Viscosity diesel fuel

Contamination of fuel with high-viscosity products or operation at excessively low temperatures can increase the viscosity of fuel and result in fuel pumping problems. Also, if diesel fuel viscosity at 0°F (-17.8°C) is greater than 45 cSt, fuel pumping problems are likely to occur. 

For a long time the official specifications for diesel fuel set only a mciximum viscosity of 9.5 mm /s at 20°C. Henceforth, a range of 2.5 mm /s minimum to 4.5 mm /s maximum has been set no longer for 20°C but at 40°C which seems to be more representative of injection pump operation. Except for special cases such as very low temperature very fluid diesel fuel and very heavy products, meeting the viscosity standards is not a major problem in refining. 

Lubricants, Fuels, and Petroleum. The adipate and azelate diesters of through alcohols, as weU as those of tridecyl alcohol, are used as synthetic lubricants, hydrauHc fluids, and brake fluids. Phosphate esters are utilized as industrial and aviation functional fluids and to a smaH extent as additives in other lubricants. A number of alcohols, particularly the Cg materials, are employed to produce zinc dialkyldithiophosphates as lubricant antiwear additives. A smaH amount is used to make viscosity index improvers for lubricating oils. 2-Ethylhexyl nitrate [24247-96-7] serves as a cetane improver for diesel fuels and hexanol is used as an additive to fuel oil or other fuels (57). Various enhanced oil recovery processes utilize formulations containing hexanol or heptanol to displace oil from underground reservoirs (58) the alcohols and derivatives are also used as defoamers in oil production. 

Long-chain esters of pentaerythritol have been used as pour-point depressants for lubricant products, ranging from fuel oils or diesel fuels to the high performance lubricating oils requited for demanding outiets such as aviation, power turbines, and automobiles. These materials requite superior temperature, viscosity, and aging resistance, and must be compatible with the wide variety of metallic surfaces commonly used in the outiets (79—81). 

Diesel fuel kinematic viscosity is measured by ASTM D445, and is reported in units of mm /s at 40°C. Desired viscosity is a function of fuel grade and ranges from a minimum of 1.3 mm /s for 1-D to a maximum of 24 mm /s for 4-D. 

Liquid fuels for ground-based gas turbines are best defined today by ASTM Specification D2880. Table 4 Hsts the detailed requirements for five grades which cover the volatility range from naphtha to residual fuel. The grades differ primarily in basic properties related to volatility eg, distillation, flash point, and density of No. 1 GT and No. 2 GT fuels correspond to similar properties of kerosene and diesel fuel respectively. These properties are not limited for No. 0 GT fuel, which allows naphthas and wide-cut distillates. For heavier fuels. No. 3 GT and No. 4 GT, the properties that must be limited are viscosity and trace metals. 

Diesel fuel makeup can represent various combinations of volatility, ignition quality, viscosity, sulfur level, specific gravity, and other characteristics. Various additives are used to impart special properties... 

There has been a recent revival in interest in the use of ethanol-diesel fuel blends (E-diesel) in heavy-duty vehicles as a means to reduce petroleum dependency, increase renewable fuels use, and reduce vehicle emissions [27]. E-diesel blends containing 10-15% ethanol could be prepared via the use of additives. However, several fuel properties that are essential to the proper operation of a diesel engine are affected by the addition of ethanol to diesel fuel - in particular, blend stability, viscosity and lubricity, energy content and cetane number (increasing concentrations of ethanol in diesel lower the cetane number proportionately) [28]. Materials compatibility and corrosiveness are also important factors that need to be considered. 

The addition of ethanol to diesel lowers fuel viscosity and lubricity. Lower fuel viscosities lead to greater pump and injector leakage, reducing maximum fuel delivery and hence power output. Hot start problems may also be encountered as insufficient fuel may be injected at cranking speed when fuel leakage in the high-pressure pump is amplified because of the reduced viscosity of the hot fuel. 

An extensive review has been conducted to identify potential oxygenates for blending into diesel fuels [55]. Over 70 molecules were identified and tested, taking into account numerous physical properties such as oxygen content, flash point, viscosity, cetane number, corrosivity, toxicity, and miscibility with diesel blends. Five key aspects were considered critical to develop commercially valuable diesel additives ... 

Today s diesel fuel grades are blends which may contain straight-run distillate, cycle oil, various gas oils, and heavy cracked distillates. Kerosene or jet fuel may be blended into the diesel to improve the low-temperature viscosity and handling characteristics of the fuel. 

Fuel grade is based primarily upon the viscosity of the fuel and the intended application. Both diesel fuel and fuel oil grades exist. Diesel fuel grades and their intended applications are outlined in TABLE 3-12. 

When diesel fuel is injected into the high-pressure environment of a combustion chamber, it must fully penetrate into the pressurized air in order to completely combust. Fuel with a low viscosity does not have enough thrust to penetrate effectively through the pressurized air and disperse completely. The result is a soft, nonpenetrating spray which does not spread throughout the chamber. Poor combustion efficiency and engine power result. 

Diesel fuel prevents wear of high-pressure fuel pumping and injection equipment parts. If the viscosity of diesel fuel is low, its ability to form a hydrodynamic lubricating film between moving metal parts diminishes. The term lubricity is used to describe the wear-inhibiting capability of distillate fuels. 

If a diesel fuel is low in viscosity due to kerosene dilution or solvent dilution, its lubricity is probably poor. The possibility of wear of the high-pressure fuel injection pump parts will increase. The effect of kerosene dilution on the lubricity of a typical low sulfur diesel fuel is shown in FIGURE 5-2. 

Additives identified as lubricity improvers are sometimes used to improve the wear-inhibiting properties of low-viscosity 1 diesel fuel and higher viscosity hydrotreated low-sulfur 2 diesel fuel. Lubricity improvers are available as single products or may be contained within a diesel fuel performance additive package. In addition to distillate fuel lubricity, gasoline lubricity is being investigated. 

Crude oil and high-boiling-point, high-viscosity petroleum fractions such as 6 fuel oil, atmospheric tower bottoms, and vacuum gas oil can contain wax which crystallizes at temperatures often above room temperature. It is not unusual for these oils to have base pour points of 100°F (37.8°C) or greater. In order to utilize these heavy oils, the pour point and viscosity of these oils must be reduced. One method which is used to accomplish this is to dilute the heavy oil with lower-viscosity components such as diesel fuel or kerosene. The oil then becomes pumpable at lower temperatures. 

The distillation profile will provide some indication of the low-temperature performance of diesel fuel. IBP values >350°F (>176.7°C) and EP temperatures >700°F (>371.1°C) indicate that the fuel viscosity will probably be high at low temperatures. Even fuel treated with a wax crystal modifier may be difficult to pump due to the high viscosity of the fuel components. 

ASTM D-86 look for high EP or residual material. The diesel fuel could be contaminated with high-boiling-point, high-viscosity material. 

Add lower viscosity fuel components such as kerosene or 1 diesel fuel. 

Low-viscosity diesel fuels will not penetrate and mix well into pressurized air. As a result of this, fuel will not become involved in the entire combustion chamber volume. Thus exposure to available air within the chamber is limited. Incomplete utilization of fuel volume and low power result. 

Shearing of high-viscosity diesel fuel by the fuel injection pump can result in excessive heat buildup and distortion of the pump components. 

Check fuel viscosity viscosity may be too high Minimize the amount of kerosene blended into 2 diesel fuel or low-viscosity fuel Use diesel fuel with a cetane number of 40 or higher Check fuel for an unusually low BTU rating fuel... 

Viscosity 40°C Low limits are similar to conventional diesel fuel ... 

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