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This research examines the interdependence of the control strategies of a high-pressure exhaust gas recirculation (HP-EGR) and a variable geometry turbocharger (VGT) on a medium-duty diesel engine in transient load operation. The effect on fuel economy, particulate and NO production were investigated through multiple tests of synchronously controlled VGT and EGR positions. An optimal steady-state strategy of the above determinants was defined as a function of the VGT’s boost pressure and EGR percent mass. The optimal steady-state strategy was then used to investigate the interdependence of the VGT and HP-EGR in transient load acceptence events which occurred over a range of 2 to 10 seconds. The faster transients increased deviations of boost and EGR levels from steady-state calibration values which consequently led to corresponding fuel consumption and particulate matter emission increases.

This study's objective was to characterize thermal-shock errors on a specific Kistler pressure transducer and to determine if a thermal-shock correction algorithm using transducer surface temperature could be developed. Atmospheric measurements were made using a thermal-shock rig which intermittently exposed the transducer to a known heat flux while maintaining atmospheric pressure on the transducer diaphragm. Any change in output is attributable to thermal shock. Surface temperature was measured using a separate eroding-type surface thermocouple. The data showed a strong correlation between heat-flux induced temperature change and thermal shock and were used in a least-squares error estimation algorithm to create a model of the thermal shock as a function of transducer surface temperature. The model was calibrated using baseline measurements and tested against measurements made at different heat flux intensities and exposure duration and frequency.

An investigation was performed to try to quantify the relative importance of large-scale mixing and turbulence in a multi-valve spark-ignited automotive engine converted to use natural gas fuel. The role of mixing was examined by comparing single-point versus multi-point combustion performance at several operating conditions. The fuel-air mixture passed through a static mixer prior to entering the intake manifold in the single point case. This configuration was assumed to produce a well-mixed charge entering the combustion chamber. The fuel was delivered just upstream of the intake port in the multi-point configuration. The charge was assumed to be stratified in this case. The results showed a significant degradation in combustion stability and maximum power but little difference in ignition delay and fully-developed burn duration using multi-point injection. The relative role of turbulence was examined by altering the intake-flow configuration to create three levels of inlet swirl.

This paper describes a technique which can accurately measure firing-cylinder full-load absolute pressure during critical intake events, thereby providing useful cylinder-pressure data for valve-timing optimization. To achieve this, an absolute-pressure transducer is connected to a port drilled through the cylinder wall at an axial location uncovered approximately midway through the piston stroke. This placement spares the transducer from thermal shock caused by flame-front impingement upon the diaphragm, since the combustion is normally completed by the crank angle of passage exposure. The described technique was used to study valve-timing and manifold-runner design effects on the intake process of a V-8 engine and to determine thermal-shock magnitudes and their effect on conventionally-measured pumping-loop data.

A first step is taken toward the standardization of cylinder-pressure based knock-characterization methods. Toward this goal, background is presented outlining existing knock theories and providing a knock definition. Eleven methods found in the literature are described and knock data acquired and analyzed using seven of the described methods for comparison. Issues are discussed regarding identification of knocking cycles, filtering-frequency bands and effects of transducer-mounting techniques. The methods examined each had their own particular advantages and disadvantages which are summarized in the conclusions. Recommendations are provided regarding further work required to establish standard knock-characterization methods.