What the dowty retarder working principle？

As a device to ensure railway safety, dowty retarder has an extremely important role in railway safety. The working principle of dowty retarder is introduced below.

The dowty retarder is composed of a sliding oil cylinder assembly and a housing. There is a piston rod inside the sliding cylinder, and the piston rod is provided with a speed valve which can judge the speed of the vehicle and a pressure valve which can brake the vehicle. The sliding cylinder is filled with a certain amount of oil and nitrogen.

The critical speed is a main performance index of dowty retarder. The speed valve is set to identify the speed of the vehicle. According to work requirements, when the vehicle speed is lower than the critical speed of the deceleration top, the speed valve is open: and when the vehicle speed is higher than the critical speed of the top, the pressure difference caused by the fluid flow inside the cylinder makes the speed valve close quickly. Therefore, the critical pressure difference corresponding to the critical speed is the basis for designing the speed valve.