Investigation into the Durability of High-Efficiency Spark-Ignited Gasoline Engines Employing Dedicated EGR Technology

Paper #:
  • 2018-01-0884

Published:
  • 2018-04-03
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Abstract:
The durability of power cylinder components within light-duty, spark ignited engines employing exhaust gas recirculation from a dedicated rich operating cylinder was evaluated using radioactive tracers to label select contact surfaces. Unique labels were generated for both the ring and liner contact areas of the cylinders operating with stoichiometric fueling as well as for the cylinder operating fuel-rich. Simultaneous detection of wear rates in both cylinder arrangements allows for wear comparisons of fueling strategy and the dedicated exhaust configuration in adjacent cylinders without the need to perform independent studies on multiple engines. Using a high efficiency germanium gamma ray detector and indirect oil sampling, high sensitivity on-line measurements returned five minute incremental data on six unique radioactive isotopes. Cumulative isotope data is used to plot instantaneous and steady state wear rates for each mode of operation defined in the design of experiments. Mild wear rate separation was noted between the stoichiometric fueled cylinders and the rich operating dedicated cylinder during the engine study, but did not exceed 1 nanometer per hour in sustained operation. Following the run-in procedure the labeled liner surfaces decreased in wear rate so drastically that operating condition changes yielded little discrimination between conditions or cylinders. The study did not test oil ageing effects where by additional fueling in the dedicated cylinder could result in increases in localized fuel dilution compromising the film strength and viscosity of aged lubricant past a threshold that could generate significant wear. Barring data on aged oils at heavy fuel dilution percentages, no conditions tested in the design of experiments resulted in a significant wear increase in the dedicated cylinder over the stoichiometric cylinders. Of the labeled power cylinder components in the study, the observed wear rates are comparable to historical turbocharged GDI engines tested previously.
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