Assuming you are given an engine with the ability to control the EGR rate and start of injection (SOI). The engine produces 1000 parts per million (ppm) of NOx. The engine development process has set a target of 500 ppm NOx to be produced from the engine.
a) What changes would you do to the EGR rate to reduce NOx?
b) What would be your limitation in using this strategy?
c) If your engineering team decides to provide you with a selective catalytic reduction (SCR) aftertreatment system and promises you a 95% reduction in engine-out NOx, what changes will you make to EGR and SOI? What is the reasoning behind the change in strategy?
Provide a brief answer to part a, b and c of the question.