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A study has been undertaken with a single-cylinder engine, based on the Mitsubishi GDi combustion system, that has the option of either port injection or direct injection. Tests have been undertaken with pure fuel components (methane, iso-octane, toluene and methanol), and a representative gasoline that has also been tested with the addition of 10% methanol and 10% ethanol. The volumetric efficiency depends both on the fuel and its time and place of injection. For stoichiometric operation with unleaded gasoline, changing from port injection to direct injection led to a 9% increase in volumetric efficiency, which was improved by a further 3% when 10% methanol was blended with the gasoline. The improvements in volumetric efficiency will be used to quantify the extent of charge cooling by fuel evaporation, and these will be compared with predictions assuming the maximum possible level of fuel evaporation.

A thermodynamic model of spark ignition engine combustion, with multiple burned gas zones, has been extended to permit the different burned gas zones to have different mixture strengths. The NO formation is predicted in each burned gas zone using the extended Zeldovich mechanism. The model has been used to study stratified charge spark ignition engine combustion, in order to investigate the influence of overall equivalence ratio and degree of stratification on the NO emissions and the engine brake specific fuel consumption. For fixed throttle operation, it is concluded that the best trade-off is with an overall weak mixture that is close to homogeneous. For maximum power output using a slightly rich of stoichiometric mixture, then the mixture should also be close to homogeneous.

Experimental data was obtained from a Rover K4 optical access engine and analyzed with a combustion analysis package. Cyclic NO values were calculated by mass averaging the measurements obtained by a fast NO analyzer. While the mass averaged results were used as the basis of comparison for the model, results indicate that mass averaging a fast NO signal is not nearly as critical as mass averaging a fast FID signal. A computer simulation (ISIS - Integrated Spark Ignition engine Simulation) was used to model the NO formation on a cyclic basis by means of the extended Zeldovich equations. The model achieves its cyclic variability through the input of experimentally derived burn rates and a completeness of combustion parameter, which is based on the Rassweiler and Withrow method of calculating mass fraction burned and is derived from the pressure-crank angle record of the engine.

This paper investigates a technique of calculating the completeness of combustion on a cycle-by-cycle basis. The technique introduces the normalized pressure rise due to combustion parameter (Ψ) to describe the completeness of combustion. This parameter is based on the Rassweiler and Withrow method of calculating mass fraction burned and is derived from the pressure-crank angle record of the engine. Experimental data were obtained from a Rover K4 optical access engine and analyzed with a combustion analysis package. A computer simulation was then used to model the data on a cyclic basis, both with and without the completeness of combustion parameter. The inclusion of completeness of combustion improved the simulation's ability to model the experimental data both in a statistical sense (COV of IMEP) and on a cycle-by-cycle basis.

This work examines the possibility of detecting misfires via measurements of the angular acceleration of the engine block. Measurements were taken on a production 4-cylinder engine which was modeled as a single degree of freedom torsional oscillator. The torque waveform was estimated and compared to the torque calculated via cylinder pressure measurements. Further analysis was conducted in the frequency domain. Results indicate that metrics based on low frequency information were most reliable, but this is impractical for vehicular applications. The accuracy of high frequency metrics was degraded due to the limitations of the model and the non-rigid behavior of the block at high engine speeds.