bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of a Wave Rotor Topped Demonstrator Gas Turbine Engine Concept
Authors: Snyder Philip H. , Fish Raymond E.
Published: February 2015

A wave rotor topped gas turbine engine has been identified which incorporates five basic requirements of a successful demonstrator engine. Predicted performance maps of the wave rotor cycle have been used along with maps of existing gas turbine hardware in a design point study. The effects of wave rotor topping on the engine cycle and the subsequent need to rematch compressor and turbine sections in the topped engine are addressed. Comparison of performance of the resulting engine is made on the basis of wave rotor topped engine versus an appropriate baseline engine using common shaft compressor hardware. The topped engine design clearly demonstrates an improvement in shaft horsepower and SFC. Predicted off design part power engine performance for the wave rotor topped engine is presented including that at engine idle conditions. Operation of the engine at off design is closely examined with wave rotor operation at less than design burner outlet temperatures and rotor speeds. Challenges remaining in the development of a demonstrator engine are addressed.
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.
Experiments With a Gas Turbine Model Combustor Firing Blast-Furnace Gas
Authors: Liu Yansong , Schmidli Jürg
Published: February 2015

On-site atmospheric experiments using a one-fifth-scale model combustor of the ABB gas turbine type 11N2-LBtu have been recently carried out at the Kawasaki Steel Works in Mizushima, Japan. A diffusion type burner of special design was used to match the extremely low heating value (2360 kJ/kg) and the high stoichiometric fuel/air ratio (1.6 kg/kg) of the Blast-Furnace Gas (BFG). Except for pressure, all burner inlet conditions were simulated as in the actual gas turbine. The burner demonstrated an excellent burning stability behaviour over the entire operation range and stably burned pure BFG down to an equivalence ratio of 0.25, without any supplementary fuel. Due to the low adiabatic flame temperature and slow kinetics, approximately 1 ppm NOx was measured in the exhaust gas. The chemical kinetics of NOx production and CO burnout were also calculated using a chemical kinetics code and reasonable agreement with the experimental results was obtained. In dual-fuel operation (BFG with oil, propane, or coke-oven gas) the burner also demonstrated a wide flame stability range.
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.
Indicators of Incipient Surge for Three Turbofan Engines Using Standard Equipment and Instrumentation
Authors: Baran Adam J. , Dunn Michael G.
Published: February 2015

Engine controller data have been interrogated for indications of incipient surge for three turbofan engines; a large Pratt and Whitney, a large General Electric, and a small Williams International. Versions of these engines are currently operating in the field and all have compression ratios of 18 or greater. The Pratt and Whitney engine was surged only at full power while the other two were surged at partial power and at full power. The interest in this work was in detecting the presence of warning signatures for a current inventory of engines. A constraint was imposed on the experiments to use only existing engine instrumentation. The frequency response of the controller and the engine instrumentation limited the high frequency detection capability to about 100 Hz for the large engines and about 200 Hz for the small engine, For the large engines, it was not possible to detect a surge warning but for the small engine a sufficient warning of incipient surge was detected.
BladeCAD: An Interactive Geometric Design Tool for Turbomachinery Blades
Authors: Miller Perry L. , Oliver James H. , Miller David P. , Tweedt Daniel L.
Published: February 2015

A new methodology for interactive design of turbomachinery blades is presented. Software implementation of the methods provides a user interface that is intuitive to aero-designers while operating with standardized geometric forms. The primary contribution is that blade sections may be defined with respect to general surfaces of revolution which may be defined to represent the path of fluid flow through the turbomachine. The completed blade design is represented as a non-uniform rational B-spline (NURBS) surface and is written to a standard IGES file which is portable to most design, analysis, and manufacturing applications.
Flow Development in Radial Turbine Rotors
Authors: Baines Nicholas C.
Published: February 2015

This paper surveys the development of the primary and secondary flows in the rotors of radial-inflow turbines. Information previously scattered throughout the literature has been brought together, and it has been possible to create a coherent picture and a good understanding of the complex flow processes which occur. The secondary flow is generated by cross-passage forces due to the turning of the blades, and Coriolis forces. Near the leading edge these give rise to a strong vortex adjacent to the pressure surface, moving low momentum fluid from hub to tip. This feature helps to explain why best efficiency occurs typically at 20°–30° negative incidence. Attempts to correlate the optimum incidence angle using traditional slip factor expressions can give quite misleading results, but a new approach based on the blade loading shows considerable promise. Nearer the exit there is motion of fluid from hub to tip near the suction surface and a vortex in the suction surface-shroud corner, and this is linked to the highly non-uniform flow at exit. The latter effect makes the prediction and correlation of rotor deviation information very difficult, despite the development of a rational exit averaging procedure. The present deviation data are sparse and not easy to correlate.
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.
Externally Fired Evaporative Gas Turbine With a Condensing Heat Exchanger
Authors: Yan Jinyue , Eidensten Lars , Svedberg Gunnar
Published: February 2015

The integration of externally fired gas turbines and evaporative gas turbines (e.g., the HAT cycle) can offer the features from both systems: using solid fuel without requiring particulate clean up to protect the gas turbine path, and having the potential to enhance the power output and increase the efficiency without including a bottoming steam turbine. Exhaust gases from externally fired evaporative gas turbines have a high moisture content. Using a condensing heat exchanger makes it possible to recover more exhaust heat, thereby providing more potential for improving the system performance. This paper presents a new system with integration of a condensing heat exchanger in an externally fired evaporative gas turbine. The first and second laws of thermodynamics have been used to analyze the system. This study extends the overall knowledge on the externally fired evaporative gas turbine system and provides an investigation of the system with a condensing heat exchanger.
The Transfer Matrix–Component Mode Synthesis for Rotordynamic Analysis
Authors: Taiping Huang
Published: February 2015

The transfer matrix–component mode synthesis has been developed for the analysis of critical speed, response to imbalance and rotordynamic optimal design of multi–spool rotor system. This method adopted the advantages of the transfer matrix method for the train structure and the component mode synthesis for reducing degrees of freedom. In this method, the whole system is divided into several subsystems at the boundary coordinates. The constrained vibration modes and the static deflection curves of the constrained rotor subsystems are analysed by the improved transfer matrix method. The whole system is connected together by the component mode synthesis in accordance with the coordinate transformation. Numerical examples show that this method is superior to the traditional transfer matrix method and the component mode synthesis by FEM. This method has been successfully used for the rotordynamic analysis and optimal design of the compressors and the gas turbine aeroengines.
Origin of Split Resonance and Backward Whirl in a Simple Rotor
Authors: Millsaps Knox T. , Vejvoda Curtis E.
Published: February 2015

Split resonance and backward whirl in a simple rotor, were investigated both analytically and experimentally. A two degree-of-freedom rotor model was developed to simulate the steady state, lateral vibration characteristics of a simply supported, single disk rotor. This model included the effects of direct and cross coupled, linear damping and stiffness. The computer model was used to quantify the influence of bearing characteristics on rotordynamic response. In the absence of gyroscopic effects, split resonance is due to separate and distinct natural frequencies in the two orthogonal lateral directions created by non-equal direct stiffnesses. Backward whirl can occur between these two frequencies if the direct damping is sufficiently low. The model was able to predict the observed response of a simply supported rotor, including split resonance and backward whirl. The cause of the asymmetric direct stiffnesses in the experimental apparatus, which created split resonance and backward whirl was investigated. In particular, the influence of geometric imperfections in the plain bearing sleeve, gravitational forces, degree of imbalance and bearing support stiffness asymmetries were isolated using the experimental apparatus. It was determined that the bearing asymmetry was caused by the gravitational influence. However, larger imbalances increased the asymmetry and large damping was able to suppress backward whirl.
Implementing New Uncertainty Guidelines and Standards in Turbine Testing
Authors: Coleman Hugh W. , Steele W. Glenn
Published: February 2015

The use and application of uncertainty analysis in engineering has evolved considerably over the past decade. The methods formulated in the 1970’s and 1980’s that were incorporated into ANSI/ASME Standards and that were used during the AGARD-sponsored Uniform Engine Test Programme (UETP) have been superseded by more rigorous approaches. In this paper, the uncertainty methodogy used in the UETP is compared with the newer approaches that will need to be implemented in future turbine test programs.
A New Gas Compressor Product Development
Authors: Porter Ronald P.
Published: February 2015

A high efficiency, low cost gas compressor is under development. Design has been completed and fabrication is in process. The manufacturer’s background in centrifugal compressor design and current methodology is discussed along with product definition. Assembly and test of the first unit is planned for summer 1996. The design features a single-stage overhung centrifugal compressor, variable inlet guide vanes, and dry gas seals.
Smart Structures and Fiber Optic Technology for 21st Century Control Applications
Authors: Spillman W. B.
Published: February 2015

Throughout the 20th century, the evolution of control systems has proceeded from extremely simplistic systems to those with large complicated architectures and strong centralized control. Recently, the advantages of more distributed control architectures have been increasingly recognized, including even closing the loops at the actuation locations. This trend toward more distributed control systems has been mirrored in the new field of so-called “smart” structures in which the enhanced performance, multi-functionality and efficiency of biological constructs (arising from their ability to adapt and the distributed hierarchical nature of their organization) is emulated in new advanced structural designs. Considerable work has been carried out to develop fiber optic technology for smart structures applications. Recent developments in fiber optic communications and in fiber optic sensing indicate that fiber optic technology will be very important to the successful development of many of the smart structures of the future. It has long been recognized that one of the key functionalities required for a structure to be termed smart is an ability to sense, i.e. if the results of an action cannot be observed, closed loop control is impossible. For advanced control purposes, the use of long gauge length fiber optic sensors configured as matched filters for the preprocessing of large amounts of data appears to offer considerable potential benefit. In this paper, a formal definition of a smart structure is provided and an overview of the technologies involved in the smart structures area is given. Potential beneficial use of these technologies in advanced control systems is then discussed with specific emphasis placed on the appropriate application of fiber optic technology.
Three-Dimensional Flow Field Measurements in a Transonic Turbine Cascade
Authors: Giel P. W. , Thurman D. R. , Lopez I. , Boyle R. J. , Van Fossen G. J. , Jett T. A. , Camperchioli W. P. , La H.
Published: February 2015

Three-dimensional flow field measurements are presented for a large scale transonic turbine blade cascade. Flow field total pressures and pitch and yaw flow angles were measured at an inlet Reynolds number of 1.0 × 106 and at an isentropic exit Mach number of 1.3 in a low turbulence environment. Flow field data was obtained on five pitchwise/spanwise measurement planes, two upstream and three downstream of the cascade, each covering three blade pitches. Three-hole boundary layer probes and five-hole pitch/yaw probes were used to obtain data at over 1200 locations in each of the measurement planes. Blade and endwall static pressures were also measured at an inlet Reynolds number of 0.5 × 106 and at an isentropic exit Mach number of 1.0. Tests were conducted in a linear cascade at the NASA Lewis Transonic Turbine Blade Cascade Facility. The test article was a turbine rotor with 136° of turning and an axial chord of 12.7 cm. The flow field in the cascade is highly three-dimensional as a result of thick boundary layers at the test section inlet and because of the high degree of flow turning. The large scale allowed for very detailed measurements of both flow field and surface phenomena. The intent of the work is to provide benchmark quality data for CFD code and model verification.
Calculation of Tip Clearance Effects in a Transonic Compressor Rotor
Authors: Chima Rodrick V.
Published: February 2015

The flow through the tip clearance region of a transonic compressor rotor (NASA rotor 37) was computed and compared to aerodynamic probe and laser anemometer data. Tip clearance effects were modeled both by gridding the clearance gap and by using a simple periodicity model across the ungridded gap. The simple model was run with both the full gap height, and with half the gap height to simulate a vena-contracta effect. Comparisons between computed and measured performance maps and downstream profiles were used to validate the models and to assess the effects of gap height on the simple clearance model. Recommendations were made concerning the use of the simple clearance model. Detailed comparisons were made between the gridded clearance gap solution and the laser anemometer data near the tip at two operating points. The computed results agreed fairly well with the data but overpredicted the extent of the casing separation and underpredicted the wake decay rate. The computations were then used to describe the interaction of the tip vortex, the passage shock, and the casing boundary layer.
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.
IGV-Rotor Interaction Analysis in a Transonic Compressor Using the Navier-Stokes Equations
Authors: Arnone Andrea , Pacciani Roberto
Published: February 2015

A recently developed, time-accurate multigrid viscous solver has been extended to handle quasi-three-dimensional effects and applied to the first stage of a modern transonic compressor. Interest is focused on the inlet guide vane (IGV):rotor interaction where strong sources of unsteadiness are to be expected. Several calculations have been performed to predict the stage operating characteristics. Flow structures at various mass flow rates, from choke to near stall, are presented and discussed. Comparisons between unsteady and steady pitch-averaged results are also included in order to obtain indications about the capabilities of steady, multi-row analyses.
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.
A Numerically Supported Investigation of the 3D Flow in Centrifugal Impellers: Part II — Secondary Flow Structure
Authors: Hirsch Ch. , Kang S. , Pointel G.
Published: February 2015

The three-dimensional flow in centrifugal impellers is investigated on the basis of a detailed analysis of the results of numerical simulations. An in-depth validation has been performed, based on the computations of Krain’s centrifugal compressor and a radial pump impeller, both with vaneless diffusers and detailed comparisons with available experimental data, discussed in Part I, provide high confidence in the numerical tools and results. The low energy, high loss ‘wake’ region results from a balance between various contributions to the secondary flows influenced by tip leakage flows and is not necessarily connected to 3D boundary layer separation. A quantitative evaluation of the different contributions to the streamwise vorticity is performed, identifying the main features influencing their intensity. The main contributions are: the passage vortices along the end walls due to the flow turning; a passage vortex generated by the Coriolis forces proportional to the local loading and mainly active in the radial parts of the impeller; blade surface vortices due to the meridional curvature. The analysis provides an explanation for the differences in wake position under different geometries and flow conditions. A secondary flow representation is derived from the calculated 3D flow field for the two geometries validated in Part I, and the identified flow features largely confirm the theoretical analysis.
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.
Unsteady Flow in the Vaned Diffuser of a Medium Specific Speed Pump
Authors: Muggli Felix A. , Wiss Donald , Eisele Klaus , Zhang Zhengji , Casey Michael V. , Galpin Paul
Published: February 2015

This paper describes experimental and computational work to examine the unsteady flowfield in the vaned diffuser of a medium specific speed pump. The time periodic flowfield in the diffuser has been examined experimentally with laser optical techniques and with unsteady pressure transducers. The flow has been computed with a general purpose Navier-Stokes CFD code, whereby the unsteady effects have been simulated by a time periodic inlet profile which translates across the diffuser inlet and represents the wakes and potential interaction from the impeller. Comparisons of a steady simulation with time-average inlet conditions, an unsteady simulation with a time periodic inlet profile and the time-average of the unsteady simulation are used to validate the code developments and to examine features of the unsteady flow through the diffuser. Comparisons with experimental data identify that this simple computational model with a time periodic inlet profile is able to simulate the convection and decay of disturbances passing through the diffuser.
Calculation of Transition in Adverse Pressure Gradient Flow by Conditioned Equations
Authors: Steelant J. , Dick E.
Published: February 2015

Conditionally averaged Navier-Stokes equations are used to describe transitional flow in adverse pressure gradient combined with a transport equation for the intermittency factor γ. A transport equation developped in earlier work has been modified to eliminate the use of a distance along a streamline. An extension of the correlations is proposed to determine the spot growth parameter in adverse pressure gradient. This approach is verified against flows over a flat plate with an elliptical leading edge.
Comparison and Prediction of Local and Average Heat Transfer Coefficients Under an Array of Inline and Staggered Impinging Jets
Authors: Van Treuren Kenneth W. , Wang Zoulan , Ireland Peter , Jones Terry V. , Kohler S. T.
Published: February 2015

Recent work, Van Treuren et al. (1993, 1994), has shown the transient method of measuring heat transfer under an array of impinging jets allows the determination of local values of adiabatic wall temperature and heat transfer coefficient over the complete surface of the target plate. Using this technique, an inline and staggered array of impinging jets was tested over a range of average jet Reynolds numbers (10,000–40,000) for three impingement plate to target plate separations (1, 2 and 4). The array was confined on three sides and spent flow was allowed to exit in one direction. Local and average values are presented. These values for the two array configurations are then compared with each other as well as with previously published data in related geometries. A new correlation technique is presented, based on the local data, which breaks the target surface into jet and crossflow areas of interest, with excellent results. The correlation uses the local jet Reynolds number and local jet-to-crossflow mass velocity ratio. This new technique compared favourably with published correlations. Also presented is the influence of the impingement plate on the target plate heat transfer in the form of an effectiveness parameter. This influence is accounted for in the correlation.
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.
Jet Fuel Oxidation and Deposition
Authors: Knight Colette C. , Carnahan James C. , Janora Kevin , Ackerman John F.
Published: February 2015

The chemistry leading to homogeneous deposit formation when Jet A fuel is heated between 170–300°C was investigated by characterizing both the deposits and changes in the fuel after deposit formation. The maximum amount of deposits that form from static Jet A fuel heated at 200°C with a continuous airflow is ∼5 wt. % indicating the presence of a finite concentration of easily oxidizable species that lead to the deposits. The deposits were characterized using CPMAS NMR, FTIR, elemental analysis, GCIR and chemical derivatization. They are highly aromatic, enriched in oxygen, nitrogen and sulfur relative to the fuel, and contain carboxylic acids and ketone functional groups. The role of nitrogen and sulfur containing compounds is also discussed. Gel permeation chromatography (GPC) of derivatized heated fuel shows a substantial growth in molecular weight. We find hydrocarbons equivalent to C-70 oxidation compounds in fuel heated in an air environment. In Jet A fuel, whose deposit formation capacity is not exhausted, the latter can continue to react at room temperature to form deposits. This is a concern especially for recirculating applications since it implies that once the fuel has been heated, deposits can precipitate in the holding tanks even when the fuel is cool.
Enhancing Undergraduate Education: Design of a Gas Turbine Laboratory Facility
Authors: Hiles Kirk E. , Dixon Gregg W.
Published: February 2015

An undergraduate gas turbine laboratory facility was designed and installed by four senior Mechanical Engineering students for their capstone design project at the U. S. Coast Guard Academy. The seniors instrumented a 65 horsepower gas turbine auxiliary power unit from an HH-3F Pelican helicopter and installed it in the existing engine laboratory. The objective of this project was to provide an opportunity for engineering students to better understand thermodynamic principles of gas turbine operation through hands-on experimentation. The laboratory facility was designed to allow students to determine the performance characteristics of the T-62-16B gas turbine and relate them to a Brayton cycle model. This paper details the installation and instrumentation of the gas turbine, the design of the data acquisition system, the results obtained with initial system tests, and future experimental plans.
ATEC: The Aerodynamic Turbine Engine Code for the Analysis of Transient and Dynamic Gas Turbine Engine System Operations: Part 2 — Numerical Simulations
Authors: Garrard Doug
Published: February 2015

A new one-dimensional, time dependent aerothermodynamic mathematical model and computer simulation of the gas turbine engine has been developed. The Aerodynamic Turbine Engine Code (ATEC) simulates the operation of the gas turbine engine by solving conservation equations, expressed as one dimensional, time dependent Euler equations, with turbomachinery source terms. Development of the mathematical models were discussed in Part 1. Part 2 presents the results of exercising the simulation for several different problems. Results are presented for a subsonic, converging / diverging nozzle to demonstrate the validity of the numerical flow solvers and to demonstrate the functionality of the variable time step routine. Gas turbine engine simulation results are presented to demonstrate the capabilities of the ATEC simulation and for calibration purposes. The simulation results were obtained using the operating characteristics of a turboshaft engine.
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.
Development of a Diagnostic Tool to Trouble Shoot LM2500 Performance and Controls Problems
Authors: Thompson Bruce D. , Raczkowski Richard
Published: February 2015

A diagnostic tool (computer program) has been developed by the US Navy to provide the operators of LM2500 gas turbines (which are used as main propulsion on 6 ship classes in the USN) and the supporting technical staff, an assessment of the performance of this engine and the calibration of the engine control system. Typically, USN LM2500s do not mechanically degrade to the point where they will physically not be capable of making the required power. Instead, drift or lack of calibration of the engine sensors or its signal conditioning, mechanical wear and drift in the engine fuel scheduling control will cause the engine, after a period of time, either to not meet its performance expectations or report a performance level that is different from the actual condition. This can cause the engine to fail to meet the performance expectations of the propulsion control system, whether it is a real problem or a reporting problem (due to sensor mis-calibration), and in the worst case can cause an engine failure. To address these issues a performance diagnostic tool was developed that allowed the troubleshooter to compare engine performance, as reported by engine sensors etc., against what should be expected from the engine. Based on any differences, the tool provides the investigator guidance on the most likely source for the problem. To make such a tool, required integrating engine steady state performance models, with knowledge of the engine control loops as well as engine sensor, signal conditioning accuracy and calibration requirements. At present the diagnostic tool is being used by Fleet Technical Support Center Pacific to diagnose engine and controls problems. The goal is to provide ship’s force with the capability to diagnose most of their own problems and to provide a history of a particular engine’s performance.
Nondestructive Evaluation of Locally Repaired Coating for Gas Turbine Blades
Authors: Shen Y. , Pietranera N. , Guerreschi U. , Corcoruto S. , Gandini E.
Published: February 2015

Ultrasonic examination methods have been developed to qualify the locally repaired coating on gas turbine blades. The acoustic velocity of the MCrAlY coating obtained by Inert Gas Plasma Spray (IGPS) has been measured and compared with that of Vacuum Plasma Spray (VPS) coating. The thickness of the locally repaired coating on specimens and blades has been evaluated. The coating adhesion on the base material and its distribution have been investigated by A-scan and C-scan data display methods. The influence of surface roughness on the test results has also been examined.
Prediction of Effectiveness and Heat Transfer Using a New 2-D Injection and Dispersion Model of the Film Cooling Process
Authors: Neelakantan S. , Crawford M. E.
Published: February 2015

A new model is developed to predict laterally-averaged film cooling. At the injection location, the near-hole region is leapt over and the injectant is distributed according to an existing jet in cross flow model and experimental data. The subsequent dispersion of the injectant is simulated to reflect the augmented mixing and the 3-dimensionality of the flow field. The new model is calibrated to predict effectiveness and heat transfer using the experimental data bases of Schmidt et al. (1994), Sen et al. (1994), Kohli et al. (1994), and Sinha et al. (1991). The geometries include injection angles of 35° and 55° with compound angles of 0° and 60° and hole spacings of 3 and 6 diameters. The new model yields improved effectiveness predictions over previous 2-D models.
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.