And Butanol-Gasoline Fuel Blends, and Their Impact on Performance, Emissions and Soot Index P Anselmi, M Matrat, L Starck, F Duffour
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Combustion characteristics of oxygenated fuels Ethanol -and Butanol-gasoline fuel blends, and their impact on performance, emissions and Soot Index P Anselmi, M Matrat, L Starck, F Duffour To cite this version: P Anselmi, M Matrat, L Starck, F Duffour. Combustion characteristics of oxygenated fuels Ethanol -and Butanol-gasoline fuel blends, and their impact on performance, emissions and Soot Index. JSAE/SAE 2019 Powertrains, Fuels and Lubricants International meeting, Aug 2019, Kyoto, Japan. pp.SAE 2019-01-2307, 10.4271/2019-01-2307. hal-02890598 HAL Id: hal-02890598 https://hal-ifp.archives-ouvertes.fr/hal-02890598 Submitted on 6 Jul 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Combustion characteristics of oxygenated fuels Ethanol -and Butanol- gasoline fuel blends, and their impact on performance, emissions and Soot Index P. Anselmi, M. Matrat, L. Starck, F. Duffour IFP Energies nouvelles Copyright © 2019 SAE Japan and Copyright © 2019 SAE International ABSTRACT consequently their engine combustion behaviour may differ, as has been highlighted by Regalbuto et al. [5]. Oxygenated fuels are studied in spark combustion For example, the viscosity of iso-butanol almost engines because of their potentially positive impact on doubles compared to n-butanol, and this property can greenhouse emissions, and as part of alternative contribute to affect the spray formation and the wall renewable fuels. Furthermore, engine test results wetting within the combustion chamber. Three key position them as a promising lever to reduce combustion properties must be considered. Firstly, the engine-out emissions, and most notably, particles. laminar flame speed, mostly related to the high This study focuses on oxygenated fuel Butanol, which temperature fuel reactivity, is essential for the flame is a potential output of recent developments on Algae kernel development. The second parameter is related and Cyanobacteria harvest process. Its blending into to the auto-ignition delay, as it is a first order factor on gasoline and application into spark ignition engines is knocking behaviour in gasoline engines. Finally, the investigated. Blending levels of n-Butanol and intermediate combustion products are of interest to iso-Butanol have been proposed based on standard apprehend the fuel effect on exhaust emissions. gasoline’s octane number, RON, at two ethanol Sarathy et al. [6] reported the butanol isomers effects concentration levels, 10 and 25%. Fuel blend impact on these key combustion parameters based on an on combustion, and on regulated and non-regulated exhaustive review. A slight laminar flame speed emissions is analysed. Fuel knock resistance increase is reported for n-butanol, compared to the properties, RON and MON, determine the knocking branched isomers, all of whom have similar flame tendencies for ethanol and butanol at 2000 rpm. speed. The auto-ignition properties of the isomers are However, test results highlight different knocking also quite different as highlighted by their respective sensibility behaviour at higher engine speed. octane numbers. The most reactive isomer under Emission results also illustrate a strong advantage of engine relevant conditions is n-butanol, due to an Butanol on particle mass emissions. Soot indices, that important contribution of the peroxy chemistry, are conventionally used to quantify the impact of a fuel favoured by the linear alkyl chain. The speciation at over particle emissions, are studied and confronted to high temperature of these four isomers is related to results obtained on ethanol blends. The deviation in complex reaction pathways, as emphasized by Particle Matter Indices obtained for butanol blends is Sarathy et al. [6]. It underlines a strong contribution of analysed, on the basis of specific operating points. It light oxygenated species, such as formaldehyde, but highlights different particle emissions responses to the also C2 to C4 intermediates including -but not limited increase of oxygenates ethanol and butanol, not to- several aldehydes: acetaldehyde, propanal, uniquely correlated to oxygen and aromatic acetone or butanal and alcohols: ethanol, concentration. iso-propenol or 2-propenol. These data are mostly related to academic experimental measurements and INTRODUCTION provide some insight on the combustion effects of these isomers. Butanol fuels have become of increasing interest as alternative fuels when blended into gasoline. Several Considering butanol potential particle reduction, and studies identify butanol as a product of algae and its high knocking resistance for branched isomers, several studies have proposed butanol isomer microalgae [1, 2], food waste [3] and gas waste (CO2, blending to improve gasoline engine performance CO, H2) [4], and hence their production processes have a potential to reduce dependence on petroleum [7–9]. Of the four isomers, n-butanol is the most fuels, recycle carbon dioxide, and reduced reported, where studies have been carried out with greenhouse effects. concentration ranging from 3 to 100%, for indirect port-fuel injection systems (PI), and up to 30 % with Butanol is present in four different isomers: n-butanol, direct injection (DI). Other isomers investigated are iso-butanol, tert-butanol and s-butanol. Their physical iso-butanol, tert-butanol, and in less proportion, and chemical properties vary quite significantly, and s-butanol. It has been demonstrated that the use of ethanol or additions will potentially affect the first two. The key iso-butanol enables to decrease soot emissions, parameters that must be considered in these cases attributed mainly to the increased oxygen content in are the temperature, the oxygen availability, and the the fuel [10]. Butanol is considered as a potential reaction intermediates arising from fuel substitute to ethanol, as oxygenated blending decomposition. An increase of nitrogen oxides component. Moreover, some results found in literature emissions could be expected considering the higher highlight the higher particle reduction of n-butanol as O/C ratio. Indeed, it provides oxygen locally which compare to ethanol, even if a lower O/C ratio is could contribute to enhance the NOx formation. obtained for the n-butanol/gasoline mixture, However, literature [11, 17] describes a decrease in suggesting that other parameters are of interest [11]. nitrogen oxides, a tendency which indicates that other However, some results have indicated an increase in parameters are of interest. Some publications have particle numbers under certain levels of oxygenated demonstrated that the combustion duration can concentration, or engine configurations [12, 13]. Tests decrease for n-butanol/gasoline blends. This have indicated that particle size distribution is also contributes to the decrease of the exhaust affected. For example, Costagliola [14] has compared temperature and extends the post-oxidation time [17]. ultra-fine (< 10nm) particle emissions of ethanol and Other NOx formation routes, such as the prompt NO, butanol gasoline blends. Under low load operation, remains to be investigated to better characterize ethanol offers the strongest particle reduction, but at butanol effect. higher loads butanol shows an advantage on these emissions. Recent work on particle matter indices, to The use of oxygenated fuels also affects unregulated predict a fuel’s behaviour over particle emissions, has emissions [17, 18]. Indeed, the literature indicates the been only recently extended to oxygenated fuels increase in oxygenated emissions when alcohols are [15–17] but remains to be improved on the specific incorporated into gasoline. Storey et al. [18] measured effects of each oxygenated compound. the emissions of aldehydes when iso-butanol (48%vol) and ethanol (30%vol) are blended to Oxygenated fuels can also impact carbon monoxide gasoline, and identifies butyraldehyde (C4H9O) as the (CO), unburned hydrocarbons (UHC) and nitrogen main contributor of oxygenated C4. This tendencies oxide (NOx) emissions. Results presented by have been confirmed by Karavalakis et al. [10] with Karavalakis et al. [13], on different vehicles, driving ethanol blends (up to 30%vol) and iso-butanol blends cycles with ethanol and butanol blends; show a (up to 34%vol). Both studies are carried-out on vehicle reduction of UHC for spray guided engines, for all driving cycles. blends. Generally, the reduction becomes stronger as the oxygenate concentration increases. Due to high These works suggest that butanol behaviour is O/C ratios, oxygenated fuels can contribute to limit strongly dependent on the engine technology, e.g. UHC emissions. Moreover, results obtained by injection system and compression ratio, as well as Lattimore et al. [11] on a DI spray guided (SG) engine, butanol blending and isomer. A study on a state of the showed that the decrease obtained with ethanol is art engine, under enhanced aerodynamics and direct stronger than butanol (at same concentration), despite injection seems necessary to clarify behaviour of the fact that ethanol presents