Particle Free Exhaust Gas Recirculation by Molecular Diffusion:
Proof of Concept 2003-01-0769
This work included design and fabrication of a particle free exhaust gas recirculation element (PF-EGR-E) that included two concentric tubes, one for a clean air stream and the other for a simulated exhaust stream. The inner tube was a perforated tube to allow molecular diffusion between the two streams. The design and dimension of the PF-EGR-E was guided with the help of theoretical prediction of gas and particle diffusion. The goal was to build a PF-EGR-E that retains particles in a dilute exhaust stream while allowing maximum molecular exchange with the air stream. The performance of the PF-EGR-E was investigated using dilute diesel engine exhaust and clean air flowing in parallel at different flow and temperature levels. Measurements of NOX, CO2, and particle concentration at inlet and exit of the perforated tube demonstrated that it was possible to achieve high molecular transfer between a dilute exhaust stream and clean air stream while particle transfer was still at minimum level.
This work proofed the concept of achieving particle free EGR with a single perforated tube using molecular and particle diffusion principles. The next step will be to demonstrate this concept in a prototype system to be used on a diesel engine.