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The U.S. military, as a member of the North Atlantic Treaty Organization (NATO), interchanges fuels and other materials with other member nations throughout Europe. NATO is planning to use a single fuel for all battlefield operations, substituting NATO code F-34 (JP-8) for F-40 (JP-4) in aircraft and for F-54 (diesel fuel) in ground equipment. As part of this conversion process, the U.S. Army has been evaluating the impact of this fuel change on the operation of its diesel-fueled ground equipment. This paper covers some of the initial diesel engine durability testing being conducted and also reports some preliminary data of the operation of selected combat and tactical vehicles on F-34 (JP-8). This work, as well as other projects referenced, was a predecessor to the full conversion of an Army base to JP-8 as a final demonstration prior to the conversion within NATO. Fort Bliss, located near El Paso, TX, was converted to F-34 (JP-8) beginning February 1989.

Previous research by the U.S. Army defined requirements For heavy-duty diesel engine lubricants for military equipment deployed in arctic regions. These products have provided excellent performance for nearly 20 years-first as a purchase description in 1969, and fielded under specification MIL-L-46167 since 1974. Although this specification provides for use of mineral base or synthetic base oils, the performance requirements are such that only synthetic base lubricants (nominal 6 cSt) have been qualified.

Borderline oil-pumpability temperatures (BPTs) were determined for U.S. Army diesel engine oils by conducting diesel engine motoring experiments in a cold box. Times for pumped lubricant to reach critical components were measured in unfired engines at simulated idle speeds (600-800 rpm). The variables-investigated included: four different diesel engine types found in the U.S. Army fleet; four different oil viscosity grades; and three different viscosity index improver chemical types. In general, for a given oil, the severity of engine oil pumpability by engine type in decreasing order was; the Continental LDT-465-1C and the Cummins VTA-903T were the most severe, and were approximately equivalent. The GM 6.2L engine was the next least severe with the DDC 6V-53T engine being the overall least severe. The different viscosity index improver chemistries of specially blended test oils included: olefin copolymer (OCP), styrene-iso-prene polymer (SI), and polymethacrylate (PMA).

Combustion studies on various potential alternative fuels were performed for the U.S. Array Belvoir Research and Development Center in a two-stroke heavy duty diesel engine. One cylinder of the engine was instrumented with a pressure transducer. A high-speed data acquisition system was used to acquire cylinder pressure histories synchronously with crankangle. The heat release diagrams, along with the calculated combustion efficiencies of the fuels were compared to a referee grade diesel fuel. The calculated and measured combustion parameters include heat release centroids, cumulative heat release, peak pressure, indicated horsepower, peak rate of pressure rise, indicated thermal efficiency, energy input, and ignition delay. Regression analyses were performed between various fuel properties and the calculated and measured combustion performance parameters. The fuel properties included specific gravity, cetane number, viscosity, boiling point distribution.

Four military engines were tested to determine the effect of fuel properties on engine performance. These engines were the Detroit Diesel (DD) 4-53T, Continental Motors LDT-465-1C, Cummins NTC-350, and the Caterpillar 3208T. For this program, 18 fuels were blended to attain wide variations in kinematic viscosity, cetane number, ten-percent boiling point (10%BP), and aromatic content. Each of the eighteen fuels was run at the same relative speed and energy levels in each engine. Loads attained from the given speed-energy points were analyzed using the computer program SAS. These multiple linear regression analyses yielded a stable load prediction equation for each engine with energy, speed, aromatic content, inlet air temperature, kinematic viscosity, and 10%BP as the independent variables. Two additional fuel blends were run as cross-validations. Predicted loads agreed well with observed loads for these fuels except at low speed-energy points in some engines.

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.

Several multiviscosity grade oils were subjected to a special 240-hour endurance test procedure in an Army high-output two-cycle diesel engine, and certain of the oils were laboratory tested in the Army's multifuel, four-cycle compression ignition engine and in the Army's air-cooled four-cycle diesel tank engine. Certain of the lubricants were also subjected to standard hydraulic/power transmission tests because acceptable power transmission performance will now be a formal requirement in the D-revision to the engine lubricant specification MIL-L-2104. Parallel to these laboratory evaluations, pilot field tests were conducted in combat/tactical vehicles (engines and power shift transmissions) at three Army bases. The limited field tests indicated that the use of arctic/conventional multiviscosity grade lubricants at ambient temperatures up to 38°C(100°F) may be possible, and their introduction under MIL-L-2104 should be pursued.

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.

AN INVESTIGATION OF THE EFFECTS of methanol fuel on spark ignition engine wear and deposits is being conducted using a Ford 2.3-liter engine and a modified ASTM sequence V-D test procedure. This testing indicates that at the low temperature conditions of this procedure, methanol reduces the buildup of engine deposits but greatly increases the engine wear rate. Various experiments to identify the wear mechanisms were conducted in a CLR single-cylinder engine and are reported here.

Crude oils with a wide range of properties were investigated for direct use as fuel in U. S. Army high-speed four-cycle diesel engines. Crude oil properties were divided into two groups; 1. those properties which would be of importance for short-term operational effects, and 2. those properties whose effects would manifest during longer-term operation. Effects of crude oil use on engine subsystem hardware such as fuel filters and fuel injection pumps were investigated. Performance and combustion data were determined using pre-cup and direct injection configurations of the single cylinder CLR diesel engine operating on various crude oils. Performance data, wear and deposition effects of crude oil use were obtained using the TACOM single cylinder diesel engine. Results of this investigation showed that a wide range of crude oils with proper selection and pretreatment are feasible emergency energy sources for U. S. Army four-cycle high-speed diesel engines.