This paper examines the effect of labyrinth seal structure on the evolution of vortex systems and the performance of the cascade. It is found that the labyrinth seal leakage leads to the circumferential development of the separation vortex, and the axial influence region of the concentrated shedding vortex also expands, which increases the flow loss and reduces the diffuser capacity. Among all the cases, the deteriorating effect of the cavity without a labyrinth seal is the most significant. This results in an 83% increase in total pressure loss compared to the prototype cascade. The straight tooth labyrinth and the straight tooth labyrinth with block structures can effectively reduce the leakage from the sealing cavity and weaken the deterioration caused by labyrinth seal leakage. Among these schemes, the straight tooth with block scheme has the most considerable effect, resulting in a 19% reduction in total pressure loss. As the incidence angle increases, the recirculation zone on the end wall of each scheme gradually shrinks toward the leading edge. Meanwhile, the static pressure rises, and the velocity decreases near the leading edge. Compared with the straight tooth scheme, the straight tooth with block scheme can reduce the high-loss zone by 14% at most. In addition, as the sealing clearance gradually increases, the inhibitory effect of the straight tooth with block scheme on the deterioration of cascade performance caused by the labyrinth sealing cavity is gradually enhanced compared to the straight tooth structure. The improvement effect is optimal under 0.5 mm sealing clearance.

Uneven pressure drops among stages of multistage brush seal (MBS) leads to early failure of single-stage seal units, which directly affects service life of the seal used in aeroengines, gas turbines, and steam turbines. In this paper, influence factors of interstage pressure drop were studied to analyze formation mechanism of the uneven pressure drops. Moreover, an MBS with differentiated structure was presented, and its interstage pressure drops were further investigated. The results showed that the MBS with several same single-stage seal units had uneven pressure drops among stages under high inlet/outlet pressure ratios. In view of remarkably increasing velocity and decreasing pressure in downstream region of bristle pack near rotor surface during flow of airflow, adjustments of structural parameters (i.e., increasing height of backing plate to rotor surface Hb, increasing seal clearance Hg, and decreasing axial width of bristle pack B) could improve the uneven pressure drops among different stages due to increasing outlet air flow area of the stage. The closer pressure drop proportions of different stages to ideal average value indicated increase of Hb had a more effective effect to balance the pressure drops among different stages compared to increase of Hg and decrease of B. An MBS with differentiated structure, in which both Hb and Hg of all the single-stage seal units were increased progressively and B was decreased step by step, showed a good performance to obtain even interstage pressure drops.

To study the influence of taper seal clearance on the static and rotor-dynamic characteristics of hole-pattern damper seals, this paper develops three-dimensional transient computational fluid dynamic methods, which comprise single-frequency and multi-frequency elliptical orbit whirl model, by the transient solution combined with a mesh deformation technique. Through the investigations, it is illustrated that: (1) In the present paper, the leakage rates of convergent-tapered hole-pattern damper seals are less than divergent-tapered hole-pattern damper seals for the same average seal clearance, and the maximum relative variation reaches 16%; (2) Compared with a constant clearance hole-pattern damper seal, the maximum relative variation of the rotor-dynamic coefficients is 1,865% for nine taper degrees in this paper; (3) Convergent-tapered hole-pattern damper seals have smaller reaction forces and effective damping coefficient, larger cross-over frequency, and direct stiffness coefficient, while divergent-tapered damper seals have the opposite effects; (4) Divergent-tapered hole-pattern damper seals alleviate the rotor whirl because of a larger effective damping coefficient when the rotor system has large natural frequency and small eccentricity. Convergent-tapered damper seals provide both sealing and journal bearing capabilities at the same time, and are more advantageous to the stability of the rotor system when rotor eccentricity is the main cause of rotor instability.

In order to study the oil–gas two-phase flow characteristics of an aero-engine bearing chamber and improve the scavenge effect of lubricating oil, the two-phase flow solution model of a bearing chamber based on the Euler–Euler method was established. Three improvement schemes were proposed for the ventilation structure and scavenge structure of the bearing chamber. The flow characteristics and scavenge characteristics of a conventional bearing chamber and three improvement schemes under different working conditions were analyzed in depth. The results show that after the conventional bearing chamber ventilation structure is embedded (Embed) and improved, with the increase in the embedding depth, the oil in the cavity is further blocked in the cavity, the amount of oil flowing out from the vent is further reduced, and the scavenge efficiency is further improved. After the slope improvement of the scavenge structure of the conventional bearing chamber, due to the increase in the depth of the oil return groove, the drag effect of the air shear force in the cavity on the oil in the oil return groove is further weakened, and the oil accumulation area on the right side of the scavenge port is further suppressed. The volume fraction of the oil in the cavity is further reduced, and the scavenge efficiency is further improved. The combined improvement scheme (ES) can take into account the advantages of embedding and slope improvement schemes, and further improve the scavenge efficiency. Compared to the conventional bearing chamber, when the oil flow rate is 200 L/h and the speed is 15,000 r/min, the oil return efficiency of the embedded (h = 12 mm), slope (l = 56 mm) and combined improvement schemes are increased by 20.19%, 13.43%, and 37.94%, respectively.

Aiming at the problem of abnormal wear caused by the poor dynamic characteristics of aeroengine segmented annular seals, according to the hydrodynamic lubrication theory, based on the conventional structure featuring the Rayleigh step profile rectangular pocket (RP), novel structures with the circumferential linear convergent pocket (CLCP) and the circumferential parabolic convergent pocket (CPCP) were proposed. A model was developed to analyze both the static and dynamic characteristics of three types of segmented annular seals, utilizing the local differential quadrature (LDQ) method. Once the accuracy of the solution model was confirmed, the effects of working conditions and design features on both static and dynamic characteristics were analyzed. Results indicate that the circumferential wedge convergent pockets can effectively improve the dynamic characteristics of the seal system. Under different rotational speeds, compared with the RP seal, the CLCP seal’s stiffness coefficient and damping coefficient increases by an average of 60.76% and 65.27%, respectively. As the rotational speed increases, the RP seal damping ratio decreases, and the seal system transitions from an overdamped state to an underdamped state, resulting in reduced stability. Nevertheless, under different rotational speeds and pressure ratios, the CLCP and the CPCP seals are both in an overdamped state. Taking into account the static and dynamic characteristics, the CLCP seal is the optimal structure in this study.