Visual, Thermodynamic, and Electrochemical Analysis of Condensate in a Stoichiometric Spark-Ignited EGR Engine

The objectives of this project were to investigate the corrosivity of condensate in a stoichiometric spark-ignited (SI) engine when running exhaust gas recirculation (EGR) and to determine the effects of sulfur-in-fuel on corrosion. A 2.0 L turbocharged direct-injected SI engine was operated with low-pressure EGR for this study. The engine was instrumented for visual, thermodynamic, and electrochemical analyses to determine the potential for corrosion at locations where condensation was deemed likely in a low-pressure loop EGR (LPL-EGR) engine. The electrochemical analysis was performed using multi-electrode array (MEA) corrosion probes. Condensate was also collected and analyzed. These analyses were performed downstream of both the charge air cooler (CAC) and the EGR cooler. It was found that while conditions existed for sulfuric acid to form with high-sulfur fuel, no sulfuric acid was detected by any of the measurement methods. Chemical analysis showed that condensate from the engine’s intake air downstream of the compressor possessed the greatest potential for corrosion and that high-sulfur fuel increased the potential. The probe measurements showed that the level of corrosion was significantly below the threshold for sustained corrosion of aluminum alloys regardless of measurement location or fuel sulfur content. The potential for corrosion was shown to be low based on the plurality of measurement methods.