bluuebunny/crossref_metadata_2025 huggingface dataset:
A Supercharged Turbojet for High Altitude Atmospheric Science Investigations
Authors: Cyrus John D. , Bents David J. , Overholt David M.
Published: December 2014

A study was conducted for NASA Dryden Flight Research Center to investigate the viability of developing an externally powered zero stage booster fan to boost the altitude performance of a high altitude turbojet from 80 kft. to over 90 kft., in order to realize a very high altitude subsonic remotely piloted aircraft (RPA) capable of atmospheric science missions.

A modified non-airbreathing torpedo engine powers the booster fan. The powered fan is grafted onto an airbreathing turbojet (the General Electric YJ97 jet engine) and is used to supercharge the engine (boost inlet pressure and airflow) at altitudes above its original design limits. The inlet boost keeps the engine operating and delivering thrust, at subsonic speeds, to mission altitudes over 95,000 ft.

If this modified engine were grafted back into the air vehicle it was originally designed for (the Viet Nam era AQM-91A Compass Arrow) the modifications would enable the vehicle to increase its maximum altitude from 80,000 ft to over 88,000 ft for periods up to 45 min. With some additional wing area, the aircraft, which is in the 5000 lbm TOGW class, could carry a 500 lbm payload to altitudes over 92,000 kft with an operational radius over 1500 NMi.

This study examined a number of candidate component arrangements to realize this fan-boosted propulsion system. Performance was estimated for the subsystem components, the resulting propulsion systems, and the associated RPA. In addition, the study estimated the time and cost to demonstrate/validate this concept in a full-scale propulsion system wind tunnel test program.

This paper describes the concept, summarizes the concept selection efforts and performance analysis conducted during the study, and explains the rationale behind this unusual approach. A description of the proposed development and test program, and the cost estimate, lies beyond the scope of this paper.
Effect of Axial Swirl Vane Location on Combustion Dynamics
Authors: Straub Douglas L. , Richards Geo A.
Published: December 2014

This paper reports the effect of changing the location of axial swirl vanes on premix combustion dynamics. Tests are conducted in a specially designed single-injector combustor operating at a pressure of 7.5 atmospheres and an inlet air temperature of 588K (600F). All of the tests are conducted using natural gas as the fuel. The air velocity and equivalence ratio are varied over an operating map for four different axial swirl vane positions in the premix nozzle. In contrast to earlier studies reported from this combustor, the fuel injection location is fixed. The results confirm the importance of the convective fuel time lag for the different swirl vane locations, but also show that changing the vane location at a fixed time lag can significantly affect the magnitude of the combustion oscillations.
Prediction of Thermoacoustic Instabilities With Focus on the Dynamic Flame Behavior for the 3A-Series Gas Turbine of Siemens KWU
Authors: Krüger Uwe , Hüren Jens , Hoffmann Stefan , Krebs Werner , Bohn Dieter
Published: December 2014

Self-induced combustion driven oscillations are a crucial challenge in the design of advanced gas turbine combustors. Lean premixed combustion, typically used in modern gas turbines, has a pronounced tendency to produce these instabilities.

Thus, the prediction of these thermoacoustic instabilities in the design phase of an engine becomes more and more important. A method based on linear acoustic four-pole elements to predict the instabilities of the ring combustor of the Siemens 3A-series gas turbines will be presented in this paper. The complex network includes the entire system starting from both compressor outlet and fuel supply system and ending at the turbine inlet.

Most of the transfer elements can be described by analytical data. Nevertheless, the most important elements, “flame” and “combustion chamber”, have to be investigated more in detail due to their complex 3D acoustics.

For the turbulent, premixed and swirled flame, a numerical simulation of the transient behavior after a sudden jump in mass flow at the inlet (step-function approach) is used to obtain the flame frequency response for axial direction as well as circumferential direction. This method has been verified for numerous different flame types (Krüger et al. (1998), Bohn et al. (1997), Bohn et al. (1996)). The four-pole element of the annular combustor is derived by an eigenfrequency analysis of the chamber, including a numerical predicted temperature and flow distribution.

The results show the principle possibilities of the instability analysis described. The frequencies predicted correspond well with experience from engine test fields. The importance of several elements for self-induced combustion driven oscillations is pointed out clearly.
Modelling Combustion Instabilities Using Computational Fluid Dynamics
Authors: Brookes Steve J. , Cant R. Stewart , Dowling Ann P.
Published: December 2014

The drive for lower emissions has forced combustor designers to consider lean premixed combustion systems. Unfortunately, premixed combustion systems are particularly susceptible to instabilities, raising large periodic fluctuations in heat release and pressure, that may cause structural damage. A reliable computational tool for predicting the onset of these oscillations would be extremely useful during the design process.

The work contained in this paper utilises computational fluid dynamics to model a simple premixed combustor, consisting of a bluff-body stabilised flame burning within a cylindrical duct. State of the art models are used to represent the combustion heat release and the turbulent transport within the combustor. Both forced oscillations and a nearly self-excited condition are modelled and compared with experiment.
Enhanced Gas Turbine Combustor Performance Using H2-Enriched Natural Gas
Authors: Phillips Jeffrey N. , Roby Richard J.
Published: December 2014

A screening level study has been carried out to examine the potential of using H2-enriched natural gas to improve the combustion performance of gas turbines. H2 has wider flammability limits and a higher flame speed than methane. Many previous studies have shown that when H2 is added to fuel, more efficient combustion and lower emissions will result. However, to date no commercial attempt has been made to improve the combustion performance of a natural gas-fired gas turbine by supplementing the fuel with H2. Four potential options for supplementing natural gas with H2 have been analyzed. Three of these options use the exhaust heat of the gas turbine either directly or indirectly to partially reform methane. The fourth option uses liquid H2 supplied from an industrial gas producer.
Experimental Study of Showerhead Cooling on a Cylinder Comparing Several Configurations Using Cylindrical and Shaped Holes
Authors: Reiss H. , Bölcs A.
Published: December 2014

Film cooling and heat transfer measurements on a cylinder model have been conducted using the transient thermochromic liquid crystal technique. Three showerhead cooling configurations adapted to leading edge film cooling of gas turbine blades were directly compared: ‘classical’ cylindrical holes versus two types of shaped hole exits. The experiments were carried out in a free jet test facility at two different flow conditions, Mach numbers M = 0.14 and M = 0.26, yielding Reynolds numbers based on the cylinder diameter of 8.6e4 and 1.55e5, respectively. All experiments were done at a main stream turbulence level of Tu = 7% with an integral lengthscale of Lx = 9.1mm (M = 0.14), or Lx = 10.5mm (M = 0.26) respectively. Foreign gas injection (CO2) was used yielding an engine-near density ratio of 1.6, with blowing ratios ranging from 0.6 to 1.5.

Detailed experimental results are shown, including surface distribution of film cooling effectiveness and local heat transfer coefficients. Additionally, heat transfer and heat load augmentation due to injection with respect to the uncooled cylinder are reported.

For a given cooling gas consumption the laid-back shaped hole exits lead to a clear enhancement of the cooling performance compared to cylindrical exits, whereas laterally expanded holes give only slight performance enhancement.
An Investigation on the Onset of Wake-Induced Transition and Turbulent Spot Production Rate Using Thermochromic Liquid Crystals
Authors: Kittichaikarn C. , Ireland P. T. , Zhong S. , Hodson H. P.
Published: December 2014

Wakes shed by upstream blade rows are known to cause boundary layer transition in both the compressor and turbine stages of axial flow gas turbines. This transition process is believed to take place via discrete zones of turbulence known as turbulent spots which occur in an otherwise laminar boundary layer. However, the process of transition over the blade surface cannot, at present, be reliably predicted. This is due to a lack of information on where and when these turbulent spots form and how they grow and merge as they convect downstream to form the turbulent boundary layer.

This paper presents detailed experimental information on the process of boundary layer transition induced by a bar generated wake travelling over a zero pressure gradient laminar boundary layer on a flat plate. The Reynolds number was 3×105. The peak turbulence intensity within the wakes varied from 3 to 6 % by using different bar of different diameters. An encapsulated cholesteric liquid crystals coating has been employed on a heated flat plate to reveal detailed information over the full surface. The information includes the thermal characteristics, the spot onset and formation rate. Data were obtained at high resolution on a grid of 30,000 points. The results were compared to intermittency plots and time-distance diagrams obtained by using surface-mounted thin film gauges and found to be similar. The data were also consistent with well established correlations and other published data from the literature for existing wake-induced transition models.
Numerical Investigation of the Dynamical Behavior of a Row of Square Jets in Crossflow Over a Surface
Authors: Muldoon Frank , Acharya Sumanta
Published: December 2014

Results of a three dimensional unsteady computational study of a row of jets injected normal to a cross-flow are presented with the aim of understanding the dynamics of the large scale structures in the region near the jet. The jet hole is square in cross-section, and the jet to cross-flow velocity ratio is 0.5. The calculations are based on higher-order finite differences, and are performed on extremely refined spatial and temporal meshes so that all the important energy-carrying scales are resolved. Results obtained indicate that the near field large scale structures include the shear layer vortices, the counter rotating vortex pair (CVP), the horseshoe vortex system, and wake and wall vortices. The dynamics of these structures appear to be significantly influenced by a time-periodic interaction between the jet hole boundary layer and the approaching crossflow. This periodic behavior involves the approaching crossflow periodically ingressing into the jet hole region and pushing the injected jet back toward the trailing edge at a Strouhal number of 0.44 based on the jet velocity and diameter. A new mechanism for the formation of shear layer vortices is identified and consists of alternate shedding of positive vorticity from the hole leading edge boundary layer and negative vorticity from the leading horseshoe vortex. Comparison of the predicted turbulent statistics with experimental measurements are made and reasonable agreement is observed.
Development of Hip Diffusion Bonding Processes for ODS Alloy Turbine Vanes
Authors: Matsuda Yoshihiro , Takikita Toshihiro , Noumi Shin-ichiro , Akikawa Naofumi , Yoshida Toyoaki , Taki Masanobu
Published: December 2014

Turbine inlet temperature of gas turbine engines have been increased in order to improve engine efficiency but is closing in on the upper limit of capacity for current casting materials and thermal barrier coating systems. To cope with such situations, it is necessary to develop new material applications which have superior heat resistant properties than current casting superalloys, ODS alloys are one of the candidate materials.

In this study, optimum HIP (Hot Isostatic Pressing) diffusion bonding parameters and a manufacturing process for turbine vanes of Ni base ODS (Oxide Dispersion Strengthened) alloy, MA754, were developed for the purpose of introducing advanced internal cooling structures. By using these parameters and process, HIP diffusion bonded MA754 turbine vanes were manufactured experimentally. As another application of the bonding process, MA754 turbine vanes HIP diffusion bonded with pure Cu internal cooling structure which has high thermal conductivity were also manufactured.
Assessing the Errors in Practical Gas Turbine Modelling
Authors: Evans Ceri , Rees David
Published: December 2014

This paper deals with the three most important sources of error in the practical identification of linear gas turbine models. These are noise, nonlinearities and unmodelled linear dynamics. Techniques are described which allow each of these sources of error to be studied and their influence to be assessed.
An Infrared Technique for Evaluating Turbine Airfoil Cooling Designs
Authors: Sweeney Patrick C. , Rhodes Jeffrey F.
Published: December 2014

An experimental approach is used to evaluate turbine airfoil cooling designs for advanced gas turbine engine applications by incorporating double-wall film-cooled design features into large scale flat plate specimens. An infrared (IR) imaging system is used to make detailed, two-dimensional steady state measurements of flat plate surface temperature with spatial resolution on the order of 0.4 mm. The technique employs a cooled zinc selenide window transparent to infrared radiation and calibrates the IR temperature readings to reference thermocouples embedded in each specimen, yielding a surface temperature measurement accuracy of ±4 °C. With minimal thermocouple installation required, the flat plate/IR approach is cost effective, essentially non-intrusive, and produces abundant results quickly. Design concepts can proceed from art to part to data in a manner consistent with aggressive development schedules.

The infrared technique is demonstrated here by considering the effect of film hole injection angle for a staggered array of film cooling holes integrated with a highly effective internal cooling pattern. Heated freestream air and room temperature cooling air are used to produce a nominal temperature ratio of 2 over a range of blowing ratios from 0.7 to 1.5. Results were obtained at hole angles of 90° and 30° for two different hole spacings and are presented in terms of overall cooling effectiveness.
Modelling of a Microslip Friction Damper Subjected to Translation and Rotation
Authors: Csaba Gabor
Published: December 2014

This paper presents a friction interface model where one of the mating surfaces is curved. The model is based on a discretization of the Winkler elastic foundation model and is general in the sense that it allows for relative motion in all six degrees of freedom. The variables for the contact model are based on damper geometry and material data, except coefficient of friction and tangential stiffness coefficient, which have to be measured. Simulated and experimental hysteresis curves are presented.

A model of a curved wedge damper has been developed using the contact model. An algorithm for solving forces and displacement when the damper is allowed to move in all six degrees of freedom has been presented. The governing algebraic equations are solved using a nonlinear least-square method routine in a commercial software package.

Forced response of a beam-damper-beam test set-up has been simulated and compared with experiments. The results highlighted some effects which have not been modelled e.g. the actual contact area between damper and blade is influenced by surface roughness for low normal loads. It is assumed that this effect resulted in problems in getting agreement between experiments and analysis. The influence of surface roughness is assumed to be negligible when vibrations of real turbomachinery are considered. This is due to the fact that both normal and excitation force on the clamper are about ten times higher than what was used in the experiments and simulations in this paper.

Variation of contact radius of the damper shows that a larger radius e.g. a flatter contact gives better damping and increases the resonance frequency. The disadvantage is that the alignment of the damper becomes more unreliable.
Comparison of Different Acceleration Techniques and Methods for Periodic Boundary Treatment in Unsteady Turbine Stage Flow Simulations
Authors: von Hoyningen-Huene Martin , Jung Alexander R.
Published: December 2014

This paper studies different acceleration techniques for unsteady flow calculations. The results are compared with a non-accelerated, fully-explicit solution in terms of time-averaged pressure distributions, the unsteady pressure and entropy in the frequency domain and the skin friction factor. The numerical method solves the unsteady three-dimensional Navier-Stokes equations via an explicit time-stepping procedure. The flow in the first stage of a modern industrial gas turbine is chosen as a test case. After a description of the numerical method used for the simulation, the test case is introduced. The comparison of the different numerical algorithms for explicit schemes is intended to ease the decision about which acceleration technique to use for calculations as far as accuracy and computational time are concerned. The convergence acceleration methods under consideration are, respectively, explicit time-stepping with implicit residual averaging, explicit time-consistent multigrid and implicit dual time stepping. The investigation and comparison of the different acceleration techniques are applicable to all explicit unsteady flow solvers.

As another point of interest, the influence of the stage blade count ratio on the flow field is investigated. For this purpose, a simulation with a stage pitch ratio of unity is compared with a calculation using the real ratio of 78:80, which requires a more sophisticated method for periodic boundary condition treatment. This paper should help to decide whether it is vital from the turbine designer’s point of view to model the real pitch ratio in unsteady flow simulations in turbine stages.
Local Swirl Chamber Heat Transfer and Flow Structure at Different Reynolds Numbers
Authors: Hedlund C. R. , Ligrani P. M.
Published: December 2014

Local flow behavior and heat transfer results are presented from two swirl chambers, which model passages used to cool the leading edges of turbine blades in gas turbine engines. Flow results are obtained in an isothermal swirl chamber. Surface Nusselt number distributions are measured in a second swirl chamber (with a constant wall beat flux boundary condition) using infrared thermography, in conjunction with thermocouples, energy balances, and in situ calibration procedures. In both cases, Reynolds numbers Re based on inlet duct characteristics range from 6000 to about 20000. Bulk helical flow is produced in each chamber by two inlets which ore tangent to the swirl chamber circumference. Important changes to local and globally-averaged surface Nusselt numbers, instantaneous flow structure from flow visualizations, and distributions of static pressure, total pressure, and circumferential velocity are observed throughout the swirl chambers as the Reynolds number increases. Of particular importance are increases of local surface Nusselt numbers (as well as ones globally-averaged over the entire swirl chamber surface) with increasing Reynolds number. These are tiad to increased advection, as well as important changes to vortex characteristics near the concave surfaces of the swirl chambers. Higher Re also give larger axial components of velocity, and increased turning of the flow from each inlet, which gives Görtler vnrtex pair trajectories greater skewness as they are advected downstream of each inlet.
Measurements of Heat Transfer Characteristics for Film Cooling Applications
Authors: Licu Dragos N. , Findlay Matthew J. , Gartshore Ian S. , Salcudean Martha
Published: December 2014

A new experimental technique based on wide-band liquid crystal thermography and transient one-dimensional heat conduction has been developed and implemented. The technique combines a real-time, true colour imaging system with the use of a wide-band liquid crystal and multiple event sampling for the simultaneous determination of the film cooling effectiveness and heat transfer coefficient from one transient test. For a test case of compound angle square jets in a crossflow, very good agreement was obtained between the film cooling effectiveness calculated from the transient heat transfer experiments and the film cooling effectiveness measured in isothermal mass transfer experiments using a flame ionization detector technique. Three different blowing ratios of M = 0.5, 1.0, and 1.5 are investigated with a constant jet Reynolds number (Re2) of around 5000. Detailed quantitative comparisons of spanwise film cooling effectiveness profiles are made for all blowing ratios examined, and contour plots of film cooling effectiveness and heat transfer coefficient are also presented.
Thermodynamic, Environmental and Economic Assessment of Exhaust Gas Recirculation for NOx Reduction in Gas Turbine Based Compressor Station
Authors: Botros K. K. , Price G. R. , Kibrya G.
Published: December 2014

A thermodynamic, environmental and economic assessment of an exhaust gas recirculation (EGR) system for NOx reduction has been carried out on an RB211 gas turbine based compressor station. The configured system was evaluated using a commercial process simulation software ASPEN PLUS® for the EGR process, along with a one dimensional model for the prediction of NOx. The assessment was focused on a realistic system of 20% gas recirculation cooled 300 °C with an aerial cooler. Detailed economic analysis based on present value cost per unit mechanical energy (kWh), showed that there is no economic advantage in implementing an EGR system in an existing gas turbine based station. Although the environmental cost was lower with the EGR system, it was offset by the cost of the EGR system itself combined with the additional incremental cost of fuel due to the decrease in the thermal efficiency.
Analysis of Actively Controlled Coulomb Damping for Rotating Machinery
Authors: Vance John M. , San Andrés Luis A.
Published: December 2014

Attempts have been made in the past to use Coulomb damping for vibration suppression in rotating machinery. Typically, a dry friction damper is designed to operate on a flexible bearing support. These designs have usually been unsuccessful in practice, partly because the Coulomb coefficient changes with temperature, with ingress of dirt or lubricant, and with the surface wear conditions. It is known that purely Coulomb damping forces cannot restrain the peak rotor whirl amplitudes at a critical speed. The invention of a disk type of electroviscous damper, utilizing a fluid with electrorheological (ER) properties, has recently revived the interest in Coulomb type dampers. Several investigations have suggested that a Coulomb friction model was the best representation for an ER damper with voltage applied. This model was used to study the feasibility of developing actively controlled bearing dampers for aircraft engines. This paper analyzes the imbalance response of two different rotordynamic models with Coulomb friction damping and shows the benefit of adding active control. Control laws are derived to achieve minimum rotor vibration amplitudes while avoiding large bearing forces over a speed range that includes a critical speed. The control laws are derived for purely Coulomb type of damping and assuming a combination of Coulomb and viscous damping effects. It is shown that the most important feature of Coulomb damping for minimal rotordynamic amplitude response is the control of rotor support stiffness, i.e. leading to the relocation of critical speeds, rather than control of a damping coefficient.
Comparison of the Dynamic Characteristics of Smooth Annular Seals and Damping Seals
Authors: Darden J. Mark , Earhart Eric M. , Flowers George T.
Published: December 2014

Annular seals are known to enhance rotordynamic stability margins and minimize vibration response levels in high-speed rotating machinery. Theoretical predictions for the rotordynamic characteristics of annular seals exist but additional experimental data is needed to properly anchor these results. NASA’s Marshall Space Flight Center (MSFC) has developed an annular seal test rig and facility to experimentally characterize axially-fed annular seals. Annular seals with deliberately roughened stators (i.e. damping seals) have been shown analyticalty to increase stability margins of rocket engine turbomachinery by reducing the seal’s whirl frequency ratio. The capabilities of MSFC’s annular seal test rig have been enhanced to allow high fluid inlet preswirl testing that is more representative of actual turbopump seal bounder conditions. The purpose of this paper is to describe the effect of this realistic preswirl on the stabilizing capability of both damping and smooth seals. Centered seal results are presented for both a smooth annular seal and a damping seal. These results were obtained for a range of seal pressure differentials, shaft rotational speeds, and two levels of inlet fluid preswirl.
Negative Stiffness Coefficients for Magnetic Actuators Using Laplace’s Equation
Authors: Stephens Lyndon S. , Casemore Mark A.
Published: December 2014

Magnetic bearings offer high speed and low power losses as compared to film riding and rolling element bearings. Significant efforts are underway to apply magnetic bearings to gas turbines and jet aircraft engines. Negative stiffness coefficients for magnetic actuators can have a significant impact on shaft rotordynamics. These coefficients are typically computed as the sensitivity of a magnetic force expression derived from a lumped parameter reluctance network. However, as the complexity of magnetic actuator designs increases, the reluctance network method may become impractical for, or even incapable of, coefficient determination. In this paper, an alternative method is presented for determination of negative stiffness coefficients for a large class of magnetic actuators. The method solves the Dirichlet boundary value problem (BVP) for the magnetomotive force (MMF) in the actuator air gap, subject to periodic boundary conditions that can be represented by Fourier series. A conformal transformation to bipolar coordinates is used that results in a BVP that is solvable using separation of variables. Negative stiffness coefficients are presented and the method is benchmarked against well-known solutions using the reluctance network method.
Designing Turbomachinery Blades Using Evolutionary Methods
Authors: Giannakoglou K. C.
Published: December 2014

A method based on computational intelligence is presented for the inverse design of 2D turbomachinery blades producing desirable wall pressure or velocity distributions under certain flow conditions. Blade airfoil shapes are parameterized through the combined use of circular arcs and Bezier functions. The design variables are controlled by Genetic Algorithms, employed in order to minimize the difference between target and numerically predicted distributions for each candidate shape. All numerical evaluations are carried through a primitive variable flow solver for unstructured grids. By employing Artificial Neural Networks, trained to correlate shapes and fitness scores, a great number of costly shape evaluations is overcome. The proposed combination of GAs for the optimization and ANNs for part of the evaluation phase is attractive and dramatically reduces the design cost. This paper discusses issues such as the regular re-training of the ANN or the selection of the threshold for numerical flow evaluations.
Some Modelling Issues on Trailing Edge Vortex Shedding
Authors: Ning Wei , He Li
Published: December 2014

A numerical study has been carried out to investigate modelling issues on trailing edge vortex shedding. The vortex shedding from a circular cylinder and a VKI turbine blade is calculated using a 2-D unsteady multi-block Navier-Stokes solver. The unsteady stresses are calculated from the unsteady solutions. The distributions of the unsteady stresses are analysed and compared for the cylinder case and the cascade case, respectively. The time-averaged equations are then solved and the effectiveness of the “unsteady stresses” in suppressing trailing edge vortex shedding is checked. Finally, the time-independent solution produced by solving the time-averaged equations is compared with the time-averaged solution obtained by integrating the unsteady solutions. The numerical results have demonstrated that a time-independent vortex shedding solution can be achieved by solving the Navier-Stokes equations with the unsteady stresses and the time-averaged effects of the vortex shedding can be included.
Co-Gasification of Coal/Biomass Blends in a Pressurized Fluidized-Bed Gasifier: The Advantageous Synergies in the Process
Authors: Chen Guanxing , Yu Qizhuang , Brage Claes , Rosén Christer , Sjöström Krister
Published: December 2014

An experimental study on co-gasification of coal and biomass blends in an oxygen-containing atmosphere has been carried out in a pressurized fluidized-bed gasifier. Several different biomass materials including wood and energy crops were used in the study, whereas two coals ranked of bituminite from Poland and UK were used in the investigation. The gasifier used was a Laboratory Development Unit (LDU) with an inner diameter of 144 mm. The operation temperature was 900 °C, and the pressure was 0.4 MPa. The research was part of the European Commission’s APAS and JOULE III clean coal technology programs.

The study was focused on possible synergistic effects in the thermochemical treatment of the fuel blends. The char formed was examined. The tar produced in the process was analyzed. The environmentally concerned nitrogen compounds emitted from the process were detected. An unexpected result was that the blends of the fuels and their char formed in situ exhibited higher gasification reaction rate under the studied conditions. The yield of char diminished and consequently the gas production increased. Furthermore, both the formation of tar and nitrogen compounds seemed also affected synergistically in co-gasification process of the fuel blends. The yields of tar and ammonia were lower than expected.
Conditioning and Detailed Analysis of Biomass Derived Fuel Gas Ongoing and Planned Work by Battelle
Authors: Anson Don , Paisley Mark A. , Ratcliff M. A.
Published: December 2014

Gas turbine based power and cogeneration schemes are likely to become more favored as turbine efficiencies improve, but the economics of local power generation may depend on the use of low cost fuels other than natural gas. Opportunities may arise in the application of gas turbines in the pulp and paper industry and the wider use of biomass derived fuels in general.

These fuels, as produced, typically contain inorganic impurities originating from ash forming substances and other minor constituents of the feedstock. Also, depending on the biomass treatment process, they contain varying amounts of complex organic derivatives, commonly referred to as tars, and some simpler condensable vapors.

The Department of Energy is sponsoring work aimed at providing realistic data on low level constituents and impurities in gas derived by indirect gasification of wood, some of which may have disproportionately severe effects on turbine operation, durability, and emissions performance. It is planned to sample gas from both laboratory scale (up to 20 tons/day) and pilot scale (200 tons/day) installations and to assess the effectiveness of wet scrubbing procedures and catalytic reforming of condensables in cleaning up the gases. This paper discusses the rationale for this work, experimental approach, and analytic procedures that will be used. The work will include the operation of a small (220-kWe) gas turbine to provide direct information on the impact of using the final biomass derived gas delivered by the system.

The laboratory scale work is currently under way, with a planned completion date in mid 2000. The second phase is dependent on arrangements for integration of the R&D effort with the operation of the pilot plant.
Heat Transfer Enhancement in Triangular Ducts With an Array of Side-Entry Wall/Impinged Jets
Authors: Hwang J.-J. , Cheng C.-S. , Tsia Y.-P.
Published: December 2014

An experimental study has been performed to measure local heat transfer coefficients and static well pressure drops in leading-edge triangular ducts cooled by wall/impinged jets. Coolant provided by an array of equally spaced wall jets is aimed at the leading-edge apex and exits from the radial outlet. Detailed heat transfer coefficients are measured for the two walls forming the apex using transient liquid crystal technique. Secondary-flow structures are visualized to realize the mechanism of heat transfer enhancement by wall/impinged jets. Three right-triangular ducts of the same altitude and different apex angles of β = 30 deg (Duct A), 45 deg (Duct B) and 60 deg (Duct C) are tested for various jet Reynolds numbers (3000≦Rej≦12600) and jet spacings (s/d = 3.0 and 6.0). Results show that an increase in Rej increases the heat transfer on both walls. Local heat transfer on both walls gradually decreases downstream due to the crossflow effect. At the same Rej, the Duct C has the highest wall-averaged heat transfer because of the highest jet center velocity as well as the smallest jet inclined angle. Moreover, the distribution of static pressure drop based on the local through flow rate in the present triangular duct is similar to that that of developing straight pipe flows. Average jet Nusselt numbers on the both walls have been correlated with jet Reynolds number for three different duct shapes.
Development of a Composite Inlet Housing for GTX100
Authors: Andersson Roger S. , Eriksson Ingemar A. G. , Granström Olov C.
Published: December 2014

The development of the new industrial gas turbine GTX100 offered possibilities to introduce new applications for materials and design.

The characteristics of the inlet housing are not just important from a power output viewpoint but also from a flow field distortion and compressor blade excitation point of view. This paper describes the evolutionary process and considerations in the development of the GTX100 composite inlet housing. The goal, which has been accomplished, was to find a new design that would result in lower manufacturing costs and improved performance.
Rotor Dynamic Response at Blade Loss
Authors: Karlsson B. Agne , Bergström C. Pontus , Domeij J. Thomas F.
Published: December 2014

This paper shows the influence of the method of modelling the support structure, i.e. the casings, support struts and skid, on the rotor dynamics and forced response in a gas turbine structure. Numerical examples, based on the conceptual design of GTX100 in the simple cycle configuration, are given for the blade loss case.

The standard method of analysing the rotor dynamics of a stationary gas- or steam-turbine rotor train, with hydrodynamic bearings, is based on beam theory. The bearings are modelled as a system of linear springs and dampers and are in some cases modelled as if there is no cross-coupling between the bearings. The support structure is normally based on a simple FE-analysis. This method is normally sufficient for the analysis of rotor dynamics characteristics at normal running if the stiffness of the bearings are much lower than the stiffness of the support structure.

In analysing the case of blade loss, the dynamic characteristics of the casing and the support structure have a much stronger influence on the rotor dynamics and the forced response in the structure. At the high unbalance forces present at a blade loss, the stiffness of the bearings will be of the same magnitude as that of the structure.

Results are given and discussed for the analysis of the rotor dynamic response based on coupled 3D-FE models, and on beam theory with the dynamic characteristics of the support structure described by various FE models.
Sliding Mode Control of Magnetic Bearings: Comparison of Sensed and Self Sensing Performance
Authors: Ueno S. , Lee J. H. , Allaire P. E. , Okada Y.
Published: December 2014

A sliding mode control algorithm has been designed for control of a balance beam on two symmetric magnetic bearings. A state space model of the system is developed and the controller is separated into a linear and non-linear component. A reaching condition to bring the system to the sliding surface is developed and a continuous function boundary layer approach is evaluated to avoid chattering. Previous works have discussed theoretical and experimental sliding mode control with physical sensors. This paper represents the first use of a simple envelope filter for sliding mode self sensing. The system simulation demonstrates arrival at the hyperplane surface within 0.003 sec and converges to the zero angular displacement value within 0.008 sec. Experimental results produced system convergence to zero angular displacement within approximately 0.35 sec both for the case when an eddy current position sensor was used and the case when system self sensing was employed. Some small scale chatter was observed in the experimental results with a peak to peak magnitude of approximately 3 times larger in the self-sensing case as compared to the case with a physical sensor.
Adaptive Unstructured Grids for Simulating Transsonic Flows in Turbomachinery
Authors: Roehl C. , Simon H.
Published: December 2014

A method for simulations of the two-dimensional compressible flow in aerodynamically highly loaded turbomachinery on unstructured adaptive grids is presented in this paper. The discretization of the conservative laws in space is executed by the finite volume method. For high efficiency an implicit solution procedure is used. The flux vector of the inviscid flow is calculated by a modified difference splitting method described by Reichert and Simon (1994). To predict the turbulent flow an explicit algebraic stress model in conjunction with k and ε equations is used (Lenke and Simon, 1997). Both for the generation of the initial grid as well as for the grid adaptation the same algorithm is used which is based on the advancing-front method according to Peraire et.al. (1987). For the simulation of high Reynoldsnumber flow within thermal turbomachinery it is most favorable to use quadrilateral elements in the boundary layers in addition to the triangular elements in the main flow region. To adapt the so-called combined grids, some kind of key variables are chosen, e.g. change in total pressure in combination with a shock detector.
Navier-Stokes Simulation of the MIT Flapping Foil Experiment Using an Unstructured Finite Volume Method
Authors: Kang Dong Jin , Bae Sang Soo , Kim Jae Won
Published: December 2014

A Navier-Stokes simulation of the MIT flapping foil experiment is presented. The MIT experiment was designed to provide a good quality database for unsteady boundary layer flows. The unsteady boundary layer around a hydrofoil was generated by flapping two airfoils upstream of the hydrofoil. Present Navier-Stokes simulation is carried out on the entire experimental domain, including the flapping airfoils as well as the downstream fixed hydrofoil. Present Navier-Stokes code uses an unstructured finite volume method based on the SIMPLE algorithm. It uses QUICK scheme for the convective terms and the second order Euler backward differencing for time derivatives to keep second order accuracy spatially and temporally. All other spatial derivatives are approximated by using central difference scheme. All comparisons of present time averaged and unsteady solutions with the corresponding experimental data are satisfactory: all unsteady solutions are compared in terms of time mean and first harmonic. The first harmonic of the velocity shows a peak inside the boundary layer along the surfaces of the hydrofoil and has a local minimum near the edge of the boundary layer. The local minimum becomes manifest as the boundary layer grows. The unsteadiness in the free stream is transferred inside the boundary layer when an unsteady vortex impinges on the surface. The entrained unsteadiness travels with a local velocity slower than that in the free stream. This causes phase lag of the first harmonic between the free stream and the boundary layer and local minimum of the first harmonic near the edge of the boundary layer.
3-D Internal Flow and Conjugate Calculations of a Convective Cooled Turbine Blade With Serpentine-Shaped and Ribbed Channels
Authors: Bohn Dieter E. , Becker Volker J. , Kusterer Karsten A. , Otsuki Yokiu , Sugimoto Takao , Tanaka Ryozo
Published: December 2014

Modern cooling configurations for turbine blades include complex serpentine-shaped cooling channel geometries for internal-forced convective cooling. The channels are ribbed in order to enhance the convective beat transfer. The design of such cooling configurations is within the power of modem CFD-codes with combined heat transfer analysis in solid body regions. One approach is the conjugate fluid flow and heat transfer solver, CHT-Flow, developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It takes into account of the mutual influences of internal and external fluid flow and heat transfer. The strategy of the procedure is based on a multi-block-technique and a direct coupling module for fluid flow regions and solid body regions.

The configuration under investigation in the present paper is based on a test design of a convective cooled turbine blade with serpentine-shaped cooling passages and cooling gas ejection at the blade tip and the trailing edge. The numerical investigations focus on secondary flow phenomena in the ducts and on the heat transfer analysis at the cooling channel walls. In the first part, the cooling channels are investigated with adiabatic smooth & ribbed walls. The calculations are carried out for the stationary and rotating configuration. Concerning the heat transfer analysis, the results of the ribbed configuration with a fixed thermal boundary condition at the walls in the stationary case are presented.

Furthermore, in order to demonstrate the capability of the conjugate method to work without thermal boundary conditions, the cooling configuration is calculated including the external blade flow and the blade walls with internal and external heat transfer under typical operation conditions of gas turbines. The numerical code is used to determine the blade surface temperatures.
A Helical Surface Model for 3-D Shock Structure Analysis
Authors: Shan Peng , Zhou Sheng
Published: December 2014

This paper is Part I of a comprehensive study on the blade leading edge sweep/bend of supersonic and transonic axial compressors. The objective of the paper is to develop an analytical shock surface model which links a blade leading edge with the 3-D shock structure, and can be eventually explored as a means to estimate the direct and indirect shock losses. The model surface is composed of helixes on a set of cylinders with aerodynamically determined ascendent for each helix. One kind of the relation between the ascendent and 2-D aerodynamics on S1 stream surface has been established for a leading edge attached shock surface. The succeeding research has revealed that the concepts of a forward/backward swept shock surface, and their qualitative and quantitative natures, can be analysed by the model in uniformity. The model is constructed as such that it can also be used in the inverse method of design process. Two leading edge shock surfaces from two high loading transonic fans are simulated by the model.
Pioneering Turbojet Developments of Dr. Hans von Ohain — From the HeS 1 to the HeS 011
Authors: Meher-Homji Cyrus B. , Prisell Erik
Published: December 2014

On March 13th, 1998, Dr. Hans Joachim Pabst von Ohain co-inventor of the turbojet passed away at the age of 86. As a young doctoral student, von Ohain conceived of and built a demonstrator turbojet engine. He was hired by the Heinkel Aircraft Company in 1936 and under intense time pressure imposed by Ernst Heinkel, designed the world’s first flight turbojet engine. This paper traces the technical antecedents leading to historic jet-powered flight made on August 27, 1939 by a Heinkel He 178 aircraft powered by von Ohain’s HeS 3B turbojet. During his tenure at Heinkel and thereafter at the Heinkel-Hirth Company, he was responsible for a series of turbojet engines culminating in the advanced second generation HeS 011 with a thrust of 2,860 lbs. This paper is a tribute to an outstanding scientist who made possible the turbojet revolution and who will forever be remembered as the inventor of the world’s first flight turbojet.
Optimization of Rotor Disk Shape Considering Equalization of Residual Stress Distribution Around Central Hole
Authors: Sekihara M. , Machida T.
Published: December 2014

A method for optimizing a rotor disk shape so that it equalizes the residual stress distribution around the central hole has been developed. The shape around the central hole is considered a variable, and it is changed in order to determine the optimum for reducing the equivalent stress of the central hole. As a result, the optimized shape that equalizes the residual stress distribution to within 23% variation was found.

Second, experiments with aluminum rotors verified the effectiveness of the optimized shape by measuring residual deformations and stresses. And it was confirmed that the measured residual deformations coincide with the calculated deformations well.

It is therefore possible to equalize the stresses on the surface in the central hole by adopting the optimized shape.
The Development of a New Experimental Facility for the Simulation of Civil Aircraft Engine Air-Intakes at High Reynolds Number
Authors: Murgatroyd Jeremy D.
Published: December 2014

A unique wind tunnel based method for simulating the engine air intakes of civil aircraft at high Reynolds numbers is described. The method combines a newly developed test rig with the 8ft × 8ft subsonic / supersonic wind tunnel at DERA Bedford. Commissioning tests of the rig took place in November 1997.

Previous studies have shown that Reynolds number can have a significant effect on intake flow characteristics in certain flight regimes. One such regime is high incidence manoeuvre, such as the emergency pull-up, where engine performance may be seriously degraded by distorted airflow from the intake cowl. Common methods for artificially simulating increased Reynolds number, such as boundary layer transition fixing, are not practical for intake model tests due to the widely varying position of the attachment line on the cowl. Hence, for intake tests, there can be significant gains from testing at the highest available Reynolds number, preferably approaching the full-scale value.

The new DERA facility offers accurate and cost effective performance assessment of large-scale intake models at near full-scale Reynolds numbers, across a Mach number range of 0.37 to 0.7. Throat choked mass flows can be achieved at Reynolds numbers up to approximately 11 million based on a model highlight diameter of 0.4 m. Model incidence can be varied between −10° and +30° (with and without sideslip). It is believed that this range of test conditions cannot be matched elsewhere in the world, without the additional risk and expense imposed by full-scale flight testing.

This paper details the conceptual design of the rig and the principles behind its operation. Special mention is made of the innovative use of theoretically based methods to calibrate the rig in the absence of experimental equipment with sufficient flow capacity. These theoretical methods significantly reduced the development time and cost of the rig.