Semi Salix Leaf Textured Gas Mechanical Face Seal with Enhanced Opening Performance

Seal performance of a novel gas mechanical face seal with semi salix leaf textures was introduced and theoretically investigated with the purpose of enhancing hydrostatic and hydrodynamic opening performance. First, a theoretical model of a laser surface textured gas mechanical face seal with semi salix leaf textures was developed. Second, the impact of operating and texturing parameters on open force, leakage, and friction torque was numerically investigated and has been discussed based on gas lubrication theory. Numerical results demonstrate that the semi salix leaf textured gas face seal has larger hydrostatic and hydrodynamic effects than the semi ellipse textured seal because of the effect of the inlet groove. All semi salix leaf textured surfaces had better open performance than the semi ellipse textured surface, which means that the inlet groove plays an important role in improving open performance and consequently decreasing contact friction during the start-up stage. Texturing parameters also influenced the seal performance of thee semi salix leaf textured gas face seal. When the inclination angle was 50°, the radial proportion of the inlet groove was 0.8, the dimple number was 9, and the open force resulted in the maximum value. This research has demonstrated the positive effects of the applications of a semi salix leaf textured gas mechanical face seal that combines the excellent hydrostatic and hydrodynamic effects of groove texture and the excellent wear resistance of microporous textures.

Hydrodynamic effect of non-closed elliptical grooves of bi-directional rotation gas face seals

Purpose The purpose of this paper is to improve opening performance of bi-directional rotation gas face seals by investigating the hydrodynamic effect of non-closed elliptical grooves. Design/methodology/approach A model of non-closed elliptical groove bi-directional rotation gas face seal is developed. The distribution of lubricating film pressure is obtained by solving gas Reynolds equations with the finite difference method. The program iterates repeatedly until the convergence criterion on the opening force is satisfied, and the sealing performance is finally obtained. Findings Non-closed elliptical groove presents much stronger hydrodynamic effect than the closed groove because of drop of the gas resistance flowing into grooves. Besides, the non-closed elliptical groove presents significant hydrodynamic effect under bi-directional rotation conditions, and an increase of over 40 per cent is obtained for the opening force at seal pressure 4.5 MPa, as same level as the unidirectional spiral groove gas seal. In the case of bi-directional rotation, the value of the inclination angle is recommended to set as 90° presenting a structure symmetry so as to keep best opening performance for both positive and reverse rotation. Originality/value A model of non-closed elliptical groove bi-directional rotation gas face seal is established. The hydrodynamic mechanism of this gas seal is illustrated. Parametric investigation of inclination angle and integrity rate is presented for the non-closed elliptical groove bi-directional rotation gas face seal.

A closed-form contact model for gas face seals during the opened operation

Purpose Face contact has a strong impact on the service life of non-contacting gas face seals; the current research which mainly focuses on the face contact had appeared during the startup or shutdown operation. This paper aims to present a closed-form contact model of a gas face seal during the opened operation. Design/methodology/approach Referring to the axial rub-impact model of rotor dynamics, a closed-form contact model is developed under a nonparallel plane contact condition that corresponds to the local face contact of sealing rings arising from some disturbances during the opened operation. The closed-form contact model and a direct numerical contact model are performed on Gaussian surfaces to compare the contact behavior. Findings The closed-form contact model is in a good agreement with the direct numerical contact model. However, the closed-form contact model cannot involve the influence of grooves on the sealing ends. The error is eliminated in some other types of gas face seals such as coned gas face seals. Besides non-contacting face seals, the closed-form model can be applied to the axial rub impact of rotor dynamics. Originality value A closed-form contact model of a gas face seal is established during the opened operation. The closed-form contact model is validated by a direct numerical contact model. The closed-form contact model also suits for axial rub-impact of rotor dynamics.

Dry Gas Face Seal Design With Arbitrary Gap Shape

Active use of dry gas seals for gas turbine engines is constrained by several important factors. One of them is a significant deformation of the sealing rings. This paper is dedicated to the creation of a technique of designing of a dry gas seal with spiral grooves with a consideration of arbitrary gap shape. A large number of studies for this type of seal have been conducted. But the technique of the seal designing which combines sealing leakage calculation with the calculation of the actual rings deformation has not been implemented. This article proposes a solution for this significant problem. Indeed, the increase in temperature and pressure drop results in a deformation of the rings surfaces. For the small gap, the impact of force and thermal deformation is critical. The seal designing without consideration of the surfaces deformation can lead to significant errors, but also to the failure of the seal in operation in the worst case. An improved mathematical model for calculating the leakage is proposed. On its basis, the designing technique has been developed. This technique combines the analytical calculation and calculation of deformation by finite element method. Implementation of this technique has a good practical result. The seal was created for a gas pumping unit. Experimental results have confirmed the computational results.

Gas Dynamic Face Seal Tightness Under Non-Stationary Loading

Aircraft engines have multiple operation modes for different flight conditions. However, each element of an engine is generally designed for one particular operating mode (maximum load or maximum duration). Mode alteration leads to the variation of pressure and temperature in sealing cavities. Therefore, it is important to consider the full load range into the design process of separate units. This paper presents an original technique of leakage calculation for the spiral-grooved mechanical gas face seal on the different operation modes of the aircraft engine. This type of seal has never used in aircraft engine design. However it has a history of excellent performances in comparison with the traditional type of seals, such as labyrinth or face contact seals. The value of sealing rings deformation must be determined for all operation modes. The flow model of the gas face seal is used to define heat transfer coefficients of seal ring surfaces. Using transient analysis, the influence of the load change rate on the sealing rings can be determined. The developed technique investigates the effect of the engine operating mode alteration on the temperature loads and deformations. Results of the simulation are compared with the experimental data.