bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inverse Aeroacoustic Design of Axial Fans Using Genetic Optimization and the Lattice-Boltzmann Method
Authors: Stadler Michael , Schmitz Michael B. , Laufer Wolfgang , Ragg Peter 
Published: November 2013

The noise emitted by axial fans plays an integral role in product design. When conventional design procedures are applied, aeroacoustic properties are controlled via an extensive trial-and-error process. This involves building physical prototypes and performing acoustic measurements. In general, this procedure makes it difficult for a designer to gain an understanding of the functional relationship between noise and geometrical parameters of the fan. Hence, it is difficult for a human designer to control the aeroacoustic properties of the fan.
To reduce the complexity of this process, we propose an inverse design methodology driven by a genetic algorithm. It aims to find the fan geometry for a set of given objectives. These include, most notably, the sound pressure frequency spectrum, aerodynamic efficiency, pressure head and flow rate. Individual bands of the sound pressure frequency spectrum may be controlled implicitly as a function of certain geometric parameters of the fan.
In keeping with inverse design theory, we represent the design of axial fans as a multi-objective, multi-parameter optimization problem. The individual geometric components of the fan (e.g., rotor blades, winglets, guide vanes, shroud and diffusor) are represented by free-form surfaces. In particular, each blade of the fan is parameterized individually. Hence, the resulting fan is composed of geometrically different blades. This approach is useful when studying noise reduction.
For the analysis of the flow field and associated objectives, we utilize a standard RANS solver. However, for the evaluation of the generated noise, a meshless Lattice-Boltzmann solver is employed. The method is demonstrated for a small axial fan, for which tonal noise is reduced.
Coupled Aero-Thermodynamics Optimization for the Cooling System of a Turbine Vane
Authors: Chi Zhongran , Ren Jing , Jiang Hongde 
Published: November 2013

Cooling system design for the air-cooled turbine is a critical issue in modern gas turbine engineering. Advances in CFD technology and optimization methodology is providing new prospects for turbine cooling system design, that the optimum cooling system of the vanes and blades could be designed automatically by the optimization search coupled with the Conjugate Heat Transfer (CHT) analysis.
An optimization platform consists of the Generic Algorithms (GA), a mesh generation tool (Coolmesh), and the CHT solver (ANSYS CFX) is presented in this paper. The optimization study was aimed at finding the optimum cooling structure for the 2nd stage vane of the E3 engine, with acceptable metal temperature distribution and limited coolant amount simultaneously. The vane was installed with impingement and pin-fin cooling structure. The optimization search involved the design of critical parameters of the cooling system, including the size of impingement tube, diameter and distribution of impingement holes, and the size and distribution of pin-fin near trailing edge.
The optimization design was carried under two engine operating conditions to explore the affect of different boundary conditions. A constant pressure drop was assumed within the cooling system during each optimization. To make the problem computationally faster, the simulations were approached for the interior only (solid and coolant). A weighed function of temperature distribution and coolant mass flow was used as the objective of the Single Objective Generic Algorithms (SOGA). The result showed that the optimal cooling system configuration with considerable cooling performance could be designed through SOGA optimization without human interference.
N+3 and N+4 Generation Aeropropulsion Engine Combustors: Part 2 — Medium Size Rich-Dome Engines and Lean-Domes
Authors: Mongia Hukam C. 
Published: November 2013

Comprehensive assessment of the medium size rich-dome engines was conducted leading to the following emissions correlations:
(1) LTO NOx = 1.129 × OPR 1.0899 with R 2 = 0.9248
Takeoff NOxEI given by
(2) NOxEI = 0.0729 × OPR 1.7197 with R 2 = 0.9603
COEI idle = 396.42 NOxEI Takeoff 0.814
These correlations may be compared with the following for the CFM56 Tech Insertion:
Takeoff NOxEI CFM_TI = 0.0744 × OPR 1.7151
Idle COEI CFM_TI = 396.42 Takeoff NOxEI 0.814
Idle HCEI CFM_TI = 0.1609 × Idle COEI - 3.1959
TALON II takeoff NOxEI data are reproduced well by:
NOxEI TALON II = 0.0167 × OPR 2.1403
TALON II gives 10% lower NOx at 26 OPR and its NOx is comparable with the CFM_TI at 34 OPR.
The CFM DAC technology is competitive with LEC’s for the low rated thrust engines. However, interaction between the two domes leads to early quenching with resultant higher idle COEI plateau. On the other hand, the 40 OPR lean DAC gave 25% higher NOx than LEC. Moreover, lean DAC (Gen-1) impacted fuel burn adversely making its likelihood to continue as product discouraging.
The second generation lean dome technology initially kicked off under NASA sponsorship with significantly larger funding support from the CFMI and GE Aviation (GEA) led to successful introduction of TAPS into products (GEnx-1B and Gen-2B) with potential applications in other future GEA engines.
Fuel Flexible Rich Catalytic Lean Burn System for Low BTU Fuels
Authors: Alavandi Sandeep K. , Etemad Shahrokh , Baird Benjamin D. 
Published: November 2013

Limited fuel resources, increasing energy demand, and stringent emission regulations are drivers to evaluate process off-gases or process waste streams as fuels for power generation. Often these process waste streams have low energy content and their operability in gas turbines leads to issues such as unstable or incomplete combustion and changes in acoustic response. Due to above reasons, these fuels cannot be used directly without modifications or efficiency penalties in gas turbine engines.
To enable the use of the wide variety of ultra-low and low Btu fuels in gas turbine engines, a rich catalytic lean burn (RCL®) combustion system was developed and tested in a subscale high pressure (10 atm.) rig. Previous work has shown promise with fuels such as blast furnace gas (BFG) with Lower Heating Value (LHV) of 3.1 MJ/Nm3 (85 Btu/scf). The current testing extends the limits of RCL® operability to other weak fuels by further modifying and improving the injector to achieve enhanced flame stability. Fuels containing low methane content such as weak natural gas with an LHV of 6.5 MJ/Nm3 (180 Btu/scf) to fuels containing higher methane content such as landfill gas with an LHV of 21.1 MJ/Nm3 (580 Btu/scf) were tested. These fuels demonstrated improved combustion stability with an extended turndown (defined as the difference between catalytic and non-catalytic lean blow out) of 140°C–170°C (280°F–340°F) with CO and NOx emissions lower than 5 ppm corrected to 15% O2.
Investigation of a Generic Gas Turbine Combustor With Exhaust Gas Recirculation
Authors: Ulmer Sebastian , Joos Franz 
Published: November 2013

On the topic of CO2 capture from gas turbines, exhaust gas recirculation (EGR) is a commonly discussed method to increase CO2 concentration at a gas turbine outlet to make the CO2 capture process more efficient. This paper presents the influence of the recirculation on heat release rate and emissions. The investigation is made using the commercial RANS solver ANSYS CFX coupled with an in-house code for a hybrid transported PDF/RANS simulation using detailed chemistry of GRI 3.0.
Initially an investigation on reactivity was made using numerical calculation of laminar flame speed. It is found that exhaust gas recirculation has only a minor effect on reactivity in lean premixed combustion. Therefore, the operation point of the combustor can be kept constant with and without EGR.
Simulations of the combustor with exhaust gas recirculation using the hybrid PDF/RANS with GRI 3.0 show a minor influence of NO and NO2 doping of the vitiated air on the flame speed and the doping delays heat release slightly. CO doping has no effect on heat release rate. CO emissions at combustor exit remain unaffected by NO, CO or NO2 doping.
Seeding the vitiated air with 50ppm nitric oxides reveal that any NO2 present in the vitiated air is reduced to NO in the flame. NO2 emissions increase with NO2 doping but are still 2 magnitudes lower than NO emissions. It is found that NO is reduced by 3% due to of NO reburn. Based on literature data it is concluded that there is a deficit of the GRI 3.0 reaction mechanism. Experimental data taken from literature reveal of NO reburn by approximately 20%. Therefore emission data of nitric oxides of flames that should show a considerable reburn effect should be used with caution, while heat release and CO emissions are predicted more accurately.
It is shown, that with the model created for the generic gas turbine combustor it is possible to study the effects of exhaust gas recirculation on the combustion process in detail and resolve detailed kinetic effects.
CFD Simulations of Full Surface Passive Effusion Mass Injections in a Rectangular S-Bend Diffuser
Authors: Ng B. C. N. , Birk A. M. 
Published: November 2013

A coarse grid CFD methodology was employed to simulate internal flow passages with full coverage effusion cooling by imposing momentum sinks on effusion cooled surfaces based on a perforated plate pressure loss analogy. The methodology was implemented by specifying 1D Porous Jump boundary conditions (available in ANSYS FLUENT) on the effusion cooled surfaces.
Numerical simulations were conducted based on the experimental data of an S-duct diffusing passage where ambient air was passively drawn into the sub-atmospheric passage along the different effusion surfaces with 1 mm diameter holes spaced 4 mm apart. The porous wall simulations were also compared to an alternative CFD approach with mass inlet boundary specified on the effusion surfaces.
The proposed porous wall model is promising for practical design applications with the reasonable simulations of the S-duct flow fields with effusion injections. A reasonable accuracy in the results of injection mass flow rates was also obtained for the different effusion configurations. Discrepancies in the simulations of flow momentum components were mainly contributed to the diminishing effects of discrete injections at the aft-section of cooling surface due to the development of a shear layer across the free surfaces (porous jump boundaries) between the main flow and coolant flow.
Using Hydrogen as Gas Turbine Fuel: Premixed Versus Diffusive Flame Combustors
Authors: Gazzani Matteo , Chiesa Paolo , Martelli Emanuele , Sigali Stefano , Brunetti Iarno 
Published: November 2013

This work aims at estimating the efficiency gain resulting from using lean premixed combustors in hydrogen fired combined cycles with respect to diffusive flame combustors with significant inert dilution to limit NOX emissions. The analysis is carried out by considering a hydrogen fired, specifically tailored gas turbine whose features are representative of a state-of-art natural gas fired F-class gas turbine.
The comparison between diffusion flame and lean premixed combustion is carried out considering nitrogen and steam as diluents, as well as different stoichiometric flame temperatures and pressure drops. Results show that the adoption of lean premixed combustors allows to significantly reduce the efficiency decay resulting from inert dilution. Combined cycle efficiency slightly reduces from 58.5–57.9% when combustor pressure drops vary in the range 3 to 10%. Such efficiency values are comparatively higher than those achieved by diffusive flame combustor with inert dilution.
Finally, the study investigated the effects of decreasing the maximum operating blade temperature so as to cope with possible degradation mechanisms induced by hydrogen combustion.
Experimental and Numerical Characterization of the Dry Low NOx Micromix Hydrogen Combustion Principle at Increased Energy Density for Industrial Hydrogen Gas Turbine Applications
Authors: Funke H. H.-W. , Boerner S. , Keinz J. , Kusterer K. , Haj Ayed A. , Tekin N. , Kazari M. , Kitajima J. , Horikawa A. , Okada K. 
Published: November 2013

In the future low pollution power generation can be achieved by application of hydrogen as a possible alternative gas turbine fuel if the hydrogen is produced by renewable energy sources such as wind energy or biomass. The utilization of existing IGCC power plant technology with the combination of low cost coal as a bridge to renewable energy sources such as biomass can support the international effort to reduce the environmental impact of electricity generation. Against this background the dry low NOx Micromix combustion principle for hydrogen is developed for years to significantly reduce NOx emissions. This combustion principle is based on cross-flow mixing of air and gaseous hydrogen and burns in multiple miniaturized diffusion-type flames. The two advantages of this principle are the inherent safety against flash-back and the low NOx concentrations due to a very short residence time of reactants in the flame region of the micro-flames.
The paper presents experimental results showing the significant reduction of NOx emissions at high equivalence ratios and at simultaneously increased energy density under preheated atmospheric conditions. Furthermore the paper presents the feasibility of enlarged Micromix hydrogen injectors reducing the number of required injectors of a full-scale Micromix combustion chamber while maintaining the thermal energy output with significantly low NOx formation.
The experimental investigations are accompanied by 3D numerical reacting flow simulations based on a simplified hydrogen combustion model. Comparison with experimental results shows good agreement with respect to flame structure, shape and anchoring position. Thus, the experimental and numerical results highlight further potential of the Micromix combustion principle for low NOx combustion of hydrogen in industrial gas turbine applications.
Comparative Experimental Investigation on Aerodynamic Performance of a Steam Turbine Cascades: Part II — Stator Vanes
Authors: Gao Lei , Zheng Qun , Chen Hang 
Published: November 2013

In this paper, the eighth and the ninth stage stator blades of a marine steam turbine are improved and the experimental research has been carried out on aerodynamic performance at 50% blade height of the original and the improved plane cascades. The experimental results indicate that both of the two original stator blades are uniform loading type, which are improved and designed as the aft-loaded.
The results also show that, comparing with the original blade, the improved one can shorten the length of reverse pressure gradient, therefore the reverse pressure gradient is reduced and the adaptability of cascades to incidence variation is enhanced. Meanwhile, the thin trailing edge of aft-loaded blade not only increases the base pressure of the wake region, but also reduces the width of the wake region. In addition, the results reveal that the losses of modified blades are lower than the original ones under the experimental conditions of different exit Mach numbers and different angle of incidences.
Heat Transfer and Flow Characteristics in 90 deg Ribbed Duct Using Different Coolants
Authors: Elwekeel Fifi N. M. , Zheng Qun , Abdala Antar M. M. 
Published: November 2013

Several of industrial applications such as electronic devices, heat exchangers, gas turbine blades, etc. need cooling processes. The internal cooling technique is proper to some applications. In the present work, computational simulations were made using ANSYS CFX to predict the improvements of internal heat transfer in rectangular ribbed channel using different coolants. Several coolants such as air, steam, air/mist and steam/mist were investigated. The shear stress transport model (SST) is selected by comparing the predictions of different turbulence models with experimental results.
The results indicate that the heat transfer coefficients are enhanced in ribbed channel at injection small amount of mist. The heat transfer coefficients of air/mist, steam and steam/mist increase by 12.5%, 49.5% and 107% than that of air, respectively. Furthermore, comparing with air, the air/mist heat transfer coefficient enhances by about 1.05 to 1.14 times when mist mass fraction increases from 2% to 8%, respectively. For steam/mist heat transfer coefficient increases by about 1.12 to 1.27 times higher than that of steam over the consider range of mist mass fraction.
Characterizing Combustion of Synthetic and Conventional Fuels in a Toroidal Well Stirred Reactor
Authors: Vijlee Shazib Z. , Kramlich John C. , Mescher Ann M. , Stouffer Scott D. , O’Neil-Abels Alanna R. 
Published: November 2013

The use of alternative/synthetic fuels in jet engines requires improved understanding and prediction of the performance envelopes and emissions characteristics relative to the behavior of conventional fuels. In this study, experiments in a toroidal well-stirred reactor (TWSR) are used to study lean premixed combustion temperature and extinction behavior for several fuels including simple alkanes, synthetic jet fuels, and conventional JP8. A perfectly stirred reactor (PSR) model is used to interpret the observed behavior.
The first portion of the study deals with jet fuels and synthetic jet fuels with varying concentrations of added aromatic compounds. Synthetic fuels contain little or no natural aromatic species, so aromatic compounds are added to the fuel because fuel system seals require these species to function properly. The liquid fuels are prevaporized and premixed before being burned in the TWSR. Air flow is held constant to keep the reactor loading roughly constant. Temperature is monitored inside the reactor as the fuel flow rate is slowly lowered until extinction occurs. The extinction point is defined by both its equivalence ratio and temperature. The measured blowout point is very similar for all four synthetic fuels and the baseline JP8 at aromatic concentrations of up to 20% by volume. Since blowout is essentially the same for all the base fuels at low aromatic concentrations, a single fuel was used to test the effect of aromatic concentrations from 0 to 100%. PSR models of these complex fuels show the expected result that behavior diverges from an ideal, perfectly premixed model as the combustion approaches extinction.
The second portion of this study deals with lean premixed combustion of simple gaseous alkanes (methane, ethane, and propane) in the same TWSR. These simpler fuels were tested for extinction in a similar manner to the complex fuels, and behavior was characterized similarly. Once again, PSR models show that the TWSR behaves similar to a PSR during stable combustion far from blowout, but as it approaches blowout and becomes less stable a single PSR no longer accurately describes the TWSR.
This work is a step towards developing chemical reactor networks (CRNs) based on computational fluid dynamics (CFD) of the simple gaseous fuels in the TWSR. Ultimately, CRNs are the only realistic way to accurately perform detailed chemical modeling of the combustion of complex liquid fuels.
Heat Transfer Characteristics of a Blade Trailing Edge With Pressure Side Bleed Extraction
Authors: Saxer-Felici H. , Naik S. , Gritsch M. 
Published: November 2013

This paper investigates the heat transfer and pressure loss characteristic in the internal cooling system of the trailing edge of a gas turbine blade. The geometrical profile of the blade trailing edge and the operating conditions considered are representative of that normally found in a heavy-duty gas turbine. The trailing edge geometry consists of two radial passages with inclined turbulators which are connected with a bend. The trailing edge section consists of pins rows and a flow ejection cut-out slot. The impact of a cross-over hole in the web connecting the serpentine passages is also investigated.
Both numerical and experimental studies were conducted at several passage Reynolds numbers ranging from 104 to 106. Experiments were conducted in a Perspex model at atmospheric conditions. The internal heat transfer coefficients were measured via the transient liquid crystal method and the pressure drop was measured via pressure taps. The impact of blade rotation on the heat transfer and pressure drop was also assessed numerically.
Comparison of the measured and predicted heat transfer coefficients and pressure drops shows a good agreement for several flow conditions. The three-dimensional flow field in the passage and in the downstream pin banks was well captured numerically, with and without coolant injection via cross-over hole.
Numerical Analysis of Effusion Plates for Combustor Liners Cooling With Varying Density Ratio
Authors: Andrei L. , Andreini A. , Bianchini C. , Facchini B. , Mazzei L. 
Published: November 2013

Effusion cooling technology has been assessed in past years as one of the most efficient methods to maintain allowable working temperature of combustor liners. Despite many efforts reported in literature to characterize the cooling performances of those devices, detailed analysis of the mixing process between coolant and hot gas are difficult to perform especially in case superposition and density ratio effects become important. Furthermore, recent investigations on the acoustic properties of these perforations pointed out the challenge to maintain optimal cooling performance also with orthogonal holes which showed higher sound absorption.
This paper performs a CFD analysis of the flow and thermal field associated with adiabatic wall conditions to compute the cooling effectiveness. The geometry consists of an effusion cooling plate drilled with 18 holes and fed separately with a cold and hot gas flow. Two types of perforations equivalent in porosity and pitches are investigated to assess the influence of the drilling angle between 30 and 90 deg. The reference conditions considered in this work comprehend an effective blowing ratio ranging between 1 and 3 at isothermal conditions (reaching a maximum hole Reynolds number of 10000) and high inlet turbulence intensity (17%). This set of conditions was exploited to perform a validation of the numerical procedure against detailed experimental data presented in another paper. Inlet turbulence effects highlighted by measurements for the slanted perforation were also investigated simulating a low turbulence condition corresponding to 1.6% of intensity. Furthermore the nominal DR = 1.0 was increased up to 1.7 to expand the available data set towards typical working conditions for aero-engines.
Steady state RANS calculations were performed with the commercial code ANSYS® CFX, modeling turbulence by means of the k — ω SST. In order to include anisotropic diffusion effects due to turbulence damping in the near wall region, the turbulence model is corrected considering a tensorial definition of the eddy viscosity with an algebraic correction to dope its stream-span components. Computational grids were finely clustered close to the main plate and inside the holes to obtain y+ < 1, to maximize solver accuracy according to previous similar analysis.