bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigations Into the Performance of a Turbogenerated Biogas Engine During Speed Transients
Authors: Thompson Ian , Spence Stephen , McCartan Charles , Thornhill David , Talbot-Weiss Jonathan
Published: May 2012

Turbogenerating is a form of turbocompounding whereby a Turbogenerator is placed in the exhaust stream of an internal combustion engine. The Turbogenerator converts a portion of the expelled energy in the exhaust gas into electricity which can then be used to supplement the crankshaft power. Previous investigations have shown how the addition of a Turbogenerator can increase the system efficiency by up to 9%. However, these investigations pertain to the engine system operating at one fixed engine speed. The purpose of this paper is to investigate how the system and in particular the Turbogenerator operate during engine speed transients. On turbocharged engines, turbocharger lag is an issue. With the addition of a Turbogenerator, these issues can be somewhat alleviated. This is done by altering the speed at which the Turbogenerator operates during the engine’s speed transient. During the transients, the Turbogenerator can be thought to act in a similar manner to a variable geometry turbine where its speed can cause a change in the turbocharger turbine’s pressure ratio. This paper shows that by adding a Turbogenerator to a turbocharged engine the transient performance can be enhanced. This enhancement is shown by comparing the turbogenerated engine to a similar turbocharged engine. When comparing the two engines, it can be seen that the addition of a Turbogenerator can reduce the time taken to reach full power by up to 7% whilst at the same time, improve overall efficiency by 7.1% during the engine speed transient.
Effect of Variable Guide Vanes and Natural Gas Hybridization for Accommodating Fluctuations in Solar Input to a Gas Turbine
Authors: Kitzmiller Kyle , Miller Fletcher
Published: May 2012

In recent years, several prototype solar central receivers have been experimentally demonstrated to produce high temperature and high pressure gas capable of driving a gas turbine engine [1–4]. While these prototype receivers are generally small (< 1 MWth), advancements in this technology will allow for the development of solar powered gas turbine engines at a commercial level (sizes of at least several megawatts electric (MWe)). The current paper analyzes a recuperated solar powered gas turbine engine, and addresses engine considerations, such as material limitations, as well as the variable nature of solar input. In order to compensate for changes in solar input, two operational strategies are identified and analyzed. The first is hybridization, meaning the solar input is supplemented via the combustion of fossil fuels. Hybridization often allows for an increase in net power and efficiency by adding heat during periods of low solar thermal input. An alternative strategy is to make use of variable guide vanes on the compressor of the gas turbine engine, which schedule to change the air flow rate into the system. By altering the mass flow rate of air, and assuming a fixed level of heat addition, the operating temperature of the engine can be controlled to maximize power or efficiency. The paper examines how to combine hybridization with variable guide vane operation to optimize gas turbine performance over a wide range of solar thermal input, from zero to solar-only operation. A large material constraint is posed by the combustor, and to address this concern two alternative strategies — one employing a bypass valve and the other a combustor modified to allow higher temperature inlet air — are presented. Combustor modifications could include new materials and/or increased cooling air. The two strategies (bypass vs. no bypass) are compared on a thermodynamic basis. Finally, a yearly assessment of solar share and thermodynamic performance is presented for a 4.8 MWe gas turbine to identify the overall benefits of the operational strategies.
Improved Map Scaling Methods for Small Turbocharger Compressors
Authors: Ernst Benedikt , Kammeyer Jasper , Seume Joerg R.
Published: May 2012

Today engine performance simulations are essential in the preliminary design of turbocharged combustion engines, e.g. when matching the engine and the turbocharger. In order to optimize this matching process and to enable a preliminary selection of different turbocharger types and sizes, realistic modifications of the compressor and turbine maps are needed. This paper discusses several published approaches for compressor diameter scaling methods. In this context, an improved method to determine the efficiency changes due to diameter scaling of small turbocharger compressors is presented. Besides diameter scaling, trim scaling is a possibility to change the operating range of a compressor. Therefore, a trim scaling method is provided. In order to validate the scaling methods, scaled compressor maps are compared to measured nominal maps.
A Residual Stress Measurement Technique for Turbine Blade Dovetails
Authors: Kawamura Takero , Baba Masanobu , Ozawa Naoto , Sugiyama Yukihisa
Published: May 2012

In aeroengines or industrial gas turbine blades, it is important to estimate the residual stresses at the surface of the blade root to ensure the structural integrity of the part. Most turbine blades are investment cast superalloys and it is difficult to apply the standard X-ray diffraction method to measure the residual stresses, because of the presence of a coarse grain size in these parts. Therefore a special technique was adopted to enable an estimate of the residual stresses at the surface of the turbine blade dovetail, which is a typical feature of the blade root. This method consists of a combination of the curvature method and the FE analysis. After obtaining a good agreement between the results using this method with the standard X-ray diffraction method in wrought Alloy 718 that possesses a very fine grain size, the residual stress distributions in the subsurface region of cast turbine blade dovetails were successfully obtained.
Fluidic Jet Barriers for Sealing Applications
Authors: Hogg Simon I. , Gomez Ruiz Isabel
Published: May 2012

The turbine industry is continually looking for new developments to improve thermodynamic performance and sealing has received significant attention over the years. Fluidic seals employ aerodynamic flow features to create blockage/loss and reduce leakage, rather than relying on physical barriers to flow such as brush seal bristle packs etc. They are also potentially cheaper to implement than contacting seal technologies such as brush seals. The fundamental mechanism by which fluid jets inclined in an upstream direction produce blockage and reduce the flow along leakage channels are examined in the paper. Computational Fluid Dynamics is used to quantify the net gain in leakage performance that can be achieved in simple channel flow for various operating conditions and jet configurations. These results are used to guide further CFD calculations in which the potential for leakage reduction from adapting conventional labyrinth turbomachinery seal designs to include fluidic jets is investigated. Calculations are carried out for operating conditions that are typical of gas and steam turbine applications, in order to demonstrate the potential of new seal designs of this generic type. The device considered in the paper is essentially a conventional labyrinth seal design which is modified to include internal flow channels within the structure supporting the labyrinth fins, to supply the fluidic jets. The new technology is therefore a modification to an existing component with potential for application in existing turbine designs, requiring no/minimal changes outside of the seal design space to implement.
Heat Transfer Enhancement due to Combination of Dimples, Protrusions, and Ribs in Narrow Internal Passage of Gas Turbine Blade
Authors: Murata Akira , Nishida Satomi , Saito Hiroshi , Iwamoto Kaoru , Okita Yoji , Nakamata Chiyuki
Published: May 2012

Internal convective cooling of gas-turbine airfoil is essential because turbine inlet temperature becomes higher for pursuing higher thermal efficiency. For higher cooling performance, heat transfer is often enhanced by installing ribs and/or pin-fins in the internal passage. In this study, in order to enhance heat transfer, the combination of spherical dimples, cylindrical protrusions, and transverse square ribs was applied to one wall of a narrow passage. As for the cylindrical protrusions, two different diameter cases were examined. The heat transfer enhancement was measured by a transient infrared thermography method for the Reynolds number of 2,000, 6,000, and 10,000. The pressure loss was also measured in the experiments, and RANS simulation was performed to give a rationale for the experimental results. The present results clearly showed the spatial variation of the local Nusselt number: the high Nusselt number was observed on the rib top-surface and also near the leading edge on the protrusion top-surface. In addition, the areas around the dimple’s trailing-edge on the oblique line connecting the neighbor dimples showed moderately enhanced heat transfer. When two different protrusion-diameter cases were compared, both the mean Nusselt number and the friction factor were similarly higher in the larger protrusion case than the smaller protrusion case, and therefore the larger protrusion case was more effective in cooling even when the pressure loss was taken into account.
Experimental and Numerical Analyses of Radial Turbine Blisks With Regard to Mistuning
Authors: Ho¨nisch Peter , Ku¨hhorn Arnold , Beirow Bernd
Published: May 2012

The effect of blade frequency mistuning on the forced response of integral radial turbines is studied by means of experimental and numerical analyses. Blade dominated frequencies representing the mistuning are identified based on blade by blade measurements using the example of a MTU ZR140 turbine blisk. Based on these results, numerical simulations of the blade by blade measurements are performed, aiming to update the originally ideal (tuned) finite element model. The damping information to be considered in the update process is taken from results of an experimental modal analysis. The quality of the model is proved by well correlated frequency response functions (FRF) of numerical and experimental analyses. Finally, the models are used to simulate the forced response due to travelling wave excitations. As a result, mode localization phenomena and response amplifications compared to tuned blisks are proved. In order to round off the contribution to a more enhanced understanding of the radial turbine blisk dynamics optically based geometry measurements are performed to assess the influence of geometrical deviations on frequency mistuning. It is shown that geometric imperfections can be the main driver causing a mistuned response characteristic.
F-Class DLN Technology Advancements: DLN2.6+
Authors: Venkataraman Krishna , Lewis Skigh E. , Natarajan Jayaprakash , Thomas Stephen R. , Citeno Joseph V.
Published: May 2012

GE’s DLN2.6 system opened the doors to single digit NOx emissions for F-Class industrial gas turbines. Today more than 500 DLN2.6 systems are installed worldwide. GE has recently advanced the technology of F-Class “Dry Low NOx” (DLN). The new DLN2.6+ technology achieves low-NOx emissions for 9FA and 9FB turbines. Turndown in NOx and CO compliance for 9FB turbines to 32% load and 9FA turbines to 28% load has been demonstrated in the field. This paper will summarize the development history of DLN2.6 and 2.6+ combustion systems and the operating experience of the DLN2.6+. Field validation performance results of the systems will be shared as well as fuel-flexibility results with the DLN2.6+ system.
NPSS Volume Dynamic Capability for Real-Time Physics Based Engine Modeling
Authors: Argote Christopher , Kestner Brian K. , Mavris Dimitri N.
Published: May 2012

This paper introduces a new capability and method for solving transient engine cycles for the potential application of real-time simulation in the cycle analysis code Numerical Propulsion System Simulation (NPSS). This method utilizes a new element which models volume dynamics, a set of equations that characterize the unsteady behavior of fluid dynamic and thermodynamic properties with respect to a volume and boundary conditions. These equations are derived from the Euler equations for conservation of mass, momentum, and energy. Physics based real-time engine models often consider the effects of volume dynamics; however it is normal to see the momentum conservation drop out. This is largely due to the high frequency response of momentum which yields smaller time steps thus increasing the cost associated with computation time. The new high fidelity volume dynamics element is introduced with all three conservations laws working together. NPSS’s interpreted language provides the flexibility to allow the volume dynamics to be solved explicitly, however by rearranging the momentum equation, it can be solved implicitly therefore increasing the critical time step. In addition to improving transient modeling fidelity, the new volume dynamics element can be used to drive the cycle. Rather than balancing error terms in a Newton-Raphson solver, the volume dynamic equations provide the necessary communication between the engine cycle and boundary conditions. These equations alone can drive the engine model towards a steady state solution. Using a basic forward Euler numerical integration technique to solve the volume dynamic equations the engine cycle only requires a single pass per time step. This document illustrates the development of both the new element and the methodology in cycle modeling using the volume dynamics. Two example models are created and analyzed in this paper, first, a simple inlet, duct, nozzle system is analyzed. Second, a separate flow long duct turbojet is examined. These two models are used to demonstrate the real time capabilities of the high fidelity transient analysis, as well as highlight some of the challenges in the implementation of volume dynamics on a given cycle.
Effect of Tip Clearance on the Prediction of Non-Synchronous Vibrations in Axial Compressors
Authors: Drolet Martin , Vo Huu Duc , Mureithi Njuki W.
Published: May 2012

This work investigates the effect of tip clearance size and operating temperature on the predictions of the critical rotor speed at which Non-Synchronous Vibrations (NSV) can be encountered in a turbine engine axial flow compressor. It has been proposed that the tangential tip clearance flow, observed at high blade loading near stall, can act as an impinging resonant jet on the upcoming blades and could be the underlying physics behind NSV. A model, in the form of an equation to predict the critical blade tip speed at which NSV can occur, was proposed based on the Jet-Core Feedback Theory and was experimentally verified by Thomassin et al. [8]. In the equation, a factor k that was called the “tip instability convection coefficient” was measured experimentally and found to be influenced by the tip clearance size and operating temperature. This factor has a significant impact on the accuracy of the NSV predictions obtained using the proposed model. This paper propose a numerical experiment to determine the effect of tip clearance size and temperature on k, in order to improve the critical NSV tip speed predictions using the proposed model. A review of the NSV model is presented along with the relevant background theory on the subject. Two different blade geometries are simulated to provide a generic approach to the study. The leakage flow velocity is calculated to estimate k and a correlation is proposed to model the behavior of the k parameter as a function of the tip clearance size. The latter was found to significantly improve the critical NSV speed predictions. The effect of operating temperature on k is also discussed. Finally, the variation of k with the aerodynamic loading is assessed and compared with available data in the literature to strengthen the generic nature of the results.
Development of an Optimization Design Method for Turbomachinery by Incorporating the Cooperative Coevolution Genetic Algorithm and Adaptive Approximate Model
Authors: Song Peng , Sun Jinju , Wang Ke , He Zhilong
Published: May 2012

An optimization design method is developed, which is motivated by the optimal design of a cryogenic liquid turbine (including an asymmetric volute, variable stager vane nozzles, shroud impeller and diffuser) for replacement of the Joule-Thompson throttling valve in the internal compression air-separation unit. The method involves mainly three elements: geometric parameterization, prediction of objective function, and mathematical optimization algorithm. Traditional parameterization approach is used for the geometry representation, while some novel work in the latter two aspects (i.e. objective function evaluation and optimization algorithm) is done to reduce the computing time and improve the optimization solution. A modified Cooperative Coevolution Genetic Algorithms (CCGA) is developed by incorporating a modified variable classification algorithm and some new self-adapted GA operators, which help to enhance the global search ability with an excessive number of optimization variables. Design of Experiment (DOE) is carried out to initialize the kriging approximation model, which is used to approximate the time-costly objective function. Then the CCGA is started, and once a potential superior individual is found, a decision will be made by the in-house code on whether or not it needs a updating. If required, the true objective function prediction based on the real model will be conducted and the obtained value of objective function will be used to update the kriging model. In such a way, the CCGA can complete its optimal searching with a limited number of real evaluations for objective function. All the above features are integrated into the optimization framework and encoded for the optimal turbine design. In addition, CFD software ANSYS CFX is used for the real objective function evaluations, and a well-organized batch code is developed by the authors for calling the CFD simulation which helps to promote this automation of the optimization process. For validation, the optimization method is used to solve some classical mathematical optimization problems and its effectiveness is demonstrated. The method is then used in the optimal design of the cryogenic liquid turbine stage, it is demonstrated that the optimal design method can help to reduce significantly the searching time for the optimal design and improve the design solution to the liquid turbine.
LBO Performance Comparison Between Two Combustors With Different Swirl Cups
Authors: Yuan Yixiang , Guo Baoting , Tan Chunqing , Zhang Chi , Lin Yuzhen , Liu Gaoen , Fan Hailin
Published: May 2012

Lean Blowout (LBO) performance is very important to the aero and ground gas turbine combustors. A typical liquid-fueled gas turbine combustor is the one with swirl cup dome which plays an important role to the LBO. The swirl cup dome comprises swirlers and nozzle usually. The swirlers serve to generate a toroidal flow reversal that entrains and recirculates a portion of the hot combustion products to mix with the incoming fresh air and fuel, so it makes the recirculation region the sustainable source of ignition. Swirlers in present study generally are two or three stages, and the nozzle takes different atomization styles, such as pressure-swirl atomization, prefilming and airblast atomization. Different swirlers matching various nozzles form all kinds of swirl cup domes, and each swirl cup dome of combustor would have different LBO performance and other combustion properties resulting from its structure characteristics. The flow flux arrangement and spray distribution are the two important factors to determine the combustor performance. Two combustor dome test rigs were investigated, of which one comprises with three air swirlers and a fuel prefilming nozzle (dome A), and the other is composed of two air swirlers and a fuel pressure nozzle (dome B). Tests were conducted to get the LBO fuel air ratio at atmospheric pressure. To explain the experimental results, numerical simulations were performed for cool flow fields of two combustors, also the cold flow field and spray of the two combustors’ dome downstream were measured by PDA with water instead of kerosine. The flame pictures near LBO were taken. The preliminary results indicated that the combustor with dome A had better spray uniformity than the one with dome B, but it had a little worse LBO performance. The air flow mass percentage of the inner swirler of dome A should decrease to some extent in order to establish a lower pressure region at the outlet of dome A, which would be helpful to decrease the LBO fuel air ratio and so as to improve the LBO performance. The two domes had their own advantages, and if the benefits of both were integrated, it was possible to design a better swirl cup dome.
An Energy Based Critical Fatigue Life Prediction Method
Authors: Letcher Todd , Shen M.-H. Herman , Scott-Emuakpor Onome , George Tommy , Cross Charles
Published: May 2012

The capability of a critical life, energy-based fatigue prediction method is analyzed in this study. The theory behind the prediction method states that the strain energy accumulated during monotonic fracture and fatigue are equal. Therefore, a precise understanding of the strain energy density behavior in each failure process is necessary. The initial understanding of energy behavior shows that the accumulated strain energy density during monotonic fracture is the area underneath the experimental stress-strain curve, whereas the sum of the constant area within every stress-strain hysteresis loop of the cyclic loading process is the total strain energy density accumulated during fatigue; meaning, fatigue life is determined by dividing monotonic strain energy density by the strain energy density in one cycle. Further observation of the energy trend during fatigue shows that strain energy density per cycle is not constant throughout the process as initially assumed. This finding led to the incorporation of a critical life effect into the energy-based fatigue prediction method. The analysis of the method’s capability was conducted on Al 6061-T6 ASTM standard specimens. The results of the analysis provide further improvement to the characterization of strain energy density for both monotonic fracture and fatigue; thus improving the capability of the energy-based fatigue life prediction method.
A Novel Quasi-3D Design Method for Centrifugal Compressor Impeller on the Blade-to-Blade Plane
Authors: Poursadegh Farzad , Hajilouy-Benisi Ali , Nili-Ahmadabadi Mahdi
Published: May 2012

In this research, a novel quasi-3D design method is developed for the centrifugal compressor impeller on the blade-to-blade plane. In this method, an iterative inverse design method called Ball-Spine Algorithm (BSA) is incorporated into the quasi-3D analysis code solving the Euler equations on the blade-to-blade and meridional planes at each shape modification step. In design procedure, the difference between the target and current pressure distribution along the suction or pressure sides of the impeller causes the blade-to-blade profile to be changed and the target pressure distribution to be satisfied. In order to validate the quasi-3D analysis code, the centrifugal compressor of a gas turbine is investigated numerically using a full 3D Navier-Stokes analysis code. The meridional and blade-to-blade planes pressure distributions obtained from quasi-3D and 3D analysis codes are compared showing good agreement between them. Furthermore, the pressure ratio and efficiency of the centrifugal compressor is obtained by some experiments in which the flow parameters at the compressor inlet and outlet are measured. Comparison of 3D analysis results with the experimental results shows good agreements. Finally, the current pressure distribution along the pressure side at 50% span is smoothed and considered as the target pressure distribution. The quasi-3D design procedure converges to a new profile after 400 modification steps. The designed impeller is numerically analyzed showing the flow pattern of the impeller is improved and the total to static efficiency of impeller increases by 0.64 percent and the total pressure ratio increased by 3.38 percent.
Investigation of Coriolis Effect on Vibration Characteristics of a Realistic Mistuned Bladed Disk
Authors: Xin Jianqiang , Wang Jianjun
Published: May 2012

Mistuning, which refers to inevitable variations in blades properties, will change the vibration of bladed disks dramatically. Bladed disks are exposed to effects of forces caused by bladed disk rotation, such as centrifugal and Coriolis forces. However, there is little research on the vibration behavior of a realistic bladed disk with Coriolis force. An investigation of the speed effect, i.e., the effects of centrifugal and Coriolis forces, on the vibration characteristics of a realistic mistuned bladed disk model is presented in this paper. Finite element method (FEM) is used to obtain the system mass, stiffness and damping matrix. The effects of Coriolis force and centrifugal force on the modal frequency and harmonic response characteristics of tuned bladed disk are investigated first, then the modal localization and response characteristics of mistuned bladed disk are researched. This investigation indicates that: Coriolis force has efficient influences on the modal and response characteristics of a realistic mistuned bladed disk: it can both increase and decrease the localization of the mistuned bladed disk for different situations.
Improvement of Oxide/Oxide CMC and Development of Combustor and Turbine Components in the HiPOC Program
Authors: Gerenda´s Miklo´s , Cadoret Yannick , Wilhelmi Christian , Machry Thays , Knoche Ralf , Behrendt Thomas , Aumeier Thomas , Denis Sandrine , Go¨ring Ju¨rgen , Koch Dietmar , Tushtev Kamen
Published: May 2012

Three different oxide/oxide ceramic matrix composite (CMC) materials are described. Design concepts for the attachment of the CMC component to the metal structure of the gas turbine are developed in a first work stream focused on the combustion chamber and the turbine seal segment. Issues like environmental barrier coating (EBC)/thermal barrier coatings (TBC), application and volatilization, allowance for the different thermal expansion and the mechanical fixation are addressed. The design work is accompanied by CFD and FEM simulations. A variation of the microstructural design of the three oxide/oxide CMC materials in terms of different fiber architecture and processing of matrix are considered. Also, mechanical properties of these variations are evaluated. The material concepts are developed further in a second work stream. The CMCs are tested in various loading modes (tension, compression, shear, off-axis loading) from room temperature to maximum application temperature focusing on tensile creep behavior. By modification of the matrix and the fiber-matrix interface as well as EBC coatings, the high temperature stability and the insulation performance are enhanced. An outline of the “High Performance Oxide Ceramic”-program HiPOC for the following years is given, including manufacturing of a high-pressure tubular combustor and turbine seal segments from the improved materials as technology samples, for which validation testing up to technology readiness level 4 is scheduled for 2011.
Wavelet Analysis of Vortical Structures in Turbomachinery Applied to PIV Data
Authors: Schaefer Philipp , Cierpka Christian , Rehder Hans-Ju¨rgen , Roehle Ingo
Published: May 2012

In this paper the unsteady flow field of a highly loaded turbine rotor blade at different transonic Mach numbers by means of Particle Image Velocimetry (PIV) is investigated. The experiments are performed using the linear cascade wind tunnel at DLR Go¨ttingen at isentropic exit Mach numbers 0.7, 0.9, and 1.1. The process of vortex shedding at the trailing edge of the blade and its proceeding downstream in the wake area is analyzed using a wavelet based vortex identification algorithm. The wavelet algorithm automatically detects vortices and extracts e.g. their position, their vorticity, and their convection velocity. This procedure enables a statistical analysis on the basis of numerous PIV recordings. The vortex production, the downstream transport and the vortex decay are observed successfully. The Strouhal number and the shedding frequency are directly derived from the vortex position and confirm previous investigations. The PIV combined with a wavelet based analysis constitutes a remarkable insight to time dependent flow structures.
A Thermodynamic Analysis of Chemical Looping Combustion
Authors: Heyes Andrew L. , Botsis Loukas , McGlashan Niall R. , Childs Peter R. N.
Published: May 2012

Recently, interest has grown in chemical looping combustion (CLC) because it is seen as a technique that may allow cost-effective carbon capture and storage (CCS). In CLC the overall reaction by which chemical energy is released is between a hydrocarbon and air as in conventional combustors. However, the reaction is completed in two separate oxidation and reduction steps occurring in different reaction vessels. In the oxidizer (or air reactor) an oxygen carrier, usually a metal, is exothermically oxidized in air resulting in an oxide and a hot air stream (oxygen depleted). The exhaust gasses may be expanded through a turbine to produce work, while the oxide passes to the reduction vessel (or fuel reactor). Here, it reacts with the fuel, is reduced and the metal regenerated. The metal then returns to the oxidizer to complete the loop. The exhaust gasses from the reducer contain only carbon dioxide and water so that, after expansion and work extraction, the water may be condensed leaving a stream of pure CO2 ready for storage. Hydrocarbon fuels will continue to be used for decades, so, in the face of ambitious emission reduction targets, CCS is an important technology and methods, such as CLC, that offer automatic CO2 separation (so-called inherent carbon capture) are particularly attractive. Despite this obvious advantage CLC was not originally conceived for the purposes of CCS, but rather as a means to produce pure carbon dioxide free from contamination by inert gases such as nitrogen. In the context of power generation it was then proposed as a means to improve the exergetic efficiency of energy conversion processes using hydrocarbons. Combustion is usually a highly irreversible process and necessitates the rejection of large quantities of heat from power cycles leading to the low thermal efficiency of gas turbines and the like. The two-stage reaction approach of CLC can reduce the irreversibility and the extent of heat rejection and hence provide improved cycle efficiency. Ideally, both goals would be simultaneously achieved thereby offsetting both the cost of carbon capture and of compression, transportation and storage. In the paper we present a thermodynamic analysis of CLC to illustrate its potential for improving efficiency. We will then develop a methodology for selecting oxygen carriers based on their thermodynamic properties and review several candidate materials. In particular, we will compare, from a thermodynamic perspective, solid phase oxygen carriers as used in fluidised bed based reaction systems and the liquid/vapour phase carriers previously suggested by the authors. Finally, comments on practical implementations of CLC in power plant will be presented.
Design Optimisation of Casing Grooves Using the Zipper Layer Meshing Method
Authors: Carnie Greg , Wang Yibin , Qin Ning , Shahpar Shahrokh
Published: May 2012

In an earlier paper by the authors [1], a buffer layer method for linking two non-matching structured meshes was introduced for computational simulation of multi-component geometries, each requiring high quality structured meshes. Based on the work, a new algorithm, named the zipper layer method [2], has been developed to link multi-block meshes for gas turbine applications. Numerical results for a turbomachinery rotor flow case are included to demonstrate the solution behaviour across the zipper layer. In the present paper, we will report our work on the optimisation of the casing groove geometries in relation to stall margin and efficiency of a transonic rotor using this new meshing methodology. Six grooves are parameterised by their independent depths and a width to gap ratio. An advanced response surface method based on Sobol Design of Experiment (DoE) and Krigging Response Surface Model (RSM) are used for the optimisation. A leave-one-out cross-validation (LOOCV) method is used to calculate the quality of the response surface metric. The final optimized groove configuration was obtained through an optimisation cycle using the Rolls-Royce SOPHY (SOFT-PADRAM-HYDRA) software [3], which not only improves the Stall Margin (SM) of the rotor but also maintains its peak efficiency. The optimized grooves on the casing side show large variations in their depth from upstream to downstream of the rotor.
The Use of Perforated Damping Liners in Aero Gas Turbine Combustion Systems
Authors: Rupp Jochen , Carrotte Jon , Macquisten Michael
Published: May 2012

This paper considers the use of perforated porous liners for the absorption of acoustic energy within aero style gas turbine combustion systems. The overall combustion system pressure drop means that the porous liner (or ‘damping skin’) is typically combined with a metering skin. This enables most of the mean pressure drop, across the flame tube, to occur across the metering skin with the porous liner being exposed to a much smaller pressure drop. In this way porous liners can potentially be designed to provide significant levels of acoustic damping, but other requirements (e.g. cooling, available space envelope etc) must also be considered as part of this design process. A passive damper assembly was incorporated within an experimental isothermal facility that simulated an aero-engine style flame tube geometry. The damper was therefore exposed to the complex flow field present within an engine environment (e.g. swirling efflux from a fuel injector, coolant film passing across the damper surface etc.). In addition, plane acoustic waves were generated using loudspeakers so that the flow field was subjected to unsteady pressure fluctuations. This enabled the performance of the damper, in terms of its ability to absorb acoustic energy, to be evaluated. To complement the experimental investigation a simplified 1D analytical model was also developed and validated against the experimental results. In this way not only was the performance of the acoustic damper evaluated, but also the fundamental processes responsible for this measured performance could be identified. Furthermore the validated analytical model also enabled a wide range of damping geometry to be assessed for a range of operating conditions. In this way damper geometry can be optimized (e.g. for a given space envelope) whilst the onset of non-linear absorption (and hence the potential to ingest hot gas) can also be identified.
Process Integration and Automated Numerical Design Optimization of an Eigenfrequency Analysis of a Compressor Blade
Authors: Hecker Philipp , Delimar Damir , Brandl Herbert , Lo¨tzerich Michael
Published: May 2012

Modern gas turbines for applications in power plants have to fulfill more and more demands defined by customer and grid requirements. These requirements address for example reduced time for run up and increased power output while providing maximum single or combined cycle efficiency. The demanding market requirements increase the pressure to further improve the design process of gas turbine parts by reducing the overall development time and simultaneously improving the quality of the design. This paper describes the implementation of an automated optimization process for the mechanical assessment of compressor blades applied during the preliminary design process. Previous work from Fedorov, Szwedowicz, et al [1], has shown that it is important to apply 3D FE methods for the accurate prediction of the dynamic behavior of compressor blades already in the early stage of the design phase. These key ideas were picked up in the present work while the FE model from [1] was extended to a complete 3D model of the compressor blade including airfoil and blade root geometry. The new approach completely automates the 3D FE analysis of compressor blades including CAD model generation, FE pre-processing, FE analyses, FE post-processing and takes it to the further level by integrating the FE analysis procedure into an automated design loop using the commercial optimization software iSight FD. The target of this optimization loop is to drive the frequency of critical mode shapes into allowed ranges by modifying airfoil parameters such as airfoil thickness and chord length. A scalar optimization technique is applied solving the design problem using penalty functions for excitation sources, mode shapes and eigenfrequencies. In order to achieve a smooth distribution of airfoil parameters Bezier-Spline approximations are used to parameterize the design space. The implementation of the mechanical analysis for compressor blades into a standardized and automated process was one of the main achievements of the presented work. The process was completely implemented in Abaqus CAE including 3D FE model preparation and post-processing. It was key to a successful integration into an overall optimization loop, which helped to substantially reduce the amount of manual work required to perform the design task.
Performance Optimization of Wind Turbine Rotors With Active Flow Control
Authors: Pechlivanoglou G. , Nayeri C. N. , Paschereit C. O.
Published: May 2012

This paper presents a series of investigations performed at the Hermann Fo¨ttinger Institute of TU Berlin. The initial scope of the investigations was the identification of Active Flow Control (AFC) solutions with significant implementation potential on wind turbine rotors. Several Active Flow Control solutions were thoroughly investigated based on extensive literature research. The performance of all the investigated solutions was ranked according to objective performance criteria and then the best performing solutions were selected for further numerical and experimental investigation. The selected Active Flow Control solutions were experimentally investigated with steady state wind tunnel measurements as well as steady state CFD simulations. The results of these investigations and the potential of each AFC solution are presented and discussed. The steady state tests were followed by a dynamic wind tunnel test campaign where the performance of one AFC solution (active Gurney flap) on a pitching test wing was investigated. The results of the static and dynamic investigations were very positive and proved the large load reduction potential of AFC on wind turbines.
A Quasi-One-Dimensional CFD Model for Multistage Compressors
Authors: Du W. , Le´onard O.
Published: May 2012

In this contribution a quasi-one-dimensional tool for stationary and transient simulations of post-stall flows in multistage axial compressors is presented. An adapted version of the 1D Euler equations with additional source terms is discretized with a finite volume method and solved in time by a fourth-order Runge-Kutta scheme. The equations are discretized at mid-span both inside the blade rows and the non-bladed regions. The source terms express the blade-flow interactions and are estimated by calculating the velocity triangles for each blade row. Several loss and deviation correlations are implemented and compared to experimental data in normal flow, stalled flow and reversed flow regions. Transient simulations are carried out and a parameter study is presented to analyze the shape of the surge cycles and the frequency of the surge oscillations. At last, a bleeding control strategy is implemented to study the recoverability of the instabilities in a compression system.
Improving the Application of Turbine Maps in 1D Engine Process Modelling
Authors: Vogt Mathias , Frese Florian , Mai Holger , Baar Roland
Published: May 2012

The new Euro 6 emission limits represent a major challenge to the development of internal combustion engines. One way to achieve this goal is to enhance the 1D engine process simulation of supercharged engines. In contrast to the widely-used 1D-modelling of pipe flow, turbochargers are generally modelled using maps of mass flow and efficiency. The turbines of turbochargers are usually mapped with constant back pressure and constant inlet temperature on special test beds. Standard non-dimensional values for flow and impeller speed should allow the turbine operating point to be recalculated depending on its boundary conditions. This procedure does not work sufficiently for operating conditions that, e.g. occur in two stage turbocharging or at high temperature offsets to the mapping conditions. This especially concerns the turbine efficiency. Methods like varying the turbine inlet temperature and the turbine back pressure expand the information of the turbine characteristic map. Both methods, used as additional boundary conditions, improve the precision of 1D simulation. The effects of the adjustments will be demonstrated using the example of a 1D engine process simulation of a turbocharged engine.
Investigation of GTL-Like Jet Fuel Composition on GT Engine Altitude Ignition and Combustion Performance: Part II—Detailed Diagnostics
Authors: Mosbach Thomas , Gebel Gregor C. , Le Clercq Patrick , Sadr Reza , Kannaiyan Kumaran , Al-Sharshani Ali
Published: May 2012

The ignition and combustion performance of different synthetic paraffinic kerosenes (SPKs) under simulated altitude relight conditions were investigated at the altitude relight test rig at the Rolls-Royce Strategic Research Centre in Derby. The conditions corresponded to a low stratospheric flight altitude between 25,000 and 30,000 feet. The combustor under test was a twin-sector representation of an advanced gas turbine combustor and fuel injector. Five different SPKs and Jet A-1 were tested at different mass flow rates of air and fuel, and at two different sub-atmospheric air pressures and temperatures. The fuel temperature was kept approximately constant. Simultaneous high-speed imaging of the OH* and CH* chemiluminescence, and of the broadband luminosity was used to visualize both the transient flame initiation phenomena and the combustion behavior of the steady burning flames. In addition, flame luminosity spectra were recorded with a spectrometer to obtain spectrally resolved information concerning the different chemiluminescence bands and the soot luminosity. These investigations were performed in conjunction with the comparative evaluation of the ignition and stability regimes of the five SPKs, which is the subject of a separate complementary paper [1]. We found that the observed flame initiation phenomena, the overall combustion behavior and the different ratios of the chemiluminescence from the OH*, CH* and C2* radicals were not strongly dependent on the fuels investigated. But, the SPK flames showed for all combustor operating conditions significantly lower soot luminosities than the corresponding Jet A-1 flames, indicating a potential benefit of the SPK fuels.
Numerical Simulations of Confined, Turbulent, Lean, Premixed Flames Using a Detailed Chemistry Combustion Model
Authors: Di Domenico Massimiliano , Gerlinger Peter , Noll Berthold
Published: May 2012

In this paper numerical simulations of a confined, high strained jet flame employing a detailed chemistry combustion model are presented. Unlike other configurations available in literature, the geometry under investigation presents the jet axis shifted one side of the confining chamber in order to get non-symmetric recirculation zones and a flame stabilization mechanism based on the recirculation of a high percentage of hot combustion products. Fully three-dimensional unsteady simulations are carried out with finite-rate chemistry effects included by means of a detailed reaction scheme. Turbulence-chemistry interaction is taken into account by employing a presumed PDF approach, which is able to close species source terms by solving two additional transport equations. The use of the hybrid RANS/LES SST-SAS turbulence model is able to include large unsteady turbulent structures according to the local grid size and flow conditions. The approach presented here allows an in-depth investigation of flame stabilization mechanisms, ignition phenomena and influence of recirculation regions on flame stability. Additional simulations adopting simpler combustion models (i.e. Eddy-dissipation Concept) are also presented in order to assess the prediction capabilities of methods widely used in design environments. The paper also includes experimental data while comparison in terms of radial profiles at different heights above the burner are provided.
Effect of Swirl Number and Fuel Type Upon the Combustion Limits in Swirl Combustors
Authors: Abdulsada Mohammed , Syred Nicholas , Griffiths Anthony , Bowen Phil , Morris Steve
Published: May 2012

Increasing interest in lean fuel premixed swirl combustors has arisen because of reduced NOx emissions. Alternative fuels, including hydrogen-enriched natural gas and by products of process industries such as coke oven gas are now receiving increasing attention. This gives rise to areas of concern including, flashback, temperature levels, blow-off and combustion instability. Flashback with hydrogen containing fuels is of special concern, owing to the high flame speed of hydrogen, to such an extent that diffusion combustion is commonly employed resulting in high NOx emissions. This paper examines the effect of hydrogen containing fuels upon flashback and blow-off in a generic, compact, premixed swirl burner in swirl number regimes representative of those found in practical systems. All results are obtained at atmospheric pressure without air preheat as a precursor to pressurised tests, the burner firing freely into atmosphere for most tests. The swirler has radial tangential inlets firing into a swirl chamber, which then feed into the exhaust. A central fuel injector just extends into the exhaust and is ∼40% of the exhaust diameter, a common industrial size. Four tangential inlets are used for S = 1.47, while nine has been used for S = 1.04 and S = 0.8. Flashback and blow-off are sensitive to the level of swirl, the exhaust configuration and the type of fuel. High swirl numbers, S = 1.47, gave flashback limits with methane considerably worse than those produced at S = 1.04 and S = 0.8, although there were differences in exhaust nozzle configuration. At equivalence ratios ∼1 total mass flow at which flashback occurred (hence velocities) was reduced by a factor of two. Changes in flashback behaviour were especially noticeable when the hydrogen content in fuel blends was > 60% by volume. Blow-off was very much a function of hydrogen content of the fuel and Swirl Number. Best blow-off limits for all fuel blends are obtained at S = 0.8, the worst for S = 1.47. Coke Oven gas (COG) with 65% hydrogen content gave best blow-off limits of the fuels tested, although data was not available for pure hydrogen due to rig limitations.