It was found that the too-lean-mixed fuel could explain a maximum of 20% of the HC emission; the remaining amount is caused by other sources.

Samples of the gas from the vicinity of the wall of a spark-ignition engine operating on iso-octane has been obtained by the use of a hydraulically controlled high-speed gas-sampling valve (operating time 1 msec), during an earlier investigation (1)*. A theoretical model describing the flow through the gas-sampling valve is developed. This model is used to interpret the experimental data to compute the thickness of the quenching layer (the quenching distance). The resulting quenching distance is in reasonable agreement with the results obtained by other investigators using different theoretical experimental techniques.

A theoretical model has been developed describing the propagation of a laminar, one-dimensional flame in a combustion chamber. The model aims specifically at illuminating the processes surrounding the flame propagation in the vicinity of the combustion chamber wall and the extinction of the flame (the quenching). The model assumes constant pressure for a two-reaction scheme with 6 chemical components (CnHm, O2, CO2, CO, H2O and N2). The equations describing the conservation of energy, mass, and species constitute a system of coupled parabolic differential equations, which are solved through a finite difference scheme with 9 grid-points. The boundary conditions specify the propagation or quenching situation. Temperature as well as concentration profiles through the flame are computed. Flame velocities and quenching distances are computed for a range of air-fuel ratios, physical constants and properties, both for methane and iso-octane.