bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat Transfer Coefficient and Adiabatic Effectiveness on a Film-Cooled Pressure Side: Results and Assessment of the IR-Based Measurement Technique Reliability
Authors: Bacci T. , Picchi A. , Galeotti S. , Facchini B. , Cubeda S. 
Published: October 2022

Abstract
The precise knowledge of the external heat transfer coefficient and of the film cooling coverage characteristics is crucial to an efficient design of a turbine nozzle guide vane. From an experimental point of view, thermal methods allow to retrieve both the heat transfer coefficient and the adiabatic wall temperature, but their reliability is generally questionable, as they suffer from problems as thermal conduction. In the present work, a well-known literature nozzle guide vane (VKI LS89 profile) was provided with a simplified cooling system made by a single row of cylindrical holes on the pressure side. A transient thermal technique was employed to characterize both the adiabatic effectiveness and the heat transfer coefficient. The uncertainty and the reliability of thermal technique, which are generally a weak point, were evaluated. The former aspect was addressed by means of virtual experiments, considering both the effect of the measured temperature noise and of the inaccuracies introduced by the physical model adopted for the post-processing. For the latter aspect, adiabatic effectiveness findings were compared to the ones achieved on the same test article from Pressure Sensitive Paint measurements, which have a limited and known degree of uncertainty. The overall results showed that, once a proper approach is taken, the thermal technique is able to accurately retrieve reliable results with an acceptable resolution, even on a test case with dimensions close to real engines. Different fluid-dynamic conditions were investigated to assess the effect of blowing ratio and free-stream turbulence on film cooling performances. The results indicate that the introduction of film cooling on the vane surface significantly enhances the heat transfer coefficient with respect to the uncooled case. Net Heat Flux Reduction was also computed, showing that film effectiveness can not always compensate for the HTC augmentation, highlighting the necessity of properly considering the heat transfer coefficient enhancement.
Optimum Control Scheme for Deformable Blades Applied to Horizontal Wind Turbine
Authors: Jauregui-Correa Juan Carlos , Duran-Castillo Azael 
Published: October 2022

Abstract
Deformable blades are an option for load alleviation and power improvement for Horizontal Wind Turbines. The advantage of using a deformable blade is the load alleviation, the reduction of fatigue loads, and a small increment in power generation. The main drawback is the cost of the mechanical actuators and the need for special materials. Implementing shape morphing mechanisms requires new control schemes in the existing controllers. The proposed design is a cost-efficient and straightforward mechanism. These designs consist of a flexible glass fiber surface deformed with an elastic beam and a cam mechanism that modifies the aerodynamic profile. A single actuator moves a set of adjustable beams distributed along the blade. The operating conditions require the adjustment of two variables: the pitch angle and the modified profile. This paper presents an optimum scheme control that locates the best pitch angle and blade shape combination for incrementing the generated power and reducing the bending moment. The optimum control scheme results from the bending moment analysis and the estimation of the power coefficient for maximum power production. The mapping of these conditions was constructed using the Blade Element Momentum, and the results were verified with a Computational Fluid Dynamics analysis. The optimization process permits the definition of lookup tables that feed the control algorithm and set the controller’s parameters within the wind changes interval.
Low Reynolds Number Effects on the Endwall Flow Field in A High-Lift Turbine Passage
Authors: Donovan Molly H. , Rumpfkeil Markus P. , Marks Christopher R. , Robison Zachary , Gross Andreas 
Published: October 2022

Abstract
Understanding the endwall flow phenomena surrounding low-pressure turbine blades is key to improving performance, as these flow features contribute significantly to loss generation at low Reynolds number cruise. It is well documented that a horseshoe vortex system forms at the junction of the endwall and turbine blade. The vortices develop and gain significant strength in the passage and contribute to total pressure losses. During low Reynolds number conditions, the flow through a low-pressure turbine passage can be greatly impacted by a number of factors, including Reynolds number and incoming turbulence. The focus of this paper is on significant changes to the endwall flow field observed in experimental measurements and an accompanying implicit large-eddy simulation of the flow through a linear cascade of high-lift front loaded low-pressure turbine blades at low Reynolds number. Results show a significant effect on both the time-averaged endwall flow topology and the unsteady vortical flow characteristics when the Reynolds number based on inlet conditions was decreased to 30,000. Various techniques, such as spectral proper orthogonal decomposition, were used to analyze and compare both high-speed particle image velocimetry measurements and numerical results in order to extract the dominant structures and their unsteady behavior. The total pressure loss development through the passage was assessed in order to better understand how the observed changes in endwall flow structures contribute to the overall losses.
Numerical Modeling of Water Droplets in Compressible Two-Phase Flows Based on Eulerian-Eulerian Method
Authors: Furusawa Takashi , Sasao Yasuhiro , Takata Ryo , Miyazawa Hironori , Yamamoto Satoru 
Published: October 2022

Abstract
The slip velocity between water droplets and gas phase causes losses in steam turbines. The accurate prediction of the motion of coarse water droplets in wet-steam flows is crucial for the prediction of efficiency and erosion. In this study, the Eulerian-Eulerian method, which assumes water droplets as a continuous phase, was developed to simulate the motion of coarse water droplets in compressible two-phase flows. The conservation equations consisting of mass, momentum, energy, and number density for coarse water droplets, were coupled with compressible Navier-Stokes equations. Additionally, drag forces owing to the slip velocity between the water droplets and the gas phase were included in the model. Dry-air and moist-air flows through a subsonic turbine cascade were simulated. The inlet droplet sizes were set to 0.5, 5.0, and 10.0 μm in each computational case. Under dry conditions, the numerical results produced the increase in the loss in the wake region. Under wet condition, 0.5 μm droplets went through the cascade without colliding with the blade surface because of the high drag coefficient for fine droplets. 5.0 and 10.0 μm droplets partially collided with the blade surface owing to the slip velocity between the droplets and the gas phase. While the nondimensional losses in case of the 0.5 μm droplets were higher than experimental results at each pitch position, those of the 10.0 μm droplets had a maximum peak in the wake region. The present method enables to produced losses by the slip velocity in each droplet size. The nondimensional losses of the experiments were reproduced by considering the particle size distribution and volume rate of droplets.
LES Investigation of Low Rossby Number Buoyant Flow in Rotating Cavities
Authors: Sun Zixiang , Gao Feng , Chew John , Amirante Dario 
Published: October 2022

Abstract
Flow and heat transfer in axial compressor disc cavities involve strong interaction of axial throughflow at the disc bores with centrifugal buoyant flow in the cavities. This paper presents large eddy simulation (LES) of flow and heat transfer in rotating cavities with a heated shroud and a relatively weak axial cooling throughflow. The conditions considered for a single cavity configuration correspond to Rossby numbers Ro = 0.2 and 0.3, rotational Reynolds numbers ReΩ = 3.2 × 105 and 7.7 × 105, and buoyancy parameters βΔT = 0.24 and 0.26. Reasonable agreement of the results with shroud heat transfer measurements was confirmed for the Ro = 0.2 condition for which test data were available. A dual cavity configuration for Ro = 0.3 and ReΩ = 3.2 × 105 is also modelled.
The simulations show that, at low Ro conditions, flow reversals occur along the length of the bore flow path, upstream and downstream of the rotating cavities. With dual cavity this causes strong, unsteady interactions between the flows in the two cavities. These flow interactions result in less stable flow structures, higher air temperatures within the cavities and lower shroud and disc heat transfer compared to the single cavity case. FFT analysis reveals a complex phase-locking mechanism between flows in the two cavities.
Film Cooling and Cold Streaks Tracking on a Fully Cooled Nozzle Guide Vane Under Representative Combustor Outflow Conditions
Authors: Babazzi Giulia , Bacci Tommaso , Picchi Alessio , Facchini Bruno , Cubeda Simone 
Published: October 2022

Abstract
The pronounced non uniform temperature distribution in the core engine flow path is a recurring problem of gas turbine engine design process. Specifically, turbine entry conditions are usually characterised by severe temperature distortions, often referred to as hot and cold streaks, ascribed to combustor burners and combustor liners cooling systems. Temperature distortions remain an issue even at the exit section of the nozzle guide vane (NGV), where additional cold streaks coming from the vane film cooling system are injected into the flow. A precise knowledge of thermal field and its evolution is thus essential to mitigate their impact on turbine performance and lifetime. Various studies focus on the description of streaks migration through a direct investigation of the thermal field, providing an effective evaluation of the global phenomenon. As a deeper understanding is often required, experimental techniques based on the detection of tracer gases can be successfully adopted.
In this study, a realistic combustor outlet swirl profile was imposed on a fully cooled NGV cascade to analyse both film-cooling behaviour and cold streaks migration and redirection. A concentration probe based on the fluorescence behaviour of an oxygen sensor, fully characterised in a previous work, was here employed to track the position of the film cooling flows at the NGV cascade exit plane, while the adiabatic film-cooling effectiveness was evaluated on the NGV surfaces employing the Pressure Sensitive Paint (PSP) technique. Overall, the swirling structure strongly affect both the film-cooling behaviour and cold streaks migration through and downstream the vane. The importance of examining the unsteady aspect is also highlighted to better estimate actual components operating temperatures. A global understanding of the occurring phenomena is therefore provided, as well as significant pieces of information that can be extremely useful for the design phases of both the NGV and the following rotor cascade.
Full Rejuvenation Heat Treatment of GTD 111DS
Authors: van Esch Hans , Pietersen Stijn , Greaves Wayne , Bridges Alex , Scheibel John 
Published: October 2022

Abstract
Previous studies performed by TEServices, Sulzer and EPRI showed that GTD111 DS metallurgical and mechanical [stress rupture (SR) and low cycle fatigue (LCF)] properties can be restored close to new with and without hot isostatic pressing (HIP) followed by full solution heat treatment (FSHT). Based on this success, a full rejuvenation heat treatment (FRHT) was developed that can obtain GTD 111DS metallurgical condition and mechanical properties which are better than new.
This paper will show the metallurgical condition differences between new material, partial solution heat treatment (PSHT), FRHT and the related mechanical (SR and LCF) properties. A mechanical test was developed that varied exposure of FSHT and FRHT specimens between stress (SR) and fatigue (LCF) which is especially important for high starts and relatively low hour gas turbine operation.
This study proved that the FRHT provides superior metallurgical and mechanical properties when compared to FSHT and new GTD 111DS.
Numerical Study of Flow Characteristics of a Central-Staged Swirl Combustor
Authors: Feng Xiangzhou , Suo Jianqin , Zhu Pengfei , Li Yue , Li Qiandong 
Published: October 2022

Abstract
The two-combustion-zone design approach is adopted in order to achieve good idle LBO in a central-staged swirl combustor. The flow characteristics of the combustor are investigated through large eddy simulation (LES). The numerical method is validated by comparing the numerical results of time-average velocity profiles with PIV results at various axial locations. The grid scale is analyzed through Pope’s criterion to guarantee that most turbulent kinetic energy can be resolved by the present mesh. The coherent structures are isolated from turbulence flow by proper orthogonal decomposition (POD) method. Multiple monitor probs are set up in swirling flow and shear layers. The fast Fourier transform (FFT) is used to obtain frequency characteristic of time-domain signal. The difference between time-average velocity field and instantaneous velocity field is first explained. The recirculation zones are sorted by the locations and formation mechanism. The precessing vortex core (PVC) is found to be the crucial coherent structure of central-staged combustor. The spatial structure and temporal evolution of PVC are captured. Both single-helix and double-helix modes are discovered through POD method. By using phase-averaged method, the interaction between PVC and axial velocity field is investigated.
An Experimental Test Case for Transonic Low-Pressure Turbines – Part I: Rig Design, Instrumentation and Experimental Methodology
Authors: Simonassi Loris , Lopes Gustavo , Gendebien Samuel , Torre Antonino Federico Maria , Patinios Marios , Lavagnoli Sergio , Zeller Nicolas , Pintat Ludovic 
Published: October 2022

Abstract
The ultra-high bypass ratio geared turbofan is a key concept to reduce the environmental impact of the next generation aircrafts. The increase in rotational speed of the low-pressure turbine (LPT) enabled by the geared architecture offers potential benefits in efficiency and considerable savings in engine weight, overall dimension, and cost. High-speed LPTs operate at transonic exit Mach numbers and low Reynolds numbers. For this combination of operating conditions, where compressibility influences the blade aerodynamics and loss mechanisms, there is a critical lack of openly available detailed experimental data concerning the combined effects of unsteady wakes, purge streams, leakages, and secondary flows for CFD models validation.
The current research project focuses on the full characterization of an experimental test case concerning the impact of unsteady wakes and purge flows on the blade aerodynamics and loss mechanisms in a high-speed LPT cascade tested at engine-scaled conditions. The extensive experimental dataset is collected in an open-access database, providing novel validation material for comparison with numerical computations.
In this two-part paper, a comprehensive study on the design, commissioning and testing of a transonic low-pressure turbine blade at on and off-design is presented. Part I describes the design of components and accurate instrumentation required to investigate steady quasi-3D flows in a linear cascade environment at low-Reynolds and transonic exit Mach numbers. A novel concept to perform blade radial traverses to obtain spanwise distributions of high-resolution blade measurements is presented. The repeatability and periodicity of the rig flow conditions are demonstrated. This work critically evaluates the methodology used for the design and adaptation of the existing rig for testing of unsteady three-dimensional flows in linear cascade experiments.
Gas Turbine Transition Duct Gap Assessment for Unsymmetrical Thermal Boundary Conditions
Authors: Sambandam Manoharan , Colantoni Simone 
Published: October 2022

Abstract
The transition duct (TD) in a gas turbine (GT) twin shaft variant provides an aerodynamic coupling between its high-pressure gas generator module and low-pressure power module. Since the TD defines the flow passage, it interfaces with the high-pressure rotor and shroud at the forward end and the low-pressure rotor and stator at the aft end. Normally, the GT twin shaft variant is equipped with part-load capability. To fulfill this need and to comply with the emission norms, only desired number of burners, adjacent to each other, are used to burn fuel. Using some of the burners during the GT operation is referred to as staging. The GT operation under staging conditions result in non-uniform temperature distribution in the angular locations at any axial position and thus non-uniform thermal growth in the radial and axial directions. This non-uniform thermal growth in radial and axial direction leads to the interface definition very challenging. During the staging operation, the rotor parts experiences uniform radial and axial growth at all the angular locations. Whereas the interfacing stator parts experience temperature distribution like that of the TD and results in non-uniform thermal growth in the radial and axial directions. Appropriate interface definition is vital for efficient operation of the GT. Any interference condition of the TD with rotating parts result in rubbing and with stationary parts result in thermal binding, impacting the GT normal operation. Any generous gap adversely impacts the GT performance due to consumption of more cooling medium. Thus, an assembly gap which results in no interference and consumption of less cooling medium throughout the staging operation is considered as optimum assembly gap. Thorough gapping assessment is performed considering all the transient time points to ensure that the gap values are set optimally. This paper is intended to describe the steps followed in assessing the anticipated interference and gap situations at various interfaces.
Particle Deposition on HPT Nozzle: Full 3D Investigation and Secondary Flows Effect
Authors: Casari Nicola , Oliani Stefano , Pinelli Michele , Suman Alessio , Carnevale Mauro 
Published: October 2022

Abstract
Gas turbines can operate in an environment dispersed with particles that, if ingested by the machine, may have a detrimental effect on the aerodynamic performances. Therefore, the aim of this work is to gather information about how particles adhesion is influenced by geometrical features of gradually growing complexity. At this scope, the particle deposition problem is investigated from the numerical standpoint. Specifically, the LS-89 transonic high pressure turbine (HPT) vane is simulated and an encounter with a volcanic ash cloud is modelled. Three simulations are carried out: a 2D simulation has been compared with the set of 3D simulations. Different levels of complexity of the geometry have been considered for the 3D case: the endwall effect has been assessed considering the presence of a variable radius fillet and comparing it with the prediction obtained by a cylindrical extrusion. The proposed analysis provides indications on the 2D and 3D prediction with regards to particle deposition problems. The sticking pattern of the particle has been investigated in relation to the different nature of secondary flows.
Design and CFD Study of an ORC Radial Turbine for Multiple Working Fluids
Authors: Djaname Tchable-Nan , Deligant Michael , Bakir Farid , Marinelli Marzia , Capurso Tommaso , Torresi Marco 
Published: October 2022

Abstract
Organic Rankine cycle is an available solution for the conversion of low-grade thermal energy into electricity. In this way, it contributes to enhance the global plant efficiency hence to the reduction of the power plant carbon footprint (CO2 production). However, contrary to water Rankine cycle or Brayton cycle, in ORC the working fluid may change depending on the characteristics of hot and cold sources. Expander cost is estimated to be around half of the total cost of an organic Rankine cycle installation. Hence, developing a given turbine for multiple applications will help reducing the cost of ORC systems. In this work a radial turbine will be numerically investigated. The design and performance analysis of such a turbine will be analyzed for three working fluids taking into account real gas effect under expansion. An iterative process using preliminary design combined with meanline analysis allows the selection of the final geometry. Finally, 3D CFD simulations are computed on the obtained geometry with the selected working fluids for different operating conditions. Small deviations can be observed between the 3D CFD results and the prediction code. The different fluids have been selected based on safety (ASHRAE A1 and A2), environmental (GWP less than 150, ODP near to 0) and thermodynamic properties criteria (dry or isentropic fluid). The operating conditions have been selected to start the expansion in the low compressibility zone and featuring high rotational speed (up to 60000 rpm), low power (up to 9kW) and high maximum efficiency.
The Effect of an Entirely Eroded Airfoil on the Aerodynamic Performance of a Supersonic Compressor Cascade
Authors: Hartmann Jan , Lorenz Max , Klein Markus , Staudacher Stephan 
Published: October 2022

Abstract
In-service performance of modern axial compressors of aircraft engines is strongly dependent on deterioration processes such as solid particle erosion. So far the resulting aerodynamic losses have been studied by analyzing pre-set shape changes of locally eroded airfoil regions with a focus on the leading edge contours. However, the aerodynamic losses caused by solid particle erosion are the result of the entire shape change of the deteriorated airfoils. These shapes are assignable to the particular erosive conditions and the amount of particles ingested. The midspan airfoil shapes of the NASA Rotor 37 experimentally deteriorated in a linear cascade form the basis of the presented numerical study. The shapes of the eroded airfoils are used to perform supersonic numerical simulations at near stall conditions. The losses and flow patterns caused by different degrees of erosion are discussed. Cascade performance is deteriorated up to 25% due to solid particle erosion. The shock systems for different erosion shapes are evaluated and their influence on the overall losses is demonstrated. It is concluded that the analysis of isolated erosion phenomena such as leading edge changes in shape provide an incomplete understanding of the aerodynamic losses caused by solid particle erosion. The interaction of the entire shape change of the airfoils is needed to fully understand the losses in turbomachines caused by erosion.