US2959915A - Fuel for and method of operating a jet engine - Google Patents

Description

Wappingers Falls," N.Y., assignors to Texaco Inc., a corporationof Delaware No Drawing. Filed Dec.'27,-1955,S er.No.555,Z42

5 Claims; c1. so -35.4

invention relates to a novel composition having excellent high temperature stability and a method for cooling heated materials utilizing said composition.

The composition of the present invention has particular; application in the operation of jet aircraft. The advanced high speed engines employed in jet aircraft have extremely high combustion temperatures and many of the materials which necessarily are exposed to such temperatures are decomposed to the extent that they cannot perform their assigned tasks. Compositions used to lubricate the moving parts of jet engines, for instance, may break down with a loss of viscosity and the formation ofslud g'e and deposits which tend to prevent proper lubrication. It is therefore most important that some means or method be utilized to keep these materials at temperatures in which they may function properly.

The use'ofthe jet fuel as a heat' sink for cooling vital aircraft components such as the lubricating oil provides one solution to the problem of high temperatures. This technique is exemplified by passing the fuel in heat exchange relationship with thelubricating oil prior to fuel consumption. This use has imposed a new and serious fe'quirement of extremely high thermal stability on jet fuel. Heat stability is of the utmost importance because/thermal degradation of the fuel will result in carbon build-up and clogging of the fuel lines and will in time prevent operation of the jet aircraft. Thermal stability has been imparted to jet fuel in two main ways, namely, by refining techniques such as hydrogenation and by the use of additives. This invention provides a thermally stable jet fuel by the use of a particular type of additive.

In accordance with the present invention, an excellent-heat stable composition is formed by the addition of from 0.001 to 0.03 pencent by weight of at least one compound selected from the group consisting of alkyl primary and alkyl secondary amines,- hav-ing atotal of from 16'to 32 carbon atoms in thealkyl radicals, to a' major-portion of a hydrocarbon stock boiling within the range of from 250 to 700 F. The preferred addition range" of said alkyl amines is from 0.005 to 0.02 percent by' Weight. The preferred alkyl primary amines in accordance withthis invention are those having from'18 to 24 carbon atoms in a tertiary alkyl radical. The preferred alkyl secondary amines are those substituted with a tertiary C to C alkyl radical and Withan alkylsubstituted aralkyl radicalhaving-IO to 14 carbon atoms in the substituted alkyl group. Some examples of other primary amines which may be used either individually or in mixtures with other amines in accordance with this invention are as" follows: cetyl amine, Z-ethylpentadecyl amine, stearyl amine, neostearyl amine, behenyl amine, cerotyl amine, montaiiyl amine, myricyl amine, melissyl amine, lacceryl amine, and ceromelissyl amine. Examples of'some useful secondary amines are as follows: 2 isobutylhexyl-2-ethylhexyl benzyl amine, 2,2,5-

2,959,915 Patented Nov. 15, 1960 In order to demonstrate the superior heat stability of'the composition'in accordance with the present invention, the base fuel alone and together with various types of amine's have been tested in'an Erdco Fuel Coker Test Unit. When testing fuels with this unit, the f el under consideration is pumped through a preheater in the form of an annular heat exchanger? The heated fuel is then passed through a heated sinteredsteel filter.

1 Sludge and sediment formed by the heating of the fuel trimethylhexylQ,2 diriiethyldecylbenzyl amine, 2-ethyl-2- butylnonyl-Z-hexyldecylbenzyl amine, neostearyl'myristyl deposit on the filter. Test conditions on all the runs, the results of which are published in'the following tables, were as follows: preheater temperature, 400 F.; filter temperature, 500 F.; fuel flow, 4 lbs./hr.; fuel pressure, 150'p.s.i.g. The thermal stability of a fuel is indicated by the time for a filter'to partially plug. In order to determine this, the test is run until the drop in pressure (AP) across the filter reaches either 25 inches of mercury or a test duration of 5 hours. A good fuel in this testis one which obtains a' filter AP below 20 inches of mercury in five hours or more. r The base fuels with which the additives were tested included a JP-4 fuel which is used by the military and commercial air lines and com-prises a mixture of about 65 percent gasoline and 35- percent light distillate. This product also adheres to the following characteristics:

Gravity API n 45-57 Reid vapor pressure, lbs. 2:3 Freezing point max -76 Smoke pt. volatility index min 54 Water reaction max; -1 Sulfur, percent max 0.4 Mercaptan sulfur, percent (1) max 0005 Aromatics percent by vol. max 25 Olefins percent by vol. max 5.0 Bromine No. max 5.0 Potential gum, mg./ 100 -max 14 Existent gum, mg./100 ml. max' 7 Heating value, B.t.u./lb. min 18,400 Distillation:

20% F. max 2 70 50% F. max 370 F. max 470' Another fuel used was a so-called JP4 Referee fuelwhichcan be described as a'specia'l grade of JP4 fuel. The fuel is designed to be typical of lower quality JP'-4 fuel which would be available in wartime. It is used almost exclusively in the developing and testing of mili-' tary jet engines; It'maybe further distinguished from the ordinary JP-4 fuel by reference to the following characteristics:

Gravity API 457-50 Smoke point volatility index 50-54 Sulfur, percent 0.15-0.40. Heating value, B.t.u./lb. 18,40018,750 Distillation: r v n 20% 250-290 50% 350-390 90% 450-490 The remaining characteristics are essentially the same asthose listed for the ordinary JP-4 fuel.

Still another fuel used for the investigation of' these ASTM distillation:

IBP, F. 350

FBP 534 API gravity 37.9 Existent gum rng./100 ml 0.6 Accelerated gum mg./ 100 ml 0.6 Sulfur, total wt. percent 0.027 Mercaptan sulfur, wt. percent 0.0009 Freezing point, F. 40 Heating value B.t.u./lb 18,473 Aniline gravity constant 4991 Viscosity at 30 F. Q. cs 13.4 Volume percent aromatics 21.8 Volume percent olefins 9.5 Smoke point, mm. Water tolerance Pass Flash point (P.M.), F. 150

The Erdco Fuel Coker Unit Test results with respect to heat stability of jet fuels are set forth in the following tables. A mixture of C C tertiary alkyl primary amines sold as Primene JM-R and a secondary amine of the general formula:

RNHR

wherein R is a mixture of C to C tertiary alkyl groups and R is a C alkyl substituted benzyl radical which was supplied as Ell-974, an experimental amine, were the amines used in Table I.

1 Fuel shortage prevented completion.

The foregoing table demonstrates that alkyl primary and alkyl secondary amines at concentrations of 0.018 weight percent (50 lbs./ 1000 bbl.) will greatly improve the heat stability of an unstable jet fuel. Although the run in which the additive Primene JM-R was tested was not completed due to fuel shortage, the negative AP indicates that the AP in 300 minutes would still remain below zero.

The following table is set forth to compare the effectiveness of other amines as heat stabilizing additives for jet fuels.

The product Armeen DM-18D is a tertiary amine which contains 92 percent of distilled dimethyl stearyl amine.

The foregoing table shows that a tertiary amine (Armeen DM-lSD) is of no value as a heat stabilizing additive. Further, the table shows that aromatic amines,

represented by l-naphthylamine, diphenylamine and N,- N-di-sec-butyl-p-phenylene diamine at additive percentages of 0.018 by weight have no value as additives for heat stabilizing jet fuels.

These results further emphasize the unexpectedness of the fact that the alkyl primary and secondary amines of this invention are excellent additives for high temperature fuel stability at surprisingly low concentrations.

0k. 50. 2 Fuel shortage prevented completion.

The above Table III demonstrates the effectiveness of a tertiary Gig-C24 alkyl primary amine as a heat stabilizing additive at extremely low concentrations. Even at the extremely low concentration of 00018 percent by weight in a jet fuel (5 lbs./ 1000 bbls.) its effectiveness is surprisingly evident. Although a fuel shortage prevented the completion of this run, it is quite apparent that the fuel was effectively stabilized by this small amount of additive.

In the development of an effective jet fuel additive it is also necessary to reject those additives which although effective in promoting heat stability in the fuels, also lend to the fuel an affinity for water. In order to determine a limiting value for the solubility of water in jet turbine fuels, the fuels must pass a water tolerance test.' The following is a description of the ASTMD109450T Water Tolerance Test of aircraft fuels which was used on the fuel compositions of this invention.

An ml. sample of the fuel to be tested is shaken vigorously at room temperature with 20 ml. of distilled Water in a ml. glass stopper graduated cylinder for at least 2 minutes and thereafter allowed to settle. The change in volume of the aqueous layer after 5 minutes of settling is reported to the nearest 0.5 ml. A pass rating denotes an increase of 1 ml. or less in either layer. This change in volume is taken as the water tolerance of the fuel. The following table sets forth the results of water tolerance tests on various effective heat stabilizing additives.

Table IV Fuel Additive Water wt., percent Tolerance ZIP-4 Primene .TM-R 0.009 Pass. JP-4 Primene JMR 0.0036 Do. JP-4 Primene JM-R 0.0018 Do. F- Primene JMR 0. 018 Do. F-105 alkyl-sec-amine 0. 018 D0. F 105 polyoxyethylene sor laureate 0. 018 Fail. F-105 basic metal sulfonate 0. 018 o F-105 Nitrogen substituted methacrylate polymer 0. 018 Do. F-105 Nitrogen substituted methacryllate polymer 0.0061 Do. JP-4 Referee +normal barium sulfonate- 0. 018 Do.

It is evident from the above table that manyadditives although imparting effective heat stability to fuels will fail to provide good water tolerance characteristics to the fuel composition and, therefore, be undesirable as jet turbine propellant additives.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A method of operating a jet aircraft comprising cooling the lubricant employed in the lubrication of jet engines by indirect heat exchange with a composition consisting essentially of a hydrocarbon stock boiling within the range of from 250 to 700 F. containing 0.001 to 0.03 percent by weight of at least one amine selected from the group consisting of alkyl primary and alkyl, aralkyl secondary amines containing a total of 16 to 32 carbon atoms in the alkyl radicals and subsequently using said hydrocarbon for fuel for operation of said jet engine.

2. A heat stable jet fuel composition consisting essentially of a major proportion of a hydrocarbon stock boiling Within the range of from 250 to 700 F. and from 0.005 to 0.02 percent by weight of a compound having the general formula:

wherein R is selected from the group consisting of C to C alkyl groups and mixtures thereof and R is a C alkyl substituted benzyl radical.

3. A method of cooling a jet aircraft component comprising passing the jet fuel composition, consisting essentially of a hydrocarbon stock boiling within the range of from 250 to 700 F. containing from 0.001 to 0.03 percent by weight of at least one compound selected from the group consisting of alkyl primary amines having from 16 to 32 carbon atoms in the alkyl group and a compound having a general formula:

amine.

5. A method of cooling the engine lubricant in a jet aircraft comprising passing the jet fuel composition consisting essentially of a hydrocarbon stock boiling within the range of from 250 to 700 F. containing from 0.005 to 0.02 percent by weight of a tertiary'alkyl primary amine having from 18 to 24 carbon atoms in the alkyl group, in indirect heat exchange relationship with said lubricant.

References Cited in the file of this patent UNITED STATES PATENTS 2,474,183 King June 21, 1949 2,573,471 Malina et a1. Oct. 30, 1951 2,607,665 Duncan Aug. 19, 1952 2,675,671 Malgieri Apr. 20, 1954 FOREIGN PATENTS 627,386 Great Britain Aug. 8, 1949

Claims (1)

1. A METHOD OF OPERATING A JET AIRCRAFT COMPRISING COOLING THE LUBRICANT EMPLOYED IN THE LUBRICATION OF JET ENGINES BY INDIRECT HEAT EXCHANGE WITH A COMPOSITION CONSISTING ESSENTIALLY OF A HYDROCARBON STOCK BOILING WITHIN THE RANGE OF FROM 250 TO 700*F. CONTAINING 0.001 TO 0.03 PERCENT BY WEIGHT OF AT LEAST ONE AMINE SELECTED FROM THE GROUP CONSISTING OF ALKYL PRIMARY AND ALKYL, ARALKYL SECONDARY AMINES CONTAINING A TOTAL OF 16 TO 32 CARBON ATOMS IN THE ALKYL RADICALS AND SUBSEQUENTLY USING SAID HYDROCARBON FOR FUEL FOR OPERATION OF SAID JET ENGINE.