bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validation of Transonic Axial Compressor Stage Unsteady-State Rotor-Stator Simulations
Authors: Galpin Paul , Hansen Thorsten , Scheuerer Georg , Kelly Ryan , Hickman Adam , Jemcov Aleksandar , Morris Scott C. 
Published: August 2017

The paper describes the validation of steady-state and unsteady CFD simulations against experimental data from a single-stage, transonic axial compressor stage. The experimental data include overall compressor performance, high-resolution traverses of total pressure and total temperature, and unsteady-state total pressure measurements downstream of the rotor.
Various numerical rotor-stator interaction methods were applied across the operational speedline. These included a steady-state method mixing plane, and a transient time inclination method that accounts for the unsteady rotor to stator pitch change. Best practice procedures were employed to assess and quantify the sensitivity of the simulations to numerical error like mesh and timestep size, turbulence model error and systematic errors related to tip gap, and steady-state or unsteady-state flow assumptions. The effect of turbulence on the mean flow is modelled by a URANS approach based on the SST model and its extensions for laminar-turbulent transition and reattachment prediction.
The complex unsteady flow interactions between the rotor and stator were validated against steady-state and unsteady experimental data. The compressor flow is explained in detail including transonic flow features like shock boundary layer interactions. Comparisons are made between the various rotor-stator interaction simulation methods and the experimental data.
Numerical and Experimental Evaluation of a Dual-Fuel Dry-Low-NOx Micromix Combustor for Industrial Gas Turbine Applications
Authors: Funke H. H.-W. , Beckmann N. , Keinz J. , Abanteriba S. 
Published: August 2017

The Dry-Low-NOx (DLN) Micromix combustion technology has been developed originally as a low emission alternative for industrial gas turbine combustors fueled with hydrogen. Currently the ongoing research process targets flexible fuel operation with hydrogen and syngas fuel.
The non-premixed combustion process features jet-in-crossflow-mixing of fuel and oxidizer and combustion through multiple miniaturized flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame.
The paper presents the results of a numerical and experimental combustor test campaign. It is conducted as part of an integration study for a dual-fuel (H2 and H2/CO 90/10 Vol.%) Micromix combustion chamber prototype for application under full scale, pressurized gas turbine conditions in the auxiliary power unit Honeywell Garrett GTCP 36-300.
In the presented experimental studies, the integration-optimized dual-fuel Micromix combustor geometry is tested at atmospheric pressure over a range of gas turbine operating conditions with hydrogen and syngas fuel. The experimental investigations are supported by numerical combustion and flow simulations. For validation, the results of experimental exhaust gas analyses are applied.
Despite the significantly differing fuel characteristics between pure hydrogen and hydrogen-rich syngas the evaluated dual-fuel Micromix prototype shows a significant low NOx performance and high combustion efficiency. The combustor features an increased energy density that benefits manufacturing complexity and costs.
The Effect of Lewis Number on Instantaneous Flamelet Speed and Position Statistics in Counter-Flow Flames With Increasing Turbulence
Authors: Salusbury Sean D. , Abbasi-Atibeh Ehsan , Bergthorson Jeffrey M. 
Published: August 2017

Differential diffusion effects in premixed combustion are studied in a counter-flow flame experiment for fuel-lean flames of three fuels with different Lewis numbers: methane, propane, and hydrogen. Previous studies of stretched laminar flames show that a maximum reference flame speed is observed for mixtures with Le ≳ 1 at lower flame-stretch values than at extinction, while the reference flame speed for Le ≪ 1 increases until extinction occurs when the flame is constrained by the stagnation point. In this work, counter-flow flame experiments are performed for these same mixtures, building upon the laminar results by using variable high-blockage turbulence-generating plates to generate turbulence intensities from the near-laminar u′/SLo=1 to the maximum u′/SLo achievable for each mixture, on the order of u′/SLo=10. Local, instantaneous reference flamelet speeds within the turbulent flame are extracted from high-speed PIV measurements. Instantaneous flame front positions are measured by Rayleigh scattering. The probability-density functions (PDFs) of instantaneous reference flamelet speeds for the Le ≳ 1 mixtures illustrate that the flamelet speeds are increasing with increasing turbulence intensity. However, at the highest turbulence intensities measured in these experiments, the probability seems to drop off at a velocity that matches experimentally-measured maximum reference flame speeds in previous work. In contrast, in the Le ≪ 1 turbulent flames, the most-probable instantaneous reference flamelet speed increases with increasing turbulence intensity and can, significantly, exceed the maximum reference flame speed measured in counter-flow laminar flames at extinction, with the PDF remaining near symmetric for the highest turbulence intensities.
These results are reinforced by instantaneous flame position measurements. Flame-front location PDFs show the most probable flame location is linked both to the bulk flow velocity and to the instantaneous velocity PDFs. Furthermore, hydrogen flame-location PDFs are recognizably skewed upstream as u′/SLo increases, indicating a tendency for the Le ≪ 1 flame brush to propagate farther into the unburned reactants against a steepening average velocity gradient.
Methods for the Calculation of Thermoacoustic Stability Margins and Monte Carlo-Free Uncertainty Quantification
Authors: Mensah Georg A. , Magri Luca , Moeck Jonas P. 
Published: August 2017

Thermoacoustic instabilities are a major threat for modern gas turbines. Frequency-domain based stability methods, such as network models and Helmholtz solvers, are common design tools because they are fast compared to compressible CFD computations. Frequency-domain approaches result in an eigenvalue problem, which is nonlinear with respect to the eigenvalue. Nonlinear functions of the frequency are, for example, the n–τ model, impedance boundary conditions, etc. Thus, the influence of the relevant parameters on mode stability is only given implicitly. Small changes in some model parameters, which are obtained by experiments with some uncertainty, may have a great impact on stability. The assessment of how parameter uncertainties propagate to system stability is therefore crucial for safe gas turbine operation. This question is addressed by uncertainty quantification. A common strategy for uncertainty quantification in thermoacoustics is risk factor analysis. It quantifies the uncertainty of a set of parameters in terms of the probability of a mode to become unstable.
One general challenge regarding uncertainty quantification is the sheer number of uncertain parameter combinations to be quantified. For instance, uncertain parameters in an annular combustor might be the equivalence ratio, convection times, geometrical parameters, boundary impedances, flame response model parameters etc. Assessing also the influence of all possible combinations of these parameters on the risk factor is a numerically very costly task.
A new and fast way to obtain algebraic parameter models in order to tackle the implicit nature of the eigenfrequency problem is using adjoint perturbation theory. Though adjoint perturbation methods were recently applied to accelerate the risk factor analysis, its potential to improve the theory has not yet been fully exploited. This paper aims to further utilize adjoint methods for the quantification of uncertainties. This analytical method avoids the usual random Monte Carlo simulations, making it particularly attractive for industrial purposes. Using network models and the open-source Helmholtz solver PyHoltz it is also discussed how to apply the method with standard modeling techniques. The theory is exemplified based on a simple ducted flame and a combustor of EM2C laboratory for which experimental validation is available.
Identifying the Approach to Significantly Improve the Performance of NK-36ST Gas Turbine Power Plant
Authors: Baturin Oleg , Tkachenko Andrei , Krupenich Ilia , Popov Grigorii , Goryachkin Eugene 
Published: August 2017

Collaboration between the Samara National Research University [1] and the JSC “KUZNETSOV” [2] included the research efforts in the field of increasing the performance of NK-36ST [3] gas turbine power plant intended for use as a driving unit of a gas compression station. The requirements included 3% increase in engine efficiency while keeping the maximum number of engine parts unchanged.
First, the thermogasdynamic simulator of the NK-36ST gas turbine power plant was developed and verified using the results of experimental investigations. The impact of various parameters of the engine upon its efficiency was thoroughly investigated and the approach to modernization preserving most of the engine parts was suggested. This approach included increasing the values of work process parameters, the hydraulic efficiency of turbomachinery and reducing the cooling air consumption.
Second, the analysis of the working process of turbomachinery was carried out. The air-gas channel in a meridional section was kept unchanged for the first iteration, thus keeping the parts of the initial engine unchanged, except for the blades and vanes of turbomachinery. For this variant, the parameters of compressors (head ratio and flow ratio) changed to more favorable values, supposedly providing 1–2% higher efficiency. Unfortunately, for this variant and the given restrictions the points, corresponding to the parameters of turbines moved at the Smith diagram to the unfavorable areas, thus making the increase in turbine efficiency very unlikely. The analysis had shown that to provide more convenient values of turbine parameters the blades should be shortened, and this decrease in blade length provides the possibility to increase the rotational speed of the rotor with the same strain levels of the blades and disks. As the result, the gas channel configuration and values of rotational speeds for the turbines providing the increase in their efficiency by 0.5%–1.0% were suggested. The suggested gas channel configuration preserves the same inner diameters thus keeping the disks layout the same.
At the next stage, the shapes of the low-pressure turbine and compressor blades and the blades of free turbine were optimized using the Profiler program (developed at the Samara University), the NUMECA [4] system and the IOSO [5] optimization package, providing the 0.5%–1.0% increase in the efficiency in comparison to the initial variant.
The results of the described research efforts provide the increase in engine efficiency of about 3% while providing the possibility to keep most of the rotor parts of the engine unchanged.
Flow Field and Wall Temperature Measurements for Reacting Flow in a Lean Premixed Swirl Stabilized Can Combustor
Authors: Park Suhyeon , Gomez-Ramirez David , Gadiraju Siddhartha , Kedukodi Sandeep , Ekkad Srinath , Moon Hee-Koo , Kim Yong , Srinivasan Ram 
Published: August 2017

Designing gas turbine combustors requires accurate measurement and prediction of the violent, high-temperature environment in reacting flow. One important factor in combustor design is the heat load on the inner surface of the combustor liner during combustion. To properly analyze the heat load, the mechanisms of thermal energy transfer must be investigated. Of these, the convective heat transfer has not been fully characterized, representing an important challenge in the field of combustor research. The flow field is closely related to the combustion dynamics from the swirling flame in modern burners, and has a direct impact on the convective heat transfer. Most of the flow field measurements reported in the literature have relied on custom research nozzles. However, the development of modern low emission, lean-premixed combustors requires experimental results from realistic industrial fuel nozzles. This paper experimentally investigates the effects of combustor operating conditions on the reacting flow in an optical single can combustor. The swirling flow was generated by an industrial lean pre-mixed, axial swirl fuel nozzle manufactured by Solar Turbines Incorporated.
Planar particle image velocimetry (PIV) data were acquired and analyzed to understand the characteristics of the flow field. Experiments were conducted at Reynolds numbers ranging between 50000 and 110000 (with respect to the nozzle diameter, DN); equivalence ratios between 0.55 and 0.78; and pilot fuel split ratios of 0 to 6%. Characterizing the impingement location on the liner, and the turbulent kinetic energy (TKE) distribution were a fundamental part of the investigation. Self-similar characteristics were observed at reacting conditions. Jet impingement locations on the liner were at x ≈ 1.16 DN for seven different reacting cases, and it was observed that the impingement location was not significantly affected by the combustion parameters studied. However, non-reacting flow was significantly different in flame structure and impingement locations. Combustor liner wall temperature distributions were measured in reacting condition with an infrared camera for a single case. The temperature profile was explained qualitatively with the flow features measured with PIV. Peak wall temperature close to impingement location on the liner wall reached about 900 K, and peak heat flux was measured as ≈ 23 kW/m2 at x ≈ 2.3 DN.
Toward Affordable Uncertainty Quantification for Industrial Problems: Part II — Turbomachinery Application
Authors: Ghisu Tiziano , Shahpar Shahrokh 
Published: August 2017

Uncertainty Quantification (UQ) is an increasingly important area of research. As components and systems become more efficient and optimized, the impact of uncertain parameters (such as boundary and operating conditions, geometrical variations due to manufacturing or in-service deterioration, etc.) is likely to become critical. It is therefore fundamental to consider the impact of these uncertainties as early as possible during the design process, with the aim of producing more robust designs (less sensitive to the presence of uncertainties). The cost of UQ with high-fidelity simulations becomes therefore of fundamental importance.
The companion part I paper presented an efficient approach for UQ based on Polynomial Chaos expansions, demonstrating its applicability to multi-fimensional uncertainty quantification problems. This paper focuses on the application of this approach to quantify the variability in the performance of two large bypass-ratio jet engine fans in the presence of shape uncertainty due to possible manufacturing processes. The impacts of shape uncertainty on the two geometries are compared, and sensitivities to the location of the blade shape variability are extracted. The mechanisms at the origin of the change in performance are analyzed in detail, as well as the differences between the two configurations. These results provide important information both for controling the manufacturing process, and for designing blades that are less sensitive to the presence of manufacturing uncertainties.
Integration of CFD to Design Experiments for Enhanced Spatial and Temporal Discretization
Authors: De Maesschalck C. , Lavagnoli S. , Paniagua G. 
Published: August 2017

The availability of high fidelity Computational Fluid Dynamics (CFD) suitable for turbomachinery design offers a powerful tool to define an effective experimental measurement campaign. This paper describes approaches to integrate Reynolds-Averaged Navier-Stokes simulations into experiment design. CFD simulations are used to a priori estimate the measurement errors induced by the finite spatial sampling and inherent limited sensor bandwidth for space-resolved and time-resolved turbine aerothermal measurements. The CFD predictions are employed to optimize the probe placement and traversing while minimizing the measurement errors associated with the finite spatial sampling. Additionally, time-resolved CFD traces serve to quantify the measurement errors as a function of the measurement chain bandwidth.
This approach was applied to a recent turbine test program, focused on the aerothermal characterization of the turbine over-tip casing endwall and downstream flow field. Based on the 3D simulations of the different rotor geometries, the discrete radial positions of the aerothermal probes located downstream of the stage were optimized to minimize the uncertainty on the individual aerodynamic quantities, as well as to mitigate the propagated uncertainty on the turbine loss coefficient. Furthermore, the effect of the implicit time-averaging of all sensors, due to the limited frequency response, was quantified.
This manuscript illustrates the benefits of CFD in the design and planning of a turbine experimental campaign. Based on the proposed procedure, the experimentalist can find the best compromise between measurement precision and instrumentation costs by establishing the minimum sensor performance requirements to obtain the target accuracies.
RT61 Power Turbine 100K MTBO Life Extension - Life Cycle Cost Reduction
Authors: Thirumurthy Deepak , Singh Jaskirat , Peng Mark 
Published: August 2017

RT61 is a three-stage industrial power turbine which couples with industrial RB211-24GT gas generator. This power turbine was designed and developed by the turbomachinery group in Mount Vernon, Ohio. It was designed based on the 3-D vortex theory during the early 2000 for increased power output and efficiency. It was also designed for low weight with modular construction for ease in maintainability. The industrial RB211-GT61 product serves both oil & gas and power generation market.
Recent drop in crude oil prices has posed significant challenges to the oil & gas customers. To increase the profitability, the entire oil & gas industry (upstream, midstream, and downstream) is looking for opportunities to decrease the operating cost. This served as the main motivation for the life extension of the RT61 power turbine. In order to reduce customer life cycle cost, Siemens Energy, Inc., has extended the life of its most efficient power turbine from 50,000 hours to 100,000 hours.
This paper discusses the efforts taken in extending the meantime between overhaul lives of various RT61 industrial power turbine components from 50,000 hours to 100,000 hours. Measures taken to increase the reliability and minimize the product life cycle cost are presented. New coatings were incorporated for the stage 1 vane and blade for oxidation protection. The thermal characteristics of the power turbine were validated using a comprehensive thermocouple survey of the casings.
Numerical and Experimental Investigations for Flow Fields Under Non-Reacting and Reacting Conditions Through a Lean Premixed Fuel Nozzle
Authors: Kedukodi Sandeep , Park Suhyeon , Gadiraju Siddhartha , Ekkad Srinath , Kim Yong , Srinivasan Ram 
Published: August 2017

Numerical methods coupled with experimental benchmarking approaches, are typically used as effective tools for solving engineering problems due to their significant time saving benefits. In this paper, the swirling flow through an industrial lean-premixed fuel nozzle as used in actual gas turbine combustors is numerically analyzed and compared with experimental observations. The analysis is performed under both non-reacting and reacting conditions for a specific Reynolds number. The reacting experiments were performed using compressed methane as the fuel and air as the oxidizer. A specific inlet Reynolds number flow was studied to understand the combustor flow field with an overall equivalence ratio of 0.65 and 6% pilot fuel.
Steady state simulations were performed using Fluent solver using Realizable k-ε turbulence model. The reacting flow was simulated using Flamelet Generation Manifold (FGM) model to simulate partially premixed combustion. The non-reacting simulations predicted the combustor flow profiles with certain deviation from Particle Image Velocimetry (PIV) data within the central recirculation region. This deviation may be attributed to the inherent limitations of turbulence model in predicting the central vortex accurately. However, the simulated flow fields were in very good agreement with PIV data under reacting conditions. Additionally, the study was also extended to investigate the sensitivity of inlet swirl on the jet impingement location along the combustor wall. It was found that reaction significantly modifies the jet impingement location for lower inlet swirl angles and showed negligible impact under non-reacting conditions.
The presented studies in this paper provide a comprehensive summary of modified flow features under non-reacting and reacting conditions and also demonstrates the sensitivity of inlet swirl changes on the location of liner wall impingement. This study is believed to offer a strong base for future studies involving heat transfer characterization along the combustor walls under reacting conditions; and also provide valuable information to the gas turbine combustor design community towards improved liner wall designs using simplistic numerical modeling approaches.
Experimental Investigation of Numerically Optimized Wavy Microchannels Created Through Additive Manufacturing
Authors: Kirsch Kathryn L. , Thole Karen A. 
Published: August 2017

The increased design space offered by additive manufacturing can inspire unique ideas and different modeling approaches. One tool for generating complex yet effective designs is found in numerical optimization schemes, but until relatively recently, the capability to physically produce such a design had been limited by manufacturing constraints.
In this study, a commercial adjoint optimization solver was used in conjunction with a conventional flow solver to optimize the design of wavy microchannels, the end use of which can be found in gas turbine airfoil skin cooling schemes. Three objective functions were chosen for two baseline wavy channel designs: minimize the pressure drop between channel inlet and outlet, maximize the heat transfer on the channel walls and maximize the ratio between heat transfer and pressure drop. The optimizer was successful in achieving each objective and generated significant geometric variations from the baseline study.
The optimized channels were additively manufactured using Direct Metal Laser Sintering and printed reasonably true to the design intent. Experimental results showed that the high surface roughness in the channels prevented the objective to minimize pressure loss from being fulfilled. However, where heat transfer was to be maximized, the optimized channels showed a corresponding increase in Nusselt number.