bluuebunny/crossref_metadata_2025 huggingface dataset:
Fault Detection and Identification in an IM270 Gas Turbine Using Measurements for Engine Control
Authors: Kurosaki Masahiro , Morioka Tadashi , Ebina Kosuke , Maruyama Masatoshi , Yasuda Tomoshige , Endoh Makoto
Published: February 2009

A unique fault detection and identification algorithm using measurements for engine control use is presented. The algorithm detects an engine fault and identifies the associated component, using a gas path analysis technique with a detailed nonlinear engine model. The algorithm is intended to detect step-like changes in component performance rather than gradual change of all components. Since simultaneous multiple faults are unlikely, a single component fault is assumed, which reduces the number of unknown parameters to less than two. By setting the number of adjustable parameters to that of the available measurements, the parameters are computed using an engine model. After computing all of the six possible combinations of adjustable parameters, the average magnitude of the parameter deviation vectors is used to detect an engine fault. Component performance deviation (efficiency and flow rate) is represented by a magnitude and a phase. The phase is selected to minimize the error of matrices consisting of normalized adjustable parameter deviation vectors. Then the magnitude is computed by the average magnitude ratio of the vectors. Since the algorithm is simple, it is easily applied to newly developed engines. A fault detection and identification program was specifically developed for IM270 engine, a single shaft gas turbine with 2MW output capacity. By utilizing operational data obtained at a remote monitoring center, the algorithm was able to quantitatively identify the compressor and the turbine performance deviation. Although the algorithm correctly identifies the turbine as the faulty component, there remains some ambiguity. Analysis of linear dependency of the measurement deviation vectors shows that identification capability varies with phase. There are several phases where identification is impossible in the current IM270 sensor system.
On-Line Performance Monitoring and Engine Diagnostic Using Robust Kalman Filtering Techniques
Authors: Dewallef Pierre , Le´onard Olivier
Published: February 2009

In this contribution, an on-line engine performance monitoring is carried out through an engine health parameter estimation based on several gas path measurements. This health parameter estimation makes use of the analytical redundancy of an engine model and therefore implies the knowledge of the engine state. As the latter is a priori not known the second task is therefore an engine state variable estimation. State variables here designate working conditions such as inlet temperature, pressure, Mach number, rotational speeds, … Estimation of the state variables constitutes a general application of the Extended Kalman Filter theory, while the health parameter estimation is a classical recurrent regression problem. Recent advances in stochastic methods [1] show that both problems can be solved by two Kalman filters working jointly. Such filters are usually named Dual Kalman Filters. The present contribution aims at using a dual Kalman filter modified to provide robustness. This procedure should be able to cope with as much as 20 to 30% of faulty data. The resulting online method is applied to a turbofan model developed in the frame of the OBIDICOTE 1 project. Several tests are carried out to check the performance monitoring capability and the robustness that can be achieved.
Evaluation of Operational Performance of Gas Turbine Cogeneration Plants Using an Optimization Tool: OPS-Operation
Authors: Yokoyama Ryohei , Ito Koichi
Published: February 2009

To attain the highest performance of gas turbine cogeneration plants, it is necessary to rationally select the numbers and capacities of gas turbines and auxiliary equipment in consideration of their operational strategies corresponding to energy demands which change with season and time. It is also important to rationally select the options such as the variable heat to power by the steam injection or combined cycle, and the inlet air cooling by the ice storage combined with electric compression refrigeration or steam absorption refrigeration. The evaluation of the effects of these alternatives on the performance is an important work for designers. However, it takes much time to conduct the work thoroughly. The authors have developed an optimization tool named “OPS-Operation” to assess the operational strategies for given configurations and specifications of energy supply plants. This tool has a user-friendly interface for the functions of data registration, graphical flowsheet editing, automatic programming and optimization calculation, and graphical representation of results. In this paper, the effects of the aforementioned alternatives on the operational performance of gas turbine cogeneration plants are evaluated using the optimization tool in terms of many criteria including operational cost, energy consumption, and CO2 emission. It is demonstrated that the tool is very effective to evaluate the performance rationally, flexibly, and easily.
Assessment of Traditional and Flamelets Models for Micro Turbine Combustion Chamber Optimisation
Authors: Croce Giulio , Mori Giulio , Anisimov Viatcheslav V. , Parente Joa˜o
Published: February 2009

Different approaches for numerical simulation of premixed combustion are considered, in order to assess their usefulness as design tools for micro gas turbine systems. In particular, a flamelet concept routine by N. Peters has been developed taking into account both mixture fraction Z and G function as scalar flame locators, thus allowing computation of complex fully or partial premixed flame structure. The model can be used also in the thin reaction regime. Scalar transport equations for G, Z and their variance are added to the standard Navier Stokes and turbulence set of equation, in order to track the flame position. However, no chemical term appears explicitly in such equations, since the chemical effects are taken into account via pre-computed locally one-dimensional flamelet solutions. Here, the deep interaction between chemical and turbulence has been introduced through flamelets library built in non equilibrium conditions using CHEMKIN modules. The results of this model are compared the data obtained with a standard EBU model and different reaction mechanisms. Models validation has been carried out through experimental data coming from Aachen University for an axisymmetric Bunsen flame; finally, the code was applied to the analysis of a newly designed micro gas turbine combustor.
Application of Low Solidity Vaned Diffusers to Prevent Rotating Stall in Centrifugal Compressors: Experimental Investigation
Authors: Cellai A. , De Lucia M. , Ferrara G. , Ferrari L. , Mengoni C. P. , Baldassarre L.
Published: February 2009

Rotating stall is a key problem in centrifugal compressors especially for high-pressure applications. Among the several solutions proposed to prevent this problem, low solidity vaned diffusers (LSDs) have been successfully applied. The aim of this research is to find an optimized LSD configuration in terms of stall inception and performance for the tested compressor. The influence of the vane leading and trailing edge radii, maintaining the same solidity and null deflection were investigated. The geometrical parameters of tested configurations were methodically chosen in order to achieve a design of experiment (DOE) analysis. In view of the above, a series of tests on five low solidity vaned diffuser configurations were carried out. Tests allowed determination of 2 different LSDs that showed the best behavior in terms of working range and performance. These LSDs were then compared with the standard and the reduced-width vaneless diffuser to better understand the best solution to the stall problem.
Experimental Investigation and Characterization of the Rotating Stall in a High Pressure Centrifugal Compressor: Part III — Influence of Diffuser Geometry on Stall Inception and Performance (2nd Impeller Tested)
Authors: Cellai A. , Ferrara G. , Ferrari L. , Mengoni C. P. , Baldassarre L.
Published: February 2009

Vaneless diffuser rotating stall is a serious problem for centrifugal compressors since it limits their working range. In particular the last stage seems to be the most critical from this point of view. In the literature some good correlations can be found for predicting stall inception but they hardly cover the case of last stage configuration, especially for very low blade-outlet-width-to-impeller-radius-ratio impellers typically used in high-pressure applications. Extensive research has been planned to define diffuser stall limits for this family of stages: three impellers characterized by different blade-outlet-width-to-impeller-radius-ratios are tested. The basic configuration comprises a 1:1 geometrical scale stage with a return channel upstream, a 2D impeller with a vaneless diffuser and a volute with a constant cross sectional area downstream. Several diffuser types with different widths, pinch shapes and diffusion ratios were tested. The results for the first impeller have already been reported in part I and II. In this part the effects of the above mentioned geometric parameter changes on stage stability and performance are presented with respect to the second impeller.
Performance of Strongly Bowed Stators in a 4-Stage High Speed Compressor
Authors: Fischer Axel , Riess Walter , Seume Joerg R.
Published: February 2009

The FVV-sponsored-Project “Bow Blading” (c.f. acknowledgments) at the Turbomachinery Laboratory of the University of Hannover addresses the effect of strongly bowed stator vanes on the flow field in an 4-stage high speed axial compressor with controlled diffusion airfoil (CDA) blading. The compressor is equipped with more strongly bowed vanes than have previously been reported in the literature. The performance map of the present compressor is being investigated experimentally and numerically. The results show that the pressure ratio and the efficiency at the design point and at the choke limit are reduced by the increase in friction losses on the surface of the bowed vanes, whose surface area is greater than that of the reference (CDA) vanes. The mass flow at the choke limit decreases for the same reason. Because of the change in the radial distribution of axial velocity, pressure rise shifts from stage 3 to stage 4 between the choke limit and maximum pressure ratio. Beyond the point of maximum pressure ratio, this effect is not distinguishable from the reduction of separation by the bow of the vanes. Experimental results show that in cases of high aerodynamic loading, i.e. between maximum pressure ratio and the stall limit, separation is reduced in the bowed stator vanes so that the stagnation pressure ratio and efficiency are increased by the change to bowed stators. It is shown that the reduction of separation with bowed vanes leads to a increase of static pressure rise towards lower mass flow so that the present bow bladed compressor achieves higher static pressure ratios at the stall limit.
Two-Dimensional Flashback Simulation in Strongly Swirling Flows
Authors: Kiesewetter Frank , Hirsch Christoph , Fritz Jassin , Kro¨ner Martin , Sattelmayer Thomas
Published: February 2009

In lean premixed swirl stabilized gas turbine combustors a common burner design goal is to obtain lowest NOx-emissions by increasing the mixing length without deterioration of the burner reliability. In these burners flame flashback from the combustion zone into the mixing zone leading to thermal overload and subsequent rapid destruction of the burners must be avoided under all operating conditions. In previous experimental studies (Fritz et al. 2001, Kro¨ner et al. 2002) a new phenomenon, the combustion induced vortex breakdown (CIVB), has been identified as the predominant cause for flashback in swirl stabilized burners. The current work aims at providing a theoretical analysis of this phenomenon as well as tools for the investigation of arbitrary geometries on the basis of a URANS-CFD model. A two-dimensional axialsymmetric model has been developed, which allows to include the computation of the upstream flow path as well as the swirl generator. Following this strategy, the specification of predetermined velocities at the swirler inlet which become unphysical during flashback can be avoided. As the benefit, a much better simulation of the transient flame propagation process is obtained. Comparisons of the numerical results obtained so far with the experiments from the previous studies reveal that the two-dimensional model accurately captures the essential features of the process although the reacting flow exhibits a three-dimensional structure during flashback in reality.
Experimental Investigation of the Heat Transfer in a Rib-Roughened Leading-Edge Cooling Channel
Authors: Larsson Thomas , Hjalmarsson Christer
Published: February 2009

To investigate how different rib heights influence the heat transfer in a leading edge cooling channel, a plexiglas model was built. The model was heated using foil-heaters and the temperature was measured with thermocouples and an infrared camera. Wall static pressures were measured to get the pressure drop. The rib heights and Reynolds number were varied while the pitch between the ribs was constant. A smooth pipe was also investigated to get a reference for calculation of the enhancement factor. The investigation outcome was: • the effect of rib height on the heat transfer in the noncircular pipe becomes weaker with increased Reynolds number. • increasing the rib height by 40% cause an increase of pressure drop by a factor of 2. • the test without ribs, “smooth pipe”, resulted in a correlation for Nusselt number, Nu = 0.0232× Re0.8 for developed turbulent flows. The tests described above helped to optimize the internal geometry of the blade leading edge and, to some extent, to expand the available heat transfer database.
Numerical Investigation of Wake-Shock Interactions and Clocking in a Transonic HP Turbine
Authors: Marconcini Michele , Pacciani Roberto
Published: February 2009

A quasi-three-dimensional, blade-to-blade, time-accurate, viscous solver was used for the clocking optimization of a modern transonic heavy-duty, two stage gas turbine. Both stators and rotors operate in a transonic regime with fish-tail shock systems at the blade row exit. These shock systems interact with both stator and rotor wakes. A sensible reduction in the strength of shock waves was observed due to the upstream blade row wake passing. Such wake-shock interactions occur in the inter-blade gap, around locations which are fixed in the frame of reference of the downstream blade-row. The exploitation of such an effect to optimize the axial/circumferential position of blade rows is still compatible with the axial gap values commonly used for these kinds of stages. The results of the clocking investigation will be presented and discussed in terms of unsteady blade loading and efficiency variations.
Statistical Methodologies for Reliability Assessment of Gas Turbine Measurements
Authors: Pinelli M. , Venturini M. , Burgio M.
Published: February 2009

All measurements, although taken as accurately as possible, are subjected to uncertainty. So the analysis of errors and uncertainty is crucial in all applications since such errors need to be estimated and, when possible, reduced. In particular, when gas turbine mathematical models based on the processing of field measurements (such as the Gas Path Analysis models) are used, the evaluation of measurement reliability is a key point. In fact, it has been demonstrated that these kinds of techniques are sensitive to measurement errors: thus, tools for field data processing to evaluate the presence of the so-called outliers are advisable. In this paper, some statistical methodologies for the assessment of the reliability of the measurements taken on a gas turbine are presented. The methodologies, taken from literature and used for historical measurements, are discussed. Moreover, a new methodology, based on a modified t-Student distribution, is proposed.
Study of Flame Transfer Function With Three Dimensional Calculations
Authors: Zhu M. , Dowling A. P. , Bray K. N. C.
Published: February 2009

Combustors with fuel-spray atomisers are particularly susceptible to a low-frequency oscillation at idle and sub-idle conditions. For aero-engine combustors, the frequency of this oscillation is typically in the range 70–120Hz and is commonly called ‘rumble’. The mechanism involves interaction between the plenum around the burner and the combustion chamber. In our previous work, the CFD calculation has been conducted in an idealised 2D axisymmetric annular combustor to calculate unsteady combustion flow at idle conditions. In this work, in order to investigate the effects of asymmetrical geometry and flow distributions on the transfer functions of flame and shape factors, the CFD code has been extended to fully three-dimensional geometries. The results are compared with those from 2D calculations. Though the differences of the distribution local flow properties are evident, the integrated results for the 3D flow are broadly similar to those obtained in 2D. One substantial difference arises due to the more accurate modelling of the downstream contraction near the combustor exit, which is treated as a smooth contraction in our 3D calculations and as an abrupt change in the simplified 2D geometry. The gradual downstream contraction not only accelerates the fluid near the combustor exit but also unifies the flow properties. As the consequence, we can see that, near the exit, the phase of the flame transfer function increases rapidly, and the shape factors tend toward unity. This work is a further development of our systematic investigation into the ‘rumble’ phenomenon, and gives encouragement that much of the essential physics can be captured in a quasi-one-dimensional model.
Robust Design of the Coaxial Jet Cluster Nozzle Burner for DME (Dimethyl Ether) Fuel
Authors: Kobayashi Nariyoshi , Inoue Hiroshi , Koizumi Hiromi , Watanabe Tomoko
Published: February 2009

DME (dimethyl ether) is currently attracting worldwide attention due to its potential as a clean fuel. But, DME has a low auto-ignition temperature and a higher combustion velocity compared with other power generation gas fuels (LNG, LPG). Therefore, in the case of lean-premixed design to limit the formation of NOx in the burning zone, a shorter premixing length than that for natural gas is required. In this research, the main objective is the development of a low NOx emission and high efficiency combustion system that is suited to quick and uniform mixing between the air and gaseous DME. A coaxial jet cluster nozzle burner configuration is proposed as the low NOx combustion system, and 18 different configuration burners are designed and tested by the robust design. Based on the analysis of test results, the optimized configuration of a coaxial jet nozzle burner is selected.
Analysis of Tangential-Against-Rotation Injection Lomakin Bearings
Authors: Arghir Mihai , He´le`ne Mathieu , Frene Jean
Published: February 2009

This work presents a thin film flow model for analyzing the static and dynamic characteristics of centered, eccentric or misaligned tangential-against-rotation injection Lomakin bearings. The Lomakin bearing is a recent device intended for use in modern turbomachinery and having characteristics similar to hybrid bearings. It can be described as an ensemble of two opposing straight annular seals separated by a circumferential feeding groove. The fluid is supplied to the groove via orifice restrictors. Their tangential inclination generates an against-rotation circumferential flow in the groove that further penetrates into the thin film. This effect, known from annular seals as the pre-rotation speed, improves the dynamic characteristics of the bearing. The zero and first order analyses are carried out by recognizing the crucial importance of taking into account the interaction between the flow in the thin film lands, the circumferential groove and the supply orifices. Due to the high Reynolds number regime, the land flow is governed by the two dimensional thin film inertia equations (the “bulk flow” model). A one-dimensional circumferential flow dominated by inertia forces is assumed to take place in the groove and is described by an appropriate bulk flow equation. The flows in the supply orifices, the groove and the thin film lands are linked together by the same mass flow rate balance algorithm as used for hydrostatic and hybrid bearings analysis. The algorithm is extended to Lomakin bearings by considering the groove areas surrounding each orifice as a row of intercommunicating feeding pockets. This approach enables the analysis of centered, eccentric or misaligned Lomakin bearings. Comparisons with water-lubricated test results are used to validate the present model. For the zero eccentricity case a good agreement is obtained for the cross-coupled stiffness and for the whirl frequency ratio. A parametric study shows the variation of the bearing characteristics with increasing static eccentricity or misalignment. The limits of the developed thin film model are further estimated by comparing the static and zero eccentricity thin film results with a full Navier Stokes calculation.
CO2-Free Power Generation: A Study of Three Conceptually Different Plant Layouts
Authors: Mo¨ller Bjo¨rn Fredriksson , Assadi Mohsen , Linder Ulf
Published: February 2009

Ever since the release of the Kyoto protocol the demand for CO2-free processes have been increasing. In this paper three different concepts with no or a very small release of CO2 to the atmosphere are evaluated and compared concerning plant efficiency and investment cost. A novel approach to biomass gasification is proposed to provide fuel for a combined gas turbine cycle, where the biomass is considered to be a renewable fuel with zero impact regarding CO2 in the exhaust gases. The gasification concept used is a Dual Pressurised Fluidised Bed Gasifier (DPFBG) system, using steam and recycled product gas as fluidising agent in the gasification reactor. In the separate combustion reactor air is used as fluidising agent. The second cycle is a hybrid fuelled Humid Air Turbine (HAT) cycle with post-combustion CO2-separation. Steam used for regenerating the amines in the separation plant is produced using a biomass boiler, and natural gas is used as fuel for the humid air turbine. With this fuel mix the net release of CO2 can even be less than zero if the exhaust gas from the steam generator is mixed and cleaned together with the main exhaust gas flow. The third cycle proposed is a combined cycle with postcombustion CO2-separation and the steam generation for the CO2-separation integrated in the bottoming steam cycle. All power cycles have been modelled in IPSEpro™, a heat and mass balance software, using advanced component models developed by the authors. An equilibrium model is employed both for the gasification and the separation of CO2 from exhaust gases. All three power cycles show efficiencies around 45%, which is high for a biomass gasification cycle. The HAT and the combined cycle show efficiency drops of about 8 percentage points, due to the post-combustion treatment of exhaust gases.
Numerical Investigation of Three-Dimensional Clocking Effects in a Low Pressure Turbine
Authors: Arnone Andrea , Marconcini Michele , Del Greco Alberto Scotti , Spano Ennio
Published: February 2009

One and a half stages of a low pressure turbine were investigated using a three-dimensional, time-accurate, viscous solver. Unsteady analyses were carried out by varying the circumferential relative position of consecutive vanes to study the effects of clocking on performance. Assuming that efficiency improvements by clocking are linked to the wake tangential position with respect to the successive blade, a certain circumferential shift in this position can be observed along the blade height due to blade twist and non-radial stacking, giving different contributions. In order to assess this phenomenon, results from three-dimensional computations were compared with a quasi three-dimensional analysis at mid-span. The effects of clocking on wake interaction mechanisms and unsteady blade loadings are presented and discussed.
Rainbow Test of Laser Reconditioned Frame 6 Buckets
Authors: van Beek M. C. , Hendriks M. G. H. M. , Wilms D. C. M.
Published: February 2009

The procurement and reconditioning of turbine buckets and vanes drive the maintenance cost for gas turbines. The use of advanced repair methods like laser welding can help to reduce these costs. The main advantage of the laser welding process is that high-grade filler metals can be used with the possibility to extend current repair-limits. Before the laser welding process can be applied for industrial repairs the method has to be extensively tested for attained mechanical properties and for the performance during exposure in an actual turbine. This paper discusses the first rainbow test as performed on a frame 6 gas turbine of the Bergum power plant in the Netherlands. For a set of first stage buckets with 12139 operating hours (OH) 6 buckets were reconditioned using conventional TIG repair and 6 buckets using the laser-powder welding process. In both cases In 625 was used as the filler metal. The remaining buckets were not reconditioned. Monitoring of the performance of the reconditioned buckets is done using pyrometry and by boroscopic inspections. The reconditioned buckets are about 17°C cooler than the others. Moreover, it is found that the buckets repaired using laser welding have lower tip temperatures compared to the buckets reconditioned using conventional TIG welding. The overall lower temperature is partly caused by the difference in colour between the reconditioned and non-reconditioned buckets, which affects the emissivity. This difference was found still present during a boroscopic inspection 1776 OH after the overhaul. The other possible factors affecting the temperature difference are identified but are not yet fully understood.
Variable Fuel Placement Injector Development
Authors: Brundish K. D. , Miller M. N. , Morgan L. C. , Wheatley A. J.
Published: February 2009

This paper presents the progress made on the development of a dual spray, direct injection airblast fuel nozzle capable of variable fuel placement. It is anticipated that by varying the fuel placement within the confines of a combustion chamber it will be possible to control localised zonal ‘Fuel Air Ratio’ and thus extend both stability and emissions performance in respect of engine power range. The extension of combustion stability is particularly desirable to high pressure, temperature and turndown ratio aero engines where the ratio between maximum and flight idle fuel flow is extreme. Target performance data for the design has been derived from anticipated future engine cycles. A number of initial concepts were examined and recent development work has focused on the most successful design to date. Combustor testing has been performed at both atmospheric and high pressure. The combustor utilised was a single sector tubular combustor with combustor volume and airflow distributions representative of the cycle for which the fuel injector was designed. Two fuel injector configurations were examined, having different design flow structures. Combustion stability testing was performed with air inlet conditions of atmospheric pressure and 293K. Stability and ignition data were derived over a range of combustor pressure drops. Fuel injector AFRs of over 100:1 were achieved. An ignition loop was also derived although optimisation studies were not performed at this stage. High pressure emissions evaluation was also performed up to 13 Bar. Idle and scaled climb-out power conditions were tested, with a range of fuel scheduling between the pilot and main. Idle efficiency of over 99.5% was achieved. Low emissions performance was also achieved with less than 10 EINOx at climb out power settings. Future work will include testing at up to 40 Bar pressure to establish actual full power performance in addition to further development work on stability and ignition performance.
Adaptive Closed-Loop Control on an Atmospheric Gaseous Lean-Premixed Combustor
Authors: Riley A. J. , Park S. , Dowling A. P. , Evesque S. , Annaswamy A. M.
Published: February 2009

Active control of pressure oscillations has been successfully applied to a lean premixed prevapourised (LPP) combustion rig operating at atmospheric conditions. The design of the rig is based on the primary stage of the Rolls-Royce RB211-DLE industrial gas turbine. Control was achieved by modulating the fuel flow rate in response to a measured pressure signal. The feedback control is an adaptive, model-based self-tuning regulator (STR), which only requires the total time delay between actuation and response to achieve control. The STR algorithm achieves a reduction of up to 30 dB on the primary instability frequency. This performance was an improvement of 5–15 dB over an empirical control strategy (simple time-delay controller) specifically tuned to the same operating point. Initial robustness studies have shown that the STR retains control for a 20% change in frequency and a 23% change in air mass flow rate.
Experimental and Numerical Investigation of the Impact of Swirl on the Performance of Industrial Gas Turbines Exhaust Diffusers
Authors: Vassiliev V. , Irmisch S. , Claridge M. , Richardson D. P.
Published: February 2009

In order to investigate the effect of inlet conditions on the performance of an axial strutted annular exhaust diffuser, as used in heavy duty gas turbines, a scaled test-rig was built which allows the systematic variations of inlet conditions like inlet swirl, Mach number and turbulence level. This rig, which is of modular design, is used for the analysis of the flow-structures in typical GT-exhaust configurations and provides the performance data used in the diffuser design process. The present work shows the influence of inlet swirl and Mach number on the performance of a specific diffuser configuration. The first strut was designed for a certain flow angle distribution (so-called design conditions), and the measurements have been done for a range of inflow parameters including design and off-design conditions. The measurements allowed to reveal the impact of 3D effects on the diffuser characteristic. Comparison of measurements with correlations available from literature (annular diffuser configurations) show that the application of the latter is of limited use for the design of real GT diffusers, because standard correlations do not account for inlet swirl / struts interaction. The experimental data has been used to validate the numerical procedure developed by the authors for the analysis of axial GT exhaust diffusers. The results of computations are in reasonable agreement with measurements.
Role of Shock and Boundary Layer Separation on Unsteady Aerodynamic Characteristics of Oscillating Transonic Cascade
Authors: Aotsuka Mizuho , Watanabe Toshinori , Machina Yasuo
Published: February 2009

The unsteady aerodynamic characteristics of an oscillating compressor cascade composed of Double-Circular-Arc airfoil blades were both experimentally and numerically studied under transonic flow conditions. The study aimed at clarifying the role of shock waves and boundary layer separation due to the shock boundary layer interaction on the vibration characteristics of the blades. The measurement of the unsteady aerodynamic moment on the blades was conducted in a transonic linear cascade tunnel using an influence coefficient method. The cascade was composed of seven DCA blades, the central one of which was an oscillating blade in a pitching mode. The unsteady moment was measured on the central blade as well as the two neighboring blades. The behavior of the shock waves was visualized through a schlieren technique. A quasi-three dimensional Navier-Stokes code was developed for the present numerical simulation of the unsteady flow fields around the oscillating blades. A k-ε turbulence model was utilized to adequately simulate the flow separation phenomena caused by the shock-boundary layer interaction. The experimental and numerical results complemented each other and enabled a detailed understanding of the unsteady aerodynamic behavior of the cascade. It was found that the surface pressure fluctuations induced by the shock oscillation were the governing factor for the unsteady aerodynamic moment acting on the blades. Such pressure fluctuations were primarily induced by the movement of impingement point of the shock on the blade surface. During the shock oscillation the separated region caused by the shock boundary layer interaction also oscillated along the blade surface, and induced additional pressure fluctuations. The shock oscillation and the movement of the separated region were found to play the principal role in the unsteady aerodynamic and vibration characteristics of the transonic compressor cascade.
Gas Turbine Technology and Cycle Selection for Combined Cycle Power Plants: Decision Criteria, Economic Aspects and Risk Mitigation
Authors: Fetescu Mircea
Published: February 2009

Gas Turbine technology and cycle selection have a major impact on the economic performance of Combined Cycle Power Plants projects. The main objective of this paper is to investigate decision criteria and their relative importance in the selection of gas turbine technology and cycle configuration. Relevant factors influencing the choice of technology are investigated and their impacts on the economic performance of the Combined Cycle Power Plant are quantified. Sensitivities on relevant parameters are provided. Due to the fact that uncertainties and risks associated with the Combined Cycle Power Plants are major decision criteria, special focus has been placed on risk identification and quantification as well as recommendation for their mitigation. The conclusion of the investigation is that besides the overall accepted and commonly used criteria such as fuel efficiency and specific capital investment, there are other important contributors to the economic performance of a Combined Cycle Plant. The most important are operating and maintenance costs, availability factor, performance degradation and operating mode (utilization factor, load profile, start-up and shutdown frequency).
Numerical 3-D Conjugate Flow and Heat Transfer Investigation of a Transonic Convection-Cooled Thermal Barrier Coated Turbine Guide Vane With Reduced Cooling Fluid Mass Flow
Authors: Bohn Dieter E. , Tu¨mmers Christian
Published: February 2009

The aerodynamics and aerothermics of a transonic convection-cooled turbine guide vane are investigated by application of a conjugate fluid flow and heat transfer solver, CHT-Flow. The code developed at the Institute of Steam and Gas Turbines, Aachen University, does not need any heat transfer data beforehand. Since the numerical results for the uncoated vane showed good agreement with experimental data, numerical investigations are extended for the coated vane. The investigated configuration consists of an APS (Athmospheric Plasma Spray) layer, while the external vane shape is preserved. For the coated configuration a parametric study of the cooling fluid mass flow has been performed with the aim of a smoothed temperature distribution in the blade material. Furthermore, with the help of a simplified thermal stress analysis the influence of the reduced cooling fluid mass flow on the thermal stresses in the blade material will be discussed in detail.
Influence of Open and Closed Shroud Cavities on the Flowfield in a 2-Stage Turbine With Shrouded Blades
Authors: Bohn Dieter E. , Balkowski Ingo , Ma Hongwei , Tu¨mmers Christian , Sell Michael
Published: February 2009

An important goal of the development of turbine bladings is to increase the efficiency for an optimized use of energy resources. This necessitates the most possible insight into the complex flow phenomena in multi-stage turbine bladings. This paper presents a combined numerical and experimental investigation of the flow field in a 2-stage axial turbine with shrouded blades, where the axial gap between the shroud and the endwall is varied between 1mm (closed cavities) and 5 mm (opened cavities). In the experimental setup at the Institute of Steam and Gas Turbines, Aachen University, the turbine is operated at a low pressure ratio of 1.4 with an inlet pressure of 3.2 bar. The rotating speed is adjusted by a water brake, which is integrated into a swing frame running in hydrostatic bearings. The rotor power dissipates in the water brake, which enables a very accurate angular momentum determination. The mass flow is measured through a calibrated nozzle installed upstream of the turbine inlet at an accuracy of better than 1%, from which stage efficiencies can be derived. For both geometric configurations (open and closed shroud cavities), the flow field at both inlet and outlet is measured using 5-hole probes as well as temperature probes at three operating conditions. The test rig is especially designed to investigate the influence of the cavity size. Therefore, the radial gaps between shroud and casing is held near zero in order to prevent an axial flow through the cavities. The experimental results are used as boundary conditions for corresponding numerical multi-stage calculations of the 3D flow through the 2-stage turbine, using the highly accurate steady Navier-Stokes inhouse computer code, CHT-Flow. The flow field measurements and the numerical simulations give deeper insight into some of the cavity-related flow field phenomena. The measurement results as well as the simulations indicate that the stator leading edge has little influence on the inlet flow field. The flow through the shroud cavities has a significant influence on the field and therefore on the machine’s performance.
Homogenization of Material Properties of Transpiration Cooled Multilayer Plates
Authors: Laschet Gottfried M. , Rex Stephan , Bohn Dieter , Moritz Norbert
Published: February 2009

To predict the aerothermal behaviour of transpiration cooled gas turbine components, a multiscale approach based on the homogenization method of periodic material structures is developed. This method allows to calculate effective equivalent thermophysical properties either for each layer or for the multilayer of superalloy, bondcoat and thermal barrier coating. From the 3-D conjugate fluid flow and heat transfer analysis, the stationary state is extracted and transferred to the microscale unit cell discretized by finite elements. Effective permeabilities of different designs of the cooled multilayer are determined and analyzed in detail for the TBC layer. For two efficient shaped cooling designs different hot gas velocities and blowing rates of the cooling gas are analyzed. The influence of the corresponding aerothermal results on the effective thermal conductivities of each monolayer and the multilayer are then discussed for both shaped cooling configurations.
Burner Development for Flexible Engine Operation of the Newest Siemens Gas Turbines
Authors: Prade Bernd , Meisl Ju¨rgen , Berenbrink Peter , Streb Holger , Hoffmann Stefan
Published: February 2009

The newest Siemens gas turbine family has already been well received by the market. Nevertheless, the market drives continuing development of the family and the combustion system. Central focus is put on further increasing reliability and component lifetime and on increased inspection cycles, as well as increasing the engine power output and efficiency, which is directly linked to higher turbine inlet temperatures. Increasing attention, however, is given to the flexibility concerning fuel quality and according fluctuations. Additionally, more and more strict emission requirements must be considered. This paper especially reports on demonstration of the capability of the Siemens gas turbines with an annular combustion system to fulfil the requirements for the highest operational flexibility. Thus, the combustion system has been tested and qualified for the highest operating flexibility with special fuel requirements such as burning Naphtha, Light Oil #2 and Natural gas with an extremely wide range of heating values as well. Also special operation modes such as fuel changeover, fastest load changes for island grid operation, frequency response and load rejection require this highly flexible combustion system without any hardware exchange. In different frames when fired with natural gas, base load is reached with the NOx emissions ranging well below 25 ppmvd, confirming the high potential of this advanced hybrid burner. In liquid fuel operation, dry NOx emissions of 75ppmvd were demonstrated but by injecting fuel / water emulsion NOx emissions were reduced to below 42 ppmvd with different liquid fuel qualities. Combustion dynamics, unburned Hydrocarbons, CO and soot emissions remained always below the required limits.
Conjugate Flow and Heat Transfer Investigation of a Turbo Charger: Part I — Numerical Results
Authors: Bohn Dieter , Heuer Tom , Kusterer Karsten
Published: February 2009

In this paper a three-dimensional conjugate calculation has been performed for a passenger car turbo charger. The scope of this work is to investigate the heat fluxes in the radial compressor which can be strongly influenced by the hot turbine. As a result of this, the compressor efficiency may deteriorate. Consequently, the heat fluxes have to be taken into account for the determination of the efficiency. To overcome this problem a complex three-dimensional model has been developed. It contains the compressor, the oil cooled center housing, and the turbine. 12 operating points have been numerically simulated composed of three different turbine inlet temperatures and four different mass flows. The boundary conditions for the flow and for the outer casing were derived from experimental test data (part II of the paper). Resulting from these conjugate calculations various one-dimensional calculation specifications have been developed. They describe the heat transfer phenomena inside the compressor with the help of a Nusselt number which is a function of an artificial Reynolds number and the turbine inlet temperature.
Automated Diagnostics of Rotating Machinery
Authors: El-Shafei A. , Rieger N.
Published: February 2009

This paper provides an overview of the current available technologies for automated machinery condition evaluation and fault diagnosis within an overall plant asset management system. The paper presents a basic overview of an integrated plant asset management system, and focuses on the available technologies for automated diagnostics including statistical analysis of data, parametric model diagnosis, non-parametric model diagnosis (artificial neural networks), and rule-based diagnostics including expert systems and fuzzy logic. The current state-of-the-art and the expected realistic future developments are discussed.
Influence of Sealing Air Mass Flow on the Velocity Distribution In and Inside the Rim Seal of the Upstream Cavity of a 1.5-Stage Turbine
Authors: Bohn Dieter E. , Decker Achim , Ma Hongwei , Wolff Michael
Published: February 2009

The phenomenon of hot gas ingestion at the rim seal section of turbines has been investigated for the front cavity and inside the sealing gap of an 1.5-stage turbine. This paper presents velocity distributions in and inside the rim seal. The experiments were performed using an unsteady 2D Laser Doppler Velocimetry system with a high local and time-based resolution. The hot gas ingestion has been examined for different parameters such as the non-dimensional seal flow rate and includes measurements at 17 circumferential positions with each 5 axial positions at dimensionless radii of 0.985 and 0.952. It is shown that the flow field inside the gap is influenced by the rotor blades as well as by secondary phenomena originating from the guide vanes. The location of hot gas ingestion is moving with the rotor blades and its strength is depending on the amount of seal flow rate. Unsteady interactions between rotor and stator blades have been investigated.
Preliminary Results of a Cold Flow Test in a Fuel Cell Gas Turbine Hybrid Simulation Facility
Authors: Tucker David , Lawson Larry , Gemmen Randy
Published: February 2009

The dynamic interdependencies created during the integration of fuel cell and a gas turbine in a hybrid power generation system are not well understood. Because these systems are new, there are risks that unexpected complications might arise during both steady state operation and transient events. A 250kW experimental fuel cell gas turbine simulation facility has been constructed at the National Energy Technology Laboratory (NETL), U.S. Department of Energy to examine the effects of transient events on the dynamics of these systems. A natural gas burner controlled by a real-time fuel cell model is used in the facility to simulate the thermal output of a solid oxide fuel cell during transient events. Pressure vessels are used for simulating the cathode and post combustion volumes, and are integrated into the system with a modified turbine and the fuel cell simulator. Preliminary results of system characterization are presented and discussed in context of the test scenarios proposed for experimental evaluation of thermal and mechanical transient impact on fuel cell and the gas turbine systems.
Gas Turbines in Alternative Fuel Applications: How to Predict the Stability of Olefin-Containing Process Gases
Authors: Glaude P. A. , Mahier O. , Warth V. , Fournet R. , Moliere M. , Hu I.
Published: February 2009

Throughout the history of combustion engines, the Heavy Duty Gas Turbine stands out as the most fuel-flexible prime mover in the field. This gas turbine (GT) is suited for a rich portfolio of gaseous fuels that include: natural gas, liquefied petroleum gas, coal and biomass-derived syngases, and a great variety of process gases with diverse compositions (hydrogen, carbon monoxide, olefins, etc.). Process gas fuels provide a promising array of alternative fuel opportunities in the major sectors of the industry such as the Coal, Oil & Gas, Steel, Chemical and Petrochemical branches. In an increasingly uncertain fuel environment, this significant match between gas turbine capabilities and the energy schemes of industrial plants can lead to further business opportunities.
Heat Transfer and Aerodynamics of an Intermediate Pressure Nozzle Guide Vane With and Without Inlet Temperature Non-Uniformity
Authors: Chana Kam S. , Povey T. , Jones Terry V.
Published: February 2009

In modern gas turbine engines the combustor exit flow has a non-uniform temperature profile because of the discrete nature of the injection of fuel and dilution air, and the wall cooling flows. The affect of this non-uniform temperature profile on the aerodynamics and heat transfer rate of nozzle guide vanes and turbine blades is difficult to predict, and knowledge of this is important for estimating turbine component life and efficiency. Measurements of heat transfer have been conducted on an annular transonic intermediate pressure nozzle guide vane operating downstream of a high pressure rotating turbine stage. Measurements were made with and without a radial and circumferential inlet temperature profile. The experiments were conducted in the Isentropic Light Piston Facility (ILPF) at QinetiQ, a short duration engine size turbine facility with 1.5 turbine stages, in which Mach number, Reynolds number and gas-to-wall temperature ratios are correctly modelled. Experimental results are compared to predictions performed using boundary layer methods.