Class 2 (2nd Engineer) MEKM 📅 Apr 2023

Exam Question

Explain why the use of residual fuels for the operation of large slow speed or of medium speed engines, may be responsible for the following problems with turbocharger nozzles, shrouds and blades and how in each, the problem may be minimized: (16)

(a) Build-up of deposits;

(b) Hot corrosion;

Reference Answer

(a) Build-up of Deposits
Residual fuels are inexpensive, incompletely distilled petroleum products that contain high levels of impurities. These include carbon residue , ash, and sediments, along with elements like sulfur, vanadium, aluminum, and silicon. When combustion is incomplete, which can be caused by improper fuel treatment, incorrect viscosity, or issues with fuel injection timing and pressure, the heavy carbon particles don't fully convert to carbon dioxide. Instead, they get deposited on hot surfaces, such as the turbocharger's nozzles and blades, where they stick and accumulate. This buildup reduces the efficiency of the turbocharger and can cause imbalanced rotation.
Minimization:
Ensure the fuel is purified correctly to remove impurities like sediments and water.

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