bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of 1500-r/min 75-Inch Ultra-Long Last Stage Blades for Nuclear Steam Turbine
Authors: Yu Deqi , Yang Jiandao , Lu Wei , Zhou Daiwei , Cheng Kai , Yang Rui 
Published: August 2017

The 1500-r/min 1905mm (75inch) ultra-long last three stage blades for half-speed large-scale nuclear steam turbines of 3rd generation nuclear power plants have been developed with the application of new design features and Computer-Aided-Engineering (CAE) technologies.
The last stage rotating blade was designed with an integral shroud, snubber and fir-tree root. During operation, the adjacent blades are continuously coupled by the centrifugal force. It is designed that the adjacent shrouds and snubbers of each blade can provide additional structural damping to minimize the dynamic stress of the blade. In order to meet the blade development requirements, the quasi-3D aerodynamic method was used to obtain the preliminary flow path design for the last three stages in LP (Low-pressure) casing and the airfoil of last stage rotating blade was optimized as well to minimize its centrifugal stress. The latest CAE technologies and approaches of Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA) and Fatigue Lifetime Analysis (FLA) were applied to analyze and optimize the aerodynamic performance and reliability behavior of the blade structure.
The blade was well tuned to avoid any possible excitation and resonant vibration. The blades and test rotor have been manufactured and the rotating vibration test with the vibration monitoring had been carried out in the verification tests.
Engine Fleet-Management: The Use of Digital Twins From a MRO Perspective
Authors: Kraft Joern , Kuntzagk Stefan 
Published: August 2017

Engine operating cost is a major contributor to the direct operating cost of aircraft. Therefore, the minimization of engine operating cost per flight-hour is a key aspect for airlines to operate successfully under challenging market conditions.
The interaction between maintenance cost, operating cost, asset value, lease and replacement cost describes the area of conflict in which engine fleets can be optimized.
State-of-the-art fleet management is based on advanced diagnostic and prognostic methods on engine and component level to provide optimized long-term removal and work-scoping forecasts on fleet level based on the individual operation. The key element of these methods is a digital twin of the active engines consisting of multilevel models of the engine and its components. This digital twin can be used to support deterioration and failure analysis, predict life consumption of critical parts and relate the specific operation of a customer to the real and expected condition of the engines on-wing and at induction to the shop. The fleet management data is constantly updated based on operational data sent from the engines as well as line maintenance and shop data.
The approach is illustrated along the real application on the CFM56-5C, a mature commercial two-spool high bypass engine installed on the Airbus A340-300. It can be shown, that the new methodology results in major improvements on the considered fleets.
Influence of Backward and Forward Facing Steps on the Flow Through a Turning Mid Turbine Frame
Authors: Bauinger Sabine , Malzacher Franz , Goettlich Emil , Heitmeir Franz 
Published: August 2017

For this work, reality effects, more precisely backward and forward facing steps, and their influence on the flow through a two-stage two-spool turbine rig under engine-relevant conditions were experimentally investigated. The test rig consists of a HP and a LP stage, with the two rotors rotating in opposite direction with two different rotational speeds. An S-shaped transition duct, which is equipped with turning struts (so-called turning mid turbine frame or TMTF) and making therefore a LP stator redundant, connects both stages and leads the flow from a smaller to a larger diameter.
This test setup allows the investigation of a TMTF deformation, which occurs in a real aero-engine due to non-uniform warming of the duct during operation — especially during run up — and causes backward and forward facing steps in the flow path. This happens for non-segmented ducts, which are predominantly part of smaller engines. In the case of the test rig, steps were not generated by varying temperature but by shifting the TMTF in horizontal direction while the rotor and its casing were kept in the same position. In this way, both backward and forward facing steps between duct endwalls and rotor casing could be created. In order to avoid steps further downstream of the interface between HP rotor and TMTF, the complete aft rig was moved laterally too. In this case, the aft rig incorporates amongst others the LP rotor, the LP rotor casing and the deswirler downstream of the LP stage.
In order to catch the influence of the steps on the whole flow field, 360 deg rake traverses were performed downstream of the HP rotor, downstream of the duct and downstream of the LP rotor with newly designed, laser-sintered Combi-Rakes for the measurement of total pressure and total temperature. Only the compact design of the rakes, which can be easily realised by additive manufacturing, makes the aforementioned 360 deg traverses in this test rig possible and allows a number of radial measurements positions, which is comparable to those of a five hole probe. To get a more detailed information about the flow, also five hole probe measurements were carried out in three measurement planes and compared to the results of the Combi-Rakes.
Numerical Investigation of Effect of Inlet Distortion on Compressor Flow Field and Stability
Authors: Zhang HaoGuang , An Kang , Tan Feng , Wu YanHui , Chu WuLi 
Published: August 2017

The compressor aerodynamic design is conducted under the condition of clean inlet in general, but a compressor often operates under the condition of inlet distortion in the practical application. It has been proven by a lot of experimental and numerical investigations that inlet distortion can decrease the performance and stability of compressors. The circumferential or radial distorted inlet in mostly numerical investigations is made by changing the total pressure and total temperature in the inlet ring surface of the compressors. In most of inlet distortion experiments, distorted inlets are usually created by using wire net, flashboards, barriers or the generator of rotating distortion. The fashion of generating distorted inlet for experiment is different from that for numerical simulation. Consequently, the flow mechanism of affecting the flow field and stability of a compressor with distorted inlet for experiment is partly different than that for numerical simulation.
In the numerical work reported here, the inlet distortion is generated by setting some barriers in the inlet ring surface of an axial subsonic compressor rotor. Two kinds of distorted inlet are investigated to exploring the effect of distorted range on the flow field and stability of the compressor with ten-passage unsteady numerical method. The numerical results show that the inlet distortions not only degrade the total pressure and efficiency of the compressor rotor, but also decrease the stability of the rotor. The larger the range of distorted inlet is, the stronger the adverse effect is. The comprehensive stall margin for the inlet distortion of 24 degrees and 48 degrees of ten-passages is reduced about 3.35% and 5.88% respectively. The detailed analysis of the flow field in the compressor indicates that the blockage resulted from tip clearance leakage vortex (TLV) and the flow separation near the suction surfaces of some blades tip for distorted inlet is more serious than that resulted from TLV for clean inlet. Moreover, the larger the range of distorted inlet is, the larger the range of the blockage is. The analysis of unsteady flow shows that during this process, which is that one rotor blade passes through the region affected by the distorted inlet, the range of the blockage in the rotor passage increases first, then reduces, and increases last.
Numerical Studies on the Intrusive Influence of a Five-Hole Pressure Probe in a High-Speed Axial Compressor
Authors: Sanders Christoph , Terstegen Marius , Hölle Magnus , Jeschke Peter , Schönenborn Harald , Fröbel Tobias 
Published: August 2017

In this investigation, CFD calculations are conducted to evaluate the differences between five-hole pressure probe-determined flow quantities and the unaffected flow quantities without the probe’s intrusive influence. The blockage effect of the probe is described and evaluated. Furthermore, the influence of this effect is used to estimate the error when using measured stator outflows as forcing functions for the following rotor blades.
To compare the flow field, both with and without the probe’s influence, a five-hole pressure probe is traversed numerically at midspan behind each stator row of a 2.5-stage axial compressor. For reproducing the blockage of the probe accurately, the full annulus of the respective stator row has to be modeled. In order to minimize the calculation time, a study to reduce the number of stator passages was successfully performed. To evaluate the flow quantities using the probe, a calibration polynomial is set up numerically. CFD simulations of the probe geometry within a uniform flow field for each pitch and yaw angle, as well as Mach number combination, are performed for this purpose. Moreover, the pressure probe data for the numerical traverses are corrected to account for velocity gradients in the wake region. The comparison of Mach number, with and without the probe’s influence, shows differences both in the width and the depth of the wake. The results of the Fourier-transformed wake profile for both cases are compared and changes in the first harmonic of Mach number of up to −13% identified. Finally, the first harmonic of the flow quantities is used to perform linearized CFD calculations and to evaluate the influence of disturbed forcing functions on the aerodynamic work of the following rotor blade. The average difference in aerodynamic excitation is about −12% with a maximum deviation of more than −30%.
The results presented aim to draw attention to intrusive probe influences and their consequences for validating numerical results against experiments. Special attention is given to the discrepancies of forced response calculations with varying gust boundary conditions.
On the Impact of Simulation Approaches on the Predicted Aerodynamic Damping of a Low Pressure Steam Turbine Rotor
Authors: Fuhrer Christopher , Vogt Damian M. 
Published: August 2017

The determination of the aerodynamic damping is a major task in predicting flutter stability and therefore safety margins for turbine operation. Throughout the current work the energy method is employed to predict the aerodynamic damping for a last stage rotor blade numerically. The focus is put on the prediction of the aerodynamic damping with different traveling wave mode representations and on the influence of the blade fixation at the root. The Fourier transformation-method, the influence-coefficients-method and a direct traveling wave mode calculation are employed.
The investigated rotor geometry was taken from the open literature, a root was designed and an iterative process was installed to determine the cold blade geometry. It became apparent, that the influence-coefficients-method is capable of predicting the overall stability curve computationally efficient, whereas the Fourier-transformation-method showed advantages in the identification of the least stable point for a finer mesh. Nevertheless, all methods predicted a potential flutter risk for the current operating point. The influence of the additional blade root with a completely fixed support on the aerodynamic damping is minor.
Optimization of Statistical Methodologies for Anomaly Detection in Gas Turbine Dynamic Time Series
Authors: Ceschini Giuseppe Fabio , Gatta Nicolò , Venturini Mauro , Hubauer Thomas , Murarasu Alin 
Published: August 2017

Statistical parametric methodologies are widely employed in the analysis of time series of gas turbine sensor readings. These methodologies identify outliers as a consequence of excessive deviation from a statistically-based model, derived from available observations. Among parametric techniques, the k-σ methodology demonstrates its effectiveness in the analysis of stationary time series. Furthermore, the simplicity and the clarity of this approach justify its direct application to industry. On the other hand, the k-σ methodology usually proves to be unable to adapt to dynamic time series, since it identifies observations in a transient as outliers.
As this limitation is caused by the nature of the methodology itself, two improved approaches are considered in this paper in addition to the standard k-σ methodology. The two proposed methodologies maintain the same rejection rule of the standard k-σ methodology, but differ in the portions of the time series from which statistical parameters (mean and standard deviation) are inferred. The first approach performs statistical inference by considering all observations prior to the current one, which are assumed reliable, plus a forward window containing a specified number of future observations. The second approach proposed in this paper is based on a moving window scheme.
Simulated data are used to tune the parameters of the proposed improved methodologies and to prove their effectiveness in adapting to dynamic time series. The moving window approach is found to be the best on simulated data in terms of True Positive Rate (TPR), False Negative Rate (FNR) and False Positive Rate (FPR). Therefore, the performance of the moving window approach is further assessed towards both different simulated scenarios and field data taken on a gas turbine.
SGT-750 Fuel Flexibility: Engine and Rig Tests
Authors: Lindman Olle , Andersson Mats , Bonaldo Alessio , Larsson Anders , Janczewski Jacek , Persson Magnus 
Published: August 2017

This paper provides a description of the fuel flexibility tests performed in:
• a gas turbine
• a high pressure combustion rig
• an atmospheric combustion rig
with the combustion system used in Siemens recently developed gas turbine SGT-750.
The gas turbine test campaign was run with natural gas blends with up to 50vol% nitrogen or 40vol% carbon dioxide. Ignition and engine starts with inert gas blends were also tested.
The fuel flexibility tests were continued in a single burner high pressure combustion rig. Both inert and reactive gas blends were tested. High concentrations of inert gases were tested at simulated cold ambient conditions (down to −60°C) at high and low loads. Reactive gases, such as ethane, propane, butane and hydrogen, were tested at high load operation. Also syngas blends were tested.
To simulate ignition at extreme arctic conditions an atmospheric rig test was performed with cold air supplied from evaporated liquid air.
The different gas fuel blends were run with low NOx emissions, often below 10 ppm, without water injection.
This paper includes description of the test setups and evaluation of the emissions and combustion stability for the tested gas blends.
Inlet Compatibility and Fan Aeromechanics of HBP Turbofan Engine
Authors: Wang Zhonglin , Chen Jingjing , Chen Yong 
Published: August 2017

As an integrated system, turbofan engine airworthiness certification is a complex network because design, operating conditions and multi-disciplines are interlaced. Inlet compatibility specified in FAR regulations is to demonstrate satisfactory of engine operating characteristics throughout the flight envelope, which can be affected by engine installation and operation conditions. One limited operating condition is the high crosswind on the ground. Flow separated at engine inlet, unsteady and non-uniform, passing through the diffuser to the fan face, stimulated the fan blade at a broad frequency range, which could lead to high cycle fatigue.
A ground crosswind test was conducted by an airplane company to demonstrate the engine inlet compatibility with engine mounted on the rear of the aircraft under various crosswind conditions [1] including 90-degree crosswind, quarterly headwind (315-degree) and quarterly tailwind (225-degree). Results showed that among all tested ambient wind conditions, the engine was the least stable under quarterly tailwind (225-degree).
To predict the fan blade response driven by inlet separation, a process of evaluating inlet separation induced stimulus was illustrated in this paper. The stimuli were classified in two parts, i) synchronous stimulus induced by inlet distortion, and ii) non-synchronous stimulus induced by turbulence. Vibration of a wide-chord fan blade was evaluated by modal analysis and Campbell diagram. Test data of total pressure distortion at fan face were analyzed by Fast Fourier Transform (FFT), and the excitations in frequency domain were applied to fan blade for harmonic analysis. Results revealed that the synchronous excitation caused the blade resonating at an elevated stress level, as expected. This study provided a preliminary assessment and a better understanding of fan aeromechanics, when the engine is operating at the unsteady, unstable, and non-uniform flow environment. Discussions of how to control and how to decrease the vibration level were given in the study.
Methodology to Evaluate the Characteristics of a Twin-Scroll Turbocharger With Various Approaches for the Computation of Thermodynamic Properties
Authors: Mai Holger , Kaufmann André 
Published: August 2017

When it comes to evaluating the thermodynamic and fluid dynamic behavior of a turbocharger (TC) and ensuring the best possible matching to the internal combustion engine, a precise measurement of the characteristic maps is required. Measured on a hot-gas test bench under steady-state conditions, the maps of the compressor and turbine give detailed information about the turbocharger performance and provide boundary conditions for simulating the engine processes of a turbocharged engine.
At the moment there is no comprehensive standard on how to measure a TC on a test bench. All existing guidelines such as SAE J1826 & J922 and ASME PTC 10 contain more general information with recommendations, but turbocharger mapping on a hot-gas test bench is highly complex and has a large dependence on heat transfer. The characteristics are not determined directly, but have to be computed using the measured quantities and the thermodynamic properties of the working fluid. For that reason, all influences that may occur during the measurement have to be taken into account for the comparability of different turbochargers or the repeatability for the same turbocharger specimen.
As a consequence, this paper deals with the methodology of thermodynamic computation for a mono-scroll and a twin-scroll turbocharger in general and the impact of different approaches for computing the thermodynamic properties of the individual species on compressor and turbine efficiencies in particular.
For computing the characteristics of a mono-scroll turbocharger, a methodology is used that matches good practice and state-of-the-art technology. For computing the characteristics of a twin-scroll turbocharger, a new methodology is developed to provide a practical approach for the evaluation of pressure ratios and efficiencies of a twin-entry turbine. The use of the closed-loop unit for the extension of the turbine is included.
Computing the thermodynamic state changes, power, and efficiencies of the compressor and turbine requires knowledge of the physicochemical properties of the involved fluids. These fluids are humid air (compressor) and exhaust gas (turbine) and depend on the gas composition, pressure, and especially temperature with respect to the relative humidity.
Turbocharger efficiencies are very sensitive to deviations in the thermodynamic properties of the individual species. Different forms of polynomials with different levels of complexity and precision are available in literature. In this paper, the most commonly used polynomials for computing the thermodynamic properties such as caloric perfect gas, humid air, VDI 4670, NASA9, CHEMKIN, NIST, and SAE J1826 will be used for the characteristic maps of a twin-scroll turbocharger. The results will be discussed in terms of the impact on turbocharger efficiencies and the relevance to achieving a desired quality level for turbocharger mapping.
Plasma-Assisted Combustor Dynamics Control at Ambient and Realistic Gas Turbine Conditions
Authors: Kim Wookyung , Cohen Jeffrey 
Published: August 2017

The central objective of this study is to investigate the effectiveness of implementing a plasma discharge to improve combustor dynamics and flame stability. Specifically, a nano-second pulsed plasma discharge (NSPD) was applied to a premixed gaseous fuel/air dump combustor for mitigation of dynamic combustion instabilities with a minimal NOX penalty. This paper addresses the scaling of this technology from ambient pressure and temperature conditions to more realistic gas turbine combustor conditions.
A model combustor operating at representative conditions of O (102) m/s flow velocity, ∼ 580 K combustor inlet temperature, and ∼ 5 atm in-combustor pressure was selected to simulate a typical low-power environment of future aero engine gas turbine combustors. Fully premixed methane or propane was utilized as a fuel. Similar to a previous ambient-pressure study, a significant reduction of pressure fluctuation level was observed, by a factor of 2X to 4X over a wide range of velocity at the baseline temperature and pressure. The plasma power required for the reduction increased linearly with increasing velocity. The change of fuel from methane to propane showed that propane requires significantly (2X) higher plasma power to achieve a similar level of noise reduction. It was also observed that the lean blowout (LBO) limit was significantly extended in the presence of the plasma, however, substantial incomplete combustion occurs in the extended regime. NOX measurements showed that the incremental NOX production due to the presence of the plasma was low (∼ < 1EINOX) in general, however, it increased with decreasing velocity and pressure, and increasing temperature.
Influence of Gas-to-Wall Temperature Ratio on By-Pass Transition
Authors: Cação Ferreira Tânia S. , Arts Tony 
Published: August 2017

An investigation of thermal effects on bypass transition was conducted on the highly-loaded turbine guide vane LS89 in the short-duration isentropic Compression Tube (CT-2) facility at the von Karman Institute for Fluid Dynamics (VKI).
Measurements from high response surface-mounted thin films coupled with analog circuits provided the time-resolved wall heat flux history whereas pneumatic probes, differential pressure transducers and thermocouples allowed the accurate definition of the inlet and outlet flow conditions.
The gas-to-wall temperature ratio, ranging from 1.11 to 1.55, was varied by changing the inlet total temperature. The isentropic exit Mach number ranged from 0.90 to 1.00 and the global freestream turbulence intensity value was set at 0.8, 3.9 and 5.3%. The isentropic exit Reynolds number was kept at 106.
The onset of transition was tracked through the wall heat flux signal fluctuations. Within the present operating conditions, no significant effect of the gas/wall temperature ratio was put in evidence. At the present (design) transonic exit conditions, the local free-stream pressure gradient appears to remain the main driver of the onset of transition. A wider range of operating conditions must be considered to draw final conclusions.