bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Considerations for Naphtha Fuel Systems in Combustion Turbines
Authors: Brushwood John , McElwee Timothy
Published: December 2014

Naphtha fuel for combustion turbines possesses some unique physical properties that must be considered in the design of the fuel delivery system for trouble free operation. The fuel system must be designed to start the turbine on natural gas; distillate or naphtha, transfer to the secondary fuel and back to the original fuel; over a defined load range. The timing and permissives required for these events to occur smoothly, without tripping the unit, demand full control over the flow, temperature and pressure of all fuels involved. The same delivery system is often used to deliver other fuels that differ in density, volatility, vapor pressure and flow, compounding the design process. This paper examines some of the design attributes employed in Westinghouse combustion turbines that are fueled by naphtha and natural gas. The design considerations and modifications to the conventional fuel delivery system are the subjects of this paper.
Development of an LCV Fuel Gas Combustor for an Industrial Gas Turbine
Authors: Constant Douglas R. , Bevan D. Mark , Cannon Michael F. , Kelsall Gregory J.
Published: December 2014

Advanced coal based power generation systems, such as the Air Blown Gasification Cycle (ABGC), offer the potential for high efficiency, electricity generation with minimum environmental impact. An important component of the ABGC development is the gas turbine combustion system. It must bum low calorific value (LCV) coal derived fuel gas, at high turbine inlet temperatures with minimum pollutant emissions. A phased development programme has been completed burning LCV fuel gas (3.6–4.1 MJ/m3) with low emissions, particularly NOx derived from fuel bound nitrogen. Performance tests were carried out on a generic tubo-annular, prototype combustor, at Mach numbers generally lower than those typical to engine applications, with encouraging results. Five design variants, operating at conditions selected to represent a particular medium sized industrial gas turbine each returned an improvement in combustor performance. A further five variants were investigated to establish which design characteristics and operating parameters most affected NOx emissions.
Intercooled Advanced Gas Turbines in Coal Gasification Plants, With Combined or “HAT” Power Cycle
Authors: Chiesa Paolo , Lozza Giovanni
Published: December 2014

Due to their high efficiency and flexibility, aeroderivative gas turbines were often considered as a development basis for intercooled engines, thus providing better efficiency and larger power output. Those machines, originally studied for natural gas, are here considered as the power section of gasification plants for coal and heavy fuels. This paper investigates the matching between intercooled gas turbine, in complex cycle configurations including combined and HAT cycles, and coal gasification processes based on entrained-bed gasifiers, with syngas cooling accomplished by steam production or by full water-quench. In this frame, a good level of integration can be found (i.e. re-use of intercooler heat, availability of cool, pressurized air for feeding air separation units, etc.) to enhance overall conversion efficiency and to reduce capital cast. Thermodynamic aspects of the proposed systems are investigated, to provide an efficiency assessment, in comparison with mare conventional IGCC plants based on heavy-duty gas turbines. The results outline that elevated conversion efficiencies can be achieved by moderate-size intercooled gas turbines in combined cycle, while the HAT configuration presents critical development problems. On the basis of a preliminary cost assessment, cost of electricity produced is lower than the one obtained by heavy-duty machines of comparable size.
Creating Global Mechanical Engineers Through New Education-Industry Partnerships
Authors: Lloyd John R. , Rosenberg Ronald C.
Published: December 2014

A new language-based global undergraduate mechanical engineering education program is being developed to produce “globally educated” mechanical engineers ready for practice in the 21st century. The Global Education Program is accomplished through partnerships established with middle and high schools, companies, a network of international engineering schools and Michigan State University. Typically the incoming students have studied French, Spanish, or German, but we also find students in increasing numbers who have had Japanese and Chinese. The MSU Mechanical Engineering Global Education Program begins by partnering with key middle and high schools for recruiting of top quality, properly prepared students. At Michigan State University during the first two years they complete their language preparation and their cultural awareness preparation. In the third year the students study and co-op abroad. In the fourth year the students serve as mentors to underclass students in the program. Industrial partners participate by sponsoring students, recommending international academic partners, helping in the development of curriculum, and by providing co-op opportunities. This partnership for education program has the long term goal of involving 50% of the MSU Mechanical Engineering BS graduates in a global education experience.
Some Applications of the Monte Carlo Method to Gas Turbine Performance Simulations
Authors: Kurzke Joachim
Published: December 2014

The instrumentation readings taken during engine performance tests will show a random scatter that can be simulated with the Monte Carlo method. From such an exercise one can get the standard deviation of quantities that are derived from the pressure and temperature measurements like low pressure turbine efficiency of a high bypass engine, for example.

With the Monte Carlo Method a batch of engines can be simulated that have randomly distributed properties. Engine manufacturing tolerance in terms of thrust and specific fuel consumption can be derived from component production tolerance (efficiency, flow capacity) and internal air system variations. The Monte Carlo method is especially well suited for this task when complex interactions with the control system must be taken into account.

The Monte Carlo method can also be used to evaluate the confidence with which an overall engine performance level will be achieved from statements of component designers about the probability of achieving their design targets.

Tasks as described above can also be solved analytically, However, the Monte Carlo method is easier to use and also much less prone to error during its application.
Experimental Studies on Unsteady Aerodynamic Loss of a High-Pressure Turbine Cascade
Authors: Funazaki Ken-ichi , Sasaki Yoshinori , Tanuma Tadashi
Published: December 2014

The objective of this study is to investigate how the wake passage impacts the aerodynamic performance of turbine rotor blades in turbomachines. Despite a number of research activities, information on aerodynamic loss generation in turbine rotors under the influence of unsteady flows encountered in actual turbomachines is still limited. This paper describes our newly started research project which aims to gain insight into the physics of the aerodynamic interaction between turbine rotors and incoming periodic wakes, and to establish a method for evaluation of unsteady aerodynamic losses of turbine rotors generated by the wakes. In this study, using a linear turbine cascade and a wake generator, the wake-affected flow field upstream and downstream of the cascade is measured in detail with a five-hole pneumatic pressure tube and a hot-wire probe in order to obtain time-averaged as well as time-resolved characteristics of the flow field. It is accordingly found that the wake passing affects the flow field around the turbine cascade, which yields considerable change in the two-dimensional cascade loss as well as in the secondary vortex structure. Moreover, it is also revealed that a so-called negative jet effect associated with the wakes plays an important role in unsteady loss generation of the turbine cascade, which is in contradiction to the findings by Hodson and Dawes (1996).
Characteristics of a Turbine Cascade at Low Reynolds Numbers
Authors: Murata Koji , Abe Hiroyuki , Tsutsui Yasukata
Published: December 2014

The aerodynamic characteristics of turbine cascades are thought to be relatively satisfactory due to the favorable pressure of the accelerating flow. But within the low Reynolds number region of 50,000 where the 300kW ceramic gas turbines which are being developed under the New-Sunshine Project of Japan operate, the characteristics such as boundary layer separation and reattachment which lead to prominent power losses cannot be easily predicted.

In this research, experiments have been conducted to evaluate the performance of a linear two dimensional turbine cascade. Surface pressure distributions of the airfoil were measured for a range of blade chord Reynolds numbers from 40,000 to 160,000 (at inlet), and at 1.3% inlet turbulence intensity. In addition, the wake of the cascade was measured simultaneously using a five hole pilot tube. Traverses of the wake show that there is a drastic increase in the mean total pressure loss at the wake between the Reynolds number of 80,000 to 40,000, and in some conditions, a rise as much as 10% was confirmed. Thus, in accordance with the pressure distribution of the surface of the airfoil, a relation between the total pressure loss and the length of the laminar separation bubble formed on the airfoil could be seen.
Off-Design Flow Analysis and Performance Prediction of Axial Turbines
Authors: Petrovic Milan V. , Riess Walter
Published: December 2014

Through-flow methods for calculations in axial flow turbines are limited by two facts: they cannot handle local flow reversal, and loss prediction at off-design operating conditions is not sufficiently accurate. An attempt to overcome these limitations is presented in this paper. The developed calculation method is based on the through-flow theory and the finite element solution procedure, but it also includes extensions and improvements. Consequently, the method may be used to predict the flow field and the turbine performance at the design load as well as for wide range of part loads. The code is able to calculate flow in axial turbines at subsonic and transonic conditions. The reliability of the method is verified by calculations for several gas and steam turbines. Results of flow calculation and performance prediction of 4-stage experimental air turbine and LP steam turbine are also presented herein. Low load operation with flow reversal in the hub region behind the last rotor blade row and loads, at which part of blading operates with power consumption, are especially analyzed. All numerical results are compared to the results of extensive experimental investigations. The correspondence, even for low loads, is very good.
Single-Digit Emissions in a Full Scale Catalytic Combustor
Authors: Schlatter James C. , Dalla Betta Ralph A. , Nickolas Sarento G. , Cutrone Martin B. , Beebe Kenneth W. , Tsuchiya Toshiaki
Published: December 2014

Catalytic combustion offers the possibility of attaining the firing temperatures of current and next generation gas turbines [up to ∼1450°C (2640°F)] with nitrogen oxides (NOx) production as low as 1 part per million by volume (ppmv). Such catalytic combustion technology has been under development at Catalytica for several years, and the first full scale test of the technology took place at the General Electric Company under TEPCO sponsorship in 1992. The results of the most recent and most successful full scale test in this program are reported in this paper.

The catalytic combustor system was designed for the GE Model MS9001E gas turbine fired with natural gas fuel. The 508-mm (20-in) diameter catalytic reactor was operated at conditions representative of the startup and load cycle of that machine. It was verified that the observed NOx levels were produced not in the catalyst, but in the diffusinn flame of the preburner used to start the system and maintain the necessary catalyst inlet temperature. Even so, NOx levels below 5 ppmv (at 15% O2) were achieved at the simulated base load operating point. Carbon monoxide (CO) and unburned hydrocarbons (UHC) emissions were likewise below 10 ppmv at that condition. Single digit emissions levels also were recorded at conditions representative of the combustor operating at 78% load, the first such demonstration of the turndown capability of this system. Throughout the test, dynamic pressure measurements showed the catalytic combustor to be quieter than even the diffusion flame combustors currently in commercial service.
An Introduction to Harmonic Wavelet Analysis of Machine Vibrations
Authors: Bonel-Cerdan Jose I. , Nikolajsen Jorgen L.
Published: December 2014

The Fast Wavelet Transform (FWT) is a powerful new tool which can be used for vibration analysis and condition monitoring of advanced rotating machinery. The main advantage of wavelet analysis for condition monitoring is that so-called wavelet maps can be produced showing three dimensional plots of amplitude versus frequency and time. This is in contrast to Fast Fourier Transform (FFT) analysis, in which the time domain of the signal is lost. The wavelet maps provide striking visual indications of tiny changes in machine behaviour which cannot be detected in a normal frequency spectrum. This improves the chances of averting catastrophic failures and expands the time window available to take corrective action. Additional advantages of wavelet analysis over FFT analysis include: (1) no requirements for periodicity of the signal, (2) extremely fast computation, (3) the location of patterns in the time domain and (4) an effective detection of high frequency details.

Wavelet analyses of all types are available but user-friendly information is hard to come by and this has a detrimental effect on progress towards practical commercial applications. Thus, the main purpose of this paper is to provide a simple and clear introduction to wavelet analysis and its use in machine condition monitoring. The paper has been written for an audience having some familiarity with spectrum analysis but no prior knowledge of wavelets.
Field-Experience on DLN Typhoon Industrial Gas Turbine
Authors: Scholz Marcus H. H. , DePietro Simon M.
Published: December 2014

The second Generation of EGT’s G30 DLE combustion system was introduced after a successful series of high pressure rig and engine tests. This paper covers how operational problems with field commissioning hardware on the lead DLN machine were dealt with, leading to achievement of reliable low NOx hardware. Several changes were applied to the early design which improved the mixing and reduced the effects of high temperature distortion and combustor dynamics. This resulted in increased life of the burner and changed the characteristics of dynamics. It also led to very low emission levels with an outstanding capability for turndown of CO with NOx below 25 ppmvd (15% O2) over the whole load range. Further coverage is given to the effect of field tuning, and of fuel composition on the amplitudes and frequencies of dynamics. The installation has been supported by on-line condition monitoring of engine parameters, emission levels and ambient conditions, which are also discussed. The general overview of site history is followed by a summary of lessons learnt in field comparison to development test bed.
Effective Automatic Expert Systems for Dynamic Predictive Maintenance Applications
Authors: Flanagan Michael A. , Andersson Carsten , Surland Peter
Published: December 2014

As the need for specialist decision-making has increased with the volume of data produced by modern monitoring systems, and the current trend towards downsizing and external sourcing (for example, specialist consultant companies) has continued, the demand for computer-based expert systems for automatic machine condition (vibration and process) analysis and diagnosis has intensified.

Various levels of success have been achieved, but most expert systems available today do not reflect the actual reasoning process of a human expert; are inherently obsolete for the continuous learning capability required for dynamic applications; and/or require considerable skills in computer simulation or statistical methods to update the system.

In this paper, new techniques and tools are presented that address the basic elements in the reasoning process of a human expert, and offer solutions to the practical implementation of effective and reliable automatic machine diagnosis. Essential tools for optimum automatic spectrum analysis are first introduced, and then a method presented that allows system results to be automatically qualified and improved upon to reflect actual machine conditions. The paper then introduces neural-network technology as a means of implementing a workable, user-defined knowledge base that can be used to augment the expert system with the user’s own knowledge and experience, and the idiosyncrasies of individual machines.
The International Engineering Student Exchange Program at the University of Waterloo
Authors: Howard Joseph H. G. , Ratz Herbert C.
Published: December 2014

The importance of international engineering student exchange programs in today’s increasingly global marketplace is well accepted. This report describes aspects of the experience of the University of Waterloo with such a program which involves 26 institutions in 14 countries. A major element in a successful link is close collaboration between faculty coordinators at the two institutions.
Development and Fabrication of Silicon Nitride Components for Ceramic Gas Turbine
Authors: Makino Keisuke , Mizuno Ken-Ichi , Shimamori Toru
Published: December 2014

NGK Spark Plug Co., Ltd. has been developing various silicon nitride materials, and the technology for fabricating components for ceramic gas turbines (CGT) using theses materials. We are supplying silicon nitride material components for the project to develop 300 kW class CGT for co-generation in Japan. EC-152 was developed for components that require high strength at high temperature, such as turbine blades and turbine nozzles.

In order to adapt the increasing of the turbine inlet temperature (TIT) up to 1,350 °C in accordance with the project goals, we developed two silicon nitride materials with further unproved properties: ST-1 and ST-2. ST-1 has a higher strength than EC-152 and is suitable for first stage turbine blades and power turbine blades. ST-2 has higher oxidation resistance than EC-152 and is suitable for power turbine nozzles.

In this paper, we report on the properties of these materials, and present the results of evaluations of these materials when they are actually used for CGT components such as first stage turbine blades and power turbine nozzles.
Numerical Analysis of Transonic Compressor Rotor Flow Near Stall Points
Authors: Masaki Daisaku , Kaji Shojiro
Published: December 2014

A three-dimensional Navier-Stokes solver based upon a high resolution shock-capturing scheme has been developed in order to analyze complex flow phenomena inside transonic fan/compressor rotors, especially tip clearance flow. The aim of this research is to find out a key element concerned with aerodynamic instability of transonic fan/compressor rotors such as rotating stall and surge by using this newly developed numerical tool. The numerical analysis of this research is twofold. First it investigates the flowfield of a transonic compressor rotor along the design speed operating line. It obtains definite flow structures around the tip region and clear description of the transition of the flow pattern inside the clearance gap between operating points, which shows that shock-tip leakage vortex interaction plays an important role on both loss generation and the failure of steady flow, or surge. A model will be proposed on the onset of tip stall in transonic compressor rotors according to the calculated results.

Secondly, the above model will be examined through a series of numerical experiments by altering tip clearance height white keeping the design speed. From qualitative point of view, the model works fairly well and seems geometry-independent for typical transonic fan/compressor rotors. A clue to the optimum clearance is also obtained.
Quantifying Unmixedness in Lean Premixed Combustors Operating at High Pressure, Fired Conditions
Authors: Barnes J. C. , Mellor A. M.
Published: December 2014

Lean premixed combustor manufacturers require premixer concepts that provide homogeneity (mixedness) of the fuel which burns in the main flame. Ideally premixer evaluation would be conducted under realistic combustor operating conditions. However, current techniques typically are limited to cold—flow, low pressure (<14 atm) conditions or comparison of measured NOx emissions with others obtained in premixed systems. Thus, a simple, consistent method for quantifying unmixedness in lean premixed combustors operating at high pressure, fired operating conditions is proposed here, using the characteristic time model developed in the companion paper.
Simple Analytical Techniques to Determine the Disperant Capacity and Metal Deactivator Additive Concentration of JP-8+100 and Other Jet Fuels
Authors: Kauffman Robert E.
Published: December 2014

The US Air Force is developing an additive package to improve the thermal stability of JP-8 fuels by 100°F. Consequently, JP-8 fuels containing the developed additive package are referred to as JP-8+100 fuels. Field tests of the JP-8+100 fuels have shown that the additive package greatly reduces maintenance cost and labor in comparison to JP-8 fuels by minimizing fuel system malfunctions caused by fuel deposition, e.g., fuel control changeouts, combustor damage, etc. The developed additive package contains three components: antioxidant, dispersant/detergent, and metal deactivator.

This paper presents simple analytical techniques that can be performed on-site or in the laboratory to determine the dispersant capacity and metal deactivator additive concentrations of JP-8+100 fuels. Since several dispersant/detergent candidates are being evaluated for use in the JP-8+100 additive package, the analytical techniques were developed to measure the dispersant capacity of the additive package instead of the concentration of one particular dispersant/detergent. The dispersant capacity test measures the ability of a fuel sample to suspend a metal oxide powder/water/isopropanol mixture. The dispersant capacity test can be used to identify jet fuels which contain the JP-8+100 additive package and to rate the dispersant capacity of a JP-8+100 fuel.

In contrast to the dispersant capacity test, the metal deactivator additive (MDA) tests were designed to determine the concentration of N,N′-disalicylidene-1,2-propanediamine which is the primary MDA used in jet fuels. The MDA tests use fuel soluble compounds or aqueous extraction to chemically react MDA to form colored species. The color of the MDA compound is measured visually for qualitative determinations or spectrometrically for quantitative determinations. Combination of the different MDA tests allows MDA to be detected down to 0.1 ppm regardless of fuel color, age, or type.
An Overall Correlation of Film Cooling Effectiveness From One Row of Holes
Authors: Baldauf S. , Schulz A. , Wittig S. , Scheurlen Michael
Published: December 2014

Film cooling effectiveness of a single row of cylindrical holes on a flat plate was analyzed. It was found, that the flow can be divided into two typical regimes along the downstream distance. Near the ejection location a complex flow domain of cooling film formation with strong 3-D character was recognized. Further downstream a domain of a diluting cooling film with 2-D character was identified. An analytical solution for the film cooling effectiveness along the downstream distance was derived in the 2-D regime. Based on literature data, correlations for the formation length, i.e. the length of the 3-D domain, and the corresponding film cooling effectiveness at the start of the 2-D film were developed. These correlations provide the initial conditions of the analytical solution of the 2-D film flow. A damping function was introduced to connect the two regimes and to model the lateral averaged film cooling effectiveness distribution within the 3-D flow domain. From this, a correlation was established, taking into account the full set of parameters, which was presented in an earlier study [1]. The correlation was tested over a wide range of parameters, and an error estimation is given to demonstrate the quality of the correlation.
The Influence of Downstream Passage on the Flow Within an Annular S-Shaped Duct
Authors: Sonoda Toyotaka , Arima Toshiyuki , Oana Mineyasu
Published: December 2014

Experimental and numerical investigations were carried out to gain a better understanding or the flow characteristics within an annular S-shaped duct, including the influence of the shape of the downstream passage located at the exit of the duct on the flow. A duct with six struts and the same geometry as that used to connect the compressor spools on our new experimental small two-spool turbofan engine was investigated. Two types of downstream passage were used. One type had a straight annular passage and the other a curved annular passage with a similar meridional flow path geometry to that of the centrifugal compressor.

Results showed that the total pressure loss near the hub is large due to instability of the flow, as compared with that near the casing. Also, a vortex related to the horseshoe vortex was observed near the casing, in the case of the curved annular passage, the total pressure loss near the hub was greatly increased compared with the case of the straight annular passage, and the spatial position of the above vortex depends on the passage core pressure gradient. Furthermore, results of calculation using an in-house-developed three-dimensional Navier-Stokes code with a low Reynolds number k-ε turbulence model were in good qualitative agreement with experimental results. According to the simulation results, a region of very high pressure loss is observed near the hub at the duct exit with the increase of inlet boundary layer thickness. Such regions of high pressure loss may act on the downstream compressor as a large inlet distortion, and strongly affect downstream compressor performance.
Energy Input of a Centrifugal Stage Into the Attached Piping System During Mild Surge
Authors: Ribi Beat , Gyarmathy George
Published: December 2014

Subjected to an oscillating flow rate a compressor may feed additional (excitational) energy into the attached piping system. The relation between this additional energy input and the instantaneous behavior of a centrifugal compressor stage is dealt in a first part. Modeling the stage behavior by taking into account either inertia of the enclosed fluid mass or a first-order transient element or transient stall in any component leads to a different energy input.

The energy input at a flow rate oscillation of given frequency and amplitude was calculated as a function of the slope of the characteristic and the reduced frequency applying a previously published model to describe the instantaneous behavior of the stage. In this model transient stall in the diffuser is taken into account. At reduced frequencies above unity the energy input of the diffuser was reduced by a considerable amount due to the specified instantaneous behavior of the diffuser. This indicates a potential to reduce the additional energy input of the diffuser either by increasing the time constant of the stall process or by increasing the mild surge frequency. For the investigated diffuser size the required reduced frequencies imply mild surge frequencies in a range being too high for industrial application (> 200 Hz). Still, this method turned out to give useful insight into the link between the instantaneous behavior of the compressor and its energy input.

In a second part for the same centrifugal compressor the energy contribution of several stage segments during mild surge oscillations was determined from detailed instantaneous measurements. As a result the contribution of each stage segment to the conservation of the mild surge pulsation emerges. Although at the investigated mild surge frequencies the stage segments no longer behave strictly quasi-steadily their contribution to the additional energy input is found to be mainly determined by the slope of their quasi-steady characteristic.
Progress on the Hybrid Vehicle Turbine Engine Technology Support (HVTE-TS) Program
Authors: Sinnet George T. , French J. Mark , Groseclose Lance E.
Published: December 2014

The purpose of the HVTE-TS program is to develop gas turbine engine technology in support of U.S. Department of Energy/automotive industry programs exploring the use of gas turbine generator sets in hybrid-electric automotive propulsion systems.

The primary objective is the development of four key technologies to be applied to advanced turbogenerators for hybrid vehicles:

• structural ceramic materials and processes

• low emissions combustion systems

• regenerators and seal systems

• insulation systems and processes.

The HVTE-TS program builds upon the significant technology base already established by the previous DoE/NASA Advanced Turbine Technology Applications Project (ATTAP).

HVTE-TS activities during 1996 included: ceramic component design, materials and component characterization, ceramic component process development and fabrication, ceramic component rig testing, and test-bed engine installation and setup. Progress has also been made in the durability testing of various regenerator materials and components, as well as in the application of unique insulation systems. This paper highlights recent progress and current status of each of the four key technologies described above.
Numerical Prediction of Trailing Edge Wake Shedding
Authors: Arnone Andrea , Pacciani Roberto
Published: December 2014

A recently developed, time-accurate multigrid solver has been used to investigate the capability of predicting trailing edge vortex shedding by means of the Reynolds-Averaged Navier-Stokes equations and algebraic turbulence models. The study has been performed on a turbine stator blade for which experiments have recently been carried out. Calculations using a mixing-length based model for turbulence closure indicate the inception of shedding even on relatively coarse trailing edge (C-type) grids.
Numerical Simulation of the Flow Through the Rotor of a Radial Inflow Turbine
Authors: Amedick V. , Simon H.
Published: December 2014

An existing Navier-Stokes solver to simulate the turbulent transonic flow using block-structured grids has been used to optimize the guide vanes of radial inflow turbines. The code has been extended to calculate the flow in the rotating parts of turbomachines and is now used to simulate the turbulent flow through the rotor of a radial inflow turbine.

The results of three calculations are presented (inviscid and viscous flow without tip clearance, viscous flow with tip clearance). The flowfield is investigated at design conditions where a large incidence angle exists at the entrance of the rotor. Unsteady effects are neglected.

The comparison of the results of the inviscid and viscous simulations shows the strong influence of the viscous forces. Strong secondary flow patterns are found in the vicinity of the blades and the walls. Special attention has been paid to the analysis of the flow through the gap between the casing and the blades. The determination of the mass flow rate through the gap shows that mass is transported from the suction towards the pressure side of the blade at the beginning of the blade (6.1% of the blade length). Thereafter, the mass flow through the gap changes its direction.
Automatic Mesh Generation by a Mixed Advancing-Front Delaunay Approach
Authors: Corral Roque , Barroso Juan Manuel , Burgos Manuel Antonio
Published: December 2014

A simple, three-dimensional, unstructured grid generation system is discussed and relevant results for turbomachinery and exhaust systems applications are presented. The method makes special emphasis in algorithm selection based in a small development effort to grid quality ratio. Engineering decisions based on state of the art grid technology knowledge have been adopted to balance fast development progress and turnover time.

The system is based in the sequential execution of Advancing Front and a Delaunay algorithms to produced solution adapted meshes. In a first step a coarse background grid is created by the Advancing-Front method. During this phase boundaries are strictly preserved due to the nature of the approach. At this stage a Delaunay algorithm is employed and the boundary faces are blocked so that they cannot be destroyed in further triangulations. Since both techniques collaborate in the solution of the problem it is possible to write simplified versions of the algorithms that retain nearly all the benefits and eliminate most of the troubles while keeping still reasonable performances.
Origins of Loss Within a Multistage Turbine Environment Under Conditions of Partial Admission
Authors: Wakeley Guy R. , Potts Ian
Published: December 2014

A partially admitted first stage is routinely used in a wide variety of turbo-machines to match the turbine swallowing capacity to the cycle pressure ratio over a range of outputs. Such a configuration is often favoured for applications in which optimised part-load efficiency is a design requirement. Partial admission is achieved by dividing the stator row into discrete arcs, each of which can be separately supplied with fluid. This arrangement creates circumferential discontinuities and considerable unsteadiness in the flow field within the intra-stage gap, and this unsteadiness can propagate through several downstream rows of fully admitted blading.

In the current work an unsteady, multi-stage, multi-passage, Navier-Stokes solver has been validated against experimental results from a multistage axial flow air turbine. Interstage traverses of static and total pressure are shown to agree well with the CFD predictions, and the measured and predicted partial admission loss is compared with published correlations. It is further shown that the operating point of downstream stages is influenced by the degree of partial admission in the first stage. Additionally, increased alternating blade bending stresses are predicted. These phenomena are not included in any published turbine design methods, and are discussed within the context of large output steam turbine optimisation.
Systematic Study on the Fluid Dynamical Behaviour of Streamwise and Laterally Inclined Jets in Crossflow
Authors: Baier R.-D. , Koschel W. , Broichhausen K.-D. , Fritsch G.
Published: December 2014

The design of discrete film cooling holes for gas turbine airfoil applications is governed by a number of parameters influencing both their aerodynamic and thermal behaviour. This numerical and experimental study focuses on the marked differences between film cooling holes with combined streamwise and lateral inclination and film cooling holes with streamwise inclination only. The variation in the blowing angle was chosen on a newly defined and physically motivated basis. High resolution low speed experiments on a large scale turbine airfoil gave insights particularly into the intensified mixing process with lateral ejection. The extensive computational study is performed with the aid of a 3D block-structured Navier-Stokes solver incorporating a low-Reynolds-number k-ε turbulence model. Special attention is paid to mesh generation as a precondition for accurate high-resolution results. The downstream temperature fields of the jets show reduced spanwise variations with increasing lateral blowing angle; these variations are quantified for a comprehensive variety of configurations in terms of adiabatic film cooling effectiveness.
A Fast Method for the Prediction of Dynamic Stall Onset on Turbomachinery Blades
Authors: Jones K. D. , Platzer M. F.
Published: December 2014

A computational approach is described for the rapid and systematic prediction and evaluation of the onset of dynamic stall due to rapid incidence changes or unsteady pitch or plunge motions. The method combines an unsteady, two-dimensional panel code with a two-dimensional boundary layer code. The panel code provides incompressible, inviscid flowfields about arbitrary airfoils undergoing prescribed motions. The boundary layer code computes laminar, transitional and turbulent regimes, with transition onset predicted by Michel’s criterion. Presented results demonstrate that the delay in dynamic stall onset is directly related to the dynamic pressure lag, in agreement with previous Navier-Stokes simulations, but in apparent disagreement with several aspects of the ‘moving wall’ analogy suggested in the past as an explanation for delayed dynamic stall onset.
Casing Distortion Control Using Pseudo Flanges
Authors: Eastman John A.
Published: December 2014

Axial ribs have been added to gas turbine stationary casings to reduce casing ovalization and allow tighter blade tip clearances to be maintained. Test experience showing blade rub patterns on stator casings due to casing ovalization is presented. Classical solution techniques are presented which demonstrate trends and the relative roundness and attenuation benefits of adding the axial ribs which increase the order of the casing response. The results of finite element studies using 2D solid modeling techniques are compared to the classical solutions. Examples of applications on industrial gas turbine hardware are presented.
Touchdown Bearing Development for a Magnetic Bearing System Used in a High Temperature Gas Turbine
Authors: Marchand Francis P.
Published: December 2014

This papers describes the design and development of a touchdown bearing system. The touchdown bearing is one of the important elements in any high speed magnetic bearing system. The touchdown bearing functions to fully off-load or load share with the magnetic bearing and prevent catastrophic system failures. The proper design of this component is a critical step in the design of the total system and was not treated as a stand-alone sub-component. The impact loads which these bearings have to endure is a challenge to the designer. The high temperature environment on this bearing adds additional constraints to the design options which the designer has to work with. A design was produced, which will function under these conditions. The use of silicon nitride balls with sliver coated CPM Rex 20 races will be described. The bearing is mounted on a replaceable journal, which in turn is mounted on the magnetic bearing. Design and test data for use of these bearing materials in a high temperature gas turbine application is included in this paper.
A Magnetic Bearing Suspension System for High Temperature Gas Turbine Applications: Part III — Magnetic Actuator Development
Authors: Kelleher William P. , Kondoleon Anthony S.
Published: December 2014

Magnetic bearings, unlike traditional mechanical bearings, consist of a series of components when mated together, form a stabilized system. A series of four papers will summaries the results carried out at Draper in the development of a high temperature magnetic bearing suspension system for a gas turbine application. Part I [1] will document our approach for rotordynamics modeling of the turbine shaft and the development of models for use in our simulation programs. Part II [2] documents the simulation efforts and the control system which resulted from this effort. Parts III and IV [3] document the design and fabrication of the magnetic bearing actuators and the auxiliary touchdown bearings.

This paper, part III, deals with the design of the high temperature magnetic bearing actuators. Two radial and one axial magnetic bearing actuator were designed to meet the requirements for the turbine application. No bias coils are included in these design. The biasing flux is provided by current from the control power amplifiers. All the coils are made from ceramic coated copper wire and are terminated to high temperature connectors designed into the actuators. The new high strength Hiperco 50 HS material was chosen for the rotor lamination material for the radial bearings. A customized heat treatment process for this material in a high vacuum environment was developed to insure the maximum strength was obtained with the maximum magnetic properties. High temperature ceramic coated copper wire and bonding and potting material used for the coil assembly were tested up to 650 degrees C without failures.
Optimization of Friction Damper Weight, Simulation and Experiments
Authors: Csaba Gabor , Andersson Magnus
Published: December 2014

A new friction damper has been designed by Volvo Aero Corporation. It is used in the high pressure turbine stage of a turbojet engine. The objective of this paper was to find the optimal weight of the new damper that minimizes the blade response amplitude for six and nine engine order excitation and to compare the new damper design with that currently used. Another objective was to compare how well simulation results agree with experimental results from spin pit tests. Simulations were made with a damper model that incorporates the possibility of both micro- and macro-slip in the blade-damper contact interface. Turbine blades were modeled using finite element beam elements. Experimental data were provided from spin pit tests with a completely bladed high pressure turbine rotor. Results show that the simulation model can be used to give qualitative results but has to be further developed to incorporate mistuning effects and coupled modes of vibration for the blade. The spin pit test shows that the new damper design is more efficient in reducing resonance stresses than the old design. It was not possible to see if simulations predict the right optimal damper weight by comparing with experimental data because the rotor could not be excited up to the design point.
Mechanisms of Turbulence Transport in a Turbine Blade Coolant Passage With a Rib-Turbulator
Authors: Panigrahi P. K. , Acharya S.
Published: December 2014

This paper provides detailed measurements of the flow in a ribbed coolant passage, and attempts to delineate the important mechanisms that contribute to the production of turbulent shear stress and the normal stresses. It is shown that the separated flow behind the rib is dictated by large scale structures, and that the dynamics of the large scale structures, associated with sweep, ejection, and inward and outward interactions all play an important role in the production of the turbulent shear stress. Unlike the turbulent boundary layer, in a separated shear flow past the rib, the inward and outward interaction terms are both important accounting for a negative stress production that is nearly half of the positive stress produced by the ejection and sweep mechanisms. It is further shown, that the shear layer wake persists well past the re-attachment location of the shear layer, implying that the flow between ribbed passages never recovers to that of a turbulent boundary layer. Therefore, even past re-attachment, the use of statistical turbulence models that ignore coherent structure dynamics is inappropriate.
Effects of Very High Free-Stream Turbulence on the Jet-Mainstream Interaction in a Film Cooling Flow
Authors: Kohli Atul , Bogard David G.
Published: December 2014

Dispersion of coolant jets in a film cooling flow field is the result of a highly complex interaction between the film cooling jets and the mainstream. Understanding this complex interaction, particularly near the injection location, is critical for improving the predictive capabilities of existing film cooling models, especially when very high free-stream turbulence levels exist. This study uses a high frequency response temperature sensor to investigate the mean and fluctuating thermal field of a film cooling flow for two vastly different free-stream turbulence levels (0.5% and 20%). The high frequency response temperature sensor provides new information about the film cooling flow in terms of actual rms levels (Θ′), probability density functions (pdf’s), and frequency spectra of the thermal field. Results are presented for both free-stream conditions using round holes inclined at 35°, at a momentum flux ratio of I = 0.156 and density ratio of DR = 1.05.

The mean thermal field results show severe degradation of the film cooling jet occurs with very high free-stream turbulence levels. Temperature rms results indicate levels as high as Θ′ = 0.25 exist at the jet-mainstream interface. More information is provided by the temperature pdf’s which are able to identify differences in the jet-mainstream interaction for the two free-stream conditions. With small free-stream turbulence, strong intermittent flow structures generated at the jet-mainstream interface disperse the jet by moving hot mainstream fluid into the coolant core, and ejecting coolant fluid into the mainstream. When the free-stream has large scales and very high turbulence levels, the jet-mainstream interface is obliterated by large scale turbulent structures originating from the free-stream which completely penetrate the coolant jet causing very rapid dispersion of the film cooling jet.
A Semi-Analytical Finite Rate Two-Reactor Model for Gas Turbine Combustors
Authors: Tonouchi J. H. , Held T. J. , Mongia H. C.
Published: December 2014

A gas turbine combustor is modeled using a two-reactor, finite-rate mixing and chemistry gas particle approach. The first reactor, used to simulate combustion in the primary zone, permits independent definition of the rates of macromixing and micromixing within the reactor, and the amount of premixing of fuel and air entering the reactor. Finite-rate macromixing is simulated by consideration of the fluid particle residence time distribution frequency function and the ages of the particles in the reactor. Finite-rate micromixing is simulated using a modified Coalescence-Dispersion (C-D) model. The second reactor model simulates combustion in the dilution zone of the combustor, and is modeled as a plug flow reactor with cross-flowing jets of dilution air and co-flowing streams of cooling film air. The primary zone reactor model predicts physically reasonable trends in mean temperature, and CO and NOx emissions as the macromixing and micromixing parameters are varied with respect to the perfectly-stirred reactor limit. The model also has shown to predict the correct trends in modeling NOx and CO emissions from aircraft engine gas turbine combustors.
Analysis of Separated Flows Inside an Annular Compressor Cascade Using a Low-Re-Number k-ϵ and an Algebraic Reynolds-Stress-Model
Authors: Lücke Jürgen R. , Gallus Heinz E.
Published: December 2014

The flow field inside an annular compressor cascade is numerically investigated. The mean flow features are complex three-dimensional zones of turbulent separation at hub and shroud at high inflow angles. The flow field is investigated with an implicit three-dimensional Navier-Stokes code. To predict turbulent effects the flow solver includes two different variants of a Low-Re-number k-ϵ-model and an algebraic Reynolds-stress-model. Using the Low-Re-number model the structure of the regions of separated flow are fairly well predicted. However, intensity and size of these zones are too small compared with the experimental data. Better results are produced using the anisotropic algebraic Reynolds-stress-model combined with a stagnation point modification of the turbulent production term. Stucture and intensity of the vortex systems are simulated in more detail. Static pressure distributions and loss contours are in a very good agreement with the experiments.