bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated Gas Turbine Sensor Fault Diagnostics
Authors: Jombo Gbanaibolou , Zhang Yu , Griffiths Jonathan David , Latimer Tony
Published: August 2018

Sensors provide a means of detecting the actual operating condition of the gas turbine at any point in time. As such, detecting when they exhibit anomalous behaviour is very important to prevent inaccurate performance predictions and costly gas turbine component failures. This paper presents an automated sensor fault detection approach based on the maximal overlap discrete wavelet transform for the detection of the presence of anomalies such as bias, spike, stuck signal, cross-talk and erratic fault in a sensor signal. A multi-sensor validation scheme based on using the median signal as a reference signal within a sensor group is shown to be a robust technique to differentiate sensor anomalies due to gas turbine transient operation from actual sensor faults. The approach presented in this paper lends itself not only suitable for gas turbines in service, but also for gas turbines undergoing acceptance testing. As the timescales involved during a gas turbine acceptance test are just in hours, the conventional approach of trending and setting alarm limits are not sensitive to sensor anomalies which occur within the set alarm limits. Wavelet-based approach combined with a multi-sensor validation scheme provides a viable alternative.
The Pressure Field at the Output From a Low Pressure Exhaust Hood and Condenser Neck of the 1090 MW Steam Turbine: Experimental and Numerical Research
Authors: Hoznedl Michal , Živný Antonín , Macálka Aleš , Kalista Robert , Sedlák Kamil , Bednář Lukáš , Tajč Ladislav
Published: August 2018

The paper presents the results of measurements of flow parameters behind the last stage of a 1090 MW nominal power steam turbine in a nuclear power plant. The results were obtained by traversing a pneumatic probe at a distance of about 100 mm from the trailing edges of the LSB (Last Stage Blade). Furthermore, both side walls as well as the front wall of one flow of the LP (Low Pressure) exhaust hood were fitted with a dense net of static pressure taps at the level of the flange of the turbine. A total of 26 static pressures were measured on the wall at the output from the LP exhaust hood. Another 14 pressures were measured at the output from the condenser neck. The distribution of static pressures in both cross sections for full power and 600 and 800 MW power is shown. Another experiment was measured pressure and angle distribution using a ball pneumatic probe in the condenser neck area in a total of four holes at a distance up to 5 metres from the neck wall.

The turbine condenser is two-flow design. In one direction perpendicular to the axis of the turbine cold cooling water comes, it heats partially. It then reverses and it heats to the maximum temperature again. The different temperature of cooling water in the different parts of the output cross section should influence the distribution of the output static pressure. Differences in pressures may cause problems with uneven load of the tube bundles of the condenser as well as problems with defining the influential edge output condition in CFD simulations of the flow of the cold end of the steam turbine Due to these reasons an extensive 3D CFD computation, which includes one stator blade as well as all moving blades of the last stage, a complete diffuser, the exhaust hood and the condenser neck, has been carried out. Geometry includes all reinforcing elements, pipes and heaters which could influence the flow behaviour in the exhaust hood and its pressure loss. Inlet boundary conditions were assumed for the case of both computations from the measurement of the flow field behind the penultimate stage. The outlet boundary condition was defined in the first case by an uneven value of the static pressure determined by the change of the temperature of cooling water. In the second case the boundary condition in accordance with the measurement was defined by a constant value of the static pressure along all the cross section of the output from the condenser neck. Results of both CFD computations are compared with experimental measurement by the distribution of pressures and other parameters behind the last stage.
Validation of CFD Analysis Method for Seal Dynamic Coefficients With Various Labyrinth Seal Types
Authors: Iwasaki Makoto , Murata Kenichi , Kawashita Rimpei , Tokimasa Yasunori , Matsumoto Kazuyuki , Kamishita Makoto
Published: August 2018

Seal flows in labyrinth seals can produce fluid destabilization forces, which in turn can cause subsyncrhonous vibration in turbomachinery such as steam turbines and centrifugal compressors. In this study, an experiment measuring the dynamic coefficients of several types of labyrinth seal is conducted. Analytical results are obtained by computational fluid dynamics (CFD) and are compared with experimental results. For the experiment, a 500mm diameter rotor was used so that size of the labyrinth seal can be close to the large-scale steam turbine. A rotor was excited in a circular whirl orbit at the natural frequency of the parallel mode of the rotor by an electromagnetic actuator. The stator reaction force was measured with load cells and the dynamic force of the stator was corrected with measurements from accelerometers. The tests are conducted at an operating point of 8000rpm with airflow corresponding to a 0.2MPa pressure difference as rated condition. Labyrinth seal types include a staggered labyrinth seal with an abradable coating and a stepped labyrinth seal with straight fins and with slanted fins. For the CFD calculation, a steady state calculation can estimate not only the stiffness coefficients but also the damping coefficients of the seals by solving in a rotating frame of reference during rotor whirl. It was found that both the CFD analysis results and the experimental results were in reasonable agreement for all types of seal. Therefore a CFD analysis method for obtaining seal dynamic coefficients has been validated with various labyrinth seal types.
LES of a Pressurized, Sooting Aero-Engine Model Combustor at Different Equivalence Ratios With a Sectional Approach for PAHs and Soot
Authors: Grader Martin , Eberle Christian , Gerlinger Peter , Aigner Manfred
Published: August 2018

Large-eddy simulation (LES) of a pressurized, swirl stabilized, well-characterized aero-engine model combustor have been conducted at different operating conditions. The combustor is fueled by ethylene and features a secondary air injection system to mimic the rich-quench-lean concept (RQL) of aircraft engine combustors. This paper discusses the influence of three different equivalence ratios on the sooting behavior by means of numerical simulation. A finite-rate chemistry model (FRC) with assumed probability density function model (APDF) is used to describe the turbulent combustion. Polycyclic aromatic hydrocarbons (PAHs), their radicals and soot are modeled by a recently developed sectional approach. Feedback effects such as consumption of gaseous soot precursors by growth of soot are inherently captured by solving the governing equations simultaneously. Quantitative measurement data obtained by different laser diagnostic techniques are used for validation. Predicted temperatures and velocities are in excellent agreement to the measurements. The influence of different equivalence ratios on the sooting behavior of the combustor is qualitatively captured well by the soot model. Details of the soot evolution are discussed and the remaining differences between the simulation and the measurements are analyzed in detail.
Effect of Prior Creep Strain on High Cycle Fatigue Life of Ti 834
Authors: Wu Xijia , Seo Dongyi , Head Marc , Chan Stephen
Published: August 2018

Room-temperature fatigue tests were conducted on Ti 834 with prior creep strains accumulated under constant load at 550°C and 600°C, respectively. Microstructural and fractographic examinations on specimens with prior creep strain > 3% revealed the failure process consisting of multiple surface crack nucleation and internal void generation by creep, followed by fatigue crack propagation in coalescence with the internally distributed damage, leading to the final fracture. The amount of prior creep damage increased with creep strain. The fatigue life of Ti 834 was significantly reduced by prior creep straining. The behavior is rationalized with the integrated creep-fatigue theory.
Estimating Recoverable Performance Degradation Rates and Optimizing Maintenance Scheduling
Authors: Allen Cody W. , Holcomb Chad M. , de Oliveira Mauricio
Published: August 2018

Many of the components on a gas turbine are subject to fouling and degradation over time due to debris buildup. For example, axial compressors are susceptible to degradation as a result of debris buildup on compressor blades. Similarly, air cooled lube oil heat exchangers incur degradation as a result of debris buildup in the cooling air passageways. In this paper, we develop a method for estimating the degradation rate of a given gas turbine component that experiences recoverable degradation due to normal operation over time. We then establish an economic maintenance scheduling model which utilizes the derived rate and user input economic factors to provide a locally optimal maintenance schedule with minimized operator costs. The rate estimation method makes use of statistical methods combined with historical data to give an algorithm with which a performance loss rate can be extracted from noisy data measurements. The economic maintenance schedule is then derived by minimizing the cost model in user specified intervals and the final schedule results as a combination of the locally optimized schedules. The goal of the combination of algorithms is to maximize component output and efficiency, while minimizing maintenance costs. The rate estimation method is validated by simulation where the underlying noisy data measurements come from a known probability distribution. Then, an example schedule optimization is provided to validate the economic optimization model and show the efficacy of the combined methods.
Experimental and Numerical Investigation of Environmental Barrier Coated CMC Turbine Airfoil Erosion
Authors: Okita Yoji , Mizokami Yousuke , Hasegawa Jun
Published: August 2018

Ceramic matrix composite (CMC) have higher temperature durability and lower density property compared to nickel-based super-alloys which so far have been widely applied to hot section components of aero-engines / gas turbines. One of promising CMC systems, SiC-SiC CMC is able to sustain its mechanical property at higher temperature, though it inherently needs environmental barrier coating (EBC) to avoid oxidation. There are several requirements for EBC. One of such critical requirements is its resistance to particle erosion, whereas this subject hasn’t been well investigated in the past.

The present work presents the results of a combined experimental and numerical research to evaluate the erosion characteristics of CMC+EBC material developed by IHI.

First, experiments were carried out in an erosion test facility using 50 micron diameter silica as erosion media under typical engine conditions with velocity of 225 m/s, temperature of 1311 K, and impingement angles of 30, 60, and 80deg. The data displayed brittle erosion mode in that the erosion rate increased with impact angles.

Next, multi-phase flow simulations were carried out for the experimental setup and the predicted erosion rates were compared with the measured data, and consequently, the applied numerical method was verified.

The validated numerical method was then applied to compute three dimensional flow field, particle trajectories, and erosion profile around a generic turbine airfoil to assess the erosion characteristics of the proposed CMC+EBC material when applied to airfoil. The trajectories indicated that the particles primarily impacted the airfoil leading edge and the pressure surface. Surface erosion patterns were predicted based on the calculated trajectories and the experimentally-based erosion characteristics.
Design and Evaluation of Hybrid Magnetic Bearings for Turbo Compressors
Authors: Park Cheol Hoon , Park Jun Young , Yoon Eui Soo
Published: August 2018

Recently, high capacity and high efficiency turbo machines such as turbo blowers and turbo compressors have been being developed. To keep up with this trend, magnetic bearings are increasingly being applied to turbo machines instead of air foil bearings. In this study, a hybrid magnetic bearing composed of a permanent magnet and an electromagnet was applied to 300-HP (horsepower) turbo compressors with rated speeds of 50,000 rpm. The length of the shaft should be reduced as short as possible so that the compressor rotor can rotate stably while maintaining a small vibration at a rotation speed of 50,000 rpm. In this study, the additional shaft length for the axial gap sensor is eliminated by applying a new layout in which the axial gap sensor is placed on the inner surface of the thrust magnetic bearing. No-load tests and full-load tests in the manufactured turbo compressors were performed to evaluate the performance of the designed magnetic bearings. The biggest obstacle to this development is the heat problems caused by compressor impellers and high-speed motors. Thanks to the cooling system using water and air, the problem of thermal expansion of the rotor in the axial direction can be avoided. Thrust forces were estimated using the control current for thrust magnetic bearings. The experiment is also performed to evaluate the vibration of each turbo compressor and the results are presented. Based on the evaluated vibration, it has been confirmed that the hybrid magnetic bearings and the new axial gap sensor layout can support the turbo compressors stably.
Selecting Optimal Features for Cross-Fleet Analysis and Fault Diagnosis of Industrial Gas Turbines
Authors: Zhang Yu , Martínez-García Miguel , Latimer Anthony
Published: August 2018

This paper studies the behavior of Industrial Gas Turbines (IGTs) based on time-series measurements with low sampling rates. The aim is to find the most suitable set of statistical/time-domain features derived from the measurements, which can represent the characteristic behavior of the IGTs, or alternatively, which can discriminate between different engines or different states of an engine. For this end, a scheme of optimal feature selection process is proposed in the paper. For cross-fleet analysis, signals from a group of inter-duct thermocouples on IGT engines are studied. A feature matrix is formulated at each sliding time step, by calculating the statistical features of the sensor group, after the time-domain features of the individual sensor measurements are calculated. Feature matrix values from different engines are then clustered, and a modified Davies–Bouldin index is introduced to measure the quality of the clusters. Finally, grid search is run to find the optimal set of the features, which form the clusters with the most similarity, or otherwise, the most discrepancy across the IGT engines. The window size effect is also investigated. To demonstrate that the optimal feature selection process is also useful for fault diagnosis of IGTs, the proposed scheme is then applied on a group of different measurements on an IGT, i.e. from burner tip thermocouples, in a fault diagnostic scenario, which is subsequently validated using a k-nearest neighbor classification algorithm. The case studies have demonstrated that, ultimately, the developed techniques can be broadly applied to other groups of measurements for both cross-fleet analysis and fault diagnosis of IGTs.
Wall Temperature Measurements in Gas Turbine Combustors With Thermographic Phosphors
Authors: Nau Patrick , Yin Zhiyao , Lammel Oliver , Meier Wolfgang
Published: August 2018

Phosphor thermometry has been developed for wall temperature measurements in gas turbines and gas turbine model combustors. An array of phosphors has been examined in detail for spatially and temporally resolved surface temperature measurements. Two examples are provided, one at high pressure (8 bar) and high temperature and one at atmospheric pressure with high time resolution.

To study the feasibility of this technique for full scale gas turbine applications a high momentum confined jet combustor at 8 bar was used. Successful measurements up to 1700 K on a ceramic surface are shown with good accuracy. In the same combustor, temperatures on the combustor quartz walls were measured, which can be used as boundary conditions for numerical simulations.

An atmospheric swirl-stabilized flame was used to study transient temperature changes on the bluff body. For this purpose, a high-speed setup (1 kHz) was used to measure the wall temperatures at an operating condition where the flame switches between being attached (M-flame) and being lifted (V-flame) (bistable). The influence of a precessing vortex core (PVC) present during M-flame periods is identified on the bluff body tip, but not at positions further inside the nozzle.
A Porous Media Function That Mimics the Effect of Discrete Holes
Authors: Cerantola D. J. , Birk A. M.
Published: August 2018

Simulating full-coverage film cooling remains an elusive task for aerodynamicists given the small scale of the holes relative to the duct size where the holes are applied. Source term models were developed to simulate the effect through a perforated surface; however, the documented approaches failed to adequately describe how source term locations within the computational domain were selected. This paper presents a continuous ‘checker-board’ surface function that enables a distributed selection of cells where the source terms are applied; furthermore, the source term strengths applied to cells within a given hole are weighted. A 3:1 aspect ratio S-duct with an 1.5 area ratio exhaust diffuser, and 4% porosity applied to the upstream convex bend was evaluated. Steady-RANS obtained with the realizable k-ε model and source terms derived based on the approach of Andreini et al. (2014) had good pressure distribution, outlet velocity, and coolant mass flow agreement with respect to experiment when the hole diameter was resolved with two nodes. Reducing the computational domain element count by 75% and simulating hole diameters 2.8-times larger with 4% surface porosity gave back pressure and outlet distortion coefficients within grid uncertainty of the finest grid solution; however, local-convex-surface-averaged quantities showed grid dependency.
Experimental Study of the Leakage and Rotordynamic Coefficients of a Long Smooth Seal With Two-Phase, Mainly-Oil Mixtures
Authors: Zhang Min , Childs Dara W. , Mclean James E. , Tran Dung L. , Shrestha Hari
Published: August 2018

Tests are conducted on a newly developed 2-phase annular seal stand (2PASS) at the Turbomachinery Laboratory of Texas A&M University. The test fluid is a mixture of silicone oil (PSF-5cSt) and air. Two spargers are used to produce mainly-oil mixtures by injecting air bubbles into the oil flow.

The test seal is a smooth annular seal with inner diameter D = 89.306 mm, length-to-diameter ratio L/D = 0.65, and radial clearance Cr = 0.188 mm. Tests are performed with inlet gas-volume-fraction GVF = 0%, 2%, 4%, 6%, and 10%, rotor speed ω = 5, 7.5, 10, and 15 krpm, inlet temperature Ti = 39.4 °C, exit pressure Pe = 6.9 bars, and pressure drop PD = 31, 37.9, and 48.3 bars. The test seal is centered, and there is no intentional prerotation of the fluid at the seal inlet.

The complex dynamic stiffness coefficients of the test seal are measured and fitted by the frequency-independent stiffness Kij, damping Cij, and virtual-mass Mij coefficients.

Test results show that adding air into the oil flow does not change the seal’s mass flow leakage ṁ discernibly but significantly impacts the seal’s rotordynamic characteristics.

Some planned 5 krpm cases with low inlet GVFs at PD = 31 and 37.9 bars are not accomplished due to stator instabilities, which are likely caused by negative stiffness of the test seals. For ω = 5 krpm when PD = 31 and 37.9 bars, direct stiffness K decreases from positive to negative as inlet GVF decreases.

For all PDs and speeds, K increases as inlet GVF increases from zero to 10% except for 6% ≤ inlet GVF ≤ 10% when PD = 48.3 bars, where K decreases as inlet GVF increases. The K increment will increase a pump rotor’s natural frequency and critical speed. Increasing the rotor’s natural frequency would also increase the onset speed of instability (OSI) and improve the stability of the rotor. Adding air into the oil flow has little effect on cross-coupled stiffness k and direct damping C. Increasing inlet GVF has negligible effects on direct virtualmass M when ω ≤ 10 krpm and PD ≤ 37.9 bars, but generally decreases M when ω = 15 krpm or PD = 48.3 bars.

Increasing inlet GVF has little effect on effective damping Ceff and does not change the seal’s resultant stabilizing force discernibly. Ceff = C − k/ω + mqω, where mq is the cross-coupled virtual-mass.

Test results are compared to predictions from San Andrés’s [1] model. The model is based on a bulk-flow model and the Moody friction formula assuming that the liquid-gas mixture is isothermal and homogenous. The model reasonably predicts ṁ, C, and Ceff. All predicted K values are positive, while measured K values are negative for some test cases. Predicted k values are close to measurements when ω = 5 krpm and are larger than test results when 7.5 ≤ ω ≤ 15 krpm. M predictions are smaller than measurements, and the discrepancy between predicted and measured M values generally increases as inlet GVF increases.
Effects of Nonlinear Modal Interactions on the Thermoacoustic Stability of Annular Combustors
Authors: Orchini Alessandro , Mensah Georg A. , Moeck Jonas P.
Published: August 2018

In this theoretical and numerical analysis, a low-order network model is used to investigate a thermoacoustic system with discrete rotational symmetry. Its geometry resembles that of the MICCA combustor; the FDF employed in the analysis is that of a single-burner configuration, and is taken from experimental data reported in the literature. We show how most of the dynamical features observed in the MICCA experiment, including the so-called slanted mode, can be predicted within this framework, when the interaction between a longitudinal and an azimuthal thermoacoustic mode is considered. We show how these solutions relate to the symmetries contained in the equations that model the system. We also discuss how considering situations in which two modes are linearly unstable compromises the applicability of stability criteria available in the literature.
Optimised Test Rig for Measurements of Aerodynamic and Aeroacoustic Performance of Leading Edge Serrations in Low-Speed Fan Application
Authors: Biedermann Till M. , Kameier F. , Paschereit C. O.
Published: August 2018

With the aim of analysing the efficiency of leading edge serrations under realistic conditions, an experimental rig was developed where a ducted low-speed fan is installed that allows to gather data of both, aerodynamic and aeroacoustic nature. Turbulent inflow conditions were generated via biplane-square grids, resulting in turbulence intensities of different magnitude and of high isotropic character that were quantified by use of hotwire measurements. The fan blades were designed according to the NACA65(12)-10 profile with interchangeable features and an independently adjustable angle of attack. Altogether, five different parameters can be analysed, namely the serration amplitude and wavelength, the angle of attack, the inflow turbulence and the rotational speed. In addition, the blade design allows for a variation of the blade skew, sweep and dihedral as well. The presented work focusses on validating and optimising the test rig as well as a detailed quantification of the turbulent inflow conditions. Furthermore, first aerodynamic and aeroacoustic results of fan blades with straight leading edges are compared to those of serrated leading edges. The aerodynamic performance was found to be mainly affected by the serrations as a function of the serration amplitude. Aeroacoustically, a clear sensitivity towards different incoming turbulence intensities and serration parameters was detected, showing significant broadband noise reduction below 2 kHz with an overall noise reduction of ΔOASPL = 3.4 dB at maximum serration amplitudes and minimum wavelengths.
Mistuning Identification Approach With Focus on High-Speed Centrifugal Compressors
Authors: Weber Robby , Kühhorn Arnold
Published: August 2018

Blade vibrations are one of the main cost drivers in turbo-machinery. Computational blade vibration analysis facilitates an enormous potential to increase the productivity in the design of bladed components. Increasing computing power as well as improved modeling and simulation methods lead to comprehensive calculation results. This allows for a more precise prediction and assessment of experimental data.

Usually, in the field of turbomachinery, identical blades are assumed to lower the required computational resources. However, mistuning is unavoidable, since small deviations due to the manufacturing process will lead to slightly different blade behavior. Potential effects such as mode localization and amplification can be treated statistically and have been thoroughly studied in the past. Since then, several reduced order models (ROMs) have been invented in order to calculate the maximum vibration amplitude of a fleet of mistuned blisks. Most commonly, mistuning is thereby modeled by small material deviations from blade to blade, e.g. Young’s modulus or density.

Nowadays, it is common knowledge that the level of manufacturing imperfection (referred as level of mistuning) significantly influence mode localization as well as vibration amplification effects. Optical measurements of the geometric deviations of manufactured blades and converting to a high-fidelity finite element model make huge progress. However, to the knowledge of the authors, there is no reliable method, that derives a characteristic quantity from the geometric mistuning, that fits into the mentioned statistically approaches.

Therefore, experimental data is needed to quantify the level of mistuning. Several approaches, which isolate blade individual parameters, are used to identify the dynamic behavior of axial compressors and turbines. These methods can be applied to medium-speed centrifugal turbine wheels but tend to fail to evaluate high-speed compressor with splitter blades. This paper briefly presents the original approach and discusses the reasons for failure. Thereafter, a new approach is proposed. Finally the level of mistuning and important quantities to perform a statistical evaluation of a high-speed compressor is shown.
Through-Flow Modeling of Single- and Two-Shaft Gas Turbines at Wide Operating Range
Authors: Wiedermann Alexander , Petrovic Milan V.
Published: August 2018

A program suite of coupled analysis tools for all components of industrial gas turbines developed by the authors was applied to off-design operation of single- and two-shaft gas turbines. The through-flow methods are based on a stream function approach and a finite element solution procedure. They include high-fidelity loss and deviation models with improved correlations. Advanced radial mixing and end-wall boundary layer models were applied to simulate 3D flow effects. For air-cooled turbine analysis, various types of cooling air injection were encompassed: film cooling, trailing edge injection and disc/end-wall coolant flow.

Several improvements and extensions of the meridional solvers involved were employed. For axial compressor analysis, the original perfect gas treatment was replaced with the same real gas library that had already been implemented for flow computations in air-cooled expansion turbines and combustion modules. Ambient conditions with wet inflow of the compressor can now be taken into account. Compared to the previous model, better closure of the thermodynamic cycle can be achieved with the new approach. The meridional flow solver applied to the cooled turbine was upgraded and has become more stable for transonic outlet Mach numbers. With regard to the cooling flow supply, the codes offer greater freedom at the compressor extraction and turbine injection stations, allowing more realistic modeling of the secondary flow bifurcation.

Off-design operating conditions and sensitivity studies for both single- and two-shaft gas turbines covering the entire range of interest are presented and are compared with experimental rig-engine data where available.
Investigating Efficient Clusters of Savonius Wind Turbines
Authors: Ibrahim Ahmed , Elbaz Ahmed M. R.
Published: August 2018

The wake effect is the biggest challenge when locating downwind turbines in wind farms which imposes large separation distances between turbines. In the present work, CFD simulations are presented to study possible configurations of wind farms of Savonius wind turbines. The farm is composed by in steps, starting from two-turbine configuration, adding one turbine until reaching a cluster of closely set ten rotors with an average power coefficient of 0.225. This value is very close to the single rotor’s power coefficient. The power density of the cluster is 7.55 W/m2 which is much higher than similar ten turbines located far apart to avoid wake effect. The maximum Cp of a downstream rotor in the cluster reached 0.323 which is about 40% higher than the single rotor. The adopted philosophy for placing downstream rotors is locating the rotor’s returning bucket in the low velocity region of the wake of the upstream rotor to get the least negative torque while the advancing bucket is located at the high velocity region getting higher positive torque which increases the performance. After that, two crosswind clusters are added to increase the power generated. The predicted average power coefficient for the 30 rotors farm is 0.246 which is higher than a similar isolated turbine. The increase of the Cp occurs due to the positive interactions between the clusters. The highest Cp in the farm rotors is found to be 0.411 which is higher than the single rotor’s Cp by 78%. The farm also provides a high power-density of 4.65 W/m2 which is 5 times higher than a farm with the same number of turbines located far apart.
Development of Method and Computer Program for Multistage Axial Compressor Design: Part I — Mean Line Design and Example Cases
Authors: Banjac Milan , Petrovic Milan V.
Published: August 2018

An axial compressor loss and deviation model that was developed and presented during previous research has now been used to develop a computer program for multistage compressor design. A set of input data including overall parameters such as pressure ratio and mass flow rate and the first-stage parameters such as inlet flow coefficient and rotor tip Mach number are used to determine a number of stages and their geometry, speed and relevant flow properties. Then a subsequent redistribution of parameters for separate stages can be carried out in order to increase the stability indicators and efficiency over a desired operating range. A selected stage vortex law determines velocity triangles and blading geometry for hub and tip sections, which allows the generation of a realistic flow path shape. The developed program is considered to be a flexible and stable tool useful for tasks of manual or automated optimization when combined with an external optimization algorithm. This paper presents a basic mathematical model and the level of accuracy achieved. This is demonstrated through examples of manual design and redesign cases, while automated optimization will be included in future research.
The Effect of Tip Shroud Geometries on Last Turbine Stage Efficiency
Authors: Granovskiy Andrey , Afanasiev Igor
Published: August 2018

Last stages of steam turbines and heavy-duty power gas turbines contribute significantly to output power and efficiency of whole turbine. Moreover, radial distribution of parameters downstream of the last stage provides boundary conditions for diffuser design. Thus, the increase of the last stage efficiency and obtainment of favorable radial distribution downstream of the last rotor blade is very important. Due to the long blades of last stages, resonance might occur. To avoid dangerous frequencies a damping wire or damping bolts are used. Such damping elements result in additional losses, so to minimize these losses a damping shroud is used instead. In general, the full damping shroud has to provide both the aerodynamic loss reduction and the resonance frequency offset. However, in most cases due to mechanical integrity limits instead of the full shroud a partial shroud is used. In this case the loss reduction feature of the partial shroud is diminished as compared with the full shroud. Sometimes, the use of the partial shroud results in the decrease of the efficiency compared with a stage with unshrouded rotor blades at small tip clearances. In this paper, a numerical investigation of the flow structure around full and partial shrouds with various geometries as well as the effect of the various shroud geometries on the turbine stage efficiency is carried out. Eight geometries with different number of fins of various heights are studied. Moreover, stage efficiencies for both shrouded and unshrouded blade are compared. Based on this comparison, reasonable design recommendations aimed to reduce the losses within the radial gap over the shroud are developed. In particular, filling the space in the gap with the additional honeycombs is considered and the effect on the flow structure and the last stage efficiency investigated.

Numerical results obtained in the paper correspond well to the published test data.
Inlet Air Filter Elements Site and Laboratory Tests of Four Different Manufacturers
Authors: Ingistov Steve , Kohn Joshua
Published: August 2018

This Paper describes three-month onsite testing utilizing travelling laboratory furnished with four dedicated air ducts and required instrumentation needed to determine efficiency of filtration for submicron size particles. It also describes the subsequent testing of seasoned filters in offsite Laboratory furnished with instrumentation and equipment to conduct the dry and wet tests on previously Watson-field tested filters.

The opportunity to simultaneously test four different IAFE, provided by four different Manufacturers, was unique and helpful in discerning the differences between these filters.
Engine Testing for the Demonstration of a 3D-Woven Based Ceramic Matrix Composite Turbine Vane Design Concept
Authors: Watanabe Fumiaki , Manabe Takashi
Published: August 2018

In this paper, the authors present a solid vane concept which uses 3D woven fabric based SiC/SiC CMC and the result of engine testing which was conducted to demonstrate this concept.

The authors devised a design concept, in which a vane is made from a folded woven, for the uncooled turbine vanes of the aircraft engines. The advantage of this concept is that there is no structural weak point because a whole vane including outer / inner platform consists of one continuous woven.

In order to demonstrate the applicability of this concept to the actual engine parts, CMC turbine vanes were tested with IHI-IM270 that is a small industrial gas turbine engine. After 862 hour testing, there was no defect such as cracks, wear, and deformation.
An Efficient Approach for the Frequency Analysis of Non-Axisymmetric Rotating Structures: Application to a Coupled Bladed Bi-Rotor System
Authors: Dumartineix Cécile , Chouvion Benjamin , Thouverez Fabrice , Parent Marie-Océane
Published: August 2018

The improvement of efficiency in the design of turbomachines requires a reliable prediction of the vibrating behavior of the whole structure. The simulation of blades vibrations is decisive and this is usually based on elaborated finite element model restricted to the bladed-disk. However the blades dynamic behavior can be strongly affected by interactions with other parts of the engine. Global dynamic studies that consider these other parts are required but usually come with a high numerical cost. In the case of a bi-rotor architecture, two coaxial rotors with different rotating speed can be coupled with a bearing system. The mechanical coupling between the shafts generates energy exchange that alters the dynamic behavior of the blades. The equations of motion of the whole structure that take into account the coupling contain periodic time-dependent coefficients due to the difference of rotational speed between both rotors. Equations of this kind, with variable coefficients, are typically difficult to solve. This study presents a preprocessing method to guarantee the elimination of time-dependent coefficients in the bi-rotor equations of motion. This method is tested with a simplified finite element model of two bladed-disks coupled with linear stiffnesses. We obtain accurate results when comparing frequency analysis of preprocessed equations with time-integration resolution of the initial set of equations. The developed methodology also offers a substantial time saving.
CFD Study on the Influence of Geometric Parameters on the Aerodynamics Within an Ejector Injection System for Compressor Stabilization
Authors: Brehm Sebastian , Kern Felix , Niehuis Reinhard
Published: August 2018

Injection of high-momentum air into the tip-gap region of rotor stages is a measure of active aerodynamic stabilization of turbo compression systems. The Institute of Jet Propulsion at the University of the German Federal Armed Forces Munich advanced the concept of conventional tip air injection by deliberately deploying the ejector effect in order to increase the mass flow rate of the air injected. A novel Ejector Injection System (EIS) has been developed for the Larzac 04 jet engine and its intended ejector performance was proven in experimental pre-investigations. In addition to that, the corresponding CFD setup has been validated and an approach for highly efficient CFD simulations of the EIS ejector aerodynamics (node number reduction > 90%) was developed, verified, and validated. Thus, optimization of the ejector geometry in order to enhance the ejector aerodynamics and subsequently the stabilization performance of the EIS comes into focus now. Within this paper, a parametric CFD study is conducted to determine the influence of three main geometry parameters of the EIS ejector design on the ejector’s performance. The parameters, namely the injection nozzle spacing, the mixing duct length, and the ejector nozzle height, are introduced in the context of the overall EIS design and functionality. For efficiency purposes, a script-based procedure which deploys ANSYS ICEM CFD and ANSYS CFX has been developed in order to conduct the CFD parameter study covering 205 simulations fully automated. Each ejector geometry is thereby simulated with five different primary air mass flow rates supplied to the EIS covering a range from low-speed to transonic operation. It is revealed that all three geometry parameters investigated show partially significant impact on the ejector performance in terms of the entrainment ratio μ. In order to get a detailed insight into the inner EIS aerodynamics, also primary air Mach and Reynolds numbers, the state of mixing between primary and secondary air, and velocity profiles in the LPC’s tip region are subjects of investigation. Based on these findings and the general aerodynamic coherences discovered, recommendations for optimizing the current EIS ejector design are presented.
Effects of Inlet Disturbances on Fan Stability
Authors: Lee Kuen-Bae , Wilson Mark , Vahdati Mehdi
Published: August 2018

This paper investigates the effects of inlet disturbance caused by crosswind on a fan blade operation and addresses the possible aerodynamic instabilities which can arise for such a fan-intake system. The work is carried out by using a three-dimensional unsteady CFD model (AU3D), and for a modern low-speed fan rig for which extensive measured data is available. The computational domain includes the fan, with outlet guide vanes (OGV) for the bypass flow and engine-section stators (ESS) for the core and a symmetric intake upstream of the fan (a whole low-pressure domain). The unsteady full annulus simulations under crosswind are performed to analyze the effects of inlet disturbances on the operation of this blade. It was observed that, for sufficiently high amplitudes of crosswind, the intake lip separates, and results in a significant loss of stall margin. Moreover, even in the absence of lip separation, the blade can still stall prematurely due to non-homogeneous flow caused by the two contra-rotating trailing vortices.

In the 2nd phase of this study, the effects of fan loading on the suppression of flow separation in the intake, and the consequent stall margin of the fan blade was explored. The results indicated that, as the fan speed increases it becomes more capable of reducing the inlet distortion levels, and consequently it can extend the stall margin of the fan blade.
Optical Measurements of a LCV-Combustor Operated in a Micro Gas Turbine With Various Fuel Compositions
Authors: Zornek Timo , Mosbach Thomas , Aigner Manfred
Published: August 2018

In a recent joint research project, a new FLOX®-combustion system was developed to couple a fixed-bed gasifier with a micro gas turbine. Product gases from biomass gasification exhibit low calorific values and varying compositions of mainly H2, CO, CO2, N2 and CH4. Furthermore, combustion characteristics differ significantly compared to the commonly used natural gas. As the FLOX®-technology is considered as efficient and fuel-flexible featuring low emissions of hazardous pollutants, the design of the LCV-combustor is based on it. It contains a two-staged combustor consisting of a jet-stabilized main stage adapted from the FLOX®-concept combined with a swirl stabilized pilot stage. The combustor was operated in a Turbec T100 test rig using an optically accessible combustion chamber, which allowed OH*-chemiluminescence and OH-PLIF measurements for various fuel compositions. In particular, the hydrogen content in the synthetically mixed fuel gas was varied from 0 % to 30 %. The exhaust gas composition was additionally analysed regarding CO, NOx and unburned hydrocarbons. The results provide a comprehensive insight into the flame behaviour during turbine operation. Efficient combustion and stable operation of the micro gas turbine was observed for all fuel compositions, while the hydrogen showed a strong influence. It is remarkable, that with hydrogen contents higher than 9 % no OH radicals were detected within the inner recirculation zone, while they were increasingly entrained below hydrogen contents of 9 %. Without hydrogen, the inner recirculation zone was completely filled with OH radicals and the highest concentrations were detected there. Therefore, the results indicate a different flame behaviour with low and high hydrogen contents. Although the flame shape and position was affected, pollutant emissions remained consistent below 10 ppm based on 15% O2. Only in case of 0% hydrogen, CO-emissions increased to 43 ppm, which is still meeting the emission limits. Thus, the combustor allows operation with syngases having hydrogen contents from 0% to 30%.
Fuzzy Analytic Hierarchy Process Evaluation Method of Gas Turbine Based on Health Degree
Authors: Cao Yunpeng , Hu Pan , Yang Qingcai , He Yinghui , Li Shuying , Yu Fang , Du Jianwei
Published: August 2018

In this paper, a gas turbine fuzzy analytic hierarchy process based on health degree is proposed to determine the current health state and remaining useful life of the gas turbine. The concept of health degree is introduced to quantitatively represent the health state of gas turbine and its components and parameters. The probability density function is used to calculate the health degree of the evaluation parameters to avoid the complexity of evaluation caused by different orders of magnitude. This paper proposes the weights hiding method that reflects the inhomogeneity of the evaluation parameters and proposes a remaining useful life prediction algorithm based on the health degree. Finally, the training data set from the Commercial Modular Aero-Propulsion System Simulation (CMAPSS) simulator is used to validate the proposed health evaluation method and the remaining useful life prediction algorithm. The results show that the gas turbine health degree obtained by the method in this paper can be used to accurately predict the degradation trend of gas turbine, and the predicted remaining useful life coincides with the result of the test data set, thereby demonstrating the validity and practicability of the proposed method of using health degree to describe the gas turbine health state.
Dual Drive Booster for a Two-Spool Turbofan: High Shaft Power Offtake Capability for MEA and Hybrid Aircraft Concepts
Authors: Kloos Vadim , Speak Trevor H. , Sellick Robert J. , Jeschke Peter
Published: August 2018

The effects of high shaft power offtake in a direct drive, a geared drive, and a novel turbofan configuration are investigated. A design and off-design performance analysis shows the configuration specific limitations and advantages.

The more electric aircraft (MEA) concept promises to offer advantages with respect to aircraft performance, maintenance and operating costs. The engines for the MEA concept are based on conventional turbofan architectures. These engines are designed for significantly increased shaft power offtake that is required by the airframe, and the shaft power is usually taken off the high-pressure spool. This can impair the off-design performance of the engine and lead to compromises during engine design and to operability limitations. Taking the power off the low-pressure spool mitigates some of the problems but has other limitations. In this work, an alternative novel turbofan architecture is investigated for its potential to avoid the problems related to high shaft power offtakes. This architecture is called the dual drive booster because it uses a summation gearbox to drive the booster from both the low- and high-pressure spool. The shaft power, if taken off the booster spool, is effectively provided by both the low- and high-pressure spools, which allows the provision of very high power levels. This new concept is benchmarked against a two-spool direct drive and a geared drive turbofan. Furthermore, it is described, how the new architecture can incorporate an embedded motor generator. The presented concept mitigates some of the problems which are encountered during high power offtake in conventional configurations. In particular, the core compressors are less affected by a change in shaft power offtake. This allows higher power offtakes and gives more flexibility during engine design and operation. Additionally, the potential to use the new configuration as a gas turbine-electric hybrid engine is assessed, where electrical power boost is applied during critical flight phases. The ability to convert additional shaft power is compared with conventional configurations. Here, the new configuration also shows superior behavior because the core compressors are significantly less affected by power input than in conventional configurations. The spool speed and its variation is more suitable for electrical machines than in conventional configuration with low-pressure spool power transfer.

The dual drive booster concept is particularly suited for applications with high shaft power offtakes and inputs, and should be considered for propulsion of more electric aircrafts.