working principle
(1) Together with the cylinder head and piston constitute the cylinder working space.
(2) The cylinder of the cylindrical piston diesel engine bears the piston side thrust and becomes the lead of the reciprocating movement of the piston.
(3) Transfer the heat of the piston assembly and itself to the cooling water to make the working temperature appropriate.
(4) The cylinder of the two-stroke diesel engine is arranged with an air port, which is opened and closed by the piston to achieve gas distribution.
(5)In some crosshead diesel engines, the lower space of the cylinder doubles as an auxiliary scavenging pump space.
Working condition
(1) Upper – cylinder head installation preload force
(2) Inner wall – high temperature, high pressure, corrosion of gas, friction, knock and side thrust of piston
(3) Outside – corrosion and cavitation of cooling water
Job requirement
It should have sufficient strength and stiffness;
Good wear resistance, corrosion resistance;
There should be good lubrication and cooling in the work;
The joint surface of the cylinder liner and the cylinder head should have a good air seal and water seal;
The two-stroke cylinder liner should have a reasonable air port shape and cross-section size.
Main material
Cylinder block: gray cast iron, ductile cast iron,Cast steel,Forged steel (Adding chromium, molybdenum and nickel to cast iron)
Cylinder liner: gray cast iron, wear-resistant alloy cast iron, ductile cast iron
The inner surface of cylinder liner is chrome plated, nitriding, phosphating, surface quenching and spraying wear resistant alloy
Tips:Gray cast iron commonly used in small and medium diesel engines,
Main Composition
Cylinder: It is composed of cylinder sleeve and cylinder block.
Cylinder block: Integral type (small and medium-sized diesel engines)
Combined type (large diesel engines)
The composition and structural characteristics of the cylinder
The cylinder liner of diesel engine has three forms: wet type, dry type and with cooling water jacket.
Cylinder head function and working conditions
Working condition
(1) Corrosion – the bottom surface is subjected to the thermal and chemical erosion of high temperature and high pressure gas, and the cooling water chamber is corroded by water;
(2) Installation stress — affected by the pre-tightening force of the cylinder head fastening bolt and the reaction force of the cylinder liner;
(3) Thermal stress, mechanical stress – due to the complex structure, uneven distribution of metal materials, large temperature difference, the distribution of mechanical stress and thermal stress is uneven; Moreover, due to the constraint of the fastening force of the cylinder head bolt, the thermal expansion of the high temperature part is inhibited, which causes great thermal stress in the narrow area between the valve holes.
Working demand
(1) It is required to have sufficient strength and rigidity – to ensure that cracks or leaks will not occur because of excessive stress and deformation;
(2) The bottom plate of the cylinder head, especially between the hole valve and the high temperature part, needs good cooling – reducing the temperature and temperature difference of the wall;
(3) Simple structure, easy to disassemble, repair and management, the scale of cooling water is easy to remove;
At the same time, the material should also have good casting technology.
