bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Review of the Prospect and Challenges for Developing and Marketing a Brayton-Cycle Based Power Genset Gas-Turbine Using Supercritical CO2: Part I — The General System Challenges
Authors: Chen Jinbo , Engeda Abraham 
Published: January 2021

Abstract
Around the 1960s, the proposal of the supercritical dioxide (s-CCO2) power-cycle was first introduced; however, because of various obstacles, the development was slow at that time. With current worldwide emission and power problems, the s-CO2 power cycle has regained more attention because of its unique properties as a working fluid for power-cycle, and zero-emission potential. Each s-CO2 power cycle requires various components for compression, expansion, and heat exchange operation. Among various working fluid, s-CO2 has four significant advantages favorable for developers: 1. Relatively low and achievable critical conditions (∼7.3Mpa, ∼31°C). 2. The high density (∼400kg/m3) results in a very compact turbomachinery design. 3. The low dynamic-viscosity of s-CO2 can reduce the overall flow friction loss. 4. Low compressibility value which can reduce the overall system compression works. All these advantages make the s-CO2 the perfect working fluid for next-generation high-efficiency power-cycle design. This paper in two parts reviews the s-CO2 cycle technologies for power generation and critically assesses the recent challenges and development status. This paper, Part I, focuses on the general cycle concepts, thermodynamic properties, materials selection, and other components considerations.
Prospect and Challenges for Developing and Marketing a Brayton-Cycle Based Power Genset Gas-Turbine Using Supercritical CO2: Part II — The Turbomachinery Components Design Challenges
Authors: Engeda Abraham , Chen Jinbo 
Published: January 2021

Abstract
Since the 1960s the idea of using supercritical dioxide (S-CO2) as the working fluid in a Brayton power-cycle has been entertained [1]. But due to technical limitations of the time, the idea did not progress forward much. Presently, due to the availability of more knowhow, better technological platform, and advanced analysis tools, many believe it is time to revisit the idea of using supercritical dioxide (s-CO2) as the working fluid for power generation. Among various working fluids, s-CO2 has several significant advantages over other fluids. Primarily the attractive qualities of s-CO2 are high efficiency, much smaller turbomachinery size and plant footprint (and therefore lower capital cost), and the potential for full carbon capture. However, the realization of these benefits will depend on overcoming several technical, engineering and materials science challenges. Even though theoretically, the concept is highly attractive and promising, there is yet a major hurdle to be passed, namely the designing, developing, and testing of a reasonable size (10MWe or higher) prototype of a s-CO2 Brayton-cycle-based power gas turbine. This paper, Part II, in two parts reviews the s-CO2 Brayton cycle technologies for power generation and critically assesses the recent challenges and development status. This present paper (Part-II) in two parts focuses on the turbomachinery components (specifically the compressor) design and challenges.
Preliminary Research on Future Smart Engine Architecture
Authors: Liu Yudong , Chen Min , Tang Hailong 
Published: January 2021

Abstract
Aero engines that fit the future have now increasingly attracted the attention of aerospace industry and academia. With this trend, many research projects have been carried out to explore future aero engine technologies. This paper focuses on engine design field, and aims to satisfy the future flight missions that may be unpredictably varying. However, the intrinsic strong coupling of engine component matching mechanism blocks acceleration of engine design. Under this condition, this paper comes up with the concept of smart engine architecture that via a series of engine decoupling strategies, the components can be decoupled to an extent that by properly selecting and assembling them, an engine that satisfies certain flight mission can be designed, this is named mission-oriented pluggable design mode in this paper. Following this idea, a multi-purpose engine design scheme is presented to demonstrate the potential of this engine design mode, and further value of smart engine architecture is discussed.
BEARCAT: The SAFRAN Brand New Test Engine Heavily Instrumented for Accurate Comparison With CFD Calculations
Authors: Champion-Réaud Jean-Louis , Bidan Guillaume , Breining Jean-Luc , Lambert Pierre-Alain , Mendes Carlos , Zouloumian Nicolas 
Published: January 2021

Abstract
In this paper, we detail the development and goals of a brand new turboshaft engine called BEARCAT. “BEARCAT” is an acronyme for ‘’Banc d’Essai Avancé pour la Recherche en Combustion et Aérothermique des Turbomachines’’. BEARCAT is based on a MAKILA engine, a turboshaft developed by Safran Helicopter Engines (formerly Turboméca) and powering the H215 (2 Makila 1A1, 1820 SHP each) and the H225 (2 Makila 2A1, 2000 SHP each) of Airbus Helicopters. BEARCAT is developed by SAFRAN-Tech, the Research and Technology Center of the SAFRAN Group. This test engine is devoted to the fine characterization of aero-thermal phenomena occurring within the combustion chamber and the High Pressure Turbine as well as their interactions. Therefore, BEARCAT differs from a standard test engine by the implementation of metrologies inside the combustion chamber and the 2-stage High Pressure Turbine, in order to perform both steady and non-steady flow measurements which will be used to validate CFD codes and models. The engine instrumentation induces thorough modifications of several engine parts and also the development of original technical solutions to ensure metrologies integration in minimizing their impact on performances.
Downstream Vortex Generators to Enhance Film-Cooling Effectiveness
Authors: Lee Chien-Shing , Bryden Kenneth M. , Shih Tom I-P. 
Published: January 2021

Abstract
CFD simulation based on steady RANS were performed to assess the usefulness of adding a pair of “downstream” vortex generators (VGs) to improve the effectiveness of film cooling a flat plate through one row of inclined holes. Each VG in the pair is a rectangular plate with span S, chord C, and thickness t that is oriented at +45 or −45 degrees with respect to a plane that passes through the center of the film-cooling hole and placed at a distance D downstream of the hole, where D is the hole diameter. The separation between the VGs in the pair is smallest at their leading edges (0.72D) so that the VGs form a V-shape. Parameters studied include: S/D = 0.0, 0.25, 0.5, 1.0; C/D = 0.0, 0.2, 0.4; and blowing ratios of BR = 0.5, 1.0, and 2.0. Results obtained show “downstream” VGs can significantly increase lateral spreading of the film-cooling jet and thereby greatly improve film-cooling effectiveness. Results obtained also show the effects of S/D, C/D, and BR on adiabatic effectiveness, pressure loss, and vortical structures formed.
Pre-Stall Waves: Precursors to Stall Inception in a Contra-Rotating Axial Fan
Authors: Madasseri Payyappalli Manas , Pradeep A. M. 
Published: January 2021

Abstract
Stall in a compressor or a fan is often associated with pre-stall waves, that could act as precursors. The present study aims to understand in detail the pre-stall waves leading to instabilities in a low aspect ratio, low hub-tip ratio contra-rotating axial fan. Apart from a clean inflow condition, experiments on the contra-rotating fan are also carried out for two radial distortion conditions, namely, hub-radial and tip-radial distortions, and three circumferential distortion conditions, namely, simple-circumferential, hub-complex-circumferential and tip-complex-circumferential distortions. The results primarily concluded that operating rotor-2 at a speed higher than the design speed could possibly suppress the pre-stall disturbances. Towards the fully developed stall, the waves that are associated with low frequencies speed up and thus these waves become intermediate frequency waves. The fluid phenomena that trigger the stall are associated with high frequencies and these subsequently stretch to low frequencies at the onset of fully developed stall. The low-frequency waves and high frequency waves compromise to reach an intermediate frequency range during the fully developed stall. Further, it is observed that disturbances associated with low frequencies as well as high frequencies co-exist during the fully developed stall regime. There is also a region in the frequency spectra where no disturbances are excited and this region appears to be a “no excitation zone”. This paper thus concludes that there possibly exists a mechanism through which the energy is transferred between different frequencies during the pre-stall and fully developed stall regimes.
Towards Quantitative Wall Shear Stress Measurements: Calibration of Liquid Crystals
Authors: Melekidis Stefanos , Elfner Maximilian , Bauer Hans-Jörg 
Published: January 2021

Abstract
The wall shear stress distribution on an aerodynamically loaded component is of both practical and fundamental importance. Significant examples are the improvement of the performance of a vehicle, e.g. drag reduction, and more basic problems, such as the characterization of surface flows, e.g. with respect to flow control. The liquid crystal technique represents a promising diagnostics for measuring wall shear stress magnitude and orientation. In contrast to most other techniques, the direct measurement of two-dimensional wall shear stress distributions is straightforward.
In order to establish quantitative measurements of wall shear stress using the liquid crystal technique, an in-depth understanding of the influencing parameters is required. For their investigation, a novel generic flat plate test section was designed. The experiments are performed in such a way that a turbulent boundary layer is triggered at a corresponding Reynolds number within the test section. Due to the generic test case, precise and well-known flow boundary conditions can be established, which in turn are validated by probe measurements. Velocity and temperature profiles are recorded with high spatial resolution using a miniaturized combined Pitot-thermocouple probe. Furthermore, the operational range of the new test rig is presented. Preliminary wall shear stress measurements confirm the well-defined flow conditions in the test section and the potential of the measurement technique.
Topological Optimization of Under-Platform Dampers With Moving Morphable Components and Global Optimization Algorithm for Nonlinear Frequency Response
Authors: Denimal E. , El Haddad F. , Wong C. , Salles L. 
Published: January 2021

Abstract
To limit the risk of High Cycle Fatigue, underplatform dampers are traditionally used in aircraft engines to control the level of vibration. Many studies demonstrate the impact of the geometry of the damper on its efficiency, thus the consideration of topological optimization to find the best layout of the damper seems natural. Because of the nonlinear behaviour of the structure due to the friction contact interface, classical methods of topological optimization are not usable. The present study proposes to optimize the layout of an underplatform damper to reduce the level of nonlinear vibrations computed with the Multi-Harmonic Balance Method. The approach of topological optimization employed is based on the Moving Morphable Components framework together with the Kriging and the Efficient Global Optimization algorithm to solve the optimization problem. The results show that the level of vibration of the structure can be reduced of 30% and allow for the identification of different efficient geometries.
Investigation of Film Cooling Using Time-Resolved Stereo Particle Image Velocimetry
Authors: Stichling Katharina , Elfner Maximilian , Bauer Hans-Jörg 
Published: January 2021

Abstract
In the present study an existing test rig at the Institute of Thermal Turbomachinery (ITS), Karlsruhe Institute of Technology (KIT) designed for generic film cooling studies is adopted to accommodate time resolved stereoscopic particle image velocimetry measurements. Through a similarity analysis the test rig geometry is scaled by a factor of about 20. Operating conditions of hot gas and cooling air inlet and exit can be imposed that are compliant with realistic engine conditions including density ratio. The cooling air is supplied by a parallel-to-hot gas coolant flow-configuration with a coolant Reynolds number of 30,000. Time-resolved and time-averaged stereo particle image velocimetry data for a film cooling flow at high density ratio and a range of blowing ratios is presented in this study. The investigated film cooling hole constitutes a 10°-10°-10° laidback fan-shaped hole with a wide spacing of P/D = 8 to insure the absence of jet interaction. The inclination angle amounts to 35°. The time-resolved data indicates transient behaviour of the film cooling jet.
A High-Fidelity Modeling Tool to Support the Design of Oxy-Combustors for Direct-Fired sCO2 Cycles
Authors: Zambon Andrea C. , Hosangadi Ashvin , Weathers Tim , Winquist Mark , Mays Jeff , Miyata Shinjiro , Subbaraman Ganesan 
Published: January 2021

Abstract
The challenge in the design of oxy-combustors for direct-fired supercritical CO2 (sCO2) cycles is in addressing disparate performance metrics and objectives. Key design parameters to consider include among others: injector design for mixing and flame stability, split of recycled CO2 diluent between injectors and cooling films, target flame temperatures to control non-condensable products, and strategies to inject the diluent CO2 for film cooling and thermal control. In order to support novel oxy-combustor designs, a high-fidelity yet numerically efficient modeling framework based on the CRUNCH CFD® flow solver is presented, featuring key physics-based sub-models relevant in this regime. For computational efficiency in modeling large kinetic sets, a flamelet/progress variable (FPV) based tabulatedchemistry approach is utilized featuring a three-stream extension to allow for the simulation of the CO2 film cooling stream in addition to the fuel and oxidizer streams. Finite-rate chemistry effects are modeled in terms of multiple progress variables for the primary flame as well as for slower-evolving chemical species such as NOx and SOx contaminants. Real fluid effects are modeled using advanced equations of states. The predictive capabilities of this computationally-tractable design support tool are demonstrated on a conceptual injector design for an oxy-combustor operating near 30 MPa. Simulations results provide quantitative feedback on the effectiveness of the film cooling as well as the level of contaminants (CO, NO, and N) in the exhaust due to impurities entering from the injectors. These results indicate that this framework would be a useful tool for refining and optimizing the oxy-combustor designs as well as risk mitigation analyses.
Controller Design for Acceleration and Deceleration of a Turbofan Aircraft Engine
Authors: Zhou Jian , Xin Changkun 
Published: January 2021

Abstract
Controls for transient operation of aircraft engine are highly important due to the fact that the transient performance depends on how the engine responds to throttle command via the control system. The Ndot control is widely used in modern aircraft engine that can produce a consistent acceleration/deceleration throughout the complicated engine conditions.
Two different forms of Ndot controllers are designed for a commercial turbofan engine, which are proposed in this paper. One controller is based on PI controller in tandem with an integrator. And the other is an integral controller associated with feedforward structure. The control structure also contains two cascaded 1-order filters in the feedback loop and a lead compensator on the forward path to improve transient response. The anti-windup design is highlighted in this paper, and a bumpless transfer can be expected during the entire MAX/MIN fuel selection process. The controller design procedure and parameter tuning are fully demonstrated to make the engineering approach more straightforward.
Those two control schemes are further evaluated and compared under engine nominal condition and deteriorated conditions via digital simulation. The simulation results are satisfactory and implicates that both of the controllers can meet the design requirements. The control accuracy of the one with feedforward structure is a little better than the other of PI with integrator. However, the latter design demonstrates better robustness and provides more consistent performance for all engine conditions.
Gas Turbine Transient Performance Simulation With Simplified Heat Soakage Model
Authors: Li Zhuo-Jun , Li Yi-Guang , Korakianitis Theodosios 
Published: January 2021

Abstract
Reliable transient performance is crucial in handling an aircraft gas turbine engine from one steady state to another. The assessment of transient performance stability is normally done during the detailed design stage when component design details become available. Consequently, design iterations may be necessary and costly if engine transient handling and stability are not satisfactory. To make engine design more cost and time effective, it has become important to assess the transient performance stability at conceptual and preliminary design stage with the inclusion of key impact factors such as fuel control schedule, rotor dynamics and heat soakage. However, due to lack of detailed engine structural and geometrical information at the initial design stage, such transient performance simulation and assessment may have to ignore heat soakage effect.
In this paper, a novel generically simplified heat soakage model for three major gas path components of gas turbine engines including compressors, turbines and combustors has been introduced to support more realistic transient performance simulation of gas turbine engines at conceptual and preliminary design stage. Such heat soakage model only requires thermodynamic design parameters as input, which is normally available during such design stages. The model has been implemented into in-house transient performance simulation software and applied to a model twin-spool turbojet engine to test its effectiveness. A comparison between transient performance simulated with and without the heat soakage effects demonstrate that the results are promising.
Although the introduced heat soakage model is less accurate than that using detailed component geometrical information, it is able to include the major heat soakage effect in transient performance simulation and provide engine transient stability analysis to support conceptual and preliminary engine designs.
Modeling of Axial Compressor With Large Tip Clearances
Authors: Evans Simon , Yi Junsok , Nolan Sean , Joseph Liselle , Ni Michael , Kulkarni Sameer 
Published: January 2021

Abstract
In the drive for lower fuel consumption through increased bypass ratio and increased overall pressure ratio (OPR), engine designs for the next generation of single-aisle aircraft will require core sizes below 3 lb/s and OPRs above 50. Traditionally, these core sizes are the domain of centrifugal compressors, but materials limit pressure ratio in these machines to well below 50. An all-axial high pressure compressor (HPC) at this core size, however, comes with limitations associated with the small blade spans at the back of the HPC, as clearances, fillets and leading edges do not scale with the core size. The result is a substantial efficiency penalty, driven primarily by the tip leakage flow produced by the larger clearance-to-span ratio, which negates the cycle efficiency benefits of the high OPR. In order to enable small-core, high-OPR, all-axial compressors mitigating technologies need to be developed and implemented to reduce the large clearance-to-span efficiency penalty. However, for this technology development to be successful, it is imperative that predictive design tools accurately model the overall flow physics and trends of the technologies developed. In this paper we describe an effort to determine whether different modeling standards are required for a large clearance-to-span ratio, and if so, identify criteria for an appropriate solver and/or mesh. Multiple models are run and results compared with data collected in the NASA Glenn Research Center’s Low-Speed Axial Compressor. These comparisons show that steady Reynolds-Averaged Navier-Stokes (RANS) solvers can predict the pressure-rise characteristic to an acceptable level of accuracy, if careful attention is paid to mesh topology in the tip region. However, unsteady tools are necessary to accurately capture radial profiles of blockage and total pressure. The Delayed-Detached Eddy Simulation model was also used to run this geometry, but did not resolve any additional features not captured by the unsteady RANS simulation near stall.
Towards Multidisciplinary Turbine Blade Tolerance Design Assessment Using Adjoint Methods
Authors: Liefke Alexander , Jaksch Peter , Schmitz Sebastian , Marciniak Vincent , Janoske Uwe , Gottschalk Hanno 
Published: January 2021

Abstract
This paper shows how to use discrete CFD and FEM adjoint surface sensitivities to derive objective-based tolerances for turbine blades, instead of relying on geometric tolerances. For this purpose a multidisciplinary adjoint evaluation tool chain is introduced to quantify the effect of real manufacturing imperfections on aerodynamic efficiency and probabilistic low cycle fatigue life time.
Before the adjoint method is applied, a numerical validation of the CFD and FEM adjoint gradients is performed using 102 heavy duty turbine vane scans. The results show that the relative error for adjoint CFD gradients is below 0.5%, while the FEM life time gradient relative errors are below 5%. The adjoint assessment tool chain further reduces the computational cost by around 85% for the investigated test case compared to non-linear methods.
Through the application of the presented tool chain, the definition of specified objective-based tolerances becomes available as a design assessment tool and allows to improve overall turbine efficiency and the accuracy of life time prediction.