Condensing LPL EGR Mixer with Mid-Pressure Loop 2015-01-1257

Cooled LPL EGR is a proven means of improving the efficiency of a Gasoline Turbocharged Direct-Injection engine. One of the most significant hurdles to overcome in implementing a LPL EGR system is dealing with condensation of water near the entrance of the turbocharger's compressor wheel. A gasoline engine, and to a greater extent a spark ignition engine running on Natural Gas, will encounter enough water condensation at some steady-state conditions to damage the compressor wheel due to the high-speed collision between the compressor blades and the water droplets. As an alternative to not utilizing beneficial EGR at the condensing conditions, the team at BorgWarner have developed a LPL EGR mixer that is effective at condensing and collecting the water droplets and routing the water around the compressor wheel.

The new Condensing EGR mixer was developed from the known concept of utilizing a mild venturi section to enhance EGR delivery and mixing. The developed system was designed to both maximize condensation and separation of liquid water from the EGR stream, as well as manage its disposal through the engine in a manner that both avoids damage to the compressor and minimizes liquid freezing potential in very low ambient conditions. The system architecture includes a Mid-Pressure path that is utilized to both purge the system of liquid water as, well as provide engine efficiency improvements at moderate load operation points compared to utilizing pure LPL EGR.

In this paper we present the system design concept and engine test results of the prototype mixer.