Juan Wang

Finger seals operate over extended periods under complex conditions involving high-pressure differentials, elevated rotational speeds, and rotor radial runout. Intense convective heat transfer arises within the seal, significantly impacting its structural deformation. To elucidate the influence of temperature on finger-seal deformation during convective heat transfer, the present study derives heat transfer energy equations for finger seals based on the Local Thermal Non-Equilibrium (LTNE) model. A three-dimensional porous-media flow-field model incorporating the LTNE framework, along with a solid thermal-deformation model, is developed. The effects of pressure differential and interference-fit magnitude on the structural deformation and average contact pressure of finger seals are analyzed under both the Local Thermal Equilibrium (LTE) and LTNE models. The results indicate that the LTNE model predicts a higher maximum seal temperature and a lower leakage rate compared to the LTE model. In both models, the deformation of individual seal-blade layers increases with rising pressure differentials and interference-fit magnitudes. Furthermore, the overall blade deformation is more pronounced under the LTNE model, suggesting a substantial thermal influence on sealing performance. The effects of pressure difference and interference fit on the thermal deformation of the seal plate are similar: both have the greatest impact on radial deformation, followed by circumferential deformation and axial deformation. Within the pressure difference range, the radial deformation of the third-layer seal plate in the LTNE model increases by 14.55%. When the interference fit increases from 0.05 mm to 0.2 mm, the radial deformation of each layer of the seal plate in the LTNE model increases by 0.18 mm. The average contact pressure increases with both pressure differential and interference-fit magnitude across both models. At a given pressure differential, the LTNE model yields a higher average contact pressure than the LTE model, with a maximum observed difference of 0.01 MPa. When the interference-fit magnitude is small, the pressure difference between the models remains minimal; however, at the maximum interference-fit, the difference reaches 0.08 MPa.

The top beam of a hydraulic support, serving as the central component of the hydraulic support assembly, directly withstands the impact loads generated by the subsidence of overlying rock strata. The structural strength and design rationality of the top beam directly determine the support effectiveness of the hydraulic support. In response to this issue, this study focuses on newly developed hydraulic combined supports for tunneling operations. Transient dynamic simulations were conducted at various positions on the top beams of individual supports under different working conditions, yielding stress and displacement changes in various regions of the support canopy when subjected to impact. We obtained the dynamic characteristics of the key parts of the hydraulic unit support during load bearing stress. Future work will explore the hydraulic system model and the interaction between mechanical and hydraulic subsystems.

To effectively address the issue of premature failure caused by the unbalanced distribution of pressure drops between the stages of a traditional two-stage finger seal, this study proposes a method to improve the pressure drop balance by increasing the protection height of the second stage back plate. We established a new numerical calculation model for a two-stage finger seal, based on the porous media model. After verifying the precision of the model, we conducted a numerical analysis to examine the impact of the protection height of the second stage back plate on the flow and heat transfer characteristics of the two-stage finger seal. We then conducted a differentiated structural design for each stage of the two-stage finger seal. The research results are as follows: the pressure drop at the second stage of the traditional two-stage finger seal exceeds that of the first stage; when the protection height of the second stage back plate of the traditional two-stage finger seal is increased from 1.5 mm to 1.57 mm, forming a two-stage pressure equalizing finger seal structure, the pressure drop between the two stages is balanced, but the leakage is greater than that of the traditional two-stage finger seal; a grate seal structure was arranged between the first and second stages of the two-stage pressure equalizing finger seal to form a two-stage pressure equalizing finger seal with grate teeth, which exhibits significantly lower leakage compared to the two-stage pressure equalizing finger seal. However, the proportion of pressure drop at the first and second stages of the two-stage pressure equalizing finger seal is 36.8% and 42.1%, respectively, while the grate tooth stage accounts for 21.1%, resulting in an imbalanced pressure drop once again. Increasing the protection height of the second stage back plate in the two-stage pressure equalizing finger seal with grate teeth to 1.6 mm results in a 37.5% pressure drop at the first and second stages, and a 25% pressure drop at the grate tooth stage. The two-stage finger seal balances the pressure drop and matches the leakage of the traditional two-stage finger seal. The maximum temperatures of the first and second stages of the finger seal are 0.7% lower and 2.6% higher compared to the traditional two-stage finger seal. This suggests that a differential multi-stage finger seal is the optimal structure.