Exhaust gas turbocharger consists of:
- Turbine Side, and
- Blower or Compressor Side
Turbocharger efficiency = Mechanical efficiency x Blower efficiency x Turbine efficiency
If either blower or turbine side or both get fouled, efficiency of the turbocharger drops substantially. Inefficient turbocharger supplies less quantity of air for the internal combustion engine, which result in improper combustion, increased exhaust gas temperature, reduced engine output, and so on. It may result in black exhaust gas, scavenge fire, economizer fire, etc. Once fouling starts it accelerates deposits on blades. Periodical water washing and grit washing to be carried out for both blower side and turbine side.
Exhaust gases passing over turbine blades may cause carbon particles or ash to deposit on it. Deposition will be severe when engine is when engine runs at low loads for long periods. At low load turbocharger runs at low rpm. Since turbine same turbine shaft drives blower, less air is supplied to the engine, thereby causing inefficient combustion. Due to improper combustion, un-burnt carbon particles escape with exhaust gas and get deposited in turbine blades. Similarly, quality of fuel burnt also have an effect on deposits.
- Generally fouling is severe in nozzle ring, if fitted.
- Ash deposit takes place for fuels with high ash content.
- Presence of sodium and vanadium in fuel cause vanadium pent-oxide (V2O5), thereby inducing fouling and hot corrosion.
- Calcium carbonate (CaCO3) deposits may be caused by burning cylinder lube oil.
Removal of Deposits
- Regular water washing of turbine side.
- Grit washing / dry cleaning
- Use of good quality fuel with correct treatment (purification, filtration and maintaining required viscosity).
- Timely maintenance of fuel injectors, fuel pumps, etc.
- Remove seawater content from fuel by proper purification.
- Adjust cylinder oil feed according to sulphur content in the fuel and control lube oil quality.
- Complete dismantling and manual cleaning of turbocharger.
- Formed oil vapour, cargo residues and dust from engine room.
- Deposits reduce overall efficiency of turbocharger.
- Deposits reduces amount of air supplied to the engine for combustion.
- Engine output reduces because of low boost air pressure
- Exhaust temperature increases
Removal of Deposits
- Grit wash / water wash blower side regularly.
- Cover blower side with canvas when not in use.
- Use cleaning agents at prescribed quality and quantity as mentioned by manufacturer.
- Carry out planned maintenance on turbocharger
- Dismantle and overhaul turbocharger.