ZURUECK HOCH VOR INHALT SUCHEN

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Proposing Institution

Lehrstuhl für Thermodynamik,TUM
Project Manager

Michael Jud
Boltzmannstr. 15
85748 Garching
Abstract
Emission standards for marine diesel engines have been tightened up in the past few years, and will become even more restrictive in the future. A promising concept for meeting emission limits is to use pilot ignited lean-burn natural gas engines. Apart from the reduced CO2 emissions, the low C/H-ratio of natural gas leads to lower flame temperatures and thus lower NOX emissions. Nevertheless homogeneous charge combustion with lean natural gas mixtures suffers from considerable methane slip and restricts high compression ratios due to the knocking limit.Direct injection of main fuel and pilot fuel allows more flexible control of the combustion process regarding the mixture formation and fuel burnout, thus fuel slip can be reduced and the compression ratio increased – leading to higher efficiency. Furthermore, this concept is ideally suited for various combinations of gaseous and liquid fuels. This is of great importance when considering the fact that future fuel mixes will become more diverse and will include more biofuels. Up till now there has been little research done on injection, mixing, ignition and fuel burnout of this concept. In the course of this project dual fuel direct injection combustion for flexible fuels will be experimentally and numerically investigated.The 3D-CFD simulation of diesel injection including spray break-up, ignition and combustion is investigated using existing models. Modeling direct injection of natural gas, however, is very challenging due to high pressure ratios. This leads to high gas velocities and under-expanded nozzle flow. Ignition delay times differ a lot from those of pure diesel combustion depending on the injection strategy. An extension for dual fuel combustion will be developed on the basis of existing ignition and combustion models for diesel engines.

Impressum, Conny Wendler