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Talks and Poster Presentations (with Proceedings-Entry):

T. Lauer, N. Pizzirani, S. Murakami:
"Numerical method to optimize the efficiency of a large gas engine";
Talk: International MTZ Conference, Kiel (invited); 11-15-2011 - 11-16-2011; in: "Heavy-Duty, On- and Off-Highway Engines 6th International MTZ Conference", Springer Fachmedien Wiesbaden GmbH, (2011), 14 pages.



English abstract:
Restrictive future emission legislations and the increased cost of primary energy carriers force the engine manufacturers to introduce new strategies to increase the engine efficiency and to reduce the exhaust gas emissions. Especially the market of large gas engines requires regular reductions of the operating costs.
It is generally acknowledged that high efficiency can be achieved with early ignition timing and a fast combustion process. Additionally, due to the high octane number of the natural gas, high fuel economy can be reached with high compression ratios. Nevertheless, the resulting high cylinder temperatures are critical in terms of NO-emissions and irregular combustion (knock).
The target of highest efficiency within the NO-emission and knock limits can be reached through the optimization of the combustion process. This can be achieved with numerical methods. Many alternative engine designs and operating conditions can be quickly analysed reducing the test bed investigations.
The one-dimensional simulation is a powerful tool to support combustion development. Combined with the design of experiments (DoE) approach, the engine efficiency, the NO-emissions and the relation of the knock probability to the operating conditions can be quickly and accurately investigated.
A research project was carried out for a large 4-stroke gas engine operated with natural gas. Designed for stationary duty conditions, it runs at 1500 RPM and it is charged with a very lean air-fuel mixture.
Target of the project was the definition of the optimum engine operating point in terms of highest efficiency and with respect to the TA-Luft nitric oxide emission limits. Additionally, the knocking combustion has been taken into account for the optimization process as an important boundary condition.
From previous investigations it could be shown that a fast combustion and late ignition are favourable for high efficiency and low emissions assuming a constant in-cylinder-charge composition. With the present study the investigations are extended to a wide range of charge pressures, equivalence ratios and residual gas concentrations.
Therefore, numerical investigations have been carried out with the goal to find an optimum combination of ignition timing and cylinder charge composition that meets the targets for the efficiency, the NO-formation and the knock in the best way. Hence, a thermodynamic model of the engine has been created with BOOSTŪ commercial software and a design of experiment approach has been carried out in order to understand the influence of the charge composition on the combustion process. Moreover, several predictive knock models are investigated.

Created from the Publication Database of the Vienna University of Technology.