Cylinder Design 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 Dry liners are inserted into wet liners Only Wet Liners are normally used in large Diesel Engines

Cylinder Design 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. For long-life industrial and commercial use Separate removable cylinder liners are used Repair and replacement is possible Appropriate materials can be used cast iron is preferred steel is occasionally used

Cylinder Liner Loading The liner thickness may be calculated from tl = Liner thickness (m) sc= Permissible cicumferential stress (kN/m2) Pmax= Maximum combustion Pressure (kPa) D = Inner liner Diameter (m) sc = (1.0 - 1.5 ) x 105 kN/m2 for steel sc = (0.2 - 0.3 ) x 105 kN/m2 for cast iron tl = tl1 + tl2 for composite dry liners tsteel > 2 mm

Effect of Thermal Stresses

Typical Wet Liner Configuration

Typical Dry Liner Configuration

Advantages of Wet Type Liners It can be removed and replaced with great ease and without the need for any special tools or equipment. It is possible to provide for a high-velocity water circulation around the liner and therefore reduce the piston temperature. 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 Suitable when cylinder block and crankcase are formed in one piece with detachable cylinder heads Cooling water can come nearer to the top end of the liner No gas or water joints are required Stiffness of the cylinder block is increased Main Disadvantage A dry liner must be pressed or shrunk into the cylinder barrel. It is difficult to remove or replace without special equipment

Lcen/D = 1. 20 - 1. 28 for SI engines Lcen/D = 1. 25 - 1 Lcen/D = 1.20 - 1.28 for SI engines Lcen/D = 1.25 - 1.30 for CI engines

Liner Flange Design Calculation Taking moments around A ; Section Modulus of the cross-section between B&C ;

Design Notes on Water Cooled Cylinder Blocks Walls are tensioned by the gas forces transmitted to the studs via the cylinder head Tensile forces are only applied to the walls of the water jacket and the partitions between the cylinders In-Line and V-Engines with water cooling usually have cylinders cast integral with the upper half of the crankcase Main casting forming the cylinder block and crankcase may be made from alimimium alloy.

Design Notes on Cylinder Blocks The crankcase width is determined from the trajectory of the extreme point of the connecting rod bolt head. Minimum distance between bolt head and internal surface of crankcase is 10-15 mm Wall Thicknesses Cast-Iron crankcase walls and partitions are 5 - 8 mm Cast-Iron water jacket thickness : 4 - 7 mm Aluminium casting thicknesses are 1 - 2 mm more. Die-cast Aluminium thickness is less than cast-iron