This study proposes a new near zero-wear non-contact self-impact seal based on the passive fluid blocking principle and the Tesla valve structure, which is characterised by near zero-wear, a long lifetime, a simple structure and high stability. Research shows that the impact-blocking effect of a three-dimensional leakage channel can realise the stepwise throttling effect of the sealing medium. Furthermore, the pressure, number of seal stages and seal spacing significantly affect leakage. Leakage can be effectively controlled by increasing seal series and reducing seal spacing. The proposed near zero-wear impact seal is more suitable for the gas medium. Compared with the conventional sealing form, the new seal is simplified significantly. Large spacing and fixed design can significantly improve the ability to seal pairs to resist vibration and impact during operation, and the sealing performance is not restricted by the rotation speed. The form of the proposed seal will enable a new non-contact mechanical seal technology and a new structure to be developed, thereby advancing the existing seal field.

The size and change of leakage channel within the mechanical seal interface are investigated to calculate and predict the leakage rate of mechanical seal. Based on the percolation theory, the computing method of the leakage channel within the mechanical seal interface is analyzed; the critical size and change of leakage channel and leakage rate are obtained. The results show that during the period of normal wear, the magnification of the leakage channel increases exponentially with load and time, the height of leakage channel follows a polynomial decline with load and decays exponentially with time. According to the load-dependence or time-dependence of magnification and height, the size of the leakage channel and the leakage rate of the mechanical seal could be calculated and predicted, which is helpful for the optimum design and safe operation of the mechanical seal.

It is well accepted that the ratio of the dimple depth-over-diameter is a key geometric parameter in surface texturing design. In this article, the effect of this ratio on the average pressure is investigated by solving Reynolds equation numerically, where the Jakobsson–Floberg–Olsson cavitation theory is implemented using a mass-conservative algorithm. The results show that the optimum dimple depth-over-diameter ratio should be determined at the given depth or diameter larger than a critical value. Otherwise, the considerably smaller maximum value of average pressure will be obtained. Moreover, a dimple depth or diameter should be selected carefully in conjunction with the operating conditions to determine the optimum dimple depth-over-diameter ratio.

Numerical analysis is employed to investigate the influence of parting surface and combined thermal factor (rotation) on deformation of split mechanical seal. Parting surface takes little effect on the temperature distribution, verified by comparison experiment. Shaft rotation speed does not much affect the radial temperature gradient of the seal end faces but can raise the temperature when being increased. The simulated model turns to a drum, with the parting surfaces, close to the primary sealing interface presenting a convergent taper, becoming open-shaped. Increasing rotation dramatically intensifies the seal end face deformation of both split stationary and rotating seal rings and slightly increases the convergent taper size of the primary sealing interface. However, it takes little effect on the parting surface deformation. Compared with integral mechanical seal, parting surfaces distinctly reduce the primary sealing interface cone as well as the seal end face deformation of both split seal rings.

It is well known that the dimple area density is a key parameter for the design of mechanical seal with dimples. In the present paper, the integrated influence of sliding velocity, outlet pressure, and seal clearance on optimum dimple area density, represented by dimple number along the dimple column taken from the seal surface, are conducted theoretically by solving Reynolds equation, where the Floberg– Jakobsson–Olsson (JFO) cavitation theory is implemented using a mass-conservative algorithm to accurately predict the behavior of cavitation. The results show that the optimum dimple area density is closely related to the operation parameters and the influence of each operation parameter can be divided into three regions. Moreover, for each operation parameter, both of the range of the divided regions and the corresponding values of the optimum dimple area density are strongly associated with the other two operation parameters. In addition, the influences of operation parameters on optimum dimple area density can be investigated by their effects on the maximum pressure caused by dimples.