Investigation of a Second Exhaust Valve Lift to Improve Combustion in a Methane - Diesel Dual-Fuel Engine

  • In recent years, the utilization of dual-fuel combustion has gained popularity in order to improve engine efficiency and emissions. With its high knock resistance, methane allows operation in high compression diesel engines with lower risk of knocking. With the use of diesel fuel as an ignition source, it is possible to exploit the advantages of lean combustion without facing problems to provide the high amount of ignition energy necessary to burn methane under such operating conditions. Another advantage is the variety of sources from which the primary fuel can be obtained. In addition to fossil sources, methane can also be produced from biomass or electrical energy. As the rate of substitution of diesel by methane increases, the trade- off between nitrogen oxide and soot is mitigated. However, emissions of carbon monoxide and unburned methane increase. Since carbon monoxide is toxic and methane has 25 times the global warming potential of carbon dioxide, these emission components pose a problem. Because of the stability of the molecule, methane catalysts require an exhaust gas temperature of over 500 °C in order to work effectively. In this work, the effect of conventional cooled external exhaust gas recirculation (EGR) and additional hot internal EGR are investigated for different substitution rates in a nonroad tractor engine converted to dual-fuel operation. The internal EGR rate is controlled by a variable second exhaust valve lift during the intake stroke – an approach which promises to benefit dual-fuel engines by increasing the in-cylinder gas temperature, thus favoring more complete combustion. A simulation model of the engine is used to determine the internal EGR rates and in-cylinder temperatures based on the experimental data. When internal EGR is used in combination with external EGR, the resulting emissions show additional reductions in nitrogen oxide (up to -51 %), carbon monoxide (up to -18 %) and methane (up to -28 %) with increasing internal EGR, while still maintaining low soot levels due to the substitution of diesel fuel for methane.
Author:Florian Müller, Michael Günthner, Alexander Weigel, Matthias Thees
Parent Title (English):WCX SAE World Congress Experience 2022
Publisher:SAE International
Document Type:Article
Language of publication:English
Date of Publication (online):2022/03/29
Year of first Publication:2022
Publishing Institution:Technische Universität Kaiserslautern
Date of the Publication (Server):2022/10/19
Issue:WCX SAE World Congress Experience 2022
Faculties / Organisational entities:Kaiserslautern - Fachbereich Maschinenbau und Verfahrenstechnik
DDC-Cassification:6 Technik, Medizin, angewandte Wissenschaften / 620 Ingenieurwissenschaften und Maschinenbau
Licence (German):Zweitveröffentlichung