Face Packing Research Articles

Numerical Simulation of 2-Way FSI Problem of Face Packing Seal: Impact of Parameters Change

The article is devoted to creating a refined computer model of the face packing seal (FPS) based on the solution of the two-way fluid-structure interaction (2-way FSI) problem. An approach to the average gap was proposed based on the micro-space’s working medium leakage between the friction pair’s roughness elements. Three FPS designs were studied, in which the following operating parameters were alternately changed: inlet pressure, load factor, stuffing box parameters, and friction coefficient. Young’s modulus, Poisson’s ratio, and the thickness of the annular plate at the bottom of the stuffing box were also changed. The model was created considering the actual geometry of the FPS. The shaft rotation was considered by applying the rotation condition on the wall of the fluid model. The calculation was carried out using the ANSYS Multiphysics software. The results of the calculations were presented in the form of graphic dependences with a comparison of the hydrostatic and contact pressure distributions over the friction pair width. The values of the magnitudes of leakage from the changing parameters were presented. Based on the obtained results, an optimal combination of parameters was evaluated for the most efficient design of the FPS.

Physical Model and Calculation of Face Packing Seals

Increasing the reliability and service life of dynamic-pump shaft seals is the most important requirement for their creation. The most common type of seals is still traditional stuffing box seals, which are controlled leakage assemblies that are periodically restored during operation. A radical change in the design of standard stuffing box seals is the transition to face packing seals with a constant pressure against the packing. It is shown that face packing seals can successfully combine the advantages of mechanical face seals and the simplicity and relatively low cost of traditional stuffing box seals. Mechanical face seals, in which one of the packing rings is replaced by a stuffing box packing, have advantages that significantly expand the application of traditional stuffing box seals. A scheme and a physical model of the face packing seal operation are described. During the operation of the seal, the packing is pushed away from the mating metal surface by the pressure of the medium. In this case, a confusor gap is formed, the length of which is proportional to the ratio of the sealed pressure to the pre-compression pressure of the packing. The calculation of the distribution of the hydrostatic pressure and gap along the radius of the face joint of the seal is presented. The irregularity of the contact pressure along the radius, caused by the pressing out of the packing by the sealed inlet pressure, causes premature wear of the overloaded areas of contact surfaces. Expressions are proposed for estimating friction power losses in face packing seals. It is shown that these losses are significantly lower in comparison with the power losses in traditional stuffing box seals. Assessment of the thermal state of face packing seals has been carried out. An expression has been obtained for determining the flow rate that provides the average contact-surface temperature not exceeding the permissible value. Our studies have shown that the load factor of face packing seals, in contrast to mechanical face seals, must be close to unity. The obtained dependencies make it possible to calculate face packing seals at their design stage.

Effect of double bond conjugation on hole mobility of thiophene-based hole transport materials in perovskite solar cells

It is of great significance to fully explore the relationship between π-bridge size and intermolecular packing for improving the hole mobility of hole transport materials in perovskite solar cells. We performed the density functional theory (DFT) computations of a series of Z26 derivatives (Z26-2, Z26-3, and Z26-4) and investigated the effect of the size of π-bridge and intermolecular packing on hole mobility of hole transport materials. The calculated results show that Z26-2 (7.7 × 10−4 cm2 V−1 s−1) and Z26-3 (1.3 × 10−3 cm2 V−1 s−1) have larger hole mobility than Z26 (5.60 × 10−4 cm2 V−1 s−1) due to their appropriate conjugated length leading to effective face to face packing. The smallest hole mobility of Z26-4 (4.20 × 10−5 cm2 V−1 s−1) is attributed to its overlong conjugation with four double bonds on each side, which produces a long centroid-to-centroid distance and small electronic coupling. The present theoretical study on the relationship between the size of π-bridge and intermolecular packing provides insight for the future design of thiophene-based hole transport materials.

An Analysis of Axial Vibration in Face Packing Seals

This paper deals with the dynamics of face packing seals, in which one of the sealing rings is made of elastic sealant. The study involved analyzing the axial vibration of the flexible ring for two configurations of its housing in the seal and determining the frequency characteristics and the condition of maintaining face-to-face contact between the sealing rings with considerably different elastic properties subjected to two types of external excitations. The derived analytical relationships were verified using a calculation example for real operating conditions of face packing seals in two pumps.

Selected Dynamic Problems of the Face Packing Seal

This paper analyzes the statics and dynamics of face packing seals, in which one of the sealing rings is made of elastic sealant. The study involved analyzing the axial vibration of the flexible ring for two configurations of its housing in the seal and determining the frequency characteristics and the condition of maintaining face-to-face contact between the sealing rings with considerably different elastic properties subjected to two types of external excitations. The derived analytical relationships were verified using a calculation example for real operating conditions of face packing seal in the pump.

Experimental investigation of mechanical properties of stuffing box packings

This article provides experimental results of work that aims to determine the surface roughness profile and mechanical properties of stuffing box packing made from polytetrafluoroethylene fibrous yarn, filled with graphite and saturated with silicone oil. In addition, it describes experimental, computational and field investigations of new prospective designs of face packing seals for centrifugal pumps.

Crystal engineering of a three-dimensional coordination polymer based on both covalent and O–H⋯O hydrogen bonding interactions of bifunctional ligands

A three-dimensional coordination polymer, [(H2O)2Cu(pdc)] 1 (pdc⊕=⊕pyridine-3,5-dicarboxylate), has been rationally designed and synthesized under hydrothermal reaction conditions. The structure is self-assembled from bifunctional pyridinecarboxylates and water molecules. Carboxylate groups in 1 contribute to both covalent and hydrogen bonds. The structure is stabilized by offset aryl–aryl face–face packing interactions.

Structural analysis of photosystem II in far-red-light-adapted thylakoid membranes. New crystal forms provide evidence for a dynamic reorganization of light-harvesting antennae subunits.

We studied two-dimensional crystals of the major pigment-protein complex, photosystem II, in far-red-light-adapted thylakoid membranes of the viridis-zb63 mutant of barley. Significantly larger grana membranes were produced with an increased synthesis of the entire photosystem II complex. These red-light-adapted membranes also contained two-dimensional crystals with a high frequency. Three different crystal forms of photosystem II were observed, providing the following data which further our understanding of the architecture of the native complex. (a) The oligomeric form of photosystem II in the membrane was monomeric in all crystal forms, but with a clear non-crystallographic pseudo-twofold symmetry. This was more apparent on the lumenal face of the complex. (b) The variability of unit cell contacts in different crystal forms implied that the peripheral light-harvesting antenna complex and the core of the complex were loosely connected. These peripheral subunits were predicted to rearrange so that they can either encircle the core complex or associate in parallel channels separated by lines of core complexes. (c) Grana membranes were found to retain a double-layered inside-out character, with a stromal face-to-stromal face packing. However, the presence of a crystal in one membrane did not necessarily impose crystallinity on its pair.

Hard-sphere cluster-ion structures

A series of hard-sphere cluster-ion structures have been constructed, based on the notion of a central stable dimer ion core. Starting from a structure representative of icosahedral Ar+19, two separate packing sequences are considered; edge packing and face packing, and clusters containing up to 310 atoms have been generated. It is shown that many of the symmetric structures derived from the two packing sequences coincide with the ‘‘magic’’ numbers observed both in the mass spectra and fragmentation patterns of argon and krypton cluster ions. A slice through the cluster shows that the central dimer ion core is part of a linear chain of atoms, which offer the possibility for further charge delocalization as suggested in recent molecular orbital calculations.

Rotor packing of an atomic-power-station centrifugal cooling pump

Centrifugal cooling pumps have to be highly reliable because of the complex conditions under which they operate in atomic power stations. Fabrication of reliable shaft packings is therefore a major task. Of the known mechanical, hydrostatic and other types of face packings, the requirements are best met by the face packing with a self-adjusted gap. The working parameters and the design elements of such a packing were worked out and its working capacity was checked on a testing unit and directly in the pumps. The experimental data showed the power input of one packing stage, with allowance for losses due to disk friction, depends little on the pressure differential to be sealed and increases substantially with increase of the rotation speed. The data made it possible to choose the requisite leakages for each packing stage and to distribute the pressure and temperature in the stages. Examination after preliminary tests showed that the rubbed surfaces of the first stages of both packings were in a good state and were free from wear, chippings, scratches and other defects. The working capacity of the packing units was also checked in emergency situations arising from the stoppage of supply of sealing and cooling water.more » The test results showed that the packings ensure satisfactory pump operation in the emergency situations over the requisite time.« less

Strengthening of face packing surfaces with powders

The primary reason for failure of centrifugal pumps used in chemical fiber production plants is failure of the tightness of the rubbing surfaces of the face packing surfaces caused by mechanical-corrosion wear. To increase the life, coatings of Ni-Cr-B-Si selffluxing alloy powders are normally applied to their working surface. A process has been developed for induction coalescing under the action of an activating pressure at the sintering temperatures of powder under conditions of accelerated heating and realization of the socalled effect of limited space. Preliminary tests made with the help of mathematical experiment planning methods made it possible to establish that temperature and pressure have the most significant influence on shrinkage of the powder layer. The experiments showed that for each value of the activating pressure in the considered, there is a very definite temperature the exceeding of which leads to a sharp increase in the rate of contraction of the powder layer. On the basis of the results obtained a method was developed for strengthening the face packing surfaces of centrifugal pumps operating in the production of chemical fibers. A uniform temperature field and good coating quality were obtained by heating the part with a single-turn inductor located belowmore » the zone of the groove.« less