新版轮机英语unit7lubricatingsystem.ppt

Cleanse（清洁） hot moving parts of carbonaceous deposits, resist oxidation(氧化) and wash away（冲洗，带走） wear detritus(磨屑). The selection of an oil from the commercially(商业上） available（可利用的） range depends to a great extent on the operating conditions, the design of the engine and the type of fuel to be burned. a total loss system(全消耗系统) feeding the cylinders and a circulating system lubricating the running gear（运动部件） and cooling the pistons. and in some designs it is timed so that the oil impinges(射到) only on the piston ring belt（活塞环环带）, thus ensuring the most efficient lubrication. Acidic酸性，alkalinity碱性 Some of these are acidic, particularly if residual fuels are being used and can cause corrosive conditions which promote（促进） heavy rates（比率，速率） of wear（加剧磨损）. To counteract（抵消，中和） these undesirable effects cylinder oils usually contain additives formulated(配制) to impart(给予) a high degree of alkalinity(碱度) and detergency(去垢能力). CRANKCASE LUBRICATION Operating conditions in the crank chamber are very different from those in the cylinder and it is the need for the oil to perform its functions over a very long period, which determines the properties（性质，特性） required in the lubricant（润滑剂）. 1. They must have good lubricating properties(性能） and be able to resist（抵抗） rupture(破裂) of the film separating the moving parts in order to ensure minimum friction losses. which in turn results in a considerable reduction in heat transfer with subsequent（后来的） overheating and thermal cracking(裂纹）. The lubricating oil is also used as a cleaner（清洁剂） and in some engines as a coolant（冷却液）. The oil is drawn from this tank（循环油柜） through a strainer（粗滤器，滤网）, one of a pair of pumps, into one of a pair of fine filters（细滤器）. The branch pipe for a particular cylinder may feed the main bearing, for instance（例如）. Pumps and fine filters are arranged in duplicate（双联） with one as standby. The fine filters will be arranged so that one can be cleaned while the other is operating. A level gauge（标准尺，量表） gives