Experimental and Numerical Investigation on Windage Power Losses in High Speed Gears

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Daniele Massini ◽  
Tommaso Fondelli ◽  
Antonio Andreini ◽  
Bruno Facchini ◽  
Lorenzo Tarchi ◽  
...  
Keyword(s):  
High Speed ◽  
Spur Gear ◽  
Relative Magnitude ◽  
Navier Stokes ◽  
Power Losses ◽  
Test Rig ◽  
Viscosity Models ◽  
Image Velocimetry ◽  
And Performance ◽  
Aero Engines

Enhancing the efficiency of gearing systems is an important topic for the development of future aero-engines with low specific fuel consumption. An evaluation of its structure and performance is mandatory in order to optimize the design as well as maximize its efficiency. Mechanical power losses are usually distinguished into two main categories: load-dependent and load-independent losses. The former are all those associated with the transmission of torque, while the latter are tied to the fluid dynamics of the environment, which surrounds the gears. The relative magnitude of these phenomena is dependent on the operative conditions of the transmission: load-dependent losses are predominant at slow speeds and high torque conditions, load-independent mechanisms become prevailing in high speed applications, like in turbomachinery. A new test rig was designed for investigating windage power losses resulting by a single spur gear rotating in a free oil environment. The test rig allows the gear to rotate at high speed within a box where pressure and temperature conditions can be set and monitored. An electric spindle, which drives the system, is connected to the gear through a high accuracy torque meter, equipped with a speedometer providing the rotating velocity. The test box is fitted with optical accesses in order to perform particle image velocimetry (PIV) measurements for investigating the flow field surrounding the rotating gear. The experiment has been computationally replicated, performing Reynolds-averaged Navier–Stokes (RANS) simulations in the context of conventional eddy viscosity models, achieving good agreement for all of the speed of rotations.

Experimental and Numerical Investigation on Windage Power Losses in High Speed Gears

2017 ◽  
Author(s):  
D. Massini ◽  
T. Fondelli ◽  
A. Andreini ◽  
B. Facchini ◽  
L. Tarchi ◽  
...  
Keyword(s):  
High Speed ◽  
Power Transmission ◽  
Fluid Dynamic ◽  
Spur Gear ◽  
Cooling Capacity ◽  
Relative Magnitude ◽  
Power Losses ◽  
Test Rig ◽  
Aero Engines ◽  
Cooling And Lubrication

Enhancing the efficiency of gearing systems is an important topic for the development of future aero-engines with low specific fuel consumption. The transmission system in fact has a direct impact on the engine overall efficiency by means of its weight contribution, internal power losses and lubrication requirements. Thus, an evaluation of its structure and performance is mandatory in order to optimize the design as well as maximize its efficiency. Gears are among the most efficient power transmission systems, whose efficiencies can exceed 99 %, nevertheless in high speed applications power losses are anything but negligible. All power dissipated through losses is converted into heat that must be dissipated by the lubrication system. More heat leads to a larger cooling capacity, which results in more oil, larger heat exchangers which finally means more weight. Mechanical power losses are usually distinguished in two main categories: load-dependent and load-independent losses. The former are all those associated with the transmission of torque, while the latter are tied to the fluid-dynamics of the environment which surrounds the gears, namely windage, fluid trapping and squeezing between meshing gear teeth and inertial losses resulting by the impinging oil jets, usually adopted in high speed transmission for cooling and lubrication purposes. The relative magnitude of these phenomena is strongly dependent on the operative conditions of the transmission. While load-dependent losses are predominant at slow speeds and high torque conditions, load-independent mechanisms become prevailing in high speed applications, like in turbomachinery. Among fluid-dynamic losses, windage is extremely important and can dominate the other mechanisms. In this context, a new test rig was designed for investigating windage power losses resulting by a single spur gear rotating in a free oil environment. The test rig allows the gear to rotate at high speed within a box where pressure and temperature conditions can be set and monitored. An electric spindle, which drives the system, is connected to the gear through a high accuracy torque meter, equipped with a speedometer providing the rotating velocity. The test box is fitted with optical accesses in order to perform particle image velocimetry measurements for investigating the flow-field surrounding the rotating gear. The experiment has been computationally replicated, performing RANS simulations in the context of conventional eddy viscosity models. The numerical results were compared with experimental data in terms of resistant torque as well as PIV measurements, achieving a good agreement for all of the speed of rotations.

Numerical Study of Deterministic Fluxes in Compressor Passages

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Navier Stokes ◽  
Design Stage ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Radial Profiles ◽  
And Performance ◽  
Stage Matching ◽  
Unsteady Effects

Computational fluid dynamics (CFD) has been widely adopted in the compressor design process, but it remains a challenge to predict the flow details, performance, and stage matching for multistage, high-speed machines accurately. The Reynolds Averaged Navier-Stokes (RANS) simulation with mixing plane for bladerow coupling is still the workhorse in the industry and the unsteady bladerow interaction is discarded. This paper examines these discarded unsteady effects via deterministic fluxes using semi-analytical and unsteady RANS (URANS) calculations. The study starts from a planar duct under periodic perturbations. The study shows that under large perturbations, the mixing plane produces dubious values of flow quantities (e.g., whirl angle). The performance of the mixing plane can be considerably improved by including deterministic fluxes into the mixing plane formulation. This demonstrates the effect of deterministic fluxes at the bladerow interface. Furthermore, the front stages of a 19-blade row compressor are investigated and URANS solutions are compared with RANS mixing plane solutions. The magnitudes of divergence of Reynolds stresses (RS) and deterministic stresses (DS) are compared. The effect of deterministic fluxes is demonstrated on whirl angle and radial profiles of total pressure and so on. The enhanced spanwise mixing due to deterministic fluxes is also observed. The effect of deterministic fluxes is confirmed via the nonlinear harmonic (NLH) method which includes the deterministic fluxes in the mean flow, and the study of multistage compressor shows that unsteady effects, which are quantified by deterministic fluxes, are indispensable to have credible predictions of the flow details and performance of compressor even at its design stage.

Hybrid RANS-LES Modeling of the Aerothermal Field in an Annular Hot Streak Generator for the Study of Combustor–Turbine Interaction

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
A. Andreini ◽  
T. Bacci ◽  
M. Insinna ◽  
L. Mazzei ◽  
S. Salvadori
Keyword(s):  
Navier Stokes ◽  
Test Rig ◽  
Complex Flow ◽  
Lean Burn ◽  
Flow Physics ◽  
Safety Margins ◽  
Viable Approach ◽  
Sas Model ◽  
Aero Engines ◽  
Eu Project

The adoption of lean-burn technology in modern aero-engines influences the already critical aerothermal conditions at turbine entry, where the absence of dilution holes preserves the swirl component generated by burners and prevents any control on pattern factor. The associated uncertainty and lack of confidence entail the application of wide safety margins in turbine cooling design, with a detrimental effect on engine efficiency. Computational fluid dynamics (CFD) can provide a deeper understanding of the physical phenomena involved in combustor–turbine interaction, especially with hybrid Reynolds-averaged Navier–Stokes (RANS) large eddy simulation (LES) models, such as scale adaptive simulation (SAS), which are proving to overcome the well-known limitations of the RANS approach and be a viable approach to capture the complex flow physics. This paper describes the numerical investigation on a test rig representative of a lean-burn, effusion cooled, annular combustor developed in the EU Project Full Aerothermal Combustor-Turbine interactiOns Research (FACTOR) with the aim of studying combustor–turbine interaction. Results obtained with RANS and SAS were critically compared to experimental data and analyzed to better understand the flow physics, as well as to assess the improvements related to the use of hybrid RANS-LES models. Significant discrepancies are highlighted for RANS in predicting the recirculating region, which has slight influence on the velocity field at the combustor outlet, but affects dramatically mixing and the resulting temperature distribution. The accuracy of the results achieved suggests the exploitation of SAS model with a view to the future inclusion of the nozzle guide vanes in the test rig.

Comparison of the CFD Results to PIV Measurements in Kinematics of Spilling and Plunging Breakers

2020 ◽  
Author(s):  
Bülent Düz ◽  
Jule Scharnke ◽  
Rink Hallmann ◽  
Jan Tukker ◽  
Siddhant Khurana ◽  
...  
Keyword(s):  
High Speed ◽  
Piecewise Linear ◽  
Sampling Rate ◽  
Navier Stokes ◽  
Computational Domain ◽  
Cfd Simulations ◽  
High Sampling Rate ◽  
Interface Reconstruction ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Cfd

Abstract The kinematics under spilling and plunging breakers are investigated using both experimental and numerical methods. In a modular laboratory flume, the breakers were generated using dispersive focusing, and the kinematics underneath them were measured utilizing the Particle Image Velocimetry (PIV) technique. Using the state-of-art high-speed video cameras and lasers, the kinematics were measured at a high sampling rate without needing phase-locked averaging. Afterwards, Computational Fluid Dynamics (CFD) simulations were carried out for comparison purposes. These simulations were run in single-phase using a finite-volume based Navier-Stokes solver with a piecewise-linear interface reconstruction scheme. The spilling and plunging breakers from the measurements were reconstructed in the computational domain using an iterative scheme. As a result a good match with the measured waves was obtained in the simulations. Results indicate that even though measured kinematics are somewhat higher than the simulated ones especially in the spilling and overturning regions, the CFD simulations can accurately capture the relevant details of the flow and produce reasonably accurate kinematics in comparison with the PIV results.

Hybrid RANS-LES Modeling of the Aero-Thermal Field in an Annular Hot Streak Generator for the Study of Combustor-Turbine Interaction

2016 ◽  
Author(s):  
A. Andreini ◽  
T. Bacci ◽  
M. Insinna ◽  
L. Mazzei ◽  
S. Salvadori
Keyword(s):  
Navier Stokes ◽  
Test Rig ◽  
Lean Burn ◽  
Turbine Cooling ◽  
Safety Margins ◽  
Viable Approach ◽  
Sas Model ◽  
Aero Engines ◽  
Eu Project ◽  
Nozzle Guide

Turbine entry conditions are characterized by unsteady and strongly non-uniform velocity, temperature and pressure fields. The uncertainty and the lack of confidence associated with these conditions require the application of wide safety margins during the design of the turbine cooling systems, with a detrimental effect on engine efficiency. The adoption of lean-burn technology in modern aero-engines to reduce NOx emissions exacerbates the situation, as the absence of dilution holes keeps the strong swirl component generated by the burners up to the combustor outlet and prevents to control the pattern factor. Complexity and costs associated with the experimental investigation of combustor-turbine interaction, makes Computational Fluid Dynamics (CFD) paramount to understand the physical phenomena involved. Moreover, due to the well-known limitations of the Reynolds-Averaged Navier-Stokes (RANS) approach and the increase in computational resources, hybrid RANS-LES models, such as Scale Adaptive Simulation (SAS), are proving to be a viable approach to capture the main structures of the flow field. This paper reports the main findings of the numerical investigation on a test rig representative of a lean-burn, effusion cooled, annular combustor, developed in the context of the EU Project FACTOR (Full Aerothermal Combustor-Turbine interactiOns Research) with the aim of studying combustor-turbine interaction. Results obtained with RANS and unsteady SAS were critically compared to experimental data and analysed in order to better understand the flow physics within such a device, as well as to assess the improvements related to the use of hybrid models. The main discrepancies between RANS and SAS are highlighted in predicting the recirculating region, which has slight influence on the velocity field at the combustor outlet, but affects dramatically mixing and the resulting temperature distribution. Accuracy of the results achieved suggest a possible exploitation of SAS model with a view to the future inclusion of the nozzle guide vanes within the test rig.

Downward pointing winglet design and assessment within the M-DAW research project

2009 ◽  
Vol 113 (1142) ◽  
pp. 221-232 ◽  
Author(s):  
J.-L. Hantrais-Gervois ◽  
R. Grenon ◽  
A. Mann ◽  
A. Büscher
Keyword(s):  
Performance Analysis ◽  
Wind Tunnel ◽  
Design Process ◽  
High Speed ◽  
Bending Moment ◽  
Navier Stokes ◽  
Structural Modifications ◽  
And Performance ◽  
Wing Tip ◽  
Transonic Wind Tunnel

AbstractThe design and performance analysis of a wing tip device proposed within the M-DAW project by ONERA is presented. A proto-design process is described and the device was thoroughly assessed (mainly with Reynolds-Averaged Navier-Stokes simulations). The process was further explained through wind-tunnel tests at both low speed and high speed in the pressurised and cryogenic European transonic wind tunnel in Cologne. The device is a downward pointing winglet designed for a retrofit scenario (the wing could be modified only within the 96% – 100% bounds of the span). It was designed to keep the wing root bending moment of the clean wing at cruise unchanged so that the aerodynamic gains are the net gains provided by the device that can be directly installed without structural modifications of the wing.

scholarly journals PIV Measurements of the Wake Formation from a Rough Flat Plate

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Sean Lawrence ◽  
Callum Atkinson ◽  
Julio Soria
Keyword(s):  
Surface Roughness ◽  
Flat Plate ◽  
High Speed ◽  
Large Scale ◽  
Near Wake ◽  
Image Velocimetry ◽  
Wide Range ◽  
Smooth Body ◽  
And Performance ◽  
Effect Of Surface

Wake flows are prevalent in a wide range of engineering applications and their behaviour can significantly impact engineering design and performance. A considerable body of work exists on smooth body wake structures and flows over rough bodies, however, there is a lack of fundamental physical understanding of the amalgamation of the two fields. Two-component two-dimension particle image velocimetry (2C-2D PIV) is used to investigate the effect of surface roughness on the formation of large scale structures in the near wake of a thin flat plate. Both high-speed and low-speed, high-resolution PIV setups have been used to investigate the effect of surface roughness on the boundary layer and the near wake of the plate to gain insight into the underlying physical connection between these regions.

Windage and Churning Effects in Dipped Lubrication

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Anant S. Kolekar ◽  
Andrew V. Olver ◽  
Adam E. Sworski ◽  
Frances E. Lockwood
Keyword(s):  
Energy Loss ◽  
Spur Gear ◽  
Inertial Forces ◽  
Simple Test ◽  
Power Losses ◽  
Test Rig ◽  
Liquid Lubricant ◽  
Medium Speed ◽  
Significant Interest ◽  
Fluid Properties

In dipped (splash) lubrication, a rotating component, such as a gear, is partly submerged in a reservoir of liquid lubricant and acts to distribute it within the lubricated machine. Dipped lubrication is widely used for low to medium speed applications in the industrial and automotive sectors and there is a significant interest in the associated energy loss (the “churning” loss) because of its influence on efficiency and fuel consumption. In this study, a simple test rig consisting of a spur gear rotating in a cylindrical enclosure, partly filled with a liquid, was used to study the effect of fluid properties on the churning loss. The inertia rundown method was used to determine the power losses. Lubricating oils, water and aqueous glycerol solutions were among the fluids used. Correlations with Froude and Reynolds and Bond numbers are presented. It was found that the churning losses were significantly affected by the fluid disposition within the housing. In turn this was affected by the ratio of inertial forces to gravity (Froude number) and by air pressure. The influence of the pressure of the air within the enclosure was also investigated. When the air was evacuated from the enclosure, the churning losses increased, by a factor of up to 4.5 times. This can be explained by the effect of air (windage and aeration) on the liquid disposition, factors neglected in most previous work.

Rotating tip clearance asymmetry and role of endwall injection in stability desensitization of a transonic fan

2021 ◽  
pp. 095765092110567
Author(s):  
Hossein Khaleghi
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Transonic Compressor ◽  
And Performance ◽  
Tip Injection ◽  
The Stability ◽  
Transonic Fan

The current study is aimed at understanding the effect of rotating tip clearance asymmetry on the operability and performance of a transonic compressor. Another objective of this investigation is to determine the influence of tip injection on reducing the detrimental effects of clearance asymmetry. Three dimensional unsteady Reynolds-averaged Navier–stokes simulations have been performed from choke to stall for different arrangements of non-uniform blade heights in a transonic fan. Furthermore, numerical computations have been conducted with endwall injection of air. The numerical results have been validated against experimental data. Results show that having the same mean tip clearance, the asymmetric compressor is less stable than the axisymmetric configuration. However, the peak pressure rise is found to be almost linearly correlated to the mean tip clearance for both the axisymmetric and asymmetric compressors. It is found that tip injection can desensitize the compressor to the tip clearance asymmetry. Results further reveal that tip clearance asymmetry does not change the compressor path to instability. However, endwall injection is found to be able to change the compressor stalling mode. Investigations concerning rotating non-uniformity (caused by non-uniform blade heights) are very few in open literature. The obtained results can assist in predicting the effect of rotating tip clearance asymmetry on the stability and performance of high-speed compressor rotors. Furthermore, the results uncover how tip injection can desensitize the compressor stability and affect its path into instability, which is one of the most important questions in the turbomachinery world.

Application of a Multistage Casing Treatment in a High Speed Axial Compressor Test Rig

2011 ◽  
Author(s):  
T. Kroeckel ◽  
S. J. Hiller ◽  
P. Jeschke
Keyword(s):  
High Speed ◽  
Flow Analysis ◽  
Axial Compressor ◽  
Aircraft Engine ◽  
Test Rig ◽  
Local Flow ◽  
Casing Treatment ◽  
And Performance ◽  
The Impact ◽  
Casing Treatments

The subject of this paper is the experimental investigation of the overall performance and local aerodynamics of a 2.5 stage axial compressor test rig with a two stage casing treatment. Casing treatments are a well known method to aerodynamically stabilize the near stall compressor aerodynamics. However, in the past, casing treatments have only been applied to high aspect ratio front stages. This investigation puts the focus on the impact of advanced casing treatments applied to both rotors of a high speed compressor test rig. The rotors’ geometric and aerodynamic features are identical to those seen in the rear stages of aircraft engine high pressure compressors. Based on experimental results, we explain the casing treatment’s effect on the local flow phenomena as well as its influence on the compressor operability and performance. In order to clearly quantify the casing treatment’s influence, all measurements are conducted twice: for the rig without casing treatments and for an identical rig with casing treatments. The analysis of experimental data confirms that multistage casing treatments are able to significantly push the surge line towards higher pressure ratios and lower mass flow rates without any significant degradation of the peak efficiency. However, detailed flow analysis and the comparison of the configurations with and without casing treatments reveal that the flow is significantly redistributed by the effect of the casing. The present effort was conducted as part of the EU integrated program for New Aero Engine Core Concepts (NEWAC).

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