In the case of low speed and high pressure, the wear of dry gas seal is more serious, therefore, the preparation of DLC film by static ring is proposed, and the friction characteristics of the end face of the static and dynamic ring are analyzed with the groove structure. The dry gas seal with different spiral angle was tested by friction and wear machine, and the change law of temperature rise, friction coefficient and surface wear morphology were tested. The test results show that with the increase of load and speed, the friction temperature rises, friction coefficient and grinding mark of 16° spiral angle are less than 18°. Under the same working condition, the value of average friction coefficient of 18°spiral angle is 0.02 larger than that of 16°spiral angle, and the average friction temperature is increased by 5 ℃. On the one hand, because of the different spiral angle, the interface method is different and the wear degree of the end face of 18° spiral angle is greater than 16° spiral angle. On the other hand, with the increase of load and speed, the graphitization degree of DLC films is increased, which shows DLC films and spiral groove play a key role in the friction and wear of end faces. At the same time, it is found that the wear degree of the two kinds of spiral angle inner ring is greater than the outer ring, so the spiral groove can reduce the wear degree of the end face. The test results laid a foundation for the optimization design and practical application of spiral groove dry gas seal.

The Weierstrass-Mandelbrot function was introduced, which can characterize the rough surface topography. Two methods to evaluate the fractal parameters of the rough surface topography (i.e. power spectrum and structure function) were analyzed. The radial and circumferential profiles of friction pair of GY70 mechanical seals were measured by the AF-LI type stylus profilometer, and the fractal characteristics of the profiles were analyzed by the structure function. The radial and circumferential fractal dimensions of the rotating ring end face are 1.293 and 1.291 respectively, and that of the stationary ring end face are 1.288 and 1.283. The results indicate that the rotating and stationary ring profiles of friction pair are isotropic and have the statistical self-affine dimension characters.

The friction of the seal faces was the most important phenomenon in working process of mechanical seals for pumps. The friction factor was a key parameter for expressing the friction state of the seal faces. The relationship between friction factor and friction state of the end faces of mechanical seals was discussed from a microscopic point of view. On the self-designed computer aided testing device of the mechanical seal system, the friction factor of GY70 mechanical seal used for pumps was tested. The test results indicate that the bigger the spring pressure, the bigger the friction factor. When the spring pressure is less, the bigger [KG*4]the rotational speed, [KG*4]the [KG*4]bigger the friction factor. [KG*4]But [KG*4]when the spring pressure [KG*4]reaches about 0.086 6 MPa, the friction factor is not almost influenced by the rotational speed. When the rotational speed and spring pressure are less, the medium pressure has a less influence on the friction factor. When the rotational speed or spring pressure is bigger, the bigger the medium pressure, the less the friction factor.