bluuebunny/crossref_metadata_2025 huggingface dataset:
Rough Set Diagnostic Frameworks for Gas Turbine Fault Classification
Authors: Wang L. , Li Y. G. , Abdul Ghafir M. F.
Published: November 2013

Fault classification has become one of the main features in gas turbine health monitoring. Hence techniques such as gas path analysis, artificial neural networks, expert systems, fuzzy logic and many others have been developed for this purpose in the past. In this paper, an alternative rough set based diagnostic method using enhanced fault signatures combined with three fault classification frameworks for gas turbine fault classification have been introduced, i.e. Framework 1 with a single step to classify single and dual component faults, Framework 2 with the first step to identify weather it is a single or dual component faults and the second step to identify the individual faults, and Framework 3 with the first step to identify faults associated with component types and the second step to identify the individual faults. Such frameworks have been applied to the fault classification of a model two-spool turbofan gas turbine engine implemented with single and dual component faults to test the effectiveness of the frameworks. It has been demonstrated in the application that all three framework configurations can provide satisfactory fault classification and that Framework 1 has higher fault classification success rate than that of Frameworks 2 and 3. In addition, Frameworks 2 and 3 have better performance in identifying fault types than Framework 1.
Combined Heat and Power: Gas Turbine Operational Flexibility
Authors: DiCampli James
Published: November 2013

Combined heat and power (CHP) is an application that utilizes the exhaust heat generated from a gas turbine and converts it into a useful energy source for heating & cooling, or additional electric generation in combined cycle configurations. Compared to simple-cycle plants with no heat recovery, CHP plants emit fewer greenhouse gasses and other emissions, while generating significantly more useful energy per unit of fuel consumed. Clean plants are easier to permit, build and operate. Because of these advantages, projections show CHP capacity is expected to double and account for 24% of global electricity production by 2030. An aeroderivative power plant has distinct advantages to meet CHP needs. These include high thermal efficiency, low cost, easy installation, proven reliability, compact design for urban areas, simple operation and maintenance, fuel flexibility, and full power generation in a very short time period.

There has been extensive discussion and analyses on modifying purge requirements on cycling units for faster dispatch. The National Fire Protection Association (NFPA) has required an air purge of downstream systems prior to startup to preclude potentially flammable or explosive conditions. The auto ignition temperature of natural gas fuel is around 800°F. Experience has shown that if the exhaust duct contains sufficient concentrations of captured gas fuel, and is not purged, it can ignite immediately during light off causing extensive damage to downstream equipment.

The NFPA Boiler and Combustion Systems Hazards Code Committee have developed new procedures to safely provide for a fast-start capability. The change in the code was issued in the 2011 Edition of NFPA 85 and titled the Combustion Turbine Purge Credit. For a cycling plant and hot start conditions, implementation of purge credit can reduce normal start-to-load by 15–30 minutes. Part of the time saving is the reduction of the purge time itself, and the rest is faster ramp rates due to a higher initial temperature and pressure in the heat recovery steam generator (HRSG).

This paper details the technical analysis and implementation of the NFPA purge credit recommendations on GE Power and Water aeroderivative gas turbines. This includes the hardware changes, triple block and double vent valve system (or drain for liquid fuels), and software changes that include monitoring and alarms managed by the control system.
Ridge Estimation and Principal Component Analysis to Solve an Ill-Conditioned Problem of Estimating Unmeasured Gas Turbine Parameters
Authors: Shevchenko Maksim , Yepifanov Sergiy , Loboda Igor
Published: November 2013

This paper addresses the problem of estimation of unmeasured gas turbine engine variables using statistical analysis of measured data. Possible changes of an engine health condition and lack of information about these changes caused by limited instrumentation are taken into account. Engine thrust is under consideration as one of the most important unmeasured parameters. Two common methods of aircraft gas turbine engine (GTE) thrust monitoring and their errors due to health condition changes are analyzed. Additionally, two mathematical techniques that allow reducing in-flight thrust estimation errors in the case of GTE deterioration are suggested and verified in the paper. They are a ridge trace and a principal component analysis.

A turbofan engine has been chosen as a test case. The engine has five measured variables and 23 health parameters to describe its health condition. Measurement errors are simulated using a generator of random numbers with the normal distribution. The engine is presented in calculations by its nonlinear component level model (CLM). Results of the comparison of thrust estimates computed by the CLM and the proposed techniques confirm accuracy of the techniques. The regression model on principal components has demonstrated the highest accuracy.
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.
Optimal Arrangement of Combined-Hole for Improving Film Cooling Effectiveness
Authors: Han Chang , Chi Zhongran , Ren Jing , Jiang Hongde
Published: November 2013

Film cooling technique is widely used to protect the components from being destroyed by hot mainstream in a modern gas turbine. Combining round-holes is a promising way of improving film cooling effectiveness. A batch simulation of 75 cases focusing on the arrangements of combined-hole unit with two holes for improving film cooling performance are carried out in this work, and the influence of an aerodynamic parameter, blowing ratio, is considered as well. The lateral distance and compound-angle of the two holes have relative influence on the film cooling performance of a combined-hole unit. At a small lateral distance, the film cooling effectiveness increases significantly as compound-angle increases, whereas it deteriorates at a large distance and it is barely influenced by compound-angle at a medium lateral distance. Asymmetrical compound-angle is introduced aiming to balance the two branches of vortexes, but its film cooling performance is not as good as expected. The general film cooling effectiveness is in the position between that of the adjacent symmetrical compound-angle. Besides, the optimal arrangement of combined-hole unit for improving film cooling performance is relative to local aerodynamic parameter. The combination of the lateral distance of the two holes with their compound-angles for the highest film cooling effectiveness is different at different blowing ratios.
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.
Control Strategy Study of the Series Sequential Turbocharging Using 1-D Simulation
Authors: Zhang Q. , Brace C. , Akehurst S. , Burke R. , Capon G. , Smith L. , Garrett S. , Zhang K.
Published: November 2013

The series sequential turbocharging arrangement is a promising technology to turbocharge downsized diesel engines to higher ratings with combined benefits in transient performance, fuel efficiency and emissions reduction. However, the control of such a complex charging system proves to be problematic. Without a robust control strategy, the potential of series sequential turbocharging will not be fully exploited. Worse still, a badly constructed control strategy could have serious negative impact on the turbocharger/engine system. In this paper, several control strategies of the series sequential turbocharging system were proposed and implemented in simulations.
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.
Effect of Upstream Purge Slot on a Transonic Turbine Blade Passage: Part 1 — Aerodynamic Performance
Authors: Blot Dorian M. , Roy Arnab , Ekkad Srinath V. , Ng Wing , Lohaus Andrew S. , Crawford Michael E.
Published: November 2013

In this paper, detailed experimental results of total pressure loss and secondary flow field are presented for a high turning (127°) airfoil passage in presence of an upstream purge slot (with and without coolant injection). The experiments were performed at Virginia Tech’s quasi 2D linear turbine cascade operating at transonic conditions. Measurements were made at design exit Mach number 0.88 and design incidence angle. The selected coolant to mainstream mass flow ratio (MFR) was set at 1.0%. In order to match engine representative inlet/exit blade loading, a diverging endwall was utilized where the span increased from the inlet to the exit at a 13 degree angle. A 5-hole probe traverse was used to measure exit total pressure. Pressure loss coefficients were calculated both along pitchwise and spanwise directions at 0.1 axial chord downstream of the blade trailing edge. CFD studies were conducted to compliment the experimental results. The backward facing step present with the upstream slot affects the approaching boundary layer and influences the passage horse-shoe vortex strength. The addition of coolant from the purge slot further increased the aerodynamic losses. However, the backward facing step of the upstream slot seems to be the predominant factor in affecting pressure losses when compared to with or without blowing cases. These results provide further understanding of the passage secondary flow characteristics and aid towards improved design of endwall passages. The heat transfer experiments, designed to find the heat transfer coefficient and the film cooling effectiveness are described in detail in part II of this paper [1].
Full-Coverage Film Cooling: Heat Transfer Coefficients and Film Effectiveness for a Sparse Hole Array at Different Blowing Ratios and Contraction Ratios
Authors: Ligrani Phillip , Goodro Matt , Fox Michael D. , Moon Hee-Koo
Published: November 2013

The present experimental investigation considers a full coverage film cooling arrangement with differrent streamwise static pressure gradients. The film cooling holes in adjacent streamwise rows are staggered with respect to each other, with sharp edges, and streamwise inclination angles of 20 degrees with respect to the liner surface. Data are provided for turbulent film cooling, contraction ratios of 1 and 4, blowing ratios (at the test section entrance) of 2.0, 5.0, and 10.0, coolant Reynolds numbers of 12,000, freestream temperatures from 75°C to 115°C, a film hole diameter of 7 mm, and density ratios from 1.15 to 1.25. Non-dimensional streamwise and spanwise film cooling hole spacings, X/D and Y/D, are 18, and 5, respectively. Data illustrating the effects of contraction ratio, blowing ratio, and streamwise location on local, line-averaged and spatially-averaged adiabatic film effectiveness data, and on local, line-averaged and spatially-averaged heat transfer coefficient data are presented. Varying blowing ratio values are utilized along the length of the contraction passage, which contains the cooling hole arrangement, when contraction ratio is 4. Dependence on blowing ratio indicates important influences of coolant concentration and distribution. For example, line-averaged and spatially-averaged adiabatic effectiveness data show vastly different changes with blowing ratio BR for the configurations with contraction ratios of 1 and 4. These changes from acceleration are thus mostly due to different blowing ratio distributions along the test section. In particular, much larger effectiveness alterations are present as BR changes from 2.0 to 10.0, when significant acceleration is present and Cr = 4 (in comparison with the Cr = 1 data). When BR = 10.0, much smaller changes due to different contract ratios are present. This is because coolant distributions along the test surfaces are so abundant that magnitudes of streamwise acceleration (and different streamwise variations of blowing ratio) have little effect on near-wall film concentration distributions, or on variations of film cooling effectiveness.
A Novel Chemical-Looping Hydrogen Generation System With Multi-Input Fossil Fuels
Authors: Zhang Xiaosong , Jin Hongguang
Published: November 2013

This paper proposes a multi-input chemical looping hydrogen generation system (MCLH), which generates hydrogen, through the use of natural gas and coal. In this system, a new type of oven, burning coal instead of natural gas as heating resource for hydrogen production reaction, is adopted. Coal can be converted to hydrogen indirectly without gasification. Benefits from the chemical looping process, the CO2 can be captured without energy penalty. With the same inputs of fuel, the new system can product about 16% more hydrogen than that of individual systems. As a result, the energy consumption of the hydrogen production is about 165J/mol-H2. Based on the exergy analyses, it is disclosed that the integration of synthetic utilization of natural gas and coal plays a significant role in reducing the exergy destruction of the MCLH system. The promising results obtained may lead to a clean coal technology that will utilize natural gas and coal more efficiently and economically.
Algebraic Anisotropic Turbulence Modeling of Compound Angled Film Cooling Validated by PIV and PSP Measurements
Authors: Li Xueying , Qin Yanmin , Ren Jing , Jiang Hongde
Published: November 2013

The complex structures in the flow field of gas turbine film cooling lead to the anisotropic property of the turbulent eddy viscosity and scalar diffusivity. An algebraic anisotropic turbulence model is developed while aiming at a more accurate modeling of the Reynolds stress and turbulent scalar flux. In this study the algebraic anisotropic model is validated by a series of in-house experiments for cylindrical film cooling with compound angle injection of 0, 45, and 90 deg. Adiabatic film cooling effectiveness and flow field are measured using PSP and PIV techniques on film cooling test rig in Tsinghua University. Detailed analyses of computational simulations are performed. The algebraic anisotropic model gives a good prediction of the secondary vortices associated with the jet and the trajectory of the jet, therefore improves the prediction of the scalar field. On one hand, the anisotropic eddy viscosity improves the modeling of Reynolds stress and the predictive flow field. On the other hand, the anisotropic turbulent scalar-flux model includes the role of anisotropic eddy viscosity in modeling of scalar flux and directly improves the turbulent scalar flux prediction.
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.
Development and Validation of Oxide/Oxide CMC Combustors Within the HiPOC Program
Authors: Gerendás Miklós , Wilhelmi Christian , Machry Thays , Knoche Ralf , Werth Erich , Behrendt Thomas , Koch Dietmar , Hofmann Severin , Göring Jürgen , Tushtev Kamen , Volkmann Eike
Published: November 2013

In the framework of the High Performance Oxide Ceramics program (HiPOC), three different oxide/oxide ceramic matrix composite (CMC) materials are studied for a combustion chamber application in continuation of the work reported in Gerendas et al. [1]. A variation in the micro-structural design of the three CMC materials in terms of different fiber architecture and matrix processing are considered in a first work stream. By modification of the matrix and the fiber-matrix interface as well as the application of an environmental barrier coating (EBC), the high temperature stability is enhanced. Furthermore, design concepts for the attachment of the CMC component to the metal structure of the engine are finalized in a second work stream. Issues like sealing of cooling leakage paths, allowance for the different thermal expansion and the mechanical fixation are addressed. An interim standard of the mechanical attachment scheme is studied on a shaker table. Also the friction coefficient between the metallic and ceramic components is analyzed in order to set the proper tightening torque. The manufacturing of the CMC combustor is improved in several iterations in order to achieve a high quality material with optimized fiber architecture. Afterwards, two CMC materials are selected for the combustion testing and the finalized design of the metallic and CMC components is manufactured. A fit check is performed prior to EBC application and laser drilling of the effusion holes in order to evaluate the impact of the manufacturing tolerances on the function of the sealing and attachment scheme and to correct small issues at this stage. First results from the validation testing in a high-pressure tubular combustion rig up to a Technology Readiness Level 4 (TRL4) are reported.
Experimental and Numerical Analysis of an Ignition Sequence in a Multiple-Injectors Burner
Authors: Cordier M. , Vandel A. , Renou B. , Cabot G. , Boukhalfa M. A. , Esclapez L. , Barré D. , Riber E. , Cuenot B. , Gicquel L.
Published: November 2013

The design of a gas turbine combustion chamber integrates multiple contradicting objectives. Among all the parameters available to the engineers, the number of fuel injection systems and their spacing are crucial information which need to be fixed early on in the design phase. Indeed, such choices not only impact the cost and size of the combustor but they also affect the operability of the future engine. One key objective behind these parameters is the ignition time delay needed for the whole combustion chamber to successfully light. To gather knowledge in the ignition process that takes place in real gas turbine engines, current research orient towards the development of experimental facilities that complement high fidelity unsteady numerical simulations. In this context, a multi-injectors experimental set-up located at CORIA (France) is used to validate Large Eddy Simulation (LES) tools developed by CERFACS, IFP-EN and CORIA (France). Preliminary validations against experimental data show that for a given inter-injector distance, LES stationary and ignition transient predictions are very promising and recover the main features found in the experiment. Exit mean and root mean square velocity profiles of the steady flow are in good agreement with measurements obtained for all injectors at multiple axial locations. The simulation of the ignition transient phase well captures global events such as the propagation of the flame front from one injector to its neighbors and the related mechanisms. Improvement is however still needed to recover the proper ignition time of the whole burner.
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.
Toward Efficient Computational Aeroacoustic Analysis of High Speed Jets
Authors: Nelson Chris , Cain Alan , Du Yongle , Morris Philip , Spyropoulos John
Published: November 2013

Recent improvements in the algorithms and associated processes have resulted in significant improvements in the users’ ability to obtain aeroacoustics analysis of hot supersonic jets in a timely manner using only moderate computational resources. This paper discusses these approaches using the example of the Compressible High Order Parallel Acoustics (CHOPA) solver. The fundamental strategy looks to balance computational expense with the accuracy required to predict the most important effects. The objective is to resolve the larger eddies accurately, but exchanges the resolution of fine turbulent structures in return for decreased computational resource requirements. These strategies continue to be developed, along with the corresponding software. As the work progresses, the team expects additional improvements in the near future.
Combined Solar Thermal Gas Turbine and Organic Rankine Cycle Application for Improved Cycle Efficiencies
Authors: Kusterer Karsten , Braun René , Köllen Linda , Sugimoto Takao , Tanimura Kazuhiko , Bohn Dieter
Published: November 2013

Concentrating Solar Power (CSP) technologies are considered to provide a significant contribution for the electric power production in the future. Different kinds of CSP technologies are presently in operation or under development, e.g. parabolic troughs, central receivers, solar dish systems and Fresnel reflectors. In such applications, electricity is produced by thermal energy conversion cycles. For high MW-class CSP applications usually water/steam cycles (Rankine cycles) are used. Alternative technologies, especially for central receiver applications, are open and closed gas turbine cycles (Brayton cycles), where higher receiver fluid outlet temperatures can be applied. Therefore, there is the potential of higher cycle efficiencies and the advantage of reduced water consumption. The paper presents the results for design considerations to improve a gas turbine cycle of a 2 MWel class industrial gas turbine for solar-thermal application, where solar heat is fed in by a central receiver technology. The reference process is improved significantly by application of an intercooler between the two radial compressor stages and a recuperator, which recovers heat from the exhaust gases to the compressed air before the air is further pre-heated by the solar receiver. Hybrid operation of the gas turbine is considered. In order to further improve the overall cycle efficiency, the combined operation of the gas turbine and an Organic Rankine Cycle is investigated. The ORC can be coupled to the solar-thermal gas turbine cycle at the intercooler and after the recuperator. Therefore, waste heat from different cycle positions can be transferred to the ORC for additional production of electricity. The investigations have been performed by application of improved thermodynamic and process analysis tools, which consider real gas behavior of fluids and a huge number of organic fluids for application in ORCs. The results show that by choice of a suitable organic fluid the waste heat recovery can be further improved for the investigated gas turbine cycle. The major result of the study is that by combined operation of the solar thermal gas turbine and the ORC, the combined cycle efficiency is approximately 4%-points higher than in the solar-thermal gas turbine cycle.
Development of Fuel Droplet Vaporization Rate Measurement Techniques for Realistic Burning Spray Applications
Authors: Tedder Sarah A. , Siedlak Dennis J. L. , Carter Steven G. , ReMine Daniel S.
Published: November 2013

Technology to support design for the next generation of aircraft fuel injectors is being developed by NASA’s Fundamental Aeronautics Program to reduce emissions, increase efficiency, and enable fuel flexible aircraft. The design of these fuel injectors can be aided by measuring the vaporization rates of jet fuel droplets in realistic, burning sprays. Currently, in this environment, no instantaneous vaporization rate measurement techniques have been applied. After surveying techniques for potential development for this application, two techniques were identified: stimulated Raman scattering (SRS) and droplet lasing spectroscopy (DLS). Plans were developed for the modification of these techniques for this specific application. Developments of the SRS technique were tested including measurement of a water droplet diameter change rate. SRS spectra were also collected from jet fuel droplets.
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.
The Effect of Turbulence and Real Gas Models on the Two Phase Spontaneously Condensing Flows in Nozzle
Authors: Patel Yogini , Patel Giteshkumar , Turunen-Saaresti Teemu
Published: November 2013

The aim of the paper is to analyse the effect of turbulence and real gas models on the process of spontaneous condensation in converging diverging (CD) nozzle by using commercial Computational Fluid Dynamics (CFD) code. The calculations were based on the 2-D compressible Navier-Stokes (NS) equations coupled with two-equation turbulence model, and the non-equilibrium spontaneous condensing steam flow was solved on the basis of the classical nucleation theory. The results were validated to the available experimental data.
Effect of Reynolds Number on Deposition in Fuels Flowing Over Heated Surfaces
Authors: Moses Clifford
Published: November 2013

An increasing demand is being put on the fuel as a heat sink in modern aircraft. In the end, the fuel flows through the atomizer which on the one hand is the hottest part of its thermal history, but on the other hand the most critical for resisting deposition. Most studies have concentrated on the chemistry of deposition, and in recent years there have been modeling efforts. Deposition is really the end product of a coupling between heat transfer to the fuel, chemical reactions to form insoluble gums, followed by the transport of these gums to the surface to form deposits. There is conflicting evidence and theory in the literature concerning the effect of turbulence on deposition, i.e., whether deposition increases or decreases with increasing Reynolds number. This paper demonstrates through a heat transfer analysis that the effect of Reynolds number depends upon the boundary/initial conditions. If the flow is heated from the surface, deposition decreases with increasing Reynolds number; however, for isothermal flows, i.e., preheated, deposition will increase with Reynolds number.
Numerical Simulation of Film Cooling on Rotating Blade Tips Within a High-Pressure Turbine
Authors: Lu K. , Schobeiri M. T. , Han J. C.
Published: November 2013

This paper numerically investigates the aerodynamics and film cooling effectiveness of high pressure turbine blade tips. Two different rotor blade tip configurations have been studied: the plane tip with tip hole cooling and the squealer tip with tip hole cooling. The geometry of the blades is determined based on the blade profiles within the three-stage multi-purpose turbine research facility at the Turbomachinery Performance and Flow Research Laboratory (TPFL), Texas A&M University. Seven perpendicular holes along the camber line are used for the tip hole cooling. The clearance between the blade tip and casing is 1.0% of the blade span. For each blade tip configuration, the coolant is ejected through the cooling holes under blowing ratios of M = 0.5, 1.0 and 1.5. In this paper, a comparison between the plane tip and the squealer tip has been presented. The detailed flow structures and film cooling effectiveness are discussed.
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.
Numerical Study on the Effect of Jet Slot Height on Flow and Heat Transfer of Swirl Cooling in Leading Edge Model for Gas Turbine Blade
Authors: Liu Zhao , Li Jun , Feng Zhenping
Published: November 2013

In this paper a numerical simulation is conducted to predict the swirl cooling performance of an internal leading edge cooling passage model for gas turbine blade. The Shear-Stress Transport (SST) κ-ω model is adopted for the simulation as this model was found as the best one based on authors’ previous work. Two rectangular section inlets that cause flow to impinge tangentially on the internal surface of the circular cooling passage are arranged to investigate the swirl cooling performance and its effectiveness. The effects of the Reynolds numbers, the ratio of swirl chamber radius to jet slot height with constant ratio of swirl chamber radius to jet nozzle length, and the ratio of swirl chamber radius to jet slot height while jet nozzle area is constant on the local and average flow and heat transfer characteristics for swirl cooling on cylindrical pipe are studied. The results indicate that the position of the swirl flow center is changing along the axial of the swirl chamber, and the swirl flow center of one constant axial section is not uniform as well in different ratios of swirl chamber radius to jet slot height. And larger ratio of swirl chamber radius to jet slot height and larger Reynolds number are desirable to improve the performance of swirl cooling on the turbine leading edge, though the pressure loss of the swirl chamber will increase.
Impact of Fuel Composition on Blow Off and Flashback in Swirl Stabilized Lean Premixed Combustion
Authors: Akbari Amin , McDonell Vincent , Samuelsen Scott
Published: November 2013

Co firing of natural gas with renewable fuels such as hydrogen can reduce greenhouse gas emissions, and meet other sustainability considerations. At the same time, adding hydrogen to natural gas alters combustion properties, such as burning speeds, heating values, flammability limits, and chemical characteristics. It is important to identify how combustion stability relates to fuel mixture composition in industrial gas turbines and burners and correlate such behavior to fuel properties or operating conditions. Ultimately, it is desired to predict and prevent operability issues when designing a fuel flexible gas turbine combustor. Fuel interchangeability is used to describe the ability of a substitute fuel composition to replace a baseline fuel without significantly altering performance and operation. Any substitute fuel, while maintaining the same heating load as the baseline fuel, must also provide stable combustion with low pollutant emissions. Interchangeability indices try to predict the impact of fuel composition on lean blowoff and flashback. Correlations for operability limits have been reported, though results are more consistent for blowoff compared to flashback. Yet, even for blowoff, some disagreement regarding fuel composition effects are evident. In the present work, promising correlations and parameters for lean blow off and flashback in a swirl stabilized lean premixed combustor are evaluated. Measurements are conducted for fuel compositions ranging from pure natural gas to pure hydrogen under different levels of preheat and air flow rates. The results are used to evaluate the ability of existing approaches to predict blowoff and flashback. The results show that, while a Damköhler number approach for blowoff is promising, important considerations are required in applying the method. For flashback, the quench constant parameter suggested for combustion induced vortex breakdown was applied and found to have limited success for predicting flashback in the present configuration.
Assessment of Transition Modeling for the Design of Controlled Diffusion Airfoil Compressor Cascades
Authors: Marciniak Vincent , Longhitano Marco , Kügeler Edmund
Published: November 2013

The aim of this paper is to investigate whether correlation-based transition models can be used for the design of CDA profiles. To this end, a CDA compressor cascade has been widely experimentally investigated at DLR Cologne. Off-design measurements have been carried out and the influence of the variation of four flow parameters has been investigated: The inlet Mach number, the incidence, the chord-based Reynolds number and the free-stream turbulence intensity. The inlet Mach number has been varied from 0.5 up to 0.8. The incidence was varied over the whole working range and beyond. Realistic values of the Reynolds number and of the free-stream turbulence intensity have been attained. Hence, the test case apt to assess the capacity of the DLR’s in-house turbomachinery specific CFD code TRACE to design modern compressor blades. In this paper, computations simulating the influence of those four parameters on the performance of the CDA profile are presented and compared to the measurements. Two transition models are used for this study: an in-house model denoted MultiMode model and the γ-ReΘ model. In addition, two turbulence models (Wilcox k-ω and Menter k-ω SST) and their turbomachinery extensions have also been used for this study. The results between the different numerical simulations and the measurements are discussed in term of loss coefficients and Mach number distributions. The computed losses are close to the experimental values and the physics of the flow is also well reproduced. Bypass transition as well as laminar separation bubbles have been simulated in accordance with the experimental observations. Hence, the TRACE code is able to predict the onset of transition over a wide range of flow conditions.
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.