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C16.0066: Optimal fuel blends for natural gas engines

English title C16.0066: Optimal fuel blends for natural gas engines
Applicant Frouzakis Christos
Number 174833
Funding scheme COST (European Cooperation in Science and Technology)
Research institution Institut für Energietechnik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Mechanical Engineering
Start/End 01.01.2017 - 30.06.2019
Approved amount 116'088.00
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Keywords (5)

CM1404; natural gas combustion; greenhouse gas emissions reduction; spark ignited gas engine; methane slip

Lay Summary (German)

Lead
Erdgas gilt als einer der vielversprechendsten alternativen Kraftsoffen. Fossil Erdgas besteht hauptsächlich aus Methan, das dank des hohen Wasserstoff-Kohlenstoff-Verhältnisses (H/C) bei der Verbrennung ca. 25% weniger CO2 pro thermischer Energieeinheit als Ölprodukte aus höheren Kohlenwasserstoffen produziert. Weitere Vorteile für die Umwelt können durch die Verwendung von erneuerbarem Erdgas (Bio-Erdgas) realisiert werden.
Lay summary

Inhalt und Ziel des Forschungsprojekt

Erdgasmotoren geniessen steigende Marktanteile in der dezentralenStrom-Wärme-Kopplung, in Schiffsantrieben und potenziell auch inStrassenfahrzeugen. Die Herausforderungen für fortgeschrittenefremdgezündeten, vorgemsichten Gasmotoren werden mitwidersprüchlichen Leistungszielen konfrontiert, nämlich dem Abwägenzwischen einer stabilen Verbrennung unter extrem mageren Bedingungenmit minimalen Stickoxid-Emissionen einerseits und hohenthermodynamischen Wirkungsgrad und Unterdrückung der end-GasSelbsentzündung andererseits.
Das Ziel des Projektes ist es,eine numerische Methode zu entwickeln,welche dieSelektion von gasförmiger Additivenzu Methan eruiert,um die Zusammesetzung zu berechnen, die die widersprüchlichenAnforderungen am besten erfüllt.

Wissenschaftlicher und gesellschaftlicher Kontext desForschungsprojekts

Kohlendioxid, das wichtigste Treibhausgas in den Abgasen, kanndurch eine Verbesserung der Motoreneffizienz und durch das Verbrennenvom Brennstoffes mit einem H/C Verhältnis reduziert werden. Diekomplexen Wechselwirkung der Reaktionskinetik des Kraftstoffes undder Strömung kann zu einem gewissen Grade von den Konstruktions- undBetriebsparametern der Verbrennungskammer geformt werden. Die Kinetikkann durch Mischen von Erdgas mit anderen Komponenten modifiziertwerden. Die Entwicklung von numerischen Verfahren, um den aktuellenAnsatz von Trial-and-Error-Verfahren für die Auswahl von Additivenzu ersetzen, soll beschleunigt werden.

Direct link to Lay Summary Last update: 17.06.2017

Responsible applicant and co-applicants

Employees

Publications

Publication
Numerical optimization of methane-based fuel blends under engine-relevant conditions using a multi-objective genetic algorithm
Paykani Amin, Frouzakis Christos E., Boulouchos Konstantinos (2019), Numerical optimization of methane-based fuel blends under engine-relevant conditions using a multi-objective genetic algorithm, in Applied Energy, 242, 1712-1724.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
1st International Conference on Smart Energy Carriers Poster Optimization of Methane-Hydrogen Blends in a Spark-ignition Engine Using a Quasi-dimensional Combustion Model and Genetic Algorithm 21.01.2019 Napoli, Italy Paykani Amin; Frouzakis Christos;
3rd general Meeting and Workshop on SEC in Industry of the SMARTCATs COST Action Talk given at a conference Optimization of Composition of Methane/syngas Mixtures at Engine-relevant conditions: A NSGA-II Coupled TOPSIS Approach 25.10.2017 J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Prage, Czech Republic Paykani Amin; Frouzakis Christos;


Abstract

Concerns about greenhouse gases (GHG), air pollutants, and shortage of petroleum-based fuels have led to the development of new combustion technologies and the search for alternative fuels. Carbon dioxide, the main greenhouse gas in the exhaust gases, can be reduced by improving the engine efficiency, using a fuel with high hydrogen to carbon (H/C) ratio, and using renewable fuels.Natural gas (NG) is regarded as one of the most promising alternative fuels. Fossil NG consists of 90-95% methane, which, thanks to its high H/C ratio produces about 25% less CO 2 per thermal energy unit than oil products consisting of higher hydrocarbons. Additional environmental advantages can result from renewable natural gas (RNG) or biomethane produced by anaerobic biological decomposition of organic matter including manure, wastewater, sludge, municipal solid waste (including landfills) or any other biodegradable feedstock. The entire process of collecting, purifying and using methane gas emissions from landfill and biomass decomposition is fairly straightforward, especially when compared with the Fischer-Tropsch process used in gas-to-liquid and biomass-to-liquid processes, and yields far lower GHG emissions during the production process (see, for example, the waste-to-wheel analysis in [2]). Other options for fuels are offered by synthetic gaseous components like hydrogen from electrolysis using renewable electricity, syngas from solar thermo-chemical processes, or wood pyrolysis. Natural gas engines enjoy increasing market share in decentralized power/heat co-generation, in marine propulsion and potentially in road vehicles. NG has a H/C ratio close to 4 compared to about 1.8 for Diesel and gasoline, and relatively wide flammability limits. Due to the low autoignition propensity of its main component at low to medium temperatures, natural gas is widely used in externally-ignited, premixed-mode combustion engines (Otto cycle). Current research efforts also aim at developing non-premixed systems (Diesel cycle) with auxiliary ignition (using, for example, a small quantity of diesel fuel). The challenges for advanced Otto-gas-engines are associated with conflicting performance goals, namely the trade-off between stable combustion under ultra lean conditions and minimal nitrogen oxide (NOx) emissions on one hand, and high mean effective pressure (and therefore high thermodynamic efficiency) and knock suppression (end-gas autoignition) on the other. The NO x -combustion stability trade-off under lean operation is due to the rapidly decreasing adiabatic flame temperatures (favorable for minimal NOx), which however also suppresses flame propagation (lower flame propagation speed), thus enhancing the cycle-to-cycle combustion variability in the engine mainly due to the stochastic interaction between early flame growth and local turbulent flow field. The knock limit/lean-burn limit trade-off on the other hand leads to a narrower equivalence ratio operating window with increasing mean effective pressure (and therefore power density and thermodynamic efficiency) since the laminar flame speed of methane decreases strongly with pressure while at the same time autoignition times also decrease with increasing pressure.An emerging concern for natural gas engines is the “methane slip”, the relatively high engine-out methane emissions. While CH 4 is locally not an environmental pollutant, it is a highly-relevant GHG with a global warming potential (GWP) about 25 times larger than CO2 (per unit mass). Methane emission levels of state-of-the-art gas engines in lean operation corresponds in GWP terms to about 11-20% of the engine-out CO 2 emissions. In addition to performance and emissions issues, the exhaust gas temperature for highly efficient lean-burn engines is not sufficiently high for significant conversion rates in oxidation catalysts. Engine efficiency at lean-burn operation increases and pollutant emissions decrease as the equivalence ratio decreases. However, at some point the “lean limit” is reached where the burning rate becomes too slow for complete combustion. Even before the limit is reached, there is a small range of equivalence ratio for which intermittent misfiring results in increased cyclic variability and higher exhaust emission levels. The aim of the proposed work is to examine in a systematic way to what extent the conflicting requirements can be met by adding gaseous species to methane so that engines can be operated stably and reliably at the lean limit with minimal methane slip and pollutant emissions.
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