Bearing Design Variables Research Articles

Loss analysis of radial magnetic bearing using genetic algorithm and gradient based method

Radial magnetic bearing (RMB) works on magnetic levitation principle. Use of magnetic forces for supporting a shaft has been topic of interest of researchers. Shaft supported using magnetic force eliminates the use of lubricant and these bearing are free from rubbing action between the surfaces. Application of turbine rotor 60 mm diameter is taken into consideration and RMB of eight poles with NSNS pole configuration has been designed. Bearing is designed such that it is capable of generating electromagnetic force to levitate rotor with constant air gap 0.5 mm in dynamic condition. However these bearing encounter various energy losses. Loss optimization of eight poles RMB is carried out using variables like air gap, turbine speed, and laminating layer thickness over the constraints. Optimum results of bearing design variables obtained using Genetic Algorithm (GA) ensures minimum total loss in bearing. These optimized variables are used as initial iteration in reduced gradient based method. Results obtained in GA are validated using Reduced Gradient method.

Effects of Tilting Pad Journal Bearing Design Parameters on the Pad-Pivot Friction and Nonlinear Rotordynamic Bifurcations

This study numerically analyzes and investigates the effects of the bearing design parameters of a tilting pad journal bearing (TPJB) on the pad-pivot friction-induced nonlinear rotordynamic phenomena and bifurcations. The bearing parameters were set to the pad preload, pivot offset, spherical pivot radius, and bearing length to diameter (L/D) ratio. The Stribeck curve model (SCM) model was applied at the contact surface between the pad and the pivot, which varied to the boundary-mixed-fluid friction state depending on the friction condition. The rotor-bearing model was set up with a symmetrical five-pad TPJB system supporting a Jeffcott type rigid rotor. The fluid repelling force generated in the oil film between each pad and the shaft was calculated using a finite element method. The simulation recurrently conducted the transient numerical integration to obtain the Poincaré maps and phase states of the journal and pad with various bearing design variables, then the nonlinear properties of each condition were analyzed by expressing the bifurcation diagrams. As a result, the original findings of this study are: (1) The pad preload and pivot offset significantly influenced the emergence of Hopf bifurcations and the associated limit cycles. In contrast, (2) the pivot radius and L/D ratio contributed relatively less to the friction-induced instability. Resultantly, (3) all the effects diminished when the rotor operated under the larger mass eccentricity of the disc.

Optimal design of spherical roller bearings based on multiple tasking operating requirements

PurposeThe fatigue, thermal and wear-based bearing lives are the most important factors in the design of spherical roller bearings (SRBs). The main novelty of the present work is consideration of thermal effects as an additional objective function. The dynamic capacity (Cd), the elasto-hydrodynamic minimum film thickness (hmin) and the maximum bearing temperature (Tmax) are related directly with overall lives of the bearing, and these constitute the multiple tasking operating requirements for the design of bearings.Design/methodology/approachThese tasks depend upon various bearing design variables and associated constraints to help in formulating the realistic design optimization problem and in the present work these have been used to get optimal designs of SRBs in the form of Pareto-optimum fronts by using genetic algorithms.FindingsThe optimized lives show higher values as compared to the standard lives and better design choices as compared to that are available in the literature. The robustness of obtained designs are shown by conducting the sensitivity analysis of optimized operating requirements by perturbing optimum bearing variables.Research limitations/implicationsThe robustness of the design could be improved by optimizing tolerances of design variables based on desired variation in multiple tasking operating requirements.Practical implicationsFor the aerospace and space applications such critical design of bearings are required based on multiple tasking operating requirements. For example for higher temperature application in gearboxes, turbines and drilling equipment.Originality/valueIn critical applications, multiple tasking operating requirements are essential and often bearings put limit to the life of satellites and aircraft, and bearing design methodology proposed and implemented in the present paper addresses these issues, especially addition of thermal issue in bearing design.

Rotordynamic Optimization of Fixed Pad Journal Bearings Using Response Surface Design of Experiments

The design process of journal bearings of turbomachines is complex and time-consuming due to the many geometric and physical variables involved. This paper reports on the design of experiments (DOE) and the response surface design of experiments (RSDOE) methods employed on the design of the drive-end and free-end three-lobe journal bearings supporting a centrifugal compressor rotor. The suitability of each technique is discussed. The bearing design variables employed are bearing slenderness ratio, radial clearance, preload, and lubricant inlet temperature. The rotordynamic response variables selected were the critical speed location, the vibrations at critical speed and operating speed for both bearings, and the threshold speed of instability. The use of a nonlinear (quadratic) RSDOE model is justified. An optimization approach combining an SRDOE and rotordynamic finite element modeling is presented. This method leads to arrive to a multivariate model for multi-objective optimization with very few computations. Identification of the dominant design variables and their effects on several response variables allows establishing engineering feasible solutions with focus on manufacturing versus operating conditions tradeoff.

프로세스 고속 경량 원심 압축기의 로터다이나믹 안정성 강화를 위한 설계해석 - Part II: 로터다이나믹 안정성 개선

In this Part II study, rotordynamic stability analyses were carried out to confirm improvements to the stability of a process high-speed lightweight centrifugal compressor, depending on the effects of tilting pad journal bearing designs. The bearing design variables considered were the clearances, LBPs, LOPs, and preloads. The results showed that the rotordynamic stability of the subject compressor rotor-bearing system improves exactly in accordance with the effects of the bearing design variables, which were determined in the preceding Part I study, owing to reduced bearing stiffnesses. Specifically, it was confirmed that the stability of the rotor system can be greatly improved by increasing both the machined and assembled bearing clearances, but there were no stability improvements by simply changing from an LBP to an LOP design. In addition, it was confirmed that for given fixed machined bearing clearances, the stability can be additionally improved by decreasing the preloads, i.e., by increasing the assembled clearances. In conclusion, it may be necessary to improve the designs of the original tilting pad bearings to obtain a sufficient margin of rotordynamic stability against a possible aerodynamic cross-coupled stiffness in a process high-speed centrifugal compressor. Thus, increasing the machined and assembled bearing clearances and decreasing the preload could be effective solutions.

825 動圧空気フォイル軸受の理論安定限界速度に及ぼすトップフォイルの浮上および後縁の取付状態の影響 : 摩擦がないモデル軸受を用いた場合の設計変数の影響

825 動圧空気フォイル軸受の理論安定限界速度に及ぼすトップフォイルの浮上および後縁の取付状態の影響 : 摩擦がないモデル軸受を用いた場合の設計変数の影響

프로세스 고속 경량 원심 압축기의 로터다이나믹 안정성 강화를 위한 설계해석 - Part I: 베어링 설계의 영향

Part I of this study analyzed the effects of tilting pad bearing designs to reduce the stiffness of the bearings used in a process high-speed lightweight centrifugal compressor intended for a domestic refinery use. This was done in an attempt to enhance the robustness of its rotordynamic stability against possible aerodynamic cross-coupled stiffness. The bearing design variables reviewed were the clearances, LBPs, LOPs , and preloads. The results showed that there was practically no difference between the LBP and LOP designs in terms of the bearing stiffness, because the compressor rotor was lightweight and the bearings had relatively high preloads. Increasing both the machined and assembled clearances in bearing designs has resulted in the bearing stiffness being greatly reduced. In addition, it has been confirmed that an additional reduction in the bearing stiffness can be obtained for given fixed machined clearances by decreasing the preloads, i.e., by increasing the assembled clearances. Keywordsprocess compressor (프로세스 압축기), rotordynamic stability (로터다이나믹 안정성), effects of bearing design (베어링 설계의 영향), tilting pad bearing (틸팅 패드 베어링), reducing bearing stiffness (베어 링 강성 감소), bearing clearance (베어링 틈새)

403 動圧空気フォイル軸受の理論安定限界速度に及ぼすトップフォイルの浮上および後縁の取付状態の影響 : 静摩擦が大きい場合のモデル軸受と設計変数の影響(第3報)(機素潤滑設計1)

403 動圧空気フォイル軸受の理論安定限界速度に及ぼすトップフォイルの浮上および後縁の取付状態の影響 : 静摩擦が大きい場合のモデル軸受と設計変数の影響(第3報)(機素潤滑設計1)

914 動圧空気フォイル軸受の理論安定限界速度に及ぼすトップフォイルの浮上および取付状態の影響 : 静摩擦が大きい場合のモデル軸受と設計変数の影響(第2報)(CMP加工3)

914 動圧空気フォイル軸受の理論安定限界速度に及ぼすトップフォイルの浮上および取付状態の影響 : 静摩擦が大きい場合のモデル軸受と設計変数の影響(第2報)(CMP加工3)

3-로브 베어링으로 지지된 중형 고속 터보차저 로터의 선형 및 비선형 동적 안정성 특성 규명

In this study linear and nonlinear dynamic stability characteristics of a medium-size high-speed turbocharger, whose rotor is supported by two 3-lobe journal bearings, are analyzed to evaluate and identify the effects of its bearing design variables. The rotor has the rated speed of 40,500 rpm and maximum continuous speed of 45,000 rpm. At first, utilizing the linear stability analysis method, bearing designs of yielding stable or unstable LogDecs as small as possible are searched by manipulating with machined bearing clearances and preloads. As next, utilizing the nonlinear analysis method, limit cycles of the rotor responses at the rated and maximum continuous speeds are simulated to check their acceptances. Results have shown that for the turbocharger rotor-bearing system considered, the 3-lobe journal bearing design with a smaller machined clearance and a larger preload are preferred for the stable rotor responses. More importantly, since there exists a good correlation between the linear and nonlinear stability analysis results, it is concluded that firstly the linear stability analysis method may be applied to screen quickly the ranges of bearing designs for stable or least unstable solutions and then, lastly the nonlinear stability analysis method may be deployed to check an absolute motion stability in terms of the limit cycle.

Effect of Detachment and Attachment of Top Foil on Predicted Maximum Load Carrying Capacity of Bump Foil Journal Bearings(Part 2: Extensive Survey of Bearing Design Variables)

Bump foil journal bearings are prospective applicants that can support small-sized high-speed rotating machinery. In the previous report, the maximum load carrying capacity of the bearing was predicted, considering the detachment of top foil and the style of attachment of its trailing edge to the bearing housing, and these effects on the capacity were shown to be small. However, the result was obtained only from a base case of the bearing design variables. In this report, the capacity is presented extensively in other cases of the bearing design variables. It is found that the result is applicable to the capacity of the bearing where an excessive static friction acts between the top and the bump foils. On the other hand, the effects of the detachment and the attachment on the capacity of the bearing without the friction between the two foils could be large in the cases of larger values of rigidity of top foil, preload factor, attached angle of top foil, width diameter ratio and pitch angle of bump-equivalent springs.

Effect of Design Variables on Maximum Load Capacity of Hydrodynamically Air-Lubricated Foil Journal Bearings with Assembly Preload Applied

Hydrodynamically air-lubricated foil journal bearings are prospective applicants for machine elements that can support a small-sized rotor of high-speed rotary machinery, such as a micro gas turbine. The smooth surface of the bearing deforms elastically, depending on an applied bearing load, since it is a flexible foil that is supported elastically. Bump foil journal bearing is a kind of the bearings. The bearing consists of two foils. One is cylindrical and named as a top foil. The other is corrugated and named as a bump foil. The top foil is supported elastically by the bump foil. As the foils are forced into the bearing sleeve in assembling the bearing, the top foil deforms due to the assembly preload from the bump foil. The previous prediction was conducted without the preload being considered. This study aims at predicting the maximum load capacity of the bearing with the preload, by using two models. One corresponds to the bearing with an infinitely static friction between the two foils and the other to the bearing without the friction. It is found that each of the bearing design variables has an effect on the capacity obtained with the preload being considered.

Optimization of externally pressurized bearings for minimum power and low temperature rise

This paper discusses selection of suitable values for hydrostatic bearing design variables with a view to minimizing power dissipation and reducing the temperature rise. It is suggested that there is an optimum still width ratio for any bearing and that the optimization process is most conveniently carried out by reference to a dimensionless optimization parameter, S H. At optimum conditions hydrodynamic lift is always small in comparison to hydrostatic load support irrespective of speed.