bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of the Operating Mode Influence Onto Energy Consumption of a Natural Gas Storage Plant
Authors: Arnulfi Gianmario L. , Cravero Carlo , Marini Martino 
Published: December 2013

Natural gas carrying from production sites to users’ facilities is made by marine shipping in liquid phase or by terrestrial pumping in gaseous phase through long pipelines. In the latter case several storage stations are distributed along the pipeline nets to move the natural gas from its deposits to users’ terminals. Storage stations are set up to compensate seasonal fluctuations of the consumer demand versus methane supply, storing the gas in various kinds of reservoirs.
In most of such plants centrifugal compressors are used, where the energy and the time that a complete charge takes are affected by the operation scheduling of the compressor from the minimum to the maximum storage levels. While the pressure in the reservoir enforces the instant operation pressure, the flow rate is limited within a quite wide range. Here an in-house code, based on the lumped parameter approach and a quasi-steady dynamics, is applied to a complete charge. The natural gas behavior is modeled by the pseudo-ideal gas in order to get a fair accuracy keeping the usual gas dynamics equations.
The compression path has been parameterized and a multi objective optimization, embedding the simulation code, has been implemented to find the most suitable management of the compression station for the minimization of time and energy. The most significant paths are analyzed to pick out the effects of the compression strategy.
Optimization of Advanced Liquid Natural Gas-Fuelled Combined Cycle Machinery Systems for a High-Speed Ferry
Authors: Tveitaskog Kari Anne , Haglind Fredrik 
Published: December 2013

This paper is aimed at designing and optimizing combined cycles for marine applications. For this purpose, an in-house numerical simulation tool called DNA (Dynamic Network Analysis) and a genetic algorithm-based optimization routine are used. The top cycle is modeled as the aero-derivative gas turbine LM2500, while four options for bottoming cycles are modeled. Firstly, a single pressure steam cycle, secondly a dual-pressure steam cycle, thirdly an ORC using toluene as the working fluid and an intermediate oil loop as the heat carrier, and lastly an ABC with inter-cooling are modeled. Furthermore, practical and operational aspects of using these three machinery systems for a high-speed ferry are discussed.
Two scenarios are evaluated. The first scenario evaluates the combined cycles with a given power requirement, optimizing the combined cycle while operating the gas turbine at part load. The second scenario evaluates the combined cycle with the gas turbine operated at full load.
For the first scenario, the results suggest that the thermal efficiencies of the combined gas and steam cycles are 46.3% and 48.2% for the single pressure and dual pressure steam cycles, respectively. The gas ORC and gas ABC combined cycles obtained thermal efficiencies of 45.6% and 41.9%, respectively. For the second scenario, the results suggest that the thermal efficiencies of the combined gas and steam cycles are 53.5% and 55.3% for the single pressure and dual pressure steam cycles, respectively. The gas ORC and gas ABC combined cycles obtained thermal efficiencies of 51.0% and 47.8%, respectively.
Experimental Investigation of the TurboClaw® Low Specific Speed Turbocompressor
Authors: Pullen K. R. , Etemad S. , Cattell R. 
Published: December 2013

For both radial and axial turbocompressors there are well established design methods which direct the designer to the optimum shaft speed for a given flow rate and pressure rise. This shaft speed is relatively narrow in range if the highest efficiency is to be obtained. However, there are many reasons why shaft speed is dictated by other considerations and it is more common to find that the turbocompressor must operate far below the preferred shaft speed. The present contribution describes numerous applications where this occurs, the majority of which are when volume flow rates are relatively low.
Many researchers have attempted to find solutions to this problem and the starting point is to take a radial compressor and design it for operation at lower than optimal speed. This creates high windage and tip leakage losses relative to the useful work component which becomes punitive as the exit blade width is reduced. In addition to this, for small machines, the size of the exit blade width itself becomes an issue as it reduces to less than around 3mm leading to high relative tip clearances and narrow passages.
The purpose of this paper is to describe a novel solution that has been developed which is based on a combination of a partial entry rotor and extremely high forward sweep, a new class of machine denoted TurboClaw®. The level of forward sweep is substantial, at almost 90° that it is beyond the experience of fully bladed machines with levels of forward sweep below 30°. The machine is stable with extremely high tangential to radial Mach number ratios well over 20 being achieved. Experimentally produced maps for various sizes of machine are presented which demonstrate that the characteristic is very similar to that of an equivalent radial machine which would have to operate at speeds between two to four times greater.
Further experimental work is described which has taken place on both small prototype machines and on a larger version using a specially designed test rig capable of producing accurate performance measurements based on shaft torque. The test rig has been designed to allow flow visualization and non intrusive flow measurements. A selection of results from these tests is also described. At the levels of performance reached to date this class of machine is already suitable for a number of commercial applications including fuel cell air management systems, electric supercharging, and other industrial applications. Results of research and development programs in these areas are also described.
Shape Memory Effect and Hysteresis Behavior of Shape Memory Alloy Metal Rubber
Authors: Hong Jie , Liu Baolong , Zhang Dayi , Ma Yanhong 
Published: December 2013

The present work focuses on the shaping craft of shape memory alloy metal rubber (SMAMR) and its temperature dependent mechanical properties. Heat treatment process was conducted to form a stable SMAMR sample beyond the general procedure of metal rubber (MR) in order to resist the shape memory effect (SME). The influence of the heat treatment procedure on the mechanical properties was tested. The quasi-static experimental investigations were carried out to obtain the storage modulus and energy loss factor varying with the structural parameter, strain amplitude, and material temperature.
It is found from the experiment results that the SMAMR sample which underwent the heat treatment was able to remember its original moulding shape and recover from the overloading plastic deformation when heated above the phase transition temperature. For comparison, another sample without the heat treatment was heated to the same temperature after the plastic deformation, but the final shape deviated from the original one. It is also confirmed that the heat treatment procedure obviously increased the storage modulus and loss factor of SMAMR.
Just like the variety elastic modulus of shape memory alloy (SMA), the storage modulus of SMAMR increased obviously while the material was heated above the phase transformation temperature due to the elastic modulus change of SMA wire. The quasi-static experiments showed a hysteretic property of the stress–strain curve in a certain temperature. But the hysteretic curve was temperature and structural parameter dependent.
It is concluded that the heat treatment process is necessary to obtain a stable SMAMR during the phase transformation. The varying storage modulus and superior loss factor performances of SMAMR make itself a kind of attractive functional material which will be available in the active suppression of vibration. For example, it can be fabricated to a rotor bearing with changeable stiffness and damping, which is of practical significance in the active control of synchronous vibration of rotors crossing resonance condition.
Forced Response Analyses of Mistuned Radial Inflow Turbines
Authors: Giersch Thomas , Hönisch Peter , Beirow Bernd , Kühhorn Arnold 
Published: December 2013

Radial turbine wheels designed as blade integrated disks (blisk) are widely used in various industrial applications. However, related to the introduction of exhaust gas turbochargers in the field of small and medium sized engines a sustainable demand for radial turbine wheels has come along. Despite those blisks are state of the art, a number of fundamental problems, mainly referred to fluid-structure-interaction and therefore to the vibration behavior, have been reported. Aiming to achieve an enhanced understanding of fluid-structure-interaction in radial turbine wheels a numerical method, able to predict forced responses of mistuned blisks due to aerodynamic excitation, is presented.
In a first step the unsteady aerodynamic forcing is determined by modeling the spiral casing, the stator vanes and the rotor blades of the entire turbine stage. In a second step the aerodynamic damping induced by blade vibration is computed using a harmonic balance technique. The structure itself is represented by a reduced order model being extended by aerodynamic damping effects and aerodynamic forcings. Mistuning is introduced by adjusting the modal stiffness matrix based on results of blade by blade measurements that have been performed at rest.
In order to verify the numerical method, the results are compared with strain-gauge data obtained during rig-tests. As a result a measured low engine order excitation was found by modeling the spiral casing. Furthermore a localization phenomenon due to frequency mistuning could be proven. The predicted amplitudes are close to measured data.
Computational Fluid Dynamics of a Radial Compressor Operating With Supercritical CO2
Authors: Pecnik Rene , Rinaldi Enrico , Colonna Piero 
Published: December 2013

The merit of using supercritical CO2 (scCO2) as the working fluid of a closed Brayton cycle gas turbine is now widely recognized, and the development of this technology is now actively pursued. scCO2 gas turbine power plants are an attractive option for solar, geothermal and nuclear energy conversion. Among the challenges which must be overcome in order to successfully bring the technology to the market, the efficiency of the compressor and turbine operating with the supercritical fluid should be increased as much as possible. High efficiency can be reached by means of sophisticated aerodynamic design, which, compared to other overall efficiency improvements, like cycle maximum pressure and temperature increase, or increase of recuperator effectiveness, does not require an increase in equipment cost, but only an additional effort in research and development.
This paper reports a three-dimensional CFD study of a high-speed centrifugal compressor operating with CO2 in the thermodynamic region slightly above the vapor-liquid critical point. The investigated geometry is the compressor impeller tested in the Sandia scCO2 compression loop facility [1]. The fluid dynamic simulations are performed with a fully implicit parallel Reynolds-averaged Navier-Stokes code based on a finite volume formulation on arbitrary polyhedral mesh elements. The CFD code has been validated on test cases which are relevant for this study, see Ref. [2,3]. In order to account for the strongly nonlinear variation of the thermophysical properties of supercritical CO2, the CFD code is coupled with an extensive library for the computation of properties of fluids and mixtures [4]. Among the available models, the one based on reference equations of state for CO2 [5,6] has been selected, as implemented in one of the sub-libraries [7]. A specialized look-up table approach and a meshing technique suited for turbomachinery geometries are also among the novelties introduced in the developed methodology.
A detailed evaluation of the CFD results highlights the challenges of numerical studies aimed at the simulation of technically relevant compressible flows occurring close to the liquid-vapor critical point. The data of the obtained flow field are used for a comparison with experiments performed at the Sandia scCO2 compression-loop facility.
Decreasing Bladed Disk Response With Dampers on a Few Blades: Part I—Optimization Algorithms and Blade-Only Dampers Applications
Authors: Murthy Raghavendra , Mignolet Marc P. 
Published: December 2013

This two part paper focuses on the optimum placement of a limited number of dampers, i.e. fewer than the number of blades, on a bladed disk to induce the smallest possible amplitude of blade response with or without involuntary, random mistuning. Intentional mistuning is also considered as an option to reduce the amplitude of blade response and the pattern of two blade types (referred to as A and B blades) is then part of the optimization effort in addition to the location of the dampers on the disk.
This first part focuses on the formulation and validation of dedicated algorithms for the selection of the damper locations and, when appropriate, of the intentional mistuning pattern. Given the limited number of dampers, there is a concern that the failure of one or several of them could lead to a sharp rise in blade response and this issue is addressed by including the possibility of damper failure in the optimization process to yield a fail-safe optimized solution. The high efficiency and accuracy of the optimization algorithms is assessed in comparison with computationally very demanding exhaustive search results.
A General Model for Two-Point Contact Dry-Friction Whip and Whirl
Authors: Wilkes Jason C. 
Published: December 2013

Numerous papers have investigated the behavior of dry-friction whip and whirl; most of them consider contact between a rotor and stator at a single location. For rotors running on multiple magnetic bearings, air bearings, or bushings, equipment failure may result in rub at more than one location. For these cases, it is important to have an analytical model that characterizes possible regions of two-point contact dry-friction whip and whirl.
Until a recent publication by Childs and Kumar in 2011, there were no attempts to analytically describe the behavior of dry-friction whip and whirl at more than one location. In their work, they assume that forces at the two rotor/stator contacts are either in-phase, or out-of phase. The current work presents a method that is more general, allowing for an arbitrary phase between contact locations. In theory this method can be applied to more than two contact locations; however, a two-point contact example case is developed and compared to numerical simulations in the current work.
Improving Tilting-Pad Journal Bearing Predictions: Part I—Model Development and Impact of Rotor-Excited Versus Bearing-Excited Impedance Coefficients
Authors: Wilkes Jason C. , Childs Dara W. 
Published: December 2013

The floating-bearing-test-rig concept was initially developed by Glienicke in 1966 and has since been used to test many tilting-pad journal bearings (TPJBs). The impedances measured during these tests have been compared to rotor/journal perturbed impedance predictions. Since the inertial acceleration of a pad is different for bearing perturbed and rotor perturbed motions, the bearing’s reaction force components for bearing perturbed and journal perturbed motions will also differ. An understanding of how bearing perturbed and rotor perturbed impedances differ is needed to assess the validity of past, present, and future comparisons between TPJB test data and predictions.
A new TPJB perturbation model is developed including the effects of angular, radial, and transverse pad motion and changes in pad clearance due to pad bending compliance. Though all of these pad variables have previously been included in different analyses, there are no publications containing perturbations of all four variables. In addition, previous researchers have only perturbed the rotor, while both the bearing and rotor motions are perturbed in the present analysis. The applicability of comparing rotor-perturbed bearing impedance predictions to impedances measured on a bearing-perturbed test rig is assessed by comparing rotor perturbed and bearing perturbed impedance predictions for an example bearing.
Tilting Pad Journal Bearings: A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot Flexibility
Authors: Wilkes Jason C. , Childs Dara W. 
Published: December 2013

For several years, researchers have presented predictions showing that using a full tilting-pad journal bearing (TPJB) model (retaining all of the pad degrees of freedom) is necessary to accurately perform stability calculations for a shaft operating on TPJBs. This paper will discuss this issue, discuss the importance of pad and pivot flexibility in predicting impedance coefficients for the tilting-pad journal bearing, present measured changes in bearing clearance with operating temperature, and summarize the differences between measured and predicted frequency dependence of dynamic impedance coefficients.
The current work presents recent test data for a 100 mm (4 in) five-pad TPJB tested in load on pad (LOP) configuration. Measured results include bearing clearance as a function of operating temperature, pad clearance and radial displacement of the loaded pad (the pad having the static load vector directed through its pivot), and frequency dependent stiffness and damping. Measured hot bearing clearances are approximately 30% smaller than measured cold bearing clearances and are inversely proportional to pad surface temperature; predicting bearing impedances with a rigid pad and pivot model using these reduced clearances results in overpredicted stiffness and damping coefficients that are several times larger than previous comparisons.
The effect of employing a full bearing model versus a reduced bearing model (where only journal degrees of freedom are retained) in a stability calculation for a realistic rotor-bearing system is assessed. For the bearing tested, the bearing coefficients reduced at the frequency of the unstable eigenvalue (subsynchronously reduced) predicted a destabilizing cross-coupled stiffness coefficient at the onset of instability within 1% of the full model, while synchronously reduced coefficients for the lightly loaded bearing required 25% more destabilizing cross-coupled stiffness than the full model to cause system instability.
The same stability calculation was performed using measured stiffness and damping coefficients at synchronous and subsynchronous frequencies. These predictions showed that both the synchronously measured stiffness and damping and predictions using the full bearing model were more conservative than the model using subsynchronously measured stiffness and damping, an outcome that is completely opposite from conclusions reached by comparing different prediction models. This contrasting outcome results from a predicted increase in damping with increasing excitation frequency at all speeds and loads; however, this increase in damping with increasing excitation frequency was only measured at the most heavily loaded conditions.
Validation of Blade Repair
Authors: Hasselqvist Magnus , Moverare Johan 
Published: December 2013

Methodology for repair of oxidation damaged turbine components has been developed, including development of new filler alloys which combine high oxidation resistance with useful weldability. In the first part of the validation phase, described in detail elsewhere, it was shown that there is no extensive cracking, and that the weld material has at least the same oxidation resistance as the base alloy CMSX-4.
After a brief description of this work, we proceed with a discussion on Si as alloying element. Also, we present further validation work to test OP TMF crack initiation and crack propagation resistance of the repair weld, which is seen as important since oxidation typically occur at local hot spots which also experience OP TMF loadings.
A novel test specimen has been designed and will be presented, and the notch TMF test rig which will be used is described. We hope that this work will have generic value for validation of weld repair TMF life.
Challenges in Advanced-USC Steam Turbine Design for 1300°F / 700°C
Authors: Lückemeyer N. , Kirchner H. , Almstedt H. 
Published: December 2013

With global warming being one of mankind’s greatest challenges together with, an increasing demand for electricity world-wide, and studies showing that fossil resources like coal and gas will remain a major source for electricity for the next couple of decades, research into the development of highest efficiency fossil power plants has become a top priority. Calculations for coal fired power plants have shown that by increasing the live steam parameters to 700°C and 350bar CO2 emissions can be reduced by as much as 8% compared to the current state-of-the-art. This is equivalent to a reduction of 24% compared to the current steam power plant fleet within the European Union.
To achieve the desired operating hours at this temperature the application of nickel (Ni) based alloys for the main steam turbine components such as rotors, inner casings and valves is necessary. The use of Nickel base alloys for selected gas turbine components is common practice. But with steam turbine rotors being solid, 1000mm in diameter and casings with wall thicknesses >100mm the gas turbine application range and experience for nickel base alloys are well exceeded.
This paper discusses a basic product design concept in order to identify the core challenges in developing Ni based steam turbine components. These include casting, forging, non-destructive testing and welding. The material property requirements for such components (steam-oxidation resistance, creep and fatigue resistance) are also identified.
Based on these challenges and requirements a number of research projects have been carried out in Europe which have selected Alloy617 as being most suitable for forged components and Alloy625 for cast components. Further projects are currently being initiated.
The last major step in steam turbine development for high temperatures was to switch from low alloyed chromium (Cr) steels to high alloyed Cr steels. The identified challenges in using Nickel base alloys for large steam turbines are compared to this last material switch to characterize the level of complexity and difficulty of the development of the 700°C steam turbine technology.
Numerical Simulation of Evacuated Tube Solar Water Heaters
Authors: Pinelli Michele , Suman Alessio , Vanti Michele 
Published: December 2013

This paper evaluates the characteristics of water-in-glass evacuated tube solar water heaters including assessment of the circulation rate through single ended tubes. A numerical model of the fluid flow inside a single ended evacuated tube has been developed assuming no interaction between adjacent tubes in the collector array. The numerical model is firstly validated by means of literature data. Then, the performance in terms of circulation mass flow rate in different heat flux condition and at different inclination angle of the collector are evaluated.
Moreover, a sensitivity analysis on the effect of the assumptions of different reference parameters and of the choice of the values of the fluid thermophysical properties is carried out and a quantitative analysis of the expected uncertainty is presented. Finally, an extension of previous literature correlations in terms of non-dimensional Reynolds and Rayleigh numbers is proposed. Regarding heating boundary conditions, the circumferential heat distribution was found to be an important parameter influencing the flow structure and circulation rate through the tube.