新版轮机英语unit6STARTINGSYSTEM.ppt

LESSON 6 TEXT STARTING SYSTEM,理解起动空气系统的原理、联锁机构和起动空气系统的组成；了解起动空气系统的安全措施；,Diesel engines are started by supplying compressed air into the cylinders in the appropriate(合适）sequence（顺序，次序）for the required direction.,A supply of compressed air is stored in air reservoirs or bottles or receivers at pressures about 30 or 40 bar ready for immediate（直接的，立即的）use.,Some times compressed air pressure is dropped to a lower value by means of a reducing valve(减压阀)for other uses.The receivers are charged（充气）by compressors.,The design of starting air systems,including the number and capacity of compressors and receivers,the provision（附件）of features and drainage（放残）facilities are the subject of stringent(严格)requirements by Classification Societies(船级社).,Up to 12 starts are possible with the stored quantity of compressed air.The starting air system usually has interlocks to prevent starting if any thing is not in order（异常）.,The compressed air is supplied by a large bore pipe to a remote operating non-return or automatic valve and then to the cylinder air start valves(气缸起动阀).,The opening of each cylinder air start valves will admit（承认，接纳）compressed air into the corresponding（相应的）cylinder.,The automatic valve（遥控阀）and the cylinder start valves are controlled by a pilot air system.,Each cylinder start valve will be opened immediately after the top dead centre(TDC)position has been passed and closed just before the exhaust ports are due to open according to the direction of rotation required.,【3】Thus,when compressed air from the main supply is supplied to the starting system of an engine at rest it enters those cylinders in which the pistons are in a position corresponding to some part of the power stroke,the resulting pressure on the pistons causes the engine to rotate.,When a sufficiently（足够的）high speed,say about 30 r/min,has been achieved the air supply is cut off and fuel is injected causing the cylinders to fire（发火）and continue to run in the normal way.,Cylinder air start valve,Air distributor,Master valve(automatic valve),Air bottle,Air start lever,a pilot air control valve,Non-return valve,The pilot air is drawn from the large pipe（主空气管）and passes to a pilot air control valve(起动控制阀）which is operated by the engine air start lever（起动控制杆）.,When the air start lever is operated,supply of pilot air enables the pilot air control valve to open either manually or with a pneumatic cylinder when a bridge control system is fitted.,Pilot air for the appropriate direction of operation is also supplied to an air distributor(空气分配器).,This device is usually driven by the engine camshaft and supplies pilot air to the control cylinders（控制汽缸）of the cylinder air start valves（汽缸起动阀）.,The pilot air is then supplied in appropriate（适当的）sequence for the direction of operation required.,The cylinder air start valves are held closed by springs when not in use and opened by the pilot air enabling the compressed air direct from the receivers to enter the engine cylinder.,As soon as the engine fires the air starting lever（起动手柄）is brought back.The pilot air control valve returns to the off position,venting the pilot air lines and the remote air starting valve and allowing it to close.,A number of interlocks（连锁装置）are provided in connection with the air starting system to safeguard the engine and personnel（人身）.These are:,1.The turning gear(盘车机)interlock valve（连锁阀）which is arranged to shut off（切断)the starting air pilot line when the turning gear is engaged(啮合),thus preventing the engine being started.,2.To prevent operation of the starting air system whilst（同时）the engine is running a pilot air interlock valve（控制空气连锁阀）is operated by the main control lever（主控制杆.,The valve remains open during the starting sequence,i.e.until the main control lever is removed just beyond the starting position,but remains closed after this point and does not open again until the main lever is moved back to the stop position.,3.A mechanical interlock is provided in the control box（控制箱）to prevent（阻止）the main control lever being moved beyond the starting position while the starting air lever is either the ahead or astern starting position.,4.Another mechanical interlock is provided to prevent the main control lever being moved until starting air is admitted to the cylinders.This prevents fuel being admitted to the cylinders when the engine is at rest（停用）.,Lubricating oil from the compressor will pass along the air lines and deposit on them.,In the event of a cylinder air starting valve leaking,hot gases would pass into the air pipes and ignite the lubricating oil.,If starting air is supplied to the engine this would further feed the fire and could lead to an explosion in the pipelines.,In order to prevent such an occurrence,cylinder starting valves should be properly(适当的）maintained and the pipelines regularly drained（放残）.,Also oil discharged from compressors should be kept to a minimum,by careful maintenance.,In an attempt to reduce the effects of an explosion,flame traps(阻焰器),relief valves(安全阀)and bursting caps or discs(防爆帽)are fitted in the pipelines.,In addition an isolating（隔离）non-return valve(the automatic valve)is fitted to the system,which prevents further compressed air by the engine into system.,The loss of cooling water from an air compressor could lead to an overheated（过热）air discharge and possibly an explosion（爆炸）in the pipelines leading to the air reservoir.,A high temperature alarm or a fusible（可熔的）plug（塞子）(易熔塞),which will melt(融化,熔化),is used to guard against this possibility.,Design features and working principleTwo air compressors,with automatic（自动的）start and stop,maintain a starting air of 30 bar in the starting air receivers.,The main engine is supplied with 30 bar starting air directly from the starting air receivers.,Through a pressure reduction station（减压装置）,compressed air at 7 bar is supplied as control air for the engine maneuvering system（操纵系统）,and as safety air for the emergency system.,Starting air and control air for the auxiliary engine(s)is also supplied from the same starting air receivers,via reducing valves（减压阀）that lower the pressure to a valve suited to the actual type of MAN B&W four stroke auxiliary engines chosen.,An emergency air compressor and a starting air bottle are installed for redundant（冗余的）emergency start of the auxiliary engines.,If high humidity air is sucked in by the air compressors,an oil and water separator will remove moisture（湿气）drops（滴）present in the 30 bar compressed air.,When the pressure is subsequently reduced to 7 bar,as for the main engine maneuvering system,the humidity（湿度）in the compressed air will be very slight.,Consequently（因此）,further air drying is considered unnecessary.,