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While standardized laboratory-scale wear tests are available to predict the lubricity of liquid fuels under ambient conditions, the reality is that many injection systems operate at elevated temperatures where fuel vaporization is too excessive to perform the measure satisfactorily. Alternative fuels such as Dimethyl Ether (DME) are gaseous at ambient conditions and must be pressurized to form a lubricating liquid. The present paper describes an apparatus purposely designed to evaluate fuel lubricity in a pressurized environment at temperatures of up to 30°C. The remaining test parameters are identical to those of the widely standardized High Frequency Reciprocating Rig (HFRR), which allows use of previously developed correlations to full-scale injection equipment. Results obtained using the High Pressure High Frequency Reciprocating Rig (HPHFRR) indicate that DME, as well as other volatile fuels evaluated, have very poor lubricity.

Lower explosion limits (LEL) and the chemical compositions of JP-8, Jet A and JP-5 fuel vapors were determined in a sealed combustion vessel equipped with a spark igniter, a gas-sampling probe, and sensors to measure pressure rise and fuel temperature. Ignition was detected by pressure rise in the vessel. Pressure rises up to 60 psig were observed near the flash points of the test fuels. The fuel vapors in the vessel ignited from as much as 11°F below flash-point measurements. Detailed hydrocarbon speciation of the fuel vapors was performed using high-resolution gas chromatography. Over 300 hydrocarbons were detected in the vapors phase. The average molecular weight, hydrogen to carbon ratio, and LEL of the fuel vapors were determined from the concentration measurements. The jet fuel vapors had molecular weights ranging from 114 to 132, hydrogen to carbon ratios of approximately 1.93, and LELs comparable to pure hydrocarbons of similar molecular weight.

Several test programs have shown that the combustion of methanol in spark ignition engines can cause unusually high corrosive wear of the upper cylinder bore and ring areas. In this study, a 2.3-liter engine fueled with methanol was operated in a nitrogen-free atmosphere to determine the importance of nitric acid in the corrosion mechanism. A 20-hour steady-state test was carried out using neat methanol as the fuel and a mixture of oxygen, argon, and carbon dioxide in place of air. Only trace amounts of NOx and nitric acid were found in the exhaust products during this test. The wear, indicated by iron buildup in the lubricant, was found to be essentially the same in the nitrogen-free test as that detected in baseline engine tests combusting methanol-air mixtures. It was concluded that nitric acid does not play a role in the corrosion mechanism.

An investigation of the effects of lubricant composition changes on spark ignition engine wear and deposits when using alcohol fuel was jointly sponsored by the U.S. Department of Energy and the U.S. Army Mobility Equipment Research and Development Command. In the work covered by this paper, tests were conducted with methanol fuel in a 2.3-liter engine using a modified ASTM Sequence V-D procedure. The baseline lubricant was a 10W-30 grade product, qualified under MIL-L-46152, for which a large amount of field and laboratory data were available. Eleven variations of the baseline lubricant were supplied and tested. The results indicate that a magnesium-based detergent additive was less effective in controlling methanol-related engine wear than was a calcium-based additive. Ashless dispersant chemistry was also determined to be of importance in controlling wear with methanol fuel.

It is now a fairly well established fact that excessive ring and cylinder bore wear can result from the operation of an S. I. engine on neat methanol. The mechanism leading to the excessive wear were investigated using both engine and bench tests. Engine tests using prevaporized superheated methanol indicated that the wear results from reactions between the combustion products and the cast iron cylinder liner, where the presence of liquid methanol in the combustion chamber appears to be an important part of the mechanism. These reactions were investigated using a spinning disc combustor. The spinning disc combustor was used to provide a source of burning methanol droplets which were subsequently quenched on a water-cooled cast iron surface. The condensate formed on the cast iron surface was collected and analyzed for chemical composition. Infrared analysis indicated the presence of large quantities of iron formate, a reaction product of iron and formic acid.

An investigation of the effects of alcohol fuels and lubricant formulations on spark ignition engine wear and deposition was jointly sponsored by the U.S. Department of Energy and the U.S. Army Mobility Equipment Research and Development Command. Tests were conducted using neat methanol, anhydrous ethanol, and alcohol blends as fuel in a 2.3-liter engine using a modified ASTM Sequence V-D test procedure. This dynamometer testing indicates that alcohol fuels reduce the buildup of engine deposits. Also, it was found that neat methanol greatly increases engine wear rates while anhydrous ethanol and alcohol-gasoline blends do not increase wear rates over that of unleaded gasoline. A 20-hour steady-state test was developed which shows that engine wear is inversely related to engine oil temperature when using methanol as fuel. The study shows that one lubricant appears to best control methanol-related engine wear, but still not to acceptable levels.

A T-63 combustor rig has been used to study the sensitivity of combustor performance to the physical and chemical properties of fuels. The purpose was to determine the impact of broadening fuel specifications and using non-specification fuels in emergencies. The fuel properties of special concern were the composition, the distillation curve and viscosity. The first property is associated with the chemistry of carbon formation while the latter two are related to mixing as they affect the atomization and vaporization. Six fuels were blended from a JP-5 base fuel and used to determine the effects of aromatic content, types of aromatics, and end point. Three JP-5s derived from coal, shale oil, and tar sands, were used to see if they correlated the same as the petroleum-derived fuels despite their different chemistry. Seven more fuels that were blends of marine diesel, JP5, and gasoline were used to examine all aspects but with emphasis on viscosity and distillation curve.