Class 1 (Chief Engineer) Engineering Management 📅 Mar 2023

Exam Question

Exhaust emission control is a major global issue and under serious consideration by world shipping. In this context, comment on the following:

(a) Primary NOx reduction vis-a-vis secondary NOx reduction measures (8)

(b) Scavenge Air Moisturizing & Exhaust Gas Recirculation for main engine (8)

Reference Answer

### Introduction to NOx Formation and Control
Nitrogen Oxides (NOx), primarily NO and NO₂, are harmful pollutants formed during high-temperature combustion in a diesel engine's cylinder. The formation is governed by the Zeldovich mechanism, which is highly dependent on three key factors:
1. **High Peak Combustion Temperature**: Formation accelerates exponentially above 1800°C.
2. **Oxygen (O₂) Concentration**: Sufficient oxygen must be available to react with atmospheric nitrogen (N₂).

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