BRAKE THERMAL EFFICIENCY IMPROVEMENTS OF A COMMERCIALLY BASED DIESEL ENGINE MODIFIED FOR OPERATION ON JP 8 FUEL

The majority of commercial off the shelf (COTS) diesel engines rely on EGR to meet increasingly stringent emissions standards, but these EGR systems would be susceptible to corrosion and damage if JP-8 were used as a fuel due to its high sulfur content. Starting with a Cummins 2007 ISL 8.9L production engine, this program demonstrates the modifications necessary to remove EGR and operate on JP-8 fuel with a goal of demonstrating 48% brake thermal efficiency (BTE) at an emissions level consistent with 1998 EPA standards. The effects of injector cup flow, improved turbo match, increased compression ratio with revised piston bowl geometry, increased cylinder pressure, revised intake manifold for improved breathing, and piston, ring and liner designs to reduce friction are all investigated. Testing focused on a single operating point, full load at 1600 RPM. This engine uses a variable geometry turbo and high pressure common rail fuel system, allowing control over air fuel ratio, rail pressure, and start of injection. These parameters were optimized for several component combinations to provide an estimate of the best engine efficiency that could be achieved for various levels of engine modification. While the program goal is to have emissions consistent with 1998 EPA standards, testing was also conducted at higher emissions levels to determine the additional gain in BTE that could be possible if emissions were not a constraint.