bluuebunny/crossref_metadata_2025 huggingface dataset:
Noise Reduction of Blade-Passing Frequency Components in a Centrifugal Blower
Authors: Ohta Yutaka , Outa Eisuke
Published: November 2008

A hybrid-type noise control method is applied to fundamental and higher-order blade-passing frequency components, abbreviated to BPF components, radiated from a centrifugal blower. An active cancellation of the BPF noise source is conducted based on a detailed investigation of the noise source distribution by using correlation analysis. The sound pressure level of 2nd- and/or 3rd-order BPF can be reduced by more than 15 decibels and discrete tones almost eliminate from the power spectra of blower-radiated noise. On the other hand, the sound pressure level of the fundamental BPF is difficult to reduce effectively by the active cancellation method because of the large amplitude of the noise source fluctuation. However, the fundamental BPF is largely influenced by the frequency-response characteristics of the noise transmission passage, and is passively reduced by appropriate adjusting of the inlet duct length. Simultaneous reduction of BPF noise, therefore, can be easily made possible by applying passive and active control methods on the fundamental and higher-order BPF noise, respectively. We also discuss the distribution pattern of BPF noise sources by numerical simulation of flow fields around the scroll cutoff.
Parametric Studies for a Performance Analysis of a SOFC/MGT Hybrid Power System Based on a Quasi-2D Model
Authors: Song Tae Won , Sohn Jeong L. , Kim Jae Hwan , Kim Tong Seop , Ro Sung Tack , Suzuki Kenjiro
Published: November 2008

Solid oxide fuel cell / micro gas turbine (SOFC/MGT) hybrid power system has been theoretically demonstrated that it can achieve higher thermal efficiency than any other power generation systems. To understand performance characteristics of the SOFC/MGT hybrid power system, it is necessary to analyze sensitivities of operating and design parameters on its performance. In this study, a quasi-2D model for the mathematical modeling of a tubular type indirect internal reforming solid oxide fuel cell (IIR-SOFC) is proposed and applied to a performance analysis of a SOFC/MGT hybrid power system. Using this model, temperature distributions along the longitudinal direction of the IIR-SOFC, which cannot be predicted by the lumped model, are calculated. In addition, sensitivities of parameters governing fuel cell performance such as current density, fuel utilization factor, steam-carbon ratio and parameters governing gas turbine performance such as pressure ratio, turbine inlet temperature, adiabatic efficiencies of compressor/turbine, and heat exchange effectiveness of the recuperator on the performance of the SOFC/MGT hybrid power system are investigated. Results in this study show how a quasi-2D model can improve accuracy of the performance analysis and its implementation to the performance analysis with discussion about sensitivities of design and operating parameters to the performance of the SOFC/MGT hybrid power system.
Performance of Integrated Combined and Cogeneration Cycles Using Latest Gas Turbines
Authors: Sanjay  , Singh Onkar , Prasad B. N.
Published: November 2008

The paper deals with the thermodynamic performance of combined and cogeneration cycles using the state of the art gas turbines. A configuration has been conceptualized using the latest gas turbine MS9001H that uses steam to cool the hot gas path components. In order to study the effect of cooling means, the same gas turbine is subjected to transpiration air cooling. Using the above mentioned conceptualized topping cycle, the bottoming cycle selected consists of a two-pressure reheat heat recovery steam generator (HRSG) with reheat having two options. First option is the integrated system (IS), which is a combined/cogeneration cycle, and the other is called the normal cogeneration cycle (NC). Both of these cycles are subjected to steam and transpiration air-cooling. The cycle performance is predicted based on parameteric study which has been carried out by modeling the various elements of cycle such as gas, compressor combustor, cooed gas turbine, HRSG steam turbine, condenser, etc. The performance is predicted for parameters such as fuel utilization efficiency (ηf), power-to-heat-ratio (PHR), coolant flow requirements, plant specific work, etc. as a function of independent parameters such as compressor pressure ratio (rpc) and turbine inlet temperature (TIT), etc. The results predicted will be helpful for designers to select the optimum compressor pressure ratio and TIT to achieve the target fuel utilization efficiency, and PHR at the target plant specific work.
CFD-Analysis of Conjugate Effects of Turbulence and Swirl Intensity on Spray Combustion in a Single Gas Turbine Combustor
Authors: Sadiki A. , Chrigui M. , Maneshkarimi M. R. , Janicka J.
Published: November 2008

On the basis of an Euler-Lagrangian approach, two examples of CFD analysis of the spray evolution in single gas turbine combustors are investigated to highlight the effects of two of the major controlling factors of the gas turbine combustion. The first example deals with the effects of turbulence properties on droplet dispersion, vaporization and mixing of a non-reacting spray. The second example includes the swirl intensity effects and focuses on the conjugate spray combustion. In contrast to existing works, advanced models for turbulence, evaporation and modulation are combined. The results reveal that 1) an agreement with experiments is better achieved with the non-equilibrium evaporation model; 2) the turbulence intensity influences the efficiency of the droplet interface transport; 3) an increase in swirl degree enhances obviously the mixing rate; 4) from both effects the mixing of gaseous fuel and air is confirmed to become a controlling process of combustion.
Off-Design and Transient Analysis of Saturators for Humid Air Turbine Cycles
Authors: Cevasco Riccardo , Parente J. , Traverso A. , Massardo A. F.
Published: November 2008

Considering the growing interest in the possible applications of HAT technology, characterized by the introduction of the humidification tower (saturator), this work proposes a novel model to analyze the saturator under both off-design and transient conditions. On the basis of this model, the TRANSAT code was developed and tested with experimental results from the pilot plant installed at the University of Lund in Sweden. Both off-design and transient analysis were performed. Saturator off-design analysis showed that the water inlet temperature and air/water mass flow ratio are the main parameters that control saturator operating behavior, especially saturator water and gas outlet conditions. On the assumptions made for the transient analysis, relevant results were achieved. The saturator showed a fast response to all the input variations. In particular, its characteristic times were essentially determined by the fluid residence time in the humidification tower. With regard to plant control, the main conclusion is that the integration of the saturator and the power plant is not expected to be critical for the control of the whole system.
Development, Design, and Testing of a Standard Gas Turbine Control
Authors: Oceanak Scott , Baker Brian
Published: November 2008

This paper outlines the key elements in the development and design of a standard digital control for use in fuel metering control of a gas turbine. A definition and understanding of standard versus custom controls will be presented. The major components or design steps, including digital control hardware, software programming algorithms and modeling/simulation tools for testing, will be discussed. The implementation of a flexible I/O layout, a multi-tiered software architecture and user-friendly control configurability will be introduced. These features allow the standard gas turbine control functionality to be extended to address unique user requirements without directly modifying the standard program. Recent trends in the gas turbine market have included mergers and acquisitions of many OEM suppliers. This has prompted the need for a control system that can be quickly and easily reconfigured to accommodate differences in gas turbine manufacturers’ designs. An important element for success is the understanding that this work is done by service providers at various levels of the supply chain, including OEMs, generator or compressor equipment packagers, and gas turbine retrofitters. This offering details the control development and design process and emphasizes the critical need for high fidelity modeling and simulation tools to promote robust initial control software design. It also highlights the additional value of leveraging this work to support control software application changes that evolve over the lifecycle of the control product.
Heat Transfer Analysis of a Wedge Shaped Duct With Pin Fin and Pedestal Arrays: A Comparison Between Numerical and Experimental Results
Authors: Andreini Antonio , Carcasci Carlo , Magi Andrea
Published: November 2008

The use of pin fin arrays in channels is one of the best choices to enhance overall heat transfer in gas turbine trailing edge blade cooling. Furthermore, in this particular application, the use of cross-pins in the trailing edge section of a turbine blade is a good way for supplying structural integrity to the blade itself. In this paper, results of several 3D RANS calculations performed in channels with cross-pins disposition such as in a typical trailing edge of a gas turbine blade are shown. Numerical calculations were compared with experimental results obtained on the same geometries using a transient Thermochromic Liquid Crystals (TLC) based technique. Goals of this comparison are both the evaluation of the accuracy of CFD packages with standard two equation turbulence models in heat transfer problems with complex geometries and the analysis of flow details to complete and support experimental activity. Two computational domains have been considered: they both consist in a wedge shaped channel with a stream-wise normal pin fin or pedestal arrays. The aim of the numerical analysis is the evaluation of convective Heat Transfer Coefficient (HTC) on the planar bottom surface of the wedge-shaped duct: this surface is commonly named “endwall” surface. Detailed analysis of the flow field points out the coexistence of an horse-shoe vortex, a stagnant wake behind the pin and a mean flow acceleration due to convergent shape of the channel. Calculations reveal the presence of a weak jet-like flow field toward endwall surfaces caused by the strong recirculation behind each pin.
High Speed, High Temperature, Fault Tolerant Operation of a Combination Magnetic-Hydrostatic Bearing Rotor Support System for Turbomachinery
Authors: Jansen Mark , Montague Gerald , Provenza Andrew , Palazzolo Alan
Published: November 2008

Closed loop operation of a single, high temperature magnetic radial bearing to 30,000 RPM (2.25 million DN) and 540°C (1,000°F) is discussed. Also, high temperature, fault tolerant operation for the three axis system is examined. A novel, hydrostatic backup bearing system was employed to attain high speed, high temperature, lubrication free support of the entire rotor system. The hydrostatic bearings were made of a high lubricity material and acted as journal-type backup bearings. New, high temperature displacement sensors were successfully employed to monitor shaft position throughout the entire temperature range and are described in this paper. Control of the system was accomplished through a stand alone, high speed computer controller and it was used to run both the fault-tolerant PID and active vibration control algorithms.
Efficient Fracture Design for Complex Turbine Engine Components
Authors: McClung R. Craig , Enright Michael P. , Lee Yi-Der , Huyse Luc J. , Fitch Simeon H. K.
Published: November 2008

Many high-energy turbine engine components are fracture critical. However, the complex three-dimensional (3d) geometries and stress fields associated with these components can make accurate fracture analysis impractical. This paper describes a new computational approach to efficient fracture design for complex turbine engine components. The approach employs a powerful 3D graphical user interface (GUI) for manipulation of geometry models and calculated component stresses to formulate simpler 2D fracture models. New weight function stress intensity factor solutions are derived to address stress gradients that vary in all directions on the fracture plane.
Adiabatic Effectiveness Measurements of Endwall Film-Cooling for a First Stage Vane
Authors: Knost D. G. , Thole K. A.
Published: November 2008

In gas turbine development, the direction has been towards higher turbine inlet temperatures to increase the work output and thermal efficiency. This extreme environment can significantly impact component life. One means of preventing component burnout in the turbine is to effectively use film-cooling whereby coolant is extracted from the compressor and injected through component surfaces. One such surface is the endwall of the first stage nozzle guide vane. This paper presents measurements of two endwall film-cooling hole patterns combined with cooling from a flush slot that simulates leakage flow between the combustor and turbine sections. Adiabatic effectiveness measurements showed the slot flow adequately cooled portions of the endwall. Measurements also showed two very difficult regions to cool including the leading edge and pressure side-endwall junction. As the momentum flux ratios were increased for the film-cooling jets in the stagnation region, the coolant was shown to impact the vane and wash down onto the endwall surface. Along the pressure side of the vane in the upstream portion of the passage, the jets were shown to separate from the surface rather than penetrate to the pressure surface. In the downstream portion of the passage, the jets along the pressure side of the vane were shown to impact the vane thereby eliminating any uncooled regions at the junction. The measurements were also combined with computations to show the importance of considering the trajectory of the flow in the near-wall region, which can be highly influenced by slot leakage flows.
Rotordynamic Coefficients for a Tooth-on-Stator Labyrinth Seal at 70 Bar Supply Pressures — Measurements Versus Theory and Comparisons to a Hole-Pattern Stator Seal
Authors: Picardo Arthur , Childs Dara W.
Published: November 2008

Rotordynamic and leakage coefficients are presented for a labyrinth seal that was tested at a supply pressure of 70 bar-a and speeds up to 20200 rpm. Tests were conducted at clearances of 0.1mm and 0.2mm, pressure ratios of 0.10, 0.31 and 0.52, and three pre-swirls ratios. Comparisons are made between test data and predictions from one-control-volume and two-control-volume bulk-flow models. Generally, theoretical predictions agree poorly with the test results, with the one-control volume model giving better predictions. The one-control-volume model provides a conservative prediction for effective damping; i.e., this parameter is underestimated. Both models under predict leakage rates. Comparisons are also made between rotordynamic coefficients of labyrinth and hole-pattern seals.
A Study of the Effects of Inlet Preswirl on the Dynamic Coefficients of a Straight-Bore Honeycomb Gas Damper Seal
Authors: Sprowl Tony B. , Childs Dara W.
Published: November 2008

In high-pressure centrifugal compressors, honeycomb seals are often used as replacements for labyrinth seals to enhance dynamic stability. A concern exists with the loss of this enhanced stability if the honeycomb cavities become clogged with debris over time. So, static and dynamic tests were conducted on a constant-clearance honeycomb and a constant-clearance smooth-bore seal under three inlet preswirl conditions, with the smooth-bore seal representing the honeycomb seal with completely clogged cells. Comparing results for the two seals shows increased leakage flowrate and decreased stiffness and dynamic stability for the honeycomb seal with clogged cells. Also, results for the honeycomb seal under the influence of preswirl were used to evaluate a two-control-volume theory by Kleynhans and Childs.
Performance of a Dry Low NOx Gas Turbine Combustor With an Improved Innovative Fuel Supply Concept
Authors: Wakabayashi Tsutomu , Moriya Koji , Koga Shonosuke , Shimodaira Kazuo , Kurosawa Yoji , Yamamoto Takeshi , Yoshida Seiji , Suzuki Kazuo , Okazaki Yasuhide , Osone Masanori , Kawaguchi Osamu
Published: November 2008

This paper describes the combustion performance of a dry low-NOx gas turbine combustor designed with an innovative fuel supply concept using gaseous fuel. This concept uses spontaneous fuel distribution achieved by an interaction between the gaseous fuel jet and the airflow. Previously, we proved that fuel distribution based on the innovative fuel supply concept actually occurred according to the load by means of pressurized combustion tests using a prototype combustor. However, NOx was not low enough at high loads, and combustion efficiency was not high at medium and low loads. Further, the pressure loss of the combustor was high. Therefore, the prototype combustor was improved from the viewpoint of NOx, combustion efficiency and combustor pressure loss. This paper describes the detailed structure of the improved combustors and the results of the pressurized combustion experiments.
Modeling and Validation of the Thermal Effects on Gas Turbine Transients
Authors: Nielsen Annette E. , Moll Christoph W. , Staudacher Stephan
Published: November 2008

Secondary effects, such as heat transfer from fluid to engine structure and the resulting changes in tip and seal clearances affect component performance and stability. A tip clearance model to be used in transient synthesis codes has been developed. The tip clearance model is derived as a state space structure. The model parameters have been identified from thermo-mechanical finite element models. The model calculates symmetric rotor tip clearance changes in the turbo-machinery and symmetric seal clearance changes in the secondary air system for engine transients within the entire flight envelope. The resulting changes in efficiency, capacity and cooling air flows are fed into the performance program. Corrections for tip clearance changes on the component characteristics are derived from rig tests. The effect of seal clearance changes on the secondary air system is derived using sophisticated air system models. The clearance model is validated against FE thermo-mechanical models. The modeling method of modifying the component characteristics is verified comparing engine simulation and test data which show good agreement. Based on a representative transient maneuver typical transient overshoots in fuel flow and turbine gas temperature and changes in component stability margins can be shown. With the use of this model in the performance synthesis the transient engine performance can be predicted more accurate than currently in the engine development program.
Progress in the Development of a Low Cost 1MW SOFC Hybrid
Authors: Agnew Gerry D. , Townsend James , Moritz Robert R. , Bozzolo Michele , Berenyi Steve , Duge Robert
Published: November 2008

Rolls-Royce Fuel Cell Systems (RRFCS) is developing a low cost 1MW fuel cell hybrid system package, supported by a prototype demonstration of a 250kW module in 2006. This paper describes the detailed design process that has been carried out to produce the fuel cell stack, tailored turbo-machinery and other plant components for this hybrid. Progress in demonstrating components is described. Component interfacing, operability and control challenges have been assessed prior to assembly of the complete system and are reviewed. The baseline plant will be highly efficient compared to incumbent power generation technologies but is primarily optimised around cost-reduction. Evolution of the product will include opportunities for further increases in efficiency and power density. Opportunities for improvement are discussed.
Transition on Concave Surfaces
Authors: Dris Antonis , Johnson Mark W.
Published: November 2008

Boundary layer measurements have been made on the concave surfaces of two constant curvature blades using hot wire anemometry. All the current experiments were performed with negligible streamwise pressure gradient. Grids were used to produce a range of freestream turbulence levels between 1% and 4%. The freestream velocity increases with distance from a concave wall according to the free vortex condition making the determination of the boundary layer edge difficult. A flat plate equivalent boundary layer procedure was adopted therefore to overcome this problem. The Taylor-Goertler (T-G) vortices resulting from the concave curvature were found to make the laminar and turbulent boundary layer profiles fuller and to increase the skin friction coefficent by up to 40% compared with flat plate values. This leads to a more rapid growth in boundary layer thickness. The evolution in the intermittency through transition is very similar to that for a flat plate, however the shape factors are depressed slightly throughout the flow due to the fuller velocity profiles. For all the current experiments, curvature promoted transition. This was very marked at low freestream turbulence level but remained significant even at the highest levels. It appears that the velocity fluctuations associated with the T-G vortices enhance the freestream turbulence resulting in a higher effective turbulence level. A new empirical correlation for start of transition based on this premise is presented. The ratio of end to start of transition momentum thickness Reynolds numbers was found to be approximately constant.
Predicting Transitional Separation Bubbles
Authors: Redford John A. , Johnson Mark W.
Published: November 2008

This paper describes the modifications made to a successful attached flow transition model to produce a model capable of predicting both attached and separated flow transition. This transition model is used in combination with the Fluent CFD software, which is used to compute the flow around the blade assuming that it remains entirely laminar. The transition model then determines the start of transition location and the development of the intermittency. These intermittency values weight the laminar and turbulent boundary layer profiles to obtain the resulting transitional boundary layer parameters. The ERCOFTAC T3L test cases are used to validate the predictions. The T3L blade is a flat plate with a semi-circular leading edge, which results in the formation of a separation bubble the length of which is strongly dependent on the transition process. Predictions were performed for five T3L test cases for differing freestream turbulence levels and Reynolds numbers. For the majority of these test cases the measurements were accurately predicted.
Blade Manufacturing Tolerances Definition for a Mistuned Industrial Bladed Disk
Authors: Capiez-Lernout Evange´line , Soize Christian , Lombard Jean-Pierre , Dupont Christian , Seinturier Eric
Published: November 2008

This paper deals with the characterization of the blade manufacturing geometric tolerances in order to get a given level of amplification in the forced response of a mistuned bladed-disk. It is devoted to an industrial application in order to validate the theory previously developed [1] and in order to show that this theory is suited to any industrial bladed-disks. It should be noted that the development of an adapted methodology for solving the inverse problem, in order to characterize the manufacturing tolerances, is an important challenge for industries in this area. Let us recall that this theory is based on the use of a nonparametric probabilistic model of random uncertainties in the blade [2]. The dispersion parameters controlling the nonparametric model are estimated as a function of the geometric tolerances. Such an identification is carried out in a computational context by using the numerical Monte Carlo simulation and by using the reduced model method presented in [3]. The industrial application is devoted to the mistuning analysis of a 22 blades wide chord fan stage. Centrifugal stiffening due to rotational effects is also included. The results obtained validate the efficiency and the reliability of the method on three dimensional bladed disks.
Forced Response Prediction: Methodology for the Design of HP Compressors Bladed Disks
Authors: Seinturier Eric , Lombard Jean-Pierre , Dumas Michel , Dupont Christian , Sharma Virendra , Dupeux Je´roˆme
Published: November 2008

This paper presents a general approach related to bladed disk forced response prediction and a typical way to use it in the design process. Firstly, a good confidence level in prediction tools must be reached. The first application is a highly instrumented HP compressor blisk representative of a real engine environment. Simulation of forced response is compared to measurements in order to check the accuracy of prediction. For this test case, the results obtained are in very good agreement with measurements. The good quality of prediction is due to the complete characterization performed on the test case: all the influent parameters were identified before testing. But during the design process, many important parameters are unknown and this level of accuracy can not be obtained. Nevertheless, forced response prediction in the early design process can provide interesting information even if uncertainties are high for some parameters. As an illustration, a second application is proposed, based on the design experience of a new HP compressor of a known engine family. Some forced response predictions were performed during development and compared afterwards with measurements obtained during engine testing. This analysis has permitted to confirm some technical choices and to assess the High Cycle Fatigue risk associated to this new engine configuration.
Performance of a Longitudinal Circular-to-Slot Gas Turbine Exhaust Duct With a 90 Degree Bend
Authors: Bottenheim S. , Birk A. M. , Poirier D. J.
Published: November 2008

In some gas turbine applications, it is desirable to redirect the exhaust flow through 90 degrees and mix this flow with the ambient air for the purposes of structural integrity and heat signature suppression. A method to achieve this is to transform the flow from a circular profile to a rectangular slot of high aspect ratio. The increase in wetted perimeter allows for greater mixing with the ambient air; however the shape of such a duct causes significant amounts of flow distortion and poor pressure recovery. This paper presents preliminary experimental results of the performance of such a duct and discusses the ability of a commercial CFD software package to numerically predict this performance. Significant crossflows and reversed flows were observed at the duct outlet leading to inefficient use of the outlet area, high back pressure and consequently a high loss coefficient. These trends are exacerbated with an increasing inlet swirl angle. The preliminary numerical predictions captured the general trends of the flow but could not capture the extent of the reversed flow, leading to over-prediction of the effective area ratio, E, and under-prediction of the loss coefficient, k.
On Annulus Flow Characteristics and Performance of Dilution Holes in a Gas Turbine Combustor
Authors: Agrawal M. D. , Bharani Sanjeev
Published: November 2008

Experimental investigations on discharge coefficient (Cd) of a row of plunged dilution holes of a reverse-flow gas turbine combustor were carried out using water as the working fluid. Studies were carried in a wide range of inlet Re (0.5 × 104 – 1.65 × 104) on an individual row of dilution holes (Dd = 7 mm; 1/Dd = 0.428; s/Dd = ∞ − 2) as well as in combinations with two rows of skirted cooling holes (Dc = 2 mm; 1/Dc = 0.67) and a row of plain primary holes (Dp = 3 mm; 1/Dp = 1) using a plane annulus model. The model represented narrow outer annulus, a passage between outer casing and liner of a combustor. The downstream end of the annulus was closed, as is the case in all combustors, to establish its impact on the pressure distribution and discharge coefficient of plunged dilution holes. It is observed that presence of the other liner holes (cooling and primary), when operating together, and formation of recirculation zones towards the closed end significantly diminish pressure values at the row of dilution holes and reduce its Cd to a lower range as compared to its performance when operating individually. In this case, static pressure at all the four rows of liner holes increased parabolically up to a magnitude of Re = 1.35 × 104 and decreased thereafter with further increase in the Re. The Cd of the row of dilution holes, when operating alone, remained in the range of 0.95 to 0.81 for s/Dd = 2. For a single hole Cd varied from 0.96–98, which compares well with the data present in the literature. These values reduced in the presence of first cooling holes (by ≈ 19–23%) and primary holes (by ≈ 16–18%), while with second row of cooling holes no significant change was observed. Similarly, in combination with a pair of other rows of holes also Cd values were affected, while with all the four rows of the liner holes operating together reduced the range of Cd values to ≈ 0.88–0.85 (K = 25–27).
Parametric Study of Tip Clearance – Casing Treatment on Performance and Stability of a Transonic Axial Compressor
Authors: Beheshti Behnam H. , Teixeira Joao A. , Ivey Paul C. , Ghorbanian Kaveh , Farhanieh Bijan
Published: November 2008

The control of tip leakage flow (TLF) through the clearance gap between the moving and stationary components of rotating machines is still a high-leverage area for improvement of stability and performance of aircraft engines. Losses in the form of flow separation, stall, and reduced rotor work efficiency are results of the tip leakage vortex (TLV) generated by interaction of the main flow and the tip leakage jet induced by the blade pressure difference. The effects are more detrimental in transonic compressors due to the interaction of shock-TLV. It has been previously shown that the use of slots and grooves in the casing over tip of the compressor blades, known as casing treatment, can substantially increase the stable flow range and therefore the safety of the system but generally with some efficiency penalties. This paper presents a numerical parametric study of tip clearance coupled with casing treatment for a transonic axial-flow compressor NASA Rotor 37. Compressor characteristics have been compared to the experimental results for smooth casing with a 0.356 mm tip clearance and show fairly good agreement. Casing treatments were found to be an effective means of reducing the negative effects of tip gap flow and vortex, resulting in improved performance and stability. The present work provides guidelines for improvement of steady-state performance of the transonic axial-flow compressors and improvement of the stable operating range of the system.
Spray Impingement and Evaporation Through Porous Media
Authors: Sankara Chinthamony Sathish K. , Periasamy Chendhil , Gollahalli S. R.
Published: November 2008

This paper presents an experimental study on spray impingement and fuel evaporation processes in porous media. Aviation-type kerosene (Jet-A) was used as the fuel and an open-cell, silicon carbide coated, carbon-carbon ceramic foam was used as the porous medium. The fuel was sprayed into a coflowing, preheated air environment using an air-blast atomizer. A Phase Doppler Particle Analyzer (PDPA) was used to measure Sauter mean diameter (SMD), liquid mass flux, and axial velocity of the droplets. The porous medium was resistively heated to simulate heat feedback from the combustion zone. An organic vapor analyzer, based on catalytic oxidation, was used to measure the concentration of kerosene vapor downstream of the porous medium. The temperature and flow rate of coflow air were held constant, while the fuel flow rate, and hence, the overall equivalence ratio, was varied from 0.3 to 0.6. Higher liquid mass flux was recorded away from the spray core region, due to the swirling action of atomizing air. Surface temperature measurements of porous media revealed the uniformity of thermo-electrical properties of the medium. Vapor concentration measurements with combustion heat feedback (a heat input of 33 kW/m2) increased the average vapor concentration by 63% and 43% than that of no heat feedback case for 0.3 and 0.6 equivalence ratios respectively.
Experiments on Gas Ingestion Through Axial-Flow Turbine Rim Seals
Authors: Roy R. P. , Feng J. , Narzary D. , Saurabh P. , Paolillo R. E.
Published: November 2008

It has been suggested by researchers that ingestion, through rim seals, of mainstream gas into axial-flow turbine disk cavities is a consequence of the prevailing unsteady three-dimensional flow field. The cause-effect relationship is complex — to help understand it, experiments were performed in a model single-stage turbine rig using two different vane-blade configurations. Selected measurements from one of the configurations were reported earlier (1999–2001). The second configuration is new, featuring smaller numbers of vanes and blades and a larger vane turning angle. Selected measurements are presented and compared to those from the first configuration. The measurements include: unsteady and time-average static pressure spatial distributions, and spatial distribution, in the rotor-stator cavity, of time-average ingestion. The parameters in the experiments were: main air flow rate, purge/seal air flow rate, and rotor speed. Unsteady three-dimensional CFD simulation may be helpful in identifying the roles of the many intertwined phenomena in the ingestion process.
Evaluation of Topping and Bottoming Cycle Hybrid Power Plants With MCFC-Micro Turbine
Authors: Zhang Huisheng , Weng Shilie , Su Ming
Published: November 2008

The increasing use of electronic appliance has put a strain on the existing electrical supply system. The growing trend of distributed generation could result in small turbo generators being used in the home or rural area. Because small turbo-generator is ideally suited for coupling with a Molten Carbonate Fuel Cell (MCFC) stack, a high efficiency and flexible hybrid system representing a new total energy concept for the distributed power market is presented. This paper presents hybrid concept of bottoming and topping cycle MCFC-micro turbine system. The simulation models for micro turbine, MCFC stack and hybrid system are established. Based on an existing 10kW MCFC stack, we carried out the simulation on hybrid system. The results of the simulation are presented and discussed with particular regards to the selection of design point of different configurations of Hybrid System and design point performance of topping cycle and bottoming cycle Hybrid System.
The Influence of Metallurgical and Mechanical Pre-Damage on Creep-Crack and Fatigue-Crack Growth Rates of CrMoV Steel
Authors: Sekihara Masaru , Sakurai Shigeo
Published: November 2008

The effects of mechanical degradation on the creep- and fatigue-crack growth rates in power plants operated long-term were studied. Creep-crack growth tests and fatigue-crack growth tests were performed using creep-pre-strained and repetitive-strained CrMoV rotor-steel specimens. It was found that the creep-crack growth rates, da/dt, of the creep-pre-damaged specimens were larger than those of virgin specimens under constant load. It was also found that under the same stress intensity factor K, da/dt in the case of about 10%-crept and creep void induced specimens was increased five times, while in the case of 0.8%- and 2.8%-crept specimens, it only increased a little. However, all the data fell in a narrow scatter band in the relationship between C* and da/dt. The effect of long-term operating degradation appeared on the creep- and fatigue-damage under the Slow-Fast waveform. Also the crack density was larger in the damaged specimens compared with the virgin specimens. Other results showed that the fatigue-crack growth rates, da/dN, of creep- and fatigue-pre-damaged specimens were larger than those of virgin specimens. Under the same stress intensity factor range ΔK, da/dN in a specimen with approximately 10%-creep was increased 20 times. Moreover da/dN in fatigue-pre-damaged specimens was accelerated 10 times. However, the results of the strain-controlled crack growth test fell in a narrow scatter band in the relationship between J integral range ΔJ and da/dN. These results suggest that the creep remaining lives and fatigue remaining lives of mechanically damaged CrMoV steel can be estimated using the C* & ΔJ values considering the creep rate and the deformation rate of the pre-damaged materials and the da/dt and da/dN values of the virgin material.
Large Eddy Simulation of Flow and Heat Transfer in a Channel Roughened by Square or Semicircle Ribs
Authors: Ahn Joon , Choi Haecheon , Lee Joon Sik
Published: November 2008

The internal cooling passage of a gas turbine blade can be modeled as a ribbed channel. So far, most studies have considered square ribs. However, the ribs can be rounded due to improper manufacturing or wear during the operation. Round ribs have also been tested expecting that they may enhance the thermal and aerodynamic performance. Hence, we have studied two different rib geometries in this study, i.e. square and semicircle ribs. Large eddy simulations (LES) of turbulent flow in a ribbed channel with a dynamic subgrid-scale model are performed. In our simulation, the no-slip and no-jump conditions on the rib surface are satisfied in Cartesian coordinates using an immersed boundary method. We have also conducted an experimental study to validate the simulation. The velocity and temperature fields are measured using hot wire and thermocouple, respectively. The surface heat transfer is measured using the thermochromic liquid crystal with a high spatial resolution. LES predicts the detailed flow and thermal features such as the turbulence intensity around the ribs and the local heat transfer distribution between the ribs, which have not been captured by simulations using turbulence models. By investigating the instantaneous flow and thermal fields, we propose the mechanisms responsible for the local heat transfer distributions between the ribs; i.e. the entrainment of the cold fluid by the vortical motions and the impingement of the entrained cold fluid on the ribs. We also discuss the local heat transfer variation of the ribs in connection with flow separation and turbulent kinetic energy. The total drag and heat transfer are calculated and compared between the square and semicircle ribs, showing that two ribs produce nearly the same heat transfer, but the semicircle one yields lower drag than the square one.
Oil Pumping in High Speed and High Loaded Ball Bearings
Authors: Flouros Michael
Published: November 2008

Trends in aircraft engine design cause increased mechanical stress requirements for rolling bearings. Consequently high amounts of heat are rejected which results in high oil scavenge temperatures. The direction of oil flow in the bearing can considerably affect the heat transported by the oil. An RB199 turbofan bearing and its associated chamber were modified to carry out the survey. The test bearing was a 124mm PCD ball bearing. The bearing has a split inner-ring employing under-race lubrication by two individual jets. The total oil flow could be devided to any ratio through the jets. This had an impact on the oil scavenge temperatures and the scavenge flows on both sides of the bearing. Significant reduction in the ‘heat to oil’ was achieved when oil was fed at certain proportions (ratio). This work is part of the European Research programme Brite Euram ATOS (Advanced Transmission and Oil Systems).
Experimental Characterization of the Coolant Film Issuing From a Cooling Tile
Authors: Chua K. H. , Carrotte J. , Denman P. , Spencer A.
Published: November 2008

In modern, low emission, gas turbine combustion systems the amount of air available for cooling of the flame tube liner is limited. This has led to the development of more complex systems, such as cooling tiles, as opposed to the use of more conventional cooling slots. Within a cooling tile the flow passes around a large number of pedestals located between 2 skins that promote the removal of heat from the hot surface. This flow is then discharged from a slot at the rear of the tile to form the coolant film. This paper characterises the flow passing through a tile and, in particular, the coolant film that is formed along the tile surface. Data is presented for both a standard tile geometry and one in which the coolant film is enhanced by effusion cooling. A large-scale facility incorporating a 10 times full size cooling tile has been developed. The aerodynamic characteristics of the coolant film have been defined using pneumatic probes, hot wire anemometry and PIV instrumentation, while gas tracing is used to indicate mixing of the coolant film with the mainstream flow. For low mainstream turbulence the results show that the initial condition of the cooling film dominates the subsequent development and mixing of the film along the tile length. Relative to this configuration, high mainstream turbulence levels with large turbulent scales were introduced by placing a cylinder upstream of the tile. The turbulent mainstream flow quickly penetrates the coolant film and a more rapid break up of the coolant film is observed. This includes an almost linear increase in thickness of the coolant film together with a linear reduction in wall film effectiveness along the tile length. Relative to this conventional tile the use of effusion cooling was shown to restore the film effectiveness along the rear of the tile. In addition to the time averaged characteristics the time dependent behaviour of the coolant film was also investigated. In particular, unsteadiness associated with vortex shedding within the mainstream flow was observed within the coolant film and adjacent to the tile surface.
Development and Experimental Validation of a Compressor Dynamic Model
Authors: Venturini M.
Published: November 2008

In recent years, transient response analysis of energy systems is becoming more and more important in optimizing plant operation and control. Furthermore, dynamic analyses are also used to integrate steady-state diagnostic analyses, since they allow the detection of malfunctions characterized by time-dependent effects. The paper deals with the development of a non-linear modular model for compressor dynamic simulation. After developing the compressor mathematical model through a physics-based approach (laws of conservation and thermal balances), the model is implemented through the Matlab® Simulink tool. Then, a sensitivity analysis is carried out to evaluate the influence of model parameters on the model response. Finally, the model is calibrated on a multi-stage axial-centrifugal small size compressor running in the test facility of the University of Ferrara (Italy) and validated through experimental data taken on the compressor under investigation.
Numerical Investigation of Different Stack Design Solutions in a Cogeneration Power Plant
Authors: Pinelli M. , Bucci G.
Published: November 2008

In cogeneration and combined cycle plants, the presence of a by-pass stack has a great importance since it allows the modulation of heat-to-power generation to follow variable daily demand and thus the optimal management of the heat and power production. Hence, among the various aspects that have to be analysed in a plant design, the exhaust gas stack design can represent a critical aspect, in particular when a by-pass stack is present, since it may influence the entire system working condition. To properly take into account the large number of the different requirements (economic, structural, geometrical, acoustic, etc.) which enter in a stack design, a multidisciplinary analysis involving CAD/CFD/FEM integrated approaches can be adopted in order to obtain an optimally designed stack system. In this paper, the design of the exhaust gas stack in a cogeneration plant is performed numerically. In the considered plant, a single stack, in which the gases coming from both the utility heat exchangers and the by-pass at the gas turbine exit are mixed, is used. Different design solutions of the by-pass system are simulated through a three-dimensional integrated numerical code and the results discussed in detail.
Numerical Investigation of Blade Profile Effects on Aerodynamic Performance of Ultra-Highly Loaded Turbine Cascades
Authors: Tsujita Hoshio , Mizuki Shimpei , Yamamoto Atsumasa
Published: November 2008

The increase of blade loading of a turbine cascade makes it possible to reduce the number of blades and stages, and consequently to decrease both the weights and the costs for manufacturing and maintenance. However, strong secondary flows appear in such highly loaded turbine cascades due to the high turning angles which reduce the efficiency. In the present study, the effects of blade profile on the aerodynamic performance of a stationary linear ultra-highly loaded turbine cascade (UHLTC), which will be used for the future gas turbine engines of hypersonic transport, were investigated numerically. The two and three dimensional calculations were carried out for the flows within the three types of UHLTC, which have the same design turning angle of 160 degree and with the different profile of the suction surface. The first was named ‘Original’. The others were ‘Up’ and ‘Down’ which had the longer length of suction surface and the shorter one than that of the Original, respectively. In the present computational code, the governing equations for the incompressible turbulent flow which include the standard k-ε turbulence model were solved by the SIMPLE algorithm. The convection term was estimated by the third order upwind difference scheme. The present computed results were examined by comparing with the experimental results. The total pressure loss, the profile loss, the secondary loss and the blade loading distribution for the three types of UHLTC were compared in detail with each other to reveal the effect of blade profile on the aerodynamic performance of UHLTC.
Probabilistic Lifetime Analysis for Turbine Blades Based on a Combined Direct Monte Carlo and Response Surface Approach
Authors: Voigt Matthias , Mu¨cke Roland , Vogeler Konrad , Oevermann Michael
Published: November 2008

The paper addresses a probabilistic approach to lifetime prediction of cooled gas turbine blades. Variations of load and material parameters are taken into account by a combination of a direct Monte Carlo Simulation and a Response Surface Method. The proposed approach allows a reduction in the number of finite element analyses especially for problems with low failure probability. Therefore, the computational effort becomes acceptable even for full-scale 3D and 2D analysis models. Results of a probabilistic life assessment are shown for two cooled turbine blades. The probability of failure and the sensitivity of material and loading parameters are presented.
A Numerical Evaluation of Different Oxy-Fuel Concepts for a Gas Turbine Combustor
Authors: Stro¨hle Jochen , Myhrvold Tore , Ro̸kke Nils A.
Published: November 2008

In the present study, a numerical evaluation of different oxy-fuel concepts for a typical gas turbine combustor is performed to investigate how the inlet conditions affect fuel and CO burnout, NOx and soot emissions, and wall heat fluxes. Three oxy-fuel cases with different distribution of oxygen to the inlets are compared with a reference case using air as an oxidiser. Three-dimensional numerical simulations are performed using the in-house CFD code SPIDER. Turbulent combustion is modelled by the Eddy Dissipation Concept (EDC) with detailed chemistry and soot formation reactions. Whereas low oxygen concentrations at the fuel inlet lead to extinction of the flame, the temperature in the primary combustion zone becomes very high leading to unacceptable wall heat fluxes at high oxygen concentrations. NOx, hydrocarbons and soot emissions are very low while CO emissions are relatively high for the oxy-fuel cases.