Large Eddy Simulations of the Combustor Turbine Interface: Study of the Potential and Clocking Effects

2016 ◽  
Author(s):  
Charlie Koupper ◽  
Guillaume Bonneau ◽  
Laurent Gicquel ◽  
Florent Duchaine
Keyword(s):  
Flow Field ◽  
Leading Edge ◽  
Integrated Approach ◽  
Potential Effect ◽  
Interface Plane ◽  
Mean Flow ◽  
Lean Burn ◽  
Large Eddy ◽  
Inlet Conditions ◽  
Hot Streak

With the generalization of Lean Burn combustors, the flow field entering the turbine tends to feature higher levels of swirl, turbulence, while different hot streak patterns often emerge if compared to the previous generation of combustion chambers. In this context, the combustor-turbine interactions and more specifically the transport of hot streaks through the turbine need to be further analysed to gain engine performance and improved turbine life. Considering this new context, a non-reactive axial combustor simulator representative of a Lean Burn architecture, together with a 1.5 high pressure turbine stage is developed within the European project FACTOR. The interaction between these two modules is numerically investigated by performing Large Eddy Simulation (LES) of the combustor simulator equipped with two Nozzle Guide Vanes (NGVs). By using such an integrated approach, the combustor-turbine interface (plane 40) disappears, allowing: (i) more realistic inlet conditions to the turbine by suppressing all the assumptions associated with averaged profiles; (ii) to account for the potential effect of the vanes on the chamber. Note that if compared to classical approaches, the use of time-resolved LES has the advantage of well predicting the combustor mean flow and turbulence, resulting in more realistic flow properties at the turbine inlet as confirmed by previous works on this configuration. This paper focuses first on two LESs of the combustor-turbine specific configurations: i.e., two clocking positions of the hot streak relative to the NGVs. Significant changes on the thermal field around the vanes are highlighted. When the hot streak is injected in front of a vane leading edge, it considerably heats up the pressure side compared to the adjacent vane although the temperature field is quite uniform at the NGV exit because of the enhanced mixing of the hot streak. On the other hand, when the hot streak is injected in the passage between two adjacent vanes, it remains away from the vane walls preventing them from heating up. The hot streak however crosses the vane passage without being significantly distorted resulting in a more heterogeneous flow field at the rotor inlet. Second, the potential effect induced by the presence of the vanes is investigated by comparing the flow field inside the chamber with and without NGVs. It is found that the potential effect does not alter temperature patterns while a significant radial and azimuthal mass flow redistribution is observed up to about 25% axial chord length upstream of the vanes. The turbulence level is affected by the presence of vanes up to plane 40 when the hot streak is aligned with the passage.

Flow Field and Hot Streak Migration Through a High Pressure Cooled Vanes With Representative Lean Burn Combustor Outflow

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Tommaso Bacci ◽  
Tommaso Lenzi ◽  
Alessio Picchi ◽  
Lorenzo Mazzei ◽  
Bruno Facchini
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Flow Field ◽  
Fuel Injection ◽  
Leading Edge ◽  
Flame Stabilization ◽  
Lean Burn ◽  
Aero Engine ◽  
University Of Florence ◽  
Hot Streak

Modern lean burn aero-engine combustors make use of relevant swirl degrees for flame stabilization. Moreover, important temperature distortions are generated, in tangential and radial directions, due to discrete fuel injection and liner cooling flows respectively. At the same time, more efficient devices are employed for liner cooling and a less intense mixing with the mainstream occurs. As a result, aggressive swirl fields, high turbulence intensities, and strong hot streaks are achieved at the turbine inlet. In order to understand combustor-turbine flow field interactions, it is mandatory to collect reliable experimental data at representative flow conditions. While the separated effects of temperature, swirl, and turbulence on the first turbine stage have been widely investigated, reduced experimental data is available when it comes to consider all these factors together.In this perspective, an annular three-sector combustor simulator with fully cooled high pressure vanes has been designed and installed at the THT Lab of University of Florence. The test rig is equipped with three axial swirlers, effusion cooled liners, and six film cooled high pressure vanes passages, for a vortex-to-vane count ratio of 1:2. The relative clocking position between swirlers and vanes has been chosen in order to have the leading edge of the central NGV aligned with the central swirler. In order to generate representative conditions, a heated mainstream passes though the axial swirlers of the combustor simulator, while the effusion cooled liners are fed by air at ambient temperature. The resulting flow field exiting from the combustor simulator and approaching the cooled vane can be considered representative of a modern Lean Burn aero engine combustor with swirl angles above ±50 deg, turbulence intensities up to about 28% and maximum-to-minimum temperature ratio of about 1.25. With the final aim of investigating the hot streaks evolution through the cooled high pressure vane, the mean aerothermal field (temperature, pressure, and velocity fields) has been evaluated by means of a five-hole probe equipped with a thermocouple and traversed upstream and downstream of the NGV cascade.

Flow Field and Hot Streak Migration Through High Pressure Cooled Vanes With Representative Lean Burn Combustor Outflow

2018 ◽  
Author(s):  
T. Bacci ◽  
T. Lenzi ◽  
A. Picchi ◽  
L. Mazzei ◽  
B. Facchini
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Flow Field ◽  
Fuel Injection ◽  
Leading Edge ◽  
Flame Stabilization ◽  
Lean Burn ◽  
Aero Engine ◽  
University Of Florence ◽  
Hot Streak

Modern lean burn aero-engine combustors make use of relevant swirl degrees for flame stabilization. Moreover important temperature distortions are generated, in tangential and radial directions, due to discrete fuel injection and liner cooling flows respectively. At the same time, more efficient devices are employed for liner cooling and a less intense mixing with the mainstream occurs. As a result, aggressive swirl fields, high turbulence intensities and strong hot streaks are achieved at the turbine inlet. In order to understand combustor-turbine flow field interactions, it is mandatory to collect reliable experimental data at representative flow conditions. While the separated effects of temperature, swirl and turbulence on the first turbine stage have been widely investigated, reduced experimental data is available when it comes to consider all these factors together. In this perspective, an annular three-sector combustor simulator with fully cooled high pressure vanes has been designed and installed at the THT Lab of University of Florence. The test rig is equipped with three axial swirlers, effusion cooled liners and six film cooled high pressure vanes passages, for a vortex-to-vane count ratio of 1:2. The relative clocking position between swirlers and vanes has been chosen in order to have the leading edge of the central NGV aligned with the central swirler. In order to generate representative conditions, a heated mainstream passes though the axial swirlers of the combustor simulator, while the effusion cooled liners are fed by air at ambient temperature. The resulting flow field exiting from the combustor simulator and approaching the cooled vane can be considered representative of a modern Lean Burn aero engine combustor with swirl angles above ±50°, turbulence intensities up to about 28% and maximum-to-minimum temperature ratio of about 1.25. With the final aim of investigating the hot streaks evolution through the cooled high pressure vane, the mean aerothermal field (temperature, pressure and velocity fields) has been evaluated by means of a five hole probe equipped with a thermocouple and traversed upstream and downstream of the NGV cascade.

Investigation on hydrodynamic forces leading to coarse particle entrainment using Large-Eddy Simulations

2021 ◽  
Author(s):  
Gaston Latessa ◽  
Angela Busse ◽  
Manousos Valyrakis
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Large Scale ◽  
Large Eddy Simulations ◽  
Flow Conditions ◽  
Mean Flow ◽  
Protection Measures ◽  
Practical Applications ◽  
Particle Entrainment ◽  
Large Eddy

<p>The prediction of particle motion in a fluid flow environment presents several challenges from the quantification of the forces exerted by the fluid onto the solids -normally with fluctuating behaviour due to turbulence- and the definition of the potential particle entrainment from these actions. An accurate description of these phenomena has many practical applications in local scour definition and to the design of protection measures.</p><p>In the present work, the actions of different flow conditions on sediment particles is investigated with the aim to translate these effects into particle entrainment identification through analytical solid dynamic equations.</p><p>Large Eddy Simulations (LES) are an increasingly practical tool that provide an accurate representation of both the mean flow field and the large-scale turbulent fluctuations. For the present case, the forces exerted by the flow are integrated over the surface of a stationary particle in the streamwise (drag) and vertical (lift) directions, together with the torques around the particle’s centre of mass. These forces are validated against experimental data under the same bed and flow conditions.</p><p>The forces are then compared against threshold values, obtained through theoretical equations of simple motions such as rolling without sliding. Thus, the frequency of entrainment is related to the different flow conditions in good agreement with results from experimental sediment entrainment research.</p><p>A thorough monitoring of the velocity flow field on several locations is carried out to determine the relationships between velocity time series at several locations around the particle and the forces acting on its surface. These results a relevant to determine ideal locations for flow investigation both in numerical and physical experiments.</p><p>Through numerical experiments, a large number of flow conditions were simulated obtaining a full set of actions over a fixed particle sitting on a smooth bed. These actions were translated into potential particle entrainment events and validated against experimental data. Future work will present the coupling of these LES models with Discrete Element Method (DEM) models to verify the entrainment phenomena entirely from a numerical perspective.</p>

scholarly journals Interpreting Aerodynamics of a Transonic Impeller from Static Pressure Measurements

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Fangyuan Lou ◽  
John Charles Fabian ◽  
Nicole Leanne Key
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Pressure Measurements ◽  
High Loss ◽  
Supersonic Inlet ◽  
Mach Numbers ◽  
Inlet Conditions

This paper investigates the aerodynamics of a transonic impeller using static pressure measurements. The impeller is a high-speed, high-pressure-ratio wheel used in small gas turbine engines. The experiment was conducted on the single stage centrifugal compressor facility in the compressor research laboratory at Purdue University. Data were acquired from choke to near-surge at four different corrected speeds (Nc) from 80% to 100% design speed, which covers both subsonic and supersonic inlet conditions. Details of the impeller flow field are discussed using data acquired from both steady and time-resolved static pressure measurements along the impeller shroud. The flow field is compared at different loading conditions, from subsonic to supersonic inlet conditions. The impeller performance was strongly dependent on the inducer, where the majority of relative diffusion occurs. The inducer diffuses flow more efficiently for inlet tip relative Mach numbers close to unity, and the performance diminishes at other Mach numbers. Shock waves emerging upstream of the impeller leading edge were observed from 90% to 100% corrected speed, and they move towards the impeller trailing edge as the inlet tip relative Mach number increases. There is no shock wave present in the inducer at 80% corrected speed. However, a high-loss region near the inducer throat was observed at 80% corrected speed resulting in a lower impeller efficiency at subsonic inlet conditions.

Reducing Instrumentation Errors Caused by Circumferential Flow-Field Variations in Multistage Axial Compressors

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
M. Chilla ◽  
G. Pullan ◽  
S. Gallimore
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Sampling Error ◽  
Leading Edge ◽  
Stagnation Pressure ◽  
Wave Number ◽  
Stagnation Temperature ◽  
Sampling Errors ◽  
Mean Flow ◽  
Axial Compressors

Abstract The effects of blade row interactions on stator-mounted instrumentation in axial compressors are investigated using unsteady numerical calculations. The test compressor is an eight-stage machine representative of an aero-engine core compressor. For the unsteady calculations, a 180-deg sector (half-annulus) model of the compressor is used. It is shown that the time-mean flow field in the stator leading edge planes is circumferentially nonuniform. The circumferential variations in stagnation pressure and stagnation temperature, respectively, reach 4.2% and 1.1% of the local mean. Using spatial wave number analysis, the incoming wakes from the upstream stator rows are identified as the dominant source of the circumferential variations in the front and middle of the compressor, while toward the rear of the compressor, the upstream influence of the eight struts in the exit duct becomes dominant. Based on three circumferential probes, the sampling errors for stagnation pressure and stagnation temperature are calculated as a function of the probe locations. Optimization of the probe locations shows that the sampling error can be reduced by up to 77% by circumferentially redistributing the individual probes. The reductions in the sampling errors translate to reductions in the uncertainties of the overall compressor efficiency and inlet flow capacity by up to 50%. Recognizing that data from large-scale unsteady calculations are rarely available in the instrumentation phase for a new test rig or engine, a method for approximating the circumferential variations with single harmonics is presented. The construction of the harmonics is based solely on the knowledge of the number of stators in each row and a small number of equispaced probes. It is shown how excursions in the sampling error are reduced by increasing the number of circumferential probes.

Experimental and Numerical Investigation of the Unsteady Leakage Flow Through the Rotor Tip Labyrinth of a 1.5-Stage Axial Turbine

2005 ◽  
Author(s):  
K. Wolter ◽  
A. Giboni ◽  
P. Peters ◽  
J. R. Menter ◽  
H. Pfost
Keyword(s):  
Flow Field ◽  
Flow Direction ◽  
Three Dimensional ◽  
Calculated Data ◽  
Leading Edge ◽  
Numerical Data ◽  
Potential Effect ◽  
Main Flow ◽  
Leakage Flow ◽  
Axial Turbine

This paper presents the results of unsteady probe measurements and numerical flow calculations in a 1.5-stage low speed axial turbine with a straight labyrinth seal on a rotor shroud. The unsteady development of the leakage flow in the three cavities is described and analysed in detail. For the investigation of the leakage flow detailed time-accurate measurements of the three-dimensional flow field were carried out in five measurement planes from casing to the rotor shroud over more than one pitch. These measurements were carried out with a miniature pneumatic five-hole probe and miniature triple hot-wire probes. Both probes have a spherical head for better adjustment in flow direction. The high resolution of 330 measurement points in each of the five measurement planes represents the flow field in great detail. The unsteady experimental data was compared with the results of the unsteady numerical simulation of the turbine flow, calculated by the 3D-Navier-Stokes Solver CFX-TASCflow. The calculated data correspond well with the experimental results and allow a detailed analysis of the flow in the cavities of the labyrinth. As demonstrated in this paper the investigations show that the leakage flow at the inlet ant outlet of the labyrinth is strongly influenced by the different positions of the rotor to the stator. The unsteady experimental and numerical data indicates intensive effects of the leakage flow caused and influenced by the trailing edge of the first stator and the potential effect of the rotor leading edge. An intensive vortex develops depending on the rotor position in the first cavity. This vortex is also influenced by a small corner vortex above the axial inlet gap of the labyrinth. After the fins this unsteady influence of the leakage flow decreases and below the jet a large vortex moves in circumferential direction. The intensity of this circulation vortex is reduced at the end of the last cavity due to the interaction with the main flow and the flow direction out of the labyrinth. Therefore the unsteady behaviour of the leakage flow grows up, which is also caused by its uneven entry into the main flow.

Assessment of RANS Against LES for the Aero-Thermal Behavior of High Pressure Turbine Stages Under Realistic Inlet Conditions

2016 ◽  
Author(s):  
Stefano Vagnoli ◽  
Tom Verstraete ◽  
Charlie Koupper ◽  
Guillaume Bonneau
Keyword(s):  
High Pressure ◽  
Thermal Behavior ◽  
Turbulence Modeling ◽  
Engine Performance ◽  
High Pressure Turbine ◽  
Lean Burn ◽  
Field Development ◽  
Safety Margins ◽  
Inlet Conditions ◽  
Hot Streak

Modern Lean Burn combustors generate a complex field at the High Pressure turbine (HPT) inlet, characterized by non-uniform velocity and temperature distributions, together with very high turbulence levels (up to 25%). For these extreme conditions, classical numerical methods employed for the HPT design, such as Reynolds Averaged Navier Stokes (RANS) simulation, suffer from a lack of validation. This leads to a reduced confidence in predicting the combustor-turbine interactions, which requires to use extra safety margins, to the detriment of the overall engine performance. Within the European FACTOR project, a 360° non reactive combustor simulator and a 1.5 HPT stage are designed to get more insight into the mutual interaction of these two components. A first experimental and numerical campaign has demonstrated the potential of Large Eddy Simulations (LES) to accurately reproduce the turbulent flow field development at the combustor outlet. The aim of the present paper is to exploit the accuracy of LES to validate less time-consuming RANS models in predicting the hot streak migration in the turbine stage. In this sense, LES results are used as a reference to discriminate the different RANS simulations in terms of turbulence modeling and aerothermal predictions. The current investigations clearly indicate that turbulence and hot streak diffusion within the HPT are strongly linked. In this sense, the choice of the RANS turbulence model and the inlet turbulent conditions plays a major role in modeling the thermal behavior for the stator and rotor blades.

The Impact of Compressor Exit Conditions on Fuel Injector Flows

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
C. L. Ford ◽  
J. F. Carrotte ◽  
A. D. Walker
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Numerical Data ◽  
Flow Fields ◽  
Main Reaction ◽  
Fuel Injector ◽  
Lean Burn ◽  
Field Development ◽  
Inlet Conditions ◽  
The Impact

This paper examines the effect of compressor generated inlet conditions on the air flow uniformity through lean burn fuel injectors. Any resulting nonuniformity in the injector flow field can impact on local fuel air ratios and hence emissions performance. The geometry considered is typical of the lean burn systems currently being proposed for future, low emission aero engines. Initially, Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) predictions were used to examine the flow field development between compressor exit and the inlet to the fuel injector. This enabled the main flow field features in this region to be characterized along with identification of the various stream-tubes captured by the fuel injector passages. The predictions indicate the resulting flow fields entering the injector passages are not uniform. This is particularly evident in the annular passages furthest away from the injector centerline which pass the majority of the flow which subsequently forms the main reaction zone within the flame tube. Detailed experimental measurements were also undertaken on a fully annular facility incorporating an axial compressor and lean burn combustion system. The measurements were obtained at near atmospheric pressure/temperatures and under nonreacting conditions. Time-resolved and time-averaged data were obtained at various locations and included measurements of the flow field issuing from the various fuel injector passages. In this way any nonuniformity in these flow fields could be quantified. In conjunction with the numerical data, the sources of nonuniformities in the injector exit plane were identified. For example, a large scale bulk variation (+/−10%) of the injector flow field was attributed to the development of the flow field upstream of the injector, compared with localized variations (+/−5%) that were generated by the injector swirl vane wakes. Using this data the potential effects on fuel injector emissions performance can be assessed.

Computational investigation and passive control of vehicle sunroof buffeting

2019 ◽  
Vol 26 (9-10) ◽  
pp. 747-756
Author(s):  
Yansong He ◽  
Quanzhou Zhang ◽  
Changfa An ◽  
Yong Wang ◽  
Zhongming Xu ◽  
...  
Keyword(s):  
Flow Field ◽  
Passive Control ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
The Road ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Utility Vehicle

A computational fluid dynamics simulation method based on large eddy simulation is presented and applied to compute the sunroof buffeting of a sport utility vehicle. The simulation result, i.e. the buffeting level curve, coincides well with the road test. The simulation method is then employed to investigate the sunroof buffeting of a vehicle during the development process in the range of 30 km/h–90 km/h. The results show that the most severe sunroof buffeting occurs at 70 km/h, which corresponds to the resonant frequency of the cabin. Flow field visualizations reveal that strong pressure fluctuations are generated inside the cabin due to vortex shedding from the leading edge and impinging onto the trailing edge of the sunroof opening, which explains the mechanism of sunroof buffeting. A new deflector with a gap and a notched upper edge is designed to replace the original castle type deflector. The simulation results show that the newly designed deflector can reduce the buffeting level to 97.9 dB; that is, the sunroof buffeting is completely eliminated. Moreover, the phenomenon of sunroof buffeting reduction is explained by comparing and analyzing the flow field between the newly designed deflector and the original deflector.

scholarly journals Large Eddy Simulation of Self-Excited Oscillation Pulsed Jet (SEOPJ) Induced by a Helmholtz Oscillator in Underground Mining

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2161 ◽  
Author(s):  
Zhenlong Fang ◽  
Qiang Wu ◽  
Mengda Zhang ◽  
Haoyang Liu ◽  
Pan Jiang ◽  
...  
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Coherent Structure ◽  
Underground Mining ◽  
Operating Pressure ◽  
Mean Flow ◽  
The Core ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Field Characteristics

Pulsed waterjet can break rocks effectively by taking advantage of the water hammer effect, and is thus widely used in mining, petroleum, and natural gas fields. With the aim to further clarify the flow field characteristics of pulsed jets induced by a Helmholtz oscillator, large eddy simulation was conducted under different operating pressures. The velocity distribution, mean flow field, and the coherent structure were examined using the oscillators of different cavity lengths and diameters. The results clearly showed that the major frequency of jet pulsation gradually increased with the increase of operating pressure. A stable periodic velocity core was formed at the outlet of the Helmholtz oscillator, while the external flow field was subjected to periodic impact. As a result, the ambient fluid was strongly entrained into the jet beam. With the increase of the cavity length, the length of the core segment decreased while the energy loss caused by the cavity increased, which was also accompanied by a rapid attenuation of the axial velocity at the jet outlet. The coherent structure of the jet in the oscillator with small cavity diameter was more disordered near the nozzle outlet, and the vortex scale was larger. The effect of cavity diameter can be reflected in the feedback modulation of the jet in the cavity. Compared with the conical nozzle, the length of the core section of the jet was shorter, but the jet had better bunching, a smaller diffusion angle, and better mixing performance. These results provide a further understanding of the characteristics of pulsed water jet for better utilizations in the fields of energy exploitation.

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