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New Approach Of Spark IgnitionEngine Fueled with Ethanol

Sun Jun You Fubing Li Gesheng Gao Xiaohong

School of Energy and PowerEngineeringWuhan University of Technology,Wuhan, 430063 China

E-mail:[email protected]: Amid growing concerns about unstableoil supplies and the impact of fossil fuels on global

warming, bio-fuels are receiving increased attention.Ethanol bio-fuel could play an important role in

reducing fossil fuels consumption and greenhouse gasemissions when applying to the transport facilities. Inthis article a new approach ethanol steam reforming

was introduced for the existing spark ignition engines

with few structure changes. Moreover, the waste heat

from exhaust can be used as energy source for ethanol

steam evaporating and reforming. The combustion

characteristics of hydrous-ethanol reforming mixturesgas using a const-volume bomb and high speed

schlierenphotography technique and the performances

of the reformed ethanol engine, such as power,

economy and emissions, have been studied. The

experimental results indicate that hydrous-ethanol isreformed to hydrogen-rich mixture gas which is an

excellent fuel for engines, In addition the

hydrogen-rich mixture gas allows operation at much

higher compression ratio due to its intrinsic octanenumber which could contribute to the power

performance, and the NOx, CO, THC emissions arereduced remarkably because of lean combustion

realized in the cylinder.

Keywords: hydrous-ethanol, reform, sparkignition engine

1. INTRODUCTION

With increasing concerns about energy

shortage and environmental protection, changing

energy framework and reducing emissions fromautomobiles are necessary steps toward less

dependence on fossil fuel, improving air quality

and decreasing greenhouse gases. A variety of

potential alternative fuels are currently being

investigated: solar energy, wind energy, ocean

energy, geothermal and biomass. To the

technology of present status, ethanol is fit for thetransport facilities in comparison with all other

alternative fuels because of its relatively greater

power density. For ethanol as engine fuel, there

is a variety of types from E100 to E5 which are

mature in the market, specially in Brazil and

USA. But all need anhydrous ethanol (99.5%)

which takes a lot of non-renewable energy and

then results in CO2 emissions during further

distillation process from hydrous-ethanol. Andthere are many structure modifications when

ethanol is used to the existing engines in high

rate.

In this paper, a new approach ethanol steam

reforming, which uses common industry alcohol,

is introduced for the existing spark ignition

engines with few structure changes. In addition,

the waste heat from engine exhaust can be used

as energy source for ethanol steam evaporating

and reforming. The combustion characteristics

of hydrous-ethanol reforming mixtures gas using

a const-volume bomb and high speed schlieren

photography technique and the performances of

the reformed ethanol engine, such as power,

economy and emissions, have been studied.

2.SCHEMATIC OF HYDROUS-ETHANOL

REFORMING ENGINE

The hydrous-ethanol reforming engine is

based on a direct injection spark ignition (SI)

engine. Figure 1 shows the schematic of thehydrous-ethanol reforming engine, which

consists of a baseline SI engine with the

compression ratio changing from 7.0 to 8.5, and

a set of hydrous-ethanol supply system with an

evaporator and a reactor. In addition, there is agas chromatography for analyzing thecompositions of the reformate from ethanol

steam.

Figure 1 Schematic of the Hydrous-ethanol

Reforming Engine System

1.SI engine 2.Ethanol tank 3.Flowmeter 4.Ball valve5.Evaporator & Reactor 6.Exhaust outlet 7.Air/Fuel inlet

8.Venturi mixer 9.Pressure regulator 10.Sample valve

11.Gas chromatography 12.Computer

The engine exhaust emission measurements

were accomplished with an exhaust analyzing

system from Horiba, Horiba MEXA-1500D

Exhaust Analyzer. This system was used to

measure oxygen(O2), carbon dioxide(CO2),carbon monoxide(CO), oxides of nitrogen(NOx)

978-1-4244-4813-5/10/$25.00 2010 IEEE

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and total hydrocarbons(THC), via a heat pipe from the engine.

3.COMBUSTION CHARACTERISTICS OF

HYDROUS-ETHANOL REFORMING

MIXTURE GAS3.1 Reaction pathways of ethanol steam

reforming

The reaction pathways and thermodynamicsof ethanol steam reforming have been studied

extensively [1-4]. The possible reaction

pathways of ethanol steam reforming are

summarized in Table II. It can be seen that

hydrogen production varies significantly withdifferent reaction pathways. In order to control

the compositions in the reformate, it is crucial to

ensure sufficient supply of steam and to

minimize ethanol dehydration and

decomposition. For fuel cell, it is important to

minimize CO production and other poisonouscompositions. But for engines, all compositions

in the reformate are fuels. Otherwise, althoughthe reaction of ethanol steam reforming is

endothermic, the energy density of the reformate

will be very low for engines if water is too muchin hydrous-ethanol.

In this paper, 75 percent (v/v) hydrous-ethanol,

in which the mole ratio of water/ethanol is about

1.09, is selected.

TableReaction pathways of ethanol steam reforming

3.2 Compositions of the reformate gasIn the above-mentioned reversible reactions,

and analyzed by gas chromatography GC-TCD,the gas chromatography (GC) analysis indicates

that The main compositions of the reformate gas

is H2, CO, CH4 and CO2. Table II has shown the

volume concentration of the compositions in thereformate gas reformed by the catalysts CB-7

and J106-2Q respectively.

3.3Const-volume bomb experimental apparatus

and experimental results

In order to study conveniently the

combustion characteristics of the reformate gas,

a const-volume bump and high speed schlieren

technology are generally adopted. The research

experimental apparatus is shown in Figure 2.

The system has six sub-systems: the

const-volume combustion bombgas mixing

box ignition system high speed camera

system time-ordered control system and the

measure system of combustion pressure in theconst-volume bomb etc .

Figure 2 Schematic drawing of the experimental apparatus

Figure 3 shows the different time that the

flame kernel of five mixture gas fuels : H2

H2+CO75 percent (v/v) hydrous-ethanol+ H2

+CO 75 percent (v/v) hydrous-ethanol steam

and CO, propagate to the same diameter after

sparked in the const-volume bomb. Figure 4

shows the five fuels relation of flamepropagation distance and time. Figure 5 shows

the pressure development in the const-volume

bomb of the five fuels.

Figure 3 Different fuels schlierenphotograph of flame

propagationFrom the figures the flame propagation

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speed ofH2 is the fastest and it verifies that H2

has excellent combustion characteristics. The

flame propagation speed ofCO is the slowest.

The flame propagation speed of 75 percent (v/v)

hydrous-ethanol+ H2 +CO is obviously faster

than that of 75 percent (v/v) hydrous-ethanol

steam. It burns faster reaches the peak of

combustion pressure quickly and the combustion

time is shorter than the hydrous-ethanol.

Figure 4 Different fuels relation of flame propagation

distance and time

Figure 5 pressure development in the const-volume bomb

of different fuels

The reformate from hydrous-ethanol is

hydrogen-rich gas. Hydrogen has a relatively

high auto-ignition temperature due to its high

fuel octane number. This has important

implications when a hydrogen-air mixture is

compressed. In fact, the auto-ignition

temperature is an important factor in

determining what compression ratio an engine

can use, since the temperature rise during

compression is related to the compression ratio.

4.PERORMANCE OF

HYDROUS-ETHANOL REFORMANIN

ENGINE

The engine is still started by gasoline.

When the temperature of the exhaust reaches

about 300C, the fuel is shifted from gasoline to

hydrous-ethanol.From figure 6 to figure 9 show at the same

conditions of 2000rpm the emissions NOx, CO,

THC and energy consumption compared to the

baseline. The plots illustrate that the emissions

NOx, CO, THC of the hydrous-ethanol

reforming engine are lower than those of thebaseline engine, and the energy consumption is

reduced about 6% except in low loads.


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5. CONCLUSIONThe reforming hydrous-ethanol boostengine approach could provide a cost effective

way to meet near term goals of reducing

gasoline consumption and emissions. The

experimental results indicate that

hydrous-ethanol is reformed to hydrogen-rich

mixture gas which is an excellent fuel for

engines, In addition the hydrogen-rich mixture

gas allows operation at much higher

compression ratio due to its intrinsic octane

number which could contribute to the power

performance, and the NOx, CO, THC emissions

are reduced remarkably because of leancombustion realized in the cylinder.

The other advantages of this approach are

that the waste heat from engine exhaust can be

used as energy source for hydrous-ethanolevaporating and reforming, and it involves only

modest changes to the present gasoline engine

systems and fueling infrastructure.

The further researches for common industry

alcohol as engine alternative fuel are significant

works.

ACKNOWLEDGEMENTS

This research was funded by the Science and

Technology tackling key problem item ofWuhan City (NO.200810321161) and the key

item of Hubei Province natural science fund

(NO.2009CDA029). The authors wish to express

their appreciation to Professor Zhang Xintang,

Professor Pan Zhixiang and Professor Wang

Zhongjun etc, the staff of the Alternative Fuel

Laboratory in Wuhan University of Technology

for their support in the experimental

measurements.

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