The fluidity of diesel is mainly represented by viscosity, freezing point and cold filter point.
Viscosity is an important performance item for diesel. It is closely related to diesel rated supply, atomization, flammability and lubricity. When the high-speed diesel engine is running, the injection time is only 0.001 to 0.002 seconds each time. In such a short period of time, the injected diesel oil is gasified and self-ignited, and the diameter of the droplet cannot exceed 0.025 mm to ensure complete combustion. The atomization depends on the viscosity. If the viscosity is too large, the droplets are large, the air is mixed unevenly, and the combustion does not completely form carbon deposits;
If the viscosity is too small, the atomization is good, but the spray angle is large and close, and it cannot be completely mixed with the air, and the lubricating performance of the components such as the injector is deteriorated, and the wear is increased.
In the standard, the kinematic viscosity of No. 0 diesel at 20 ° C is 3.0-8.0 mm 2 / s, only in this range.
It can ensure that the diesel has better lubricity to the engine fuel supply system, and ensure that the diesel has better atomization performance and supply, so that the diesel has better combustion performance.
2, freezing point, cold filter point
The freezing point and the cold filter point are the two main indicators for assessing the low-temperature fluidity of diesel. The diesel oil in China is classified according to the freezing point, and the freezing point is the highest temperature at which diesel cannot flow. However, in actual use, before the diesel oil is completely solidified, wax crystals are precipitated, and the crystallization reaches a certain size, which may cause the filter screen to become clogged, so that the diesel oil cannot be used before it reaches the freezing point.
The maximum temperature at which diesel cannot pass through the filter under specified conditions is called the cold filter point of diesel. The cold filter point has a good correspondence with the performance of diesel. The actual operating temperature range of each grade of diesel is divided by the cold filter point.