Higher parameters of centrifugal machines are constantly required, such as the pressure of the medium to be sealed and the speed of rotation of the shaft. However, as the parameters increase, it becomes more and more difficult to ensure the effectiveness of sealing. In addition, sealing systems affect the overall safety of equipment operation, especially vibration. In order to harmonize the sealing functions and increase the dynamic rigidity of the rotors of centrifugal machines, a method for modeling complex sealing systems has been developed. Non-contact seals are considered as hydrostatic–dynamic bearings that can effectively dampen rotor oscillations. A general approach to the analysis of non-contact seals as automatic control systems and an algorithm for constructing their dynamic characteristics at the design stage were proposed for the first time. Models of “rotor-gap seal”, impulse seal and “rotor–hydraulic face” systems, and seal-supports of a shaftless pump have been studied to assess the effect of these seal systems on the oscillatory characteristics of the rotor. Analytical dependencies are obtained for calculating the dynamic characteristics and stability limits of seals as hydromechanical systems. The directions for improving the safety of operation of critical pumping equipment due to a targeted increase in the rigidity of non-contact seals are determined, which leads to an increase in the vibration resistance of the rotor and the environ-mental safety of centrifugal machines. The paper proposes a method for designing sealing systems based on the configuration of sealing components in order to achieve harmonization between sealing and vibration reliability, taking into account oscillatory processes due to hydrodynamic sealing characteristics.

Groove seals are considered as hydrostatic bearings capable of effectively damping rotor vibrations. In order to determine the dynamic characteristics, a model of the rotor-groove seals system is considered. The radial forces and moments in groove seals had been estimated. Expressions of joint radial-angular rotor vibrations in groove seals had been obtained. Formulas had been proposed for constructing amplitude and phase frequency characteristics. An example of calculating the dynamic characteristics of a centrifugal machine rotor model is presented. The directions of increasing the vibration reliability of NPP pumping equipment by purposefully increasing the rigidity of groove seals are determined.

The paper presents the analysis of existing designs of NPP reactor coolant pumps (RCP) rotor sealing systems. The most common design solutions of sealing units that provide the necessary tightness, reliability and service life under high pressure, temperature and sliding speeds typical for RCP, as well as trends for their improvement to increase tightness and environmental safety of activities were identified. Designs of impulse seals with a self-adjusting clearance are presented as the most promising assemblies for sealing pump shafts with high parameters. A computer model of impulse mechanical seal as an automatic control system is proposed. A framework for calculating impulse mechanical seals has been developed, allowing the choice of their main geometric parameters to ensure the optimal value of the mechanical clearance and the friction moment on the sealing contact surfaces. Expressions are obtained for constructing the static and flow characteristics of a impulse mechanical seal, the condition for its dynamic stability is determined. The paper presents the shaft sealing system of RCP, main nodes of which are several stages of impulse mechanical seals with a self-regulating clearance.

With an increase of equipment parameters, such as the pressure of the sealing medium and the speed of shaft rotation, the problems ensuring its hermetization efficiency are rising up. In addition to hermetization itself, the sealing system affect the overall operational safety of the equipment, especially vibratory. Groove seals are considered as hydrostatodynamic supports capable of effectively damping rotor oscillations. To determine the dynamic characteristics, models of grooved seals and single-disc rotors with grooved seals are examined. The obtained analytical dependences for computation of dynamic characteristics for the hydromechanical rotor-seals system, describing radial-angular oscillations of the centrifugal machine rotor in groove seals are presented as well as the formulas for computation of amplitude frequency characteristics. An example for the computation dynamic characteristics of one of the centrifugal machine rotor models is drawn.

Development of pulse mechanical seal calculation methods on the basis of its physical model construction

The operating experience of mechanical seals shows that as a result of angular deformations of the rings, wear of the contact surfaces along radius is uneven. In the area of hydrodynamic load support in the case of a confusor joint or a converging film, the slope of the pressure diagram is such that a decrease in the film thickness increases the hydrodynamic support. This enables stable non-contact sealing operation. When designing mechanical seals, it is necessary to calculate the deformations of the sealing rings caused by both the pressure of the medium being sealed and thermal effects in order to predict the size and direction of the radial cone and avoid unstable operation of the seal. The execution of the rubbing surfaces of the interface of the end pair should ensure the formation of the calculated confusor shape of the sealing gap in all modes of operation.