Q9
With respect to fuel injection system of diesel engines,
(a) What is the purpose of VIT?
(6)
(b) How is the end of injection controlled in a 2 stroke propulsion engine and 4 stroke medium speed auxiliary engine?
(6)
(c) Explain the purpose of a draw card.
(4)
Reference Answer
### (a) Purpose of VIT (Variable Injection Timing) Variable Injection Timing (VIT) is a system designed to automatically advance or retard the start of fuel injection relative to the piston's position, primarily to optimize engine performance across a wide load range. Its main purpose is to maintain the maximum combustion pressure (Pmax) at its optimal design value, thereby ensuring maximum fuel efficiency (lowest Specific Fuel Oil Consumption - SFOC). **Mechanism and Principles:** 1. **Operation at Part Load (e.g., below 85% MCR):**
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