combustion performance of high water content hydrous ethanol

8/9/2019 Combustion Performance of High Water Content Hydrous Ethanol

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Speakers information- Virtual Powertrain Conferences

Combustion performance of high water content hydrous ethanol

Rafael Lago SariGabriel Ae!edo "atsch

#acklini $alla %ora#ario &duardo dos Santos #artins

"hompson $iordinis #etka Lanano!a

Federal University of Santa Maria


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ABSTRACTThe need to tackle global warming and to reduce greenhouse gaseous emissions calls for the ever growing research ofrenewable and alternative fuels. Novel processes and ways to use current fuels have been extensively addressed.iomass products like ethanol! renewable and well established as an excellent fuel for "# engines! would be of even moreimportance should its production costs get reduced. $ne of the ways to reduce the cost of ethanol made from cropfermentation would be to use it with a higher water percentage. #urrently! the normal composition of ethanol fuel has

around %&'( of water! due to the a)eotrope mixture reached during distillation. *owever! the production costs could bedramatically reduced if the energy consuming distillation process could be interrupted earlier! leaving a higher waterpercentage. *owever! this may impose combustion issues that may call for a different thinking regarding current enginesThis paper evaluates both via simulation and experiments the performance of an engine fueled with high&water contentethanol mixtures! varying from +&,-( of water. The engine used was a naturally aspirated -.%%&/ single&cylinder port&in0ected S" engine! with swirl&chamber spark&ignition. #ombustion related parameters were analy)ed through in&cylinderpressure data processed with 12/ oost3! providing several experimental and calculated results. 4esults show thatcombustion duration remains more or less constant despite of the water addition. *igher efficiency "M56 values werepossible with increased water content. "t was possible to reali)e that increased water content enhances knock avoidancecapabilities and makes wet ethanol even more promising for high efficiency engine concepts and with a lower fuel cost.

INTRODUCTIONFossil fuels currently used have a significant environmental impact concerning pollutant and greenhouse gas emissions.4esearch aiming at developing environmentally friendly engines with low carbon footprint has lead the automotiveindustry use alternative fuels! being ethanol originated from biomass one of the ma0or players.

"n ra)il! ethanol began to be used in internal combustion engines since 789-. "n the year of 78:7! when a decreere;uired the addition of +( ethanol in gasoline! it became even more usual. "n the78'-s the ra)ilian 1lcohol 6rogram7?. Nowadays! the country is now the largest user of ethanoas an automotive fuel. This occurs due to its great amount of solar radiation! large territory! an abundant water resource>9?. "t is estimated that in the future! with increased productivity of sugarcane per hectare and the higher efficiency ofethanol production process! the environmental impacts per unit of fuel produced will decrease even more > :?. #omparingwith gasoline! ethanol has a higher octane number! inflammability limits! laminar burning velocities and vapori)ation heatThese properties enable run with higher compression ratio! the combustion duration decreases and makes possible tooperate with lean mixtures! achieving higher efficiency over the gasoline in internal combustion engines. Some negativepoints in this comparison are the lower energy density! corrosion! lower vapor@s pressure! total miscibility with water andaldehydes emissions >,?

The obtaining process of ethanol consists in agricultural production! transportation! cooking and crushing! fermentationand distillation. 1t the end of the process! high amount of energy is necessary to obtain the biggest concentration ofethanol in function of energy dispended in distillation! which grows exponentially in a percentage higher than -( asshowed in figure 7. Thus! the use of ethanol with higher water percentages can be a good alternative in order to reduceproduction costs! and increase market competitiveness compared to fossil fuels.


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'igure ( dispended energy in distillation process relati!e to ethanol L)V

4esearches were made using a single cylinder engine :'+ centimeter cubic of volumetric displacement! carbureted!combustion chamber in / and compression ratio of '.+A7! utili)ing water and gasoline emulsions. The water in gasolinepercentage varied from -( to 7+( of volumetric content in regular operation. Bith the water increase! was possible tosave fuel! showing the better results for 7-( of water in the mixture. The water addition makes the combustiontemperature decrease! since water consumes part of the heat generated to evaporate! taking at a lower N$ xemissions#$ emissions decreased! but in other hand hydrocarbons emissions increased >+?.#hristensen! M.C Dohansson evaluatedthe water addition effects at the inlet manifold and combustion processes using a 2olvo six cylinders engine! 7.%/! withcompression ratio of 7A7. The study was carried deactivating five cylinders and 0ust one cylinder operated in *##"operation cycle. The engine ran with iso&octane! ethanol and natural gas! in order to control auto&ignition the inlet air washeated. The water utili)ation increased the limit of power generation without Enock occurrence by the reduction of the incylinder charge temperature. $n the other hand! there was an expressive increase in *# and #$ 9emissions due to thelower combustion efficiency with the water addition >%?.

Studies carried out by "daho University in partnership with 41"


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Mack et al. evaluated the wet ethanol utili)ation effects in a range from -( to %-( in volumetric content of water mixturesThe research ob0ect was an engine 2olkswagen 7.8/! , cylinders! with compression ratio of 7'A7! 6F" in0ection running in*##" combustion mode. The air heating was made by an electrical pre heater with the aim to control the ignition start andto evaporate completely the water&ethanol mixture before entry in the cylinder. To high charge dilution 8?. "n 9-79! this work was extended with the aim to use energy recovery of exhaust gases topre&heat the inlet air by a heat exchanger. 4unning with only one cylinder! the turbo compressor utili)ation wascompromised. Thus! an electrical compressor was used to simulate the behavior of the turbo compressor. The waterpercentages reached 9-(! higher power were achieved when compared with the previous study by the use of rich air fuelmixtures. Enock limit was controlled by the inlet air temperature! which have direct influence in the combustion start!therefore was demonstrated that is possible use ethanol with 9-( of hydration! what reduces the energy dispended in theproduction process! decreasing the fuel final cost! improving energetic balance in ethanol lifecycle >7-?.

This research aim evaluates the wet ethanol@s utili)ation from +( to ,-( of water in volumetric content in a single cylinderengine running in $tto cycle trough simulation and experimentally.

EXPERIMENTAL SETUP

The study was carried on an originally iesel fuelled engine! modified to run with $tto cycle. Made for agricultureapplications! 1grale M8- engine has a swirl chamber diesel in0ection system! which was modified receive a spark pluginstead of the diesel in0ector. The modified engine characteristics are showed in the Table 7.The main modifications weremade in the cylinder head. 1part from the insertion of the spark plug! compression ratio was decreased using a spacerbetween the cylinder head and the engine block. 1n electronic management system was installed to control in0ection andspark timing. 1 Fueltech F,-- control unit


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'igure * Location of sensors and throttle body

To ac;uire crank&angle resolved pressure data! a variable reluctance sensor was used with a toothed wheel with :%-teeth. oth where linked to a data National "nstruments N"&%9+8 data ac;uisition board which was also used for ac;uiringintake and exhaust pressures as well as their respective temperatures. The data was then post&processed with a Matlabroutine. Fuel consumption was measured in a burette with a resolution of -.9 milliliters. The engine operated with water&in&ethanol volume ranging from +( to ,-( with a maximum permissible deviation of -.+(. Five tests were performedA +(!7-(! 9-(! :-( and ,-( water content. 1n 1ston hydrometer ,+--M 6aar M1 was used to characteri)e the ethanol&in&water mixture. The fuel was named J5xxBxxK where J5K stands for ethanol! JBK for water and the JxxK for the volumetricpercentages of ethanol and water. For instance! a fuel blend 58-B7- contains 8-( ethanol and 7-( of water in it.5xperimental tests were carried at constant M56 for various water&in&ethanol blends using an eddy currentdynamometer and a commercial load cell for tor;ue measurement. 5ach test followed the se;uenceA

7. 5ngine warm&up using 58+B-+


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Qwi L Ball heat flow


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Since the use of fuel compounds and blends is difficult to implement directly within the 12/ oost@s urn tool! pure ethanolwas used and its /*2 was corrected according to the amount of water and its latent heat of vapori)ation! which! in otherwords! reduces the actual /*2 of the fuel blend.

.

'igure , A!l boost model

resultsThis section shows the results obtained for MT and knock&limited spark timing. The values are averaged over ,-cycles. The spark timing advance was limited by knock occurrence when running with +( of water! being at MT in allother percentages. Table 9 shows the experimental test points! with their respective engine speed! and ignition timingadvance. M56


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raction%!7,?! water enhances the anti&knock characteristicof the mixture! working as a naturally occurring and effective anti&knock additive.

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-.7+

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rakeefficiency


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This paper reports a preliminary assessment of the influence of water in combustion performance of hydrous ethanol withhigh water percentages. "t was investigated the combustion of several water&in&ethanol fuel blends on a swilr&chamberspark&ignited engine Testes where performed in a dynamometer and combustion was post&processed and analy)ed withthe 7& simulation software 12/ oost. The following conclusions could be drawnA

Stable engine operation was possible until ,-( of water&in&ethanol volumetric contentC

"ncreased anti&knock characteristic allowed optimum spark timingC

#ombustion duration increases for blends with higher water percentages due the reduction in laminar burningvelocitiesC

4educed exhaust temperature may improve the use of 2GT turbochargers.

4eduction in charge temperature due to higher water content enables the possibility of some aggressive downsi)ingtechni;ues such as higher compression ratios and higher turbo&boost pressures as well as some exhaust heatrecovery technologies


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CONTACTMario Martins! 6h & Senior /ecturerFederal University of Santa MariaMechanical 5ngineering epartment5&mailA mariomecanica.ufsm.brTel. ++ ++ 8%99 9:': H ++ ++ :99- 9+7 5xt. 97

1venida 4oraima! n7--- & #idade UniversitVria & #amobi#56A 8'7-+&8--Santa Maria W 4S & ra)il

combustion performance of high water content hydrous ethanol

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