bluuebunny/crossref_metadata_2025 huggingface dataset:
Airfoil Deflection Characteristics During Rub Events
Authors: Turner Kevin E. , Dunn Michael , Padova Corso
Published: January 2011

The turbomachinery industry continually struggles with the adverse effects of contact rubs between airfoils and casings. The key parameter controlling the severity of a given rub event is the contact load produced when the airfoil tips incur into the casing. These highly non-linear and transient forces are difficult to calculate and their effects on the static and rotating components are not well understood. To help provide this insight, experimental and analytical capabilities have been established and exercised through an alliance between GE Aviation and The Ohio State University Gas Turbine Laboratory. One of the early findings of the program is the influence of blade flexibility on the physics of rub events. The focus of this paper is to quantify the influence of airfoil flexibility through a novel modeling approach that is based on the relationship between applied force duration and maximum tip deflection. Results from the model are compared to experimental results, providing sound verification.
Test Plan and Preliminary Test Results of a Bench Scale Closed Cycle Gas Turbine With Super-Critical CO2 as Working Fluid
Authors: Hasuike Hiroshi , Yamamoto Takashi , Fukushima Toshihiko , Watanabe Toshinori , Utamura Motoaki , Aritomi Masanori
Published: January 2011

Development of a closed cycle gas turbine using supercritical carbon dioxide as a working fluid is underway to generate power from industrial waste heat sources of a low or intermediate temperature range. Its demonstration test plan using a reduced scale turbomachine is described herein. Principal specifications include the following: net power output of 10 kWe and recirculation CO2 with flow rate of 1.2 kg/s under given turbine inlet conditions of 550 K and 12 MPa. The optimized ranges of compressor inlet temperatures and pressures are investigated in this study. Given these inlet conditions, primary and auxiliary component development is done. Coupled with cycle analysis, the design rotational speed of the co-axially aligned turbomachine was determined as 100,000 rpm. Aerodynamic CFD analyses were conducted for the centrifugal compressor considering real gas properties. Preliminary test results show indirect evidence of compressor work reduction inherent to the supercritical CO2 gas turbine concept.
Effects of a Realistically Rough Surface on Vane Heat Transfer Including the Influence of Turbulence Condition and Reynolds Number
Authors: Erickson E. L. , Ames F. E. , Bons J. P.
Published: January 2011

Heat transfer distributions are experimentally acquired and reported for a vane with both a smooth and a realistically rough surface. Surface heat transfer is investigated over a range of turbulence levels {low (0.7%), grid (8.5%), aero-combustor, (13.5%), and aero-combustor with decay (9.5%)} and a range of chord Reynolds numbers {ReC = 500,000, 1,000,000, and 2,000,000}. The realistically rough surface distribution was generated by Brigham Young University’s accelerated deposition facility. The surface is intended to represent a TBC surface which has accumulated 7500 hours of operation with particulate deposition due to a mainstream concentration of 0.02 ppmw. The realistically rough surface was scaled by 11 times for consistency with the vane geometry and cast using a high thermal conductivity epoxy (k = 2.1 W/m/K) to comply with the vane geometry. The surface was applied over the foil heater covering the vane pressure surface and about 10% of the suction surface. The 958 by 573 roughness array generated by Brigham Young on a 9.5 by 5.7 mm region was averaged to a 320 by 191 array for fabrication. The calculated surface roughness parameters of this scaled and averaged array included the maximum roughness, Rt = 1.99 mm, the average roughness, Ra = 0.25 mm and the average forward facing angle, αf = 3.974°. The peak to valley roughness, Rz, was determined to be 0.784 mm. The sand grain roughness of the surface (ks = 0.466 mm) was estimated using a correlation offered by Bons [1]. Based on estimates of skin friction coefficient using a turbulence correlation with the vane chord Reynolds numbers representative values for the surface’s roughness Reynolds number are 23, 43, and 80 for the three exit condition Reynolds numbers tested. Smooth vane heat transfer distributions exhibited significant laminar region augmentation with the elevated turbulence levels. Turbulence also caused early transition on the pressure surface for the higher Reynolds numbers. The rough surface had no significant affect on heat transfer in the laminar regions but did cause early transition on the pressure surface in every case.
Block-Spectral Approach to Film-Cooling Modeling
Authors: He L.
Published: January 2011

Gas turbines performance improvement requires efficient and accurate prediction tools for film-cooling of high pressure turbine blades. Use of computational fluid dynamics in the cooling design faces a challenge due to a wide range of length scales to be resolved. The difficulty is also seriously compounded by the basic feature that each blade has a large number of cooling holes. In the present paper, a new spectral approach is proposed to address this modeling difficulty. The motivation is to resolve the aerothermal flow field and mixing process of film-cooling by the numerical solution to the first principle based governing equations, whilst avoiding large computational resources required in directly solving a large number of cooling holes. By using a spectral representation for each corresponding mesh point, the block-to-block (hole-to-hole) variation can be accurately and efficiently modelled. The number of mesh blocks (cooling holes) to be solved is then dictated by the number of unknowns required to determine the spectrum. Consequently, the aerothermal field for a large number of cooling-hole blocks can be obtained by solving a much smaller set of blocks. The modeling consideration, method formulation, validation and demonstration results will be presented.
The Effect of Unequal Admission on the Performance and Loss Generation in a Double-Entry Turbocharger Turbine
Authors: Copeland Colin D. , Newton Peter , Martinez-Botas Ricardo , Seiler Martin
Published: January 2011

The current work investigates a circumferentially-divided turbine volute designed such that each gas inlet feeds a separate section of the turbine wheel. Although there is a small connecting interspace formed between the nozzle and the mixed flow rotor inlet, this design does well to preserve the exhaust gas energy in a pulsed-charged application by largely isolating the two streams entering the turbine. However, this type of volute design produces some interesting flow features as a result of unequal flows driving the turbine wheel. To investigate the influence of unequal flows, experimental data from the turbocharger facility at Imperial College has been gathered over a wide range of steady-state, unequal admission conditions. These test results show a significant drop in turbine performance with increasing pressure difference between inlets. In addition, the swallowing capacities of each gas inlet are interdependent, thus indicating some flow interaction between entries. To understand the flow physics driving the observed performance, a full 3-D CFD model of the turbine was created. Results show a highly disturbed flow field as a consequence of the non uniform admission. From these results, it is possible to identify the regions of aerodynamic loss responsible for the measured performance decrease. Given the unequal flows present in a double-entry design, each rotor passage sees an abrupt change in flow conditions as it rotates spanning the two feeding sectors. This operation introduces a high degree of unsteady flow into the rotor passage even when it operates in steady conditions. The amplitude and frequency of this unsteadiness will depend both on the level of unequal admission and the speed of rotor rotation. The reduced frequency associated with this disturbance supports the evidence that the flow in the rotor passage is unsteady. Furthermore, the CFD model indicates that the blade passage flow is unable to fully develop in the time available to travel between the two different sectors (entries).
Wet Compression Effects on Axial Compressor Performance Using Pitch-Line Models
Authors: Gopinath Arathi K. , Jothiprasad Giridhar , Wood Trevor , Tran Le
Published: January 2011

The impact of wet compression technology on compressor performance is studied using a coupled water-evaporation-pitch-line numerical model. The model uses an iterative approach to compute the modified flow conditions at blade-row stations due to inter-stage evaporation of water droplets introduced at the compressor inlet. The evaporation rate predicted by the model is compared with experimental data for stationary droplets in a duct. Performance predictions are compared with data for a GE-proprietary compressor. Study of various water droplet sizes and various water-to-air mass ratios is discussed.
Senior Undergraduate Design Project for the Development of a Pressurized Connector Spool
Authors: Pacheco Jorge , Maier William , Strupczewski Ken , Sholomskas Matt , Hunstman Shane , Keiser Todd , Shultz Trevor
Published: January 2011

This paper presents the objectives, design procedure and results of a senior design project during the spring semester of 2009. A team of five mechanical engineering senior students were challenged to design a pressurized connector spool for the original equipment manufacturer’s Integrated Compression System (ICS). This system is comprised of two modules: a separator/compressor and a high-speed, direct drive electric motor. In this concept, the motor and separator/compressor each are mounted on two magnetic bearings and their shafts are connected together using a flexible coupling. Because the flexible coupling has to be installed after both of the individual shafts are inserted into their casings (from opposite ends), the connector spool accessibility is a main concern. The students developed eight initial concepts that were compared using a concept screening matrix. The top two scored ideas were selected for further review. One dimensional simplified calculations were performed to roughly size these concepts. The final design chosen was then further developed using solid modeling and finite element stress analysis. The proposed design met the requirements for mechanical integrity, ease of manufacturability and improved accessibility.
Modeling Issues Associated With a Lip Seal Operating on a Textured Shaft
Authors: Li Wei , Stephens Lyndon Scott
Published: January 2011

This paper discusses issues related with constructing a numerical model that will be used to predict the performance of a radial lip seal with surface texture on the shaft. 2-D Reynolds equation with JFO cavitation condition is solved to obtain the hydrodynamic fluid pressure of the lubricant. Finite element method is used to calculate the solid deformation. Different material properties like linear elasticity, hyperelasticity are suggested. The mutual influence between the fluid pressure and the solid deformation is also considered. Fluid pressure is relaxed due to the deformation of the lip seal. Different factors both in physics and numerical aspects that may influence the accuracy of the simulation are discussed. A simulation case is conducted and compared to previously published experiment results. Wear mechanisms and their influence on the simulation are briefly discussed.
Framework for Multidisciplinary Optimization of Turbomachinery
Authors: Turner Mark G. , Park Kevin , Siddappaji Kiran , Dey Soumitr , Gutzwiller David P. , Merchant Ali , Bruna Dario
Published: January 2011

A multidisciplinary optimization framework is presented for turbomachinery that looks at weight and efficiency as multiple objective functions. Both the blades and disks are considered in a multi-level optimization approach. An axisymmetric solver with loss models is used for the flowpath and blade design, and optimized disks are created at each step of the process. Constraints include temperature dependent strength requirements for many common materials. The other constraint limits the work done by the component. A genetic algorithm is used to find the pareto front for the multi-objective functions. Optimization of the 10 stage GE EEE compressor is presented to demonstrate the framework. Detailed parameter based CAD models are also produced so these can be used as a starting point for higher fidelity optimization.
Combustion Characteristics and Hydrogen Addition Effects on the Performance of a Can Combustor for a Micro Gas Turbine
Authors: Shih Hsin-Yi , Liu Chi-Rong
Published: January 2011

To better understand the combustion performance by using hydrogen/methane blended fuels for an innovative micro gas turbine which is designed originally as a natural gas fired engine, the combustion characteristics of a can type combustor has been modeled and the effects of hydrogen amount were investigated. The simulations were performed using the commercial code STAR-CD, in which the three-dimension compressible k-ε turbulent flow mode and presumed probability density function for chemical reaction between methane/hydrogen/air mixtures were used. The results showed the detailed flame structures including the flow fields, distributions of flame temperature, major species and gas emissions. A variable volumetric fraction of hydrogen from 0% to 80% and the fuel injection velocities of this blended fuel ranging from 20 m/s to 60 m/s were studied. When hydrogen amount is higher, the flame temperature and exit gas temperature increase; high temperature region becomes wider and shifts to the intermediate zone. As fuel inlet velocity decreases from 60 m/s to 20 m/s, the high temperature region shifts to the side of the combustor due to the high diffusivity of hydrogen. Compared to the combustion using pure methane, NOx emissions increase with blended fuel, but the increase of hydrogen amount does not produce any significant effect over emission level of NOx. However, CO emission reduction is more remarkable at low hydrogen fraction, but the level of CO emission increases drastically when the fuel injection velocity is lower. Further modifications of the combustor designs including the fuel injection and cooling strategies are needed to improve the combustion performance for the micro gas turbine engine with hydrogen blended fuel as an alternative.
Film Cooling Performance of Waist-Shaped Slot Holes
Authors: Liu Cun-liang , Zhu Hui-ren , Bai Jiang-tao , Xu Du-chun
Published: January 2011

Film cooling performance of a new shaped hole: waist-shaped slot hole is studied in this paper. Experimental measurement and numerical simulation are carried out to investigate the film cooling character and physics of this new shaped hole. And comparisons between the waist-shaped slot hole and two kinds of console holes are also performed. Both the cooling effectiveness distribution and the heat transfer coefficient distribution of the waist-shaped slot hole are similar with those of the console hole with large divergence angle because of the effect of the waist-shaped slot hole’s structure. The middle constriction structure of the waist-shaped slot hole and the coupled vortices make jets from the waist-shaped slot holes produce higher cooling effectiveness in the midspan region between adjacent holes. And also due to the effect of the middle constriction structure, the heat transfer coefficient of the waist-shaped slot hole is very high in the upstream midspan region. However, the heat transfer coefficient in the downstream midspan region is lower than that in the region near the hole centerline because of the effect of the coupled vortices. The waist-shaped slot holes provide the surface with very good thermal protection, especially in the upstream region. Although the console holes with small exit-entry area ratio provide better thermal protection than the waist-shaped slot holes due to small turbulence intensity, the flow resistance characteristic of the waist-shaped slot hole is much better.
The Impact of Real Geometries on Three-Dimensional Separations in Compressors
Authors: Goodhand Martin N. , Miller Robert J.
Published: January 2011

This paper considers the effect of small variations in leading edge geometry, leading edge roughness, leading edge fillet and blade fillet geometry on the three dimensional separations found in compressor blade rows. The detrimental effects of these separations have historically been predicted by correlations based on global flow parameters, such as blade loading, inlet boundary layer skew etc, and thus ignoring small deviations such as those highlighted above. In this paper it is shown that this may not to be the case and that certain, engine representative geometry deviations can have an effect equivalent to an increase in blade loading of 10%. Experiments were performed at the stator hub of a low-speed, single-stage compressor. The results show that any deviation which causes suction surface transition to move to the leading edge over the first 30% of span will cause a large growth in the size of the hub separation, doubling its impact on loss. The geometry deviations that caused this, and are thus of greatest concern to a designer, are changes in leading edge quality and roughness around the leading edge, characteristic of an eroded blade.
Design Validation on Pressurized Test Rig of Upgraded VeLoNOx™ Combustion System for F-Class Engine
Authors: Zito Domenico , Bonzani Federico , Piana Carlo , Chiarioni Aldo
Published: January 2011

The design of future combustion system for F-class heavy duty gas turbine is driven by very low emission requirements, high reliability, long lifetime, fuel flexibility and combustion instability free operation. The present paper introduces the process of design validation, at test rig, of the new VeLoNOx™ burner prototypes for the most recent upgrades of the AE94.3A engine families, equipped with 24 annular combustors. Full scale testing is usually a very costly process. At the first design stage it can be reduced on a single burner housed in a cylindrical flame tube, whose shape is representative of 1/24 of the real annular combustion chamber. Because the thermo acoustic behaviour of one single burner can be greatly different than on the real engine, the design validation process cannot rely only on emission levels but should take into account the assessment of some correlations relating both test rig and field behaviour. Tests are carried out on a pressurized test rig, covering all relevant conditions of the engine, starting from Full Speed No Load to 105% of the Base Load. Each prototype, and its relevant design process, is then assessed by applying a design validation procedure to the results of experimental test campaign on the rig. Particular attention is given to analyze the acoustic response of each system as function of air to fuel ratio, flame mode, emission levels, rangeability and thermal power output. From the acoustic point of view, each burner is accurately analysed both at steady state conditions and during ramps. This paper shows the results of different VeLoNOx™ burner prototypes tested in order to identify the most promising solution to be fitted onto the AE94.3A engines.
Predictions of Enhanced Heat Transfer of an Internal Blade Tip-Wall With Hemispherical Dimples or Protrusions
Authors: Xie Gongnan , Sunde´n Bengt , Wang Quiwang
Published: January 2011

The blade tip region encounters high thermal loads because of the hot gas leakage flows, and it must therefore be cooled to ensure a long durability and safe operation. A common way to cool a blade tip is to design serpentine passages with 180-deg turn under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase the blade tip lifetime. Dimples and protrusions are well recognized as effective devices to augment heat transfer in various applications. In this paper, enhanced heat transfer of an internal blade tip-wall has been predicted numerically. The computational models consist of a two-pass channel with 180-deg turn and arrays of hemispherical dimples or protrusions internally mounted on the tip-wall. Inlet Reynolds numbers are in the range of 100,000 to 600,000. The computations are three dimensional, steady, incompressible and non-rotating. The overall performance of the two-pass channels is also evaluated. It is found that due to the combination of turning impingement and protrusion crossflow or dimple advection, the heat transfer coefficient of the augmented tip is a factor of 2.0 higher than that of a smooth tip. This augmentation is achieved at the cost of a penalty of pressure drop by around 5%. By comparing the present dimples or protrusions performance with others in previous works, it is found that the augmented-tips show the best performance, and the dimpled or protruded tips are superior to those pin-finned tips when the active area enhancement is excluded. It is suggested that dimples and protrusions can be used to enhance blade tip heat transfer and hence improve blade tip cooling.
Fuel Flexibility With Low Emissions in Heavy Duty Industrial Gas Turbines
Authors: Popovic Predrag , Myers Geoffrey , Citeno Joseph , Symonds Richard , Campbell Anthony
Published: January 2011

In the 1990’s GE introduced low-emissions combustion technology primarily for gas turbines burning natural gas (NG) fuel. Today, industrial gas turbine fuels are more diverse than ever. As a result, diverse diffusion and premixed combustion technologies are used to burn gaseous fuels with low emissions. This paper summarizes combustion and gas turbine control challenges when firing diverse fuels, and advancements in technology when burning a wide range of fuels with low emissions.
Thermal Steam Power Plant Fired by Hydrogen and Oxygen in Stoichiometric Ratio, Using Fuel Cells and Gas Turbine Cycle Components
Authors: Jericha H. , Hacker V. , Sanz W. , Zotter G.
Published: January 2011

This proposal fully complies to the demands of a zero emission power plant since only hydrogen and oxygen as obtained from splitting water are provided as fuel in a working gas cycle of pure water. Distributed power plants based on solar radiation, solar heat, wind power and water power from river flow, tidal flow and even wave motion should drive electrolysers producing hydrogen and oxygen. The units are connected with a pipeline system delivering hydrogen and oxygen at high pressure into respective storage tanks in the vicinity of the proposed power plant. So periods of generation of hydrogen and oxygen can overlap and these fuel gases are available to produce peak power according to demand. The proposed plant is an hybrid plant incorporating SOFC fuel cells into an innovative power cycle with steam as working fluid. Twelve fuel cells of 2.5 MW power produce electricity and heat up working fluid from 600 to 800°C. In a succeeding combustion chamber the fuel cell surplus hydrogen as well as the gas turbine hydrogen demand is burned with pure oxygen leading to a working gas (steam) of 1550°C and 40 bar. The working gas is expanded in an innovative cycle producing additional 109 MW of electrical energy. So an overall output of 139 MW can be achieved with a thermal efficiency of 73.8% based on fuel taken from the storage tanks for hydrogen and oxygen at 60 bar.
On Reliable Performance Prediction of Axial Turbomachines
Authors: Heß Michael , Pelz Peter F.
Published: January 2011

There is a need to reliably predict the performance (efficiency and total pressure rise) of axial turbomachines from model tests for different load ranges. The commonly used scale-up formulas are not able to reliably predict the performance, especially beyond the design point. Furthermore these formulas do not regard changes in relative roughness as they usually occur in practice. An improved scale-up formula is proposed which achieves not only the reliable scale-up of efficiency, but also the scale-up of the pressure coefficient. It is motivated from measurements on two geometric similar axial model fans with a diameter of 1000 mm respectively 250 mm at different rotational speeds, hence Reynolds numbers. By bonding grains of sand to the impeller the influence of relative roughness was investigated. For applying the formula to different load ranges a factor V is introduced that depends on the quotient of effective flow coefficient to optimal flow coefficient.
Development of Innovative Coating Technology, MSCoating, Using Electrical Discharge
Authors: Nakano Yoshikazu , Araki Takeshi , Yamada Akira , Teramoto Hiroyuki , Okane Masahiro , Goto Akihiro
Published: January 2011

MSCoating is a new coating technology using pulse discharge. This coating technology, which is developed by Mitsubishi Electric and IHI, has been put into practical use as an anti-wear coating for low-pressure turbine blades in aero engines. Normally, Z-notch, which is the edge of a low-pressure turbine blade in an aero engine, is treated with anti-wear coating by welding because these edges are frictioned together while the engine is running. However, coating by welding requires pre-heating, removal of excess thickness and advanced skill to ensure high reliability. Therefore, improvement of productivity and cost reduction are required for the anti-wear coating of Z-notch. MSCoating is an innovative coating technology that is able to meet these requirements. MSCoating can eliminate the above processing needed for coating by welding, and has superb productivity and reliability for machine work. It is confirmed that anti-wear performance of the coating formed by MSCoating is about 10 times as high as that formed by welding in a fretting wear test under conditions similar to the real operating condition. It is suggested that hard precipitate such as carbide and oxide of chrome and cobalt oxide in the MSCoating layer play a role in the advantages of the anti-wear performance.
Unstructured Large Eddy Simulation Technology for Prediction and Control of Jet Noise
Authors: Khalighi Yaser , Ham Frank , Moin Parviz , Lele Sanjiva K. , Colonius Tim , Schlinker Robert H. , Reba Ramons A. , Simonich John
Published: January 2011

Development of concepts for reduction of jet noise has relied heavily on expensive experimental testing of various nozzle designs. For example, the design of nozzle serrations (chevron) and internal mixer/ejector nozzles have relied largely on laboratory and full-scale testing. Without a deeper understanding of the sources of high-speed jet noise it is very difficult to effectively design configurations that reduce the noise and maintain other performance metrics such as nozzle thrust. In addition, the high complexity of the flow limits the success of a parametric black-box optimization.
CFD Predictions of Single Row Film Cooling With Inclined Holes: Influence of Hole Outlet Geometry
Authors: Oguntade Habeeb Idowu , Andrews Gordon E. , Burns Alan , Ingham Derek , Pourkashanian Mohammed
Published: January 2011

A CFD investigation of a single row of round inclined film cooling holes in a crossflow has been carried out with the view of investigating the discrepancies in the literature between predicted and measured results. The experimental results of Sinha et al. [1], Kohli et al. [40], Pedersen et al. [3] and others form the data base for validation of the CFD prediction of film cooling. Previous work in the literature is reviewed to show that CFD has had difficulty in obtaining agreement with these basic experimental film cooling results. However, most previous work has used tetrahedral meshes which gave poor agreement with experiments in the near hole region. In the present work it is shown by direct comparison of tetrahedral and hexahedral meshes, using the FLUENT code, with the same turbulence models, that only hexahedral meshes give good agreement with the experimental results in the near hole region. It is postulated that the reason is that the mesh structure is aligned with the flow and has more computational nodes in the important film cooling boundary layer. The hexahedral mesh was used with five turbulence models, which showed the standard k-epsilon model consistently gave the best agreement with experimental data for narrow angle film cooling. This CFD methodology was shown to be capable of predicting the influence on film cooling effectiveness of trench hole and larger diameter outlet hole geometries.
Design and Selection of Turbo-Machinery for Solar and Geothermal Power Plants
Authors: Zachary Justin
Published: January 2011

Several important sources of renewable energy, such as biomass, concentrated solar panels, waste heat, geothermal, or tidal, use different types of turbo-machinery for conversion to electrical power. The diverse nature of the heat sources and their cyclic behavior make the design of the turbo-machinery power generation equipment quite different than that of the steam turbines used in conventional power plants. The high capital cost of these renewable facilities and the limited hours of operation are powerful drivers to increase the turbo-machinery efficiency. The paper reviews the state-of-the-art hardware designs for each application from an engineering, procurement, and construction (EPC) Contractor’s perspective. Specifically for geothermal power, the discussion covers the application of working fluids other than steam, organic fluid, various mixtures of fluids etc. The benefits and limitations of each method are addressed, along with the impact of geothermal source flow and temperature on the cycle efficiency. The paper also covers the special requirements for single- and multiple-stage arrangements for geothermal applications. For concentrated thermal solar either in high-temperature applications, such as the power tower, or in medium-temperature applications, such as the solar troughs collector field, the paper addresses the unique requirements for performance, integration, and fast startup of the turbines, including the impact of various thermal storage options. Since most of the concentrated thermal solar applications are in arid regions, the paper discusses the heat sink selection (air-cooled condenser [ACC], hybrid, Heller tower, etc.) and how it impacts the plant design and performance. In conclusion, the paper deals with practical issues of achieving a balance between the economics of generation and cost of equipment and reliability for renewable power plants.
Investigations of Influential Factors on the Aerodynamic Performance of a Steam Turbine Exhaust System
Authors: Fu Jing-Lun , Liu Jian-Jun
Published: January 2011

The purpose of this paper is to investigate the influences of different parameters on the three-dimensional flow fields in the low-pressure steam turbine exhaust hood of a typical power station. The complex flows in both small-scale and full-scale turbine exhaust systems under different inlet flow conditions were simulated. The effects of inlet Reynolds number, inlet Mach number and fluid properties on the aerodynamic performance and flow fields in the exhaust systems were analyzed. The influential rules of inlet tangential flow angle distributions in the radial direction for a low speed small-scale model and a full speed full-scale exhaust system were summarized and compared. It is found that the inlet tangential flow angle at different radial position has different effects on the aerodynamic performance for both small-scale and full-scale exhaust systems. The influences of inlet Reynolds number on the aerodynamic performance depend on the inflow swirl conditions. The changing of inlet Mach number leads to the flow pattern variations in the exhaust system. The influences of fluid properties on the exhaust system performance are small.
CO2 Sequestration by Conventional and Alternative Means
Authors: Zachary Justin , Wen Harvey
Published: January 2011

In the present climate of uncertainty about CO2 emissions legislation, owners and power plant planners are looking into the possibility of accommodating “add-on” CO2 capture and sequestration (CCS) solutions in their current plant designs. The variety of CCS technologies currently under development makes it a very challenging task. Nevertheless, it is evident that the new generation of plants must address the CO2 capture issue. The underground sequestration of CO2 is associated with technical, legal and public acceptance issues. Current demonstration project will require years of operation in order to determine long term impact in the injection process on the environment. Alternative methods are used to convert CO2 into minerals that can be reused or at least stored in a solid form. The paper will review several of these alternative methods, identifying the advantages as well as the associated technical limitations. In addition to chemical or physical methods, the paper will address several other technologies that employ carbonation and algae as means of converting CO2 into a potential reusable material or transportation fuel. Finally the paper will address beyond the technical feasibility the economic and environmental impact of various alternative sequestration methods.
Fault Diagnosis and Failure Prediction by Thrust Load Analysis for a Turbocharger Thrust Bearing
Authors: Zhang Jizhong , Sun Harold , Hu Liangjun , He Hong
Published: January 2011

The axial thrust load of a turbocharger is generated due to the pressure differential between the compressor and turbine. Changes in compressor and turbine geometry and variations in test conditions can influence the thrust load. Once the axial force exceeds the loading capacity limit of a thrust bearing, the balance of the thrust bearing system cannot be maintained, which may lead to a catastrophic failure of the turbocharger. In this paper, a fault diagnosis of a turbocharger that experienced a catastrophic failure during flow bench testing is analyzed. A detailed analysis of a turbocharger thrust load, based on empirical formulae and CFD verification, is presented. The thrust prediction at high rotation speed is helpful for further flow bench testing and to avoid the future turbocharger failure.
Investigation of Low Solidity LP Turbine Cascade With Flow Control: Part 1—Active Flow Control Using Jet-Flap
Authors: Chen Ping-Ping , Qiao Wei-Yang , Luo Hua-Ling , Hashmi Farhan Ali
Published: January 2011

Increasing the airfoil lift and decreasing the solidity of turbine cascade are the effective ways to decrease blade count which lead to the reduction of weight and hardware cost of gas turbine in aircraft engine. The challenge with this effort is to prevent the flow separation on blade suction surface and to keep the efficiency at high levels. Recent investigations on the blade-flap have demonstrated dramatic reduction in the separation losses of turbine. It would be very attractive to integrate the blade-flap in the design of enhanced loaded turbine. The critical science that will enable this design innovation is a comprehensive understanding of the effect of flow control device on the boundary layer separation. The purpose of the present work was to investigate the impact of turbine cascade solidity on loss mechanisms (airfoil lift level) and to study the feasibility to develop low solidity and highly loaded LP turbine cascade blade using blade flap. This paper is the Part I of the study concerned with performance improvement of low solidity and highly loaded LP turbine cascade blade with jet-flap. The Part II is concerned with the Gurney-flap. Investigation on three turbine cascades with same type of airfoil but different solidity is presented in this paper. These turbine cascades are all constructed with the P&W LPTs highly loaded airfoil Pack B. Two dimensional steady Reynolds-averaged Navier-Stokes equations are solved for the flow of these cascades. It is shown that appropriate jet flap could decrease turbine cascade solidity about 12.5% without the considerable increase in loss, the flow deflection of the turbine cascade mainstream can be increased by jet-flap, and then contribute to increased blade loading. Because of the augmented deflection of the cascade mainstream, the flow velocity at suction side of the adjacent blade increases. This results in extension of the flow accelerating region and reduction of flow diffusion on the blade suction surface, consequently there is a delay in the boundary layer separation and/or makes the reattachment point advanced. In fact, the neighboring blade boundary layer flow is affected by the deflection of the mainstream, not on the flow of local boundary directly.
Investigation of Low Solidity LP Turbine Cascade With Flow Control: Part 2—Passive Flow Control Using Gurney-Flap
Authors: Chen Ping-Ping , Qiao Wei-Yang , Luo Hua-Ling
Published: January 2011

Numerical simulations were performed to investigate the effects of a passive flow control device named Gurney-flap on the laminar separation bubble and associated losses, aiming at assessing the feasibility of designing low solidity and highly-loaded LP turbine cascade with Gurney-flap. It was shown that with appropriate Gurney-flap the turbine cascade solidity could be decreased by 12.5% without loss increase. The deflection of the cascade mainstream due to Gurney flap can accelerate the flow at suction side of the adjacent blade, and decrease the adverse pressure gradient within the diffusion zone, which delay the boundary layer separation, thin the separation bubble and delay transition onset, contributing to reductions of both the separation-bubble-generated loss and the turbulent boundary-layer-generated loss. The numerical results indicate that the Gurney-flap height and type have significant impacts on the cascade performance, and the round Gurney-flap is the optimal flap type being the most effective for the reduction of flow losses.
On Swirl Stabilized Flame Characteristics Near the Weak Extinction Limit
Authors: Marinov Svetoslav , Kern Matthias , Merkle Klaus , Zarzalis Nikolaos , Peschiulli Antonio , Turrini Fabio , Sara O. N.
Published: January 2011

One of the most promising methods for reducing NOx emissions of jet engines is the lean combustion process. In order to realize this concept the percentage of air flowing through the combustor dome has to be drastically increased. This requirement leads to nozzles with high effective area and to high mean velocities in the primary zone of the combustor chamber. The investigation of the lean blow out limit for those nozzles is of main interest for the design of lean combustor technology. It is reported on investigation of a kerosene-fueled, swirl stabilized flame at atmospheric conditions. Two lean operation conditions are investigated, one in stable regime and the other very close to the weak extinction limit. It has been determined, that the flame shape changes when shifted from the stable regime to the other one close to the weak extinction limit (also referred to further as LBO — lean blowout). Since all field measurement schemes are similar, the gained data can be associated and conclusions regarding the flame stabilization at lean conditions can be drawn. The velocity data yields information about the topology of both isothermal and reacting flow fields in the combustion chamber. The internal recirculation and the corner recirculation zones can be well distinguished, because it can be measured directly in the nozzle exit plane. The comparison of the experimental data at stable and near LBO conditions shows the importance of inner and outer recirculation zones for the stabilization process. Furthermore, a comparison with a gaseous fuel nozzle will exhibit the differences between liquid and gaseous fuel combustion.
Steady-State Modeling of Gas Turbine Engines Using the Numerical Propulsion System Simulation Code
Authors: Jones Scott M.
Published: January 2011

The Numerical Propulsion System Simulation (NPSS) code was created through a joint United States industry and National Aeronautics and Space Administration (NASA) effort to develop a state-of-the-art aircraft engine cycle analysis simulation tool. Written in the computer language C++, NPSS is an object-oriented framework allowing the gas turbine engine analyst considerable flexibility in cycle conceptual design and performance estimation. Furthermore, the tool was written with the assumption that most users would desire to easily add their own unique objects and calculations without the burden of modifying the source code. The purpose of this paper is twofold: first, to present an introduction to the discipline of thermodynamic cycle analysis to those who may have some basic knowledge in the individual areas of fluid flow, gas dynamics, thermodynamics, and turbomachinery theory but not necessarily how they are collectively used in engine cycle analysis. Second, this paper will show examples of performance modeling of gas turbine engine cycles specifically using Numerical Propulsion System Simulation concepts and model syntax. Current practices in industry and academia will also be discussed. While NPSS allows both steady-state and transient simulations and is written to facilitate higher orders of analysis fidelity, the pedagogical example will focus primarily on steady-state analysis of an aircraft mixed flow turbofan at the 0-D and 1-D level. Ultimately it is hoped that this paper will provide a starting point by which both the novice cycle analyst and the experienced engineer looking to transition to a superior tool can use NPSS to analyze any kind of practical gas turbine engine cycle in detail.
Investigation of Sand Particle Deposition and Erosion Within a Short Pin Fin Array
Authors: Cowan Jonathan B. , Tafti Danesh K. , Kohli Atul
Published: January 2011

This paper investigates the erosion and deposition characteristics of sand particles in a short pin fin array. The simulation is carried out using a LES solver for the fluid (carrier) phase and a Langragian approach for the particle (dispersed) phase. Three particles Stokes numbers (0.78, 3.1 and 19.5) are explored as well as three non-dimensional particle softening temperatures (θST = 0, 0.37 and 0.67). The deposition is shown to increase with decreasing particle Stokes number from 0.005% for Stp = 19.5 to 13.4% for Stp = 0.78 and is almost completely concentrated on the channel walls (99.6%–100%). The erosion potential is shown to increase with Stokes number and is highest on the pin faces. The deposition increases with decreasing softening temperature from 13.4% at θST = 0.67 to 79% for θST = 0. Overall, the channel walls of the array show the greatest potential for deposition. On the other hand, the pin faces show the greatest potential for erosion.
Numerical Simulation of a Highly Loaded LPT Cascade With Strong Suction Side Separation Under Periodically Unsteady Inflow Conditions
Authors: Schwarze Marco , Niehuis Reinhard
Published: January 2011

The effects of periodically unsteady inflow conditions on boundary layer development of a highly loaded low pressure turbine cascade have numerically been studied using an unsteady Reynolds averaged Navier-Stokes solver. The numerical results show good agreement with measurement data by means of time mean profile pressure distribution and unsteady boundary layer development. In particular a reduction of the suction side separation bubble caused by the wakes is well reproduced. For increasing wake passing frequencies this reduction becomes even more pronounced. An independent variation of the flow coefficient reveals that the trajectory of the wake through the blade passage is influenced and velocity disturbances induced by the wake interact more strongly with the boundary layer on the blade as the flow coefficient decreases.
CFD Analysis of Effects of Damage Due to Bird Strike on Fan Performance
Authors: Bohari Baizura , Sayma Abdulnaser
Published: January 2011

Bird ingestion has been a hazard that affects the structural integrity and survivability of turbofan engines. It can result in deformation of one or more fan blades, in which case, the engine is likely to surge and not recover. Numerical studies and simulations of bird strikes have become essential to optimize the design of engine components simultaneously to increase the engine capabilities for acceptable damage tolerance. Good understanding of these phenomena and the implications on the behaviour of the flow field with respect to the damage affecting the fan blades are usually investigated using computational techniques and/or experimental methods. The purpose of this paper is to present a Computational Fluid Dynamics (CFD) method for the analysis of the aerodynamic behaviour of an aero-engine fan affected by a bird strike. NASA rotor 67 was used as a test case because of the availability of experimental data that can be used to calibrate the model for the undamaged fan. The undamaged fan characteristic was mapped using a modification to the methodology developed by Sayma (2007). In this method a downstream variable throttle is added which allows changing the operating point on the speed characteristic without having to change downstream boundary conditions. This approach allows for changes in fan operating point to come out of the calculation as opposed to those dictated by the downstream static pressure boundary conditions used in typical computations. The methodology is automated allowing for a sweep along a speed characteristic or along a working line in one calculation in the same way as a rig test is conducted. Agreement with experimental data when available was excellent. This provided the base line for the undamaged blades. A damaged blade was inserted among undamaged blades in the fan assembly and the fan characteristic was mapped for a range of rotational speeds. Two different degrees of damage were analysed in an attempt to establish a correlation between the extent of the damage and the locus of the stall boundary. It was found that small increments on the damage lead to significant reduction in stall margin particularly at higher rotational speeds.
Numerical Characterization of the Inlet Flow for Eleven Radial Turbomachines
Authors: Packard Nathan O. , Japikse David , Maynes R. Daniel , Gorrell Steven E.
Published: January 2011

Successful modeling of a turbomachine stage requires attention to many details, including a realistic understanding of the inlet flow field. Various levels of modeling, from 1-D to 3-D viscous, plus various levels of measurement, from a simple inlet shroud pressure tap to complex inlet surveys, are considered in design and development work. In this study, a careful review is made of measurement and calculation options for inlet modeling. Historical practice places a static pressure tap on the shroud just upstream of the impeller leading edge for experimental characterization of centrifugal turbomachines. Previously developed statistics based meanline models rely in part on this measured data. However, the location of the tap may be vulnerable to high gradients which would decrease the dependability of the developed models. Computational Fluid Dynamics (CFD) and Multi-Stream Tube (MST) analyses were performed to test the appropriateness of the historically placed static pressure tap location and to characterize the inlet flow of typical radial flow turbomachines. Eleven ConceptsNREC machines were chosen for investigation to provide a wide variety of inlet geometric and flow conditions. The results derived from the CFD and MST analyses suggest that the historically placed static pressure tap location is an inappropriate anchor point for model development. While the focus of this work is not intended to reveal why the inlet behaves as it does, it does reveal that for a wide variety of inlet configurations and impeller sizes, the presumed inlet tap location should no longer be used in experimental work. Steep gradients in the static pressure indicate that a relatively minor movement of the static pressure tap would significantly alter the experimental measurements and generate noise in statistical modeling. While large variations in the pressure field are apparent near the impeller leading edge for all machines considered, the study results show that the flow field is uniform and very predictable when well upstream of the impeller leading edge. A point approximately 3 blade heights upstream from the impeller leading edge appears to be a sound location to anchor 1-D meanline model development, as well as for future experimental investigation.