Presentation on theme: "Cylinder Design u Cylinder Liner (Barrel) Design The liner functions both as –a structural member –a bearing surface for the piston and rings Material."— Presentation transcript:
Cylinder Design u Cylinder Liner (Barrel) Design The liner functions both as –a structural member –a bearing surface for the piston and rings Material –Cast Iron for wet liners –Steel for dry liners u Dry liners are inserted into wet liners u Only Wet Liners are normally used in large Diesel Engines
Cylinder Design u In passenger car engines and small industrial engines –Liner is cast integrally with the jacket structure »Worn-out bore surfaces may be refinished to a larger diameter, and over-sized pistons are inserted. u For long-life industrial and commercial use –Separate removable cylinder liners are used »Repair and replacement is possible »Appropriate materials can be used u cast iron is preferred u steel is occasionally used
Cylinder Liner Loading u The liner thickness may be calculated from t l = Liner thickness (m) c = Permissible cicumferential stress (kN/m 2 ) P max = Maximum combustion Pressure (kPa) D = Inner liner Diameter (m) c = ( ) x 10 5 kN/m 2 for steel c = ( ) x 10 5 kN/m 2 for cast iron t l = t l1 + t l2 for composite dry liners t steel > 2 mm
Effect of Thermal Stresses
Typical Wet Liner Configuration
Typical Dry Liner Configuration
Advantages of Wet Type Liners u It can be removed and replaced with great ease and without the need for any special tools or equipment. u It is possible to provide for a high- velocity water circulation around the liner and therefore reduce the piston temperature. u Since the liner is held only by a flange at the top end, it is free to expand without any restraint.
Advantages of Dry Liners u Suitable when cylinder block and crankcase are formed in one piece with detachable cylinder heads u Cooling water can come nearer to the top end of the liner u No gas or water joints are required u Stiffness of the cylinder block is increased Main Disadvantage u A dry liner must be pressed or shrunk into the cylinder barrel. –It is difficult to remove or replace without special equipment
Lcen/D = for SI engines Lcen/D = for CI engines
Liner Flange Design Calculation u Taking moments around A ; u Section Modulus of the u cross-section between B&C ;
Design Notes on Water Cooled Cylinder Blocks u Walls are tensioned by the gas forces transmitted to the studs via the cylinder head u Tensile forces are only applied to the walls of the water jacket and the partitions between the cylinders u In-Line and V-Engines with water cooling usually have cylinders cast integral with the upper half of the crankcase u Main casting forming the cylinder block and crankcase may be made from alimimium alloy.
Design Notes on Cylinder Blocks u The crankcase width is determined from the trajectory of the extreme point of the connecting rod bolt head. u Minimum distance between bolt head and internal surface of crankcase is mm Wall Thicknesses u Cast-Iron crankcase walls and partitions are mm u Cast-Iron water jacket thickness : mm u Aluminium casting thicknesses are mm more. u Die-cast Aluminium thickness is less than cast-iron