Performance in jet fuels

10 August 2018

We’ve been using jet engine fuels for over sixty years, and the demand for high performance, cost-effective and environmentally friendly fuels increases all the time. Once the fuel has been produced, its performance may also be dependent on a number of other factors, including the way it is used and elements that are added to it. So let’s look at some well-known fuel types sold by jet fuel suppliers, and how their performance is assessed.

ICAO Jet A1 fuel

ICAO Jet A1 and the similar but less common Jet-A1 are the most commonly used fuels in civilian jets. Made from kerosene, Jet A1 is designed to fuel gas turbine jet engines. It is much safer than the fuel used in piston engine aircraft, because its flash point is much higher.

Russian TS-1 jet fuel 

Russia has its own standard (GOST) for jet fuel suppliers, although it aligns with international standards. TS-1 is its fuel grade for use in jets that are flying at subsonic speeds. Combustion efficiency is delivered through high volatility. The fuel combines high heat from combustion with combustion efficiency, to provide longer distance flight times. High pumpability (see below) is essential to keep the fuel flowing to the combustion chamber at low temperatures. A low rate of formation of deposits means that engine parts aren’t subject to wear and corrosion.

TS-1 is tested for mercaptan and total sulphur before it is released, and can be hydrotreated and further blended if the sulphur is too high.

Performance specifications for fuels

With fuel for passenger jets, safety is paramount, and therefore lab-tested consistency is overwhelmingly important. The planes may encounter extreme weather conditions or temperature ranges, and the fuels must conform to the agreed specification, designed to provide safe operation in these conditions. However, there are still differences, and there is no one worldwide standard.

Combustion efficiency, thermal stability, pumpability, lubricity, cleanliness, non-corrosivity, energy content and environmental impact are all aspects of jet fuel performance that are measured.

Pumpability and energy content

Pumpability is a key safety feature in jet fuels such as Jet A1. The fuel must be pumpable even when the aircraft is operating in a low temperature environment, as we saw with the Russian TS-1. If it thickens, and can’t be pumped, the fuel supply to the engine will be cut off, so this is a clear safety issue. When a new fuel or additive is being proposed, its viscosity, flow and pumpability in various environments will be carefully measured.

Energy content is a measurement of how much heat is released when a certain amount of fuel is burned. For testing of performance fuels, the test environment has to be carefully controlled, to ensure that variations in the environment don’t lead to false results.

Performance testing of fuels is a highly complex and specialised business, especially when one element of the fuel specification is changed, and the results may affect safety. This is the expert arena in which Coryton is a leader.

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