Question:easy
Which ONE or MORE of the following can be caused by scavenging in a two-stroke Diesel engine?
Which ONE or MORE of the following can be caused by scavenging in a two-stroke Diesel engine?
Show Hint
Remember scavenging in a Diesel engine moves only air, not a fuel-air mixture, and some of that air always escapes with the exhaust.
Updated On: Jul 28, 2026
- Dilution of incoming fuel-air mixture
- Loss of incoming air
- Pushing out exhaust gases by incoming air
- Autoignition
Show Solution
The Correct Option is B, C
Solution and Explanation
Step 1: Recall what scavenging physically does.
Fresh air enters near bottom dead centre and sweeps the burnt gas out through the exhaust port before the next compression stroke.
This sweeping action is exactly what option C describes, so it is correct.
Step 2: Check the known scavenging loss.
Because inlet and exhaust ports are open together for a short overlap period, part of the fresh air passes straight out with the exhaust gas instead of staying in the cylinder.
This wasted air is the loss described in option B, so B is correct too.
Step 3: Rule out the remaining options.
A Diesel engine injects fuel after the air charge is already trapped and compressed, so there is no fuel-air mixture present during scavenging to dilute, ruling out A.
Autoignition depends on compression ratio and injection timing, not on the scavenging air flow, ruling out D.
Final Answer:
Scavenging causes loss of some fresh air and is itself the act of pushing exhaust gas out.
Options B and C are the correct choices.
Fresh air enters near bottom dead centre and sweeps the burnt gas out through the exhaust port before the next compression stroke.
This sweeping action is exactly what option C describes, so it is correct.
Step 2: Check the known scavenging loss.
Because inlet and exhaust ports are open together for a short overlap period, part of the fresh air passes straight out with the exhaust gas instead of staying in the cylinder.
This wasted air is the loss described in option B, so B is correct too.
Step 3: Rule out the remaining options.
A Diesel engine injects fuel after the air charge is already trapped and compressed, so there is no fuel-air mixture present during scavenging to dilute, ruling out A.
Autoignition depends on compression ratio and injection timing, not on the scavenging air flow, ruling out D.
Final Answer:
Scavenging causes loss of some fresh air and is itself the act of pushing exhaust gas out.
Options B and C are the correct choices.
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