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This CASE website gives a clearer understanding of what the main engine emission problems are, and how the manufacturers are using technology to reach the new standards.
The website provides a clear layout that describes all the issue surrounding the engine emission targets. This includes a description of why engine emissions are being focused on, with brief sections on climate change, emissions and air quality, and emissions and health. Off-road engines are responsible for 47% of particulate matter (PM) and 25% of nitrogen oxides (NOx). PM is produced because small carbon particles and other substances are produced because not all the fuel is burned during combustion. NOx are produced during combustion when the engine runs at its hottest. Reductions in PM and NOx will reduce the amount of greenhouse gases emitted and reduce health related problems such as asthma.
Tier 4 engine requirements target a 90% reduction in emissions compared to Tier 3! The website then describes the two solutions being used by most manufacturers to reach the emission targets, which are as follows:
- Selective catalytic reduction (SCR) – because an engine is tuned for maximum efficiency, PM is reduced, but the high temperatures that result increase NOx. SCR works by treating the exhaust gases with a diesel exhaust fluid that creates a chemical reaction. This transforms the NOx into nitrogen and water.
- Cooled exhaust gas recirculation (CEGR) – exhaust gases are cooled, mixed with fresh air and returned to the combustion chamber. This reduces temperatures and therefore NOx. PM is then reduced through an exhaust filter system.
The CASE website provides much more interesting information through a downloadable brochure. This gives excellent diagrams that show how the above works, and graphs that show the emission reduction targets. The advantages of both methods are described. Source: www.t4cleanpower-case.com