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Complying with emissions legislation presents ever increasing challenges for heavy duty diesel engines. These challenges are being met through the use of ever more sophisticated engine hardware. An example of such hardware is common rail fuel injection equipment which gives the flexibility of controlling fuel injection timing, pressure and quantity independently of engine speed and load. However, this greater flexibility increases the complexity of the engine optimisation process. The use of statistical experimental design, mathematical models and genetic algorithm techniques allows efficient and accurate quantification of the trade-offs needed to make sound engineering decisions during the optimisation process.

The spatial variation of instantaneous heat transfer in a highly rated DI diesel engine (130 mm bore, 150 mm stroke) has been investigated. Measurements have been made at key locations within the combustion chamber (valve bridge, above the piston bowl lip and bore edge) at test conditions covering the engine speed and load range. Total and radiative heat flux probes have been designed and developed to enable both the convective and radiative heat transfer components to be quantified. Transient calibration techniques have also been developed to establish the dynamic characteristics of the heat flux probes. This has removed the uncertainty normally associated with surface thermocouple diffusivity values. Considerable spatial variations in both peak and mean heat transfer have been found. The measured spatial and temporal variation in heat flux have been compared with established heat transfer models.

Conventional exhaust gas analyzers are of limited use in transient engine testing as the dynamics of the analyzers cause distortion of the emissions measurement during transients. An advanced technique is presented which uses signal reconstruction to determine the actual emissions during engine transients from the distorted output of a conventional exhaust gas analyzer. The reconstruction technique is based on the design of a finite horizon filter which is a dual of generalized predictive control theory. Results are presented which demonstrate the use of this technique for reconstruction of instantaneous emissions from a diesel engine over a part of the US heavy duty test cycle. The results show that the reconstructed emissions recover significant information which is otherwise obscured by the distortion introduced by the analyzer dynamics.

Ricardo have developed a systematic approach for the design of transient engine control strategies using advanced control techniques. The methodology was initially applied to the design of a testbed speed and torque controller. This enabled complex transient tests to be carried out with equipment normally used for steady-state testing. The same techniques were applied to the design of a controller for a variable geometry turbocharger aimed at vehicle applications. The influence of different control strategies on emissions and fuel economy was evaluated on a heavy-duty diesel engine over a section of the US FTP cycle. Particulate reductions of up to 34% were achieved without increasing NOx.