Exam Question
With reference to the construction of a turbocharger, sketch and describe
(a) The rotor bearing and its method of lubrication (6)
(b) Labyrinth seal and explain how such a seal work. (6)
(c) Impeller and diffuser (4)
Class 4 (4th Engineer)
MEKM
📅 Jan 2023
Reference Answer
### (a) Turbocharger Rotor Bearing and Lubrication
**1. Construction and Type of Bearings:**
* **Type:** Modern, large two-stroke engine turbochargers predominantly use plain white metal journal bearings. These are designed to support the high radial loads generated by the rotor, which operates at very high speeds (e.g., 8,000 to 20,000 RPM). Some smaller or older designs may utilize anti-friction bearings like ball or roller types, as mentioned in the reference.
* **Bearing Material:** The bearings consist of a steel backing shell with a thin layer of bearing material, typically a tin-based white metal (Babbitt metal). This soft material provides excellent embeddability for small contaminants and compatibility with the steel shaft.
**1. Construction and Type of Bearings:**
* **Type:** Modern, large two-stroke engine turbochargers predominantly use plain white metal journal bearings. These are designed to support the high radial loads generated by the rotor, which operates at very high speeds (e.g., 8,000 to 20,000 RPM). Some smaller or older designs may utilize anti-friction bearings like ball or roller types, as mentioned in the reference.
* **Bearing Material:** The bearings consist of a steel backing shell with a thin layer of bearing material, typically a tin-based white metal (Babbitt metal). This soft material provides excellent embeddability for small contaminants and compatibility with the steel shaft.
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