Nox Control in Heavy-Duty Diesel Engines - What is the Limit?

Methods to reduce direct injected diesel engine emissions in the combustion chamber will be discussed in this paper. The following NO_x emission reduction technologies will be reviewed: charge air chilling, water injection, and exhaust gas recirculation (EGR). Emphasis will be placed on the development of an EGR system and the effect of EGR on NO_x and particulates.

The lower limit of NO_x that can be obtained using conventional diesel engine combustion will be discussed. Further reductions in NO_x may require changing the combustion process from a diffusion flame to a homogeneous charge combustion system.