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The influence of swirl on performance and emissions was investigated using a single cylinder Hydra research engine fitted with a high pressure electronic unit injector and a variable swirl mechanism. A large amount of emission data was collected together with the cylinder pressure, fuel line pressure and needle lift signals at a wide range of operating conditions. The influence of a fixed swirl ratio on emissions was also investigated on a Ford HSD425 York engine with conventional injection system and a synopsis of the results is discussed. Laser illuminated high speed cinematography was used to study the interaction of swirl with spray and combustion processes. Data is presented on air- fuel mixing, spray trajectories and flame movement at different operating conditions. Data is also presented to highlight the influence of swirl on the heat release rate, cylinder pressure rise and its relation to measured emission levels, particularly NOx and particulates.

A large number of high speed photographs have been taken of combustion in a high speed direct injection diesel engine. A frame rate of upto 20,000 frames/sec has been achieved at engine speeds up to 3000 rev/min. This has been achieved by computer controlled synchronization of a Cu-vapour laser illumination source, the high speed camera and the electronically controlled fuel injection equipment. In addition to the photography, the basic macroscopic parameters of combustion were recorded simultaneously: this enables the photographic information to be related to the heat release information. The parameters investigated include the influence of swirl ratio, injection system, engine speed, load, injection timing, and combustion chamber shape on spray and combustion. The influence of various parameters on spray growth, ignition and combustion is discussed. Combustion processes in open and reentrant open bowl combustion chambers are examined.

The atomisation characteristics of DI diesel engine fuel injection nozzles have been the subject of intensive study over the last decade. Much of this work has been related to clean, single hole nozzles spraying into quiescent air, at either ambient conditions or elevated pressures and temperatures. Experience shows that fuel injector nozzles may foul very rapidly in field service, and that this might have a significant effect on the performance of the engine particularly with regard to emissions. The build up of material on the injector nozzle can be controlled by the addition of suitable fuel additives. This paper describes test procedures developed to assess deposit build up and to indicate the efficacy of keep clean additives. The paper then goes on to describe high speed photographic techniques for studying the fuel spray characteristics of clean and fouled injectors in a firing engine.

The use of cycle simulation computer programs for the study of both the steady and transient performance of turbocharged diesel engines has provided very useful information for their design and development. This paper describes the development of a dynamic simulation of a two-stroke turbocharged diesel engine. The mathematical model for the system has been developed using the filling and emptying concept. The simulation also includes the characteristics of the turbocharger compressor, turbine, scavenge blower and intercooler. A single zone combustion model has been used to calculate the rate of heat release in the engine cylinder from the fuel injection data. The steady state performance calculation shows a very good correlation with experimental results. Parametric studies were undertaken into the effect of friction and combustion during transient running; these show that the level of friction and the rate of combustion have a great effect on the response rate.

IC Engines are widely used as power plants for automobiles. The rapid growth in the number of automobiles has caused increased environmental pollution. Therefore, emission legislation was introduced to keep the pollution within acceptable limits. It is becoming more stringent day by day, and is the driving force for the development and application of various experimental and computational techniques for engine combustion and emission studies. Multi-stage fuel injection, VCO nozzles, retarded fuel injection timing, reentrant combustion chamber, etc. are some of the means of reducing the exhaust emissions. A study involving in-cylinder combustion visualisation and an optical method (spectroscopic method) is reported in this paper. Using this technique, the effect of multi-stage fuel injection at various engine operating conditions was studied. A Ricardo Hydra single cylinder, direct injection optical diesel engine was used for this study.