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Jet fuel (RT, TC)

Jet fuel is a hydrocarbon-based aviation fuel for aircraft planes with turbojet engine.

 

Range and Production

 

Jet fuels are produced for subsonic aircrafts in accordance with GOST 10227-86 and supersonic aircrafts in accordance with GOST 12308-89. There are five grades of fuel for subsonic aircrafts (ТС-1, Т-1, Т-1С, Т-2 and РТ) and two grades of fuel for supersonic aircrafts (Т-6 and Т-8В). ТС-1 fuels (superior and premium grade) and РТ fuel (superior grade) are currently massively produced.

 

ТС-1 Fuel

 

TC-1 fuel is a product of straight run distillation of sour crude (desired cut — 150—350 °C). If sulfur and RSH contents are significantly high, it is hydrotreated or demercaptanised and used in the mixture with straight run cut. The content of hydrotreated component is limited to 70% concentration to prevent minimization of wear-reducing properties of the fuel. The most popular type of jet fuel is for subsonic aircrafts. It is used both in military and civil aviation. It is also used for enrichment through flotation technique.

 

Т-1 Fuel

 

Product of distillation of low sulfur content naphthene based oil with boiling range of 130—280 °C. It contains a large volume of naphthenic acids and therefore has a high acidity level. It is leached and washed with water after fractionation. Heterotopic naphthenic compounds in the fuel provide good wear-reducing properties and chemical stability. On the other hand, fuel has very low thermal oxidative stability. Continuous tests have demonstrated that when this type of fuel is used in НК-8 (Tu-154 (А,Б,Б-1,Б-2) and Il-62) engines, this leads to increased resin deposits and reduced life term of the engine. Only premium fuel grades are currently produced with limited volumes. 

 

The deficit oil grades with very low sulfur content can serve as raw materials for production.

 

Т-2 Fuel

 

Product of distillation oil of wide fractional composition— 60-280 °C. It contains up to 40 % gasoline cuts which leads to high pressure of saturated vapours, low viscosity and density. The maximized pressure of saturated vapours will lead to potential formation of vapour locks in the fuel system of the aircraft which limits its flight altitude.

The fuel is not produced; it is considered to be a back-up fuel with regard to ТС-1 and РТ.

 

RT Fuel

 

It is produced by means of hydrotreatment of straight cut distillation of jet fuel with boiling range of 135—280 °C. As a result of hydrotreatment the content of sulfur and RSH gets minimized, but wear-reducing properties and chemical stability deteriorate. Wear-reducing and autooxidising additives are added into the fuel in order to prevent deterioration of properties.

RT fuel fully corresponds to international norms and even exceeds certain indicators. It has good wear-reducing properties, high chemical and thermal oxidative stability, low sulfur content and almost no RSHs. The fuel can be stored up to 10 years and fully serves engine requirements.

 

Т-6 Fuel

 

It is produced by means of deep hydration of straight run cuts of 195—315 °C, from naphthenic oils. It is used in supersonic aviation mainly in the Air Forces of the Russian Federation.

 

Т-8В Fuel

 

It represents a hydrotreated cut with boiling range of 165—280 °C. In the event of naphthenic low sulfur oils straight run cut is allowed to be used without hydrotreatment. It is used in supersonic aviation mainly in the Air Forces of the Russian Federation.

 

Additives

 

Аntistatic Additives

 

The long-term experience of domestic and international aircraft operation demonstrates that static electricity can accumulate in the course of fuel transfer or fuelling of aircrafts. There is a potential for explosion at any time due to unpredictability of the process. Antistatic additives are added into fuel to prevent this dangerous explosion. They improve electrical conductivity of the fuel up to 50 pCm/m, which ensures safety in the course of fuelling and transfer of fuels. ASA-3 (Shell) and Stadis-450 (Innospec) additives are used abroad. Sigbol additive (Specification 38.101741-78) that can be added to fuels ТС-1, Т-2, РТ and Т-6 in the amount of 0,0005 % is popular in the CIS countries.

 

Anti-icing Additives

 

The temperature in the fuel tank drops to -35C during 5 hour flight after fuelling under −5…+17 °C. The record temperature drop is −42 °C (Тu-154) and −45 °C (the tanks feeding end engines Il-62М). The fuel forms ice crystals under this temperature that plug fuel filters which may lead to termination of fuel supply and engine shutdown. Aircraft filters with 12-16 mcm pore size start getting plugged with water content of 0,002 % (mass).

To prevent formation of ice crystals under low temperatures anti-icing additives are added into fuel directly at the place of aircraft fuelling. Ethyl cellosolve (Liquid I) in accordance with GOST 8313-88, Tetrahydro Furan (THF) in accordance with GOST 17477-86 and their 50% mixtures with ethanol (И-М, THF-М additives) are widely used. The additives can be added practically to any fuel.

 

Аntioxidising Additives

 

They are added to hydrotreated fuels (РТ, Т-6, Т-8В) to compensate minimised chemical stability as a result of hydrotreatment. Аgidol-1 (2,6-de-three-butyl-4-methylphenol) is used in Russia in accordance with Specification 38.5901237-90 in 0,003-0,004 % concentration. It almost completely prevents fuel oxidation in such concentrations, including maximized temperatures (up to 150 °C).

 

Wear-reducing Additive

 

It is designed to reinstate wear-reducing properties of fuels as a result of hydro treatment. They are added to same fuels as autooxidising additives. Sigbol and Sigbol composition of additives and PMAM-2 are widely used in Russia (polymetalcrylate type— Specification 601407-69). «K» additive is widely used for РТ fuels (GOST 13302-77), which corresponds to Sigbol additive based on efficiency as well as due to deficit of “K” additive - Hitech-580 additive of “Etil”.