While examining a used fuel injection nozzle(s), one finds worn and enlarged orifices. What does this indicate about that cylinder's performance prior to nozzle replacement(s)?
• Effect of worn/enlarged injector orifices on spray pattern and droplet size • How changes in atomization, penetration, and ignition delay affect combustion efficiency in a diesel cylinder • Relationship between injection pressure, fuel quantity, and air–fuel mixing
• If the nozzle holes are enlarged and worn, what happens to droplet size and the fineness of atomization? Better or worse? • How would poorer or better atomization change ignition delay, penetration into the combustion chamber, and overall combustion efficiency? • Does enlarged orifices tend to increase or decrease injection pressure for a given pump stroke, and what does that do to spray characteristics?
• Be clear on the meaning of atomization (fine spray vs coarse droplets) and penetration (how far the spray travels into the air charge). • Decide whether worn/enlarged orifices generally improve or degrade combustion efficiency in practice. • Check which option best matches the typical chain: enlarged orifices → changed injection pressure → change in droplet size → change in ignition delay and penetration → effect on combustion efficiency.
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