The Influence of Lubricant Supply Conditions and Bearing Configuration on the Performance of (Semi) Floating Ring Bearing Systems for Turbochargers

2017 ◽  
Author(s):  
Luis San Andrés ◽  
Feng Yu ◽  
Kostandin Gjika
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Engine Oil ◽  
Large Temperature ◽  
Oil Viscosity ◽  
Supply Pressure ◽  
The Impact ◽  
Bearing System

Engine oil lubricated (semi) floating ring bearing (S)FRB systems in passenger vehicle turbochargers (TC) operate at temperatures well above ambient and must withstand large temperature gradients that can lead to severe thermo-mechanical induced stresses. Physical modeling of the thermal energy flow paths and an effective thermal management strategy are paramount to determine safe operating conditions ensuring the TC component mechanical integrity and the robustness of its bearing system. On occasion, the selection of one particular bearing parameter to improve a certain performance characteristic could be detrimental to other performance characteristics of a TC system. The paper details a thermohydrodynamic model to predict the hydrodynamic pressure and temperature fields and the distribution of thermal energy flows in the bearing system. The impact of the lubricant supply conditions (pressure and temperature), bearing film clearances, oil supply grooves on the ring ID surface are quantified. Lubricating a (S)FRB with either a low oil temperature or a high supply pressure increases (shear induced) heat flow. A lube high supply pressure or a large clearance allow for more flow through the inner film working towards drawing more heat flow from the hot journal, yet raises the shear drag power as the oil viscosity remains high. Nonetheless, the peak temperature of the inner film is not influenced much by the changes on the way the oil is supplied into the film as the thermal energy displaced from the hot shaft into the film is overwhelming. Adding axial grooves on the inner side of the (S)FRB improves its dynamic stability, albeit increasing the drawn oil flow as well as the drag power and heat flow from the shaft. The predictive model allows to identify a compromise between different parameters of groove designs thus enabling a bearing system with a low power consumption.

On the Influence of Lubricant Supply Conditions and Bearing Configuration to the Performance of (Semi) Floating Ring Bearing Systems for Turbochargers

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Luis San Andrés ◽  
Feng Yu ◽  
Kostandin Gjika
Keyword(s):  
Thermal Energy ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Engine Oil ◽  
Large Temperature ◽  
Oil Viscosity ◽  
Supply Pressure ◽  
Oil Flow ◽  
The Impact ◽  
Bearing System

Engine oil-lubricated (semi) floating ring bearing ((S)FRB) systems in passenger vehicle turbochargers (TC) operate at temperatures well above ambient and must withstand large temperature gradients that can lead to severe thermomechanical induced stresses. Physical modeling of the thermal energy flow paths and an effective thermal management strategy are paramount to determine safe operating conditions ensuring the TC component mechanical integrity and the robustness of its bearing system. The paper details a model to predict the pressure and temperature fields and the distribution of thermal energy flows in a bearing system. The impact of lubricant supply conditions, bearing film clearances, and oil supply grooves is quantified. Either a low oil temperature or a high supply pressure increases the generated shear power. Either a high supply pressure or a large clearance allows more flow through the inner film and draws more heat from the hot journal, thought it increases the shear drag power as the oil viscosity remains high. Nonetheless, the peak temperature of the inner film is not influenced by the changes on the way the oil is supplied into the film as the thermal energy displaced from the hot shaft into the film is overwhelming. Adding axial grooves on the inner side of the (S)FRB improves its dynamic stability, albeit increasing the drawn oil flow as well as the drag power and heat from the shaft. The results identify a compromise between different parameters of groove designs thus enabling a bearing system with a low power consumption.

On the Effect of Thermal Energy Transport to the Performance of (Semi)Floating Ring Bearing Systems for Automotive Turbochargers

2012 ◽  
Author(s):  
Luis San Andrés ◽  
Vince Barbarie ◽  
Avijit Bhattacharya ◽  
Kostandin Gjika
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Energy Transport ◽  
Operating Conditions ◽  
Engine Oil ◽  
Distinct Advantage ◽  
Oil Viscosity ◽  
Wide Range ◽  
Thermal Energy Transport ◽  
Bearing System

Bearing systems in engine-oil lubricated turbochargers (TCs) must operate reliably over a wide range of shaft speeds and withstanding severe axial and radial thermal gradients. An engineered thermal management of the energy flows into and out of the bearing system is paramount to ensure the components mechanical integrity and the robustness of the bearing system. The bearings, radial and thrust type, act both as a load bearing and low friction support with the lubricant carrying away a large fraction of the thermal energy generated by rotational drag and the heat flow disposed from a hot shaft. The paper introduces a thermohydrodynamic analysis for prediction of the pressure and temperature fields in a (semi) floating ring bearing system. The analysis solves simultaneously the Reynolds equation with variable oil viscosity and the thermal energy transport equation in the inner and outer films of the bearing system. Flow conditions in both films are coupled to the temperature distribution and heat flow thru the (semi)floating ring. Other constraints include calculating the fluid films’ forces reacting to the externally applied load and to determine the operating journal and ring eccentricities. Predictions of performance for a unique realistic (S)FRB configuration at typical TC operating conditions reveal distinct knowledge: (a) the heat flow from the shaft into the inner film is overwhelming, in particular at the inlet lubricant plane where the temperature difference with the cold oil is largest; (b) the inner film temperature increases quickly as soon as the (cold) lubricant enters the film and due to the large amount of energy generated by shear drag and the heat transfer from the shaft; (c) a floating ring develops a significant radial temperature gradient; (d) at all shaft speeds, low and high, the thermal energy carried away by the lubricant streams is no less that 70% of the total energy input; the rest is conducted through the TC casing. To warrant this thermal energy distribution, enough lubricant flow must be supplied to the bearing system. The efficient computational model offers a distinct advantage over existing lumped parameters thermal models and with no penalty in execution time.

On the Effect of Thermal Energy Transport to the Performance of (Semi) Floating Ring Bearing Systems for Automotive Turbochargers

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Luis San Andrés ◽  
Vince Barbarie ◽  
Avijit Bhattacharya ◽  
Kostandin Gjika
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Energy Transport ◽  
Operating Conditions ◽  
Engine Oil ◽  
Distinct Advantage ◽  
Oil Viscosity ◽  
Wide Range ◽  
Thermal Energy Transport ◽  
Bearing System

Bearing systems in engine-oil lubricated turbochargers (TCs) must operate reliably over a wide range of shaft speeds and withstand severe axial and radial thermal gradients. An engineered thermal management of the energy flows into and out of the bearing system is paramount in order to ensure the component’s mechanical integrity and the robustness of the bearing system. The bearings, radial and thrust type, act both as a load bearing and low friction support with the lubricant carrying away a large fraction of the thermal energy generated by rotational drag and the heat flow disposed from a hot shaft. The paper introduces a thermohydrodynamic analysis for the prediction of the pressure and temperature fields in a (semi) floating ring bearing (S)FRB system. The analysis simultaneously solves the Reynolds equation with variable oil viscosity and the thermal energy transport equation in the inner and outer films of the bearing system. Flow conditions in both films are coupled to the temperature distribution and heat flow through the (semi) floating ring. Other constraints include calculating the fluid films’ forces reacting to the externally applied load and to determine the operating journal and ring eccentricities. The predictions of performance for a unique realistic (S)FRB configuration at typical TC operating conditions reveal a distinct knowledge: (a) the heat flow from the shaft into the inner film is overwhelming, in particular, at the inlet lubricant plane where the temperature difference with the cold oil is largest; (b) the inner film temperature quickly increases as soon as the (cold) lubricant enters the film and is due to the large amount of energy generated by shear drag and the heat transfer from the shaft; (c) a floating ring develops a significant radial temperature gradient; (d) at all shaft speeds, low and high, the thermal energy carried away by the lubricant streams is no less than 70% of the total energy input; the rest is conducted through the TC casing. To warrant this thermal energy distribution, enough lubricant flow must be supplied to the bearing system. The efficient computational model offers a distinct advantage over existing lumped parameters thermal models and there is no penalty in the execution time.

Off-Design of a Pumped Thermal Energy Storage Based on Closed Brayton Cycles

2021 ◽  
Author(s):  
Guido Francesco Frate ◽  
Luigia Paternostro ◽  
Lorenzo Ferrari ◽  
Umberto Desideri
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Electric Energy ◽  
Packed Bed ◽  
Operating Conditions ◽  
Part Load ◽  
Storage Technologies ◽  
Thermodynamical Behavior ◽  
The Impact

Abstract The growth of renewable energy source requires reliable, durable and cheap storage technologies. In this field, the Pumped Thermal Energy Storage (PTES), is drawing some interest as it appears not to be affected by geographical limitations and use very cheap materials. PTES is less efficient than pumped hydro and batteries, but it could achieve satisfactory efficiencies, show better economic performance and be characterized by negligible environmental impacts. A PTES stores the electric energy as thermal exergy in solid packed beds, by operating two closed Brayton cycles, one for charging and the other one for discharging. Although PTES thermodynamical behavior is well understood, the interaction between the components is rarely investigated. This study investigates the impact of packed-bed behavior on turbomachines operating conditions. In this way, PTES off-design and part-load performance are estimated. A control strategy especially suited for closed Brayton cycles, i.e. the inventory control, is used to control the system. As it resulted, PTES is characterized by an excellent part-load performance, which might be a significant advantage over the competing technologies. However, the off-design operation induced by the packed-bed thermal behavior might significantly reduce the system performance and, in particular, that of the discharge phase.

A Thermo-Hydrodynamic Model for Thermal Energy Flow Management in a (Semi) Floating Ring Bearing System for Automotive Turbochargers

2020 ◽  
Author(s):  
Luis San Andrés ◽  
Wonbae Jung ◽  
Seong-Ki Hong
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Energy Flow ◽  
Power Loss ◽  
Energy Transport ◽  
Engine Oil ◽  
Viscous Drag ◽  
Shaft Speed ◽  
Thrust Bearings ◽  
Viscous Shear

Abstract Oil-engine lubricated turbochargers (TCs) operate at high temperature and must withstand large temperature gradients that produce severe thermo-mechanical stresses in the TC mechanical components. Thus, an insight into the thermal energy flows and an effective thermal management are paramount to ensure reliable TC operation. The paper analyzes the transport of energy and heat flows in semi-floating ring bearings (SFRBs) for automotive TCs with integrated heat and fluid flow models for both (turbine and compressor sides) radial bearings and thrust bearings to produce a complete thermo-hydrodynamic analysis predictive tool. The model couples the energy transport equations and the lubrication Reynolds equations in the inner and outer films of a SFRB and the adjacent thrust films to a three-dimensional heat conduction in the floating ring and along with thermal soaking into the TC casing. Cold lubricant, supplied at a specific temperature and pressure, flows to fill the films of the radial bearings, and then the thrust bearings. The lubricated bearings, radial and axial, support shaft loads, static and dynamic, and produce drag power losses. The streams of lubricant warm up as they take away a sizable portion of the heat flow from the hot shaft plus that due to viscous shear drag. Another fraction of thermal energy flow sinks into the floating ring which presents a distinct temperature field varying along the radial, circumferential and axial directions. The computational analysis contemplates a TC operating at shaft speeds (Ω) ranging from 30 krpm to 240 krpm (4 kHz) and a SFRB supplied with engine oil at PSUP = 3.0 bar and TSUP = 120 °C. The analysis focuses on a brass-made turbine bearing as it is the one that disposes most thermal energy flow since the shaft surface is hot at Ts = 213 °C (just below the lubricant flash point temperature at 230 °C) while the casing temperature is TC = TSUP. The ring with length/diameter = 1.6 has radial bearings with four equally spaced feed holes and four axial grooves, and the ratio outer film clearance/inner film clearance equals 5.3 at room temperature. As shaft speed increases (= 100 m/s max. surface speed), the inner film temperature increases proportionally; albeit the heat flow from the shaft into the inner film decreases while the viscous drag power raises rapidly. The outer film heats to just a few degrees above TSUP since the non-spinning ring does not generate viscous shear drag. The ring heats unevenly, radially with a ∼20 °C temperature gradient from its inner to outer diameters (ID and OD), and axially with up to a ∼50 °C difference from the thrust bearing side that also produces a drag power loss. At a low shaft speed (45 krpm), heat flowing from the shaft overwhelms the drag power loss induced by shearing the inner film; whereas as shaft speed increases (240 krpm), the contribution from the drag power loss to the total energy flow disposed increases significantly, from 3% to 63%. The lubricant flows, inner plus outer, advect most of the thermal energy flow, 74% to 81%, over the range of shaft speeds, low to high. The floating ring conducts a sizeable portion of thermal energy flow, 39% to 49% of the total, though varying little with shaft speed. Similarly does the fraction of heat, 9% to 13% of the total, conducted into the TC casing. A more conductive ring material or an outer film with a longer length conduct more heat into the ring although the lubricant flows still carry most of the thermal energy flow generated by viscous drag losses and heat from the shaft. The results demonstrate the importance of designing a SFRB system with adequate clearances and proper materials to offer an adequate thermal management and avoiding too high temperatures that could varnish, even flash and burn, the engine oil. The improvements in the energy transport and heat flow modeling of a SFRB system will produce significant savings in TC performance.

The Impact of Model Assumptions on the CFD Assisted Design of Gas Turbine Packages

2019 ◽  
Author(s):  
Gabriele Lucherini ◽  
Vittorio Michelassi ◽  
Stefano Minotti
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Structural Integrity ◽  
Ventilation System ◽  
Gas Diffusion ◽  
Computational Effort ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Fuel Gas ◽  
The Impact

Abstract A gas turbine is usually installed inside a package to reduce the acoustics emissions and protect against adverse environmental conditions. An enclosure ventilation system is keeps temperatures under acceptable limits and dilutes any potentially explosive accumulation of gas due to unexpected leakages. The functional and structural integrity as well as certification needs of the instrumentation and auxiliary systems in the package require that temperatures do not exceed a given threshold. Moreover, accidental fuel gas leakages inside the package must be studied in detail for safety purposes as required by ISO21789. CFD is routinely used in BHGE (Baker Hughes, a GE Company) to assist in the design and verification of the complete enclosure and ventilation system. This may require multiple CFD runs of very complex domains and flow fields in several operating conditions, with a large computational effort. Modeling assumptions and simulation set-up in terms of turbulence and thermal models, and the steady or unsteady nature of the simulations must be carefully assessed. In order to find a good compromise between accuracy and computational effort the present work focuses on the analysis of three different approaches, RANS, URANS and Hybrid-LES. The different computational approaches are first applied to an isothermal scaled-down model for validation purposes where it was possible to determine the impact of the large-scale flow unsteadiness and compare with measurements. Then, the analysis proceeds to a full-scale real aero-derivative gas turbine package. in which the aero and thermal field were investigated by a set of URANS and Hybrid-LES that includes the heat released by the engine. The different approaches are compared by analyzing flow and temperature fields. Finally, an accidental gas leak and the subsequent gas diffusion and/or accumulation inside the package are studied and compared. The outcome of this work highlights how the most suitable approach to be followed for industrial purposes depends on the goal of the CFD study and on the specific scenario, such as NPI Program or RQS Project.

Construction equipment engine performance degradation due to environmental and operation factors in Latin America

2019 ◽  
Vol 25 (3) ◽  
pp. 499-524
Author(s):  
Kurt Azevedo ◽  
Daniel B. Olsen
Keyword(s):  
Operating Conditions ◽  
Mitigation Strategies ◽  
Sensor Data ◽  
Engine Oil ◽  
Construction Equipment ◽  
Base Number ◽  
Oil Viscosity ◽  
Mining Operations ◽  
Content Type ◽  
Engine Wear

Purpose The purpose of this paper is to determine whether the altitude at which construction equipment operates affects or contributes to increased engine wear. Design/methodology/approach The study includes the evaluation of two John Deere PowerTech Plus 6,068 Tier 3 diesel engines, the utilization of OSA3 oil analysis laboratory equipment to analyze oil samples, the employment of standard sampling scope and methods, and the analysis of key Engine Control Unit (ECU) data points (machine utilization, Diagnostic Trouble Codes (DTCs) and engine sensor data). Findings At 250 h of engine oil use, the engine operating at 3,657 meters above sea level (MASL) had considerably more wear than the engine operating at 416 MASL. The leading and earliest indicator of engine wear was a high level of iron particles in the engine oil, reaching abnormal levels at 218 h. The following engine oil contaminants were more prevalent in the engine operating at the higher altitude: potassium, glycol, water and soot. Furthermore, the engine operating at higher altitude also presented abnormal and critical levels of oil viscosity, Total Base Number and oxidation. When comparing the oil sample analysis with the engine ECU data, it was determined that engine idling is a contributor for soot accumulation in the engine operating at the higher altitude. The most prevalent DTCs were water in fuel, extreme low coolant levels and extreme high exhaust manifold temperature. The ECU operating data demonstrated that the higher altitude environment caused the engine to miss-fire and rail pressure was irregular. Practical implications Many of the mining operations and construction projects are accomplished at mid to high altitudes. This research provides a comparison of how construction equipment engines are affected by this type of environment (i.e. higher altitudes, cooler temperatures and lower atmospheric pressure). Consequently, service engineers can implement maintenance strategies to minimize internal engine wear for equipment operating at higher altitudes. Originality/value The main contribution of this paper will help construction equipment end-users, maintenance engineers and manufacturers to implement mitigation strategies to improve engine durability for countries with operating conditions similar to those described in this research.

Effect of Stationary Natural Gas Engine Oils on Fuel Economy

2012 ◽  
Author(s):  
Nikhil Dayanand ◽  
John D. Palazzotto ◽  
Alan T. Beckman
Keyword(s):  
Natural Gas ◽  
Fuel Consumption ◽  
Fuel Economy ◽  
Operating Conditions ◽  
Specific Fuel Consumption ◽  
Engine Oil ◽  
Brake Specific Fuel Consumption ◽  
Oil Viscosity ◽  
Gas Engine ◽  
Natural Gas Engine

In order to investigate the possible environmental and economic benefits of lubricants optimized for stationary natural gas engine efficiency, a decision was made to develop a test stand to quantify the effects of lubricant viscosities and formulations on the brake specific fuel consumption. Many fuel economy tests already exist for evaluating gasoline and heavy duty diesel motor oils which have proven the benefit of fuel economy from different lubricant formulations. These engines would not be suitable tools for evaluating the fuel economy performance of lubricating oils formulated specifically for stationary natural gas engines, since there are significant differences in operating conditions, fuel type, and oil formulations. This paper describes the adaptation of a Waukesha VSG F11 GSID as a tool to evaluate fuel consumption performance. The performance of brake specific fuel consumption when using different formulations was measured at selected high loads and rated speed. The results of the testing program discuss the viscosity and additive effects of stationary natural gas engine oil formulations on brake specific fuel consumption. The results will detail the change in brake specific fuel consumption between natural gas engine oil formulations blended to varying viscosities and compared to a typical natural gas engine oil formulation with a viscosity of 13.8 cSt @ 100°C. The second portion of the test program explores the effect of different additive packages that were blended to the same finished oil viscosity. It was acknowledged that there were statistical differences in brake specific fuel consumption characteristics between lubricants different in viscosity and additive formulations.

Off-Design of a Pumped Thermal Energy Storage Based On Closed Brayton Cycles

2021 ◽  
Author(s):  
Guido Francesco Frate ◽  
Luigia Paternostro ◽  
Lorenzo Ferrari ◽  
Umberto Desideri
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Electric Energy ◽  
Packed Bed ◽  
Operating Conditions ◽  
Part Load ◽  
Storage Technologies ◽  
Thermodynamical Behavior ◽  
The Impact

Abstract The growth of renewable energy source requires reliable, durable and cheap storage technologies. In this field, the Pumped Thermal Energy Storage (PTES), is drawing some interest as it appears not to be affected by geographical limitations and use very cheap materials. PTES is less efficient than pumped hydro and batteries, but it could achieve satisfactory efficiencies, show better economic performance and be characterized by negligible environmental impacts. A PTES stores the electric energy as thermal exergy in solid packed beds, by operating two closed Brayton cycles, one for charging and the other one for discharging. Although PTES thermodynamical behavior is well understood, the interaction between the components is rarely investigated. This study investigates the impact of packed-bed behavior on turbomachines operating conditions. In this way, PTES off-design and part-load performance are estimated. A control strategy especially suited for closed Brayton cycles, i.e. the inventory control, is used to control the system. As it resulted, PTES is characterized by an excellent part-load performance, which might be a significant advantage over the competing technologies. However, the off-design operation induced by the packed-bed thermal behavior might significantly reduce the system performance and, in particular, that of the discharge phase.

A Thermo-Hydrodynamic Model for Thermal Energy Flow Management in A (Semi) Floating Ring Bearing System for Automotive Turbochargers

2021 ◽  
Vol 143 (1) ◽  
Author(s):  
Luis San Andrés ◽  
Wonbae Jung ◽  
Seong-Ki Hong
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Energy Flow ◽  
Power Loss ◽  
Energy Transport ◽  
Engine Oil ◽  
Viscous Drag ◽  
Shaft Speed ◽  
Thrust Bearings ◽  
Viscous Shear

Abstract Oil-engine lubricated turbochargers (TCs) operate at high temperature and must withstand large temperature gradients that produce severe thermomechanical stresses in the TC mechanical components. Thus, an insight into the thermal energy flows and an effective thermal management are paramount to ensure reliable TC operation. The paper analyzes the transport of energy and heat flows in semifloating ring bearings (SFRBs) for automotive TCs with integrated heat and fluid flow models for both (turbine and compressor sides) radial bearings and thrust bearings to produce a complete thermohydrodynamic analysis predictive tool. The model couples the energy transport equations and the lubrication Reynolds equations in the inner and outer films of an SFRB and the adjacent thrust films to a three-dimensional heat conduction in the floating ring and along with thermal soaking into the TC casing. Cold lubricant, supplied at a specific temperature and pressure, flows to fill the films of the radial bearings, and then the thrust bearings. The lubricated bearings, radial and axial, support shaft loads, static and dynamic, and produce drag power losses. The streams of lubricant warm up as they take away a sizable portion of the heat flow from the hot shaft plus that due to viscous shear drag. Another fraction of thermal energy flow sinks into the floating ring, which presents a distinct temperature field varying along the radial, circumferential, and axial directions. The computational analysis contemplates a TC operating at shaft speeds (Ω) ranging from 30 krpm to 240 krpm (4 kHz) and an SFRB supplied with engine oil at PSUP = 3.0 bar and TSUP = 120 °C. The analysis focuses on a brass-made turbine bearing (TB) as it is the one that disposes most thermal energy flow since the shaft surface is hot at Ts = 213 °C (just below the lubricant flash point temperature at 230 °C) while the casing temperature is TC = TSUP. The ring with length/diameter = 1.6 has radial bearings with four equally spaced feed holes and four axial grooves, and the ratio outer film clearance/inner film clearance equals 5.3 at room temperature. As shaft speed increases (= 100 m/s max. surface speed), the inner film temperature increases proportionally; albeit the heat flow from the shaft into the inner film decreases while the viscous drag power raises rapidly. The outer film heats to just a few degrees above TSUP since the nonspinning ring does not generate viscous shear drag. The ring heats unevenly, radially with a ∼20 °C temperature gradient from its inner to outer diameters (ID and OD), and axially with up to a ∼50 °C difference from the thrust bearing side that also produces a drag power loss. At a low shaft speed (45 krpm), heat flowing from the shaft overwhelms the drag power loss induced by shearing the inner film; whereas as shaft speed increases (240 krpm), the contribution from the drag power loss to the total energy flow disposed increases significantly, from 3% to 63%. The lubricant flows, inner plus outer, advect most of the thermal energy flow, 74% to 81%, over the range of shaft speeds, low to high. The floating ring conducts a sizeable portion of thermal energy flow, 39% to 49% of the total, though varying little with shaft speed. Similarly does the fraction of heat, 9% to 13% of the total, conducted into the TC casing. A more conductive ring material or an outer film with a longer length conduct more heat into the ring although the lubricant flows still carry most of the thermal energy flow generated by viscous drag losses and heat from the shaft. The results demonstrate the importance of designing an SFRB system with adequate clearances and proper materials to offer an adequate thermal management and avoiding too high temperatures that could varnish, even flash and burn, the engine oil. The improvements in the energy transport and heat flow modeling of an SFRB system will produce significant savings in TC performance.

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