bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat-Transfer and Mixing Enhancement by Vortex Generators Used in Heat Exchanger-Reactors
Authors: Ferrouillat S. , Tochon P. , Garnier C. , Peerhossaini H.
Published: February 2009

Compact heat exchangers are well known for their ability to transfer a large amount of heat while retaining low volume and weight. The purpose of this paper is to study the potential of using this device as a chemical reactor, generally called a heat exchanger-reactor (HEX reactor). Indeed, the question arises: can these geometries combine heat transfer and mixing in the same device? Such a technology would offer many potential advantages, such as better reaction control (through the thermal aspect), improved selectivity (through intensified mixing, more isothermal operation and shorter residence time, and sharper RTDs), byproduct reduction, and enhanced safety. Several geometries of compact heat exchanger based on turbulence generation are available. This paper focuses on one type: vortex generators. The main objective is to contribute to the determination of turbulent flow inside various geometries by computational fluid dynamics methods. These enhanced industrial geometries are studied in terms of their thermal-hydraulic performance and macro-/micro-mixing ability. The longitudinal vortices they generate in a channel flow turn the flow perpendicular to the main flow direction and enhance mixing between the fluid close to the fin and that in the middle of the channel. Two kinds of vortex generators are considered: a delta winglet pair and a rectangular winglet pair. For both, good agreement is obtained between numerical results and data in the literature. The vortex generator concept is found to be very efficient in terms of heat-transfer enhancement and macro-mixing. Nevertheless, the micro-mixing level is poor due to strong inhomogeneities: the vortex generator must be used as a heat-transfer enhancement device or as a static mixer for macro- and meso-mixing.
Optimal Vortex Ring Formation: A Study of Vortex Ring Formation in Starting and Pulsed Jets (Keynote)
Authors: Gharib Morteza
Published: February 2009

Pulsatile jet flows are found in many industrially relevant fluid mechanical problems. A common feature of these flows is that they are fundamentally a series of fluid pulses. This aspect of pulsatile jets implies vortex rings are a basic element of the resulting flow. The significance of this observation is based in part on the tendency of vortex rings to entrain ambient fluid during their formation, but more so on the recent discovery of the phenomenon of vortex ring pinch off. This phenomenon was characterized for starting jets (individual pulses) showing that for pulses sufficiently long with respect to the nozzle diameter (i.e., sufficiently large L/D), the vortex ring stops forming and pinches off from the generating jet. This represents a maximization principle for vortex ring formation and suggests that any effects associated with vortex ring formation in pulsatile jets (e.g., enhanced entrainment), might be able to be optimized by properly selecting the L/D for each pulse.
Premixing Air and LCV Gas in a Gas Turbine Compressor
Authors: van der Wel M. C. , Kramer M. , van Buijtenen J. P.
Published: February 2009

When a gas turbine is operated on low calorific value (LCV) gas instead of natural gas, the operating point of the compressor will shift towards the surge line. The compressor pressure ratio can rise to a level where stall or surge can occur. Premixing LCV gas with air inside the compressor of a gas turbine can solve this problem. With all fuel premixed, no fuel needs to be injected through the normal fuel inlet. The mass flow balance between turbine and compressor is restored and matching problems will not occur. From calculations with two LCV gases it could be concluded that all LCV gas could be premixed with compressor air when a low percentage of hydrogen gas was present in the LCV gas. The LCV gas could not be fully premixed in case of a high amount of hydrogen. The calculations show that an OPRA OD 500 gas turbine operated on premixed LCV gas with a low amount of hydrogen can maintain its original efficiency and a loss of 14 efficiency points can be prevented.
Application of an Advanced Performance Monitoring System to Detect an Implanted Fault on a Twin Spool Aero Derived Gas Turbine
Authors: Razak A. M. Y. , Dosanjh M. S.
Published: February 2009

The profitability of industries that use gas turbines is very much dependent on the satisfactory performance of their engines. Deterioration in performance of engines, results in loss of power and thermal efficiency which together contributes to higher fuel costs, lower revenue and reduced profitability. The purpose of a performance monitoring system is to identify any faults developing at engine component level and the extent of the deterioration. (e.g. the extent to which compressor fouling has occurred). The ability of such a system to predict the impact on power available is also important. This paper discusses the application of a performance monitoring system in detecting an implanted fault in an actual gas turbine.
A Review of Gas Turbine Flow Path Analysis: From Paper Calculation to Artificial Neural Networks
Authors: Genrup Magnus , Assadi Mohsen , Torisson Tord
Published: February 2009

Today many methods are available for gas turbine flow path analysis. Some of them are very simple but yet very useful, since they give an indication of the compressor capacity with almost no calculation effort. The state of the art today is the heat and mass balance models (HMB), which are more sophisticated. This paper presents a general overview of these methods, including the most recent trend, Artificial Neural Networks (ANN). In the future, the ANN-based flow path analysis system will probably, to some extent, replace the HMB-based systems, or become a complementary tool for monitoring and performance analysis of power production units. This paper will give a comprehensive explanation of how to build a flow path analysis system in an equation-solving package (e.g. spreadsheet program), by using relationships presented here. This may give a system that is well within the capabilities of most commercially available systems, used and developed by consultant companies (third party companies).
A High-Fidelity Real-Time Simulation Code of Gas Turbine Dynamics for Control Applications
Authors: Camporeale S. M. , Fortunato B. , Mastrovito M.
Published: February 2009

A novel high-fidelity real-time simulation code based on a lumped, non-linear representation of gas turbine components is presented. The aim of the work is to develop a general-purpose simulation code useful for setting up and testing control equipments. The mathematical model and the numerical procedure are specially developed in order to efficiently solve the set of algebraic and ordinary differential equations that describe the dynamic behavior of the gas turbine engine. The paper presents the model and the adopted solver procedure. The code, developed in Matlab-Simulink using an object-oriented approach, is flexible and can be easily adapted to any kind of plant configuration. For high-fidelity purposes, the mathematical model takes into account the actual composition of the working gases and the variation of the specific heats with the temperature, including a stage-by-stage model of the air-cooled expansion. Simulation tests of the transients after load rejection have been carried out for a single-shaft heavy-duty gas turbine and a double-shaft industrial engine. Time plots of the main variables that describe the gas turbine dynamic behavior are shown and the results regarding the computational time per time step are discussed.
Staged Combustion Control System Development for Aviation Gas Turbine Engines
Authors: Breikin T. V. , Hargrave S. M. , Thompson H. A. , Fleming P. J. , Riley S. J.
Published: February 2009

This paper is focused on the control-related problems of a staged combustion system for a large civil high-bypass ratio engine. Methods to obtain optimal fuel distribution and an analysis of the fuel distribution control system are presented in the paper. Additionally, an overview of a closed-loop control scheme based on AFR estimation is described.
An Air-Cooled Jacket Designed to Protect Unsteady Pressure Transducers at Elevated Temperatures in Gas Turbine Engines
Authors: Ivey Paul C. , Ferguson Derek G.
Published: February 2009

Current unsteady pressure sensors have a limiting upper temperature range and with few exceptions cannot survive at the temperatures experienced in gas turbine aero-engines. This paper describes a design and development study of an air-cooled commercially available unsteady pressure transducer capable of operation at temperatures exceeding 900 °C. The research objective for this work is the following: To design a cooling adapter, using air as the cooling media, capable of protecting a standard unsteady pressure transducer, whose maximum operating temperature is around 250 °C. in a gas turbine engine environment where temperatures typically reach 800–l500 °C. In addition the provision of thermal protection must not adversely effect the measurement of unsteady pressure and the cooling adapter and transducer assembly must be small enough to access critical parts of the engine. Current transducer can operate at temperatures exceeding 250 °C; the purpose of this paper is to demonstrate the additional protection offered by air-cooling. The paper describes the validation experiments conducted for this design, the level of thermal protection achieved and the frequency response of the transducer/cooling jacket assembly.
Gas Turbine Corrected Parameters Control: Humidity Correction – Sensors Evaluation and Selection
Authors: Arar Malath I.
Published: February 2009

Gas Turbine, GT, control methodology applied to power generation is being evaluated. Corrected parameter control methodology has been adopted for this purpose. This method uses the corrected physical ambient conditions such as pressure, temperature and humidity in controlling the GT operations. Humidity correction becomes increasingly important in this control scheme. The following are the reasons for accurate and robust humidity measurement: (1) Humidity measurement is important to the operation control of the dry low NOX, DLN, combustor system. (2) GT inlet performance enhancing devices, such as evaporative coolers and inlet foggers, depend upon the accurate humidity measurement to determine the amount of water needed for inlet temperature depression. (3) Humidity measurement is used to determine the amount of water to be injected in the combustor for NOX abatement when running on liquid fuel as an alternative to natural gas fuel. In order to obtain accurate and reliable humidity readings, several commercially available humidity sensors were extensively tested and evaluated in a controlled laboratory environment. The sensors were tested for their measurement accuracy, saturation conditions, power interruption and surge, sudden temperature changes and medium air speed. Test ambient temperature ranges from −30 °C to 50 °C. This covers the operating ambient conditions range for the Gas Turbine. The test criterion is that the error in the response of the sensor shall not exceed ±1 °C from the test reference for all the tests conducted on the sensors. The combustion requirements for Dry Low NOX operations and mode transfer dictate this criterion. Also, as a DLN requirement, error in specific humidity shall not exceed 0.904 g/g of air. This test criterion also satisfies the water injection requirements for NOX abatement and inlet performance enhancing devices. The results show that for ±1 °C error in the sensor measurement, the resulting error in NOX calculation is less than 0.2 ppm. The test results show that all sensors except the current one in use have met the test criterion. The current sensor, General Eastern DT-2, has a large measurement error in the order of ±5 °C. Programs have been launched to field test and evaluate these sensors in order to replace the current one.
Fuel-Cooled Thermal Management for Advanced Aero Engines
Authors: Huang He , Spadaccini Louis J. , Sobel David R.
Published: February 2009

Fuel-cooled thermal management, including endothermic cracking and reforming of hydrocarbon fuels, is an enabling technology for advanced aero engines and offers potential for cycle improvements and pollutant emissions control in gas-turbine engine applications. The successful implementation of this technology is, however, predicated on the use of conventional multi-component hydrocarbon fuels and an understanding of the combustion characteristics of the reformed fuel mixture. The objective of this research is to develop and demonstrate the technologies necessary for utilizing conventional multi-component hydrocarbon fuels for fuel-cooled thermal management, including the development of the endothermic potential of JP-7 and JP-8+100, a demonstration of the combustion of supercritical/endothermic fuel mixtures, and conceptual design of a fuel-air heat exchanger. The ability to achieve high heat sinks with existing jet fuels (e.g., JP-7 and JP-8+100) was demonstrated with a bench-scale test rig operating under flow conditions and passage geometries simulative of practical heat exchangers for aircraft and missile applications. Key measurements included fuel heat sink, reaction products, and extent of conversion. Full-scale sector rig tests were conducted to characterize the combustion and emissions of supercritical jet fuel, and demonstrate the safety and operability of the fuel system, including a fuel-air heat exchanger.
On-Line Fuel Deoxygenation for Coke Suppression
Authors: Spadaccini Louis J. , Huang He
Published: February 2009

Fuel deoxygenation is being developed as a means for suppressing autoxidative coke formation in aircraft fuel systems, thereby increasing the exploitable cooling capacity of the fuel, enabling major increases in engine operating temperature and cycle efficiency. Reduced maintenance is an added benefit. A prototype membrane filter module for on-line removal of dissolved oxygen, which would otherwise react to form coke precursors, was constructed and successfully demonstrated. The fuel flows over the membrane, while oxygen diffuses through it at a rate that is proportional to the difference in oxygen partial pressures across the surface. Tests were conducted over a range of fuel flow rates (residence times) and temperatures. The filter was operated with air-saturated jet fuel for several hours at a steady-state condition, verifying the capability to remove essentially all of the dissolved oxygen (to <1 ppm) and proving the viability of the concept. A convincing demonstration of coke suppression was performed when air-saturated (normal) and deoxygenated jet fuels were tested in a standard ASTM heated tube apparatus at wall temperatures as high as 850 F. With deoxygenated fuel, there was a dramatic reduction (more than an order of magnitude) in coke deposition relative to air-saturated Jet A, which will allow the maximum fuel temperature to be increased by more than 200 F, doubling the available heat sink. Moreover, deoxygenated Jet A was shown to perform as well as JP-7, the Air Force’s highest thermal stability fuel. An analytical model for oxygen permeation through the membrane was formulated, and used in conjunction with the test data to estimate the filter size required for a practical (i.e., low-volume/high-flowrate) deoxygenator.
Non-Intrusive Measurements of a LPP Combustor Under Elevated Pressure Conditions
Authors: Fink R. , Hupfer A. , Rist D.
Published: February 2009

To meet increasingly tight regulations on emission control appropriate combustor designs need to be developed. With different combustion concepts like RQL (Rich Quench Lean) and LPP (Lean Premixed Prevaporized) it has been proven that it is possible to reach the objective of a significant reduction of the NOX emissions. To gain further insight into the real combustion process it is of importance to be able to “look into” the flame without interfering with the actual combustion process. At the combustion laboratory of the Institute of Flight Propulsion at Munich University of Technology a combustion test facility is set up to study combustion characteristics under pressure up to 6 bar and inlet airflow temperature up to 650 K. A newly designed LPP concept was adapted into an optically accessible model combustion chamber. The objective of the study was to operate the LPP combustor under semi-realistic conditions and to obtain more knowledge on the influence of pressure on the combustion process. With suitable non-intrusive laser-spectroscopic measuring techniques like LIF (Laser Induced Fluorescence) the fuel spray, the nitric oxides and the hydroxyl radical were detected in several planes parallel to the combustor axis at different combustor pressures. As expected the pressure has a strong effect on droplet distribution and evaporation. Also with increasing pressure it was possible to operate the combustor under leaner conditions. A strong dependence on pressure of the formation of nitric oxides was detected. To quantify these results samples with a water-cooled probe were taken, analyzed and compared with the non intrusive measurements.
The Development of the Ramgen Engine Combustion System
Authors: Chenevert Blake C. , Kendrick Donald W. , Trueblood Ben , Tonouchi Jon , Lawlor Shawn P. , Steele Robert C.
Published: February 2009

The research and development of a unique combustion engine is presented. The engine converts the thrust from ramjet modules located on the rim of a disk into shaft torque, which in turn can be used for electrical power generation or mechanical drive applications. A test program was undertaken that included evaluation of the pre-prototype engine and incorporation of improvements to the thrust modules and supporting systems. Fuel mixing studies with vortex generators and bluff body flame holders demonstrated the importance of increasing the shear-layer area and spreading angle to augment flame volume. Evaluation of flame-holding configurations (with variable fuel injection methods) concluded that the heat release zone, and therefore combustion efficiency, could be manipulated by judicious selection of bluff body geometry, and is less influenced by fuel injection distribution. Finally, successful operation of novel fuel and cooling air delivery systems have resolved issues of gas (fuel and air) delivery to the individual rotor segments. The lessons learned from the pre-prototype engine are currently being applied to the development of a 2.8MW engine.
Experimental and Numerical Spray Characterization of a Gas Turbine Fuel Atomizer in Cross Flow
Authors: Tap F. A. , Dean A. J. , Van Buijtenen J. P.
Published: February 2009

An experimental and numerical characterization of a macrolaminate pressure atomizer, placed perpendicularly to a high-velocity, turbulent air stream, is presented in this work. The purpose of the study was to compare detailed spray measurements with computations using a commercial CFD code. This study was part of the development of the premixing section of a midsize gas turbine, redesigned to meet low emissions and dual fuel market requirements. First, the spray characteristics were determined by injecting into a quiescent environment at ambient conditions. This data provided input for CFD calculations. Then the fuel injector was placed in a test section, at ambient conditions as well, that simulated the cross flow position of the atomizer in the prototype combustor. Droplet size and velocity were measured downstream of the injector nozzle, using a one-dimensional Phase Doppler Particle Analyzer. Measurements were done in two measuring planes. Flow field measurements were made to establish a common base for the computations. 2D computations were made of these experiments, using a k-ε turbulence model. The droplet trajectories were calculated with a Lagrangian ‘random walk’ technique, including drop break-up. The computed droplet size and velocity show agreement with the measurements. Drop break-up was also well represented by the model. The computed dispersion of the injected mass is not in agreement with the measured profile. This discrepancy in droplet dispersion is possibly due to high turbulence levels in the flow field, which were not well captured in the model.
A Combustion Study of Gas Turbines Using Multi-Species/Reacting Computational Fluid Dynamic
Authors: Armand Sasan , Chen Mei
Published: February 2009

A multi-species/reacting combustion study was performed. The focus of the study was to quantify the effects of variation in air extraction and power rates on flame/outlet temperatures of a General Electric (GE), Frame 5 gas turbine. The environmental contamination level due to generation of carbon monoxide was also reported. GE, Frame 5 gas turbine has been widely used around the world for power generation, and as mechanical drives. The combustion products were examined throughout a range of air extraction rates, upon which it was determined that the combustion liners were susceptible to damage at air extraction rates above 10%, and the environmental contamination level due to carbon monoxide was increased. Furthermore, the gas flow exiting the combustion liner became non-homogeneous (i.e. a pocket of relatively hot gas formed in the middle of the flow path), which would cause damage to the downstream components. In conclusion, the short-term monetary gains from using compressed air from a gas turbine do not justify the costs of down time for repairs and the replacement of expensive hot-gas-path components.
Assessment of the Potential of Combined Micro Gas Turbine and High Temperature Fuel Cell Systems
Authors: Bohn Dieter , Po¨ppe Nathalie , Lepers Joachim
Published: February 2009

The present paper reports a detailed technological assessment of two concepts of integrated micro gas turbine and high temperature (SOFC) fuel cell systems. The first concept is the coupling of micro gas turbines and fuel cells with heat exchangers, maximising availability of each component by the option for easy stand-alone operation. The second concept considers a direct coupling of both components and a pressurised operation of the fuel cell, yielding additional efficiency augmentation. Based on state-of-the-art technology of micro gas turbines and solid oxide fuel cells, the paper analyses effects of advanced cycle parameters based on future material improvements on the performance of 300–400 kW combined micro gas turbine and fuel cell power plants. Results show a major potential for future increase of net efficiencies of such power plants utilising advanced materials yet to be developed. For small sized plants under consideration, potential net efficiencies around 70% were determined. This implies possible power-to-heat-ratios around 9.1 being a basis for efficient utilisation of this technology in decentralised CHP applications.
Molten Carbonate Fuel Cell Gas Turbine Combined Cycle for Marine Propulsion: Part A — Design Point Operation
Authors: Basurto Maria-Teresa , Pilidis Pericles , Hales Richard
Published: February 2009

Molten Carbonate Fuel Cell/Gas Turbine (MCFC/GT) hybrid power systems could represent a modern, efficient and clean alternative to the currently used marine propulsion systems. The objective of this paper is to present the results of the study of a MCFC/GT hybrid power systems used on marine propulsion. The results are quite promising, but they are subjected to the current uncertainties derived from MCFCs early stage of development. Therefore, the interest of the authors is to summarise the research work done and the results, providing the understanding and a general view of the main concerns, benefits, identifying the next steps on the development of these systems. The study is summarised into two papers: “Molten Carbonate Fuel Cell Gas Turbine Combined Cycle for Marine Propulsion. Part A: Design Point Operation”, that describes the selection of the design point, and “Molten Carbonate Fuel Cell Gas Turbine Combined Cycle for Marine Propulsion. Part B: Part Load Operation” (Basurto et al., 2002), that describes the off-design performance of the system, and it compares the system against conventional diesel and gas turbine systems. The study is based on previous work published by the authors on the integration of MCFCs and gas turbines (Basurto et al., 2001).
Off-Design Performance Analysis of a Hybrid System Based on an Existing MCFC Stack
Authors: Bedont Pietro , Grillo Olivia , Massardo Aristide F.
Published: February 2009

This paper addresses the off-design analysis of a hybrid system (HS) based on the coupling of an existing Ansaldo Fuel Cells (formerly Ansaldo Ricerche) molten carbonate fuel cell (MCFC) stack (100 kW) and a micro gas turbine. The MCFC stack model at fixed design conditions has previously been presented by the Authors [1]. The present work refers to an off-design stack model, taking into account the influence of the reactor layout, current density, air and fuel utilisation factor, CO2 recycle loop, cell operating temperature, etc. Finally, the design and off-design model of the whole hybrid system is presented. Efficiency at part load condition is presented and discussed, taking into account all the constraints for the stack and the micro gas turbine, with particular emphasis on CO2 recycle control.
The R-ATR and the R-REF Gas Turbine Power Cycles With CO2 Removal: Part 1 — The R-ATR Cycle
Authors: Fiaschi Daniele , Lombardi Lidia , Tapinassi Libero
Published: February 2009

The relatively innovative gas turbine based power cycles R–ATR and R–REF (Recuperative – Auto Thermal Reforming GT cycle and Recuperative–Reforming GT cycle) here proposed are mainly aimed to allow the upstream CO2 removal by the way of natural gas fuel reforming. The power unit is a Gas Turbine (GT), fuelled with reformed and CO2 cleaned syngas produced by adding some basic sections to the simple GT cycle: • Auto Thermal Reforming (ATR) for the R-ATR solution, where the natural gas is reformed into CO, H2, CO2, H2O and CH4; this endothermic process is completely sustained by the heat released from the reactions between the primary fuel (CH4), exhausts and steam. • Water Gas Shift Reactor (WGSR), where the reformed fuel is, as far as possible, shifted into CO2 and H2 by the addition of water. • Water Condensation, in order to remove a great part of the fuel gas humidity content (this water is totally reintegrated into the WGSR). • CO2 removal unit for the CO2 capture from the reformed fuel. Among these main components, several heat recovery units are inserted, together with GT Cycle recuperator, compressor intercooler and steam injection in combustion chamber. The CO2 removal potential is close to 90% with chemical scrubbing using an accurate choice of amine solution blend: the heat demand is completely provided by the power cycle itself. The possibility of applying steam blade cooling by partially using the water released from the dehumidifier downstream the WGSR has been investigated: in these conditions, the R-ATR has shown an efficiency range of 44–46%. High specific work levels have also been observed (around 450–550 kJ/kg). These efficiency values are satisfactory, especially if compared with ATR combined cycles with CO2 removal, more complex due to the steam power section. If regarded as an improvement to the simple GT cycle, R-ATR shows an interesting potential if directly applied to a current GT model; however partial redesign with respect to the commercially available version is required. Finally, the effects of the reformed fuel gas composition and conditions on the amine CO2 absorption system have been investigated, showing the beneficial effects of increasing pressure (i.e. pressure ratio) on the thermal load per kg of removed CO2.
Exergy Analysis of Part Flow Evaporative Gas Turbine Cycles: Part 1 — Introduction and Method
Authors: Jonsson Maria , Yan Jinyue
Published: February 2009

The evaporative gas turbine (EvGT) cycle is an advanced cycle with a high electrical efficiency and specific power output. The heat in the exhaust gas is used to evaporate water directly into the compressed combustion air. This increases the volumetric flow rate through the expander without increasing the compressor work. In part flow evaporative cycles, only a fraction of the compressed air passes through the humidification system; the rest of the air bypasses the humidifier. In this study, exergy analyses of different part flow cases for two evaporative cycles have been performed, in order to evaluate part flow humidification. The evaporative cycles are based on the industrial gas turbine GTX100 and the aeroderivative Trent. This paper is divided into two parts. The first part contains an introduction to the EvGT cycle and the methods used in the study. The second part contains the results, discussion, and conclusions.
Inherent CO2 Capture Using Chemical Looping Combustion in a Natural Gas Fired Power Cycle
Authors: Brandvoll O̸yvind , Bolland Olav
Published: February 2009

In this paper an alternative to the so-called “oxy-fuel” combustion for CO2 capture is evaluated. “Chemical looping combustion” (CLC), is closely related to oxy-fuel combustion as the chemically bound oxygen reacts in a stoichiometric ratio with the fuel. In the CLC process the overall combustion reaction takes place in two reaction steps in two separate reactors. In the reduction reactor, the fuel is oxidised by the oxygen carrier, i.e. the metal oxide MeO. The metal oxide is reduced to a metal oxide with a lower oxidation number, Me, in the reaction with the fuel. In this manner, pure oxygen is supplied to the reaction with the fuel without using a traditional air separation plant, like cryogenic distillation of air. The paper presents a thermodynamic cycle analysis, where CLC is applied in a Humid Air Turbine concept. Main parameters are identified, and these are varied to examine the influence on cycle efficiency. Results on cycle efficiency are presented and compared to other CO2 capture options. Further, an evaluation of the oxygen carrier, metals/oxides, is presented. An exergy analysis is carried out in order to understand where losses occur, and to explain the difference between CLC and conventional combustion. The oxidation reactor air inlet temperature and the oxidation reactor exhaust temperature have a significant impact on the overall efficiency. This can be attributed to the controlling effect of these parameters on the required airflow rate. An optimum efficiency of 55.9% has been found for a given set of input parameters. Crucial issues of oxygen carrier durability, chemical performance and mechanical properties have been idealized, and further research on the feasibility of CLC is needed. Whether or not the assumption 100% gas conversion holds, is a crucial issue and remains to be determined experimentally. Successful long-term operation of chemical looping systems of this particular type has not yet been demonstrated. The simulation points out a very promising potential of CLC as a power/heat generating method with inherent capture of CO2. Exergy analysis show reduced irreversibilities for CLC compared to conventional combustion. Simulations of this type will prove useful in designing CLC systems in the future when promising oxygen carriers have been investigated in more detail.
A New Scaling Method for Component Maps of Gas Turbine Using System Identification
Authors: Kong Changduk , Ki Jayoung , Kang Myoungcheol
Published: February 2009

A scaling method for characteristics of gas turbine components using experimental data or partially given data from engine manufacturers was newly proposed. In case of currently used traditional scaling methods, the predicted performance around the on-design point may be well agreed with the real engine performance, but the simulated performance at off-design points far away from the on-design point may not be well agreed with the real engine performance generally. It would be caused that component scaling factors, which were obtained at on-design point, is also used at all other operating points and component maps are derived from different known engine components. Therefore to minimize the analyzed performance error in the this study, firstly component maps are constructed by identifying performances given by engine manufacturers at some operating conditions, then the simulated performance using the identified maps is compared with performances using currently used scaling methods. In comparison, the analyzed performance using the currently used traditional scaling method was well agreed with the real engine performance at the on-design point but had maximum 12% error at off design points within the flight envelope of a calculation example turboprop engine. However the performance result using the newly proposed scaling method had maximum 6% reasonable error even at all flight envelope.
The Effect of Freestream Turbulence on Film Cooling Heat Transfer Coefficient
Authors: Mayhew James E. , Baughn James W. , Byerley Aaron R.
Published: February 2009

The film-cooling performance of a flat plate in the presence of low and high freestream turbulence is investigated using thermochromic liquid crystal thermography. Full-surface distributions of the convective heat transfer coefficient are determined for three blowing rates on a model with three straight holes spaced three diameters apart. An increase in heat transfer coefficient due to mass injection is clearly observed in the images and is quantitatively determined for both the low and high freestream turbulence cases. The increase in heat transfer coefficient is greater than in previously published research, possibly due to the use of different, more representative thermal boundary conditions upstream of the injection location. These boundary conditions, along with high resolution images, may account for the appearance of “fork tine” patterns of high heat transfer due to the presence of these vortices, not previously seen. Although the driving potential for heat transfer is less, it is observed that in some instances film cooling may cause an increase in overall heat transfer due to the increase in heat transfer coefficient.
LES Simulation and Experimental Measurement of Fully Developed Ribbed Channel Flow and Heat Transfer
Authors: Watanabe Kazunori , Takahashi Toshihiko
Published: February 2009

Ribbed channel flow is adopted for internal cooling of a 1300 °C class gas turbine first stage rotor blade. Heat transfer characteristics of transverse ribbed channel flow were examined using LES (Large Eddy Simulations) and by experiments. The flow was examined over the range of Reynolds number around 105 that are closer to the actual engine conditions. Computational results agreed reasonably well with experimental results. Heat transfer enhancement mechanism in a ribbed channel flow was shown to be caused by advecting eddy structure and interference of a rib.
Experimental and Numerical Investigation of a Steam-Cooled Vane
Authors: Bohn Dieter , Wolff Andreas , Wolff Michael , Kusterer Karsten
Published: February 2009

Closed circuit steam cooling of blades and vanes in modern gas turbines is a promising alternative to film-cooling using compressor air. This technology is becoming part of commercial gas turbines in combination with a steam turbine cycle. There is still a great demand for further development of steam-cooled vanes and blades. Thus, detailed experimental and numerical investigations of the thermal load of a steam-cooled test vane are the main topic of the paper presented. An experimental test rig has been set up, which consists of a rectangular duct containing a three-vane cascade. The central vane can be convectively cooled by supplying steam or compressor air to 22 straight radial cooling passages. The surface temperatures of the cooled vane are measured by application of temperature sensors and a thermographic visualization technique. For the present configuration sufficient cooling can be achieved for the main body of the vane, but, high thermal load has been detected in the thin trailing edge region. A parametric study of steam supply conditions has been performed. The measurements are used to create a data base for steam-cooled vanes, which can serve for the validation of numerical codes. The experimental investigations are accompanied by 3-D numerical investigations using the conjugate calculation technique. That means, the external hot gas flow and the steam flow in the cooling tubes are calculated directly coupled to the vane solid body, which is also part of the calculation. Thus, numerical prediction of the temperature field in the vane solid body is possible. The numerical results are in accordance with the experimental data although the external walls of the duct have been prescribed as adiabatic walls. The results show also a very high thermal load at the trailing edge.
Unsteady and Calming Effects Investigation on a Very High Lift LP Turbine Blade: Part II — Numerical Analysis
Authors: Roux Jean-Michel , Lefebvre Michae¨l , Liamis Nicolas
Published: February 2009

In the first part of the present article (Coton et al. [1]), experimental data on a very high lift blade subject to bars generated incoming wakes are presented in terms of losses at mid span, secondary losses and unsteady heat transfer coefficient. In the present part, time-accurate 3D Reynolds averaged Navier-Stokes (RANS) computations have been performed including the simulation of the transition process for attached and detached boundary layers. First, the capability of the method to take into account the Reynolds number effect is presented in the case of steady inlet condition, and comparisons are shown for all the available experimental data. Particular attention has been taken to the influence of the numerical spatial scheme. 3D unsteady computations have been performed for two different rotational speeds. The wake effects are presented in terms of turbulence intensity and static pressure fluctuation, which are both important to describe the unsteady transitional phenomenae.
Measurements of the Effects of Freestream Turbulence on Separation-Bubble Transition
Authors: Yaras M. I.
Published: February 2009

In this paper, measurements are presented on the effects of freestream turbulence on laminar-to-turbulent transition in separation bubbles, and correlations are proposed for the locations of transition and reattachment on the basis of this data. The boundary layer development is measured on a smooth, flat plate upon which streamwise pressure gradients are imposed by a flexible, contoured wall opposite to the test plate. Two variations in the streamwise pressure distribution are investigated, and two Reynolds numbers are considered for each pressure-gradient setting. For each combination of pressure distribution and Reynolds number, the freestream turbulence intensity and length scale are adjusted systematically by varying the open-area-ratio and cell size of the grid installed at the test-section inlet. Measured quantities consist of velocity obtained with a single-hot wire probe and surface pressures measured through pressure taps.
An Investigation of the Scales in Transitional Boundary Layers Under High Free-Stream Turbulence Conditions
Authors: Volino Ralph J.
Published: February 2009

The scales in a transitional boundary layer subject to high (initially 8%) free-stream turbulence and strong acceleration (K as high as 9×10−6) have been investigated using wavelet spectral analysis and conditional sampling of experimental data. The boundary layer shows considerable evolution through transition, with a general shift from the lower frequencies induced by the free-stream unsteadiness to higher frequencies associated with near wall generated turbulence. Within the non-turbulent zone of the intermittent flow, there is considerable self-similarity in the spectra from the beginning of transition to the end, with the dominant frequencies in the boundary layer remaining constant at about the dominant frequency of the free-stream. The frequencies of the energy containing scales in the turbulent zone change with streamwise location and are significantly higher than in the non-turbulent zone. When normalized on the local viscous length scale and velocity, however, the turbulent zone spectra also show good self-similarity throughout transition. Turbulence dissipation occurs almost exclusively in the turbulent zone. The velocity fluctuations associated with dissipation are isotropic, and their normalized spectra at upstream and downstream stations are nearly identical. The distinct differences between the turbulent and non-turbulent zones suggest the potential utility of intermittency based transition models in which these zones are treated separately. The self-similarity noted in both energy containing and dissipation scales in both zones suggests possibilities for simplifying the modeling for each zone.
Separated Flow Transition Under Simulated Low-Pressure Turbine Airfoil Conditions: Part 1 — Mean Flow and Turbulence Statistics
Authors: Volino Ralph J.
Published: February 2009

Boundary layer separation, transition and reattachment have been studied experimentally under low-pressure turbine airfoil conditions. Cases with Reynolds numbers (Re) ranging from 25,000 to 300,000 (based on suction surface length and exit velocity) have been considered at low (0.5%) and high (9% inlet) free-stream turbulence levels. Mean and fluctuating velocity and intermittency profiles are presented for streamwise locations all along the airfoil, and turbulent shear stress profiles are provided for the downstream region where separation and transition occur. Higher Re or free-stream turbulence level moves transition upstream. Transition is initiated in the shear layer over the separation bubble and leads to rapid boundary layer reattachment. At the lowest Re, transition did not occur before the trailing edge, and the boundary layer did not reattach. Turbulent shear stress levels can remain low in spite of high free-stream turbulence and high fluctuating streamwise velocity in the shear layer. The beginning of a significant rise in the turbulent shear stress signals the beginning of transition. A slight rise in the turbulent shear stress near the trailing edge was noted even in those cases which did not undergo transition or reattachment. The present results provide detailed documentation of the boundary layer and extend the existing database to lower Re. The present results also serve as a baseline for an investigation of turbulence spectra in Part 2 of the present paper, and for ongoing work involving transition and separation control.
Computation of Flow Between Two Discs Rotating at Different Speeds
Authors: Kilic Muhsin , Owen J. Michael
Published: February 2009

Discs rotating at different speeds are found in the internal cooling-air systems of most gas turbines. Defining Γ as the ratio of the rotational speed of the slower disc to that of the faster one then Γ = −1, 0 and +1 represents the three important cases of contra-rotating discs, rotor-stator systems and co-rotating discs, respectively. A finite-volume, axisymmetric, elliptic, multigrid solver, employing a low-Reynolds-number k-ε turbulence model, is used for the fluid-dynamics computations in these systems. The complete Γ region, −1 ≤ Γ ≤ +1, is considered for rotational Reynolds numbers of up to Reφ = 1.25 × 106, and the effect of a radial outflow of cooling air is also included for nondimensional flow rates of up to Cw = 9720. As Γ → −1, Stewartson-flow occurs with radial outflow in boundary layers on both discs and between which is a core of nonrotating fluid. For Γ ≈ 0, Batchelor-flow occurs, with radial outflow in the boundary layer on the faster disc, inflow on the slower one, and between which is a core of rotating fluid. As Γ → +1, Ekman-layer flow dominates with nonentraining boundary layers on both discs and a rotating core between. Where available, measured velocity distributions are in good agreement with the computed values.
Influence of Rub-Grooves on Labyrinth Seal Leakage
Authors: Denecke J. , Schramm V. , Kim S. , Wittig S.
Published: February 2009

An experimental investigation on the influence of stator rub-grooves on labyrinth seal leakage is presented in the present paper. In current labyrinth seal designs, abradable lands allow the rotor labyrinth teeth to rub grooves into the stator. These rub-grooves have a large influence on the seal leakage characteristic and impair the overall engine efficiency. To improve the understanding of rub-groove effects, discharge coefficients were determined using a plain non-rotating labyrinth seal model of scale 4:1 considering a wide variation of rub-groove geometries at different seal clearances. Three labyrinth seal types were covered in this investigation that are generally used in gas turbines, namely (1) straight-through labyrinth seals, (2) stepped labyrinth seals with forward facing steps and (3) stepped labyrinth seals with backward facing steps. To attain a deeper insight into the flow mechanisms, water-channel visualizations were performed. The large data set generated in this study, provides the basis to analyze and quantify the influence of rub-grooves on the seal leakage for the three labyrinth seal types listed above. Current results were in agreement with previous studies on worn labyrinth seals for several seal geometries.
Application of Methodologies to Evaluate the Health State of Gas Turbines in a Cogenerative Combined Cycle Power Plant
Authors: Pinelli M. , Venturini M.
Published: February 2009

In the paper, a comprehensive methodology for gas turbine health state determination is applied to a single-shaft Fiat Avio TG 20 gas turbine working in the cogenerative combined cycle power plant of Fiat – Mirafiori (Italy). In order to determine operating state variations from new and clean condition, the following procedures were applied to historical field measurements: • normalization procedure to determine the variations between measured and expected values; • inverse cycle technique to calculate the values of the characteristic parameters that are indices of the machine health state. The application of these techniques to long period operating data allowed measurement validation and the determination of the machine health state. The results showed the good capability of the developed techniques for the determination and the analysis of performance drop due to compressor fouling and to turbine malfunction.
Development of a 20MW-Class High-Efficiency Gas Turbine L20A
Authors: Sugimoto Takao , Nagai Katsushi , Ryu Masanori , Tanaka Ryozo , Kimura Takeshi , Nagatomo Takashi
Published: February 2009

The L20A gas turbine is a newly developed 20 MW class single-shaft machine. With its high simple-cycle efficiency and high exhaust gas temperature, it is particularly suited for use in distributed power generation, cogeneration and combined cycle applications. A design philosophy has been adopted for the turbine which includes a high efficiency transonic axial-flow compressor with eight can-type combustors and a high inlet temperature of 1250°C. This results in a thermal efficiency of 35% and an overall thermal efficiency of 80% for cogeneration system. In addition, the NOx emissions from the combustor is low and the L20A has a long service life. These features permit long-term continuous operation under various environmental limitations. Due to the engine’s high efficiency and its low component totals, the lowest life cycle cost is achieved. Development testing has verified that the performance, the mechanical characteristics and the emission have satisfied the initial design goals. The engine has been in operation from November 2001 as the first operating unit in a co-generation system at Kawasaki Akashi Works.