1 - Engine Types and Their Operation
1.4 - Engine Components :
1- The cast iron monolithic block
The use of cast iron blocks has been wide spread due to low cost as well as formability.The iron for the block
is usually gray cast iron having a Pearlite microstructure .
Gray cast iron is so called because its fracture has a gray appearance.
Ferrite in the microstructure of the bore wall should be avoided because too much soft ferrite tends to cause scratching, thus increasing blow-by.
The cast iron monolithic block manufacturing process
Cast iron blocks are produced by sand casting.
For cast iron , the Die casting process using a
steel die is fairly rare .The lifetime of the steel die
is not adequate for repeated heat cycles caused
by melting iron.
sand casting uses a mold that consists of sand.
the preparation of sand and the bonding are a critical
and very often rate - controlling step . Permanent
patterns are used to make sand molds.
2 - Aluminum blocks with enclosed
cast iron sleeves to improve cooling
The aluminum block can be both much lighter and almost as strong as the cast iron block .In a recent comparison, an aluminum block can attain 40% reduction in weight compared to its cast iron equivalent.
Despite the greater cost of aluminum,the demand for better fuel consumption has resultedin a significant increase in the production volume of light aluminum blocks.
The aluminum alloys used for blocks have a thermal conductivity of 150 W/(m · K).Cast iron has a thermal conductivity as low as 50 W/(m·K).
The thermal conductivity of aluminum is therefore three times that of cast iron. Since the Density is 1/3 that
of cast iron , aluminum alloy can give high cooling performance at a lower weight.
However , it is soft and the Wear resistance is generally low . to deal with this problem aluminum alloy
blocks with enclosed iron liners normally cast iron this type is called Heterogeneous " cast-in liner " as
it's structure as Aluminum block enclosing cast iron liner " Sleeves " Liner is enclosed in block (typically
, JIS-ADC12. die casting , JIS-AC4B shell molding ) by casting- in with various Casting methods . so it
have better cooling performance than Monolithic " linerless or cast iron integrated types " so it is widely used.
The main functions of cylinder block we can metion as the folllowing
* it hold lubrication passages so we can say it have lubrication system inside
* holding other engine component pistons ,cylinders and oil pump
* hold crankshaft and camshaft that convert rotating motion to reciprocating motion
Summery on Engine block
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