Assertion (A) : A very high compression ratio is favoured for a CI engine, in order to attain high mechanical efficiency without knocking
Reason (R): The delay period in CI combustion effect rate of pressure rise and hence knocking
Option (A)
Both A and R are individually true and R is the correct explanation of A
Option (B)
Both A and R are true but R is not the correct explanation A
A is true but R is false
A is false but R is true
Correct Option:
Question Solution:
Compression ignition engine operate at compression ratios which are considerably higher than those used by SI engines. High compression ratios of CI engines are necessary in order to compress the air to the point producing a temperature necessary to promote satisfactory combustion. This air temperature of course, must be higher than the ignition temperature of the fuel used An increase in compression ration increase the thermal efficiency of the engine, and for given compression ration the CI engine cycle is less efficient than the Si engine cycle