bluuebunny/crossref_metadata_2025_split huggingface dataset:
Blade Vibrations of a High Speed Compressor Blisk-Rotor: Numerical Resonance Tuning and Optical Measurements
Authors: Frischbier J. , Schulze G. , Zielinski M. , Ziller G. , Blaha C. , Hennecke D. K. 
Published: February 2015

A major challenge during the design process of a modern low aspect ratio high speed axial compressor is to find rotor blade geometries that meet both, aerodynamic and mechanical requirements. This paper deals with the mechanical design of a transonic compressor blade. In order to meet the mechanical requirements in a short development time, new methods were used: A numerical optimization tool and an optical blade vibration measurement method:
The numerical resonance tuning took advantage of a semi-automatic optimization technique, based on a Finite Element vibration anlysis tool. The intention was to find a geometry which has no critical resonances (with fundamental engine orders) within the operation range.
To verify the calculated blade natural frequencies and eigen-values standard shaker tests using a laser holography system were carried out. Blades under g-load in the running compressor were investigated with an in-house developed vibration measurement system. This system is able to measure frequencies and amplitudes of the rotor blade vibrations without blade instrumentation but small optical probes, mounted in the compressor casing. The measured resonance points are in good agreement with the predictions. All amplitudes are far below the blade fatigue limits.
Development of an Improved Hybrid Burner: Initial Operating Experience in a Gas Turbine
Authors: Prade Bernd , Streb Holger , Berenbrink Peter , Schetter Bernhard , Pyka Gottfried 
Published: February 2015

Hybrid burners have demonstrated proven reliability in the premixed combustion of both natural gas and liquid fuels. NOx emission levels below 10 ppmv (gas dry, 15% O2) have been achieved in gas turbine models V94.2, V84.2 and retrofitted predecessor gas turbines. With increasing turbine inlet temperature (increasing efficiency), the pressure ratio and compressor discharge temperature will rise and auto ignition will become more critical. Therefore the development of an improved hybrid burner was an obvious necessity. Compatibility of the new burner with existing gas turbines was a basic requirement.
The new burner was tested in a 10 MW Gas Turbine equipped with a SIEMENS silo combustor and in a V64.3 GT in Dresden, Germany.
The paper presents the development and results of on-site measurements of NOx and CO emissions. At base toad NOx emissions below 25 ppmv were obtained by the revised hybrid (HR) burner without any combustion driven oscillation (< 5 mbar) in the V64.3. Additionaly the stability of the premixed flame was improved, so that the operation range of premix mode could be increased by three percent of base load.
Deposit Formation From No. 2 Distillate at Gas Turbine Conditions
Authors: Dean Anthony J. , Bradt Jean E. , Ackerman John F. 
Published: February 2015

Carbon deposit tests using No. 2 distillate fuel were performed in a flowing fuel/flowing atmosphere chamber utilizing a heated vertical test plate which simulates the interactions of fuel spray with combustor surfaces in a gas turbine downstream of the fuel nozzle. This type of interaction can occur in the premixing region of a low-NOx combustor operating on No. 2 fuel and can impact performance and reliability.
Deposit formation was studied as a function of surface temperature, surface composition, duration of exposure, atmospheric composition, and fuel type. Surface temperature and oxygen content in the atmosphere appear to have the greatest effect upon deposition: whereas the surface composition and exposure duration have a negligible effect. Conversion of fuel to deposits decreases somewhat as fuel flaw rate increases. A peak conversion to deposits of 0.1 grams per kg of fuel (0.01% conversion) occurred at a surface temperature of 345 C (653 F). The conversion fraction dropped to less than 1% of [he peak conversion below 225 C (437 F) and above 410 C (777 F). A comparison with published data from horizontal plate tests show different rates at specific temperatures which can be attributed to the test geometry, flow rate and residence time.
Combustion of Liquid Fuels in the Well Stirred Reactor
Authors: Zelina J. , Blust J. W. , Ballal D. R. 
Published: February 2015

The design and development of low-emissions, lean premixed aero, or industrial gas turbine combustors is very challenging because of a need to satisfy conflicting requirements of combustion performance and emissions. A toroidal well stirred reactor (WSR) provides a laboratory idealization of an efficient, highly compact primary zone of a gas turbine combustor and facilitates the study of combustion and emissions. The WSR was used to study emissions from heptane and JP-7 fuels.
It was found that the measured concentrations of CO2 and O2 agreed closely with the predictions of the equilibrium concentration. CO emissions for ϕ > 0.77 followed the equilibrium predictions reasonably well. But for ϕ < 0.77, the measured CO values were much higher than the equilibrium values. NOx emission increased as equivalence ratio approaches unity. Tests conducted at a constant equivalence ratio and residence time demonstrated an appreciable increase in CO and a modest increase in NOx with an increase in the (C/H) mole ratio. Therefore, a combustor designer should be concerned that jet fuels with lower hydrogen content will produce increased emissions of gaseous pollutants.
Dynamic Response of Fuel Nozzles for Liquid-Fueled Gas Turbine Combustors
Authors: Ibrahim Mounir , Sanders Terry , Darling Douglas , Zaller Michelle 
Published: February 2015

To imitate resonances that might occur in the fuel delivery system of gas turbine combustors, the incoming liquid streams of two pressure swirl nozzles were perturbed using a piezoelectric driver. Frequencies of perturbations examined were from 3 to 20 kHz, and water was used as the test fluid. A video camera and a Phase Doppler Particle Analyzer (PDPA) were used to study the effect of perturbations on the mean flow quantities of the sprays. Various lighting arrangements were used for the video photography: back lighting, front lighting, a strobe synchronized with the input to the piezoelectric, and a laser sheet oriented along the midplane of the sprays.
The study showed that the piezoelectric drive had an effect an the spray system at discrete frequencies. At these particular frequencies, by increasing the input voltage, it was found that the piezoelectric drive affected the atomization in the following ways: (1) the mean flow rate decreased, (2) the spray cone angle decreased, (3) the break up length decreased, (4) the peak of the spatial distribution of the mean droplet size decreased, and (5) the mean droplet sizes and velocities increased near the spray center line and decreased in the outer region of the spray. A hysteresis effect of the drive frequency on the spray cone angle was observed. The results indicated that more fundamental research is needed to gain an in-depth understanding of the physical processes induced in the spray by the piezoelectric drive.
Simulation of 3D-Unsteady Stator/Rotor Interaction in Turbomachinery Stages of Arbitrary Pitch Ratio
Authors: Jung Alexander R. , Mayer Jürgen F. , Stetter Heinz 
Published: February 2015

This paper presents a computational method for the calculation of unsteady three-dimensional viscous flow in turbo-machinery stages. The method is based on a Finite-Volume Navier-Stokes solver for structured grids in a multiblock topology. The meshes at the stator/rotor interface are overlapped by two grid cells. An implicit residual smoothing method applicable to global time-stepping is used to accelerate the solution process.
The problem of periodic boundary treatment for unequal pitches is handled using a method of time-inclined computational domains for three dimensions. The method applies a time transformation to the stator domain and to the rotor domain and uses different time-steps in the two domains.
The results of a numerical simulation of the flow in a transonic turbine stage with a pitch ratio of 1.364 are presented. The time-averaged solution is compared to experimental data and satisfactory agreement is stated. Complex 3D-unsteady flow phenomena (shock motion, vortex shedding) are observed. Unsteady blade pressure fluctuations at various positions in spanwise direction are shown and the fluctuations are found to vary considerably along span. Instantaneous distributions of static pressure, Mach number, and entropy are presented.
Navier-Stokes Simulation of the Flow Around a Leading Edge Film-Cooled Turbine Blade Including the Interior Cooling System and Comparison With Experimental Data
Authors: Vogel Dirk T. 
Published: February 2015

The three dimensional flow around an extensively investigated slot film cooled turbine blade is numerically investigated using a multi block finite volume Navier-Stokes solver.
Three blowing rates are simulated including the whole geometry of the interior blade cooling system and slots. Due to the ejection at the blade leading edge and the geometry of the cooling slots a very complex turbulent three dimensional flow field is generated.
The size and shape of the flow separation zones depending on the film cooling ejection is systematically investigated using several two-equation models, e.g. the standard and low Reynolds k–ε-Model of Lam and Bremhorst (1981) r[4], the extension of Kato/Launder (1993) [3] and the k–ω-Model of Wilcox (1991) [10], whereas the results of the standard k–ε-Model are presented. Experimental data obtained by Laser velocimetry, oil-flow pictures and pressure probes are used to understand the complex flow field and to validate the Navier-Stokes solver.
The multi-block code applies a traditional Jameson type solver and an implicit solver using several spatial discretization schemes for the convective fluxes. The two-equation models are solved using an RED-BLACK implicit technique with first order spatial upwind discretization to guarantee stability.
Low NOx Premixed Combustion of MBtu Fuels in a Research Burner
Authors: Döbbeling K. , Eroglu A. , Winkler D. , Sattelmayer T. , Keppel W. 
Published: February 2015

The paper reports on the development and testing of a premix research burner for MBtu fuels. The burner has a quartz glass annular mixing section and a quartz glass flame tube to allow visualization of the flame. A central lance is used to mount modules for fuel injection, swirl generation and flame stabilization. This allows a large number of variants with different swirl strength, mixing section length, fuel injection geometry and flameholder size and shape to be easily tested. Experiments have been performed at atmospheric pressure and under high pressure conditions (14 bar pressure, 400°C air preheat temperature) for syngas with a H2/CO ratio of up to 5. In a preliminary study the mixing quality of the tested variants has been assessed with planar laser induced fluorescence (LIF).
High pressure combustion tests show that low NOx (< 10 vppmd @ 15% O2) premix combustion of MBtu fuels under industrial GT conditions without dilution is feasible.
Catalytic Combustion of Natural Gas Over Supported Platinum: Flow Reactor Experiments and Detailed Numerical Modeling
Authors: Bond Tami C. , Noguchi Ryan A. , Chou Chen-Pang , Mongia Rajiv K. , Chen Jyh-Yuan , Dibble Robert W. 
Published: February 2015

The use of a noble-metal combustion catalyst such as platinum or palladium in a natural-gas fired turbine can lower NOx (nitrogen oxides, consisting of both NO and NO2) emissions for two reasons. First, most of the combustion occurs on the catalyst surface; surface production of NOx is low or nonexistent. Second, the catalyst permits low temperature combustion below the traditional lean limit, thus inhibiting NOx formation routes in the gas phase. Due to the complexity of the catalytic combustion process, the catalyst has traditionally been modeled as a “black box” that produces a desired amount of fuel conversion. While this approach has been useful for proof-of-concept studies, we expect practical applications to emerge from a greater understanding of the details of the catalytic combustion process.
We have constructed a numerical model of catalytic combustion based on the well-accepted CHEMKIN chemical kinetics formalism for gas-phase and surface chemistry. To support the model development, we built a research combustor. We present measured and modeled axial profiles of temperature, fuel conversion, and pollutant emissions for natural-gas combustion over platinum catalysts supported on ceramic honeycomb monoliths. NOx emissions are below 1 ppm, and CO is observed at ppm levels. The data are taken at several lean equivalence ratios and flow rates. Fuel conversion rates occur in two regimes: a low, constant conversion rate and a higher conversion rate that increases linearly with equivalence ratio.
The agreement of the numerical model with the measured data is good at temperatures below 900 K; above this temperature, fuel conversion is underpredicted by as much as a factor of two. The predicted surface ignition temperatures agree well with the measured values. Results from the numerical model indicate that the fractional conversion rate of fuel has a linear dependence on the fraction of available surface reaction sites.
The Prediction of Laminar Flame Speeds for Weak Mixtures
Authors: Kretschmer D. , Odgers J. 
Published: February 2015

In a recent publication [3], the authors tentatively explored the prediction of propane flame speeds using the calculated burned gas temperature (Tb) and the predicted flame extinction temperature (Ti). A formula was developed which utilised the above temperatures together with correction factors for inlet temperature and the oxygen/inert ratio.
The present paper has extended this technique so that data from 20 different fuels have been examined over a range of conditions which include significant variations of both inlet temperature and pressure.
Limitations of the technique are discussed, as are possible related applications to other premixed systems such as laminar flames and well-stirred reactors.
Investigation of Wedge Probe Wall Proximity Effects: Part 1 — Experimental Study
Authors: Smout Peter D. , Ivey Paul C. 
Published: February 2015

Conventional 3-hole wedge probes fail to measure the correct static pressure when operating in close proximity to a wall or boundary through which the probe is inserted. The free stream pressure near the outer wall of a turbomachine may be over indicated by upto 20% dynamic head.
This paper reports a series of experiments aimed at quantifying this so-called ‘wall proximity effect’. It is shown from a factorial experiment that probe wedge angle, stem design and free-stream Mach number all have a significant influence. The yaw angle sensitivity of wedge probes is also found to depend on the proximity of the probe to the wall of introduction. Flow visualisation studies on large scale probe models are described, and a qualitative model of the probe local flow structures is developed. This model is used to explain the near wall characteristics of the actual size wedge probes. In Part 2 of this paper, the experimental data is used to validate CFD calculations of the flow field around a wedge probe. A simple analytical model of the probe/flow interaction is developed from the CFD solutions.
Investigation of Wedge Probe Wall Proximity Effects: Part 2 — Numerical and Analytical Modelling
Authors: Smout Peter D. , Ivey Paul C. 
Published: February 2015

An experimental study of wedge probe wall proximity effects is described in Part 1 of this paper. Actual size and large scale model probes were tested to understand the mechanisms responsible for this effect, by which free stream pressure near the outer wall of a turbomachine may be over indicated by upto 20% dynamic head.
CFD calculations of the flow over two-dimensional wedge shapes and a three-dimensional wedge probe were made in support of the experiments, and are reported in this paper. Key flow structures in the probe wake were identified which control the pressures indicated by the probe in a given environment. It is shown that probe aerodynamic characteristics will change if the wake flow structures are modified, for example by traversing close to the wall, or by calibrating the probe in an open jet rather than in a closed section wind tunnel. A simple analytical model of the probe local flows was derived from the CFD results. It is shown by comparison with experiment that this model captures the dominant flow features.
Performance of Low Solidity and Conventional Diffuser Systems for Centrifugal Compressors
Authors: Amineni Naresh K. , Engeda Abraham , Hohlweg William C. , Direnzi Gregory L. 
Published: February 2015

Centrifugal compressors have the widest compressor application area, covering aircraft engines, small stationary gas turbines, process and refinery industries, the refrigeration industry, and turbochargers. Despite the vast literature coverage of diffuser systems for centrifugal compressors, there are not more than twenty publications in the open literature on the family of vaned diffusers known as Low Solidity Vaned Diffuser (LSVD). This is highly surprising, in light of the fact, that practically all process and refrigeration compressors manufacturers, at one time or another, have attempted to design and test LSVD. Therefore with the strong belief that any work on LSVD either theoretical or experimental will be welcomed, this paper presents the performance of two newly designed LSVD.
Comparative experimental studies on diffuser systems for centrifugal compressors, performed at the Michigan State University Turbomachinery Lab are presented. A vaneless, a conventional vaned and two low solidity vaned diffusers were tested. The results are compared for the effect of the diffuser systems on the stage performance, the maximum efficiency, and the operating range of the compressor. The effect of the vane number in low solidity vaned diffuser on the performance is also discussed.
Heat Transfer Measurements on a Turbine Airfoil at Various Reynolds Numbers and Turbulence Intensities Including Effects of Surface Roughness
Authors: Hoffs A. , Drost U. , Bölcs A. 
Published: February 2015

This paper presents heat transfer measurements on a turbine airfoil in a linear cascade at various exit Reynolds and Mach numbers ranging from 3.2e5 to 1.6e6 and 0.2 to 0.8, respectively, which have been conducted with the transient liquid crystal technique. Two series were performed at turbulence intensities of 5.5% and 10%, the latter being created by a squared-bar mesh placed 10 meshsizes upstream of the turbine airfoils. While normally polished liquid crystals were used additional experiments were done at the high turbulence intensity with naturally rough liquid crystals.
All measurements indicate a gradual increase in heat transfer and an upstream shift of the laminar-to-turbulent transition with increasing Reynolds number and turbulence intensity. The leading edge heat transfer agrees well with correlations if the turbulence length scale is taken into account. The measurements conducted with rough liquid crystals show an earlier transition on the suction side. Calculations with a two-dimensional boundary layer code agree well with the measurements.
Variable Geometry Pipe Diffusers
Authors: Salvage J. W. 
Published: February 2015

Theoretical analyses and experimental results are reported for two unique variable geometry techniques used with pipe diffusers to enhance off-design performance. One technique mechanically closes the diffuser throat in an unusual manner. The other allows flow recirculation to close the throat artificially while attempting to improve diffuser inlet flow characteristics.
Results clearly show that surge margin may be significantly improved by either method and that flow recirculation may offer improved efficiency.
Aerodynamic Performance of Rear Axial Compressor Stage With Annular Diffuser and Outlet Chamber
Authors: Cyrus Václav 
Published: February 2015

A detailed investigation of aerodynamic performance of three low-speed rear axial compressor stage bladings with the aspect ratios: 0.75, 1.0 and 1.25 was carried out. The bladings of industrial type consist of rotor, stator and outlet guide vanes. The outer and inner diameters of the stage are constant. The hub/tip ratio is 0.871 and the outer diameter is 800 mm. Stage blading is followed by an annular diffuser with outlet chamber.
The effect of blade aspect ratio on compressor stage performance was also analysed with the use of straight cascade data. This data supported the test stage experimental results. We found that the effect of aspect ratio on stage performance is not remarkable in the considered range. There are some differences at off-design conditions. The lowest value of blading efficiency was obtained in the case with the lowest aspect ratio value.
Three inlet velocity profiles were modelled with the use of lengthened inlet annulus and a screen specially designed. It was found that there is a significant effect of inlet velocity profile distortion on rear compressor stage blading performance for all aspect ratios.
Aerodynamic characteristics of compressor stage blading with annular diffuser and outlet chamber were determined. During the investigation we also removed the outlet guide vanes. Therefore the effect of swirl and inlet velocity profile could be investigated.
Health Monitoring of Turbine Engine Gas Path Components and Measurement Instruments
Authors: Lee Y. H. , Singh R. 
Published: February 2015

A performance simulation program has been used to simulate deteriorated performance of a new augmented turbofan engine developed for fighter aircraft and generate a fault pattern library.
This fault pattern library forms a basis for both understanding degradation trends of engine usage and in developing an engine health monitoring system. An efficient health monitoring method is proposed to identify the engine faults along with measurement uncertainties and faulty instruments, and to reduce false alarms. A pattern matching method is used to discriminate the engine faults by matching the measurement patterns throughout the fault pattern library.
The comparison of this approach to conventional gas path analysis has demonstrated that this approach has comparable ability to monitor engine gas path performance degradation, and provides some capability to handle measurement uncertainties and faults. It also provides a good base for future capability in conjunction with other engine inspection and/or monitoring methods.