In the future large four-stroke diesel engines will increasingly utilise two-stage exhaust gas turbochargers. The high mean effective pressures result in exceptionally compact and economic efficient engines. At the Institute of Energy Systems it has been shown that the operation of such high-powered engines with cylinder pressures up to ca. 400 bar makes thermodynamically sense and is principally feasible.

These large diesel engines of the next but one generation must be operated in the ECA zones with substantially reduced nitrogen oxide emissions. The fulfillment of the NOx limits of IMO Tier III is possible by post-processing the exhaust gas with a SCR catalyst. The motor industry seeks, however, other solutions, trying to avoid large and expensive catalysts.

Aim of this research project is solely by Miller-valve timing, emission-optimised injection strategies and especially exhaust gas recirculation meet also the NOx limits of IMO Tier III in a large research diesel engine with extremely high median operating pressures.

The approach adopted here is:

•  Testing of the exhaust gas recirculation unit with a screw compressor (9 bar)
• Optimisation of the operating parameters and the engine variables through modelling in GT-Power
• Reference measurements 
• Tests with exhaust gas recirculation: variation of, among others, the EGR Rate, the valve timing, the compression ratio and the injection strategies
• Analysis of the results and summary of the findings for high-pressure large diesel engines