The function of exhaust System :1> To discharge 2>To reduceengine exhaust pressure in to the exhaust line atmosphere And eliminate outside the most of noise. building and
The componets of exhaust System : : cylinders muffler exhaustmanifold pipe
Working The exhaust manifold connects the enginecylinders exhaust outlet to the exhaust pipe .the exhaust gases from the cylinders collect in the exhaust manifold & are conveyed to the atmosphere through the exhaust pipe.
* The exhaust pipe is provided with amuffler(silencer) to reduce pressure in exhaust line & eliminate most of noise which may results if gases are discharged directly into the atmosphere. The exhaust manifold is connected with exhaustpipe by one or two flexible expansion joints to allow for the expansion & to minimize the effect of engine vibration on system.
The temperature of exhaust gases leaving the engine isabout 400 C when it works under full load conditions.Therefore large engine exhaust gases contains large amountof heat. This heat can be recovered and utilized in threemanner as1 To heat the water which is supplied to the cylinder jackets2 To generate low pressure steam in the water heat boilerwhich can be used for process heating3 To heat ventilating air which is supplied to the engine
Designing an exhaust System1. The exhaust noise should be reduced to the desired level.2 The exhaust should be discharged sufficiently height above theground level in order to reduce the air pollution at ground level.3 The expansion joints should be used to reduce the enginevibration on the exhaust system4 The pressure loss in the exhaust system should be minimum.5 There should be provision to recover the heat of exhaust gases toincrease the efficiency of the plant.
There are two engines:1 Diesel engine that is main engine. 2 Small petrol engine.
JoiningDiesel engine and petrol engine arejoined by clutch and gear arrangements.Small petrol engine can be easily startedby means of manual operations
Working process:First clutch is disengaged and petrol engine is started byhand operated system.Then cluth gradually engaged and the power is transferredto diesel engine .Automatic disengagement of clutch takes place after mainengine has started.The capacity of the starting petrol engine is just sufficientto overcome the friction of the main diesel engine.
The compressed air system is generally used for startinglarge diesel engine employed for power plant . In thissystem compressed air a pressure of 17 bar is suppliedfrom an air bottle to the engine cylinder either through adistributor or directly through inlet manifold .In case of multicylinder engines, atleast one cylinderremains on the suction stroke.
When compressed air under the pressure enters cylinder, itpushes the cylinder thereby causing entire engine crankshaftassembly to rotate.Meanwhile the suction stroke of some other cylinder takesplace and the compressed air again pushes the piston of thiscylinder and causes the engine crank assembly to rotate.Gradually the engine gains momentum and by turning on thefuel supply , engine will start running.
The main advantages of electric starting are itssimplicity and effectiveness. This system is usedfor small diesel engine.This system consist of an electric motor which isdrives pinion which engages a gear toothed rimon engine .A storage battery of 12 to 36 volts is used tosupply power to an electric motor.
The first method from above as stopping fuel supply is the mostcommonly used for stopping diesel engine ,in which the fuel supplyto injection pump is cut with the help of solenoid value as fig.The solenoid valve is placed in the fuel supply line close to the inletof the injection pumps. The valve needle has a megnatic head whichis located inside a solenoid .When electric current is passed thoughthe coil,a magnetic force is set up which moves the valve needle andallows fuel flow.When hand operated switch button is the electric circuit is broken theneeded come back and closes the valve and hence engone is stopped.
The motor draws a heavy current and is designed toengaged continuously for about 30 seconds only,after which it is required to cool off for a minutes orso, and then re-engaged. This is done till the enginestarts up.There is also arrangement for automaticdisengagement after the engine has started.When the engine is running a small d.c. generatoron the engine serves to charge the engine serves tocharge the battery otherwise small electric generatordriven from the engine may be used.
The engine should not be stopped abruptly. in order to stop engine, the speed shouldbe decreased gradually until no power isdelivered by generator .Then the engine isdisconnected from the bus bars and isallowed to run idle for sometime.
engine can be shut down with of the any one of the following methods. 2. keeping 1. Stopping exhaust fuel supply value open 4. stopping 3. shutting the action of air of injection supply pump.