bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Efficient Computational Model for Premixed Turbulent Combustion at High Reynolds Numbers Based on a Turbulent Flame Speed Closure
Authors: Zimont Vladimir , Polifke Wolfgang , Bettelini Marco , Weisenstein Wolfgang 
Published: December 2014

Theoretical background, details of implementation and validation results of a computational model for turbulent premixed gaseous combustion at high turbulent Reynolds numbers are presented. The model describes the combustion process in terms of a single transport equation for a progress variable; closure of the progress variable’s source term is based on a model for the turbulent flame speed. The latter is identified as a parameter of prime significance in premixed turbulent combustion and is determined from theoretical considerations and scaling arguments, taking into account physico-chemical properties of the combustible mixture and local turbulent parameters. Specifically, phenomena like thickening, wrinkling and straining of the flame front by the turbulent velocity field are considered, yielding a closed form expression for the turbulent flame speed that involves, e.g., speed, thickness and critical gradient of a laminar flame, local turbulent length scale and fluctuation intensity. This closure approach is very efficient and elegant, as it requires only one transport equation more than the non-reacting flow case, and there is no need for costly evaluation of chemical source terms or integration over probability density functions.
The model was implemented in a finite-volume based computational fluid dynamics code and validated against detailed experimental data taken from a large scale atmospheric gas turbine burner test stand. The predictions of the model compare well with the available experimental results. It has been observed that the model is significantly more robust and computationally efficient than other combustion models. This attribute makes the model particularly interesting for applications to large 3D problems in complicated geometries.
Results of Experiments and Models for Predicting Stability Limits of Turbulent Swirling Flames
Authors: Hoffmann S. , Lenze B. , Eickhoff H. 
Published: December 2014

Swirling flames are used in many industrial applications like process furnaces, boilers and gas turbines due to their excellent mixing, stability, emission and burnout characteristics. The wide-spread use of swirl burners in the process and energy industries and, in particular, new concepts for the reduction of NOx-emissions raise the need for simple-to-use models for predicting lean stability limits of highly turbulent flames stabilized by internal recirculation.
Based on recently published experimental data of the first author concerning the reaction structures of swirling flames operating near the extinction limit, different methods for predicting lean blow-off limits have been developed and tested. The aim of the investigations was to find stabilization criteria that allow predictions of blow-off limits of highly turbulent recirculating flames without the requirement for measurements in those flames.
Several similarity criteria based on volumetric flow rates, burner size and material parameters of the cold gases, were found to be capable of predicting stability limits of premixed and (in some cases) nonpremixed flames at varying swirl intensities, burner scales and fuel compositions. A previously developed numerical field model, combining a k,ϵ-model with a combined “assumed-shape Joint-PDF”/Eddy-Dissipation reaction model was also tested for its potential for stability prediction.
The Evaporative Gas Turbine [EGT] Cycle
Authors: Horlock J. H. 
Published: December 2014

Humidification of the flow through a gas turbine has been proposed in a variety of forms. The STIG plant involves the generation of steam by the gas turbine exhaust in a heat recovery steam generator [HRSG], and its injection into or downstream of the combustion chamber. This increases the mass flow through the turbine and the power output from the plant, with a small increase in efficiency. In the evaporative gas turbine [or EGT] cycle, water is injected in the compressor discharge in a regenerative gas turbine cycle [a so-called CBTX plant-compressor [C], burner [B], turbine [T], heat exchanger [X]]; the air is evaporatively cooled before it enters the heat exchanger. While the addition of water increases the turbine mass flow and power output, there is also apparent benefit in reducing the temperature drop in the exhaust stack. In one variation of the basic EGT cycle, water is also added downstream of the evaporative aftercooler, even continuously in the heat exchanger. There are several other variations on the basic cycle [e.g. the cascaded humidified advanced turbine (CHAT)].
The present paper analyses the performance of the EGT cycle. The basic thermodynamics are first discussed, and related to the cycle analysis of a dry regenerative gas turbine plant. Subsequently some detailed calculations of EGT cycles are presented. The main purpose of the work is to seek the optimum pressure ratio in the EGT cycle for given constraints [e.g. fixed maximum to minimum temperature]. It is argued that this optimum has a relatively low value.
Active Stabilization of Rotating Stall and Surge in a Transonic Single Stage Axial Compressor
Authors: Weigl H. J. , Paduano J. D. , Fréchette L. G. , Epstein A. H. , Greitzer E. M. , Bright M. M. , Strazisar A. J. 
Published: December 2014

Rotating stall and surge have been stabilized in a transonic single-stage axial compressor using active feedback control. The control strategy is to sense upstream wall static pressure patterns and feed back the signal to an annular array of twelve separately modulated air injectors. At tip relative Mach numbers of 1.0 and 1.5 the control achieved a 11% and 3.5% reduction in stalling mass flow respectively, with injection adding 3.6% of the design compressor mass flow. The aerodynamic effects of the injection have also been examined.
At a tip Mach number, Mtip, of 1.0, the stall inception dynamics and effective active control strategies are similar to results for low-speed axial compressors. The range extension was achieved by individually damping the first and second spatial harmonics of the pre-stall perturbations using constant gain feedback.
At a Mtip of 1.5 (design rotor speed), the pre-stall dynamics are different than at the lower speed. Both one-dimensional (surge) and two-dimensional (rotating stall) perturbations needed to be stabilized to increase the compressor operating range. At design speed, the instability was initiated by approximately 10 rotor revolutions of rotating stall followed by classic surge cycles. In accord with the results from a compressible stall inception analysis, the zeroth, first, and second spatial harmonics each include more than one lightly damped mode which can grow into the large amplitude instability. Forced response testing identified several modes traveling up to 150% of rotor speed for the first three spatial harmonics; simple constant gain control cannot damp all of these modes and thus cannot stabilize the compressor at this speed. A dynamic, model-based robust controller was therefore used to stabilize the multiple modes which comprise the first three harmonic perturbations in this transonic region of operation.
Design, Optimization, and Analysis of a High-Turning Transonic Tandem Compressor Cascade
Authors: Weber Anton , Steinert Wolfgang 
Published: December 2014

As a feasibility study for a stator guide vane a highly loaded transonic compressor stator blade row was designed, optimized, and tested in a transonic cascade facility.
The flow entering the turning device with an inlet Mach number of 1.06 has to be turned by more than 60° and diffused extremely to leave the blade row without swirl. Therefore, the basic question was: Is it feasible to gain such a high amount of flow turning with an acceptable level of total pressure losses?
The geometric concept chosen is a tandem cascade consisting of a transonic blade row with a flow turning of 10° followed by a subsequent high-turning subsonic cascade. The blade number ratio of the two blade rows was selected to be 1:2 (transonic: subsonic).
Design and optimization have been performed using a modern Navier-Stokes flow solver under 2D assumptions by neglecting side wall boundary-layer effects. In the design process it was found to be necessary to guide the wake of the low turning transonic blade near the suction surface of the subsonic blade. Furthermore, it is advantageous to enlarge the blade spacing of the ‘wake’ passage in relation to the neighbouring one of the high turning part.
The optimized design geometry of the tandem cascade was tested in the transonic cascade windtunnel of the DLR in Cologne. At design flow conditions the experiments confirmed the design target in every aspect. A flow turning of more than 60°, a static pressure ratio of 1.75, and a total pressure loss coefficient of 0.15 was measured. The working range at design inlet Mach number of 1.06 is about 3.5° in terms of the inlet flow angle. A viscous analysis of various operating points showed excellent agreement with the experimental results.
A Navier-Stokes Inverse Method Based on a Moving Blade Wall Strategy
Authors: Léonard Olivier , Demeulenaere Alain 
Published: December 2014

A two-dimensional viscous inverse method for the design of compressor and turbine blades is presented. An initial geometry is modified iteratively to reach a target pressure distribution imposed on the blade surfaces. The Navier-Stokes equations are solved in a numerical domain of which some boundaries (the blade walls) move during the transient part of the computation. The blade modifications are based on the transpiration principle. The transpiration flux is computed from the difference between the actual and the prescribed pressure distributions.
A high-resolution Navier-Stokes solver has been developed for this purpose, based on a Finite-Volume formulation. Multi-block structured grids allow for a selective concentration of discretization points in the zones of higher gradients. Both explicit (Runge-Kutta) and implicit (Newton-Krylov) time integration schemes have been implemented.
Applications to turbine and compressor blade design illustrate the accuracy of the flow computation, and the efficiency of the inverse method.
Development of a Corrosion Resistant Directionally Solidified Material for Land Based Turbine Blades
Authors: Cheruvu N. S. 
Published: December 2014

Advanced turbines with improved efficiency require materials that can operate at higher temperatures. Availability of these materials would minimize cooling flow requirements and thus, improve the efficiency of a turbine. Advanced processing such as directional solidification (DS), can improve temperature capability of the majority of Ni based superalloys. However, results of earlier work on IN-738 reveal that the DS process does not significantly improve temperature capability of this alloy. A research program was initiated to develop a corrosion resistant Ni-based DS blade material for land-based turbines.
In this program, eight heats with varied Cr, Al, Ti, Ta, and W contents were selected for evaluation. Screening tests performed on these heats in the DS condition include tensile, creep, and corrosion. The results of experimental heats were compared with those of IN-738 in the equiaxed condition. From these results, two chemistries offering approximately 100°F temperature advantage at typical row 1 turbine blade operating stress, were selected for castability and further mechanical property evaluation. Several row 1 solid and cored turbine blades were successfully cast. The blades were evaluated for grain structure and mechanical properties. Tests were also conducted to evaluate the effects of withdrawal rates on properties. These results are summarized in this paper.
Extensive Industrial Gas Turbine Experience With Second Generation Single Crystal Alloy Turbine Blades
Authors: Brentnall W. D. , Aurrecoechea J. M. , Rimlinger C. M. , Harris K. , Erickson G. L. , Wahl J. B. 
Published: December 2014

The rhenium containing second generation single crystal alloy CMSX-4® was introduced for turbine blading in the Solar® Turbines Incorporated Mars® T-14000 engine in 1990. Based on the initial success with the first 4,000 hour engine test, the alloy was confirmed as bill of material for the stage 1 turbine blades in the T-14000 engine. Field experience has been excellent and there are now about 1,500,000 hours total accumulated engine time with several engines having completed their first overhaul cycle (Typically 30,000 hours). Use of this alloy is now being considered by Solar for other turbine airfoil components.
This update provides the results of metallurgical evaluations on high time blades. A detailed analysis of the substrate and coating, microstructure following the 25,000 hours field exposure was conducted and the results reported herein. A brief discussion of the effect of PtAl coatings on fatigue properties is also included.
Application of the Shell DeNOx System on Gas Turbine-Heat Recovery Steam Generators
Authors: Croce Gregory P. , Yistra Wessef , Kinsfather Richard , Hamilton David 
Published: December 2014

The Shell DeNOx System (SDS) is an innovative selective catalytic reduction (SCR) system in which NOx emission reduction efficiencies greater than 90% can be achieved from fluegas streams at temperatures as low as 163 °C (325 °F).
The low temperature capability allows the SDS to be positioned at the tail-end of a furnace convection section or gas turbine HRSG. This feature permits the installation of SDS without the extensive retrofit costs associated with the implementation of conventional (medium or high) temperature SCRs which require a 288–385 °C (550–725 °F) or 427–593 °C (800–1100 °F) temperature window, respectively.
This paper will discuss the application and operating experience of the SDS on gas turbines heat recovery steam generators (GT-HRSG).
LNG Receiving Terminal Associated With Gas Cycle Power Plants
Authors: Chiesa Paolo 
Published: December 2014

LNG regasification process needs a considerable quantity of thermal energy that is usually obtained by cooling sea water or by burning a fraction of the evaporated natural gas. These systems, though offering low cost and high reliability, are thermodynamically inefficient: they require energy for water pumping or fuel to provide heat and do not exploit the physical exergy related to the initial conditions of LNG to produce mechanical work.
The present paper aims to assess the performances of various gas turbine based cycles which use the LNG regasification process as a low temperature heat sink for power cycles. In particular it will focus on the following configurations:
• Closed loop gas cycles
• Gas-gas combined cycles
• Combined gas-organic Rankine cycles
Two different sendout pressure (70 and 30 bar, corresponding respectively to the supply of long-distance pipelines or power plants based on heavy-duty gas turbines) are considered. Their performances are calculated and proper effectiveness indexes (e.g. thermal and exergetic efficiency) are introduced to carry out a comprehensive comparison among the systems considered. A simple economical analysis completes the discussion.
Use of Artificial Neural Networks for the Simulation of Combined Cycle Transients
Authors: Desideri Umberto , Fantozzi Francesco , Bidini Gianni , Mathieu Philippe 
Published: December 2014

Due to techno-economic assets, the demand of combined cycles (CC) is currently growing. Nowadays, in a diversified electricity mix, these plants are often used on a load cycling duty or in the intermediate load range. The ability to start quickly and reliably may be a decisional criterion for the selection of the plant, in addition to the design performance, the cost and the pollutant emissions. Therefore, together with the simulation of CC transients, a proper monitoring system aimed at keeping high plant performance during the transients is required.
With the help of advanced measurement and monitoring devices, artificial intelligence (AI) techniques as expert systems (ES) and neural networks (NN) can fulfill this duty.
The goal of this paper is to show that a NN technique can be used reliably to obtain the response of a complex energetic system, such as CCs, during a slow transient and consequently as part of an on-line monitoring system.
In this work, a CC power plant is simulated by dividing it into three blocks, which are representative of the three main elements of the CC: namely the gas turbine (GT), the heat recovery steam generator (HRSG) and the steam turbine (ST). To each of them a NN is associated. Once the training and testing of the NNs is carried out, the blocks are then arranged in a series cascade, the output of a block being the input of the subsequent one. With this solution, the NN-based system is able to produce the transient response of a CC plant when the input information are the GT inlet parameters.
The transient data, not easy to obtain from measurements on existing plants, are provided by the CCDYN simulator (Dechamps, 1995). The performance obtained by the NN based system are observed to be in good agreement with those given by CCDYN, the latter being validated on the basis of measurements in an existing plant. The NN code, providing the departures of the measured data from the predicted ones, can be considered as a proper system for on-line monitoring and diagnosis.
Multivariate Experiments to Assess the Effect of Combustor Dome Geometry on Fuel Distribution and Stability
Authors: Arellano Leonel , Ateshkadi Arash , Fukushima Hirokazu , McDonell Vincent G. , Samuelsen Scott 
Published: December 2014

The geometric and operational features of gas turbine engine combustors are receiving increased scrutiny due to a growing concern regarding environmental impact, performance, durability, and manufacturability. To minimize the risk associated with new projects, optimization of designs which are similar to those in current operation is attractive. To achieve this goal, a methodology that is efficient and can reveal interactions between parameters that affect performance is necessary. An approach which addresses these requirements is statistically designed experiments (e.g., multivariate experiments or “design of experiments”), which offers efficiency as well as the ability to identify interactions between variables. This approach was adopted and demonstrated in the present study utilizing a set of hardware specifically developed to allow multivariate experiments to be conducted. A radial mixer geometry consisting of four parameters (primary and secondary swirl vane angles, the presence of a venturi, and the co-/counter swirl sense) was examined. The design was developed to maintain constant effective area and overall dimensions. The responses selected for study were stability (i.e., reaction lean blow-out) and fuel distribution.
The results reveal that (1) the multivariate approach is effective in the present application, (2) the swirl sense between the primary and secondary swirlers play an influential role in determining the uniformity of the spray, (3) the size of the fuel spray area is affected by the mixer venturi and the swirl sense, (4) the symmetry of the fuel presentation is affected by the interaction of the swirler angles, (5) Lean Blow Out (LBO) is not affected by the parameters selected, and (6) the parameters affecting fuel distribution and combustion stability differ, indicating that the combustion performance is not described entirely by fuel distribution.
Development of a Low-Emission Combustor for a 100-kW Automotive Ceramic Gas Turbine (IV)
Authors: Sasaki Masafumi , Kumakura Hirotaka , Ichikawa Hiroyuki , Ohkubo Youichiro , Yoshida Yuusaku 
Published: December 2014

A low emission combustor, which uses a prevaporization-premixing lean combustion system for the 100-kW automotive ceramic gas turbine (CGT), has been subjected to performance tests. A second combustor prototype (PPL-2). which incorporates improvements intended to overcome a flashback problem observed in an initiel combustor prototype (PPL-1), had been tested. Now combustors with further improvements accomplished to the PPL-2 prototype, is tested.
Test results of the PPL-2 combustor showed that, increasing the air distribution ratio in the lean combustion region to aviod flashback, and by providing a uniform flow layer at the entrance of the combustion region so as to supress flashback, were effective in expanding the stable combustion range by substantially improving the flashback characteristics.
To improve the flashback characteristics further more, we have redesinged the bluffbody and the swirl chamber so as to obtain uniform flow of the mixture, in the prevaporization premixing zone.
Test results shows that the flashback characteristics has been greatly improved, and a wide stable combustion range, needed to operate the 100-kW CGT engine, was obtained.
Facilities for Automotive Gas Turbine Ceramic Components
Authors: Avran Patrick , Leclair Alain , Payen Gérard 
Published: December 2014

The first part of this paper describes the test facility to characterize the catalytic combustor. The combustion chamber is a LPP combustor (Lean Premixed Prevaporised), made of preheater, premix duct, catalytic part and after burner. Each component will be validated separately for the required conditions (steady state and transient conditions). All the measurements and data acquisition are described.
The second part deals with the test facility for the hot spin test of the ceramic wheel. The base of the test bench is a modified turbocharger (maximum rotating speed: 125000 r.p.m.). With this configuration it will be possible to test the ceramic radial wheel within the AGATA specifications; in this case the compressor is used like a brake.
The last part is devoted to two ceramic heat exchanger test rigs: the first rig is to evaluate the themomechanical stresses on the samples; the second rig to assess the performance compared to the AGATA specifications and to duplicate the transient and thermal shock conditions. In this program the heat exchanger is fixed.