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L & M
K = It is the distance between the compressor end cover mounting face and shaft end .Mark it as K.
Pull the rotor shaft towards the compressor side until the impeller comes in contact with the insert and determine K2.
Impeller clearance L = K – K2
Thrust the rotor shaft towards the turbine side until the turbine disc and nozzle ring comes in contact with each other and measure K1
Disc clearance M = K1 – K
The above measured clearance is very important as this will determine the proper functioning of the labyrinth seal between the impeller and exhaust shield and also the alignment of the shaft.
K
To ensure that rotating impeller does not to touch the stationary blower casing cover in case of thrust bearing worn out.
Shroud ring
The area around the turbine is always in contact with highly corrosive exhaust gases.
shroud ring protects the turbine inner casing, can be easily replaced.
Turbocharger surging
- It is the back flow of air from discharge to suction and it is characterized by noise and vibration of turbocharger.
Causes of turbocharger surging
Exhaust System
- Uneven load
- ME load too high
- Exhaust valve defective
- Damage T/C flaps
Fuel
- Defective injector
- Defective suction valve
- Pressure too low, fuel Pump leaking, cir pump/supply pump pressure low
- Air lock
Scavenge
- Air cooler dirty
- Scavenge port chock
- Too high Scavenge temp
- EGE dirty/fouled
Turbocharger
- Air filter dirty
- Nozzle ring dirty
- Silencer dirty
- Blower side dirty
- Turbine Side dirty
- Fans not running
- Load reduction too fast
- Bearing failure
- Heavy Weather
- Scavenge Fire
Action to be taken
- Inform bridge to reduce rpm
- Monitor all parameters
- Conduct Blower side waster washing
- Turbine side grit washing
- Change Air filter
- Check fuel system
- Reduce engine load
Differences between sleeve and roller bearing
Sleeve bearing advantages
Cheap in design
Indefinite life
Not prone to vibration
Load is disperse to the side
Low running cost
Disadvantages
Prone to oil contamination
Poor performance at low load
Sensitive to lub oil failure
High friction at low load
Roller bearing advantages
Low load good performance
Low friction at low and high load
Not affected by lub oil contamination
Does not need special oil
Disadvantages
High running cost
More prone to damages
Sensitive to vibration and fatigue
Actions in case surging
- Inform bridge to slow down , reduce rom
- Monitor all parameters
- Conduct blower side water wash
- Turbine side grit wash
- Change air filter, check fuel system, reduce load
How is sealing achieve
- The labyrinth seal on turbine side of turbocharger prevent gas contaminating with bearing lub oil supply
- The seals consist of series of fine turns opposite to the steps on casing
- It provide a narrow space which exhaust gas leaks
- As gas passes through, it is subjected to throttling, pressure energy convert to kinetic energy.
- Kinetic energy dissipate, as it passes down the gland
- Sealing air is bled from compressor end to mid turbine gland which expands in both direction.
Air tightness between diffuser ring casing and impeller back
- Space between the casing and impeller back pressurized from impeller discharge,
- Air will attempt to access the exhaust gas passage,
- Grooves machine behind regulate the leak.
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