bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unsteady Aerodynamics on Multi-Passage LP Last Stage Induced by Flow Separation Under Low Load Flow
Authors: Zhang Jing , Xie Danmei , Wu Fan , Du Haifen , Chen Wei 
Published: November 2019

Abstract
With the rapid development of renewable energy generation, the requirement for operational flexibility of power plants has increased. This has led to steam turbine operating frequently at low load flow conditions.
This paper focuses on the investigation of unsteady aerodynamic excitation in the last stage of LP under low load flow, which was conducted by assuming one single passage, to provide detailed flow information for optimization design. We present a numerical investigation of unsteady pressure forces on Multi-passage LP last blade rows caused by flow separation under low load flow. The flow field of the turbine was calculated by transient 3D computational fluid dynamic (ANSYS CFX16.0).
The results indicate the vortex strength induced by high incidence angle under low load flow having the characteristic of spatial non-uniformity and time non-uniformity. We found that the unsteady pressure forces on the rotor are significantly influenced by the separation vortex and have different phase pressure fluctuation between neighboring two rotor blades. The variation in the forces indicates that the neighboring rotor blades experience a load imbalance at every time step which may results in oscillation in the last long moving blades. In particular, the tip vortex plays a crucial part in unsteady aerodynamics.
Evaluation of Arabian Super Light and Arabian Extra Light Crude Oil for Use in Dry Low NOx (DLN) Combustion Systems
Authors: Goldmeer Jeffrey , Glaser Paul , Mohammad Bassam 
Published: November 2019

Abstract
The Kingdom of Saudi Arabia has seen significant transformation in power generation in the past 10 years. There has been an increase in the number of F-class combined cycle power plants being developed and brought into commercial operation. There has also been a shift to the use of natural gas as primary fuel. At the same time, there has been an interest in switching the back-up fuel for new power plants from refined distillates to domestic crude oils. Both Arabian Super Light (ASL) and Arabian Extra Light (AXL) have been proposed for use in new F-class gas turbine combined cycle power plants. This paper provides details on the combustion evaluations of ASL and AXL, as well as the first field usage of ASL in a gas turbine.
Experimental and Numerical Investigation on Film Cooling Performance and Flow Structure of Film Holes
Authors: Cao Nan , Li Xue , Wu Ze-yu , Luo Xiang 
Published: November 2019

Abstract
Discrete hole film cooling has been commonly used as an effective cooling technique to protect gas turbine blades from hot gas. There have been numerous investigations on the cylindrical hole and shaped hole, but few experimental investigations on the cooling mechanism of the novel film holes with side holes (anti-vortex hole and sister hole) are available. This paper presents an experimental and numerical investigation to study the film cooling performance and flow structure of four kinds of film holes (cylindrical hole, fan-shaped hole, anti-vortex hole and sister hole) on the flat plate. The film holes have the same main hole diameter of 4mm and the same inclination angle of 45°. The adiabatic film cooling effectiveness is obtained by the steady-state Thermochromic Liquid Crystal (TLC). The flow visualization experiment and numerical investigation are performed to investigate the flow structure and counter-rotating vortex pair (CRVP) intensity. The smoke is selected as the tracer particle in the flow visualization experiment. The mainstream Reynolds number is 2900, the blowing ratio ranges from 0.3 to 2.0, and the density ratio of coolant to mainstream is 1.065. Experimental results show that compared with the cylindrical hole, the film cooling performance of the anti-vortex hole and sister hole shows significant improvement at all blowing ratios. The sister hole can achieve the best cooling performance at blowing ratios of 0.3 to 1.5. The fan-shaped hole only performs well at high blowing ratios and it performs best at the blowing ratio of 2.0. Flow visualization experiment and numerical investigation reveal that the anti-vortex hole and sister hole can decrease the CRVP intensity of the main hole and suppress the coolant lift-off because of side holes, which increases the film coverage and cooling effectiveness. For the sister hole, the side holes are parallel to the main hole, but for the anti-vortex hole, there are lateral angles between them. The coolant interaction between the side holes and main hole of the sister hole is stronger than that of the anti-vortex hole. Therefore, the sister hole provides better film cooling performance than the anti-vortex hole.
Investigation of Combustor-Turbine-Interaction in a Rotating Cooled Transonic High-Pressure Turbine Test Rig: Part 2 — Numerical Modelling and Simulation
Authors: Gövert Simon , Ferraro Federica , Krumme Alexander , Buske Clemens , Tegeler Marc , Kocian Frank , di Mare Francesca 
Published: November 2019

Abstract
Reducing the uncertainties in the prediction of turbine inlet conditions is a crucial aspect to improve aero engine designs and further increase engine efficiencies. To meet constantly stricter emission regulations, lean burn combustion could play a key role for future engine designs. However, these combustion systems are characterized by significant swirl for flame stabilization and reduced cooling air mass flows. As a result, substantial spatial and transient variations of the turbine inlet conditions are encountered. To investigate the effect of the combustor on the high pressure turbine, a rotating cooled transonic high-pressure configuration has been designed and investigated experimentally at the DLR turbine test facility ‘NG-Turb’ in Göttingen, Germany. It is a rotating full annular 1.5 stage turbine configuration which is coupled to a combustor simulator. The combustor simulator is designed to create turbine inlet conditions which are hydrodynamically representative for a lean-burn aero engine. A detailed description of the test rig and its instrumentation as well as a discussion of the measurement results is presented in part I of this paper. Part II focuses on numerical modeling of the test rig to further extend the understanding of the measurement results. Integrated simulations of the configuration including combustor simulator and nozzle guide vanes are performed for leading edge and passage clocking position and the effect on the hot streak migration is discussed. The simulation and experimental results at the combustor-turbine interface are compared showing a good overall agreement. The relevant flow features are correctly predicted in the simulations, proving the suitability of the numerical model for application to integrated combustor-turbine interaction analysis.
Control Strategies of an Academic Rotor/Stator Cavity Through Sensitivity Analysis
Authors: Queguineur Matthieu , Gicquel Laurent , Staffelbach Gabriel 
Published: November 2019

Abstract
Strong hydrodynamic instabilities are often observed in rotating cavities of turbomachinery in the aerospace industry for specific thermal and operating conditions. This highly unsteady motion of the flow, often referred to as ‘pressure bands’ phenomenon can be detrimental and jeopardize the structural integrity of aeronautical engines by damaging turbomachinery components or turbopumps in the context of space applications. In order to avoid this fluid structure interaction, a deeper understanding of the stability of the flow of rotating cavities becomes compulsory. A few studies enabled to point out the spatial distribution and origins of such multi-frequency flow. However control solutions have not yet been set up. In this context, an academic stator/rotor cavity is studied in this paper with a sensitivity analysis to base flow modification based on linear stability analysis. This latter points out the regions of the stator boundary layer of each mode where the flow should be modified. Possible passive control strategies are then proposed from the interpretation of the results. The more relevant solution being suction and injection actuators directly introduced on the stationary disk of the cavity.
Inlet and Outlet Characteristics Boundary Conditions for Large Eddy Simulations of Turbomachinery
Authors: Odier Nicolas , Poinsot Thierry , Duchaine Florent , Gicquel Laurent , Moreau Stéphane 
Published: November 2019

Abstract
Inlet an outlet boundary conditions are essential elements of any CFD predictions and this is even more so for turbomachinery Large Eddy Simulations, either applied to academic or industrial configurations. For compressible solvers, non-reflecting, characteristic inlet boundary condition imposing total pressure, total temperature and flow direction is usually needed, while an outlet relaxation methodology that automatically adapts the outlet static pressure as a function of the desired mass-flow rate rate is used for turbomachinery flow predictions. Establishing such a framework is clearly desirable especially for industrial use of LES. Development and validations remain necessary in such a fully unsteady context as detailled hereafter.
Investigation of Steam Turbine Warm-Keeping by Use of Air
Authors: Toebben Dennis , Luczynski Piotr , Wirsum Manfred , Mohr Wolfgang F. D. , Helbig Klaus 
Published: November 2019

Abstract
The changing energy landscape leads to a rising demand of more flexible power generation. A system for steam turbines warm-keeping provides the ability to shutdown conventional power plants during periods with a high share of renewable power. Simultaneously, these power plants are ready for grid stabilization on demand without an excessive consumption of lifetime during the start-up. One technical solution to keep a steam turbine warm is the use of hot air which is passed through the turbine. In addition, the air supply prevents corrosion during standstill and also enables the pre-warming after maintenance or long outages.
This paper investigates the warm-keeping process of an intermediate pressure steam turbine (double shell configuration) through the use of dynamic numerical Finite-Elements (FE) simulations. As a representative test-case, warm-keeping calculations during a weekend shutdown (60h) are conducted to investigate the temperatures, their distribution and gradients within the rotor and the casing. For this purpose an improved numerical calculation model is developed. This detailed 3D FE model (including blades and vanes) uses heat transfer correlations conceived for warm-keeping with low air mass flows in gear mode operation. These analytical correlations take heat radiation, convection and contact heat transfer at the blade roots into account. The thermal boundary conditions at the outer walls of rotor and casing are determined by use of experimental natural cool-down data. The calculation model is finally compared and verified with this data set.
The results offer valuable information about the thermal condition of the steam turbine for a subsequent start-up procedure. The warm-keeping operation with air is able to preserve hot start conditions for any time period. Most of the heat is transferred close to the steam inlet of the turbine, which is caused by similar flow directions of air and steam. Thus, temperatures in the last stages and in the casing stay well below material limits. This allows higher temperatures at the first blade groove of the turbine, which are highly loaded during a turbine startup and thus crucial to the lifetime.
Investigation and Thermal Modeling of the Thermal Contact Resistance at a Steam Turbine Blade Root
Authors: Toebben Dennis , Goerner Alexander , Luczynski Piotr , Wirsum Manfred , Mohr Wolfgang F. D. , Helbig Klaus 
Published: November 2019

Abstract
Increasing load ramps and temperature gradients in steam turbines, especially during start-ups, have a high impact on the component lifetime. Calculation models are commonly used to predict the lifetime consumption during such start-up procedures. However, the changing energy landscape requires innovative solutions to increase the power plant flexibility. In order to accelerate the start-ups with a simultaneously reduced lifetime consumption, hot air can be used to keep the steam turbine warm during shut downs. The calculation of heat fluxes within the steam turbine is crucial for the accurate prediction of the thermal state and the resulting lifetime consumption. Improved models enable the determination of life cycles as exact as possible.
During warm-keeping and pre-warming operations, the steam turbine rotates slowly. Thus, low centrifugal forces lead to high thermal contact resistances (TCR) at the blade roots, which influence the temperature distribution at the lifetime limiting locations, e.g. blade grooves. The paper presents heat transfer correlations, which describe the TCR depending on the rotational speed of the rotor. For this purpose, an experimental setup is designed in order to investigate the influence of contact pressure, ambient pressure and surface properties. For the detailed investigation of the complex heat fluxes at the T-root, a 3D Finite-Elements (FE) model is developed. This model calculates the TCR and specific heat fluxes based on measurement data. On the basis of the detailed evaluation, different analytical heat transfer correlation approaches with respect to the application in an overall steam turbine model are developed. These heat transfer correlations are integrated into the FE model and validated with additional measurements.
Modelling Geared Turbofan and Open Rotor Engine Performance for Year-2050 Long-Range and Short-Range Aircraft
Authors: Sebastiampillai Joshua , Jacob Florian , Mastropierro Francesco S. , Rolt Andrew 
Published: November 2019

Abstract
The paper provides design and performance data for two envisaged year-2050 state-of-the-art engines: a geared high bypass turbofan for intercontinental missions and a contra-rotating pusher open rotor targeting short to medium range aircraft. It defines component performance and cycle parameters, general powerplant arrangements, sizes and weights. Reduced thrust requirements for future aircraft reflect expected improvements in engine and airframe technologies. Advanced simulation platforms have been developed, using the software PROOSIS, to model the engines and details of individual components, including custom elements for the open rotor engine.
The engines are optimised and compared with ‘baseline’ year-2000 turbofans and an anticipated year-2025 entry-into-service open rotor to quantify the relative fuel-burn benefits. A preliminary scaling with non-optimised year-2050 ‘reference’ engines, based on Top-of-Climb (TOC) thrust and bypass ratio, highlights the trade-offs between reduced specific fuel consumption (SFC) and increased weight and engine diameter. These parameters are then converted into mission fuel burn using linear and non-linear trade factors from aircraft models.
The final turbofan has an optimised design-point bypass ratio (BPR) of 16.8, and a maximum overall pressure ratio (OPR) of 75.4 for a 31.5% TOC thrust reduction and a 46% mission fuel burn reduction per passenger kilometre compared to the respective year-2000 baseline engine and aircraft combination. The final open rotor SFC is 9.5% less than the year-2025 open rotor and 39% less than the year-2000 turbofan, while the TOC thrust increases by 8% versus the 2025 open rotor, due to assumed increase in aircraft passenger capacity. Combined with airframe improvements, the final open rotor-powered aircraft has a 59% fuel-burn reduction per passenger kilometre relative to its year-2000 baseline.
Experimental Investigation of Surge Phenomena in a Transonic Centrifugal Compressor
Authors: Ito Sasuga , Furukawa Masato , Gunjishima Satoshi , Usuki Hiroki , Ota Takafumi , Yamada Kazutoyo 
Published: November 2019

Abstract
Surge is an unsteady flow phenomenon occurring at low flow rates in the pipeline system including compressors. The surge is a phenomenon that must be avoided because of the danger in the operation: the pipeline equipment can be damaged or the operation cannot be continued. Experimental work is required not only to understand the unsteady behavior but to also validate the CFD used for more localized analysis and development of the understanding of the flow phenomena when operating near surge. Nevertheless, there are still many unclear points not only about the flow phenomenon at the inception of the surge which is important for the prediction of the surge but also about the surge behavior itself. Especially, as for the surge occurring in transonic centrifugal compressors, there are currently few experimental research cases due to the difficulty of the unsteady measurement.
In this research, we measured the time variations in pressure and flow rate in a transonic centrifugal compressor for a vehicle turbocharger which consists of an impeller, vaneless diffuser and scroll. In the experiments, the measurement pipes were set upstream and downstream of the compressor and the velocity and the wall static pressure were measured with an I-type hot wire probe and high response pressure transducers, respectively. In addition, to investigate the process and the occurrence point of the back flow in surge, the wall static pressure was measured by means of high response pressure transducers which were mounted on the shroud upstream of the impeller and the diffuser hub at the two-circumferential positions, respectively. As the result of the experiments, the unsteady flow process during the mild and deep surges was measured and the inception of deep surge was clarified.
Analysis of the Self-Excited Dynamics of a Heavy-Duty Annular Combustion Chamber by Large-Eddy Simulation
Authors: Michelassi Vittorio , Meloni Roberto , Riccio Giovanni , Ceccherini Gianni 
Published: November 2019

Abstract
This paper discusses the use of LES to predict the performance of an annular combustion chamber in stable operating conditions and in presence of self-exited dynamics. The availability of high-accuracy data taken in a full-scale combustion test facility allowed an extensive validation of the prediction capability. The analysis focuses on a small size heavy duty annular gas turbine whose size allows to test and compute the entire 360° combustion chamber.
The comparison with measurements confirms that, if the correct operating conditions are implemented, LES is capable to discern between stable and unstable operating conditions, as well as predict several other engineering relevant parameters, although the model is sometime affected by a limited shift in frequency.
The post processing of LES results in presence of combustion dynamics is not a trivial task. Here the results of the simulations have been post-processed by means of a triple decomposition method to determine a mean flow, a deterministic unsteady flow at the main instability frequency and a turbulent stochastic flow. Such decomposition indicated the instability triggering mechanism together with the cross-talk mechanism between different components. This approach is currently used for design phase, while further validation is on-going to include different geometries and operating conditions with the goal of reducing both risks and number of tests.
Updating the Helicopter Gas Turbine Engine Mass Model for the Defining of the Turboshaft Engine Optimal Operating Cycle Parameters
Authors: Kalabuhov D. S. , Grigoriev V. A. , Zagrebelnyi A. O. , Diligensky D. S. 
Published: November 2019

Abstract
The article describes the adjusted parametrical turboshaft gas turbine engine mass model that is applied for the helicopter engine operating cycle parameters optimization during a conceptual engineering.
During the operation of the take-off mass, which indirectly characterizes the cost of materials for the entire designed aircraft system, one of the main components which determines the coordination of the helicopter and its engine parameters is a mass of the gas turbine power unit. Moreover, during the parametrical studies the designed mass of a power unit should be defined by the parameters of a gas turbine engine; however, this type of dependencies is not that well enough studied for today. Therefore the evaluation of the dependency between the engine mass and its operational parameters is performed by using either generalized statistical data for existing designs or by parametrical mass models since there is nothing more precise up to date. However as new types of gas turbine engines appear it is required to update the values of parametrical model coefficients.
This article describes the influence of different cooling system units on the engine mass and also clarifies the coefficients that specify the engine mass advance by introducing the structural-technological measures. The last one is highly dependent on the designed gas turbine engine (GTE) serial production year. It also has been proposed to represent some coefficients that are used in the model as dependencies of the main operational parameters. This has allowed to perform the parametrical study and to gain predictive solutions in correspondence to the modern engine design level.
Developing Secondary Flow and Heat Transfer in the Entrance Region of a Square Channel With 45° Crossed Rib Arrangement
Authors: Wieler M. , Woerz B. , Jeschke P. , Rabs M. 
Published: November 2019

Abstract
This paper presents developing secondary flow and heat transfer measurements in a ribbed cooling channel. Experiments are carried out for Reynolds number ranging from 25,000–140,000. Regionally averaged local heat transfer measurements are conducted using heated copper segments. Flow measurements are carried out using a miniature five-hole pressure probe and presented for cross sections at intervals of 1.8 hydraulic diameters dh in flow direction. Results are compared to numerical simulations using explicit algebraic Reynolds stress and turbulent heat transfer models. The paper focuses on the entrance region where secondary flow structure has not emerged yet. The findings show that the well-known secondary flow structure of the crossed rib configuration, consisting of one large single rotating secondary flow, is not established until approximately 6–7 dh in main flow direction. Instead two opposed vortices are identified which dominate the flow characteristics and provide an increase in heat transfer of up to 15–20% when compared to the periodically developed flow condition. Thus, for the first time to the author’s knowledge, the paper describes in detail the developing secondary flow in a crossed rib arrangement and links it to the heat transfer distribution observed. In summary, this paper stresses the importance of the developing flow region for the design process in convection cooled gas turbines, especially for short channels of high pressure blades and vanes, as it has a significant effect on cooling channel heat transfer performance.