bluuebunny/crossref_metadata_2025 huggingface dataset:
Dilution Rate Analysis of Repairing 316L Stainless Steel Pump Impeller by Laser Cladding Inconel 625 Powder
Authors: Ahmed Rakan A. , Khan Raja S. , Qahtani Mohammed M. , Alsayoud Abduljabar , Bukhari Abdulhameed S.
Published: August 2024

In the oil and gas industry, critical rotating equipment reliable performance is crucial in the seamless operation of production and processing facilities. This paper uses a pump impeller as the basis for a deep dive into novel repair methods. The impeller retained excessive damage to the wear ring landing area while the wall thickness of the damaged location was critically reduced, making it hard to repair using conventional methods or welding techniques. It is observed that the traditional welding techniques, due to excessive heat, could lead to deformation leading to potential challenges in assembling the pump rotor.

Laser cladding (LC) provides distinct advantages for precision control over the heat input, reducing the deformation and cooling time required. LC technology was crucial to the current study because it caters for intricate, complex geometries and sizes, which is impossible with conventional technologies. The process parameters such as laser power, traverse speed and powder feed rate enable tailored repairs that could mitigate deformation and preserve the mechanical properties of the base metal. The use of Inconel 625 powder with SS 316 base metal is well known to provide superior corrosion resistance and enhanced mechanical properties. While the capability of the technology and powder is well charted, its specific application in pump repairs needs further research and development.

This research takes an experimental approach, focusing on understanding the effect of the process parameters on the base metal from a microstructure point of view. A series of 27 samples were analyzed under microstructural analysis, which helps to decipher the impact of variations in the laser power, powder feed rate, and cladding speed. The study calculates the dilution rate to identify the optimum parameters for repairing the damaged impeller.
Reassessment of the Conventional: Numerical Validation of a 1D Model for the Prediction of Volute Losses
Authors: Ceyrowsky Thomas , Hildebrandt André , Heinrich Martin , Schwarze Rüdiger
Published: August 2024

The flow inside the volute of a centrifugal compressor is complex and three-dimensional. The fluid follows a swirling flow pattern, and under many operating conditions, the flow quantities are highly inhomogeneous in radial and circumferential directions. Despite the complex flow physics, the common one dimensional approach to predict losses inside a volute is simple: The kinetic energy of each velocity component at volute inlet is charged with a loss coefficient. In case of the radial velocity, it is assumed to be constant, while the loss coefficient of the tangential velocity depends on whether the flow inside the scroll is de- or accelerated. In the former case, the loss of a sudden expansion is assumed, while in the latter case, it is presumed to be zero. The loss coefficient of the conical diffuser is also assumed to be equal to that of a sudden expansion. However, considering the complex flow physics inside the volute, it is questionable how valid these assumptions are. In this work, the authors present a comprehensive assessment of these conventional 1D predictions by investigating an extensive database of CFD calculations of one volute as a standalone component. The volute has been supplied with different diffuser widths, and the inlet boundary conditions have been selected to allow for separate investigation of the effects of flow angle and flow rate. The aim is to validate the 1D model against the CFD results across the volute’s entire operating range. Therefore, the CFD-predicted total pressure losses within the two subcomponents of the volute (the scroll and the conical diffuser) are assigned to the respective velocity components at volute inlet, in analogy to the 1D predictions. The results show that the loss coefficient of the radial velocity varies notably across the volute’s loss map, opposing the 1D assumption of a constant loss coefficient. Conversely, the loss coefficient of the tangential velocity inside the scroll agrees well with the CFD results: High matching coefficients (i.e. lower than design flowrates) lead to high loss coefficients, which decrease almost continuously towards low matching coefficients (i.e. higher than design flowrates). The losses inside the conical diffuser depend not only on the matching coefficient but also on the flow angle at volute inlet, contrary to what the 1D model assumes. The fundamental characteristics of the global loss coefficient are predicted satisfactorily by the 1D model, while it generally overpredicts losses. Additionally, the CFD results reveal that the matching coefficient that gives minimum loss coefficients varies with the flow angle, which is not accounted for by the 1D model. Therefore, it is not adequate for assessing volute matching.
An Experimental Study on the Effects of Non-Uniform Vane Spacing on Forced Response Reduction in a Mistuned Rotor Blisk in a Multistage Axial Compressor
Authors: Leng Yujun , Dodda Jhansi R. , Key Nicole L.
Published: August 2024

Stators with non-uniform vane spacing (NUVS) are known to effectively reduce the forced response of adjacent rotors by spreading the primary engine order (EO) excitation at a certain speed to a series of weaker excitations at nearby EOs over a wider speed range. To be used in a real gas turbine engine, it is essential to know the forced response vibratory reduction that can be achieved for a specific NUVS configuration at different operating conditions. The classical estimation method to predict the blade response reduction is to quantify the reduction of the forcing function at a potential resonance crossing by conducting a circumferential Fourier analysis of the asymmetric flow field. However, besides excitation reduction, the blade forced response also depends on other factors, such as damping and blade-to-blade interactions due to mistuning.

To study the blade forced response reduction in a realistic environment, a comprehensive experimental study was conducted in the Purdue 3-stage axial research compressor at three different loading conditions. The vibratory response of the 1st torsion (1T) mode forced response of Rotor 2 was measured by strain gages (SG) for two different upstream Stator 1 configurations: the symmetric 38-vaned Stator 1 configuration and the NUVS Stator 1 configuration with 18–20 vane halves. As expected, the strong 38EO-1T response from the symmetric stator reduced to a series of weaker responses from 35EO to 41EO in the NUVS configuration. The overlap of adjacent EO responses caused considerable beating phenomena in the blade SG time-history data. There was substantial blade-to-blade variation in blade response for both the symmetric and asymmetric Stator 1 configurations due to the inherent non-intentional mistuning in the Rotor 2 blisk. This, in turn, causes a large blade-to-blade variation in the reduction factors. While higher responding blades tend to have larger reduction factors, some blades show almost no forced response reduction when switching to the NUVS stator. In addition, the reduction factors for each blade and the maximum reduction factor for the whole blisk also change significantly with loading conditions. The measured reduction factors and the peak response EO are not well predicted by the classical estimation method. This indicates that both damping and mistuning effects need to be considered in the NUVS reduction factor prediction.
Twofold Adaptive Design Space Reduction for Constrained Bayesian Optimization of Transonic Compressor Blades
Authors: Pretsch Lisa , Arsenyev Ilya , Raponi Elena , Duddeck Fabian
Published: August 2024

As turbomachinery designs become more complex, shape optimization tasks involve computationally expensive simulations and many constraints and design variables. Bayesian optimization (BO) is a class of adaptive surrogate-based methods for global optimization. It can efficiently utilize a small budget of high-fidelity evaluations and handle a large number of constraints. However, it suffers from a hampered convergence rate for problems with a large number of design variables. Adaptive design space reductions via principal component analysis (PCA) and trust region (TR) approaches have been shown to improve the scalability in different phases of the optimization. Extending existing methods, we implement the ability to benefit from parallel high-fidelity evaluations and to handle constraints. We then sequentially combine our PCA-BO and TR-BO in a hybrid method to profit from their respective complexity reduction strategies. We assess the performance of our hybrid algorithm by comparing it to vanilla BO on two problems: a 40D analytical test function and a 55D aerodynamic compressor blade design. The empirical results show that PCA-BO enhances the convergence rate in the initial optimization phase, while TR-BO allows for further improvements in the later iterations. Moreover, the algorithm computation time is more than halved. For the compressor blade case, our approach yields an equally good design as vanilla BO after only 20 instead of 96 iterations. The proposed approach has the potential to extend the good performance of BO to even higher-dimensional constrained problems, including multi-stage turbomachinery optimizations.
Global Stability and Forced Response Analysis of Swirling Flows in Aviation Combustors
Authors: Patki Parth , Emerson Benjamin , Lieuwen Timothy
Published: August 2024

Swirling jets are canonical flow fields used to stabilize flames in many gas turbine combustion systems. These flows amplify background acoustic disturbances and perturb the flame, producing combustion noise and potentially combustion instabilities. Hydrodynamic flow response to acoustic excitations in reacting flows is an important modeling task for understanding combustion noise and combustion instabilities.

This study utilizes a global hydrodynamic stability analysis in a Bi-Global and Tri-Global framework to model the vortical hydrodynamic modes of a reacting, swirling LES mean flow based on a commercial nozzle. After conducting a unforced, natural Bi-Global stability analysis to study the unstable eigenmodes of the flow, linearized equations of motion are used to study flow response of the flow to forcing. An empirical velocity transfer function is constructed by determining the flow response to a harmonically varying 150–1500 Hz u′ velocity disturbance at the inflow boundary. These disturbances are strongly amplified, with amplification factors ranging from about 20 to 50 and peaking at about 1050 Hz, or St = 0.375.

A comparison study with a cartesian, three-dimensional reacting base flow is also performed where the base-flow varies spatially in three-dimensions. The study utilizes a stable, high accuracy, but computationally effective centered finite difference scheme based on a three-dimensional structured mesh. Illustrative results present the qualitative modes and quantitative transfer functions for Bi-Global and Tri-Global stability analyses.
Design Guidelines for Arrays of Closely Spaced Darrieus Turbines
Authors: Mohamed Omar Sherif , Melani Pier Francesco , Soraperra Giuseppe , Brighenti Alessandra , Balduzzi Francesco , Bianchini Alessandro
Published: August 2024

The efficiency gains observed in a pair of closely spaced Darrieus turbines are suggesting the deployment of multiple turbines as an appealing solution for wind and, particularly, hydrokinetic applications, where the inflow direction is constant. The present study develops some design guidelines for closely spaced hydrokinetic Darrieus turbines by analyzing the trends of both power augmentation and wake development within arrays of multiple rotors, including not only an even number of rotors, which is the usual case in the literature, but also an odd one. The analysis is carried out by means of two-dimensional Computational Fluid Dynamics simulations and includes not only the assessment of instantaneous blade forces but also locally sampled flow fields past each blade that allowed the reconstruction of dynamic polar data, contributing to a more comprehensive understanding of the physical mechanisms at play in such compact setups. The study demonstrates a consistent power augmentation mechanism across different layouts, even in the case of an odd number of rotors. This enhancement originates from flow blockage in the mutual interaction areas, favorably altering the inflow angle and subsequently increasing the angle of attack and lift generation. While this mechanism aligns with previous observations on arrays of counter-rotating pairs, its application to multiple turbines introduces complexities due to potential asymmetries in inflow, leading to an uneven power enhancement across turbines within the array. The identified efficiency improvement pattern suggests that maximizing leeward mutual interactions within an array of multiple Darrieus turbines would enhance the overall efficiency of the setup.
Assessment of a Liquid Hydrogen Conditioning System for Retrofitting on Kerosene Designed Turbofan
Authors: Rompokos Pavlos , Kyritsis Vasileios , Mourouzidis Christos , Roumeliotis Ioannis
Published: August 2024

As energy transition to alternative fuels for civil aviation is likely to be gradual, hydrogen’s first entry to service may be implemented on existing gas turbine engines. In this paper a novel liquid hydrogen conditioning system for retrofitting on kerosene designed geared turbofans is assessed in terms of performance and engine rematching. The aim of the analysis is to identify emerging requirements for the design of the fuel and thermal management system within the constraints of a certified engine design. The conditioning system proposed, an LH2 preheater, enables the control of the gaseous hydrogen temperature at combustor entry and consists of a secondary combustor and a heat exchanger. The examined configuration considers various bleed source locations within the engine to supply the preheater system.

For performing the analysis, a kerosene fuelled engine has been designed and suitable integrated models capable to simulate the retrofitted hydrogen fuelled engine as well as the LH2 preheater operation have been developed. The system performance has been analysed for the different bleed source locations identifying operating limits and performance changes. From all the examined bleed source positions, utilizing the bypass duct minimizes the impact on component rematching and engine efficiency. Additionally, through a gas path geometry multi-parametric analysis, it was found that by readjusting the capacity of the high-pressure turbine and the core nozzle area the certified limits can be met for the retrofitted engine.
Implementation of a TBLE-Based Wall Model With Pressure Gradient in a Massively Parallel LES Solver
Authors: Cizeron Mehdi , Odier Nicolas , Duchaine Florent , Gicquel Laurent Y. M. , Nicoud Franck
Published: August 2024

Wall modeling is a common approach to reduce the cost of Large-Eddy Simulations (LES) of high Reynolds number flows. The selection of the wall model is however crucial due to the underlying assumptions made to derive these models. The most frequently employed wall models rely on strong hypotheses such as the absence of pressure gradient, curvature, and the assumption of stationarity. These assumptions are questionable for turbomachinery configurations, which can involve complex phenomena and may result in mispredictions. This work aims to investigate the resolution of a Thin Boundary Layer Equation (TBLE) approach including the pressure gradient effect and evaluate the gain compared to a classical logarithmic law approach. The proposed approach accounts for the pressure gradient directly through a source term. Two configurations are investigated to validate this approach and its performance. First, a planar turbulent channel without pressure gradient is investigated to ensure the model’s ability to accurately predict a turbulent boundary layer. The second case, the periodic hill test case available on the ERCOFTAC database, is used to assess the wall model’s performance on a flow submitted to pressure gradient effects. The conclusions of this work are twofold. First, such wall models can be sensitive to the unsteady pressure gradient fluctuations present in the LES prediction even for cases without mean pressure gradient; temporal averaging can thus be required to reach satisfying results. Second, substantial improvement is found in the periodic hill problem if compared to the algebraic wall model, in terms of mean velocity profiles, recirculation bubble size, reattachment zone, and friction profiles. Promising contributions of such tools can therefore be expected for turbomachinery configurations.
Large-Eddy Simulations of a High-Speed Low-Pressure Turbine Cascade With Purge Flow
Authors: Perkins David W. , Duchaine Florent
Published: August 2024

Future turbofan designs are expected to include gearboxes to allow for the decoupling of the fan and the low-pressure turbine. Doing so will increase overall engine efficiency, but change the design point for low-pressure turbines by allowing to increase the rotation speed. To study these new high-speed turbines, an experimental configuration from the European project SPLEEN, supported by the Von Karman Institute (VKI) and SAFRAN Aircraft Engines, is investigated using Large Eddy Simulation (LES). Three simulations based on the experimental SPLEEN cascade are performed: a baseline case without the purge flow cavity, a case with the purge flow cavity, and a case with the purge flow cavity and 0.9% mass flow rate relative to the main flow. These simulations capture engine-relevant turbulence, transition, and transonic Mach number physics that are expected in this operating regime. The losses in the cascade are analyzed and compared to experiment, showing good predictive capabilities of LES.
Field Performance Testing and Test Codes for Gas Compressors
Authors: Brun Klaus , Kurz Rainer
Published: August 2024

Field testing of gas compressor packages requires the accurate determination of efficiency, capacity, head, and power in sometimes less than ideal working environments. The results of field tests have significant implications for the compressor manufacturers and their customers, as economic considerations demand that the performance and efficiency of an installation are verified to assure a project’s return on investment. Thus, for the compressor manufacturers, as well as for the end-user, an accurate determination of the compressor performance in the field is of vital interest.

While field performance tests have to be executed under conditions dictated by the situation at site, factory test codes like ASME PTC10 and ISO 5389 provide guidance. The former code was recently revised, so a discussion of this revised code in the context of site performance testing is appropriate. A key change in PTC10 is the method to calculate polytropic work, which affects data reduction. It also affirms a method to calculate error propagation and test uncertainties. The discussion includes the appropriate use of Equations of State, and the definition of steady state requirements. Different methods to define valid operating conditions for the test, based on similarity considerations are compared.

However, field tests, unlike factory tests, are ultimately conducted based on the conditions at site which may or may not conform with test codes, Therefore, calculation of test uncertainties, and the use of observations not covered by the codes are emphasized. The paper attempts to provide guidance for the conduct of field performance tests.
Green Methanol Demonstrated as an Alternative Fuel to Decarbonise Gas Turbines
Authors: Clifford Tyler , Booth Charlie , Houde Michel , Fowler Regis , MacLean Cameron , Basu Madhubanti , Witzel Benjamin , Bulat Ghenadie
Published: August 2024

Power generation from gas turbines is responsible for up to 79% of the CO2 emissions generated by the UK Oil and Gas (O&G) industry. Thus, decarbonizing gas turbines is key to reducing emissions in the industry. Siemens Energy, in partnership with The Net Zero Technology Centre (NZTC) and Rolls Wood Group (RWG), successfully demonstrated an SGT-A20 gas turbine running on 100% bio-methanol, reducing the overall CO2 footprint by 60%. The demonstration test was a key milestone in Phase 1 of the Alternative Fuel Gas Turbine project funded by the Scottish government and industry partners. The SGT-A20 bio-methanol test demonstrated the engine operating at various conditions including start-up, shut-down, idle to full power, and transient maneuvers. The engine performed as expected within the standard operating limits. The test also confirmed a reduction in NOx emissions of approximately 80%, a 15% reduction in CO, and elimination of visible smoke in the gas turbine exhaust compared to kerosene fuel.
Prognostics and Health Management for Electrified Aircraft Propulsion: State of the Art and Challenges
Authors: Tang Liang , Saxena Abhinav , Younsi Karim
Published: August 2024

In recent years, the aviation industry has witnessed a transformative wave of innovation in electrified aircraft propulsion (EAP), driven by sustainability and efficiency goals. Integration of novel electrical subsystems, including high-voltage power electronics, motors/generators, and energy storage devices, has introduced intricate complexities. In this context, an intensified focus on Prognostics and Health Management (PHM) is imperative, considering the heightened reliability needs in a transportation propulsion application. This paper extensively analyzes the current state-of-the-art in PHM applicable to various EAP systems and components crucial for the functioning of electric aircraft. Typical fault modes and fault management strategies are analyzed at various levels of systems hierarchy. An integral aspect of our investigation involves the identification of critical gaps within existing PHM frameworks, guiding the research agenda for enhanced reliability and performance. Moreover, the distributed nature and increasing complexity of electric propulsion systems underscore the importance of Model-Based Systems Engineering (MBSE). We advocate for the exploration of MBSE not only to inform the design and implementation of PHM solutions but also to facilitate certification and Verification and Validation (V&V) activities. Additionally, the paper offers insights into existing tools and simulation software packages capable of integrating traditional gas turbine modules with electric subsystems, as well as simulating various faulty conditions in EAP relevant to PHM development. Key gaps in these tools are emphasized, drawing attention to areas that require further refinement and development. This comprehensive exploration aims to pave the way for future advancements in PHM tailored for the unique challenges posed by electric aircraft propulsion systems.
Thermodynamic Modelling of Air Management System for Commercial Aircraft Environmental Control Systems
Authors: Spurthy Subramanya , Joksimović Aleksandar , Carbonneau Xavier , Rebholz Sarah , Tong-Yette Frederic
Published: August 2024

For a short-medium-range aircraft at cruise, the Environmental Control System (ECS) consumes about 75% of the total extracted engine bleed air on average. The Air Management System (AMS) of the ECS significantly reduces the bleed air pressure and temperature to meet the inlet requirements of the Pressurized Air Conditioning Kit (PACK). This paper aims to understand the impact of the conventional AMS on the engine performance and proposes an alternative AMS architecture for effective utilization of the bleed off-take pressure and temperature. Subsequently, a steady-state 0D thermodynamic analysis of the conventional and alternative AMS architectures is carried out using PROOSIS™ software, to study their impact on engine performance for different mission phases. Based on this preliminary thermodynamic analysis the alternative AMS shows a potential improvement of the engine performance mainly in terms of the TSFC, up to 0.7% across different mission phases.
Reconstruction of the Reflection Coefficient Downstream of a Flame From Dual SISO Flame Response Measurements
Authors: Ganji Hamed F. , Kornilov Viktor , van Oijen Jeroen , Lopez Arteaga Ines
Published: August 2024

This study introduces an innovative approach to assess the thermoacoustic characteristics of components downstream of a flame, employing two sets of distinct Single-Input-Single-Output (SISO) acoustic measurements. Conventional direct assessments of downstream reflection coefficients face challenges due to the need for measurements in the high-temperature downstream region and complexities arising from heat inflow from the flame. To address these challenges, we leverage the widely adopted dispersion relation format from the theory of radio-frequency circuits. In the current methodology, the flame transfer function (TF) technique, as a well-established tool in thermoacoustics, is used. The second method utilizes a standard impedance tube test based on a one-port acoustic reflection test, conducted on the upstream/cold side with a flame present. To demonstrate the effectiveness of our approach, we applied the method to a ducted premixed burner-stabilized Bunsen-type flame. The straightforward reconstruction of downstream reflection coefficients revealed strong sensitivity to noise and uncertainty, particularly in higher frequencies, necessitating specialized data treatment. To mitigate this sensitivity, we conducted multiple tests with slight changes in operating conditions, creating a dataset expected to yield nearly identical downstream reflection coefficients. We then formulated an over-determined system of linear equations, employing the least-squares method to minimize errors and sensitivity. This work showcases a significant reduction in sensitivity through the use of multiple tests and data treatment techniques. The reconstructed downstream acoustics were employed to construct the reflection coefficient measured at upstream side of active subsystem and flame TF at a thermal power close to that corresponding to the reconstructed downstream acoustics, demonstrating substantial improvements in accuracy and reliability.
Unsteady Flow Structure of Rotating Instability in a 1.5-Stage Axial Compressor
Authors: Fujisawa Nobumichi , Ohta Yutaka , Yamagami Mai , Goto Takashi , Kato Dai
Published: August 2024

Unsteady flow structure of the rotating instability (RI) in a 1.5-stage axial compressor is investigated through experimental and numerical analyses. In the tested compressor, the total pressure rise of the rotor stagnates at a certain flow coefficient before it increases again towards lower flow rate in a case involving a wide tip clearance. The RI appears beyond this stagnant point as the compressor is throttled. The RI indicates a gentle hump in the frequency spectra of wall pressure or the flow velocity near the tip in a range approximately 20 to 40% of the blade-passing frequency. As the flow rate decreases, the mode order of the RI increases, in contrast to more commonly reported tendency, while the propagation velocity remains constant. These features are well captured by DES of the half-annulus model, with which the unsteady flow structure is further investigated. At its onset, RI is formed by the collision of the tip leakage vortex onto the pressure surface of the adjacent blade and subsequent vortex segmentation. This vortex structure spans two blade passages and propagates in the direction opposite to the rotor rotation. As the compressor is throttled, RI becomes more dominated by the circumferential propagation of vortex breakdown of tip leakage vortices, which occur simultaneously among neighboring passages with slight phase differences. The mechanism is discussed in relation to the temporal change in the blade tip loading. The frequency of vortex shedding increases with the reduction in flow rate and thus the increase in the number of RI disturbances.
TPMS Turbojet Precooler Design Methodology and Case Study
Authors: Cerantola David J. , Schmidt Graeme , Handford Daniel , Dass Pradeep
Published: August 2024

Turbojet precoolers can benefit from additively manufactured triply periodic minimal surfaces (TPMS). Although literature has quantified heat exchanger performance improvements with specifically gyroid or diamond lattice structures and how to utilize optimization frameworks, pressure loss and heat-transfer correlations appear to be geometry-specific and a precooler design methodology is not apparent. Parametric steady-RANS CFD studies that employed the SST turbulence model with a zero-thickness shell interface were conducted on 50-50 and 80-20 volume ratio cross-flow gyroid and diamond arrays where air was the hot fluid and hydrogen gas was the cold fluid between the Reynolds numbers of 5,000 and 2e5. Better fits for drag coefficient and Nusselt number occurred when tortuosity and viscosity ratio were included as independent parameters. Given compressor inlet temperature and H2 pressure loss constraints, a methodology was proposed to determine the optimal volume ratio for an unit cell. A cross-flow precooler case study showed that weight was minimum as TPMS cell size Δx decreased whereas pressure loss was minimum at Δx = 4.5cm.
Integration a Rotary Pressure Exchanger in Transcritical CO2 Refrigeration System: Modeling and Annual Energy Saving Estimation
Authors: Sarawate Neelesh , Deshmukh Arnav , Thatte Azam
Published: August 2024

This paper presents the use of a rotary gas pressure exchanger (PX) in enhancing the efficiency of transcritical CO2 refrigeration systems. Pressure Exchanger based system utilizes the high-pressure discharge from the condenser/gas cooler as a driving fluid, effectively compressing the low-pressure gas (either from flash gas in receiver or from a bypass source) with minimal external energy. This process significantly lowers the power consumption of the main compressor. Concurrently, the PX expands the high-pressure supercritical/liquid CO2 into a two-phase state, preparing it for heat absorption and thereby mirroring the role of a standard high-pressure expansion valve.

The study delves deeper into the architecture of CO2 refrigeration systems that incorporate the PX as a mechanical subcooler. The source of high-pressure fluid is derived from the gas cooler, while the low-pressure gas originates from a bypass line connected to the main gas cooler exit flow. This bypassed flow undergoes expansion and is then utilized to lower the temperature of the flow exiting the main gas cooler, achieved through a counter-flow heat exchanger. The superheated flow from the bypass serves as the low-pressure inlet to the PX. Such integration markedly diminishes the flash gas presence in the receiver, leading to a reduction in the overall workload of the compressor and a consequent boost in energy efficiency. The paper presents a detailed modeling approach that addresses the simultaneous energy and mass balance equations integral to the cycle when integrated with PX G. It also establishes mass flow constraints, which are contingent on the internal physics of PX G and the density ratio of the low and high-pressure streams as they enter PX G.

The analysis encompasses various performance metrics such as the overall system Coefficient of Performance (COP), the work done by medium-temperature (MT) and low-temperature (LT) compressors, liquid content post-expansion through PX G, flash gas production, and superheat control. These factors are evaluated across a broad spectrum of conditions, including diverse ambient temperatures, evaporator duties, and load splits between MT and LT evaporators.

Additionally, the paper discusses multiple techno-economic scenarios considering different system parameters and architectures. These architectures include an adiabatic gas cooler, a parallel compressor, and an internal heat exchanger. An analysis of annualized work savings across various geographical locations in North America and Europe is presented, highlighting the variance in temperature patterns. The findings demonstrate that PX presence enables the system to operate more frequently under extreme temperatures and reduces the likelihood of operational shutdowns during heatwaves, particularly on hot summer days. A single PX unit can approximately add about 5.4 m3/hr or a 20% capacity increase to a standard 150 kW store.
Investigation of Methanol Spray Combustion in a Swirling Hot Coflow
Authors: Alam Zafar , Patel Riya , Bhatia Bharat , De Ashoke
Published: August 2024

Clean combustion technologies and efficient energy harvesting methods are the focal points of current combustion research. The swirling flows are employed to achieve a well-mixed, homogenous fuel-air mixture for an efficient combustion in a gas turbine engine. The current study simulates an air-diluted methanol spray in a swirling hot co-flow. Atomization, the phase change of liquid fuel, and the mixing of the gaseous fuel with the oxidizer are essential physical processes that must be modeled to simulate liquid fuel combustion. The study involves using an Eulerian-Lagrangian method, a common technique in multiphase simulations, wherein it resolves the continuous gas phase using the Eulerian approach. In contrast, the dispersed liquid phase is handled using the Lagrangian approach. The Flamelet Generated Manifold (FGM), a computationally efficient yet accurate combustion model, simulates the gas-phase reactions within the multiphase simulations. An increase in swirl provides better fuel-oxidizer mixing and higher turbulence to the flow. The former is desirable for efficient combustion; the increase in the latter may tend to cause local flame extinction or delayed auto-ignition. Analysis of swirl numbers between 0.2 and 0.6 is carried out to analyze its effect on the auto-ignition and flame stability. It is noted that the lift-off height increases as the swirl number increases due to a delayed ignition. Further, Proper Orthogonal Decomposition (POD) is used to analyze the ignition kernel and flame propagation around different vortical structures contributing to the evolution of the swirl-dominated flow field.
A Carbon Footprint Comparison Through LCA of Forging vs. Wire Arc Additive Manufacturing (WAAM) Processes for the Internal Casing of a Gas Turbine
Authors: Orlandi Rachele , Pucciarelli Martina , Ragni Giacomo , Serra Angela , Fantozzi Francesco
Published: August 2024

The European Commission is increasingly investing efforts on regulating and standardizing Environmental Footprint (EF) assessment for both Products and Organizations. In the framework of UN Agenda 2030, proactivity in performing Life Cycle Assessment (LCA) on products is becoming of vital importance for companies, as well as having internal initiatives for carbon reduction and implementation of eco-design practices. Energy and turbomachinery industries are focal points in this context, and these industries should pioneer such initiatives. For such consolidated industries, it is important to assess the environmental impact of their more traditional processes and products, such as gas turbines (GT), in comparison to innovative ones. As a case study, this paper showcases a Life Cycle Assessment evaluation of two different manufacturing processes, taking internal case of gas turbines as an example. These items are commonly manufactured by forging process. The aim of this paper is to compare the carbon footprint of producing these components through forging or Wire Arc Additive Manufacturing (WAAM) process. The applied methodology is Life Cycle Assessment as per ISO 14040:2006 and ISO 14044:2006, using EF 1.03 as calculation method. Modelling was performed on SimaPro software and for background data Ecoinvent (vv. 3.5) was employed. In addition, uncertainty of the results of both the technologies have been assessed using the pedigree matrix.
Development of High-Temperature, Interlaminar Tension (ILT) Test Methodology for Ceramic Matrix Composites (CMCs)
Authors: Mattison Jacob T. , Faucett David C. , Choi Sung R.
Published: August 2024

This paper was to present how an affordable, high-temperature, interlaminar tension (ILT) strength testing method was explored and developed for ceramic matrix composites (CMCs), leading to development of a diametral-compression test methodology. The test methodology was first delved and verified at ambient temperature by employing a model, 2D-woven polymer matrix composite (PMC) with various test-specimen configurations. The test method was then applied to and confirmed with two different gas-turbine grade CMCs of 2D MI SiC/SiC and 2D N720/alumina oxide/oxide at both ambient and elevated temperatures. Life prediction testing was also conducted at 1316°C for the MI SiC/SiC to validate the effectiveness of test method for a long-term life prediction testing. All of the results on strength and life prediction testing indicated an applicability and feasibility as an appropriate high-temperature ILT test methodology in CMCs with provisions of simplicity, affordability, and technical soundness.
Expanding the Capability of a Legacy Combustion Flametube to Test High Temperature Engine Materials in Relevant Environments
Authors: Harder Bryan J. , Liebfried Carl W. , Luginbuhl Thomas R. , Smith Andrew D. , Stalker Amy R. , Presby Michael J.
Published: August 2024

New materials and component designs are needed to advance gas turbine engine technology and provide the performance and efficiency needs for future applications. In order to advance these materials, testing in combustion environments is a critical step prior to engine testing. In this work, we detail the design and the fabrication of a materials test sector in a flametube combustor facility. The facility simulates a combustion environment similar to that experienced by components in gas turbine engines. The flow regime is characterized by a combination of high-temperature, high-heat flux, and high-velocity that components experience in gas turbine engines. Exposure of components in this facility allows for the study of combined environmental effects and the impact on both coating and substrate durability. The test facility may operate across a wide range of pressures from 275–400 psig (1,896–2,758 kPa) and an airflow rate of 5 lb/s (2.27 kg/s). While combustion gas temperature is expected in excess of 3,000°F (1,649°C), 900°F (482°C) cooling air may be supplied to the backside of components or test articles. The flametube combustor was previously used to evaluate fuel injectors and combustion products, and the new test configuration will also allow for materials exposure to complex, engine-like conditions. The interior of the Test Section was additively manufactured from GRCop-84 and cryogenically fit and brazed to a stainless steel 304 housing. The use of a copper liner minimizes welds and with active cooling, is expected to provide better durability over traditional hardware using stainless steel or Inconel with a ceramic liner. The Test Section has two opposing 9.5” × 3.125” (241 mm × 80 mm) removable windows that can accommodate articles up to 3.5” (89 mm) tall. This modular design allows for custom platforms to hold coupons, panels, or airfoil shapes to be tested with minimal re-engineering or fabrication. The bolted joint and sealing remains consistent, so any new testing only needs to work within the existing design footprint. This paper will provide an overview of the facility capabilities, design considerations, as well as thermal and structural analysis of the hardware. Future testing of ceramic matrix composite (CMC) airfoils and advanced environmental barrier coatings (EBCs) will also be discussed.
Entry Region Heat Transfer Augmentation With Pins, Fins, and Turbulators in Circular Channels
Authors: Lundburg Evan , Lynch Stephen , Lyall Michael
Published: August 2024

Entry region heat transfer is known to provide significantly higher heat transfer than fully developed conditions. Utilizing entry region heat transfer would provide an additional heat sink at the inlet of an aircraft engine before the fan, but requires further investigation of the convective heat transfer augmentation and downstream boundary layer impacts. The addition of near wall heat transfer augmentation features only in the entry region at high Reynolds numbers is uncommon. Thus, heat transfer enhancement comparing small features in the entrance region of a circular channel and the effect on the downstream boundary layer has not been investigated. This study investigates three heat transfer augmentation features: pins, fins, and turbulators, mounted on the wall at the inlet of a circular channel. Two boundary layer probes, one mounted immediately after the augmentation features and one located three diameters downstream of the features are used to evaluate the growth of the boundary layer due to the features. The convective heat transfer is evaluated using a constant heat flux surface with surface temperature measurements using infrared thermography. All features are evaluated at Reynolds numbers ranging from 1.0*105 to 5.0*105. Each type of geometry is capable of producing augmented heat transfer relative to a smooth entry region, with the maximum overall heat transfer coefficient augmentation of 2.8 compared to a smooth entry region. Fin arrays produced the lowest average total pressure losses, doubling the losses compared to a smooth channel. Overall, the fin arrays also provided the highest overall heat transfer coefficient performance with minimal total pressure boundary layer losses, but also exhibit a sensitivity to Reynolds number.
A Coupling Model of Ice Crystal Icing in a Three-Stage Compressor
Authors: Zheng Haoran , Cheng Xianda , Dong Wei
Published: August 2024

The occurrence of engine power loss due to ice crystal accretion has been recorded since 1990s. Ice crystals at high altitudes can pose a threat to aircraft engine compression, including the degradation of compressor performance, engine rollback, compressor surge and flame out. The ice crystal accretion is attributed to ice crystals partially melting and sticking on the static components of the compression system. An ice crystal icing model in a whole three-stage compressor, consisting of the flowfield simulation module, the ice crystal tracking in three dimensions and phase change, and interactions of particle and surface. The performance of the compressor is simulated by S2 relative stream surface with a circumferential average, providing the flowfield condition for ice crystal simulation. The particle trace of ice crystals with different sizes and initial positions at the inlet are obtained by Lagrangian method. Ice crystals will bounce, fragment or stick when impacting the blade surface. The ice crystals simulation module is coupled with the compressor performance module by the heat transfer between air and particles. The possible icing position can be predicted by the model and the influence of ice crystals on the flowfield is also discussed in this research. Heat transfer to ice crystals has effects of decreasing the pressure ratio and the outlet temperature on the compressor performance.
Gas Turbine Gas-Path Fault Diagnosis Based on Decision Fusion of Model-Based and Data-Driven Methods
Authors: Cheng Xianda , Zheng Haoran , Dong Wei
Published: August 2024

Model-based methods (MBMs) and data-driven methods (DDMs) are currently the primary approaches for gas turbine (GT) gas-path fault diagnosis. However, the accuracy of model-based methods can be decreased due to the mismatch between the real engine and model, while data-driven methods struggle to handle untrained fault types. To solve this problem, this study proposes a fusion framework based on the Bayesian network (BN) for decision fusion of model-based and data-driven methods, aiming to enhance the reliability of the gas-path fault diagnosis system. Firstly, a health parameter estimation system is constructed using the component-level model (CLM) of the GT and the unscented Kalman filter (UKF). This system is then combined with a fault identification system based on the fuzzy inference approach to form a model-based diagnostic system. Subsequently, a data-driven diagnostic system is developed using historical operational data and the artificial neural networks. Next, the BN is adopted for decision fusion of diagnostic results. A new BN parameter calculation methodology is proposed based on the characteristics of MBMs and DDMs. The resultant Bayesian network can effectively fuse two different diagnostic methods. Finally, the fusion diagnostic results are compared with those obtained from the individual diagnostic systems. The results indicate that decision fusion method effectively overcomes the limitations of individual diagnostic systems and enhances the scope of health state identification, leading to improved overall performance in GT gas-path fault diagnosis. This research has significant importance for the performance monitoring and maintenance of GTs.
Air Jets to Modulate Flow in a Nozzle Vane Passage Within a Linear Cascade
Authors: Ferguson Tyson , Mohr Jim , Heitland Greg , Burnes Dan , Martel Matos Alberto
Published: August 2024

In gas turbines, it is difficult to effectively incorporate variable geometry within the pressurized hot section of the engine. To avoid using complex mechanical linkages that may wear and leak, an approach using pneumatic actuation with air jets can be deployed eliminating the need for any internal moving parts. An application for an internal pneumatic actuator was conceived and studied. After initial conceptual assessment and CFD analysis of air jets within a turbine nozzle vane passage, a linear cascade rig was assembled to validate and demonstrate the modulation of flow capacity within a nozzle vane passage using the jet flow. This paper will explain the concept, reflect on the supportive analysis demonstrating feasibility, and will show test results from the linear cascade rig. The additive manufactured test section, method, and instrumentation is described including the various configurations evaluated. Data show that flow capacity can be altered with the injection of air at high momentum flux ratios upstream of the throat plane. Incurred pressure losses are sufficiently small to favor integration in engine for cycle thermal efficiency increases at part load operation. Parameters investigated include total pressure losses, flow reduction, flow angle and momentum flux ratio. Geometry variations assessed included hole positioning relative to nozzle throat, injection hole designs. Airfoil geometry was representative of a center section of a low-pressure turbine. Also included is the detailed normalized data analysis and conclusions.