Exam Question
(a) Explain briefly how the different moving parts of a main engine are subjected to various stresses. (8)
(b) Name the stresses and justify by stating how they originate. (8)
Class 4 (4th Engineer)
MEKM
📅 Jun 2024
Reference Answer
### (a) Explanation of how different moving parts of a main engine are subjected to various stresses
The intricate operation of a main propulsion engine involves a complex interplay of forces and motions, subjecting its moving parts to a dynamic and varied range of stresses. These stresses originate from the combustion process, the inertia of reciprocating and rotating masses, and the mechanical interactions between components.
* **Piston, Piston Rod, and Connecting Rod Assembly:**
* **Combustion Pressure:** During the power stroke, the extremely high pressure from the burning fuel-air mixture acts directly on the piston crown, forcing it downwards (or upwards in an opposed-piston engine). This compressive force is transmitted through the piston rod (in crosshead engines) and connecting rod.
The intricate operation of a main propulsion engine involves a complex interplay of forces and motions, subjecting its moving parts to a dynamic and varied range of stresses. These stresses originate from the combustion process, the inertia of reciprocating and rotating masses, and the mechanical interactions between components.
* **Piston, Piston Rod, and Connecting Rod Assembly:**
* **Combustion Pressure:** During the power stroke, the extremely high pressure from the burning fuel-air mixture acts directly on the piston crown, forcing it downwards (or upwards in an opposed-piston engine). This compressive force is transmitted through the piston rod (in crosshead engines) and connecting rod.
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