Knocking
knocking
Knocking : knocking is sharp metallic sound,similar to rattling of hammer which is produced in the internal combustion engine owing to immature ignition of air gasoline mixture .
→thus due to this there is huge loss of energy and it causes damage to piston & cylinder.
→a mixture of petrol vapour and air acts as a fuel in an internal combustion engine.
→in the down stroke of the piston ,a mixture of gasoline or petrol vapour & air is drawn from carburetor into the cylinder & on stroke mixture is compressed .
→the ratio of the original volume of the fuel mixture to that of final volume obtained after the compression is called as the compression ratio .
→efficiency of the engine is depend on this comprssion ratio , higher the C.R higher the efficiency of the engine.
→due to the presence of some constituents in the gasoline the rate of oxidation increases & fuel air mixture get ignited instantaneously ,producing explosive violence known as knocking .
→knocking is maximum in the fuel containing straight chain parrafins.so, straight chain hydrocarbons are the worst & aromatic and branched chain carbons are best.
→order is given by:
Straight chain hydrocarbons > branched chain > olefins >cycloparaffins >aromatics
→knocking can be decreased by adding antiknocking components which increases octane number & decreases knocking called antiknocking components .
→tetraethyl lead (TEL) is used as antiknocking compound
4Pb-Na + 4C_4 H_5 Cl → Pb(C_2 H_5 )_4 + 3Pb + 4NaCl
→TEL is colourless liquid having sweet odour . It is highly poisonous .
→In addition to TEL ,lead oxide is produced & reduced to mettalic lead which deposits on spark plug joints ,cylinder walls &piston head.
→to avoid to this , ethylene bromide also added to convert that lead into volatile lead bromide which swept out with exhaust gases .
→Knocking characteristics of the fuel are usually expressed by octane number.
Knocking : knocking is sharp metallic sound,similar to rattling of hammer which is produced in the internal combustion engine owing to immature ignition of air gasoline mixture .
→thus due to this there is huge loss of energy and it causes damage to piston & cylinder.
→a mixture of petrol vapour and air acts as a fuel in an internal combustion engine.
→in the down stroke of the piston ,a mixture of gasoline or petrol vapour & air is drawn from carburetor into the cylinder & on stroke mixture is compressed .
→the ratio of the original volume of the fuel mixture to that of final volume obtained after the compression is called as the compression ratio .
→efficiency of the engine is depend on this comprssion ratio , higher the C.R higher the efficiency of the engine.
→due to the presence of some constituents in the gasoline the rate of oxidation increases & fuel air mixture get ignited instantaneously ,producing explosive violence known as knocking .
→knocking is maximum in the fuel containing straight chain parrafins.so, straight chain hydrocarbons are the worst & aromatic and branched chain carbons are best.
→order is given by:
Straight chain hydrocarbons > branched chain > olefins >cycloparaffins >aromatics
→knocking can be decreased by adding antiknocking components which increases octane number & decreases knocking called antiknocking components .
→tetraethyl lead (TEL) is used as antiknocking compound
4Pb-Na + 4C_4 H_5 Cl → Pb(C_2 H_5 )_4 + 3Pb + 4NaCl
→TEL is colourless liquid having sweet odour . It is highly poisonous .
→In addition to TEL ,lead oxide is produced & reduced to mettalic lead which deposits on spark plug joints ,cylinder walls &piston head.
→to avoid to this , ethylene bromide also added to convert that lead into volatile lead bromide which swept out with exhaust gases .
→Knocking characteristics of the fuel are usually expressed by octane number.
for octane number : https://octanenumberdefinitionandnotes.blogspot.com/2020/01/octane-number.html
For cetane number click the link:
For cetane number click the link:
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