1996-02-01

Improving NOx Versus BSFC with EUI 200 Using EGR and Pilot Injection for Heavy-Duty Diesel Engines 960843

An experimental study has been carried out on a single-cylinder pressure-charged engine with a near quiescent combustion system. An improvement in the NOx/BSFC trade-off was achieved by two different approaches, namely exhaust gas recirculation and pilot injection.
Without EGR, a reference EUI-200 system with 1900 bar peak injection pressure gave a low soot particulate level of 0.013 g/bhp h over a simulation of the US FTP cycle. The results with EGR show how higher levels of EGR can be used at more advanced injection timings to give substantially improved NOx versus BSFC results compared with timing retard alone. It was possible to reduce the NOx from 4.85 to 3.6 g/bhp h for no increase in BSFC over the simulated US FTP cycle and with a total calculated particulate of 0.075 g/bhph.
The results with electronically-controlled pilot injection show improvements in NOx versus BSFC, lower NOx before HC increase with retard, or reduced combustion noise at certain test modes. Simulated US FTP cycle results show that a pilot injection strategy could be used to reduce NOx from 4.94 to 3.82 g/bhp h for a 6.6% increase in BSFC compared with an increase of 10% in BSFC if timing retard alone is used.

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