Note: Descriptions are shown in the official language in which they were submitted.
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A METHOD OF BLENDING FUEL
The present invention relates to fuels, their use in
internal combustion engines in vehicles and their
production. Specifically, the present invention relates to
blended fuels, particularly including methanol with
stoichiometric air-fuel ratios similar to that of E85.
It is known to produce fuels by blending ethanol and
gasoline in various proportions. Such fuels can be used in
unmodified gasoline internal combustion engines, e.g. in
automobiles, or gasoline internal combustion engines with
only minor modifications.
Ethanol-based fuels are usually denoted by the letter "E"
followed by the proportion by volume of ethanol, expressed
as a percentage. For example, a common blend is E85; a
mixture of 85% ethanol by volume with 15% gasoline by
volume. These two-component blended fuels may contain other
additives, but these additives are not fuel components, do
not have significant volume and do not significantly affect
the proportions of the major fuel components, ethanol and
gasoline, which together can be considered the only
significant fuel components. In the following description
the term component(s) refers exclusively to a fuel
component(s).
Gasoline fuel (sometimes called petrol) is itself a blend of
hydrocarbons, typically aliphatic hydrocarbons obtained by
fractional distillation of petroleum, enhanced with iso-
octane or the aromatic hydrocarbons toluene and benzene.
The term gasoline is used throughout this specification to
refer to fuel suitable for use in an internal combustion
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engine running spark-injection ("SI")combustion or
Homogenous Charge Ignition Combustion ("HCCI") which is
composed of hydrocarbons (typically between 4 and 12 carbon
atoms per molecule) and is substantially free of oxygenated
components, e.g. alcohols and ethanols, (less than 5% oxygen
content) and which has a stoichiometric Air-fuel ratio in
the range 14:1 to 15:1. Preferably the fuel has a Research
Octane Number (RON) of 86 to 105. The term gasoline is used
to include fuels such as those defined by British Standard
BS/EN228 and/or American Standard ASTM-D-4814.
In the UK it is now possible to purchase for use in internal
combustion engines of motor vehicles E5 (5% ethanol, 95%
gasoline). The use of E10 (10% ethanol, 90% gasoline) for
motor vehicle internal combustion engines is increasing in
the US.
It is now becoming popular to manufacture internal
combustion engines which are specifically configured to run
on a fuel blend of gasoline and ethanol. For example, in
Brazil, all gasoline internal combustion engines (e.g. which
run using the Otto cycle) are manufactured to run on blended
fuels in the range E20 to E25.
The highest proportion of ethanol generally used for Otto-
cycle internal combustion engines of vehicles is 85% by
volume (E85), although it is known exceptionally to use 100%
ethanol (E100).
The use of ethanol-based blended fuels is more
environmentally friendly than simply using more gasoline,
since the ethanol is typically produced from biomass.
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Furthermore, the use of ethanol reduces a country's
dependence upon imports of foreign petroleum. However, the
supply of ethanol from biomass is limited.
It is therefore advantageous to find fuel blends which can
extend use renewable components of the fuel blends.
According to a first aspect of the present invention, there
is provided a method as claimed in claim 1.
According to a second aspect of the present invention there
is provided a blended fuel as claimed in claim 17.
According to a third aspect of the present invention there
is provided a blended fuel as claimed in claim 18.
According to a fourth aspect of the present invention there
is provided a blended fuel as claimed in claim 19.
According to a fifth aspect of the present invention there
is provided a method as claimed in claim 20.
According to a sixth aspect of the present invention there
is provided a method as claimed in claim 21.
The present invention will now be described, by way of
example only, with reference to the accompanying drawings,
in which:
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Figure 1 shows a graph showing the relative proportions of
ethanol, gasoline and methanol in a blended fuel equivalent
to E85; and
Figure 2 shows a graph showing the relative proportions of
methanol, gasoline and ethanol in a blended fuel equivalent
to M85.
Preferred embodiments of three-component blended fuels in
accordance with the invention can have the same properties
as known two-component blended fuels, to thereby provide
good performance in internal combustion engines of motor
vehicles that have been designed to run on known two-
component blended fuels. Importantly they can be used by
existing internal combustion engine with no structural
modifications of such engines, and preferably without any
need for the engine management system to run a different
operating regime for the new fuels (i.e. there is no need to
ass to the memory of the engine management system new
operating regime maps for the new fuels).
In order for a fuel to be compatible with an existing design
of motor vehicle internal combustion engine (i.e., to offer
significantly the same behaviour as the fuel on which the
engine has been configured to run), the most preferable
property of the fuel to be the same as the fuel on which the
engine was designed to run, is the stoichiometric air-fuel
ratio. This is the ratio (conventionally, and hereinafter,
represented as a ratio by mass) of air to fuel which will
theoretically provide complete combustion of the fuel.
Alternatively, since internal combustion engines that are
configured to run on alcohol-based fuels comprise an alcohol
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sensor for determining the ratio of alcohol to gasoline in
the fuel it may be advantageous to provide a blended fuel
that provides substantially the same response when measured
by an alcohol sensor as the fuel on which the engine was
5 designed to run. Such a response may be, for example, that
the resistance across the sensor changes as a result of
varying proportions of ethanol in the fuel. Preferably, the
resistance will be the same for the three-component blended
fuel as for the fuel on which the engine was designed to
run. Typically, the engine management system will use this
measurement to determine the volume of fuel to be delivered
in each engine cycle.
As a further alternative, it may be advantageous to provide
a blended fuel that provides the same lower heating value
(e.g. volumetric or gravimetric) as the fuel on which the
engine was designed to run.
According to a first embodiment of the invention there is
provided a blended-fuel having an equivalent stoichiometric
air-fuel ratio (AFR) as E85.
The stoichiometric AFR of ethanol is approximately 8.96:1.
The stoichiometric AFR of gasoline is approximately 14.53:1.
A blend of 85% ethanol with 15% gasoline has a
stoichiometric AFR of 9.74:1.
Any ethanol-gasoline blended fuel will have a stoichiometric
AFR lying between the upper and lower bound defined by the
stoichiometric AFRs of gasoline and ethanol, respectively.
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If a larger proportion of gasoline is used, then the
stoichiometric AFR will increase. This is because gasoline
has a larger stoichiometric AFR than ethanol. Clearly, the
maximum stoichiometric AFR achievable with these two
components is 14.53:1, which is achieved by 0% ethanol and
100% gasoline.
In order to provide a fuel having a stoichiometric air-fuel
ratio that is the same as E85, whilst reducing the
proportion of ethanol, it is necessary to add a fuel
component having a lower stoichiometric AFR than E85.
In the first embodiment, methanol is blended with ethanol
and gasoline to provide a fuel having 65% ethanol by volume
and a stoichiometric AFR of 9.74:1 (i.e., the same
stoichiometric AFR as E85).
The stoichiometric AFR of methanol is approximately 6.44:1.
The blend of 65% ethanol with gasoline and methanol that
provides a stoichiometric AFR of 9.74:1 is approximately:
65% ethanol; 21.5% gasoline; and 13.5% methanol.
Advantageously, a fuel with less ethanol can therefore be
produced without significantly increasing the reliance upon
fossil fuels. This is because methanol can be synthesised
from hydrogen and atmospheric carbon dioxide and/or carbon
monoxide or made from wood waste (although less
advantageously, the methanol could be made from coal or
natural gas).
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A blended fuel with increased methanol will offer better
performance than E85 when starting the internal combustion
engine in low temperature conditions. Typically, where an
E85 blend is offered in summer conditions, a winter blend of
E70 is offered in colder conditions. A blend with methanol
could remove the need for providing a more gasoline rich
blend of ethanol-based fuel (i.e. the winter-grade E70
blend) in cold conditions.
According to a second embodiment of the invention there is
provided a method of producing a blended fuel having an
equivalent stoichiometric air-fuel ratio (AFR) as E85.
For the methodology described below the following values are
used:
Fuel Stoichiometric Gravimetric Density Molecular
Component AFR (:1) LHV (MJ/kg) (kg/1) Mass (-)
Ethanol 8.5982 26.8 0.7892 46
Gasoline 14.5298 42.7 0.7359 114.56
Methanol 6.4375 19.9 0.7913 32
LHV stands for Lower Heating Valve (also known as calorific
value) and is defined as the amount of heat released by
combusting a specified quantity (mass or volume) in
controlled temperature conditions.
Figure 1 shows a graph of proportion by volume of ethanol
against corresponding proportions of gasoline (denoted by
triangles)and methanol (denoted by circles). (That is, the
X-axis represents the proportion of ethanol and the Y-axis
represents the proportion of both gasoline and methanol).
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The lines are provided by the following equations:
Vgag = 42.641 - 0.3255 X Veth (Equation 1)
Vmeth = 57.359 - 0.6745 X Veth (Equation 2)
where Veth, Vgag and Vmeth are, respectively, the proportions
of ethanol, gasoline, and methanol by volume that provide
the stoichiometric AFR of E85.
The method of the second embodiment comprises blending a
desired proportion of ethanol with a first proportion of
gasoline and a second proportion of methanol such that the
resulting blended fuel has the same stoichiometric AFR as
E85.
For example, if a fuel is desired with only 50% ethanol, the
blend of ethanol, gasoline and methanol that provides the
same stoichiometric AFR as E85 would be approximately: 50%
ethanol; 26.4% gasoline; and 23.6% methanol.
The desired proportion is entered as Veth into Equation 1 to
determine the first proportion, and into Equation 2 to
determine the second proportion.
The above disclosed blends of ethanol, gasoline and methanol
would be usable in internal combustion engines that have
been configured to run on E85. Advantageously, the use of
methanol as a third fuel component does not adversely effect
the operation of the engine, since the variation in ethanol
sensor measurements to fuel also including methanol is only
small.
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In various embodiments, the amount of ethanol by volume in
the fuel would be in the range of 40% to 85%. Over this
range, the variation in output level from a typical ethanol
sensor will vary by no more than 3.5%
Another advantageous feature of blending methanol with
ethanol and gasoline is that the volumetric lower heating
value (LHV) of the blend remains substantially unchanged
over the range of 0% to 85% ethanol by volume as compared
with E85. This change is less than 1%, which is smaller
than the variation caused by different sources of gasoline.
As such, it is not necessary to modify the operating regime
employed by or the parameters of the engine management
system to command the fuel injector to deliver a different
amount of fuel. This result has also been found to be the
case for other standard vehicle engine alcohol sensors when
other three-component blended fuels replace two-component
blended fuels (e.g. replacing M85 with a blend of ethanol,
methanol and gasoline).
However, if desired, the engine management system can be
modified to compensate for the new fuel by using the
following equation:
Volumetric LHV = 22.496 + (0.0025 X Veth) '(Equation 3)
where Volumetric LHV is measured in MJ/1, and Veth is the
proportion of ethanol by volume.
Equation 3 is derived from a line of best-fit through
empirical data obtained from measuring the volumetric lower
heating value of a number of blended fuels having
proportions of ethanol, gasoline, and methanol, related by
equations 1 and 2.
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Since, as disclosed above, the variation of LHV is so small,
any modification of the volume of fuel to be delivered will
lie within the operating range of the fuel injector.
In the above embodiments a fuel and a method of producing
the same have been disclosed for a fuel that has
substantially the same stoichiometric AFR as E85.
However, it may be desirable to provide a blended fuel with
low ethanol content that has substantially the same
stoichiometric AFR as a different ethanol-gasoline based
fuel (i.e. a fuel having substantially only ethanol and
gasoline as components), such as E65 or E50.
As will be appreciated by the skilled person, since methanol
has a lower stoichiometric AFR than either ethanol or
gasoline (and therefore also a lower stoichiometric AFR than
any ethanol-gasoline blend), any ethanol-gasoline based fuel
having a significant proportion of ethanol may be replaced
by one having less ethanol but the same stoichiometric AFR,
by blending different amounts of ethanol, gasoline and
methanol.
Moreover, the skilled person will appreciate that the above
disclosed concept is not limited to methanol and that any
component having a lower stoichiometric AFR than the,
ethanol-based fuel to be replaced may be blended with
ethanol and gasoline to thereby provide a blended fuel with
a suitable stoichiometric AFR. Preferably, such a component
would belong to at least one of the following groups: pure
hydrocarbons; alcohols; ethers; or furans.
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Similarly, gasoline may be replaced with any component
having a higher stoichiometric AFR than the ethanol-based
fuel to be replaced.
Although the above has been described as providing the same
stoichiometric AFR as ethanol-based fuel blends, blended
fuels may be developed with any first, second and third
components to provide a blended fuel having the same
stoichiometric AFR as any fuel to be replaced, provided that
two of the components have a higher and lower stoichiometric
AFR, respectively, than the fuel to be replaced (i.e., the
target stoichiometric AFR).
In other words, for vehicles designed to run on a two-
component blended fuel having a first component and a second
component, a three-component fuel can be provided having the
first component and the second component and a third
component. The three-component fuel can have a smaller
proportion of the first component than the two-component
fuel whilst having the same stoichiometric AFR, provided
that the second and third components have a stoichiometric
AFR greater than and lower than the stoichiometric AFR of
the two-component blended fuel (or vice versa).
According to a third embodiment of the present invention,
there is provided a method of producing a three-component
blended fuel for an internal combustion engine that has been
configured to run on a two-component blended fuel formed
from methanol and gasoline. Specifically, in this
embodiment, the two-component fuel is M85. However, the
skilled person will appreciate that the following describes
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a technique which may be applied to any methanol-gasoline
blend (and furthermore, as described above, any two-
component blended fuel).
As with the second embodiment, the three-component fuel is
chosen to have the same stoichiometric AFR as the two-
component fuel. However, it is possible to produce a three-
component blended fuel in which a different property (such
as volumetric LHV or the signal produced by an ethanol or
methanol sensor) of the fuel is the same as for the two-
component blended fuels.
Figure 2 shows a graph of proportion by volume of gasoline
against corresponding proportions of methanol (denoted by
triangles)and ethanol (denoted by circles). (That is, the
X-axis represents the proportion of gasoline and the Y-axis
represents the proportion of methanol or ethanol).
The lines are provided by the following equations:
Vmeth = 54.687 + 2.026 X Vgas (Equation 4)
Veth = 45.313 - 3.026 X Vgas (Equation 5)
where Veth, Vgas and Vmeth are, respectively, the proportions
of ethanol, gasoline, and methanol by volume that provide
the stoichiometric AFR of M85.
The method of the third embodiment comprises blending a
desired proportion of gasoline with a first proportion of
methanol and a second proportion of ethanol such that the
resulting blended fuel has the same stoichiometric AFR as
M85.
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The desired proportion is entered as Vgas into Equation 4 to
determine the first proportion, and into Equation 5 to
determine the second proportion.
Accordingly, the proportion of gasoline can be reduced from
the level present in M85 (i.e., 15%) by the addition of an
ethanol component, whilst maintaining a constant
stoichiometric AFR. This is because ethanol has a lower
stoichiometric AFR than gasoline and a higher stoichiometric
AFR than methanol.
These equations can be rewritten as:
Vgas = 14.976 - 0.3305 x Veth (Equation 6)
Vmeth = 85.024 - 0.6695 x Veth (Equation 7)
to thereby provide the appropriate proportions of gasoline
and methanol for a desired proportion of ethanol.
The above disclosed blends of ethanol, gasoline and methanol
would be usable in internal combustion engines that have
been configured to run on M85.
Although the disclosed fuel blends have been described as
providing the same stoichiometric AFR by mass (this is the
most preferable property of the blended fuel to control) as
the fuel to be replaced, it is also possible to provide a
fuel blend having a different equivalent parameter. For
example, the fuel blend may produce the same reading on an
ethanol sensor as the fuel to be replaced. Alternatively,
the fuel blend may have the same LHV (volumetric or
gravimetric) as the fuel to be replaced. Also, it may be
desirable to match the three-component blended fuels
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stoichiometric AFR by volume with that of the fuel being
replaced.
Although the above embodiments describe a method of
producing a blended fuel having three components, the
invention is applicable to a fuel having more than three
components and a desired value of stoichiometric AFR or
another property. The existing fuel might, for instance, be
a three component fuel, and the new comparable fuel produced
by the method a four component fuel.
Thus the invention can provide starting with an existing
three component fuel (e.g. gasoline, ethanol and methanol)
and it is possible to use the above methods to obtain a
blended fuel with more than three components because
collectively, the first component and the additional
components in excess of three can be thought of as a single
component.
