Light diesel oil, a kind of relatively light densitydiesel oil。Usually 180~370 ℃fraction。It is generally obtained by blending straight run diesel oil from natural oil with secondary processing diesel oil.Some cracking products are sometimes mixed in.AndHeavy diesel oilIn comparison, the quality requirements are stricter,Cetane numberHigh viscosity, low freezing point and sulfur content.
Light diesel oil is widely used in diesel vehicles, tractors and high-speed diesel engine fuel for ships, mines, power generation, drilling and other equipment.
Same as vehiclegasolineSimilarly, diesel has different brands.The basis for diesel oil classification is freezing point.
At present, light diesel oil used in China is divided into 6 brands according to its freezing point: 10 # diesel oil, 0 # diesel oil, - 10 # diesel oil, - 20 # diesel oil, - 35 # diesel oil and - 50 # diesel oil.[1]
The selection of diesel oil is based on the temperature during use.The last five brands of diesel are mainly used for diesel vehicles, and 0 # diesel is used when the temperature is above 4 ℃;- 10 # diesel oil is selected when the temperature is 4 ℃ - 5 ℃;- 20 # diesel oil is selected when the temperature is - 5 ℃ - 14 ℃;- 35 # diesel oil is selected when the temperature is - 14 ℃ - 29 ℃;- 50 # diesel oil is selected when the temperature is - 29 ℃ - 44 ℃.If the brand of diesel oil is lower than the above temperaturefuel system It may be waxed and blockedOil circuit, affecting the normal operation of the engine.[2]
characteristic
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Light diesel oil refined from petroleum for high speed (above 1000 rpm)Diesel engineFuel used.Light diesel oilBy oilStraight runIt is made by mixing the distillate, catalytic cracking distillate and refined thermal cracking distillate.High speed diesel engines using light diesel as fuel have high thermal efficiency and low specific fuel consumption (fuel consumption per kilowatt hour), so they are widely used in heavy and some medium-sized trucks, as well as a small number of light vehicles and cars.Railway diesel locomotives, construction machinery and agricultural machinery also use light diesel oil as fuel.The light diesel oil shall have good ignitability and low temperature fluidity, as well as proper evaporation, viscosity and stability.
pyrophoric
The performance of light diesel fuel injected into the cylinder and spontaneously ignited when encountering high temperature and high pressure air, expressed by cetane number.High cetane number indicates good ignition performance of light diesel oil, stable and soft operation of diesel engine, and good low-temperature starting performance;If the cetane number is too low, the ignition will be slow, and the accumulated combustible in the cylinderMixtureMany, the pressure and temperature rise violently after the ignition, the diesel engine works rough, the operation is unstable, the noise is large, and the bearing bush may be damaged.If the cetane number is too high (more than 65-70), the light diesel will ignite too fast and burn before it can be fully mixed with air, which will result in long afterburning period, incomplete combustion and increased fuel consumption.The cetane number of light diesel oil for automobiles is generally 40-50.[2]
Low temperature fluidity
The flow performance of light diesel oil when the working environment temperature of diesel engine decreases.Good low-temperature fluidity can ensure that light diesel oilFuel supply systemNormal filtration and conveying in the.Low temperature fluidity can be evaluated by such indicators as cloud point, condensation point or cold filter plugging point.The cloud point is the highest temperature at which the wax crystals begin to precipitate when the light diesel oil is cooled, thus presenting turbidity;Solidification point is the highest temperature at which light diesel loses its fluidity after continuous cooling;The cold filter point is the maximum temperature at which the paraffin crystals separated from the light diesel oil can block the specified low-temperature filter device.Most commercial light diesel oil is paraffin basedcrude oilIn refining, the minimum temperature controlled by cloud point is too strict, and that controlled by condensation point is too wide.In the late 1970s, the cold filter plugging point was preferred as the low-temperature fluidity index.China's light diesel oil is divided into four grades: 0, - 10, - 20 and - 35 according to the solidification point.The condensation point is low, and the distillate is relatively light.The solidifying point of light diesel oil for automobiles shall be at least 5 ℃ lower than the minimum operating ambient temperature.
Evaporativity
The ability of light diesel oil to change from liquid to gas under certain temperature and pressure.It affects the starting performance, working reliability, fuel economy and engine wear of diesel engines.The vaporization of light diesel oil is controlled by 50%, 90% or 95% distillation temperature.If the distillate is too heavy and evaporates slowly, it is difficult to start at low temperature, the afterburning period is long, the combustion is incomplete, and it is easy to cause oil dilution and increase engine wear;If the distillate is too light (there are many compounds with low boiling point), the cetane number is low, it is not easy to ignite, and the evaporation is fast, which is more likely to make the diesel engine work roughly.
viscosity
The property of internal friction resistance between molecules when liquid flows.The viscosity of light diesel oil is an index to ensure the atomization of fuel injection, the distance of fuel injection, and the lubrication requirements of high-pressure fuel pump and nozzle plunger pair.The viscosity of diesel oil for high-speed diesel engine is 2.5~8.0 centistokes at 20 ℃.
Stability Light diesel oil containing cracked fraction has poor stability and is easy to produce during storagecolloidAnd organic acids.Colloid and organic acid are easy to cause nozzle coking and increase carbon deposit in combustion chamber.The stability of light diesel oil can be improved by adding an appropriate amount of anti oxygen and anti gel agent.
In addition, the sulfur content of light diesel oil is also an important performance indicator, which affects the wear of cylinder.In many countries, the allowable sulfur content is 0.5%, and in China, it is not more than 0.2%.In order to prevent the corrosion of acidic combustion products of light diesel oil, alkalineLubricating oilLubrication.
Common sense
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Diesel engines of construction machinery often use light diesel oil as fuel. Proper use is conducive to improving the efficiency of diesel engines and prolonging the service life of machines.
Selection Instructions
There is a good correspondence between the freezing point of diesel oil and the actual operating temperature. The diesel oil shall be selected according to the freezing point of diesel oil compared with the lowest temperature of the local month.The brand of light diesel oil is divided according to its freezing point. If the oil is selected according to its freezing point, the freezing point should be 4-6 ℃ lower than the lowest temperature of the month to ensure that the diesel oil will not solidify at the lowest temperature.The applicable areas of different grades of diesel oil are: No. 0 oil is applicable to areas with minimum temperature above 4 ℃-No. 10 oil is suitable for areas where the minimum temperature is above - 5 ℃-No. 20 oil is suitable for areas with a minimum temperature of - 5-14 ℃-No. 35 oil is suitable for areas with a minimum temperature of - 14-29 ℃.
Different brands of diesel can be blended to reduce the freezing point temperature of high freezing point diesel.However, it should be noted that there is no strict addition relationship for the adjustment of freezing point.For example, after mixing 50% of No. 10 and No. 20 diesel respectively, the freezing point is not - 15 ℃, but between - 13-14 ℃.In addition, 10% - 40% cracking can be added into diesel oilkeroseneTo reduce the setting point, pay attention to mixing evenly after mixing.[1]
Cannot be mixed with gasoline
Diesel oil shall not be mixed with gasoline for use, because the autoignition temperature of gasoline is higher than that of diesel oil, and the ignition performance is poor.Mixed use will lead to difficulty in starting the diesel engine, black smoke from the exhaust pipe, or even failure to start;Sometimes, the diesel engine will appear detonation vibration, which will aggravate the wear of engine parts. At the same time, the combustion chamber and exhaust system will produce a large amount of gum or carbon deposit, which will seriously damage the lubrication and lead to early damage of the diesel engine.
Reasonable low temperature startup
The main way to solve the difficulty of diesel engine starting at low temperature is to selectviscositySuitable lubricating oil, preheating, battery insulation, etc;The auxiliary starting method can also be used, that is, the low temperature starting liquid with light fraction, good volatility, low self ignition point and a certain cetane number can be used. When using, a set of starting liquid using device can be attached, or a syringe can be used to directly inject 10-25mL of low temperature starting liquid into the air inlet pipe.
The main components of starting fluid areEtherThe boiling point is only 34.5 ℃, and the saturated vapor pressure at 40 ℃ is 0.12MPa,flash pointThe temperature is 41 ℃.It can spontaneously ignite in air at 188 ℃, so it is easy to ignite and compress.Do not mix low temperature starting fluid with diesel oil, or "air lock" may occur.
Diesel must be purified
If diesel contains impurities, it is very easy to cause blockage or jamming of precision parts of the fuel system.Therefore, diesel oil must be subject to sedimentation and filtration before use, and the sedimentation time shall not be less than 48h;At the same time, replace or clean it in timeDiesel filter To maintain its good filtering effect.
Safe use
Diesel oil is inflammable and explosive dangerous goods.The self ignition point is 335 ℃, and the heat value after combustion is very high. Once a fire occurs, the oil will be vaporized in a large amount, which makes the fire expand rapidly and difficult to extinguish.Therefore, reasonable fire and explosion prevention measures must be taken in use to ensure safe use.
First of all, it is necessary to strengthen the kindling management of the diesel depot and strictly prohibit the entry of kindling.Secondly, the rags, cotton yarn and oil gloves stained with oil should not be stored in the oil depot or hangar, but should be placed in the designated covered iron bucket, which can prevent oxidation and spontaneous combustion, and can be recycled, cleaned and reused in time.In addition, when welding the diesel tank, steam cleaning and water filling shall be carried out until there is no oil smell when the cover is opened, so as to prevent the tank explosion.[3]
Strict fire control measures
The diesel depot and construction machinery must be equipped with necessary fire-fighting equipment to put out the burning oil in time.Never use water to extinguish the fire after the diesel is on fire.Because diesel is lighter than water and can burn on the water surface, the injected water will flow diesel to a larger range, expanding the combustion area.In case of diesel fire, foam or dry powder fire extinguisher shall be used to put out the fire, or wet fire quilt or sand can be used to cover the fire.
