How does the auto-ignition temperature of diesel fuel compare to that of petrol_________________?
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Answer: B. lower
Explanation
Diesel fuel has a lower auto-ignition temperature compared to conventional petrol or gasoline. This lower threshold allows diesel vapor to ignite spontaneously under high compression temperatures. Engine combustion relies on this property to achieve fuel ignition without needing an electric spark plug. Auto-ignition temperature is the minimum temperature required to trigger self-combustion without an external spark source. Diesel engines operate on compression ignition, squeezing air until its temperature exceeds the fuel auto-ignition point. Petrol engines use spark ignition because petrol has a higher auto-ignition temperature to prevent premature knocking.
Heavy-duty commercial trucks and industrial generators utilize diesel engines for high torque and thermal efficiency. Engine knock occurs in petrol engines if fuel auto-ignites prematurely due to excessively high cylinder temperatures. Understanding fuel ignition points is critical for preventing accidental fires and optimizing internal combustion design. Option A suggests diesel has a higher threshold, which would prevent compression ignition from working properly. Option C incorrectly assumes both fuels share identical chemical ignition characteristics under engine conditions. Option D is incorrect because auto-ignition values are intrinsic chemical properties defined by standard test methods.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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