1. Function of cylinder liner
1) Formed cylinder working space with cylinder cover and piston.
2) Cylinder liner of trunk piston diesel withstands side thrust of piston, so it becomes lead of piston reciprocating action.
3) Transmit heat of piston assembly and self-heat to cooling water tokeep its proper working temperature.
4) Cylinder liner of two stoke diesel engine is equipped with vent; it ishoisted by piston to achieve air distribution.

2. Workingcondition
Inside cylinder liner is directly affected by high-temperature andhigh-pressure gas, and always produce high-speed slide friction with pistonrings and piston skirts. While its outer touch with cooling water, producingserious thermal stress under big difference in temperature and corroded bycooling water. Side thrust from piston not only acerbates inside friction ofcylinder liner, but also makes it bent. When side thrust changes its direction,piston will strike cylinder. Besides, it has to withstand high installationpreload.
Gas pressure make cylinder face produce tangential tensile stress and radialcompressive stress, which is maximal inside, this kind of stress is radiofrequency pulsating stress.
Serious thermal stress produced by difference in temperature between inside andoutside of cylinder face, so, under normal temperature, inside wall producescompressive stress while cooling face produces tensile stress. But underextremely high temperature, metal of inside wall will be distorted and formresidual stress when cooling. This low frequency caused by engine starting andstopping will make the material tired.

3. Requirements
Diesel engine cylinder liner should be with high strength, hardness,heat-resisting and abrasion-proof property. Smooth lubrication and coolingshould be available during working.
Cylinder liner usual uses wear-resisting cast iron alloy including phosphor orboron as its material, such as HT25-47、HP-CuCrMo, etc. Inside cylinder liner sometimes is in processof chrome plating (spongy chromium plating, oil stored chromium plating),nitrogen and phosphorization to improvewear-resisting performance. Inside temper must be bigger than HB200 and fit wellwith piston ring temper; proper roughness with oil storing ability andrunning-in characteristic; with enough roundness and cylindricityprecision to assure position accuracy between installing bearing face andcentral inner hole.