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Direct flame imaging and pressure analysis were applied to the combustion of gasoline and compressed natural gas (CNG) in a single-cylinder, four-valve spark-ignition engine equipped with optical access via quartz windows in the cylinder liner and piston crown. Tests were performed at three engine speed/load conditions and at equivalence ratios of 1.0, 0.9 and 0.8. The four-valve head incorporated two different port geometries, with and without metal sleeves to deflect the intake air flow, in order to investigate the effect of tumble strength on combustion and engine-out emissions of unburned hydrocarbons and NOx. The results showed that sleeving of the intake ports produced a significant increase in IMEP and a reduction in CoV IMEP for both CNG and gasoline, due to the greatly reduced bum duration.

A laser-induced fluorescence (LIF) system has been developed to obtain measurements of the instantaneous lubricant film thickness in the piston-cylinder assembly of a firing single-cylinder, direct-injection diesel engine. Measurements were made at top-dead-centre (TDC), mid-stroke and bottom-dead-centre (BDC) position by means of three fibre optic probes inserted into the cylinder liner and mounted flush with its surface. Following extensive repeatability tests, the cycle-averaged lubricant film thickness was estimated for different multi-grade oils as a function of engine speed, load and temperature. The results quantified the dependence of the film thickness ahead, under and behind the piston rings on oil chemistry and viscometric properties, thus confirming the important role of the LIF technique in the development and formulation of new engine oils.

Mixed-lubrication models comprising of Patir and Cheng's [1,2] average Reynolds equation and Greenwood and Tripp's [3] asperity interaction formulations have hitherto been widely used in predicting piston-ring performance. In this paper a number of models have been developed to allow mixed-lubrication of both Newtonian and shear thinning fluids to be simulated. Lubricating action usually involves two anisotropic solid surfaces of statistically different profiles. Various forms of the average Reynolds equation and the asperity interaction models require parameters representing the composite surface roughness and profile parameters at the contact. Here a strategy for determining these equivalent composite parameters is presented. Mathematical simulations indicate that when the composite RMS and composite summit RMS roughness of the contact approach the same value, the performance of the mix-lubrication model becomes dominated by the asperity interaction formulation.

Variations in air-fuel ratio within a 16-valve port-injection spark-ignition engine have been examined as a consequence of rapid transients in load at constant speed with fuel injection controlled by the production engine-management system and by a custom-built controller. The purpose was to minimize excursions from stoichiometry by the use of a controller to impose an injection strategy, guided by results obtained with the production management system. The strategy involves a model that takes account of manifold filling and the delays in transport of fuel from the injectors to the cylinder. The results show that the excursions in air-fuel ratio from stoichiometry were reduced from more than 25% to 6%.

Experiments have been performed in one cylinder of a production two-valve engine under firing conditions and quantify the velocity, size and number density of droplets as a function of position, crank angle, injection timing, rotational speed, load and cooling water temperature. They were obtained with a phase-Doppler velocimeter with measurements ensembled in relation to an optical shaft encoder. The engine was also instrumented to provide pressure traces, air and fuel flow rates and temperatures. The injection timings included those with open and closed inlet valve. The results show that most of the droplets emerge in a comparatively small region of the inlet valve and that the characteristics of the spray are important mainly when injection takes place with the inlet valve open.