bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Steam Chest With Valve for Steam Extraction in Cogeneration
Authors: Hao Zhenzhen , Jiang Puning , Ye Xingzhu , Chen Gang , Hu Yifeng , Zhang Junhui 
Published: September 2014

Cogeneration has been identified as a key technical solution to improve environment, by reducing the impact of global climate change and reducing local emissions, such as particulates, sulphur and nitrogen oxides. In cogeneration, a certain pressure of steam has to be extracted from steam turbine. A mechanical device shall be used to maintain the pressure of the extracted steam. In this paper a new steam chest with valve used for cogeneration which is installed in the steam flow is introduced. Different amount of steam extractions need different valve openings. In order to obtain these several valve openings in typical operating conditions, CFD-program is used to simulate the flow path in the steam chest. The pressure distribution on the surface of valve disc can be calculated through CFD method, and corresponding steady aerodynamic forces and torques can be calculated by integral. Pulsatile flow will change the forces and moments acting on the valve discs with time constantly. Frequency spectrograms of the aerodynamic forces are obtained by using the fast Fourier transforms and compared to the characteristic frequencies of the valve disc obtained by mode analysis.
For the purpose of validating the accuracy of CFD model, a test with test model scale of 1:5 has been designed. In the test, the pressure distribution on the valve disc surface and the flow field in the steam chest are acquired respectively by the method PSP (Pressure-Sensitive Paint) and PIV (Particle Image Velocimetry). CFD calculations and experimental results have been compared and it is shown that CFD calculations using K-ε turbulence model has satisfactory precision to calculate the pressure distribution, flow field and the torques.
Successful Power Limit Increase Testing of SGT5/6-2000E Gas Turbines on the Basis of Si3D Turbine Blading
Authors: Stapper Martin G. , Kliesch Simon I. , Holzapfel David P. 
Published: September 2014

One of the most innovative solutions for making SGTx-2000E gas turbines more competitive and more cost-effective is the Si3D upgrade product. The profile of the Si3D turbine blades and vanes is aerodynamically optimized. Based on this new Si3D design optimization, a Power Limit Increase (PLI) upgrade was developed in close cooperation with customers. The Power Limit Increase upgrade is a change of the engines rating which allows operating the engine at a higher maximum electrical power output. The PLI not only shows a much higher power output of up to 16 % but also a significant increase in efficiency at low ambient temperatures — especially for district heating power plants.
In 2011/2012 at a Finnish SGT5-2000E an opportunity arose to carry out an extensive program of measurements for testing and validating how the power limit can be increased in parallel with the blading upgrade (no compressor modification). The essential feature of this campaign was a non-intrusive stress measurement of blade vibration by means of optical probes. The campaign was successfully completed, and the Finnish customer is able to take advantage of optimized winter operation. The main benefit is operation of the engine at base load, especially at very low ambient temperatures with a higher power output and efficiency potential. On the basis of these encouraging results, Siemens prepared a fleet release for a power limit increase of all SGT5-2000E gas turbines with Si3D airfoils in stages 1 to 4 from 173 MW to 186 MW (with compressor mass flow increase) or even up to 196.5 MW.
In addition, a second opportunity arose 2013 to execute the similar test campaign in the USA for the 60 Hz Si3D turbine blading with a compressor mass flow increase. Thereby not only the same test equipment was used, but several additional investigations had to be done prior to the test campaign.
This publication describes details of the technical evaluation and conversions required to perform these tests and accomplish an increase of the power limit of the SGTx-2000E fleet.
Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade: Part I — Experimental Investigations
Authors: Krug Andreas , Busse Peter , Vogeler Konrad 
Published: September 2014

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step towards the characterisation of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analysed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions.
Part I of this two-part paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-PIV measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.
Computational Investigation of Flows and Pressure Fields Associated With Spur Gear Meshing
Authors: Al Baydu C. , Simmons Kathy , Morvan Herve P. 
Published: September 2014

The efficiency of power transmission systems is increasingly targeted with a view to reducing parasitic losses and improving specific fuel consumption (SFC). One of the effects associated with such parasitic losses is the successive compression and expansion of fluid within the cavities between teeth of a meshing gear pair as they rotate. This process is cyclic and there are multiple cavities compressed and expanded at the same time.
During the meshing process the volume of the cavity between the teeth suddenly contracts and as a result pressure rises. The fluid is therefore expelled primarily in the axial direction (for spur gears) since this area is considerably larger compared to the backlash area. Once the cavity starts to expand fluid is drawn into the cavity between the teeth by the negative pressure. Besides the air flow in the gear box, the meshing point is of particular interest to the oil flow, since oil is typically injected at or upstream of the meshing point. Good understanding of such flows can be used to balance lubrication needs with the need to minimise the required oil volumes and parasitic losses.
This paper proposes the use of Computational Fluid Dynamics (CFD) as a means to investigate the phenomenon. A simplified two-dimensional CFD approach has been developed to study flows and pressure fields associated with spur gear meshing. The influence of the rotational speed has been investigated. Good validation is shown for the transient pressure variation within the tooth space. The limitations and potential applications of the modelling strategy are then discussed.
A 3-Dimensional Computational Study of Pulsating Flow Inside a Double Entry Turbine
Authors: Newton Peter , Martinez-Botas Ricardo , Seiler Martin 
Published: September 2014

The double entry turbine contains two different gas entries, each feeding 180° of a single rotor wheel. This geometry can be beneficial for use in turbocharging and is uniquely found in this application. The nature of the turbocharging process means that the double entry turbine will be fed by a highly pulsating flow from the exhaust of an internal combustion engine, most often with out of phase pulsations in each of the two entries.
Until now research on the double entry turbine under pulsating flow conditions has been limited to experimental work. Although this is of great value in showing how pulsating flow will affect the performance of the double entry turbine, the level of detail with which this can be studied is limited. This paper is the first to use a 3 dimensional computational analysis to study the flow structures within a double entry turbine under conditions of pulsating flow. The analysis looks at one condition of pulsating flow with out of phase pulsations. The computational results are validated against experimental data taken from the turbocharger test facility at Imperial College and a good agreement is found.
The analysis first looks at the degree of mass flow storage within different components of the turbine and discusses the effect on the performance of the turbine. Each of the volute limbs is found to be subject to a large degree of mass storage throughout a pulse cycle demonstrating a definite impact of the unsteady flow. The rotor wheel shows a much smaller degree of mass flow storage overall due to the pulsating flow, however each rotor passage is subject to a much larger degree of mass flow storage due to the instantaneous flow inequality between the two volute inlets. This is a direct consequence of the double entry geometry.
The following part of the analysis studies the loss profile within the turbine under pulsating flow using the concept of entropy generation rate. A significant change in the loss profile of the turbine is found throughout the period of a pulse cycle showing a highly changing flow regime. The major areas of loss are found to be due to tip leakage flow and mixing within the blade passage.
An Experimental Study of Mist/Air Film Cooling With Fan-Shaped Holes on an Extended Flat Plate: Part 2 — Two-Phase Flow Measurements and Droplet Dynamics
Authors: Ragab Reda , Wang Ting 
Published: September 2014

A Phase Doppler Particle Analyzer (PDPA) system is employed to measure the two-phase mist flow behavior including flow velocity field, droplet size distribution, droplet dynamics, and turbulence characteristics. Based on the droplet measurements made through PDPA, a projected profile describing how the air-mist coolant jet flow spreads and eventually blends into the hot main flow is prescribed for both cylindrical and fan-shaped holes. The mist film layer consists of a typical coolant film layer and a wider droplet layer. The droplet layer is identified by a wedge-shaped enclosure prescribed by the data rate (droplet number per second) distribution. The apex of the enclosure, depicting by the maximum data rate, roughly indicating the core region of the coolant film. The upper boundary of the film layer, characterized by active mixing with the main flow, is found to be close to relatively high values of local Reynolds shear stresses. Thanks to higher inertia possessed by larger droplets (>20 μm in diameter) at the injection hole, the larger droplets tend to shoot across the coolant layer, resulting in a wider droplet layer than the cooling film layer.
With the prescribed coolant film and droplet layer profiles, the heat transfer results on the wall presented in Part 1 are reexamined. The 3-D droplet measurements show that the droplets injected from the fan-shaped holes tend to spread wider in lateral direction than cylinder holes and accumulate at the location where the neighboring coolant film layers meet. This flow and droplet behavior explains the higher cooling performance as well as mist-enhancement occurs between the fan-shaped cooling holes, rather than along the hole’s centerline as demonstrated in the case using the cylindrical holes.
Probabilistic Analysis of the Secondary Air System of a Low-Pressure Turbine
Authors: Brack Stefan , Muller Yannick 
Published: September 2014

The present investigation aims at performing a probabilistic analysis of the secondary air system of a three-stage low-pressure turbine rotor in a jet engine. Geometrical engine to engine variations due to the tolerance of the different parts as well as the variation of engine performance parameters are taken into account to analyse the impact on the aerodynamic behaviour of the secondary air system. Three main functions of the secondary air system have been investigated at one engine condition — take-off. At first the variation of the turbine rotor cooling flow consumption was studied. Secondly the axial bearing loads were considered and finally the system was analysed with regard to its robustness towards disc space hot gas ingestion.
To determine the uncertainty in the accomplishment of these tasks and to identify the major variation drivers, a Latin Hypercube sampling method coupled with the correlation coefficient analysis was applied to the 1D flow model. The incapability of the correlation coefficient analysis to deal with functional relationships of not monotonic behaviour or strong interaction effects was compensated by additionally applying in such cases an Elementary Effect analysis to determine the influential variables. As the 1D flow model cannot consider thermal and centrifugal growth effects, a simple mathematical model was deduced from the physical dependencies enhancing the 1D flow model to approximately capture the impact of these effects on the labyrinth seals.
Results showed that the cooling mass flow and axial bearing load are both normally distributed while their uncertainties are mainly induced by the uncertainties of the state variable of the primary air system. The investigated chamber temperature ratio to analyse the hot gas ingestion showed a not normally distributed histogram and a strong influence of interaction terms. Therefore the results of the correlation coefficient analysis were complemented with the results of an Elementary Effect analysis.
Study on the Stiffness Loss and the Dynamic Influence on Rotor System of the Bolted Flange Joint
Authors: Wang Cun , Zhang Dayi , Zhu Xiaobin , Hong Jie 
Published: September 2014

The bolted flange joint is a kind of widely used joint structure in the rotor system. Its discontinuous mechanical characteristics result from the existing of the contact surface, which will slide and deform when the spool deforms. As a consequence, the joint’s stiffness is always smaller than that of fixed configuration, which affects rotor’s stiffness distribution and the rotor’s dynamics further.
The objective of this study is to investigate the mechanical characteristics of the bolted flange joint, the affecting factors and the influence on rotor’s dynamics.
According to the characteristics of structure and mechanical state, using the existing equivalent axial spring-bending beam model to describe the tension and compression stiffness of bolted flange joint section, then the bending stiffness model of whole bolted flange joint is established based on that. The results show that there is a significant effect of the bolted flange joint on the local stiffness of the rotor, the loss of local bending stiffness reach a high level when the number of bolts is few. The mathematical description between stiffness loss and structure size, load and assembling condition is obtained through the analytical results.
A bolted flange joint simulation model, taking the characteristics of the contact into account, is built by the nonlinear finite element method. The trends of numerical results agree with the analytical conclusion, and show the stiffness of bolted flange joint is smaller than that of the fixed configuration. The stiffness of bolted flange joint decreases a small amount with the increasing moment. When the number and the pretension force increases, the stiffness increases nonlinearly.
Based on the mechanism of stiffness loss, the equivalent stiffness is used to replace the fixed configuration stiffness on the location of bolts in finite element model of high pressure rotor system. The results of dynamic analysis shows that the stiffness loss has a greater impact on bending modes than the rigid modes while the static analysis shows that the stiffness loss has a small negatively effect on clearances.
The study shows that, the stiffness loss of bolted flange joint has a close relationship with the load and assembling conditions. The results show the effectiveness in controlling the mechanical and dynamic properties of the rotor with bolted flange joints by careful adjusting of structural parameter, load parameter and assembling parameter during designing.
Experimental Study on Heat Transfer Characteristics to Supercritical Hydrocarbon Fuel in a Horizontal Micro-Tube
Authors: Fu Yanchen , Tao Zhi , Xu Guoqiang , Deng Hongwu , Jia Zhouxia 
Published: September 2014

Supercritical hydrocarbon fuel experimental loop was constructed at Beihang University to study the heat transfer characteristics to supercritical hydrocarbon fuel. The test section, a stainless tube (1.86mm I.D., 2.26mm O.D., 1Cr18Ni9Ti) with the length of 300mm, was placed horizontally above the ground and the local heat transfer coefficients of the test section were systematically measured at fixed supercritical pressure of 5MPa. The mass flux varied from 786.5 to 1573 kg/ (m2 ·s), with the uniform heat flux from 180 to 450kW/m2 and the inlet fuel temperature ranged from 373 to 673K. The experimental investigation was confined to supercritical flows with heat addition only. Hence, heat losses were measured to be taken into consideration for every experimental condition.
The experimental results were analyzed that heat transfer enhances at the reduced temperature Tb/Tpc rising from 0.95 to 1.04 and deteriorates when Tb/Tpc is larger than 1.04. The criterions of Shitman and Jackson were selected to judge the heat transfer characteristics in a horizontal micro-tube. The results indicated that buoyancy effects are ignored as the K<0.01 for the micro-scale tube and thermal acceleration is the main factor for the heat transfer characteristics. By direct comparison with an assortment of experimental data, a new correlation was proposed to be more accurate than others in predicting heat transfer phenomena for Chinese RP-3 hydrocarbon fuel in a horizontal micro-tube.
Quantifying the Economic Benefits of Wind Turbine Condition Monitoring
Authors: Williams Richard , Crabtree Christopher , Hogg Simon 
Published: September 2014

This paper presents a cost benefit analysis for wind turbine condition monitoring systems. It is widely acknowledged that performing proactive maintenance actions can reduce the number and severity of wind turbine failures. However, the use of condition monitoring systems to determine the health of the system is often viewed as costly and of little financial benefit. In this analysis the increased costs associated with condition monitoring were offset by the positive effect of early fault detection, with faults being detected before they reach a critical stage. The continual growth in turbine output and the emergence of far-offshore wind farm sites make the economic case for cost of energy reduction from timely and accurate fault detection ever stronger.
An assessment of the capability of the monitoring system was undertaken through allowance for the true to false condition monitoring detection ratio and the ability of the system to detect the severity of a fault. The analysis also compared onshore and offshore assets where the access availability can severely influence the downtime.
The results show a clear financial justification for wind turbine condition monitoring and indicate the successful detection ratio required before a condition monitoring system can offer a financial benefit.
Effect of Unguided Turning Angle and Trailing Edge Shape on Cooled Blade Loss
Authors: Granovskiy Andrey , Kostege Mikhail , Vassiliev Vladimir 
Published: September 2014

A significant part of the overall loss in modern gas turbines is the trailing edge loss. This loss is, more strongly than other constituents, affected by operation, because the trailing edge can significantly change its shape due to degradation. Also by manufacturing of new parts and reconditioning the same tolerances as in other parts of blade lead to higher deviations of aerodynamic characteristics. Therefore the understanding of trailing edge loss generation mechanisms is of utmost importance for a sound blade design. In this work the results of combined experimental and numerical investigation of the trailing edge impact on the transonic cooled blade loss are presented.
This study comprises the investigation of the unguided flow angle and the trailing edge shape on the profile losses and a base pressure. The unguided flow angle characterizes the curvature distribution on the aerofoil suction side. The numerical and experimental investigation of transonic cooled turbine cascades have shown that the increase of the unguided flow angle results in loss reduction due to increase of the base pressure downstream of the trailing edge. At the same time the deviation of the trailing edge from a round shape has detrimental effect on performance and conducted investigations allow quantification of this effect.
The measurements were performed in a transonic wind tunnel and numerical simulations were done using in-house 2D Navier-Stokes code. The comparison of calculations with measurements showed that they are in reasonable agreement.
The validated numerical procedure has been used for demonstration of possibility to reduce loss in aerofoil with thick trailing edge by tuning of the unguided flow angle. The use of the thick trailing edges at HP cooled turbines reduces restriction on tolerances, improves of manufacturability and reduces cost.
All-Mach Number Density Based Flow Solver for OpenFOAM
Authors: Heinrich Martin , Schwarze Rüdiger 
Published: September 2014

A density-based solver for turbomachinery application is developed based on the central-upwind schemes of Kurganov and Tadmor using the open source CFD-library OpenFOAM. Preconditioning of Weiss and Smith is utilized to extend the applicability down to the incompressibility limit. Implicit residual averaging, bulk viscosity damping and local time stepping are employed to speed up the simulations. A low-storage 4-stage Runge-Kutta scheme and dual time-stepping are used for time integration.
The presented solver is compared with results from ANSYS Fluent 13.0 and measurement data. Three different test cases are conducted to analyze different flow conditions: The circular bump for low and high speed inviscid flows and computational performance assessment, the two-dimensional VKI turbine guide vane for viscous flows and the the three-dimensional DLR high speed centrifual compressor validating the performance for rotating turbo-machinery. All three test cases show a very good agreement between OpenFOAM and ANSYS Fluent.