Enhanced CFD Modelling and LDA Measurements for the Air-Flow in an Aero-Engine Front Bearing Chamber: Part I

2014 ◽  
Author(s):  
J. Aidarinis ◽  
A. Goulas
Keyword(s):  
Flow Field ◽  
Ball Bearing ◽  
Computational Study ◽  
Air Flow ◽  
Full Range ◽  
Scale Model ◽  
Type I ◽  
Two Phase ◽  
Aero Engine ◽  
Lubrication Oil

Modern aero-engine development requires also a gradual increase in the overall effectiveness of lubrication systems. This particularly applies to bearing chambers where a complex two-phase flow is formed by the interaction of the sealing air and the lubrication oil. It is important to increase the level of understanding of the flow field inside the bearing chamber and to develop engineering tools in order to optimize its design and improve its performance. To achieve this an experimental and a computational study of the whole front bearing chamber were carried out for a range of shaft rotational speeds and sealing air mass flow. The experimental measurements of the air velocity inside the chamber were carried out using a Laser Doppler Anemometer (LDA) in two-phase air/oil flow conditions. The experimental facility is a 1:1 scale model of the front bearing chamber of an aero-engine. Computational 3D modeling of the bearing chamber was performed. The bearing gap and the presence of lubrication oil was modeled as an anisotropic porous medium with functions relating the pressure loss of the air coming through the gap and the tangential component of velocity of the air exiting the gap of the ball bearing with the air-flow rate through the gap and the rotational speed of the shaft. The methodology to obtain the above mentioned functions and the results of the detailed study are given in [1]. The enhanced computational model of the chamber implementing the law of pressure drop of the ‘lubricated’ bearing and the function of modeling the tangential velocity of the air exiting the bearing, was used to calculate the flow field for the full range of the measurements. A limiting curve dividing the operational map of the bearing chamber into two areas was predicted. Large vortical and swirling structures dominate the flow and they vary in size according to the position of the operation point relative to the limiting curve. Operation above the limiting curve leads to flow classified as type I with air going through the ball bearing while for operation below the limiting curve line the flow is classified as type II, there is no air-flow through the bearing gap.

Enhanced Computational Fluid Dynamics Modeling and Laser Doppler Anemometer Measurements for the Air-Flow in an Aero-engine Front Bearing Chamber—Part I

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
J. Aidarinis ◽  
A. Goulas
Keyword(s):  
Flow Field ◽  
Ball Bearing ◽  
Air Flow ◽  
Laser Doppler Anemometer ◽  
Laser Doppler ◽  
Scale Model ◽  
Type I ◽  
Two Phase ◽  
Aero Engine ◽  
Lubrication Oil

Modern aero-engine development requires also a gradual increase in the overall effectiveness of lubrication systems. This particularly applies to bearing chambers where a complex two-phase flow is formed by the interaction of the sealing air and the lubrication oil. It is important to increase the level of understanding of the flow field inside the bearing chamber and to develop engineering tools in order to optimize its design and improve its performance. To achieve this, an experimental and a computational study of the whole front bearing chamber were carried out for a range of shaft rotational speeds and sealing air mass flow. The experimental measurements of the air velocity inside the chamber were carried out using a laser Doppler anemometer (LDA) in two-phase air/oil-flow conditions. The experimental facility is a 1:1 scale model of the front bearing chamber of an aero-engine. Computational 3D modeling of the bearing chamber was performed. The bearing gap and the presence of lubrication oil were modeled as an anisotropic porous medium with functions relating the pressure loss of the air coming through the gap and the tangential component of velocity of the air exiting the gap of the ball bearing with the air-flow rate through the gap and the rotational speed of the shaft. The methodology to obtain the above mentioned functions and the results of the detailed study are given (Aidarinis, J., and Goulas, A., 2014, “Enhanced CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber: Part II,” ASME Paper No. GT2014-26062). The enhanced computational model of the chamber implementing the law of pressure drop of the “lubricated” bearing and the function of modeling the tangential velocity of the air exiting the bearing was used to calculate the flow field for the full range of the measurements. A limiting curve dividing the operational map of the bearing chamber into two areas was predicted. Large vortical and swirling structures dominate the flow and they vary in size according to the position of the operation point relative to the limiting curve. Operation above the limiting curve leads to flow classified as type I with air going through the ball bearing while for operation below the limiting curve line the flow is classified as type II, there is no air-flow through the bearing gap.

Enhanced CFD Modelling and LDA Measurements for the Air-Flow in an Aero-Engine Front Bearing Chamber: Part II

2014 ◽  
Author(s):  
J. Aidarinis ◽  
A. Goulas
Keyword(s):  
Pressure Drop ◽  
Rotational Speed ◽  
Ball Bearing ◽  
Complex Geometry ◽  
Computational Study ◽  
Air Flow ◽  
Mathematical Form ◽  
Operational Parameters ◽  
Aero Engine ◽  
Flow Through

A detailed computational study of the air-flow through the outer gap of the front bearing of an aero-engine is presented. The reason to carry out this study was to understand the flow through the bearing as a function of the operational parameters of the engine, which was necessary for the modeling of the flow in the whole bearing chamber. The complex geometry and the size of the bearing gap relative to the overall dimensions of the bearing chamber and the need for very precise and detailed information of the effect on the flow within the chamber of the bearing operational parameters, prohibited the solution of the flow through the gap together with the rest of the bearing chamber. A 3-D modeling of the flow through the outer bearing gap, which included a section of the ball bearing, was performed. Functions relating the pressure drop of the air coming through the bearing gap and the tangential component of velocity of the air exiting the bearing region, to the mass of air through the gap of the ball bearing and the rotational speed of the shaft were developed. The effect of the lubrication oil within the bearing was modeled as an anisotropic porous medium with a predefined law. In order to acquire in a mathematical form the above relationships a series of computational runs were performed. These relationships, in the form of second order curves, were subsequently introduced to the model of the bearing chamber as described in [1]. The constants of the relationships were derived through comparisons of the calculations with the experimental data. From the analysis it was concluded that the pressure drop across the bearing increases with the square of the rotational speed of the shaft with the mass flow of air through the ball bearing as a parameter and vice versa. For this particular ball bearing there is a region where, for any combination of rotational speed of the shaft and pressure drop through the bearing, there is no flow of air through the bearing. In this paper the detailed modeling methodology, the computational flow field, the boundary conditions and finally the results are presented and discussed.

Enhanced Computational Fluid Dynamics Modeling and Laser Doppler Anemometer Measurements for the Air-Flow in an Aero-engine Front Bearing Chamber—Part II

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
J. Aidarinis ◽  
A. Goulas
Keyword(s):  
Pressure Drop ◽  
Rotational Speed ◽  
Ball Bearing ◽  
Computational Study ◽  
Air Flow ◽  
Cfd Modeling ◽  
Mathematical Form ◽  
Operational Parameters ◽  
Aero Engine ◽  
Flow Through

A detailed computational study of the air-flow through the outer gap of the front bearing of an aero-engine is presented. The reason to carry out this study was to understand the flow through the bearing as a function of the operational parameters of the engine, which was necessary for the modeling of the flow in the whole bearing chamber. The complex geometry and the size of the bearing gap relative to the overall dimensions of the bearing chamber and the need for very precise and detailed information of the effect on the flow within the chamber of the bearing operational parameters, prohibited the solution of the flow through the gap together with the rest of the bearing chamber. A 3D modeling of the flow through the outer bearing gap, which included a section of the ball bearing, was performed. Functions relating the pressure drop of the air coming through the bearing gap and the tangential component of velocity of the air exiting the bearing region, to the mass of air through the gap of the ball bearing and the rotational speed of the shaft were developed. The effect of the lubrication oil within the bearing was modeled as an anisotropic porous medium with a predefined law. In order to acquire in a mathematical form the above relationships a series of computational runs were performed. These relationships, in the form of second order curves, were subsequently introduced to the model of the bearing chamber as described by Aidarinis and Goulas (2014, “Enhanced CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber (Part I),” ASME Paper No. GT2014-26060). The constants of the relationships were derived through comparisons of the calculations with the experimental data. From the analysis, it was concluded that the pressure drop across the bearing increases with the square of the rotational speed of the shaft with the mass flow of air through the ball bearing as a parameter and vice versa. For this particular ball bearing, there is a region where, for any combination of rotational speed of the shaft and pressure drop through the bearing, there is no flow of air through the bearing. In this paper the detailed modeling methodology, the computational flow field, the boundary conditions and finally the results are presented and discussed.

Experimental Analysis of the Two-Phase Unsteady Flow in an Aero-Engine LPP Burner

2005 ◽  
Author(s):  
Mario Caruggi ◽  
Edward Canepa ◽  
Pasquale Di Martino ◽  
Alessandro Nilberto ◽  
Marina Ubaldi ◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Gas Flow ◽  
Air Flow ◽  
Scale Model ◽  
Fuel Spray ◽  
Two Phase ◽  
Fuel Droplets ◽  
Experimental Campaign ◽  
Gas Flow Field

The present paper reports the results of an experimental investigation on the unsteady flow in a Lean Premixed Prevaporized (LPP) burner for aeronautical applications. The experiments were focused on two main aspects: understanding the effect of the fuel spray on the unsteady air flow field and characterizing the fuel spray under unsteady flow conditions in terms of velocity and spatial distribution of the fuel droplets. The experimental campaign was performed with laser-based instrumentation (LDV, PDA and PIV) on a large-scale model of the LPP burner with air preheating and fuel injection in order to allow detailed measurements of the two-phase unsteady flow. The gas flow field is dominated by a spiral vortex breakdown phenomenon, which results in a complex unsteady flow configuration and an extended recirculation zone near the axis of the burner. The fuel droplets flow field is strongly correlated to the gas flow field. By comparing the results of the present experimental campaign with results obtained without fuel spray, there is evidence of a positive effect of the spray on the air flow field. The spray effect results in a reduction of the recirculation phenomenon in the exit section of the LPP burner. At the LPP burner exit a general satisfactory degree of vaporization is obtained. However, at the periphery of the premixing duct outlet section, a significant concentration of larger droplets of not yet vaporized fuel is present, due to the secondary air blast disintegration of the liquid film formed on the internal surface of the premixer tube. This phenomenon is responsible for lack of homogeneity of the fuel distribution in time and space at the premixer duct exit.

Flow Field of a Model Gas Turbine Swirl Burner

2012 ◽  
Vol 622-623 ◽  
pp. 1119-1124 ◽  
Author(s):  
Cheng Tung Chong ◽  
Simone Hochgreb
Keyword(s):  
Flow Field ◽  
Radial Velocity ◽  
Gas Turbine ◽  
Air Flow ◽  
Atmospheric Condition ◽  
Flow Fields ◽  
Swirl Flow ◽  
Scale Model ◽  
Swirl Burner ◽  
Swirling Air Flow

The flow field of a lab-scale model gas turbine swirl burner was characterised using particle imaging velocimetry (PIV) at atmospheric condition. The swirl burner consists of an axial swirler, a twin-fluid atomizer and a quartz tube as combustor wall. The main non-reacting swirling air flow without spray was compared to swirl flow with spray under unconfined and enclosed conditions. The introduction of liquid fuel spray changes the flow field of the main swirling air flow at the burner outlet where the radial velocity components are enhanced. Under reacting conditions, the enclosure generates a corner recirculation zone that intensifies the strength of the radial velocity. Comparison of the flow fields with a spray flame using diesel and palm biodiesel shows very similar flow fields. The flow field data can be used as validation target for swirl flame modelling.

CFD Modelling and LDA Measurements for the Air-Flow in an Aero-Engine Front Bearing Chamber

2010 ◽  
Author(s):  
J. Aidarinis ◽  
D. Missirlis ◽  
K. Yakinthos ◽  
A. Goulas
Keyword(s):  
Flow Field ◽  
Cooling System ◽  
Air Flow ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Experimental Measurements ◽  
Field Development ◽  
Lubricant Oil ◽  
Aero Engine ◽  
Engine Bearing

The constant development of aero engines towards lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increased demands of the lubrication systems, such as the bearing chambers of the aero engine. For this reason, it is of particular importance to increase our level of understanding of the flow field inside the bearing chambers in order to optimize its design and performance. The flow field in such cases is of a complicated nature since there is a strong interaction between air-flow and lubricant oil together with the geometrical configurations and the shaft rotational speed inside the bearing chamber. The behavior of this interaction must be investigated in order to understand the flow field development inside the aero engine bearing and, at a next step, optimize its performance in relation to the lubrication and heat transfer capabilities. Such an effort is presented in this work where an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided in two separate smaller sections where the flow passes from the first section partially through the bearing and the holding structure, to the second one where the vent and the scavenge are placed. The investigation was performed with the combined use of experimental measurements and Computational Fluid Dynamics (CFD) modeling. The experimental measurements were carried out with the use of a Laser Doppler Anemometry (LDA) system in an experimental rig modeling the front bearing chamber of an aero engine for real operating conditions taking into account both air-flow and lubricant oil-flow and for a varying number of shaft rotating speeds. The CFD modeling was performed with the use of a commercial CFD package. The air-flow inside the bearing was modeled with the adoption of a porous medium assumption. The experimental measurements and the CFD computations presented similar flow patterns and satisfactory quantitative agreement. At the same time the effect of the important parameters such as the air and oil mass flow together with the shaft rotation speed and the effect of the chamber inside geometry were identified. These conclusions can be exploited in future attempts in combination with the developed CFD model, in order to optimize the efficiency of the lubricant and cooling system. The latter forms the main target of this work which is the development of a useful engineering tool capable of predicting the flow field inside the aero engine bearing so as to be used for optimization efforts.

An Experimental Investigation of Air Water Flow Through Different Flow Field Designs of a PEMFC Bipolar Plate in the Presence of Micronized Wax

2011 ◽  
Author(s):  
Aditya Utturkar ◽  
Abhijit Mukherjee
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Flow Field ◽  
Proton Exchange Membrane ◽  
Water Movement ◽  
Air Flow ◽  
Bipolar Plate ◽  
Proton Exchange ◽  
Management Problem ◽  
Two Phase

Water, a byproduct of the chemical reaction in a Proton Exchange Membrane Fuel Cell (PEMFC), is removed by the air flowing over the cathode. However, when water production rate is more than its rate of removal, water may flood the fuel cell cathode, cutting off the air supply and stopping the reaction. A bio-mimetic solution to the water management problem was proposed in an earlier work where micronized wax was introduced along with the air that would help encapsulate the water droplets facilitating their quick removal from the fuel cell. Based on earlier results, further investigation is done to study different bi-polar flow field designs for effective water management, using bio-mimetic micronized wax. The different flow field designs studied in this work consists of parallel and single serpentine channels on graphite plates under simulated fuel cell load conditions. The effect of micronized wax on the two-phase flow regimes at different flow field orientations is also analyzed. It is clearly observed that the presence of micronized wax significantly helps in water movement in all air flow channels designs and orientations. It is hypothesized that introduction of micronized wax along with the air flow will allow the use of parallel flow field bi-polar plate designs in operating fuel cells with significantly reduced air side pressure drop instead of the prevalent single serpentine channel flow field designs.

Magnetic bubbles dynamics and heat transfer characteristics under influence of non-uniform magnetic fields

2021 ◽  
pp. 095440622110358
Author(s):  
MM Larimi ◽  
A Ramiar ◽  
H Ramyar ◽  
Hamid Kazemi Moghadam
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Boundary Layer ◽  
External Magnetic Field ◽  
Flow Field ◽  
Thermal Boundary Layer ◽  
Computational Study ◽  
Two Phase ◽  
Navier Stokes Equation ◽  
Vof Model

The computational study of transient immiscible and incompressible two-phase flows is one of the most common and desirable way for investigation of engineering phenomena and physics science. In the previous studies, generally bubbles current have been used as an active method for increasing heat transfer, however, due to existence of hydraulic boundary layers, the bubbles were not able to cross over this layer to thinning the thermal boundary layer and consequently the efficiency of this method was not very considerable. In this study, by considering potential of magnetic field, the effect of co-applying of external non uniform magnetic field and magnetic bubbles in enhancing the heat transfer efficiency in a 3-D tube has been investigated. The computational model consisted of the Navier–Stokes equation for liquid phase and VOF model for interface tracking are carried out by OpenFOAM. The external magnetic field has been considered non-uniform and time dependent. The results predicted that magnetic bubbles and external magnetic field due to their effect on thermal boundary layer increased significantly heat transfer and Nusselt number. Furthermore, results indicated magnetic bubbles can act as an active torbulators in the flow field and can be applied for increasing recirculation and secondary flow in the flow field. The average temperature and magnetic field over times for different cases have been discussed in the results.

Unsteady Aerodynamics of an Aero-Engine Double Swirler LPP Burner

2004 ◽  
Author(s):  
Edward Canepa ◽  
Pasquale Di Martino ◽  
Piergiorgio Formosa ◽  
Marina Ubaldi ◽  
Pietro Zunino
Keyword(s):  
Flow Field ◽  
Reynolds Stress ◽  
Large Scale ◽  
Unsteady Aerodynamics ◽  
Scale Model ◽  
Flow Structures ◽  
Laser Doppler Velocimeter ◽  
Formation Mechanisms ◽  
Stress Components ◽  
Aero Engine

Lean premixing prevaporizing burners represent a promising solution for low-emission combustion in aeroengines. Since lean premixed combustion suffers from pressure and heat release fluctuations that can be triggered by unsteady large-scale flow structures, a deep knowledge of flow structures formation mechanisms in complex swirling flows is a necessary step in suppressing combustion instabilities. The present paper describes a detailed investigation of the unsteady aerodynamics of a large scale model of a double swirler aero-engine LPP burner at isothermal conditions. A 3-D laser Doppler velocimeter and an ensemble averaging technique have been employed to obtain a detailed time-resolved description of the periodically perturbed flow field at the mixing duct exit and associated Reynolds stress and vorticity distributions. Results show a swirling annular jet with an extended region of reverse flow near to the axis. The flow is dominated by a strong periodic perturbation which occurs in all the three components of velocity. Radial velocity fluctuations cause important periodic displacement of the jet and the inner separated region in the meridional plane. The flow, as expected, is highly turbulent. The periodic stress components have the same order of magnitude of the Reynolds stress components. As a consequence the flow mixing process is highly enhanced. While turbulence acts on a large spectrum of fluctuation frequencies, the large scale motion influences the whole flow field in an ordered way that can be dangerous for stability in reactive conditions.

CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
J. Aidarinis ◽  
D. Missirlis ◽  
K. Yakinthos ◽  
A. Goulas
Keyword(s):  
Flow Field ◽  
Cooling System ◽  
Laser Doppler Anemometry ◽  
Air Flow ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Experimental Measurements ◽  
Field Development ◽  
Aero Engine ◽  
Engine Bearing

The continuous development of aero engines toward lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increasing demands on the lubrication system, such as the bearing chambers of an aero engine. For this reason, it is of particular importance to increase the level of understanding of the flow field inside the bearing chamber in order to optimize its design and improve its performance. The flow field inside a bearing chamber is complicated since there is a strong interaction between the sealing air-flow and the flow of lubrication oil, and both of them are affected by and interacting with the geometry of the chamber and the rotating shaft. In order to understand the flow field development and, as a next step, to optimize the aero engine bearing chamber performance, in relation to the lubrication and heat transfer capabilities, the behavior of this interaction must be investigated. In this work, an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided into two separate sections. The flow from the first section passes through the bearing and the bearing holding structure to the second one where the vent and the scavenging system are located. The investigation was performed with the combined use of experimental measurements and computational fluid dynamics (CFD) modeling. The experimental measurements were carried out using a laser Doppler anemometry system in an experimental rig, which consists of a 1:1 model of the front bearing chamber of an aero engine. Tests were carried out at real operating conditions both for the air-flow and for the lubricant oil-flow and for a range of shaft rotating speeds. The CFD modeling was performed using a commercial CFD package. Particularly, the air-flow through the bearing itself was modeled, adopting a porous medium technique, the parameters of which were developed in conjunction with the experiments. A satisfactory quantitative agreement between the experimental measurements and the CFD computations was achieved. At the same time, the effect of the important parameters such as the air and oil mass flow, together with the shaft rotational speed, and the effect of the chamber geometry were identified. The conclusions can be exploited in future attempts in combination with the CFD model developed in order to optimize the efficiency of the lubrication and cooling system. The latter forms the main target of this work, which is the development of a useful engineering tool capable of predicting the flow field inside the aero engine bearing, which can be used subsequently for optimization purposes.

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