bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting Exhaust Gas Recirculation Impacts on Instability and Emissions of an Industrial Gas Turbine Combustor Using Large Eddy Simulations
Authors: Xu Chao , Sung Yonduck , Johnson Daniel , Steele Chris 
Published: August 2024

Abstract
Carbon capture at engine exhaust is a promising technology to reduce carbon footprint for industrial gas turbines. Exhaust gas recirculation (EGR) has been proposed as a potential solution to increase the exhaust CO2 concentration for reducing the cost of carbon capture. A key challenge of applying EGR to practical gas turbines is the enhanced combustion instability as the level of EGR increases. Hence, identifying the upper limit of EGR that maximizes the exhaust CO2 concentration while still allowing for stable combustion is critical to demonstrating the technology feasibility and reducing the number of expensive experimental tests. In this study, a large eddy simulation (LES) model is developed to predict the combustion instability and NOx emissions in an industrial gas turbine combustor under EGR conditions. Adaptive mesh refinement (AMR) is used to resolve complex local flow and flame structures. The finite rate chemistry based combustion model is used to predict the highly transient combustion and emissions behaviors. To accelerate the finite rate chemistry calculation, a 39-species skeletal chemical kinetics mechanism accounting for NOx chemistry is developed for methane/air mixture under EGR conditions for realistic gas turbine operations. The LES model is validated against experimental temperature profile at the combustor exit and good agreement is achieved between LES and experiment. The model is then employed to conduct a parametric study comprising of various levels of EGR and piloting. As EGR level increases, the instability amplitude, defined by the pressure fluctuation inside the combustor, is shown to increase monotonically attributed to the decreased flame speed. The flame jumps from a stable mode to an unstable mode at a threshold EGR level. Piloting is shown to promote or inhibit the instability amplitude depending on the level of EGR. Analysis of adiabatic flame temperatures for both main and pilot flames shows that piloting may not be effective in suppressing combustion instability when the corresponding pilot flame temperature is lower than the main flame temperature. Instead, the instability amplitude is found to be strongly correlated to the laminar flame speed of the main flame alone. On the other hand, when increasing EGR level, the NOx emissions first decrease in the stable regime, then increases abruptly as flame transitions from the stable to unstable mode, and finally decreases again within the unstable regime. Such complex response of NOx is found to be associated with the availability of excess O2 as well as the change of flame size and flame surface area.
A Reduced-Order Model for Predicting Flow and Temperature in a Rotating Tapered Duct Under Constant Thermal Loading
Authors: Kim Wanjae , Shih Tom I-. P. , Bryden Kenneth Mark , Dalton Richard P. 
Published: August 2024

Abstract
Blades in gas turbines have cross sections at the root that are larger than those at the tip so that internal cooling passages in blades are tapered. In this study, a reduced-order model (ROM) — based on the integral continuity, momentum, and energy equations for a thermally and calorically perfect gas was developed to enable rapid assessments of radially outward flow in a tapered duct subjected to constant heat flux with and without rotation. The following parameters were investigated by using the ROM developed: taper angle (α = 0°, 1.5°, 3.0°), ratio of mean radius to hydraulic diameter (Rm/Dh = 45, 150), rotation number (Ro = 0, 0.025, 0.25), Reynolds number (Re = 37,000, 154,000), and thermal loading (q” = 5 × 104, 105 W/m2). Results obtained show the density and pressure variation along the duct to be most affected by rotation number; velocity to be more affected by duct’s taper angle; and temperature by rotation number and taper angle. Results obtained also show the temperature along the duct could decrease if the taper is sufficiently large even with high heat flux into the duct because taper increases velocity, which converts thermal energy to mechanical energy. Within the range of parameters studied, the mass flow of the cooling flow could be reduced by as much as 44% for a tapered duct to achieve bulk temperature variation similar to that of a duct without a taper. The ROM developed was validated by comparing its predictions with grid-converged CFD results obtained by steady RANS with the SST turbulence model. The maximum relative errors for density, velocity, temperature, and pressure distributions along the duct were found to be 0.6%, 3.3%, 0.4%, 0.3% for the smooth section of the duct and 3.2%, 5.6%, 0.9%, 3.0% for the ribbed section of the duct. Thus, the ROM developed performs nearly as well as CFD based on RANS but orders of magnitude more efficient computationally.
Experimental Study of the Effect of Swirling Inflow on Full-Film Cooling of Turbine Guide Vane
Authors: Yan Hao-nan , Liu Cun-liang , Zhou Tian-liang , Zhang Fan , Ren Ming 
Published: August 2024

Abstract
The use of compact engines reduces the distance between the combustor and the turbine, leading to the interaction of the remaining inhomogeneous swirling flow at the combustor outlet with the mainstream of the turbine vane cascade. Consequently, previous turbine vane cooling designs may struggle to meet the cooling requirements for swirling inflow conditions. This study aims to investigate the impact of swirling inflow on the full-film cooling of turbine guide vanes. The film cooling effectiveness (η) of the turbine vanes under two inflow conditions and three mass flow ratios was measured using the pressure-sensitive paint technique. The cylindrical film holes on the suction and pressure surfaces of the vane were replaced with different types of laid-back fan-shaped holes (LBFS), and the cylindrical holes at the leading edge were replaced with droplet holes. The results revealed that swirling flow alters the coolant outlet flow from the film holes on the vane surface, causing deflection of the film. Droplet holes at the leading edge were found to reduce the coolant outlet momentum and improve η, in comparison to cylindrical holes. Furthermore, LBFS demonstrated a significant advantage in mitigating the negative effects of swirling flow. Specifically, LBFS with wider outlet width were found to be more suitable for the pressure side, while no additional outlet width of the air film holes was required for the suction side.
The Use of Artificial Neural Networks With a Systems Engineering Approach for Data Enhancement in Humidified Micro-Gas Turbine Application
Authors: Jamil Ahmad , Dinh Tina , De Paepe Ward , Nikpey Somehsaraei Homam 
Published: August 2024

Abstract
Globally the energy sector is being transformed by innovations based on decarbonization, decentralization, and digitalization. These encompass transitioning towards a future with distributed generation systems having an increased share of renewables, artificial intelligence, and digital solutions. Micro-gas turbines are a competitive enabling technology in distributed power generation owing to benefits like fuel flexibility, reduced operation and maintenance costs, and emissions. However, its economic performance stumbles when not running in combined heat and power mode, requiring cycle modifications to increase electrical efficiency.
The humidified micro-gas turbine is one such modification that shows great potential. For its viability in digitalized future energy systems with ever-growing amounts of data, there needs to be reliable and deployable advanced tools for performance and health management. This requires access to sufficient quality data, making data quality management an essential need. Therefore, the study presented in this paper investigates the use of a special type of artificial neural network called an autoencoder for data enhancement of a humidified micro-gas turbine. Data from 15 sensors has been enhanced by denoising for use in any subsequent data-driven insight and decision. To achieve this, different neural network models have been developed and compared to predict the denoised values. The auto-encoder network model that can best produce satisfactory denoised results has been identified as having 3 bottleneck and 6 mapping layer nodes. Furthermore, a systems engineering framework has been adopted for effective information and complexity management amongst all stakeholders. The framework sets a foundation for employing model-based systems engineering concepts in developing digital solutions.
The results demonstrate the functionality of deploying denoising autoencoders with a systems engineering approach for data quality management of the humidified micro-gas turbine. The outcomes from this work can be used for data-driven performance and health management of the humidified micro-gas turbine. This will improve the system’s reliability and promote its use in energy systems of the future.
Transitional Flows Within Cooled HP Turbines
Authors: Clark Christopher J. , Atkins Nicholas R. , Stokes Mark , Vazquez-Diaz Raul 
Published: August 2024

Abstract
All modern gas turbines, from a small business jet to a large civil engine, make use of film cooling within the HP turbine. Transition on the blade surfaces has a large impact on blade heat transfer and profile loss. Many studies have considered the role of freestream turbulence and surface roughness on transition, yet no systematic study of the role of film cooling on transition has been reported.
This paper shows that film cooling is as potent at causing transition as roughness typically found on the suction surface of end-of-life engines, and more so than freestream turbulence. For the blades tested, film cooling induced transition begins at the rear of the suction surface, the transition point moving forward to the film cooling hole with a doubling in Reynolds number. Averaging the acceleration parameter over a fixed distance downstream of the cooling hole collapses the transitional behaviour for varied film ejection locations. A model is proposed to capture the Reynolds sensitivity of film cooling induced transition.
The simultaneous presence of freestream turbulence and roughness as well as film cooling, are shown to enhance transition compared to any mechanism in isolation, despite the localised nature of the film cooling holes. It is likely that the combined effect of the mechanisms is maximised when each mechanism in isolation would result in transition at a similar Reynolds number. Therefore a method of mapping each transition mechanism in isolation is demonstrated to identify which mechanism is dominant, the proximity of other mechanisms and hence their likely enhancement of transition.
By testing combinations of film cooling, roughness and freestream turbulence typical of a cooled HP rotor the transitional region is found to cover the range 300,000 &lt; Rex &lt; 1,000,000, where transition will be primarily dependent on surface roughness and film cooling. Below Rex = 300,000 transition is likely via a laminar separation bubble and above Rex = 1,000,000 the suction surface boundary layers will be fully turbulent. Large civil engines sit within the top of the transitional range at cruise and smaller engines span the entire range between cruise and take-off conditions.
Steam Turbine Diaphragms Re-Design and Manufacturing Challenges
Authors: Alamoudi Abdullah M. , Khan Raja S. , Shaik Javeed , Alqahtani Mohammed M. 
Published: August 2024

Abstract
This paper illustrates a recent project to resolve the issue of unavailable major spare parts for one of the heavy duty steam turbines utilizing reverse engineering principles in order to re-manufacture the critical components.
Steam Turbines are critical prime movers within the company’s various hydrocarbon and refinery plants. Single stage turbines are used for light duty applications while multi stage steam turbines are used to run large gas compressors or pumps. Many of the steam turbines have been running for more than 40 years with well-established designs and technology. For the large multistage special purpose steam turbines, the spare parts such as casing, rotor, shaft and diaphragms are not shelf items and usually will take over 12 months to manufacture and supply by out of kingdom manufacturers which compromises the plant productivity and reliable operations, not to mention the high costs involved.
Mechanical Services Shops Department, a machinery services organization within the company, was approached by one of the operating plants to overhaul a 6-stage steam turbine due to low performance and as part of a planned plant T&I shutdown. Upon dismantling, excessive pitting, erosion and micro-cracking was found on all 5 stages diaphragms, nozzle ring and bucketing diaphragm which led to the decision of replacing all diaphragms. Due to the unavailability of spare parts and long lead time, it was decided to reverse engineer these critical spare parts locally.
Material of construction analysis were performed in order to understand how the original parts were manufactured. FEA study was conducted on various designs alternatives and materials to investigate how different types of materials are affecting the diaphragm ability to handle thermal and mechanical stresses and deformation. Accordingly, materials and design were selected based on the study outcome which showed 48% Improvement in stress load capability and 27% greater resistance to deformation due to thermal expansion compared to the original design.
3D scanning of the old parts was performed in order to create 3D models which are a digital replica of the existing parts. These models have been modified in order to compensate for the material lost due to the excessive erosion. Detailed manufacturing drawings were developed and manufacturing method of the new parts was changed from fabrication and welding of different components to a more modern method of 5 axis CNC machining from one single billet of forged metal.
Effect of Film Cooling Hole Geometry on Thermal Stress Based on Thermo-Solid Coupled Analysis
Authors: Yan Xiao , Huang Tong , Su Xinrong , Yuan Xin 
Published: August 2024

Abstract
This article examines the impact of various cooling hole shapes on the surface cooling effect and thermal stress distribution of flat utilizing the thermal-fluid structure coupling method. A thermo-solid coupling model was adopted, which accounted for the influence of solid thermal conductivity on the results. Five shape parameters were selected to analyze 46 samples, comparing them with the standard 7-7-7 hole. Among the 46 samples, the highest average effectiveness of the main wall reaches 0.294, while the lowest von Mises stress is 479.55 MPa. They correspond to different geometries. Further analysis revealed a negative correlation between the surface average effectiveness and the outlet velocity of the coolant gas in the z-direction. By further comparing the cooling and mechanical properties of all samples, the optimal geometric shape was identified. This geometric design can serve as a reference for further optimization, which is significant for achieving high cooling efficiency while ensuring structural strength in turbine blade design.
On the Development of an Efficient Sliding Mesh Interface for the Harmonic Balance Method, Part I: Implementation and Verification
Authors: Geiser Georg , Schwarzenthal Felix , Ashcroft Graham , Hartmann Maximilian , Schlüß Daniel 
Published: August 2024

Abstract
In recent years the Harmonic Balance method has become a popular tool in the field of turbomachinery design. While it can efficiently capture nonlinear effects in time-periodic flows, its application to complex configurations such as cavities or casing treatments requires sophisticated domain coupling methods. To address this topic, in a series of two papers, we present and validate an algorithm for the coupling of non-conforming mesh topologies across domain boundaries. In this first paper the basic algorithm and its verification are presented in detail. In the second paper the method is applied to analyze the impact of a casing treatment on blade flutter in a compressor stage. It is shown in this paper that memory layout can have a strong impact on memory usage and CPU time. To handle indexed modes, i.e., modes with the same frequency but different inter-blade phase angles, we introduce virtual passage segments on which the required spatial Discrete Fourier Transform (DFT) is performed. Using Almost Periodic Fourier Transforms (APFT) to transfer the temporal solution harmonics we show that the computational overhead can be significantly reduced when compared to a standard temporal DFT ansatz. In this context a simple, but robust algorithm is proposed to determine the temporal sampling interval and distribution of the sampling points such that a bound on the condition number of the resulting APFT matrix is satisfied. The method is verified and analyzed using three academic test cases: the propagation of an entropy wave across moving interfaces in an empty duct with a rotating mean flow; the aerodynamic excitation of a simple rotor blade exposed to a time-periodic gust disturbance; and the flow in a duct with an attached cavity.
Applications and Recent Developments of the Open-Source Computational Fluid Dynamics High-Fidelity Spectral/Hp Element Framework Nektar++ for Turbomachinery Configurations
Authors: Vivarelli Guglielmo , Isler João Anderson , Montomoli Francesco , Cantwell Chris , Sherwin Spencer J. , Frey-Marioni Yuri , Vazquez-Diaz Raul 
Published: August 2024

Abstract
Reynolds-Averaged-Navier-Stokes (RANS) modelling has had a significant amount of success within the industrial setting. In fact, such techniques are used on a daily basis to compute the flow field around a broad spectrum of geometries in very different conditions. To this end, many codes have now reached a good level of maturity in terms of capabilities and robustness.
However, there is a growing need for more efficient designs and higher performance. Therefore, aspects that are either challenging or impossible to capture by means of standard second-order steady discretisations are starting to become of interest. The computational hardware improvements seen over the decades and the persistent development of high-order numerical techniques, are allowing Implicit Large Eddy Simulation (iLES) if not Direct Numerical Simulation (DNS). These would allow accurate capturing of unsteady flow phenomena that can be critical to properly understand aspects such as flow separation, reattachment and transition to turbulence in components relevant to the turbomachinery community.
The advantage that high-order solvers, such as Nektar++, have over their standard second-order discretisation counterpart, relates to their ability to reach higher fidelity solutions with a saving in terms of number of degrees of freedom and therefore computational cost.
In this paper, a detailed introduction to the characteristics and features of the open-source high-order Nektar++ Computational Fluid Dynamics (CFD) framework will be given. An initial discussion of the numerics will be provided, therefore explaining the main features of this solver, followed by a set of different capabilities that are of interest to the turbomachinery community, such as meshing, incompressible and compressible solvers and post-processing.
Examples of successful deployment of these features to jet engine components will then be presented. To start, preliminary design components, such as flat plates with different loadings will be discussed. In these cases, the effects of adverse and favourable pressure gradients representative of those seen on modern engine intakes and fan blades, respectively, on boundary layers will be studied. Following, a description on low and high pressure turbine components will be provided with a discussion relating to the relevant experimental comparison. Finally, future developments and improvements to the code will be detailed, such as new schemes and interfaces to hardware enhancements, i.e. Graphical Processing Units.
Detection of Flow Induced Aerodynamic Performance Characteristics of Centrifugal Compressors Using Acoustic Measurements
Authors: Srinivasan Anand , Fowler Edward , Fuzak Corey , Kurz Rainer 
Published: August 2024

Abstract
Inline centrifugal compressors are prevalent in the oil & gas industry. The process conditions for these compressors necessitate operation over a range of inlet flows, suction & discharge pressures and speeds. In many instances, operation is at high pressures in excess of 200 bar. The aerodynamic performance characteristics vary as a function of the inlet flow. The head versus flow map depicts the operating range of the compressor, with typical operation near a flow condition located in the mid portion of the map (i.e., the design operating point or the best-efficiency point). Upstream or downstream demand can necessitate changes to the flow conditions during operation. As flow is throttled, the compressor approaches the surge line. The onset of reversal of flow near surge can trigger flow induced characteristics in the downstream piping, which can result in elevated non-synchronous vibrations on the shaft displacement probes. On the high flow side, choking of the flow triggers flow induced characteristics that often result in super-synchronous vibrations on the shaft probes. In this paper, the use of acoustic microphones as a tool to aid in detecting flow induced characteristics at various locations on a head-flow map in a high pressure environment are presented. The influence of vaned diffusers on the flow induced characteristics is also presented. Case studies are presented in this paper that illustrate the use of acoustic devices in detecting flow induced vibration characteristics for centrifugal compressors, both in low pressure and high pressure conditions.
Development of an Additively Manufactured Stationary Diffusion System for a Research Aeroengine Centrifugal Compressor
Authors: Clement Jack T. , Coon Adam T. , Key Nicole L. 
Published: August 2024

Abstract
This paper introduces the next generation of the Centrifugal Stage for Aerodynamic Research (CSTAR) facility at the Purdue University Compressor Research Lab. The research centrifugal compressor is designed with an additively manufactured stationary diffusion system which comprises a vaned diffuser, a turn-to-axial bend, and deswirler vanes. The dimensional accuracy and surface finish of the diffusion system has allowed for rapid prototyping of several iterative diffusion system designs and has allowed for configuration of in-situ pressure and temperature measurements to experimentally evaluate the aerodynamics and performance of centrifugal compressor diffusion systems. The diffusion system is manufactured from a commercially available stereolithography (SLA) resin, and the design of the parts is adapted to the constraints imposed by current technological and material limits of resin 3D printing. The implementation of additive manufacturing in the prototyping of the diffusion system has allowed for decreased cost and lead time while allowing rapid turnaround to generate experimental data. Performance data have verified the repeatability and temperature independence of the additively manufactured diffusion system through several design iterations. A survey of candidate materials for additively manufacturing these parts is also presented, and the tradeoffs of their material properties discussed.