Labyrinth seal and honeycomb seal.

There is a fundamental difference between the honeycomb-type steam seal structure and the comb-toothed steam seal. In the structure of the labyrinth comb-toothed steam seal, teeth of different heights are arranged alternately, whereas in the honeycomb labyrinth steam seal, the lower teeth are removed, and honeycomb strips are brazed throughout the channels between the two higher teeth； For helical or equally-height straight-toothed shaft end steam seals, all the original comb teeth are replaced with honeycomb strips, and the brazing of these honeycomb strips to the ring body is carried out in a vacuum brazing furnace. The cellular material is stainless steel foil made of nickel-based high-temperature alloys, with Hastelloy being a commonly used material. Given the soft texture of this material and its honeycomb-like structural pattern, it will not damage the surface of the shaft even when in friction with it; therefore, its radial clearance can be kept small. The honeycomb strip is composed of honeycomb cells with a regular hexagonal inner pore cross-section. Principle of cellular steam seals: The mechanism of cellular seals is fundamentally different from that of labyrinthine comb-tooth seals. The physical mechanism by which cellular seals achieve sealing is vortex energy dissipation. The steam that enters the sealing chamber along the axial direction immediately fills the honeycomb pores; the energy is absorbed by the cells of the honeycomb structure, but it cannot be stored within those pores, thus creating an obstacle to the steam that leaks in ； Between the gap at the end of the cellular pore and the journal surface, a layer of air film is formed due to the high-speed rotation of the shaft, which directly prevents the axial flow of air. The combination of these two types of damping results in strong damping effects; the turbulent damping is particularly effective, leading to a greater reduction in air flow velocity and thus an improved sealing performance. As a result, honeycomb-type gas seals offer excellent sealing qualities. Advantages of honeycomb seals: 1. Most of the advantages of honeycomb steam seals are reflected in the honeycomb strip. 1) Safety and reliability of the cellular steam seal. The cellular steam seal is a component of the turbine stator, and it is the inner circular surface of the cellular strip that may come into contact with the outer surface of the rotor journal. The material of the honeycomb strip is a nickel-based heat-resistant alloy; it is thin and soft, resulting in low friction with the rotor surface and thus no wear on the rotor surface, as well as offering good passive safety. The honeycomb strip is firmly bonded to the steam seal ring, ensuring good active safety. 2) The honeycomb belt has good sealing properties. 3) The honeycomb strip divides the traditional steam seal annular chamber into honeycomb pores, and the vortices formed at the honeycomb openings exert a damping effect on the rotor. 2. High installation accuracy. The radial positioning adjustment block added to the back of the steam seal ring improves the installation accuracy of the steam seal ring as well as the efficiency of adjusting the clearance on-site. 3. The renovation cost is low. Switching to a cellular steam seal does not alter any of the existing designs outside the steam seal ring; it is cost-effective and requires a short modification period.