Mechanical Engineering - Automobile Engineering - Discussion

The property of ignition lag is generally measured in terms of retane number. Cetane, straight-chain paraffin with good ignition quality, is arbitrarily assigned a rating of 100 cetane number. It is mixed with alpha-methyl-naphthalene, a hydrocarbon with poor ignition quality, which is assigned 0 cetane number.

Straight chain paraffin is the right one.

Straight chain paraffin is the right answer.

A. Straight chain paraffin is the right answer.

Option A is the right answer.

The best fuels for compression ignition engines (commonly diesel engines) are straight-chain paraffins.

This is because straight-chain paraffins have high cetane numbers, which promote easier ignition and smooth combustion in compression ignition engines. These fuels also provide better fuel efficiency and lower emissions compared to other types like branched-chain paraffins or aromatics.

In contrast:

Aromatics can cause incomplete combustion, leading to higher emissions.
Branched chain paraffins have lower cetane numbers and thus are less ideal for compression ignition.
Naphthalenes are not typically used in diesel fuel, as they can cause poor combustion and undesirable engine performance.