8The mitigation of climate change implies the increasing use of variable renewable energy sources. Energy 9 storage and transport solutions will contribute to ensure the stability, reliability and flexibility of the energy 10 systems in that context. Ammonia is a well-known chemical of formula NH3 and, amongst other electrofuels, 11 a promising energy carrier and carbon-free combustible fuel. In the present experimental study, engine per-12 formance, combustion characteristics and pollutant emissions of a recent spark ignition engine fueled with 13 premixed ammonia/hydrogen/air mixtures were assessed. Gaseous ammonia blends in a wide range of hydro-14 gen fuel fractions and equivalence ratios were tested at two different engine loads. Results show performances 15 comparable with conventional fuel operation when the appropriate promotion strategies are used. Specifically, 16 blending up to 20% hydrogen in the fuel by volume improves the cyclic stability and avoids misfires, while 17 granting the best work output and indicated efficiencies near stoichiometry. Higher hydrogen fractions result 18 in depleted efficiency, attributed to higher wall heat losses. The combustion duration is directly correlated to 19 the LBV of the mixtures, thus being accelerated by hydrogen blending. The accelerating effect of hydrogen is 20 particularly remarkable during the initial stage of the combustion. Hydrogen appears therefore mainly as an 21 ignition promoter. Increasing the engine load improves the furnished work and allows to extend the operating 22 boundaries in terms of mixture composition. 23 48 risk of engine knock thanks to the high octane number of ammonia. This was demonstrated in early studies, 49where single-cylinder and multi-cylinder SI engine were successfully run on pure ammonia fuel [17][18][19].
50However, gasoline-like performances were only achieved by using one or several promoting strategies, in-51 cluding an improved ignition system, increasing the engine load or CR and H2 doping of the NH3 fuel. A 52 minimum H2 amount depending on the engine speed and CR of some percent by mass was necessary to ensure 53 satisfying performance and decrease NH3 emissions but at the cost of increased NOx emissions.
54Contemporary studies also investigated ammonia/gasoline fueling of SI engine, either to reduce carbon-based 55 emissions of gasoline engines, or to promote the combustion with ammonia as a main fuel. Granell et al.
56proposed a 70% NH3 / 30% gasoline blend by energy as a good trade-off at full load in a Collaborative Fuel 57 Research (CFR) engine [21,22]. The authors suggested supercharging the engine instead of increasing the CR, 58 due to the detrimental thermodynamic consequences of the early spark advance required by the NH3 fuel.
59Engine-out NH3 emissions proportional to the NH3 input are reported, up to 22000 ppmvw for stoichiometric 60 NH3/air at CR=10:1. Ryu et al. investigated direct gaseous NH3 injection in a CFR engine (CR = 10:1) with 61 gasoline as the base fuel, and reported acceptable performance ...
Résumé -Évaluation de mélange butanol-essence dans un moteur à allumage commandé à injection indirecte -Cet article évalue le potentiel de l'utilisation de différents mélanges butanolessence dans un moteur à allumage commandé à injection indirecte afin de quantifier l'influence de l'ajout de butanol sur les émissions des hydrocarbures imbrûlés (HC), le monoxyde de carbone (CO) et les oxydes d'azote (NOx). De plus, l'influence sur la stabilité de combustion, le délai d'inflammation et sur la durée de la phase de combustion turbulente développée y sont également présentés. Les principaux résultats : 1) un mélange de 40 % butanol et 60 % essence (B40) par volume diminue les émissions de HC ; 2) aucun effet significatif sur les émissions de NOx n'a été observé à l'exception du mélange 80% butanol/20 % essence ; 3) l'ajout de butanol améliore la stabilité de combustion ; 4) l'ajout de butanol réduit le délai d'inflammation, quantifié par la durée pour consommer 10% de masse de gaz frais; et 5) la consommation spécifique de carburant pour un mélange stoechiométrique de B40 est 10% supérieure à celle de l'essence. [0][1][2][3][4][5][6][7][8][9][10]
Abstract -Evaluation of Butanol-Gasoline Blends in a Port Fuel-Injection, Spark-Ignition Engine -This paper assesses different butanol-gasoline blends used in a port fuel-injection, spark-ignition engine to quantify the influence of butanol addition on the emission of unburned hydrocarbons, carbon monoxide, and nitrogen oxide. Furthermore, in-cylinder pressure was measured to quantify combustion stability and to compare the ignition delay and fully developed turbulent combustion phases as given by
International audienceThe impact of dilution on laminar burning speed of two different fuels (methane and isooctane) is studied. In the present study, three different diluents are used--nitrogen, carbon dioxide, and a mixture representative of exhaust gases issued from a stoichiometric combustion of methane. Experimental results and PREMIX computations of the CHEMKIN package, using two different kinetic schemes, are presented and compared with literature results, when available. Initial pressure and temperature conditions are respectively 0.1 MPa and 300 K. For both fuels, a larger decrease of the laminar burning speed is obtained for carbon dioxide dilution than for nitrogen dilution. This observation is directly linked to the increase in heat capacity of the dilution gas but also to the carbon dioxide dissociation, even if the heat capacity effect seems to be predominant
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