bluuebunny/crossref_metadata_2025 huggingface dataset:
Enlarging the Fuel Flexibility Boundaries: Theoretical and Experimental Application to a New Heavy-Duty Gas Turbine (MS5002E)
Authors: Asti Antonio , Stewart Jesse F. , Forte Annalisa , Yilmaz Ertan , D’Ercole Michele
Published: August 2009

GE Oil&Gas has recently launched a new heavy-duty gas turbine, the MS5002E, which underwent an extensive theoretical and experimental study on fuel flexibility. Today, fuel flexibility is one of the most challenging requirements in the Oil&Gas market. The fuel flexible operation demands a wide variety of assessments, ranging from rig tests of the combustor to theoretical consolidation of the results. The present paper describes the used methodology to increase the capabilities of burning diverse gaseous fuels, at fixed geometry. It analyzes all factors affecting the operation of the combustor with the goal to identify and extend the boundaries. Such boundaries are a result of multiple variables, like resistance to flashback and autoignition, emissions, pressure pulsations and capability of igniting. Flashback is when the reaction velocity overtakes the flow velocity and the flame moves back to the fuel injection points, threatening the integrity of the hardware. The resistance of the MS5002E to flashback and flame holding was evaluated by performing extensive experiments on a single fuel nozzle. Flame holding test results were then used to develop a transfer function for the prediction of the flame holding behavior of different mixtures. Another variable of interest is the resistance to autoignition: MS5002E took advantage of previously defined transfer functions from GE Energy that estimate the temperature above which a given mixture is likely to autoignite, at fixed pressure. Since the MS5002E is a DLN machine, it was also necessary to exclude the possibility of lean-blow-out in the whole operating range: dedicated tests on a single-can basis were used for this scope. Emissions and pressure pulsations were extensively measured on a single-can basis, since these parameters are fundamental for a lean premixed combustor. For particular mixtures, like those with high content of inert gases, the capability of igniting repeatably and reliably is an additional requirement that needs experimental validation. The combination of all the aforementioned variables determines the composition limit of the fuel mixture that the machine can tolerate. As a result of all the assessment, it was possible to achieve an increase in the maximum allowable concentrations for the following constituents: propane (up to 20%), nitrogen (up to 20% with no modifications to the control algorithms; up to 25% with minor modifications to the control algorithms) and hydrogen (up to 5%). Future tests will deliver increased capabilities also for ethane and butane.
Fixed-Bed Coal Gasifiers Integrated With MCFC-GT Hybrid Systems for Distributed Power and Heat Generation
Authors: Cocco Daniele , Serra Fabio , Tola Vittorio
Published: August 2009

In this paper, a performance assessment of coal gasification processes integrated with molten carbonate fuel cells (IG-MCFC) is reported on. The main aim of the study was to evaluate the performance of small and medium size IG-MCFC systems based on fixed-bed gasifiers for distributed power and heat generation. In particular, the plant configuration considered here was developed on the basis of the 700 kg/h fixed-bed up-draft coal gasifier located in the Sotacarbo Research Centre in Carbonia, Italy. The MCFC section is based on the DFC/T® hybrid system developed by FCE Inc., and includes a MCFC stack integrated with an indirectly heated gas turbine. Two different coals, namely a low and a high sulphur coal, were considered. Moreover, the performance of MCFC hybrid systems fuelled by natural gas and coal gas were also compared. The results of the performance assessment show that the optimum value of the gas turbine pressure ratio is around 3, which is very similar to that used by the DFC/T systems proposed by FCE Inc. and fuelled by natural gas. However, replacing methane with coal gases leads to a significant decrease in MCFC efficiency, on the order of 10–11 percentage points. On the whole, the performance assessment carried out in this paper demonstrates that IG-MCFC systems could be an interesting option for small- and medium-size power generation plants fuelled by coal as they can reach efficiencies of nearly 40%.
Heat Transfer on Rotating Channel With Various Heights of Pin-Fin
Authors: Park Jun Su , Kim Kyung Min , Lee Dong Hyun , Cho Hyung Hee , Chyu Minking K.
Published: August 2009

Pin-fins have been used to enhance the heat transfer near the trailing edge of a turbine airfoil. Previous pin-fin heat transfer studies focused mainly on the array geometry of pin height-to-diameter equal to unity in a stationary frame. This study experimentally examines the effects of pin height-to-diameter ratio (Hp/Dp) from 2 to 4 and rotation number (Ro) from 0 to 0.2. The tested model used a staggered pin-fin array with an inter-pin spacing of 2.5 times the pin-diameter (S/D = 2.5) in both longitudinal and transverse directions. Detailed heat/mass transfer coefficients were measured using the naphthalene sublimation technique with a heat-mass transfer analogy. The data measured suggest that an increase in Hp/Dp increases the level of array heat/mass transfer. Array averaged Sherwood numbers for Hp/Dp = 3 and Hp/Dp = 4 are approximately 10% and 35% higher than that of Hp/Dp = 2. The effect of rotation induces notable difference in heat/mass transfer between the leading surface and the trailing surface. The heat transfer coefficients change a little although the rotating number increases in the tested range because the pin-fins break the rotation-induced vortices.
Effects of Rotating Blade Wakes on Separation and Pressure Recovery in Turbine Exhaust Diffusers
Authors: Sieker Olaf , Seume Joerg R.
Published: August 2009

Highly efficient turbine exhaust diffusers can only be designed by taking into account the unsteady interactions with the last rotating row of the turbine. Therefore, a scale model of a typical gas turbine exhaust diffuser consisting of an annular and a conical diffuser is investigated experimentally. To investigate the influence of rotating wakes, a variable-speed rotating spoke wheel with cylindrical spokes as well as with NACA bladed spokes generates high-energy turbulent wakes simulating turbine rotor wakes. For the rotor with the NACA blades, the drive of the wheel is run in motor as well as in generator mode. Additional measurements in a reference configuration without a spoke wheel allow the detailed analysis of changes in the flow pattern. 3-hole pneumatic probes, static pressure taps, as well as a 2D-Laser-Doppler-Velocimeter (LDV) are used to investigate velocity profiles and turbulent characteristics. Without the wakes generated by a spoke wheel, the annular diffuser (with a 20° half cone opening angle) separates at the shroud for all swirl configurations. Increasing the swirl results in increasing pressure recovery at the shroud whereas the hub boundary is destabilized. For a non-rotating spoke rotor and low swirl numbers, the 20° annular diffuser separates at the shroud. Increasing the swirl number, a strong deceleration of the axial velocity at the shroud is generated without separation and a higher pressure recovery is achieved. The boundary layer at the shroud of the 20° annular diffuser separates for all operating points with the bladed rotor. A partly stabilized 20° annular diffuser can only be achieved for much higher values of the flow coefficient than that for the design point. At this high mass flow, the NACA-bladed rotor operates as a turbine, resulting in the generator mode of the electric drive. Contrary to the numerical design calculations, the flow at the shroud of a 15° annular diffuser does not separate for all swirl configurations in the experiment. Pressure recovery of the 15° annular diffuser can be increased by increasing the inlet swirl whereas the hub boundary layer is destabilized. For the NACA bladed rotor, the flow in the 15° annular diffuser as well as the pressure recovery strongly depend on the flow coefficient. For flow coefficients lower than the design value, the flow partly separates at the shroud whereas large flow coefficients result in increased pressure recovery. The pressure recovery also depends on the direction of swirl and thus the swirl number.
The Use of Eddy Current Sensors for the Measurement of Rotor Blade Tip Timing: Sensor Development and Engine Testing
Authors: Cardwell D. N. , Chana K. S. , Russhard P.
Published: August 2009

The advent of tip-timing systems makes it possible to assess turbomachinery blade vibration using non-contact systems. Currently, the most widely used systems in industry are optical systems. However, these systems are still only used on development engines, largely because of contamination problems from dust, dirt, oil, water etc. Further development of these systems for in-service use is problematic because of the difficulty of eliminating contamination of the optics. Hence, alternatives need to be developed that are immune to contamination but have equivalent resolution and bandwidth as the optical system. Experimental measurements have been carried out using alternative sensors. An eddy current sensor has been developed in a series of laboratory and engine tests to measure rotor blade arrival times. Comparisons are made with an industry standard optical blade tip timing system. The results show that it is possible to acquire high quality blade tip timing data for use in engine condition monitoring using an eddy current sensor. This sensor allows measurements to be taken that do not suffer from flow contamination and allow deployment for hotter flow environments.
Steady and Unsteady Flow Field in a Multistage Low-Speed Axial Compressor: A Test Case
Authors: Ku¨nzelmann Mario , Mu¨ller Ralf , Mailach Ronald , Vogeler Konrad
Published: August 2009

This paper introduces a new test case for compressor aerodynamics. The dataset is provided for the Dresden four-stage Low-Speed Research Compressor (LSRC), which was put into operation in 1995. The compressor consists of four identical stages, which are preceded by an inlet guide vane. The data set will be provided for the reference blading of the compressor with cantilevered stator vanes. This blading was developed on the basis of the profiles of a middle stage of a high-pressure compressor of a jet engine. This paper makes available the blading geometry as well as a variety of flow field measurement results. This includes the compressor map, selected pressure distributions and other results of flow field measurements with conventional techniques (e.g. Pitot probes, 5-hole probes). Furthermore different aspects of blade row interactions were addressed in this compressor within recent years. The periodical unsteady flow field within a selected rotor blade row was investigated using Laser-Doppler-Anemometry. Further results on the unsteady profile pressures and profile boundary layers will be provided. Supplementary, numerical results will be compared to the experiments. Results are available for several stages of the compressor and different operating points. With this test case a unique database for the aerodynamics in a multistage axial compressor will be provided that can be used for the validation of numerical codes.
Misalignment in Gas Foil Journal Bearings: An Experimental Study
Authors: Howard Samuel A.
Published: August 2009

As gas foil journal bearings become more prevalent in production machines, such as small gas turbine propulsion systems and microturbines, system level performance issues must be identified and quantified in order to provide for successful design practices. Several examples of system level design parameters that are not fully understood in foil bearing systems are thermal management schemes, alignment requirements, balance requirements, thrust load balancing, and others. In order to address some of these deficiencies and begin to develop guidelines, this paper presents a preliminary experimental investigation of the misalignment tolerance of gas foil journal bearing systems. Using a notional gas foil bearing supported rotor and a laser-based shaft alignment system, increasing levels of misalignment are imparted to the bearing supports while monitoring temperature at the bearing edges. The amount of misalignment that induces bearing failure is identified and compared to other conventional bearing types such as cylindrical roller bearings and angular contact ball bearings. Additionally, the dynamic response of the rotor indicates that the gas foil bearing force coefficients may be affected by misalignment.
Using Profiled Endwalls, Blade Lean and Leading Edge Extensions to Minimize Secondary Flow
Authors: Gregory-Smith David , Bagshaw David , Ingram Grant , Stokes Mark
Published: August 2009

Methods to reduce secondary flows and losses in turbines have been studied for many years. This paper presents the latest results from a series of projects using profiled end walls, blade lean and modifying the blade profile near the end wall. In addition a review is made of the series of designs and experiments with the aim of improving our understanding of these methods. Three distinct mechanisms are identified, the first reducing the cross passage pressure gradient in the early part of the blade passage by the wall profiling. The second uses reversed compound lean which reduces mid-span losses and forces the secondary flow region closer to the end wall by inducing spanwise pressure gradients. The third uses a leading edge extension, resulting in local sweep at the end wall which reduces the blade loading at the leading edge, and hence the early cross passage pressure gradient. The results are shown not to be additive, and although large reductions in secondary flow can be achieved, these do not always result in reduced losses. Computational based design techniques, backed up by experiment are essential to produce optimal designs.
Turbo Fans With Very High Bypass Ratio but Acceptable Dimensions
Authors: Schmidt-Eisenlohr Uwe L. H. , Kosing Oliver E.
Published: August 2009

Turbofan engines for commercial aircraft will have to improve substantially in fuel burn, noise level and NOx emissions to fulfil the ACARE 2020 environmental goals. No doubt very high bypass ratios (VHBR) will be necessary to achieve the ambitious noise reduction targets. But weight and drag of the nacelle cannot increase further and under wing installation must always be feasible. Several innovative design options such as counter rotating turbo components, air breathing nacelle, and off axis core are presented and discussed in the paper which could help to overcome the increasing dimensions of the fan and the nacelle with increasing bypass ratio.
Advanced Dry Low NOx Combustor for Mitsubishi G Class Gas Turbines
Authors: Tanimura Satoshi , Nose Masakazu , Ishizaka Koichi , Takiguchi Satoshi , Rodriguez Jose
Published: August 2009

Design features and verification results for Mitsubishi Heavy Industries’ (MHI) latest gas Dry Low NOx (DLN) combustor technology for 1500°C G-class gas turbines is presented. Key design improvements include: A) Inlet aerodynamics: CFD based design air inlet for improved flow uniformity into the pre-mixers. B) Fuel/air mixing: integrated fuel injector and swirler to decrease local flame hot-spots and reduce NOx while preventing flashback. C) Combustor aerodynamics: redesigned flame holding baffle and combustor outer wall to achieve better flame stability and NOx reduction. D) Acoustic resonator: two acoustic resonators, one in the liner to prevent high frequency combustion dynamics and the other in the bypass valve for low frequency dynamics. Tests were conducted to verify the new DLN combustor by installing it in a M501G1 gas turbine at MHI’s T-Point combined cycle power plant, with more than 1500 special measurements. Following the preliminary verification period the combustor was installed at the same plant for long-term operation. The results demonstrate the following capabilities: A) Less than 15ppm NOx operation with turn down to 60% load. B) Stable combustion dynamics at all load levels. C) High combustor ignition reliability. D) Suitable for daily start and stop (DSS) operation. E) Good reliability and durability. F) Retrofitable to existing 501G and 701G gas turbines.
Adiabatic and Overall Effectiveness Measurements of an Effusion Cooling Array for Turbine Endwall Application
Authors: Ceccherini A. , Facchini B. , Tarchi L. , Toni L.
Published: August 2009

An experimental analysis for the evaluation of adiabatic and overall effectiveness of an effusion cooling geometry is presented in this paper. Chosen configuration is a flat plate with 98 holes, with a feasible arrangement for a turbine endwall. Fifteen staggered rows with equal spanwise and streamwise pitches (Sx/D = Sy/D = 8.0), a length to diameter ratio of 42.9 and an injection angle of 30 degrees are investigated. Measurements have been done on two different test samples made both of plastic material and stainless steel. Adiabatic tests were carried out in order to obtain adiabatic effectiveness bidimensional maps. Even if a very low conductivity material (PVC) was used, adiabatic tests on a typical effusion geometry suffer, undoubtedly, from conductive phenomena: a full 3D FEM post-processing procedure for gathered experimental data was therefore developed for reckoning thermal fluxes across the surface and then correctly obtaining adiabatic effectiveness distributions. Objective of the tests performed on the conductive plate, having the same flow parameters as the adiabatic ones, was the estimation of overall efficiency of the cooled region. Experimental measurements were carried out imposing two different crossflow Mach numbers, 0.15 and 0.40, and varying blowing ratio from 0.5 to 1.7; effectiveness of the cooled surface was evaluated with a steady-state technique, using TLC (Thermochromic Liquid Crystal) wide band formulation. Finally, RANS steady-state calculations were performed employing an open source CFD code: an adiabatic case have been simulated, using both a standard and an anisotropic turbulence model. Numerical achievements have then been compared to experimental measurements. Results show that the post-processing procedure correctly succeeded in deducting undesired thermal fluxes across the plate in adiabatic effectiveness evaluation. The increasing blowing ratio effect leads to lower adiabatic effectiveness mean values, while it makes overall effectiveness to grow.
Lean and Straight Nozzle Vanes in a Variable Geometry Turbine: A Steady and Pulsating Flow Investigation
Authors: Rajoo Srithar , Martinez-Botas R. F.
Published: August 2009

Variable Geometry Turbines (VGT) are widely used to improve engine-turbocharger matching and currently common in diesel engines. VGT has proven to provide air boost for wide engine speed range as well as reduce turbo-lag. This paper presents the design and experimental evaluation of a variable geometry mixed flow turbocharger turbine. The tests have been carried out with a permanent magnet eddy current dynamometer within a velocity ratio range of 0.47 to 1.09. The peak efficiency of the variable geometry turbine corresponds to vane angle settings between 60° and 65°, for both the lean and straight vanes in the region of 80%. The variable geometry turbine was tested under pulsating flow with straight and lean nozzle vanes for different vane angle settings, 40Hz and 60Hz flow. In general, the range of mass flow parameter is higher in the straight nozzle vanes with an average of 66.4% and 69.7% for 40Hz and 60Hz flow respectively. The straight nozzle vanes also shows increasing pressure ratio range compared to the lean nozzle vanes, which is more apparent in the maximum pressure ratio experienced by the turbine in an unsteady cycle. In overall, the cycle averaged efficiency in the straight vane configuration is marginally higher than the lean vane. Furthermore, the difference to the equivalent quasi-steady is better in the straight vane configuration compared to the lean vane.
Experimental Investigation of the Time-Averaged Flow in an Intermediate Turbine Duct
Authors: Axelsson Lars-Uno , Johansson T. Gunnar
Published: August 2009

Intermediate turbine ducts are used in modern multi-spool jet engines to connect the high pressure turbine with the low-pressure turbine. The trend towards turbofan engines with larger by-pass ratios requires the radial off-set between the high-pressure and low-pressure turbines to increase with a corresponding increase in radial off-set for the intermediate turbine ducts. Other improvements of the ducts is to make them shorter and more diffusing but this strive towards more aggressive design increases the risk for separation. This paper deals with an experimental investigation of the time-averaged mean flow field and turbulence development in an aggressive intermediate turbine duct (downstream a rotating turbine stage) using a 5-hole probe and 2-component hot-wire anemometry. In addition the duct endwall static pressure distribution is discussed. The investigation revealed the complex flow structure development within the duct, where co-rotating vortices emanating from the break-up of the tip gap shear-layer dominates the flow pattern.
From Test Rig to Field Operation: A Lesson Learned
Authors: Bonzani Federico , Piana Carlo
Published: August 2009

In order to finalize the typical design process of new combustion systems, the last step to face with is usually the assessment of the correlation estimating the confidence of installing the prototype on a real engine on field. This scenario has been experienced during the validation of the new design of a premixed piloted burner to be installed on a F class engine V94.3A to reduce the NOx level below 15 ppm. The new Ansaldo Energia combustion system called VeLoNOx™ (Very Low NOx) has been designed not only to meet the challenge of the much more stringent emission requirements, but also to comply with the newer functional requirements typical of modern energy markets such as tighter grid frequency requirements. The real challenge of the design process has been investigating and validating a cross correlation between the findings of the high pressure combustion tests performed on a single burner test rig and the test campaign on a real engine with 24 burners housed in an annular combustor. Different parameters have been investigated and correlated such as combustion induced pressure oscillations, emissions, combustion efficiency and operating sensitivity. The paper describes the different steps performed in order to validate the correlation mentioned above in order to mitigate the possible risks and to estimate the confidence prior to introduce the prototype on a engine in commercial operation. Results achieved on laboratory and on field are shown and compared. Up to now Ansaldo Energia VeLoNOx™ combustion system has accumulated more than 15000 EOH on three sites with different climate conditions showing very good performances and fully meeting the design expectations. Orders for many retrofit applications have been awarded already.
Design Method of a Subsonic Aspirated Cascade
Authors: Godard Antoine , Fourmaux Antoine , Burguburu Ste´phane , Lebœuf Francis
Published: August 2009

A direct two-dimensional method for designing subsonic aspirated cascades is presented in this paper. This approach implements a specific aspiration strategy by means of a novel prescribed-curvature blading model, based on classical differential geometry. The derivation of the blade shape from the curvature distributions of the suction and pressure sides is addressed, with particular emphasis on the key design features for an efficient design with aspiration. As an application, a subsonic aspirated stator cascade, producing a 60-degree flow turning for a diffusion factor of 0.73 is achieved, with 1.1% of the inlet mass flow removed. With this method, the aspirated mass flow rate to meet design requirements is almost insensitive of the inlet Mach number. On the other hand, the same mass flow rate is found to be strongly dependent on the inlet flow angle.
A New Frequency-Speed Diagram Weighted With Strength of Modes in Rotating Machinery
Authors: Seo Yun-Ho , Lee Chong-Won
Published: August 2009

The coincidence of operating speed and critical speed must be avoided in the design of a rotor system. If the rotor system has various critical speeds as well as many modes, the determination of dangerous modes is a first step of the design stages. In this paper, the use of a new frequency-speed diagram that displays the significance of modes in order to help the design and analysis of a rotor system is suggested. The diagram is a modified version of a waterfall chart. The method graphically shows the magnitude of the forced responses by the directional frequency response matrices in accordance with operating speed because the responses are the most important criterion to determine significance of modes. In addition, because the excitation force of a rotor system such as mass unbalances is not known before the completion of manufacturing, the concept of summation of matrix norms, which is more conservative than conventional H∞ norm, is used in order to consider the worst of the worst case. A simple rotor system and a real generator system, which has both anisotropy and asymmetry, are demonstrated for usefulness of the proposed diagrams. The information of the diagram is then used to analyze the dynamic characteristics of the generator system.
Prediction of Heat Transfer and Flow Transition on Transonic Turbine Airfoils Under High Freestream Turbulence
Authors: Luo Jiang , Razinsky Eli H.
Published: August 2009

Accurate modeling of the laminar-turbulent transition remains a challenge for the prediction of external heat transfer on turbine airfoils. This paper presents a numerical study for turbine heat transfer and by-pass transition under high freestream turbulence using advanced turbulence models. Reynolds-Averaged Navier-Stokes (RANS) analyses have been carried out for two transonic turbine airfoils, with inlet turbulence intensity ranging from 12% to 16%, and exit Reynolds number varying from 8×105 to 1.5×106. The RANS results are compared against the recent data from Virginia Tech, as well as the predictions from a 2-D boundary layer code — TEXSTAN. The effects of inlet turbulence length scale on the freestream turbulence decay and boundary layer transition are investigated using different models, including a Reynolds stress model. It is found that a postulation by Steelant and Dick can be used to set up plausible turbulence length scales at the inlet. It is observed that maintaining a proper decay rate of freestream turbulence inside the turbine passages is necessary to achieve reasonably good prediction of transition and heat transfer. The V2F, SST, and k-ε turbulence models have been assessed.
Time Accurate Simulations of a Counter-Rotating Aspirated Compressor
Authors: Knapke Robert D. , Turner Mark G. , List Michael G. , Galbraith Daniel S. , Beach Tim , Merchant Ali A.
Published: August 2009

The 3D time accurate simulation of the MIT counter-rotating aspirated compressor is presented. The unsteady solver, TURBO, has been used with a phase-lag boundary condition to solve for the two counter-rotating rotors. An inlet boundary condition has been imposed to simulate the swirl and loss of the IGV. Cases with and without aspiration have been simulated. Comparison with data of the aspirated solution is good, especially near the tip picking up detailed features of the measured profile. On a 1D basis, the experimental efficiency is 87.9%, and the aspirated simulation is 89.4%. A comparison between the aspirated and non-aspirated simulations show the aspirated simulation is 2.2% higher in efficiency than the non-aspirated case. Flow details of the time-averaged solution in the second rotor show dramatic radial migration of high entropy fluid from the tip that gets ingested into the suction slot. This and other flow details shed light on the details of the counter-rotating aspirated design.
Computational Predictions of Endwall Film Cooling for a Turbine Nozzle Vane With an Asymmetric Contoured Passage
Authors: Okita Yoji , Nakamata Chiyuki
Published: August 2009

This paper presents results of a computational study for the endwall film cooling of an annular nozzle cascade employing a circumferentially asymmetric contoured passage. The investigated geometrical parameters and the flow conditions are set consistent with a generic modern HP-turbine nozzle. Rows of cylindrical film cooling holes on the contoured endwall are arranged with a design practice for the ordinary axisymmetric endwall. The solution domain, which includes the mainflow, cooling hole paths, and the coolant plenum, is discretized in the RANS equations with the realizable k-epsilon model. The calculated flow field shows that the pressure gradients across the passage between the pressure and the suction side are reduced with the asymmetric endwall, and consequently, the rolling up of the inlet boundary layer into the passage vortex is delayed and the separation line has moved further downstream. With the asymmetric endwall, because of the effective suppression of the secondary flow, more uniform film coverage is achieved especially in the rear part of the passage and the laterally averaged effectiveness is also significantly improved in this region. The closer inspection of the calculated thermal field reveals that, with the asymmetric passage, the coolant ejected from the holes are less deflected by the secondary vortices, and it attaches better to the endwall in this rear part.
Field Identification of Stiffness and Damping Characteristics of Fluid Film Bearings
Authors: Tawfick Sameh H. , El-Shafei Aly , Mokhtar M. O. A.
Published: August 2009

A method for field identification of stiffness and damping characteristics of fluid film bearings FFB is derived. The method relies on measuring both the shaft and the housing’s vibration response. Two independent unbalance runs are performed and the synchronous response is recorded. Using the housing vibration data, the amount of unbalance acting on the bearing, as well as the flexible shafts’ “modal mass” can be experimentally determined. Thus, with this method, field engineers can identify the bearings impedance in flexible rotor-bearing systems. A test rig comprising a flexible shaft supported on two cylindrical journal bearings is used to verify the proposed method. The amount of uncertainty in the derived coefficients is calculated.
Model of a Coal Fired IGCC Process With Hydrogen Membrane Reactor and Capture of CO2
Authors: Sander Frank , Span Roland
Published: August 2009

A drastic reduction of greenhouse gas emissions can only be achieved if CO2 capture will be introduced to fossil fueled power plants. Since CO2 capture lowers the efficiency of the overall power cycle tremendously, technologies have to be developed which reduce the loss in efficiency as much as possible. Due to the resources of fossil fuels, coal will still play an important role in future power generation processes. Especially, the emerging and developing countries such as India and China are already using an enormous amount of coal for power production. In this work, an IGCC process with an integrated H2-selective membrane has been investigated to substitute the CO2 capture unit by such a membrane reactor. Hydrogen-selective membranes have been studied intensively in combination with power generation processes [22, 23]. Palladium has been considered as membrane material in the present study. Due to its catalytic surface, high hydrogen permeability, and infinite hydrogen selectivity palladium and Pd-based alloys show a high potential for hydrogen separation [24, 25, 26]. The investigation has shown that the advantage of the H2-selective membrane reactor, it uses nitrogen as sweep gas on the permeate side of the membrane reactor, cannot defeat the existing drawbacks of the process layout: small mass flow rate through the gas turbine (and consequently through the HRSG) and higher energy requirements for oxygen production and CO2 compression, respectively. The net efficiency of the investigated IGCC process with integrated hydrogen-selective membrane reactor and capture of CO2 is compared with other IGCC concepts — with and without CO2 capture. The net efficiency of the overall process is 34.30%, which is about 3%-points lower compared to an IGCC process with chemical absorption and cryogenic ASU. Moreover, in comparison with an IGCC process with integrated OTM reactor and CO2 capture the efficiency is 1.7 percentage points lower than that of the process option with the lowest efficiency. Although no cost evaluation has been carried out, it can be assumed that hydrogen-selective membrane reactor would increase the capital cost of the overall IGCC process. The results indicate that the IGCC process with integrated hydrogen-selective membrane reactor and CO2 capture is less attractive from the thermodynamic point of view but also from a thermo-economic point of view.
Investigation of the Secondary Flow Structure in the Mixed Flow Turbine for a High Pressure Ratio Turbocharger
Authors: Chen Li , Zhuge Weilin , Zhang Yangjun , Zhang Shuyong , Zhang Jizhong
Published: August 2009

A numerical investigation into aerodynamic features of the mixed flow turbine used in a high pressure ratio turbocharger was conducted. The S-A turbulence model and Jameson’s center scheme have been applied in order to get good viscous resolution, accuracy and computing efficiency. Limiting streamlines on the wall surface as well as different flow characteristics, such as entropy generation of the cross sections, were evaluated, while detailed endwall flow and secondary flow structure were analyzed. The development of different vortex, especially the tip leakage vortex, passage vortex and horseshoe vortex were discussed. The results have shown that there is a great secondary flow feature and complicated vortex system in the mixed flow turbine.
Effect of Coolant Entry Orientation on Flow and Heat Transfer in the Trailing Region Channels of a Gas Turbine Vane
Authors: Kulasekharan N. , Prasad B. V. S. S. S.
Published: August 2009

The present work is concerned with the computational analysis of flow and heat transfer from the circular pin fin channels in the trailing edge region of a gas turbine vane. Combined effects of channel shape, conjugate boundary condition and flow orientation are studied. Four different channel shapes: Straight Rectangular, Straight Converged, Cambered Rectangular and Cambered Converged are considered. Both straight and lateral coolant entry are investigated at a nominal Reynolds number of 20,000. Numerical simulations are performed for the steady, incompressible, turbulent flow with the help of a computational fluid dynamics code. A structured hexahedral mesh having about 5 million cells is generated in the domain. The computational methodology is validated against the data from a standard ERCOFTAC bench mark test case. Flow and heat transfer characteristics at various locations in the channel and the axial temperature variation for a chosen pin are reported.
Numerical Simulation of a Padded Finger Seal
Authors: Yue Guoqiang , Zheng Qun , Zhu Rongkai
Published: August 2009

The leakage of turbomachinery is important to its performances. A type of non-contacting finger seal was introduced in this paper. The fluid flows through the finger seal are numerically analyzed. Multi-block structured grid of the fluid field was generated by commercial software packages ICEM CFD. The leakage and the pressure distribution on pads’ bottom surface were simulated by CFX, and the displacement of the pad was calculated in ANSYS.
Derivation of Correlations for Small Turbojet Engines
Authors: Gauthier J. E. Donald , Stowe Robert
Published: August 2009

When analysing the performance of aero-engines with incomplete input data, it is often necessary to estimate the value of the missing parameters. This paper describes the work completed to develop correlations linking various turbojet parameters using a database of nearly 100 data points. The study was limited to small single-spool turbojets with static thrust up to about 8896 N (2000 lbf). For afterburning turbojets, the information for dry operation was used. Two approaches were implemented. A Single-Input-Multiple-Output (SIMO) approach was tried with thrust as the single input variable. This approach met with success, but for only a few cases. A Multiple-Input-Single-Output (MISO) approach was tried with the specific thrust as the single output parameter. This approach worked well only when the number of known input variable values was large. For example, using the correlations derived in this research, a propulsion analyst could estimate the specific thrust from known turbine inlet temperature, fuel-to-air ratio and the pressure ratio with a reasonable degree of confidence. In the process of deriving SIMO and MISO correlations, a number of Single-Input-Single-Output (SISO) correlations were also developed. Some give fine results while others lead to excessive scatter. The paper describes the process of deriving the correlations and reports on the quality of the fits.
Investigation of Multi-Material Bird Models for Predicting Impact Loads
Authors: Nizampatnam Lakshmi S. , Horn Walter J.
Published: August 2009

This research work investigated the use of multi-material bird models for accurately predicting bird impact loads. Numerical simulations carried out using the SPH (Smoothed Particle Hydrodynamics) technique of LS-Dyna showed excellent correlation with the experimental results. The multi-material bird models of this work are more rigorous than in any previously published work, and include a realistic bird shape. Each material model was distinct, having its own density value (different from the other materials) and an associated equation of state. Results indicated that using a multi-material bird with various combinations of materials permits better correlation with experimental results.
Large Eddy Simulations of Film Cooling Flow Fields From Cylindrical and Shaped Holes
Authors: Leedom D. H. , Acharya S.
Published: August 2009

Large Eddy Simulations (LES) of cylindrical, laterally diffused, and console holes are performed, and the resulting flow field data is presented. The motivation for performing LES is to enable more accurate simulations and to obtain a better understanding of the flow physics associated with complex hole shapes. The simulations include the coolant delivery tube and the feeding plenum chamber, and are performed for a specific mass flow rate of coolant per unit width of blade. A crossflow inlet is used on the plenum, and the resulting asymmetric flow characteristics are investigated. Coolant delivery tube flow fields are investigated in detail. Results show qualitative agreement with reported trends of improved film coverage with diffused and console holes.
Investigation on Flow Characteristics and Stability of Control Valves for Steam Turbines
Authors: Liu Guanwei , Wang Shunsen , Guo Hui , Mao Jingru , Feng Zhenping , Xiang Xiaowei
Published: August 2009

Through-flow capability and flow stability of some steam turbine control valves were studied by experimental investigation and numerical simulation. Based on the analysis of thermodynamic process in control valve, the relationship of flow coefficient, area ratio of valve outlet section to seat diameter section, pressure ratio and total pressure loss coefficient was deduced, and the expression of polytropic exponent was obtained. The relative deviations between formula results and experimental results are within 3%. Both expressions can be used for design and optimization to determine control valve parameters quantitatively. The results of 3D numerical simulation indicate that the topological structure of flow fields in all control valves is similar. The results of valve stability show that the airflow force acted on the valve disc depends on the vortex strength of flow around valve stem bush and valve disc, the asymmetric transonic impinging jet under the valve disc and the diffusing action. The valve operates steadily when the inlet and outlet Mach number are less than 0.15. As the unload degree is about 85%, stem vibrates at the operating conditions when pressure ratio is less than 0.8 and opening ratio is from 10% to 18%. A multihole annular orifice can make flow steady at all operating conditions.
Performance Improvement of Centrifugal Compressor Impellers by Optimizing Blade-Loading Distribution
Authors: Yagi Manabu , Kishibe Tadaharu , Shibata Takanori , Nishida Hideo , Kobayashi Hiromi
Published: August 2009

The improvement of efficiency and operating range by optimizing blade-loading distribution of three-dimensional (3D) centrifugal compressor impellers is investigated using computational fluid dynamics (CFD) analyses and performance tests. The design points of suction flow coefficients investigated in the present study were 0.05 and 0.073. Two design approaches for 3D impeller were employed: a conventional method and a newly developed one. In order to achieve higher efficiency and wider operating range, the blade loading and relative velocity distribution were optimized in the new design procedure. In addition, to clarify the performance improvement of 3D impellers against current two-dimensional (2D) ones, both performance characteristics were compared. The test results showed the efficiencies of the newly designed 3D impellers were increased by about 0.5–1.5% in comparison with those of the conventional impellers, while the operating ranges of both were almost the same. Further, the efficiencies of the newly designed 3D impellers increased by about 3% in comparison with those of the 2D impellers at both design points. At the same time, the operating ranges of the former impellers were about 2.1–2.8 times as wide as those of the latter.
Evaluation of Weighted Sum of Grey Gases Coefficients for Combustion Gases Using Predicted Emissivities From High Resolution Spectroscopic Databases
Authors: Bahador Mehdi , Sunden Bengt
Published: August 2009

A new set of weighted sum of grey gases coefficients have been predicted using new total emissivity databases for CO2-H2O mixtures and pure H2O in different ranges of pressure. For this purpose, available high temperature spectroscopic databases were verified and suitable databases were selected. By line by line calculations, the total emissivity was calculated and the effects of total and partial pressures on this parameter were investigated. Finally, sets of total emissivity data on the wide range of temperatures and pressure path lengths were predicted which were used to estimate a new weighted sum of grey gases coefficients.
Model Based Compressor Fault Identification Using Stage Stacking Technique and Nonlinear Diagnostic Systems
Authors: Hosseini Seyyed Hamid Reza , Khaledi Hiwa , Ghofrani Mohammad Bagher
Published: August 2009

Compressor fault identification is an important part of gas turbine diagnostic systems. Model based techniques have been used widely in this field. In this paper the performance of two compressors has been simulated using stage stacking method. One of them is the NASA 10 stage constant tip diameter compressor. The other one is the Siemens V94.2 engine’s compressor. Then a new and more real compressor fault model is introduced and the effect of different faults on compressor performance has been studied. In this paper an intelligent fault diagnostic system has been developed which is able to detect different faults of the compressor. In all of the cases of faults, degradation in inlet flow coefficient of the compressor has been considered besides degradation of pressure rise coefficient and stages’ efficiencies, which has not been considered in any available study. It is shown that the fault identification system is very powerful in detecting single type faults. In the case of combined faults it was found that the faults which have been distributed in more than two stages will be identified.
Effect of Geometry Variations on the Cooling Performance of Fan-Shaped Cooling Holes
Authors: Saumweber Christian , Schulz Achmed
Published: August 2009

The flow conditions at both, the cooling hole exit as well as the cooling hole entrance affect in a very different way the cooling performance downstream of cylindrical and fan-shaped holes. The consequences of a change in a flow parameter very obviously depend on the respective hole geometry. To gain an as complete as possible view of the specific effects of varying operating conditions and hence an enhanced understanding of the dominating mechanisms, a variation of the hole geometry is imperative. The expansion angle of the diffuser, the inclination angle of the hole, and the length of the cylindrical part at the hole entrance are considered to be the most important geometric parameters of diffuser holes. The effect of a change of exactly these parameters on the film cooling performance will be analyzed. For a better assessment of the characteristic effects associated with contouring of the hole, every dif-fuser hole is compared to an adequate cylindrical hole. The comparison will be performed by means of discharge coefficients and local and laterally averaged adiabatic film cooling effectiveness and heat transfer coefficients derived from experiments.
Investigation of Innovative Trailing Edge Cooling Configurations With Enlarged Pedestals and Square or Semicircular Ribs: Part 1—Experimental Results
Authors: Facchini Bruno , Tarchi Lorenzo
Published: August 2009

This paper describes a heat transfer experimental study of several trailing edge cooling configurations based on the combination of two different heat transfer enhancing devices: enlarged pedestals and ribs. The baseline geometry consists of a wedge shaped duct with two arrays of enlarged pedestals. Square or semicircular turbulators were arranged in between the pedestals of the first row in three different positions: first on the pressure side (PS), then on the suction side (SS) and finally on both end-walls of the duct. For each configuration heat transfer and pressure loss measurements were made keeping the Mach number at 0.3 and varying the Reynolds number from 9000 to 27000. Detailed maps of heat transfer coefficient over the PS surface were measured using the transient technique with thermo-chromic liquid crystals. Results show that the combined effect of flow acceleration and turbulators lead to a significant increase of the heat transfer. The comparison between square and semicircular ribs shows that the wall heat transfer enhancement capability of the former shape is definitely higher only in the configuration with both ribbed surfaces; in like manner, square ribs generate higher pressure losses. In the configurations with one ribbed surface there are no remarkable differences between the two shapes. It is anyway interesting that the ribs placed on one side do not affect significantly the opposite smooth endwall behavior while they enhance HTC on their side, highlighting the possibility to increase cooling performance only on the airfoil side exposed to higher temperatures.