bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Pulsed Blowing on the Boundary Layer of a Highly Loaded Low Pressure Turbine Blade
Authors: Mack Marion , Brachmanski Roland , Niehuis Reinhard 
Published: November 2013

The performance of the low pressure turbine (LPT) can vary appreciably, because this component operates under a wide range of Reynolds numbers. At higher Reynolds numbers, mid and aft loaded profiles have the advantage that transition of suction side boundary layer happens further downstream than at front loaded profiles, resulting in lower profile loss. At lower Reynolds numbers, aft loading of the blade can mean that if a suction side separation exists, it may remain open up to the trailing edge. This is especially the case when blade lift is increased via increased pitch to chord ratio. There is a trend in research towards exploring the effect of coupling boundary layer control with highly loaded turbine blades, in order to maximize performance over the full relevant Reynolds number range.
In an earlier work, pulsed blowing with fluidic oscillators was shown to be effective in reducing the extent of the separated flow region and to significantly decrease the profile losses caused by separation over a wide range of Reynolds numbers. These experiments were carried out in the High-Speed Cascade Wind Tunnel of the German Federal Armed Forces University Munich, Germany, which allows to capture the effects of pulsed blowing at engine relevant conditions. The assumed control mechanism was the triggering of boundary layer transition by excitation of the Tollmien-Schlichting waves.
The current work aims to gain further insight into the effects of pulsed blowing. It investigates the effect of a highly efficient configuration of pulsed blowing at a frequency of 9.5 kHz on the boundary layer at a Reynolds number of 70000 and exit Mach number of 0.6. The boundary layer profiles were measured at five positions between peak Mach number and the trailing edge with hot wire anemometry and pneumatic probes. Experiments were conducted with and without actuation under steady as well as periodically unsteady inflow conditions. The results show the development of the boundary layer and its interaction with incoming wakes. It is shown that pulsed blowing accelerates transition over the separation bubble and drastically reduces the boundary layer thickness.
N+3 and N+4 Generation Aeropropulsion Engine Combustors: Part 1 — Large Engines’ Emissions
Authors: Mongia Hukam C. 
Published: November 2013

A comprehensive assessment of emissions characteristics of the 1st, N and N+1 generation rich-dome combustion products has been done to identify the lowest emissions products. Focus of this paper is on the large rich-dome engines with its potential application for the (N+3) and (N+4) mixers with inspirational target takeoff NOxEI of 5 at 55 OPR.
A total of ten engine models of the 1st generation were selected in addition to eight recently certified large engines. After evaluating several choices for conducting comparative assessment, the following three expressions were proposed for average takeoff NOxEI, idle COEI and HCEI entitlements, respectively:
NOxEI L = 0.0288 × OPR 1.991
Idle COEI L = 815.36 Takeoff NOxEI L 1.159
Idle HCEI L = 0.15 × Idle COEI L - 2.0
In regard to application of the rich-dome technology to the (N+2) cycle based (N+3) mixers, the author tentatively gives it low probability of success barring success story stemming from Lee et al. [2012].
Forced-Air Diesel Locomotive Cooling: Prediction of Noise and Energy Consumption Under Realistic Operational Conditions
Authors: Knirsch Sebastian , Mandt Dietmar , Mauch Uwe , Bamberger Konrad , Carolus Thomas 
Published: November 2013

An important subsystem in most surface transport vehicles is the forced-air cooling module. Under specific operational conditions of the vehicle the cooling system is the major noise source and the component with the largest consumption of energy. A comprehensive time domain simulation model was developed for simulation of the cooling module in a Diesel locomotive under realistic operational conditions. It includes the components that produce waste heat such as the engine, the turbo transmission, the brake, etc. and the cooling module with its fans. Given the operation of the locomotive e.g. in terms of speed vs. time along a track and its load, data from experimental full scale tests agree well with predictions from the time domain model. The onset of cooling fan operation is predicted well, with it their instantaneous energy consumption and sound radiation. Three optimized cooling unit assemblies for the new locomotive Voith Gravita 15L had been developed and pre-assessed utilizing the model and eventually tested in the locomotive under realistic operational conditions. A new thermodynamically advanced cooling unit with aerodynamically and acoustically optimized fans was found superior by approx. 2 dB (A) less sound power radiation and some 30% less energy consumption as compared to the benchmark. It is anticipated that those advantages are even more distinct as the ambient temperature decreases.
The work is part of the European FP7 transport research project ECOQUEST.
Acoustic Measurements of Perforated Liners in Hot and Pressurized Flow
Authors: Lahiri Claus , Knobloch Karsten , Bake Friedrich , Enghardt Lars 
Published: November 2013

Thermo-acoustic instabilities in gas turbine combustors can prevent the implementation of modern combustion concepts, which are essential for higher efficiency and lower emissions. Perforated combustor liners, especially in combination with a bias flow through the liner, are able to suppress the instabilities by increasing the acoustic losses of the system. Some insight into the parameter dependencies of the acoustic absorption has been gained by means of atmospheric testing at ambient temperature. The next step towards realistic testing conditions is taking into account high temperature and high pressure, which increases the effort of the experimental tests and the complexity of their analysis significantly. Tests in a real combustor can serve as a quality check of a given liner design, but are not appropriate for parameter studies. So far, numerical models accurate enough to enable the design of hot stream liners are simply not available, so that the experimental investigation of the liner’s dependency on temperature and pressure is essential for the transfer of laboratory scale results to a real engine application.
A new test rig has been designed to overcome these problems. The Hot Acoustic Test rig (HAT) enables the study of the influence of pressure and temperature on the damping performance in an acoustically well defined environment, although the high temperature and high pressure conditions are challenging in terms of accurate acoustic measurements.
This paper introduces the Hot Acoustic Test rig with its features and limitations and shows first examples of test results. The focus lies on the hardware, instrumentation, and analysis techniques that are necessary to obtain high quality acoustic data in hot and pressurized flow environments.
Ansaldo AE94.3A Combustion Improvement Towards Flexibility Through Extensive Field Testing
Authors: Malavasi Francesco , Pesce Paolo , Pesenti Alice Virginia , Traverso Paolo , Zito Domenico 
Published: November 2013

Being the European energy market in a sort of stagnation, flexibility is nowadays particularly profitable, with increasing care of environmental minimum load, maximum load and loading/unloading rate.
For its F class model AE94.3A4, Ansaldo Energia has identified two technical keys for success:
- Combustion stability
- Combustion efficiency
Thanks to a cooperation agreement with ENEL PRODUCTION, the largest Italian electricity utility, Ansaldo Energia had the possibility to design, introduce on one GT and test several combustion system modifications addressed to improve the performance of the whole GT by a synergy between proven design burners and cooling / sealing air optimization.
During 3 months, 5 combustion system configurations have been installed and tested on the GT made available from ENEL. Taking into account that each burner is equipped with different kinds of pilot injections, the number of effective tested configurations amounts to 11.
The configurations have been chosen in a large range of premixing ability, from high premixing to high diffusion rate. Due to the optimization of secondary air system, it has been necessary to install additional instrumentation in order to monitor the impact on the hot gas path components, with the aim of maintaining temperature conditions consistent with long life requirements.
In the end, 3 combustion configurations were identified as able to cover 3 ranges of environmental requirements as:
1 – High populated residential areas (NOx emission < 30 mg/Nm3)
2 – Medium populated or light industrial (NOx emission < 40 mg/Nm3)
3 – Very low populated areas or heavy industrial (NOx emission < 50 mg/Nm3)
Premixing is generally the more effective element to defeat N2 oxidation, with the side effect of making the combustion process particularly sensitive to pressure pulsations. So the efforts of the combustion designer have been spent to carefully modulate the injection of fuel in order to allow a good compromise between stability and emission.
Optimization of an Oxyfuel Combined Cycle Regarding Performance and Complexity Level
Authors: Dahlquist Adrian , Genrup Magnus , Sjoedin Mats , Jonshagen Klas 
Published: November 2013

The aim of this paper is to establish and motivate the design parameters of a 125 MW Oxyfuel Combined Cycle (OCC) also referred to as the Semi-Closed Oxyfuel-Combusted Combined Cycle (SCOC-CC). This paper proposes a compatible OCC that does not include any unconventional features, beyond what is state-of-the-art in gas turbine technology today. Such features could challenge the feasibility to bring the concept to the market in a reasonable time.
The OCC requires a higher pressure ratio compared to a conventional combined cycle in order to achieve exhaust conditions that fit the design of the bottoming cycle. However, a high gas turbine pressure ratio increases the complexity of the machine and must be weighted against the gain in efficiency. The OCC gas turbine is modeled using a cooling model which keeps the metal temperature of all cooled turbine stages constant while seeking the optimum pressure ratio.
As the cycle is semi-closed the compressor inlet temperature is a design parameter: it is shown that there is an efficiency optimum clearly in the range of what is normally achievable. As the gas properties of the OCC flue gas differ from the conventional plant, the effects of this on the HRSG design are explored.
Adaptive Flow Field Thermal Modeling Techniques for Turbine Rotor-Stator Cavities
Authors: Rey Villazón Jose Maria , Berthold Martin , Kühhorn Arnold 
Published: November 2013

At preliminary design stages of the turbine discs design process, reducing uncertainty in the thermal prediction of critical parts models is decisive to bid a competitive technology in the aerospace industry. This paper describes a novel approach to develop adaptive thermal modeling methods for non-gaspath turbine components. The proposed techniques allow automated scaling of disc cavities during preliminary design assessment of turbine architectures.
The research undertaken in this work begins with an overview of the past investigations on the flow field in cavities of the air system surrounding the turbine discs. A theoretical approach is followed to identify the impact of the design geometry and operation parameters of a simplistic rotor-stator cavity, with special focus on swirl and windage effects. Then, a parametric CFD process is set up to conduct sensitivity analysis of the flow field properties. The CFD sensitivity analysis confirmed the parameter influences concluded from the theoretical study.
The findings from the CFD automated studies are used to enhance the boundary conditions of a thermal FE-model of an actual high pressure turbine. The new set of thermal boundary conditions adapts the flow field to changes in the cavity parameters. It was found that the deviation to experimental data of the traditional preliminary modeling technique is about 4 times higher as the deviation of the CFD-enhanced technique. When running the FE-model through a transient cycle, the results from the CFD-enhanced method are significantly closer to the test data than those from the traditional method, which suggests there is high potential for using these adaptive thermal techniques during turbine preliminary design stages.
Modeling Unsteady Flow of a Lean Partially Premixed Flame on a Dry Low NOx Combustion System
Authors: Matarazzo Salvatore , Laget Hannes , Vanderhaegen Evert , Kok Jim B. W. 
Published: November 2013

The phenomenon of combustion dynamics (CD) is one of the most important operational challenges facing the gas turbine (GT) industry today. The Limousine project, a Marie Curie Initial Training network funded by the European Commission, focuses on the understanding of the limit cycle behavior of unstable pressure oscillations in gas turbines, and on the resulting mechanical vibrations and materials fatigue. In the framework of this project, a full transient CFD analysis for a Dry Low NOx combustor in a heavy duty gas turbine has been performed. The goal is to gain insight on the thermo-acoustic instability development mechanisms and limit cycle oscillations. The possibility to use numerical codes for complex industrial cases involving fuel staging, fluid-structure interaction, fuel quality variation and flexible operations has been also addressed. The unsteady U-RANS approach used to describe the high-swirled lean partially premixed flame is presented and the results on the flow characteristics as vortex core generation, vortex shedding, flame pulsation are commented on with respect to monitored parameters during operations of the GT units at Electrabel/GDF-SUEZ sites.
The time domain pressure oscillations show limit cycle behavior. By means of Fourier analysis, the coupling frequencies caused by the thermo-acoustic feedback between the acoustic resonances of the chamber and the flame heat release has been detected. The possibility to reduce the computational domain to speed up computations, as done in other works in literature, has been investigated.
Comparative Study of Solar Thermal Brayton Cycles Operated With Helium or Argon
Authors: Kusterer Karsten , Braun René , Moritz Norbert , Sugimoto Takao , Tanimura Kazuhiko , Bohn Dieter 
Published: November 2013

Concentrating Solar Power (CSP) plants often use Rankine cycles operated with water/steam as energy conversion cycles. Since the solar central receiver technology could provide receiver fluid outlet temperatures higher than 900°C, open and closed gas turbine technologies become a promising alternative. Closed solar Brayton cycles operating with appropriate fluids can reach similar or higher thermal efficiencies than water/steam Rankine cycles but have the advantage of less consumption of fresh water.
This paper presents the results of a comparative thermodynamic and process study of closed solar thermal Brayton cycles operated with Helium or Argon as working fluids. The main components of the cycles are two axial compressors with an intercooler, a recuperator and one axial turbine. The solar heat is fed in by a central receiver technology. It is assumed that the transferred heat to the cycles is constant and the turbine inlet temperature is 900°C.
A first one-dimensional design approach for both cycles is performed based on the results of the thermodynamic considerations. The major parameters like stage types, number of stages, rotational speed, etc. are determined and discussed.
The thermodynamic and process investigation results for the described closed Brayton cycles show that thermal efficiencies over 46% can be established for both fluids. The design considerations show that both cycles are feasible, but with respect to design dimensions the Argon based cycle can be built up with fewer stages and more compact, if compared to the Helium cycle.
Design and Operating Experience on the Recent Application of the Fuel Staging Technology for AE94.3A Gas Turbine
Authors: Alecci Marco , Bulli Alessia , Gottardo Enrico , Mori Giulio , Piana Carlo , Rio Roberto , Rizzo Sergio , Zito Domenico 
Published: November 2013

The paper describes the experience made on the first, recent application of the fuel staging technology on AE94.3A gas turbine engine. The experience started in the frame of combustion upgrade projects by the beginning of 2011 when some conceptual ideas rose.
The most effective solution was found in the application of radial fuel staging through the modification of an existing, dual fuel, diagonal swirler. CFD calculation was carried out in order to evaluate numerically the differences that the introduction of the radial fuel staging would have brought in comparison with the standard, reference configuration. After that one promising solution was selected and applied to a prototype, the test phase started. The experimental test was initially performed at the engine conditions on a high pressure test rig. The rig architecture was designed to be as representative as possible of the GT annular combustion chamber. The rig was equipped with the most advanced instrumentation in order to monitor and store all the main parameters of the burner during the test. High pressure tests showed a good agreement with the CFD calculation and an effective capability of the prototype to stage the fuel by generating a “co-pilot” flame. The word “co-pilot” was coined for the behaviour of the resulting flame to act as a second pilot in supporting and stabilizing the main premix flame. The on site validation was carried out on Enel La Casella GT1 power plant, downstream the upgrade of the gas turbine with the last recent AE94.3A model. The validation phase was performed according to two separate sessions: the first one using the standard, reference burner solution and the second one with the radial staged configuration.
The advantage of the fuel staging technique was twofold. The first one was concerning the minimum environmental load: the contribution of the fuel staging was approximately 7 MW. The second one was concerning the global performance of the whole combined cycle power plant at the base load. It was possible to increase turbine inlet temperature of about 30 °C and the GT power output of about +7% in comparison with the standard, reference burner solution.
Experimental Investigation of Flow Instability in a Turbocharger Ported Shroud Compressor
Authors: Gancedo Matthieu , Guillou Erwann , Gutmark Ephraim 
Published: November 2013

Turbocharger centrifugal compressors are equipped with a “ported shroud” to reduce flow instabilities at low mass flow rate. This passive stability control device using flow recirculation has been demonstrated to extend the surge margin of a compressor, without substantially sacrificing performance. However, the actual working mechanisms of the system remain not well understood.
In this paper, the relationship between inlet flow recirculation and instability control is studied using stereoscopic particle image velocimetry (PIV) in conjunction with dynamic pressure transducers at the inlet of a turbocharger compressor with and without a ported shroud. Both stable and unstable operational points are analyzed with use of phase-locked PIV measurements in surge.
Detailed description of unstable flow in a centrifugal compressor is presented with the reconstruction of the complex flow structure evolution at the compressor inlet during surge. Rather than one-dimensional, the surge flow is described by a three-dimensional axisymmetric structure of combined entering and exiting swirling flows, alternating in magnitude during the self-excited pressure cycle. The correlation between pressure and velocity measurements shows that the development of compressor unsteadiness is accompanied with swirling reversed flow at the impeller tip. The influence of the ported shroud on the inlet velocity flowfield is seen with the presence of localized flow recirculation. Stability improvement with a ported shroud is thus explained by removing swirling backflow at the impeller inducer tip and recirculating it to the impeller inlet to increase the near shroud inlet blade loading and incidence angle.
Mathematical Model of MCFC (Molten Carbonate Fuel Cell) for Power Plant Simulations
Authors: Milewski Jarosław , Wołowicz Marcin , Miller Andrzej 
Published: November 2013

An MCFC model concept is presented. The MCFC model was built in HYSYS.Plant environment is based on its standard libraries. The main elements of the MCFC model and chemical reactions are presented. Selected performance characteristics at the design point of MCFC are presented.
A new equation is given to define MCFC voltage, which was obtained based on new assumptions and which can be used instead of the classical approach.
On Kinematic Relaxation and Deposition of Water Droplets in the Last Stages of Low Pressure Steam Turbines
Authors: Starzmann J. , Kaluza P. , Casey M. V. , Sieverding Frank 
Published: November 2013

In the first part of the paper steady two-phase flow predictions have been performed for the last stage of a model steam turbine to examine the influence of drag between condensed fog droplets and the continuous vapour phase. In general, droplets due to homogeneous condensation are small and thus kinematic relaxation provides only a minor contribution to the wetness losses. Different droplet size distributions have been investigated to estimate at which size inter-phase friction becomes more important.
The second part of the paper deals with the deposition of fog droplets on stator blades. Results from several references are repeated to introduce the two main deposition mechanisms which are inertia and turbulent diffusion. Extensive post-processing routines have been programmed to calculate droplet deposition due to these effects for a last stage stator blade in three-dimensions. In principle the method to determine droplet deposition by turbulent diffusion equates to that of Yau and Young [1] and the advantages and disadvantages of this relatively simple method are discussed.
The investigation includes the influence of different droplet sizes on droplet deposition rates and shows that for small fog droplets turbulent diffusion is the main deposition mechanism. If the droplets size is increased inertial effects become more and more important and for droplets around 1 μm inertial deposition dominates. Assuming realistic droplet sizes the overall deposition equates to about 1% to 3% of the incoming wetness for the investigated guide vane at normal operating conditions.