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Development of optical microscopy techniques enables evaluation of the dispersancy quality of new engine lubricating oils and permits prediction of sludge deposition severity before and during engine operation. By observing MIL-L-2104B engine oil samples under a microscope, size of the sludge agglomerates was related to sludge deposition potential and correlated to engine sludge ratings. Thus the prediction of engine sludging at any time during an LTD test is possible without the benefit of engine inspection. Sludge agglomeration temperature was found to be the basic criteria for determining dispersant quality of an oil. Using this principle and the microscope, a method was developed for screening new dispersant oils. Correlation of analytical and fleet ratings are also presented.

This paper describes full-scale engine studies conducted to determine the feasibility and compatability of ammonia combustion in various systems. Briefly outlined is the spark-ignition investigation undertaken by the Army Laboratory to learn the potential and effect of ammonia as a fuel and to study the influence of engine variables on combustion. A study of compression-ignition performance was made to ascertain the ability of ammonia to be pumped in existing injection systems and various means of achieving ammonia combustion were explored. Conclusions drawn from these studies on the use of ammonia as a fuel are given.

Under low temperature engine operation, sludge appears as insolubles in the lubricating oil or as deposits on engine parts. Its formation is initiated by liquid oxidation products, inorganic salts, and polymerized organic compounds that pass the piston ring zone. The liquid oxidation products undergo further chemical reaction in the crankcase oil medium, forming solid “sludge binders.” These “binders” are the essential ingredients that the oil must contain before the organic solids (carbonyls, sulfur, and nitrogen derivatives and polymerized hydrocarbons), inorganic salts, wear particles, and soot can be deposited as sludge.

A method of cooling piston engines by direct injection of a fluid into the combustion chamber is described. Significant changes in power performance, fuel octane or cetane number requirements, exhaust emission quality, engine life, and engine configuration can be expected from injection cooling. This paper includes a theoretical discussion of the process and then presents a description of the laboratory apparatus and procedures and an evaluation of experimental data.

An investigation of conventional glassware techniques for determining the thermal-oxidation stability of gear lubricants revealed a lack of correlation with field service results. Therefore, a new apparatus and procedure were developed to provide industry with a reliable method of qualifying military gear lubricants. The history of the technique development is presented in this paper as well as test data. The results show that the thermal-oxidation stability of gear lubricants may be satisfactorily predicted with good repeatability and the test data agree with field results in both order and magnitude of rating. Following the development of the test technique, a new project was initiated to enhance existing knowledge of temperature and oxygen influences on the thermal-oxidation phenomena using the apparatus previously described. The effect of oxygen was studied by conducting tests with oxygen, air, and various inert gases while keeping the test oil temperature constant.

The influence of low temperature on fuel injection and combustion in compression-ignition engines was studied. Both unit injector and plunger pump-remote injection nozzle systems were investigated, and findings on spray characteristics such as penetration, cone angle, and injection timing are presented. Fuels used in these tests ranged from the minimum practical viscosity as well as varying densities through the use of Blended Fuels. A summary of findings and test results are included, together with recommendations for subsequent investigations.

When combustion products, commonly called “blowby,” are prevented from reaching an engine's crankcase, sludge formation is inhibited and lubricant life extended. This paper discloses the concept, developed at the Army Fuels and Lubricants Research Laboratory, which prevents leakage of blowby gases into the crankcases of piston engines. “Blowby diversion” is accomplished, by one or a combination of four basic methods, at the piston ring zone where the blowby gases are intercepted after leaking by the bottom compression ring, but before reaching the crankcase. Single-cylinder engine studies have demonstrated that the principle of blowby diversion is feasible and can prevent better than 90% of the blowby from entering the crankcase. The studies further indicated a significant reduction in sludge formation rates (increase in engine cleanliness), with decreases in ring wear and air pollution. Blowby diversion appears to be reliable and easily adapted to conventional engines at low cost.