A Comparison of EGR Condensate Composition between EGR and Dedicated-EGR Combustion Strategies 2021-01-0484

Water injection is an effective method for knock control in spark-ignition engines. However, the requirement of a separate water source and the cost and complexity associated with a fully integrated system creates a limitation of this method to be used in volume production engines. The engine exhaust typically contains 10-15% water vapor by volume which could be condensed and potentially stored for future use. In this study, the exhaust condensate composition was assessed for its use as an effective replacement for distilled water. Specifically, condensate samples were collected pre and post-three-way catalyst (TWC) and analyzed for acidity and composition. The composition of the pre and post-TWC condensates was found to be similar however, the pre-TWC condensate was mildly acidic. The mild acidity has the potential to corrode certain components in the intake air circuit.

The study was further extended to include condensate analysis from an engine operating a dedicated-EGR (D-EGR) strategy running on two similar octane number, E0 and E85 fuels. These condensate samples were compared with a baseline and 0% EGR case. The analysis revealed increased concentrations of nitrite, acetate, and ammonium for D-EGR condensate samples compared to the traditional 25% EGR operation for both E0 and E85 fuels. None of the samples obtained exhibited acidic properties based on their pH values in this second part of the study. Ion analysis of the condensates revealed exhibited lower cation and anion concentrations for the E85 fuel compared to the E0 fuel for 25% conventional and D-EGR condensates. Further, the overall cation and anion formation were higher for the 25% rich D-EGR stream compared to the 25% stoichiometric EGR which was counter-intuitive to the pH measurement of the condensate samples.