The working temperature of exhaust valves in marine diesel engine components

The working conditions of exhaust valves are extremely harsh. The bottom surface of the valve is in direct contact with the high-temperature combustion products. During the valve opening period, it also withstands high temperatures (900 - 1000°C) and the high-speed (up to 600 m/s) erosion of corrosive gases. The center temperature of the valve is as high as 700 - 800°C, and in the middle section of the transition arc between the valve disc and the valve stem, the temperature is also 600 - 700°C. The temperature distribution of the exhaust valve during operation.

Excessive temperature will reduce the mechanical properties of the metal material and cause thermal deformation. When the valve face is not sealed properly, it will cause the burning of the valve face by the high-temperature gas. When the valve seats, under the combined action of the inertial force of the valve and the spring force, also withstands a considerable impact and alternating load. When the valve jumps or the valve clearance and diameter increase, this load will increase significantly. The impact between the valve and the valve seat is likely to cause deformation of the sealing surface and severe wear. Since most marine diesel engines are turbocharged diesel engines, the fresh air pressure in the intake passage prevents the possibility of obtaining lubricating oil from the valve guide, so dry friction is likely to occur between the metal surfaces.