Application of gas-magnetic bearings in turbine compressors of marine ICE pressurizing systems

В статье приводится обоснование применения газомагнитных подшипников в судовых турбокомпрессорах систем наддува дизелей. Показаны отрицательные стороны применения наиболее распространенных подшипниковых узлов с масляной системой смазки. Для подтверждения эффективности применения газомагнитных опор в турбокомпрессорах необходимо провести целый ряд исследований. Первым шагом исследований явилось определение и изучение основных эксплуатационных характеристик газомагнитного подшипника – коэффициентов несущей способности и жесткости смазочного слоя. В качестве методов исследования использовался теоретический анализ и физический эксперимент, для реализации которых были разработаны методика расчета, в основе своей базирующаяся на решении модифицированного уравнения Рейнольдса теории газовой смазки, и экспериментальный стенд для исследования эксплуатационных характеристик радиальной газомагнитной опоры. Результаты сравнительного анализа экспериментальных и теоретических характеристик показали на их вполне удовлетворительное согласование, что позволяет в дальнейшем проведение широкомасштабные теоретических исследований. The article gives a justification for using gas-magnetic bearings in marine turbine compressors of diesel engine pressurizing systems. The drawbacks of using the most common bearing units with oil lubrication are shown. A number of studies is required to confirm the efficiency of using gas-magnetic bearings in turbine compressors. The first step is to determine and study the main operational characteristics of a gas-magnetic bearing: bearing capacity factor and lubricating film stiffness. The study methods included theoretical analysis and a physical experiment. A calculation method has been developed for their implementation based on the solution of the modified Reynolds equation from gas lubrication theory and a test bench for studying operational characteristics of a radial gas-magnetic bearing. The results of comparative analysis of experimental and theoretical characteristics has shown that they correspond well which allows performing future large-scale theoretical studies.

Oil Film Stiffness of Double Involute Gears Based on Thermal EHL Theory

Lubrication failure is one of the main failure forms of gear failure. Time varying meshing stiffness is an important factor affecting the dynamic behavior of gears. However, the influence of oil film stiffness is usually ignored in the research process. In this paper, according to the meshing characteristics of double involute gears, based on the non-Newtonian thermal EHL theory, a new calculation method of normal and tangential oil film stiffness for double involute gears is established by the idea of subsection method. The oil film stiffness difference between double involute gears and common involute gears is analyzed, and the influence of tooth waist order parameters, working conditions, and thermal effect on the oil film stiffness are studied. The results reveal that there are some differences between normal and tangential oil film stiffness between double involute gears and common involute gears, but there is little difference. Compared with the torque, rotation speed and initial viscosity of the lubricating oil, the tooth waist order parameters have less influence on the oil film stiffness. Thermal effect has a certain influence on normal and tangential oil film stiffness, which indicates that the influence of thermal effect on the oil film can not be ignored. This research proposes a calculation method of normal and tangential oil film stiffness suitable for double involute gears, which provides a theoretical basis for improving the stability of the transmission.

Influence of turbulent cavitating flow on performance characteristics of spiral groove liquid film seal

Spiral groove liquid film seal is expected to be the prime candidate for application to high-speed liquid-oxygen turbopumps, and the lubricant flow between the sealing faces is turbulent due to the liquid-oxygen properties and the working conditions. Based on the Ng–Pan model and mass-conserving algorithm, the modified dynamic Reynolds equation considering flow regime and cavitation is obtained, which is solved by the finite-difference method. The effects of flow regime and cavitation on the performance of spiral groove liquid film seal are analyzed. The results indicate that the balanced film thickness and opening force increase due to the turbulent flow. The cavitation ratio increases in the laminar–turbulent transition region, which reduces the opening force and liquid film stiffness.

Laser-Induced Graphene on a Quartz Crystal Microbalance for Humidity Sensing

In this study, a simple method for synthesizing graphene layer directly on a quartz crystal microbalance (QCM) using a laser was developed. This laser-induced graphene (LIG) was used for sensing surface to simultaneously measure changes in the adsorbed mass, film stiffness, and electrical resistance during water adsorption. The developed LIG-QCM is convenient because its fabrication process is free of any tedious masking and vacuuming steps. A thin layer of polyimide (PI) film was spin-coated on one side of a quartz crystal microresonator, and interdigitated electrodes (IDE) were patterned on the PI surface using a laser engraver. The adsorption of water molecules on the sensing surface induced changes in mass, stiffness, and electrical conductivity, which were measured from the changes in resonance frequency, Q factor of the quartz crystal, and electrical resistance, respectively. The results indicated that the developed sensor could be a humidity sensing platform using LIG.

On the behavior of a ferrofluid-lubricated herringbone-grooved hybrid slot-entry bearing

The behavior of a slot-entry hybrid herringbone-grooved journal-bearing system lubricated with a ferrofluid lubricant has been numerically studied. The modified Reynolds equation of a ferrofluid bearing model based on the Stokes micro-continuum theory has been numerically solved by a finite-element method. A MATLAB code based on the Gauss–Seidel iteration scheme has been solved to numerically simulate the bearing performance. The simulated results reveal that the use of a ferrofluid lubricant provides enhanced values of lubricant film thickness, fluid film stiffness/damping coefficient, and better stability threshold speed.

Analytical Study of Non-Recessed Conical Hole Entry Hybrid/Hydrostatic Journal Bearing with Constant Flow Valve Restrictor

The present work studies the analysis of a non recessed hole entry conical hybrid/hydrostatic journal bearing adjusted for constant flow valve (CFV) restriction. The paper provides effectiveness between the conical bearings with hole entry operating in hybrid and hydrostatic mode. The Reynolds formulae, for the flow of fluid through the mating surfaces of a conical journal and bearing, are numerically worked out in both the modes considering the finite element analysis (FEA) and the necessary boundary preconditions. Holes in double row are marked on conical bearing circumference to accommodate the CFV restrictors, the angular distance between two holes are 30o apart from the apex. Qualitative features of the conical journal bearing system with hole entry have been elaborated to analyze bearing performance for radial load variation Wr = 0.25-2. Numerical results obtained from the present study indicate that load carrying capacity of conical bearing, operating in hydrostatic mode, is enhanced by the maximum pressure, direct fluid film damping and direct film stiffness coefficients vis-a-vis corresponding hybrid mode.

A comprehensive multi-objective, multi-parameter and multi-condition optimization of a spiral groove in dry gas seals

Dry gas seals are widely used in rotating equipment for fluid leakage control and operating efficiency enhancement. Multi-dimensional optimization of geometric parameters of the spiral groove was conducted with considering the comprehensive effect of working conditions, objective functions and the other geometric parameters. Different optimization methods were proposed for solving the multi-dimensional optimization problems. The optimal values of groove width ratio, groove length ratio and spiral angle for the excellent steady performance of spiral grooves under different working conditions were obtained by employing a genetic algorithm and loop iteration optimization method. The performance comparison of two dry gas seals with different geometric parameters was conducted experimentally to verify the effectiveness of numerical results. The results showed that optimal geometric parameters of the spiral groove were significantly influenced by working conditions, objective function and the other geometric parameters. Maximum film stiffness and stiffness-leakage ratio of the spiral groove dry gas seal obtained by genetic algorithm enhanced up to 30% and 45% larger than those obtained by the conventional single factor optimization. The film stiffness and stiffness-leakage ratio were more sensitive to geometric parameters of a spiral groove than that of opening force. The optimization results obtained in this paper provide a theoretical and experimental reference for the design of dry gas seals in different working conditions to meet various sealing performance requirements.