Lesson Two Text Diesel Engine Construction (I) 轮机英语教学课件.ppt

Bedplate(机座) and Frame(机架) The bedplate, which in most cases is of the welded design, is bolted to the seating which forms part of the double bottom of the ship. These bearings, known as main bearings, each consist of two shells(轴瓦) which are supported in housings(轴承座) machined in the bedplate and secured by means of studs(双头螺栓)and bearing caps(轴承盖). The thrust block or thrust bearing(推力轴承), located at the aft end of the engine, may be integral with, or separate from, the bedplate. The frames are mounted on and bolted to the bedplate cross girders. At the top of the A-frames there is a strong cast iron frame called the scavenging air box, which is built of a number of sections provided with vertical flanges(法兰) enabling them to be bolted together to form a block for 1-3 cylinders in front of the chain transmission, and a block with 4-6 cylinders aft of the chain transmission. These frames are known as cylinder blocks or cooling jackets(冷却水套), which are provided with vertical flanges enabling them to be bolted together in the foremost and aftmost groups in the same way as the scavenging air boxes. The cylinder liners are made of alloyed cast iron and the cylinder surfaces are sometimes chromium-plated(镀铬). The cylinder liners are extend somewhat down in the scavenging air box, and sealing between the liner and the top of the scavenging air box is achieved by the rubber rings fitted into the slots machine-turned(机加工的) in the liners. These ports are located at such a height that they are just exposed by the upper edge of the piston when the piston is in the bottom dead-center position. The cover is mounted against a flat surface at the top of the cylinder liner and located on the liner by means of a machine-turned guide edge. The cylinder covers and the liners are bolted together by means of studs screwed into the cylinder frames. The cylinder liner has drillings for cylinder lubrication, and, in later types, has drillings for cooling water at the uppermost par