bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design Consideration of Fogging and Wet Compression Systems as Function of Gas Turbine Inlet Duct Configurations
Authors: Chaker Mustapha , Mee Thomas R. 
Published: August 2015

Ambient temperature strongly influences gas turbine performance with power output dropping between 0.5 to 0.9 % for every 1 °C of temperature rise. This is accompanied by a significant increase in the heat rate, resulting in increased operating costs. As an increase in power demand often coincides with high ambient temperatures, power augmentation during the hot part of the day is of value to gas turbine operators. This is true for both the utility industry, where peak-rate power payments often apply, and to the petrochemical and process industries, where throughput can be improved or held constant as ambient conditions change. Evaporative fogging and wet compression are relatively low-cost solutions for recovering reduced gas turbine output.
This paper addresses the important design considerations for fogging and wet compression systems for different sized gas turbines with different duct configurations. These design considerations include the selection of appropriate ambient psychrometric design conditions, selection of appropriate fog nozzles and the optimization of fog nozzle manifold locations in the inlet ducts. For this research, Computational Fluid Dynamics (CFD) software is used to analyze the interaction between the atomized water droplets and the airflow within the confined geometry of inlet air ducts. The location of the nozzle manifolds is simulated in the inlet ducts for four different inlet duct configurations. Experimentally obtained spray data is used to simulated water atomization in the inlet ducts. The effect of the duct geometry is analyzed in term of fog-spray cooling efficiency based on both nozzle manifold location and droplet size distribution.
Mechanical Design and Manufacturing of Improved GT24 SEV Burner
Authors: Tschuor Remigi , Fruechtel Gerhard , De Jonge Jeffrey , Meng Patrik , Graber Christof 
Published: August 2015

This work details an integrative mechanical design process for combustion chambers. A major challenge in the development process of modern gas turbine combustors is to achieve low NOx emissions whilst ensuring the stability of the combustion process at all phases of the guaranteed operation regimes. The burner hardware plays a crucial role in determining emissions and maintaining a suitable aero- and thermo-acoustic performance of the combustion process. In addition, the burner hardware must be manufacturable at a reasonable cost. Efficient burner development requires a design process able to judge this behaviour at an early phase. This process must predict the combustor behaviour, the thermoacoustic mechanisms, the mechanical integrity as well as the life cycle of the burner. Based on the Alstom SEV (Sequential EnVironmental) burner for the reheat combustor of the GT24 gas turbine, this paper describes an exemplary process for the mechanical design, mechanical integrity, cooling and manufacturing. The acoustic aspects and the successful engine validation are addressed in separate papers.
The improved GT24 SEV burner has been developed with the following key features:
a) A Straight Mixing Zone aerodynamic design (SMZ) resulting in increased velocity and improved reactant pre-mixing
b) Multi-layered and braze constructed Front Panel design integrating combined and novel cooling and high frequency damping features
c) Optimised alloy selection for extended lifetime and improved manufacturability
In addition to the mechanical design and manufacturing process further details will be provided on aspects of cooling and mechanical integrity.
Development of a New Titanium 54’’ LSB: Static and Dynamic Assessment
Authors: Hlous Jan , Misek Tomas , Kubin Zdenek , Mestanek Petr 
Published: August 2015

Today’s power generation market requests high efficiency for steam turbines. One key factor in fulfilling these demands is the increase of exhaust area: efficiency is increased by reducing exhaust losses and lower costs are reached by a lower number of flows. The 54″ last stage blade for a steam turbine has been developed with the application of modern design features. It was designed with integral cover, mid-span tie-boss connection, and straight fir-tree dovetail. Blades are continuously coupled by the blade untwist due to the centrifugal force, so vibration control and increased structural damping are provided.
This paper describes in detail the design characteristics used in the development of the blade including non-linear structural analysis methods. The blade airfoil was optimized from point of view of minimization of its centrifugal force. The blade was well tuned in order to have natural frequencies safely away from possible excitation. Because of connection members, the number of the resonant vibration modes can be reduced by virtue of the vibration characteristics of the circumferentially continuous blades. Coupled rotor-blade frequencies were also analysed.
Extensive material tests were performed to check titanium properties, which showed lower erosion and low cycle fatigue properties. New procedures were developed to improve titanium characteristics, so the material behaviour is acceptable for last stage blade construction.
To validate the results, full scale rotational vibration test in vacuum chamber was carried out and suitable dynamic properties as well as mechanical integrity of the blade were confirmed.
Open Rotor Design Strategy: From Wind Tunnel Tests to Full Scale Multi-Disciplinary Design
Authors: Vlastuin Jonathan , Dejeu Clément , Louet Anthony , Talbotec Jérôme , Lepot Ingrid , Lonfils Timothée , Leborgne Michaël 
Published: August 2015

For several years, Safran has been involved in the design and optimization of contra rotating open rotors. This innovative architecture is known for allowing drastic reduction in fuel burn, but its development is facing complex technological challenges such as acoustics, aerodynamics, and weight penalty due to the mechanical complexity of an Open Rotor. Since 2010, Safran has been developing the experimental test bench HERA (1/5 mock-up scale) to improve the understanding of the complex aerodynamics and acoustics phenomena involved in the counter rotating propellers configuration. Isolated and installed low speed and high speed wind tunnel campaigns, including PIV measurements have been extremely helpful in defining design guidelines for full scale open rotor specification. These tests have been used as CFD feed-back among other purposes. An iterative process involving CFD optimization (in close collaboration with Cenaero) and wind tunnel test campaigns has been developed over the last 4 years and has led to the definition of an innovative design strategy, which has been successfully tested during the process of the full scale counter rotating propellers design for the SAGE2 ground test demonstrator engine. This phase has evidenced the absolute necessity of a multi-disciplinary design method when it comes to full scale and “rig-ready” design. Ensuring high propulsive efficiency and at the same time, minimizing the acoustic level, while maintaining severe mechanical constraints such as weight, inertia and proper dynamic positioning under control, requires a dedicated and integrated “all inclusive” design process.
The aim of this paper is to present the design methodology and some of the wind tunnel tests results carried out over the last 4 years, which have led to the definition of a novel multidisciplinary design methodology that involves CFD, FEM and acoustics.
A Practical Approach to Implementing Linear Elastic Fracture Mechanics in Gas Turbine Rotor Disk Analyses
Authors: Keller Scott 
Published: August 2015

The failure of vital components is not uncommon in the gas turbine industry. In the event excessive degradation occurs within a component, e.g. extensive cracking in a turbine blade or vane, solutions exist to either repair or replace defective parts. Such parts are readily accessible and mostly exchangeable in the field, limiting the amount of outage time and assessment required for defective parts. When more critical components exhibit extreme wear or cracking, e.g. a crack in a rotor disk, repairs typically necessitate a complete rotor destack and refurbishment or have the potential to require the replacement of individual disks. In extreme cases, defects found in rotor disks can be known to retire an entire compressor or turbine rotor. The OEM solution of replacing disks puts a substantial cost on the customer, thus providing an incentive for characterization and advanced analyses to determine the residual life in critical rotating components.
Considered an advanced analysis, linear elastic fracture mechanics (LEFM) provides the theory and fundamental structure to conduct crack growth analyses in components that exhibit nominally elastic behavior. Successful implementation of LEFM requires extensive characterization of the material, engine operating boundary conditions, and high fidelity finite element models. Upon the detection of a flaw, whether an internal or external indication, the results from finite element analyses can be used to derive the crack tip stress field and subsequent crack tip driving parameters. These parameters are then utilized in a comprehensive crack propagation model, calibrated to temperature- and load-dependent material data, to determine the number of cycles to unstable propagation. As a result, the remaining life of a component with a given indication is readily obtained, enabling our engineering team to provide a thorough life assessment of critical rotating components.
An overview of the linear elastic fracture mechanics crack growth analyses conducted is presented, with a special emphasis on compressor and turbine disks.
Consistent Conceptual Design and Performance Modeling of Aero Engines
Authors: Samuelsson Sebastian , Kyprianidis Konstantinos G. , Grönstedt Tomas 
Published: August 2015

During the conceptual design process of an engine, a thermodynamic cycle is initially defined. This is done to ensure that all aircraft requirements, defined in a number of discrete operating points, can be met. Critical component requirements can then be screened off from these operating points underpinning the conceptual design process. As an example, this has traditionally meant that aerodynamic sizing for low specific thrust turbofan engines occurs at top-of-climb and mechanical and temperature constraints are set at take-off.
By providing additional parameters indicating the level of technology assumed, such as diffusion factors and stage loadings, a basic geometric representation of the engine can be mapped out as part of the conceptual design process. However, by choosing the parameters representing the component technology levels explicitly, the ability to trade efficiency for weight, or efficiency for cost, becomes less potent. In general, an explicit parameter choice will mean that a suboptimal solution is found.
Hence, it makes sense to develop methods that allow including these technology parameters into the conceptual design and performance modeling process in a consistent way. If, for instance, component efficiency is modeled based on turbomachinery stage loading, including the stage loading parameters into the optimization means that the efficiency must be updated based on the stage loading variation. In general, a consistent method requires that conceptual design input is collected in a number of performance operating points, transferred into the conceptual design process and that output from the conceptual design process is returned to the optimizer.
To illustrate the consistent conceptual design and performance modeling process, turbomachinery component models are included in the paper, interrelating polytropic efficiency, Reynolds number, size effects and component entry into service. These equations are solved consistently in the conceptual design and performance modeling to establish an optimum year 2020 engine. The method is then further illustrated by comparing the year 2020 engine with two year 2030 engines. The first year 2030 engine is established by an optimization assuming fixed polytropic turbomachinery efficiencies. The other case is defined by assuming the same engine architecture, i.e., the same number of turbomachinery stages as the year 2020 engine. In this case, the efficiency modeling is done using a consistent conceptual design optimization. The consistent optimization produced a more efficient engine despite the fact that the stage numbers were limited to the year 2020 configuration. The benefit is obtained by more thoroughly exploring the pressure ratio distribution between the engine components, as a result of the consistent optimization methodology.
Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks
Authors: Dua Dipankar , Vasantharao Brahmaji 
Published: August 2015

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine.
This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach.
Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks.
Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives.
The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.
Loss Audit of a Turbine Stage
Authors: Yoon Sungho , Vandeputte Thomas , Mistry Hiteshkumar , Ong Jonathan , Stein Alexander 
Published: August 2015

In order to achieve high aerodynamic efficiency of a turbine stage, it is crucial to identify the source of aerodynamic losses and understand the associated loss generation mechanisms. This helps a turbine designer to maximize the performance of the turbine stage.
It is well known that aerodynamic losses include profile, endwall, cooling/mixing loss, leakage, and trailing edge loss components. However, it is not a trivial task to separate one from the others because different loss sources occur concurrently and they interact with each other in a machine. Consequently, designers tend to rely on various empirical correlations to get an approximate estimate of each aerodynamic loss contribution.
In this study, a systematic loss audit of an uncooled turbine stage has been undertaken by conducting a series of numerical experiments. By comparing entropy growth across the turbine stage, aerodynamic losses are broken down within the stator, rotor, and inter-bladerow gap. Furthermore, losses across each blade row are broken down into profile, leakage, endwall and trailing edge losses. The effect of unsteady interaction due to the relative motion of the stator and the rotor was also identified.
For the examined turbine stage, trailing edge losses of the rotor dominated, contributing to more than a third of the total aerodynamic loss. The profile loss across the stator and the rotor, unsteady loss between the stator and the rotor, and the stator endwall loss were also identified to be significant loss sources for this turbine stage. The design implications of the findings are discussed.
Numerical Analysis of Bladed Disk-Casing Contact With Friction and Wear
Authors: Almeida P. , Gibert C. , Thouverez F. , Ousty J.-P. 
Published: August 2015

In order to increase the aerodynamic performances of their engines, aircraft engine manufacturers try to minimize the clearance between rotating and stationary parts in axial and centrifugal compressors. Consequently, the probability of contact increases, leading to undesirable phenomena caused by forced excitation of the natural modes, or by modal interaction. Due to the complexity of these phenomena, many numerical studies have been conducted to gain a better understanding of the physics associated with them, looking primarily at their respective influence on potential unstable behaviors. However, the influence of other physical phenomena, such as friction and wear, remains poorly understood. The aim of this work is to show some effects associated with friction and wear on the dynamic behavior resulting from blade-to-casing interaction.
The numerical study reported here is based on a simplified finite element model of a rotating bladed disk and a flexible casing. The contact algorithm uses an explicit time marching scheme with the Lagrange multipliers method. Friction and wear are formulated using respectively Coulomb’s and Archard’s Laws. The rotational speed is set to critical speed giving rise to modal interaction between a backward mode of the casing and a counter-rotating mode of the bladed disk with one nodal diameter. Contact is initiated by a dynamic excitation of the stator.
In the presence of friction, the system becomes unstable when a sideband of the excitation frequency coincides with a one nodal diameter mode of the bladed disk. The introduction of wear leads to a vibration reduction, while the abradable material is removed by the wear process. The number of wear lobes produced on the casing is related to the ratio between the vibration frequency of the blades and the rotating speed. The ratio obtained by means of the FE model corroborates experimental observations.
Experimental and Tomography-Based CFD Investigations of the Flow in Open Cell Metal Foams With Application to Aero Engine Separators
Authors: de Carvalho Thiago P. , Morvan Hervé P. , Hargreaves David , Oun Hatem , Kennedy Andrew 
Published: August 2015

Oil-air separation is a key function in aero engines with closed-loop oil systems. Typically, aero engine air/oil separators employ the use of a porous medium such as open cell metal foams, as a secondary separation mechanism. Assessing its impact on overall separation is important since non-captured oil is released overboard. Computational fluid dynamics offers a possibility to evaluate the metal foam separation effectiveness.
A pore scale numerical modelling methodology is applied to determine the transport properties of fluid flow through open cell metal foams. Microcomputer tomography scans were used to generate a 3D digital representation of commercial open cell metal foams of different grades. Foam structural properties such as porosity, specific surface, pore size distribution and the minimum size of a representative elementary volume are directly extracted from the CT scans. Subsequently, conventional finite volume simulations are carried out on the realistic tomography-based foam samples. Simulations were performed for a wide range of Reynolds numbers. The feasibility of using standard Reynolds-averaged Navier-Stokes (RANS) turbulence models is investigated here. As part of the method validation, samples with varying lengths were simulated. Pressure drop values were compared on a length-normalized basis against in-house experimental data.
The oil phase was modelled using a Lagrangian particle tracking approach. Boundary conditions for the oil phase were extracted from a previous CFD simulation of a full breather device in the ground idle regime (worst separation effectiveness). Steady state particle tracking simulations were run for droplet diameters ranging from 0.5–15 μm, and for flow inlet velocities ranging from 10–60 m/s. Stochastic tracking was taken into account in order to model the effects of turbulence on the particle trajectories. Simulations were run on different types of foam and the results are compared qualitatively. The procedure has shown that pore scale modelling is a valid tool to capture the flow field and model oil separation inside open cell metal foams. However, at the moment there is no experimental data available for validation of the oil phase modelling.
Design Improvement Survey for NOx Emissions Reduction of a Heavy-Duty Gas Turbine Partially Premixed Fuel Nozzle Operating With Natural Gas: Experimental Campaign
Authors: Cerutti Matteo , Modi Roberto , Kalitan Danielle , Singh Kapil K. 
Published: August 2015

As government regulations become increasingly strict with regards to combustion pollutant emissions, new gas turbine combustor designs must produce lower NOx while also maintaining acceptable combustor operability. The design and implementation of an efficient fuel/air premixer is paramount to achieving low emissions.
Options for improving the design of a natural gas fired heavy-duty gas turbine partially premixed fuel nozzle have been considered in the current study. In particular, the study focused on fuel injection and pilot/main interaction at high pressure and high inlet temperature.
NOx emissions results have been reported and analyzed for a baseline nozzle first. Available experience is shared in this paper in the form of a NOx correlative model, giving evidence of the consistency of current results with past campaigns.
Subsequently, new fuel nozzle premixer designs have been investigated and compared, mainly in terms of NOx emissions performance. The operating range of investigation has been preliminarily checked by means of a flame stability assessment. Adequate margin to lean blow out and thermo-acoustic instabilities onset has been found while also maintaining acceptable CO emissions.
NOx emission data were collected over a variety of fuel/air ratios and pilot/main splits for all the fuel nozzle configurations. Results clearly indicated the most effective design option in reducing NOx. In addition, the impact of each design modification has been quantified and the baseline correlative NOx emissions model calibrated to describe the new fuel nozzles behavior.
Effect of inlet air pressure has been evaluated and included in the models, allowing the extensive use of less costly reduced pressure test campaigns hereafter. Although the observed effect of combustor pressure drop on NOx is not dominant for this particular fuel nozzle, sensitivity has been performed to consolidate gathered experience and to make the model able to evaluate even small design changes affecting pressure drop.