bluuebunny/crossref_metadata_2025 huggingface dataset:
A Kalina Cycle Application for Power Generation
Authors: Ibrahim Mounir B. , Kovach Ronald M.
Published: March 2015

A multi-component (NH3/H2O) Kalina type cycle that utilizes the exhaust from a gas turbine is investigated in this paper. The turbine inlet pressure, 5.96∗106 N/m2 (850 psig), and temperature, 755.372 K (900 F), were kept constant as well as the working fluid temperature at the condenser outlet, 290 K (62.3 F). The NH3 mass fraction at the turbine inlet was varied along with the separator temperature, and the effects on the cycle efficiency were studied. The relationship between turbine inlet flow and separator inlet flow is shown in this paper in addition to the upper and lower NH3 mass fraction bounds. The multi-component working fluid cycle investigated is 10% to 20% more efficient than a Rankine cycle at the same border conditions.
Viscous Analysis of Three-Dimensional Turbomachinery Flows on Body Conforming Grids Using an Implicit Solver
Authors: Weber K. F. , Delaney R. A.
Published: March 2015

A 3-D Navier-Stokes analysis for turbomachinery flows on C- or O-type grids is presented. The analysis is based on the Beam and Warming implicit algorithm for solution of the unsteady Navier-Stokes equations and is derived from an early version of the ARC3D flow code developed at NASA Ames Research Center. The Navier-Stokes equations are written in a Cartesian coordinate system rotating about the z-axis, and then mapped to a general body-fitted coordinate system. All viscous terms are calculated and the turbulence effects are modelled using the Baldwin-Lomax turbulence model. The equations are discretized using finite differences on stacked body-conforming grids. Modifications made to convert ARC3D from external flow to internal turbomachinery flows and to improve solution accuracy are given in detail. The body-conforming grid construction procedure is also presented. Calculations for several rotor flows have been made, and results of code experimental verification studies are presented. Comparisons of the solutions obtained on the C- and O-type grids are also presented, with particular attention to shock resolution.
Motion and Evaporation of Shear-Driven Liquid Films in Turbulent Gases
Authors: Wittig S. , Himmelsbach J. , Noll B. , Feld H. J. , Samenfink W.
Published: March 2015

Detailed measurements of wavy liquid films driven by the shear stress of turbulent air flow are obtained for different air temperatures, air velocities and flow rates of the liquid. The experimental conditions are chosen from characteristic data of liquid film flow in prefilming airblast atomizers and film vaporization employing combustors.

For the measurement of the local film thickness and film velocity a new optical instrument — based on the light absorption of the liquid — has been developed, which can be used at high temperatures with evaporation.

The measured data of the gas phase and the liquid film are compared with the results of a numerical code using a laminar as well as a turbulent model for the film flow and a standard numerical finite volume code for the gas phase.

The results utilizing the two models for the liquid film show that the film exhibits laminar rather then turbulent characteristics under a wide range of flow conditions. This is of considerable interest when heat is transferred across the film by heating or cooling of the wall. With this information the optical instrument can also be used to determine the local shear stress of the gas phase at the phase interface.

Using time averaged values for the thickness, the velocity and the roughness of the film the code leads to relatively accurate predictions of the interaction of the liquid film with the gas phase.
Two Stage Slagging Combustor Design for a Coal-Fueled Industrial Gas Turbine
Authors: Cowell L. H. , LeCren R. T. , Tenbrook C. E.
Published: March 2015

A full size combustor for a coal-fueled industrial gas turbine engine has been designed and fabricated. The design is based on extensive work completed through one-tenth scale combustion tests. Testing of the combustion hardware will be completed with a high pressure air supply in a combustion test facility before the components are integrated with the gas turbine engine. The combustor is a two-staged, rich-lean design. Fuel and air are introduced in the primary combustion zone where the combustion process is initiated. The primary zone operates in a slagging mode inertially removing coal ash from the gas stream. Four injectors designed for coal-water mixture (CWM) atomization are used to introduce the fuel and primary air. In the secondary combustion zone additional air is injected to complete the combustion process at fuel lean conditions. The secondary zone also serves to reduce the gas temperatures exiting the combustor. Between the primary and secondary zones is a Particulate Rejection Impact Separator (PRIS). In this device much of the coal ash that passes from the primary zone is inertially separated from the gas stream. The two-staged combustor along with the PRIS have been designated as the combustor island. All of the combustor island components are refractory lined to minimize heat loss. Fabrication of the combustor has been completed. The PRIS is still under construction. The combustor hardware is being installed at the Caterpillar Technical Center for high pressure test evaluation. The design, test installation, and test plan of the full size combustor island are discussed.
Numerical Prediction of Wakes in Cascades and Compressor Rotors Including the Effects of Mixing: Part I — Cascade Wakes Including the Effects of Incidence and Freestream Turbulence
Authors: Suryavamshi N. , Lakshminarayana B.
Published: March 2015

The results of a numerical investigation to predict the flow in the wake regions of compressor cascades, and wakes and mixing in rotors are presented in this paper. Part I deals with flow in compressor cascades including the effects of change in loading (incidence) and the inlet freestream turbulence intensity. Part II of the paper deals with the predictions of the rotor flow field, including wakes and spanwise mixing. The wake behaviour has been studied numerically using a three-dimensional incompressible Navier-Stokes solver with a high Reynolds number form of the k–ε turbulence model. The equations are solved using a time dependent implicit technique. The agreement between the measured data and predictions is good; including the wake profile, decay, and losses. The ability of the pseudo-compressibility scheme to predict the entire flow field including the wake profile and its decay characteristics, effect of loading and the viscous losses of a compressor cascade is demonstrated. The numerical analysis shows a slight increase in the total pressure loss coefficient through the cascade with increasing turbulence levels. The results also show a slight increase in the rate of decay of the wake at higher turbulence levels but the change in the spreading of the wake was found to be very small with increased turbulence levels.
Performance Deterioration in Industrial Gas Turbines
Authors: Diakunchak Ihor S.
Published: March 2015

This paper describes the most important factors affecting the industrial gas turbine engine performance deterioration with service time and provides some approximate data on the prediction of the rate of deterioration. Recommendations are made on how to detect and monitor the performance deterioration. Preventative measures, which can be taken to avoid or retard the performance deterioration, are described in some detail.
Finite Element Simulation of the Upset Welding Process
Authors: Nied H. A.
Published: March 2015

A finite element model of an elevated temperature upset welding process was developed to simulate the process and to study the role and sensitivity of the major process parameters. Particular attention was focused on the deformation characteristics by studying the displacement and stress fields generated for the purpose of obtaining a better understanding of this solid-state welding process. The paper describes the finite element formulation, the experiments used to validate the modeling, and a selected application for upset welding of a titanium alloy.
Design Stage Acoustic Analysis of Natural Gas Piping Systems in Centrifugal Compressor Stations
Authors: Rogers L. E. (Larry)
Published: March 2015

This paper presents design stage methods to acoustically analyze centrifugal compressor station piping. The methods have been successfully applied to the design of 26 stations since 1988. Full details of the calculation procedures are given, as well as guidelines for interpreting predicted results. Finally, the relationships between acoustical and mechanical response are described.
Design of a Hydraulic Actuator for Active Control of Rotating Machinery
Authors: Rashidi Majid , Dirusso Eliseo
Published: March 2015

A Hydraulic actuator was designed and is described herein. This actuator consists of: a pump which generates the nominal pressure, a hydraulic servo-valve, and a thin elastic plate which transduces the generated pressure variations into forces acting on a mass which simulates the bearing of a rotor system. An actuator characteristic number is defined to provide a base for an optimum design of force actuators with combined weight, frequency, and force considerations. This characteristic number may also be used to compare hydraulic and electromagnetic force actuators. In tests this actuator generated 182.3 Newton force at a frequency of 100. Hz. and a displacement amplitude of 5.8×10−5 meter.
Experimental and Analytical Investigation of Hybrid Squeeze Film Dampers
Authors: El-Shafei A.
Published: March 2015

A new concept for actively controlling high speed rotating machinery is investigated both analytically and experimentally. The controlling mechanism consists of a hybrid squeeze film damper (patent pending) that can be adaptively controlled to change its characteristics according to the instructions of a controller. In an extreme case the hybrid damper can act as a long damper which is shown to be effective in reducing the amplitude of vibration of rotating machinery. In the other extreme the hybrid damper acts as a short damper which is shown to be effective in reducing the force transmitted to the support. In the long damper configuration the oil flow is circumferential, while in the short damper configuration the oil flow is predominantly axial. The hybrid damper is designed to operate in either of the short or the long damper configurations by controlling the positions of two movable sealing rings. The hybrid damper was tested on a Bently Nevada Rotor Kit and it is shown experimentally that the long damper configuration is extremely efficient at controlling the amplitude of vibration and the short damper configuration reduces the force transmitted to the support.
The Effects of Friction in Axial Splines on Rotor System Stability
Authors: Artiles Antonio F.
Published: March 2015

An in depth parametric evaluation of the effects of Coulomb friction in an axial spline joint on the stability of the rotor-bearing system was conducted through time transient integration of the equations of motion. Effects of: spin speed, friction coefficient, spline torque, external damping, imbalance and side load as well as asymmetric bearing stiffnesses were investigated.

A subsynchronous instability is present at the bending critical speed when the spin speed is above this critical. The limit cycle orbit is circular, is proportional to the product of the friction coefficient and spline torque (μT), is inversely proportional to the external damping and is independent of spin speed.

When imbalance is applied to the rotor, beating between the subsynchronous natural frequency and the synchronous (spin speed) frequency occurs. The subsynchronous component of the orbit is proportional to μT, while the synchronous component is proportional to the imbalance.

When a static side load is applied, the unstable node at the center of the orbitally-stable limit cycle grows into an elliptical orbitally-unstable limit cycle, separating stable - from unstable regions of the phase plane. Below a threshold value of side load, the transient motion approaches one of two asymptotic solutions depending on the initial conditions: the larger stable limit cycle or a point at the center of the smaller unstable limit cycle. Beyond the threshold value of side load the rotor-bearing system is stable and all motions decay to a point.

Asymmetry in the bearing stiffnesses reduces the size of the subsynchronous whirl orbit.
Film Cooling Research on the Endwall of a Turbine Nozzle Guide Vane in a Short Duration Annular Cascade: Part 1 — Experimental Technique and Results
Authors: Harasgama S. P. , Burton C. D.
Published: March 2015

Heat transfer and aerodynamic measurements have been made on the endwalls of an annular cascade of turbine nozzle guide vanes in the presence of film cooling. The results indicate that high levels of cooling effectiveness can be achieved on the endwalls of turbine nozzle guide vanes (NGV). The NGV were operated at the correct engine non-dimensional conditions of Reynolds number, Mach number, gas-to-wall temperature ratio and gas-to-coolant density ratio.

The results show that the secondary flow and horse-shoe vortex act on the coolant which is converted towards the suction side of the NGV endwall passage. Consequently the coolant does not quite reach the pressure side/casing trailing edge, leading to diminished cooling in this region. Increasing the blowing rate from 0.52 to 1.1 results in significant reductions in heat transfer to the endwall. Similar trends are evident when the coolant temperature is reduced. Measured heat transfer rates indicate that over most of the endwall region the film cooling reduces the Nusselt number by 50% to 75%.
Performance Improvements of Compressor Cascades by Controlling the Profile and Sidewall Boundary Layers
Authors: Sturm Wolfgang , Scheugenpflug Hermann , Fottner Leonhard
Published: March 2015

For increasing the thrust-to-weight ratio of modern turbojet engines, the number of stages of the turbo components or at least the number of blades per stage have to be minimized. This inevitably forces a higher loading of the remaining blades, for which — especially in the compressor — even the use of modern controlled diffusion airfoil concepts is limited due to the danger of flow separation. Therefore, boundary layer control can be taken into consideration. The use of blowing proves to be most obvious for applications in turbojet engines, because the required pressurized air is — due to the working process — already available. Basic investigations on this topic are described in this paper, and both the midspan and the sidewall region are covered. As a review of the pertinent literature disclosed the lack of reliable design criteria, fundamental experiments in a cascade wind-tunnel were performed. The results of these measurements are reported and recommendations concerning the application of blowing in compressor cascades are given.
The Role of Laminar-Turbulent Transition in Gas Turbine Engines
Authors: Mayle Robert Edward
Published: March 2015

A critical study of laminar-turbulent transition phenomena and its role in aerodynamics and heat transfer in modern and future gas turbine engines is presented. In order to develop a coherent view of the subject, a current look at transition phenomena from both a theoretical and experimental standpoint are provided and a comprehensive state-of-the-art account of transitional phenomena in the engine’s throughflow components given. The impact of transitional flow on engine design is discussed and suggestions for future research and developmental work provided.
A Two Dimensional Flow Analysis Model for Designing a Nozzle-Less Volute Casing for Radial Flow Gas Turbines
Authors: Owarish H. O. , Ilyas M. , Bhinder F. S.
Published: March 2015

This paper describes a two dimensional model for flow analysis and design of a single entry nozzle-less volute casing for inward flow radial turbines. The model takes into account the cross-sectional shape of the casing by dividing it into a number of segments which are further sub divided into control volumes. Changes in flow properties are calculated by considering the changes in momenta of fluid in the tangential and the radial directions across each control volume. The model, has been computerized using Fortran 77 for the IBM AT or 100% compatible micro computers.
Heat Transfer in Rotating Serpentine Passages With Trips Normal to the Flow
Authors: Wagner J. H. , Johnson B. V. , Graziani R. A. , Yeh F. C.
Published: March 2015

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi–pass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant–to–wall temperature ratio, Rossby number, Reynolds number and radius–to–passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat transfer increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces, where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.
Prediction of Unsteady Rotor-Surface Pressure and Heat Transfer From Wake Passings
Authors: Tran Le T. , Taulbee Dale B.
Published: March 2015

The research described in this paper is a numerical investigation of the effects of unsteady flow on gas turbine heat transfer, particularly on a rotor blade surface. The unsteady flow in a rotor blade passage and the unsteady heat transfer on the blade surface as a result of wake/blade interaction are modeled by the inviscid flow/boundary layer approach. The Euler equations which govern the inviscid flow are solved using a time accurate marching scheme. The unsteady flow in the blade passage is induced by periodically moving a wake model across the passage inlet. Unsteady flow solutions in the passage provide pressure gradients and boundary conditions for the boundary-layer equations which govern the viscous flow adjacent to the blade surface. Numerical solutions of the unsteady turbulent boundary layer yield surface heat flux values which can then be compared to experimental data. Comparisons with experimental data show that unsteady heat flux on the blade suction surface is well predicted, but the predictions of unsteady heat flux on the blade pressure surface do not agree.
Deterministic Blade Row Interactions in a Centrifugal Compressor Stage
Authors: Kirtley K. R. , Beach T. A.
Published: March 2015

The three-dimensional viscous flow in a low speed centrifugal compressor stage is simulated using an average passage Navier-Stokes analysis. The impeller discharge flow is of the jet/wake type with low momentum fluid in the shroud-pressure side corner coincident with the tip leakage vortex. This nonuniformity introduces periodic unsteadiness in the vane frame of reference. The effect of such deterministic unsteadiness on the time-mean is included in the analysis through the average passage stress, which allows the analysis of blade row interactions. The magnitude of the divergence of the deterministic unsteady stress is of the order of the divergence of the Reynolds stress over most of the span, from the impeller trailing edge to the vane throat. Although the potential effects on the blade trailing edge from the diffuser vane are small, strong secondary flows generated by the impeller degrade the performance of the diffuser vanes.
Thermal Details in a Rotor-Stator Cavity at Engine Conditions With a Mainstream
Authors: Ko S. H. , Rhode D. L.
Published: March 2015

This investigation involves a numerical study of enclosed rotor-stator cavities of gas turbine engines. The complete elliptic form of the 2-D, axisymmetric Navier-Stokes equations for compressible turbulent flow were solved. Included are the complete fluid and thermal effects of the hot mainstream gas interacting with the cooling cavity purge flow at actual engine flow conditions for generalized geometries. Additional flow conditions above and below that for engine nominal conditions are also considered. The relationships among the important flow parameters are investigated by examining the entire set of computations. The predictions reveal that a small recirculation zone in the stator shroud axial gap region is the primary mechanism for the considerable thermal transport from the mainstream to the turbine blade root/retainer region of the rotor.
Analytical Condition Inspection and Extension of Time Between Overhaul of F3-30 Engine
Authors: Nakao Masato , Ikeyama Masataka , Abe Shinji
Published: March 2015

F3-30 is the low-bypass-ratio turbofan engine developed to power the T-4 intermediate trainer for the Japan Air Self Defense Force (JASDF). The actual field service was started in September, 1988.

The program to extend time between overhaul (TBO) of the F3-30 has been running. Analytical condition inspection (ACI) and accelerated mission testing (AMT) were conducted to confirm the sufficient durability to extend TBO.

Most deteriorations of parts and performance due to AMT were also found by ACI after field operation with approximately same deterioration rate. On the other hand, some deteriorations were found by ACI only. These results show that ACI after field operation is also necessary to confirm the TBO extension, though AMT simulates the deterioration in the field operation very well. The deteriorations which would be caused by the field operation during one extended-TBO were estimated with the results of ACI and AMT, and it was concluded that the F3-30 has the sufficient durability for TBO extension to the next step.
Biomass-Gasifier/Gas-Turbine Cogeneration in the Pulp and Paper Industry
Authors: Larson Eric D.
Published: March 2015

Increasing atmospheric carbon dioxide from fossil fuel combustion is raising new interest in using renewable biomass for energy. Modest-scale cogeneration systems using air-blown gasifiers coupled to aeroderivative gas turbines are expected to have high efficiencies and low unit capital costs, making them well-suited for use with biomass. Biomass-gasifier/gas-turbine (BIG/GT) technology is not commercial, but efforts aimed at near-term commercialization are ongoing worldwide. Estimated performance and cost and prospects for commercial development of two BIG/GT systems are described, one using solid biomass fuel (e.g. wood chips), the other using kraft black liquor. At an energy-efficient kraft pulp mill, a BIG/GT cogeneration system could produce over three times as much electricity as is typically produced today. The mill’s on-site energy needs could be met and a large surplus of electricity would be available for export. Using in addition currently unutilized forest residues for fuel, electricity production would be nearly five times today’s level. The total cost to produce the electricity in excess of on-site needs is estimated to be below 4 cents per kWh in most cases. At projected growth rates for kraft pulp production, the associated biomass residue fuels could support up to 100 GW of BIG/GT capacity at kraft pulp mills worldwide in 2020 (30 GW in the US). The excess electricity production worldwide in 2020 would be equivalent to 10% of today’s electricity production from fossil fuels.
Modelling of Unsteady Transitional Boundary Layers
Authors: Addison J. S. , Hodson H. P.
Published: March 2015

In turbomachinery, a considerable proportion of the blade surface area can be covered by transitional boundary layers. This means that accurate prediction of the profile loss and boundary layer behaviour in general depends on the accurate modelling of the transitional boundary layers, especially at low Reynolds numbers. This paper presents a model for determining the intermittency resulting from the unsteady transition caused by the passage of wakes over a blade surface. The model is founded on work by Emmons (1951) who showed that the intermittency could be calculated from a knowledge of the behaviour of randomly formed turbulent spots.

The model is used to calculate the development of the boundary layer on the rotor of a low Reynolds number single-stage turbine. The predictions are compared with experimental results obtained using surface-mounted hot-film anemometers and hot-wire traverses of the rotor mid-span boundary layer at two different rotor-stator gaps. The validity and limitations of the model are discussed.
Coal-Fueled Gas Turbine Hot End Simulation Rig Design and Development
Authors: Galica M. A. , Stephenson M. D. , Aurrecoechea J.
Published: March 2015

Effects of the exhaust of a coal fueled gas turbine combustion system on turbine hot section materials and coatings are being determined. A system has been developed to evaluate currently used turbine materials and coatings exposed to coal combustion exhaust. Using an engine to test these materials is not feasible due to the inordinately expensive fuel costs associated with running the engine. Therefore, a scaled-down Hot End Simulation Rig (HESR) was designed and built to economically evaluate turbine components operating with a coal-water mixture (CWM) flow rate of 3.8–7.6 liters/hour (1–2 gallons/hour). The rig incorporates primary and secondary combustion zones, a ceramic barrier filter, and a housing for the material samples. Cooling air is metered to the samples to simulate the material temperatures of subsequent turbine stages. Because of the small scale of the rig, much development focused on the design of an adequate fuel injector that would operate reliably for long periods without plugging. Long-term testing is planned to subject the test specimens to coal exhaust using the alkali level in the fuel as the principle variable. An initial level of 300 ppm is used for a 1000 hour preliminary test. The design, development, and test procedure of the HESR are discussed.
Effects of Turbine Design on Particulate Erosion of Turbine Airfoils
Authors: Wagner J. H. , Johnson B. V. , Geiling D. W.
Published: March 2015

An analytic study was conducted to determine the effects of turbine design, airfoil shape and material on particulate erosion of turbine airfoils in coal-fueled, direct-fired gas turbines used for electric power generation. First-stage, mean-line airfoil sections were designed for 80 MW output turbines with 3 and 4 stages. Two-dimensional particle trajectory calculations and erosion rate analyses were performed for a range of particle diameters and densities and for ductile and ceramic airfoil materials. Results indicate that the surface erosion rates can vary by a factor of 5 and that erosion on rotating blades is not well correlated with particle diameter. The results quantify the cause/effect turbine design relationships expected and assist in the selection of turbine design characteristics for use downstream of a coal-fueled combustion process.
Highly Efficient Automated Control for an MGR Gas Turbine Power Plant
Authors: Yan X. L. , Lidsky L. M.
Published: March 2015

A control system design for the Modular High Temperature Gas-Cooled Reactor Gas Turbine power plant (MGR-GT) is presented. The control system is designed to provide full-scale automated control functions for power output regulation and plant protection in accordance with utility requirements for modular nuclear power plants. Control of the plant power output is based on a unique integration of inventory control and bypass control, which not only enables required load following capabilities but also offers 45% electric generating efficiency over the power ranges from 100% to 50% of the rated level. The reactor power is controlled based on the strategy of maintaining constant core outlet temperature. This approach minimizes the occurrence of thermal transients and temperature redistribution in the core during reactor power changes. In addition, the control system also provides emergency protective control to protect the plant components and to mitigate the likelihood of bounding safety events in case of severe accidents. The operation of the control system is automated by controllers implemented based on the state-space feedback control methodology. A spectrum of transients in both normal and far-off normal conditions has been simulated to evaluate the operability of the plant. The simulation results for a few selected events will be described. The design demonstrates that the MGR-GT is a highly efficient and robust controllable power plant.
Non-Intrusive Measurement of Blade Tip Vibration in Turbomachines
Authors: Andrenelli L. , Paone N. , Rossi G. , Tomasini E. P.
Published: March 2015

It is discussed the need for non-intrusive monitoring of rotating blade vibration. The advantages over conventional techniques are outlined.

The vibration of a compressor blade has been investigated by strain gages, with particular attention to time evolution of the frequency spectra, at different operating speeds of the machine. These information are fundamental to the correct design of the non-intrusive measurement system.

The non-intrusive measurement technique has been presented, with special attention on uncertainty and resolution. The necessary hardware is discussed and the design of an optical sensor is presented.
Scalar Measurements in Bluff Body Stabilized Flames Using Cars Diagnostics
Authors: Pan J. C. , Vangsness M. D. , Heneghan S. P. , Ballal D. R.
Published: March 2015

Measurements of mean and rms temperature fluctuations were performed in confined turbulent premixed methane-air flames, stabilized on a conical flameholder. A CARS system was used for these measurements. These tests employed flameholders of different blockage ratios (13% and 25%), and mixtures with different equivalence ratios (0.56, 0.65, 0.8, and 0.9) and approach turbulence intensity (2%, 17%, and 22%).

It was found that the recirculation zone closely resembles a perfectly well-stirred reactor. Blockage ratio, equivalence ratio, or approach turbulence intensity did not alter the scalar field. The turbulent flame structure enveloping the recirculation zone comprises: (i) an ignition/thin flame region in the vicinity of the flameholder base, (ii) a reacting shear layer region of large-scale coherent structures, and (iii) a thick flame region where entrainment is the dominant mechanism. Finally, analysis suggests that the scalar gradient-diffusion relationship is valid and areas of non-gradient diffusion, if any, are probably small.
Development and Bench Test of High-Temperature Combustion Chamber With Structural Ceramic Components
Authors: Sudarev A. V. , Zakharov J. I. , Ljubchik G. N. , Butovsky L. S. , Granovskya E. A.
Published: March 2015

The most effective method of increasing the thermal efficiency of a simple cycle gas turbine unit involves elevation of the gas temperature upstream of the turbine. This requires development of appropriate operational procedure principles and adequate combustion chamber design.
Development of Improved Processing and Evaluation of Silicon Nitride
Authors: Pujari V. K. , Amin K. E. , Tewari P. H.
Published: March 2015

The goals of this program are to develop and demonstrate significant improvements in processing methods, process controls, and nondestructive evaluation (NDE) which can be commercially implemented to produce high-reliability silicon nitride components for advanced heat engine applications at temperatures to 1370°C. Achievement of this goal is being sought by

• The use of silicon nitride - 4% yttria composition which is consolidated by glass encapsulated HIP’ping.

• The generation of baseline tensile strength data from an initial process route involving injection molding.

• Fabrication of tensile test bars by colloidal techniques, e.g. injection molding and colloidal consolidation.

• Identification of (critical) flaw populations through NDE and fractographic analysis of tensile bars.

• Correlation of measured tensile strength with flaw populations and process parameters.

• Minimization of these flaws through innovative improvements in process methods and controls.

The program goals are:

• mean room temperature tensile strength of 900 MPa and Weibull modulus of 20;

• mean 1370°C fast fracture tensile strength of 500 MPa;

• mean 1230°C tensile stress rupture life of 100 hours at 350 MPa.

This report describes the progress made to date in developing injection molding and colloidal consolidation processes for the net shape forming (NSF) of tensile bars, nondestructive evaluation of processed material, and tensile testing of net shape bars in green and densified states.
Conversion of Two MS5001P Gas Turbines to Meet Emission Requirements in the Netherlands
Authors: Dijkgraaf P. A. M. , Luessen H. P.
Published: March 2015

Two older MS5001P gas turbines at the Netherlands Refining Company were converted by the addition of steam injection for NOx abatement. The project involved upgrading the gas turbines to the “P Advanced Technology” hardware along with the necessary material for the addition of steam injection. The control system was changed from SPEEDTRONIC™ MKII to SPEEDTRONIC™ Simplex. A Continuous Emissions Monitoring Skid was also added for the purposes of steam trim and measuring NOx. This paper gives the details of the project along with some special technical considerations for being able to display NOx in g/GJ instead of the usual ppm format.
Rotordynamic Coefficients for Partially Roughened Annular Gas Seals
Authors: Scharrer Joseph K. , Nelson Clay C.
Published: March 2015

The basic equations are derived for compressible flow in an annular seal with partially roughened surfaces. The flow is assumed to be completely turbulent in the axial and circumferential directions with no separation, and is modeled by Moody’s equation for roughness. Linearized zeroth and first-order perturbation equations are developed for small motion about a centered position by an expansion in the eccentricity ratio. The zeroth-order continuity and momentum equations are solved exactly, yielding the axial and circumferential velocity components and the pressure distribution. The first-order equations are reduced to three ordinary, complex, differential equations in the axial coordinate Z. The equations are integrated to satisfy the boundary conditions and yield the perturbation pressure distribution. This resultant pressure distribution is integrated along and around the seal to yield the force developed by the seal and the corresponding dynamic coefficients.

Since no test data exist for this type of seal, the results of a parametric study on the effect of the rough length/smooth length ratio on the seal leakage and rotordynamic coefficients is presented.
A Comparison of Fluids Used to Superabrasively Machine a Titanium Alloy
Authors: Campbell James D.
Published: March 2015

The objective of this paper was to compare the creep feed superabrasive machining of an alpha-beta structural titanium alloy, using a water-soluble and a straight oil grinding fluid, in terms of residual stress, specific energy, power flux and microstructure. The statistical effect of process variables on these criteria was investigated using a Taguchi screening design of experiment. Grinding wheel peripheral velocity, abrasive size and fluid type were the most important factors contributing to compressive residual stress. After the depth of cut, fluid type contributed the most variation to specific energy and power flux. Both fluids produced testpieces that were microstructurally sound, and were essentially stress free or had favorable compressive residual stress.
Testing at the U.S. Navy’s Gas Turbine Systems Engineering Complex: Part II
Authors: Preisel John H.
Published: March 2015

Full-scale testing has continued at the US Navy’s Gas Turbine Systems Engineering Complex. The test complex, which is based on the US Navy’s DDG-51 class propulsion plant, has fully transitioned from the construction phase to the testing phase. A complete LM 2500-based propulsion train exists, as well as an electrical generation, distribution and control system. The purpose of this paper is to provide an update to last year’s test report, and to document the new tests and systems integration tasks that have taken place.

Particular areas to be discussed include:

- electrical system design, installation and testing

- crew training and integrated plant operations

- full-scale casualty control exercises

- integration and testing of an Auxiliary Power Unit

- control system upgrades and communication testing

At the time that this paper is being written, final design approval has been given to move a second 2500 kW gas turbine generator to the test site. This will be a cogeneration system, since it has a waste heat recovery system installed in the exhaust system. The paper describes the plans for integrating this system into the gas turbine complex. The proposed electrical system test plan is also discussed.

The paper concludes by outlining the component and system testing programs that are planned for the future. The future tests represent a continuing commitment to land based test sites and full scale integration testing.
Verifying Conceptual Design Gas Turbine Blade Life Predictions by Comparison With Fleet Data
Authors: Bentz John C. , Cote Scott M.
Published: March 2015

The Navy Engine Life Executive Routine, LIFER, is a PC based computer code which is used to assess the life of turbine engine components. The code has been developed to ascertain life for the components which have the highest wear out failure rates. The code has been successfully employed in the evaluation of a number of life-related problems for Naval aircraft engines. However, prior to this study, LIFER estimations for engine component life have not been compared to the component life as determined by component failure data. This paper presents the results of a comparison between the analytical predictions of LIFER and fleet experience for engine component failures. The comparison was made for the high pressure turbine blades of the TF34-GE-400 engine and the low pressure turbine blades of the F404-GE-400 engine. The blade failure data were analyzed using the Weibull technique. The difference between the component life, as predicted by LIFER, and the component characteristic life, as determined by the Weibull method, was less than 7.5 percent.
Garrett GTP50-1 Multipurpose Small Power Unit Technology Demonstrator Program
Authors: Annati R. E. , Smyth J. R.
Published: March 2015

The Multipurpose Small Power Unit (MPSPU) Advanced Development Program is providing the United States Army and other Department of Defense branches with advanced technology for current and future auxiliary power units (APUs)/secondary power systems (SPSs) in aircraft, combat vehicles, and mobile shelters. The design includes low specific fuel consumption (SFC), weight and volume, acquisition and life cycle costs (LCC), and high reliability and durability.

The Garrett Auxiliary Power Division (GAPD) Model GTP50-1 MPSPU has demonstrated major advances in small gas turbine power unit design and manufacturing technologies. Component test rigs have completed extensive development testing. Power unit operation of 214 hours, with 557 starts, has been accumulated. Power unit and rig testing has demonstrated program goals and identified areas for continued technical development. The program has demonstrated 77.6 kW (104 shp), corrected to sea level standard day, at an SFC of 0.5 kg/kW-hr (0.8 lb/hp-hr).
Off-Design Evaluation of a Multiple Expansion Reheating Gas Turbine in Cogeneration Applications
Authors: Benvenuti Erio , Bettocchi Roberto , Cantore Giuseppe , Di Montenegro Giorgio Negri
Published: March 2015

The multiple expansion reheating gas turbine proves to have a potential of good operational flexibility for the intrinsic capability of responding to variations in electric and thermal power demands without appreciable impact on efficiency.

The present study deals with evaluation of the performance attainable in off-design operation, with power control obtained through changes in the first and second combustor firing temperatures and in the compressor intake air flow achieved by means of variable inlet guide vanes.

Because of the important impact of the hot part cooling air flows on performance, the study includes also a hypothesis of controlling such flows in off-design operation through external means.

The predicted off-design performance results superior in the hypothesis of external cooling air flow control, thus making such a system worthy of consideration for possible future developments of machines in this category.

To evaluate the suitability of the multiple expansion reheating gas turbine in cogeneration applications, the electric efficiency and the electrical index have been taken into consideration.

The capability of varying the reheating temperature represents an effective way of controlling the electrical index with good efficiencies in industrial cogeneration with strongly varying electric power and process heat requirements.

With regard to the cooling air control through external means, implementation of such a more complex system seems to be avoidable at least when the gas turbine is intended specifically for application in cogeneration, because of its smaller impact on the overall efficiency of the system.
Development of Reheat Combustor-Power Turbine Package
Authors: Nakhamkin M. , Swensen E. C. , Cohn Arthur
Published: March 2015

This paper describes the first phase of an intended project to develop a reheat combustor-power turbine (RCPT) package which when added to an aircraft derivative gas generator would produce a commercially attractive reheat gas turbine for combined cycle and cogeneration applications. This first phase includes the identification of gas generators and establishes the relative merits of the RCPT package at various inlet temperatures based upon evaluated benefits. Our calculations show that in combined cycle application with the RCPT at an easily feasible power turbine inlet temperature of 1700°F, the steam flow increases by approximately 2.5 times, the combined cycle power by about 30%, and the combined cycle efficiency by about 5% compared to an unfired aeroderivative combined cycle. Compared to the duct fired combined cycle with the same power output, the efficiency increases by approximately 7.5%, leading to a lower cost of electricity of about 10 per cent for the economic assumptions of the study.
Ceramic Matrix Composites and its Application in Gas Turbine Engines
Authors: Naik Subhash K. , Massar Andrew , Lecostaouec Jean F. , Thomson Bruce
Published: March 2015

The key technology requirement for advanced gas turbine engines is the availability of lightweight, higher temperature materials which will allow the components to operate with little or no cooling air. Ceramic Matrix Composites represent one such category. An interturbine duct has been selected as the first component for introducing silicon carbide fiber reinforced silicon nitride composites in advanced engines.

An ongoing program is focused on process development, fabrication of components and measurement of mechanical properties. A significant property base continues to be developed for both uni-directional and multi-directional reinforced ceramic composites. The results of the program are presented.
An Investigation of Two Cooling Technologies as Applied to a Distributed Propulsion Control Architecture
Authors: Cox Tyler G. , Weiss Carl F.
Published: March 2015

The use of vortex tubes and thermoelectric coolers were investigated in a study of cooling the remote electronics of a future distributed propulsion control architecture. Vortex tubes operating off environmental control system air accommodate the diverse cooling requirements of new applications, but the system weight penalty from tubes and plumbing may be unacceptable depending on the application. Thermoelectric elements combined with a fuel heat sink could be used under select conditions, but only up to fuel temperature of 230°C for the near future.
Coal-Burning Exhaust-Heated-Cycle Gas Turbine With a Regenerative Heat Exchanger
Authors: Wilson David Gordon , Frenkel Richard Gregory , Kowalick David Jude , Nahatis Harry Michael , Silverstein Seth Michael , Tampe Luis Alberto
Published: March 2015

A preliminary design study of four coal-burning gas-turbine engines using the exhaust-heated cycle and state-of-the-art components has been completed. In the exhaust-heated cycle the combustor takes air from the turbine exhaust and delivers hot combustion products to a heat exchanger. In the program reported here a rotary ceramic-matrix regenerator is used; in it the temperature of the compressor-delivery air is raised to that required at the turbine inlet. Some initial experiments on the flow of hot coal-combustion products through ceramic passages and of cold ash-laden air through a rotary ceramic-matrix regenerator have been conducted. Highly favorable results have been obtained on all aspects on which definite conclusions could be drawn.
Small Diameter Film Cooling Hole Heat Transfer: The Influence of the Hole Length
Authors: Andrews G. E. , Bazdidi-Tehrani F. , Hussain C. I. , Pearson J. P.
Published: March 2015

The overall surface averaged heat transfer was determined for air passing through arrays of small diameter holes drilled at 90° through thin metal walls. The influence of the wall metal thickness, L, was investigated for a range of hole diameters, D, and pitch, X. L/D was varied from 0.43 to 8.3 using 13 different test geometries. It was found that although the influence of L/D was significant, there was only a ±20% data scatter on a correlation of the results that ignored the influence of L/D for 0.8<L/D<10. The results showed that the heat transfer was dominated by the hole approach flow and this surface area Ax was the appropriate heat transfer area for the determination of the heat transfer coefficient. The dominant parameters that affected the heat transfer were G and X/D. An improved correlation for a range of L/D was achieved if the heat transfer surface area was taken as the sum of Ax and Ah, the hole internal surface area.
Hydrogen Gas Cooling Capability of Combustor Wall for a Turbo-Ram-Engine
Authors: Tamaru T. , Saito T. , Shimodaira K. , Horiuchi S. , Yamada H.
Published: March 2015

The possibility of combustor wall cooling by a hydrogen fuel gas in a supersonic/hypersonic flight engine was demonstrated in this paper. Heat transfer tests on subsonic ram combustor models showed that the temperature of the wall cooled by the hydrogen gas was maintained within the temperature limit of conventional material without excessive temperature increase of the fuel. The analysis showed the possibility of the application for the scaled-up models.