Performance Analysis of the Cylinder Gas Film Seal between Dual-Rotor Reverse Shafts Considering Lubrication and Centrifugal Expansion Effects

Abstract

The cylinder gas film seal between dual-rotor reverse shafts is a new method for sealing aircraft engines that has excellent developmental prospects. We propose a novel method for determining if the sealing ring is fully fluid-lubricated using the average Reynolds equation. Considering surface roughness and centrifugal expansion, we calculated the dynamic pressure, gas film force and friction power consumption with and without inlet pressure differences for each of the four rotation modes. The gas film’s dynamic pressure effects were weakest when the dual rotors rotated in a reverse direction (Mode 3), with or without differences in inlet pressure, since solid contact is most likely to occur under counter-rotation. When the dual rotors were in counter-rotation with an inlet differential pressure of 80 kPa and fixed inner and outer rotor speeds (e.g., 3000 rpm), we calculated the minimum sealing ring film thickness, leakage rate, friction power consumption and gas film force. Changes in outer rotor speed greatly influenced the minimum film thickness and the sealing ring’s performance. Meanwhile, changes in the inner rotor speed had little influence on the minimum film thickness and sealing ring’s lubrication performance. When the speed difference was fixed and the sealing ring was fully fluid-lubricated, lubrication performance changes were mainly affected by changes in centrifugal expansion caused by the outer rotor speed. Given a fixed rotor speed and under dual-rotor counter-rotation, we calculated the effects of inlet differential pressure changes on minimum gas film thickness, leakage rate, friction power consumption, gas film force and other sealing performance variables. Leakage rate and the friction power consumption increase as inlet differential pressure increases. Our results provide a theoretical reference for avoiding solid contact of the cylinder seal between dual-rotor reverse shafts.

Performance Analysis of the C/C Composite Cylindrical Reverse Inter-Shaft Gas Film Seal

“…To validate the proposed analytical method for cylindrical reverse inter-shaft gas film seals based on fluid-solid coupling, the calculation results are compared with experimental and simulation results in the literature [18]. The test sealing ring material is graphite (elastic modulus 18 GPa, Poisson's ratio 0.3, and density 1.8 g/cm 3 ).…”

“…Figure 7. Comparison of leakage rates simulated in this paper and reference [18] under diff rotational speed combinations of inner and outer rotors.…”

“…The cylindrical inter-shaft seal structure proposed by Zhao et al [18] is similar to the floating ring seal structure. There has been a lot of research on the performance of floating ring seals.…”

“…Hou et al proposed a flexible cylindrical seal structure with metal rubber [17] and used numerical methods to calculate the effects of rotor tilt, centrifugal expansion, and other factors on the gas film pressure distribution under stable conditions. Zhao et al [18] analyzed the performance of graphite ring cylindrical reverse inter-shaft seals in different lubrication states and found that centrifugal expansion and rotational speed of the seal ring have a significant impact on the sealing performance.…”