Exam Question
With reference to medium speed trunk piston engines:
(a) Explain the purpose of an anti-polishing ring (5)
(b) Describe how effective piston cooling is provided; (5)
(c) Where is the thrust bearing fitted and why? (6)
Class 4 (4th Engineer)
MEKM
📅 Feb 2025
Reference Answer
### (a) Purpose of an Anti-Polishing Ring (5 Marks)
An anti-polishing ring, also known as a carbon cutting ring or fire ring, is a critical component fitted at the top of the cylinder liner in many modern medium-speed trunk piston engines. Its primary purpose is to prevent a phenomenon known as 'bore polishing' or 'liner glazing'.
**Mechanism and Function:**
1. **Prevention of Carbon Build-up:** During engine operation, especially at low loads, hard, abrasive carbon deposits can form on the piston's top land (the area between the top piston ring and the crown).
An anti-polishing ring, also known as a carbon cutting ring or fire ring, is a critical component fitted at the top of the cylinder liner in many modern medium-speed trunk piston engines. Its primary purpose is to prevent a phenomenon known as 'bore polishing' or 'liner glazing'.
**Mechanism and Function:**
1. **Prevention of Carbon Build-up:** During engine operation, especially at low loads, hard, abrasive carbon deposits can form on the piston's top land (the area between the top piston ring and the crown).
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