Effect of High Sulfur Military JP-8 Fuel on Heavy Duty Diesel Engine Emissions and EGR Cooler Condensate

Low-sulfur “clean” diesel fuel has recently been mandated in the U.S. market. However, quality of diesel fuel, particularly the sulfur content, varies significantly in other parts of the world. Due to logistical issues in various theaters of operation, the Army is often forced to rely on local fuel supplies, which exposes vehicles to diesel fuel or jet fuel (JP8) with elevated levels of sulfur. Currently, modern diesel engines typically use cooled Exhaust Gas Recirculation (EGR) to meet emissions regulations. Using high sulfur fuels and cooled EGR has potential to lead to EGR cooler fouling and corrosion of engine components. Therefore, an experimental study has been setup to investigate the EGR heat exchanger condensate in a heavy duty diesel engine running on JP-8 fuel doped with 3512 ppm of sulfur. Gas was sampled from the EGR cooler and analyzed. A Condensate Collection Device (CCD) was developed and setup according to a modified ASTM 3226-73T standard, to perform analysis of sulfur condensate species of SO₂ and H₂SO₄ in the EGR system. Results have shown that SO₂ values to have the highest concentration of gaseous sulfur species. SO₂ is also shown to increase as sulfur content in JP-8 increases, but not by the same order of magnitude. Results have also shown low levels of H₂SO₄ from 2–5 ppm with negligible differences while varying sulfur content in JP-8, EGR levels of the engine, and condenser temperatures in the CCD. Due to suspicion that all sulfur has not been accounted for in experiments with the modified CCD, further experiments were performed using a Fourier Transform Infrared (FTIR) emissions bench for gaseous SO₂ emissions and a Differential Mobility Spectrometer (DMS) for particulate size spectrum analysis. FTIR results yielded similar results for gaseous SO₂ as the modified CCD with SO₂ levels increasing as sulfur content in fuel increases but not by the same order of magnitude. While the results from the DMS have shown that increasing sulfur content in JP-8 will increase the particle sizes in the particle size distribution curve. This also translates to an increase in PM mass concentration in the exhaust stream when sulfur content is increased in JP-8 on an engine with and without EGR.