bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study of Atomization Feature of Coaxial Parallel Flow Airspray Nozzle in Crossflow
Authors: Li Yue , Suo Jianqin , Ju Hongyu
Published: August 2024

To improve the atomization efficiency of the direct injection nozzle, a ring-shaped air layer is enveloped on the outer side of the liquid jet, forming a structure of co-flowing air atomization nozzle with liquid and gas phases. This paper experimentally studies its atomization characteristics when subjected to cross-flow injection in lateral air streams. The effects of ring-shaped air channel height (0.4mm, 0.7mm, 1.0mm, 1.3mm), different lateral air flow velocities (28.7m/s, 35.9m/s, 43.1m/s), and liquid flow rates (2.5g/s, 4.72g/s, 6.94g/s) on the atomization performance of the nozzle were investigated. Pulsed laser was used as the light source to obtain clear transient images of the liquid spray field. Marvin laser particle size analyzer was employed to measure the particle size at different locations in the liquid spray field. With the constant momentum flux ratio of the liquid-gas jet ensured, a larger ring-shaped air channel height leads to a stronger atomization enhancement effect, resulting in a smaller SMD (Sauter Mean Diameter) of the liquid spray field. The ring-shaped air significantly reduces the influence of lateral air flow velocity and liquid flow rate on the distribution area of the liquid spray field.
Sealing Flow Rate Effects on Unsteady Loss Production in a Low Pressure Turbine Stage
Authors: Barsi Dario , Biassoni Daniele , Lengani Davide , Simoni Daniele , Ubaldi Marina
Published: August 2024

Efforts to increase efficiency in aircraft and power generation turbines have raised turbine inlet temperatures (TIT), necessitating advanced cooling technologies to maintain material integrity. Preventing the ingestion of hot gases into components not suited for high temperatures, like stator/rotor cavity disks, is crucial.

Current gas turbine performance strategies focus on minimizing leakage and optimizing sealing systems. Notably, losses from main flow and cavity interactions are prominent in stator/rotor systems. Using Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations, this study explores the unsteady interaction in a low-pressure turbine’s stator/rotor cavity. Numerical simulations of the University of Genova’s cavity rig are validated against experimental results.

The investigation examines stator/rotor interaction effects, including wake ingestion from upstream rotor bars and the blocking impact of downstream rotor bars on cavity sealing. Varied cooling air injection rates in multiple calculations reveal insights into stage efficiency and cavity leakage. Emphasis is on unsteady loss mechanisms downstream of the vane row and in the region where the cavity flow is reintroduced in the main channel, providing a better understanding of losses influenced by cooling flow rates. The analysis of the loss amount along the axial direction demonstrates that losses generated in the vane row are increased prior to entering into the downstream rotor bars, due to cavity main flow interaction. This provide useful information about the production of losses due to sealing flow rate.
Comparison of Rim Sealing Effectiveness in Different Geometrical Configurations
Authors: Orsini Lorenzo , Picchi Alessio , Facchini Bruno , Bonini Alessio , Innocenti Luca
Published: August 2024

The flow field developing inside the stator-rotor cavities of gas turbines is characterized by a complex unsteady behaviour which still requires expensive and time consuming CFD simulations to be accurately modelled. Hence, the experimental characterization of the rim sealing effectiveness by means of scaled down geometries that replicate the rim seals found in actual engines still represent a widely used approach in literature. However, the obtained results can greatly depend on the specific geometry of the tested rim seal. Moreover, different geometrical parameters can vary during the operation of the engine, especially under transient or off-design conditions, thus influencing the resulting effectiveness values. For this reason, the sealing performance of seven different configurations of radial rim seals has been investigated and the obtained dataset has been correlated by using the Orifice Model. Hence, a detailed comparison of the results allowed the evaluation of the impact of different values of axial overlap, different distances between the vanes trailing edge and the blades leading edge and different values of radial gap. In particular, a three times greater axial overlap and a modest increase in the distance between the trailing edge of the vanes and the leading edge of the blades were both found to provide a limited improvement in the sealing performance, with a respective average reduction in Φmin of approximately 5% and 6%. A radial gap 2.4 times greater was instead found to lead to an average increase in the required quantity of sealing flow rate of approximately 44%. Hence, the amount of purge flow required to fully seal a cavity was not found to exhibit a linear increase with the radial gap.
Experimental Evaluation of a Premixed Swirl-Stabilized Gas Burner With a Focus on Mixture Stratification
Authors: Payri Raul , García-Oliver José M. , Martí Gómez-Aldaraví Pedro , Ramírez-Correa Elkin
Published: August 2024

The present work reports an experimental evaluation of the flame stabilization, structure and pollutant emissions for a swirl-stabilized premixed burner at atmospheric conditions. The burner has been designed to accommodate two inlet streams, namely a swirling air and a non-swirling fuel-air mixture, which are fed into a mixing chamber. By modifying the air mass distribution between the swirling and non-swirling streams, the burner can produce different swirl numbers at the chamber, as well as different fuel-air mixture stratification. A central tube acts as a bluff body to help stabilize the flame.

Experimental diagnostics include high speed flame visualization in terms of OH* chemiluminescence, and NOx pollutant at the burner outlet. The study has been carried out using both hydrogen and methane as fuels. A sweep of conditions has been carried out to identify the lean blow-off limit over the burner operational map. Results for methane indicate that the lean blow-off limit is strongly affected by the air distribution between the swirling and non-swirling parts. In contrast, air distribution has a more significant effect on NOx emissions for hydrogen. Different flame shapes are analyzed over the operational map, where strong differences in lift-off, flame width, and reaction zone chemiluminescence have been identified.
Accuracy Analysis of Multi-Plane Unbalance Identification Using Different Model Order Reduction Techniques
Authors: Shehzad Khurram , Ranjan Gyan , Choudhury Tuhin , Nutakor Charles , Sopanen Jussi
Published: August 2024

The estimation of multi-plane unbalance in rotating machinery is a field of active research. To identify the magnitude and phase of residual unbalances from vibration responses, different model-based identification algorithms are being used. However, when the number of measurement planes is limited, model reduction techniques are typically employed in these identification algorithms. While these techniques can reduce the model’s degrees of freedom (DOFs), they may also affect the system’s dynamic behavior. Therefore, it is necessary to examine the accuracy of the prediction of the faults in scenarios where the model is reduced. This study compares various model-based methods for detecting imbalances at multiple planes. It involves implementing different reduction techniques, including Guyan reduction, dynamic reduction, dynamic reduction with gyroscopic effect, and system equivalent reduction expansion process (SEREP). As an example, rotor bearing systems with multiple disks located between bearings and in overhung conditions are considered to ensure the algorithm’s general applicability in industrial applications with various impeller configurations. The vibration responses of the disk locations are taken into account for estimating the unbalances. It is observed that the accuracy of estimation varies greatly with different reduced-order models, particularly in the proximity of resonance and at higher speeds due to the presence of gyroscopic effects in the system. The percentage error in estimating unbalance is compared using different reduction methods across multiple operating speeds. These findings help to determine the appropriate speed range for the applicability of different reduction methods to be used in balancing.
Heat Transfer Enhancement of Wedge-Shaped Channels Using the Interpretable Multi-Objective Generative Design Method
Authors: Kaibin Hu , Shengquan Zhong , Yu Rao , Li Yang
Published: August 2024

Gas turbine blade cooling is crucial for enhancing turbine efficiency and durability. In particular, wedge-shaped channels are commonly used for trailing edge internal cooling. However, conventional cooling channel structures such as pin fins have limitations in achieving uniform heat transfer. To address this issue, a new approach using bionic cooling structures generated through self-organized equation had been proposed. Additionally, a multi-objective Bayesian approach is utilized to optimize the topological parameters, with comprehensive emphases on two specific design objectives: improving heat transfer and reducing pressure loss. Simultaneously, data mining techniques are applied to automatically extract design principles and clarify the enhanced performance characteristics resulting from optimization. Then the study investigates the performance of optimized self-organized structures in comparison to pin-fin structures. Results show that self-organized structures provided better heat transfer performance with lower pressure drop, and more uniform temperature distribution. Specifically, under the same level of pressure loss, the selected self-organized structure increases heat transfer by 35%. Data mining identifies the material orientation and the material generation on the left side region as critical factors in topological structures, significantly influencing pressure loss and overall heat transfer efficiency. This research highlights the potential of self-organized structures as a design methodology for turbine blade cooling.
Using Hydrogen for the Generation of Non-Propulsive Energy in Civil Aviation - Design and Performance of Combined Micro Gas Turbine and Organic Rankine Cycle Systems
Authors: Arenas-Fernández Alejandro , Rodríguez-de Arriba Pablo , Escamilla-Perejón Antonio , González-Almenara Rafael , Sánchez David
Published: August 2024

The interest in using hydrogen for civil aircraft propulsion is well known and has already been explored by the aero industry extensively. In this context, Iron NPE is a 25 M€ project funded by the Government of Spain with the aim to develop an efficient, flexible and compact generator of non-propulsive energy running on hydrogen. Aiming to achieve very high efficiency by exploiting the favourable boundary conditions at flight altitude ambient temperature as low as −65°C), micro combined cycle systems are explored as an alternative to the more standard solution based on PEM fuel cells. These systems deliver a stream of hot gases which is harvested by a bottoming Organic Rankine Cycle system downstream, to further enhance global performance.

This paper presents a preliminary analysis to benchmark the generation of non propulsive energy based on fuel cells, explore the thermodynamic potential of stand-alone of micro gas turbines with small and large recuperators and assess the benefits of sacrificing micro gas turbine performance in order to enhance waste-heat-to-power recovery in a bottoming organic Rankine cycle. Key aspects of the independent systems involved as well as the integrated combined system are assessed. Eventually, it is revealed that the utilisation of combined systems with bottoming ORC units running on either propane or isobutane enable close to 50% conversion efficiency. Moreover, even if the efficiency attained by the system incorporating a bottoming isobutane ORC system is slightly higher, it seems that adopting a subcritical ORC unit running on propane allows for easier and more compact design of components at minimum performance drop.
Predicting NOx Emissions of a Lean Hydrogen Flame Using High and Low Order CFD Models
Authors: Amerighi Matteo , Andreini Antonio , Orsino Stefano , Verma Ishan , Yadav Rakesh , Reichel Thoralf , Tanneberger Tom , Paschereit Oliver
Published: August 2024

Recent efforts in numerical methods to study hydrogen combustion have allowed the development of affordable and reliable strategies that can reproduce the main structure of the flame. Although this objective represents a vital goal of the design process of a new combustor, properly estimating the emission remains an aspect that must be further investigated. In fact, due to the lack of experimental data, few numerical works addressed the evaluation of NOx emissions in hydrogen-fueled rigs. The present work aims to study turbulent combustion and NOx emission formation through different numerical approaches on a laboratory-scale atmospheric rig. The burner consists of a swirl-stabilized, technically premixed hydrogen-air flame, with detailed NOx emissions estimated via an experimental campaign at the Technische Universitat Berlin (TUB). A first estimation is obtained through a high-fidelity simulation performed in order to assess the capability of a computationally expensive strategy to estimate NOx emissions. A species transport simulation adopting a Thickened Flame Model in which NOx chemistry is included in the chemical mechanism is carried out. After that, a cost-efficient method is explored, allowing a quick assessment of the NOx. With this approach, named LES-to-RANS, time average fields are evaluated from an LES species transport simulation with simplified chemistry. In particular, the NOx equations are performed on a frozen RANS framework as a post-processed stage. The capabilities of the model are then tested under two different scenarios: adiabatic and non-adiabatic wall temperature. The computational accuracy of each approach is compared and discussed, with emphasis on computational cost.
Effect of Turbulence Transition Models on the Flow Field of a Centrifugal Compressor Operating in Low Reynolds Number Condition
Authors: Kong Weihan , Wang Baotong , Zheng Xinqian , Ishikawa Yoshihiro , Kanzaka Tadashi
Published: August 2024

Centrifugal compressors are widely employed in various small power systems, such as automotive turbocharger, electric compressor and centrifugal chiller. As a key component of such power systems, the performance of centrifugal compressors plays an important role for the energy conversion efficiency. Numerical approach is widely applied to evaluate the performance of compressors, and accurate simulation of flow behavior is the foundation to study the flow loss mechanism and improve the performance. In the small compressor with low working Reynolds number, the boundary layer transition is an important flow feature, and a reliable turbulence transition model is indispensable to correctly capture the behavior of boundary layer development and transition. Therefore, the capability of turbulence transition model is critical to accurately simulate the flow pattern of the compressors. The motivation of this paper is to establish applicable CFD method which can guide the design of small size centrifugal compressors suffering from low Reynolds number effect. As the first step to realize this target, the effects of various transition models including Standard SST model, γ model, γ-Reθ model and Improved γ model on the flow feature in a centrifugal compressor operating in a low Reynolds number condition are carefully investigated by comparing the overall performance and flow details. Based on the results, the γ-Reθ model shows superior capability to capture the flow pattern and evaluate the performance while operating in a low Reynolds number condition.
Numerical Study of Flow and Heat Transfer Characteristics in Channel With Dumbbell Pin-Fin
Authors: Yan Shuangjie , Liu Jianjun , An Baitao
Published: August 2024

In this paper, numerical simulation was conducted to investigate the flow and heat transfer characteristics in the channel with dumbbell pin-fin, and the channel with circular pin-fin is used as the baseline to evaluate the enhanced heat transfer performance of the dumbbell pin-fin. The dumbbell pin-fin consists of thick segment at both ends and thin segment in the middle. The effect of length and diameter of the thin segment is investigated at Reynolds numbers ranging from 10000 to 40000. Numerical simulation results show that either extending the length or shrinking the diameter of thin segment of the dumbbell pin-fin, can significantly reduce the friction factor with slightly changing the Nusselt number. Dumbbell pin-fins induce relatively small wake, which enhances the heat transfer in the first three rows of the pin-fin channel. The dumbbell pin-fin reduces the stagnation resistance while disturbing the flow, which weakens the turbulence and heat transfer on downstream of the pin-fin channel compared with the baseline pin-fin. The structural parameter Dt/D of the dumbbell pin-fin has a greater impact on the overall thermal performance than the parameter C/H. The dumbbell pin-fin with Dt/D = 0.4, C/H = 0.5 produces the greatest overall thermal performance, which increased by 22.5%,16.8%,16.6% and 12.7% compared with the baseline pin-fin at Reynolds number of 10000, 20000, 30000 and 40000, respectively. The dumbbell pin-fin can be used to reduce the flow resistance of turbine trailing edge channel while ensuring a certain heat transfer.
ASME PTC 10-2022: Concise Update Overview
Authors: Taher Matt
Published: August 2024

ASME PTC 10 is a globally recognized code for performance testing of axial and centrifugal compressors. The ASME PTC 10-2022 has gone through a major revision after 25 years since its previous revision in 1997. Among the major changes in the revised code are (1) the use of real gas relationships instead of the ideal gas model (2) the adoption of a polytropic process throughout the code (3) with new calculation methods for the polytropic work and the polytropic efficiency, (4) an updated definition of the polytropic process based on a constant polytropic efficiency along the polytropic path, (5) an updated range for allowable test machine Reynolds number, (6) a new correction method for the Reynolds number effect (7) new requirements for flow rate corrections based on difference of leakage ratios, (8) multi-point test requirements to verify performance curves, (9) test stabilization for readings and calculated values, (10) updated requirements on test instruments, test data treatment, and methods of measurement, (11) new methods to calculate test total pressure and temperature, (12) updates on casing heat transfer for test power measurements (13) a new chapter on test uncertainty, (14) a new non-mandatory appendix on performance testing of back-to-back compressors, and (15) the addition of metric units.

This paper aims to present a concise overview of the significant technical updates incorporated in the ASME PTC 10-2022 revision as perceived by the chair of its code committee.
The Design of High Temperature Heat Pump Compressor Using the Inverse Design Method
Authors: Zhang Luying , Zhang Jiangnan , Zangeneh Mehrdad
Published: August 2024

High temperature heat pumps (HTHP) have the potential to reduce CO2 emission in multiple industrial processes. It is a key technology for the heat recovery from various sources and will contribute to the decarbonization pathways. The selection of high temperature refrigerant is important to the system performance, cost-effectiveness and environmental-friendly requirement. It also leads to some challenges for the compressor design, which is an area under active development. In this work, a methodology for HTHP centrifugal compressor design is presented. The heat pump cycle analysis and the compressor meanline design are coupled in the initial phase to study the selection of refrigerants and its impact on compressor design. Following this, the impeller was designed using a 3D inverse design method. Automatic optimization was carried out to optimize the impeller performance. The downstream volute was also designed by using a unique inverse design method. Finally, the performance of the compressor stage was verified by computational fluid dynamics simulations. The structural integrity of the compressor was also examined by finite element analysis. The result shows it is important to couple the compressor design with the refrigeration cycle analysis and through the state-of-art compressor design/optimization techniques centrifugal compressor designs can be efficiently generated for HTHP applications.
On the Challenges of Integrating a Rotating Detonation Combustor With an Industrial Gas Turbine and Important Design Considerations for Row-1 Blades
Authors: Rathod Dharmik S. , Meadows Joseph
Published: August 2024

With the ever-growing demand for power generation to support the world economy and electric transportation needs, efficient gas turbine power cycles need to be investigated to match the anticipated high demands of the future. Decarbonization efforts around the world to achieve Net Carbon Zero by 2050 have also brought many new challenges for the development of these systems due to the unique constraints imposed by less carbon-intensive fuels. In this effort to increase the efficiency and performance of such gas turbine power cycles, pressure gain combustion (PGC) has gained significant interest. The potential for an increase in the thermodynamic efficiency over the constant-pressure Brayton Cycle has made detonation combustors, a type of PGC, an attractive alternative to traditional deflagration-type combustors. Since Rotating Detonation Combustors (RDC) can provide a quasi-steady mode of operation when compared to Pulse Detonation Combustors (PDC), research has been triggered to integrate RDC with power-generating gas turbines. However, the presence of subsonic and supersonic flow fields which are generated due to the shock waves that stem from the detonation wave front and the highly non-uniform temperature and velocity profiles may cause a depreciation in the turbine performance.

The current study seeks to investigate the challenges of integrating the RDC with nozzle guide vanes (NGV) of an industrial, can-annular gas turbine and attempts to understand the major contributors that impact efficiency and identify the key areas of optimization that need to be considered for maximizing performance. To match F-class engine conditions, a geometric model of RDC developed by the Air Force Research Laboratory (AFRL) was scaled to achieve the desired flow conditions. The RDC was integrated with the NGVs through a non-optimized straight duct-type geometry with a diffuser cone. 3-Dimensional Numerical analyses were performed to investigate sources of total pressure loss and to understand the unsteady effects of RDC which contribute towards the deterioration of performance. The entropy generation at different regions of interest was calculated to identify the major irreversibilities in the system. Finally, total pressure and temperature distribution along the radial direction at the exit of the transitional duct is presented to understand the various constraints imposed by the RDC when integrating with an Industrial gas turbine engine NGV.
A Novel Thermally Integrated CO2-Carnot Battery Utilizing Cold Thermal Storage
Authors: Shamsi Syed Safeer Mehdi , Barberis Stefano , Burlando Andrea , Maccarini Simone , Traverso Alberto
Published: August 2024

The growing integration of renewable energy sources in the energy grid presents challenges related to intermittency and negative pricing, necessitating large-scale energy storage solutions. Pumped Thermal Energy Storage (PTES) is an innovative system designed to address these issues by storing and delivering substantial energy in the form of heat using thermal heat pump and power cycles respectively. High temperature heat pump development is crucial to the deployment of PTES as it needs to store heat at > 450°C above the ambient temperature to ensure a reasonable round trip efficiency (RTE). Currently however, it is not a technological possibility for heat pump machinery to achieve these temperatures even with integration of freely available heat sources (200°C to 400°C) which can support the heat pump cycle from a RTE standpoint. This study explores a potential layout of TI-PTES system that exploits commercially available equipment by storing heat below the ambient temperature while still being able utilize the freely available heat source (Solar, Waste heat, biomass etc.) to support the overall RTE, in the power cycle instead. The charging phase employs a well-established CO2-refrigeration cycle to accumulate energy below the ambient temperature in a cold thermal storage. While the discharging phase runs a trans-critical CO2 power cycle between the freely available heat source and the cold thermal storage. Overall, offering a practically implementable model for the PTES system with market available components. The study investigates design of this innovative system presenting the relevance of different operating and machine parameters as well as the contribution of freely available heat source in the overall performance. Finally benchmarking the technology with other long duration energy storages.
Performance Evaluation of Different Rotating Detonation Combustor Designs Using Simulations and Experiments
Authors: Raj Piyush , Talukdar Shaon , Meadows Joseph , Agrawal Ajay
Published: August 2024

Rotating Detonation Engines (RDEs) present a potential avenue for enhancing the efficiency of gas turbine combustors through the utilization of a detonation-driven process. However, integrating an RDE with a downstream turbine poses a significant challenge due to the shock-laden and highly unsteady nature of the RDE exit flow, coupled with a high degree of flow periodicity. In contrast, gas turbines are designed to operate with relatively small velocity and temperature fluctuations at the turbine inlet. The objective of the present study is to develop an understanding of how geometric profiling can improve RDE performance and mitigate exhaust flow field unsteadiness. Three RDE designs are analyzed: an annular combustor with a constant cross-sectional area, an annular combustor with a converging nozzle near the exit, and an annular combustor with a rapid to gradual (RTG) area convergence. Three-dimensional unsteady reacting simulations are conducted for each configuration using the same fuel-oxidizer composition and mass flow rate condition. All simulations are validated against experimental measurements, and RDE performance is assessed based on total pressure gain/loss, unsteadiness at the exit of the RDE, and detonation effectiveness. Results show significant performance improvement for both the convergent nozzle and the RTG profile compared to the constant cross-sectional area configuration, and the RTG design performed better than the convergent nozzle design. Therefore, strategically constricting the flow in an RDE can be used to optimize the performance of an RDE and should be considered in future designs.
Conjugate Heat Transfer on the Effect of Impinging Distance for Film-Cooled Blade Leading Edge With Staggered-Oblique Impinging Jets
Authors: Li Hongye , Du Qiang , Xu Qingzong , Xu Jiawei , Xu Guangyao , Liu Haoyang , Wang Pengfei
Published: August 2024

As turbine inlet temperature gradually increases, cooling demands on the blade leading edge become notably more pronounced. Staggered-oblique impingement scheme has been proved to be a favorable scheme for achieving great cooling performance while ensuring a uniform temperature distribution on the blade leading edge. Conjugate heat transfer simulations are conducted to investigate the effects of impinging distance on the flow structures and heat transfer characteristics of film-cooled blade leading edge with staggered-oblique impinging jets. Three different impinging distances (L/djet = 3, 4, 5) are discussed at jet Reynolds number of 6000, 12000, and 18000 using a validated SST k-ω turbulence model. Results indicate that Nusselt number and overall cooling effectiveness are enhanced by increasing jet Reynolds number. With an increasing impinging distance, the impingement stagnation point moves far away from the blade stagnation line, enlarging the influenced target area. However, this leads to a reduction in the area-averaged Nusselt number due to diminished wall jet momentum. As the impinging distance increases, there is a slight increase for the area-averaged overall cooling effectiveness on the concerning leading edge wall, while a decrease is observed in the mainstream stagnation region. Moreover, higher impinging distances contribute to improved temperature uniformity on the leading edge external wall. Consequently, the staggered-oblique impingement scheme with impinging distance of L/djet = 4 appears to be the most optimal choice.
Modelling and Optimisation of Energy Systems: Lessons Learned From Six Years of Project Work With Master’s Students, Fostering a Systemic Approach
Authors: De Paepe Ward
Published: August 2024

Engineering students, especially those in the field of mechanical engineering, often tend to focus on specific components or fields, and in doing so, they may overlook the broader system in which these components are used and operate. This issue becomes particularly pronounced when addressing the ongoing energy transition, which demands a systemic approach to achieve sustainable energy production. At the University of Mons (UMONS), our Energy System Modelling and Optimisation course and related project are designed to instil this systemic perspective in our students. In this project, we challenge our first-year master’s students to integrate their specialised knowledge of energy system components, specifically focusing on turbomachinery components, to simulate and optimise a thermal energy system. Through an integrated approach that includes literature reviews, group work, discussions, presentations, and self-evaluation, we aim to enhance their systemic analysis and thinking skills. This paper presents a six-year overview of the project, detailing continuous improvements and evaluations and outlining our future plans for further enhancements. The projects encompassed modelling a micro Gas Turbine (mGT) cycle or a Combined Cycle Gas Turbine (CCGT) (with or without reheat), its optimisation using deterministic optimisation methods and the evaluation of off-design performance employing commercial software. Context, course content, project objectives, and evaluation are shared and discussed. Finally, lessons learned, key messages, and points for improvement are indicated and formulated, as well as the steps required for the implementation of this method in a course in general, allowing for the improvement of educational practices in the future. The key takeaway message is that communication is essential.
Three-Dimensional Fluid Topology Optimization for Intakes and Exhausts Flow Uniformity
Authors: Furino Stefano , Canova Alessandro , Pietropaoli Marco
Published: August 2024

In this work, Fluid Topology Optimization (TO) is used to optimize flow uniformity for intake manifolds and heat exchangers of industrial gas turbines. In manifold intakes, the solver minimizes the inflow distortion to the intake, while preserving mass flow, minimizing losses, and adopting a design that can be manufactured with standard processes. The core of the methodology is an in-house Fluid Topology Optimization solver, ToffeeX, extended in this work to minimize the deviation between the velocity profile at the outlet and a specified target. The TO method relies on emulating the natural sedimentation process inside a design domain. The fluid dynamic system is numerically solved, and a scalar design variable is iteratively updated following a Lagrangian optimization approach which ensures meeting the constraints as well as the minimization of the objective functions. In this regard, the optimization is multi-objective. Pressure losses and flow profile variance are simultaneously minimized. At the end of the process, the design solution is the set of regions with high impermeability (solid structures). The optimizer generates coherent structures that channel the flow to match the velocity target while maintaining low-pressure losses. Different levels of complexity and deviation coefficient are shown accordingly with the relative weights imposed on the multi-objective optimization. Even though related theoretical modelling and similar approaches have been briefly described in the literature, this is the first time that the algorithm has been successfully applied to a realistic geometry with correct Reynolds and in its operating conditions.
Dynamic Performance and Control Analysis of a Supercritical CO2 Recuperated Cycle
Authors: Tucker Swatara , Maccarini Simone , Mantelli Luca , Traverso Alberto
Published: August 2024

Supercritical CO2 (sCO2) power cycles represent a promising technology for driving the energy transition. In fact, various research projects around the world are currently studying the possible applications of this technology, which is characterized by high efficiency, competitive costs, compact machinery and enhanced flexibility with respect to competing systems, such as steam-based power cycles. Within this context, the EU-funded SOLARSCO2OL project aims to build a MW-scale sCO2 pilot facility coupled with a concentrated solar power (CSP) plant. A transient model of the demonstration plant was previously developed in the TRANSEO simulation tool by the Thermochemical Power Group (TPG) of University of Genoa to study the operational envelope of the cycle.

In the present work, the model is upgraded to take into account all the relevant fluid-dynamic and thermodynamic phenomena affecting the transient behaviour of the plant. In particular, a detailed crossflow sCO2-air cooler model is now included, which is crucial for assessing the compressor inlet temperature behaviour and controllability. The system has to comply with several constraints, such as compressor surge margin, turbomachinery inlet temperatures, and compressor inlet pressure. The desired net power output should also be guaranteed. The dynamic responses of the system to step variations in various input variables were recorded and used to design and tune the main operational controls. The input variables considered include: 1) compressor rotational speed, 2) anti-surge valve fractional opening, 3) mass flow rate of air through the cooler, 4) mass flow rate of the molten salts through the heater, and 5) CO2 inventory for injection and extraction of working fluid.

The implemented control structure includes proportionalintegral-derivative controllers (PIDs), feedforward action, and their combinations. The controllers are tuned using a mix of established methods, such as Cohen-Coon response-based PID tuning and adjustments from feedforward controls. The feedforward controls were designed taking into account the steady-state values from off-design simulations, as well as the interactions between each controller and the other controlled variables. The final control setup is tested on various power ramps to assess the capability of the prototype cycle in load following and disturbance rejection, showing very good performance in set-point tracking.
STEP 10 MWe sCO2 Turbine Commissioning
Authors: Moore J. Jeffrey , Klaerner John D. , Wade Jonathan L. , Mortzheim Jason , Jothiprasad Giridhar
Published: August 2024

A 10 MWe sCO2 turbine was developed for the Supercritical Transformational Electric Power (STEP) demo pilot plant, which is a supercritical carbon dioxide (sCO2) test facility located at Southwest Research Institute (SwRI) in San Antonio. The plant was fully assembled for simple cycle operation, and the initial commissioning of the turbine was performed. The project was developed in partnership between Southwest Research Institute, GTI Energy, and GE Vernova Research Center and is sponsored by the U.S. Department of Energy (DOE) as part of the $169 million STEP Demo project. The goal of the program is to demonstrate cycle efficiency in both the simple and recompression recuperated Brayton cycle. Initial testing in the simple cycle configuration will be performed with turbine inlet temperatures up to 500°C. In the RCBC configuration at 700°C, the turbine has a 16 MW output yet weighs under 100 kg, making it one of the highest power densities of any industrial turbine. This paper provides design and assembly information and commissioning results for turbine ancillaries like lube oil and dry gas seal systems. The initial rotation of the turbine is described along with the test results of the over-speed trip system. Other mechanical test data will be presented, including radial vibration and thrust position, along with the operating conditions of the test loop.
Design Options for GHG Reduction of Gas Turbine Driven LNG Plants
Authors: Taher Matt , Meher-Homji Cyrus B. , Gülen S. Can
Published: August 2024

Gas turbines have been traditionally used as drivers of refrigeration compressors in LNG liquefaction plants. The current trend is toward increasing the overall efficiency while reducing greenhouse gas emissions.

The main sources of carbon emissions in LNG liquefaction plants include CO2 in feed gas and CO2 in flue gas from the exhaust of gas turbines and fired heaters.

In LNG liquefaction plants, CO2e/tonne LNG produced is typically in the range of 0.2 to 0.4. In order to further reduce the CO2e/tonne LNG produced a combination of hybrid drives (e.g., gas turbine and steam turbine, or gas turbine and motor) can be used for the refrigeration compressors. Also, bottoming power cycle(s) such as steam Rankine cycle or organic Rankine cycle can be employed to recover the waste heat energy from the gas turbine exhaust.

This paper explains the design options and challenges involved in decarbonization of gas turbine driven LNG liquefaction plants in both brownfield and greenfield applications. Moreover, challenges associated with burning high hydrogen-content fuels in gas turbines and different transcritical CO2 compression pathways are briefly addressed.
Efficiency Gains in a Water-Enhanced Turbofan Compressor – A CFD Study
Authors: Zawadzki Natan , Szymański Artur , Igie Uyioghosa
Published: August 2024

In pursuing energy-efficient, low-emission propulsion concepts, civil aviation takes a renewed interest in compressor water injection (CWI). The unprecedented heat capacity of water can be utilised for effective compressor cooling through evaporation, thus substantially reducing the highly temperature-sensitive nitrogen oxide (NOx) emissions formed in the combustion process. It is also well known that evaporative cooling increases thermodynamic cycle efficiency and thus improves specific fuel consumption. However, relatively little consensus exists on the exact effects of CWI on compressor efficiency and operating limits, raising concerns about the deployment of water injection in aero-engines.

A generic turbofan compressor was studied in detail using Computational Fluid Dynamics (CFD) analysis to shed light on how finely atomised water affects compressor efficiency. The compressor layout comprised an integrated fan stage and a two-stage booster, and water was introduced at the inlet to the core. Take-off operation was simulated under dry (no water) and wet conditions with 1% and 2% injection rates (water to air mass) and varying droplet diameters of 10 and 20 microns. A universal, second thermodynamic law approach was used to quantify the overall entropy generation in the compressor.

The study demonstrated that compressor inter-cooling by evaporating water reduces entropy generation of compression at a rate that can supersede the entropy yield due to phase change. For very small droplet sizes and a moderate injection rate, a staggering 4% efficiency gain was projected when compared to the dry case with no water injection, thus reaffirming the performance benefit of a wet-operated compressor.
Retracted: “Use of Performance Models for Powerplant Performance Testing” [ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition, Volume 6, June 24–28, 2024, London, United Kingdom, Conference Sponsors: International Gas Turbine Institute, ISBN: 978-0-7918-8798-1, Copyright © 2024 by ASME. Paper No. GT2024-129317, V006T09A018; 9 pages; doi: https://doi.org/10.1115/GT2024-129317]
Authors: Conlon William M. , Venetos Milton , Pechtl Peter
Published: August 2024

This paper was removed at the author’s request on November 5, 2024.
Using Simultaneous Differential Scanning Calorimetry and Thermogravimetric Analysis to Develop Braze Processes for Porous FELTMETAL™ Abradable Seal Material
Authors: Volpe Erin , Motyka Elaine , Roeseler Stefan , Plessinger Ryan , Noyes Tyler , Kweder Jonathan
Published: August 2024

The diffusional solidification of high-temperature brazing compounds interacting with open-pore metallic FELTMETAL™ (FM) materials was investigated using simultaneous differential scanning calorimetry analysis and thermogravimetric analysis (DSC-TGA). As a sintered particle material with an open-pore structure and high total pore volume, FM is an effective abradable seal material primarily used to sustain pressure differentials between stages in propulsion and power generation turbines. FM is commonly vacuum brazed into the turbine stage directly to the outer shroud or backing ring and the braze layer affects the pore structure and properties of this abradable. To facilitate the overhaul and repair of FM abradable seals while in-field and away from a particular service center, investigation into factors affecting non-vacuum brazing processes to bond FM abradables was done using simultaneous DSC-TGA and metallography. Previous work indicated that oxidation of the alloys can begin below the solidus of the brazing compound under a cover gas but that the presence of boron in the brazing alloy can increase the oxidation onset temperature, thus reducing the extent of oxidation. In this work, further investigation was done by including the factors of 1) type of cover gas, 2) heating rate, and 3) type of braze compound. This research demonstrates that simultaneous DSC-TGA can be used to determine which of these factors most facilitate non-vacuum brazing, specifically by minimizing oxidation, achieving sufficient eutectic phase transformation, and forming a diffusional bond. Further, metallography confirmed the diffusional solidification required for bonding the abradable material and extent of oxidation indicated by the DSC-TGA results.
A Framework and Approach for Leveraging Unsteady Response in Turbocompressor Flowfields
Authors: Krivitzky Eric M. , Larosiliere Louis M.
Published: August 2024

Based on the thesis that critical destabilizing flow structures exhibit coherent response to periodic excitation and can be usefully organized via tuned periodic forcing, the work presented herein emphasizes the dynamical behavior of a representative compressor flowfield under periodic transients and the difficulty in extracting useful information on flowfield response in the poststall regime. The paper begins by developing a surrogate model to understand the onset of rotating stall. This model takes the form of a two-dimensional (2D) linear cascade, which serves as a simplified representation of essential turbocompressor flow dynamics. Steady and unsteady Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) modeling is conducted on both single and multi-passage domains. This analysis aims to highlight the advantages and limitations of domainperiodic extent, providing insights into the behavior of the compressor flow under different conditions. The research evaluates both established and developing rotating stall phenomena from a passage control volume perspective. This approach helps identify dynamical traits and underlying flowfield features that contribute to stall inception and development.

Stability analysis and resolvent analysis techniques are applied to the surrogate compressor flowfield to understand the causes of instability onset and potential mechanisms for controlling spike-type stall inception structures. These analyses provide valuable insights into the dynamics of rotating stall and strategies for managing its effects. The paper concludes by demonstrating an example approach for managing rotating stall, showing promising results for improving flowfield robustness to destabilizing perturbations. This approach involves the implementation of tailored periodic forcing to mitigate the effects of stall and enhance compressor usable work transfer.
Investigations on Unsteady Flow Structure Formation in Tandem Bladed Axial Flow Compressor Stage
Authors: Singh Ajey , Mistry Chetankumar S.
Published: August 2024

The axial compressors suffer from the risk of flow separation upon increasing the loading beyond a certain limit due to increased boundary layer thickness on blade surface. The aerodynamic loading of axial compressors can be enhanced by implementing tandem configuration on rotor. The tandem configuration re-energizes the stalling boundary layer over blade suction surface as well as increases the overall loading of the blade. This increase in loading comes at the cost of increased blade row interaction between rotor and stator which impacts stage stability and losses. This study explores the unsteady rotor-stator interaction at design point of an experimental tandem bladed axial flow compressor. The axial compressor stage consists of highly loaded tandem bladed rotor and single bladed stator fine-tuned to match the dual wake rotor exit flow. The stage has a high mean flow coefficient of 1.05 and design pressure rise of 1400 Pa. The tandem configuration results in impingement of dual wakes emanating from the rotor on the downstream stator resulting in unconventional flow structure on the stator entry. The steady state simulations predict the overall flow field but important rotor-stator aerodynamic interaction is undermined due to numerical averaging at the interface plane. The experimentation analysis though real, is limited to finite number of measuring stations for detailed analysis. Important flow interactions within the rotor and stator passage is difficult to access in experimental program due to limitations of probe placement and associated technicalities. Hence a detailed unsteady numerical investigation has been carried out to explore the flow structure at design mass flow rate. The unsteady computations are performed by blade row transformation methods using ANSYS CFX. The effect of radially varying loading is pronounced on the unsteady aerodynamics of stage. The study is carried out at 60% axial distance between rotor and stator. The tandem configuration leads to formation of dual wakes from the rotor. The radial variation in loading and tandem nozzle strength leads to interaction of fore blade wake with nozzle flow for part span and continuation of distinct wakes for rest of the span. This sets out a highly three dimensional flow incidence for the stator leading to high bpf oscillations inside the stator passage. Overall this contributes explores the propagation of unsteadiness from rotor to stator domain.