bluuebunny/crossref_metadata_2025 huggingface dataset:
Latent Heat Recovery and Performance Studies for an Open Cycle Absorption Heat Transformer
Authors: Wei Fan , Xiao Yunhan , Zhang Shijie
Published: August 2009

Latent heat recovery from the flue gas has received considerable attention due to its large quantities especially in gas boilers or humid gas turbine cycles (such as HAT cycle). Furthermore, the cost of water consumption can be reduced in gas turbine systems by water recovery along with latent heat recovery. In this paper, an open cycle absorption heat transformer (OAHT) is developed for latent heat and water recovery from flue gas. The exhaust gas is used as the heat source to boil the weak solution and water-calcium chloride as the desiccant to absorb water. The discharged heat from absorber can be used for district heating. Comparing with the conventional condensation method, the heat and water recovery from the OAHT is analyzed by employing the flow sheet simulation method. The results show that under the same working condition, the amount of recovered heat in the OAHT is 1.6 times that in the condensation method, the latent heat is 2.8 times; the amount of water recovery increases by 7.3 fold. The performance and the parametric analysis of the OAHT are also developed. The Coefficient of Performance (COP) of the system is 0.65. The discharged heat from the absorber is 4.807kW at the temperature of 50°C which can be used for district heating. Parametric analysis show that COP will increase with high gas temperature and humidity, high cooling water temperature and flow rate, high strong solution concentration and high flow rate of working fluid; while high flow rate of gas and weak solution concentration will make COP decrease. The advantages of the OAHT are demonstrated in the water and latent heat recovery. Comparing with the closed cycle absorption heat transformer, the OAHT has more advantages because of the relative similar COP and the simple configuration which can reduce the system cost.
Modeling of Turbulent Combustion and Radiative Heat Transfer in a Object-Oriented CFD Code for Gas Turbine Application
Authors: Andreini Antonio , Cerutti Matteo , Facchini Bruno , Mangani Luca
Published: August 2009

One of the driving requirements in gas turbine design is the combustion analysis. The reduction of exhaust pollutant emissions is in fact the main design constraint of modern gas turbine engines, requiring a detailed investigation of flame stabilization criteria and temperature distribution within combustion chamber. At the same time, the prediction of thermal loads on liner walls continues to represent a critical issue especially with diffusion flame combustors which are still widely used in aeroengines. To meet such requirement, design techniques have to take advantage also of the most recent CFD tools that have to supply advanced combustion models according to the specific application demand. Even if LES approach represents a very accurate approach for the analysis of reactive flows, RANS computation still represents a fundamental tool in industrial gas turbine development, thanks to its optimal tradeoff between accuracy and computational costs. This paper describes the development and the validation of both combustion and radiation models in a object-oriented RANS CFD code: several turbulent combustion models were considered, all based on a generalized presumed PDF flamelet approach, valid for premixed and non premixed flames. Concerning radiative heat transfer calculations, two directional models based on the P1-Approximation and the Finite Volume Method were treated. Accuracy and reliability of developed models have been proved by performing several computations on well known literature test-cases. Selected cases investigate several turbulent flame types and regimes allowing to prove code affordability in a wide range of possible gas turbine operating conditions.
Particulate Monitor for Gas Turbine Cooling Air
Authors: Bunce Richard H. , Dovali-Solis Francisco , Baxter Robert W.
Published: August 2009

It is important to monitor the quality of the air used in the cooling system of a gas turbine engine. There can be many reasons that particulates smaller than the minimum size removed by typical engine air filters can enter the secondary air system piping in a gas turbine engine system. Siemens has developed a system that provide real time monitoring of particulate concentrations by adapting a commercial electrodynamic devise for use within the confines of the gas turbine secondary air system with provision for a grab sample option to collect samples for laboratory analysis. This on-line monitoring system is functional at typical engine cooling system piping operating pressure and temperature. The system is calibrated for detection of iron oxide particles in the 1 to 100 micrometer range at concentration of from 1 to 50 parts per million mass wet (ppmmw) The electro dynamic device is nominally operable at 800°C. The particulate monitoring system requires special mounting and antenna. This system may be adjusted for other materials, sizes and concentrations. The system and its developmental application are described. The system has been tested and test results are reviewed. The test application was the cooling air piping of a Siemens gas turbine engine. Multiple locations were monitored. The cooling system in this engine incorporates an air cooler and the particulate monitoring system was tested upstream and downstream of the air cooler for temperature contrast. The monitor itself is limited to the piping system and not the engine gas-path.
CFD Predictions of Low NOx Radial Swirlers With Vane Passage Fuel Injection With Comparison With Internal Gas Analysis Flame Composition
Authors: King Phil T. , Escott Nick H. , Andrews Gordon E. , Pourkashanian Mohammed M. , McIntosh Andrew C.
Published: August 2009

Radial swirlers with vane passage natural gas injection, similar to those used in some industrial low NOx gas turbines, were investigated for their flame structure both experimentally and using CFD. The radial swirler NOx emissions at 600K and 1 atmosphere pressure were shown to be 3–4 ppm at 15% oxygen at 1800K and 1–2 ppm at 1700K. These levels were similar to the best published low NOx emissions using any flame stabilizer design. A flame at O̸ = 0.5 and 600K air temperature was investigated for its structure using a 10mm OD water cooled gas sample probe with a 1mm gas sample inlet on the upstream side of the probe. This showed that the mixing in the vane passage and outlet duct was very good. The maximum unmixedness at the first traverse location, 10mm downstream of the dump expansion zone, was 20% of the mean and the unmixedness was less than 5% within 30mm from the dump expansion. The flame structure was shown to involve a thick turbulence reaction zone of about 100mm thickness to the 90% heat release point. The CFD predictions were made using the RSM and k-ε turbulence models and the flamelet combustion model with a strain rate library. The isothermal aerodynamics predictions were in good agreement with others for similar geometries. There was an inner and outer recirculation zone with a swirling shear layer between. The peak turbulent kinetic energy was predicted to be on the inside of the shear layer. The experimental results showed that the flame developed in this region of high turbulence and low axial velocities. The flamelet model was less successful at predicting the flame development. The NOx results were predicted to be 2ppm less than the experimental results, due to the shorter predicted heat release region with associated lower prompt NOx.
Application of Casing Circumferential Grooves to Counteract the Influence of Tip Clearance
Authors: Mileshin Victor , Brailko Igor , Startsev Andrew
Published: August 2009

Widening of surge margin of a transonic compressor stage is the main objective of the paper. This stage is a typical middle stage of a modern high pressure compressor (HPC) with decreased number of stages. Hot tip clearance of the stage being integrated into a six-stage HPC providing total pressure ratio π* HPC ≥ 12 and mass flow-rate < 16 kg/sec is estimated at 2.5 – 3% of blade height and is classified as a large tip clearance. In this paper experimental and 3D viscous numerical performances of the stage are obtained for two values of rotor tip clearance — equal to 0.76% (small size) and 2.66% (large size) of blade height. In doing so, tip clearance enlargement from 0.76% to 2.66% has been made by increase of casing (shroud) radius. This increase is manufactured as a circumferential trench (recess) with axial width 30% larger than rotor axial chord. Below this tip clearance is called “recessed” tip clearance. A distinguishing feature of leakage flow in case of large tip clearance is a formation of reversed flow near rotor casing. This backflow being intensified by throttling causes increase of incidence at the rotor leading edge and development of rotor stall. Casing treatments are intended to inhibit and delay the process. Among them circumferential grooves is the simplest casing treatment. Investigated in this paper casing circumferential grooves cover 82% of rotor axial chord. Numerical visualization of the near-casing streamlines demonstrates that tip leakage flow drains into the casing grooves giving rise to extended domains of positive axial velocity. Calculated mass flow-rate through groove’s cross-section demonstrates maximum over the rotor blade tip (flow into the groove) and minimum at mid-pitch (flow out of the groove). Amplitude of this variation depends on the groove location and stage throttling.
Multi-Stage Compressor Model for Transient Performance Simulations
Authors: Schulte Holger , Schmidt Klaus-Ju¨rgen , Weckend Arne , Staudacher Stephan
Published: August 2009

This paper describes the development of a multi-stage compressor model for transient performance calculations. The aim of the model is to simulate the interaction of the compressor stages with each other and the rest of the engine components during transient engine maneuvers. Especially rematching effects caused by transient heat flows and tip clearance changes are of interest, since they have a major impact on the stability of the compressor. In the first section of the paper the stage stacking ability is implemented in the performance tool. Therefore the compressor is split into several stages each of which is represented by a single compressor module. The specifics of this approach are discussed and the validity of the multi-stage model is shown by a comparison with results calculated with a conventional compressor model. Then the model is extended to simulate transient heat flows and tip clearance changes in each compressor stage. This is achieved by a state space approach which allows the calculation of the thermo-mechanical effects based on a set of previously identified matrices. The thermal calculation modules are linked to the performance model, and the quality of the combined simulation is shown by a comparison of results for two transient maneuvers with reference data. Finally the stage working line excursions of an acceleration are compared with those of a hot reslam demonstrating the advantage of the combined multistage performance model.
Condition Monitoring of Rotor Using Active Magnetic Actuator
Authors: Sawicki Jerzy T. , Friswell Michael I. , Pesch Alex H. , Wroblewski Adam
Published: August 2009

It has been widely recognized that the changes in the dynamic response of a rotor could be utilized for general fault detection and monitoring. Current methods rely on the monitoring of synchronous response of the machine during its transient or normal operation. Very little progress has been made in developing robust techniques to detect subtle changes in machine condition caused by rotor cracks. It has been demonstrated that the crack-induced changes in the rotor dynamic behavior produce unique vibration signatures. When the harmonic excitation force is applied to the cracked rotor system, nonlinear resonances occur due to the nonlinear parametric excitation characteristics of the crack. These resonances are the result of the coexistence of a parametric excitation term and different frequencies present in the system, namely critical speed, the synchronous frequency, and excitation frequency from the externally applied perturbation signals. This paper presents the application of this approach on an experimental test rig. The simulation and experimental study for the given rig configuration, along with the application of active magnetic bearings as a force actuator, are presented.
An Object-Oriented Parallel Finite-Volume CFD Code
Authors: Becker Dulceneia , Barbosa Joa˜o Roberto , Tomita Jesuino Takachi
Published: August 2009

This paper concerns the parallelization and optimization of an in-house three-dimensional unstructured finite-volume computational fluid dynamics (CFD) code. It aims to highlight the use of programming techniques in order to speedup computation and minimize memory usage. The motivation for developing an in-house solver is that commercial codes are general and sometimes simulations are not in agreement with actual phenomena. Moreover, in-house models can be developed and easily integrated to the solver. The original code was initially written in Fortran 77 though the most recent added subroutines include Fortran 90 features. Due to language restrictions and the initial project objectives, issues such as memory usage minimization were not considered. The new code uses an object-oriented paradigm aiming to enhance code reuse and increase efficiency during application development. The parallel code is fully written in Fortran 90 using MPI and hence portable to different architectures. Numerical experiments of typical 3D cases, such as flat plate with uniform incoming flow and a converging-diverging supersonic nozzle, were carried out showing good parallel efficiency. The serial version of the ported code has shown a considerable reduction on the execution time compared to the original code. Convergent solutions agree with the solution of the original code.
Experimental Research on Pyrolysis Process About Corn Stalk and Rice Husks
Authors: Yan Guihuan , Sun Li , Xu Min , Sun Rongfeng , Sun Fengzhong , Meng Xiangmei
Published: August 2009

Pyrolysis is one of the most promising conversion routes for biomass utilization, wherein biomass can be converted to solids, liquids and permanent gases, which are all used as a fuel. Researchers have proved that non-condensable gases can be translated into electric power by the gas turbine unites and liquid fuels can be used in vehicles after refined. In this paper, we mainly researched the distribution properties of pyrolysis products, as well as the characteristics of permanent gases under different reaction temperature and residence time. The experiments prove that the main process of prolysis is the transformation of biomass to liquid at low temperature. Along with the increase of reaction temperature, hydrocarbons further crack into small-molecule gases, so the whole reaction gradually changes into the production of permanent gases. The results show that the reaction temperature which is closely related with the compositions of permanent gases has a more important influence on the pyrolysis products than the residence time. With the increase in the reaction temperature, the volume content of H2 rises sharply, while CO and CO2 both decrease obviously in the volume content. Meanwhile the volume content of CH4 increases slightly, especially when the temperature is lower than 500°C. And the highest volume content of light hydrocarbons achieves at about 500°C. As the reaction temperature changes from 400°C to 500°C, the LHV of permanent gases increases from 12.5MJ/Nm3 to 16MJ/Nm3. When the temperature exceeds 500°C, the LHV of permanent gases changes gently in a range of 16∼17 MJ/Nm3.
The Influence of Blade Lean on Straight and Annular Turbine Cascade Flow Field
Authors: D’Ippolito Gabriele , Dossena Vincenzo , Mora Alessandro
Published: August 2009

The paper proposes a detailed description of the flow field throughout leaned turbine nozzles and reports a sensitivity analysis with respect to the lean angle. A phenomenological approach focuses the attention on pressure contours distribution both inside and outside the passage. The study involves both straight and annular cascades mounting a typical intermediate reaction degree section, designed for steam turbines. Blades are built by stacking the same 2-D profile along different linear axis, characterized by different angles with respect to the normal or radial direction: α = 0 deg for prismatic blade and α = 10, 15 and 20 deg for the leaned ones are considered. Experimental and numerical tests were performed at the nominal inlet flow angle in order to avoid any effect related to blade sweep. Experimental tests were carried out at the design outlet Mach number of 0.65; measurements were performed at the Laboratorio di Fluidodinamica delle Macchine (LFM) of Politecnico di Milano. Only linear cascades with prismatic and 20 deg leaned blades were experimentally tested providing data both downstream and inside the blade passage by means of pressure probe traversing, endwall pressure taps and oil flow visualization. Experimental results were also used to validate the numerical set-up, which provided a detailed computational picture of the flow field throughout the channel. The influence of pressure contours shape on secondary vorticity activity downstream of the passage is highlighted and discussed, focusing the attention on secondary structures and loss distribution in this region. The resulting description of the flow field, based on the representation of pressure contours, supports the sensitivity analysis with respect to the blade lean angle, identifying the mechanism that leads the secondary vorticity to grow in regions where secondary losses and blade loading decrease.
Radial Swirlers and Mixing Tube Assembly Aerodynamics and Performance Parameters Evaluation: Part 1—Hot-Wire Measurements in the Swirler Exit Plane
Authors: Canepa Edward , Di Martino Pasquale , Lengani Davide , Ubaldi Marina , Zunino Pietro
Published: August 2009

Swirling flows have been widely used to generate the suitable conditions for self substained flames inside modern aeroengine combustors, both for the recirculation generation capability and turbulence intensity. Nevertheless the recent attempt to employ lean premixed prevaporized burners, which can be affected by pressure and velocity fluctuations, requires a deep knowledge of the parameters influencing the swirlers aerodynamics. The purpose of this experimental work is to characterize the aerodynamics of the assembly composed by a centripetal swirler and a straight mixing tube as a function of basic geometrical design parameters. The typical geometrical configuration of the centripetal swirler – mixing tube assembly allows to identify a group of geometrical parameters which can influence the characteristics of the flow leaving both the swirler and the straight duct: the swirler geometrical angle, the vane pitch to chord ratio, and the swirler axial height to mixing tube diameter ratio. Their range of variation has been obtained through the analysis of existing prototypes. According to the range of variation analysis a minimum number of geometries (combinations of the fundamental geometrical parameters) has been defined and tested in order to obtain significant information on the relationships between geometrical parameters and aerodynamic performances. The complex aerodynamic phenomena, which take place both inside and downstream the swirler–mixing tube assembly, have been studied with different and complementary techniques in order to have a complete characterization of the effect of the geometrical parameters variation on many aspects of the flow. All the measuring campaign has been performed at fixed total pressure drop between the settling chamber and the mixing tube outlet section. Present work has been divided in two parts. In the first part, which is here presented, velocity components, turbulence intensity and the flow angle has been measured by means of a two-components crossed miniature hot-wire probe, which has been traversed circumferentially downstream of the swirler vanes. Results from the hot-wire anemometer measuring campaign allow basically to evaluate two main performance parameters which are the swirler velocity reduction coefficient and the mass averaged flow angle, that is actually the main indicator of the swirler capability to deflect the flow and consequently it influences largely the phenomena which can occur in the mixing tube or downstream of the discharge section.
Investigation of Leakage Flow and Heat Transfer in a Gas Turbine Blade Tip With Emphasis on the Effect of Rotation
Authors: Yang Dianliang , Yu Xiaobing , Feng Zhenping
Published: August 2009

In this paper, numerical methods have been applied to the investigation of the effect of rotation on the blade tip leakage flow and heat transfer. Using the first stage rotor blade of GE-E3 engine high pressure turbine, both flat tip and squealer tip have been studied. The tip gap height is 1% of the blade height, and the groove depth of the squealer tip is 2% of the blade height. Heat transfer coefficient on tip surface obtained by using different turbulence models was compared with experimental results. And the grid independence study was carried out by using the Richardson extrapolation method. The effect of the blade rotation was studied in the following cases: 1) blade domain is rotating and shroud is stationary; 2) blade domain is stationary and shroud is rotating; and 3) both blade domain and shroud are stationary. In this approach, the effects of the relative motion of the endwall, the centrifugal force and the Coriolis force can be investigated respectively. By comparing the results of the three cases discussed, the effects of the blade rotation on tip leakage flow and heat transfer are revealed. It indicated that the main effect of the rotation on the tip leakage flow and heat transfer is resulted from the relative motion of the shroud, especially for the squealer tip blade.
Design, Validation and Application of a Radial Cascade for Centrifugal Compressors
Authors: Simpson Alexander , Aalburg Christian , Schmitz Michael , Pannekeet Robbert , Larisch Florian , Michelassi Vittorio
Published: August 2009

A novel sector test rig has been used to evaluate a new airfoil concept for multistage radial compressors. The test rig is supported by a blow-down facility where the operation conditions are adjusted by controlling mass flow, pressure and temperature. At inlet to the sector test rig itself a set of adjustable inlet guide vanes provide the test vanes with the correct inlet three-dimensional flow-field. The rig is equipped with instrumentation to allow a detailed description of the inlet and outlet conditions, as well as the blade pressure loading. This rig, using rapid prototyped vanes, allows design candidates to be screened quickly and is ideal for conducting an experimental investigation of a design space using a Design-of-Experiments approach. In this paper the rationale for the sector approach is described, the design of the test rig with 3D-CFD methods is outlined and a detailed validation of the rig is presented. For the vane in question detailed investigations of different operation points close to stall are reported, blade pressures and inlet and exit flow profiles are given. Where applicable, measurement data from the sector rig was compared to 3D-CFD calculations of the full annulus multistage configuration, to 3D-CFD calculations of the sector rig itself and to the test results from a 1.5-stage rotating test rig. The measurement data are compared to the CFD predictions and served as a calibration basis for the design tools.
Design and Testing of Multistage Centrifugal Compressors With Small Diffusion Ratios
Authors: Aalburg C. , Simpson A. , Schmitz M. B. , Michelassi V. , Evangelisti S. , Belardini E. , Ballarini V.
Published: August 2009

Two stators of a multistage centrifugal compressor with progressively smaller outer radii have been designed, built and tested. The aim was to achieve a significant reduction in outer diameter of the compressor stage without compromising performance. The reduction of size was achieved by reducing the diffusion ratio (outer radius/inner radius) of the vaneless diffuser in two steps. In the first step the outer diameter of the entire stage was reduced by 8% compared to the baseline design. In the second stage the outer diameter was reduced by 14%. The outer radius of the smallest design was limited by the impeller exit diameter, which was kept constant, as was the axial length of the stage. The large radius baseline design has been tested on a rotating rig in a 1.5 stage setup. This setup aimed at simulating multistage behavior by applying a pseudo stage upstream of the main stage. The pseudo stage consisted of a set of non-rotating preswirl vanes, in order to mimic an upstream impeller, and was followed by a scaled version of the return channel of the main stage. The experimental database was then used to calibrate a 1D analysis code and 3D-CFD methods for the ensuing design and optimization part. By applying extensive Design-Of-Experiments (DOE), the endwalls as well as the vanes of the stator part were optimized for maximum efficiency and operation range. In order to preserve multistage performance, the optimization was constrained by keeping the circumferentially averaged spanwise flow profiles at the exit of the smaller radius stages within close limits to the original design. The reduced radius designs were then tested in the same 1.5 stage setup as the baseline design. The results indicate that the reduction in size was feasible without compromising efficiency and operation range of the stage.
Parametric Analysis of Variable Nacelle Nozzle Throat Area Using Warped Chevrons
Authors: Sloan B. , Spence S. , Wang J. , Raghunathan S.
Published: August 2009

Simulations of the NASA Rotor 67, Stator 67A stage integrated into a bespoke nacelle were performed using ANSYS CFX. The throat area of the nacelle nozzle was varied by use of warped chevrons. 8, 12 and 16 chevron nozzles were simulated to evaluate the impact of the variation in geometry upon the nacelle wake and local forces. The force produced from the nozzle and fan, is compared to the baseline case where the throat area is optimised for cruise conditions. The variation in gross thrust between cases is also analysed. The turbulence kinetic energy and total temperature variation through the wake is compared. A reduction in peak wake mixing massflow-averaged turbulent kinetic energy of 11.9% was attained. Surface force measurements of the rotor, stator and nozzle duct indicate a rising thrust loss with increasing nozzle throat area. However, measurement of the nozzle exit velocities and massflow rates enable subsequent estimation of the gross thrust which indicate a rise of 2.4% relative to the baseline is achievable.
Heat Transfer Augmentation Downstream of Rows of Various Dimple Geometries on the Suction Side of a Gas Turbine Airfoil
Authors: Dees Jason E. , Bogard David G. , Bunker Ronald S.
Published: August 2009

Heat transfer coefficients were measured downstream of a row of shaped film cooling holes as well as elliptical, diffuser, and teardrop shaped dimples simulating depressions due to film coolant holes of different shapes. These features were placed on the suction side of a simulated gas turbine vane. The dimples were used as approximations to film cooling holes after the heat transfer levels downstream of active fan shaped film cooling holes was found to be independent of film cooling. The effects of the dimples were tested with varying approach boundary layers, freestream turbulence intensity, and Reynolds numbers. For the case of an untripped (transitional) approach boundary layer, all dimple shapes caused approximately a factor of two increase in heat transfer coefficient relative to the smooth baseline condition due to the dimples effectively causing boundary layer transition downstream. The exact augmentation varied depending on the dimple geometry: diffuser shapes causing the largest augmentation and teardrop shapes causing the lowest augmentation. For tripped (turbulent boundary layer) approach conditions, the dimple shapes all caused the same 20% augmentation relative to the smooth tripped baseline. The already turbulent nature of the tripped approach flow reduces the effect that the dimples have on the downstream heat transfer coefficient.
Dynamic Fusion and Parameter Optimization of Multiple Classifier Systems
Authors: Kodali Anuradha , Donat William , Singh Satnam , Choi Kihoon , Pattipati Krishna
Published: August 2009

We propose a fusion architecture that combines a set of classifier decisions over a time window to isolate dynamically evolving faults in gas turbine engines. The dynamic fusion problem is formulated as a maximum a posteriori decision problem of inferring the fault sequence based on uncertain outcomes of multiple classifiers over time. The resulting problem is solved via a primal-dual optimization framework. The fusion process involves three steps: the first step transforms the multi-class problem into dichotomies using error correcting output codes (ECOC) and thus solving the concomitant binary classification problems; the second step fuses the outcomes of multiple binary classifiers over time using a sliding window dynamic fusion method that exploits temporal data correlations over time. The window size provides a trade-off between diagnostic errors and decision delays. The third step optimizes the fusion parameters using a genetic algorithm. The probability of detection and false alarm probability of each classifier are the fusion parameters; these probabilities are jointly optimized as part of the fusion architecture instead of optimizing the parameters of each classifier separately. The proposed algorithm is demonstrated by computing the diagnostic performance metrics on a twin-spool commercial jet engine data.
High Efficiency Gas Turbine Based Power Cycles—A Study of the Most Promising Solutions: Part 2—A Parametric Performance Evaluation
Authors: Bhargava Rakesh K. , Bianchi Michele , Campanari Stefano , De Pascale Andrea , Negri di Montenegro Giorgio , Peretto Antonio
Published: August 2009

In general, two approaches have been used in the gas turbine industry to improve Brayton cycle performance. One approach includes increasing Turbine Inlet Temperature (TIT) and cycle pressure ratio (β), but it is quite capital intensive requiring extensive research and development work, advancements in cooling (of turbine blades and hot gas path components) technologies, high temperature materials and NOx reducing methods. The second approach involves modifying the Brayton cycle. However, this approach did not become very popular because of the development of high efficiency gas turbine (GT) based combined cycle systems in spite of their high initial cost. This paper discusses another approach that has gained lot of momentum in recent years in which modified Brayton cycles are used with humidification or water/steam injection, termed “wet Cycles”, resulting in lower cost/kW power system, or with fuel cells, obtaining “hybrid Cycles”; the cycle efficiency can be comparable with a corresponding combined cycle system including better part-load operational characteristics. Such systems, that include advanced Steam Injected cycle and its variants (STIG, ISTIG, etc.), Recuperated Water Injection cycle (RWI), humidified air turbine cycle (HAT) and Cascaded Humidified Advanced Turbine (CHAT) cycle, Brayton cycle with high temperature fuel cell, Molten Carbonate Fuel Cell (MSFC) or Solid Oxide Fuel Cells (SOFC) and combinations of these with the modified Brayton cycles, have not yet become commercially available as more development work is required. The main objective of this paper is to provide a detailed parametric thermodynamic cycle analysis of the above mentioned cycles and discussion of their comparative performance including advantages and limitations.
Aerothermal Impact of Stator-Rim Purge Flow and Rotor-Platform Film Cooling on a Transonic Turbine Stage
Authors: Pau M. , Paniagua G. , Delhaye D. , de la Loma A. , Ginibre P.
Published: August 2009

This paper describes the effects on the mainstream flow of two types of cooling techniques in a transonic turbine stage: purge gas ejected out of the cavity between the stator rim and the rotor disk, as well as film cooling gas discharged from the rotor-platform. The tests were carried out in a full annular stage fed by a compression tube, at M2is = 1.1, Re = 1.1×106, and at temperature ratios reproducing engine conditions. The stator outlet was instrumented to allow the aerothermal characterization of the purge flow. The rotor blade was heavily instrumented with fast-response pressure sensors and double-layer thin film gauges. The tests are coupled with numerical calculations performed using the ONERA’s code elsA. The stator-rotor interaction is seen to be significantly affected by the stator-rim seal, both in terms of heat transfer and pressure fluctuations. The flow exchange between the rotor disk cavity and the mainstream passage is mainly governed by the vane shock patterns. The purge flow leads to the appearance of a large coherent vortex structure on the suction side of the blade which enhances the overall heat transfer coefficient due to the blockage effect created. Secondly, the impact of the platform cooling is observed to be restricted to the platform, with negligible effects on the blade suction side. The platform cooling results in a clear attenuation of pressure pulsations at some specific locations. Finally the turbine performance was analyzed, comparing measured and CFD results. A detailed loss breakdown analysis has been done using correlations, in order to isolate the different loss component contributions. The presented results should help designers improve the protection of the rotor platform and minimize the amount of coolant used.
Harsh Environment Pressure Transducers Employing Metal Diaphragms and Silicon on Insulator Sensing Networks for Gas Turbine Application
Authors: Kurtz Anthony D. , Kochman Boaz , Ned Alex A.
Published: August 2009

It has long been necessary in many applications to measure pressure in extremely harsh environments at elevated temperatures. Examples of such applications include: gas turbine engines (both ground-based and for aircraft), automotive combustion, and down-hole applications for gas and oil industry. This paper reports on the latest developments of metal diaphragm transducers with Silicon-On-Insulator (SOI) piezoresistive sensor networks for ultra extreme environments. The design of the latest Inconel-diaphragm miniature, dynamic pressure transducers capable of operating reliably under extreme environmental conditions (temperatures up to 500°C and accelerations greater than 200g) — is described in detail. The performance of such metal diaphragm pressure transducers is presented and indicates that ruggedized, piezoresistive transducers with excellent static and dynamic performance characteristics are capable of operation in extremely harsh, high temperature gas turbine environments.
Novel 2D Transient Heat Conduction Calculation in a Cooled Rotor: Ventilation Preheating — Blowdown Flux
Authors: Solano J. P. , Paniagua G. , de la Loma A.
Published: August 2009

An alternative to classical data reduction techniques for thin film gauges in short duration facilities is presented. A finite element model of the two-dimensional unsteady heat conduction equation is solved in the cross-sectional area of a metallic airfoil bounded with a polyamide sheet, on which thermal sensors are deposited. As a result, the transient temperature field in the multilayered substrate and the experimental wall heat flux distribution are derived. The methodology allows for capuring all 2D heat conduction effects that are irremediably neglected with the 1D data reduction technique. The application of this technique in a compression tube facility allows an exact evaluation of the initial wall heat flux into cooled rotor blades. During the spinning up period, the rotor of this type of fully rotating transient facilities is spun up to nearly its nominal speed (from 0 RPM to 6200 RPM) resulting in preheating due to drag losses. The long duration of this experiment (∼450 s) and the magnitude of the wall temperature increase result in significant 2D conduction effects that are not accounted for using the 1D approach. In addition, short duration experiments confirm the existence of 2D effects at smaller time scales (∼0.5 s), as well as the influence of the initial non-uniform temperature distribution in the rotor blade. The resulting flux with such an initial condition appears to be the superposition of the wall heat flux at the end of the spinning up before the test and the flux due to the blow-down itself.
Temperature and Pressure Measurements in a Hot Cascade With Film Cooled Endwalls and Airfoils
Authors: Post James W. , Acharya Sumanta
Published: August 2009

Measurements of endwall and vane cooling effectiveness are reported in a pressurized hot cascade consisting of a natural-gas-fired combustor and film-cooled guide-vanes and endwall. The experiments are performed for operating conditions that are more realistic than typical low-speed cascade studies. Measurements are reported for a maximum pressure ratio (Po,∞/Ps) of 2, combustor exit temperature of 750 °F (399 °C), blowing ratios in the range of 1–2, and coolant to freestream density ratio (DR) of around 2. Results reported include pressure ratios, surface temperature ratios and cooling effectiveness along the endwall and airfoil surfaces. Cooling effectiveness (non-dimensional surface temperature) values in the range of 0.2–0.3 are generally observed along the endwall with poorer coverage in the vicinity of the suction surface.
Design, Development and Testing of an In-Engine Radial Traverse System for the Trent Engine
Authors: Anderson S. J. , Chaha K. S. , Wilson A. J. W.
Published: August 2009

With development timescales reducing there is less time available for rig testing during an engine development programme. Consequently, there is a growing requirement for experimental techniques that can be used to gain an understanding of the in-engine performance of major components. Rolls-Royce has recently completed a major engine test programme aimed at measuring the installed performance of the turbine components of a Trent engine. Rolls Royce and QinetiQ believe that this is the first time that traversing of this type has been completed during a full aero engine performance test. The main element of this programme was radial traversing downstream of the HP and IP turbines. Four traverse systems were designed and developed by QinetiQ, two operating at HP exit and two at IP exit. Each probe was capable of measuring total pressure, yaw angle, total temperature and Mach number across the entire operating range of the engine. The design presented a number of major challenges for the system including the high temperatures and pressures experienced by the probes (up to 1600K and 30 bar), the hostile environment at the traverse system location (550K), and the constraints of fitting within the space available on a real engine. The paper describes how the traverse systems were designed and developed and how the challenges of the harsh testing environment were overcome. The successful testing of the traverse system and results obtained during a full engine performance test on a Trent 900 engine are described in detail.
Full-Parametric Design System to Improve the Stage Efficiency of a High-Fidelity HP Turbine Configuration
Authors: Milli Andrea , Shahpar Shahrokh
Published: August 2009

This paper presents the application of an in-house automatic design system to the aerodynamic optimisation of one HP turbine stage. The main objectives of this study are: point out the importance of parametric geometry modelling and meshing for automatic design optimisation; move a step forward towards the exploitation of novel numerical tools to improve modern turbine performance with high-fidelity geometry configurations. In the present work, the system has been applied to the non-axisymmetric hub endwall optimisation of a research Rolls-Royce design HPT stage. The following main issues have been taken into account: high-fidelity CFD by means of multirow 3D simulations; parametric modelling and rapid meshing of real geometry features; modelling of film cooling flows. It is demonstrated that the integration of parametric models of secondary geometrical features within the mesh generator is a key issue in order to develop an effective and fully automated design procedure. It is shown that some of the benefits achieved optimising a simplified model of the stage are lost when applying the high-fidelity geometry configuration. A significant reduction of secondary flows and a corresponding increase of stage efficiency are achieved when taking into account the main real geometry features directly into the optimisation, even if at the cost of higher computational requirements.
Conceptual Design of a Multistage High-Speed Motor Driven Air Compressor
Authors: Saari Juha , Backman Jari L. H. , Peussa Jouko
Published: August 2009

Centrifugal compressors operate with relatively high rotational speeds. A high rotational speed can be reached by a gearbox-coupled standard motor or by a high-speed motor with a frequency converter. The motivation for using high-speed motors is usually related to features like performance, size and total life cycle costs. A comparison of these features for the high-speed motor and gearbox driven air compressors are presented. The delivered pressure of oil-free plant air compressors is 600–900 kPa(g). Traditional gearbox driven turbo compressors have typically two or three compressor stages. In these machines, the cost impact for the additional stages is not as high as in the case of high-speed motor compressors, where only two stages can easily be coupled to one motor. The performance characteristics of a two-, three- and four-stage high-speed motor compressors are compared to each other. Based on the feasibility study, the two-stage compressor was selected for further analysis. The aim was to design a 250 kW plant air compressor. The optimization process to obtain the best performance for the compressor is discussed. This includes careful analysis of stage-specific speeds, electric motor performance, bearing performance, rotor dynamics, as well as material strengths and cooling. The predicted performance of the high-speed motor and compressor is presented.
Applicability of Neuber’s Rule for Thermomechanical Fatigue
Authors: Gordon Ali P. , Williams Eric P. , Schulist Michael
Published: August 2009

Gas turbine components, such as blades and vanes, are routinely subjected to non-isothermal fatigue conditions. Accurate service life predictions can be made from analyzing transient stress-temperature histories and constitutive modeling. The local stress and strain histories at geometric discontinuities are typically calculated with stress shakedown approaches (i.e., Neuber’s Rule, Molski-Glinka Approach, Calladine Method) based on elastic responses rather than coupled elastic-plastic deformation observed from low cycle fatigue (LCF). For the notched material subjected to thermomechanical fatigue (TMF), there is no widely-accepted method for correlating remotely applied load with notch root behavior. In this study, a notched specimen of the Ni-base superalloy IN939 is modeled by means of Finite Element Analysis (FEA) via the ANSYS general purpose software. Calculations made from the Neuber Rule are compared with numerical simulations of the notch root response. Limitations of this classic stress shakedown approach are identified. Although the candidate material of this study is a generic polycrystalline, dual-phase Ni-base superalloy, the presented techniques are likely to be straightforwardly transferable to other materials. When combined with S-N data from experiments on tensile specimens, the method can be used to correlate notch tip response under TMF with fatigue life.
Comparison of Microturbines and Reciprocating Engine Generator Sets
Authors: Gillette Stephen
Published: August 2009

Microturbines are a relatively new technology for generation of electric power. Questions are often raised by potential customers, engineering firms, OEM’s, and government agencies about how microturbines differ from the traditional means of generating power using reciprocating engines as the prime mover. This paper describes the major construction elements of microturbines, along with the significant differences between microturbines and reciprocating engine generator sets. The comparisons are based on published manufacturer’s specifications at the time of writing and include exhaust emissions, electrical and total thermal efficiencies, fuel flexibility, maintenance, size, weight, vibration, required auxiliary equipment, and other application considerations.
Performance Analysis and Comparison of Hybrid SOFC-GT Cycles Fuelled With Methanol
Authors: Fiaschi Daniele , Manfrida Giampaolo , Anselmi Stefano
Published: August 2009

Some hybrid methanol fuelled SOFC-GT power cycles including a few innovative features are analyzed, compared and discussed. The low reforming temperature of methanol allows high heat recovery from the exhaust of hybrid fuel cell gas turbine cycles, which produces high overall efficiency. Different layouts of hybrid SOFC-GT cycles are presented and discussed, including the possibility of coupling the GT to a bottoming steam plant to further improve the overall performance. A target 10 MW GT size is taken as a reference, coupled to different possible SOFC sizes. The modeling of power cycles, reactors and SOFC is done with author-developed codes. The results show that the most efficient solutions are those considering pressurized fuel cells, which partially replace the GT combustor. Cycles with atmospheric fuel cells placed downstream of the gas turbine are also investigated. In both cases, very interesting levels of efficiency are achieved, ranging from 55 to more than 73%.
Prediction of Thermoacoustic Instability in Combustion Chamber Equipped With Passive Dampers
Authors: Camporeale S. M. , Fortunato B. , Mastrovito M.
Published: August 2009

The thermoacoustic mechanism is considered one of the causes of combustion instability in modern gas turbine combustion chambers, according to the basic mechanism proposed by Rayleigh. On this basis, several authors have proposed the use of acoustic passive dampers, in order to hinder the onset of instability or, at least, to reduce the amplitude of the pressure oscillations. The passive device will produce two main actions, cooperating to stabilize the system: dissipating the acoustic energy produced by thermal fluctuations and modifying the phase between acoustic pressure and heat release in order to reduce the production of acoustic energy. The Helmholtz resonators proposed as damping devices act as acoustic impedances whose characteristics can be modified, not only by means of the manipulation of their geometrical features (volume, length and section of the neck) but also by means of holes and cooling flow. The present paper aims at describing how a resonator connected to the combustion chamber is able not only to damp the pressure oscillation but also to modify the instability conditions and, under certain conditions, to convert an unstable condition in a stable one, in a relatively large operating range. The study has been carried for a cannular type of combustion chamber by means of a one-dimensional analytical model and modelling the Helmholtz resonator by means of the electro-acoustic analogy. Two different flame-acoustic interaction model have been examined. As a result of the application of the model the optimal design characteristics of the resonator and its position within the chamber are obtained. Moreover, unlike what it was expected, it appears that the optimal resonance frequency of the resonator does not exactly meet the frequency of the acoustic mode to be damped.