bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Modeling of a Nuclear Gas Turbine Plant: Application to Surge Prediction
Authors: Tauveron Nicolas , Leboeuf Francis , Ferrand Pascal
Published: September 2008

This work concerns the dynamic modeling of closed cycle gas turbine with a nuclear heat source. The paper focuses on a particular safety question: the consequences of a hypothetical large break accident. A model of the whole circuit of the Gas Fast Reactor (GFR) has been built using a specific turbo-machine description. The compressor modeling presented in a separate paper [1] is completed with turbine modeling. Transient simulation results point out the importance of the location of the pipe rupture: in some detailed cases, back flow through the core can occur during the first seconds. The other safety question concerns the capacity of the power conversion unit to extract the decay heat from the nuclear core after the break event.
A Simple Mathematical Approach to Data Reconciliation in a Single-Shaft Combined-Cycle System
Authors: Gulen S. Can , Smith Raub W.
Published: September 2008

The ultimate proof of the soundness and viability of a novel technology is a full-scale demonstration test in which actual components are run successfully over the entire operating envelope. Consequently, collection of accurate and meaningful test data is of utmost importance to the success of the test. Analysis of such data will validate the original design concepts and lead to paths of further improvement for the next generations thereof. Statistical fundamentals to determine accuracy and precision of measured data are amply documented and readily available in well-established standards. The yardstick that should be used for the “meaningfulness” of measured test data is the satisfaction of the fundamental laws of conservation. While it is known that the “true” values of the sensor data when inserted into the governing equations for the tested component will result in perfect balances, “actual” measured values will always result in “imbalances”. Therefore, reconciliation of the individual measurements with the governing conservation equations is a must prior to actual analysis of the data. Reconciliation in this context is estimation of the “true” values of the sensor data from “actual” sensor data by using statistical concepts. This paper describes the development of a data reconciliation concept that is universally applicable to any process or power plant system where sensor data is used. The usefulness and power of the technique is demonstrated by its application to a single-shaft combined cycle with both gas turbine and steam turbine driving a common generator. In the absence of a reliable and accurate measuring system to individually determine gas and steam turbine shaft outputs, data reconciliation is vital to the accurate analysis of data.
Heat Transfer in a Radially Rotating Square-Sectioned Duct With Two Opposite Walls Roughened by 45° Staggered Ribs
Authors: Chang Shyy Woei , Liou Tong-Minn , Yeh Wen-Hsien , Hung Jui-Hung
Published: September 2008

This paper describes an experimental study of heat transfer in a radially rotating square duct with two opposite walls roughened by 45° staggered ribs. Air coolant flows radially outward in the test channel with experiments to be undertaken that match the actual engine conditions. Laboratory-scale heat transfer measurements along centerlines of two rib-roughened surfaces are performed with Reynolds number (Re), rotation number (Ro) and density ratio (Δρ/ρ) in the ranges of 7500–15000, 0–1.8 and 0.076–0.294. The experimental rig permits the heat transfer study with the rotation number considerably higher than those studied in other researches to date. The rotational influences on cooling performance of the rib-roughened channel due to Coriolis forces and rotating buoyancy are studied. A selection of experimental data illustrates the individual and interactive impacts of Re, Ro and buoyancy number on local heat transfer. A number of experimental-based observations reveal that the Coriolis force and rotating buoyancy interact to modify heat transfer even if the rib induced secondary flows persist in the rotating channel. Local heat transfer ratios between rotating and static channels along the centerlines of stable and unstable rib-roughened surfaces with Ro varying from 0.1 to 1.8 are in the ranges of 0.6–1.6 and 1–2.2 respectively. Empirical correlations for periodic flow regions are developed to permit the evaluation of interactive and individual effects of rib-flows, convective inertial force, Coriolis force and rotating buoyancy on heat transfer.
Ground Test Data Validation Using a Subscale F/A-22 Engine Inlet Empirical Model
Authors: Bickford Randall L. , Malloy Donald J. , Monaco Jeffrey F. , Kidman David S.
Published: September 2008

The US Air Force’s two main aeropropulsion test centers, Arnold Engineering Development Center and the Air Force Flight Test Center, are developing a common suite of modeling and simulation tools employing advanced predictive modeling technologies. These modeling and simulation tools incorporate real-time data validation, system identification, parameter estimation, model calibration, and automated model updating as new test results or operational data become available. The expected benefit is improved efficiency and accuracy for online diagnostic monitoring of Air Force assets. This paper describes the integrated approach to real-time data validation. Implementation of a software package to enable efficient model handoff between test groups and centers and extension of the capability to aeropropulsion models is discussed. An F/A-22 inlet model is used to demonstrate the approach. Compact polynomial function models of the distortion and recovery flow descriptors and 40-probe pressure values are derived from quasi-steady and instantaneous subscale wind tunnel data. The total-pressure inlet distortion and recovery models are integrated in a real-time equipment health monitoring system designed to support test operations, and preliminary results are given. A companion paper describes the integrated approach to system identification, parameter estimation, and model updating.
An Analysis of Impact Structural Damages of Ceramic Blades
Authors: Yoshida Hiro , Inoue Takahiro , Li Yinsheng
Published: September 2008

A series of finite element analyses with elastic assumption were made to predict the plausible damage behavior of axial and radial type ceramic blades. Present analysis showed that the stress peaking process was strongly influenced by the interaction of various stress waves. Peaks of the maximum principal tensile (PMPT) stress are considered to lead to the structural damages. In the axial blade, locations of the PMPT stress qualitatively corresponded well with the damaged parts of the blade observed in the experiment. The maximum PMPT stress appeared on the suction (impact) surface and the averaged PMPT stress value on this surface was roughly twice as large as that in the pressure surface. On the radial blade, the maximum PMPT stress occurred in the pressure surface, contrary to the axial blade. Its value was remarkably larger than the initial impact stress due to the complex wave interactions. In spite of the elastic assumption, the present finite element analysis is useful in understanding structural fracture behavior.
Exploration of Compact Combustors for Reheat Cycle Aero Engine Applications
Authors: Zelina J. , Shouse D. T. , Stutrud J. S. , Sturgess G. J. , Roquemore W. M.
Published: September 2008

An aero gas turbine engine has been proposed that uses a near-constant-temperature (NCT) cycle and an Inter-Turbine Burner (ITB) to provide large amounts of power extraction from the low-pressure turbine. This level of energy is achieved with a modest temperature rise across the ITB. The additional energy can be used to power a large geared fan for an ultra-high bypass ratio transport aircraft, or to drive an alternator for large amounts of electrical power extraction. Conventional gas turbines engines cannot drive ultra-large diameter fans without causing excessively high turbine temperatures, and cannot meet high power extraction demands without a loss of engine thrust. Reducing the size of the combustion system is key to make use of a NCT gas turbine cycle. Ultra-compact combustor (UCC) concepts are being explored experimentally. These systems use high swirl in a circumferential cavity about the engine centerline to enhance reaction rates via high cavity g-loading on the order of 3000 g’s. Any increase in reaction rate can be exploited to reduce combustor volume. The UCC design integrates compressor and turbine features which will enable a shorter and potentially less complex gas turbine engine. This paper will present experimental data of the Ultra-Compact Combustor (UCC) performance in vitiated flow. Vitiation levels were varied from 12–20% oxygen levels to simulate exhaust from the high pressure turbine (HPT). Experimental results from the ITB at atmospheric pressure indicate that the combustion system operates at 97–99% combustion efficiency over a wide range of operating conditions burning JP-8 +100 fuel. Flame lengths were extremely short, at about 50% of those seen in conventional systems. A wide range of operation is possible with lean blowout fuel-air ratio limits at 25–50% below the value of current systems. These results are significant because the ITB only requires a small (300°F) temperature rise for optimal power extraction, leading to operation of the ITB at near-lean-blowout limits of conventional combustor designs. This data lays the foundation for the design space required for future engine designs.
Integration of Air Separation Unit With H2 Separation Membrane Reactor in Coal-Based Power Plant
Authors: Rao A. D. , Francuz D. , Verma A. , Samuelsen G. S.
Published: September 2008

A novel process configuration consisting of integrating the air separation unit with a H2 separation membrane reactor (HSMR) in a coal gasification based coproduction facility with near zero emissions is described. The plant utilizes an air separation unit operating at elevated pressure to produce an Intermediate Pressure (IP) N2 stream in addition to the O2 required by the coal gasifier. The syngas produced by the gasifier after cleanup is supplied to the membrane reactor which produces H2 by shifting the carbon monoxide while simultaneously separating the H2. The IP N2 is used as sweep gas to assist in the separation of the H2 diffusing across the membrane walls by decreasing the partial pressure of the H2 on the permeate side. The total pressure of gases on the permeate side may thus be increased such that the H2 / N2 mixture may be fed directly to the gas turbines at the required pressure without requiring cooling and compression of the H2. An added advantage is that the total pressure differential across the membrane wall is reduced. The N2 in the fuel gas functions both as a thermal diluent for reducing the formation of nitrogen oxides and as additional motive fluid for expansion in the turbine. The carbon dioxide rich gas (non-permeate) leaving the membrane reactor after catalytic oxidation of the residual combustibles constitutes the carbon capture stream which may be further compressed and pipelined for CO2 sequestration. High purity H2 may be coproduced for export from a portion of the H2-N2 stream leaving the HSMR utilizing a Pressure Swing Adsorption (PSA) unit. The techno-economic advantages of such a coproduction facility are addressed.
Local Internal Impingement Heat Transfer Near a 90 Deg Row of Film Cooling Holes: Part 2 — Effect of Jet Row Position
Authors: Xu Lei , Chang Haiping , Chang Guoqiang
Published: September 2008

Investigation of local heat transfer characteristics near a row of film cooling holes in the inner side of a simulated turbine blade midchord region with impingement has been carried out experimentally. The research about heat transfer characteristics is focused on three diameter of film cooling hole area located upstream and downstream a row of film cooling holes, which angle is at a 90 degrees. The internal impingement air is provided by a single line of equally spaced jets. The film cooling air extracts through a line of holes on the impinging target plate. The projection of the jets on the target plate is always on the center line between two film holes. The spacing of the jet holes is twice that of the film cooling holes. The effect of the streamwise arrangement of the impingement nozzles relative to the position of the film cooling holes and impinging distance on the heat transfer characteristics have been mainly investigated. The experiment is conducted under the flow condition of Reynolds number 10000∼30000, crossflow-to-jet mass flux ratio based on each channel/jet hole section area 0.1 and film outflow-to-crossflow mass flux ratio based on film cooling hole/channel section 12∼20. In the range of experimental parameter, the experimental results indicate that there is optimal ratio of the impinging distance to film hole diameter, on which the heat transfer characteristics is best. Similarly for the area upstream film cooling hole, there is the optimal ratio of distance of the impingement nozzles relative to the position of the film cooling holes to film hole diameter. As impinging holes are away from film cooling holes in the streamwise direction of crossflow, the effect of impingement on local heat transfer near film cooling holes is weakened, but film cooling extraction effect stand out. The place closer to the hole will have stronger heat transfer whether upstream the film cooling holes or downstream the holes. Based on this, the effects of position of the jets relative to the film cooling holes on the heat transfer characteristics have been obtained qualitatively and quantitatively. It can be the important reference for accurately designing gas turbine blade.
Three-Dimensional Flow Analysis and Design Improvement of Leading-Edge Film-Cooling in an Inlet Guide Vane
Authors: An Bai-Tao , Liu Jian-Jun , Jiang Hong-De
Published: September 2008

Numerical investigations on the film cooling of an inlet guide vane are performed with realistic geometry. The vane model comprises one vane passage, 131 shower-head cooling holes in 6 staggered rows around the vane leading edge, and a coolant supply plenum. A fully implicit coupled 3D N-S solver based on finite-volume method and incorporated with unstructured mixed grid, standard k–ε turbulence model and scalable wall function is employed to obtain the numerical solution. Two film cooling configurations, named original design and modified design, are presented. The original design and no cooling case are simulated to obtain flow mechanism and heat transfer characteristics of the leading edge film cooling. In addition, the effects of the meridional endwall contours on the leading edge film cooling are considered. The film cooling characteristics and interactions between jets and mainstream around the leading edge, especially near the stagnation line, are analyzed in detail. To provide better coolant coverage on the leading edge, the cooling configuration is modified by redistributing the position and direction of some rows of holes based upon the analysis and understanding of the 3D prediction for the original design. The modified design is verified under three blowing ratios and compared with the original design.
Flow-Field Investigation of Two Gas-Sampling Probes
Authors: Jiang Leiyong , Manipurath Shaji , Bourque Gilles , Houde Michel
Published: September 2008

The flow fields in and around two versions of a water-cooled gas-sampling probe, situated downstream of a gas turbine combustor, were numerically studied in an elevated pressure and temperature environment. The probes are of triple-walled stainless steel assembly, where the gas sample is transported through a centre tube, while preheated and pressurized cooling water flows through two surrounding annuli. Complex conjugate heat transfers amongst the exhaust mixture, cooling water and probe walls were modelled at a selected operating condition. The numerical results indicate over-heating and possible vaporization of water or cavitation in the upstream tip region of the probe with the original design. This is consistent with the evidence of damage observed in these probes from prolonged testing under similar conditions. For the modified probe, the effectiveness of cooling water is much improved, which is confirmed by long-term combustor rig testing. From this investigation, some recommendations for probe design and operation are provided. Moreover, the present study has proved that the numerical simulation is a valuable tool for probe design and trouble-shooting, and to accurately predict conjugate heat transfers in such flows, the laminar sub-layer in the near-wall region should be adequately resolved.
Development of an In-Situ Laser Absorption NO/NO2 Measuring System for Gas Turbine Exhaust Jets
Authors: Zhu Y. , Yamada H. , Hayashi S.
Published: September 2008

A diode-laser absorption system having the potential of simultaneous determination of NO and NO2 concentrations in the exhaust jets from gas turbines has been being developed. The sensitivities of the detection units at a typical exhaust gas temperature of 800 K were estimated as 30 ppmv-m and 3.7 ppmv-m for NO and NO2, respectively. Experiments using simulated exhaust gas flows have shown that CO2 do not have any interference with the NO and NO2 measurements. The detection limits in ppm of the system were considerably lowered by using a multi-pass optical system. A pair of off-axis parabola mirrors was useful to prevent the laser beam from straying from the detection area of the sensor due to the beam steering in the exhaust gas. Furthermore, the multi-path optical duct fabricated with 14 mirrors on the inner wall was effective in the measurement of NO and NO2 in the exhaust gas from gas turbines.
Temperature Measurement of High Speed Rotating Turbine Blades Using a Pyrometer
Authors: Taniguchi Tomoki , Sanbonsugi Koji , Ozaki Yoshihiko , Norimoto Atsushi
Published: September 2008

Temperature measurement of high speed rotating turbine blades has been conducted successfully by using an optical pyrometer. The measured blades are the first stage turbine blades of Kawasaki’s gas turbine M7A-01 and rotate at 14,000rpm. In the experiment, the radiance emitted from the blade was collected by the detector, and temperature was calculated from Planck’s equation. The resultant temperature distribution was compared with the result of thermal index paint quantitatively. Also temperature value was compared with the results obtained with thermocouples embedded in the blade. In this paper, details of measurement and analysis are described.
Chemical Reactor Network Application to Emissions Prediction for Industial DLE Gas Turbine
Authors: Novosselov I. V. , Malte P. C. , Yuan S. , Srinivasan R. , Lee J. C. Y.
Published: September 2008

A chemical reactor network (CRN) is developed and applied to a dry low emissions (DLE) industrial gas turbine combustor with the purpose of predicting exhaust emissions. The development of the CRN model is guided by reacting flow computational fluid dynamics (CFD) using the University of Washington (UW) eight-step global mechanism. The network consists of 31 chemical reactor elements representing the different flow and reaction zones of the combustor. The CRN is exercised for full load operating conditions with variable pilot flows ranging from 35% to 200% of the neutral pilot. The NOpilot. The NOx and the CO emissions are predicted using the full GRI 3.0 chemical kinetic mechanism in the CRN. The CRN results closely match the actual engine test rig emissions output. Additional work is ongoing and the results from this ongoing research will be presented in future publications.
Laser Based Investigations of Thermo-Acoustic Instabilities in a Lean Premixed Gas Turbine Model Combustor
Authors: Weigand Peter , Meier Wolfgang , Duan Xuru , Aigner Manfred
Published: September 2008

Non-intrusive laser-based and optical measurements were performed in a gas turbine model combustor with a lean premixed swirl-stabilized CH4-air flame at atmospheric pressure. The main objective was to gain spatially and temporally resolved experimental data to enable the validation of numerical CFD-results of oscillating flames. The investigated flame was operated at 25 kW and φ = 0.70 and exhibited self-excited oscillations of more than 135 dB at about 300 Hz. The applied measurement techniques were 3-D LDV for velocity measurements, OH* chemiluminescence yielding information about the heat release, and point-wise laser Raman scattering for the determination of joint PDFs of the major species concentrations, temperature, and mixture fraction. Each of these techniques was applied with phase resolution with respect to the periodic fluctuation of the pressure in the combustion chamber that was measured with a microphone probe. The measurements finally revealed that the mixing of fuel and air in this technical premixing system was strongly affected by the pressure fluctuations leading to changes in equivalence ratio during an oscillation cycle which in turn induced the pressure fluctuations.
Ultra-Low NOx Advanced Vortex Combustor
Authors: Edmonds Ryan G. , Steele Robert C. , Williams Joseph T. , Straub Douglas L. , Casleton Kent H. , Bining Avtar
Published: September 2008

An ultra lean-premixed Advanced Vortex Combustor (AVC) has been developed and tested. The natural gas fueled AVC was tested at the U.S. Department of Energy’s National Energy Technology Laboratory (USDOE NETL) test facility in Morgantown (WV). All testing was performed at elevated pressures and inlet temperatures and at lean fuel-air ratios representative of industrial gas turbines. The improved AVC design exhibited simultaneous NOx/CO/UHC emissions of 4/4/0 ppmv (all emissions are at 15% O2 dry). The design also achieved less than 3 ppmv NOx with combustion efficiencies in excess of 99.5%. The design demonstrated tremendous acoustic dynamic stability over a wide range of operating conditions which potentially makes this approach significantly more attractive than other lean premixed combustion approaches. In addition, a pressure drop of 1.75% was measured which is significantly lower than conventional gas turbine combustors. Potentially, this lower pressure drop characteristic of the AVC concept translates into overall gas turbine cycle efficiency improvements of up to one full percentage point. The relatively high velocities and low pressure drops achievable with this technology make the AVC approach an attractive alternative for syngas fuel applications.
Historical Review of Addressing the Challenges of Use of Ceramic Components in Gas Turbine Engines
Authors: Richerson David W.
Published: September 2008

Since the invention of the gas turbine engine, engineers have continuously strived to achieve higher operating temperature and improved thermal efficiency. Ceramic-based materials were considered in the 1940s and 1950s, but did not have adequate properties to survive the thermal shock and high temperature conditions. By the end of the 1960s, new materials were developed in the silicon nitride and silicon carbide families that appeared to have potential. Substantial efforts have subsequently been conducted worldwide. These efforts have identified and sought solutions for key challenges: improvement in properties of candidate materials, establishing a design and life prediction methodology, generating a material database, developing cost-effective fabrication of turbine components, dimensional and non-destructive inspection, and validation of the materials and designs in rig and engine testing. Enormous technical progress has been made, but ceramic-based turbine components still have not reached bill-of-materials status. There are still problems that must be solved. In addition, metals-based technology has not stood still. Implementation of sophisticated cast-in internal cooling passages, development of directionally solidified and later single crystal superalloy hot section components, improved alloys, and use of ceramic thermal barrier coatings have combined to allow thermal efficiency increases that exceed the 1970s goals that engineers thought could only be achieved with ceramics. As a result of these metal and design advances, the urgency for use of ceramics has decreased. Emphasis of this paper is on review of the key challenges of implementing ceramic components in gas turbine engines, progress towards solving these challenges, some challenges that still need to be resolved, and a brief review of how technology from the turbine developments has been successfully spun off to important products.
Gas Turbine Engine Performance Model Applications Using an Object-Oriented Simulation Tool
Authors: Alexiou A. , Mathioudakis K.
Published: September 2008

Engine performance models are used throughout the life cycle of an engine from conceptual design to testing, certification and maintenance. The objective of this paper is to demonstrate the use and advantages of an engine performance model, developed using an object-oriented simulation tool, for the following applications: • Building an engine model from existing engine components and running steady state and transient calculations. • Development and integration of a new cooled turbine component in the existing engine model. • Accessing the engine model from an external application. • Using an external legacy routine in the engine model.
Development and Validation of a Computational Code for Wet Compression Simulation of Gas Turbines
Authors: Bagnoli M. , Bianchi M. , Melino F. , Spina P. R.
Published: September 2008

In this paper, a calculation code developed by DIEM – University of Bologna, able to evaluate the performance of a gas turbine with all possible fogging strategies (high pressure fogging, overspray and interstage injection) is presented and discussed. The aim of the developed calculation code is to overcome the calculation limits of the most widespread commercial software, specially with regards to the two phase flow compression process simulation. The self developed calculation code was validated on results available in literature. The developed code is standard, and can be applied to evaluate the performance of any commercial gas turbine model.
Environmentally Friendly Update of Gas Turbines on Gas Transmission Lines
Authors: Vesely´ S. , Soudarev A. , Vinogradov E. , Zacharov Y.
Published: September 2008

Currently, more than 1,500 gas turbines are in operation on natural gas transmission lines all over Europe. These turbines do not comply with the requirements for toxic substances content in exhaust gases. Therefore, an environmentally friendly update of these turbines is a hot topic now, especially because these turbines are supposed to remain in operation for another 10 or 15 years. Besides, environmentally friendly update is a specific issue that differs from the development of a new low-emission combustion chamber. The authors participated in environmentally friendly update of more than 500 gas turbines of this design in Russia, Ukraine, Slovakia, Czech Republic, Germany, and Hungary. As new emission limits are expected to be issued in the EU, a new low-emission burner was developed that makes use of a combination of kinetic and diffusion combustion to achieve low NOx and CO emissions. The burner operation in combustion chambers of gas turbines is characterized by a wide range of the coefficient of excess air from idle run to full performance. Therefore, the control of the quantity of primary air is necessary. The paper will describe the main stages of the burner research. Tests were performed on an atmospheric pressure test rig where the basic characteristics were gained. The influence of pressure was examined on a special test rig at 0.75–1.1 MPa of pressure. Tests have confirmed that the required NOx and CO emission limits can be achieved with the designed burner. The low emission burner was used for the combustion chamber of a 6 MW gas turbine. The tests performed on a part of a model burner will be presented and an analysis of measurement results will be given.
A Techno-Economic Analysis of Different Options for Cogenerating Power in Hydrogen Plants Based on Natural Gas Reforming
Authors: Corradetti Alessandro , Desideri Umberto
Published: September 2008

Steam Methane Reformer is the commonest process for producing hydrogen in the world. It currently represents the most efficient and mature technology for this purpose. However, due to the high investment costs, this technology is convenient for large sizes only. Furthermore, the cooling of syngas and flue gas produce a great amount of excess steam, which is usually transferred outside the process, for heating purposes or industrial applications. The opportunity of using this additional steam to generate electric power has been studied in this paper. In particular different power plant schemes have been analyzed, including: (i) a Rankine cycle; (ii) a gas turbine simple cycle; (iii) a gas-steam combined cycle. These configurations have been investigated with the additional feature of CO2 capture and sequestration. The reference plant has been modeled according to the state of art of commercial hydrogen plants: it includes a pre-reforming reactor, two shift reactors and a pressure swing adsorption unit for hydrogen purification. The plant has a conversion efficiency of approximately 75% and produces 145,000 Stm3/hr of hydrogen (equivalent to 435 MW on LHV basis) and 63 t/hr of superheated steam. The proposed power plants generate respectively 22 MW (i), 36 MW (ii) and 87 MW (iii) without CO2 capture. A sensitivity analysis was carried out to determine the optimum size for each configuration and to investigate the influence of some parameters, such as electricity, natural gas and steam costs.
Rib Spacing Effect on Heat Transfer and Pressure Loss in a Rotating Two-Pass Rectangular Channel (AR=1:2) With 45-Degree Angled Ribs
Authors: Liu Yao-Hsien , Wright Lesley M. , Fu Wen-Lung , Han Je-Chin
Published: September 2008

Rib turbulators are commonly used to enhance the heat transfer within internal cooling passages of advanced gas turbine blades. Many factors affect the thermal performance of a cooling channel with ribs. This study experimentally investigates the effect of rib spacing on the heat transfer enhancement, pressure penalty, and thus the overall thermal performance in both rotating and non-rotating rectangular, cooling channels. In the 1:2 rectangular channels, 45° angled ribs are placed on the leading and trailing surfaces. The pitch of the ribs varies, so rib pitch-to-height (P/e) ratios of 10, 7.5, 5, and 3 are considered. Square ribs with a 1.59 mm × 1.59 mm cross-section are used for all spacings, so the height-to-hydraulic diameter (e/Dh) ratio remains constant at 0.094. With a constant rotational speed of 550 rpm and the Reynolds number ranging from 5000 to 40000, the rotation number in turn varies from 0.2 to 0.02. Because the skewed turbulators induce secondary flow along the length of the rib, the very close rib spacing of P/e = 3, has the best thermal performance in both rotating and non-rotating channels. This close spacing yields the greatest heat transfer enhancement, while the P/e = 5 spacing has the greatest pressure penalty. In addition, the effect of rotation is more pronounced in the channel with the rib spacing of 3. As more ribs are added, the channel is approaching a smooth channel, and the strength of the rotation induced vortices increases.
Influence of Hole Angle and Shaping on Leading Edge Showerhead Film Cooling
Authors: Lu Yiping , Allison David , Ekkad Srinath V.
Published: September 2008

Detailed film cooling measurements are presented on a turbine blade leading edge model with three rows of showerhead holes. Experiments are run at a mainstream Reynolds number of 19,500 based on cylindrical leading edge diameter. One row of holes is located on the stagnation line and the other two rows are located at ±15° on either side of the stagnation line. The three rows have compound angle holes angled 90° in the flow direction, 30° along the spanwise direction, and the two holes on either side of the stagnation row have and additional angle of 0°, 30°, and 45° in the transverse direction. The effect of hole shaping of the 30° and 45° holes is also considered. Detailed heat transfer coefficient and film effectiveness measurements are obtained using a transient infrared thermography technique. The results are compared to determine the advantages of shaping the compound angle for rows of holes off stagnation row. Results show that, the additional compound angle in the transverse direction for the two rows adjacent to the stagnation row provide significantly higher film effectiveness than the typical leading edge holes with only two angles. Results also show that, the shaping of showerhead holes provides higher film effectiveness than just adding an additional compound angle in the transverse direction and significantly higher effectiveness than the baseline typical leading edge geometry. Heat transfer coefficients are higher as the spanwise angle for this study is larger than typical leading edge geometries with an angle of 30° compared to 20° for other studies.
3-D Numerical Analysis of Curved Transpiration Cooled Plates and Homogenization of Their Aerothermal Properties
Authors: Laschet Gottfried , Rex Stephan , Bohn Dieter , Krewinkel Robert
Published: September 2008

Three different designs of a transpiration cooled multilayer plate — plane, convex and concave — are analysed numerically by application of a 3-D conjugate fluid flow and heat transfer solver. The geometrical setup and the fluid flow conditions are derived from modern gas turbine components. The conjugate analysis of these designs focus on the influence of the surface curvature, the cooling film development on the plate surface, the fluid structure in the cooling channels and on the cooling efficiency of the plate. Moreover, to predict the effective thermal properties and the permeability of these multilayer plates, a multiscale approach based on the homogenization technique is employed. This method allows the calculation of effective equivalent properties either for each layer or for the multilayer of superalloy, bondcoat and thermal barrier coating (TBC). Permeabilities of the different designs are presented in detail for the TBC layer. The influence of the plate curvature and the blowing ratio on the effective orthotropic thermal conductivities is finally outlined.
The Distinction Between the Cheng and STIG Cycles
Authors: Cheng Dah Yu
Published: September 2008

This paper identifies distinct features of the Cheng Cycle as compared to the steam injected gas turbine, STIG. Development started on the Cheng Cycle in 1974. After eight years of research and testing, the Cheng Cycle was commercialized in 1982. The commercial opportunity came by winning one of the State of California’s Energy Commission sponsored bids at the San Jose State University campus. The first Cheng Cycle power plant was built around the Allison 501KB gas turbine. The project was won on the merit of excellent thermal efficiency with maximum flexibility. It is also the most economical system because it can follow fluctuating electrical and steam loads independently. Financing, licensing and all appropriate permits were completed within one year. It took less than a year to construct and was on line by the end of 1984. Immediately, several distinct features were noticed: (1) the Cheng Cycle boosts power by 70% and efficiency by 40% over the simple cycle, (2) it can follow the electric and steam loads independently, (3) it demonstrated low emission and established 25 ppm NOx as BACT for the San Francisco Bay Area Air Quality District. In 1987, GE introduced their Steam Injected Gas Turbine, STIG, using the LM 2500 and LM 5000, and in the 1990’s GE also introduced the LM1600 version of STIG. The high pressure ratio of those engines resulted in low exhaust temperature. That is not efficient enough to power a steam cycle. Unfortunately, STIG confused some users into thinking that every steam injected gas turbine was a Cheng Cycle. STIG uses the traditional constant pressure waste heat boiler technology. Operation is limited to near full load because low exhaust temperature at partial load would cause dysfunctional heat imbalance in the heat recovery steam generator (HRSG). The Cheng Cycle, in comparison, adopted a variable pressure HRSG so its operating range extends from idle to full load. This variable pressure HRSG allows full heat recovery, whereas STIG has to limit its operating range to maintain heat transfer balance. This unique HRSG design means that the Cheng Cycle is a thermal feedback cycle. As in any feedback system it could oscillate, in this case the oscillations are between fuel-flow and steam-flow. The Cheng Cycle utilizes digital control technology to the system. The integrated system provides the user with smooth operation and rapid start-up and load change capability.
Correlative Analysis of Effusion Cooling Systems
Authors: Arcangeli Lorenzo , Surace Marco , Tarchi Lorenzo , Coutandin Daniele , Zecchi Stefano
Published: September 2008

Gas turbine cooling has steadily acquired major importance whenever engine performances have to be improved. Among various cooling techniques, film cooling is probably one of the most diffused systems for protecting metal surfaces against hot gases in turbine stages and combustor liners. Most recent developments in hole manufacturing allow to perform a wide array of micro-holes, currently referred to as effusion cooling. This paper presents the validation of a simplified 2D conjugate approach through comparison with the experimental results of effectiveness for an effusion plate, performed during the first year of the European Specific Targeted REsearch Project AITEB-2 (Aerothermal Investigation of Turbine Endwalls and Blades). A preliminary test is performed with the steady-state technique, using TLC (Thermochromic Liquid Crystal) wide-band formulations. Results are obtained in terms of local distributions of adiabatic effectiveness. Average values are compared with calculations to validate the numerical code. Then, Design Of Experiment (DOE) approach is used to perform several conjugate tests (about 180), so as to derive the behavior of different effusion plates in terms of overall effectiveness and mass flow rate. Data are analyzed in detail and a correlative approach for the overall effectiveness is proposed.
Effects of Inlet Flow Distortion on the Performance of Aircraft Gas Turbines
Authors: Kurzke Joachim
Published: September 2008

The main problem with aircraft engine inlet flow distortion is its effect on the stability of the compression system. However, distortion does also influence the performance delivered by the propulsion system. There are two fundamentally different reasons for the change in performance: First there is the impact of the flow distortion on the component efficiencies and thus the thermodynamic cycle and second there are performance changes due to actions of the control system. This paper describes how the fundamental effects of inlet flow distortion on the performance of gas turbines can be evaluated with any engine performance program that employs an integrated parallel compressor model. This sort of simulation is a valuable tool for evaluating the basic effects of complex flow phenomena on the performance of a gas turbine. It delivers fundamentally correct answers since even the most complex flow structures obey the laws of mass and energy conservation and that’s all what the overall system simulation is about. In the parallel compressor model both pressure and temperature distortions are quantified with coefficients which relate the pressure (respectively temperature) in the spoiled sector to the value in the clean sector. In single compressor engines the static pressure at the exit of the clean sector equals that of the distorted sector. This hypothesis does not hold true with multi-compressor engines because the short inter-compressor ducts, which often contain struts or vanes, do not allow the mass flow transfer over the sector borders which would be required for balancing the static pressures. The degree of aerodynamic coupling of compressors in series can be described in the performance simulation program by a coupling factor. From the engine system simulation results it becomes clear why inlet flow distortion has only a minor impact on the thermodynamic cycle if the comparison of the two operating conditions (with clean and distorted inlet flow) is made at the properly averaged engine inlet conditions. For each compressor the parallel compressor theory yields two operating points in the map, one for the clean sector and one for the spoiled sector. The performance loss due to distortion is small since the efficiency values in the two sectors are only a bit lower than the efficiency at a comparable operating point with clean inlet flow. However, the control system of the engine can react to the inlet flow distortion in such a way that the thrust delivered changes significantly. This is particularly true if a compressor bleed valve or a variable area nozzle is opened to counteract compressor stability problems. Especially using re-circulating bleed air to increase the surge margin of a compressor affects the performance of the engine negatively. Two examples show clearly that the pro and cons of re-circulating bleed can only be judged with a full system simulation, looking at the surge line improvement alone can be misleading.
Development of an Automated Preliminary Combustion Chamber Design Tool
Authors: Pegemanyfar Nima , Pfitzner Michael , Eggels Ruud , von der Bank Ralf , Zedda Marco
Published: September 2008

The preliminary design of a new combustion chamber requires the combination of many elements of know-how in terms of combustor design rules, aerothermal calculations and preliminary design tools. To use this knowledge more efficiently pre-competitive work on an automated knowledge-based combustor design methodology is done within the European project INTELLECT D.M. (Integrated Lean Low Emission Combustor Design Methodology) in order to set up a KBE (Knowledge Based Engineering) system. In the method presented here, the rules and calculation routines are implemented into an automated preliminary design system using an Excel-driven database to generate a parametric Unigraphics CAD model. The utilized design rules represent state-of-the-art combustor design and will be extended later by lean combustion design rules, which are currently developed within INTELLECT D.M.. The database contains all design parameters and rules to provide CAD, CFD and optimization tools with the required information. Based on a set of performance parameters the system automatically generates the parametric geometry of a combustor containing the liners with cooling devices (optionally Z-ring or effusion cooling) and mixing holes, heat shield, cowl, casings and (pre)diffusor. To estimate the required cooling air, one-dimensional heat transfer equations including convection, radiation and conduction are solved. The generated CAD model visualizes the calculated combustor geometry and forms the basis for an automated CFD mesh generation utilizing the grid generator ICEM CFD.
Performance of Prefilming Airblast Atomizers in Unsteady Flow Conditions
Authors: Mu¨ller A. , Koch R. , Bauer H.-J. , Hehle M. , Scha¨fer O.
Published: September 2008

Within the context of lean premixed prevaporized combustion (LPP) which is considered as most promising technology for the next generation of low emission combustors for aero engines, combustion instabilities are a major issue. These combustion instabilities may compromise the pollutant emissions and even cause damage to the combustion chamber structure. In the literature, numerous phenomenological studies on combustion oscillation are available, but a comprehensive theory is still missing. One potential excitation mechanism is the interaction of strong air velocity fluctuations and pressure oscillations with the airblast atomizer leading to temporal fluctuations of the spray characteristics. This phenomenon was investigated experimentally at the Institute of Thermal Turbomachinery (ITS) within a parametric study. A duct with a prefilming surface was set up as an abstraction of a prefilming airblast atomizer. A mean air velocity up to 65 m/s can be reached, and periodic oscillations can be superimposed by means of a siren with a frequency up to 570 Hz. The disintegration process of the liquid fuel was studied downstream the atomizing edge of a plain airblast nozzle. Several optical diagnostics like phase resolved LDV (Laser Doppler Velocimetry) and an improved PTV technique (Particle Tracking Velocimetry) were used. The mean air velocity, the film load, the kinematic viscosity and the surface tension of the fluid as well as the pulsation frequency and amplitude of the siren were varied, and their effect on the temporal evolution of the droplet size and droplet rate was studied. It was found that the amplitude of fluctuations of the droplet size and the droplet rate is almost proportional to the air velocity fluctuations at low frequencies. At higher frequencies, however, both are nearly unaffected. In addition, the fluctuations of droplet diameter and rate increase strongly if the mean air velocity is increased. The phase shift between particle diameter, particle rate and air velocity fluctuations was found to increase at higher excitation frequencies.
Full Authority Digital Engine Controller for Marine Gas Turbine Engine
Authors: Githanjali B. , Shobha P. , Ramprasad K. S. , Venkataraju K.
Published: September 2008

A full authority digital engine control system (FADEC) has been configured for the marine gas turbine engine being developed at the Gas Turbine Research Establishment, Bangalore, India. This paper presents the development of a prototype FADEC for this aero-derivative marine gas turbine engine. A dual-redundant architecture, with two identical digital electronic control units (DECU) in an active-standby configuration, was chosen to provide the necessary reliability, availability and maintainability. The system provides automatic control of engine fuel flow and compressor variable geometry, without exceeding parameter limits, so as to control either the speed of the gas generator or the power turbine in order to meet the power demanded. While the control units incorporate hardware and software features to detect and accommodate faults, an independent electronic trip system was included as a part of the overall control system to handle those situations resulting in uncontrolled overspeeding or safety interlock requirements. Recognizing the global trend towards the use of commercial off the shelf (COTS) technology, the system was configured with industry proven hardware and software. In addition, a hydro-mechanical backup control provides limited operational capability in the event of electronic control failure.
Accurate Boundary Conditions for the Numerical Simulation of Thermoacoustic Phenomena in Gas-Turbine Combustion Chambers
Authors: Widenhorn Axel , Noll Berthold , Aigner Manfred
Published: September 2008

The goal of this paper is to discuss the derivation and behaviour of non-reflecting boundary conditions in the framework of accurate calculations of combustion instabilities. Therefore, it is explained for the first time, how to modify the coefficients of the discrete pressure correction equation and of the discrete conservation equations, in order to apply non-reflecting boundary conditions to a pressure based SIMPLE-Algorithm. The theory and practical implementation of the boundary conditions, which are based on Poinsot & Lele’s [1] formulation, will be explained for inflow and outflow boundaries. The method will be validated based upon test cases which are relevant to the simulation of gas turbine combustion chambers. Moreover, the accuracy of non-reflecting boundary conditions is assessed for cases where combustion leads to inhomogeneous temperature and species fields. The impact of the acoustic wave propagation speed on the reflectivity of the non-reflecting boundary conditions is analysed.