bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Emissions Gas Turbine Combustor Development for Regional-Class Aircraft
Authors: Zelina J. , Penko P. F.
Published: August 2014

Sector-rig test results of four combustor configurations for medium-sized, gas-turbine engines are presented. The sector test section consists of a three-injector combustor cross-section, unrolled to a rectangular area, and simulating about a sixty-eight degree section of the combustor. Performance and emissions data are presented for four design-of-experiment (DOE) combinations of 1) air swirlers, 2) fuel injectors, and 3) primary-zone lengths. Emission concentrations from gas sampling are given for NOx, CO, and UHC as a function of inlet temperature, pressure, and overall fuel air ratio. NOx production as a function of inlet temperature, pressure, stoichiometry, and residence time are presented. The trade-off between NOx and CO is given over a range of operating conditions for each sector configuration.
Closed-Loop Combustion Control Using OH Radical Emissions
Authors: Meng Zhu (Julie) , Hoffa Robert J. , DeMilo Charles A. , Thamer Todd T.
Published: August 2014

The combustion process in gas-turbine engines produces emissions, especially nitrogen oxides (NOx) and carbon monoxide (CO), which change dramatically with combustor operating conditions. As part of this study, the application of active feedback control technologies to reduce thermal NOx emissions is modeled numerically and demonstrated experimentally.

A new optical flame sensor, designed by Ametek Power & Industrial Products, has been successfully implemented as the feedback element in a proof-of-concept control system used to minimize NOx emissions. The sensor consists of a robust mechanical package, as well as electronics suitable for severe gas-turbine environments. Results from system rig tests correlate closely to theoretical predictions, as described in literature and produced by a control system simulation model.

The control system simulation model predicts the efficacy of controlling engine operating characteristics based on chemical luminescence of the OH radical. The model consists of a fuel pump and metering device, a fuel-air mixing scheme, a combustion model, the new ultraviolet (UV) feedback flame sensor, and a simple gain block. The input reference to the proportional emissions control is the fuel-to-air equivalence ratio, which is empirically correlated to the desired low level of NOx emissions while satisfying other operating conditions, such as CO emissions and power.

Results from the closed-loop emissions control simulation and rig tests were analyzed to determine the capability of the UV flame sensor to measure and control the combustion process in a gas-turbine engine. The response characteristics, overshoot percentage, rise time, settling time, accuracy, resolution, and repeatability are addressed.
Rapid Liquid Fuel Mixing for Lean-Burning Combustors: Low-Power Performance
Authors: Leong May Y. , Smugeresky Craig S. , McDonell Vincent G. , Samuelsen G. Scott
Published: August 2014

Designers of advanced gas turbine combustors are considering lean direct injection strategies to achieve low NOx emission levels. In the present study, the performance of a multipoint radial airblast fuel injector (“Lean Burn Injector—LBI”) is explored for various conditions that target low-power gas turbine engine operation. Reacting tests were conducted in a model can combustor at 4 atm and 6.6 atm, and at a dome air preheat temperature of 533 K, using Jet-A as the liquid fuel. Emissions measurements were made at equivalence ratios between 0.37 and 0.65. The pressure drop across the airblast injector holes was maintained at 3% and 7–8%. The results indicate that the LBI performance for the conditions considered is not sufficiently predicted by existing emissions correlations. In addition, NOx performance is impacted by atomizing air flows, suggesting that droplet size is critical even at the expense of penetration to the wall opposite the injector. The results provide a baseline from which to optimize the performance of the LBI for low-power operation.
A New Hybrid Air Blast Nozzle for Advanced Gas Turbine Combustors
Authors: Mansour Adel , Benjamin Michael , Steinthorsson Erlendur
Published: August 2014

The push towards higher specific fuel consumption and smaller, lighter packaging for aerospace gas turbine engines has resulted in large increases in engine operating pressure and temperature. This is a trend that is expected to continue, and as a result, thermal management of the hot engine section including the fuel nozzle, combustor, and turbine has emerged as a critical technology area requiring further development. For the fuel injection system, nozzle thermal management, turndown ratio, and atomization performance while maintaining correct combustor aerodynamics are the most important performance features that necessitate optimization. Significant advances in fuel injection concepts are required to meet the increasingly demanding combustor requirements. Complex heat-shielded designs are often required to reduce nozzle wetted-wall temperatures and prevent the formation of carbonaceous deposits within the fuel delivery passages. To support the development of advanced combustors and address these increasing performance demands, Parker has developed a new Hybrid Air Blast nozzle. Advanced analytical and experimental design tools were applied to reduce the cut-and-try approach previously used in nozzle development. The developed hybrid air blast design achieved excellent atomization performance over a wide range of fuel flow rates and air pressure drops. Thermal analysis of the nozzle showed that the wetted wall temperatures were reduced considerably when compared to previous designs operating at the same conditions. Eight-port circumferential spray patternation results were outstanding with the patternation factor at various values of liquid flow rate ranging between 0.12 and 0.18. This patternation factor is a significant improvement over those of current state-of-the-art injectors that are typically of the order of 0.25.
Flow and Spray Characteristics of a Lean Fuel Injection Module With Radial Swirlers
Authors: Seol Woo Seok , Han Yeoung Min , Lee Dae Sung
Published: August 2014

Lean fuel modules are sometimes employed to reduce NOx emissions in aero-engine combustors. With a lean fuel module whose AFR is larger than the stoichiometric AFR, the bulk AFR remains larger than the stoichiometric AFR throughout the combustor, and hence the peak NOx producing regime can be avoided. In addition, by introducing a large amount of air at the fuel injection point and increasing the mixing rate, the existing time of local stoichiometric pockets can be reduced.

In the present study, flow and spray characteristics of a 21AFR lean fuel module, which consists of a pressure jet fuel injector and radial air swirlers, are measured by an adaptive Phase/Doppler technique. Gas phase velocity field, and distributions of droplet size, number density, and liquid phase volume flux are presented for co-swirl and counter-swirl lean modules.

The present study reveals that a strong reverse flow zone is formed by the lean fuel module with radial swirlers. The shape of the reverse flow zone and the reverse flow velocity depend on the swirl direction significantly. The lean fuel module with radial swirlers provides effective atomization, and the SMD distribution near the module exit is quite uniform. The swirl direction has significant effects on the spray characteristics, too.
Integrated Experimental and Numerical Approach for Fuel-Air Mixing Prediction in a Heavy-Duty Gas Turbine LP Burner
Authors: Mori Giulio , Razore Sandro , Ubaldi Marina , Zunino Pietro
Published: August 2014

An integrated experimental-numerical procedure has been developed for fuel-air mixing prediction in a heavy-duty gas turbine burner. Optical measurements of the degree of mixing have been performed in a full-scale test rig operating with cold flow. Experimental data have been utilized to validate a CFD RANS numerical model. In fact, it is recognized that the turbulence behavior of jets in swirling air-flow stream is not accurately described by standard k-ε turbulence models; therefore advanced turbulence models have been assessed by means of experimental data.

The degree of mixing between simulated fuel and air streams has been evaluated at the burner exit section by means of a planar Mie scattering technique. The experimental apparatus consists of a pulsed Nd:YAG laser and a high resolution CCD video camera connected to a frame grabber. The acquired instantaneous images have been processed through specific procedures that also take into account the laser beam spatial non-uniformity.

A second order discretization scheme with a RSM turbulence model gives the best accordance with the experimental data. Such CFD model will be part of a more general method addressed to numerical prediction of turbulent combustion flames in LP technology.
Feasibility Studies and Application of Laser /Optical Diagnostics for Characterisation of a Practical Low-Emission Gas Turbine Combustor
Authors: Löfström C. , Engström J. , Richter M. , Kaminski C. F. , Johansson P. , Nyholm K. , Hult J. , Nygren J. , Aldén M.
Published: August 2014

The present paper presents applications and feasibility studies of a number of laserspectroscopic techniques in a lean premixed prevaporised (LPP) combustor. Four different laser diagnostic techniques were investigated. The two more mature techniques, Planar Mie Scattering/Laser Induced Fluorescence and Planar Laser Induced Fluorescence of OH were used for fuel- and OH-visualisation, respectively. In addition, the applicability of some novel techniques in harsh industrial environments were investigated, two-line atomic fluorescence (TLAF) to obtain 2-dimensional temperature distributions, and two-photon LIF for the detection of CO. In order to investigate the degree of turbulence an ultrafast framing camera was employed to record spontaneous emission.
The Structure of Two-Stage Counterflow n-Heptane-Air Flames
Authors: Aggarwal S. K. , Xue H. S.
Published: August 2014

Partially premixed flames are formed by mixing air (in less than stoichiometric amounts) into the fuel stream prior to the reaction zone, where additional air is available for complete combustion. Such flames can occur in both laboratory and practical combustion systems. In advanced gas turbine combustor designs, such as a lean direct injection (LDI) combustor, partially premixed combustion represents an impotent mode of burning. Spray combustion often involves partially premixed combustion due to the locally fuel vapor-rich regions. In the present study, the detailed structure of n-heptane/air partially premixed flame in a counterflow configuration is investigated. The flame is computed by employing the Oppdif code and a detailed reaction mechanism consisting of 275 elementary reactions and 41 species. The partially premixed flame structure is characterized by two-stage burning or two distinct but synergistically coupled reaction zones, a rich premixed zone on the fuel side and a ‘nonpremixed zone on the air side. The fuel is completely consumed in the premixed zone with ethylene and acetylene being the major intermediate species. The reactions involving the consumption of these species are found to be the key rate-limiting reactions that characterize interactions between the two reaction zones, and determine the overall fuel consumption rate. The flame response to the variations in equivalence ratio and strain rate is examined. Increasing equivalence ratio and/or strain rate to a critical value leads to merging of the two reaction zones. The equivalence ratio variation affects the rich premixed reaction zone, while the variation in strain rate predominantly affects the nonpremixed reaction zone. The flame structure is also characterized in terms of a modified mixture fraction (conserved scalar), and laminar flamelet profiles are provided.
Alternative Fuels in Gas Turbine Applications: A Simple Method for Assessing the Influence of Fuel on Performances
Authors: Molière Michel , Pommel Frédéric
Published: August 2014

Gas turbines have by essence access to a broad range of primary energies. This advantage is essentially exploitable by the Heavy Duty branch which, thanks to moderate compression ratios, robust mechanical designs and versatile combustion systems, can utilise a wide series of commercial and process by-products fuels: natural gas, petroleum distillates, gasified coal or biomass, gas condensates, ash-forming fuels, alcohols etc. In this context, a thorough knowledge of the many-facetted fuel/machine interdependency, which seems insufficiently covered by the existing literature on gas turbines, is of prime interest.

This paper is devoted to the thermodynamic aspects of fuel influence. It offers: (i) a review of the main primary energies accessible to stationary gas turbines, (ii) a new, differential method for assessing the impact of fuel on machine thermodynamics, with original equations accounting for the changes in power output, efficiency and exhaust heat.
Flamelet Studies of Reduced and Detailed Kinetic Mechanisms for Methane/Air Diffusion Flames
Authors: Ladeinde Foluso , Cai Xiaodan , Sekar Balu
Published: August 2014

We adopt a steady-state flamelet model in this paper to study the performance of reduced and detailed kinetic mechanisms for methane/air diffusion flames. Through the numerical calculations, we investigate the sensitivity of the main and intermediate species mass fractions to the mixture fraction dissipation rate, χ. Our results seem to suggest a weak to moderate effect of χ on the calculated species mass fraction. It has also been shown in this paper that the current flamelet calculations fail to predict the extinction strain rate.
Assessment of Remote Lift Fan Jet Engines
Authors: Arnulfo Luca , Pilidis Pericles
Published: August 2014

The design of an Advanced Short Take-Off, Vertical Landing (ASTOVL) poses a major challenge. A successful aircraft of this type with a well integrated airframe and power plant must compete with Conventional Take-Off and Landing (CTOL) aircraft in the combat arena, while keeping the advantage of operations from short fields and small aircraft carriers.

To achieve a performance similar to those of CTOL planes, the recourse to a variable cycle engine appears to be a suitable solution for ASTOVL aircraft. One such design is the remote lift fan engine.

In this paper several alternatives are discussed and four engine designs based on a high performance low bypass core engine, exploiting the opportunity of variable cycle, are studied and compared. Two of these, the shaft driven and the Low Pressure Compressor exit bleed driven remote fans are predicted to be suitable alternatives.
Semi–Closed Hat (SC-HAT) Power Cycle
Authors: Carcasci Carlo , Cosi Lorenzo , Fiaschi Daniele , Manfrida Giampaolo
Published: August 2014

This new power cycle is derived from a simplified HAT cycle, with a partial recirculation of the exhaust gases added with respect to the traditional HAT configuration. The basic idea of applying recirculation to the HAT cycle stems from the interesting performance levels and general environmental advantages obtainable applying this technique to combined-cycle (SCGT/CC) and regenerative GT solutions (SCGT/RE); these power plants all share the integration with CO2 chemical scrubbing of the exhaust stack in order to reduce greenhouse effects.

A relevant advantage of the proposed configuration over the original HAT solution is the possibility of complete water recovery from the separator before the recirculation node; here the temperature level is necessarily very low, allowing thus condensation of water produced by the natural-gas combustion process. This allows the self–sustainement of the HAT cycle, from the water consumption point of view, without any external supply. For the water separator, two thermodynamic models were developed (respectively simulating a single- and a multiple temperature condensation process), which have provided similar results.

The whole cycle is modeled using a modular code, thoroughly tested against the performance of a large set of existing GTs. The layout is derived from an existing HAT configuration, with suppression of the economizer section in the regenerator and the possible practice of external (non-recuperative) intercooling between the two compressors. The first choice is imposed by the presence of an additional low-temperature heat load for the CO2 removal plant, while the second is sometimes necessary depending on the compressor pressure ratios and the possibility of including inside the cycle low-temperature internal cycle regeneration.

The expected performance of the plant is relatively high and close to those typical of HAT, SCGT/RE and SCGT/CC cycles: a LHV-based efficiency level exceeding 50% inclusive of CO2 separation and delivery at ambient pressure and temperature; the specific work levels — in the range of 680 kJ/kg for the basic configuration — are lower than those of the HAT cycle but larger than for SCGT/CC and SCGT/RE solutions; the cycle requires relatively high overall pressure ratios (35–40). A notable improvement in specific work can be obtained with reheat.
On-Design and Off-Design Performance Analysis of a Gas Turbine Combined Cycle Using the Exergy Method
Authors: Codeceira Neto Alcides , Pilidis Pericles
Published: August 2014

The present paper describes an on-design and an off-design performance study of gas turbine combined cycle based power plants. The exergy analysis has been carried out along with the performance assessment, considering the overall plant exergetic efficiency and the exergy destruction in the various components of the plant. The exergy method highlights irreversibility within the plant components, and it is of particular interest in this investigation.

A computational analysis has been carried out to investigate the effects of compressor pressure ratio and gas turbine entry temperature on the thermodynamic performance of combined gas / steam power cycles. The exergy analysis has been performed for on-design point calculations, considering single shaft gas turbines with different compressor pressure ratios and turbine entry temperatures. Nearly 100 MW shaft power gas turbine engines burning natural gas fuel have been selected in this study. The off-design calculations have been performed for one of the gas turbines selected from the on-design point studies. For this particular gas turbine engine, fuel has been changed from natural gas to a low calorific value fuel gas originated from the gasification of wood.

The exergy analysis indicates that maximum exergy is destroyed in the combustor, in the case of combined gas / steam cycles burning natural gas. For these studies on-design point, the exergy destruction in the combustor is found to decrease with increasing compressor pressure ratio to an optimum value and with increasing turbine entry temperature.

In the off-design case the gas turbine engine is burning low calorific value fuel originated from the gasification of wood. The maximum exergy destruction occurs in the gasification process, followed by the combustion process in the gas turbine.
New Concept of CO2 Removal Technologies in Power Generation, Combined With Fossil Fuel Recovery and Long Term CO2 Sequestration
Authors: Mathieu Ph. , Dubuisson R. , Houyou S. , Nihart R.
Published: August 2014

In this paper, the mentioned cycle has been transformed in a CO2 regenerative Ericsson-like cycle and therefore is named E-MATIANT. The removed CO2 can still be available at a pressure higher than the critical one (73 bar). When optimising the cycle, the calculated optimum pressure will be around 60 bar; this makes the technical issues easier to deal with than when using a supercritical fluid, namely the material strains and corrosion behavior. A sensitivity analysis is performed with respect to the CO2 delivery pressure in order to evaluate the performance changes. The fuel flexibility is an important asset of the newly designed cycle: mixtures of CO and H2 produced either in gasification or steam reforming processes can indeed be burnt in the combustion chamber. In a future work, the combination of a solid oxide fuel cell (SOFC) and this cycle both fed by a CO and H2 mixture will be considered as an option for the improvement of the global efficiency.

If not fixed in a chemical or biological system, the delivered CO2 can be used in industry or in the enhancement of fossil fuels recovery from their deposits, with a marginal compression consumption work. In this paper, CO2 injection is used to enhance methane recovery from coal seams by some 20 to 30%, in comparison with water pumping. The depleted seam can afterwards be used as the host site for long run CO2 sequestration.

As a conclusion, the combination of quasi-zero emission power plants with CO2 geological storage and enhanced fuel recovery provides a CO2 flow, otherwise considered as a waste or a byproduct, with an exergetic and a commercial added value. This makes this option a serious alternative to other CO2 control technologies.
Low Cost Recuperator Concept for Microturbine Applications
Authors: McDonald Colin F.
Published: August 2014

Currently there is a lot of interest in microturbines, with projections that these small turbogenerators will be produced in large quantities in response to the needs of the deregulated power generation market. First generation, low pressure ratio microturbines, based on state-of-the-art technology, require a recuperator to achieve an efficiency of 30 percent. With the recuperator representing 25–30 percent of the turbogenerator cost, major efforts are underway to establish new heat exchanger concepts, with low cost being paramount. In this paper a simple primary-surface recuperator concept is suggested that meets the major requirements, which include compact size and light weight, minimum number of parts, amenable to high volume automated fabrication, and packaging flexibility in either a wrap-around annular geometry or rear mounted cube form. This paper includes recuperator background information, technology bases, details of the proposed surface geometry, fabrication considerations, specific size and weight, cost target goals, and heat exchanger configurations for integration with microturbines in the power range of 5 to 75 kW.
Assessment of Molten Carbonate Fuel Cell Models and Integration With Gas and Steam Cycles
Authors: Massardo A. F. , Bosio B.
Published: August 2014

The aim of this work is to investigate the performance of Molten Carbonate Fuel Cells (MCFCs), with external reforming and Gas Turbine/Steam Turbine (GT/ST) combined cycles.

The analysis of these MCFC-GT/ST combined cycles has been carried out using the Thermo Economic Modular Program TEMP (Agazzani and Massardo, 1997) modified to allow MCFC, external sensible heat reformer, and catalytic burner performance to be carefully taken into account. The code has been verified through the use of a detailed MCFC model (Bosio et al., 1999) and of the data available for an existing MCFC unit.

The thermodynamic and exergy analysis of a number of MCFC combined cycles is presented and discussed, taking into account the influence of technological constraints, also evaluated with the sophisticated model, and the influence of the post-combustion of the fuel directly in the external catalytic burner. The results are presented and discussed in depth.
Developing the Next Generation Gas Turbine Systems — A National Partnership
Authors: Layne A. W.
Published: August 2014

The U.S. Department of Energy is in its 7th year of a 9-year program to develop the next generation of advanced turbine systems (ATS). Under this program, partnerships between industry, universities, national laboratories, government agencies and institutions, and the U.S. Department of Energy (DOE) are performing research and development required to commercialize the ATS. The ATS Program is jointly sponsored by the U.S. DOE Offices of Fossil Energy and Energy Efficiency and Renewable Energy. Supporting R&D, recent ATS accomplishments and future advanced concepts for next generation gas turbine systems are described and discussed in this paper.

As the ATS program winds down, DOE’s National Energy Technology Center (NETL) is evaluating the technology and market needs for continuing DOE support to develop advanced turbine systems. As part of this effort, NETL is sponsoring market and technology assessments, regional focus group discussions, and public workshops. The purpose of this paper is to provide the status of the ATS Program and the NETL perspective on potential options for future research and development needs, and public-private development programs addressing turbine based power generation for systems 30MW or greater in output.
Early Detection of Combustor Pulsations and Optimized Operation Through On-Line Monitoring Systems
Authors: Andersen Helmer
Published: August 2014

This article describes the objectives of an on-line monitoring system, the development and capabilities of the system and the experiences gained with it.

The objectives of the monitoring system were formulated after several transition pieces between the combustor and the turbine inlet had failed. The failures occurred within less than two months in a plant that had operated for more than 7 years without unusual problems. The system development was based on this experience and the goal to prevent future catastrophic failures. It provides:

• Data logs of selectable operational parameters

• Combustor pressure pulsations including a frequency spectrum

• True firing temperature based on a heat balance calculation

It thus provides the basis for predictive maintenance and optimum equipment performance. Several gas turbines with low NOx combustion system were equipped with the monitoring system in the summer of 1997. Data provided by the system over a period of almost 3 years identifies several parameters that are very indicative of the condition of the equipment.

These parameters are discussed as well as the consequences for the operation, maintenance and reliability of the units.
Risk-Based Inspection of Combustion Turbines
Authors: Schmidt Michael E. G. , Mauney David A.
Published: August 2014

Combustion turbine users, particularly in an unregulated environment, are faced with a multivariate optimizing problem. They need to run their machines in a way that ensures that the bondholders will be paid or maximizes shareholder value — or both, depending upon the owner’s finances. Meeting the financial challenge might require maximum reliability and availability at all times but it is more likely to require maximum reliability and availability at specific times, such as peak demand times of day or seasons. Maintenance is the biggest factor in reliability and availability control, and risk-based methods can focus maintenance for the best financial performance. One model can mathematically solve inspection program timing and component replacement decisions. Safety, environmental, financial and other constraints can bound the optimizing algorithm.

This paper outlines risk-based inspection program development. It focuses on the logical basis for a risk-based decision model, and briefly presents three simple examples. It references American Society of Mechanical Engineers (ASME) International documents that provide more information about risk-based inspection programs.
Effects of Slot Bleed Injection Over a Contoured End Wall on Nozzle Guide Vane Cooling Performance: Part II — Thermal Measurements
Authors: Burd Steven W. , Satterness Cynthia J. , Simon Terrence W.
Published: August 2014

Endwall heat transfer has become a major issue in the design of the inlet nozzle guide vane region of modern gas turbine engines. To compensate for high rates of convective heat transfer and the uncertain flow pattern along endwall surfaces, coolant flows are often excessive and distributed in a less than optimum fashion. In many instances, coolant is carried away or mixed into the core flow by the secondary flows without being effective. There is a need for more effective cooling concepts. In this paper, the results of an experimental study examining the thermal performance of bleed injection through an inclined slot positioned upstream of the nozzle airfoil leading edge plane are presented. This paper demonstrates that this type of combustor bleed cooling is a promising cooling concept. Testing is performed in a large-scale, guide vane cascade comprised of three airfoils between one contoured and one flat endwall. The Reynolds number, based upon approach velocity and true chord length, is 350,000 and the approach flow is with large-scale, high-intensity (9.5%) turbulence. Combustor bleed cooling flow is injected ahead of a contoured endwall with bleed-to-core mass flow ratios as high as 6%. Measurements are taken to document core flow temperature distributions at several axial positions within the cascade to evaluate surface adiabatic effectiveness values and local heat transfer coefficients. This film cooling arrangement offers significant thermal protection. The coolant is shown to provide thermal protection over most of the endwall as well as portions of the pressure and suction surfaces of the airfoils. To achieve this coverage, combustor bleed flow must be strong enough to overcome the influence of endwall region secondary flows.
Cooling Effectiveness Measurements With Thermal Radiometry in a Turbine Cascade
Authors: Moon H. K. , Jaiswal R.
Published: August 2014

Airfoil temperature measurements in a hot cascade were traditionally conducted with thermocouples in spite of their limitations. In the present work, a real-time full imaging of the airfoil temperature distribution is demonstrated in a turbine cascade using a thermal radiometry system. Two synthetic sapphire windows provided infrared (IR)-viewing access from the outside. The apparent emissivity of the test airfoil was calibrated with thermocouples buried flush into the wall. The turbine cascade, fabricated with actual engine hardware, provided heat transfer similarity by matching Re, Ma, and Tu. The effect of gas to coolant temperature ratio (Tg/Tc) on the cooling effectiveness was investigated.

Heating (“reverse” cooling) of the test airfoil in a relatively cold mainstream air resulted in a much more detailed temperature image than the normal (forward) cooling case, as it significantly reduced the background radiation. A methodology to correct the cooling effectiveness obtained at different gas to coolant temperature ratios than the engine condition was developed and has been experimentally validated.
Flow Measurements in a Nozzle Guide Vane Passage With a Low Aspect Ratio and Endwall Contouring
Authors: Burd Steven W. , Simon Terrence W.
Published: August 2014

The vast number of turbine cascade studies in the literature has been performed in straight-endwall, high-aspect-ratio, linear cascades. As a result, there has been little appreciation for the role of, and added complexity imposed by, reduced aspect ratios. There also has been little documentation of endwall profiling at these reduced spans. To examine the role of these factors on cascade hydrodynamics, a large-scale nozzle guide vane simulator was constructed at the Heat Transfer Laboratory of the University of Minnesota. This cascade is comprised of three airfoils between one contoured and one flat endwall. The geometries of the airfoils and endwalls, as well as the experimental conditions in the simulator, are representative of those in commercial operation. Measurements with hot-wire anemometry were taken to characterize the flow approaching the cascade. These measurements show that the flow field in this cascade is highly elliptic and influenced by pressure gradients that are established within the cascade. Exit flow field measurements with triple-sensor anemometry and pressure measurements within the cascade indicate that the acceleration imposed by endwall contouring and airfoil turning is able to suppress the size and strength of key secondary flow features. In addition, the flow field near the contoured endwall differs significantly from that adjacent to the straight endwall.
Mist/Steam Heat Transfer in Confined Slot Jet Impingement
Authors: Li X. , Gaddis J. L. , Wang T.
Published: August 2014

Internal mist/steam blade cooling technology has been considered for the future generation of Advanced Turbine Systems (ATS). Fine water droplets about 5 μm were carried by steam through a single slot jet onto a heated target surface in a confined channel. Experiments covered Reynolds numbers from 7500 to 25000 and heat fluxes from 3 to 21 kW/m2. The experimental results indicate that the cooling is enhanced significantly near the stagnation point by the mist, decreasing to a negligible level at a distance of 6 jet widths from the stagnation region. Up to 200% heat transfer enhancement at the stagnation point was achieved by injecting only ∼1.5% of mist. The investigation has focused on the effects of wall temperature, mist concentration, and Reynolds number.
An Experimental Evaluation of Advanced Leading Edge Impingement Cooling Concepts
Authors: Taslim M. E. , Setayeshgar L. , Spring S. D.
Published: August 2014

The main objective of this experimental investigation was to measure the convective heat transfer coefficient of impingement for different target wall roughness geometries of an airfoil leading edge, for jet to wall spacings and exit flow schemes. Available data in open literature are mostly for impingement on flat or curved smooth surfaces. This investigation covered two relatively new features in blade leading-edge cooling concepts namely the curved as well as roughened target surfaces. Experimental results are presented for four test sections representing the leading-edge cooling cavity with cross-over jets impinging on 1) a smooth wall, 2) a wall with high surface roughness, 3) a wall roughened with conical bumps, and 4) a wall roughened with tapered radial ribs. The tests were run for two supply and three exit flow arrangements and a range of jet Reynolds numbers. The major conclusions of this study were: a) there is a heat transfer enhancement benefit in roughening the target surface, b) while the surface roughness increases the impingement heat transfer coefficient, the driving factor in heat transfer enhancement is the increase in surface area, c) amongst the four tested surface geometries the conical bumps produced the highest heat transfer enhancement.
Application of Non-Linear k–ω Model to the Turbulent Flow Inside a Sharp U-Bend
Authors: Song B. , Amano R. S.
Published: August 2014

Simulation of the complex flow inside a sharp U-bend needs both refined turbulence models and higher order numerical discretization schemes. In the present study, a nonlinear low-Reynolds number (low-Re) k–ω model including the cubic terms was employed to predict the turbulent flow through a square cross-sectioned U-bend with a sharp curvature, Rc/D = 0.65. In the turbulence model employed for the present study, the cubic terms are incorporated to represent the effect of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. In order to accurately predict such complex flowfields, a higher-order bounded interpolation scheme (Song, et al., 1999) has been used to discretize all the transport equations. The calculated results by using both the non-linear k–ω model and the linear low-Reynolds number k–ε model (Launder and Sharma, 1974) have been compared with experimental data. It is shown that the present model produces satisfactory predictions of the flow development inside the sharp U-bend and well captures the characteristics of the turbulence anisotropy within the duct core region and wall sub-layer.
Lateral-Flow Effect on Endwall Heat Transfer and Pressure Drop in a Pin-Fin Trapezoidal Duct of Various Pin Shapes
Authors: Hwang Jenn-Jiang , Lu Chau-Ching
Published: August 2014

Effects of the lateral-flow ejection (0 ≦ ε ≦ 1.0), pin shapes (square, diamond and circular) and flow Reynolds number (6,000 ≦ Re ≦ 40,000) on the endwall heat transfer and pressure drop for turbulent flow through a pin-fin trapezoidal duct are studied experimentally. The trapezoidal duct are inserted with a staggered pin array of five rows and five columns, with the same spacings between the pins in streamwise and spanwise directions of Sx/d = Sy/d = 2.5. Three different-shaped pins of length from 2.5 < l/d < 4.6 span the distance between two endwalls of the trapezoidal duct. Results reveal that the pin-fin trapezoidal duct with a lateral-flow rate of ε = 0.3–0.4 has a local minimum endwall-averaged Nusselt number and Euler number for all pin shapes investigated. The trapezoidal duct of lateral outlet flow only (ε = 1.0) has the highest endwall heat transfer and pressure drop. Moreover, the square pin performs a better heat transfer enhancement than the diamond pin, and subsequently than the circular pin. Finally, taking account of the lateral-flow rate and the flow Reynolds number develops correlations of the endwall-averaged heat transfer for three different pin shapes.
Intercoolers in Gas Turbine Systems and Combi-Processes for Production of Electricity
Authors: Saidi Arash , Sundén Bengt , Eriksson Daniel
Published: August 2014

This paper presents a discussion of the role of intercoolers in low to medium power gas turbine systems and combined thermal processes for production of electricity. Available literature is cited and various types of intercoolers are presented. Means to improve the performance are discussed and opportunities to achieve more compact intercoolers are presented. An analysis of a specific enhanced surface intended for the air-side is presented. The volume goodness factor is defined and used as the performance is evaluated.
Influence of Cross-Flow Induced Swirl and Impingement on Heat Transfer in a Two-Pass Channel Connected by Two Rows of Holes
Authors: Pamula Gautam , Ekkad Srinath V. , Acharya Sumanta
Published: August 2014

Detailed heat transfer distributions are presented inside a two-pass coolant square channel connected by two rows of holes on the divider walls. The enhanced cooling is achieved by a combination of impingement and crossflow-induced swirl. Three configurations are examined where the cross flow is generated from one coolant passage to the adjoining coolant passage through a series of straight and angled holes and a two-dimensional slot placed along the dividing wall. The holes/slots deliver the flow from one passage to another typically achieved in a conventional design by a 180° U-bend. Heat transfer distributions will be presented on the sidewalls of the passages. A transient liquid crystal technique is applied to measure the detailed heat transfer coefficient distributions inside the passages. Results for the three hole supply cases are compared with the results from the traditional 180° turn passage for three channel flow Reynolds numbers ranging between 10000 and 50000. Results show that the new feed system, from first pass to second pass using crossflow injection holes, produce significantly higher Nusselt numbers on the second pass walls. The heat transfer enhancement in the second pass of these channels are as high as 2–3 times greater than that obtained in the second pass for a channel with a 180° turn. Results are also compared with channels that have only one row of discharge holes.
Innovative Cyclone Cooling Scheme for Gas Turbine Blade: Thermal-Hydraulic Performance Evaluation
Authors: Khalatov Artem , Syred Nick , Bowen Philip , Al-Ajmi Rashed , Kozlov Alexander , Schukin Andrey
Published: August 2014

The potential of currently used internal blade cooling technologies is nearly exhausted and the further improvements in the cooling efficiency can only be achieved through increases either in the air flow rate bled from the compressor or through reductions in the cooling passage size. This however results in the decrease of the gas turbine efficiency, and can cause dirt blockage problems. Several research programs were recently launched in the USA, UK and Germany to explore some novel concepts and to study innovative cooling techniques with improved parameters. One of them is an internal cyclone cooling technique, based on generation of swirl flow in blade cooling passages. Several designs of cyclone cooling, based on a two cooling passage configuration have been proposed and investigated in the USA and the former USSR over the last ten years, and these investigations have already demonstrated the superior heat transfer rate compared with conventional cooling techniques.

The novel three passage serpentine cyclone cooling scheme was proposed by the authors recently in which coolant moves successively through three cooling passages in two of those swirling flow is generated. New experimental data and the experimental correlations regarding heat transfer and fluid flow parameters in passages of an innovative cyclone cooling scheme have been obtained. The diagram of thermal-hydraulic performance is presented and comparison with conventional cooling techniques is given. The three passage cyclone cooling scheme has demonstrated the high rate of heat transfer and thermal-hydraulic performance at acceptable energy losses.
Scaling of Performance for Varying Density Ratio Coolants on an Airfoil With Strong Curvature and Pressure Gradient Effects
Authors: Ethridge Marcia I. , Cutbirth J. Michael , Bogard David G.
Published: August 2014

An experimental study was conducted to investigate the film cooling performance on the suction side of a first stage turbine vane. Tests were conducted on a nine times scale vane model at density ratios of DR = 1.1 and 1.6 over a range of blowing conditions, 0.2 ≤ M ≤ 1.5 and 0.05 ≤ I ≤ 1.2. Two different mainstream turbulence intensity levels, Tu∞ = 0.5% and 20%, were also investigated. The row of coolant holes studied was located in a position of both strong curvature and strong favorable pressure gradient. In addition, its performance was isolated by blocking the leading edge showerhead coolant holes. Adiabatic effectiveness measurements were made using an infrared camera to map the surface temperature distribution. The results indicate that film cooling performance was greatly enhanced over holes with a similar 50° injection angle on a flat plate. Overall, adiabatic effectiveness scaled with mass flux ratio for low blowing conditions and with momentum flux ratio for high blowing conditions. However, for M < 0.5 there was a higher rate of decay for the low density ratio data. High mainstream turbulence had little effect at low blowing ratios, but degraded performance at higher blowing ratios.
Transient Liquid Crystal Measurement of Leading Edge Film Cooling Effectiveness and Heat Transfer With High Free Stream Turbulence
Authors: Ou Shichuan , Rivir Richard , Meininger Matthew , Soechting Fred , Tabbita Martin
Published: August 2014

This paper studies the film effectiveness and heat transfer coefficients on a large scale symmetric circular leading edge with three rows of film holes. The film hole configuration focuses on a smaller injection angle of 20° and a larger hole pitch with respect to the hole diameter (P/d = 7.86). The study includes four blowing ratios (M = 1.0, 1.5, 2.0 and 2.5), two Reynolds numbers (Re = 30,000 and 60,000), and two free stream turbulence levels (approximately Tu = 1% and 20% depending on the Reynolds number). The method used to obtain the film cooling effectiveness and the heat transfer coefficient in the experiment is a transient liquid crystal technique. The distributions of film effectiveness and heat transfer coefficient are obtained with spatial resolutions of about 0.6 mm or 13% of the film cooling hole diameter. Results are presented for detailed and spanwise averaged values of film effectiveness and Frössling number. Blowing ratios investigated result in up to 2.8 times the lowest blowing ratio’s film effectiveness. Increasing the Reynolds number from 30,000 to 60,000 results in increasing the effectiveness by up to 55% at high turbulence. Turbulence intensity has up to a 60% attenuation on effectiveness between rows at Re = 30,000. The turbulence intensity has the same order of magnitude but opposite effect as Reynolds number, which also has the same order of magnitude effect as blowing ratio on the film effectiveness. A crossover from attenuation to improved film effectiveness after the second row of film holes is found for the high turbulence case as blowing ratio increases. The blowing ratio of two shows a spatial coupling of the stagnation row of film holes with the second row (21.5°) of film holes which results in the highest film effectiveness and also the highest Frössling numbers.
Reynolds Stress Transport Model Predictions and Large Eddy Simulations for Film Coolant Jet in Crossflow
Authors: Hoda Asif , Acharya Sumanta , Tyagi Mayank
Published: August 2014

Predictions of a film coolant jet in a crossflow for turbine blade cooling applications have traditionally employed k-ε and k-ω closure models of turbulence. An evaluation of several such models (Hoda and Acharya, 1999) revealed that the existing two equation models fail to resolve the highly complex flow field in the vicinity of the jet created by the jet-crossflow interaction. The eddy viscosity approximation used to obtain closure for the Reynolds stress terms in the time-averaged Navier Stokes equation is unable to represent the anisotropy of the flow and does not model the wake region created behind the jet adequately. A more accurate prediction of the stress field can be obtained by the Reynolds stress transport (RST) equations, which represent a higher level of closure for the turbulent stresses. In this paper, two formulations of the RST model have been employed to predict the flow behind a row of jets discharging normally into a crossflow. The flow field predictions and turbulent statistics are compared with the experimental data of Ajersch et al. (1995) and with k-ε predictions using the model of Lam and Bremhorst (1981). Predictions using Large Eddy Simulations (LES) are also presented to show the predictive capability of LES.
Turbulence Structures of Leading Edge Film Cooling Jets
Authors: Ardey Sabine , Wolff Stefan , Fottner Leonhard
Published: August 2014

For a better understanding of the turbulence structures attached to film cooling jets, mean flow velocities and turbulent fluctuations were measured by means of 3D hot wire anemometry in the injection zone of a linear, large scale, high pressure turbine cascade with leading edge film cooling. Near the stagnation point, the blades are equipped with one row of film cooling holes each on the suction and pressure side. Two basically different coolant jet situations are compared: On the suction side the jet features the ordinary kidney vortex. On the pressure side, the jet separates completely from the blade surface since it is located above a large recirculation zone created by a locally adverse pressure gradient and a flow separation near the pressure side injection. The measured Reynolds stresses were analyzed with regard to turbulence production and diffusion. The Bousinesque Hypothesis was tested and could not be confirmed. It was found that the turbulence is highly anisotropic.

In addition to the brief description of the experimental set up and the acquired data, given in this paper, the complete information are published as a test case (Ardey and Fottner, 1998) that is directly accessible via internet at: http://www.unibw-muenchen.de/campus/LRT12/welcome.html