bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Thermal and Stress States of the Annular Combustion Chamber Flame Tube Walls
Authors: Anisimov Vladislav M. , Zubrilin Ivan A. , Orlov Mikhail Y. 
Published: September 2016

Durability and reliability are the most important parameters of gas turbine engines combustion chamber. Combustion chamber flame tube walls are the most temperature-loaded engine components. Therefore, eliminating wall burnout is an key issue as well as keeping temperature of combustion chamber elements within the materials operating temperature range. Thus, there is a need to define thermal state of these elements. Currently, the problem of flame tube wall burnout is exacerbated by trends of increasing the compressor pressure ratio and temperature before the turbine. It is important to resolve this problem during the gas turbine engine design phase. This will reduce time and material costs for launch of their serial production. CFD is one way of resolving this problem.
The numerical method of simulating thermal state of flame tube walls was applied and tested. This method takes into account a thermal barrier coating and a cooling system. Three-dimensional geometric model consists of the flow area and the flame tube walls with multi-layer thermal barrier coating. Flow area is needed to simulate fluid dynamic processes. Flame tube walls geometry was created for heat transfer simulation. Mathematical model of the workflow in the combustion chamber had been created previously and was validated. The study is carried out by numerical methods, using the commercial software Ansys. Temperature distribution on the combustion chamber flame tube walls was obtained by the simulation. It agrees well with the results of the experiments.
The maximum temperature of the walls was reduced from 1400 K to 1100 K through the reallocation of holes area between the cooling system belts. This ensures the operability of the wall material. Then, the simulations of the flame tube walls deformation were conducted. As a result, the deformations and stresses, that occurred due to the walls heating, were evaluated using the one-way Fluid-Structure-Interaction (FSI) module. The maximum displacement along the axis of the combustion chamber was less than 2 mm, when the acceptable move in telescopic connection is 6 mm. It was found that the outer flame tube wall exposed the highest heat load. The area of the outer annular channel decreased by 18% and the area of the internal annular channel increased by 7%. Air distribution of the cooling system was changed due to walls deformation and velocity changes in annular channels, therefore the additional simulations and some modification in the design are required. The methodology created on the base of this study can be used for the simulation of the various combustion chamber designs.
Large Eddy Simulation of a Realistic Gas Turbine Combustor
Authors: Xu Baopeng , Liu Ya , Xie Rong 
Published: September 2016

This paper proposes a large eddy simulation approach for the modeling of combusting flow with spray in realistic gas turbine combustors. A one equation subgrid model is used to model the effect of the unresolved subgrid scales on the resolved large scales. Subgrid combustion is modeled by an extended eddy dissipation model in which the filtered reaction rate is controlled by the turbulent mixing rate between the fine structures and the surrounding fluids. An Eulerian-Lagrangian approach is used to model the two-phase spray flow, and spray particles are tracked by a two-way coupling Lagrangian approach.
Then the proposed approach is applied to simulate a combusting spray flow in an industrial annular combustor. The objectives of this study are to demonstrate its capability to investigate the complex flow and combustion dynamics in realistic gas turbine combustors. The predicted instantaneous and time averaged fields of velocity, temperature, pressure, fuel mass fraction are investigated. The precessing vortex core caused by the swirling flow as well as pressure oscillations is examined. The predicted results nicely reproduce the flow, spray and combustion dynamics and successfully capture the main features of the studied combustor, such as the processing vortex core. Finally, the predicted exit temperature and the total pressure loss are compared with experimental data and good agreements are obtained.
Numerical Study on the Effect of a Volute on Surge Phenomena in a Centrifugal Compressor
Authors: Jeon S. H. , Hwang D. H. , Park J. H. , Kim C. H. , Baek J. H. , Kim H. W. 
Published: September 2016

Numerical investigation of the effect of the volute on stall flow phenomenon is presented by solving three-dimensional Reynolds-averaged compressible Navier-Stokes equations. Two different configurations of a centrifugal compressor were used to compare their performance: One is an original centrifugal compressor which is composed of impeller, splitter, vaned diffuser and a volute and the other is the one without a volute. Steady calculations were performed to predict aerodynamic performance in terms of the pressure ratio, efficiency and mass flow rate. The results show that the operating range of the compressor with a volute is narrower than that of the compressor without a volute. This can be interpreted that flow instability is strongly influenced by the tongue of a volute which is highly asymmetric.
Unsteady calculations were also performed with a time-step size of 38μs corresponding to a pitch angle of 5 degrees at the given rotational speed. The flow characteristics for two configurations are analyzed and compared at various instantaneous times showing unsteady dynamic features. Based on the unsteady flow simulation, fast Fourier transform at several discrete points in semi-vaneless space was performed at peak efficiency and near surge point in order to illustrate the unstable flow physics in both configurations. It is found that the blade passing frequency is dominant, indicating that diffuser passages have a periodicity of 40 degrees due to the rotational blades. Besides blade passing frequency, there were several noticeable frequencies which affect the instability of the whole system. Those frequencies in both configurations are compared and analyzed in various aspects.
Analysis of Time-Signal of an Industrial Gas Turbine Combustor Under an Unstable Condition
Authors: Lengani D. , Zunino P. , Romoli F. , Bertolotto E. , Rizzo S. 
Published: September 2016

This paper analyzes the time-signals of pressure sensors mounted in an industrial gas turbine combustor under an unstable condition. The present investigation is aimed at the discussion of the sudden increase in amplitude due to the limit-cycle oscillations and of its temporal evolution. To this purpose, different post-processing tools are described and adopted: i.e. wavelet transform, cross-correlations, time-space Fourier transform and proper orthogonal decomposition (POD).
The properties of the wavelet transform are used in order to identify the time of occurrence and the frequency of the limit-cycle oscillations. They occur at the second harmonic of the natural frequency of the annular combustion chamber. The amplitude of the pressure fluctuations at this characteristic frequency increases to a critical value with very large amplitude in about 0.15s that corresponds to about 26 periods of the phenomenon. Within this period, the pressure signals from two neighboring burners have a quite large and increasing degree of correlation as it is observed from the cross-correlation of the signals. The time-space Fourier transform suggests that the instability couples with a natural mode of the combustion chamber. The azimuthal wave length of such mode is half of the combustion chamber circumference (this corresponds to an azimuthal mode 2). According to this findings, the POD is used to provide an identifier for the occurrence of the limit-cycle oscillations. In fact, POD is known to isolate the deterministic fluctuations based on an energy rank. Hence, the first POD mode isolates the effect of specific frequency forcing and its energy content is retained in the first POD eigenvalue which is used as identifier.
Rapid Preliminary Combustor Design Using a Flow Network Approach
Authors: du Toit B. , Theron S. 
Published: September 2016

Preliminary combustor design usually requires that an extensive number of geometrical and operational conditions be evaluated and compared. During this phase important parameters the designer sought after are typically the mass flow rate distribution through air admission holes, associated pressure losses as well as liner wall temperatures. The process is therefore iterative in nature and can become expensive in terms of engineering analysis cost considering the time required to build and execute 3D CFD models. Network codes have the potential to fill the gap during this stage of the design since they can be setup and solved in timeframes that are orders of magnitude less than comprehensive CFD models, essentially leading to cost savings since overall less time is spent on 3D simulations and rig tests. An additional advantage using this approach is that results from the network solution can be applied as boundary conditions to subsequent more detailed 3D models.
In this study a commercial flow network tool, Flownex®, was used to model a complete combustor including flow distribution, combustion and heat transfer. The integrated mass, momentum and energy balance is solved using the continuity, momentum and energy equations applied to nodes and elements. These nodes and elements are the modular building blocks, typically semi-empirical and allow users to either select appropriate built-in correlations, or to define using specific equations through scripting. Flow equations are fully compressible and applied to the gas mixture. The chemical composition of the reactants forming during combustion as well as the adiabatic flame temperature is determined from the NASA CEA package incorporated into the solution. Heat transfer mechanisms included in the model are gas-surface radiation, film convection, forced convection in ducts, surface-surface radiation, and 2D axially-symmetric conduction through solid walls. Results produced from the network were compared with test data obtained from the NASA E3 development combustor. Overall good agreement resulted, showcasing the success of the approach followed.
Investigation of Siemens SGT-800 Industrial Gas Turbine Combustor Using Different Combustion and Turbulence Models
Authors: Lörstad Daniel , Ljung Anders , Abou-Taouk Abdallah 
Published: September 2016

Siemens SGT-800 gas turbine is the largest industrial gas turbine within Siemens medium gas turbine size range. The power rating is 53MW at 39% electrical efficiency in open cycle (ISO) and, for its power range, world class combined-cycle performance of >56%. The SGT-800 convectively cooled annular combustor with 30 Dry Low Emissions (DLE) burners has proven, for 50–100% load range, NOx emissions below 15/25ppm for gas/liquids fuels and CO emissions below 5ppm for all fuels, as well as extensive gas fuel flexible DLE capability.
In this work the focus is on the combustion modelling of one burner sector of the SGT-800 annular combustor, which includes several challenges since various different physical phenomena interacts in the process. One of the most important aspects of the combustion in a gas turbine combustor is the turbulence chemistry interaction, which is dependent on both the turbulence model and the combustion model. Some turbulence-combustion model combinations that have shown reasonable results for academic generic cases and/or industrial applications at low pressure, might fail when applied to complex geometries at industrial gas turbine conditions since the combustion regime may be different.
Therefore is here evaluated the performance of Reynolds Averaged Navier-Stokes (RANS) and Scale Adaptive Simulation (SAS) turbulence models combined with different combustion models, which includes the Eddy Dissipation Model (EDM) combined with Finite Rate Chemistry (FRC) using an optimized reduced 4-step scheme and two flamelet based models; Zimont’s Burning Velocity model and Lindstedt & Vaos Fractal model. The results are compared to obtained engine data and field experience, which includes for example flame position in order to evaluate the advantages and drawbacks of each model. All models could predict the flame shape and position in reasonable agreement with available data; however, for the flamelet based methods adjusted calibration constants were required to avoid a flame too far upstream or non-sufficient burn out which is not in agreement with engine data. In addition both the flamelet based models suffer from spurious results when fresh air is mixed into fully reacted gases and BVM also from spurious results inside the fuel system. The combined EDM-FRC with a properly optimized reduced chemical kinetic scheme seems to minimize these issues without the need of any calibration, with only a slight increase in computational cost.
Industrial Gas Turbine Health and Performance Assessment With Field Data
Authors: Roumeliotis I. , Aretakis N. , Alexiou A. 
Published: September 2016

The paper presents a thorough analysis of historical data and results acquired over a period of two years through an online real-time monitoring system installed at a Combined Heat and Power (CHP) plant. For gas turbine health and performance assessment, a Gas Path Analysis tool based on the adaptive modeling method is integrated into the system. An engine adapted model built through a semi-automated method is part of a procedure which includes a steam/water cycle simulation module and an economic module used for power plant performance and economic assessment. The adaptive modeling diagnostic method allowed for accurate health assessment during base and part load operation identifying and quantifying compressor recoverable deterioration and the root cause of an engine performance shift. Next the performance and economic assessment procedure was applied for quantifying the economic benefit accrued by implementing daily on-line washing and for evaluating the financial gains if the off-line washings time intervals are optimized based on actual engine performance deterioration rates.
The results demonstrate that this approach allows continuous health and performance monitoring at full and part load operation enhancing decision making capabilities and adding to the information that can be acquired through traditional analysis methods based on heat balance and base load correction curves.
Design Exploration of a Return Channel for Multistage Centrifugal Compressors
Authors: Jariwala Vishal , Larosiliere Louis , Hardin James 
Published: September 2016

In this study, aerodynamic design improvement options are explored for a low vane count and high flow-coefficient stage return channel, which was found to produce larger than acceptable levels of residual swirl and distortion at the stage exit. A CFD-driven design exploration of three classes of return channel vanes was conducted with the goal of achieving a useful reduction in the stage exit residual swirl angle and its spanwise variance without compromising total pressure loss.
First, the approach taken to anchor the CFD model with test data and resultant aerodynamic diagnosis at design point for the baseline return channel are discussed. This is followed by a cursory parametric design screening to explore concepts that can potentially meet the design goal while adhering to the spatial envelope (stage spacing) and mechanical constraints. Results of this exploration are presented and some conclusions are offered concerning the suitability of a 3D return channel guide vane partially extended into the crossover bend.
Flow Survey of a Forward Curved Blades Centrifugal Fan for HVAC Applications
Authors: Breviario Fabio , Brivio Dario , Cardillo Lucio , Corsini Alessandro , Delibra Giovanni 
Published: September 2016

The advancements in fan technology are nowadays animated by two major drivers: the legal requirements that impose minimum fan efficiency grades for fans sold within European Union (and soon US and Asia), and the market request for better air performance and lower sound emissions.
Within HVAC (Heating, Ventilating and Air Conditioning) applications, centrifugal fans with forward curved blades are widely used due to the higher total pressure rise capability and lower acoustic emissions with respect to more efficient backward curved blades. However the continuous rise of minimum fan efficiency grades pushes the manufacturers to develop a new generation of forward curved centrifugal fans, improving previous design. Here the challenge is not only on aerodynamics, but in the overall production process, as squirrel cage fans are characterised by a cost-effective consolidated technology, based on simple blade geometries and easy series manufacturing. For example, the blades usually have circular camber lines, as results of cut cylinders. Thus, once the number of blades and the angle at the leading edge are selected, the chord and the deflection capability are constrained as well.
These concurring aspects led industry to include in the design process new tools, in particular CFD, to analyse the flow features of the current generation of fans in order to understand which phenomena are to be either controlled or exploited to increase efficiency and total pressure rise.
Here we present a numerical investigation on a forward curved blade centrifugal fan for HVAC applications, to highlight the flow features inside the impeller and in the critical region of coupling with the volute. The analysis was carried out with OpenFOAM, an open-source library for CFD. Computations were performed with the frozen rotor approach and validated against available experimental data.
Reduced Order Models for Blisks With Small and Large Mistuning and Friction Dampers
Authors: Tang Weihan , Baek Seunghun , Epureanu Bogdan I. 
Published: September 2016

In operation, rotating bladed disks (blisks) are often subject to high levels of dynamic loading, resulting in large amplitudes of forced vibrations especially at resonance. Moreover, variations in structural properties of individual sectors, referred to as mistuning, can lead to strain energy localization and can amplify forced responses. To prevent damages caused by high cycle fatigue, various frictional damping sources are introduced to dissipate vibration energy. Due to the nonlinear behavior of frictional contacts, conventional methods to study the dynamics of the blisk-damper systems are based often on numerical time integration, which is time-consuming and can be computationally prohibitive due to the large sizes of commercial blisk models. Existing techniques for model reduction either rely heavily on cyclic symmetry of the blisk-damper system, or are based on component mode synthesis (CMS). However, in the presence of mistuning, cyclic symmetry no longer exists. Also, mistuning is random and best studied statistically. Repetitive CMS condensation for a large amount of random mistuning patterns can lead to a computationally formidable task.
This paper presents a reduced-order modeling technique to efficiently capture the nonlinear dynamic responses of blisk-damper systems with both small perturbations in blade material properties (small mistuning), and significant changes in the blisk geometries (large mistuning). The reduced-order models (ROMs) are formed by projecting the blisk-damper systems onto a novel mode basis that mimics the contact behavior. This mode basis contains normal mode shapes of the mistuned blisk-damper systems with either sliding or sticking conditions enforced on the contact surfaces. These mode shapes are computed through the N-PRIME method, a technique recently developed by the authors to efficiently obtain mode shapes for blisks with simultaneous large and small mistuning. The resulting modal nonlinear equations of motion are solved by a hybrid frequency/time (HFT) domain method with continuation. In the HFT method, the contact status and friction forces are determined in the time domain by a quasi-two-dimensional contact model at each contact point, whereas the modal equations of motion are solved in the frequency domain according to a harmonic balance formulation. The forced responses computed by the proposed ROMs are validated for two systems with distinct mistuning patterns. A statistical analysis is performed to study the effectiveness of the frictional dampers under random mistuning patterns.
Review of Coal-to-Synthetic Natural Gas (SNG) Production Methods and Modeling of SNG Production in an Entrained-Flow Gasifer
Authors: Lu Xijia , Wang Ting 
Published: September 2016

In this paper, the coal-to-synthetic natural gas (SNG) technologies have been reviewed. Steam-oxygen gasification, hydrogasification, and catalytic steam gasification are the three major gasification processes used in coal-to-SNG production. So far, only the steam-oxygen gasification process is commercially proven by installing a catalytic methanation reactor downstream of the gasification process after syngas is produced, cleaned, and shifted to achieve an appropriate H2/CO ratio for methanation reaction. This process is expensive, less efficient, and time consuming. Ideally, it will be more effective and economic if methanation could be completed in an once-through entrained-flow gasifier. Technically, this idea is challenging because an effective gasification process is typically operated in a high-pressure and high-temperature condition, which is not favorable for methanation reaction, which is exothermic. To investigate this idea, a computational model is established and a sensitivity study of methanation reactions with and without catalysts are conducted in this study.
In modeling the methanation process in a gasifier, correct information of the reaction rates is extremely important. Most of known methanation reaction rates are tightly linked to the catalysts used. Since the non-catalytic reaction rates for methanation are not known in a gasifer and the issues are compounded by the fact that inherent minerals in coal ashes can also affect the methanation kinetics, modeling of methanation in an entrained-flow gasifier becomes very challenging. Considering these issues, instead of trying to obtain the correct methnation reaction rate, this study attempts to use computational model as a convenient tool to investigate the sensitivity of methane production under a wide range methanation reaction rates with and without catalysts. From this sensitivity study, it can be learned that the concept of implementing direct methanation in a once-through entrained-flow gasifier may not be attractive due to competitions of other reactions in a high-temperature environment. The production of SNG is limited to about 18% (vol) with catalytic reaction with a pre-exponential factor A in the order of 107. A further increase of the value of A to 1011 doesn’t result in more production of SNG. This SNG production limit could be caused by the high-temperature and short residence time (3–4 seconds) in the entraind-flow gasifier.