Finger seal is a new type of compliant seal configuration, which is an important part of an aero-engine and its accessory systems. It has superior sealing performance compared with conventional labyrinth seals and a lower manufacturing cost than brush seals. However, numerical simulation of the leakage characteristics of an entitative finger seal structure are very difficult to implement, because the finger laminates are in close contact with one another and the radial deformation of the fingers caused by interference between seal and rotor as well as the centrifugal and thermal expansion of the rotor can change the geometric structure of seal. The published leakage analysis models of finger seal ignore the leakage throughout the interstices between fingers or finger laminates. In view of this, the authors propose an anisotropic porous media model for leakage analysis of finger seal. The model considers the effects of the seal structure parameters, upstream and downstream axial pressure differences and the fit status between seal and rotor. First, the equations of the model and their parameters were obtained by theoretical derivations, while the correction factors were determined based on experiment leakage data in the literature. Second, the accuracy of the model was validated by calculating the leakage of a known seal structure in the literature and comparing these results with the experimental data. At last, a comparison between the anisotropic and isotropic porous media model is carried out. The results of the validation examples show that the model can simulate the leakage of finger seal very well with the errors between numerical results and experimental data are less than 10% for two-thirds of the data points.

A new three-dimensional mathematical model is proposed to predict the shape of accreted ice on helicopter rotors. The model assumes that ice accretion on a rotor’s surface occurs by flow and solidification of a thin water film on its surface. The model is developed by analyzing conservation of mass, momentum, and energy in the thin water film on a rotating curved surface. The model is expressed in rotating body-fitted nonorthogonal curvilinear coordinates, and the Coriolis-force term in the momentum equations is neglected because its effect is relatively small compared with that of the centrifugal force. The computational method is presented to solve the model, and the model is validated by comparing its results with published experimental data. The results show that the proposed model accurately predicts both the water-film thickness and the ice-layer thickness on a rotating surface. Additionally, the model has been used to study how the rotor angular speed and MVD (Median Volumetric Diameter) of the droplets affect ice accretion. The results show that an increase in both angular speed and MVD can lead to a thicker layer of ice, while the effect of MVD on ice accretion near the stagnation point becomes unobvious when MVD is larger enough.

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The flow and heat transfer characteristics of a film jet inclined to different supersonic situations with a varying Mach number of the main flow were numerically investigated. In supersonic situations, complicated waves are generated by the obstacle of the film jet. In this work, extra pressure is exerted onto the film jet, causing better film attachment to the wall. The strengthening of attachment decreases mixing between the main flow and film jet, causing better film cooling. We observed multi-interfacial layered structures caused by the film jet under the complicated effect of shock waves. At the interfaces of the film jet and shock waves, additional pressure is exerted on the film towards the wall. The pressure increases as the Mach number of the main flow increases and contributes to the increased adhesion of the gas film, which causes the cooling enhancement under a supersonic condition. In the vicinity of the film hole exit, a local low pressure region is formed under the influence of the supersonic main flow. An aerodynamic convergent–divergent state was formed in the film hole, devastating the state of supersonic congestion of the film hole and further enhancing the film cooling effect.

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