In-cylinder emission reduction in large diesel engines (NOx-Reduction)

Scope of project

As primary outcome of this collaborative effort the project team expects a significant technological progress towards an efficient, clean burning diesel engine that does not require exhaust gas after treatment to further reduce NOx or particulate emissions. One goal is set in the thorough comprehension of the physiochemical processes involved governing the NOx and soot formation under the combined application of Miller inlet valve timing with 2-stage turbo charging and EGR, water-in-fuel emulsions and pilot injections. This understanding will yield a second key deliverable, namely a fast numerical algorithm based on phenomenological models incorporating the new technological approach and having good predictions for NOx and soot.

The Large Engine Research Facility (LERF) at Paul Scherrer Institute (PSI) has been successfully established as a research platform for testing the NOx reduction potential when using Miller valve timing in combination with serial 2-stage turbo charging (MT/S2TC). In past research, a significant NOx reduction potential using this technology has been confirmed. It also became clear, however, that the stringent legislative limits set to enact in 2016 by the International Maritime Organization (IMO) cannot be reached using this technology alone and that additional measures are needed. The current project aims at combining additional measures with the already implemented approach to further reduce specific NOx emissions towards the required limit, while maintaining low CO2 emissions and close-to-zero soot emissions. The team has conceived three different technological advancements to be tested individually and combined in conjunction with Miller timing and 2-stage turbo charging. The main technological building block will focus on the arrangement of exhaust gas recirculation (EGR) together with MT/S2TC. This combination has the largest potential for meeting the NOx emission limits, but it is also expected to generate significantly increased particulate emissions. The second technological building block involves using water-in-fuel emulsions (WFE), which has positive effects on both NOx and particulate emissions. The third building block uses multiple fuel injections as means to shorten the ignition delay and thus reduce the amount of premixed combustion, a need for which has been highlighted in prior research concerning extreme Miller valve timing to allow further reduction of NOx emissions. Due to the generic nature of the problem, industry-relevant results from the LERF must be anchored on a fundamental understanding of the underlying mechanisms. To achieve this, the individual technological building blocks will be studied experimentally in different setups as well as computationally. Besides the 6- cylinder engine at PSI we will investigate the new technologies on a 1-cylinder MTU engine at ETHZ and at the newly refurbished constant volume combustion cell (HTDZ) at PSI. Using the three platforms the team is able to cover the complex system behavior and address system integration issues on the 6-cylinder engine, study processes in a more controlled environment on the 1-cylinder engine, and obtain fundamental understanding of the modified combustion through optical access to the flame at the HTDZ. In parallel, 3D simulation work based mainly on results from the HTDZ will allow the in-depth investigation of spray and combustion characteristics. All experimental and simulation results will be used to create an industry-relevant, fast phenomenological model for NOx and particulate formation/oxidation which in turn will aid the optimization towards an efficient, clean burning and low emission diesel engine for the future.

In the project, two worldwide leading companies (ABB Turbo Systems, Wärtsilä FI) and an ambitious Swiss SME (DUAP) will participate with additional funding and significant resources and are expected to substantially profit from the planned developments. If successful, this research effort will allow for the first time to perform fast, predictive modeling of efficiency and emissions of large diesel engines when using a variety of promising future technologies.


Dr. Klaus Hoyer, PSI
Telephone: +41 56 310 4093