Problems in Turbocharger Nozzles, Shrouds, and Blades

Residual fuels contain significant impurities such as carbon, ash, silica, and alumina. Additives in fuel oil can also contribute to specific fuel-related issues. Incomplete combustion, often caused by

high Conradson Carbon Residue (CCR) and ignition delay, leads to carbon deposits accumulating in the gas passages of the turbocharger.

Effects on Turbocharger Operation:

• Accumulated carbon restricts gas flow through the nozzles and blades, reducing the effective working of the turbocharger.
• Speed of rotation falls, resulting in decreased air supply to the engine.
• This leads to reduced efficiency, incomplete combustion, and further carbon deposits.

Remedies to Minimize Build-up:

1. Use the correct grade of fuel as per engine specifications.
2. Proper fuel oil treatment, including heating and purification.
3. Regular maintenance of fuel equipment (fuel pump, injectors).
4. Perform dry washing of the turbocharger as per the manufacturer’s recommendations.
5. Avoid prolonged low-load operation, which promotes carbon buildup.

Residual fuels contain sodium (Na) and vanadium (V) as impurities. At high temperatures, sodium and vanadium react (in a 1:3 ratio) to form sodium vanadate, which further oxidises to Vanadium Pentoxide (V₂O₅). Vanadium Pentoxide has a low melting point and is highly corrosive. These corrosive compounds deposit on the turbocharger and exhaust trunking, causing hot corrosion.

Effects on Turbocharger Operation:

• Corrosive deposits degrade and damage the nozzles, shrouds, and blades.
• Leads to a loss of turbine efficiency due to distortion or roughening of surfaces.
• Turbine imbalance may occur, increasing vibrations and further reducing operational reliability.

Remedies to Minimize Hot Corrosion:

1. Use the proper grade of fuel with low sodium and vanadium content.
2. Carry out appropriate fuel oil treatment to remove impurities.
3. Maintain fuel-burning equipment to ensure efficient combustion and avoid after-burning or high exhaust gas temperatures.

Turbocharger turbines operate at very high rotational speeds, making them susceptible to damage from high-impact particles present in exhaust gases. Erosive particles include unburnt fuel, ash, and abrasive contaminants like silica and alumina from residual fuel. Catfines (catalytic fines) present in untreated fuel oil are particularly abrasive.

Effects on Turbocharger Operation:

• Erosion causes surface wear and damage to the turbine blades and nozzles.
• Loss of blade profile reduces turbocharger efficiency and air delivery.
• Long-term erosion may result in turbine imbalance, vibrations, and eventual mechanical failure.

Remedies to Minimize Erosion:

1. Ensure complete combustion by maintaining fuel injection equipment (fuel pumps, injectors, atomizers).
2. Implement proper fuel purification and filtration to remove abrasive contaminants such as catfines, silica, and alumina.
3. Monitor and maintain proper fuel treatment procedures to reduce unburnt fuel and residue buildup.