新版轮机英语unit4Fueloilsystem.ppt

1、Lesson 4 Fuel oil system,理解燃油的净化 供给和燃油系统的操作,补充内容,燃油的参数：combustion Fuel oils viscosity(粘度）, cetane number（16烷值）, calorific value(燃烧值）, the sulphur content（硫分）, its carbon residues(残炭值） Ash （灰分）,maintenance flash point（闪点）, setting point（倾点）, specific gravity（比重）, viscosity（粘度cst）, water content（水分）,

2、mechanical impurities（机械杂质）,Fuel oil supply system（燃油输送系统）: Fuel supply deals with the provision(预备） of the fuel oil suitable for the use by the injection system.,Fuel injection system（燃油喷射系统） The function of fuel injection system is to provide the amount of fuel at the right moment and in a suitabl

3、e condition for the combustion process.,The “unifuel” system,The common system covers the entire fuel flow from storage tank(储存舱） to injection into the engine cylinders. Uni- 单一，一个,【1】With regard to（关于） centrifuge recommendations, fuel oils should always be considered as contaminated （污染）upon delive

4、ry （交付）and should therefore be thoroughly cleaned to remove solid as well as liquid contaminants before use.,The solid contaminants in the fuel are mainly rust, sand, dust, and refinery（精炼） catalysts（催化剂）. Liquid（液体） contaminants are mainly water, i.e. either fresh water or salt water.,Impurities in

5、 the fuel can cause damage to fuel pumps, and fuel valves, and can result in increased cylinder liner wear and deteriorations（磨损损耗，变坏） of the exhaust valve seats.,Also increased fouling（弄脏） of gas ways and turbocharger blades may result from the use of inadequately（不足的，不适当的） cleaned fuel oil.,Effect

6、ively cleaning can only be ensured by using a centrifuge（离心分离机）.,【2】Results from experimental work on the centrifuge treatment of todays residual fuel qualities have shown that the best cleaning effect, particularly in regard to removal of catalytic fines, is achieved when the centrifuges are operat

7、es in series, i.e. in purifier/clarifier mode.,This recommendation（推荐，建议） is valid（有效的，正确的） for conventional centrifuges.,For modern types, suitable for treating fuels with densities higher than 991kg/m3 at 15, it is recommended to follow the makers specific instructions（说明）.,【3】In view of（由于，考虑到） t

8、he fact that some fuel oil standards incorporate fuel grades without a density limit, and also the fact that the traditional limit of 991kg/m3 at 15 is occasionally exceeded on actual deliveries,Some improvements in the centrifuging treatment have been introduced to enable the treatment of fuels wit

9、h higher density.,With such equipment, adequate separation of water and fuel can be carried out in the centrifuge, for fuels up to a density of 10010 kg/m3 at 15。,Therefore, this has been selected as the density limit for new high density fuel grades.,Thus high density fuels are fully acceptable for

10、 our engines provided that appropriate centrifuges are installed.,They should be operated in parallel or in series according to the centrifuge makers instructions.,Design features and working principle,The fuel oil system is a common, pressurized（加压的） system in which heavy fuel oil and diesel oil ca

11、n be used.,The purpose of pressurization is primarily（主要的） to avoid boiling and cavitation（气穴现象） in the system, which may occur when the heavy fuel oil is heated to achieve the viscosity of 10-15cst required for injection.,Operation at sea,The fuel from the bunker tanks must be treated in centrifuga

12、l separators before entering the service tanks. From the service tanks, the fuel enters the supply system.,In the supply system, the fuel is pumped by the supply pumps, into a circulating system at a pressure of 4 bar. The supply system may include a fine（细） filter.,All overflow（溢流） from the supply

13、pumps is recirculated （再流通，再循环） in the bypass piping, which incorporates the overflow valve shown in order to keep the inlet pressure in the circulation（循环） loop constant, irrespective（不考虑,无关的） of the actual consumption.,The pumps in the circulation loop, raised the pressure of the fuel oil from the

14、 supply system to a constant pressure of 7-8 bar before the engines.,The inlet pressure is maintained at the specified（指定，规定，确定） level by a spring-loaded（弹簧回复的） overflow valve（溢流阀） located on the main engine.,The temperature or viscosity controlled preheater（预热器） heats the heavy fuel oil until it re

15、aches the necessary viscosity.,To safeguard the injection system components（零件，元件） on the main engine, a full-flow 50 m（micron） filter, must be installed as close to the main engine as possible. Such a filter is already built onto the auxiliary engine.,Excess fuel oil supplied to the engines is reci

16、rculated via the venting（排出） box, where gases, if any, are released by a deaerating valve, to avoid cavitation in the system.,The flexibility of the system makes it possible, if necessary, to operate an auxiliary engine on diesel oil by means of remote controlled 3-way valves, which should be locate

17、d close to the auxiliary engines.,A separate booster pump（增压泵） supplies diesel oil from the diesel oil service tank to the auxiliary engines and return any excess oil to the tank.,In order to ensure operation of the booster pump in the event of black-out（停电）, the booster pump must have an immediate

18、possibility of being powered by compressed air or by power supplied from the emergency generator.,A 3-way valve is installed immediately before each auxiliary engine for change over between the pressurized（加压系统） and the open MDO (Marine diesel oil) supply system.,In the event of a black out, the 3-way valve at each auxiliary engine will automatically change over to the MDO supply system.,The internal piping on the auxiliary engines will then , within a few seconds, be flushed with MDO and be re