What are the hazards of too high a flash point for aviation fuel?
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The flash point of our aviation fuel has been well controlled up to now. But recently, perhaps due to fluctuations in crude oil prices, the flash point of aviation fuel rose to 59.5°C, and the buyers refused to accept it. **The specification requires that the flash point of aviation fuel be no less than 38°C, with no upper limit set. So I would like to ask everyone, what are the hazards of a high flash point for aviation fuel? Note: Our 10% recovery temperature meets the **specified value (177°C; the **specified limit is no higher than 205°C), while no requirement exists for the initial boiling point (168°C).
Is the flash point too high, making it difficult to burn?
No, other parameters are specified in the national standards to ensure it can burn properly. Moreover, on many military aircraft, the flash point is required to be 50+.
Materials with a high flash point tend to develop carbon deposits, while those with a lower flash point produce fewer such deposits
The flash point of oils is actually related to their composition. A higher flash point indicates a heavier composition, with reduced volatility and flammability. As the flash point increases, both the storage safety and static electricity safety of the oil improve, but its flammability decreases slightly. If it is within the normal operating limits, there are no adverse effects. However, a too high flash point may affect the engine’s ignition characteristics and the stability of the flame.
There are also relevant specifications in national standards regarding the tendency of jet fuel to form carbon deposits. The smoke point, also known as the height of the smokeless flame, refers to the maximum height at which a fuel flame burns without producing smoke, as measured in a special lamp; it is also called the height of the smokeless flame. The maximum height of the smokeless flame, in millimeters. The smoke point is a specification parameter that controls the carbon deposition performance of aviation fuel. The higher the smoke point, the better, as it indicates a lower tendency for the fuel to form carbon deposits. The national standard requires a minimum of 25 mm, and we meet this requirement as well. The relevant dry content and residual amounts also meet the requirements. It can be said that our tendency to form carbon deposits certainly meets national standards.
In my opinion, ignition and combustion are related to the initial boiling point and the 10% recovery temperature; the amount of components is also connected to density, and these indicators of ours meet national standards as well. There should be no issues with poor ignition or combustion characteristics. I also specifically checked other standards related to coal combustion; the flash point requirement for Jet Fuel No. 5 is as high as 60°C. Jet Fuel No. 1 (RP-1) and Jet Fuel No. 2 (RP-2) are kerosene-based fuels, with boiling ranges of 135–240°C, and their freezing points are 60°C and 50°C respectively. Both of these fuels are used in military and commercial aircraft. Jet fuel No. 3 (RP-3) is a heavier kerosene-type fuel with a boiling range of 140–240°C, a freezing point not higher than 46°C, and a flash point above 38°C; it is used in civil aviation aircraft. Jet fuel No. 4 (RP-4) is a wide-range fuel with a boiling range of 60–280°C and a freezing point not higher than 40°C; it is generally used in military aircraft. Jet fuel No. 5 (RP-5) is a heavy kerosene-type fuel with a boiling range of 150–280°C, a freezing point not higher than 46°C, and a flash point above 60°C; it is suitable for use in aircraft on ships. We have been producing it using Jet Fuel No. 3 throughout, with a flash point ranging from around 45–50°C; now it has risen to 59.5°C, and AVIC does not accept it any longer.