bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Navier Stokes Computer Code for Theoretical Investigations on the Applicability of Various Turbulence Models for Flow Prediction Along Turbine Blades
Authors: Bohn Dieter , Emunds Rolf 
Published: February 2015

The quality of theoretical flow prediction in turbomachines is strongly influenced by the modeling of the turbulent fluctuations. These fluctuations are generated by various secondary flow mechanisms, the swirl of the flow occuring in blade channels and the curvature of the streamlines. Furthermore, the character of turbulence can become highly anisotropic indicating that the well known algebraic and two-equation k-ε type models might become unserviceable.
The present paper deals with the validation of a fully implicit 2-D steady-state Navier-Stokes algorithm and the comparison of the applicability of various turbulence models for predicting the flow along the blades of a turbine nozzle.
In the first section a short review is given on the basic numerical assumptions of the used computer code and on the employed two layer algebraic, one- and two-equation turbulence models. The influence of the fully implicitly formulated transport equations for the turbulent quantities, especially the influence of the discretization of the production and dissipation terms on the stability of the numerical scheme is pointed out. The validation of the numerical algorithm is done for an inviscid flow through the Hobson 2 impulse cascade, for the turbulent flow over a flat plate and for the flow through a turbine stator channel.
In a last section results obtained from calculations for a subsonic turbine stator flow inside and downstream of the blade passage with several turbulence models are presented. The apparent differences, especially in the distribution of the total pressure loss downstream of the trailing edge are discussed.
Feasibility Study on Oil Droplet Flow Investigations Inside Aero Engine Bearing Chambers: PDPA Techniques in Combination With Numerical Approaches
Authors: Glahn A. , Kurreck M. , Willmann M. , Wittig S. 
Published: February 2015

The present paper deals with oil droplet now phenomena in aero engine bearing chambers. An experimental investigation of droplet sizes and velocities utilizing a Phase Doppler Particle Analyzer (PDPA) has been performed for the first time in bearing chamber atmospheres under real engine conditions.
Influences of high rotational speeds are discussed for individual droplet size classes. Although this is an important contribution to a better understanding of the droplet flow impact on secondary air/oil system performance, an analysis of the droplet flow behaviour requires an incorporation of numerical methods because detailed measurements as performed here suffer from both strong spatial limitations with respect to the optical accessibility in real engine applications and constraints due to the extremely time consuming nature of an experimental flow field analysis. Therefore, further analysis is based on numerical methods. Droplets characterized within the experiments are exposed to the flow field of the gaseous phase predicted by use of our well-known CFD code EPOS. The droplet trajectories and velocities are calculated within a Lagrangian frame of reference by forward numerical integration of the particle momentum equation.
This paper has been initiated rather to show a successful method of bearing chamber droplet flow analysis by a combination of droplet sizing techniques and numerical approaches than to present field values as a function of all operating parameters. However, a first insight into the complex droplet flow phenomena is given and specific problems in bearing chamber heat transfer are related to the droplet flow.
Topping Combustor Status for Second Generation Pressurized Fluidized Bed Cycle Application
Authors: Domeracki William F. , Dowdy T. E. , Bachovchin Dennis M. 
Published: February 2015

Second-Generation Pressurized Fluidized Bed (PFB) combined cycles employ topping combustion to raise the turbine inlet temperature for enhanced cycle efficiency. This concept creates special combustion system requirements that are very different from requirements of conventional gas turbine systems. The topping combustor provides the means for achieving state-of-the-art turbine inlet temperatures and is the main contributor to enhanced plant performance. The objective of this program is to develop a topping combustor that provides low emissions, and is a durable, efficient device exhibiting stable combustion and manageable wall temperature. The combustor will be required to burn a low-Btu syngas under normal “coal-fired” conditions. However, for start-up and/or carbonizer outage, it may be necessary to fire a clean fuel, such as, oil or natural gas.
Prior testing has shown the Westinghouse Multi-Annular Swirl Burner (MASB) to have excellent potential for this application. Metal wall temperatures can be maintained at acceptable levels, even though most “cooling” is done by 1600°F vitiated air. Good pattern factors and combustion efficiencies have been obtained. Additionally, low conversion rates of fuel bound nitrogen to NOx have been demonstrated.
This paper presents an update of the status of an ongoing topping combustor development and test program for application to “Second Generation Pressurized Fluidized Bed Combined Cycles (PFBCC).” The program is sponsored by the Department of Energy’s Morgantown Energy Technology Center (DOE/METC) and will first be applied commercially into the Clean Coal Technology Round V Four Rivers Energy Modernization Project. Phase 1 of the program involved a conceptual and economic study (Robertson et al., 1988); Phase 2 addresses design and subscale testing of components; and Phase 3 will cover pilot plant testing of components integrated into one system.
A NOx Prediction Scheme for Lean-Premixed Gas Turbine Combustion Based on Detailed Chemical Kinetics
Authors: Polifke Wolfgang , Döbbeling Klaus , Sattelmayer Thomas , Nicol David G. , Malte Philip C. 
Published: February 2015

The lean-premixed technique has proven very efficient in reducing the emissions of oxides of nitrogen (NOx) from gas turbine combustors. The numerical prediction of NOx-levels in such combustors with multidimensional CFD codes has only met with limited success so far. This is at least to some extent due to the complexity of the NOx formation chemistry in lean-premixed combustion, i.e. all three known NOx formation routes (Zeldovich, nitrous and prompt) can contribute significantly. Furthermore, NOx formation occurs almost exclusively in the flame zone, where radical concentrations significantly above equilibrium values are observed.
A relatively large chemical mechanism is therefore required to predict radical concentrations and NOx formation rates under such conditions. These difficulties have prompted the development of a NOx post-processing scheme, where rate and concentration information necessary to predict NOx formation is taken from one-dimensional combustion models with detailed chemistry and provided — via look-up tables — to the multi-dimensional CFD code.
The look-up tables are prepared beforehand in accordance with the operating conditions and are based on CO concentrations, which are indicative of free radical chemistry. Once the reacting flow field has been computed with the main CFD code, the chemical source terms of the NO transport equation, i.e. local NO formation rates, are determined from the reacting flow field and the tabulated chemical data. Then the main code is turned on again to compute the NO concentration field. This NOx sub-model has no adjustable parameters and converges very quickly. Good agreement with experiment has been observed and interesting conclusions concerning superequilibrium O-atom concentrations and fluctuations of temperature could be drawn.
Study of Flame Stability in a Step Swirl Combustor
Authors: Durbin Mark D. , Vangsness Marlin D. , Ballal Dilip R. , Katta Viswanath R. 
Published: February 2015

A prime requirement in the design of a modem gas turbine combustor is good combustion stability, especially near lean blowout (LBO), to ensure an adequate stability margin. For an aeroengine, combustor blow-off limits are encountered during low engine speeds at high altitudes over a range of flight Mach numbers. For an industrial combustor, requirements of ultra-low NOx emissions coupled with high combustion efficiency demand operation at or close to LBO. In this investigation, a step swirl combustor (SSC) was designed to reproduce the swirling flow pattern present in the vicinity of the fuel injector located in the primary zone of a gas turbine combustor. Different flame shapes, structure and location were observed and detailed experimental measurements and numerical computations were performed.
It was found that certain combinations of outer and inner swirling air flows produce multiple attached flames, a flame with a single attached structure just above the fuel injection tube, and finally for higher inner swirl velocity, the flame lifts from the fuel tube and is stabilized by the inner recirculation zone. The observed difference in LBO between co- and counter-swirl configurations is primarily a function of how the flame stabilizes i.e., attached vs. lifted. A turbulent combustion model correctly predicts the attached flame location(s), development of inner recirculation zone, a dimple-shaped flame structure, the flame lift-off height, and radial profiles of mean temperature, axial velocity, and tangential velocity at different axial locations. Finally, the significance and applications of anchored and lifted flames to combustor stability and LBO in practical gas turbine combustors are discussed.
Differential Mass and Energy Balances in the Flame Zone From a Practical Fuel Injector in a Technology Combustor
Authors: Warren David L. , Hedman Paul O. 
Published: February 2015

This paper presents further analysis of experimental results from an Air Force program conducted by researchers at Brigham Young University (BYU) Wright-Patterson Air Force Base (WPAFB), and Pratt and Whitney Aircraft Co. (P&W) (Hedman, et al., 1994a and 1994b). These earlier investigations of the combustion of propane in a practical burner installed in a technology combustor used: 1) digitized images from video and still film photographs to document observed flame behavior as fuel equivalence ratio was varied, 2) sets of LDA data to quantify the velocity flow fields existing in the burner, 3) CARS measurements of gas temperature to determine the temperature field in the combustion zone, and to evaluate the magnitude of peak temperature, and 4) two-dimensional PLIF images of OH radical concentrations to document the instantaneous location of the flame reaction zones.
This study has used the in situ velocity and temperature measurements from the earlier study, suitably interpolated, to determine local mass and energy balances on differential volume elements throughout the flame zone. The differential mass balance was generally within about ± 10% with some notable exceptions near regions of very high shear and mixing. The local differential energy balance has qualitatively identified the regions of the flame where the major heat release is occurring, and has provided quantitative values on the rate of energy release (up to −400 kJ/m3s).
The velocity field data have also been used to determine Lagrangian pathlines through the flame zone. The local velocity and temperature along selected pathlines have allowed temperature timelines to be determined. The temperature generally achieves its peak value, often near the adiabatic flame temperature, within about 10 ms. These temperature timelines, along with the quantitative heat release data may provide a basis for evaluating kinetic combustion models.
Engine Test Facility Dynamic Data Systems Upgrade and Improvement Plan
Authors: Jones Henry T. 
Published: February 2015

The Engine Test Facility (ETF) at Arnold Engineering Development Center (AEDC) has many test cells supported with instrumentation systems for acquiring, monitoring, recording, and processing dynamic data. These systems must be updated to meet rapidly changing requirements to acquire more data at increased band-widths, increase online monitoring information, and provide rapid data processing for shortening data turnaround time.
This paper presents the rationale and plans for converting from a dynamic data system centered around analog data recorders to a digital-based system using high-density digital recorders. Transition to the digital-based system is planned over a five-year period. The current dynamic data systems are described, new technologies in advanced online monitoring systems are identified, and centralization of online monitoring stations and digital data recorders with robotic tape storage and retrieval capabilities are recommended.
Application of the Time Linearized Euler Method to Flutter and Forced Response Calculations
Authors: Kahl G. 
Published: February 2015

The Time Linearized Euler Method has proven to be a useful design tool, capable of predicting unsteady flows in turbomachinery within the accuracy required for engineering purposes while being fast enough for routine use in the design process.
This paper first briefly describes the approach and its implementation in the current method. A range of applications of the method is described for flutter calculations in turbines and compressors with different levels of complexity such as chord wise bending, single or clustered airfoils, sub- or transonic flow. Farced response calculations are shown for airfoils passing through wakes and for a rotor operating in the pressure field of a downstream outlet guide vane. The results are presented as aerodynamic damping, unsteady work distributions and unsteady flowfield plots. Data shown includes information on boundary conditions, mesh size, computation time and convergence histories.
The paper provides insight into an industry approach to modeling unsteady turbomachinery flows.
Comparison of Test Measurements Taken on a Pipeline Compressor / Gas Turbine Unit in the Workshop and at Site
Authors: Schmitt W. , Thomas V. 
Published: February 2015

The first part of this paper describes the test installation of the gas turbine and the compressor in the workshop, test execution, measuring methods, evaluation and measuring uncertainties.
The second part of this paper describes the site installation, execution of the test under full load conditions on natural gas, measuring methods, evaluation and measuring uncertainties.
The third part of this paper compares both the measurements and the Reynolds number correction which was used for the evaluation of the pipeline compressor test results in the workshop.
Off-Design Performance of Multipressure Heat Recovery Boilers
Authors: Bettagli Nicola , Facchini Bruno 
Published: February 2015

Combined cycle power plants are systems with very high thermodynamic efficiency. Off-design plant behaviour prediction is very important to allow for high efficiency regulation of systems.
The aim of this paper is to study heat recovery steam generator (HRSG) performance, varying inlet gas temperature and mass flow rate. One, two and three pressure level heat recovery boilers are considered. A HRSG simulation program based on heat transfer and thermodynamic fundamental laws is carried out.
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.
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.
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.
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.