US3167411A - Anti-icing jet fuel composition containing a hexaalkyl phosphoric triamide - Google Patents

Description

Jan. 26, 1965 J. J. BIALY ETAL 3,167,411

ANTI-ICING JET FUEL COMPOSITION CONTAINING A HEXAALKYL PHOSPHORIC TRIAMIDE Filed Feb. 28, 1962 27 .fm-@i2 1 22 i I f4 l United States Patent C) ING A HEXAALKYL PHSPHRC TRIAMIDE Jerzy J. Bialy, Beacon, and George W. Eckert, Wap- This invention relates to a novel fuel composition. More particularly, the invention rel-ates to turbine or jet fuels having outstanding anti-icing properties. This improvement is based on the effect of an anti-icing additive consisting of a polyalkyl phosphoric triarnide.

Reliability of the fuel supply under extremely severe operating conditions is a matter of paramount importance in the operation of turbine or jet engine aircraft. It is also essential that the fuel supply be absolutely free of any suspended solid particles in order not to block or impair the operation of the fuel atomizer and other fine components in the jet engine. The provision of uncontaminated fuel free of soli-d particles to the engine is assured by passing the fuel through exceedingly fine filters yin order to screenout any` contained solid particles.

let fuels always contain minor amounts of water dis- Asolved in the fuel itself. When proper care has not been taken in the handling of the fuel, water in excess of the hamount dissolved in the fuel will often be present. Jet

engine aircraft frequently encounter extremely low-temperature operating conditions which cause the water in the fuel to form ice, generally in the form of small crystals. These ice crystals are caught by the fuel filter initially restricting and finally preventing passage of the fuel therethrough resulting in engine failure from the lack of fuel. A fuel composition has now been discovered which 'inhibits or prevents the formation of ice from the water cent of apolyaikyl phosphoric triamide. Polyalkyl phosphoric triamides are represented by the formula:

R-N-iL-N-R ff if N-R' t in which R and R each represent alkyl radicals having from l to 4 carbon atoms.

The preferred polyalkyl phosphoric triamide anti-icing additives of the invention are the hexaalkyl phosphoric triamides, such as hexamethyl phosphoric triamide, hexaethyl phosphoric triarnide, hexabutyl phosphoric triamide, hexapropyl phosphoric triamide and the like. Mixed liexaalkyl phosphoric triamides are also effective as the anti-icing additive. The preferred additive of this invention is hexarnethyl phosphoric triamide.

.The anti-icing additive of this invention is employed in turbine or jet engine fuel compositions. The fuels are made up of straight run or cracked hydrocarbon components in the gasoline and kerosene boiling ranges, i.e., boiling from about 100 to about 600 F. Commercial JP-4 type jet fuel, which consists of about 65 percent gasoline and 35 percent middle distillate, is typical ofthe fuels improved by the anti-icing additive of the invention.

ICC

The jet fuel of the invention is conveniently prepared by mixing the base fuel with the polyalkyl phosphoric triamide. As noted above, the jet fuel will generally contain from about 0.02 to 0.35 weight percent of the additive. The preferred range of proportions for the additive, however, are from about 0.05 to 0.20 weight percent.

An important feature of this invention is that the outstanding anti-icing properties imparted to thefuel are obtained with relatively small amounts of the additive. Whereas heretofore, jet fuel anti-icing additives have been proposed in amounts of 0.5 to l percent or more, the present additive gives the desired properties with a very small amount of additive. For most purposes, effective anti-icing is obtained at about 0.10 weight percent of the additive.

The single figure is a schematic diagram of a test system for determining the pumpability temperature of fuels at low temperatures.

The temperature at which the iiow rate of the fuel can no longer be maintained and/ or substantial pressure drop develops across the screen is defined as the pumpability temperature. i

Water-containing jet fuels of Ithe invention were tested for their purnpability properties at low temperature. Basically, the test involved circulating the fuel in a closed system containing a fine metal screen filter while gradually reducing the temperature of the fuel. Sensitive temperature and pressure devices placed on the inlet and outlet sides of the filter indicated the temperature at which a substantial pressure drop was brought about by the formation of ice in the fuel.

Two criteria of additive performance were employed in the test; l

(l) Concentration of additive to yield 76 F. pumpability temperature with water-saturated fuel, and

(2) Concentration of additive to yield -45 F. pumpability temperature with water-saturated fuel to which 2 cc. per gallon of free water was added.

Referring now to FIGURE 1 showing a diagram of the low temperature pumpability test system, 10 is a reservoir for the fuel sample. In the test system employed, this reservoir hadl a capacity of four liters. Conduit 1l. connects the fuel reservoirwith a pump l2, and fiow meter i3 which controls the rate of flow of the fuel. The test fuel is passed through conduit 14 into cooling coil 15 which is immersed in a low temperature cooling bath in vessel 16. The temperature of the cooling bath is registered by temperature means 17 and is controlled by circulation from cooling liquid reservoir 18 and inlet and return circulating conduits i9 and 20 respectively. The test fuel is passed through conduit 21 into filtering device 2?, which has a 200 mesh screen filter 23 mounted therein for filtering the fuel. Conduit 24 is a return line for the fuel to the sample reservoir. The filter device is equipped with temperature indicating means 25 and 26 to indicate the temperature on the inlet and outlet sides of the `filtering device respectively. This device is also equipped with a sensitive pressure means 27 to show the pressure differential between that in the inlet conduit leading into the filter and the pressure in the outlet conduit from the filter. The pressure device is sensitive to a pressure differential of :t1 mm. of mercury. Plugging of the filter caused by ice formation is indicated by a sharp pressure drop across the filter.

Cooling liquid reservoir 18 contains a Dry Ice-acetone mixture which is circulated around the test cooling coil in vessel lo. Steady cooling of the test fuel is obtained by controlling the fiow of cooling liquid through conduits 19 and 20.

' The jet 'fuel employedV for ltes-ting 'the V'additive oftl'ie`vv invention had the inspection tests listed in Table I below: j

Sat'urate's a The te'st procedure followed involves adding' 4 'lit`ers of the test fuelto the reservoirfvvhich is thereafter stoppered to preventfthe'fentrance ofwater from condensation f i during the coolingpe'riod. The circulating pump'is started and airr is p ur'ged'irom` the :nanometerlinesandiiilter ;screen housing via vents providedfforthis purpose.V The -f uel flovv rateis adjusted to Y0.67 giplm. '(gallons p erminutc). zAt the start of Kthe cooling cycle, 'the Dry IceA compartment is filled with lDry Ice and the cold acetone'- Y (tial pressure continues tol increaseY at Vthisr temperatureV to the point'whereflow can nolonger'bemaintained, Athisis taken as the pumpability temperature: If vthe pressure i differential does not contnue'to rise,'the temperature is A Jet fuelfhaving'the InspectiouTe'sts shownm Table I Y 'was tested for'V itsjpurnpability temperatures in the =te'sty VYdevice and manner described.hereir xabove. The anti-icing Dry Ice solution is circulated-tothe' mainV bathr which 1 Y' contains the cooling coils of the fuel test circuit. Dry'Ice is dropped 'intothej cooling bath initiallyv in quantities'sui-V cient to coolzthe fuel rapidly to-ZO" F., then inV an amount to cool the Vfuelat the krate of about 0.5 F. per rninute. The temperaturejof the cooling bathisgfurther controlled by controlling the 'flow of thecoolng liquid. Y Wherrthey first appreciable rise (5 to 10mm. in fscr'een pressure differential occurs, th e temperature prevail? ing at that time ismaintainedfor at least 5 minutes whilec` maintaining the fuel ow at' 0 .67 g.p.m.` `Ifl the .differendecreased in 1 F. increments until a largeincrease in pressure differential occurs.'v Y- The purnpability temperature fora'Water-saturated JP-4 fuel is 'usually between-f5 and 15 l lF With l2 ml. `per gallon of Yfree water, thepumpability temperature is gen-Y additive employedv consisted Aof hexarnethyl phosphoric `-.triamide. VThe tests Were conducted onl a fuel saturated -.with,waterand also on a fuel s aturatedfwithjand con# ftaining excess -Waterin vthe amount of= 2 Inl. of excess ivwiterper gallon of'fuel'.

At ahexamethyl phosphoric triamideconcentration of 0.1 Weight',percerltLtlie fuel saturated with Water had a' pumpabilitytemperature of 76 F.

At .a f hexamethyl phosphoric triamide Vconcentration 1. AA-jet fuelrcomposition consisting essentially of (f1) Vgasoline'a'nd kerosene hydrocarbon fractions boiling fromv about 100- 60Qvdegree's P., said hydrocarbon fractions being free of `alkyl lead antiknock compounds, and (2) an 4anti-icing'amount of a hexaalkyl phosphoric triamide lin Vwhich saidalkylradicals have-from 1- tov4 carbon atoms.

l2.`A Vjet fuelcomposition "accordingtoclaim 1 containing'0.02 r to 0.35 weight percent of said'heiaallylphos'- phorictriamide. .f-,i Y3. A jet-fuel compositionaccording toclaim-l inwhich said triamide isV hexam'ethylphosphoric triamide.Y

l4. jet fuel composition according to claiml containing' fromiaboutOS to 0.20weight percent'of said hexaalkyl `phosphoric' triamide.

5.- Ajetfuelcomposition ac cording'to'claim 4 in which rsaid vhexaalkylphosphoric triamide ishexamethyl phosvphorictriarnide.

Y 0.1 Weight percent;4V the fuel saturated'vvith water and containing 2in1. of excess Water per gallon ofY fuel also had a .pumpability Atemperature'of -7 6 F.

Claims (1)

1. A JET FUEL COMPOSITION CONSISTING ESSENTIALLY OF (1) GASOLINE AND KEROSENE HYDROCARBON FRACTIONS BOILING FROM ABOUT 100-600 DEGREES F., SAID HYDROCARBON FRACTIONS BEING FREE OF ALKYL LEAD ANTI-KNOCK COMPOUNDS, AND (2) AN ANTI-ICING AMOUNT OF A HEXAALKYL PHOSPHORIC TRIAMIDE IN WHICH SAID ALKYL RADICALS HAVE FROM 1 TO 4 CARBON ATOMS.

Images