CETANE NUMBER
CETANE NUMBER
Cetane number :
→the knocking characteristics of the diesel is expressed in the terms of cetane number.
→cetane, is saturated hydrocarbon which has very short ignition lag as compare to any commercial diesel fuel. Hence it’s cetane number is taken as 100.
→on the other hand 2-methyl naphthalene (aromatic hydrocarbon ) has very long ignition lag as compare to any commertial diesel oil . Hence it’s octane number is taken zero.
→cetane number of diesel oil is defined as “the percentage of the cetane number in the mixture of the cetane & α-methyl naphthalene which exactly matches in it’s knocking characteristics with oil under test”
→the cetane number of the high speed, medium speed , low speed diesel is 45,35,25.
→cetane number of the oil can be improved by adding dopes like ethyl nitride, isoamyl nitrate , acetone peroxide etc.
→dopes are added in small amount about 2%.
→use of dopes is not common as TEL in gasoline.
→in petrol engines , knocking is due to sudden spontaneous combustion of the fuel , where as knocking in diesel engine is due to delay in the spontaneous combustion of the fuel. Thus, an oil of high octane number has low cetane number and vice-versa.
Cetane number :
→the knocking characteristics of the diesel is expressed in the terms of cetane number.
→cetane, is saturated hydrocarbon which has very short ignition lag as compare to any commercial diesel fuel. Hence it’s cetane number is taken as 100.
→on the other hand 2-methyl naphthalene (aromatic hydrocarbon ) has very long ignition lag as compare to any commertial diesel oil . Hence it’s octane number is taken zero.
→cetane number of diesel oil is defined as “the percentage of the cetane number in the mixture of the cetane & α-methyl naphthalene which exactly matches in it’s knocking characteristics with oil under test”
→the cetane number of the high speed, medium speed , low speed diesel is 45,35,25.
→cetane number of the oil can be improved by adding dopes like ethyl nitride, isoamyl nitrate , acetone peroxide etc.
→dopes are added in small amount about 2%.
→use of dopes is not common as TEL in gasoline.
→in petrol engines , knocking is due to sudden spontaneous combustion of the fuel , where as knocking in diesel engine is due to delay in the spontaneous combustion of the fuel. Thus, an oil of high octane number has low cetane number and vice-versa.
for knocking click here : https://engineeringchemistry1.blogspot.com/2020/01/knocking.html
for octane number click here :https://octanenumberdefinitionandnotes.blogspot.com/2020/01/octane-number.html
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