U.S. patent application number 09/901171 was filed with the patent office on 2002-01-17 for high octane unleaded aviation gasolines.
This patent application is currently assigned to Texaco Inc.. Invention is credited to Campbell, Teddy G., Dorn, Peter, Liiva, Peter M., Studzinski, William M., Valentine, Joseph N..
Application Number | 20020005008 09/901171 |
Document ID | / |
Family ID | 26691314 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020005008 |
Kind Code |
A1 |
Studzinski, William M. ; et
al. |
January 17, 2002 |
High octane unleaded aviation gasolines
Abstract
Novel aviation fuel compositions contain a substantially
positive or synergistic combination of an alkyl tertiary butyl
ether, an aromatic amine and, optionally, a manganese component.
The basefuel containing the additive combination may be a wide
boiling range alkylate basefuel.
Inventors: |
Studzinski, William M.;
(Wappingers Falls, NY) ; Valentine, Joseph N.;
(Newburgh, NY) ; Dorn, Peter; (Lagrangeville,
NY) ; Campbell, Teddy G.; (Brookfield, CT) ;
Liiva, Peter M.; (Greenwich, CT) |
Correspondence
Address: |
Janelle D. Waack
HOWREY SIMON ARNOLD & WHITE, LLP
750 Bering Drive
Houston
TX
77057-2198
US
|
Assignee: |
Texaco Inc.
|
Family ID: |
26691314 |
Appl. No.: |
09/901171 |
Filed: |
July 9, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09901171 |
Jul 9, 2001 |
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09217473 |
Dec 21, 1998 |
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6258134 |
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09217473 |
Dec 21, 1998 |
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08856019 |
May 14, 1997 |
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5851241 |
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60018624 |
May 24, 1996 |
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Current U.S.
Class: |
44/412 ;
44/449 |
Current CPC
Class: |
C10L 1/1852 20130101;
C10L 1/14 20130101; C10L 1/305 20130101; C10L 1/223 20130101; C10L
10/10 20130101; C10L 1/00 20130101 |
Class at
Publication: |
44/412 ;
44/449 |
International
Class: |
C10L 001/18; C10L
001/22 |
Claims
What is claimed is:
1. An unleaded aviation fuel composition comprising: (1) an
unleaded basefuel and (2) a substantially positive or synergistic
combination of (a) an alkyl tertiary butyl ether, and (b) an
aromatic amine having the formula 2wherein R.sub.1, R.sub.2,
R.sub.3 and R.sub.4 are hydrogen or a C.sub.1-C.sub.5 alkyl
group.
2. The composition of claim 1, wherein the basefuel is a wide
boiling range alkylate.
3. The composition of claim 1, wherein the alkyl tertiary butyl
ether is methyl tertiary butyl ether.
4. The composition of claim 1, wherein the alkyl tertiary butyl
ether is ethyl tertiary butyl ether.
5. The composition of claim 1, wherein the aromatic amine is
analine.
6. The composition of claim 1, wherein R.sub.1, R.sub.2, R.sub.3 or
R.sub.4 is methyl.
7. The composition of claim 1, wherein the aromatic amine is
n-methyl aniline, n-ethyl aniline, m-toluidine, p-toluidine,
3,5-dimethyl aniline, 4-ethyl aniline or 4-n-butyl aniline.
8. The composition of claim 1, wherein the composition further
comprises manganese.
9. The composition of claim 8, wherein the manganese is provided by
methyl cyclopentadienyl manganese tricarbonyl.
10. The composition of claim 1, wherein the composition comprises
0.1 to 40 vol % alkyl tertiary butyl ether, 0.1 to 10 wt % aromatic
amine and 0 to 0.5 g manganese.
11. The composition of claim 1, wherein the composition comprises
15 to 32 vol % methyl tertiary butyl ether, 1. 5 to 6 wt % aniline
and 0 to 0.1 g manganese.
12. The composition of claim 1, wherein the composition comprises
15 to 32 vol % ethyl tortiary butyl ether, 1.5 to 6 wt % aniline
and 0 to 0.1 g managanese.
13. The composition of claim 1, wherein the MON of the composition
is at least 94.
14. The composition of claim 1, wherein the MON of the composition
is at least 96.
15. The composition of claim 1, wherein the MON of the composition
is at least 98.
16. A method for preparing an unleaded aviation fuel composition
comprising: (1) selecting a substantially positive or synergistic
combination of (a) an alkyl tertiary butyl ether, and (b) an
aromatic amine having the formula 3wherein R.sub.1, R.sub.2,
R.sub.3 and R.sub.4 are hydrogen or a Cl-C.sub.5 alkyl group, and
(2) combining the combination selected in step (1) with an unleaded
basefuel.
17. The method of claim 16, wherein the basefuel is a wide boiling
range alkylate.
18. The method of claim 16, wherein the alkyl tertiary butyl ether
is methyl tertiary butyl ether.
19. The method of claim 16, wherein the alkyl tertiary butyl ether
is ethyl tertiary butyl ether.
20. The method of claim 16, wherein the aromatic amine is
analine.
21. The method of claim 16, wherein R.sub.1, R.sub.2, R.sub.3 or
R.sub.4 is methyl.
22. The method of claim 16, wherein the aromatic amine is n-methyl
aniline, n-ethyl aniline, m-toluidine, p-toluidine, 3,5-dimethyl
aniline, 4-ethyl aniline or 4-n-butyl aniline.
23. The method of claim 16, wherein the composition further
comprises manganese.
24. The method of claim 23, wherein the manganese is provided by
methyl cyclopentadienyl manganese tricarbonyl.
25. The method of claim 16, wherein the composition comprises 0.1
to 40 vol % alkyl tertiary butyl ether, 0.1 to 10 wt % aromatic
amine and 0 to 0.5 g manganese.
26. The method of claim 16, wherein the composition comprises 15 to
32 vol % methyl tertiary butyl ether, 1.5 to 6 wt % aniline and 0
to 0.1 g manganese.
27. The method of claim 16, wherein the composition comprises 15 to
32 vol % ethyl tortiary butyl ether, 1.5 to 6 wt % aniline and 0 to
0.1 g maganese.
28. The method of claim 16, wherein the MON of the composition is
at least 94.
29. The method of claim 16, wherein the MON of the composition is
at least 96.
30. The method of claim 16, wherein the MON of the composition is
at least 98.
31. A method for preparing a composition comprising combining a
wide boiling range alkylate basefuel and a synergistic amount of
all tertiary butyl ether, an aromatic amine and manganese
sufficient to raise the motor octane number of the composition to
at least 94.
32. The method of claim 31, wherein the synergistic amount is
sufficient to raise the motor octane number of the composition to
at least 96.
33. The method of claim 31, wherein the synergistic amount is
sufficient to raise the motor octane number of the composition to
at least 98.
34. A method for operating a piston driven aircraft which comprises
operating the aircraft engine with the aviation fuel composition of
claim 1.
35. A method for operating a piston driven aircraft which comprises
operating the aircraft engine with the aviation fuel composition
made by the method of claim 29.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates generally to aviation gasoline (Avgas)
compositions and methods of making and using such compositions.
More particularly, the present invention concerns high octane Avgas
compositions containing a non-leaded additive package and methods
of making and using such compositions.
[0002] Conventional aviation gasoline (Avgas) generally contains an
aviation alkylate basefuel and a lead-based additive package. The
industry standard Avgas known as 100 Low Lead (100 LL) contains the
lead additive tetraethyllead (TEL) for boosting the anti-knock
property of the Avgas over the inherent anti-knock property of its
aviation alkylate basefuel. Knocking is a condition of
piston-driven aviation engines due to autoignition, the spontaneous
ignition of endgases (gases trapped between the cylinder wall and
the approaching flame front) in an engine cylinder after the
sparkplug fires. A standard test that has been applied to measure
the anti-knock property of lead-based Avgas under various
conditions is the motor octane number (MON) rating test (ASTM
D2700). Another standard test applied to lead-based Avgas is the
supercharge (performance number) rating test (ASTM D909).
[0003] Despite the ability of lead-based Avgas to provide good
anti-knock property under the severe demands of piston-driven
aviation engines, such lead-based compositions are meeting stricter
regulations due to their lead and lead oxide emissions. Current
U.S. regulations set a maximum amount of TEL for aviation fuels at
4.0 ml/gal and concerns for the negative environmental and health
impact of lead and lead oxide emissions may effect further
restrictions.
[0004] Gaughan (PCT/US94/04985, U.S. Pat. No. 5,470,358) refers to
a no-lead Avgas containing an aviation basefuel and an aromatic
amine additive. The Avgas compositions exemplified in Gaughan
reportedly contain an aviation basefuel (e.g., isopentane, alkylate
and toluene) having a MON of 92.6 and an alkyl- or
halogen-substituted phenylamine that boosts the MON to at least
about 98. Gaughan also refers to other non-lead octane boosters
such as benzene, toluene, xylene, methyl tertiary butyl ether,
ethanol, ethyl tertiary butyl ether, methylcyclopentadienyl
manganese tricarbonyl and iron pentacarbonyl, but discourages their
use in combination with an aromatic amine because, according to
Gaughan, such additives are not capable by themselves of boosting
the MON to the 98 level. Gaughan concludes that there is little
economic incentive to combine aromatic amines with such other
additives because they would have only a very slight incremental
effect at the 98 MON level.
[0005] It would be desirable to find alternative Avgas compositions
that avoid the use of lead-based additives and have good
performance in piston-driven aviation engines. It would also be
desirable to find Avgas compositions that could use less expensive
bassefuels.
SUMMARY OF THE INVENTION
[0006] The Avgas compositions of the invention contain a
combination of non-lead additives (also referred to as the
"additive package") including an alkyl tertiary butyl ether and an
aromatic amine. The additive package may further include manganese,
for example, as provided by methyl cyclopentadienyl manganese
tricarbonyl (MMT). In a preferred embodiment, the substantially
positive or synergistic additive package is combined with a wide
boiling range alkylate basefuel. In a further preferred embodiment,
the inventive Avgas composition is an unleaded Avgas having good
performance in a piston-driven aviation engine as determined by one
or more ratings including MON, Supercharge and Knock
Cycles/Intensity at maximum potential knock conditions of an
aviation engine.
[0007] The invention is also directed to a method of making an
unleaded Avgas composition wherein the additive package is combined
with a basefuel, such as a wide boiling range alkylate. The
concentration of the additives in the Avgas may be based on a
non-linear model, wherein the combination of additives has a
substantially positive or synergistic effect on the performance of
the unleaded Avgas composition. The invention is further directed
to a method of improving aviation engine performance by operating a
piston-driven aviation engine with such Avgas compositions.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0008] For purposes of the invention, "Avgas" or "Avgas
composition" refers to an aviation gasoline. In general, an Avgas
is made of a basefuel and one or more additives.
[0009] The compositions according to the invention contain a
combination of additives including an alkyl tertiary butyl ether
and an aromatic amine. The combination may further include a
manganese component that is compatible with the other additives and
the base fuel, for example, as provided by the addition of methyl
cyclopentadienyl manganese tricarbonyl (MMT). The combination of
additives is also referred to as "the additive package."
[0010] The alkyl tertiary butyl ether in the additive package is
preferably a C.sub.1 to C.sub.5 tertiary butyl ether and more
preferably methyl tertiary butyl ether (MTBE) or ethyl tertiary
butyl ether (ETBE). This component of the additive package is also
broadly referred to as the oxygenate.
[0011] The aromatic amine in the additive package is preferably of
the formula: 1
[0012] where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are individually
hydrogen or a C.sub.1-C.sub.5 alkyl group. In a preferred
embodiment, the aromatic amine additive is aniline, n-methyl
aniline, n-ethyl aniline, m-toluidine, p-toluidine, 3,5-dimethyl
aniline, 4-ethyl aniline or 4-n-butyl aniline.
[0013] Methyl cyclopentadienyl manganese tricarbonyl (MMT) may also
be included in the additive package, particularly to provide a
magnesium component to the additive package.
[0014] The inventive Avgas compositions preferably comprise 0.1 to
40 vol % alkyl tertiary butyl ether, 0.1 to 10 wt % aromatic amine
and 0 to 0.5 g manganese. For example, the inventive composition
may comprise 15 to 32 vol % methyl tertiary butyl ether, 1.5 to 6
wt % aniline and 0 to 0.1 g manganese.
[0015] In a preferred embodiment, the additive package has a
substantially positive or synergistic effect in the Avgas
composition to which it is added. For purposes of this
specification, the term "substantially positive," in the context of
the additive package, means that a successive additive that is
added to the Avgas composition substantially boosts the performance
of the Avgas composition. In the case of MON, "substantially
positive" effect means that each successive additive boosts the
Avgas MON, preferably by 0.5, more preferably by 1.0 and most
preferably by 1.5. For example, an Avgas containing a wide boiling
range alkylate having a MON of 91.5 and an additive of 10 wt %
aniline has a MON of 97.6. When that Avgas further contains a 40
vol % ETBE, the Avgas MON is boosted to 101.1. Such a composition
contains a substantially positive combination of additives because
the overall MON of 101.1 is greater than the individual MON levels
of 97.6 (10 wt % aniline) and 96.2 (40 vol % ETBE) and the addition
of 40 vol % ETBE boosted the MON of the basefuel/10 wt % aniline
composition by 3.5.
[0016] For purposes of this specification, the term "synergistic,"
in the context of the additive package, means that the effect of
the combined additives is greater than the sum of the performance
achieved by the individual additives under the same conditions. In
the case of MON, synergistic means that the increase in MON due to
the additive package is greater than the sum of MON increases for
each additive when it is the sole additive in the basefuel.
[0017] These definitions of "substantially positive" and
"synergistic" effect are further understood in view of the numerous
combinations of additives that result only in antagonistic
combinations, wherein the overall MON does not increased or
decreases with the addition of other additives.
[0018] Combining multiple additives into a package that includes an
aromatic amine has been viewed as an undesirable approach to
improve the anti-knock property of an Avgas. (See Background of the
Invention, Gaughan.) As further shown in the following Table 1,
random mixtures of multiple octane boosting additives can result in
antagonistic octane effects.
1TABLE 1 Non-linear Blending Octane Effects (Basefuel is wide
boiling range alkylate.) Blend # ETBE (vol. %) Mn (g/gal) Aniline
(wt. %) MON 1 0 0 10 97.6 2 40 0 0 96.2 3 40 0 10 101.1 4 40 0.5 10
97.9 Legend: ETBE = Ethyl Tertiary Butyl Ether, Mn = Manganese
Concentration*, MON = Motor Octane *as provided by a corresponding
amount of MMT
[0019] As seen in Blend #4, the combination of basefuel/10% wt
aniline/40 vol % ETBE/0.5 g/gal manganese results in an
antagonistic effect wherein the additive package (40 vol % ETBE/0.5
g/gal Mn/10 wt % aniline) does not boost the MON beyond that of the
basefuel to any significant extent. Indeed, this additive package
reduces the MON boosting effect of the basefuel/10% wt aniline/40%
vol ETBE composition.
[0020] In a preferred embodiment, the additive package is combined
with a basefuel containing a wide boiling range alkylate. Under
this embodiment of the invention, an Avgas can be made with a
basefuel not conventionally used for Avgas. Under aviation
standards (ASTM D-910), the basefuel in an Avgas is an aviation
alkylate, which is a specially fractionated hydrocarbon mixture
having a relatively narrow range of boiling points. The inventive
additive package may be added to any suitable basefuel wherein the
resulting combination of additive package and basefuel is suitable
for use as an Avgas, as based on performance characteristics and
ratings and not necessarily on ASTM standards. Such basefuels
include conventional aviation alkylates (e.g. within the
specifications of ASTM-910, including specifications for boiling
points and distillation temperatures) and wide boiling range
basefuels.
[0021] For purposes of this specification, the term "wide boiling
range alkylate" is defined as an alkylate containing components
having a range of boiling points that is substantially wider than
the range of boiling points in an aviation alkylate basefuel.
Preferably, the wide boiling range alkylate contains hydrocarbons
having a range of boiling points up to at least about 350.degree.
F. More preferably, the boiling range is from about 85.degree.
F..+-.10.degree. F. to about 400.degree. F..+-.15.degree. F. (which
essentially corresponds to an automotive gasoline basefuel). The
following Table 2 provides an example of an aviation alkylate and a
wide boiling range alkylate.
2TABLE 2 Comparison of Wide boiling Range Alkylate and Aviation
Alkylate Fuels. Wide boiling range alkylate Wide boiling
Distillation Aviation range Aviation Tests Results Alkylate Tests
alkylate Alkylate IBP* 88.1.degree. F. 97.7.degree. F. API 71.5
73.0 10% 147.9 155.3 RVP 7.6 psi 6.5 psi 20% 179.4 178.5 Paraffins
99.2 vol. % 99.4 vol. % 30% 199.2 195.8 Olefins 0.2 vol. % 0.4 vol.
% 40% 209.8 206.0 Aromatics 0.6 vol. % 0.2 vol. % 50% 216.6 212.1
MON 91.4 93.9 60% 222.4 215.7 RON 93.4 97.1 70% 228.7 218.6
Perf.No. 85.4 97.4 80% 238.6 221.3 90% 262.9 224.9 FBP* 397.2 233.4
Legend: IBP = Initial Boiling Point, EBP = Final Boiling Point, API
= API Gravity, RVP = Reid Vapor Pressure @ 100F, RON = Research
Octane Number, MON = Motor Octane Number, Perf.No. = Performance
Number (ASTM - D909)
[0022] The lower octane of the wide boiling range alkylate compared
to the aviation alkylate is due primarily to lower amounts of
inherently high octane hydrocarbons, isopentane and isooctane, as
well as higher amounts of higher molecular weight, higher boiling
paraffins. Table 3 presents gas chromatographic analyses of the
aviation industry standard 100 Low Lead, which uses aviation
alkylate as the primary base stock (e.g., at least 88% vol) and the
wide boiling range alkylate and demonstrates the lower
concentrations of isopentane and the isooctane isomers in the wide
boiling range alkylate.
3TABLE 3 Comparison of Wide Boiling Range Alkylate and 100 Low Lead
Concentration in Concentration in Wide Boiling Range Alkylate 100
Low Lead (wt %) (wt %) Isopentane 9.26 5.04 2,2,4- 30.93 21.89
trimethylpentane 2,2,3- 1.06 1.40 trimethylpentane 2,3,4- 9.91
10.99 trimethylpentane
[0023] The distillation curve temperatures for the second half of
the wide boiling range alkylate are considerably higher than the
aviation alkylate because of the higher molecular weight paraffinic
hydrocarbons present in the former.
[0024] A common result of having a higher concentration of larger
paraffins, particularly with the straight chain or normal
paraffins, is a lower octane value. The larger paraffin molecules
present in the wide boiling range alkylate typically undergo more
and faster isomerization chemical reaction steps during the low
temperature portion of the oxidation chemistry leading to
auto-ignition. Isomerization steps in paraffin chemistry are very
fast routes to free radical propagation and subsequent
autoignition. The oxidation steps leading to autoignition between
the two alkylate basefuels are different thus requiring different
fuel and additive formulations for optimal performance.
Substituting high octane oxygenates for a substantial proportion of
the alkylate basefuel reduces the number of rapid isomerization
reactions and replaces them with less reactive partial oxidation
intermediates, thereby increasing the octane value of the fuel.
[0025] The preferred embodiment of the invention that uses the wide
boiling range alkylate as a basefuel offers a high quality, high
performance alternative to conventional Avgas. Such wide boiling
range alkylate basefuels offer a greater choice of basestocks for
Avgas formulations and also likely, provide a less expensive
basefuel for Avgas compared to the conventional aviation alkylate
basefuel.
[0026] In a preferred embodiment, the compositions according to the
invention have good performance in piston-driven aviation engines.
Preferably that performance is determined by one or more ratings
including MON, Supercharge and Knock Cycles/Intensity at maximum
potential knocking conditions in an aircraft engine. The inventive
Avgas compositions preferably have a MON of at least about 94, more
preferably at least about 96 and most preferably at least about 98.
Further preferred Avgas compositions have a MON of at least about
99 or more preferably at least about 100. For example, a preferred
MON range may be from about 96 to about 102. The Supercharge rating
is preferably at least about 130. The inventive Avgas compositions
also preferably minimize, or eliminate, knocking in a piston-driven
aircraft engine at maximum potential knocking conditions. The Knock
Cycle rating is preferably less than (average) 50 per 400 cycles
and the Knock Intensity rating is preferably less than 30 per
cycle.
[0027] The invention is also directed to a method for preparing an
Avgas composition that involves combining a basefuel, such as a
wide boiling range alkylate, with an additive package. The content
and concentration of the additive package is preferably selected
from an inventive non-linear model that identifies substantially
positive or synergistic additive packages. The method preferably
identifies Avgas compositions that have good performance in
piston-driven aviation engines based on ratings of MON, Supercharge
and/or Knock Cycles/Intensity.
[0028] The invention is further directed to a method for operating
a piston-driven aircraft that involves operating the piston-driven
engine with an Avgas composition made by a composition according to
the invention.
EXAMPLES
[0029] A. Determination of MON
[0030] The MON rating test (ASTM D2700) is conducted using a single
cylinder variable-compression laboratory engine which has been
calibrated with reference fuels of defined octane levels. The
sample of interest is compared to two reference fuels at standard
knock intensity and the octane number of the sample is determined
by bracketing or compression ratio (c.r.) methods. In bracketing,
the octane value of the sample is determined by interpolating
between two reference fuel octane values. In the c.r. method, the
octane value of the sample is determined by finding the compression
ratio which duplicates the standard knock intensity of a reference
fuel and the octane number is then found in a table of values.
Repeatability limits for MON determination at 95% confidence
intervals is 0.3 MON for 85-90 MON fuels while reproducibility
limits are 0.9 for 85 MON and 1.1 for 90 MON.
[0031] B. Determination of Supercharge Rating
[0032] The Supercharge rating test (ASTM - D909) determines the
knock-limited power, under supercharge rich-mixture conditions, of
fuels for use in spark ignition reciprocating aircraft engines. The
Supercharge rating is an industry standard for testing the severe
octane requirements of piston driven aircraft. For purposes of this
application, "ASTM-D909" is used interchangeably with both
"supercharge rating" and "performance number."
[0033] C. Determination of Knock Cycles and Intensity Rating
[0034] For purposes of this application, "Knock Cycle/Intensity
rating test" and "Lycoming IO-360 tests" are used interchangeably.
The Knock Cycles/Intensity rating test was performed with a Textron
Lycoming 10-360 engine ("the Lycoming engine") on a dynamometer
test stand (See FIG. 1). Each of the four cylinders of the Lycoming
engine was equipped with a Kistler 6061B piezoelectric transducer.
These transducers produce electric charges proportional to the
detected pressures in the combustion chambers in the Lycoming
Engine. The charge was then passed into four Kistler 5010 charge
mode amplifiers which were calibrated so that output voltage from
the amplifiers was equivalent to 20 atmospheres as read by the
detector. The voltage was processed through a National Instruments
NB-A2000 A/D board which reads all four channels simultaneously at
a rate of 250,000 samples per second at a resolution of 12
bits.
[0035] The data acquisition was facilitated by a computer program
(See FIG. 2) using National Instruments' Labview programming
environment. The data acquisition program stores the data from 200
to 400 consecutive firings from the engine which is typically
operated at 2700 rpm, wide open throttle at an equivalence ratio of
about 1.12 and maximum cylinder temperature of just below
500.degree. F. The data is first stored into buffers, then into the
Random Access Memory of a Macintosh 8100/80 Power PC and finally on
the hard drive. The raw data files were then backed up onto
magneto-optical discs and post-processed using a Labview
program.
[0036] Before storage and processing, data from the individual
combustion chamber firings were passed through a Butterworth 4th
order digital bandpass filter of 15 kHz-45 kHz range. This is done
to isolate frequencies which could only be significantly excited
within the combustion chamber by a knocking event. The filtered
signal was then "windowed" for 3 milliseconds near top dead center
of piston travel (compression/expansion stroke). The filtered,
windowed signal was then sent through an absolute-value function
and integrated to obtain a pressure-time-intensity expression of
the acoustic energy supplied to the filter in the 15 kHz-45 kHz
band of frequencies detected by the system. This value was used to
create a scale with which knock intensity was measured. If the
intensity of the integral was found to be greater than 20 on this
scale, it was determined to be a knocking case and the knocking
events per 200 cycles were recorded.
[0037] D. Determination of Non-Linear Models for Identifying
Aviation Fuel Compositions with Desirable MON Ratings
[0038] The effects of various fuel formulations on MON ratings were
determined using statistically designed experiments. More
specifically, the complex relationships between the in-cylinder
oxidation chemistries of the octane boosting additives and the
basefuel were investigated using face centered cube statistical
designs (See, e.g., FIG. 3).
[0039] The statistically designed experiments measured the MON
values of specific fuel formulations which were combinations of
three variables (Manganese level, aromatic amine level duo and
oxygenate level) mixed with a wide boiling range alkylate. The
three variables and their respective concentration ranges define
the x, y and z axes of the cube. (See FIG. 3). The cube faces
(surfaces) and the space within the cube define all the interaction
points for investigation. The three variable test ranges were 0-10
wt % aromatic amine, 0-0.5 g/gal manganese (Mn) and 0-40 vol. %
oxygenate (an alkyl tertiary butyl ether). The manganese may be
provided by a corresponding amount of methyl cyclopentadienyl
manganese tricarbonyl (MMT). The two oxygenates tested were methyl
tertiary butyl ether (MTBE) and ethyl tertiary butyl ether (ETBE).
In total, four test cubes were designed to measure the numerous
fuel combinations and therefore potentially different chemical
oxidation interactions. The four cube design layouts are listed in
Table 4. Aniline and n-methyl aniline were the aromatic amines
chosen for complete statistical analyses.
4TABLE 4 Design for Testing Cube Independent Variables. Cube Number
Basefuel Variable 1 Variable 2 Variable 3 1 Wide boiling range MMT
MTBE Aniline 2 Wide boiling range MMT ETBE Aniline 3 Wide boiling
range MMT MTBE n-Methyl Aniline 4 Wide boiling range MMT ETBE
n-Methyl Aniline
[0040] The MON values were measured at specific points along the
three cube axes as well as the cube center point. Multiple
measurements were made at the center point to calculate the MON
variation level with the assumption being it is constant over all
the test space of the design, i.e. essentially a ten MON number
range, 91-101. Polynomial curves were fitted to the data to define
equations which describe the three variable interactions with
respect to MON over the entire cube test space. From these
equations, the MON performance for all variable combinations can be
predicted within the test space defined by the maximum and minimum
concentration ranges of the variables. Some of the predicted and
measured MON values have been summarized in Tables 5-8. The
remainder of the predicted values can be derived from the
prediction equations.
5TABLE 5 Predicted MON versus Measured MON for Oxygenate + Aniline
Manganese = 0 g/gal 0 2 6 10 Aniline wt % wt % wt % wt % Vol. % MON
MON MON MON MON MON MON MON MTBE (p) (m) (p) (m) (p) (m) (p) (m) 0
91.5 91.1 93.8 94.6 97.1 98.6 98.8 10 92.8 95.0 98.0 99.3 20 93.8
93.6 95.8 98.6 98.9 99.6 30 94.4 96.3 98.8 99.6 40 94.7 95.2 96.5
97.0 98.7 99.2 99.0 0 2 6 10 Aniline wt % wt % wt % wt % Vol. % MON
MON MON MON MON MON MON MON ETBE (p) (m) (p) (m) (p) (m) (p) (m) 0
92.3 91.1 93.8 95.9 96.8 99.7 97.6 10 94.6 95.9 98.5 101.1 20 96.0
94.0 97.2 99.4 98.8 101.7 30 96.6 97.5 99.4 101.3 40 96.3 96.2 97.0
97.2 98.6 100.1 101.1
[0041]
6TABLE 6 Predicted MON versus Measured MON for Oxygenate + Aniline
Manganese = 0.5 g/gal 0 2 6 10 Aniline wt % wt % wt % wt % Vol. %
MON MON MON MON MON MON MON MON MTBE (p) (m) (p) (m) (p) (m) (p)
(m) 0 96.0 95.3 97.4 97.7 98.9 98.7 99.1 10 97.3 98.5 99.8 99.4 20
98.2 99.1 99.4 100.4 99.6 99.7 30 98.9 99.9 100.6 99.7 40 99.2
100.3 100.1 99.6 100.6 99.3 99.8 0 2 6 10 Aniline wt % wt % wt % wt
% Vol. % MON MON MON MON MON MON MON MON ETBE (p) (m) (p) (m) (p)
(m) (p) (m) 0 95.5 95.5 95.9 96.0 96.8 97.6 97.8 10 97.8 98.0 98.5
99.0 20 99.2 97.5 99.3 99.4 100.5 99.5 30 99.8 99.6 99.4 99.2 40
99.4 98.4 99.1 100.9 98.6 98.0 97.1
[0042]
7TABLE 7 Predicted MON versus measured MON for Oxygenate + n-Methyl
Aniline Manganese = 0.0 g/gal n- Methyl 0 2 6 10 Aniline wt % wt %
wt % wt % Vol. % MON MON MON MON MON MON MON MON MTBE (p) (m) (p)
(m) (p) (m) (p) (m) 0 92.1 91.1 93.4 94.0 95.0 95.4 94.7 10 92.6
93.7 95.0 95.0 20 93.2 93.6 94.1 95.0 94.9 94.6 30 93.7 94.5 95.0
94.2 40 94.3 95.2 94.8 94.8 95.0 93.9 94.6 n- Methyl 0 2 6 10
Aniline wt % wt % wt % wt % Vol. % MON MON MON MON MON MON MON MON
ETBE (p) (m) (p) (m) (p) (m) (p) (m) 0 92.1 91.1 92.8 93.8 94.1
95.4 95.6 10 93.3 93.8 94.6 95.5 20 94.5 94.0 94.7 95.2 95.9 95.6
30 95.7 95.7 95.7 95.7 40 96.9 96.2 96.6 96.2 96.2 95.8 96.5
[0043]
8TABLE 8 Predicted MON versus measured MON for Oxygenate + n-Methyl
Aniline, Manganese = 0.5 g/gal n- Methyl 0 2 6 10 Aniline wt % wt %
wt % wt % Vol. % MON MON MON MON MON MON MON MON MTBE (p) (m) (p)
(m) (p) (m) (p) (m) 0 97.2 97.7 99.4 97.7 96.4 95.9 10 97.7 98.0
97.7 96.0 20 98.3 98.4 97.7 97.5 95.6 30 98.8 98.8 97.7 95.3 40
99.4 99.1 98.7 97.7 94.9 95.3 n- Methyl 0 2 6 10 Aniline wt % wt %
wt % wt % Vol. % MON MON MON MON MON MON MON MON ETBE (p) (m) (p)
(m) (p) (m) (p) (m) 0 96.6 96.3 97.4 95.9 95.5 95.9 10 97.1 96.9
96.4 96.0 20 97.6 97.4 96.9 97.2 96.5 30 98.2 97.9 97.5 97.0 40
98.7 98.5 97.3 98.0 97.5 98.4
[0044] The equations which describe the three variable (oxygenate,
Manganese and aromatic amine) interactions and ultimately predict
MON levels are listed in Table 8A.
9TABLE 8A MON Prediction Equations Test Cube:
MTBE/Aniline/Manganese MON = 91.54 + (0.1466 .times. MTBE) + (8.827
.times. Mn) + (1.252 .times. Aniline) - (0.006492 .times. MTBE
.times. Aniline) - (0.8673 .times. Mn .times. Aniline) - (0.001667
.times. MTBE.sup.2) - (0.05437 .times. Aniline.sup.2) Test Cube:
MTBE/n-Methyl Aniline/Manganese MON = 92.06 + (0.05563 .times.
MTBE) + (10.23 .times. Mn) + (0.7308 .times. nMA) - (0.009273
.times. MTBE .times. nMA) - (0.8220 .times. Mn .times. nMA) -
(0.04005 .times. nMA.sup.2) Test Cube: ETBE/Aniline/Manganese MON =
92.32 + (0.2730 .times. ETBE) + (6.349 .times. Mn) + (0.7429
.times. Aniline) - (0.009016 .times. ETBE .times. Aniline) - (1.058
.times. Mn .times. Aniline) - (0.004362 .times. ETBE.sup.2) Test
Cube: ETBE/n-Methyl Aniline/Manganese MON = 92.12 + (0.1185 .times.
ETBE) + (17.04 .times. Mn) + (0.3317 .times. nMA) - (0.1306 .times.
ETBE .times. Mn) - (0.01099 .times. ETBE .times. nMA) - (0.8828
.times. Mn .times. nMA) + (0.0218 .times. ETBE .times. Mn .times.
nMA) - (16.36 .times. Mn.sup.2)
[0045] The predicted MON variability for all four design cubes is a
combination of engine measurement, fuel blending and equation
fitting variability. Table 9 shows the MON engine measurement
variability in terms of standard deviations for the four test
cubes.
10TABLE 9 Standard Deviations for Four Test Cubes. MTBE, Aniline,
Mn 0.70 MON ETBE, Aniline, Mn 0.28 MON MTBE, n-Methyl 0.60 MON
ETBE, n-Methyl 0.55 MON Aniline, Mn Aniline, Mn
[0046] The pooled standard deviations for the four test cubes is
0.614 with 18 degrees of freedom. At the 95% confidence limit this
results in a variability of 1.83 MON. Variability, as used here, is
defined as it is in ASTM MON rating method D-2700--for two single
MON measurements, the maximum difference two numbers can have and
still be considered equal. However, variability as used here is
neither purely repeatability nor reproducibility, but is somewhere
between the two definitions. All 168 test fuels were blended from
the same chemical/refinery stocks and randomly MON rated by two
operators on two MON rating engines over an 8 week period. The
accuracy and variability for the equation fitting process of the
MON data is shown in Table 10.
11TABLE 10 Equation Fitting Variability Root Mean Test Cube R.sup.2
Value Squared Error Average Error MTBE + Aniline 91.0 0.82 0.54
ETBE + Aniline 74.5 1.29 0.88 MTBE + n-Methyl Aniline 77.3 0.99
0.70 ETBE + n-Methyl Aniline 81.3 0.81 0.61
[0047] The R.sup.2 Values are the proportion of variability in the
MON that is explained by the model over the ten octane number range
tested. The fuel blending variability was not quantified but is not
expected to be a major contributor to the overall predicted MON
variability.
[0048] The majority of MON results were obtained while the aromatic
amines were set in the statistical cube design as aniline and
n-methyl aniline. Subsequent work was done to determine other
potentially high octane aromatic amines. (See Tables 11-113.)
Specific aromatic amines were substituted into two different
blends; 1) 80 vol. % wide boiling range alkylate+20 vol. % MTBE and
2) 80 vol. % wide boiling range alkylate+20 vol. % ETBE. The
substituted aromatic amines were blended at 2.0 wt %. No manganese
was added to these blends. The MON results listed in Tables 11-1 3
are average MON of two tests.
12TABLE 11 MON Values for Methyl Substitutions on Aniline Ring
80/20 vol % Wide boiling 80/20 vol % Wide boiling range alkylate +
MTBE range alkylate + ETBE aromatic amine MON dMON* MON dMON*
Aniline 96.3 -- 97.3 -- o-toluidine 94.5 -1.8 95.2 -2.1 m-toluidine
96.8 0.5 97 4 0.1 p-toluidine 96.8 0.5 96.8 -0.5 *Note: dMON =
delta MON = difference between additive of interest and Aniline
reference point.
[0049]
13TABLE 12 MON Values for di- and tri- methyl substitutions on
Aniline Ring 80/20 vol % Wide 80/20 vol % Wide boiling range
boiling range alkylate + MTBE alkylate + ETBE aromatic amine MON
dMON* MON dMON* Aniline 96.3 -- 97.3 -- 2,3-dimethyl Aniline 93.8
-2.6 94.2 -3.1 2,4-dimethyl Aniline 95.0 -1.3 95.2 -2.1
2,5-dimethyl Aniline 93.9 -2.4 95.3 -2.1 2,6-dimethyl Aniline 93.3
-3.0 93.4 -3.9 3,5-dimethyl Aniline 95.7 -0.6 96.7 -0.6
2,4,6-trimethyl Aniline 92.6 -3.8 93.7 -3.6
[0050]
14TABLE 13 MON Values for Alkyl Substitutions on Aniline's Amine.
80/20 vol % Wide boiling 80/20 vol % Wide boiling range alkylate +
MTBE range alkylate + ETBE aromatic amine MON dMON* MON dMON*
Aniline 96.3 -- 97.3 -- 4-ethyl Aniline 96.1 -0.3 97.5 0.2
4-n-butyl 95.7 -0.6 96.9 -0.5 Aniline n-methyl 95.0 -1.3 95.7 -1.6
Aniline n-ethyl Aniline 91.9 -4.4 91.9 -5.4
[0051] It can be seen from Tables 11-13 that the aromatic amines
which have a methyl substitution in the ortho- (or the 2 position)
on the aromatic ring as well as the n-alkyl substitutions on the
amine are not effective octane boosting additives for these two
basefuels. However, the meta- ring position, (positions 3- and 5-)
and the para- ring position, (position 4-) methyl substituted
aromatic amines are generally more effective octane boosting
additives for this basefuel with the exception of the p-toluidine
in the ETBE/basefuel case. The relative MON increasing
effectiveness of the different alkyl substituted aromatic amines
exemplifies the importance of mapping the chemical oxidation
reaction routes for the additives of interest relative to the MON
test environment. Further data from these experiments are shown in
FIGS. 4-15.
[0052] E. Determination of Non-linear Models for Identifying
Aviation Fuel Compositions with Desirable MON, Supercharge, and
Knock Cycle/Intensity Ratings
[0053] To better characterize the performance of fuel formulations,
the effects of various fuel formulations on MON, Supercharge and
Knock Cycle/Intensity ratings were determined using statistically
designed experiments. The subject fuel compositions were
combinations of MTBE, aniline and manganese components and the same
wide boiling range alkylate fuel as the previous designs. The three
variable test ranges for these experiments were 20-30 vol % MTBE,
0-6 wt % aniline and 0-0.1 g/gal manganese. Anti-knock ratings of
MON, Supercharge and Knock Cycle/Intensity ratings were measured at
least in duplicate.
[0054] Table 14 shows the non-linear interactions of the fuel
composition components on the Supercharge rating and average
Knocking Cycles and average Knock Intensity per 400 consecutive
engine cycles data. The eight fuel formulations shown represent the
extremes of the ranges tested.
[0055] Statistical analysis shows an interaction between the MTBE
and manganese terms in the equations for supercharge rating but
only when aniline levels are low with respect to the domain tested.
There is another significant interaction for supercharge rating
which is that as MTBE increases the interaction between manganese
and aniline becomes antagonistic. Also, the data analysis for Knock
Intensity contains an antagonistic interaction between MTBE and
aniline. The Knocking Cycles data demonstrates a three way
interaction between the MTBE, manganese and aniline.
15TABLE 14 Measured Octane Parameters with respect to Fuel
Formulation Average Mn Average Knock MTBE (g/ Aniline Supercharge
Knocking Intensity/ (vol %) gal) (wt %) MON Rating Cycles/400 400
20 0.00 0 95.4 115.5 121 49 20 0.00 6 97.6 140.2 12 32 20 0.10 0
95.6 118.1 68 40 20 0.10 6 98.0 142.5 4 24 30 0.00 0 96.2 114.1 66
35 30 0.00 6 98.3 143.9 2 33 30 0.10 0 97.4 133.5 13 33 30 0.10 6
99.3 144.5 2 20
[0056] Because of the above mentioned non-linear fuel composition
interactions, neither MON nor supercharge ratings when considered
individually will always predict the knock-free operation of the
commercial Lycoming 10-360 aviation engine. (See Table 15). The
Knocking Cycle and Knock Intensity data in Table 15 are the average
of duplicate 400 cycle tests.
16TABLE 15 Measured Octane Parameters with respect to Fuel
Formulation (II) Average Supercharge Knocking Cycles Average Knock
Fuel Number MON Rating /400 Intensity/400 1 98.4 134.9 17 30 2 98.5
142.2 0 0 3 96.5 136.1 0 0 4 96.3 115.1 73 35
[0057] The R.sup.2 values between MON, Supercharge, Knocking Cycles
and Knock Intensity are listed in Table 16.
17TABLE 16 R.sup.2 values for Knocking Cycles and Knock Intensity
Predictions Combination R.sup.2 values MON to predict Knocking
Cycles* .44 MON to predict Knock Intensity* .38 Supercharge to
predict Knocking .64 Supercharge to predict Knock Intensity* .82
Notes: (*)Outlying data points that were not representative of
population were removed after statistical analyses.
[0058] Table 17 includes the references of pure isooctane as well
as the industry standard leaded Avgas 100 Low Lead. For example,
pure isooctane has a MON value of 100 by definition but knocks
severely in the Lycoming 10-360 at its maximum potential knock
operating condition. Addition of tetraethyllead (TEL) to isooctane
is required to boost the supercharge rating sufficiently high to
prevent auto-ignition in a commercial aircraft engine.
18TABLE 17 Knock Data for Isooctane and Leaded Avgas 100 Low Lead
Knock Supercharge Knocking Intensity Fuel MON Rating Cycles/400
/400 Isooctane 100 100 85 Not Collected 100 Low Lead 105 131.2 0
0
[0059] Using centered & scaled units for the fuel properties
our equation for MON is:
MON=97.75+0.575*MTBE(s)+0.305*Mn(s)+1.135*Aniline(s)-0.485*Mn(s).sup.2.
[0060] Converting to actual units yields:
MON=92.95+0.115*MTBE+25.5*Mn+0.3783*Aniline-194*Mn.sup.2.
[0061] No interactions were statistically significant.
[0062] Using centered & scaled units for the fuel properties
our equation for supercharge (SC) is.
SC=140.008+2.325*MTBE(s)+3.9*Mn(s)+11.715*Aniline(s)+1.89375*MTBE(s)*Mn(s)-
-2.39375*Mn(s)*Aniline(s)-2.30625*MTBE(s)*Mn(s)*Aniline(s)-8.653*Aniline(s-
).sup.2.
[0063] Converting to actual units yields:
SC=122.72-0.375*NMTE-294.125*Mn+6.628*Aniline+16.8*MTBE*Mn+0.15375*MTBE*An-
iline+60.917*Mn*Aniline-3.075*MTBE*Mn*Aniline-0.9614815*Aniline.sup.2
[0064] Looking at the equation in centered and scaled units, we see
that the interaction between MTBE and Mn is synergistic
(coefficient same sign as coefficients for individual effects of
MTBE *Mn). But, because of the presence of the 3-way interaction
between MTBE, Mn, and Aniline, the size of the MTBE*Mn interaction
actually depends on the level of aniline. At the low level of
aniline, the MTBE*Mn interaction is synergistic, but as the aniline
level increases, the MTBE*Mn interaction becomes less and less
synergistic until it becomes basically zero at the high aniline
level (if anything, it is antagonistic at this point). Thus, there
is a synergism between MTBE and Mn, but generally only at low
levels of aniline.
[0065] A similar description can be used for the Mn*Aniline
interaction, where the size of this interaction depends on the MTBE
level. At low levels of MTBE, the Mn*Aniline interaction is
essentially zero, but as the MTBE level increases the Mn*Aniline
interaction becomes more and more antagonistic. Table 18 below
illustrates the above concepts.
19TABLE 18 MTBE Aniline Expected (vol %) Mn (g/gal) (wt %) Actual
SC Predicted SC SC.sup.1 20 0.00 0 122.2, 108.7 115.2 20 0.10 0
116.8, 119.4 119.4 30 0.00 0 113.0, 115.1 111.5 30 0.10 0 132.1,
134.9 132.5 115.7 20 0.00 6 137.6, 142.8 138.8 20 0.10 6 142.7,
142.8 142.7 30 0.00 6 143.8, 143.9 144.3 30 0.10 6 143.9, 145.1
146.5 148.2 .sup.1This is the expected SC value if there was no
interaction, that is if the effects of each of the fuel components
were additive.
[0066] 1--This is the expected SC value if there was no
interaction, that is if the effects of each of the fuel components
were additive.
[0067] Using centered and scaled units for the fuel properties our
equation for Knock Intensity (KInt) is:
KInt=26.5-2.138719*MTBE(s)-1.905819*Mn(s)-5.877127*Aniline(s)+2.477696*MTB-
E(s)*Aniline(s)+2.711142*Mn(s).sup.2+2.780729*Aniline(s).sup.2
[0068] Converting to actual units yields:
KInt=62.9-0.923283*MTBE-146.56206*Mn-7.9423549*Aniline+0.1651797*MTBE*Anil-
ine+1084.4568*Mn.sup.2+0.3089699*Aniline.sup.2
[0069] Again looking at the equation in the centered and scaled
units, we see that the MTBE* Aniline interaction is antagonistic.
Also, note that this interaction does not depend on the Mn level
because there is no 3-way interaction in the model. The following
Table 19 illustrates this interaction.
20TABLE 19 MTBE Mn Aniline Actual Predicted Expected (vol %)
(g/gal) (wt %) Knock Int. Knock Int. Knock Int..sup.1 20 0.00 0
52.0, 48.1, 38.0 44.4 20 0.00 6 36.1, 27.3, 26.0 27.7 30 0.00 0
34.4, 35.3 35.2 30 0.00 6 25.7, 40.0 28.4 18.5 20 0.10 0 39.4,
40.9, 38.7 40.6 20 0.10 6 19.0, 28.4, 19.0 23.9 30 0.10 0 37.6,
30.0, 28.0 31.4 30 0.10 6 21.0, 19.0 24.6 14.7 .sup.1This is the
expected Knock Intensity value if there was no interaction, that is
if the effects of each of the fuel components were additive.
[0070] 1--This is the expected Knock Intensity value if there was
no interaction, that is if the effects of each of the fuel
components were additive.
[0071] It should be pointed out that knock intensity values below
20 cannot be distinguished from each other, so the antagonistic
effect of the MTBE*Aniline interaction may not be quite so
significant at the high level of Mn (since the expected value under
the assumption of no interaction is 14.7 and the actual values were
21.0 & 19.0).
[0072] Using centered and scaled units for the fuel properties, our
equation for number of Knocking Cycles (Cycles) is:
Y=ln(Cycles+1)=1.529878-0.43339*MTBE(s)-0.376319*Mn(s)-1.469152*Aniline(s)-
+0.368344*MTBE(s)*Mn(s)*Aniline(s)+0.732549*Aniline(s).sup.2.
[0073] Converting to actual units yields:
Y=ln(Cycles+1)=4.4331281-0.0130092*MTBE+29.308018*Mn-0.3641767*Aniline-1.4-
733759*MTBE*Mn-0.0245563*MTBE*Aniline-12.278133*Mn*Aniline+0.4911253*MTBE*-
Mn*Aniline+0.0813943*Aniline.sup.2.
[0074] In either case, the predicted number of knocking cycles is
equal to e.sup.Y-1.
[0075] This variable was analyzed on the natural log (ln) scale
because it was observed that the variability was a function of mean
level. Analyzing the data on the In scale causes the variability to
be more constant across mean levels, which is necessary for the
statistical tests performed to be valid. Also, since some
observations had values of zero for number of knocking cycles (the
natural log of zero cannot be calculated), 1 was added to every
observation so that the In transformation could be used. Thus, 1
must be subtracted from Y above to get back to the original
units.
[0076] Because of the presence of the 3-way interaction in the
model and no 2-way interactions, the 3-way interaction can be
interpreted in 3 ways. We could say that there is a synergistic
interaction between MTBE & Mn at low levels of aniline and an
antagonistic interaction at high levels of aniline. This
description holds for all pairs of fuel properties.
[0077] The following Table 20 describes the MTBE*Mn interaction
being synergistic at low levels of aniline and being antagonistic
at high levels of aniline
21TABLE 20 Expect- Avg. # of Pred. # of ed # of MTBE Mn Aniline
Knocking Knocking Knocking (vol %) (g/gal) (wt %) Cycles Cycles
Cycles.sup.1 20 0.00 0 178.5, 93.0, 28.0 63.9 20 0.10 0 78.5, 48.0,
71.5 62.9 30 0.00 0 56.5, 73.0 56.0 30 0.10 0 17.0, 0.8, 17.0 11.9
55.1 20 0.00 6 13.0, 15.5, 0.5 6.2 20 0.10 6 0.0, 5.5, 0.0 0.6 30
0.00 6 1.5, 0.5 0.4 30 0.10 6 1.0, 0.0 0.4 0.0 .sup.1This is the
expected avg. # of knocking cycles value if there was no
interaction, that is if the effects of each of the fuel components
were additive.
[0078] 1--This is the expected avg. # of knocking cycles value if
there was no interaction, that is if the effects of each of the
fuel components were additive.
[0079] Note that at the high aniline level, the reason for the
antagonistic MTBE*Mn interaction is that the number of knocking
cycles cannot be reduced to a value lower than zero. Increasing Mn
to 0.10 lowers the number of knocking cycles to almost zero and
increasing MTBE to 30 also lowers the number of knocking cycles to
almost zero. Therefore, increasing both Mn and MTBE at the same
time cannot reduce the number of knocking cycles any more.
[0080] Using centered and scaled units for the fuel properties our
equation for # of Knocking Cycles is:
Cycles=4.462241-9.166427*MTBE(s)-7.93772*Mn(s)-26.077604*Aniline(s)+8.7422-
41*MTBE(s)*Aniline(s)+8.491223*Mn(s)*Aniline(s)+5.167309*MTBE(s)*Mn(s)*Ani-
line(s)+24.483337*Aniline(s).sup.2.
[0081] Converting to actual units yields:
Cycles=135.2-2.5482718*MTBE+188.15204*Mn-33.803388*Aniline-20.669236*MTBE*-
Mn+0.2383288*MTBE*Aniline-115.63548*Mn*Aniline+6.8897453*MTBE*Mn*Aniline+2-
.7203708*Aniline.sup.2.
[0082] In this case, the only synergistic interaction is between
MTBE and Mn at low aniline levels. All other interactions are
antagonistic. The MTBE*Mn synergism at low aniline levels and
antagonism at high aniline levels is shown below in Table 21.
22TABLE 21 Expect- Avg. # of Pred. # of ed # of MTBE Mn Aniline
Knocking Knocking Knocking (vol %) (g/gal) (wt %) Cycles Cycles
Cycles.sup.1 20 0.00 0 178.5.sup.2, 84.2 93.0, 28.0.sup.2 20 0.10 0
78.5, 48.0, 71.5 61.7 30 0.00 0 56.5, 73.0 58.7 30 0.10 0 17.0,
0.8, 17.0 15.5 36.2 20 0.00 6 13.0, 15.5, 0.5 7.9 20 0.10 6 0.0,
5.5, 0.0 0.0 30 0.00 6 1.5, 0.5 0.0 30 0.10 6 1.0, 0.0 8.2 0.0
.sup.1This is the expected avg. # of knocking cycles value if there
was no interaction, that is if the effects of each of the fuel
components were additive. .sup.2These observations were not
included in the analyses.
[0083] 1--This is the expected avg. # of knocking cycles value if
there was no interaction, that is if the effects of each of the
fuel components were additive.
[0084] 2--These observations were not included in the analyses.
[0085] Further data from these experiments are shown in FIGS.
16-30.
[0086] The testing and equation fitting variability of the second
set of experimentally designed demonstrated in Tables 22 and 23.
For the predicted performance parameter listed in Table 22, the 95%
total variability is a combination of engine measurement and fuel
blending variabilities. Table 22 also shows the performance
parameter engine measurement and fuel blending variability in terms
of standard deviation and total variability calculated at the 95%
confidence limit.
23TABLE 22 Variability Analysis for Second Cube Sets Performance
Parameter Standard Deviation 95% Total Variability MON 0.69 2.07
Performance Number 3.93 11.73 Knock Intensity 7.04 19.70 Knocking
Cycles (In Scale) 1.15 3.27 Knocking cycles (linear 18.6 52.60
Scale)
[0087] Total variability, as used here, is defined as it is in ASTM
Methods for two single measurements, the maximum difference two
numbers can have and still be considered equal. However,
variability as used here is neither purely repeatability nor
reproducibility, but is somewhere between the two definitions. The
accuracy and variability for the equation fitting process of the
performance parameters is shown in Table 23.
24TABLE 23 Equation Fitting Variability for Second Cube Set
Performance Root Mean Squared Parameter R.sup.2 Value Error Average
Error MON 76.8 0.63 0.47 Performance 91.2 3.99 2.50 Number Knock
Intensity 60.5 5.40 3.80 Knocking Cycles (in 74.2 0.83 0.60 small
"L" Scale) Knocking Cycles 89.1 9.30 7.10 (linear Scale)
[0088] Other features, advantages and embodiments of the invention
disclosed herein will be readily apparent to those exercising
ordinary skill after reading the foregoing disclosure. In this
regard, while specific embodiments of the invention have been
described in detail, variations and modifications of these
embodiments can be effected without departing from the spirit and
scope of the invention as described and claimed.
* * * * *