Exam Question
Write Short notes on the following:
(a) Effect of worn out rings on oil consumption and blow by (5)
(b) Cylinder liner wears. (6)
(c) Thermal loading of piston. (5)
Class 4 (4th Engineer)
MEKM
📅 Oct 2025
Reference Answer
### (a) Effect of Worn Out Rings on Oil Consumption and Blow By (5 Marks)
Piston rings are critical for sealing the combustion chamber and controlling lubrication on the cylinder liner. Wear on these rings significantly degrades engine performance and health.
**1. Increased Oil Consumption:**
* **Scraping Action:** A new piston ring has a carefully designed profile (e.g., barrel-faced or chamfered) to promote a hydrodynamic oil film during movement. As the reference states, "If the ring is worn the chamfer will disappear and the ring edges will scrape the oil off the liner wall instead of spreading the oil." This worn, sharp edge scrapes oil upwards into the combustion space where it is burned, leading to a marked increase in lubricating oil consumption.
Piston rings are critical for sealing the combustion chamber and controlling lubrication on the cylinder liner. Wear on these rings significantly degrades engine performance and health.
**1. Increased Oil Consumption:**
* **Scraping Action:** A new piston ring has a carefully designed profile (e.g., barrel-faced or chamfered) to promote a hydrodynamic oil film during movement. As the reference states, "If the ring is worn the chamfer will disappear and the ring edges will scrape the oil off the liner wall instead of spreading the oil." This worn, sharp edge scrapes oil upwards into the combustion space where it is burned, leading to a marked increase in lubricating oil consumption.
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