bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Design Concept for Highly Loaded Compressor Airfoils
Authors: Hergt Alexander , Reutter Oliver , Grund Sebastian
Published: August 2024

Compressor blade design has always faced the challenge of meeting the performance requirements of the compressor while keeping losses to a minimum. Over the past decades, a number of different airfoil types have been developed and grouped into methodologies. The best known example of such a methodology is the NACA airfoil systematic, which is still the basis for many pre-design procedures. With the introduction of modern optimization methods and AI approaches, the airfoil design changed to the development of customized blading. In the present study, a novel concept for highly loaded compressor airfoils is developed using the DLR optimization method AutoOpti and the flow solver TRACE. The aim here is to combine customized airfoil design with a new design methodology. The new approach leads to a Load Splitting Airfoil (LSA) methodology. The concept behind this airfoil method is fundamentally presented in this study on the basis of the DLR-LSA cascade. The conventional NACA 65 K48 cascade was used to define the boundary conditions and requirements for the new cascade, since it is highly loaded and provides a wide basis of comparison for the evaluation of the new airfoil concept. The inflow Mach number is 0.67 and a working range of 10 degrees is to be achieved, resulting in an extremely high aerodynamic load. Based on detailed numerical simulations, the concept of load redistribution by passive boundary layer energization is presented and described. This is followed by an experimental validation of the cascade in DLR’s Transonic Cascade Wind Tunnel (TGK). In addition to the details of the boundary layer development, the analysis also includes the evaluation of the classical performance parameters of a compressor cascade. The loss distribution, deflection, and deceleration behavior are determined over the entire operating range. The results of the experimental validation confirm the design and also the function of the load shifting approach. Finally, the performance of the novel compressor airfoil design is evaluated in comparison to the baseline NACA 65.
A Fuzzy-Adaptive ECMS Based Energy Management Strategy for Series Hybrid Electric Aircraft
Authors: Zhai Yaowei , Wang Xiangyang , Zhang Houwu
Published: August 2024

It is critical to develop an energy management strategy (EMS) for hybrid aircraft that can strike a balance between flight safety and fuel economy. This paper proposes an EMS that combines the fuzzy logic control and adaptive-equivalent consumption minimization strategy (A-ECMS), thereby being named Fuzzy-A-ECMS. This strategy is essentially an improvement of A-ECMS. While inheriting the advantages of A-ECMS, it also solves the issue that conventional A-ECMS is not ideal for aviation applications due to its constant battery state of charge (SOC) target value. SOC sustainability is an important criteria for flight safety, and the balanced energy content of the battery is considered to evaluate fuel consumption. The combination of the feedforward control of the required power with the feedback control of the SOC in the Fuzzy-A-ECMS enables it to sustain the SOC effectively. In order to assess the performance improvement of Fuzzy-A-ECMS compared to A-ECMS, two kinds of flight missions — the complete flight mission and the short-term flight missions with stochastic power requirements — are simulated in the MATLAB/Simulink environment. The results demonstrate that the Fuzzy-A-ECMS can accomplish a balance between sustaining SOC and improving fuel economy.
The Effect of Thermal Cycling on Deposition in an Impingement/Effusion Cooling Geometry
Authors: Gogidze George J. , Bons Jeffrey P. , Lundgreen Ryan
Published: August 2024

Experiments were conducted in a high-pressure deposition facility to study the effect of engine cycling on the successive buildup of deposits as aircraft shut down and power up at different intervals. The test facility simulates the pressure and temperature environment of a combustor liner or turbine vane cooling circuit. The coolant flow temperature reaches 894K (1150 °F) and discharges into a 17atm (250 psi) cavity pressure at a nominal pressure ratio of 1.027. AFRL05 test dust with a 0–10μm size distribution is added to the coolant gas stream at a loading that ranged from 80–120mg/m3. The cooling circuit consists of a double-walled impingement cooling plate and effusion cooling plate with nominal hole sizes on the order of 0.5mm in diameter. To simulate the effects of cycling, the facility is brought up to the desired operating conditions where the first batch of dust is delivered (2–8g). The facility is then ramped down to ambient conditions. Following a “dwell” period of approximately 24 hours, another batch of dust is delivered once the facility is brought back up to the desired operating condition again. Test data were acquired for one, two, and four cycles with different dust mass delivered. Values such as discharge coefficient, pressure ratio, Reynolds Number, and temperature are used to evaluate the effects of dust deposition on the impingement/effusion plate setup. Dust capture efficiency and flow blockage time histories are reported. Capture efficiency is shown to be insensitive to cycling whereas flow blockage is negatively impacted by increased number of cycles for the same total mass delivered. The sloughing of deposit structures during the cool down of the cooling circuit is postulated to be responsible for the observed behavior. Implications for engine operation in dust-laden environments are summarized.
Dynamic Performance Analysis of a Turbocharged PEMFC System
Authors: Mantelli Luca , Iester Federico , Crosa Silvia , Bozzolo Michele , Magistri Loredana , Massardo Aristide
Published: August 2024

Proton-exchange membrane fuel cell (PEMFC) systems are one of the most promising technologies for the decarbonization of the transportation and power sectors, thanks to their high efficiency, fast dynamics, and use of hydrogen as fuel.

This article investigates the dynamics of an innovative layout based on the integration of two PEMFC stacks with an electrically assisted turbocharger (TC), which is characterized by high power density and efficiencies up to almost 60%, making it very interesting for transportation applications.

A detailed dynamic model of the TC-PEMFC is developed in Matlab-Simulink including all the main devices of the cathode, anode and cooling circuits. This model is used to study the dynamic performance of the system, considering the fluid-dynamic and thermal transients of its components.

At first, the model is used to simulate the response of the TC-PEMFC to step changes of multiple input variables: openings of fuel valve and humidifier bypass valve, rotational speeds of TC, blower and cooling pump. These simulations highlight the strong sensitivity of the system to the fuel valve opening, making the need for a feedback controller clear. Many control logics are then implemented on the model to keep the operative parameters of the TC-PEMFC within an acceptable range.

The dynamic model is used to simulate the performance of the TC-PEMFC system during different power load ramps. From the results of these simulations, it is possible to assess the effectiveness of each controller and to verify the compliance of all the system constraints. During load increases, no issues are detected. Even for the fastest considered ramp rate, equal to 100 A/s, proper operation of the system is always guaranteed, and the final power setpoint is reached in less than 5 s. On the other hand, load reductions are limited by the possibility of compressor surge. A maximum ramp rate of 35 A/s is identified in this case. To overcome this limit, a possible modification to the control logics is tested in the final part of the study.
Numerical and Experimental Comparison of a Single Stage Axial sCO2 Compressor
Authors: Ghimire Saugat , Holder Justin , Ha Matthew , Turner Mark , Kang Jeongseek , Morris Scott C. , Sedlacko Kyle , Held Timothy J.
Published: August 2024

The growing shift towards renewable energy sources has underscored the need for large-scale, environmentally sustainable energy storage solutions. Among these solutions, the Supercritical Carbon Dioxide (sCO2) power cycle has emerged as a promising avenue for advanced energy conversion. In such systems, the performance of the compressor is critical to the overall system’s performance and efficiency. A multistage axial compressor has been designed using an optimization-based methodology and the first stage of this design has been built and tested experimentally. This paper compares rigorous computational simulations with detailed experimental data including the readings from total pressure rakes, total temperature rakes, mass flow measurements and casing static pressure measurements. In addition, average measured tip clearance values are used in the simulations along with the detailed prescription of the experimental boundary conditions. The Computational Fluid Dynamics (CFD) simulations do show very good comparison with the data. Additionally, the study serves as a robust validation of the design and optimization process, as the experimental results closely mirror the CFD predictions. Furthermore, computational simulations offer a deeper understanding of the associated flow physics within the compressor. The real gas effects of (sCO2) are also studied and described in how they affected the design and testing, especially considering running to the right corrected flow and corrected speed. Reynolds number effects are also studied and described.
Validation of a Methodology to Assess the Flutter Limit Cycle Oscillation Amplitude of Low-Pressure Turbine Bladed-Disks - Part II: Shaft Speed Effects
Authors: Escudero Alvaro , Rodríguez-Blanco Salvador , Corral Roque
Published: August 2024

The effect of the operating conditions on the vibration amplitude trends of an isolated low-pressure turbine rotor is described. The study utilizes an analytical model correlating the aerodynamic and dry-friction work introduced in Part I of the paper. In this Part II, the analysis has been extended to incorporate the influence of shaft speed. The force distribution and the penetration length of the fir-tree contact surfaces are key parameters within the heuristic micro-slip model used to characterize the friction forces. These parameters change with shaft speed, consequently influencing the dry-friction work involved in the process. The model is closed with numerical simulations to compute the aerodynamic damping, and it is compared against experimental data gathered from the experimental campaign detailed in Part I. The results demonstrate a significant impact of the shaft speed on flutter vibration amplitude. It has been observed that the vibration amplitude reaches a maximum near the on-design conditions. The analytical model can correctly capture this trend indicating that the essential physics is retained in it. Nonlinear friction, mistuning and 3D unsteady aerodynamics have shown to play a predominant role to explain the change of vibration amplitude with the shaft speed.
Performance Assessment of Smart District Heating Networks: The Influence of Distributed (Co)Generation on the Network Primary Energy Consumption
Authors: Alleori Riccardo , Ancona Maria Alessandra , Branchini Lisa , Melino Francesco , Ottaviano Saverio
Published: August 2024

The European and US strategies — providing for energy efficiency increase, pollutant emissions reduction and fossil fuel consumption reduction — leads to an increasing attention on the concept of complex energy networks and/or smart cities. In this scenario, an innovative approach in the heat sector is the integration between District Heating Networks and distributed generation systems, such as solar thermal panels or micro-combined heat and power generators. This approach allows to realize a bidirectional thermal energy exchange at the final users and, consequently, the development of the so-called Smart District Heating in which one or more of the thermal users are converted into prosumers.

The aim of this paper is — starting from the thermo-hydraulic analysis of an existing network located in the North of Italy which is set as case study — the evaluation of the influence on the network energy performance of the thermal prosumers location and distributed generation system typology, in order to optimize the network smart transformation and operation. Based on the optimization analysis, two smart configurations are proposed (respectively considering the transformation of one and two traditional users into smart ones) and analyzed for a whole year of operation. The analysis allowed to appropriately design the distributed cogeneration systems and to quantify the annual obtainable reduction in the electrical consumption for the pumping station, network thermal losses and primary energy consumption.

The results show that the conversion of a traditional District Heating Network into a smart one with Combined Heat and Power generators allows an increase in efficiency and goes towards the rational use of fossil fuels, increasing the fuel utilization factor of the whole system. This study also shows how the choice of the optimal smart users should be developed with reference to the introduction of two bidirectional substations in the same network.
Experimental Characterization and Emission Analysis of Hydrogen-Enriched Fuel Blends in Gas Turbine Applications
Authors: Bonuso Sara , Marseglia Guido , Di Gloria Pasquale , Otón-Martínez Ramón Antonio , Ficarella Antonio , De Giorgi Maria Grazia
Published: August 2024

The gas turbine industry is actively exploring lean premixed combustion with hydrogen (H2)-enriched fuel blends to decrease greenhouse gas and Nitrogen Oxides (NOx) emissions. Hydrogen enrichment is a crucial area for investigation, aiming to enhance combustion processes and reduce emissions. This study explores the potential of hydrogen-enriched blends to improve energy efficiency and mitigate greenhouse gas emissions.

Two flame configurations — lean and rich — are investigated at constant thermal power outputs. In rich condition and pure CH4 a lifted flame is established. Scenarios with incremental H2 additions to air/methane mixtures are examined using chemiluminescence techniques and spectral filtering for OH species. Proper Orthogonal Decomposition (POD) and Spectral Proper Orthogonal Decomposition (SPOD) methods identify coherent structures and frequency ranges of flame fluctuations. Acoustic microphone analysis provides insights into flame fluctuations, and Power Spectral Density (PSD) evaluation is performed. Measurements of exhaust temperature and emissions (NOx, CO2) further contribute to understanding hydrogen’s role in cleaner and more efficient combustion.
Techno-Economic Analysis of Green Hydrogen Energy Storage in a Cryogenic Flux Capacitor
Authors: Schmitt Joshua , Roychowdhury Bikram , Swanger Adam , Otto Marcel , Kapat Jayanta
Published: August 2024

The Cryogenic Flux Capacitor (CFC) is a cold, dense energy storage core that is being studied in the cryo-compressed, about 300 bar and 80K, region of gaseous hydrogen (GH2) storage and liquid hydrogen (LH2) region near the normal boiling point. Hydrogen storage is improved by physically bonding the molecules within the nanoscale pores of the aerogel composite blanket material. The process of bonding or debonding is governed by principles of physical adsorption (physisorption) and thermodynamics. The large surface area afforded by the nanoporous aerogel (∼1,000 m2/g) allows its storage performance to easily exceed capacities of high-pressure GH2 storage for an equivalent volume. With the integrated aerogel, subscale tests have shown that storage is increased by about 36% over a simple tank filled with GH2 at the same operating temperature and pressure. For LH2 conditions, the CFC is shown to operate at improved densities, but testing is ongoing.

For the techno-economic analysis (TEA), the source of hydrogen is compared between onsite steam methane reforming (SMR) and onsite solar photovoltaic (PV) panels providing power to electrolyzers to produce green GH2. The TEA compares pure hydrogen produced at a small scale for a 25 MW power system and at a large scale in a 500 MW power system. The system allowed for hydrogen imports and exports at a set price with a tank sized for 10 hours of power production. The two power producing technologies are a combined cycle gas turbine (CCGT) and hydrogen fuel cells. The SMR system uses natural gas as an input and includes a carbon capture and storage (CCS) system. The levelized cost of electricity (LCOE), levelized cost of hydrogen (LCOH), and levelized cost of storage (LCOS) are developed based on the capital cost and operating cost of the systems.

The results are shown for current costs using a 2021 benchmark and DOE projections for cost improvements by 2030. The TEA showed that onsite hydrogen generation from SMR has an LCOH of about 1.4 to 2 USD per kg over the life of the plant and the PV hydrogen production LCOH is about 5.2 to 5.5 USD per kg. The LCOS of conventional GH2 systems is estimated to be $210/MWh and cost of storage for LH2 systems is $205/MWh for fuel cell systems and $249/MWh for CCGT systems. CFC improved the LCOS of all these systems to $198/MWh, $191/MWh and $233/MWh respectively. The LCOE also improved with conventional systems between $171/MWh and $228/MWh improved by CFC to between $167/MWh and $212/MWh. Using projections for improvement in costs following DOE’s goals by 2030, green hydrogen improved to as low as $78/MWh LCOS and LCOE for conventional cases. CFC improved over conventional storage with the lowest LCOS being $62/MWh and the lowest LCOE being $73/MWh. These results correspond to an LCOH of $2/kg. Finally, the TEA shows how LCOE is improved for hydrogen conditioning and storage over conventional systems and caverns in the 10 to 50 hour range.
Pilot-Scale Testing of a Transcritical CO2-Based Pumped Thermal Energy Storage (PTES) System
Authors: Held Timothy J. , Miller Jason , Mallinak Jason , Avadhanula Vamshi , Magyar Luke
Published: August 2024

As the world moves toward an electrical generation system that relies heavily upon non-dispatchable resources such as solar photovoltaic and wind power, reliable, low-cost means to store electrical energy and dispatch it as supply and demand fluctuate are vital. Pumped thermal energy storage (PTES) consists of a reversible heat pump / heat engine cycle, where thermal energy is transferred between two reservoirs, one at high temperature and the other at low temperature. During the charging phase of operation, thermal energy is extracted from a low temperature reservoir (LTR), increased in temperature, and then stored in a high temperature reservoir (HTR) using an electrically driven heat pump cycle. During the generating process, the stored heat in the HTR is converted back into electricity using a heat engine cycle — essentially the heat pump operating in reverse — and the residual low-temperature thermal energy is stored in the LTR.

A simplified thermodynamic analysis of a general PTES system provided insights into the governing physics of the system, which were used to select the cycle architecture, working fluid and thermal reservoirs. A pilot-scale (c.a. 100 kW) PTES system using CO2 as the working fluid was then designed, built and tested, including two HTR concepts and an ice/water slurry LTR. Data from this test sequence was used to validate component and system steady-state performance and transient system models. Further, this experience has informed the conceptual design of a 100 MW, 12 hour PTES system that is planned for deployment in 2028.
Nonpremixed Approaches for Fuel Flexible, Low NOx Combustors in High-Efficiency Gas Turbines
Authors: Emerson Benjamin , Patel Shivam J. , Gubbi Srujan , McKinney Randal G. , Wu David , Noble David R. , Lieuwen Timothy C.
Published: August 2024

Lean, premixed combustor designs have almost completely replaced non-premixed combustors for industrial gas turbine applications where NOx emissions are regulated. Nonetheless, these designs have also introduced turndown and fuel flexibility constraints and made combustion instabilities and flashback more problematic. Moreover, modern high-efficiency machines have high enough turbine inlet temperatures that additional fuel staging is needed to manage NOx. These issues are becoming increasingly problematic in a decarbonizing energy sector. First, combustors must also be able to accommodate a range of fuels, including hydrogen or ammonia, whose levels can vary from 0–100%, blended with natural gas. Second, operational flexibility for gas turbines will become increasingly important, as their role evolves from a primary provider of energy to one of providing capacity and resilience. Moreover, they must compete for these services with a host of new technologies, including energy storage and fuel cells, and these cost-pressures require higher-efficiency machines. This pushes pressures and flame temperatures higher, both of which accelerate NOx formation rates. In this environment, having systems with broad operational boundaries, ultra-low emissions, and extreme fuel flexibility will become increasingly important.

The purpose of this paper is to propose nonpremixed, multistage designs for the next generation of high turndown, high fuel flexibility, low NOx combustion designs — referred to here as a Nonpremixed, Rich, Relaxation, Lean (NRRL) combustor. The key concept we explore is non-premixed combustion, followed by additional fuel mixing to locally fuel-rich conditions, a relaxation stage, and then a lean stage. This non-premixed approach can handle essentially any fuel composition, including pure hydrogen, liquid fuels, pure methane, pure ammonia, and any combination in between while breaking the NOx-CO tradeoff and reducing combustion instability risk. This paper provides chemical reactor network modeling calculations to identify key kinetic processes and time scales required for such a concept.

This concept has completely inverted sensitivities from lean, premixed systems which prefer short residence times, low pressures, and low temperatures to minimize NO formation. This concept prefers long residence times, high pressures, and high temperatures, indicating a very different set of design trades for part load and off-design performance.
Wall-Modeled Large Eddy Simulation and Conjugate Heat Transfer for Combustor Aerothermal Applications
Authors: Ansari Naseem , Arguinzoni Carlo , Orsino Stefano , Farokhi Reza , Verma Ishan
Published: August 2024

In modern day gas turbine hot sections, active cooling of liner walls is critical due to extremely high temperatures and long continuous operation. Reduced thermal stress increases the life cycle of engines’ components while meeting the ever-greater demands for cycle efficiency and low operational costs. A secondary flow network can be introduced to shield the metal surfaces by forming a film, increasing the durability and life of the liner. The interactions of the effusion cooling with the cross flow and properly capturing wall effects are critical for accurate heat transfer predictions. High fidelity simulations are used to improve the overall performance and durability of gas turbine engines. The simulations recover the distribution of temperature in both solid and fluid zones, thereby allowing design engineers to develop designs for next generations of gas turbines, along with prognosis of existing engine designs. However, the high level of fidelity is accompanied by computational cost, along with complex numerical modeling approaches, especially for numerical models utilized for the life cycle assessment of gas turbine engines.

This paper uses a numerical study using Ansys Fluent to evaluate Wall-Modeled Large Eddy Simulation (WMLES), along with WALE as sub grid scale model, Conjugate Heat Transfer (CHT), and radiation to explore its benefits for practical use in industrial combustion applications. The predictions from various LES methods vary significantly near the wall, where the solution depends on much finer grid resolution. Various methods for modeling WMLES are compared both in the context of computational accuracy and cost. The simulations are performed using open literature experiments such as heated nozzle exhaust over an effusion cooled plate [1], and air/air effusion/slot cooling combustor liner experiment [2]. The accuracy of the simulation approach is assessed by comparing solid plate temperature data from the experiments. In this study the effects of WMLES-CHT are explored with a focus on thermal coupling, radiation, etc. The comparisons in the paper allow the selection of best practices to accurately model CHT for practical use in gas turbine applications. In general, numerical investigation matches experiments quite well, both qualitatively and quantitatively.
Characterization of Orientation Effects of Spring Energized Seals Using 2D Simulations
Authors: Roeseler Stefan , Volpe Erin , Plessinger Ryan , Noyes Tyler , Motyka Elaine , Shealy Michael , Kweder Jonathan
Published: August 2024

Spring energized seals, such as C-Rings, employ use of a high strength spring (Alloy-90, Alloy 718 etc.) within a soft jacket and hard liner (optional) to create high load, high performance seals. This seal design maintains its highperformance sealing capability due to the high contact pressure between the hardware and the seal jacket that is created due to the combination of the spring and optional liner. As such, spring-energized seals are widely used in critical applications such as nuclear energy and aerospace. As seal environments become more challenging, C-Rings must undergo higher temperatures, pressures, and stresses than before. This work evaluates two C-Ring orientations relative to the high pressure zone (open toward and away from the high pressure) and the effect on seal performance. For both orientations, this work examines several commonly used outer jacket sealing materials: aluminum, silver, and nickel. Spring material and liner material were kept constant for each simulation and remained within recommended design considerations for each outer jacket material. Each design was modeled using two-dimensional (2D) axis-symmetric simulations with the recommended gland/flange dimensions. 2D loading/pressurization steps were applied to each design and were as follows: loading to recommended compression displacement per seal design, then increase the inner diameter pressurization to 10,000 psi. Initial orientation of the C-Ring was away from the high pressure zone, then a similarly designed seal orientation was reversed with its opening toward the high-pressure side of the seal gland, and simulations were conducted as before to show system differences and reactionary responses of the seal. The results of this work indicate that, at high pressure, orientation is an important consideration when designing high performance metallic seals. When the internal area of the seal was subjected to high pressure with the spring oriented toward the high pressure, the liner and jacket were extruded away from the spring, resulting in a decrease in contact pressure; this increases the risk of leak path generation through the center of the seal element. Conversely, when the C-Ring is facing away from the high pressure zone and the outer area of the seal is subjected to high pressure, the spring contacts the outside of the flange and the physical constraint in the system creates additional axial force that increases contact pressure. This behavior is similar to an energizing effect. It was observed through physical trials in development that the force to compress the seal is significantly higher than any energizing effect gained due to system pressure. Secondarily, it was found that orienting the C-Ring away from the high pressure system media allows the seal design exhibit greater spring resilience while also avoiding corrosion and embrittlement effects on the spring from the system environment.
Experimental Identification of Blade Tip Rub Forces at Engine Relevant Temperatures and Speeds
Authors: Reifsnyder Robin , Mathison Randall , D’Souza Kiran
Published: August 2024

Abradable casing liners are used to safely minimize the clearance between rotating turbomachinery blades and outer casings. Reduced clearance improves engine efficiency but can lead to more blade tip rub events. These blade tip rub interactions need to be well understood at engine relevant speeds and temperatures to safely design the engine. Advancements in experimental capabilities to meet these engine relevant conditions and the corresponding measurement and analysis tools will enable these developments. The Ohio State University Gas Turbine Laboratory, in collaboration with Pratt & Whitney, has expanded its capability in carrying out blade tip rubs to vary the temperature of the casing and blades for temperatures seen in a fan before rubs occur. This expansion of experimental capabilities requires a matching expansion of the methodologies used to analyze and interpret experimental data. In analyzing rubs at varying temperatures, it becomes imperative to understand how the temperature in the rub shoe affects the force transfer functions between the blades contacting the abradable liner and the load cells recording vibrations behind the casing. These transfer functions are necessary for obtaining the actual forces exerted upon the blades during the experiment but are originally obtained at room temperature. This paper examines how the load measuring unit’s frequency response function changes based on different temperature conditions and how force measurements are altered between similar tests at significantly different temperatures.
The Design, Fabrication, and Installation of the Inconel 740H Piping System for a 10 MW sCO2 Pilot Plant
Authors: Cunningham Seth , Rhodes Mitchell , Karg Bulnes Fernando , Wade Jonathan , Khawly George N.
Published: August 2024

The STEP (Supercritical Transformational Electric Power) 10 MWe sCO2 (supercritical CO2) pilot plant operates on a recompression cycle (RCBC) up to 715 °C and 255 bar at the turbine inlet. Initial testing phases for this facility will operate a simple-recuperated cycle with turbine inlet temperatures up to 500 °C as a stepwise risk mitigation. While the uncooled turbine design includes novel thermal management, the surrounding piping must also withstand these conditions. This paper summarizes the design, fabrication, and installation of the high temperature piping throughout the system. These piping sections include pipe materials of the high-nickel alloy, Inconel 740H. Through this experience, supply chain, weld procedures, general handling, and inspection were among key challenges. To support this project the supply chain needed to produce extruded pipe, pipe fittings including elbow and tees along with flanges and flange clamps. The high temperature pipe sections that used the Inconel 704H material utilized Grayloc flanges (clamp type flanges) to connect the piping to the equipment. This project involved pipe sizes and schedules that have not been previously produced with Inconel 740H. Inconel 740H requires careful attention when performing welds to ensure that the weld is not contaminated and that the correct temperatures are used with the proper shielding and purge gas mixture. With the proper weld procedure and attention to detail consistent quality welds can be produced. The paper will detail these challenges and the lessons learned that came from them resulting in a successful installation.
Transient Modeling of an Aero-Engine Using Ammonia As a Fuel Carrier
Authors: Patel Kangana , Goyal Vipul , Cotto Brandon , Otto Marcel , Vesely Ladislav , Kapat Jayanta , Shi Mingxuan
Published: August 2024

The aim of this paper is to reduce aviation emissions by changing the fuel source in a turbofan engine powered by jet fuel to hydrogen derived from ammonia cracking. Because sustainable aviation fuels (SAF) remain partially carbon-intensive, our primary focus centers on hydrogen and ammonia. Storing hydrogen necessitates extreme cryogenic conditions (−253°C) or pressurized tanks, making ammonia a more practical hydrogen carrier. While some studies have simulated continuous hydrogen use throughout a flight in a steady-state analysis, this paper concentrates on transient analysis. As airplane change flight phases, there should be a change to injected fuel mass flow rate, adjustments in bleed flow rates depending upon changes in required thrust along with the ambient conditions according to the flying altitude. The objective of transient analysis is to ascertain if the compressors and combustor’s immediate fuel and stability requirements are met. To achieve this, transient analysis simulations are conducted using Simcenter Amesim, that offers a reduced-order model of gas turbine components that is customized to explore the gas turbine’s transient behavior throughout an entire flight mission within a single simulation. In the baseline study, conventional Kerosene was used for take-off and cruise conditions, achieving a significant match and accuracy in both steady-state and transient analyses. In the latter part of this paper, the engine’s transient behavior is presented when ammonia-cracked hydrogen is employed.
Design Guidelines for Inertial Particle Separators
Authors: Bojdo Nicholas , Filippone Antonio
Published: August 2024

Inertial particle separators are air-cleaning devices integrated in air intakes or engine inlets to remove potentially harmful particles through the action of centrifuging. Their geometry is defined by a mean gas path, which sits at the centroid of a duct cross-section. Advances in additive manufacturing are opening up new opportunities to explore a wider design space and optimise for more mission-specific requirements. The current work presents design guidelines for these devices, and explores the effect of certain geometric parameters on the competing objectives of maximum separation efficiency with minimum pressure loss, through a reduced order model. The model framework computes the centripetal drag force by first transforming the principal mean gas path into the Frenet-Serret reference frame to measure the local radius of curvature, and second, solving the local one-dimensional flow field by application of the isentropic flow equations for ideal gas. Loss in pressure due to wall friction, bends, and rapid area expansion are accounted for at each point along the gas path. The capability of this approach is demonstrated through comparison with a known test case in the literature, followed by application to a hypothetical conceptual design. Primary design parameters of splitter position, throat position, gas path curvature (through spline control points), and scavenge mass flow are chosen for investigation. Key findings are that the IPS cross-sectional area and hump curvature could be used together as effective tuning parameters, to maximise separation efficiency for a given target test dust.
Extracting Meanline Modeling Parameters for Radial Turbomachinery From CFD
Authors: Oliphant Chase , Metten Jason , Gorrell Steve , Maynes Dan , Oliphant Kerry
Published: August 2024

Meanline performance models have a long history of use in the design of radial flow pumps and compressors. Most data used to create correlations are point data such as static pressures and temperature measurements at walls with occasional traverses for more details of the flow field. These point measurements along with limited traverses, while very useful, do not provide details of specific flow characteristics internal to the machine. The Two-Zone model, developed by Japikse and others, is a meanline model based on point measurements that enables prediction of machine performance. The model assumes that the flow at the impeller exit is composed of a primary zone that is isentropic and a secondary zone where losses exist. The Two-Zone model can accurately predict power when the fraction of mass flow in the secondary zone (χ) and the deviation angle in the primary (δ2p) and secondary (δ2s) zones are correctly inferred from the available data. However, it is difficult to ensure that the parameters inferred from the Two-Zone flow model structure are uniquely correct. In this paper, the specific details of the impeller exit flow fields required to generate an accurate prediction using the Two-Zone model are extracted from CFD simulations. Using CFD, flow fields at the impeller exit are obtained and analyzed to calculate the model parameters for 10 radial flow machines. The derived two zone parameters are then used to predict the power for each machine. The Two-Zone predictions match the experimental data with an average error of 3.5%.
Native Multi-GPU Solver for Complex Turbulent Flow Field Requiring Full Wheel Analysis in Turbomachinery
Authors: Patil Sunil , Kelecy Frank , Wise Michael
Published: August 2024

The landscape of GPU-based scientific computing platforms is rapidly changing and thus is making a strong case for fully native GPU-based industrial CFD solvers. One of key strengths of native GPU-based CFD solvers is their ability to accelerate the solution of large transient problems. In turbomachinery, there are certain classes of problems which necessitate a full wheel, transient analysis, such as inlet distortion, rotating stall, and hot streak migration. Solving these problems with current CPU based hardware can be time consuming and, in general, very resource intensive. Furthermore, the goal of compressing design cycle times requires fast turnaround times for both steady-state and unsteady CFD analyses, for example, computing an entire compressor map.

This paper introduces a new native multi-GPU solver framework designed to fully explore the potential of rapidly evolving GPU hardware. The solver has been developed with the goal of achieving the highest possible parallel scalability and speed on modern GPU high performance computing clusters. The new solver is based on a flexible architecture which allows its compilation and efficient use on a variety of GPU/CPU hardware platforms. In addition to fast execution of CFD solver code, they typically provide an electrical power savings of around a factor of four while reducing hardware costs by a factor of seven when compared to a CPU cluster with 1024 Intel® Xeon® Gold 6242 cores and a 6 x NVIDIA® V100 GPU server.

This paper illustrates the use of a recently developed native multi-GPU solver for two selected full wheel transient turbomachinery simulations. These cases are: (1) a 10MW wind turbine running at a fixed speed, and (2) a high pressure, multistage axial compressor. Comparisons are made with a CPU-based parallel solver which has been well-validated for its accuracy for a wide range of turbomachinery and related flows. This includes evaluating result parity between solvers, accuracy of performance against available data, effective speedup, and scalability of the numerical solutions.
Development of a Power Generation and Economic Model for Micro-Grid Applications
Authors: Pryor Owen , McClung Aaron , Khawly George , Schmitt Joshua , Allison Timothy
Published: August 2024

A model has been developed to explore the possibility of creating self-contained micro-grids using a combination of renewable energy and energy storage. The model, written in Python, uses solar and wind availability over the period of interest to estimate the amount of available renewable energy. It then compares the renewable energy generated to a given electric load profile over the same period to determine when to utilize on-site energy storage. The renewable energy calculations are performed using the NREL System Advisor Model for both solar and wind resources. Using a vector analysis, the model calculates the time periods the system could charge, or discharge energy based on the amount of additional renewable energy that is not directly utilized to the demand profile. The model includes the ability to utilize several different types of storage including lithium-ion batteries, vanadium flow batteries, pumped thermal energy storage (PTES) or any combination of storage technologies. Additional resources have been modeled including an on-site gas engine and a local utility connection. The power generation calculations can then be used to estimate the capital costs, operating costs and the levelized cost of electricity (LCOE) for the microgrid. A case study has been completed examining the Southwest Research Institute (SwRI) campus using their unique economic factors over a 30-year period. The case study shows that the SwRI would only be able to provide up to 43% of their total load using renewable energy alone while decreasing the cost of electricity by around 10%. Increasing renewable penetration and adding storage showed that the system could provide around 50% of the required load without increasing electricity costs and that the SwRI campus could provide up to 60% of its demand with an increase in the LCOE.
A New Non-Linear Time-Domain Flutter Analysis Approach for Distorted Flows
Authors: Corral Roque , Rodríguez-Blanco Salvador , Chennuru Venkata Y. T. , Vahdati Mehdi , Zhao Fanzhou
Published: August 2024

This paper aims to establish an efficient and accurate Computational Fluid Dynamic (CFD) method for calculating the flutter stability of fan blades in the presence of inlet distortion due to crosswind. Due to the asymmetry of the flow and interaction of fan and distortion, this type of analysis will require a whole assembly computational model. Therefore, reducing the computational cost needed to obtain accurate aerodynamic damping values is paramount. Mode-tracking free-flutter analyses are computationally expensive and troublesome due to the presence of many frequencies in the response signals and, hence, require long physical times to converge the aerodynamic damping. Moreover, the unsteady flow field associated with the distortion can be more significant than the one due to flutter, giving rise to additional numerical difficulties. On the other hand, the energy method approach is commonly performed for a single Nodal Diameter (ND) at a time, requiring many computations to establish the least stable ND. This paper proposes an alternative approach based on the multi-ND energy method. The underlying hypothesis is that the unsteady pressure scales linearly with the blade displacements, and the scattering of circumferential modes due to the distortion is negligible. The general method presented here is general, and can be used to compute the aerodynamic damping for other types of distortion (such as downstream distortions due to pylon and structure).
Experimental Investigation of a Physisorption-Based Hydrogen Storage System
Authors: Otto Marcel , Khlyapov Yakym , Fernandez Erik , Schmitt Joshua , Swanger Adam , Kapat Jayanta
Published: August 2024

This study discusses a practical system utilizing the principle of physisorption where hydrogen is weakly bound to the surface of a nanoporous silica aerogel blanket as an alternative to high-pressure and cryogenic hydrogen storage.

Three different experiments are conducted to simulate various scenarios of such a storage method: change in pressure and change of scale. Transient responses of the charging and discharging cycles are of particular interest. It is observed that hydrogen uptake can be increased by up to 36–38 % at ambient conditions and 77 K when utilizing the aerogel blankets. Packing density, or the artificial increase of surface per volume, increases storage capacity as it is a mainly surface-driven phenomenon. High-pressure testing up to 50 bar showed benefits of the aerogel addition whereas the maximum uptake improvement was observed for 2 bar with a 105.3 % improvement over an empty vessel at identical conditions corresponding to 6.43 wt%.

The scale-up of the system is highly sensitive to the design of the internal cooling design as aerogels are poor thermal conductors reducing the transient response of such systems. Furthermore, the high mass of metal-based pressure vessels further delays the thermal response. This makes the system suitable for day to week-long hydrogen storage but not for peak-shaving or load balancing.
Quantitative Measurements in the Exhaust Flow of a Rotating Detonation Combustor Using Rainbow Schlieren Deflectometry
Authors: Gupta Apurav , Miller Robert S. , Bell Kayla M. , Langner Dalton G. , Agrawal Ajay K.
Published: August 2024

This study employs Rainbow Schlieren Deflectometry (RSD) to characterize the unsteady, supersonic/subsonic exhaust plume of a Rotating Detonation Combustor (RDC). Firstly, RSD images are analyzed to quantify the frequency and strength of flow oscillations and their relationship to the detonation wave. Secondly, a 3D tomographic algorithm is used to obtain the local 3D density field across the whole region of interest (ROI). The tomographic analysis relies upon wave rotation to infer projection data of the 3D exhaust plume at multiple view angles using a single RSD/camera system and was previously validated using phantom data from computational fluid dynamics analysis of an RDC. The annular RDC operated on methane and 2/3 O2 – 1/3 N2 oxidizer mixture is equipped with a converging nozzle to pressurize the combustion chamber. The product flow exiting the nozzle throat expands across an unoptimized conical aerospike attached to the center body of the RDC. RSD images provide a temporal resolution of 369 ns and spatial resolution of 100 μm in a 6.4 high and 25.6 mm wide ROI of the exhaust plume. A rainbow filter is calibrated to convert hue in color schlieren images into deflection angle data. This data is used to characterize the unsteady flow oscillations that show excellent agreement with PCB pressure probe measurements acquired inside the combustion chamber. Tomographic analysis yields a 3D local density field that shows distinct features, consistent with published numerical simulations of the RDC exhaust plume. For the first time, this work demonstrates the ability of high-speed non-intrusive RSD diagnostics to acquire whole-field density measurements in an operational RDC. Such data would be valuable to validate high-fidelity numerical simulations and gain a further understanding of the exhaust flow to help with RDE-turbine integration. Further improvements to the RSD hardware and analysis procedures would enhance present capabilities to ultimately infer other thermodynamic properties such as temperature and pressure from density measurements.
Characterization of the Upgraded NASA GRC Single Stage Axial Compressor and Fan Facility
Authors: Stephens Julia E. , Lucci Barbara , Mirhashemi Arman
Published: August 2024

In order to meet the emissions and efficiency goals established by the aviation community, next generation aircraft engines will require low pressure ratio, distortion tolerant fans. Maturation of the necessary technologies will require facilities which are capable of accurately testing the fan performance. To achieve this, the Single Stage Axial Compressor and Fan facility at NASA Glenn Research Center was upgraded. Details of the goals and upgrades undertaken were documented in the 2022 Turbo Expo paper, “Upgrades to the Single Stage Axial Compressor and Fan Facility for Low Pressure Ratio Boundary Layer Ingesting Fan Research.” The performance of the upgraded facility will be documented in this paper.

This paper will review the challenges associated with testing low pressure ratio and distortion tolerant fans and briefly review the upgrades undertaken and their goals. Then the performance of the facility upgrades and the extent to which they were able to achieve the stated goals will be discussed. This includes mass flow measurements, test section temperature, pressure, flow angle at two axial locations, and turbulence levels at the inlet and test section. The paper also documents the performance of distortion generating swirl vanes and total pressure screens to achieve desired distorted conditions at the Aerodynamic Interface Plane.