分类：轮机英语会话
9、Look at the illustration and say the type of piston ring.
There are three rundamental functions of the piston rings: to distribute oil film, prevent exhaust gas from giving out and carrying away the heat. The first figure shows a rectangle ring; The second figure shows a ladder-shaped ring； The third figure shows a beveling ring; The fourth figure shows a twist ring; The fifth figure shows a normal worn piston ring.
10、Please describe the lubricating mode of main engine.
Large marine diesel engines of crooshead construction generally have two system of lubrication , a total loss system feeding tyhe cylinders and a circulating system lubricating the running gear and cooling the pistons.
As for the circulating system , oil is drown from a sump, usually located in the bedplate of the engine, by an electrically driven oil pump or by a lubricating oil pump connected to the engine, and delivered through fiters and oil coolers to the bearings ,such as main bearing, camshaft bearings and so on. A special pressure lubrication is provided for the crosshead bearing. Where the engine has oil-cooled pistons , they will be supplied from the lubricating oil system, possibly at a higher pressure produced by booster pumps.
Large slow speed engines are provided with a separated lubricating system for the cylinder liners. Oil is injected between the liner and the piston by mechanical lubricators which supply their individual cylinder. A special type of oil is used which is not recovered. In addition to lubricating , it assists in forming a gas seal and contains additives which clean the cylinder liner.
Sometimes, some 4-stroke diesel engine also uses the splash lubrication, i.e., the cylinder liner is lubricated by the splashed oil produced by the crank pin.
11、Talk about the working principle of purifier according to the picture given.
The centrifugal separation of two liquids, such as oil and water , results in the formation of a cylindrical interface between the two. The different gravity of two types of liquids. The centrifugal force of the water move towards the outside of the disc, while the oil which is smaller in gravity shall move to ward the center of the disc. This makes the separation of the two liquids. The position of this interface within the centrifuge is very important for correct operation. The setting or positioning of the interface is achieved by the use of gravity disc at eh outlet of the centrifuge. Various diameter rings are available for each machine when different densities of oil are used.
This bowl has an inlet for dirty oil and two outlets for water and clean oil. The purifier bowl contains a stack of conical bowl discs separation fo water from th oil takes place between these bowl discs.
12、Take about the working principle of oily water separtator accoridng to the picture given.
The oily water separator works on the principle of coalescing small oil droplets in the water to form larger oil drops. When the oil drops become large enough, the lower density oil drops float up and collect at the top fo the oily water separtator. the water remains at the lower porition and is pumped overboard. The oil layer is pumped into an oily bilge tank.
The oily water separator consists of a vertical cylindrical pressure vessel containing a number of inverted conical plates. The oliy water enters the separator in the upper half of the unit and is directed downwards to the conical plates. Large globules of oil is separated out in the upper apart of the separator while the smaller glolules are carried by the water into the spaces between the plates. The rising velocity of the globules carries them