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This paper presents the numerical methods for calculating the hydrodynamic characteristics of a mechanical seal, taking into account the possibility of a phase transition in its gap. In the ...numerical model, the solutions are used for the flow of both liquid and gas in the microgap of compaction obtained using the finite volume method. Regularities of the influence of the size and taper of the gap, the depth of the microgrooves, the pressure drop and the value of the saturated vapor pressure on the hydrodynamic characteristics of the seal are revealed. A method has been developed for calculating leaks, the stiffness of the lubricant layer, and the friction power in the seal gap, taking into account vaporization and thermal deformations of the sealing rings. Recommendations for the selection of the geometric parameters of the seal are offered. The cause of pulsating seal leakage has been identified. The developed technique is applicable both for cryogenic liquids and for water.
The possibility of reducing friction torque in face seals is shown based on theoretical and experimental studies. The operational, technological, and constructive means and techniques of reducing the ...friction torque in face seals are determined. The most economically promising methods for reducing the friction torque are revealed.
In this paper, we present a simulation model of a contact face seal for a multimode turbomachine in which the processes of hydrodynamics, deformations, and wear of sealing surfaces are considered in ...common. The effect of the gap shape on the characteristics of the contact face seal is studied. It was revealed that in the multimode operation of a turbomachine, the combined action of deformations and wear of the contacting sealing surfaces can qualitatively change the gap shape, as well as the contact pressure, heat release, and the amount of leakage. When calculating seals, it is necessary to take into account the history of loading to predict the lifetime and the tightness level of the seals. Complex gap shapes that arise when changing the operating mode of the turbomachine lead to significant leaks of the operating fluid and intense wear. The created software package, which allows simulating the operation of a multimode contact face seal and determining the specified parameters of the operating modes of the turbomachine to the seal life up to a certain limit, as well as the change in temperature, friction power, and leakage through the seal during the operating time, is described. The simulation model can be used to develop methods for calculating the characteristics of a seal, estimate the degree of influence on the characteristics of operational and design factors, develop accelerated test methods with a joint consideration of deformations and wear of sealing surfaces. The use of the model at the stage of fine-tuning the design of the sealing unit and the assignment of operating modes will increase the information content of tests and reduce design costs by reducing the volume of experimental research. The structure of the simulation model allows one to change individual modules by choosing the most suitable design model and allows both simulation and full-scale modeling when individual physical processes during the calculation process will be simulated on bench installations and the results are transmitted to the calculation cycle.
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The results of experimental determination of the wear intensity coefficient and the friction coefficient in the steel-bronze BrNBT and steel–molybdenum coating contact are shown. To determine the ...tribotechnical parameters of the coating, experiments were carried out on a Tribometer TRB automated friction machine of the Swiss company ANTON PAAR according to the ball–disk scheme. It is shown that the average coefficient of friction for a sample with a molybdenum coating is almost two times lower than for a sample without a coating. With the help of the SURTRONIC 25 profile meter, a profilogram was obtained to determine the coefficient of wear intensity. At a run of 50,000 m, the coefficient of wear intensity for a sample made of BrNBT material without coating at a maximum contact voltage of 507 MPa is 2.48 × 10
–4
mm
3
/m, and for a sample with a molybdenum coating was 1.98 × 10
–5
mm
3
/m, which is 12.5 times less. Recommendations for the use of a molybdenum antifriction coating are given.
Tilting-pad journal bearings are widely used in technics. Oil starvation operation regime is not common for hydrodynamic bearings. However, correctly designed low-flow journal bearing have to operate ...efficiently and consistently on high rotor speeds. An elastic support of bearing pads is a set of elastic pins made of steel. Elastic support allows pads to self-align and achieve an optimal operational mode. The article presents the thermohydrodynamic performance of an axial journal bearing. The study deals with 60 mm diameter four-pad tilting-pad journal bearing, submitted to a static load varying from 1000 to 30000 N with a rotating speed varying from 1000 to 10000 rpm. The investigation focuses on numerical studying the characteristics of low-flow tilting-pad journal bearings under oil starvation conditions. Dependencies of the bearing performance on the load, rotational speed of the shaft, and the size of the radial clearance are presented.
Modern aircraft gas turbine engines require the development of seals which can operate for a long time with low leakages. The basic type of seals applied for gas turbine engine rotor supports is face ...seal. To meet the modern requirements of reliability, leak-tightness and weight, low-leakage gas-static and hydrodynamic seals have to be developed. Dry gas seals use both gas-static and hydrodynamic principles. In dry gas seals microgrooves are often used, which ensure the reverse injection of leakages in the sealed cavity. Authors have developed a calculation technique including the concept of coupled hydrodynamic, thermal and structural calculations. This technique allows to calculate the seal performance taking into account the forces of inertia, rupture of the lubricant layer and the real form of the gap. Authors have compared the efficiency of seals with different forms of microgrooves. Results of calculations show that seal with rectangular form of microgrooves has a little gap leading to both the contact of seal surfaces and the wear. Reversible microgrooves have a higher oil mass flow rate, whereas HST micro-grooves have good performance, but they are difficult to produce. Spiral microgrooves have both an acceptable leakages and a high stiffness of liquid layer that is important in terms of ensuring of sealing performance at vibration conditions. Therefore, the spiral grooves were chosen for the developed seal. Based on calculation results, geometric dimensions were chosen to ensure the reliability of the seal operation by creating a guaranteed liquid film, which eliminates the wear of the sealing surfaces. Seals designed were tested both at the test rig and in the engine.
A Gas Lubricant Combined Support-sealing Node Falaleev, S V; Nadjari, H; Vinogradov, A S
IOP conference series. Materials Science and Engineering,
01/2018, Letnik:
302, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The purpose of the research provided in this article is to develop a gas-dynamic device capable of performing the functions of support sealing, unloading devices for axial thrust bearings and damping ...of axial vibrations of the rotor. Some kinds of seals applied in supports of aircraft engines are known. A face gas-dynamic seal is one of the most effective and standard technology solution for compressors. As the basic element of the developed device, a face gas-dynamic seal with spiral grooves is considered. It also includes the fundamental mathematical calculation of such devices and the experimental research outcomes that form the basis of which such devices can be produced and adapted for use.
A significant part of damages in end gas dynamic seals are caused by dangerous vibrations. To improve the reliability of these seals, it is necessary to develop adequate mathematical models and to ...perform integrated computational and experimental studies. In this article, the two-mass dynamic model for an end gas dynamic seal is considered, which is the most appropriate for practical cases. Theoretical and experimental analyses of the dynamic state of a seal have been performed. The scope of vibration amplitudes and frequencies has been determined for an end gas dynamic seal. The results can be used to design new seals and to implement seals in compressors with magnetic supports.
An investigation of real automobile parts produced from dual phase steel during standard periods of life cycle is presented, which considers such processes as stamping, exploitation, automobile ...accident, and further repair. The development of the phenomenological model of the mechanical properties of such parts was based on the two surface plastic theory of Chaboche. As a consequence of the composite structure of dual phase steel, it was shown that local mechanical properties of parts produced from this material change significantly their during their life cycle, depending on accumulated plastic deformations and thermal treatments. Such mechanical property changes have a considerable impact on the accuracy of the computer modelling of automobile behaviour. The most significant errors of modelling were obtained at the critical operating conditions, such as crashes and accidents. The model developed takes into account the kinematics (Bauschinger effect), isotropic hardening, non-linear elastic steel behaviour and changes caused by the thermal treatment. Using finite element analysis, the model allows the evaluation of the passive safety of a repaired car body, and enables increased restoration accuracy following an accident. The model was confirmed experimentally for parts produced from dual phase steel DP780.
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