Class 2 (2nd Engineer) MEKM 📅 Nov 2023

Exam Question

With regards to modern diesel engine raising the Life Cycle Value (LCV). Describe the importance of following:

(a) Low Sac Volume of Fuel Injection Valve (4)

(b) Fuel Valve opening Pressure regulation (4)

(d) Contamination of lube oil and impact on LCV. (4)

Reference Answer

(a) Low SAC volume of fuel injection valve:
The SAC volume refers to the small space within the fuel injector between the valve seat (fuel shut-off point) and the entrance to the final metering orifice .
This volume holds fuel that vaporizes incompletely at the end of injection and enters the cylinder at low velocity during the expansion stroke.
The unburnt fuel contributes to post-injection dripping , after-burning , and increased emissions such as unburnt hydrocarbons and NOx .

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