bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of CO2 Capture on Combined Cycle Gas Turbine Efficiency Using Membrane Separation, EGR and OEA Effects on Combustion Characteristics
Authors: Cabot G. , Calbry M. , Xavier P. , Vandel A. , de Persis S. , Belaissaoui B. , Favre E. , Pillier L. 
Published: September 2014

In an energetic world of fossil fuel, there is a need to reduce the CO2 emission released to the atmosphere. CO2 Capture and Sequestration (CCS) is one of the solutions.
To optimize the CO2 capture cost, thermodynamic cycles of power plants have to be modified, and resulting new designs inevitably lead to new combustion modes [1][2][3]. CO2 capture of post combustion gases can be performed using membrane processes, but its efficiency is interesting only if the CO2 concentration in the combustion process exhaust gases is higher than 30% [4]. Unfortunately, in classical combustion processes (e.g. gas turbine), diluted Exhaust Gases (EG) contain no more than 5 % of CO2 because combustion products are strongly diluted in air. Our objective consists in increasing the EG CO2 concentration, by using both Oxygen-Enriched Air (OEA) combustion and exhaust gas recirculation (EGR). Our approach is based on numerical simulations and on experimental work. First, operating parameters which minimize the CO2 capture cost are calculated and compared with the reference capture cost [5] (achieved by amine absorption of CO2). In parallel, experiments and additional calculations are performed in order to check the quality and the operability of such combustion mode.
This paper is organized as follows: the first part presents the optimization of a new thermodynamic GTCC cycle, using OEA and EGR to increase EG CO2 concentration and capturing it in post-combustion with membrane separator. The effects of pressure and membrane selectivity will be studied in terms of CO2 capture cost, avoided CO2, implemented membrane surface, EGR rate and OEA quality.
The second part is dedicated to the experimental and calculation [6] studies of combustion met in this type of configuration. A premixed swirl flame is fed first with Air, CH4 and CO2, then with OEA, CH4 and EGR. To neglect the thermal aspect of NOx production, measurements are performed at constant adiabatic flame temperature. The flame structure, combustion instability and pollutant emissions are presented as a function of the EGR rate dilution.
Simultaneous Robust Design and Tolerancing of Compressor Blades
Authors: Dow Eric A. , Wang Qiqi 
Published: September 2014

The manufacturing processes used to create compressor blades inevitably introduce geometric variability to the blade surface. In addition to increasing the performance variability, it has been observed that introducing geometric variability tends to reduce the mean performance of compressor blades. For example, the mean adiabatic efficiency observed in compressor blades with geometric variability is typically lower than the efficiency in the absence of variability. This “mean-shift” in performance leads to increased operating costs over the life of the compressor blade. These detrimental effects can be reduced by using robust optimization techniques to optimize the blade geometry. The impact of geometric variability can also be reduced by imposing stricter tolerances, thereby directly reducing the allowable level of variability. However, imposing stricter manufacturing tolerances increases the cost of manufacturing. Thus, the blade design and tolerances must be chosen with both performance and manufacturing cost in mind.
This paper presents a computational framework for performing simultaneous robust design and tolerancing of compressor blades subject to manufacturing variability. The manufacturing variability is modelled as a Gaussian random field with non-stationary variance to simulate the effects of spatially varying manufacturing tolerances. The statistical performance of the compressor blade system is evaluated using the Monte Carlo method. A gradient based optimization scheme is used to determine the optimal blade geometry and distribution of manufacturing tolerances.
Co-Firing of Hydrogen and Natural Gases in Lean Premixed Conventional and Reheat Burners (Alstom GT26)
Authors: Wind Torsten , Güthe Felix , Syed Khawar 
Published: September 2014

Addition of hydrogen (H2), produced from excess renewable electricity, to natural gas has become a new fuel type of interest for gas turbines. The addition of hydrogen extends the existing requirements to widen the fuel flexibility of gas turbine combustion systems to accommodate natural gases of varying content of higher hydrocarbons (C2+). The present paper examines the performance of the EV and SEV burners used in the sequential combustion system of Alstom’s reheat engines, which are fired with natural gas containing varying amounts of hydrogen and higher hydrocarbons. The performance is evaluated by means of single burner high pressure testing at full scale and at engine-relevant conditions.
The fuel blends studied introduce variations in Wobbe index and reactivity. The latter influences, for example, laminar and turbulent burning velocities, which are significant parameters for conventional lean premixed burners such as the EV, and auto-ignition delay times, which is a significant parameter for reheat burners, such as the SEV. An increase in fuel reactivity can lead to increased NOx emissions, flashback sensitivity and flame dynamics. The impact of the fuel blends and operating parameters, such as flame temperature, on the combustion performance is studied. Results indicate that variation of flame temperature of the first burner is an effective parameter to maintain low NOx emissions as well as offsetting the impact of fuel reactivity on the auto-ignition delay time of the downstream reheat burner. The relative impact of hydrogen and higher hydrocarbons is in agreement with results from simple reactor and 1D flame analyses. The changes in combustion behaviour can be compensated by a slightly extended operation concept of the engine following the guidelines of the existing C2+ operation concept and will lead to a widened, safe operational range of Alstom reheat engines with respect to fuel flexibility without hardware modifications.
Radial Lift-Based Cascade for Bi-Directional Wave Energy Air-Turbines
Authors: Moisel Christoph , Carolus Thomas H. 
Published: September 2014

Over the last decades various turbine designs have been proposed capable of handling a bi-directional flow in an oscillating water column (OWC) ocean wave power plant. The radial bi-directional lift-based turbine proposed by Kentfield in the early 1980ies is one candidate for power take-off in OWC’s. Key element of this air-turbine is a radial cascade of non-staggered blades made of symmetrical airfoils, with their mean lines geometrically mapped on the rotor’s circumference. The objective of this study is to understand and quantify the performance behavior of an isolated cascade of unstaggered radial blades under bi-directional flow by means of a numerical experiment.
3D boundary layer interaction in the corners where the blades are attached to back and front plate degrade cascade performance. But even with side wall effects neglected the through flow direction (centrifugal or centripetal) has a substantial impact. A variation of the radial cascade parameter ‘chord length/radius ratio’ revealed that the performance characteristics can be improved considerably in terms of stall margin by choosing large values of the chord length/radius ratio. This effect is more pronounced for the centrifugal but also existing for centripetal through flow direction. As one increases the chord length/radius ratio the mean flow, the cascade operates in, is modified from plane to curved.
Chordwise pressure and friction distributions on the blade surfaces did not disclose a plausible mechanism. However, one hypothesis to explain to the most favorable stall behavior of the more curved cascades is a large stable vortex detected at the blade suction that generates a new ‘blade’ contour. This allows the flow to be attached on the blade suction side at large angles of attack and hence increases lift.
Influence of Degree of Reaction on Turbine Performance for Pulsating Flow Conditions
Authors: Roclawski Harald , Gugau Marc , Langecker Florian , Böhle Martin 
Published: September 2014

This paper presents a study on the influence of the degree of reaction (DoR) on turbine performance under highly pulsating inflow. A reference test turbine wheel is designed and scaled to three different wheel diameters while an identical flow capacity of all three turbines is provided by adjusting the volute size. Hence, the three turbines differ by their DoR, inertia and efficiency characteristic. The investigation is done completely numerically using highly validated models. Naturally, the pulsating flow character of a 4-cylinder gasoline engine requires unsteady CFD. In addition steady-state turbine maps were calculated beforehand as a reference base.
The results of the steady state calculation show that for the combination of the bigger turbine wheel with the smaller turbine volute the peak efficiency is smaller but is shifted towards higher pressure ratios respectively to lower blade speed ratios. This is fundamentally beneficial for turbines in automotive turbochargers for gasoline engines characterized by highly pulsating flow conditions, in particular at lower engine speeds. For the transient flow calculations with pulsating turbine inflow, the hysteresis loop and the turbine power generation was investigated. It is shown that the smallest volute compared to the biggest one causes a more contracted hysteresis loop combined with increased power output within one pulse cycle.
In order to include the influence of moment of inertia, the turbines with varying DoR but same flow capacity were analytically compared with a 1D code simulating engine load step operation. Thus, the paper shows the effect of turbine DoR on both, steady-state turbine performance under pulsating inflow and the capability for optimum engine load step operation.
Time-Linearized Forced Response Analysis of a Counter Rotating Fan: Part I — Theoretical Concept of a Fully Time-Linear Forced Response Analysis
Authors: Blocher Michael , Gómez Fernández Io Eunice 
Published: September 2014

From 2010 to 2013, several institutes of the German Aerospace Center investigated a counter rotating fan arrangement called CRISP2. While having efficiency advantages over rotor-stator arrangements, counter rotating fans might be subject to increased aerodynamic excitation as well. It is well known that rotor-stator interaction (in this case rotor-rotor-interaction) can result in aerodynamic excitation of blades leading to high cycle fatigue. Therefore, forced response calculations and an estimation of the static and dynamic loads during operation are essential prior to production and rig tests.
At the Institute of Aeroelasticity, loosely coupled approaches for forced response calculations have been employed for a number of years (Vasanthakumar [1]).
Due to a limited time frame for the forced response simulation, it was decided to use this loosely coupled approach for the forced response simulations in CRISP2 as well and to reduce its time consumption even more by using a time-linear approach for the forcing calculations. The theoretical concepts and their implementation into a forced response simulation are highlighted. Special consideration is given to the linearized unsteady simulations with gust boundary conditions that have been implemented into the DLR in-house flow solver TRACE [2].
The advantages and drawbacks of a fully time-linear loosely coupled method compared to more accurate and complicated approaches are discussed.
Concurrent Blade Aerodynamic-Aeroelastic Design Optimization With Re-Scaled Response Surface
Authors: Valero O. , He L. , Li Y. S. 
Published: September 2014

Given the ever increasing demands on turbomachinery performance, various advanced blade shape optimizations have been actively developed and applied in modern blading designs. Multidisciplinary and concurrent optimizations have attracted considerable attention, offering the advantage of disciplinary interactions being included more simultaneously in a design process.
This paper presents the development of a multidisciplinary optimization algorithm for the concurrent blade aerodynamic and aeromechanic shape optimization of realistic 3D turbine stages. A non-gradient algorithm is enhanced by a new re-scaled response surface (RSM) model. This meta-model is able to rescale the design space and redefine the response surface during a blade shape optimization process, leading to a much enhanced convergence compared to a standard RSM approach. The optimization algorithm is developed in conjunction with an efficient nonlinear harmonic phase solution method solving the unsteady flow equations in the frequency domain, combined with a finite element analysis (FEA) to extract the structural dynamic characteristics of the blades.
The effectiveness of the concurrent method is examined for an optimized design of a realistic LP turbine stage. The optimization goals are the maximization of the isentropic stage efficiency and aeroelastic flutter stability (aero-damping). Two sets of cases are considered. In the first set, the shaping is applied only to stator blades, while for the second set, both stator and rotor blades are shaped. The concurrent cases are compared with their single-disciplinary counterparts. For both sets of the cases, the advantages of the concurrent treatment are clearly demonstrated.
CFD Evaluations of Unconventional Film Cooling Scaling Parameters on a Simulated Turbine Blade Leading Edge
Authors: Rutledge James L. , Polanka Marc D. 
Published: September 2014

While it is well understood that certain nondimensional parameters, such as freestream Reynolds number and turbulence intensity, must be matched for proper design of film cooling experiments, uncertainty continues on the ideal method to scale film cooling flow rate. This debate typically surrounds the influence of the coolant to freestream density ratio and whether mass flux ratio or momentum flux ratio properly accounts for the density effects. Unfortunately, density is not the only fluid property to differ between typical wind tunnel experiments and actual turbine conditions. Temperature differences account for the majority of the property differences; however, attempts to match density ratio through the use of alternative gases can exacerbate these property differences.
A computational study was conducted to determine the influence of other fluid properties besides density — namely specific heat, thermal conductivity, and dynamic viscosity. CFD simulations were performed by altering traditional film cooling nondimensional parameters as well as others such as the Reynolds number ratio, Prandtl number ratio, and heat capacity ratio to evaluate their effects on adiabatic effectiveness and heat transfer coefficient. A cylindrical leading edge with a flat afterbody was used to simulate a turbine blade leading edge region. A single coolant hole was located 21.5° from the leading edge, angled 20° to the surface and 90° from the streamwise direction. Results indicated that thermal properties can play a significant role in understanding and matching results in cooling performance. Density effects certainly dominate; however, variations in conductivity and heat capacity can result in 10% or higher changes in the resulting heat flux to the surface when scaling ambient rig configurations to engine representative conditions.
Forced Response Prediction of an Axial Turbine Rotor With Regard to Aerodynamically Mistuned Excitation
Authors: Figaschewsky Felix , Giersch Thomas , Kühhorn Arnold 
Published: September 2014

The design of both efficient and reliable turbomachinery blades demands a detailed knowledge of static and dynamic forces during operation.
This paper aims to contribute to the proper identification of dynamic excitation mechanisms acting on an axial turbine rotor, particularly with regard to deviations of the NGV’s nominal geometry due to the use of variable vanes or tolerances in manufacturing.
As variations of the NGV’s geometry disturb the perfectly periodic pattern of the downstream flow features, other spectral components than those correlated with the number of stator vanes are possible to appear. These frequency components may lead to low engine order excitation of fundamental blade modes at high engine speeds. Under these operating conditions the rotor is already highly loaded with centrifugal forces and additional dynamic excitation may cause unacceptable stresses.
Thus aerodynamic mistuning might be a limiting criterion for the design of a highly loaded turbine rotor.
Within this paper 2 dimensional CFD-models are used to investigate both, the determination of the wake of a geometric mistuned stator guide vane and the influence of the resulting excitation on the adjacent rotor stage due to aerodynamically mistuned flow. In order to generate a mistuned NGV geometry, variations of pitch and stagger angle are taken into account and a mesh morpher is used to produce computational domains of the mistuned geometry on the basis of a nominal mesh.
Additionally a simplified reconstruction process based on a set of CFD computations will be introduced, being able to reproduce the spectral components of the mistuned wake by specifying a certain geometric mistuning distribution.
The prediction of the resulting modal forces is carried out in time domain and approaches with lower fidelity are investigated with respect to their capability of reproducing the key features of an aerodynamically mistuned excitation mechanism.
Reverse-Pass Cooling Systems for Improved Performance
Authors: Kirollos Benjamin , Povey Thomas 
Published: September 2014

Total heat transfer between a hot and a cold stream of gas across a non-porous conductive wall is greatest when the two streams flow in opposite directions. This counter-current arrangement outperforms the co-current arrangement because the mean driving temperature difference is larger. This simple concept, whilst familiar in the heat exchanger community, has received no discussion in papers concerned with cooling of hot-section gas turbine components (e.g. turbine vanes/blades, combustor liners, afterburners). This is evidenced by the fact that there are numerous operational systems which would be significantly improved by the application of ‘reverse-pass’ cooling. That is, internal coolant flowing substantially in the opposite direction to the mainstream flow. A reverse-pass system differs from a counter-current system in that the cold fluid is also used for film cooling. Such systems can be realised when normal engine design constraints are taken into account.
In this paper, the thermal performance of reverse-pass arrangements is assessed using bespoke 2D numerical conjugate heat transfer models, and compared to baseline forward-pass and adiabatic arrangements. It is shown that for a modularised reverse-pass arrangement implemented in a flat plate, significantly less coolant is required to maintain metal temperatures below a specified limit than for the corresponding forward-pass system. The geometry is applicable to combustor liners and afterburners. Characteristically, reverse-pass systems have the benefit of reducing lateral temperature gradients in the wall.
The concept is demonstrated by modelling the pressure and suction surfaces of a typical nozzle guide vane with both internal and film cooling. For the same cooling mass flow rate, the reverse-pass system is shown to reduce the peak temperature on the suction side and reduce lateral temperature gradients on both suction and pressure sides.
The purpose of this paper is to demonstrate that by introducing concepts familiar in the heat exchanger community, engine hot-section cooling efficiency can be improved whilst respecting conventional manufacturing constraints.
Combustion System Development and Testing for MAN’s New Industrial Gas Turbines MGT 6100 and MGT 6200
Authors: Reiss Frank , Wiers Sven-Hendrik , Orth Ulrich , Aschenbruck Emil , Lauer Martin , El Masalme Jaman 
Published: September 2014

This paper describes the development and test results of the low emission combustion system for the new industrial gas turbines in the 6–7 MW class from MAN Diesel & Turbo.
The design of a robust combustion system and the achievement of very low emission targets were the most important design goals of the combustor development.
During the design phase, the analysis of the combustor (i.e. burner design, air distribution, liner cooling design) was supported with different CFD tools.
This advanced Dry Low Emission can combustion system (ACC) consists of 6 cans mounted externally on the gas turbine.
The behavior and performance of a single can sector was tested over a wide load range and with different boundary conditions; first on an atmospheric test rig and later on a high pressure test rig with extensive instrumentation to ensure an efficient test campaign and accurate data.
The atmospheric tests showed a very good performance for all combustor parts and promising results. The high pressure tests demonstrated very stable behavior at all operation modes and very low emissions to satisfy stringent environmental requirements.
The whole operation concept of the combustion system was tested first on the single-can high pressure test bed and later on twin and single shaft gas turbines at MAN’s gas turbine test facility. During the engine tests, the can combustors demonstrated the expected combustion performance under real operation conditions.
All emissions and performance targets were fully achieved. On the single shaft engine, the combustors were running with single digit ppm NOx levels between 50% and 100% load.
The validation phase and further optimization of the gas turbines and the engine components are ongoing.
The highlights of the development process and results of the combustor and engine tests will be presented and discussed within this paper.
Comparative Study of CFD Solver Models for Modeling of Flow Over Wind Turbine Airfoils
Authors: Kirk William T. , Capece V. R. , Pechlivanoglou G. , Nayeri C. N. , Paschereit C. O. 
Published: September 2014

This paper presents an evaluation of XFOIL and a commercially available CFD solver to predict the two-dimensional lift and drag coefficients of wind turbine airfoil sections for attached and separated flows. The computational solutions are correlated with the experimental data for the DU 96-W-180 airfoil that has been generated from wind tunnel testing performed at TU Delft and TU Berlin. CFD solutions are presented for turbulent calculations using the Shear-Stress Transport (SST) [1] and Spalart-Allmaras [2] turbulence models and transition calculations using the SST γ-θ model. Transition points from the CFD simulations are compared to the results obtained using XFOIL [3].
The paper culminates in a quantitative analysis identifying the deviations of the XFOIL and CFD solutions from the experimental data. This analysis uses the experimental polars generated by TU Delft and TU Berlin as a baseline for the comparison with the end goal of determining the best computational source of design polars for use in industry.