Lubricants and the Lubrication System
Diesel engines not impose make maximum demands on the loading capacity of every component but also on the lubricant , i.e. the engine oil , which is therefore a technically complex operating agent [11-1–11-3]. Since the operating conditions of car and com
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Lubricants and the Lubrication System Hubert Schwarze
11.1
Lubricants
11.1.1
Requirements for Engine Oils for Diesel Engines
Diesel engines not only impose maximum demands on the loading capacity of every component but also on the lubricant, i.e. the engine oil, which is therefore a technically complex operating agent [11-1–11-3]. Since the operating conditions of car and commercial vehicle diesel engines and large diesel engines differ considerably, differently optimized lubricating oils are employed for the intended purposes. Engine oil is not only a lubricant but also an important design element that is crucial and integral to an engine’s function and service life and must therefore be matched to an engine’s standard of technical quality. Tribologically optimized layers, which determine an engine’s friction and wear performance, only form when component surfaces and lubricants interact under mechanical and thermal loads (particularly during running in). Different engine concepts impose fundamentally different requirements on engine oil, which a manufacturer has to specify, factoring in the lubrication system, the maintenance concept, the metallurgy and the design of the engine components. What is more, initiated by the Kyoto Protocol and various national exhaust standards, new technologies that cut the emission of climatically relevant gases and pollutants make very specific additional demands, which have necessitated the development of fuel economy engine oils and catalyst compatible formulations. Engine oil is required to fulfill all of its functions, which far exceed lubricating oil’s functions, under every operating condition at least until the scheduled oil change. Characterized by chemical, physical and technological properties, the requirements for engine oil are derived from the main functions required by engine operation, namely the – separation of sliding surfaces, – transmission of forces,
H. Schwarze (*) TU Clausthal, Clausthal-Zellerfeld, Germany e-mail: [email protected]
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neutralization of undesired products, wear protection, corrosion protection, sealing and cooling.
Table 11-1 compiles the functions of engine oils together with their effective engine ranges and operating states and the complexes of requisite properties. On the one hand, certain functions must be viewed collectively rather than treated separately from one another. On the other hand, different and in part conflicting properties must exist to fulfill certain functions simultaneously to obtain optimal conditions. The properties of engine oils can be subdivided into the following somewhat simplified complexes: – viscosity and flow characteristics, – surface activity and – corrosion protection. Surface activity is differentiated according to whether it affects on engine surfaces or impurities. Corrosion protection refers to the capability to both neutralize combustion products and stabilize the lubricant itself against oxidative degradation. In addition to its main functions, the following additional requir
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