bluuebunny/crossref_metadata_2025_split huggingface dataset:
Torsional Robustness of the Combined Cycle Power Train Arrangement: Application of Statistical Methods to Accelerate Shaft-Line Design Cycles
Authors: Golebiowski Mateusz , Ling John P. C. W. , Knopf Eric , Niedermeyer Andreas 
Published: September 2016

This article presents the application of statistical methods to guide the rotordynamic design of a turbo-generator shaft-line. One of the basic requirements is all shaft components must survive the event of a short circuit at the terminals of the generator. This is typically assessed via a transient response simulation of the complete machine train (including generator’s electrical model) to check the calculated response torque against the allowable value. With an increasing demand of a shorter design cycle and competition in performance, cost, footprint and safety, the probabilistic approach is starting to play an important role in the power train design process.
The main challenge arises with the size of the design space and complexity of its mapping onto multiple objective functions and criteria which are defined for different machines. In the presented paper, the authors give an example demonstrating the use of statistical methods to explore (Design of Experiment) and understand (Surface Response Methods) the design space of the Combined Cycle Power Train with respect to the typically most severe constraint (fault torque torsional response), which leads to a quicker definition of a turbo-generator’s arrangement. Further statistical analyses are carried out to understand the robustness of the chosen design against future modifications as well as parameters’ uncertainties.
Suppression of Subsynchronous Vibrations in a 11 MW Steam Turbine Using Integral Squeeze Film Damper Technology at the Exhaust Side Bearing
Authors: Ferraro Riccardo , Catanzaro Michael , Kim Jongsoo , Massini Michela , Betti Davide , Livermore-Hardy Richard 
Published: September 2016

The presence of high subsynchronous vibrations and other rotordynamic instabilities in steam turbines can prevent operation at full speed and/or full load. The destabilizing forces generating subsynchronous vibrations can be derived from bearings, seals, impellers or other aerodynamic sources. The present paper describes the case of an 11 MW steam turbine, driving a syngas centrifugal compressor train, affected by subsynchronous vibrations at full load.
After the occurrence of anomalous vibrations at high load and a machine trip due to the high vibrations, the analysis of data collected at the site confirmed instability of the first lateral mode. Further calculations identified that the labyrinth seal at the balance drum was the main source of destabilizing effects, due to the high pre-swirl and the relatively tight seal clearance.
The particular layout of the turbine, a passing-through machine with a combined journal/double thrust bearing on the steam admission side, together with the need for a fast and reliable corrective action limited the possible solutions. Based on the analyses performed, adjusting the clearance and preload of the journal bearings could not have ensured stable operation at each operating condition. The use of swirl brakes to reduce the steam pre-swirl at the recovery seal entrance would have required a lengthy overhaul of the unit and significant labor to access and modify the parts. The final choice was a drop-in replacement of only the rear bearing (on the steam exhaust side) with a bearing featuring integral squeeze film damper (ISFD) technology. In addition to being a time efficient solution, the ISFD technology ensured an effective tuning of stiffness and damping, as proven by the field results.
The analyses carried out to understand the source of the subsynchronous vibrations and to identify possible corrective actions, as well as the comparison of rotordynamic data before and after the application of the bearing with ISFD technology, are discussed.
Experimental and Numerical Study of Heat Transfer Performance for an Engine Representative Two-Pass Rotating Internal Cooling Channel
Authors: Wang Zhi , Corral Roque , Chedevergne Francois 
Published: September 2016

This paper investigates, both experimentally and computationally, the heat transfer performance on an engine representative varying aspect ratio two-pass internal cooling channel, in both stationary and rotating conditions. The test geometry and design parameters were suggested by SNECMA as a representative HPT blade two-pass internal cooling channel. The cooling channel has radially outward flow in the first passage with an aspect ratio of 1:2.25 and after a 180 degree sharp turn, a radially inward flow in the second passage with an aspect ratio of 1:1.85. One side of the two passages is equipped with 45 degree angled rib turbulators with a rib spacing P/e=7 and blockage ratio e/Dh =0.116. The other side is smooth in order to have optical access for experiment.
The experiment was performed at three Reynolds numbers: 15,000, 25,000, and 35,000. Both forward and backward rotating directions were tested in order to study the heat transfer performance of the ribbed surface as trailing wall or leading wall individually. The tested Rotation numbers were Ro=±0.3 at Re=15,000 and Re=25,000, whereas the Rotation number was reduced to ±0.22 at Re=35,000, due to restrictions of the test facility. Infrared thermography technology is used to capture the temperature field for further evaluation of heat transfer performance.
Numerical simulations for all experimental cases were conducted using the same geometry including the air feeding system, applying the experimental wall temperature distribution in order to properly capture inlet and buoyancy effects, with the k–ω–SST turbulence model. Numerical results show overall agreement and similar trends than the experimental data. Numerical results also show that the rotation effects alter the internal flow significantly, resulting in different surface heat transfer distributions. Particularly, it is shown that heat transfer performance of the pressure side is not enhanced by the rotation in this study, which is a surprising result. This behavior was captured both in the experiments and the numerical predictions.
Alleviation of Shock-Wave Effects on a Highly Loaded Axial Compressor Through Novel Blade Shaping
Authors: John Alistair , Shahpar Shahrokh , Qin Ning 
Published: September 2016

This paper describes the use of the Free-Form-Deformation [1] parameterisation method to create a novel blade shape for a highly loaded, transonic axial compressor. The novel geometry makes use of pre-compression (via an S-shaping of the blade around mid-span) to weaken the shock and improve the aerodynamic performance.
It has been known for some time that reducing the pre-shock Mach number of transonic compressors (via pre-compression) can improve their efficiency [2]. However, early attempts at this in the 60s [3] showed undesirable results (such as bi-stable operation), leading the design community to shy away from using pre-compression [4]. This issue is re-addressed here. It is shown that using modern simulation, optimisation and a 3D design, large amounts of pre-compression may be employed without the negative effects that plagued early attempts.
This paper shows how Free-Form-Deformation offers superior flexibility over traditionally used parameterisation methods. The novel design (produced via an efficient optimisation method) is presented and the resulting flow analysed in detail. The efficiency benefit is over 2%, surpassing other results in the literature for the same geometry. The pre-compression effect of the S-shape is analysed and explained, and the entropy increase across the shock (along the mid-blade line) is shown to be reduced by almost 80%. Adjoint surface sensitivity analysis of the datum and optimised designs is presented, showing that the S-shape is located in the region predicted to be most significant for changes in efficiency. Finally the off-design performance of the blade is analysed across the rotor characteristics at various speeds.
Analytical Modeling and Experimental Validation of Heating at the Leaf Seal/Rotor Interface
Authors: Pekris Michael J. , Franceschini Gervas , Owen Andrew K. , Jones Terry V. , Gillespie David R. H. 
Published: September 2016

The secondary air system of a modern gas or steam turbine is configured to satisfy a number of requirements, such as to purge cavities and maintain a sufficient flow of cooling air to key engine components, for a minimum penalty on engine cycle efficiency and specific fuel consumption. Advanced sealing technologies, such as brush seals and leaf seals, are designed to maintain pressures in cavities adjacent to rotating shafts. They offer significant reductions in secondary air parasitic leakage flows over the legacy sealing technology, the labyrinth seal. The leaf seal comprises a series of stacked sheet elements which are inclined relative to the radial direction, offering increased axial rigidity reduced radial stiffness, and good leakage performance.
Investigations into leaf seal mechanical and flow performance have been conducted by previous researchers. However, limited understanding of the thermal behavior of contacting leaf seals under sustained shaft contact has led to the development of an analytical model in this study, which can be used to predict the power split between the leaf and rotor from predicted temperature rises during operation. This enables the effects of seal and rotor thermal growth and, therefore, implications on seal endurance and rotor mechanical integrity to be quantified. Consideration is given to the heat transfer coefficient in the leaf pack. A dimensional analysis of the leaf seal problem using the method of extended dimensions is presented, yielding the expected form of the relationship between seal frictional power generation, leakage mass flow rate and rotor temperature rise. An analytical model is derived which is in agreement. Using the derived leaf temperature distribution formula, the theoretical leaf tip temperature rise and temperature distributions are computed over a range of mass flow rates and frictional heat values.
Experimental data were collected in high speed tests of a leaf seal prototype using the Engine Seal Test Facility at Oxford University. These data were used to populate the analytical model, and collapsed well to confirm the expected linear relationship. In this form, the thermal characteristic can be used with predictions of mass flow rate and frictional power generated to estimate leaf tip and rotor temperature rise in engine operation.
Experimental Study of Mayenite-Based Catalysts Effectiveness in Reducing Pollution From Biomass Gasification in Fluidized Bed Reactors
Authors: Savuto E. , Borello D. , Di Carlo A. , Natali S. , Pantaleo A. , Rispoli F. 
Published: September 2016

Efficiency of catalyst materials used for tar reduction in biomass gasification plants is strongly affected by carbon deposition. For such reason, techniques for reducing catalyst poisoning are actively studied. Here the authors experimentally investigate the effectiveness of using a Mayenite support for Nickel catalyst. Mayenite was selected because it has a large number of free Oxygen anions that are able to combine with carbon producing COx and eventually prevent carbon deposition. [1] [2] [3].
Experiments are carried out with a bench scale gasifier coupled with a catalytic reactor in order to test the Nickel/Mayenite catalyst performance in the conversion of tar and methane. Ni/Mayenite catalyst is characterized by means of XRD, BET and SEM analyses before and after its use in the reactor, aiming to study carbon deposition and tar conversion efficiency.
In the tests carried out the tars present in major quantities like benzene, toluene and naphthalene reached conversions close to 100% in the first hour of test, and then stabilized to values of respectively 30%, 85% and 93%.
The catalyst was then subject to a regeneration procedure and then tested for some further hours, showing again very high conversion rates: benzene 92%, toluene 93% and naphthalene 96%.
The residual tars measured in the syngas are found to be lower than the limits imposed by the Biomass Technology Group [4] for feeding gas turbines; the syngas treated with the catalyst here developed can be thus considered suitable for the use in these energy production devices.
Effects of Total Pressure Inlet Distortion on Transonic Fan Blade Wake Properties
Authors: Ferrar Anthony M. , Schneck William , Wicks Alfred , O’Brien Walter 
Published: September 2016

This paper presents results of an experimental investigation of the impacts of total pressure distortions on the performance of a transonic turbofan. Fan rotor response to screen-produced total pressure distortions was measured by two high-frequency response probes (Kulite sensors). These probes measured the transient flow behind the fan rotor. Ensemble averaging based on a once-per-revolution encoder enabled separation of the pressure signal into its deterministic and stochastic components. The deterministic portion of the signal provided information about the effects of the distortion on the wake structure of the individual fan blades. The stochastic component of the signal gave indications of the effects of distortion on turbulence production (and losses) in the fan.
The qualitative trends provided by these high-frequency measurements show that the blade loading variations caused the wake depths and thicknesses to increase in the low pressure inlet regions. In addition, the turbulence production increased, peaking in the blade wakes. These behaviors indicate that the response of the fan was governed by a trailing edge separation that moves forward and backward on the upper blade surface in a dynamic manner.
This paper also includes discussion of the challenges associated with obtaining quantitative data with this type of probe. The results were significantly affected by probe frequency response and dynamic flow angle sensitivity. Resolving the blade wake structure and turbulence information requires probe tolerance to high-gradient flows and large flow angle fluctuations, with very high frequency response. The paper incorporates a discussion of improved probe design approaches to advance future research.
Operation of Reheat Combustors With Secondary Air Flow (SAF) Control Valves
Authors: Gao Xianfeng , Burri Daniel , Balmer Christian , Studerus Adrien 
Published: September 2016

GT26 reheat gas turbines have been continuously developed and upgraded to improve the engine performance and operational flexibility. In a standard SAF flow orifices configuration typically sized for the design point, the supply pressure ratios of secondary air flow systems for base-load operation vary over ambient temperatures. The adjustable secondary air flow control valves make the active control of the cooling air supply pressure ratios possible and could provide a customized cooling air consumption and adjust engine operation conditions. This control valve concept has been comprehensively tested and validated in Alstom test power plant and operated in customer engines.
This paper focuses mainly on combustor cooling improvement with this secondary air flow control valves. G26 reheat combustors with the adjustable secondary air flow control valves have improved significantly sequential combustor cooling and combustor performance. The supply pressure ratios of secondary air flow system over wide part load range which are originally lower and critical with a standard orifice configuration have been raised and results in more cooling air flows to the combustor cooling system than original standard orifice configuration. This increased cooling air flow improves SEV combustor liner and SEV burner cooling over large range of part load operation. The metal temperatures of the SEV liners and SEV burners are reduced significantly over part load, while the highest metal temperatures are recorded over part load operation with previously installed standard orifices configuration. In addition, the supply pressure ratios in secondary air flow systems with fixed throttling element are lower during oil operation than the corresponding ratios for fuel gas operation. The cooling supply pressure ratios in cooling systems with SAF control valves are optimized to supply the required combustor cooling air flow for oil operation. The optimized cooling can also be achieved through adjustment of SAF control valves for high-fogging (HF) engines between dry operation and wet operation. In addition, pulsation reduction at oil operation can be achieved by fully opening of MBH30 control valve.
Advanced and Transformational Hydrogen Turbines for Integrated Gasification Combined Cycles
Authors: Shelton Walter W. , Ames Robin W. , Dennis Richard A. , White Charles W. , Plunkett John E. , Fisher James C. , Dalton Richard P. 
Published: September 2016

The U.S. Department of Energy’s (DOE) provides a worldwide leadership role in the development of advanced fossil fuel-based energy conversion technologies, with a focus on electric power generation with carbon capture and storage (CCS). As part of DOE’s Office of Fossil Energy, the National Energy Technology Laboratory (NETL) implements research, development, and demonstration (RD&D) programs that address the challenges of reducing greenhouse gas emissions. To meet these challenges, NETL evaluates advanced power cycles that will maximize system efficiency and performance, while minimizing CO2 emissions and the costs of CCS. NETL’s Hydrogen Turbine Program has sponsored numerous R&D projects in support of Advanced Hydrogen Turbines (AHT). Turbine systems and components targeted for development include combustor technology, materials research, enhanced cooling technology, coatings development, and more. The R&D builds on existing gas turbine technologies and is intended to develop and test the component technologies and subsystems needed to validate the ability to meet the Turbine Program goals. These technologies are key components of AHTs, which enable overall plant efficiency and cost of electricity (COE) improvements relative to an F-frame turbine-based Integrated Gasification Combined Cycle (IGCC) reference plant equipped with carbon capture (today’s state-of-the-art). This work has also provided the basis for estimating future IGCC plant performance based on a Transformational Hydrogen Turbine (THT) with a higher turbine inlet temperature, enhanced material capabilities, reduced air cooling and leakage, and higher pressure ratios than the AHT.
IGCC cases from using system-level AHT and THT gas turbine models were developed for comparisons with an F-frame turbine-based IGCC reference case and for an IGCC pathway study. The IGCC pathway is presented in which the reference case (i.e. includes F-frame turbine) is sequentially-modified through the incorporation of advanced technologies. Advanced technologies are considered to be either 2nd Generation or Transformational, if they are anticipated to be ready for demonstration by 2025 and 2030, respectively. The current results included the THT, additional potential transformational technologies related to IGCC plant sections (e.g. air separation, gasification, gas cleanup, carbon capture, NOx reduction) are being considered by NETL and are topics for inclusion in future reports.
Experimental Investigation of a SOFC/MGT Hybrid Power Plant Test Rig: Impact and Characterization of a Fuel Cell Emulator
Authors: Hohloch Martina , Huber Andreas , Aigner Manfred 
Published: September 2016

The main topic of the paper is the experimental investigation of a solid oxide fuel cell (SOFC) / micro gas turbine (MGT) hybrid power plant test rig. This comprises the proof of concept, the characterization of the operational range and the influence of the coupling on the MGT. The operational concept of the hybrid power plant is designed to reach a maximum flexibility in electrical power output. Therefore the power plant is operated at different MGT shaft speeds and electrical power outputs of the SOFC, thus leading to different SOFC temperatures.
Instead of a real fuel cell an emulator was developed and built to emulate the fluid dynamic and thermodynamic behavior of a real SOFC. The test rig is based on a Turbec T100PH micro gas turbine. A specially designed interface connects the facility to the tubing system and the SOFC emulator. For the present investigation the SOFC emulator has been equipped with a gas preheater. It emulates the varying heat output of the fuel cell. The gas preheater is composed of a natural gas combustor based on the FLOX® technology, with a swirl-stabilized pilot stage and allows a wide range of emulating different SOFC outlet temperatures. In addition installations have been integrated into a pressure vessel, representing the SOFC cathode volume, to analyze the increase in residence time and pressure loss.
Initially three different configurations of the test rig, no SOFC emulator – tube only, SOFC emulator with pressure vessels and fully equipped SOFC emulator (pressure vessels, installations and gas preheater) are compared regarding the influence of the different volumes, residence times and pressure losses. The operating range of the test rig equipped with gas preheater in cold (no fuel) as well as in hot conditions is investigated. As the velocity at the entrance of the gas turbine combustor increases with increased fuel cell outlet temperature the surge margin is strongly influenced. The operating range was determined for different shaft speeds and preheating (SOFC outlet) temperatures. Finally the transient behavior of the gas preheater and its impact on the MGT is analyzed. The results provide the required basis to implement a cyber physical system, in which the SOFC emulator is controlled by a SOFC model, as well as the basis for the real coupling of MGT and SOFC.