bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Performance of Gas/Steam Combined Cycle Power Plants
Authors: Yadav R. , Singh Lakshman
Published: February 2015

In this paper, an attempt has been made to predict the comparative thermal performance of various configurations of unfired gas/steam combined cycle power plants. The prediction is based on the thermodynamic analysis of various components of the plant. The performance curves drawn may be beneficial in the selection of configuration and parameters for the design of combined cycle plants.
Prediction Model of NOx for Gas Turbine Combustor With Diffusion and Lean Premixed Flames
Authors: Maeda Fukuo , Iwai Yasunori
Published: February 2015

In order to predict the NOx concentration etc., it is necessary to carry out 3-D reacting flow analysis in the combustion zone. However, regardless of improved numerical scheme, and physics-based modeling of flow phenomena and combustion reaction, these techniques not yet reached to a level to be applied to practical combustor problem, because of vast computation time and consequently high computation costs, etc. To improve NOx characterization of new Dry Low NOx Combustor (DLNC) and optimum fuel scheduling for DLNC operations, a NOx prediction method to be applicable for practical combustor problems needs to be developed.

In this paper has been proposed a simple semi-empirical model for predicting DLNC NOx emissions that formed from lean premixed combustion flames and diffusion flames. This model comprised of experimental coefficients for adjusting or incorporating effects of practical combustion liner configurations and effects of flow conditions in combustion zone, etc. Also, the present model is applied to newly designed and redesigned DLNC for estimating NOx emission levels and its variation with gas turbine operating conditions, which are compared with the experimental data of full pressure combustion with Natural Gas (NG) fuel.
Generalized Euler’s Turbomachine Equation and Free Vortex Sheet Conditions in Separated/Cavitated Turbo-Flows
Authors: Liu Gao-Lian
Published: February 2015

In the present paper four fundamental problems in turbomachinery aerodynamic theory are studied in depth: (1) It is shown that the well–known Euler’s equation for turbomachine power is valid only for shrouded impellers. Then, a generalization of it to unshrouded impellers is carried out. (2) An equation relating the free trailing vortex distribution along the blade span to that of the swirl moment rVθ is derived, yielding a condition for the vanishing of free trailing vortex sheets. (3) The free surface conditions in separated flow are shown to be entirely different from those in cavitated flow. (4) Generlized Kutta conditions for 3–D rotor bladings in separated and caviated flows are also derived. All these results are of fundamental value in both analytical and numerical handlings of fully 3–D rotor–flows.
Rotor-Stator Interaction Analysis Using the Navier-Stokes Equations and a Multigrid Method
Authors: Arnone Andrea , Pacciani Roberto
Published: February 2015

A recently developed, time-accurate multigrid viscous solver has been extended to the analysis of unsteady rotor-stator interaction. In the proposed method, a fully-implicit time discretization is used to remove stability limitations. By means of a dual time-stepping approach, a four-stage Runge-Kutta scheme is used in conjunction with several accelerating techniques typical of steady-state solvers, instead of traditional time-expensive factorizations. The accelerating strategies include local time stepping, residual smoothing, and multigrid.

Two-dimensional viscous calculations of unsteady rotor-stator interaction in the first stage of a modem gas turbine are presented. The stage analysis is based on the introduction of several blade passages to approximate the stator:rotor count ratio. Particular attention is dedicated to grid dependency in space and time as well as to the influence of the number of blades included in the calculations.
Adaptive Vibration Control of a Rigid Rotor Supported by Active Magnetic Bearings
Authors: Lang Oliver , Wassermann Johann , Springer Helmut
Published: February 2015

In this paper a digital numerical simulation is carried out in which active magnetic bearings (AMB) are applied to control nonlinear and non-synchronous vibrations of a rigid rotor excited by non-conservative cross-coupling mechanisms. Through an adaptive control algorithm of the AMB-controller, unknown cross-coupling parameters of a rotor are estimated on-line by a standard least square estimator along with a time-varying so-called forgetting factor. The parameters of the AMB controller are adapted in order to compensate the cross-coupling effects and to stabilize the rotor system. Transient cross coupling response characteristics are calculated by numerical simulation of a rigid rotor supported by two active magnetic bearings. With this kind of control strategy the stability of the system can be guaranteed for much higher values of cross-coupling coefficients than with common non-adaptive feedback controllers, designed with pole placement or least square algorithms.
Measurement and Computation of Heat Transfer in High Pressure Compressor Drum Geometries With Axial Throughflow
Authors: Long Christopher A. , Morse Alan P. , Tucker Paul G.
Published: February 2015

This paper makes comparisons between CFD computations and experimental measurements of heat transfer for the axial throughflow of cooling air in a high-pressure compressor spool rig and a plane cavity rig. The heat transfer measurements are produced using fluxmeters and by the conduction solution method from surface temperature measurements. Numerical predictions are made by solving the Navier-Stokes equations in a full three-dimensional, time-dependent form using the finite-volume method. Convergence is accelerated using a multigrid algorithm and turbulence modelled using a simple mixing length formulation. Notwithstanding systematic differences between the measurements and the computations, the level of agreement can be regarded as promising in view of the acknowledged uncertainties in the experimental data, the limitations of the turbulence model and, perhaps more importantly, the modest grid densities used for the computations.
Free Vortex Theory for Efficiency Calculations From Annular Cascade Data
Authors: Main A. J. , Oldfield M. L. G. , Lock G. D. , Jones T. V.
Published: February 2015

This paper describes a new three dimensional theory to calculate the efficiency or loss of nozzle guide vane annular cascades from experimental area traverse measurements of the compressible downstream flow. To calculate such an efficiency, it is necessary to computationally mix out the measured flow to either a uniform state or one which is a function of radius only. When this is done by conserving momentum, mass and energy flow there is a remaining degree of freedom in that the radial distribution of circumferential velocity can be chosen. This extra freedom does not arise in two dimensional cascades. The new method mixes the flow out to an free (i.e. irrotational) vortex. This is preferred to existing methods in that it gives a physically realistic flow and also provides a unique, lossless, isentropic reference flow. The annular cascade efficiency is then uniquely defined as the ratio of the mixed out experimental kinetic energy flux to the ideal isentropic kinetic energy flux at the same mean radius static pressure. The mathematical derivation of this method is presented. This new theory has been used to process data obtained from a large, transonic, annular cascade in a blowdown tunnel. A four-hole pyramid probe, mounted on a computer-controlled traverse, has been used to map the passage flowfield downstream of the nozzle guide vanes. Losses calculated by the new method are compared with those calculated from the same data using earlier analysis methods.
A Navier-Stokes Analysis of the Effect of Tip Clearance on Compressor Stall Margin
Authors: Dring Robert P. , Sprout William D. , Weingold Harris D.
Published: February 2015

A three-dimensional Navier-Stokes calculation was used to analyze the impact of rotor tip clearance on the stall margin of a multi-stage axial compressor. This paper presents a summary of: (1) a study of the sensitivity of the results to grid refinement, (2) an assessment of the calculation’s ability to predict stall margin when the stalling row was the first rotor in a multi-stage rig environment, (3) an analysis of the impact of including the effects of the downstream stator through body force effects on the upstream rotor, and (4) the ability of the calculation to predict the impact of tip clearance on stall margin through a calculation of the rear seven airfoil rows of an eleven stage high pressure compressor rig. The result of these studies was that a practical tool is available which can predict stall margin, and the impact of tip clearance, with reasonable accuracy.
Stage Re-Matching as a Result of Droplet Evaporation in a Compressor
Authors: Ludorf Rainer K. , Elder Robin L. , Tronbøl Turid H. , Øverli Jan
Published: February 2015

An existing one dimensional stagewise compressor stability analysis programme has been extended to incorporate a model for humidity and droplet evaporation. In its modified form the model shows the extent of stage re-matching when ingesting modest amounts of water. The water distribution throughout the flow is assumed to be homogeneous. The stage interactions of an aircraft engine compressor are investigated for different environmental operating conditions. The effects of humidity on stage loading are small while the evaporation of water causes a significant shift of the operating point along the characteristics.
Predictions of the Flow in Repeating Stages of Axial Compressors Using Navier-Stokes Solvers
Authors: Bolger John J. , Horlock John H.
Published: February 2015

In a well designed multi-stage axial flow compressor the flow quickly settles down to a repeating condition in which the flow angle and axial velocity profiles do not deteriorate further; they are more or less unchanged between entry to and exit from a deeply embedded stage.

In early work, the flow in such repeating stages was studied using inviscid secondary flow analysis, coupled with empirical data on clearance flows, and also by inviscid numerical calculation. Underturning near the annulus walls was generally predicted but this was not convincingly confirmed by comparison with experimental data for repeating stage flows; it was apparent that viscous effects were important and should be taken into account.

Further investigation of the flow in repeating stages has therefore been undertaken using Navier-Stokes solvers for comparison with early experimental results and improved test data more recently available. It is established that, with care, quite a good prediction of repeating stage flows can be made using steady-flow 3D viscous methods, and more general conclusions of greater validity can be drawn about over- or underturning at the annulus walls than the universal underturning predicted in the earlier inviscid approaches for moderately loaded stages.
Development of 300kW-Class Ceramic Gas Turbine (CGT301) Engine System
Authors: Tatsuzawa Masashi , Taoka Tomoki , Sakida Takeshi , Tanaka Shinya
Published: February 2015

CGT301 is a recuperated, single-shaft ceramic gas turbine for co-generation use. Ceramic parts are used in the hot section of the engine, such as turbine blades, nozzle vanes, combustor liners, heat exchanger elements and gas path parts. These ceramic parts are designed axi-symmetrically to reduce their sizes and thermal stresses and to avoid their unexpected deformations. The turbine is a two-stage axial flow type. As a primary feature of this turbine, the rotors are composed of ceramic blades inserted into metallic disks.

The ceramic parts of the engine system have been tested before installing them in the engine to assure their reliability in the following manner. The ceramic blades have been examined by hot-spin test with the gas temperature of 1100°C and up to 110% of the engine rated speed. The ceramic stationary parts such as nozzle vanes, combustor liners and gas path parts, have been assembled and installed in a test rig with almost the same constraint and thermal conditions as the engine, and thermal fatigue tests of 100 cycles between 1200°C and 300°C have been conducted.

After the proof tests of ceramic parts, they have been installed in the engine, step by step. Finally, the engine has been operated with a TIT of 1200°C at the engine rated speed of 56000 rpm. The present paper describes the development process and shows test results of the ceramic gas turbine at a TIT of 1200°C.
Hot Streak Clocking Effects in a 1-1/2 Stage Turbine
Authors: Dorney Daniel J. , Gundy-Burlet Karen
Published: February 2015

Experimental data has shown that combustor hot streaks can lead to pressure side “hot spots” on first-stage turbine rotor blades. Previous numerical studies have confirmed that unsteady Navier-Stokes procedures can be used to predict the rotor pressure surface temperature increase associated with these combustor hot streaks, and suggest that second-stage turbine stators can also be subjected to increased surface temperatures. In the current investigation, two-dimensional unsteady Navier-Stokes simulations have been performed to study the effects of combustor hot streak position (or clocking) on the temperature distributions along first-stage rotor and second-stage stator airfoils. The predicted results indicate that if the hot streak is positioned such that it impinges upon the first-stage stator, then the suction surfaces of the rotor and second-stage stator attain higher time-averaged temperatures than the pressure surfaces. If the hot streak is positioned such that it does not impinge upon the first-stage stator, then the pressure surfaces of the downstream blades reach higher time-averaged temperatures than the corresponding suction surfaces.
The Design and Development of the Rolls-Royce/Westinghouse Trent Econopac Control System
Authors: Agrawal Rajendra K. , Paris Richard E.
Published: February 2015

This paper describes the evolution of the control system for the 50 MW Rolls-Royce/Westinghouse TRENT Econopac Power Generation Unit. The prime mover for this power plant is derived from the Rolls-Royce TRENT 800 Aero gas turbine and incorporates the new staged Dry Low Emission combustion system. The generator is standard air cooled design and is procured and integrated into the compact Econopac unit by Westinghouse.

The paper discusses the design objectives for the control system and the resulting hardware and software requirements. The design objectives include conformance to applicable safety and hazardous standards, efficient emission and fuel control for dual fuel (gas and liquid) operation, high reliability and availability and extensive fault diagnostic and condition monitoring for ease of plant operation and maintenance.

The control system design and development relies heavily on the use of real time simulator (RTS) incorporating non linear real time models of the engine and the many sub systems such as the gas fuel distribution system, liquid fuel/water system, vibration system etc. which are controlled by the control system. The paper covers the development of these models and their use in the RTS in the dry and wet hardware in the loop testing.

The paper concludes with a review of the planned engine/econopac development testing leading up to full control system validation and certification to the Rolls-Royce/Westinghouse internal and applicable external acceptance standards.
Contact Force Measurements Under a Brush Seal
Authors: Long Christopher A. , Marras Yannis
Published: February 2015

This paper discusses results of experiments carried out to measure the bristle contact force of a brush seal on a shaft. Two separate experimental techniques were used: i) indirectly through torque measurements and ii) directly using a force blade located under the bristle tips. The tests were conducted on a non-rotating shaft having a nominal diameter of 122 mm, with static radial interferences of 0.4, 0.2, 0.1 and 0.05 mm; and for the range of pressure ratios 1 to 4.5. The experimental results obtained from these measurements are compared with predictions from a simple theoretical model.

Although there are some large differences, the experimental results do show some agreement with the theoretical predictions. However, both this current simple theoretical model and the experiments have their limitations. Despite these shortcomings, the experimental results are considered to support the qualitative value of the current theoretical model.
Effects of Cycle Operating Conditions on Combustor Performance
Authors: Davis N. T. , McDonell V. G. , Samuelsen G. S.
Published: February 2015

To mitigate the environmental impact of next generation gas turbine combustors, the emission performance at each condition throughout the load duty cycle must be optimized. Achieving this with a single combustor geometry may not be possible. Rather, the mixing processes and air flow splits must likely be modified as a function of load in order to (1) abate the emission of oxides of nitrogen, (2) maintain combustion efficiency, and (3) preclude lean blow out over the entire duty cycle. The present study employs a model combustor to evaluate combustor performance as a function of load and explore the application of variable geometry to optimize performance at each condition. A parametric variation of flow splits is conducted at each load condition by independently adjusting the primary jet area and swirler choke area. The resultant impact on combustor performance is measured and quantified in terms of a cost function. The cost function is defined to increase with improving combustor performance (e.g., improving combustion efficiency and/or declining NOx emissions). Cycle operating conditions are found to alter the response mappings of efficiency and NOx. As a result, the optimal configuration of the combustor changes as the load is varied over the duty cycle. The results provide guidance on the application of active control.
The Effects of Different Sulfur Compounds on Jet Fuel Oxidation and Deposition
Authors: Kauffman Robert E.
Published: February 2015

This paper presents research which supports a proposed fuel oxidation/deposition mechanism involving acid: base reactions between “oxidizable” sulfur compounds, “basic” nitrogen compounds, and oxygen containing polymers. The reported research presents experiments which study the effects of different sulfur compounds on the high temperature (160–220°C) oxidation products and deposition tendencies of jet fuel. Surface analyses incorporating elemental analyses and depth profiles of deposits formed on steel surfaces were performed to identify the species involved in the initial stages of deposition by jet fuels. Experiments to study the effects of acid neutralizing compounds on the deposition tendencies of jet fuels are also presented.
Advanced Jet Fuels — JP-4 Through JP-8 and Beyond
Authors: Harrison W. E. , Mongia H. C. , Heneghan S. P. , Ballal D. R.
Published: February 2015

Jet fuel requirements have evolved over the years as a balance of the demands placed by advanced aircraft performance (technological need), fuel cost (economic factors), and fuel availability (strategic factors). In a modern aircraft, the jet fuel is the primary coolant for aircraft and engine subsystems and provides the propulsive energy for flight. To meet the evolving challenges, the U.S. Air Force, industry and academia have teamed to develop new and improved fuels that offer increased heat sink and thermal stability, properties that will enable improved aircraft design and decrease fuel system maintenance due to fuel fouling/coking. This paper describes the team effort to develop improved JP-8, named “JP-8+100”, that offers a 55C (100F) improvement in thermal stability and a 50% increase in heat sink.

The government, industry, and academia team has made numerous advances in the development of JP-8+100 with a more complete understanding of the fundamental processes of deposition, new approaches to reducing fouling/coking, and new tests and models to assist the designers of aircraft and engine fuel systems. Some of the principal advances are: new quantitative research devices and fuel system simulators that provide thermal stability information that cannot be obtained using the standard JFTOT test; new techniques to measure oxygen consumption and fuel degradation pathways; a free radical theory to explain behaviors such as the inverse relationship between thermal and oxidative stability, advanced CFD models with coupled degradation chemistry, and a new thermal stability ranking scale for jet fuels. The insight obtained has been applied to the development of an additive package for JP-8 that shows thermal stability improvements equal to or greater than the stated goal and enables the development of even higher thermal stability fuels such as JP-900.
Numerical and Experimental Investigation of Secondary Flow in a High Speed Compressor Stator
Authors: Ohkita Y. , Kodama H. , Nozaki O. , Kikuchi K. , Tamura A.
Published: February 2015

A series of numerical and experimental studies have been conducted to understand the mechanism of loss generation in a high speed compressor stator with inlet radial shear flow over the span. In this study, numerical simulation is extensively used to investigate the complex three-dimensional flow in the cascades and to interpret the phenomena appeared in the high speed compressor tests. It has been shown that the inlet radial shear flow generated by upstream rotor had a significant influence on the stator secondary flow, and consequently on the total pressure loss. Redesign of the stator aiming at the reduction of loss by controlling secondary flow has been carried out and the resultant performance recovery was successfully demonstrated both numerically and experimentally.
Time Accurate Euler Simulation of Interaction of Nozzle Wake and Secondary Flow With Rotor Blade in an Axial Turbine Stage Using Nonreflecting Boundary Conditions
Authors: Fan S. , Lakshminarayana B.
Published: February 2015

The objective of this paper is to investigate the three dimensional unsteady flow interactions in a turbomachine stage. A three-dimensional time accurate Euler code has been developed using an explicit four-stage Runge-Kutta scheme. Three-dimensional unsteady non-reflecting boundary conditions are formulated at the inlet and at the outlet of the computational domain to remove the spurious numerical reflections. The three-dimensional code is first validated for 2-D and 3-D cascades with harmonic vortical inlet distortions. The effectiveness of non reflecting boundary conditions is demonstrated. The unsteady Euler solver is then used to simulate the propagation of nozzle wake and secondary flow through rotor and the resulting unsteady pressure field in an axial turbine stage. The three dimensional and time dependent propagation of nozzle wakes in the rotor blade row and the effects of nozzle secondary flow on the rotor unsteady surface pressure and passage flow field are studied. It was found that the unsteady flow field in the rotor is highly three-dimensional and the nozzle secondary flow has significant contribution to the unsteady pressure on the blade surfaces. Even though the steady flow at the midspan is nearly two-dimensional, the unsteady flow is 3-D and the unsteady pressure distribution can not by predicted by a 2-D analysis.
Experimental Investigation of Steady and Unsteady Flow Field Downstream of an Automotive Torque Converter Turbine and Inside the Stator: Part II — Unsteady Pressure on the Stator Blade Surface
Authors: Marathe B. V. , Lakshminarayana B. , Maddock Donald G.
Published: February 2015

The stator flow field of an automotive torque converter is highly unsteady due to potential and viscous interactions with upstream and downstream rotors. The objective of this investigation is to understand the influence of potential and viscous interactions of the upstream rotor on the stator surface pressure field with a view towards improvement of the stator design. Five miniature fast-response pressure transducers were embedded on the stator blade. The measurements were conducted at three locations near the leading edge and two locations near the trailing edge at the mid-span location. Upstream flow field was measured using a fast response five-hole probe and is described in the first part of this paper. The experimental data were processed in the frequency domain by spectrum analysis and in temporal-spatial domain by the ensemble averaging technique. The flow properties were resolved into mean, periodic, aperiodic and unresolved components. The unsteady amplitudes agreed well with the pressure envelope predicted by panel methods. Aperiodic component was found to be significant due to the rotor-rotor and rotor-stator interactions observed in multistage, multi-spool environment.
Fracture Toughness of Structural Ceramics Under Biaxial Stress State by Anticlastic Bending Test
Authors: Ono Takashi , Kaji Masaki
Published: February 2015

Mixed-mode fracture of structural ceramics under biaxial stress state was investigated by an anticlastic bending test using the controlled surface flaw technique. The stress state of the anticlastic bending specimen is biaxial. This test enables the study of fractures under pure mode I, pure mode II, or any combination of mode I and mode II loading.

To discuss the experimental results, a parameter ‘T’ was introduced to the modified maximum hoop stress criterion. This parameter represents frictional effects of crack interfaces on the mixed-mode fracture and can be obtained experimentally. Relative magnitudes of mode I and mode II stress intensity factors and the directions of non-coplanar crack extension angles were predicted using the parameter ‘T’. Reasonable agreement with the experimental results was obtained.
Performance Assessment of an Annular S-Shaped Duct
Authors: Bailey D. W. , Britchford K. M. , Carrotte J. F. , Stevens S. J.
Published: February 2015

An experimental investigation has been carried out to determine the aerodynamic performance of an annular S-shaped duct representative of that used to connect the compressor spools of aircraft gas turbine engines. For inlet conditions in which boundary layers are developed along an upstream entry length the static pressure, shear stress and velocity distributions are presented. The data shows that as a result of flow curvature significant streamwise pressure gradients exist within the duct, with this curvature also affecting the generation and suppression of turbulence. The stagnation pressure loss within the duct is also assessed and is consistent with the measured distributions of shear stress. More engine representative conditions are provided by locating a single stage compressor at inlet to the duct. Relative to the naturally developed inlet conditions the flow within the duct is less likely to separate, but mixing out of the compressor blade wakes increases the measured duct loss. With both types of inlet conditions the effect of a radial strut, such as that used for carrying loads and engine services, is also described both in terms of the static pressure distribution along the strut and its contribution to overall loss.
Damage Tolerance Based Life Prediction in Gas Turbine Engine Blades Under Vibratory High Cycle Fatigue
Authors: Walls David P. , deLaneuville Robert E. , Cunningham Susan E.
Published: February 2015

A novel fracture mechanics approach has been used to predict crack propagation lives in gas turbine engine blades subjected to vibratory high cycle fatigue (HCF). The vibratory loading included both a resonant mode and a non-resonant mode, with one blade subjected to only the non-resonant mode and another blade to both modes. A life prediction algorithm was utilized to predict HCF propagation lives for each case. The life prediction system incorporates a boundary integral element (BIE) derived hybrid stress intensity solution which accounts for the transition from a surface crack to corner crack to edge crack. It also includes a derivation of threshold crack length from threshold stress intensity factors to give crack size limits for no propagation. The stress intensity solution was calibrated for crack aspect ratios measured directly from the fracture surfaces. The model demonstrates the ability to correlate predicted missions to failure with values deduced from fractographic analysis. This analysis helps to validate the use of fracture mechanics approaches for assessing damage tolerance in gas turbine engine components subjected to combined steady and vibratory stresses.
Wave Cycle Design for Wave Rotor Gas Turbine Engines With Low NOx Emissions
Authors: Nalim M. Razi , Resler Edwin L.
Published: February 2015

The wave rotor is a promising means of pressure-gain for gas turbine engines. This paper examines novel wave rotor topping cycles which incorporate low-NOx combustion strategies. This approach combines two-stage ‘rich-quench-lean’ (RQL) combustion with intermediate expansion in the wave rotor to extract energy and reduce the peak stoichiometric temperature substantially. The thermodynamic cycle is a type of reheat cycle, with the rich-zone air undergoing a high pressure stage. Rich-stage combustion could occur external to or within the wave rotor.

An approximate analytical design method and CFD/combustion codes are used to develop and simulate wave rotor flow cycles. Engine cycles designed with a bypass turbine and external combustion demonstrate a performance enhancement equivalent to a 200–400°R (110–220°K) increase in turbine inlet temperature. The stoichiometric combustion temperature is reduced by 300–450°R (170–250°K) relative to an equivalent simple cycle, implying substantially reduced NOx formation.
Mars™ SoLoNOx Combustion System CFD Modeling
Authors: Thomas Matthew E. , Ostrander Mark J. , Leonard Andy D. , Noble Mel , Etheridge Colin
Published: February 2015

CFD analysis methods were successfully implemented and verified with ongoing industrial gas turbine engine lean premix combustion system development. Selected aspects of diffusion and lean premix combustion modeling, predictions, observations and validated CFD results associated with the Solar Turbines Mars™ SoLoNOx combustor are presented. CO and NOx emission formation modeling details applicable to parametric CFD analysis in an industrial design environment are discussed. This effort culminated in identifying phenomena and methods of potentially further reducing NOx and CO emissions while improving engine operability in the Mars™ SoLoNOx combustion system. A potential explanation for the abrupt rise in CO formation observed in many gas turbine lean premix combustion systems is presented.
ER Fluid Squeeze Film Damper for Semi-Active Vibration Control Device: A Parametric Study
Authors: Morishita Shin , An Young Kong , Mitsui Jun’ichi
Published: February 2015

This paper deals with a successful application of Electro-Rheological (ER) fluid to a squeeze film damper which enables a flexible rotor to reduce whirling amplitude by adjusting the damping property at each rotating speed. An experimental small scale model composed of a flexible shaft and a controllable ER squeeze film damper was constructed and its performance was studied under various electric field strengths. The ER fluid used in the present experiment was a colloidal suspension of silica powder in mineral oil. Furthermore, a theoretical approach to the performance of ER squeeze film damper was made in which the short bearing approximation of a journal bearing with Bingham plastic fluid was introduced. It is shown that the natural frequencies of a flexible shaft was increased continuously as the applied electric field was strengthened in the experiment, which was caused by the mode change due to supporting damping variation, and that the optimum damping for the flexible rotor in each rotating speed can always be applied by changing the applied voltage to the ER fluid squeeze film damper. It is also shown that the simplified theory introduced in this paper shows good agreement with the present experimental results.
Development of a Second Generation Dry Low NOx Combustor for 1.5MW Gas Turbine
Authors: Kitajima J. , Kimura T. , Sasaki T. , Okuto A. , Kajita S. , Ohga S. , Ogata M.
Published: February 2015

Development of a second generation dry low NOx combustor for KHI’s 1.5MW industrial gas turbine M1A-13A is described. A lean pre-mix and multiple burners design was tested on a bench-scale can combustor using methane gas for fuel. Effects of key design variables on combustion characteristics are evaluated. The key design variables include the air flow distribution within the combustor, swirler angle, injector position relative to the swirler, and air/fuel distribution. Emission results obtained by the optimization of these design parameters were NOx < 10 ppm (at 15 % O2), CO < 15 ppm (15% O2), and negligible THC at the rated load in the engine test.
Development of a Test Rig and Experimental Verification of the Performance of HSFDs for Active Control of Rotors
Authors: El-Shafei A. , El-Hakim M.
Published: February 2015

This paper summarizes the experimental development of hybrid squeeze film dampers (HSFDs) for active control of rotor vibrations. In a recent paper (El-Shafei and Hathout, 1994) it was shown that the automatically controlled HSFD can be a very useful device for the active control of rotors. A complete mathematical model of the open-loop system was developed. An on-off control strategy based on speed feedback was proposed and was shown by the simulation results to be quite effective in controlling the rotor vibrations. In this paper, the development of a test rig for the experimental investigation of the HSFD-rotor system is presented. The design of the test rig, the HSFD and the rotor system are discussed. The experimental set-up consists of the rotor-HSFD system controlled through a pressure control servovalve for controlling the pressure in the sealing chambers. The hydraulic circuit is controlled through a digital computer with a data acquisition and control system. The on-off control strategy with feedback on speed is implemented on the computer control system and is shown to be quite effective in controlling the first mode of vibration of the rotor system.
A Comparison of Multivariable Control Design Techniques for a Turbofan Engine Control
Authors: Watts Stephen R. , Garg Sanjay
Published: February 2015

This paper compares two previously published design procedures for two different multivariable control design techniques for application to a linear engine model of a jet engine. The two multivariable control design techniques compared were the Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) and the H–Infinity (H∞) synthesis. The two control design techniques were used with specific previously published design procedures to synthesize controls which would provide equivalent closed loop frequency response for the primary control loops while assuring adequate loop de-coupling. The resulting controllers were then reduced in order to minimize the programming and data storage requirements for a typical implementation. The reduced order linear controllers designed by each method were combined with the linear model of an advanced turbofan engine and the system performance was evaluated for the continuous linear system. Included in the performance analysis are the resulting frequency and transient responses as well as actuator usage and rate capability for each design method. The controls were also analyzed for robustness with respect to structured uncertainties in the unmodeled system dynamics. The two controls were then compared for performance capability and hardware implementation issues.
High Level Heat Recovery in Coal and Coke Gasification Combined Cycle Systems
Authors: Mahagaokar Uday , Doering Egon L.
Published: February 2015

Integrated coal gasification combined cycle systems offer a very efficient and environmentally superior method for converting coal or petroleum coke to electric power. The high efficiency is derived from effective utilization of high level energy in all parts of the IGCC system. Entrained flow gasification represents one of the cleanest and most efficient technologies for converting coal or coke to syngas, and also produces significant quantities of high level sensible heat in the raw syngas exiting the gasifier. This heat can be recovered as high pressure steam through the use of syngas coolers. Alternatively, the syngas cooler capital may be saved by using a water quench at the expense of heat recovery. This paper examines the economic benefits of heat recovery in a syngas cooler relative to water quench by determining the value of the recovered energy versus the cost of recovery. The results show that for power generation in a gasification combined cycle configuration, the cost of syngas cooling is justified by the value of the energy recovered — this applies not only to coal feeds but also to low-priced feeds like petroleum coke.
The Nuclear Gas Turbine: Towards Realization After Half a Century of Evolution
Authors: McDonald Colin F.
Published: February 2015

This paper has been written exactly 50 years after the first disclosure of a closed-cycle gas turbine concept with a simplistic uranium heater. Clearly, this plant was ahead of its time in terms of technology readiness, and the closed-cycle gas turbine was initially deployed in a cogeneration mode burning dirty fuels (e.g., coal, furnace gases). In the 1950s through the mid 1980s about 20 of these plants operated providing electrical power and district heating for European cities. The basic concept of a nuclear gas turbine plant was demonstrated in the USA on a small scale in 1961 with a mobile closed-cycle nitrogen gas turbine [330 KW(e)] coupled with a nuclear reactor. In the last three decades, closed-cycle gas turbine research and development, particularly in the U.S. has focused on space power systems, but today the utility size gas turbine-modular helium reactor (GT-MHR) is on the verge of being realized. The theme of this paper traces the half century of closed-cycle gas turbine evolution, and discusses the recent enabling technologies (e.g., magnetic bearings, compact recuperator) that now make the GT-MHR close to realization.

The author would like to dedicate this paper to the late Professor Curt Keller who in 1935 filed the first closed-cycle gas turbine patent in Switzerland, and who exactly 50 years ago, first described a power plant involving the coupling of a helium gas turbine with a uranium heater.
Numerical Analysis of Fluid Flow in an Internal Turbine Blade Cooling Passage
Authors: Babich Marc L. , Yang Song-Lin , Michalek Donna J. , Arici Oner
Published: February 2015

The need to develop ultra-high efficiency turbines demands the exploration of methods which will improve the thermal efficiency and the specific thrust of the engine. One means of achieving these goals is to increase the turbine inlet temperature. In order to accomplish this, further advances in turbine blade cooling technology will have to be realized. A technique which has only recently been used in the analysis of turbine blade cooling is computational fluid dynamics. The purpose of this paper is to present a numerical study of the flowfield inside of the internal cooling passage of a radial turbine blade. The passage is modeled as two-dimensional and non-rotating. The flowfield solutions are obtained using a pseudo-compressible formulation of the Navier-Stokes equations. The spatial discretization is performed using a symmetric second-order accurate TVD (Total Variational Diminishing) scheme. Calculations are performed on a multi-block-structured grid. Turbulence is modeled using a modified κ-ω model. In the absence of experimental data, results appear to be realistic based on common experiences with fluid mechanics.
Development of Advanced Thermal Barrier Coatings for Severe Environments
Authors: Nelson Warren A. , Orenstein Robert M. , DiMascio Paul S. , Johnson Curtis A.
Published: February 2015

Air plasma sprayed yttria-stabilized zirconia thermal barrier coatings (TBCs) have been successfully used to extend life of superalloy components in utility gas turbines. GE Power Generation has over ten years of field experience with TBCs on combustor hardware, and over 20,000 hours of field experience with TBCs on turbine nozzles. Despite this promising experience, the full advantage of TBCs can be achieved only when the reliability of the coating approaches that of the superalloy component substrate. Recent work at GE has emphasized characterization of mechanical properties and physical attributes of TBCs to understand better the causes of delamination crack growth and coating spallation. In addition, unique tests to examine the TBC response under conditions simulating severe gas turbine service environments have been developed. Through evaluation of the results from comparative TBC ranking tests, pre-production application experience and field test results, gas turbine design engineers and materials process engineers are rapidly gaining the practical knowledge needed to integrate the TBC into the component design.
Transition Control and Performance of the Selective Bleed Variable Cycle Turbofan
Authors: Ulizar Inaki , Pilidis Pericles
Published: February 2015

The selective bleed turbofan is a two shaft, three compressor, variable cycle aircraft engine. At subsonic flight speeds it operates as a medium bypass turbofan. It becomes a low bypass turbofan when flying faster and is capable of supersonic cruise in the dry mode.

The aim of this paper is to outline the requirements and response of the engine during the transition phase from one mode of operation to the other. Thus it is follow-on work of Ref. 7. To achieve this several control devices can be employed. These are the fuel flow, the variable compressor stators, the nozzle areas and the valve areas of the bypass ducts.

The preliminary analysis described in this paper indicates that all the criteria of performance are satisfied and that the transition can be carried out successfully provided the control variables are co-ordinated properly.
Multistage Turbine Simulations With Vortex-Blade Interaction
Authors: Turner Mark G.
Published: February 2015

The average passage approach of Adamczyk et al (1990) has been used to simulate the multistage environment of the General Electric E3 low pressure turbine. Four configurations have been analyzed and compared to test data. These include the nozzle only, the first stage, the first stage and a half and the first two stages. A high casing slope on the first stage nozzle causes the secondary flow vortex to separate off the casing and enter the downstream rotor. The detrimental effect on performance due to this vortex interaction has been predicted by the above approach whereas isolated blade row calculations cannot simulate this interaction. The unsteady analysis developed by Chen et al (1994) has also been run to understand the unsteady flow field in the first stage rotor and compare with the average passage model and test data. Comparisons of both the steady and unsteady analyses with data are generally good, although in the region near the casing of the shrouded rotors, the predicted loss is lower than that shown by the data.
Laser Velocimeter Measurements in the Turbine of an Automotive Torque Converter: Part I — Average Measurements
Authors: Bran Klaus , Flack Ronald D.
Published: February 2015

The three-dimensional average velocity field in an automotive torque converter turbine was examined. Two significantly different operating conditions of the torque converter were tested: the 0.065 and 0.800 turbine/pump speed ratio. Velocities were measured using a one-directional, frequency shifted laser velocimeter. The instantaneous angular positions of the torque converter turbine and pump were recorded using digital shaft encoders. Shaft encoder information and velocities were correlated to generate average velocity blade-to-blade profiles and velocity vector plots. Measurements were taken in the inlet, quarter, mid, and exit planes of the turbine. From the experimental velocity measurements, mass flows, turbine output torque, average vorticities, viscous dissipation, inlet incidence flow angles, and exit flow angles were calculated. Average mass flows were 23.4 kg/s and 14.7 kg/s for the 0.065 and 0.800 speed ratios, respectively. Velocity vector plots for both turbine/pump speed ratios showed the flow field in the turbine quarter and mid planes to be highly non-uniform with separation regions and reversed flows at the core-suction corner. For the conditions tested, the turbine inlet flow was seen to have a high relative incidence angle, while the relative turbine exit flow angle was close to the blade angle.
Laser Velocimeter Measurements in the Turbine of an Automotive Torque Converter: Part II — Unsteady Measurements
Authors: Bran Klaus , Flack Ronald D.
Published: February 2015

The unsteady velocity field found in the turbine of an automotive torque converter was measured using laser velocimetry. Velocities in the inlet, quarter, mid, and exit planes of the turbine were investigated at two significantly different operating conditions: turbine/pump rotational speed ratios of 0.065, and 0.800. A data organization method was developed to visualize the three-dimensional, periodic unsteady velocity field in the rotating frame. For this method, the acquired data is assumed to be periodic at synchronous and blade interaction frequencies. Two shaft encoders were employed to obtain the instantaneous angular position of the torque converter pump and turbine at the instant of laser velocimeter data acquisition. By proper “registration” of the velocity data, visualizing the transient interaction effects between the turbine, pump, and stator was possible. Results showed strong cyclic velocity fluctuations in the turbine inlet plane as a function of the relative turbine-pump position. These fluctuations are due to the passing of upstream pump blades by the slower rotating turbine blades. Typical fluctuations in the through flow velocity were 3.6 m/s. Quarter and mid plane velocity fluctuations were seen to be lower; typical values were 1.5 m/s and 0.8 m/s, respectively. The flow field in the turbine exit plane was seen to be relatively steady with negligible fluctuations of less than 0.03 m/s. From the velocity data, the fluctuations of turbine performance parameters such as flow inlet angles, root-mean-square unsteadiness, and output torque per blade passage were calculated. Incidence angles were seen to vary by 3° and 6° for the 0.800 and 0.065 speed ratios, respectively, while the exit angles remained steady. The turbine output torque per blade passage fluctuated by 0.05 Nm for the 0.800 speed ratio and 0.13 Nm for the 0.065 speed ratio.
Transition Over C4 Leading Edge and Measurement of Intermittency Factor Using PDF of Hot-Wire Signal
Authors: Hazarika Birinchi K. , Hirsch Charles
Published: February 2015

The variation of intermittency factors in the transition region of a C4 leading edge flat plate is measured at three incidence angles in a low turbulence free-stream. During the determination of intermittency factor the threshold value of the detector function and the validity of conditional averaging are verified by a method based on the direct application of PDF of the hot-wire output. As the angle of incidence is increased, the transition progressively moves through all the three modes on the suction surface : at zero incidence the bypass transition, at 2° incidence the natural transition and at 4° incidence the separated-flow transition occur respectively. All the three modes of transition exhibited the chord-wise intermittency factor variation in accordance with Narasimha’s universal intermittency distribution, thus the method based on spot production rate is applicable to all the three modes of transition. In the transition zone of the attached boundary layers, the conditionally averaged inter-turbulent profiles are fuller than the Blasius profile while the conditionally averaged turbulent profiles follow a logarithmic profile with a variable additive parameter.