bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration Design and Performance Analysis of HAT Cycle Incorporated With Absorption Heat Pump
Authors: Wei Fan , Xiao Yunhan , Zhang Shijie
Published: March 2009

The humid air turbine (HAT) cycle is a novel advanced gas turbine cycle. However, the conventional HAT cycle has many insufficiencies considering combined heat and power generation, water recovery and exhausts emission with low temperature. This study deals with these problems by integrating absorption heat pumps into the HAT cycle. Six types of absorption heat pumps, including the single stage open cycle absorption heat transformer (connect to the HAT cycle with simple and complex manner respectively), the two stage open cycle absorption heat transformer, the open cycle absorption heat pump with the single pressure, the closed cycle two stage absorption heat transformer and the closed cycle absorption heat pump, are incorporated into the HAT cycle. The integrated systems are simulated. The results indicate that while the electrical efficiency of the original HAT cycle is 56.48%, the cycle efficiencies of the above-mentioned integrated cycles are 50.53%, 55.15%, 51.07%, 46.88%, 57.52% and 46.25%, respectively. Water recovery can be achieved in each integrated system although the recovery effects are quite different. For the open systems, the water recovery levels depend on the pressure difference of the gas and the water. Full water recovery can be realized and the temperature of the exhaust gas can be kept high. The water recovery levels of the closed systems relate to the thermal capacity of the exhaust gas, and the emission of the low temperature exhaust gas is difficult. From the point of view of the combined heat and power generation, the temperature of the exhaust gas does not influence the quantity of the heat supply. Three integrated systems can be applied for the combined heat and power generation, the heat and power efficiency are 62.85%, 76.77% and 63.83% respectively. In general, the advantages of the HAT cycle combined with the absorption heat pump system are verified in the present paper.
Lycoming T-53 Gas Turbine Engine Modification for Industrial Application
Authors: Lupandin Vladimir , Hexter Martyn , Nikolayev Alexander
Published: March 2009

This paper describes a development program active at Magellan Aerospace Corporation since 2003, whereby specific modifications are incorporated into an Avco Lycoming T-53 helicopter gas turbine engine to enable it to function as a ground based Industrial unit for distributed power generation. The Lycoming T-53 is a very well proven and reliable two shaft gas turbine engine whose design can be traced back to the 1950s and the fact of its continued service to the present day is a tribute to the original design/development team. Phase 1 of the Program introduces abradable rotor path linings, blade coatings and changes to seal and blade tip clearances. Magellan has built a test cell to run the power generation units to full speed and full power in compliance with ISO 2314. In co-operation with Zorya-Mashproekt, Ukraine, the exhaust emissions of the existing combustion system for natural gas was reduced by 30%. New nozzles for low heat value fuels and for high hydrogen content fuels (up to 60% H2) have been developed. The T-53 gas turbine engine exhaust gas temperature is typically around 620 deg C, which makes it a very good candidate for co-generation and recuperated applications. As per Phase 2 of the program, the existing helicopter integral gearbox and separate industrial step-down gearbox will be replaced with single integral gearbox that will use the same lubrication oil system as the gas turbine engine. The engine power output will increase to 1200 kW at the generator terminals with an improvement to 25% efficiency ISO. Phase 3 of the Program will see the introduction of a new silo type combustion system, developed in order to utilize alternative fuels such as bio-diesel, biofuel (product of wood pyrolysis), land fill gases, syn gases etc. Phase 4 of the Program in cooperation with ORMA, Russia will introduce a recuperator into the package and is expected to realize a boost in overall efficiency to 37%. The results of testing the first two T-53 industrial gas turbine engines modified per Phase 1 will be presented.
Hybrid Oxide-Based CMCs for Combustion Turbines: How Hybrid Oxide CMC Mitigates the Design Hurdles Typically Seen for Oxide CMC
Authors: Lane Jay E. , Morrison Jay A. , Marini Bonnie , Campbell Christian X.
Published: March 2009

Ceramic matrix composites (CMCs), in particular oxide-based systems, are of interest for use in combustion turbines. While uncoated oxide CMCs have significant hurdles to implementation in gas turbines, the Siemens hybrid oxide CMC system is able to overcome these challenges. These hybrid oxide CMCs provide distinct advantages over the current non-oxide based systems. The benefits of hybrid oxide-based systems for advanced gas turbines will be discussed. Material system developments will be discussed including those completed by a Siemens Power Generation led team in a recent NIST (National Institute of Standards and Technology) sponsored program to prove the concept of advanced hybrid oxide-oxide CMCs for gas turbine engines. The program fabricated a full scale outer combustor liner that was installed in a Solar Centaur 50S engine at a commercial end user site. In November 2006, this hybrid oxide CMC outer combustor liner met the target life goal of 25,000 hrs with 25,404 hrs of field test experience. The final hurdle for design of hybrid oxide CMC components is the ability to accurately analytically predict behavior. Methods and approaches to address this challenge are discussed as well.
Experimental Study of NOx Formation in Lean, Premixed, Prevaporized Combustion of Fuel Oils at Elevated Pressures
Authors: Gokulakrishnan P. , Ramotowski M. J. , Gaines G. , Fuller C. , Joklik R. , Eskin L. D. , Klassen M. S. , Roby R. J.
Published: March 2009

Dry low Emissions (DLE) systems employing lean, premixed combustion have been successfully used with natural gas in combustion turbines to meet stringent emissions standards. However, the burning of liquid fuels in DLE systems is still a challenging task due to the complexities of fuel vaporization and air premixing. Lean, Premixed, Prevaporized (LPP) combustion has always provided the promise of obtaining low pollutant emissions while burning liquid fuels such as kerosene and fuel oil. Because of the short ignition delay times of these fuels at elevated temperatures, the autoignition of vaporized higher hydrocarbons typical of most practical liquid fuels has proven difficult to overcome when burning in lean, premixed mode. To avoid this autoignition problem, developers of LPP combustion systems have focused mainly on designing premixers and combustors that permit rapid mixing and combustion of fuels before spontaneous ignition of the fuel can occur. However, none of the reported works in the literature has looked at altering fuel combustion characteristics in order to delay the onset of ignition in lean, premixed combustion systems. The work presented in this paper describes the development of a patented low-NOx LPP system for combustion of liquid fuels which modifies the fuel rather than the combustion hardware in order to achieve LPP combustion. In the initial phase of the development, laboratory-scale experiments were performed to study the combustion characteristics, such as ignition delay time and NOx formation, of the liquids fuels that were vaporized into gaseous form in the presence of nitrogen diluent. In phase two, an LPP combustion system was commissioned to perform pilot-scale tests on commercial turbine combustor hardware. These pilot-scale tests were conducted at typical compressor discharge temperatures and at both atmospheric and high pressures. In this study, vaporization of the liquid fuel in an inert environment has been shown to be a viable method for delaying autoignition and for generating a gaseous fuel stream with characteristics similar to natural gas. Tests conducted in both atmospheric and high pressure combustor rigs utilizing swirl-stabilized burners designed for natural gas demonstrated operation similar to that obtained when burning natural gas. Emissions levels were similar for both the LPP fuels (fuel oil #1 and #2) and natural gas, with any differences ascribed to the fuel-bound nitrogen present in the liquid fuels. Extended lean operation was observed for the liquid fuels as a result of the wider lean flammability range for these fuels compared with natural gas. Premature ignition of the LPP fuel was controlled by the level of inert gas in the vaporization process.
Aerodynamic Performance of Small Turbocharger Compressors
Authors: Shaaban S. , Seume J.
Published: March 2009

Automotive turbocharger compressors are characterized by small dimensions. These small dimensions make detailed measurements of the flow field inside the compressor very challenging. However, it is very important to investigate and understand the aerodynamic performance of these machines in order to enhance the ability to improve their performance. The present paper aims at investigating the aerodynamic performance of the individual compressor components and the interaction between these components. The aerodynamic performance of a GT1749V 70 Trim turbocharger compressor is investigated with particular attention to measurements of the static pressure distribution at the inlet and outlet of the diffuser. A 1D-model is developed to solve the conservation equations along the streamlines inside the diffuser with the measured static pressure distributions as boundary conditions. The loss coefficients of the impeller, the diffuser, and the volute as well as the slip factor of the impeller are estimated from the experimental data with the help of the 1D-model developed in the present work. The model is also validated using available experimental data from a large radial compressor and shows a good agreement with the experimental results.
Separation Control of Axial Compressor Cascade by Fluidic-Based Excitations
Authors: Zheng Xinqian , Zhang Yangjun , Xing Weidong , Zhang Junyue
Published: March 2009

Flow separation control was explored on a compressor cascade using three types of fluidic-based excitations: steady suction, steady blowing and synthetic jet. By solving unsteady Reynolds-averaged N-S equations, the effect of excitation parameters (amplitude, angle and location) on the performance were presented. The results showed that the separated flow could be controlled by the fluidic-based actuators effectively and the time-mean performance of flow filed could be remarkably improved. Generally, the positive effect is more visible when the excitation amplitude is increased. The optimal direction varies with each type of excitations and is related to physical mechanisms underlying the separation control. For two types of steady excitations, the most effective jet location is at a distance upstream of the time-mean separation point and the synthetic jet is just at the separation point.
Static and Dynamic Characteristics for a Pressure-Dam Bearing
Authors: Al-Jughaiman Bader , Childs Dara
Published: March 2009

Measured rotordynamic force coefficients (stiffness, damping, and added-mass) and static characteristics (eccentricity and attitude angle) of a pressure-dam bearing are presented and compared to predictions from a Reynolds-equation model, using an isothermal and isoviscous laminar analysis. The bearing’s groove dimensions are close to the optimum predictions of Nicholas and Allaire (1980) and are consistent with current field applications. The bearing has a diameter of 117.1 mm (4.61 in), a length-to-diameter ratio of 0.655 and, a nominal radial clearance of 0.133 mm (5.25 mils). The upper pad of the bearing has a step located at 130° and a 0.620 mm (15.75 mils) deep dam. The bottom pad has a deep, centered relief track over 25% of the pad’s axial length. Test conditions include four shaft speeds (4000, 6000, 8000 and 10000 rpm) and bearing unit loads from 0 to 1034 kPa (150 psi). Laminar flow was produced for all test conditions. A finite-element algorithm was used to generate solutions to the Reynolds equation model. Excellent agreement was found between predictions and measurements for the eccentricity ratio and attitude angles. Predictions of stiffness and damping coefficients are in reasonable agreement with measurements. However, experimental results show that the bearing has significant added mass of about 60 kg at no-load conditions, versus zero mass for predictions from the Reynolds-equation model and 40 kg using Reinhardt and Lund’s extended Reynolds equation model. The added mass drops quickly to zero as the load increases. Measured results also show a whirl frequency ratio near 0.36 at no-load conditions; however, a zero whirl frequency ratio was obtained at all loaded conditions, indicating an inherently stable bearing from a rotordynamics viewpoint.
Advanced Bottoming Cycle Optimisation for Large Alstom CCPP
Authors: Vollmer Michael , Pedretti Camille , Ni Alexander , Wirsum Manfred
Published: March 2009

This paper presents the fundamentals of an evolutionary, thermo-economic plant design methodology, which enables an improved and customer-focused optimization of the bottoming cycle of a large Combined Cycle Power Plant. The new methodology focuses on the conceptual design of the CCPP applicable to the product development and the pre-acquisition phase. After the definition of the overall plant configuration such as the number of gas turbines used, the type of main cooling system and the related fix investment cost, the CCPP is optimized towards any criteria available in the process model (e.g. lowest COE, maximum NPV/IRR, highest net efficiency). In view of the fact that the optimization is performed on a global plant level with a simultaneous hot- and cold- end optimization, the results clearly show the dependency of the HRSG steam parameters and the related steam turbine configuration on the definition of the cold end (Air Cooled Condenser instead of Direct Cooling). Furthermore, competing methods for feedwater preheating (HRSG recirculation, condensate preheating or pegging steam), different HRSG heat exchanger arrangements as well as applicable portfolio components are automatically evaluated and finally selected. The developed process model is based on a fixed superstructure and copes with the full complexity of today’s bottoming cycle configurations as well with any constraints and design rules existing in practice. It includes a variety of component modules that are prescribed with their performance characteristics, design limitations and individual cost. More than 100 parameters are used to directly calculate the overall plant performance and related investment cost. Further definitions on payment schedule, construction time, operation regime and consumable cost results in a full economic life cycle calculation of the CCPP. For the overall optimization the process model is coupled to an evolutionary optimizer, whereas around 60 design parameters are used within predefined bounds. Within a single optimization run more than 100’000 bottoming cycle configurations are calculated in order to find the targeted optimum and thanks to today’s massive parallel computing resources, the solution can be found over night. Due to the direct formulation of the process model, the best cycle configuration is a result provided by the optimizer and can be based on a single-, dual or triple pressure system using non-reheat, reheat or double reheat configuration. This methodology enables to analyze also existing limitations and characteristics of the key components in the process model and assists to initiate new developments in order to constantly increase the value for power plant customers.
Non-Linear Aeromechanical Behaviour of Axial Core Compressor Stator Vanes
Authors: Peng Caetano
Published: March 2009

This paper highlights some engine non-linearities that can affect both performance and robustness of aero engines. It pays particular attention to non-linearities generated at the stator vane contact end joints. These non-linearities resulting from friction contact joints affect the vane modeshapes, damping and forced response. This work proposes upper and lower bound solutions based on vane end restraints non-linearities to predict conservative forced response of stator vanes. Some non-linearities such as those caused by mistuning can be beneficial to the component and system. There are also non-linearities that can be detrimental to engine performance, robustness and reliability. Moreover, it proposes and discusses the concept of temporal HCF or CCF lifing method. Recent developments in FE, CFD, mistuning, forced response and probabilistic codes can help to create more integrated design tools that incorporate time-dependent non-linearities in the lifing of aero engine components. Computations performed here demonstrated some level of component virtual testing. These analyses are important component virtual testing that will be gradually extended to whole aero engine virtual testing.
Time Resolved Investigations of an Axial Compressor With Casing Treatment: Part 1 — Experiment
Authors: Emmrich R. , Ho¨nen H. , Niehuis R.
Published: March 2009

A casing treatment with axial and radial skewed slots ending in a plenum chamber has experimentally been investigated at a highly subsonic axial compressor stage. The aim was to investigate the physical phenomenon of this treatment family that is responsible for the stabilization of the blade passage flow and the drop in efficiency mostly observed. The experimentally gained performance results of this configuration showed an extension of the operating range by approximately 50%, while the efficiency for design conditions is reduced by 1.4%. Apart from this, operating points at part load conditions have been observed nearly without any loss in efficiency. The detailed flow analysis is performed by means of results from a 3D pneumatic probe with temperature sensor and a dynamic total pressure probe. The focus of the investigations is on the incidence flow to the compressor rotor, the tip clearance vortex flow in combination with the wall stall separation region and the blade stall due to suction side separation. The casing treatment configuration is investigated with a special interest in detecting those effects which have an impact on the stability and the compressor overall efficiency, including the interaction of the rotor and the stator flow fields.
Influence of ATF Dynamics and Controls on Jet Engine Performance
Authors: Bierkamp J. , Ko¨cke S. , Staudacher S. , Fiola Roland
Published: March 2009

Current and future requirements in the verification and validation of the performance of modern aircraft engines lead to continuously increasing requirements on the transient performance capability and flexibility of Altitude Test Facilities (ATF). These requirements have been investigated via numerical simulations of a medium size turbofan and a modern core engine. The simulations using the turbofan engine, document a significant influence of the boundary conditions supplied by the ATF on the dynamic behaviour of bypass engines. Variations in engine acceleration times and compressor stability have been identified. This leads to stability requirements for entry conditions at Fan face and ambient conditions at the nozzle exit. The especially demanding operability tests with core engines, challenge ATF systems due to the additional need to simulate the behaviour of low pressure components. It turns out that the interaction between test vehicle and ATF, in both cases, requires special attention and great care in the design of the ATF control system. Therefore a closed loop simulation model including, ATF, ATF controls system, test vehicle and vehicle control has been developed in order to assess and evaluate the integrated ATF - test vehicle behaviour in advance of the test. The integration of the test vehicle and vehicle control into the modular simulation tool is described. The standardized interface allows integrating different vehicle types without a lot of effort. The application of the simulation in a core engine ATF test is described as an example. The observed vehicle - ATF interaction with and without control is discussed.
A New Approach for Health Monitoring and Detection of Shaft Crack Using an Active Magnetic Actuator During Steady-State Rotor Operation
Authors: Kasarda M. , Bash T. , Quinn D. , Mani G. , Inman D. , Kirk R. G.
Published: March 2009

This work demonstrates the capability of an Active Magnetic Bearing (AMB) to be used as an actuator for interrogating a system by applying multiple forces to a rotating shaft in order to monitor and evaluate the associated responses to these inputs. Similar to modal analysis techniques which apply input signals to static structures in order to monitor responses to those inputs, this approach allows for the measurement of both input and output response in a rotating system for evaluation. However, unlike these techniques, the procedure developed here allows for multiple forms of force inputs to be applied to a rotating structure. This procedure facilitates the development of new improved techniques for diagnosing subtle changes in machinery health or for identifying faults that would potentially go undetected by conventional methods before failure. Although it is expected that this approach can be used in rotors supported in AMBs, the technique developed here uses an AMB on the rotor in conjunction with conventional support bearings. Therefore, this approach has the potential to be used on any rotating machine that can be designed or retrofitted with a single AMB actuator. To demonstrate this approach experimentally, a notched shaft was chosen to represent a shaft crack for identification purposes. Three cases were examined, including a healthy (unnotched) shaft, and three cases of a shaft with a mid-span notch extending to a depth of 10%, 25%, and 40% of shaft diameter, respectively. During testing, excitations up to 1000 Hz were applied via one axis of the AMB actuator to the four rotor cases while the rotor was operating at a steady-state speed of 2400 rpm, and corresponding responses were recorded at the proximity probes. No changes in the 1st or 2nd natural frequencies were detected, but distinct shifts in the 3rd natural frequency were detected from the Frequency Response Function (FRF) data. Since the vast majority of rotating machinery are designed to operate below the 3rd natural frequency, the effect of the notch on the 3rd natural frequency would not have been identified without the application of excitation forces through the AMB actuator. This paper represents an introduction to the new health monitoring approach and results presented here demonstrate the viability of the technique for detecting shaft cracks that might otherwise go undetected in typical steady-state vibration monitoring approaches.
Internal Cooling Inside an L-Shaped Duct With Pin-Fin Turbulators Under Rotating and Non-Rotating Conditions With and Without Sand Particles
Authors: Zhu B. , Chi X. , Dennis R. A. , Chyu M. K. , Bryden M. A. , Shih T. I.-P.
Published: March 2009

Computations were performed to study the flow and heat transfer in an L-shaped duct with pin fin turbulators arranged in a staggered fashion under rotating and non-rotating conditions. Parameters investigated include rotational speed (0, 10,000, 20,000 rpm), distance of the L-shaped duct from the center of rotation (280, 600 mm), and orientation of L-shaped duct with respect to centerline of rotation (0 and 65 degrees). Computations were also performed to examine trajectory of particles in the L-shaped duct under rotating and non-rotating conditions with particle diameters of 0.1, 1.0, and 5.0 micrometers. This computational study is based on an Eulerian-Lagrangian formulation cast in a non-inertial frame of reference fixed on the rotating L-shaped duct. The ensemble average continuity, Navier-Stokes, and energy equations closed by the ideal gas equation of state and the two-equation realizeable k-ε turbulence model were used for the gas phase, and Lagrangian tracking with interphase transport of momentum and energy were employed for the particles.
Numerical Study of Turbulent Spot Development in a Separated Shear Layer
Authors: McAuliffe B. R. , Yaras M. I.
Published: March 2009

The development of turbulent spots in a separation bubble under elevated freestream turbulence levels is examined through direct numerical simulation. The flow Reynolds number, freestream turbulence level, and streamwise pressure distribution are typical of the conditions encountered on the suction side of low-pressure turbine blades of gas-turbine engines. Based on the simulation results, the spreading and propagation rates of the turbulent spots and their internal structure are documented, and comparisons are made to empirical correlations that are used for predicting the transverse growth and streamwise propagation characteristics of turbulent spots. The internal structure of the spots is identified as a series of vortex loops that develop as a result of low-velocity streaks generated in the shear layer. A frequency that is approximately 50% higher than that of the Kelvin-Helmholtz instability is identified in the separated shear layer, which is shown to be associated with convection of these vortex loops through the separated shear layer. While freestream turbulence is noted to promote breakdown of the laminar separated shear layer into turbulence through the generation of turbulent spots, evidence is found to suggest co-existence of the Kelvin-Helmholtz instability, including the possibility of breakdown to turbulence through this mechanism.
Experimental Study of Damping Characteristic of Shrouded Blade
Authors: Hong Jie , Shi Yajie , Zhang Dayi , Zhu Zigen
Published: March 2009

To master the rules in shrouded blade design, an experimental system, including plane-shrouded blade, exciting system and measurement system, was designed to measure dynamic responses of non-rotating shrouded blade exactly, in which initial normal load can be put on the friction interface by a load disc accurately. The dynamic response of the first bending mode of the shrouded blade with various shroud contact angles and shroud situations were measured under different initial normal loads on the interface and different exciting force. The effects of the normal preload, shroud contact angle and shroud situation on the friction damping are analyzed from the test results. The results indicate that there is an optimal preload under which the shroud contact can provide optimum performance in dissipating vibratory energy for a given exciting force, and the larger is the relative motion between the interfaces, the more is the dissipating vibratory energy. Some laws that must be obeyed in the design of shroud contact angle and shroud situation are also concluded. The experimental results can be used to verify the theoretical and numerical results.
Analysis of Technical Challenges in Vaneless Counter-Rotating Turbomachinery
Authors: Ji Lucheng
Published: March 2009

Research and development of vaneless counter-rotating turbomachinery (VCRT) is briefly reviewed. Then basic technical challenges on inflow angle and off-design operation are analyzed regardless of extrinsic differences among any kinds of VCRT (either compressor or turbine or lift fan, either highly or moderately loaded). A somewhat new approach based on velocity triangle analysis played the most important role in obtaining useful results. It is shown that the range of relative inflow angle of the second rotor is narrowed by counter-rotation. And as compared with conventional turbomachinery, varying back-pressure and varying rotation speed off-design operation of VCRT are more complicated. For some rotation speed ratios and flow coefficients, VCRT leads to better operation of varying back pressure type than conventional one, whereas some not. In varying rotation speed operation, VCRT needs variable rotor to get a comparable performance. Counter-measures to overcome these challenges are also given. These analyses will be directly used to judge the applicability of VCRT and determine basic rules and ranges in selecting design parameters of VCRT.
A Model for Describing the Influences of SUC-EW Dihedral Angle on Corner Separation
Authors: Ji LuCheng , Shao WeiWei , Yi WeiLin , Chen Jiang
Published: March 2009

This paper presents a model for describing the influences of SUC-EW dihedral angle on corner separation in turbomachinery, in which SUC-EW dihedral angle refers to the dihedral angle at the intersection line between blade ‘SUCtion’ and End-Wall surfaces. Based on the physical intuition of that the three-dimensional (3D) corner boundary layer is the conflux of both blade and end wall boundary layers, an equivalent two-dimensional(2D) corner boundary layer is put forward to predict the behavior of corner boundary layer. In this procedure, the cross flow effect in corner boundary layer and the three-dimensionality of the nearby main flow are ignored. The influence of the SUC-EW dihedral angle is included by another assumption. That is, the aero blockage and momentum loss of both blade and end wall boundary layers are conserved during the procedure of superimposing the two (both blade and end wall) 2D boundary layers to form the equivalent corner one. Then the corner separation is judged by combining the behaviors of the three boundary layers, i.e. the blade, the end wall and the equivalent 2D corner boundary layers. The present model reveals the influence of the SUC-EW dihedral angle and its streamwise gradient on the corner separation. Carefully monitoring and controlling this dihedral angle and its streamwise gradient are important ways to alleviate or even eliminate the corner separation. Simple numerical investigations show that the model is qualitatively correct.
About Simplifications in Gas Turbine Performance Calculations
Authors: Kurzke Joachim
Published: March 2009

Any gas turbine performance simulation tool employs simplifications, some more, some less. It depends on the intent of the simulation which simplifications are appropriate. For beginners, many are necessary for teaching how the gas turbine works from principle. For practical applications — because of the accuracy requirements — many simplifications introduced in textbooks are not appropriate. This paper comments on the simplifications that are typically made. Simplified gas property models are quite acceptable for ideal cycle analysis. For the examination of real cycles, however, especially the model of the burner should be better than those described in most textbooks. This is because these models yield the best cycle efficiency at stoichiometric fuel-air-ratio while a realistic burner model leads to the conclusion that the best thermal efficiency happens to be at significantly lower fuel-air-ratios respectively temperatures. For off-design simulations many simplifications have the aim to avoid iterative solutions or restricting the algorithms to one-dimensional iterations. If more than one iteration variable shows up — which is the case with multi-spool engine simulations — then the problem is solved with fitting several one-dimensional iterations into each other. This methodology is described in most textbooks, but it is nearly never used in industry because the logic is more complex than necessary and difficult to adapt to special needs. The seeming simplification is actually a complication when applied to real world problems. Universities should teach as a standard the multidimensional Newton Raphson iteration technique which allows writing gas turbine cycle codes with nearly no restriction to the methods of formulating the laws of physics. The consequence of simplified mathematics is often an off-design simulation which does not employ compressor and turbine maps. Such a methodology yields accurate values for thermal efficiency respectively specific fuel consumption only within a narrow range of operating conditions; the accuracy of the results is not sufficient for real world applications. Of course also in programs for industrial use the reality is modeled with many compromises. Some simplifications which have not so obvious consequences are discussed. For example, there is an influence of the speed-flow characteristics in the booster map on its operating line if an often used type of fan performance representation is employed. Another example is that an oversimplified description of what happens in the compressor interduct can lead to wrong conclusions when the effects of inlet flow distortion on the stability of compressors in series are sought.
A Novel Free-Cooling Scheme for Combustion Turbine Inlet Air Cooling
Authors: Zamzam Montaser M. , Al-Amiri Abdalla M.
Published: March 2009

Free-cooling is a well-known concept in the HVAC industry in which the cold water produced by cooling tower is used directly to satisfy the requirement of the cooling load without assistance by the chiller, this concept, however, is not reported in the turbine inlet air cooling applications. Free-cooling works well as long as the ambient wet bulb temperature WBT is sufficiently low to produce cold water at the required temperature but once WBT reaches its threshold value hence free-cooling mode is ceased and the chiller kicks off working under its normal mode of operation i.e. free-cooling is either enabled or disabled. The proposed system in this paper provides in addition to the above modes of operation a novel mode that utilizes the cooling tower as primary source of cooling simultaneously with the chiller which serves as a secondary source at elevated WBT. This new feature significantly reduces the yearly operating hours of the chiller and possibly its size depending on the desired inlet air temperature, actual weather conditions and design WBT. Chiller size can vary between 0-100 percent as compared to a similar classical chiller system with significant reduction in the operating hours. The proposed system basically consists of chiller, cooling tower, cooling coils, interconnecting piping and controls. The arrangement of the system equipments changes with the operation modes in two configurations; dual water circulation loops and single water circulation loop. In the dual loops configurations the system has two separate loops such that the evaporator and the cooling coils are tied in one loop while the cooling tower and condenser in the other loop whereas in the single loop configuration all equipments are connected in series in one water circulation loop. This paper presents the major equipments and characteristics of the novel chiller scheme. In addition, the study outlines the potential reduction in the chiller load, size and operating hours under a generalized weather envelope. The paper in general portrays the feasibility of using the proposed cooling scheme for turbine inlet air cooling.
Gas Turbine With Ceramic and Metal Components
Authors: Iki Norihiko , Inoue Takahiro , Matsunuma Takayuki , Yoshida Hiro , Sodeoka Satoshi , Suzuki Masato
Published: March 2009

To obtain a micro gas turbine with high turbine inlet temperature and efficiency, a series of running tests has been carried out. J-850 jet engine (Sophia Precision Co., Ltd.) was chosen as a base line machine. The turbine nozzle and the rotor are replaced to ceramic type. The observed problems occurring during the running test taught us various measures to improve heat tolerance of the engine. Especially, the ceramic nozzle vanes can be installed on a metal disk very simply. The disk structure enables us to replace blades with various shape and attack angles. We tried to operate several sets of ceramic components and metal components, such as a set of a ceramic turbine nozzle and an Inconel rotor, etc.
Experimental Investigation of the Flow in a Forward Swept Transonic Compressor Rotor at Stall Inception
Authors: Bergner Jo¨rg , Schiffer Heinz-Peter
Published: March 2009

Three-dimensional laser-2-focus measurements complemented by measurements of the instantaneous static wall pressure in the casing above the rotor are used to investigate short length-scale rotating stall inception in an axial transonic compressor rotor. The data was collected at the Darmstadt Transonic Compressor using the forward swept “Rotor-3”. Detailed analysis of the experimental data reveals that in this configuration with pronounced forward sweep stall is not directly caused by the blockage created by the shock vortex interaction. Due to the reduced aerodynamic loading, the tip clearance vortex passes the shock without significant deceleration but shows some great fluctuation in terms of vortex strength. As the compressor is throttled to near stall, the tip clearance vortex eventually reaches the leading edge of the adjacent blade. It can be suggested that as an result, spill forward and so-called “self-induced vortex-oscillation” occurs. A phase-lock of both of these phenomena might be the trigger for a spike-type disturbance of the flow-field. The investigation underpins the great importance of the unsteady flow phenomena at near stall. For a thorough understanding of the flow features at the stability limit of a compressor, which is the basis of any effort to increase the operation range, special attention has to be paid to the unsteadiness of the flow in both experimental and numerical work. To study the mechanism of stall inception it might even be necessary to analyze the flow field around the whole annulus, as there appears to be significant interaction of the flow between neighboring passages.
Experimental and CFD Study of an Exhaust Ejector With Round Entraining Diffuser
Authors: Chen Qi , Birk A. M.
Published: March 2009

This paper presents experimental and CFD data for the performance of a round straight air-air ejector with a 4-ring entraining diffuser. The effects of inlet swirl angle and flow temperature on the ejector pumping, back pressure, wall pressure distribution, and diffuser pressure recovery were studied. The ejector experiments were carried out on a hot flow wind tunnel that can provide primary flow rates up to 2.2 kg/s at ambient temperature and 1.8 kg/s at 500°C. Velocity, pressure and temperature measurements were taken in the annulus upstream of the primary nozzle, on the mixing tube and diffuser walls, and at the mixing tube and diffuser ring exits. A parallel computational study was conducted along with the experimental study. A commercial CFD solver, Fluent 6.216, was used for simulation. The Realizable k-ε turbulence model and non-equilibrium wall functions were implemented on the cases. The CFD inlet boundary conditions were chosen to replicate the experimental configuration.
Performance Assessment of Turbocharged PEM Fuel Cell Systems for Civil Aircraft Onboard Power Production
Authors: Campanari Stefano , Manzolini Giampaolo , Beretti Andrea , Wollrab Uwe
Published: March 2009

In recent years, civil aircraft projects are showing a continuous increase in the demand of onboard electrical power, both for the partial substitution of hydraulic or pneumatic controls and drives with electrical ones, and for the consumption of new auxiliary systems developed in response to flight safety and environmental control issues. Aiming to generate on-board power with low emissions and better efficiency, several manufacturers and research groups are considering the possibility to produce a relevant fraction of the electrical power required by the aircraft by a fuel cell system. The first step would be to replace the conventional auxiliary power unit (APU, based on a small gas turbine) with a Polymer Membrane fuel cell type (PEM), which today is favored with respect to other fuel cell types thanks to its higher power density and faster start-up. The PEM fuel cell can be fed with an hydrogen rich gas coming from a fuel reformer, operating with the same jet fuel used by the aircraft, or relying on a dedicated hydrogen storage onboard. The cell requires also an air compression unit, where the temperature, pressure and humidity of the air stream feeding the PEM unit during land and in-flight operation strongly influence the performance and the physical integrity of the fuel cell. In this work we consider different system architectures, where the air compression system may exploit an electrically driven compressor or a turbocharger unit. The compressor type and the system pressure level are optimized according to a fuel cell simulation model which calculates the cell voltage and efficiency as a function of temperature and pressure, calibrated over the performances of real PEM cell components. The system performances are discussed under different operating conditions, covering ground operation, intermediate and high altitude cruise conditions. The optimized configuration is selected, presenting energy balances and a complete thermodynamic analysis.
A Flexible Fuel Semi-Closed Combined Cycle for Power, Refrigeration and Water
Authors: Lear W. E. , Crittenden J. F. , Khan J. R. , Sherif S. A.
Published: March 2009

The High Pressure Regenerative Turbine Engine (HPRTE) has been investigated since the mid 1990s as the distributed energy system, among other applications, for civilian or military use. Previous literature describing its modeling and experimental demonstration have indicated several benefits, especially when combined with a Vapor Absorption Refrigeration System (VARS) in a novel way. The benefits includes increased efficiency, high part power efficiency, small lapse rate, compactness, low emissions, low air exhaust flows (which decrease filtration and ducting) and condensation of fresh water. The current paper describes the preliminary design and modeling of a modified version of this system applied to distributed energy, especially in regions which are prone to major grid interruptions due to hurricanes, under-capacity, or terrorism. In such cases, the distributed energy system should support most or all services within an isolated “island” so that the influence of the power outage is limited in scope. In addition, the paper will describe the possible production of ice, under emergency conditions, using the fresh condensate plus other water sources.
Low Pressure Compression System Effects on Fan Assembly Forced Response
Authors: Sayma Abdulnaser I. , Vahdti Mehdi , Imregun Mehmet , Marshal John
Published: March 2009

This paper describes a numerical modelling methodology for fan blade forced response calculations by considering the low-pressure compression system (LPCS) as a whole in order to include flow distortions caused by the asymmetric flight intake upstream, and the pylon downstream. Emphasis also is placed on blade mistuning or mis-placement which may be due to inherent manufacturing and assembly tolerances, or to small inservice displacements. Several levels of geometric complexity were used in the analysis, ranging from an isolated fan bladerow to a complete LPCS of a large-diameter aero-engine, consisting of the intake duct, the fan assembly, the outflow guide vanes, the pylon and a downstream nozzle. The aerodynamic model was coupled to a finite element model of the fan assembly for computing the blade vibration levels. The study revealed two major findings. The first is the unsteady forcing under one engine-order (1EO) excitation is found to be linked to the mean shock position on the fan blade, the highest forcing occurring when the shock is just swallowed since this position is particularly sensitive to pressure fluctuations. The second finding is that the 1EO fan assembly forcing resulting from an asymmetric intake and the pylon are of comparable magnitude but their relative phasing is the key parameter in determining the overall fan forced response levels.
Reduction of Rotor Tip Leakage Through Cooling Injection From Casing in a High-Work Turbine: Computational Investigation Using a Feature-Based Jet Model
Authors: Mischo Bob , Burdet Andre´ , Behr Thomas , Abhari Reza S.
Published: March 2009

This paper presents a study of the impact of casing injection on the blade tip leakage. The investigation includes both the flow physics and the consequences on overall performance. With the use of three-dimensional CFD together with a feature-based injection model, the flow structure related to the injection is revealed inside the tip region. The effects on performance of different injection configurations are compared to a baseline configuration without injection. The predictions are validated with an extensive experimental database made available in a companion paper (GT2007-27269). A detailed investigation of flow physics changes in the tip region is presented for one injection configuration. It appears that the tip leakage vortex is shifted axially downward when injecting from the casing. Special attention is laid on the unsteady flow field that establishes due to the relative motion of the rotor and the stationary injection holes on the casing. Both time averaged data and instantaneous snapshots are used to reveal that the flow in the tip gap region, especially near the pressure side lip, appears to get a fluctuating character. It turns out that the tip gap mass flow is reduced by about 11% relatively to the base line when injecting from the casing. In addition, it fluctuates by as much as 1.4% over its mean value. As a corollary a fluctuation of the total injected fluid mass flow is found, of an order of 2.2%. A flow model synthesizing the observed phenomena is presented.
A Novel Multi-Functional Energy System (MES) for CO2 Removal With Zero Energy Penalty
Authors: Jin Hongguang , Han Wei , Gao Lin
Published: March 2009

In this paper, a novel multi-functional energy system (MES) is proposed, in which hydrogen and electricity are co-generated and about 90% of CO2 is removed. By integrating the methane/steam reforming reaction and combustion of coal, the natural gas and coal are utilized synthetically, in which coal is burned to provide high-temperature thermal energy to the methane/steam reforming reaction. After that, the resulting syngas enters a PSA unit to separate about 70% of hydrogen and the concentration of carbon dioxide is increased significantly from nearly 20% to 43% in the PSA tail gas. As a result, the overall efficiency of the new system is 63.2%. Compared to a conventional NG based hydrogen plant and a coal firing steam power plant without CO2 removal (the overall efficiency of the two system is 63.0%), the energy penalty for CO2 removal in the new system is nearly totally avoided. Based on the graphical exergy analysis, we disclose that the integration of synthetic utilization of fossil fuel (natural gas and coal) and CO2 removal process plays a significant role in zero energy penalty for CO2 removal and its liquefaction in the MES system. The result obtained here provides a new approach for CO2 removal with zero or low thermal efficiency reduction (energy penalty) in an energy system.