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In this paper the effect of in-cylinder crevices formed by the piston cylinder clearance, above the first ring, and the spark plug cavity, on the entrapment of unburned fuel air mixture during the late compression, expansion and exhaust phases of a spark ignition engine cycle, have been simulated using the Computational Fluid Dynamic (CFD) code KIVA II. Two methods of fuelling the engine have been considered, the first involving the carburetion of a homogeneous fuel air mixture, and the second an attempt to simulate the effects of manifold injection of fuel droplets into the cylinder. The simulation is operative over the whole four stroke engine cycle, and shows the efflux of trapped hydrocarbon from crevices during the late expansion and exhaust phases of the engine cycle.

The process of autoignition in an internal combustion engine cylinder produces large amplitude high frequency gas pressure waves accompanied by significant increases in gas temperature and velocity, and as a consequence large convective heat fluxes to piston and cylinder surfaces. Extended exposure of these surfaces to autoignition, results in their damage through thermal fatigue, particularly in regions where small clearances between the piston and cylinder or cylinder head, lie in the path of the oscillatory gas pressure waves. The ability to predict spatial and temporal' variations in cylinder gas pressure, temperature and velocity during autoignition and hence obtain reasonable estimates of surface heat flux, makes it possible to assess levels of surface fatigue at critical zones of the piston and cylinder head, and hence improve their tolerance to autoignition.

The in cylinder air motion, fuel air mixing, evaporation, combustion and exhaust emissions have been simulated for a four stroke direct injection gasoline engine using the KIVA II code. A strong controlled tumbling air motion was created in the cylinder, through a combination of a conventional pentroof four valve cylinder head, in conjunction with a piston having a stepped crown and offset combustion bowl. A range of injection strategies were employed to optimise combustion rate and exhaust emission (NOx and unburned hydrocarbons (fuel)), at two operating conditions - one with a stoichiometric air fuel mixture and the other with a lean mixture of 30:1 air/fuel ratio. Injection directed towards the piston bowl with a hollow cone jet, in a single pulse, has shown the best results regarding burned mass fraction and level of unburned HC. Fuel concentration, air motion, combustion characteristics and pollutants level are presented for lean and stoichiometric cases.

In developing high speed swirl supported direct injection diesel engines it has been a general experience that different engine results (performance, smoke and emission) may be obtained when using different intake port designs, although the swirl numbers (stationary flow test rig) of the different ports were identical. Therefore, an in-cylinder flow investigation under motoring conditions using hot wire anemometry was performed for three different inlet port designs having the same swirl number. Special emphasis was drawn on the engine design parameters being as close as possible to reality. Thus, the flow investigation and the engine tests were carried out at a typical compression ratio of 18 : 1 using a standard combustion bowl in the piston as well as produceable inlet ports. All flow measurements were carried out under motoring conditions covering the speed range from 1100 to 2400 rpm.

The absorption and desorption of fuel by cylinder lubricating oil films has been modelled using principles of mass transfer. Henry's Law for a dilute solution of fuel in oil is used to relate gas to liquid phase fuel concentrations. Mass transfer conductances in gas and liquid phases are considered, the former via use of Reynold's Analogy to engine heat transfer data, the latter through assuming molecular diffusion through an effective penetration depth of the oil film. Oxidation of desorbed fuel is assumed complete if the mean of burned gas and lubricating oil film temperatures is greater than 1100K,. Below this value the desorbed fuel is considered to contribute to hydrocarbon emissions. Comparison with engine test data corroborate the absorption/desorption hypothesis. The model indicates the equal importance of gas and liquid phase conductances.

A generalized model describing oxidation in a porous substance is developed and applied to the thermal regeneration of both monolithic and fibrous diesel particulate traps. With typical engine and trap data the regeneration process is analysed using the model. A parametric study demonstrates how the exhaust gas oxygen concentration, flow rate and initial trap particulate loading affect the regeneration time and peak trap temperatures. The model is shown to be in reasonable agreement with published experimental results.

The concept of using low power microwave energy to efficiently assist the regeneration of ceramic monolith diesel particulate traps is explained. A prototype Microwave Assisted Regeneration (M.A.R.) system is presented and is demonstrated to work reasonably well on both bench and engine tests. The system, which is inexpensive, reliable and controllable, requires 1 kW of overall electrical power for a short period prior to trap regeneration. The M.A.R. technique presented merits further consideration as an alternative to other proposed vehicle trap regeneration systems.

A basis for the comparison of engine spray penetration studies with hot and cold bomb methods, and the liquid injection technique for studying penetration is presented. A spray penetration formula is developed from experimental information on gas jet mixing, with a correction for fuel density. Agreement between the spray penetration formula developed here, and experimental data from a variety of sources is found to exist.