Field of the Invention
[0001] This invention relates to a new fuel comprising a hydrocarbon mixture being limited
to hydrocarbons within the range^C
6 to C
10, to a method for producing this fuel, and to a method of operating an improved internal
combustion engine using the fuel of the invention.
Background Information
[0002] Present day automotive gasoline consists of a mixture of hydrocarbons which range
from C
4 to about C
12. The lower molecular weight fraction, such as butane isomers, is more volatile and
it has always been the practice to include substantial portions of these volatiles
in the fuel to insure proper engine performance. This practice, however, is at best
a compromise since the presence of the volatiles, on the one hand, causes an undue
risk of explosion during storage and handling; and the inherent evaporative and emission
losses contribute to Pollution; but, on the other hand, the volatiles have always
been considered necessary for good cold engine starting. Thus, a certain amount of
the volatiles have been incorporated in gasoline. The exact amount of the volatiles
may vary according to the climate where it is sold. In fact, industry has set voluntary
limits so that each area will have a motor fuel having sufficient volatility for the
prevailing climate. High levels of volatile components assure satisfactory starting
and warm-up at the lowest temperature expected, and low levels of volatile components
protect against vapor-lock in high temperature climates.
[0003] Generally current gasolines exhibit high levels of volatiles measured in terms of
Reid Vapor Pressure. Reid Vapor Pressure is the accepted measurement of gasoline volatility
and it represents the vapor pressure at 100°F (37.78°C). Current fuels require a relatively
high amount of volatile components which raises the Reid Vapor Pressure to undesirable
levels. It is highly desirable to formulate a fuel which satisfies the volatility
requirements without raising the Reid Vapor Pressure to the undesirable level found
in the prior art fuels.
[0004] The use of these volatiles in prior art fuels is associated with several problems.
One such problem is that because present day engines depend on the volatiles, the
spontaneous loss of them in storage results in a fuel which is of inferior quality
after a period of storage. Thus, because of varying storage times, the consumer can
never be certain if the gas he is purchasing contains the required amount of volatiles
at the time of purchase. Naturally, therefore, a fuel whose efficiency and dependability
is less dependent on the presence of volatiles is more desirable.
[0005] Another problem arising out of the use of these volatiles is the evaporative loss
of gasoline which can occur in the gas tank. Industry has been hard pressed to solve
this problem for quite some time. While this problem has been recognized for some
time, industry has always been reluctant to solve the problem by reducing the volatility
of the gasoline because in doing so they would lose the benefits of the compromise
(
i.e., engine performance). In fact, this point has been expressed in the publication titled
Effects of Automotive Emission Requirements on Gasoline Requirements; Symposium, American Society for Testing and Materials; 1971. Here it is stated on
page 111 that "Severe volatility reduction could produce other problems. A more effective
method than volatility reduction can be seen to be the elimination of evaporative
losses by some mechanical device". This invention, however, seeks to reduce volatility
or Reid Vapor Pressure and still maintain a fuel which can perform well.
[0006] Present day gasoline also contains, in addition to the volatile light-weight and
the intermediate-weight components, a heavy-weight component which, like the volatile
component, is also associated with several disadvantages. For example, the gasoline
of today, when used as a fuel in present day short stroke engines, results in incomplete
combustion because there is insufficient tine or temperature to burn the heavy hydrocarbon
components. This results in a certain amount of gasoline being wasted and this contributes
to pollution. Conventional C
4-C
12 has too much energy in it for conventional internal combustion engines in that if
combusted with enough air (stoichiometric or slightly above) it will burn too hot
for the engine or it will produce high levels of nitrous oxides. Yet, in spite of
these shortcomings, the heavy components are left in present day fuel because their
presence is considered necessary to provide a fuel having suitable properties for
automotive use.
[0007] The presence of these heavy components in conventional C
4-C
12 gasoline requires considerable front end priming with light components (C
4 and/or C
5) to achieve adequate front end volatility for starting engines equipped with standard
carburetion systems. In addition, conventional C
4-C
12 gasoline which contains these heavy components (C
11 and C
12) cannot be easily gasified and maintained in the gaseous state without recondensing.
Consequently, conventional C
4-C
12 gasoline has limited utility in a more efficient carburetion system of the type which
requires gasification in the absence of air before mixing the gasified fuel with air
for combustion. Therefore, in view of the shortcomings associated with the heavy weight
hydrocarbons, especially C
11 and C
12, it would be highly desirable to formulate a fuel without these heavy components
being present while also avoiding the problems associated with the absence of these
components.
[0008] The problems associated with volatile and heavy-weight components are also outlined
in "Le Pétrole, Raffinage et Génie Chimique, Tome I, p. 19-27 (1972)", where it is
stated, that a fuel should contain hydrocarbons in the range from C
4 to C
10, and should have a Reid Vapor pressure of not more than 800 g/cm
2 in winter and not more than 650 2/cm
2 in summer. It is, however, not teached to completely eliminate heavy-weight hydrocarbons,
but to reduce their content much, that a residue of not more than 3 % remains at 250°C.
"Erdöl-Lexikon, 5th edition, p. 206", provides the information that paraffins having
from 5 to 10 carbon atoms are present in fuel for Otto engines.
[0009] The use of conventional C
4-C
12 fuels in standard carbureted internal combustion engines requires that the volatility
of the fuel be adjusted to achieve a Reid Vapor Pressure of at least 9 in the summer
and 12 in the winter. If the Reid Vapor Pressure of conventional C
4-C
12 gasoline falls below the above limits, starting and running the engine is severely
impaired. The fuels of the present invention will easily start and operate identical
engines yet these fuels have a reduced Reid Vapor Pressure in comparison to the above-mention
conventional C
4-C
12 gasoline. Thus the summer fuels of the present invention may have a Reid Vapor Pressure
less than 9 and the winter fuels may have a Reid Vapor Pressure of less than 12. In
particular, it is been discovered that the fuel of the present invention having a
Reid Vapor Pressure as low as 6 in the summer and 9 in the winter will easily start
and operate identical engines which require conventional fuels having a Reid Vapor
Pressure of 9 in the summer and 12 in the winter. The Reid Vapor Pressures can be
reduced even further by using the fuels of the present invention in combination with
the improved carburetion system of the present invention.
[0010] The ideal combustion mixture for internal combustion engines consists of a fuel in
the vapor or gaseous state thoroughly mixed with adequate air to support combustion.
In this condition, fuel-rich pockets, which are responsible for detonation or "knock,"
are eliminated and carbon deposits responsible for preignition are minimized due to
more complete combustion. Because detonation or preignition can damage or ruin an
engine, current gasolines have octane boosters such as aromatics contained therein
to reduce "knock" since current engines have fuel and air intake systems which produce
droplets of fuel that contribute to fuel rich pockets in the combustion chambers of
the engines. Slowing the burn with octane boosters lowers the combustion efficiency
of the engine and increases the exhaust pollution. Therefore, it would be highly desirable
to provide a fuel which avoids octane boosters, is rated at a lower octane value but
which has highly desirable burning characteristics so that the fuel does not produce
engine knock.
[0011] Automotive and aviation gasolines have always had an ASTM average octane number (
R+M/
2) of 80 or higher; wherein R represents the research octane number and M represents
the motor octane number. Current engines generally require an average octane number
in excess of 85.
SUMMARY OF THE INVENTION
[0012] A primary object of this invention is to provide an improved fuel which facilitates
the achievement of ideal combustion mixtures for internal combustion engines.
[0013] Another object of this invention is to provide a lower octane fuel and method of
use so as to further improve the combustion efficiency of the fuel in an internal
combustion engine.
[0014] A further object of this invention is to provide a method of operating an internal
combustion engine whereby greater combustion efficiencies can be achieved in the engine.
[0015] It is an object of this invention to provide a fuel for automotive engines which
minimizes the requirement for volatile components in the fuel without sacrificing
adequate engine performance and which lowers the Reid Vapor Pressure while maintaining
good front end volatility.
[0016] It is also an object of this invention to provide a fuel having a low Reid Vapor
Pressure which combusts more efficiently than conventional gasoline of the type having
a hydrocarbon range of C
4-C
12.
[0017] It is another object of this invention to provide a fuel which has greater tolerance
for alcohol enrichment because of low Reid Vapor Pressure.
[0018] It is yet another object of this invention to provide a fuel which minimizes the
priming needed to achieve adequate front end volatility for starting engines equipped
with standard carburetion systems.
[0019] It is a further object of this invention to provide an improved fuel which has enhanced
gasification characteristics in improved carburetion systems.
[0020] It is another object of this invention to provide an improved process for more completely
combusting the fuel of this invention in an engine thus negating the need for fuel
injection systems or catalytic converters.
[0021] These and other objects of the invention will become apparent to those skilled in
the art from the following disclosure of the invention.
[0022] The objects of the present invention are achieved by the fuel claimed in claim 3,
which can be produced by the method claimed in claim 1, and the method of operating
an internal combustion engine claimed in claim 9. The respective dependent claims
relate to preferred embodiments of the invention.
[0023] Subject matter of the present invention are the methods and the fuel as defined in
the claims. In particular, the hydrocarbon mixture of the fuel of the present invention
is limited to hydrocarbons within the range C
6-C
10. Where C
4 and/or C
5 hydrocarbons are additionally present in the fuel of the present invention, they
are a priming agent, said priming agent being present in a minimum effective amount
for raising the front end volatility of the fuel to a minimum level for cold engine
starting with said minimum effective amount being less than that required for C
4-C
12 gasoline.
[0024] The present invention is based on the discovery that front-end priming of fuel is
not necessary in gasifier type carburetors and that the heavier components in gasoline
are not stable as gases in air using gasifier type carburetors. Therefore it was possible
to develop a new fuel that has unique benefits not obtained in C
4-C
12 gasoline. In addition the new gasification method has distinct advantages over the
prior art.
[0025] The invention relates to a fuel having an intermediate hydrocarbon range relative
to conventional C
4-C
12 gasoline which contains C
4, C
5, C
6, C
7, C
8, C
10, C
11 and C
12 hydrocarbons. This fuel of the invention is made by removing the lighter volatile
component as well as the heavier component from a conventional gasoline starting material.
The resulting fuel is C
6-C
10; i.e. the hydrocarbons are limited to those in the range C
6-C
10. Also, it may be desirable to further remove the C
10 component to form a C
6-C
9 fuel for improved winter performance in gasifier type carburetors.
[0026] Suitable starting material to produce the fuel of this invention is conventional
gasoline having a range of C
4-C
12. Both the heavy and light components are removed by any of the known methods currently
available such as heat fractionization or the use of heat and vacuum in the absence
of air. Once removed, the heavy component may be "cracked" at the refinery to make
more fuel and the volatile component, most of which is being wasted today, may be
fully recovered at the refinery.
[0027] Although gasoline having a range of C
4-C
12 is mentioned as a useful starting material, it is not critical that the starting
material be precisely in this range. Rather, it is the essence of this invention to
produce a fuel of intermediate carbon range (i.e. C
6-C
10 or C
6 to C
9) relative to the given range C
4-C
12 that may be produced directly from refinery hydrocarbon streams.
[0028] It will be apparent, of course, that the C
6-C
10 and C
6-C
9 fuels of the invention cannot be used efficiently in conventional internal combustion
engines without modification of the carburetion system. It has been found, however,
that the fuel of this invention can be quickly volatilized in a heated chamber by
heating to a temperature above the final boiling point of the fuel at one atmosphere
pressure in the absence of air, and such apparatus can be readily installed in an
automobile. The resulting vapor (produced as needed) will mix readily with air to
form a homogenous mixture without formation of condensed droplets which can wet the
wall in an internal combustion engine; will not be subject to liquid phase oxidation
prior to ignition; and will ignite well in the gaseous form.
[0029] Since not all the C
6-C
10 and C
6-C
9 fuel can be used efficiently in a conventional internal combustion engine without
modification of the carburetion system, the present invention also provides an improved
fuel for use in cars having standard carburetion systems. In connection with this,
it has been discovered that the above described C
6-C
10 and C
6-C
9 fuel can be used in an internal combustion engine having a standard carburetion system
by priming the fuel with a minimum amount of C
4,C
5 or a mixture of C
4 and C
5 to produce a fuel having adequate front end volatility for starting cars equipped
with standard carburetion systems. Since the fuel may be primed with C
4 and/or C
5 , then the permissible range of the primed fuel will be C
4-C
9 (winter) and C
4-C
10 (summer). In particular, it has been discovered that the amount of C
4 or C
5 priming necessary for achieving adequate front end volatility for starting engines
equipped with a standard carburetion system is less than the amount required with
conventional C
4-C
12 gasoline. Thus, this aspect of the invention provides an improved fuel for standard
carbureted engines and this fuel advantageously contains less C
4 or C
5 than conventional C
4-C
12 gasoline while maintaining adequate front end volatility and reduced Reid Vapor Pressures.
In other words, the C
6-C
10 and C
6-C
9 fuel requires less priming to achieve adequate front end volatility for starting
engines equipped with standard carburetion systems than does normal C
4-C
12 automotive gasoline. This represents a unique and unexpected method of achieving
lower Reid Vapor Pressure in automotive fuel while maintaining adequate-front end
volatility since one would assume that lighter fuel (C
4-C
9 and C
4-C
10) would have higher Reid Vapor Pressure than heavier C
4-C
12 gasoline.
[0030] The amount of C
4, C
5 or mixture of C
4 and C
5 used to prime the C
6-C
10 or C
6-C
9 fuel is a minimum effective priming amount necessary to achieve adequate front end
volatility for starting a car equipped with a standard carburetor, the priming amount
being less than that required for C
4-C
12 gasoline.
[0031] The C
6-C
10 and C
6-C
9 fuel, primed with C
4 and/or C
5, can also be made by removing the heavy and light components from gasoline as described
above for making C
6-C
10 and C
6-C
9 with the exception that a minimum effective priming amount of C
4 and/or C
5 is retained in the product to achieve adequate front end volatility for starting
a car equipped with a standard carburetor, the priming amount being less than that
required for C
4-C
12 gasoline.
[0032] It has also been discovered that adequate front end volatility for engines equipped
with standard carburetion can be achieved by priming with additional C
5 so that adequate front end volatility can be achieved without any C
4 priming, the priming amount being less than that required for C
4-C
12 gasoline.
[0033] Prior art aviation gasoline having a carbon range of C
4 to C
9 would not require the removal of higher molecular weight constituents to be stable
as a vapor or gas in ambient air but the use of such prior art fuels would require
the lowering of the octane to increase the speed of burn, thus improving combustion
efficiency and lowering the pollutants produced during combustion.
[0034] Since the temperature of intake air used in an engine can vary widely because of
seasonable variations or altitudes, the amount of heavy molecules removed can vary,
with molecules heavier than C
10 being completely removed. Preheated intake air systems could utilize more of the
energy contained in the dense heavier molecules but this would result in too much
loss in volumetric efficiency caused by the preheating or preexpansion of the intake
air.
[0035] The conversion of the fuels of this invention into vapors or gasses, homogenizing
these vapors or gasses with intake air (ambient or heated) while maintaining gas or
vapor stability and combusting this fuel mixture in an engine represents an improved
method for achieving higher combustion efficiency while lowering the pollutants of
combustion.
Brief Description of the Drawings
[0036] Figure 1 is a graph which illustrates the fuel efficiency of selected fuels in a
1500 c.c. Volkswagon engine at various engine speeds. The vertical axis shows the
efficiency in term of lbs. of fuel/horsepower hour. The horizontal axis measures the
engine speed. Figure 1 also illustrates the fuel efficiency of the C
5-primed fuel of this invention combusted in an identical engine equipped with the
improved carburetor of this invention.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
[0037] In the manufacture of the fuel in accordance with the present invention, both the
lighter volatile component and the heavier, slow-burning component are removed from
gasoline in the C
4-C
12 range. The removal of the volatile component makes the resultant fuel have a slower
rate of burning. By also removing the heavy slow-burning component, the resultant
fuel is a C
6-C
10 or C
6-C
9 fuel having a burn rate comparable to or better than the starting stock gasoline
(C
4-C
12) from which it was made.
[0038] The most abundant of the volatile components in conventional C
4-C
12 gasoline is butane and pentane. With regard to the removal of the volatile components
it is primarily the butane and pentane which is removed from the C
4-C
12 gasoline in the practice of this invention. If the gasoline contains hydrocarbons
lighter than butane, they are removed, too. The heavy, slow-burning component consists
primarily of C
11 and C
12, each of which exists in numerous isomeric forms. These are removed and, if the starting
stock gasoline contains hydrocarbons greater than C
12, they are also removed. The light volatile components and the heavy, slow-burning
components are removed according to conventional known methods.
[0039] It is also recognized that the heavy and light components do not exist as absolutes
but rather, as points on a continuum with the most volatile being the lighter hydrocarbons,
and a gradual reduction in volatility and burning tendency as the weight is increased.
This gives rise to certain "border line" components near both ends of the continuum.
It is inevitable that some of these will be removed with the heavier and the lighter
components. In general, it is recognized that the border line weights are C
6 and C
10. According to this invention, a substantial quantity of volatile component, namely
hydrocarbons up to 5 carbon atoms, is removed to effectively reduce the potential
for explosion and minimize the loss of gasoline due to evaporation. Likewise, the
heavy component, namely hydrocarbons having more than more than 10 carbon atoms, is
also removed to raise the burn rate of the fuel and effect more complete combustion.
Both of these components are removed and this fuel is used with an improvement in
fuel combustion efficiency and engine performance.
[0040] This improvement is illustrated in Figure 1. It will be noted that Figure 1 shows
a comparison which measures the efficiency of the fuel of the present invention primed
with C
5 versus the efficiency of conventional C
4-C
12 prior art fuels at various engine speeds. The fuel efficiency is measured in terms
of Brake Specific Fuel Consumption (lbs. of fuel per horsepower hour). Lower Brake
Specific Fuel Consumption values indicate better fuel efficiency.
[0041] The C
6-C
10 fuel of this invention may be used to run an engine equipped with the improved gasifier
carburetor described herein. However, it is not necessary that volatile components
be absent from the fuels used in the improved gasifier combustors since their presence
in the fuel does not hinder the gasification process. Thus, some volatile C
4 and/or C
5 may be added to the C
6-C
10 fuel as a primer, the priming amount being less than that required for C
4-C
12 gasoline, so that the fuel can be used in a standard carbureted engine as well as
an engine equipped with the improved gasifier carburetor. For this reason the comparison
presented in Figure 1 utilized the C
6-C
10 fuel of the invention containing some C
5 volatile component as a primer, the priming amount being less than that required
for C
4-C
12 gasoline, so that the resulting C
5-C
10 fuel will run an engine equipped with an improved gasifier carburetor as well as
a standard carbureted engine. The C
5-C
10 has a boiling point range of about 49°F-345°F (9.4 to 174°C).
[0042] In order to obtain the data shown in Figure 1, identical engines were used to compare
conventional C
4-C
12 unleaded gasoline (line A) with the C
6-C
10 fuel of this invention, primed with C
5 (line B). An identical engine was used to test the use of the C
6-C
10 fuel of this invention, primed with C
5, in an improved carburetion system of the present invention (line C). It will be
noted by comparing line A with line B that at all engine speeds, more pounds of fuel
are required per horsepower hour for the C
4-C
12 gasoline than for the C
6-C
10 fuel of the present invention, primed with C
5. Therefore, the C
5-C
10, primed with C
5, is significantly more efficient when combusted in identical engines. It will also
be noted from Figure 1 that an even greater efficiency is observed when the C
6-C
10 fuel primed with C
5, is combusted in an identical engine equipped with the improved carburetion system
of the present invention.
[0043] In a preferred embodiment of this invention, the C
4-C
12 gasoline is used as a starting ingredient from which the volatile C
4 and C
5 constituents and the heavy C
11 and C
12 components are removed. In the preferred embodiment the starting C
4-C
12 gasoline contains a mixture of each of the hydrocarbons (
i.e., a mixture containing C
4, C
5, C
6, C
7, C
8, C
9, C
10, C
11 and C
12). Consequently, the C
6-C
9 and C
6-C
10 fuel of the preferred embodiment will likewise contain the same intermediate hydrocarbons
which are present in the starting gasoline. In other words, C
6-C
9 will contain, C
6, C
7, C
8, and C
9 and the C
6-C
10 fuel will contain, C
6, C
7, C
8, C
9 and C
10 hydrocarbons.
[0044] The fuels of the present invention have an intermediate hydrocarbon range relative
to conventional gasoline which has a hydrocarbon range of C
4-C
12. The conventional C
4-C
12 gasoline contains paraffinic hydrocarbons including C
4, C
5, C
6, C
7, C
8, C
9, C
10, C
11 and C
12 paraffinic hydrocarbons. Thus removing the C
4, C
5, C
11 and C
12 paraffinic components of the C
4-C
12 fuel will result in a fuel which contains paraffinic hydrocarbons, including paraffinic
C
9 and C
10 which were originally present in the C
4-C
12 paraffinic fuel from which the fuel of this invention is derived.
[0045] In one embodiment of the present invention the light and heavy components are removed
from conventional C
4-C
12 gasoline to produce a fuel having a hydrocarbon range of C
5-C
10, with C
5 being a priming agent as defined in claim 4. Such a fuel is identical to the C
6-C
10 fuel with the exception of the presence of the C
5 priming component in the C
5-C
10 fuel. Thus the C
5-C
10 fuel will have a boiling point range of about 49°F-345°F (9.45 to 174°C).
[0046] Although the starting gasoline preferably contains the entire range of hydrocarbons
from C
4-C
12 as described above, it is not absolutely essential that all of the intermediate hydrocarbons
be present in the starting gasoline. However, it is critical that the C
6-C
9 fuel contains C
9 hydrocarbon and the C
6-C
10 fuel contain C
9 and C
10 hydrocarbon.
[0047] The preferred C
6-C
10 fuel may be defined as the portion remaining when C
4-C
12 gasoline has removed therefrom lower weight volatile components (up to C
5) to substantially reduce evaporative loss and explosion potential and higher weight
components (C
11 and higher) to raise the burn rate of the remaining hydrocarbons. The C
6-C
10 fuel which has these characteristics can be made by removing the volatile and heavy
components so that the remaining hydrocarbon mixture will boil within a range of about
121°F-345°F (49.4 to 174°C) at one atmosphere. Such a boiling point range encompasses
the boiling point of the lowest boiling C
6 component and the highest boiling C
10 component. Of course, it is possible that a small amount of C
4, C
5 , C
11 and C
12 may remain after the separation process due to imperfections of gasoline fractionation
procedures.
[0048] Since the largest hydrocarbon in the C
6-C
10 fuel is C
10, then the final boiling point of such a mixture will be 345°F (174°C). It has been
discovered that hydrocarbons having boiling points above 350°F (177°C) must be substantially
eliminated so that the fuel can be gasified in a heated chamber in the absence of
air, and then mixed with ambient air (
i.e., about 70°F or 21°C) without condensing to form droplets of heavy hydrocarbons which
could wet the surfaces in an internal combustion engine. This property is an essential
aspect of the C
6-C
10 fuel because the C
6-C
10 fuel is used in a modified carburetion system in which the fuel is gasified in a
heated chamber and then mixed with air for immediate combustion in an automotive internal
combustion engine. The absence of condensed droplets allows the fuel to burn much
more efficiently than conventional C
4-C
12 gasoline and, consequently, reduces pollution and improves engine performance. By
removing C
11 and C
12 components from the starting stock gasoline, the final boiling point will be 345°F
(174°C) and, thus, the resulting fuel will have the desired gasification property.
[0049] The gasification system used for the C
6-C
10 fuel of the present invention requires heating the fuel to lower temperatures that
would be required for the gasification of C
4-C
12 gasoline. When lower temperatures are attained, the volumetric efficiency of the
air and gas mixture going into an engine is improved.
[0050] The fuel having hydrocarbons comprised of C
6-C
10 hydrocarbons will have lower Reid Vapor Pressure than conventional C
4-C
12 gasoline with functional Reid Vapor Pressures less than two. Nonetheless, the C
6-C
10 fuel will exhibit good ignition properties in the gaseous state when mixed with air.
It will also provide excellent engine starting ability, will have reduced explosive
potential and will burn more completely than C
4-C
12 gasoline. In addition, the C
6-C
10 fuel will burn cooler in the engine with the modified carburetor and consequently
the use of such a fuel will result in less lubrication requirements for the engine.
[0051] Conventional C
4-C
12 gasoline has high Reid Vapor Pressure and the Reid Vapor Pressure can be adjusted
somewhat to provide summer or winter fuels. For example, the Reid Vapor Pressure can
be increased by adding volatiles such as C
4 to enhance the winter performance of the conventional gasoline. However, the present
C
6-C
10 fuel of the invention requires lowering the Reid Vapor Pressure by removing the C
4 and C
5 components. Thus it would be expected that ability to formulate winter and summer
fuels would be lost if the hydrocarbon range is limited to C
6-C
10 hydrocarbons. It is therefore surprising that the C
6-C
10 fuel can be formulated for winter use without additional C
4 priming. It has been discovered that a winter fuel can be made in the same manner
as the C
6-C
10 summer fuel with the exception being that the C
10 component is additionally separated from the starting C
4-C
12 gasoline along with the C
4, C
5, C
11 and C
12 components to provide a fuel that when gasified will remain substantially a gas when
mixed with colder air. Thus, the present invention also provides a winter fuel having
hydrocarbons which consists of hydrocarbons in the range C
6-C
9. The C
6-C
9 winter fuel differs from the C
6-C
10 fuel only in the elimination of the C
10 component which is left in the C
6-C
10 summer fuel. Consequently, the winter C
6-C
9 fuel has a final boiling point of 303°F (151°C) and a boiling range of about 121°F-303°F
(49 to 151°C).
[0052] The C
6-C
9 fuel must contain the C
9 hydrocarbon component and preferably should contain the remaining intermediate hydrocarbons
which are C
6, C
7, and C
8 since these are preferably present in the C
4-C
12 gasoline. The C
6-C
9 winter fuel is burned in an engine in the same manner described above with respect
to the C
6-C
10 fuel and enjoys the same benefits described above with respect to the C
6-C
10 fuel.
[0053] The C
6-C
10 and C
6-C
9 fuel is gasified by heating in a chamber in the absence of air to a temperature above
the final boiling point of the fuel. The C
6-C
10 and C
6-C
9 fuels are preferably heated to a temperature 350°F (177°C). Higher temperatures may
be used but are not necessary. Conventional C
4-C
12 would require a temperature of about 75°F (24°C) higher to gasify and when mixed
with air it would still have the problem of forming condensation droplets. Additionally,
the higher temperature would lower the volumetric efficiency of the engine.
[0054] It has been emphasized that C
9 and C
10 must be present in the C
6-C
10 fuel and C
9 must be present in the C
6-C
9 fuel because heavy molecular components have the highest energy density. Since these
are the highest density components capable of being gasified and remaining a gas when
mixed with air, it is important that they remain in the fuel for production of engine
power.
[0055] It has also been discovered that the C
6-C
10 and the C
6-C
9 fuels can be adapted for use in engines having standard carburetion (
i.e., carburetors which do not require gasification in a heated chamber in the absence
of air). In particular, it has been discovered that priming the C
6-C
9 and the C
4-C
10 fuel with a small amount of a volatile component, i.e. a priming agent, will result
in the production of an improved fuel which may be used in automobiles equipped with
standard carburetion. The priming agent may be C
4, C
5, or a mixture of C
4 and C
5. Consequently the primed fuel will have hydrocarbons which consists of hydrocarbons
in the range C
4-C
10 (summer) and C
4-C
9 (winter). The C
4-C
9 and C
4-C
10 fuel is the same as the analogous C
6-C
9 and C
6-C
10 fuel except for the presence of a small amount of priming agent in both the C
4-C
9 and C
4-C
10 fuel, said small amount being the minimum effective amount for raising the front
end volatility of the fuel to a minimum level for cold engine starting with said minimum
effective amount being less than that required for C
4-C
12 gasoline.
[0056] In both the winter and summer fuel, the amount of priming agent is the minimum amount
effective to raise the front end volatility so that the fuel can be used in cars equipped
with standard carburetion. Thus the C
4-C
9 (primed with C
6-C
9) is particularly suitable for winter use and the C
4-C
10 (primed with C
6-C
10) is particularly suitable for summer use in cars equipped with standard carburetors.
It is particularly significant and surprising that the amount of C
4 or C
5 in the C
4-C
9 (primed C
6-C
9) and C
4-C
10 (primed C
6-C
10) fuel is less than the amount of C
4 or C
5 in conventional C
4-C
12 gasoline without sacrificing any of the desirable properties of the gasoline. It
is also surprising that the C
4-C
9 and C
4-C
10 fuels have adequate front end volatility yet are lower in Reid Vapor Pressure than
conventional C
4-C
12 gasoline. It is believed that this is because removal of C
11 and C
12 from C
4-C
12 gasoline means that the remaining fuel will have a higher percentage of C
4, C
5, and C
6 hydrocarbons. therefore much of the C
4 and some of the C
5 hydrocarbons can be removed from the C
4-C
10 and C
4-C
9 fuel to obtain a functionally equivalent front end volatility in comparison to the
original C
4-C
12 gasoline. This reduces the Reid Vapor Pressure.
[0057] The fuel of this invention may also contain any of the various additives presently
in use or known to be useful in gasoline. In fact, because this invention produces
a fuel having a low Reid Vapor Pressure, as compared to normal automotive gasoline,
it is possible to add large amounts of alcohol such as ethanol to the fuel of this
invention without raising the Reid Vapor Pressure above the current allowable limits.
Alcohol addition to conventional gasoline is known to raise the Reid Vapor Pressure
above the allowable limits. Additions of alcohol can be added to the fuels of this
invention in an amount of 10-20 per cent by weight without exceeding current Reid
Vapor Pressure standards.
[0058] It is also possible to add lubricants or anti-knock compounds to the fuel. For example,
a suspension of fine synthetic upper end lubricants or small amounts of anti-knock
compounds may be added the fuel of this invention.
[0059] It has also been surprisingly discovered that the fuels of this invention when gasified
burn almost completely in the engine producing equivalent torques with less fuel and
at temperatures which are lower than the temperatures achieved when combusting conventional
fuels in engines equipped with standard carburetion systems. This is true at stoichiometric
or slightly higher air-to-fuel ratios which would normally result in the development
of excessive engine temperature. Therefore, combusting the fuel of this invention
produces less nitrous oxide and allows some increase in compression or supercharging
without damage to the engine and without environmental contamination.
[0060] The fuel of this invention is a C
6-C
10 hydrocarbon fuel and naturally exists in the liquid state at standard temperature
and pressure. Thus the fuel can be shipped, stored and dispensed like conventional
gasoline and requires no further processing for use.
[0061] It has also been discovered that the fuels of this invention burn cooler than conventional
C
4-C
12 fuel. For this reason it may be advantageous to add an oxygen source to the fuel
to obtain more complete combustion. The oxygen source raises the combustion temperature.
However, due to the fact that the fuels of the present invention burn cooler than
conventional C
4-C
12 gasoline, the elevated combustion temperature can be tolerated in automobile engines.
Thus, an oxygenate compound may be added to the fuels of the present invention to
raise combustion temperatures or to effect more complete combustion. Many suitable
oxygen source may be used. Typical oxygen sources include oxygenated hydrocarbons
such as 1, 2 butylene oxide.
Example 1
[0062] C
5-C
10 fuel was made by removing the hydrocarbons lighter than C
5 and the hydrocarbons heavier than C
10 from a conventional C
4-C
12 gasoline. The C
4-C
12 gasoline which served as the starting ingredient contains C
5, C
6, C
7, C
8, C
9, and C
10 hydrocarbons in addition to the heavy and light hydrocarbons which were removed therefrom.
The resulting C
5-C
10 fuel therefore contains C
5, C
6, C
7, C
8, C
9, C
10 hydrocarbons. The C
5-C
10 fuel had a Reid Vapor Pressure of 6. The fuel was used to start and run a standard
carbureted Volkswagon engine. Measurements of fuel efficiency were taken and the results
are shown in Table I, (line B). During the test it was noted that the standard carbureted
engines started and ran easily even though the fuel had a Reid Vapor Pressure of only
6.
Example 2
[0063] For the purpose of comparison, the C
4-C
12 gasoline described in example 1 was used to start and run a Volkswagon engine which
was identical to the engine used for testing the C
5-C
10 fuel in example 1. The C
4-C
12 gasoline had a Reid Vapor Pressure of 10. The efficiency of the C
4-C
12 gasoline was measured and the results are shown in Figure 1 (line A).
Example 3
[0064] The C
5-C
10 fuel used in example 1 was also tested in an engine identical to the engine used
in example 1 with the exception that the engine used in example 3 was equipped with
an improved carburetion system of the present invention. The fuel efficiency was measured
and the results are shown in Table I (line C). During the test it was noted that the
C
5-C
10 fuel easily started and ran the engine equipped with the improved carburetor even
though the fuel had a Reid Vapor Pressure of only 6.