bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Validation of an Unsteady Ejector Model for Hybrid Systems
Authors: Ferrari Mario L. , Pascenti Matteo , Massardo Aristide F.
Published: September 2008

The aim of this work is the experimental validation of a transient ejector model for hybrid system applications. This is a mandatory step in performing the transient analysis of the whole plant to avoid critical situations and to develop the control system. So, the anodic recirculation test rig already used in previous works to study the ejector design validating the steady-state 0-D and CFD models, was used in this work to perform tests at transient conditions and to validate the ejector transient model. An initial validation was carried out at steady-state conditions, then the ejector transient model was successfully compared with the experimental data, also under unsteady conditions. A second step was carried out to better investigate the whole anodic recirculation system. So, the validated ejector transient model was connected to the components necessary to simulate the pipes, the valves and the anodic volume. Also in this case, the calculated results were successfully compared with the experimental data obtained with the laboratory test rig. The final part of the paper is devoted to the results obtained at impulse conditions. In fact, this work investigates the effects on the anodic ejector and on the whole anodic circuit coming from fuel line impulses caused by possible unsteadiness conditions. The results obtained with impulses at different frequency values were successfully compared with the experimental data.
Understanding the Aftermarket: Applying Agent-Based Modelling to Service Infrastructure Design
Authors: Cheeseman Mark J. , Smith Douglas K. , Hesketh Graham B.
Published: September 2008

In order to compete in challenging global markets, Rolls-Royce must have the capability to manage complex processes effectively. As the environment surrounding these processes is constantly changing, the ability to adapt to meet new requirements is essential. The challenge to the business is to quickly adopt an appropriate course of action for each set of circumstances, anticipated or otherwise. An individual decision-maker faced with this situation will normally have several options available. The difficulty is assessing the ramifications of each within a given time frame. To improve the quality of this evaluation, computerized decision support tools can be used. Such tools offer the ability to assess a multitude of options in a short space of time, using a combination of expert knowledge and real data. Having developed an extensive aero-engine service business, Rolls-Royce is required to maintain a highly dependable aftermarket infrastructure. Therefore, the ability to compare how any one particular aftermarket design would perform relative to another is an essential capability. Agent-based systems offer an approach that is both intuitive and interactive, modelling individual entities in the system from the bottom up, capturing low-level interactions that ultimately determine the overall performance of the system. This provides the flexibility and transparency to allow trustworthy analysis and evaluation to take place. To address this business need, an agent-based aftermarket model has been developed. An agent-based system is made up of small software programs built to operate just like a human team. Each agent has a set of capabilities and knowledge, but must work with other agents to achieve the overall goal. Agents can react to changes, adapting and re-planning if a better approach is identified. This paper describes how the model was constructed and the resulting analysis that it facilitates. The model has the ability to replicate the likely service characteristics that would be in place during the full lifecycle of the product. All aspects of the necessary infrastructure are captured, based upon the roles and capabilities of the constituent elements. Agents are used to represent a variety of objects and functions, including airports, airlines, aircraft, overhaul facilities and logistics. Through planning and negotiation, representative decisions are made by these agents to determine when an overhaul should take place and what the workscope should be based upon defined policies. A large selection of configurable parameters can be set by the user to accurately reflect the proposed scenario, providing a powerful what-if analysis tool that can be used to drive the design process, ensuring that product attributes and performance are aligned with the available maintenance infrastructure.
Savings Achieved From Installation of an On-Line Performance Monitoring System at the Naco Nogales Combined Cycle Plant
Authors: Fernandez De Bobadilla Fernando Ramos , Nasal Joe , Sutherland Sid , Noe Greg
Published: September 2008

Union Fenosa began commercial operation of the 300 MW Naco Nogales combined cycle plant in October, 2003 under a power purchase agreement with Mexico’s Comision Federal de Electricidad, and is therefore in a financial risk-reward situation depending on the operational efficiency of the facility. As part of their effort to maximize the profitability of the plant, an on-line performance monitoring system was installed to alert and advise the operating and management staff of performance improvement opportunities. The Naco Nogales Plant consists of one 501G Siemens Westinghouse combustion turbine, a Mitsui Babcock HRSG, and a Siemens steam turbine. To readily identify equipment performance deficiencies, cycle isolation problems, or instrumentation problems in a timely manner, the plant installed an on-line performance monitoring system. The system monitors, archives process data and calculated results, and automatically reports on key performance indicators. A rigorous, first principles thermodynamic model validates the accuracy of measured data and provides off-line “What-If” optimization analyses to assist in operating and business decisions. Key to achieving improved operation was a unique combination of state-of-the-art software and technology transfer through training and mentoring for the plant operations team. This combination provided the information needed for improved information as well as a knowledgeable workforce that understood how to use the “new” information and tools to improve operations and business processes. This paper, written from the Plant’s perspective, describes some key features of the performance monitoring and optimization system, the technology transfer process and several examples of savings recognized by placing an emphasis on profit through a combination of workforce training and the latest software technologies.
Lean Blowout Limits and NOx Emissions of Turbulent, Lean Premixed, Hydrogen-Enriched Methane/Air Flames at High Pressure
Authors: Griebel P. , Boschek E. , Jansohn P.
Published: September 2008

Flame stability is a crucial issue in low NOx combustion systems operating at extremely lean conditions. Hydrogen enrichment seems to be a promising option to extend lean blowout limits of natural gas combustion. This experimental study addresses flame stability enhancement and NOx reduction in turbulent, high-pressure, lean premixed methane/air flames in a generic combustor, capable of a wide range of operating conditions. Lean blowout limits (LBO) and NOx emissions are presented for pressures up to 14 bars, bulk velocities in the range of 32–80 m/s, two different preheating temperatures (673 K, 773 K), and a range of fuel mixtures from pure methane to 20% H2/80% CH4 by volume. The influence of turbulence on LBO limits is discussed, too. In addition to the investigation of perfectly premixed H2-enriched flames, LBO and NOx are also discussed for hydrogen piloting. Experiments have revealed that a mixture of 20% hydrogen and 80% methane, by volume, can typically extend the lean blowout limit by roughly 10% compared to pure methane. The flame temperature at LBO is approximately 60 K lower resulting in the reduction of NOx concentration by ≈ 35% (0.5 → 0.3 ppm/15% O2).
Design Rules for the Velocity Field of Vortex Breakdown Swirl Burners
Authors: Burmberger Stephan , Hirsch Christoph , Sattelmayer Thomas
Published: September 2008

Most gas turbine premix burners without centrebody employ the breakdown of a swirling flow at the transition between the mixing section and the combustor for aerodynamic flame stabilization. As the formation of the desired vortex breakdown pattern depends very sensibly on the shape of the axial and azimuthal velocity profiles in the mixing section, the design of suitable swirlers is typically a cumbersome process and requires an iterative approach consisting of numerical as well as experimental development steps to be iteratively applied until a geometry is found, that provides a spatially as well as temporarily stable vortex breakdown in the primary zone of the combustion chamber without backflow on the centerline of the vortex into the swirler. These difficulties stem from the lack of generally applicable aerodynamic design criteria. The paper attempts to contribute to the development of such design guidelines, which lead quickly to successful swirler designs without need for an excessive number of iterations. For this purpose a family of swirl profiles was generated and the corresponding axial velocity profiles were calculated assuming several radial total pressure distributions. In the next step, the flows were calculated using CFD in order to find out, which velocity profiles produce stable vortex breakdown bubbles at the burner exit. This study reveals that the stable breakdown of the vortex can be achieved for a wide range of velocity distributions, if the radial total pressure distribution is properly selected. However, the radial total pressure distribution in the vortex core is essential for the robustness of the design. Interestingly, velocity profiles with constant total pressure do not show a stable transition of the velocity field at the cross-sectional area change at the entrance of the combustion chamber. In addition, theoretical considerations reveal that an increase of the azimuthal velocity in the vortex core in streamwise direction avoids backflow on the centreline as well as flame flashback. This increase can be achieved using a slightly conical nozzle and introducing a swirl free jet on the centreline upstream of the mixing zone. All effects are explained using the vorticity transport equation.
Novel Technology for Gas Turbine Blade Effusion Cooling
Authors: Battisti Lorenzo , Fedrizzi Roberto , Cerri Giovanni
Published: September 2008

Gas turbine combustion chambers and turbine blades require better cooling techniques to cope with the increase in operating temperatures with each new engine model. Current gas turbine inlet temperatures are approaching 2000 K. Such extreme temperatures, combined with a highly dynamic environment, result in major stress on components, especially combustion chamber and blades of the first turbine stages. A technique that has been extensively investigated is transpiration cooling, for both combustion chambers and turbine blades. Transpiration-cooled components have proved an effective way to achieve high temperatures and erosion resistance for gas turbines operating in aggressive environments, though there is a shortage of durable and proven technical solutions. Effusion cooling (full-coverage discrete hole film cooling), on the other hand, is a relatively simpler and more reliable technique offering a continuous coverage of cooling air over the component’s hot surfaces. This paper presents an innovative technology for the efficient effusion cooling of the combustor wall and turbine blades. The dedicated electroforming process used to manufacture effusive film cooling systems, called Poroform®, is illustrated. A numerical model is also presented, developed specifically for designing the distributions of the diameter and density of the holes on the cooled surface with a view to reducing the metal’s working temperature and achieving isothermal conditions for large blade areas. Numerical simulations were used to design the effusive cooling system for a first-stage gas turbine blade. The diameter, density and spacing of the holes, and the adiabatic film efficiency are discussed extensively to highlight the cooling capacity of the effusive system.
Modeling of Turbulent Combustion of Lean Premixed Prevaporized Propane Using the CFI Combustion Model
Authors: de Jager B. , Kok J. B. W.
Published: September 2008

In this paper combustion of propane under gas turbine conditions is investigated with a focus on the chemistry and chemical kinetics in turbulent flames. The work is aimed at efficient and accurate modeling of the chemistry of heavy hydrocarbons, ie. hydrocarbons with more than one carbon atom, as occurring in liquid fuels for gas turbine application. On the basis of one dimensional laminar flame simulations with detailed chemistry, weight factors are determined for optimal projection of species concentrations on one or several composed concentrations, using the Computational Singular Perturbation (CSP) method. This way the species concentration space of the detailed mechanism is projected on a one dimensional space spanned by the reaction progress variable for use in a turbulent simulation. In the projection process a thermochemical database is used to relate with the detailed chemistry of the laminar flame simulations. Transport equations are formulated in a RaNS code for the mean and variance of the reaction progress variable. The turbulent chemical reaction source term is calculated by presumed shape probability density function averaging of the laminar source term in the thermochemical database. The combined model is demonstrated and validated in a simulation of a turbulent premixed prevaporized swirling propane/air flame at atmospheric pressure. Experimental data are available for the temperature field, the velocity field and the unburnt hydrocarbon concentrations. The trends produced by CFI compare reasonable to the experiments.
Modelling Soot Formation in Aviation Fuel Oxidation
Authors: Kyne A. G. , Pourkashanian M. , Wilson C. W.
Published: September 2008

This study outlines the development of a new chemical kinetic surrogate aviation fuel air reaction mechanism which models up to four ring Polycyclic Aromatic Hydrocarbon (PAH) growth. A sensitivity analysis has been conducted to guide us in improving the correlation with modelled and measured species’ profiles in an n-decane – air combustion environment. It was reassuring that the mechanism could be successfully applied to an out of sample set of experimental profiles for acetylene combustion and showed a noticeable improvement over a previous reaction model. In order to calculate the soot volume fraction, a previously developed soot model was employed that accounts for soot particle coagulation, aggregation and surface growth. The impact of pressure, equivalence ratio and residence time on soot formation for a surrogate aviation fuel-air combustion in a Perfectly Stirred Reactor was also investigated. Generally speaking, the level of soot increased with increasing pressure, residence time and equivalence ratio.
Performance of Gas Turbine Power Plants Controlled by Multiagent Scheme
Authors: Dambrosio Lorenzo , Mastrovito Marco , Camporeale Sergio M.
Published: September 2008

In latter years the idea of artificial intelligence has been focused around the concept of a rational agent. An agent is a (software or hardware) entity that can receive signals from the environment and act upon that environment through output signals. In general an agent always tries to carry out an appropriate task. Seldom agents are considered as stand-alone systems. Their main strength can be found in the interaction with other agents in several different ways in a multiagent system. In the present work, multiagent system approach will be used to manage the control process of a single-shaft heavy-duty gas turbine in Multi Input Multi Output mode. The results will show that the multiagent approach to the control problem effectively counteracts the load reduction (including the load rejection condition) with limited overshoot in the controlled variables (as other control algorithms do) while showing good level adaptivity readiness, precision, robustness and stability.
Study on Efficient Hydrogen Production From Biomass
Authors: Sun Li , Zhang Xiaodong , Yi Xiaolu , Xu Min
Published: September 2008

Hydrogen is crucial for the solution of future energy economy, and the development of mass and cheap production technology of hydrogen has become the central sector in overall hydrogen energy chain. For the abundance and renewability of biomass, it is of great potential to develop economically competitive and efficient biomass thermal conversion technology for hydrogen. One secondary decomposition process, combined with steam reforming, is proposed to the gaseous pyrolysis intermediate to promote hydrogen production. The method implements the sufficient utilization of hydrogen-containing components in biomass, while avoiding the influence of carbon towards the cracking of large molecule hydrocarbons. On the basis of self-energy-sustainability, hydrogen content in the product gas can be expected to reach 60 to 70 percent. From preliminary test on bench scale experimental system, hydrogen-rich gas with relatively small content of impunities was achieved, revealing the feasibility of the applied approach. The secondary decomposition of large molecule gaseous pyrolysis products and the steam reforming of some gas contents were proved to be effective in promoting the deep conversion of these components to hydrogen. When combined with efficent fuel cell system, the results of this work propose one prominent solution for the clean and local utilization of biomass.
Parametric Study of the Combined Fuel Cell-Gas Turbine Power Plant
Authors: Bhinder F. S. , Ebaid Munzer S. Y. , Mustafa Moh’d Yazid F. , Calay Raj K. , Kailani Mohammed H.
Published: September 2008

Large scale electrical power generation faces two serious problems: (i) energy conservation; and (ii) protection of the environment. High temperatures fuel cells have the potential to deal with both problems. The heat rejected by the fuel cell that would otherwise be wasted may be recovered to power a gas turbine in order to improve the energy conversion efficiency as well as power output of the combined fuel cell-gas turbine power plant. The added advantage of this approach would be to reduce thermal loading and the emission of greenhouse gases per MW electrical power generated. Serious research is being carried out worldwide to commercialise the fuel cell nevertheless there is still ample scope for studying the application of high temperature fuel cells in combination with the gas turbine for large scale electrical power generation. This paper presents the results of a parametric study of the fuel cell-gas turbine power plant to generate electricity. The paper should be of considerable interest to the designers and applications engineers working in power generation industry and other public utilities. The authors hope that the paper would lead to a stimulating discussion.
Effect of Impingement/Effusion Hole-Area Ratio on Discharge Coefficients of Double Cooling Wall
Authors: Zhang Chi , Xu Quanhong , Zhao Mengmeng , Lin Yuzhen , Liu Gaoen
Published: September 2008

This paper presents the experimental investigations on the discharge coefficients of impingement/effusion double flat wall with the impingement/effusion hole-area ratios of 1, 0.64 and 0.28. The impingement and effusion walls researched have equal numbers of holes per unit surface area in diamond arrays. The impingement holes are normal to the wall surface, the effusion holes are 30 degree to the wall surface in the sreamwise direction of the main flow, and both the impingement and effusion holes are arranged in the staggered mode. The CFD code was also applied to investigate the flow field within the impingement/effusion wall in detail. The experimental results indicated the relationship of the discharge coefficients of the single impingement wall, effusion wall and double wall with the overall pressure parameter of double wall in different impingement/effusion hole-area ratios, and were explained in the CFD results.
Circulating Fluidised Bed Gasification of Biomass: Modelling of Fuel-Bound Nitrogen Evolution
Authors: Chen Guanyi , Yan Beibei , Li Gang
Published: September 2008

A model for a CFB biomass gasifier is developed aiming at predicting the pollutant emissions. This model considers a total of eighteen chemical reactions and 8 species (C, H2, CO, H2O, CO2, CH4, NH3 and NO), of which nine reactions are related to fuel-bound nitrogen (FBN). The model implies that the FBN is transformed into gas, crude tar and char in certain proportions during fast pyrolysis, depending on the kind of biomass, operating temperature and heating rate, and shows that, of Tar-N and Char-N, less reactive-N is delaying in participating in the further reaction compared with reactive-N despite the proportion of less reactive-N to reactive-N and the time lag varies with the type of biomass and operating temperature. NH3 is the sole nitrogenous pollutant considered in the model due to the concentration of NO being much lower compared with that of NH3. The trend of NH3 concentration predicted by our model is in good accordance with previous results reported in literature. The model predicts the significant decrease of NH3 emission with temperature increase, and indicates the importance of O2 action and its contact with NH3 for the formation and destruction of NH3.
The Use of Probabilistic Reasoning to Improve Least Squares Based Gas Path Diagnostics
Authors: Romessis C. , Kamboukos Ph. , Mathioudakis K.
Published: September 2008

A method is proposed to support least square type of methods for deriving health parameters from a small number of independent gas path measurements. The method derives statistical information using sets of solutions derived from a number of data records, to produce sets of candidate solutions with a lesser number of parameters. These sets can then be processed to derive an accurate component fault diagnosis. It could thus be classified as a new type of “concentrator” approach, which is shown to be more effective than previously existing schemes. The method’s effectiveness is demonstrated by application to a number of typical jet engine component faults.
Separate Effects of Mach Number and Reynolds Number on Jet Array Impingement Heat Transfer
Authors: Park Jongmyung , Goodro Matt , Ligrani Phil , Fox Mike , Moon Hee-Koo
Published: September 2008

Limited available data suggest a substantial impact of Mach number on the heat transfer from an array of jets impinging on a surface at fixed Reynolds number. Many jet array heat transfer correlations currently in use are based upon tests in which the jet Reynolds number was varied by varying the jet Mach number. Hence, this data may be inaccurate for high Mach numbers. Results from the present study are new and innovative because they separate the effects of jet Reynolds number and jet Mach number for the purposes of validating and improving correlations which are currently in use. The present study provides new data on the separate effects of Reynolds number and Mach number for an array of impinging jets in the form of discharge coefficients, local and spatially-averaged Nusselt numbers, and local and spatially-averaged recovery factors. The data are unique because data are given for impingement jet Mach numbers as high as 0.60 and impingement jet Reynolds numbers as high as 60,000, and because the effects of Reynolds number and Mach number are separated by providing data at constant Reynolds number as the Mach number is varied, and data at constant Mach number as the Reynolds number is varied. As such, the present data are given for experimental conditions not previously examined, which are outside the range of applicability of current correlations.
Advanced Gas Turbine and High Performance Gas-Steam Combined Cycle Plant With Blade Cooling Air Controlling
Authors: Tsuji Tadashi
Published: September 2008

Air cooling blades are usually applied to gas turbines as a basic specification. This blade cooling air is almost 20% of compressor suction air and it means that a great deal of compression load is not converted effectively to turbine power generation. This paper proposes the CCM (Cascade Cooling Module) system of turbine blade air line and the consequent improvement of power generation, which is achieved by the reduction of cooling air consumption with effective use of recovered heat. With this technology, current gas turbines (TIT: turbine inlet temperature: 1350°C) can be up-rated to have a relative high efficiency increase. The increase ratio has a potential to be equivalent to that of 1500°C Class GT/CC against 1350°C Class. The CCM system is designed to enable the reduction of blade cooling air consumption by the low air temperature of 15°C instead of the usual 200–400°C. It causes the turbine operating air to increase at the constant suction air condition, which results in the enhancement of power and thermal efficiency. The CCM is installed in the cooling air line and is composed of three stage coolers: steam generator/fuel preheater stage, heat exchanger stage for hot water supplying and cooler stage with chilled water. The coolant (chilled water) for downstream cooler is produced by an absorption refrigerator operated by the hot water of the upstream heat exchanger. The proposed CCM system requires the modification of cooling air flow network in the gas turbine but produces the direct effect on performance enhancement. When the CCM system is applied to a 700MW Class CC (Combined Cycle) plant (GT TIT: 135°C Class), it is expected that there will be a 40–80MW increase in power and +2–5% relative increase in thermal efficiency.
Methods for Reducing a Thermal Finite Element Model Including the Advection Network Contribution
Authors: Botto Daniele , Zucca Stefano , Gola Muzio M.
Published: September 2008

The life monitoring concept needs on-line calculation to evaluate stresses and temperatures on aircraft engine components, in order to asses fatigue damage accumulation and residual life. Due to the amount of computational time required it is not possible for a full finite element model to operate in real time using the on-board CPU. Stresses and temperatures are then evaluated by using simplified algorithms. In the present work Guyan reduction and component mode synthesis have been applied to a thermal finite element model, including the cooling stream flow — the so called advection network — in order to reduce the size of the solving equation system. The appropriate mathematical formulation for the advection network reduction has been developed. Two reduction methods have been performed, discussed and subsequently applied to a thermal finite element model of a real low pressure turbine disk. The reduced system includes both the disk and the correlated fluid network model, simulating turbine secondary air system. The finite element model is axi-symmetric, with constant convective coefficients. Results of time integration for the reduced and the complete models have been compared. Results show that the proposed techniques gives models with a reduced number of degrees of freedom and at the same time good accuracy in temperature calculation. The reduced models are then suitable for real time computation.
An Overview of Selected Prognostic Technologies With Application to Engine Health Management
Authors: Roemer Michael J. , Byington Carl S. , Kacprzynski Gregory J. , Vachtsevanos George
Published: September 2008

The DoD has various vehicle platforms powered by high performance gas turbine engines that would benefit greatly from predictive health management technologies that can detect, isolate and assess remaining useful life of critical line replaceable units (LRUs) or subsystems. In order to meet these needs for next generation engines, dedicated prognostic algorithms must be developed that are capable of operating in an autonomous and real-time engine health management system software architecture that is distributed in nature. This envisioned prognostic and health management system should allow engine-level reasoners to have visibility and insight into the results of local diagnostic and prognostic technologies implemented down at the LRU and subsystem levels. To accomplish this effectively requires an integrated suite of prognostic technologies that can be applied to critical engine systems and can capture fault/failure mode propagation and interactions that occur in these systems, all the way up through the engine and eventually vehicle level. In the paper, the authors will present a generic set of selected prognostic algorithm approaches that can be applied to gas turbine engines, as well as provide an overview of the required reasoning architecture needed to integrate the prognostic information across the engine.
Endwall Film Cooling Through Fan-Shaped Holes With Different Area Ratios
Authors: Barigozzi Giovanna , Franchini Giuseppe , Perdichizzi Antonio
Published: September 2008

The present paper reports on the aero-thermal performance of a nozzle vane cascade, with film cooled endwalls. The coolant is injected through four rows of cylindrical holes with conical expanded exits. Two endwall geometries with different area ratios have been compared. Tests have been carried out at low speed (M = 0.2), with coolant to mainstream mass flow ratio varied in the range 0.5–2.5%. Secondary flow assessment has been performed through 3D aerodynamic measurements, by means of a miniaturized 5-hole probe. Adiabatic effectiveness distributions have been determined by using the wide banded thermochromic liquid crystals (TLC) technique. For both configurations and for all the blowing conditions, the coolant share among the four rows has been determined. The aerothermal performance of the cooled vane have been analyzed on the basis of secondary flow effects and laterally averaged effectiveness distributions; this analysis was carried out for different coolant mass flow ratios. It was found that the smaller area ratio provides better results in terms of 3D losses and secondary flow effects; the reason is that the higher momentum of the coolant flow is going to better reduce the secondary flow development. The increase of the fan-shaped hole area ratio gives rise to a better coolant lateral spreading, but appreciable improvements of the adiabatic effectiveness were detected only in some regions and for large injection rates.
Flow Reversal in a Horizontal Type Natural Circulation Heat Recovery Steam Generator
Authors: Walter Heimo , Linzer Wladimir
Published: September 2008

Natural circulation heat recovery steam generators (HRSG) are used in many applications for the thermal recycling of the waste flue gas. Many of these boilers are designed as a horizontal type HRSG (see fig. 1). The evaporator of such a steam generator is characterized by an array of parallel tubes with different heat input. The paper presents the results of a theoretical stability analysis for a HRSG with a vertical tube bank. For the horizontal type HRSG the static instability, namely the reverse flow was analysed. The study was done at low system pressures and under hot start-up conditions for the boiler. The investigations show the influence of the geometry, the system pressure and the heat absorption of the individual tubes in the evaporator on the stability of the boiler. The aim of the study was to find design criteria to avoid reverse flow in the tubes of the evaporator. Addition of flow resistance at certain locations of the evaporator can improve the stability. A higher stability will be also achieved by the homogenization of the heat absorption in the individual layers of the bundle heating surface.
Numerical Investigation of Worn Labyrinth Seals
Authors: Chougule Hasham H. , Ramerth Douglas , Ramchandran Dhinagaran , Kandala Ramnath
Published: September 2008

The objective of this study was to develop a Computational Fluid Dynamics (CFD) based methodology to obtain the flow characteristics of worn and unworn labyrinth seals which will be applicable over a wide range of seal geometries. In this paper, we present a process to analyze worn and unworn seals with honeycomb lands using the CFX suite of software. Honeycomb structure poses an additional challenge due to disparate length scales. This was addressed by using separate meshes for the honeycomb and the seal tooth and by connecting them with a generalized grid interface in CFX. The challenges involved in modeling worn seals and an approach for quality meshing of the same was discussed. Comparisons were made with the test data from seals with unworn honeycomb lands. The leakages for the worn seals were also analyzed.
Axial Compressor Overhaul: Part II — GE, Frame 7, Model EA
Authors: Ingistov Steve
Published: September 2008

This Paper is a follow up to Axial Compressor Overhaul Paper GT 2005-68378, Part I that was presented in Reno Nevada, June 2005. In addition to previously presented highlights of complete rotor overhaul, certain technical details vital to reliability of entire GT Unit, are added to ensure better GT Unit reliability. Built-up axial compressor rotors, such as a GE-fabricated, Frame No 7, Model EA GT, require thorough knowledge, experience and attention to the minute details. As this generation of CGT ages, a typical User of 7EA GT Units is facing a daunting task of replacing old blades and installing new blades into seasoned compressor wheels. This Paper deals with methods of securing the new blades into the old compressor and with problems encountered during the new blade installation.
Effects of Inlet Fogging and Wet Compression on Gas Turbine Performance
Authors: Sanaye Sepehr , Rezazadeh Hossein , Aghazeynali Mehrdad , Samadi Mehrdad , Mehranian Daryoush , Ahangaran Mohammad Kazem
Published: September 2008

Inlet fogging has been noticed widely in recent years as a method of gas turbine air inlet cooling for increasing the power output of gas turbines and combined cycle power plants. To study the effects of inlet fogging on gas turbine performance, in the first step, the evaporation of water droplets in the compressor inlet duct was modeled, and at the end of the inlet duct, the diameter of water droplets were estimated. The results of this process were compared with the results of FLUENT software. In the second step, the droplets which were not evaporated in compressor inlet duct were studied during wet compression in the compressor and the reduction in compressor discharge air temperature was predicted. Finally, the effects of both evaporative cooling in inlet duct, and wet compression in compressor, on the power output, and turbine exhaust temperature of a gas turbine with turbine blade cooling were investigated. These results for various amounts of air bleeding, without and with inlet fogging in the range of (0–2%) overspray are reported.
Number and Nominal Power of Prime Movers in Combined Heat and Power Systems
Authors: Sanaye Sepehr , Meibodi Mehdi Aghaee , Shokrollahi Shahabeddin , Fouladi Habibollah
Published: September 2008

Combined Heat and Power (CHP) systems have many economical and environmental benefits. Generally, selection of these systems is performed using the time-dependent curves of the required electricity and heating load during a year. In the selection of a CHP system, the operation of this system at off-design point also should be studied. In this paper, a method for selecting the number of prime movers, and determining their nominal power and operational strategy considering specific electrical and heating loads is presented. Three types of prime movers which are studied in this paper are gas turbine, diesel engine, and gas engine. Selecting the number of each type of prime mover and determining their nominal power as well as the operational strategy are presented here. Ambient conditions and electricity and heating load curves are assumed as known parameters. Parameters such as engine thermal efficiency, exhaust gas temperature, mass flow rate of fuel and exhaust gases are computed for three types of prime movers. After determining the optimum value of number and nominal power of prime mover(s), the operational strategy of each type of prime mover in CHP system is analyzed.
Correlation of Landfill and Digester Gas Composition With Gas Turbine Pollutant Emissions
Authors: McDonell V. G. , Effinger M. W. , Mauzey J. L.
Published: September 2008

The deployment of small gas turbines at landfills and wastewater treatment plants is attractive due to the availability of waste fuel gases generated at these sites and the need for onsite power and/or heat. The fuel gases produced by these applications typically contain 35 to 75% of the heating value of natural gas and contain methane (CH4) diluted primarily with carbon dioxide (CO2) and sometimes nitrogen (N2). Demonstrations of 30 to 250 kW gas turbines operating on these waste fuels are underway, but little detailed information on the systematic effect of the gas composition on performance is available. Growth in the use of small gas turbines for these applications will likely require that they meet increasingly stringent emission regulations, creating a need to better understand and to further optimize emissions performance for these gases. The current study characterizes a modified commercial natural gas fired 60 kW gas turbine operated on simluated gases of specified composition and establishes a quantitative relationship between fuel composition, engine load, and emissions performance. The results can be used to determine the expected impact of gas composition on emissions performance.
Separated Flow Transition on an LP Turbine Blade With Pulsed Flow Control
Authors: Bons Jeffrey P. , Reimann Daniel , Bloxham Matthew
Published: September 2008

Flow measurements were made on a highly loaded low pressure turbine blade in a low-speed linear cascade facility. The blade has a design Zweifel coefficient of 1.34 with a peak pressure coefficient near 47% axial chord (mid-loaded). Flow and surface pressure data were taken for Rec = 20,000 with 3% inlet freestream turbulence. For these operating conditions, a large separation bubble forms over the downstream portion of the blade suction surface, extending from 59% to 86% axial chord. A Single-element hotfilm measurements were acquired to clearly identify the role of boundary layer transition in this separated region. Higher-order turbulence statistics were used to identify transition and separation zones. Similar measurements were also made in the presence of unsteady forcing using pulsed vortex generator jets just upstream of the separation bubble (50% cx). Measurements provide a comprehensive picture of the interaction of boundary layer transition and separation in this unsteady environment. Similarities between pulsed flow control and unsteady wake motion are highlighted.
Syngas Burner Optimization for Fuelling a Heavy Duty Gas Turbine With Various Syngas Blends
Authors: Bonzani Federico
Published: September 2008

The IGCC power plant of Ferrera Erbognone will be the first real commercial power plant in Italy to be operated without taking into account the high benefits once available according to the national law (CIP6/1992) specifically dealing with recovery fuel usage alternative to natural gas. The syngas will be provided by the nearby refinery using tar as main feedstock. Furthermore, according to the demands of the refinery it will be possible in the gasifier island to separate hydrogen in variable quantity from the syngas thus giving a high variability composition as output fuel. Also, if the maximum quantity of hydrogen will be separated, an integration with natural gas will be performed in order to get the maximum power output of the power plant. As a consequence, the syngas burner has been designed taking into account all the fuel characteristics depending on the different composition carried out. According to these, the burner has been optimised in order to fit the various syngas blends to be fuelled when running the engine. In order to verify the modifications carried out the burner has been tested both at atmospheric and full engine conditions since the NOx requirements for this project are the more stringent experienced with respect to the past projects (NOx to be below 25 ppm). During these test the main aspect to be in investigated have been: a) Minimum load when feeding the gas turbine with syngas. b) NOx emission from 60% load up to base load. c) Change over from natural gas to syngas and vice versa. The tests have been performed successfully: commissioning on site will start on November 2005. The paper describe the design and the testing phase highlighting the main features of the burner and the fuel system with respect to the plant requirements.
Experimental Performance of a Swirl-Venturi Fuel Mixer for a Fuel Cell Reformer
Authors: Tacina Robert , Hicks Yolanda R. , Anderson Robert , Locke Randy J. , Robinson Heidi N. , Yen Chia
Published: September 2008

The objective of this work is to develop a liquid fuel injector-mixer to provide a uniform mixture of vaporized fuel, steam and air to a fuel cell reformer. This effort supports the NASA fuel cell program, which has the goal of cleaner aerospace power plants. The demonstration project is sized for a 10 kW fuel cell. The Swirl Venturi Mixer (SVM) is the fuel injector-mixer concept explored in the present study. The SVM consists of: a capillary tube to inject the fuel; a venturi tube to maximize the effective air-assist atomization of fuel injected at the throat; and a controlled expansion of radial mixing at the diffuser portion of the venturi. A swirler upstream of the venturi tube enhances turbulent mixing and improves the diffuser performance by suppressing flow separation. Variables evaluated are: swirl angle, throat diameter, throat length and diffuser length. The test section has a 76 mm diameter and includes a quartz cylinder to allow laser-based flow measurements downstream of the injector. Raman spectroscopy is used to measure chemical species distribution across the flow field while particle image velocimetry (PIV) is used to determine the field velocity profile. Test conditions consisted of an inlet air temperature of 700K, inlet steam temperature of 480K, atmospheric pressure, Jet A fuel, and mixture velocities of 1 to 3 m/s.
Military Engine Response to Compressor Inlet Stratified Pressure Distortion by an Integrated CFD Analysis
Authors: Melloni Leonardo , Kotsiopoulos Petros , Jackson Anthony , Pachidis Vassilios , Pilidis Pericles
Published: September 2008

Especially in aircraft applications, the inlet flow is quite often non uniform resulting in severe changes in compressor performance and hence, engine performance. The magnitude of this phenomenon can be amplified in military engines due to the complex shape of intake ducts and the extreme flight conditions. The usual approach to engine performance simulation is based on non-dimensional maps for compressors and turbines and assumes uniform flow characteristics throughout the engine. In the context of the whole engine performance, component-level, complex physical processes, such as compressor inlet flow distortion, can not be captured and analyzed. This work adopts a simulation strategy that allows the performance characteristics of an engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of fidelity. The methodology described in this paper utilizes an object-oriented, zero-dimensional gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional, computational fluid dynamics (CFD), low-pressure compressor model. The CFD model is based on the overall geometry and performance of the low-pressure compressor of a modern, two-spool, low by-pass ratio (LBR) military turbofan engine and is subjected to both clean and distorted inlet flows. The analysis involves the generation of two characteristic maps for the first stage of the LP compressor from CFD simulations that account for a range of operating conditions and power settings with a uniform and a distorted inlet flow. The same simulation strategy could be adopted for other engine components such as the intake or the high-pressure compressor and for different magnitudes and types of distortion (i.e. radial, circumferential). By integrating the CFD-generated maps, into the 0-D engine analysis system, this paper presents a relative comparison between the ‘uniform-inlet’ engine performance (baseline compressor stage map) and the engine performance obtained after using the map accounting for a typical extent of stratified inlet distortion. The analysis carried out by this study, demonstrates relative changes in the simulated engine performance larger than 1%.
Rotary Kiln Slow Pyrolysis for Syngas and Char Production From Biomass and Waste: Part 1 — Working Envelope of the Reactor
Authors: Fantozzi Francesco , Colantoni Simone , Bartocci Pietro , Desideri Umberto
Published: September 2008

A micro scale electrically heated rotary kiln for slow pyrolysis of biomass and waste was designed and built at the University of Perugia. The reactor is connected to a scrubbing section, for tar removal, and to a monitored combustion chamber to evaluate the LHV of the syngas. The system allows the evaluation of gas, tar and char yields for different pyrolysis temperature and residence time. The feeding screw conveyor and the kiln are rigidly connected; therefore a modification of the flow rate implies a modification of the inside solid motion and of residence time. The paper provides the theoretical and experimental calculation of the relationships between Residence Time and Flow Rate used to determine the working envelope of the reactor as a function of the feedstock bulk density and moisture content, given the actual heat rate of the electric heaters. The methodology is extendable to any rotary kiln reactor with a rigidly connected feeding screw conveyor, given its geometric and energetic specifications. Part 2 of the paper will extend the energy balance introducing also the yields of pyrolysis products.
Energy Analysis of Part Flow and Full Flow Humid Air Turbine Cycle (HAT)
Authors: Aghaei Vahid Noei , Bakhtiari Bahador , Khaledi Hiwa , Ghofrani Mohammad Bagher
Published: September 2008

Current researches on the development of gas turbine related power plants such as HAT cycle and Combined Cycle are aimed to increase the plant efficiency and output power, while reducing the cost of power generation and emission. Humid air turbine cycle (HAT) is one of innovative cycles, which are able to provide a substantial power boost of the system and an efficiency rise of several percentage points. In order to perform energy analysis of Full Flow HAT cycle and Part Flow HAT cycle an advanced thermodynamic model is developed, which is enabling evaluation of behavior of Full Flow and Part Flow Humid Air Turbines and predicting the influence of operational parameters in the performance of these cycles. Changes in level of cooling technology are introduced in the model. Results show that this parameter has great influence on the cycle efficiency, especially at high Turbine Inlet Temperature (TIT). Also to model the accurate behavior of humid air, a new thermodynamic model is used to predict thermodynamic properties of air-water mixture at elevated temperature and pressure. In The pressure, in which compressor divided into two sections (LP/HP) is considered to find the optimum performance of cycle. Finally performance of Part Flow HAT cycle at different operating conditions (compressor pressure ratio, TIT) and bypass factors is verified and compared with Full Flow HAT cycle. Results show that in Part Flow HAT cycle changes in bypass factor has little influence on performance of the cycle. Furthermore, Part Flow HAT cycle exhibits better performance (compared to Full Flow HAT cycle) at high pressure ratio region, and vice versa at low pressure ratio region.