Wide-cut fuel

The lower volatihty of JP-8 is a significant factor in the U.S. Air Force conversion from JP-4, since fires and explosions under both combat and ordinary handling conditions have been attributed to the use of JP-4. In examining the safety aspects of fuel usage in aircraft, a definitive study (15) of the accident record of commercial and military jet transports concluded that kerosene-type fuel is safer than wide-cut fuel with respect to survival in crashes, in-flight fires, and ground fueling accidents. However, the difference in the overall accident record is small because most accidents are not fuel-related. 

The increase in fuel viscosity with temperature decrease is shown for several fuels in Figure 9. The departure from linearity as temperatures approach the pour point illustrates the non-Newtonian behavior created by wax matrices. The freezing point appears before the curves depart from linearity. It is apparent that the low temperature properties of fuel are closely related to its distillation range as well as to hydrocarbon composition. Wide-cut fuels have lower viscosities and freezing points than kerosenes, whereas heavier fuels used in ground turbines exhibit much higher viscosities and freezing points. 

Briefly, JP-4 is a wide-cut fuel developed for broad availability in times of need. JP-6 is a higher cut than JP-4 and is characterized by fewer impurities. JP-5 is specially blended kerosene, and JP-7 is a high-flash-point special kerosene used in advanced supersonic aircraft. JP-8 is a kerosene fraction that is modeled on jet A-1 fuel (used in civilian aircraft). For this profile, JP-4 will be used as the prototype jet fuel, due to its broad availability and extensive use. 

Physical Form. JP-4 is a colorless to straw-colored liquid with the odor of gasoline and/or kerosene. JP-7 is a liquid, usually colorless and with the odor of kerosene. JP-4 can be made by refining either crude petroleum oil or shale oil. It is called a wide cut fuel because it is produced from a broad distillation temperature range and contains a wide array of carbon chain lengths, from 4- to 16. It consists of approximately 13% (v/v) aromatic hydrocarbons, 1.0% olefins, and 86% saturated hydrocarbons. JP-7 is made by refining kerosene, a product of refined crude petroleum. It was developed for use in advanced supersonic jets because of its thermal stability and high flash point. ... 

Aviation turbine fuels are manufactured predominantly from straight-run kerosene or kerosene-naphtha blends in the case of wide-cut fuels that are produced from the atmospheric distillation of crude oil. Straight-run kerosene from low-sulfur (sweet) crude oil will meet all the requirements of the jet fuel specification without further refinery processing, but for the majority of feedstocks, the kerosene fraction will contain trace constituents that must be removed by hydrotreating (hydrofining) or by a chemical sweetening process (Speight, 2000). 

Kerosene can vary widely in its burning quality as measured by carbon deposition, smoke formation, and flame radiation. This is a function of hydrocarbon composition—paraffins have excellent burning properties, in contrast to those of the aromatics (particularly the polynuclear aromatic hydrocarbons). As a control measure the smoke point test (ASTM D-1322, IP 57) gives the maximum smokeless flame height in millimeters at which the fuel will burn in a wick-fed lamp under prescribed conditions. The combustion performance of wide-cut fuels correlates well with smoke point when a fuel volatility factor is included, because carbon formation tends to increase with boiling point. A minimum smoke volatility index (SVI) value is specified and is defined as ... 

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. 

Synonyms JP-4 Jet Propellant-4 Jet fuel-4 MIL-T-5624-L-Amd, 1 wide cut JP-4 military (gasoline type)... 

Jet fuels are typically prepared from either straight-run kerosene or from wide-cut kerosene/naphtha blends off of the atmospheric distillation unit. TABLE 3-10 briefly describes the composition of some typical jet fuel grades. 

The manufacture of distillates either directly for fuels or for feed to downstream processing units ordinarily does not require any particular degree of fractionation between cuts. Also, wide cuts are usually acceptable. For these reasons, the distillates can be condensed by cooled pumparound reflux, grid type contacting sections and chimney draw trays. For all practical purposes, the operation of the main condensing sections can be described as a single-stage equilibrium condensation. 

Naphthenic acids occur ia a wide boiling range of cmde oil fractions, with acid content increa sing with boiling point to a maximum ia the gas oil fraction (ca 325°C). Jet fuel, kerosene, and diesel fractions are the source of most commercial naphthenic acid. The acid number of the naphthenic acids decreases as heavier petroleum fractions are isolated, ranging from 255 mg KOH/g for acids recovered from kerosene and 170 from diesel, to 108 from heavy fuel oil (19). The amount of unsaturation as indicated by iodine number also increases in the high molecular weight acids recovered from heavier distillation cuts. 

Because of its high chemical reactivity, acetylene has found wide use in synthesis of vinyl chloride, vinyl acetate, acrylonitrile, vinyl ethers, vinyl acetylene, trichloro- and tetrachloro-ethylene etc., in oxyacetylene cutting and welding, and as a fuel for atomic absorption instruments. 

A. ACTION OF THE VALVE. Valves are designed to either fail in the wide-open position or completely shut. Which action is appropriate depends on the effect of the manipulated variable on the process. For example, if the valve is handling steam or fuel, you would want the flow to be cut off in an emergency, i.e., you want the valve to fail shut. If the valve is handling cooling water to a reactor, you... 

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