The Experts below are selected from a list of 2523 Experts worldwide ranked by ideXlab platform
Luis San Andrés - One of the best experts on this subject based on the ideXlab platform.
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Effect of Pad Flexibility on the Performance of Tilting Pad Journal Bearings: Benchmarking a Predictive Model
Journal of Engineering for Gas Turbines and Power, 2015Co-Authors: Luis San AndrésAbstract:Tilting pad journal bearings (TPJBs) supporting high-performance turbomachinery rotors have undergone steady design improvements to satisfy ever stringent operating conditions that include large specific loads, due to smaller footprints, and high surface speeds that promote flow turbulence and hence larger drag power Losses. Simultaneously, predictive models continuously evolve to include minute details on bearing geometry, pads and pivots' configurations, oil delivery systems, etc. In general, predicted TPJB rotordynamic force coefficients correlate well with experimental data for operation with small to moderately large unit loads (1.7 MPa). Experiments also demonstrate bearing dynamic stiffnesses are frequency dependent, best fitted with a stiffness-mass like model whereas damping coefficients are adequately represented as of viscous type. However, for operation with large specific loads (>1.7 MPa), poor correlation of predictions to measured force coefficients is common. Recently, an experimental effort (Gaines, J., 2014, “Examining the Impact of Pad Flexibility on the Rotordynamic Coefficients of Rocker-Pivot-Pad Tiling-Pad Journal Bearings,” M.S. thesis, Mechanical Engineering, Texas A&M University, College Station, TX) produced test data for three TPJB sets, each having three pads of unequal thickness, to quantify the effect of pad flexibility on the bearings' force coefficients, in particular damping, over a range of load and rotational speed conditions. This paper introduces a fluid film flow model accounting for both pivot and pad flexibility to predict the bearing journal eccentricity, drag power Loss, Lubricant temperature rise, and force coefficients of typical TPJBs. A finite element (FE) pad structural model including the Babbitt layer is coupled to the thin film flow model to determine the mechanical deformation of the pad surface. Predictions correlate favorably with test data, also demonstrating that pad flexibility produces a reduction of up to 34% in damping for the bearing with the thinnest pads relative to that with the thickest pads. A parametric study follows to quantify the influence of pad thickness on the rotordynamic force coefficients of a sample TPJB with three pads of increasing preload, r¯p = 0, 0.25 (baseline) and 0.5. The bearing pads are either rigid or flexible by varying their thickness. For design considerations, dimensionless static and dynamic characteristics of the bearings are presented versus the Sommerfeld number (S). Pad flexibility shows a more pronounced effect on the journal eccentricity and the force coefficients of a TPJB with null pad preload than for the bearings with larger pad preloads (0.25 and 0.5), in particular for operation with a small load or at a high surface speed (S > 0.8).
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Effect of Pad Flexibility on the Performance of Tilting Pad Journal Bearings: Benchmarking a Predictive Model
Volume 7A: Structures and Dynamics, 2015Co-Authors: Luis San AndrésAbstract:Tilting pad journal bearings (TPJBs) supporting high performance turbomachinery rotors have undergone steady design improvements to satisfy ever stringent operating conditions that include large specific loads due to smaller footprints, and high surface speeds that promote flow turbulence and thus larger drag power Losses. Simultaneously, predictive models continuously evolve to include minute details on bearing geometry, pads and pivots’ configurations, oil delivery systems, etc. In general, predicted TPJB rotordynamic force coefficients correlate well with experimental data for operation with small to moderately large unit loads (1.7 MPa). Experiments also demonstrate bearing dynamic stiffnesses are frequency dependent, best fitted with a stiffness-mass like model whereas damping coefficients are adequately represented as of viscous type. However, for operation with large specific loads (> 1.7 MPa), poor correlation of predictions to measured force coefficients is common. Recently, an experimental effort [1] produced test data for three TPJB sets, each having three pads of unequal thickness, to quantify the effect of pad flexibility on the bearings’ force coefficients, in particular damping, over a range of load and rotational speed conditions. This paper introduces a fluid film flow model accounting for both pivot and pad flexibility to predict the bearing journal eccentricity, drag power Loss, Lubricant temperature rise and force coefficients of typical TPJBs. A finite element pad structural model including the Babbitt layer is coupled to the thin film flow model to determine the mechanical deformation of the pad surface. Predictions correlate favorably with test data, also demonstrating that pad flexibility produces a reduction of up to 34% in damping for the bearing with the thinnest pads relative to that with the thickest pads. A parametric study follows to quantify the influence of pad thickness on the rotordynamic force coefficients of a sample TPJB with three pads of increasing preload, rp = 0, 0.25 (baseline) and 0.5. The bearing pads are either rigid or flexible by varying their thickness. For design considerations, dimensionless static and dynamic characteristics of the bearings are presented versus the Sommerfeld number (S). Pad flexibility shows a more pronounced effect on the journal eccentricity and the force coefficients of a TPJB with null pad preload than for the bearings with larger pad preloads (0.25 and 0.5), in particular for operation with a small load or at a high surface speed (S>0.8).
Deore P. - One of the best experts on this subject based on the ideXlab platform.
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Identification and analysis of screw compressor mechanical Losses
'IOP Publishing', 2018Co-Authors: Abdan S., Stosic N., Kovacevic A., Smith I. K., Deore P.Abstract:Screw compressors are compact machines, used for a wide range of applications where gases or vapours are required to be delivered at moderate pressures with high efficiency and reliability. They are most effective when the compressed medium requires power inputs, approximately in the 10 kW - 1-2 MW range. At lower inputs alternatives such as reciprocating and scroll compressors are preferable and at higher inputs turbo-compressors are more suitable. In industrialised countries, compressors absorb 15-20% of the total electrical power generated. Hence there is a continuing demand to improve their efficiency. This is normally expressed as the specific power consumption, which is the power required to compress unit mass of gas delivered. There already exist mathematical models to assist in the design of such machines and to estimate their performance, which include the estimation of the dynamic loads acting on the rotors and bearings and these loads determine their mechanical efficiency. However, these models do not estimate the magnitude of the mechanical Losses, which are only guesstimated as an additional increment to the power required to compress the gas. Such an approximation does not enable the optimum selection of bearings and lubricating oil to minimise the frictional power Losses. The aim of the study, described in this paper, was to estimate the effect of the individual parameters responsible for mechanical power Loss in oil injected screw compressors and is focussed on the Losses incurred in the gear box, bearings and shaft seals. It was found that in the gearbox, meshing, bearing and seal Losses all increase both with speed and gear ratio. In the main rotors, it was found that sliding friction Losses in the bearings are not significantly affected by the radial load, nor are rolling friction Losses significantly dependent on the axial load. However, both axial and radial loads have a significant effect on the total frictional power Loss. Lubricant viscosity affects the frictional power Losses but the oil level does not
Abdan S. - One of the best experts on this subject based on the ideXlab platform.
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Identification and analysis of screw compressor mechanical Losses
'IOP Publishing', 2018Co-Authors: Abdan S., Stosic N., Kovacevic A., Smith I. K., Deore P.Abstract:Screw compressors are compact machines, used for a wide range of applications where gases or vapours are required to be delivered at moderate pressures with high efficiency and reliability. They are most effective when the compressed medium requires power inputs, approximately in the 10 kW - 1-2 MW range. At lower inputs alternatives such as reciprocating and scroll compressors are preferable and at higher inputs turbo-compressors are more suitable. In industrialised countries, compressors absorb 15-20% of the total electrical power generated. Hence there is a continuing demand to improve their efficiency. This is normally expressed as the specific power consumption, which is the power required to compress unit mass of gas delivered. There already exist mathematical models to assist in the design of such machines and to estimate their performance, which include the estimation of the dynamic loads acting on the rotors and bearings and these loads determine their mechanical efficiency. However, these models do not estimate the magnitude of the mechanical Losses, which are only guesstimated as an additional increment to the power required to compress the gas. Such an approximation does not enable the optimum selection of bearings and lubricating oil to minimise the frictional power Losses. The aim of the study, described in this paper, was to estimate the effect of the individual parameters responsible for mechanical power Loss in oil injected screw compressors and is focussed on the Losses incurred in the gear box, bearings and shaft seals. It was found that in the gearbox, meshing, bearing and seal Losses all increase both with speed and gear ratio. In the main rotors, it was found that sliding friction Losses in the bearings are not significantly affected by the radial load, nor are rolling friction Losses significantly dependent on the axial load. However, both axial and radial loads have a significant effect on the total frictional power Loss. Lubricant viscosity affects the frictional power Losses but the oil level does not
Stosic N. - One of the best experts on this subject based on the ideXlab platform.
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Identification and analysis of screw compressor mechanical Losses
'IOP Publishing', 2018Co-Authors: Abdan S., Stosic N., Kovacevic A., Smith I. K., Deore P.Abstract:Screw compressors are compact machines, used for a wide range of applications where gases or vapours are required to be delivered at moderate pressures with high efficiency and reliability. They are most effective when the compressed medium requires power inputs, approximately in the 10 kW - 1-2 MW range. At lower inputs alternatives such as reciprocating and scroll compressors are preferable and at higher inputs turbo-compressors are more suitable. In industrialised countries, compressors absorb 15-20% of the total electrical power generated. Hence there is a continuing demand to improve their efficiency. This is normally expressed as the specific power consumption, which is the power required to compress unit mass of gas delivered. There already exist mathematical models to assist in the design of such machines and to estimate their performance, which include the estimation of the dynamic loads acting on the rotors and bearings and these loads determine their mechanical efficiency. However, these models do not estimate the magnitude of the mechanical Losses, which are only guesstimated as an additional increment to the power required to compress the gas. Such an approximation does not enable the optimum selection of bearings and lubricating oil to minimise the frictional power Losses. The aim of the study, described in this paper, was to estimate the effect of the individual parameters responsible for mechanical power Loss in oil injected screw compressors and is focussed on the Losses incurred in the gear box, bearings and shaft seals. It was found that in the gearbox, meshing, bearing and seal Losses all increase both with speed and gear ratio. In the main rotors, it was found that sliding friction Losses in the bearings are not significantly affected by the radial load, nor are rolling friction Losses significantly dependent on the axial load. However, both axial and radial loads have a significant effect on the total frictional power Loss. Lubricant viscosity affects the frictional power Losses but the oil level does not
Kovacevic A. - One of the best experts on this subject based on the ideXlab platform.
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Identification and analysis of screw compressor mechanical Losses
'IOP Publishing', 2018Co-Authors: Abdan S., Stosic N., Kovacevic A., Smith I. K., Deore P.Abstract:Screw compressors are compact machines, used for a wide range of applications where gases or vapours are required to be delivered at moderate pressures with high efficiency and reliability. They are most effective when the compressed medium requires power inputs, approximately in the 10 kW - 1-2 MW range. At lower inputs alternatives such as reciprocating and scroll compressors are preferable and at higher inputs turbo-compressors are more suitable. In industrialised countries, compressors absorb 15-20% of the total electrical power generated. Hence there is a continuing demand to improve their efficiency. This is normally expressed as the specific power consumption, which is the power required to compress unit mass of gas delivered. There already exist mathematical models to assist in the design of such machines and to estimate their performance, which include the estimation of the dynamic loads acting on the rotors and bearings and these loads determine their mechanical efficiency. However, these models do not estimate the magnitude of the mechanical Losses, which are only guesstimated as an additional increment to the power required to compress the gas. Such an approximation does not enable the optimum selection of bearings and lubricating oil to minimise the frictional power Losses. The aim of the study, described in this paper, was to estimate the effect of the individual parameters responsible for mechanical power Loss in oil injected screw compressors and is focussed on the Losses incurred in the gear box, bearings and shaft seals. It was found that in the gearbox, meshing, bearing and seal Losses all increase both with speed and gear ratio. In the main rotors, it was found that sliding friction Losses in the bearings are not significantly affected by the radial load, nor are rolling friction Losses significantly dependent on the axial load. However, both axial and radial loads have a significant effect on the total frictional power Loss. Lubricant viscosity affects the frictional power Losses but the oil level does not
