bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotordynamic Computational and Experimental Characterization of a Convergent Honeycomb Seal Tested With Negative Pre-Swirl, High Pressure With Static Eccentricity and Angular Misalignment
Authors: Vannini Giuseppe , Mazzali Carlo , Underbakke Harald 
Published: September 2016

Hole-pattern or honeycomb seals have been commonly used for many years in the Oil & Gas industry as damper seals for turbomachinery. The main motivation has been to introduce additional damping to improve the shaft rotordynamic stability operating under high pressure conditions.
Experience has shown that the dynamic and even static characteristics of those seals are very sensitive to the operating clearance profile as well as the installation tolerances. Rotordynamic stability is related not only to the seal effective damping but to the effective stiffness as well. In fact, for this kind of seal, the effective stiffness can be high enough to alter the rotor system’s natural frequency. The seal stiffness is strictly related to the tapering contour: if the clearance profile changes from divergent to convergent, the effective stiffness may change from a strong negative to a strong positive magnitude, thus avoiding the rotor natural frequency drop as it is detrimental for the stability. Unfortunately the effective damping is reduced at the same time but this can be improved using proper devices to keep the pre-swirl low or even negative (e.g. swirl brakes, shunt holes).
This paper presents the results from an extended test campaign performed in a high-speed rotor test rig equipped with active magnetic bearings working under high pressure (14krpm, 200bar gas inlet pressure), with the aim to validate the rotordynamic characteristics of a negative pre-swirl, convergent honeycomb seal and demonstrate its ability to effectively act as a gas bearing as well as a seal.
The test plan included variations of inlet pressure, differential pressure (given the same inlet pressure) as well as rotational speed in order to fully validate the seal behaviour. This kind of test was performed in a “dynamic mode”, exciting the spinning test rotor through a pair of AMBs along linear orbits.
Additionally the impact of the seal to rotor static eccentricity and the seal to rotor angular misalignment were both experimentally investigated and compared to relevant CFD simulations. This kind of test was performed in a “static mode”, imposing through the AMBs the required eccentricity / angular misalignment and then measuring the forces needed to keep the rotor in the original position. “Dynamic mode” test was also performed in order to check the impact of the seal static eccentricity on its dynamic behaviour.
Finally the test results were compared with predictions from a state of the art bulk flow code in order to check the predictability level for future design applications.
Quasi 2D Flow-Adaptive Algorithm for Pneumatic Probe Measurements
Authors: Bartsch Christian , Hölle Magnus , Jeschke Peter , Metzler Timo 
Published: September 2016

The subject of this paper is a flow-adaptive measurement grid algorithm developed for 1D and 2D flow field surveys with pneumatic probes in turbomachinery flows. The algorithm automatically determines the distribution and the amount of measurement points needed for an approximation of the pressure distribution within a predefined accuracy.
The algorithm is based on transient traverses, conducted back and forth in the circumferential direction. The dynamic response of the pressure-measuring system is disregarded during the traverses, which serve to detect changes in the pressure field. In contrast to previous investigations by the authors, a correction of the dynamic response is applied by deconvolving the transient measurement data using the information embedded in both transient measurements. In consequence, the performance of the algorithm is — to a large extent — independent of the transient traversing speed and the geometry of the pressure-measuring system. Insertion and removal strategies are incorporated in order to reduce measurement points and increase robustness towards differing flow field conditions. By approximation of the pressure distribution, the flow-adaptive measurement data is suited for the application of post-processing corrections without any constraints. The performance of the algorithm is demonstrated for 2D flow field surveys with a pneumatic 5-hole probe in an annular cascade wind tunnel. Compared to conventional techniques for data sampling, e.g., uniform measurement grids, the measurement grid points are automatically adjusted so that a consistent resolution of the flow features is achieved within the measurement domain. Furthermore, the application of the algorithm shows a significant reduction in the number of measurement points. Compared to the measurement duration based on uniform grids, the duration is reduced by at least 7%, while maintaining a high accuracy of the measurement.
The purpose of this paper is to demonstrate the performance of measurement grids adapted to local flow field conditions. Consequently, valuable measurement time can be saved without a loss in quality of the data obtained.
Calculation of Enthalpy and Entropy From Experimentally Measurable Quantities
Authors: Coogan Shane , Brun Klaus , Simons Sarah , Ridens Brandon , Kurz Rainer 
Published: September 2016

In the design and testing of gas compressors, the correct determination of the thermodynamic properties of the gas, such as enthalpy, entropy, and specific volume from pressure, temperature, and composition, plays an important role. Due to the wide range of conditions encountered, pressure, specific volume and temperature (p-v-T) equations of state (EOS) are used to determine the isentropic or polytropic efficiency, the work input, and capacity of a compressor configuration. However, accurate equations of state may be lacking for some more complicated gas mixtures. Experimentally determined thermodynamic state information is more accurate and is needed to validate, correct, or supplant existing equations of state.
The methodology for calculating enthalpy and entropy from experimental data is presented including the full step-by-step derivation from first principles. The thermodynamic relations or calculus properties used in each step of the derivation are clearly identified to provide traceability and encourage verification. Results are presented in three forms to match all possible tabulation formats of temperature, pressure, and volume data. Calculation methods for other useful but unmeasured thermodynamic properties such as the specific heat at constant pressure and the ratio of specific heats are also given. The methodology is demonstrated in two examples. The first is a verification case where REFPROP, an equation of state software, is used to generate input data, and the enthalpy and entropy values calculated from the input data are shown to match those given directly by REFPROP. The second is a practical demonstration where the methodology is used with actual experimental data.
Conjugate Heat Transfer Analysis for Gas Turbine Film-Cooled Blade
Authors: Ho Kuo-San , Liu Jong S. , Elliott Thomas , Aguilar Bruno 
Published: September 2016

This paper presents results of a study of the conjugate heat transfer (CHT) to calculate the metal temperature for a film-cooled gas turbine blade. ANSYS CFX14.0 code was selected as the computational fluid dynamic (CFD) tool to perform the CHT simulation. The two-equation SST turbulence model with automatic wall treatment was employed. The main flow inlet and exit boundary conditions were deduced from a multi-blade-row CFD code, Fine/Turbo by NUMECA.
A core engine test operated at the maximum power condition. Thermocouples were used to validate the blade metal temperature calculations.
The blade temperature comparison between test data and CHT predictions was in good agreement except at the suction side near the leading edge region. The pressure, temperature and Mach number distributions for blade internal and external flows were presented and examined. The streamline contours of the film flows on the pressure side and suction side were plotted and used to visualize the cooling effectiveness.
In order to evaluate the influence of the turbulence model, the thermal results of four additional turbulence models (SA, RNG, K-ε, and SST with transition control) were compared to the test data. The SST model is suggested to be the appropriate turbulence model for the film-cooled blade temperature calculation in this study.
Influence of Impeller Fairing Cone Geometry on Cavitating Flow Behavior in a Cryogenic Liquid Turbine Expander
Authors: Wang Ke , Sun Jinju , Song Peng , Huo Changjiang 
Published: September 2016

A single stage cryogenic liquid turbine expander is developed as a replacement for traditional Joule-Thomson valves used in the large-scale internal compression air-separation unit for the purpose of energy saving. Similar to the conventional hydraulic turbine, detrimental swirling and cavitation flow is also encountered at turbine expander impeller exit and its successive diffuser tube, but due to significant thermodynamic effect of cryogenic fluid flow, it is much more complicated than the conventional hydraulic turbine.
In the present study, cavitating flow mechanism of the turbine expander is investigated first with a combination of the homogenous multiphase mixture model and the Rayleigh-Plesset model, where the former treats liquid and gas as a continuum mixture and the latter depicts the bubble dynamics. Then sensitivity study is conducted for the impeller fairing cone geometry on suppression of cavitating flow. The following are demonstrated: with a use of the fairing cone, flow behavior near and downstream the impeller exit is significantly improved, where the low static pressure region is reduced and the local temperature rise decreases, subsequently the cavitating flow is effectively suppressed. The cavitating flow is sensitive to a tuning of the fairing cone geometry, and an optimal design of the cone geometry is essential.
Numerical Study of Cavitating Flow in Two-Phase LNG Expander
Authors: Song Peng , Sun Jinju , Li Kaiqiang , Wang Ke , Huo Changjiang 
Published: September 2016

LNG expander is developed and used as a replacement of a J-T valve in liquefaction process of natural gas to reduce significantly the energy consumption in the LNG plant. Similar to conventional hydraulic turbines, the unexpected cavitation also occurs in the LNG expander. In the present study, cavitating flow in two-phase LNG expander is investigated. With the justified Rayleigh-Plesset cavitation model, cavitating flow characteristics is investigated for the LNG expander in the entire stage environment including an annular bend, nozzle ring, and radial inflow impeller. On the basis of cavitating flow analysis, a coaxial rotating exducer is developed and fitted downstream to the impeller, so as to reduce the cavitation in impeller and subsequently prevent impeller damage.
The following are demonstrated: (1) without exducer, significant cavitating flow is encountered at the impeller trailing edge and also in half streamline-wise region, and they are resulted from the viscous dissipation and flow separation; (3) with exducer, the impeller cavitation has diminished entirely but it has occurred in the successive exducer; (3) a use of exducer enhances the energy conversion capability of the rotors, but reduces the overall temperature drop and efficiency of the expander; (4) the design optimization of exducer is required to suppress the exducer cavitation, which also needs to be incorporated with the impeller design to achieve a better match between rotor/stator, so as to maximize the design optimization benefits.
An Experimental Study of the Aerodynamic Forcing Function in a 1.5 Steam Turbine Stage
Authors: Gatti Giacomo , Gaetani Paolo , Paradiso Berardo , Dossena Vincenzo , Arcangeli Lorenzo , Maceli Nicola , Bellucci Juri 
Published: September 2016

The usual ways to measure the aerodynamic forcing function are complex and expensive. The aim of this work is to evaluate the forces acting on the blades using a relatively simpler experimental methodology based on a time-resolved pressure measurement at the rotor discharge. Upstream of the rotor, a steady three holes probe has been used.
The post processing procedures are described in detail, including the application of a phase-locked average and of an extension algorithm with phase-lag. The algorithm for the computation of the force components is presented, along with the underlying assumptions.
In order to interpret the results, a preliminary description of the flow field, both upstream and downstream of the rotor, is provided. This gives an insight of the most relevant features that affect the computation of the forces.
Finally, the analysis of the results is presented. These are first described and then compared with overall section-average results (torque-sensor), and with the results from 3D unsteady simulations (integral of pressure over the blade surface) in order to assess the accuracy of the method. Both the experimental and the numerical results are also compared for two different operating conditions with increasing stage load.
HCF Component Tests on Full-Scale Low Pressure Steam Turbine End Stage Blades
Authors: Sheng Shilun , Flegler Johan , Becs Balazs Janos , Dankert Michael 
Published: September 2016

The design of steam turbine components is driven by high efficiency demands and also requirements for increased operational flexibility due to more renewable energy sources being added to the grid. Therefore, fossil power plants which operate reliably under these conditions must be designed. Robust low pressure (LP) end stage blades are one key factor for modern steam turbine design to meet current and future market requirements.
In operation, LP end stage blades of steam turbines are exposed to complex mechanical load, resulting in stresses mainly due to blade vibration and high centrifugal forces. Design methods accounting for high cycle fatigue (HCF) and low cycle fatigue (LCF) are required for fatigue lifetime calculation. To determine the HCF component strength and to validate the calculation procedure, an HCF component test facility for full-scale LP end stage blades has recently been established at Siemens. Besides the validation of the calculation procedures, the full-scale component tests serve as part of upfront validation to minimize risk for first time implementation of newly developed as well as next generation blades, and to demonstrate operational robustness of the existing fleet.
This paper describes the development and setup of the HCF component test facility for full-scale LP end stage blades at Siemens, the successful execution of HCF component tests with blades of different sizes, surface conditions and materials, and the evaluation of the results. In addition, crack growth and threshold behavior has been investigated in detail. Based on the test results, validation of the corresponding calculation methods has been performed. An outlook on further development of test facilities is provided.
Experimental and Numerical Development of a Dynamic Clearance Seal for Steam Turbine Application
Authors: Messenger Andrew , Williams Richard , Ingram Grant , Hogg Simon , Tibos Stacie , Seaton Jon , Charnley Bernard 
Published: September 2016

This paper presents a series of experiments on the Aerostatic Seal, a dynamic clearance seal for steam turbine application first described at the 2015 ASME Turbo Expo (Paper Number GT2015-43471). This dynamic clearance seal moves with rotor excursions and so has the potential to deliver a smaller clearance than traditional seals. The concept is an extension of the retractable seal design which is widely used in existing steam turbines.
The experimental program was carried out in a low cost static test facility using an aerostatic seal design. The seal exhibited a dynamic clearance response and will therefore respond to rotor excursions. 3D CFD was also used to aid the understanding of flow features not captured by the analytical design tool. Adjustments to both the design process and to future seal designs are proposed in the body of the paper.
This paper therefore describes an experimental proof of concept for the aerostatic seal and paves the way for future development in rotating facilities.
Sensitivity Study of S-CO2 Compressor Design for Different Real Gas Approximations
Authors: Lee Jekyoung , Cho Seong Kuk , Cha Jae Eun , Lee Jeong Ik 
Published: September 2016

With the efforts of many researchers and engineers on the Supercritical CO2 (S-CO2) Brayton cycle technology development, the S-CO2 Brayton cycle is now considered as one of the key power technologies for the future. Since S-CO2 Brayton cycle has advantages in economics due to high efficiency and compactness of system, various industries have been trying to develop technologies on the design and analysis of S-CO2 Brayton cycle components. Among various technical issues on the S-CO2 Brayton cycle technology development, treatment of thermodynamic property near the critical point of S-CO2 is very important since the property shows non-linear variation which causes large error on design and analysis results for ideal gas based methodologies.
Due to the special behavior of thermodynamic property of CO2 near the critical point, KAIST research team has been trying to develop a S-CO2 compressor design and analysis tool to reflect real gas effect accurately for better design and performance prediction results. The main motivation for developing an in-house code is to establish turbomachinery design methodology based on general equations to improve accuracy of design and analysis results for various working fluids including S-CO2. One of the key improvements of KAIST_TMD which is an in-house tool for S-CO2 turbomachinery design and analysis is the conversion process between stagnation condition and static condition. Since fluid is moving with high flow velocity in a compressor, the conversion process between stagnation and static condition is important and it can have an impact on the design and analysis results significantly. A common process for the conversion is based on the specific heat ratio which is typically a constant from ideal gas assumption. However, specific heat ratio cannot be assumed as a constant for the case of S-CO2 compressor design and analysis because it varies dramatically near the critical point.
Thus, in this paper, sensitivity study results on the state condition conversion between stagnation and static conditions with different approaches will be presented and further analysis on impact of the selected approaches on the final impeller design results will be discussed.
2nd Quadrant Centrifugal Compressor Performance: Part I
Authors: Belardini Elisabetta , Rubino Dante Tommaso , Tapinassi Libero , Pelella Marco 
Published: September 2016

Performance curves in 2nd quadrant are important to size protection equipment of both compressor and surrounding system. With reverse flow also the level and frequency of pressure fluctuations in different operating points is important to estimate blade loading and possible presence of excitation frequencies. The capability of performance predictive tools (either CFD or correlations based methods) as also mechanical design criteria are generally poor in 2nd quadrant and suffer for the scarcity and inadequacy of validation data.
The second quadrant branch for a centrifugal compressor has been experimentally tested after the standard characterization in direct flow. A test arrangement has been designed, with a booster compressor connected in parallel with the tested stage, forcing the flow to be stable in reverse flow. The compressor characteristics have been measured with static and dynamic instrumentation. Present experience showed that when machine is operated in the stable reverse flow condition, pressure fluctuations and vibration are higher with respect to the values measured in nominal direct flow operating conditions. The increase is in the order of 10–20% of the corresponding value in direct flow. The same can be stated also for axial thrust and secondary flows that increase when the gas flows in reverse direction but the increase is in the order of 10–15%. Thus in 2nd quadrant, compressor equipment (in particular impeller blades) and all other system devices experience unusual loading levels but the additional loads are not big enough to cause relevant damaging if sustained for limited time periods. This result may allow simplifying the design of system layout: in particular, if during ESD no surging cycle is expected but only a reverse flow sustained steadily by the system (which is actually the most typical experience), the additional ASV’s, such as hot or cold gas by-pass valves, may be reduced in size or eventually removed optimizing the plant BOP.
Low Pressure Steam Turbine Exhaust Flow: Part 1 — CFD Coupling of LP Turbine and Condenser Neck
Authors: Stein Peter , Telschow Dirk , Lamarque Frederic , Colitto Nuncio 
Published: September 2016

Since many years the diffuser and exhaust of low pressure (LP) turbines have been in the focus of turbine development and accordingly broadly discussed within the scientific community. The pressure recovery gained within the diffuser significantly contributes to the turbine performance and therefore plenty of care is taken in investigations of the flow as well as optimization within this part of the turbine. However on a plant level the component following the LP turbine is the condenser, which is connected by the condenser neck. Typically the condenser neck is not fully designed to provide additional enthalpy recovery. Due to plant arrangement reasons, often it is full of built-ins like stiffening struts, feed-water heaters, extraction pipes, steam dump devices and others. It is vital to minimize the pressure losses across the condenser neck, in order to keep performance benefit, previously gained within the diffuser. As a general rule, each mbar of total pressure loss in a condenser neck may reduce the gross power output up to 0.1%.
While turbines usually follow a modular approach, the condenser is typically designed plant specific. Therefore, on a plant level it is crucial to identify and evaluate the loss contributors and develop processes and tools which allow an accurate and efficient design process for an optimized condenser neck design. This needs to be performed as a coupled modelling approach, as both, turbine and condenser flow interact with each other. 3-D CFD tools enable a deep insight into the flow field and help to locally optimize the design, as they help to identify local losses and this even for small geometrical design changes. Unfortunately these tools are costly with respect to computational time and resources, if they are used to analyze a full condenser neck with all built-ins. Here 1-D modelling approaches can help to close the gap, as they can provide fast feedback, e.g. in a project tender phase, or can allow to quickly analyze design changes. For this they need a proper calibration and validation. This publication discusses the CFD modelling of a LP steam turbine coupled to a condenser neck and the validity of such calculations against measurement data. In the second publication (Part 2) a simplification of the gained information to a 1-D modelling approach will be discussed.