Investigation of N-Butanol Blending with Gasoline using a 1-D

Engine Model

Simeon Iliev

University of Ruse “Angel Kanchev”, Department of Engines and Vehicles, 8 Studentska Str., Ruse, Bulgaria

Keywords: Alternative Fuels, Butanol Blends, Engine Simulation, Gasoline, Internal Combustion Engine.

Abstract: Increasing demand and limited reserves for fossil fuel together with carbon emissions regulations have led to

producing sustainable fuels made from renewable materials. In recent years, the focus has been on using bio-

fuels as alternate energy sources. Blending bio-fuels with gasoline is one of the methods to be considered

under the search for a new source of energy. Alcohols are an important category of bio-fuels. Butanol can be

an alternative fuel since it is a liquid and has several physical and chemical properties similar to those of

gasoline fuels. Butanol don’t have many of the drawback associated with ethanol. Butanol has also a higher

molecular weight than ethanol, and therefore, has reduced vapour pressure, lower water solubility, and higher

energy density. That is why this study is aimed to develop the 1-D model of a PFI (Port Fuel Injection) engine

for predicting the effect of various blends of butanol and gasoline on engine performances and fuel

consumption. AVL Boost was used as a simulation tool to analyze the performance and emissions for different

blends of n-butanol and gasoline by volume (n-B0, n-B5, n-B10, n-B20, n-B30, n-B50 and n-B85).

1 INTRODUCTION

Ethanol, butanol and biodiesel are main biofuels.

Butanol (butyl alcohol) is a liquid alcohol fuel and

can work in the internal combustion engine with

gasoline without any modification. It can be produced

from biomass (biobutanol) or from fossil fuels

(petrobutanol). Both alcohols biobutanol and

petrobutanol have the same chemical properties. The

energy density of butanol is closer to gasoline than

the other alternative additives as ethanol and

methanol which are commonly used today. Butanol is

less hygroscopic so it does not require the different

handling that ethanol and methanol required. Also, it

means that Butanol is less corrosive than ethanol and

methanol. In comparison to ethanol, butanol is less

prone to water contamination. As a result it could be

distributed using the same infrastructure used to

transport gasoline. Butanol can burn at a wider range

of temperatures than ethanol, and has better cold start

properties. Many investigations lead to conclusion

that that it can be used alone or can be mixed with

gasoline in an internal combustion engine (ICE).

Furthermore, butanol has a high enough octane

number, close to that of gasoline and a lower vapor

pressure. The higher octane number, the more

compression the fuel can withstand before detonating.

Premature fuel ignition can damage engine, which is

a common phenomenon for lower octane number

fuel. These properties make it more suitable additive

than ethanol and methanol for gasoline fuel.

There are four butyl alcohols with the same

chemical composition consisting of 4 carbon atoms,

10 hydrogens and 1 oxygen and they have identical

chemical pattern C

O, but they differ each from

others with respect to their structure (Szwajaa and

Naber, 2010). The chemical nature of alcohols are as

follows:

 1-butanol (n-butanol, n-butylalcohol)

(CH

)

OH,

 2-butanol CH

CH(OH)CH

 3-butanol (CH

)

COH,

 iso-butanol CH

(CH

)

OH.

The common fuel properties of n-butanol in

comparison to gasoline and other alcohol fuels are

given in Table 1 (Yacoub, Bara and Gautam 2000),

(Gautam and Martin, 2000). Form this table, it can be

said that about the latent heat of vaporization of these

fuels, butanol is less attractive than others. For PFI

(port fuel injection) systems, fuels with higher latent

heat of vaporization have larger decreases in

temperature of intake charge with complete

Iliev, S.

Investigation of N-Butanol Blending with Gasoline using a 1-D Engine Model.

DOI: 10.5220/0006284703850391

In Proceedings of the 3rd International Conference on Vehicle Technology and Intelligent Transport Systems (VEHITS 2017), pages 385-391

ISBN: 978-989-758-242-4

385

Table 1: Properties of several fuels (Yacoub, Bara and Gautam 2000), (Gautam and Martin, 2000).

Fuel Chemical

formula

Specific

gravity

(kg/dm

)

Lower heating

value

(MJ/kg)

Stoichiometri

c air–fuel

ratio

(kg

air

/kg

fuel

)

Energy density of a

stoichiometric air–

fuel mixture

(MJ/kg)

Latent heat of

vaporization (at

boiling point)

(kJ/kg)

Octane number

(RON+MON)/2

Methanol CH

OH 0,7913 20,08 6,43 2,750 1098 99

Ethanol C

OH 0,7894 26,83 8,94 2,699 838 100

n-Butanol C

OH 0,8097 32,01 11,12 2,641 584 86

Gasoline C

0,7430 42,9 14,51 2,769 349 87

vaporization in the intake port. To match the

combustion characteristics of gasoline, the utilization

of butanol fuel as a substitute for gasoline requires

fuel-flow increases (though butanol has only slightly

less energy than gasoline, so the fuel-flow increase

required is only minimal, maybe 10%). Higher

oxygen content and lower octane number of n-butanol

need changes in initial engine calibration, determined

with pure gasoline. Also butanol has a higher laminar

flame propagation speed than gasoline, which makes

combustion process finish earlier and improving the

engine thermal efficiency.

Since using blended alcohol-gasoline fuels can

reduce the air pollution, many researchers have

studied the effect of these alcohol blended fuels on

the performance and exhaust emission of a spark-

ignited engine. In а study conducted by (Alasfour,

1998), NOx emissions were presented as a function

of air/fuel equivalence ratio. It is showed decreasing

in NOx emissions when a 30% butanol-gasoline

blend was used. Peak NOx emissions were received

at a slightly leaner mixture for a 30% butanol–

gasoline blend than for pure gasoline.

Switching a gasoline engine over to butanol

would in theory result in a fuel consumption penalty

of about 10% but there is no scientific study yet which

butanol effects on fuel consumption for the

commercial vehicles. While the energy density for

any mixture of gasoline and butanol can be

calculated, tests with other alcohol fuels have

demonstrated that the effect on fuel economy is not

proportional to the change in energy density (Minter,

2006).

There are many investigations on butanol

utilization in gasoline engines. The researchers

(Wallner, Miers and McConnell, 2009; Rakopoulos,

Papagiannakis and Kyritsis, 2011; Sarathy et al.,

2009) investigated the unburned hydrocarbon (HC),

carbon monoxide (CO) and nitrogen oxides (NOx)

emissions with gasoline, 10% ethanol and 10% n-

butanol blends in a direct injection spark-ignition

engine. Their results showed little difference in HC,

CO and NOx emissions between gasoline and 10% n-

butanol. The reason for this is the engine is operated

at the stoichiometric air/fuel ratio for each specific

fuel blend. The researchers (Dernotte, et al., 2010)

examined the emissions characteristics of several n-

butanol–gasoline blends (0, 20, 40, 60 and 80 vol. %

of n-butanol in gasoline) using a PFI spark-ignition

engine and found that n-butanol (B60) and n-butanol

(B80) produced 18% and 47% more unburned HC

emissions than neat gasoline, respectively. It was

found that B80 was the only n-butanol blended fuel,

which it did not produce lower CO emissions than

neat gasoline.

Other researchers (Gu X et al., 2012) tested five

gasoline butanol blendes (B0, B10, B30, B40 and

B100) and results showed that the unburned HC and

CO emissions of blends are lower than those of

gasoline. Pure n-butanol (B100) increases the

unburned HC and CO emissions compared to those of

gasoline. They also showed that the addition of n-

butanol decreased the particle emissions. In another

study (Feng et al., 2013) for pure gasoline and 35%

by volume butanol-gasoline blend. The results

showed that engine torque, brake specific fuel

consumption (BSFC) and CO and HC emissions were

better than those of pure gasoline at both full load and

partial load with 35% volume butanol addition. But

emission was worse than that of the original level

of pure gasoline.

There are many studies focused on conventional

harmful exhaust emissions (CO, HC and NOx) when

use butanol as spark ignition engine fuel. Although

is a non-toxic gas, which is not classified as an

engine pollutant, it is one of the substances

responsible for global temperature rises through the

greenhouse effect. CO

emission has not been usually

taken into account in many studies. (Emilio et al.,

2013; Ritche et al., 2012).

The objective of this paper is to investigate CO,

HC, NOx, BSFC, power and torque for various n-

butanol-gasoline blends at diferent engine speed.

SMS 2017 - Special Session on Sustainable mobility solutions: vehicle and trafﬁc simulation, on-road trials and EV charging

386

2 METODOLOGY

Engine simulation is becoming an increasingly

important engineering tool for time and cost

efficiency in the development of internal combustion

engines (ICEs). Most of results that are obtained by

simulation are rather difficult to be obtained

experimentally. The use of Computational Fluid

Dynamics (CFD) simulations allow researchers to

understand flow behaviour and quantify important

flow parameters such as mass flow rates or pressure

drops, provided that the CFD tools have been

properly validated against experimental results. For

reasons such as the aforementioned, CFD simulations

have become a valuable tool in helping both the

analysis and design of the intake and exhaust systems

of an ICEs. Many processes in the engine are 3-D but

it requires greater knowledge and large computational

time. Thus simplified 1-D simulation is often used.

There are several components that manifest a

complex three-dimensional flow behaviour, such as

turbo machinery or manifolds which cannot be

simulated properly by 1-D codes, and thus require

viscous, 3-D codes (Iliev S. 2015).

The present paper aims to develop the 1-D

simulation model of four-stroke port fuel injection

(PFI) gasoline engine for predicting the effect of n-

butanol–gasoline (n-B0, n-B5, n-B10, n-B20, n-B30,

n-B50 and n-B85) fuel blends on the performance and

emissions of SI engine. For this purpose, the

simulation of a calibrated gasoline engine model was

used as basic operating condition, and the laminar

burning velocity correlations of n-butanol–gasoline

fuel blends was considered for calculating the

different combustion duration. The engine

performances: torque and specific fuel consumption

were compared and discussed.

2.1 Simulation Setup

The 1-D engine simulation model is developed by

using the software AVL BOOST and has been

employed to study the engine performance working

on n-butanol-gasoline blends.

Figure 1: Layout of engine model.

The pre-processing step of AVL Boost enable

the user to model a 1-Dimensional (1-D) engine test

bench setup using the predefined elements provided

in the software toolbox. The various elements are

joined by the desired connectors to establish the

complete engine model using pipelines.

Table 2: Engine specification.

Engine parameters Value

Bore 86 (mm)

Stroke 86 (mm)

Compression ratio 10,5

Connection rod length 143,5 (mm)

Number of cylinder 4

Piston pin offset 0 (mm)

Displacement 2000 (cc)

Intake valve open 20 BTDC (deg)

Intake valve close 70 ABDC (deg)

Exhaust valve open 50 BBDC (deg)

Exhaust valve close 30 ATDC (deg)

Piston surface area 5809 (mm

)

Cylinder surface area 7550 (mm

)

Number of stroke 4

In Fig.1, E1 represent the engine while C1, C2,

C3 and C4 represent the number of cylinders of the

engine. MP1 to MP18 represent the measuring points.

PL1, PL2, PL3 and PL4 represent the plenum. SB1

and SB2 are for the system boundary. The flow pipes

are numbered 1 to 34. CL1 represent the cleaner. R1

to R10 represent flow restrictions, CAT1 represent

catalyst and I1 to I4 represent fuel injectors.

Investigation of N-Butanol Blending with Gasoline using a 1-D Engine Model

387

The engine model used in this simulation was

performed on a four stroke, four cylinder spark

ignition engine with port fuel injection. The gasoline

engine model was calibrated and described by (Iliev

S. 2014) and its layout is shown in Fig. 1 with engine

specification shown in Table 1.

3 RESULT AND DISCUSSON

The present study concentrated on the emission and

performance characteristics of the n-butanol-gasoline

blends. Different concentrations of the blends 0% n-

Butanol (n-B0), 5% n-Butanol (n-B5), 10% n-

Butanol (n-B10), 20% n-Butanol (n-B20), 30% n-

Butanol (n-B30), 50% n-Butanol (n-B50) and 85% n-

Butanol (n-B85) by volume were analyzed using

AVL BOOST at full load conditions for the speeds

ranging from 1000 - 6500 rpm in the steps of 500rpm.

The results are divided into different subsections

based on the parameter analyzed.

3.1 Engine Performance

Characteristics

The results of the brake power, and specific fuel

consumption for n-Butanol gasoline blended fuels at

different engine speeds are presented here.

Fig. 2 shows the influence of n-Butanol gasoline

blended fuels on engine brake power.

Figure 2: Influence of n-Butanol gasoline blended fuels on

engine brake power.

The brake power is one of the important factors that

determine the performance of an engine. The

variation of brake power with speed was obtained at

full load conditions for n-B5, n-B10, n-B20, n-B30,

n-B50 and pure gasoline n-B0, using the CFD results.

When the n-Butanol content in the blended fuel

was increased, the engine brake power decreased for

all engine speeds. The brake power of gasoline was

higher than those of n-B5 to n-B85 for all engine

speeds. The heating value of n-Butanol is lower than

that of gasoline and heating value of the blended fuel

decreases with the increase of the n-Butanol content.

As a result, a lower power output is obtained.

Butanol addition to the gasoline does not affect

engine power significantly, but especially at high

engine speed (over 4000 min

-1

) there is a sharp

reduction the power curves compared to pure gasoline

(Fig. 2). The reason of this reduction can be affected

by the low calorific value of butanol.

This may refer to some reasons as follows.

Combustion characteristic of n-butanol is different

from gasoline since the latent heat of n-butanol is

higher than that for gasoline (584 kJ/kg, 349 kJ/kg for

n-butanol and gasoline, respectively). This means that

the n-butanol absorbs more heat in order to evaporate

and burn.

Fig. 3 shows the influence of n-Butanol gasoline

blended fuels on engine torque. The increase of n-

Butanol content (n-B5 – n-B85) decreased the torque

of the engine. The brake torque of gasoline was

higher than those of n-B5-nB85.

Figure 3: Influence of n-Butanol gasoline blended fuels on

engine torque.

The calorific value of butanol is lower than the

calorific value of gasoline, therefore it is expected

that any butanol addition to the gasoline reduces the

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388

torque output of the engine. However oxygen content

of butanol improves the combustion in the cylinder

and with the 5% and %10 butanol blends similar

value are achieved with gasoline. On the other hand,

because of the existence of oxygen in the butanol

chemical component, and the increase of n-Butanol,

lean mixtures are produced that decrease equivalence

air-fuel ratio to a lower value and due to the presence

of oxygen which has entered the combustion chamber

makes the burning more efficient.

Regarding the stumpy of volumetric efficiency of

blended fuels, it is mainly due to the low saturation

pressure of n-butanol compared to gasoline fuel (2.27

kPa of n-butanol and 31 kPa for gasoline); the

saturation pressure is strongly linked to the ability of

the fuel to vaporize. The lower the saturation pressure

is, the ability of the fuel to evaporation is increased.

When fuel is evaporated, the volume of vaporized

fuel will displace some incoming air, e.g., less air.

Besides, fuels with a smaller stoichiometric air–fuel

ratio, like n-butanol 11.2, have a lower volumetric

efficiency. But, n-butanol has high heat of

vaporization, so some volumetric efficiency lost due

to air-fuel ratio and saturation pressure is partially

gained back again. Besides, it is possible to improve

the volumetric efficiency of n-butanol by cooling the

air and fuel before accessing onto the engine system.

In addition, manifolds with late fuel addition and

wider runners can be designed to further increase the

volumetric efficiency.

Figure 4: Influence of n-Butanol gasoline blended fuels on

brake specific fuel consumption.

Fig. 4 indicates the variations of the BSFC for

n-Butanol gasoline blended fuels under various

engine speeds. As shown in this figure, the BSFC

increased as the n-Butanol percentage increased. The

well-known reason, that the lower heating value and

stoichiometric air-fuel ratio for this fuel leads that for

specific air-fuel equivalence ratio, more fuel is

needed. The highest specific fuel consumption is

obtained for n-B85 blended fuel. Also, a slight

difference exists between the BSFC when using

gasoline and when using n-Butanol gasoline blended

fuels (n-B5, n-B10 and n-B20). The lower energy

content of butanol gasoline blended fuels causes some

increment in BSFC of the engine when it is used

without any modification.

3.2 Engine Emissions Characteristics

Fuels consist of Hydrogen (H) and Carbon (C)

molecules. During the combustion period in the

engine cylinder, these C and H molecules react with

oxygen (O2) in the air and converted to the CO, CO2,

HC. These exhaust tail emissions are harmful for

human health and environmental pollution. Carbon

monoxide (CO) is colorless, odorless, tasteless gas

which is lighter than air. It is highly toxic to humans

and animals in higher quantities. CO is a common

industrial hazard resulting from the incomplete

burning of natural gas and any other material

containing carbon.

Figure 5: Influence of n-Butanol gasoline blended fuels on

CO emissions.

The effect of the n-Butanol gasoline blends on CO

emissions for different engine speeds is shown in Fig.

5. It can be seen that when n-Butanol percentage

Investigation of N-Butanol Blending with Gasoline using a 1-D Engine Model

389

increases, the CO concentration decreases. This can

be explained by the enrichment of oxygen owing to

the n-Butanol, in which an increase in the proportion

of oxygen will promote the further oxidation of CO

during the engine exhaust process. Another

significant reason for this reduction is that n-Butanol

OH) has less carbon than gasoline (C

). The

lowest CO emissions are obtained with blended fuel

containing n-Butanol (n-B95).

When using gasoline as fuel in a spark ignition

engine, the unburned fuel hydrocarbons (HC) in the

exhaust consist mainly of unburned gasoline which

itself largely consists of hydrocarbons. However,

when using gasoline-Butanol blends as fuel the un-

combusted fuel constituents include both unburned

gasoline (which consists mainly of hydrocarbons as

noted) and un-combusted Butanol. Thus, the HC

emissions measured in the diluted exhaust consist of

both hydrocarbons and Butanol. From a legal

perspective, HC emissions are regulated by law, but

not Butanol emissions. This means that reported HC

emissions from vehicles fueled with alcohol-gasoline

blends are overestimated, due to the contribution of

the alcohol contents in the exhaust emitted from the

vehicle, and the larger the alcohol contents present in

the exhaust, the greater the error in estimated HC

emissions (Egeback et al., 2005).

Figure 6: Influence of n-Butanol gasoline blended fuels on

HC emissions.

The effect of the n-Butanol gasoline blends on HC

emissions for different engine speeds is shown in Fig.

6. It can be seen that when n-Butanol percentage

increases, the HC concentration decreases. The

concentration of HC emissions decreases with the

increase of the relative air-fuel ratio. The reason for

the decrease of HC concentration is similar to that of

CO concentration described above.

Nitrogen oxides (NO and NO

) are formed by the

oxidation of nitrogen from the air in the combustion

process. An important parameter for the formation of

nitrogen oxides is the combustion temperature

(increased combustion temperature results in

increased nitrogen oxide emissions). Therefore, its

probable formation is in very high temperature

regions, which are related to heat release (Raslavicius

L. 2010). It should be noted that nitrogen oxides

(NO

) are regulated pollutants that are determined

jointly, as the sum of NO and NO

contents rather

than as individual components (Egeback et al., 2005).

Figure 7: Influence of n-Butanol gasoline blended fuels on

NOx emissions.

The effect of the n-Butanol gasoline blends on

NOx emissions for different engine speeds is shown

in Fig. 7. It can be seen that when n-Butanol

percentage increases up to 50% n-B50, the NOx

concentration increase after which it decreased with

increasing n-Butanol percentage. This can be

explained by that improved combustion inside the

cylinder resulting in an increased in-cylinder

temperature. The higher percentage of n-Butanol in

gasoline reduces the in-cylinder temperature. The

reasons for the reduction in temperature are: 1. Latent

heat of evaporation of n-Butanol, which decreases the

in-cylinder temperature when they vaporizes, 2.

There are more triatomic molecules are produced, the

SMS 2017 - Special Session on Sustainable mobility solutions: vehicle and trafﬁc simulation, on-road trials and EV charging

390

higher the gas heat capacity and the lower the

combustion gas temperature will be. However the low

in-cylinder temperature can also lead to an increment

in the unburned combustion product.

4 CONCLUSIONS

The present paper demonstrates the influences of n-

Butanol addition to gasoline on SI engine

performance and emission characteristics. General

results concluded from this study can be summarized

as follows:

- When the n-Butanol content in the blended fuel

was increased, the engine brake power decreased for

all engine speeds. The engine performance of blends

is lower than gasoline due to the combustion

characteristics of n-butanol (higher latent heat and

lower calorific value than gasoline). The lower

saturation pressure of n-butanol compared to gasoline

leads to a lower volumetric efficiency for blended

fuels. The engine performance of blends could be

improved by modifying ignition time and increasing

compression ratio since n-butanol has more resistance

to detonation than gasoline.

- The BSFC increased as the butanol percentage

increased. Also, a slight difference exists between the

BSFC when using gasoline and when using gasoline

blended fuels n-B5, n-B10, n-B20 and n-B30.

- When n-Butanol percentage increases, the CO

and HC concentration decreases.

- Butanol gasoline blends the significant increase

NOx emissions with the increase of butanol

percentage. When butanol percentage increases up to

50% n-B50, the NOx concentration increase after

which it decreased with increasing butanol

percentage.

ACKNOWLEDGEMENTS

We are eternally grateful to AVL-AST, Graz, Austria

for granting use of AVL-BOOST under the university

partnership program.

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