scholarly journals PROCEDURE FOR CALCULATION AND DESIGN OF SPHERICAL ROLLER GEARS WITH DOUBLE-ROW PINION

2021 ◽  
Vol 2 (55) ◽  
pp. 18-24
Author(s):  
E.S. Lustenkova ◽  
Keyword(s):  
Load Capacity ◽  
Maximum Load ◽  
Maximum Efficiency ◽  
Efficiency Coefficient ◽  
Material Consumption ◽  
Main Criterion ◽  
Calculation Algorithm ◽  
Double Row ◽  
Wide Range ◽  
Fatigue Endurance

The article presents a method for calculating and designing spherical roller gears with a double-row pinion. The studied gears are analogs of planetary gears with a double-wheel pinion. They make it possible to implement a wide range of gear ratios. The advantages of spherical roller gears include small dimensions, low material consumption, and layout properties. A special feature of the proposed calculation algorithm is the search for optimal geometric gears parameters according to the criteria of maximum efficiency coefficient taking into account maximum load capacity for a given maximum radial dimensions. The main criterion of strength is fatigue endurance. The method includes design and verification calculations. It makes it possible to develop the small-sized speed reducers for low-speed drives for various purposes.

Foil Bearings Makes Oil-Free Turbocharger Possible

2005 ◽  
Author(s):  
Crystal A. Heshmat ◽  
Hooshang Heshmat ◽  
Mark J. Valco ◽  
Kevin C. Radil ◽  
Christopher Della Corte
Keyword(s):  
High Speed ◽  
Solid Lubricant ◽  
Load Capacity ◽  
Maximum Load ◽  
Solid Lubricant Coating ◽  
Foil Bearings ◽  
Wide Range ◽  
Rotor Bearing ◽  
Component Development ◽  
Bearing System

This paper describes an oil-free, 150 Hp turbocharger that was successfully operated with compliant foil bearings in a range of pitch and roll angles, including vertical operation, thereby demonstrating its viability for aircraft applications. On a gas test stand the turbocharger was operated to 120,000 rpm, under extreme conditions. In addition, the compliant foil bearing-supported turbocharger successfully tolerated shock and vibration of 40 g. Advanced technologies have been applied to the second generation of this turbocharger, shown in Figure 1, including self acting, compliant foil hydrodynamic air bearings with advanced coatings capable, of operation above 815 °C (1500°F). Journal foil bearings with maximum load capacity up to 670 kPa (97 psi) were used in conjunction with thrust foil bearings capable of maximum loads to 570 kPa (83 psi). Bearing component development tests demonstrated 30,000 start stop cycles at 815 °C (1500°F) with a newly developed, solid lubricant coating, KOROLON™. KOROLON™ exhibits a coefficient of friction of less than 0.1 at a wide range of temperatures. Current-designed foil bearings with KOROLON™ have immensely decreased turbolag, allowing acceleration from rest to over 100,000 rpm in less than 2 seconds. Advanced bearing stiffness maintained rotor total axial end-to-end motion within 100 microns (0.004 inch). Total radial static and dynamic motion was controlled within 25 microns (0.001 inch). Development of this high speed turbomachine included bearing and solid lubricant component development tests, rotor-bearing dynamic simulator qualification and gas stand tests of the assembled turbocharger. Gas stand and simulator test results revealed stable bearing temperatures, low rotor vibrations, good shock tolerance and the ability of the rotor bearing system to sustain overspeed conditions beyond 120,000 rpm. This combination of component and integrated rotor-bearing system technology addresses many of the issues associated with application of compliant foil bearings to industrial compressors, blowers, and gas turbine engines, overcoming many of the inherently show-stopping and debilitating features of rolling element bearings, i.e., speed and temperature limitations.

scholarly journals Numerical Modeling on the Compliance and Load Capacity of a Two-Row Aerostatic Journal Bearing with Longitudinal Microgrooves in the Inter-Row Zone

2021 ◽  
Vol 11 (12) ◽  
pp. 5714
Author(s):  
Vladimir Kodnyanko ◽  
Stanislav Shatokhin ◽  
Andrey Kurzakov ◽  
Yuri Pikalov ◽  
Iakov Pikalov ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Journal Bearing ◽  
Load Capacity ◽  
Finite Difference Methods ◽  
Injection Pressure ◽  
Maximum Load ◽  
Double Row ◽  
Environmental Friendliness ◽  
High Durability ◽  
Air Lubrication

Aerostatic bearings are attractive, with minimal friction losses, high durability, and environmental friendliness. However, such designs have a number of disadvantages, including low load-bearing capacity and high compliance due to high air compressibility and limited injection pressure. The article proposes a double-row aerostatic journal bearing with an external combined throttling system and longitudinal microgrooves in the inter-row zone. It is hypothesized that the use of microgrooves will reduce the circumferential flows of compressed air, as a result of which the compliance should decrease and the bearing capacity should increase. To test the hypothesis, we carried out the mathematical modeling, calculations, and theoretical study of stationary operation modes of the bearing for small shaft eccentricities in the vicinity of the central equilibrium position of the shaft and bearing capacity for arbitrary eccentricities. Formulas were obtained for the numerical evaluation of compliance for bearings with a smooth bushing surface and with longitudinal microgrooves. Iterative finite-difference methods for evaluating the fields of the squared pressure are proposed, on the basis of which the load capacity of the bearings is calculated. Experimental verification of the bearing’s theoretical characteristics was carried out, which showed satisfactory agreement between the compared data. The study of the compliance and load capacity of a microgroove bearing yielded impressive results. We show that the positive effect from the application of the improvement begins to manifest itself already at four microgrooves; the effect becomes significant at six microgrooves, and at twelve or more microgrooves, the circumferential flows in the bearing gap practically disappear; therefore, the bearing characteristics can be calculated on the basis of one-dimensional models of air lubrication longitudinal flow. Calculations have shown that for a length of L = 1, the maximum load capacity of a bearing with microgrooves is 1.5 times higher than that of a conventional bearing; for L ≥ 1.5, the bearing capacity increases twice or more. The result obtained allows us to recommend the proposed improvement for practical use in order to increase the load capacity of aerostatic journal bearings significantly.

Challenges in Validating a Thermo-Hydrodynamic Gas Foil Bearing Model

2020 ◽  
Author(s):  
Hanns Michel ◽  
Robert Liebich
Keyword(s):  
Thermal Model ◽  
High Speed ◽  
Load Capacity ◽  
Maximum Load ◽  
Fine Tuning ◽  
Flow Paths ◽  
Operational Conditions ◽  
Foil Bearings ◽  
Wide Range ◽  
The Impact

Abstract Gas foil bearings (GFBs) are suitable for high speed and temperature applications where conventional lubricated bearing solution are not feasible. This requires the pre-diction of bearing temperatures and thus a thermal model considering the heat genera-tion and heat flow paths in the bearing. The effects of two different bump foil stiffness (Iordanoff and Le Lez [1,2]) and heat transfer models (a simplified and a detailed one) are presented in respect to measured temperatures from literature [3,4]. The compari-son is drawn over a wide range of operational conditions as well as measuring posi-tions, which in such detail has not been shown before. While good agreement is found for some of the conditions and positions, only reasonable agreement is found for others. The deviations and difficulties in validating a thermal model against experiments are highlighted in a discussion about various temperature influencing parameters, especial-ly concerning the change of clearance during operation. In conclusion it is found, that the models are able to predict temperatures reasonably well, but require delicate fine-tuning to achieve these results. Finally, the impact of the temperature on the maximum load capacity at a range of speeds is shown in a comparison between an isothermal calculation and one with temperature consideration.

Design, modeling, and performance of a bidirectional stick-slip piezoelectric actuator with coupled asymmetrical flexure hinge mechanisms

2020 ◽  
Vol 31 (17) ◽  
pp. 1961-1972
Author(s):  
Xiaohui Lu ◽  
Qiang Gao ◽  
Qi Gao ◽  
Yang Yu ◽  
Xiaosong Zhang ◽  
...  
Keyword(s):  
Piezoelectric Actuator ◽  
Load Capacity ◽  
Maximum Load ◽  
Maximum Efficiency ◽  
Flexure Hinge ◽  
Tangential Displacement ◽  
Maximum Output ◽  
Stick Slip ◽  
Force Variation ◽  
And Performance

A stick-slip piezoelectric actuator with bidirectional motion is proposed and measured, which uses coupled asymmetrical flexure hinge mechanisms and symmetrical indenter to generate controllable tangential displacement. The operating principle of the proposed stick-slip actuator is illustrated, and the normal force variation between the stator and slider is analyzed. A dynamic model based on the method of dimensionality reduction is established to simulate the displacement and load capacity. In order to obtain improved actuator properties, the design rules of the coupled flexure hinge mechanisms are discussed, and the tangential and normal displacements of the indenter are investigated by the finite element method. A prototype is fabricated, and the experiment investigation of the actuator characteristics is presented. Testing results indicate that the actuator achieves the maximum output velocity of 10.14 mm/s and its maximum load reaches 1.5 N under a voltage of 100 Vp–p and a frequency of 850 Hz in the positive x-direction. The maximum efficiency of the actuator is 0.57% with a load of 90 g, a locking force of 5 N, and the actuated velocity of 5.48 mm/s. In addition, experimental results confirm the feasibility of the presented model by comparing numerical simulation results.

Study on the Modes of Operation of a Multi-Machine Installations with Mechanical Reduction

2019 ◽  
pp. 12-22
Author(s):  
A. M. Oleynikov ◽  
L. N. Kanov
Keyword(s):  
Mathematical Description ◽  
Reactive Power ◽  
Maximum Efficiency ◽  
Wind Flow ◽  
System Of Equations ◽  
Mechanical Equilibrium ◽  
Synchronous Generators ◽  
Electromagnetic Excitation ◽  
Number Of Generators ◽  
Wide Range

The paper gives the description of the original wind electrical installation with mechanical reduction in which the output of vertical axis wind turbine with rather low rotation speed over multiplicator is distributed to a certain number of generators. The number of acting generators is determined by the output of actual operating wind stream at each moment. According to this constructive scheme, it is possible to provide effective and with maximum efficiency installation work in a wide range of wind speeds and under any schedule issued to the consumer of electricity. As there are no any experience in using such complexes, mathematical description of its main elements is given, namely windwheels, generators with electromagnetic excitation of magnetic electrical type, then their interaction with windwheel, and also the results of mathematical modeling of work system regimes under using the offered system of equations. The basis for the mathematical description of the main elements of the installation – synchronous generators – are the system of equations of electrical and mechanical equilibrium in relative units in rotating coordinates without considering saturation of the magnetic circuit. The equation of mechanical equilibrium systems includes torque and brake windwheel electromagnetic moments of generators with taking into account the reduction coefficients and friction. In addition, we specify the alternator rotor dynamics resulting from continuous torque of windwheel fluctuations under the influence of unsteady wind flow and wind speed serving as the original variable is modeled by a set of sinusoids. Model simplification is achieved by equivalization of similar generators and by disregarding these transitions with a small time constant. Calculation the installation with synchronous generators of two types of small and medium capacity taking into account the operational factors allowed us to demonstrate the logic of interactions in the main elements of the reported complex in the process of converting wind flow into the generated active and reactive power. We have shown the possibility of stable system work under changeable wind stream condition by regulating of the plant blade angle and with simultaneous varying of generator number of different types. All these are in great interest for project organizations and power producers.

scholarly journals Hybrid ZnO/MoS2 Core/Sheath Heterostructures for Photoelectrochemical Water Splitting

Applied Nano ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 148-161
Author(s):  
Katerina Govatsi ◽  
Aspasia Antonelou ◽  
Labrini Sygellou ◽  
Stylianos G. Neophytides ◽  
Spyros N. Yannopoulos
Keyword(s):  
Visible Light ◽  
Wide Band ◽  
Nanowire Arrays ◽  
Maximum Efficiency ◽  
Light Illumination ◽  
Wide Band Gap ◽  
Long Term Stability ◽  
Visible Light Illumination ◽  
Nanowire Surface ◽  
Wide Range

The rational synthesis of semiconducting materials with enhanced photoelectrocatalytic efficiency under visible light illumination is a long-standing issue. ZnO has been systematically explored in this field, as it offers the feasibility to grow a wide range of nanocrystal morphology; however, its wide band gap precludes visible light absorption. We report on a novel method for the controlled growth of semiconductor heterostructures and, in particular, core/sheath ZnO/MoS2 nanowire arrays and the evaluation of their photoelectrochemical efficiency in oxygen evolution reaction. ZnO nanowire arrays, with a narrow distribution of nanowire diameters, were grown on FTO substrates by chemical bath deposition. Layers of Mo metal at various thicknesses were sputtered on the nanowire surface, and the Mo layers were sulfurized at low temperature, providing in a controlled way few layers of MoS2, in the range from one to three monolayers. The heterostructures were characterized by electron microscopy (SEM, TEM) and spectroscopy (XPS, Raman, PL). The photoelectrochemical properties of the heterostructures were found to depend on the thickness of the pre-deposited Mo film, exhibiting maximum efficiency for moderate values of Mo film thickness. Long-term stability, in relation to similar heterostructures in the literature, has been observed.

scholarly journals Design and Analysis of an Aerostatic Pad Controlled by a Diaphragm Valve

Lubricants ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 47
Author(s):  
Federico Colombo ◽  
Luigi Lentini ◽  
Terenziano Raparelli ◽  
Andrea Trivella ◽  
Vladimir Viktorov
Keyword(s):  
Sensitivity Analysis ◽  
High Precision ◽  
Load Capacity ◽  
Design Procedure ◽  
Maximum Load ◽  
Air Gap ◽  
Diaphragm Valve ◽  
Compensation Methods ◽  
Aerostatic Bearings ◽  
Gap Height

Because of their distinctive characteristics, aerostatic bearings are particularly suitable for high-precision applications. However, because of the compressibility of the lubricant, this kind of bearing is characterized by low relative stiffness and poor damping. Compensation methods represent a valuable solution to these limitations. This paper presents a design procedure for passively compensated bearings controlled by diaphragm valves. Given a desired air gap height at which the system should work, the procedure makes it possible to maximize the stiffness of the bearing around this value. The designed bearings exhibit a quasi-static infinite stiffness for load variation ranging from 20% to almost 50% of the maximum load capacity of the bearing. Moreover, the influence of different parameters on the performance of the compensated pad is evaluated through a sensitivity analysis.

Dependency of Machine Efficiency on the Thermal Behavior of Induction Machines

Machines ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 9
Author(s):  
Svenja Kalt ◽  
Karl Ludwig Stolle ◽  
Philipp Neuhaus ◽  
Thomas Herrmann ◽  
Alexander Koch ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Electric Vehicles ◽  
Thermal Load ◽  
Load Capacity ◽  
Maximum Load ◽  
Induction Machines ◽  
Electric Machines ◽  
Model Parameters ◽  
Dynamic Operating ◽  
The Impact

The consideration of the thermal behavior of electric machines is becoming increasingly important in the machine design for electric vehicles due to the adaptation to more dynamic operating points compared to stationary applications. Whereas, the dependency of machine efficiency on thermal behavior is caused due to the impact of temperature on the resulting loss types. This leads to a shift of efficiency areas in the efficiency diagram of electric machines and has a significant impact on the maximum load capability and an impact on the cycle efficiency during operation, resulting in a reduction in the overall range of the electric vehicle. Therefore, this article aims at analyzing the thermal load limits of induction machines in regard to actual operation using measured driving data of battery electric vehicles. For this, a thermal model is implemented using MATLAB® and investigations to the sensitivity of model parameters as well as analysis of the continuous load capacity, thermal load and efficiency in driving cycles under changing boundary conditions are conducted.

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