bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Verification of Friction Behaviors Under Periodically-Varied Normal Force by Developing a Two-Directional Friction Test System
Authors: Asai Kunio , Gola Muzio M. 
Published: August 2015

In order to achieve more accurate friction damping of turbine blades equipped with shroud covers and under-platform dampers, it is necessary to clarify such friction behaviors as tangential contact stiffness, micro-slips, and dissipated energy, under periodically varied normal force instead of constant normal force. Although some analytical studies were reported on the contact mechanics under alternating normal force, only minimal research has been conducted on the experimental verification of such behaviors, as friction tests were commonly done under constant normal force. In this study, we developed an original two-directional friction test system that can apply any combination of alternating normal and tangential forces by changing the displacement-controlled loading direction. In this system, relative displacement and contact force were measured simultaneously by using a laser Doppler displacement sensor and force transducers of the strain gage type.
By using our original test system, we examined the dissipated energy under constant normal force and periodically-varied normal force whose amplitude is the same as that of tangential force with no phase difference. We then obtained a new finding that dissipated energy depends on alternating normal force under the same mean normal force and alternating tangential force. More specifically, when the tangential force coefficient, defined as the ratio of the amplitude of alternating tangential force to mean normal force, is large enough to cause a macro-slip, dissipated energy under variable normal force is smaller than that under constant normal force. Conversely, when tangential force coefficient is small in the micro-slip region, dissipated energy under variable normal force is larger than that under constant normal force. This behavior was successfully reproduced by FE analysis based on a macro-slip model, where an array of macro-slip elements was used to describe micro-slip behavior. It was found that alternating normal force makes it easier to cause a micro-slip in a certain area of the contact surface under variable normal force, resulting in higher dissipated energy than at constant normal force when tangential force coefficient is small.
In this study, basic friction data were also obtained regarding the tangential contact stiffness with variations in contact pressure, as well as the relation between a micro-slip and the tangential force coefficient. Tangential contact stiffness increases as contact pressure increases. In addition, tangential contact stiffness increases with the nominal contact area, but is not proportional to the area. The non-dimensional slip range (corresponding to the ratio of slip range to stick displacement) was confirmed as being described in a unified form against different contact area (6 and 18 mm2) and contact pressure ranging from 3 to 40 MPa.
Nacelle Aerodynamic Optimization and Inlet Compatibility
Authors: Chen Jingjing , Wu Yadong , Wang Zhonglin , Wang Anjenq 
Published: August 2015

The design of air induction system is targeting to balance the internal and external flow characteristics as well as the structure and aerodynamic integrity. An optimized air intake design that providing velocity and pressure distributions with least drag and maximum pressure recovery could end up at the expense of higher inlet flow distortion and lower stability margin. Indeed, design requirements and considerations at different operating conditions, such as takeoff, and high AOA maneuvers, could be significantly different from that of cruise and level flight. One of the most challenged operating conditions to be certified for FAR33 & FAR25 requirements is ground crosswind condition, when “Engine” is operating statically on the ground with high crosswind presented. It could accommodate inlet separation or distortion resulted from crosswind, and triggers fan or core stall, as well as induces high fan and/or engine vibrations. Studies of engine inlet compatibility become one of the major tasks required during the engine developing phase.
This research is a parametric study of using CFD to evaluate operational characteristics of the air induction system. Comparisons of various inlet designs are made and characterized into four categories, i.e., i) Inlet pressure loss, ii) Nacelle drag, iii) Inlet flow distortion, and iv) Inlet Mach distribution. The objective is to assess the impact of air induction design of turbofan upon inlet compatibility.
The research introduces the Kriging model and weighting coefficients to optimize internal total pressure loss and external drag using the isolated nacelle model. Bezier equation was used to fit the optimized curves obtained by changing several control points of the baseline configuration of nacelle. To study the impact of asymmetric lip on flow separation in ground crosswind condition, the paper built crosswind model which introduce a inlet boundary as fan face. Comparisons are then made between the original and optimal nacelle, to show correlation between inlet compatibility and air intake profile.
Effects of Heat-Treatment Residual Stress on Low Cycle Fatigue Life of a Turbine Disk in PM Superalloy
Authors: Wang Rongqiao , Li Da , Hu Dianyin , Hai Yang , Song Jun 
Published: August 2015

Turbine disks in powder metallurgy (PM) superalloy have been widely used in advanced aeroengines. The production of PM superalloy turbine disks involves a series of heat treatment processes, which would inevitably create residual stresses. It has been proved that the low cycle fatigue (LCF) life of the turbine disk is affected by the residual stresses. The computational simulation of heat treatment is considered as an effective way to evaluate the residual stresses in a turbine disk. A finite element software was used to simulate the heat-treatment processes of a FGH95 turbine disk to obtain the residual stress field.
To investigate the relaxation of residual stress in FGH95, smooth bar specimens were measured by X-ray diffraction before and after being loaded. Modified by the residual stresses, SWT model is used to predict the low cycle fatigue life of the turbine disk modified by the residual stress field obtained from the simulation of heat treatment.
By the comparison between the prediction modified by the residual stress and the prediction without modification, a considerable decrease in low cycle fatigue life is indicated.
Experimental Investigation of Fuel Composition Effects on Syngas Combustion
Authors: Bouten Thijs , Beran Martin , Axelsson Lars-Uno 
Published: August 2015

The OPRA OP16 gas turbine is an all radial single-shaft gas turbine rated at 1.9 MW with a successful track record from oil and gas applications as well as industrial and commercial CHP applications. To meet the growing demand for alternative fuels, OPRA Turbines has developed a new tubular combustor for the OP16 gas turbine fleet. The combustor has been successfully tested on a wide variety of (ultra-) low-calorific gaseous fuels in an atmospheric combustion test rig.
This paper presents an experimental investigation of syngas combustion in the low-calorific fuel combustor. The effect of the variation in fuel composition on the combustion characteristics has been investigated extensively. This includes the effect of variable heating values and variations in the ratio between hydrogen and carbon monoxide and between syngas and hydrocarbons. The effects of these variations on the combustor performance, emissions and lean blowout limits will be discussed and compared to the results obtained from the combustion of propane. Major differences in emissions have been found, mainly influenced by the flame temperature and presence of hydrogen in the fuel. Lean blowout of the combustor is largely determined by the presence of hydrogen, whereas other components are found to have less influence.
Theoretical calculation, based on le Chatelier’s rule and a method based on heat release, of the lean blowout limit has been compared to the experiments. It was found that the heat release method predicts the flammability limit more accurately than le Chatelier’s rule. This is caused by the inaccuracy of the latter to handle fuels with a large amount of hydrogen.
A Study of Spontaneous Condensation in an LP Test Turbine
Authors: Chandler Kane , Melas Mauro , Jorge Teresa 
Published: August 2015

Recent advances in computational fluid dynamics (CFD) offer the possibility to predict condensing flows in 3D LP steam turbine geometries. Correct analysis of wetness losses, droplet deposition and other two-phase effects in LP steam turbines requires accurate prediction of the non-equilibrium flow field and droplet sizes.
The paper compares numerical results from a 3D, polydispersed, condensing flow CFD code to experimental data measured in a scaled model LP turbine for a range of operating conditions. In order to compare the computed efficiencies with the measured values, a method for averaging non-equilibrium flow fields has been developed. Comparisons are made between computational and experimental results for a series of inlet temperature variation tests where the inlet and exit pressures were kept constant. The steady calculations accurately predict the temperature that the primary nucleation zone moves to an upstream row. Furthermore, the mechanism of condensation as nucleation changes rows is explored and it is shown that initially a significant degree of subcooling is maintained in the inter-blade section and, as a result, nucleation occurs at a relatively low rate in a zone that extends far downstream of the blade’s trailing edge. This produces relatively large droplets compared to when nucleation occurs predominantly within the blade passage and is clearly visible in the measured module efficiencies and local flow angles, static pressures and light extinction. The measured variation of efficiency and specific work with inlet temperature is predicted accurately by the computations.
It is concluded that steady condensing flow wet-steam calculations are able to predict the location of nucleation and the variation of flow dynamics and performance with inlet temperature accurately. A description of the condensation process as nucleation moves between rows has been given and is consistent with the numerical and experimental results.
Optimized Steam Turbine Operation by Controlled Clutch Angle Engagement
Authors: Zimmer Gerta , Pieper Daniel , van Driel Kees , Lacombe Bernd , Daenner Mirko , Bennauer Martin 
Published: August 2015

Some single shaft CCPPs are known to display increased vibrations if engaged at certain angles and a very smooth operational behavior if engaged at other angles. Neither the reason nor a mechanical mitigation for this behavior is known.
Roughly, the engagement angles can be clustered into four 90° sectors, one of them is deemed unfavorable and another one is classified as favorable with respect to vibrations of the overall power train shaft. Although the first priority is to have an assembly that runs smoothly at arbitrary engagement angles, an option to engage at a predefined ‘good’ angle provides an I&C back-up solution to avoid undue vibrations.
To meet this requirement a control method was developed to run up the steam-turbine thus that it will engage at a pre specified angle. The basic idea of the developed control algorithm is to increase the acceleration of the steam-turbine during run up if a prediction reveals an engagement angle that would be too small to be within the desired area and, conversely, decrease the acceleration if the anticipated angle would be too large.
A control algorithm to exploit this idea was developed and tested with the aid of a simulation model. The simulation model comprises a detailed thermodynamic model of the steam-turbine, the control valves and their actuators, the steam-turbine shaft and the shift clutch. I&C was modelled with all details relevant to turbine speed control. The gas-turbine/generator unit, however, is cut down to angular velocity and relative angle, respectively.
The performance of the controller was validated to comply with parameter uncertainties, different sampling times and frequency fluctuations of the electrical grid during coupling. In parallel, a high precision angular measurement device was developed and integrated into the existing turbine I&C.
Hardware-in-the-loop tests with simulated turbines and a hardware I&C system implementation also revealed a very satisfactory performance.
On site implementation of a prototype was successfully accomplished and resulted in the predicted accuracy of the preset engagement angle.
Experimental Spray Structure and Combustion of a Linearly-Arranged 5-Swirler Array
Authors: Kao Yi-Huan , Denton Michael , Wang Xionghui , Jeng San-Mou , Lai Ming-Chia 
Published: August 2015

The presented work focuses on the experimental spray structure and the combustion of a linearly-arranged 5-swirler array. The aerodynamics and spray characteristics of a non-reacting single swirler are reported first as a baseline, followed by those of a 5-swirler array to investigate the effect of swirling flow interactions on aerodynamics and combustion. For the baseline single swirler, the smaller droplets follow the air flow more closely and further dispersed away at the exit of swirler. Thus, the mean diameter of droplet increases with the flow developing further downstream. However, in the central portion of a 5-swirler array, the droplet size remains similar. It is attributed to that swirling flow interactions might provide better air/fuel mixing and the additional shear stress to break up droplet continuously and is evident by the higher turbulent intensity in the aerodynamic measurement. Due to the influence of gas phase, the distribution of liquid phase in center toroidal recirculation zone (CTRZ) is non-uniform in a 5-swirler array. The center swirler of a 5-swirler array features a larger CTRZ which is accompanied by two smaller CTRZs from its neighbors. The flame anchored by the center swirler of a 5-swirler array is richer than the other two neighboring flames when the inter-swirler spacing is 2D, where D is the diameter of swirler exit diameter. However, when the inter-swirler spacing is increased to 2.5D, all swirlers feature a similar flame, which is different from what is expected from non-reacting flow studies reported previously. The unexpected result should be attributed to the difference in swirling strength between non-reacting and reacting flows.
Moreover, the high speed imaging is employed to investigate the flame spreading during ignition process for a 5-swirler array. The high-speed movies show that the directional mechanism of flame spreading along lateral direction remains basically the same and is independent of the investigated test parameters including: two inter-swirler spacings, five fuel flow rates, five air pressure drops across swirlers, and five upstream air temperatures. An empirical correlation incorporating normalized inter-swirler spacing, air/fuel ratio, Reynolds number, and normalized air temperature is proposed and validated through a normalization procedure within around ± 10% error. The increase of Reynolds number and normalized air temperature has favorable impact on the flame spreading, which is stated by the empirical correlation.
GE Rapid Response Plant Design: Operational Flexibility and Transient Emissions Control
Authors: Smith Gordon R. 
Published: August 2015

The GE Rapid Response plant design is described and compared to conventional combined cycle plant design. Advantages of the Rapid Response improved operational flexibility are explained and compared to conventional combined cycle plants. Improvements include faster power delivery to the grid, more economical plant startup, more profitable plant startup and lower emissions during plant startup.
The capability of a drum type HRSG for the Rapid Response cycling service is explored. Joint studies between GE and HRSG suppliers are highlighted supporting the adoption of drum type HRSGs for this cycling service. Necessary modifications to other plant equipment are explained.
Quantitative comparisons of Rapid Response and conventional combined cycle plant operability are given for electrical energy production and emissions reduction.
An advanced Selective Catalytic Reduction SCR control is shown providing improvements in combined cycle plant transient emissions control. Elements of the new control are explained. Argument is made to designate the new control as a second generation GEN II control compared to all other currently existing controls designated GEN I.
A brief outline of the current state of Rapid Response plant deployment is provided.
Comparison of Supercritical Carbon Dioxide Cycles for Oxy-Combustion
Authors: McClung Aaron , Brun Klaus , Delimont Jacob 
Published: August 2015

Advanced oxy-combustion coupled with supercritical carbon dioxide (sCO2) power cycles offers a path to achieve efficient power generation with integrated carbon capture for base load power generation. One commonality among high efficiency sCO2 cycles is the extensive use of recuperation within the cycle. This high degree of recuperation results in high temperatures at the thermal input device and a smaller temperature rise to the turbine inlet. When combined with typical high side pressures ranging from 150 to 300 bar, these conditions pose a non-trivial challenge for fossil fired sCO2 cycles with respect to cycle layout and thermal integration. A narrow thermal input window can be tolerated for indirect cycles such as those used for nuclear power generation and concentrating solar power plants, however, it is at odds with traditional coal or natural gas fired Rankine cycles where the working fluid has been condensed and cooled to near ambient temperatures.
Coal fired sCO2 cycles using oxy-combustion have been examined by Southwest Research Institute and Thar Energy L.L.C. under DOE award DE-FE0009593. Under this project, an indirect supercritical oxy-combustion cycle was developed that provides 99% carbon capture with a 37.9% HHV plant efficiency. This cycle achieves a predicted COE of $121/MWe with no credits taken for the additional 9% of carbon capture, and represents a 21% reduction in cost as compared to supercritical steam with 90% carbon capture ($137/MWe).
Direct fired sCO2 cycles for natural gas or syngas are currently being evaluated by Southwest Research Institute and Thar Energy L.L.C. under DOE award DE-FE0024041. Initial evaluations of direct fired supercritical oxy-combustion cycles indicate that plant efficiencies on the order of 51% to 54% can be achieved with direct fired natural gas oxy-combustion when paired with the recompression cycle with 1,200 °C firing temperatures at 200 bar.
Direct fired natural gas or syngas sCO2 cycles still face significant technology development needs, with the pressurized oxy-combustor a significant component with a low Technology Readiness Level, (TRL) as defined by the DOE. In addition to the combustion system, significant work will be required to prepare the sCO2 turbomachinery for the turbine inlet temperatures required to achieve plant efficiencies greater than 50%.
Employing Micro-Turbine Components in Integrated Solar-MGT-ORC Power Plants
Authors: Cameretti Maria Cristina , Ferrara Francesco , Gimelli Alfredo , Tuccillo Raffaele 
Published: August 2015

The authors propose in this paper the integration of a combined power plant, with a micro gas turbine (MGT) and an ORC system, and a solar field that allows a temperature increase of the air at the MGT recuperator inlet. Consequently, an increase is also obtained for the exhausts and this leads to an enhanced heat recovery in the ORC boiler and a greater availability of thermal energy.
The purpose of the authors’ work is to analyze the effectiveness of the above proposal under several aspects, therefore, under a preliminary thermodynamic study of the plant set-up in CHP mode, the attention is paid to the choice of the organic fluid expander with a low-cost objective. Classical similarity criteria are helpful for a first estimate of the adaptability of a radial flow turbine from the down-sized turbocharger technology to an organic working fluid. A CFD validation of such choice is then carried out and this phase also determines the characteristic curves of the radial flow turbine.
Basing on the availability of the characteristic maps of all the rotating components, a reliable off-design analysis of the solar-assisted CHP plant is performed under several load levels and environmental conditions, the latter strongly influencing the solar irradiance on the parabolic trough collectors.
Finally, since the examples refer to both natural gas and biogas fuelling, a CFD analysis of the reacting flow through the MGT combustor checks the combustion effectiveness under challenging variations of the boundary conditions.
CFD Analysis of Centrifugal Compressor Stage Range Extension Using Internal Flow Recirculation
Authors: Meduri Uday K. , Selvam Kathiravan , Nawrocki Gilles 
Published: August 2015

A Centrifugal Compressor is a key component in the Oil and Gas Industry. It is used in all 3 areas of extraction, processing and transportation, namely, upstream, midstream and downstream. Generally a compressor’s life expectancy matches that of the wells it is used on. Barring retrofits and maintenance, a compressor can remain onsite for up to 20 years.
However, at the end of the life of the well or in special conditions with perennial low flow rates, the reduced gas flow rate pushes the compressor to the left of its operating limit. At this point, the compressor surges. In order to bring it back to the normal operating conditions, flow is recirculated via an external circuit involving the anti-surge valve. This drops the flange to flange performance. A simpler method would be to recycle the flow internally, thus removing the losses from the external circuit.
In this paper, internal flow recirculation is studied where flow is extracted from the stage diffuser and recycled back to the upstream return channel. This study was undertaken on a 2D impeller from the lowest flow coefficient stage of an OEM. Using 1D tools and detailed CFD methods to study this novel design, it is shown that the range can be shifted significantly.
Experimental Validation of a Curtain Type Fluidic Jet Seal on a Turbine Rotor Shroud
Authors: Hilfer Michael , Hogg Simon , Ingram Grant 
Published: August 2015

This paper describes the design and testing of a fluidic “air-curtain” type seal application to reduce tip leakages on a small high-speed single stage axial turbine.
The initial experimental investigations were carried out to demonstrate the application of the fluidic type seal on a “frozen rotor” test of a turbine. The “frozen rotor” test is carried out using an actual turbine rotor in a static test facility without rotation. These preliminary tests provide the first experimental validation of fluidic “air-curtain” type seals working to reduce over-tip leakage in a turbine shroud on a actual turbine geometry.
Ultimately the final stage of the work will be to demonstrate the fluidic seal working in a full rotating facility but these results provide a logical and important step towards that ultimate goal.