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Compare the following fuels on the basis of calorific value and knocking. LPG, CNG and bio-diesel 
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1 Answer

Parameter
LPG
CNG
Bio-diesel
Calorific value
46.4MJ/Kg LPG has consistent & higher calorific value. 
52.34 MJ/Kg Which is higher than LPG.
37.27 MJ/Kg this 9% lower than regular petro diesel
knocking
It is highly knocking resistant and does not pre-ignite easily as compared with petrol. Its octane rating is 111.
CNG is having high knock resistant than LPG & Petrol. Its octane number is 130.
Cetane number for Biodiesel is 48 to 65 which is higher than petro-diesel. So intensity of knocking is less in biodiesel compared to petro diesel.
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