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Do you know why there are multiple grades of diesel generator fuel?

June 27, 2022
Diesel fuel is the main fuel for diesel generators, which is safe and low cost, with low self-ignition point, high viscosity, high density, high flash point and stable performance, but it is easy to volatilize and deteriorate in the process of transportation and storage. According to the different requirements of various models of diesel generators, there are different requirements for the performance of the fuel used, so there are various grades of diesel, which are closely related to the following indicators.
(1) cetane number. Cetane number is to evaluate the diesel fuel self-ignition index. Self-ignition is good or bad, directly affects the quality of the diesel combustion process and work performance. High cetane value of diesel fuel, good self-ignition, the work of the cylinder can be sprayed quickly after the fire, so that the diesel engine work soft, easy to start at low temperatures, conversely, low cetane value of diesel fuel, poor self-ignition, so that the diesel engine runs rough, and cause starting difficulties. But it can not be said that the higher the cetane number the better. Because the cetane number is too high, the stability of diesel fuel is poor, after spraying into the combustion chamber, it is too late to fully mix with the air on fire, so that the diesel fuel at high temperatures to produce cracking separation of a large number of free carbon, with the exhaust gas discharge, resulting in the phenomenon of black smoke, resulting in increased fuel consumption. Therefore, the requirement of a proper cetane number, the general high-speed diesel engines used in diesel fuel cetane number of 40 ~ 60.
(2) distillation range. Diesel fuel is sprayed into the cylinder is in the excitation and then ignition combustion, within this diesel evaporative good or bad on the diesel combustion process has a significant impact. The distillation range indicates the evaporation of diesel fuel, the distillation range temperature is low (i.e. light distillate fuel content is large), the fuel and air can be well mixed, the diesel engine is also easy to start. However, light distillate fuel tends to evaporate prematurely, causing too much fuel to be burned at the same time and making the diesel engine work roughly. On the contrary, the viscosity of heavy-distillate fuel is large, poor atomization, slow vaporization, easy to cause incomplete combustion and serious carbon accumulation phenomenon. Therefore, it is required that the light and heavy fraction content of diesel fuel should not be too much, and the distillation range should be small.
(3) Movement viscosity. Viscosity of diesel fuel liquidity, viscosity of fuel atomization and fuel supply system has a close relationship with the normal work, viscosity is too high, fuel flow resistance in the pipeline and filter, spray deterioration, poor combustion. And viscosity is too low, so that the fuel system in the precision coupling lubrication conditions deteriorate, accelerate parts wear, and increase the amount of oil leakage, viscosity and temperature has a great relationship, the lower the temperature viscosity, the greater the winter dog diesel viscosity will increase, even in the pipeline flow is also difficult. Therefore, when used at low temperatures, should be properly preheated.
(4) freezing point. The viscosity of diesel fuel increases with the temperature drop, when down to a certain temperature, diesel fuel contains high molecular hydrocarbons will produce crystallization, so that the diesel fuel lost liquidity, the temperature is called the freezing point (freezing point). The standard light diesel fuel is named according to the freezing point, divided into 10, 0, -10, -20, -35, -50 six, such as -10 light diesel fuel freezing point of -10 ° C. The high freezing point of diesel fuel, in the low temperature environment, it is easy to cause the oil circuit and filter blockage, resulting in insufficient oil supply, and even interrupt the oil supply. Therefore, the use of the appropriate grade of diesel fuel must be selected according to the ambient temperature conditions.
In addition to the above-mentioned main indicators, the standard contains harmful components of diesel fuel to limit the provisions. For example, the residual carbon, ash, carbon content, mechanical impurities, moisture, acidity, water-soluble acid or alkali and actual gum, etc. The above components will have different degrees of influence on the normal work of diesel engine parts.
Various diesel engines according to the structure and performance requirements are different, in the instructions for use are clearly specified in the applicable diesel grades, high-speed diesel engines in general in the summer or ambient temperature above 0 ° C, the choice of 0 light diesel; in winter or ambient temperature below 0 ° C, the choice of -10 ° C light diesel.