Numerical Investigation of Turbulence Models for a Superlaminar Journal Bearing

Ding, Aoshuang; Ren, Xiaodong; Li, Xuesong; Gu, Chen

doi:10.1155/2018/2841303

Cited by 10 publications

(15 citation statements)

References 27 publications

(39 reference statements)

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“…The algorithm is more stable and has a better simulation performance for flow in a narrow space [23]. The corresponding turbulent kinetic energy and frequency equations are as follows [24]:…”

Section: Methodsmentioning

confidence: 99%

Effect of Tip Clearance Size on Tubular Turbine Leakage Characteristics

Zhu

2021

Processes

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To study the effect of tip clearance on unsteady flow in a tubular turbine, a full-channel numerical calculation was carried out based on the SST k–ω turbulence model using a power-plant prototype as the research object. Tip leakage flow characteristics of three clearance δ schemes were compared. The results show that the clearance value is directly proportional to the axial velocity, momentum, and flow sum of the leakage flow but inversely proportional to turbulent kinetic energy. At approximately 35–50% of the flow direction, velocity and turbulent kinetic energy of the leakage flow show the trough and peak variation law, respectively. The leakage vortex includes a primary tip leakage vortex (PTLV) and a secondary tip leakage vortex (STLV). Increasing clearance increases the vortex strength of both parts, as the STLV vortex core overlaps Core A of PTLV, and Core B of PTLV becomes the main part of the tip leakage vortex. A “right angle effect” causes flow separation on the pressure side of the tip, and a local low-pressure area subsequently generates a separation vortex. Increasing the gap strengthens the separation vortex, intensifying the flow instability. Tip clearance should therefore be maximally reduced in tubular turbines, barring other considerations.

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Section: Methodsmentioning

confidence: 99%

Effect of Tip Clearance Size on Tubular Turbine Leakage Characteristics

Zhu

2021

Processes

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“…In a tilting-pad journal bearing, the CFD results of a loaded pad simulated by 17 turbulence models were compared with the experimental data, and the shear stress transport (SST) turbulence model with low-Re correction was found the most suitable for the superlaminar bearing simulations among 17 turbulence models. 26 However, the simulation object of the above research was one loaded pad, and the research conclusion may be unsuitable for the entire bearing simulations, including the loaded and unloaded areas. Factors, such as the load direction, [27][28][29][30] can also affect the bearing flow behaviors in the change of the simulation object.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of static characteristic of a tilting-pad journal bearing using shear stress transport model and air backflow

Ding

Ren

et al. 2019

Advances in Mechanical Engineering

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Numerical simulations are important in bearing designs and should be in accordance with real working conditions. Two details are analyzed for the numerical simulations with a three-dimensional model of a large tilting-pad journal bearing included. The first detail is the flow model of the journal bearing simulations. The shear stress transport model with low-Reynolds number correction and the laminar model are used for the bearing simulations. In comparison with the laminar model, the pressure distribution of the shear stress transport model with low-Reynolds number correction is closer to and in good accordance with the experimental data. Thus, the shear stress transport model with low-Reynolds number correction is more suitable than the laminar model for the journal bearing simulations. The second detail is the backflow material of the bearing outlet boundary. Two backflow materials, air and oil, are simulated and compared with the experimental data. While the mechanical loss of the oil backflow is much higher than the experimental data, the simulated mechanical loss of the air backflow has an acceptable difference with the experimental mechanical loss. Therefore, air is a suitable backflow material for the journal bearing simulations. In summary, shear stress transport model with low-Reynolds number correction and air backflow should be used in the journal bearing simulations for accurate bearing predictions.

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“…Based on the researches, 22,23 this work uses the SST model with low-Re correction and air backflow from the bearing outlets. The present work focuses on the detailed flow characteristics of the entire bearing, which have not been discussed.…”

Section: Introductionmentioning

confidence: 99%

“…In a tilting-pad journal bearing, the CFD results of one loaded pad simulated by seventeen turbulence models were compared with the experimental data, and the shear stress transport (SST) model with low-Re correction was the most suitable for superlaminar bearing simulations among the seventeen turbulence model. 22 The above studies consider that the backflow material from the bearing outlets is oil. However, the real bearing outlet environment can be oil or air.…”

Section: Introductionmentioning

confidence: 99%

“…A study focused on the analysis of mechanical losses in the unloading area and found that the air backflow from the bearing outlets is closer to the actual bearing conditions than the oil backflow. 23 Based on the researches, 22,23 this work uses the SST model with low-Re correction and air backflow from the bearing outlets. The present work focuses on the detailed flow characteristics of the entire bearing, which have not been discussed.…”

Section: Introductionmentioning

confidence: 99%

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Numerical investigation for characteristics and oil–air distributions of oil film in a tilting-pad journal bearing

Ding

Ren

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part J:

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This paper analyzes the effects of air in the oil film of a tilting-pad journal bearing on oil–air distributions and characteristics. With a gaseous cavitation model and shear stress transport model with low-Re correction included, the air backflow from the outlet boundary is analyzed in numerical simulations of a titling-pad journal bearing at 3000 r/min rotation speed and under 180 kN load. The simulated bearing load, pressure, and mechanical loss are in good accordance with the experimental data, indicating that the simulation results of the air backflow from the outlet boundary can catch the hydrodynamic characteristics accurately. Based on the turbulence viscosity ratio analysis, the turbulence effect cannot be ignored at the high rotational speed. With the comparison between the unloaded area and the loaded area, the boundary layer and turbulent flow develops with the film thickness increasing. Based on the analyses of simulated air volume fraction and pressure distribution, the gaseous cavitation occurs around the center part of the unloaded area, following the gaseous cavitation mechanisms. The backflow air flows into the low-pressure unloaded area from the outlet boundary and has a clear interval with the air from the gaseous cavitation. The air volume fraction increases with these two air sources and affects the mixture viscosity significantly, eventually influencing the shear stress on the rotor-side wall and bearing mechanical loss.

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Numerical Investigation of Turbulence Models for a Superlaminar Journal Bearing

Cited by 10 publications

References 27 publications

Effect of Tip Clearance Size on Tubular Turbine Leakage Characteristics

Effect of Tip Clearance Size on Tubular Turbine Leakage Characteristics

Numerical investigation of static characteristic of a tilting-pad journal bearing using shear stress transport model and air backflow

Numerical investigation for characteristics and oil–air distributions of oil film in a tilting-pad journal bearing

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