bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Turbocharged Turbogenerator
Authors: Rodgers C. 
Published: December 2013

Turbocharging generally implies the attainment of higher power through increased piston engine air inlet charge density. Turbocharging has too been visualized for gas turbines in the form of an exterior or integrated low pressure compressor and turbine spool module boosting a high pressure power producing spool.
This “turbocharged” cycle has been previously developed for both simple and intercooled recuperative cycles (ICR) gas turbine versions, the latter of which are recognized as one of the most thermally efficient Brayton cycles.
The two spool ICR flowpath with a separate power turbine has been extensively pursued for vehicular and marine applications accompanied with commercialized versions of large turbofans with low pressure (LP) spool power, yet the application of a two spool ICR counterpart with power extraction from the HP spool has been sporadic.
This paper focuses upon the thermodynamic performance and transient operating characteristics of non-concentric two spool non-recuperated Brayton cycles. A hypothetical “turbocharged” adaptation of an existing conventional single shaft 150kW turbogenerator simple cycle gas turbine is chosen as an example with which to portray the concept advantage of increased specific power yet inherent characteristic of diminished hot day performance.
On the Nonlinear Dynamics of Two Types of Backup Bearings: Theoretical and Experimental Aspects
Authors: Lahriri Said , Santos Ilmar F. , Weber Hans I. , Hartmann Henning 
Published: December 2013

The possible contact between rotor and stator can for some cases be considered as a serious malfunction that may lead to catastrophic failure. Rotor rub is considered a secondary phenomenon caused by a primary source that leads to a disruption of the normal operational condition. It arises from sudden mass unbalance, instabilities generated by aerodynamic and hydrodynamic forces in seals and bearings among others.
The contact event gives rise to normal and friction forces exerted on the rotor at impact events. The friction force plays a significant role by transferring some rotational energy of the rotor to lateral motion, impacting the stator. This event results in persistent coupled lateral vibration of the rotor and stator. This paper proposes a new unconventional backup bearing design in order to reduce the rub related severity in friction. The idea is to utilize pin connections that center the rotor during impacts. In this way, the rotor is forced to the center and the lateral motion is mitigated. The four pins are passively adjustable, which allows the clearance to be customized.
A mathematical model has been developed to capture phenomena arising from impact for the conventional backup bearing (annular guide) as well for the new disk-pin backup bearing. For the conventional annular guide setup, it is reasonable to superpose an impact condition to the rub, where the rotor spin energy can be fully transformed into rotor lateral movements. Using a non ideal drive, i.e. an electric motor without any kind of velocity feedback control, it is even possible to almost stop the rotor spin under rubbing conditions. All the rotational energy will be transformed in a kind of “self-excited” rotor lateral vibration with repeated impacts against the housing. The vibration of the housing is coupled through the interaction force.
The experimental and numerical analysis shows that for the conventional annular guide setup, the rotational energy is fully transformed into lateral motion and the rotor spin is stopped. However, by employing the new disk-pin design the analysis shows that the rotor at impacts is forced to the center of the backup bearing and the lateral motion is mitigated. As a result of this, the rotor spin is kept constant.
Development of High Temperature Gas Turbine Matrix Microrecuperator Made of Laser Sintered Ceramic and Metal Structural Materials
Authors: Sudarev A. V. , Suryaninov A. A. , Sudarev B. V. , Konakov V. G. 
Published: December 2013

Analysis of trends in the development of small gas turbine engines (GTE) has shown that a significant increase in the parameters of the working media required to increase their efficiency and competitiveness in the energy market is limited by the reduced efficiency of small size blading of compressors and turbines [1].
Structural ceramic materials (SCMs), which has high heat resistance and relatively low density, allows development of light-weight and compact heat exchangers for regeneration of heat in the GTE’s which are suitable for continuous operation at the gas temperatures above 1000°C [2].
A design of the heat exchange surface for a countercurrent regenerative AH with a matrix consisting of coaxial cylindrical shells, each of which is made of heat elements (HE) in the form of circular perforated plates of equal width and different diameters, is proposed. The shells are embedded in one another and form a cylindrical matrix with longitudinal channels of circular (air) and semicircular (gas) cross sections.
The AH matrix in the area with the gas temperature over 650°C is made of SMC, while within a zone with lower temperature operation it is made of the heat-resistant alloy. The AH metal matrix model was tested with various coolants in model paths: “air-water”, “water-air” and “air-to-air.”
The experimental results confirmed the data of the thermal-engineering calculations. Such a sintered heat exchanger was designed for microGTE of 2 kW. At the present time it is being fabricated. Bench tests are scheduled for September-November 2012.
Three-Dimensional Viscous Flutter Analyses of a Turbine Cascade in Subsonic and Transonic Flows
Authors: Micallef Derek , Witteck Dirk , Wiedermann Alexander , Kluß David , Mailach Ronald 
Published: December 2013

In the present contribution the results of two three-dimensional viscous flutter analyses for a turbine cascade, Standard Configuration no. 11, are presented. The steady state and transient flow simulations were performed using the commercially available CFD solver ANSYS CFX 13.0 and a modified version of the CFD solver TBLOCK developed by Denton which is widely used in turbomachinery industry. The flutter analyses are performed under two different flow conditions. A subsonic, attached flow case and an off-design transonic case with a separated flow region near the trailing edge and a normal shock which are both located on the suction side. For each flutter analysis, the aeroelastic solution is computed for a large number of interblade phase angles. The results of ANSYS CFX and TBLOCK are compared to one another as well as to other CFD codes and experimental data. To reduce computing time, a phase-shifted boundary condition was implemented in TBLOCK. First results are shown in comparison to ANSYS CFX and its new implemented Fourier transformation method.
The results of TBLOCK and ANSYS CFX agree well with experimental results. First results applying the phase-shifted boundary condition show that this method is suitable for calculating the aerodynamic damping with less numerical effort.
Helium Brayton Cycles With Solar Central Receivers: Thermodynamic and Design Considerations
Authors: Kusterer Karsten , Braun René , Moritz Norbert , Lin Gang , Bohn Dieter 
Published: December 2013

Concentrated Solar Power (CSP) technologies are considered to provide a major contribution for the electric power production in the future. Several technologies for such kind of power plants are already in operation. Parabolic troughs, parabolic dishes, Fresnel multi-facet reflectors or heliostats in combination with a central receiver are applied for concentration of the solar irradiation. The energy conversion cycles usually are water/steam cycles (Rankine cycles), but also open gas turbine cycles (Brayton cycle) or combined cycles are possible. One option is to apply closed Brayton cycles using fluids like carbon dioxide or helium.
With respect to commercial considerations, the main parameter driving the decision on which cycle to apply for energy conversion is the thermal efficiency of the process. This is due to the fact, that in case of a power plant without additional fuel supply, no fuel costs have to be considered to determine the levelized electricity costs (LEC). Thus, in the first place the capital costs determine the LEC. In CSP plants one main driver for the capital costs are the heliostats and the mirror size, which are necessary to generate the desired amount of electric power. The necessary solar aperture area directly depends on the thermal efficiency of the energy conversion cycle.
In this paper different closed Helium Brayton Cycles for application with solar central receivers are analyzed thermodynamically. The thermodynamic calculations are performed by application of a self-developed thermodynamic calculation software, which considers the real gas properties of the fluid. The software calculates the cycle’s thermodynamic diagrams (e.g. T-s-, h-s-diagrams) and determines its efficiency.
The results show that thermal efficiencies of approximately 46.6% (and higher) can be reached with a Helium Brayton Cycle. One important parameter is the turbine inlet gas temperature, which is not less than 900 °C. This means that the pressurized receiver for this technology has to bear even higher temperatures.
Furthermore, the paper deals with design considerations for compressor and turbine within the closed Helium Brayton Cycle. Based on dimensionless parameters, the major parameters like stage types, number of stages, rotational speed etc. are determined and discussed.
On the Design and Matching of Turbocharger Turbines for Pass Car Gasoline Engines
Authors: Gugau Marc , Roclawski Harald 
Published: December 2013

With emission legislation becoming more stringent within the next years, almost all future internal combustion gasoline engines need to reduce specific fuel consumption, most of them by using turbochargers. Additionally, car manufactures attach high importance to a good drivability, which usually is being quantified as a target torque already available at low engine speeds that is fast reached in transient response operation. These engine requirements result in a challenging turbocharger compressor and turbine design task, since for both not one single operating point needs to be aerodynamically optimized but the components have to provide for the optimum overall compromise for maximum thermodynamic performance. The component design targets are closely related and actually controlled by the matching procedure that fits turbine and compressor to the engine. Inaccuracies in matching a turbine to the engine full load are largely due to the pulsating engine flow characteristic and arise from the necessity of arbitrary map extrapolation to low turbine blade speed ratios and the estimation of turbine efficiency for low engine speeds.
This paper addresses the above described standard problems, presenting a methodology that covers almost all aspects of thermodynamic turbine design based on a comparison of radial and mixed flow turbines. Wheel geometry definition with respect to contrary design objectives is done using CFD, FEA and optimization software. Parametrical turbine models, composed of wheel, volute and standard piping allow for fast map calculation similar to steady hot gas tests but covering the complete range of engine pulsating mass flow. These extended turbine maps are then used for a particular assessment of turbine power output under unsteady flow admission resulting in an improved steady state matching quality. Additionally, the effect of various design parameters like either volute sizing or the choice of compressor to turbine diameter ratio on turbine blade speed ratio operating range as well as its inertia is analyzed. Finally, this method enables the designer to comparatively evaluate the ability of a turbine design to accelerate the turbocharger speed for transient engine response while still offering a map characteristic that keeps fuel consumption low at all engine speeds.
Steam Turbine Inlet Geometry From a Structural and Fluid Dynamics Point of View
Authors: Hecker Simon , Rohe Andreas , Stoff Horst 
Published: December 2013

This work presents guidelines for designing a ring-type inlet duct of an intermediate pressure steam turbine. It looks at aerodynamic characteristics of the flow field in the analyzed ducts as well as the impact of the duct topology on the radial clearances influencing casing deformations in different load cases.
To show the reliability of the CFD-program used, calculated results are compared to measured data. The numerical method reflects the main physical effects observed in the reference cases with high accuracy.
The inlet duct shape influences the loss of total pressure within the duct and the following stator blades as well as the leakage losses in the whole turbine casing. To minimize these losses, geometric parameters such as area ratios within the duct and the shape of its flow channels, are considered and the influence of these parameters on the losses is quantified. The optimization of the inlet duct leads to a geometry with minimum losses from an aerodynamic and mechanical point of view.
Practical Aspects of Fatigue Crack Growth in Aero-GTE Applications
Authors: Lenets Youri N. 
Published: December 2013

In an attempt to mitigate future accidents and to harmonize the U.S. and European engine certification requirements, the Federal Aviation Administration (FAA) has recently revised engine certification standards related to the design of engine life-limited parts, also called “critical parts” in European regulations. The updated rule introduces new requirements for engine manufacturers to conduct damage tolerance assessment of all rotating structural parts as well as major static structural parts whose primary failure is likely to result in hazardous engine effects.
Several practical aspects of such damage tolerance assessment, centered on the fatigue crack growth (FCG) testing of aero-GTE materials, are considered in the following. They include, but are not limited to the discussion of the appropriate test specimen geometry and conditions to characterize the behavior of relatively small semi-elliptical cracks emanating from highly stressed surface locations, and fundamental features of the test data analysis. Two novel test approaches — compression pre-cracking and focused ion beam notching — are discussed in detail and associated methodologies developed to study slow FCG and small crack anomalies, respectively, are illustrated by examples.
Development of a Generalized LCF-TMF Lifing Model for a Nickel-Base Superalloy
Authors: Buchholz Björn , Gampe Uwe , Beck Tilmann 
Published: December 2013

The growing share of power generation from volatile sources such as wind and photovoltaics requires fossil fuel fired power generation units be available and capable of high load flexibility to adjust to the changing capacity of the electrical grid. Additionally, back-up units with quick start capability and energy storage technologies are needed to fill the power shortfall when volatile sources are not available. Gas turbine and combined-cycle gas and steam turbine power plants are able to meet these demands. However, safe component design for improved cycling capability, combined with optimum utilization of material regarding its mechanical properties, requires design procedures and lifing models for the complex loadings resulting from this increased volatility of power demand. Since hot gas path components like turbine blades and vanes are highly stressed by cyclic thermal and mechanical loadings, resulting Thermo-Mechanical Fatigue (TMF), life prediction models such as the classic strain-life Coffin-Manson-Basquin method do not capture the influences of thermal cycling satisfyingly. Advanced TMF prediction models are thus necessary to accurately predict the durability of hot section components.
This paper addresses life prediction of the Nickel-base superalloy René 80 at elevated temperature for various loading conditions. For this purpose, isothermal Low Cycle Fatigue (LCF) and corresponding TMF tests, with various temperature ranges and thermal-mechanical phase shifts, have been performed. On this basis, a systematic approach has been developed which allows assessing the key influences on TMF life. Moreover, a generalized model for fatigue has been derived, which has the potential to predict TMF life on the basis of LCF data. The knowledge gained from the model development allows an improved life prediction and better utilization of the material capabilities. Additionally, the required number of material tests for a general insight in the materials behaviour can be reduced significantly.
Power Loss in High-Speed Micro Turbomachinery: An Experimental Study
Authors: Walton James F. , Heshmat Hooshang , Tomaszewski Michael 
Published: December 2013

In the paper the authors present the results of a study to investigate the windage and foil bearing losses in modern high-speed micro-turbomachinery such as motors, turboexpanders and turbogenerator rotor systems. Areas investigated include clearance between rotor and static structure; surface roughness; and ambient pressure conditions. Comparisons between experiments and theoretical windage loss models show excellent correlation at high speeds. Testing also indicated that some optimum rotor stator gaps are possible to minimize windage loss and that surface roughness can significantly impact windage. It was also shown that for rotor systems with foil bearings, at lower speeds rapid deceleration occurs. This is most likely due to the reduction in film thickness and onset of asperity contact between rotor and bearing surfaces. As expected ambient pressure also impacts windage losses.
The theoretical rotor windage loss models, their range of applicability and key limitations of those loss models are discussed. While bearing losses are not included in theoretical windage loss models, it was shown that they do need to be considered, especially when developing very high speed motor/generators. Approaches to properly account for the wide array of losses in order to develop high power density power sources are recommended.
Experimental and Numerical Investigation Into the Aerodynamics of a Novel Steam Turbine Valve and its Field Application
Authors: Zanazzi Giorgio , Baumgartner Felix , Rice Timothy , Pengue Fabio , Mokulys Thomas , Ridoutt Colin , Sell Michael 
Published: December 2013

Control valves are one of the key steam turbine components that guarantee operational safety in a power plant.
There are two aerodynamic aspects, which are the current focus for the development of Alstom’s valves. One is the reduction of the aerodynamic loss to increase the efficiency of the power plant. The other is operational flexibility, which is increasingly demanded to react faster to load requirements from the electric grid. This is becoming more important as power generation becomes increasingly decentralized, with a growing contribution from renewable energy sources. For this reason, a fast control loop is required for valve operation, which depends on an accurate linearization of the valve characteristic.
In this paper the flow fields in an existing steam control valve have been analysed and subsequently optimized using CFD techniques. The approach specifically designed for drilled strainers is further illustrated. Following the validation of the baseline design with model testing, an improved diffuser has been designed using CFD analysis and the resulting performance benefit has been confirmed with further testing.
The required grid frequency support requires control valve throttling. For this reason, an accurate prediction of the linearization table is extremely important to support the required response time limits. Further numerical work has been carried out with various opening positions of the valve, leading to an improved valve linearization characteristic. It is demonstrated that the numerical prediction of the linearization curve agrees very well with data obtained from operating power plants.
Cast-in-Pair Blade Release Simulation and Comparison to Experiments With a Full Scale Rig
Authors: Cristóbal Erlantz , Moñux Sergio , Cerezo Carlos , Cendón David , Galvez Francisco , Erice Borja 
Published: December 2013

This paper deals with the simulation of a Low Pressure Turbine (LPT) blade release and the subsequent impact onto the casing. The blade design is a cast-in-pair novel configuration where two airfoils are attached to a single firtree. This design solution was implemented in the first stage of the Low Pressure Turbine of the TP400-D6 engine using a directionally solidified M247 alloy. Due to the novelty of the design configuration a case containment test was carried out for certification versus CS-E810 EASA airworthiness requirement. The test was full scale reproducing engine-operating temperature and red line rotational speed.
The objective of the present work is the simulation of the blade release failure event including the interaction with the trailing blades and the severe impact onto the casing. The simulation is compared and validated against the results of the full-scale rig.
Material behaviour under impact working condition is characterised through Hopkinson bar tests, ballistic tests and triaxial traction tests. Johnson-Cook constitutive and failure material models are generated for the blade casting, the case forge material and the shroud seal segment. This material model is a temperature and strain-rate dependant flow stress model.
Containment simulation is carried out with LS-DYNA implicit/explicit solver. Simulation work includes meshing and boundary conditions effects on model fidelity. Case damage progression is linked to each of the different airfoil portions as contact occurs. The friction contribution to the case and blades interface and to the case final form is also revised.
In addition, the importance of the trailing blades and the interaction with the released blade is assessed. Interaction effect comprises both the resulting damage between airfoils and the change in primary release trajectory.
Finally, simulation results are compared to the full scale rig results. Case-impacted final geometry and internal energy from simulation are checked against test evidences.
Experimental and Numerical Investigations on a Rotating Centrifugal Compressor
Authors: Almeida Patricio , Gibert Claude , Leblanc Xavier , Ousty Jean-Philippe , Thouverez Fabrice 
Published: December 2013

Controlling the dynamic behavior of turbomachines requires an experimental validation phase to ensure their safety. The application of two experimental techniques to measure the modal properties of a rotating centrifugal compressor impeller is described in this paper. The impeller was tested in a vacuum chamber with excitation provided by piezoelectric actuators mounted on the rear side of the impeller disk.
The most common technique used to measure the dynamic behavior of a rotating structure is based on strain gauges and a telemetry system or a slip ring for signal transmission. Nevertheless, in some cases this method is an intrusive technique that could introduce damping and blade mistiming, and it can also be time consuming to prepare. Strain gauge measurement has been compared to measurements performed under the same conditions by Scanning Laser Doppler Vibrometer associated with a derotator optical system, which allows measurement at fixed points on a rotating part.
This work focuses on the study of the dynamic behavior of a centrifugal compressor impeller in view to preparing stator contact interaction tests requiring precise characterization of frequencies and nodal diameters and of the influence of rotation speed and other possible parameters.
The advantages and disadvantages of the two methods used have been assessed for this particular application. A correlation between the experiments and the numerical simulations using the finite element method is provided.