bluuebunny/crossref_metadata_2025 huggingface dataset:
A Machine Learning Approach for Probabilistic Evaluation of Finite Element Analysis
Authors: Diermeier Florian , Voigt Matthias , Mailach Ronald , Meyer Marcus
Published: September 2023

The geometric shape of turbine blades varies due to manufacturing scatter and wear. The influence of these variations on the stresses can be quantified using probabilistic methods. This requires several finite element analyses. However, to obtain statistically reliable results, a large number of deterministic calculations are required. In this context, the use of deep neural networks (DNN) is a promising approach to replace finite element calculations. Unlike traditional surrogate models such as polynomials, DNNs are able to use data from multiple nodes simultaneously. They can exploit the interdependence of result values from locally nearby nodes without the need for a topologically identical mesh in the finite element analysis (FEA). This is a significant advantage over conventional surrogate models that must be evaluated at topologically identical positions.

To introduce and validate the approach, a probabilistic analysis of an FEA model of a beam is performed. Training and benchmark data are generated by means of a Monte Carlo simulation (MCS). The separate benchmark data is used to validate the model. A sensitivity analysis using the Coefficient of Importance serves as a demonstration example of probabilistic methods. The developed method is then applied to local results on an evaluation mesh of a cooled turbine blade model. A sensitivity study is carried out with the validated model and the results are compared with a previous publication.

Finally, a DNN model is trained on the MCS data of the turbine blade model without using an evaluation mesh. Good agreement is obtained with the approximation of a new parameter set using this model. It is shown that the DNN is a promising surrogate model for probabilistic analysis.
Applicability of Numerical Simulation to the Classification of Fluid Dynamic Loss in Aeroengine Transmission Gears
Authors: Arisawa Hidenori , Tanaka Mitsuaki , Hashimoto Hironori , Goi Tatsuhiko , Banno Takahiko , Imai Hideyuki
Published: September 2023

In high-speed gear systems for aeroengines, reducing the fluid dynamic loss, which accounts for the majority of power loss, can significantly improve fuel economy. However, few practical numerical examples are available regarding high-speed gas-liquid two-phase flows involving gear meshing and gear shrouds (gear enclosures, which are effective for loss reduction).

Therefore, in this study, the porosity method for object boundaries including the gear meshing, the volume of fluid method, and the surface compression method for the gas-liquid interface were used as fast and numerically stable calculation methods. In addition, a gap was provided at the contact surface of the gear tooth surface to improve the calculation stability, and the oil properties were set considering the difference between the flow resistance in a two-phase flow and that in a single-phase flow (due to the separation of oil particles) to improve the calculation accuracy.

To validate the numerical simulation method, a two-axis helical gearbox with a maximum peripheral speed of 100 m/s with specifications equivalent to aeroengine gears was used, and the air flow, oil flow, and fluid dynamic losses were validated. Once the practical accuracy was confirmed, the numerical simulation was used to understand the relationship among air and oil flows, torque, and the effect of the shroud. Consequently, the fluid dynamic loss could be classified phenomenologically.
The Effect of Unsteady Boundary Conditions on Simulations of Prefilming Airblast Atomisation
Authors: Wetherell Jack R. J. , Garmory Andrew
Published: September 2023

Liquid fuelled gas turbines are likely to remain a dominant force in aviation propulsion for the foreseeable future, and therefore understanding the atomisation process is key to meeting future emissions and performance legislation. To make experiments and simulations possible, simplified geometry and boundary conditions are often used, for example, simulations of primary atomisation often use a fixed film height and velocity. This paper aims to quantify the effect of a fully developed unsteady film on the atomisation process. A custom Coupled Level Set & Volume of Fluid (CLSVOF) solver with adaptive meshing built in OpenFOAM v9 is used. Two CLSVOF simulations are presented. The first is of the film development, and the second of the atomisation process. The second uses data from the first as inlet boundary conditions. These results are compared to previous CLSVOF simulations from Wetherell et al. (2020) using traditional boundary conditions. The unsteady film has doubled the modal ligament length and widened the distribution. The SMD has been increased by 58%. The ligament length distribution and SMD are now closer to the experimental results. Comparisons of the time-history of the inlet film mass flow and spray properties has shown a clear correlation between the film mass flow and spray. The delay between inlet and spray has been quantified and lies within expected values. The drop size distribution has not changed significantly, however the volume weighted distribution shows that a much greater proportion of the spray is contained in larger droplets, and the non-weighted distribution is biased by the large number of small droplets. Further work is required to understand how large-scale temporal variations of the type seen in this paper would affect real combustion system performance.
Modification of a Radial Pump Characteristics With Fluid Suction in the Vaneless Space
Authors: Deniz Sabri
Published: September 2023

Flow instability is a common unsteady phenomenon in the field of turbomachinery that often causes large pressure fluctuations, performance penalties, and strong noise as these machines operate under part-load operating conditions. Avoiding the flow instability as a hydro pump operates under such conditions, i.e., high head and small flow rate is usually difficult. Flow control methods such as fluid injection or suction can be applied to suppress, weaken, or delay the occurrence of flow instabilities in turbomachines.

This paper presents results of a hydro pump flow control application with fluid suction (or removal) in order to modify the pump head (pressure ratio) vs. flow rate characteristics and to eliminate the regions of positive slopes so that pump operation becomes stable. Flow control with fluid suction from the vaneless space (between the runner and vaned diffuser) is applied on a model pump at HSLU (Lucerne University of Applied Sciences) Switzerland Hydro Laboratory at different diffuser opening angles. Flow suction is carried out using 10 holes (openings) distributed circumferentially in the vaneless space. The experimental work i.e., suction of fluid on the model pump at the test rig is supported with numerical (CFD) simulations of the tested low specific speed (nq = 25) radial pump. Numerical results are compared with the experimental data.

The pump head – flow rate characteristics are first measured and calculated (CFD) without fluid suction for different diffuser opening angles. Then, flow control with fluid suction from the vaneless space is implemented and the pump head – flow rate characteristics are modified for different diffuser opening angles. The agreement between the experimental data and CFD predictions of the pump head – flow rate characteristics are good for the case without flow control and with fluid injection, but not satisfactory for the flow control case of fluid suction.

The effect of flow suction or fluid removal in the vaneless space on the pump efficiency is also determined. Flow control with fluid suction results are also compared with the results of flow control with fluid injection experiments carried out during a previous research.
Towards Sparse and Interpretable Classification for Damage Assessment of Jet Engine Components
Authors: Tsilifis Panagiotis , Ravi Sandipp Krishnan , Zhang Feng , Pandita Piyush , Bhaduri Anindya , Kulkarni Ambarish , Wang Liping
Published: September 2023

Developing damage models for jet engine components has been an essential research pursuit for engineers and designers. With the advent of data-driven modeling techniques, great progress has been made towards building versatile damage models catering to unknown\limited physics knowledge and multi-modal failures. There are however key limiting factors that prevent further proliferation of data-driven damage models such as black-box nature of models, overparameterization of the models and noisy data. The work presented in the paper seeks to tackle those challenges under a classification problem setting. Two primary methodologies are explored. They are namely Variational Relevance Vector Machine (VRVM) and Maximum Relevance - Minimum Redundancy Based Linear Model (MRMR-BLM). The proposed methodology incorporates interpretability, sparsity and probabilistic characteristics into the developed classification models. The proposed methodogies are tested on synthetic data generated from assumed polynomial and exponential damage models. Furthermore, the models are also tested on skewed positive class cases replicating real-world scenarios to understand the robustness of the models.
Effects of Manufacturing Tolerances on Double Wall Effusion Cooling
Authors: van de Noort Michael , Ireland Peter T. , Telisinghe Janendra C.
Published: September 2023

As aeroengine designers seek to raise Turbine Entry Temperatures for greater thermal efficiencies, novel cooling schemes are required to ensure that components can survive in increasingly hotter environments. By utilising a combination of impingement cooling, pin-fin cooling and effusion cooling, Double-Wall Effusion Cooling is well equipped to achieve the high metal cooling effectiveness required for such challenges whilst keeping coolant consumption at an acceptably low level. However, this high performance can drop-off within the variability of common manufacturing tolerances, which can also expose cooling schemes to issues such as hot gas ingestion.

This paper uses an experimentally validated Low Order Flow Network Model (LOM) to assess the cooling performance of a Double Wall Effusion Cooling scheme employed in a High Pressure Turbine Nozzle Guide Vane, subject to the variability of geometric parameters set by their manufacturing tolerances. The relative significance of each geometric parameter is examined by varying it individually and comparing the effects on the cooling performance. A Monte Carlo analysis is then conducted to assess the likelihood of performance variation for a baseline design. Finally, multiple optimisation studies are conducted for the cooling scheme, with the simultaneous objectives of reducing coolant usage and maximising the design tolerances to reduce manufacturing cost, all whilst maintaining acceptable metal cooling effectiveness and backflow margins.
Impact of Installation on the Performance of an Aero-Engine Exhaust at Wind-Milling Flow Conditions
Authors: Goulos Ioannis , MacManus David , Rebassa Josep Hueso , Tejero Fernando , Au Andy , Sheaf Christopher
Published: September 2023

This paper presents a numerical investigation of the effect of wing integration on the aerodynamic behaviour of a typical large civil aero-engine exhaust system at wind-milling flow conditions. The work is based on the Dual Stream Jet Propulsion (DSJP) test rig, as will be tested within the Transonic Wind Tunnel (TWT) located at the Aircraft Research Association (ARA) in the UK. The DSJP rig was designed to measure the impact of the installed pressure field due to the effect of the wing on the aerodynamic performance of separate-jet exhausts. The rig is equipped with the Dual Separate Flow Reference Nozzle (DSFRN), installed under a swept wing. Computational fluid dynamic simulations were carried out for representative ranges of fan and core nozzle pressure ratios for “engine-out” wind-milling scenarios at End of Runway (EOR) take-off, diversion, and cruise conditions. Analyses were done for both isolated and installed configurations to quantify the impact of the installed pressure field on the fan and core nozzle discharge coefficients. The impact of fan and core nozzle pressure ratios, as well as free-stream Mach number and high-lift surfaces on the installed suppression effect were also evaluated. It is shown that the installed pressure field can reduce the fan nozzle discharge coefficient by up to 16%, relative to the isolated configuration for EOR wind-milling conditions. The results were used to inform the design and set-up of the experimental activity which is planned for 2023.
Predicting the Performance of Turbine Exhaust Diffuser-Collector Systems Across the Operating Range: Comparison of Lattice-Boltzmann Method Simulations With Experiments
Authors: Langford Matthew , Siorek Michal , Guillot Stephen , Ng Wing F.
Published: September 2023

The predictive capability of the lattice-Boltzmann very large eddy simulation (LBM-VLES) methodology was evaluated for industrial gas turbine exhaust diffuser-collector applications. The effort focused on evaluating the accuracy of performance predictions against experimental rig data gathered at engine representative conditions including the Reynolds number, Mach number and inlet flow conditions. The performance prediction capability of LBM-VLES simulations was also compared against Reynolds-averaged Navier-Stokes (RANS) simulations. Evaluations were completed for two distinct exhaust rig geometries at conditions indicative of their respective design points, and the performance prediction capability was also evaluated at conditions depicting two off-design cases. The off-design conditions were represented by an increase in inlet swirl angle and associated incidence on the diffuser struts.

Overall, the authors found that LBM-VLES simulations were a suitable approach for predicting the performance of gas turbine exhaust diffuser-collector systems at both on- and off-design conditions. The LBM-VLES simulation accuracy was substantially better than that achieved by RANS simulations, with 66% lower RMS pressure recovery error between CFD and experiments for the four cases studied, and an 89% reduction in error for the furthest off-design case. The computational cost of the transient LBM-VLES simulations was roughly the same as the RANS simulations performed using best practices for that solver.
Design and Parameter Identification of a Compliantly Damped Porous Carbon Hybrid Gas Bearing
Authors: Balaji Suryanarayan , Delgado Adolfo , Kang Sang-Guk , Kweon Chol-Bum M.
Published: September 2023

Power density and process lubrication represent two key challenges in turbomachinery systems, guided by the pursuit of cleaner and more sustainable energy requirements. Novel developments in gas bearing technologies allow for improvements in both of these areas. One such development is the use of porous carbon as a delivery mechanism for hydrostatic lubrication in bearings due to its ability to create an even distribution of gas, effectively increasing bearing load capacity. Utilizing porous carbon in a compliantly damped hybrid gas bearing (CHGB) also allows preventing catastrophic failure in the event of intermittent contact, rubbing, or loss of air pressurization, due to the high lubricity of graphite and low friction surface. The use of a compliant bearing support structure allows the bearing to accommodate misalignment, centrifugal growth, large rotor excursion, and develop larger damping forces by integrating an external damper which works in series with the gas film. A MW-class turboexpander rotor is used as a reference point in the design of compliant bearing support structures with specific radial, angular, and transverse stiffness properties. This paper presents the design of a compliant bearing structure coupled to a porous carbon mechanical mate, test rig, and experimental results for non-rotating dynamic characterization tests. Non-rotating uniaxial tests are performed as part of the dynamic characterization of a single compliantly mounted pad and external damper, with excitation frequencies ranging between 30 and 500 Hz. Static loading tests show that the compliant supports dominate the stiffness of the system. Mechanically preloading the pad through external loading results in an increased equivalent stiffness and improves the stiffness ratio between the gas film and the pad support. The external damper develops high damping levels at low frequencies, which indicates good transmissibility between the pad structure and damper. Experimental data shows promising results for using this design in MW-class rotor applications, with frequency dependent behavior and damping entitlement as the primary hurdles to achieving system level operation.
A Study on Quantities Driving Maintenance, Repair, and Overhaul for Hybrid-Electric Aeroengines
Authors: Schuchard Lukas , Bień Maximilian , Ziaja Karl , Blanken Norman , Göing Jan , Friedrichs Jens , di Mare Francesca , Ponick Bernd , Mailach Ronald
Published: September 2023

Hybrid-electric propulsion for commercial aircraft is currently a key industry interest. Consequently, publications on its design and performance estimation are manifold. However, models addressing characteristics of maintenance, repair, and overhaul (MRO) are virtually unavailable — even though direct maintenance costs (DMC) represent a significant part of direct operating costs in commercial aviation. Detailed analysis of hybrid-electric aircraft propulsion degradation and maintenance scenarios must integrate both methods of sizing and design as well as operational factors for conventional and electric subsystems, as operator-specific utilisation strongly influences MRO.

Accordingly, a holistic engine analysis model is currently being developed using the example of an Airbus A320 aircraft, taking into account flight mission, engine performance, degradation, and MRO. This paper presents an implementation of hybridisation into the gas turbine thermodynamic cycle calculation for parallel hybrid-electric engine architectures with 2 and 5 MW electric motors, and the approach necessary for re-sizing hybridised gas turbine components. Turbomachinery loading throughout representative short-haul missions is analysed for conventional and hybrid-electric configurations based on the V2500 high-bypass turbofan engine, whereby unknown or uncertain boundary conditions are considered in a probabilistic sensitivity study. As a result, MRO-driving quantities such as engine performance parameters, atmospheric conditions, and ingested aerosols can be compared.

The findings suggest that DMC related to the gas turbine may be considerably lowered through hybridisation, as it allows for reduced peak temperatures and more uniform gas turbine operation. However, these gains are at least partially offset by additional components’ DMC. For electric machines, bearings and the stator winding insulation are life-limiting; where the latter becomes increasingly dominant for higher power densities associated with high current densities and copper losses. Thermo-mechanical stresses are considered as driving mechanisms in power electronic systems degradation. Consequently, powerful lightweight machines must be balanced against tolerable thermal and electrical loads to achieve suitable service life.
Compressible Flow Calculation for Brush Seals Embedded Within Stepped Labyrinth Tooth Arrays
Authors: Collis Robert , Crudgington Peter , Bowsher Aaron , Chupp Raymond
Published: September 2023

In this paper an existing compressible flow calculation for stepped labyrinth tooth arrays is modified to incorporate brush sealing technology. The aim of this paper is to provide a calculation which can quickly be used by engineers to evaluate any benefits which could be provided by implementing brush seals in their machine design. This eliminates the need for more complex computer simulations which can add upfront cost to a feasibility study. The labyrinth/brush iterative calculation method is supported by physical tests to provide an approximation of the performance gains possible.
Rotordynamic Optimization Strategy of Three Spool Arrangement for Variable Cycle Engine
Authors: Wang Weibin , Wang Yongfeng , Ma Yanhong , Hong Jie
Published: September 2023

Variable cycle engines provide better fuel economy, additional thrust, and more durability than the state of art, because of solving the inherent contradiction between subsonic and supersonic flight through different thermal cycles, which is a promising solution for the future aero-engine. Aiming at the new multi bypass intake variable cycle configuration with interstage combustor, in order to improve the rotordynamic problems caused by the variable cycle characteristics, this paper proposes a rotordynamic optimization strategy for a matching three spool arrangement. The rotational directions and support stiffness are optimized to avoid the coupling vibration of model between the two rotors of core engine with innershaft bearing in the wide and variable working speed range. And the configuration of turbine journal is optimized to improve the critical speed margin and control the bearing dynamic load of flexible rotor with large aspect ratio. Results of the simulation show that, the optimized three spool arrangement displays more sufficient critical speed margin, weaker coupling vibration and lower bearing dynamic load than the former design, which meets the requirements of rotordynamic design and has a promising engineering application prospect.
Heat Transfer Characteristics of an Internal Cooling Channel With Pin-Fins Using Recessed-Extruded Endwall Coupling in Gas Turbine Blade
Authors: Pham Gia-Diem , Cong Do Khanh-Duy , Chung Duy-Hung , Park Sung-Goon , Plourde Frédéric , Kim Kwang-Yong , Dinh Cong-Truong
Published: September 2023

This work numerically explores the vortices creation and preservation in a channel with pin-fins for two endwall-turbulation systems: the flat endwall and the recessed-extruded endwall, while studying the flow structure therein. The heat transfer characteristics, including Nusselt number, friction factor, and HTEI, are analyzed and compared with the smooth endwall case at Reynolds numbers ranging from 7400 to 36000. The simulations are carried out with the RANS method. It is reported in the results that, with the new endwall configuration, the high heat transfer areas near the pin-fins are noticeably enlarged compared to the flat endwall at all the tested Reynolds numbers. Besides, the new endwall design increases the heat transfer level near the pin-fins, represented by an enhancement of 64.3% of the Nusselt number compared to the flat endwall at Re = 36000. However, the growth in friction factor due to the flow obstruction at all the Reynolds numbers is trivial. It has been discovered that the enhancement in heat transfer capacity is induced mainly by the combination of the indentations and protrusions that the geometry creates. When considering the heat transfer performance, the HTEI of the recessed-extruded endwall is increased by approximately 62.4% at Re = 21500 compared to the flat endwall, with a height of 2.5% channel height. These findings demonstrate the tremendous potential for enhancing the pin-fin’s heat transfer by altering the endwall design.
Large-Eddy-Simulation of Turbulent Non-Premixed Hydrogen Combustion Using the Filtered Tabulated Chemistry Approach
Authors: Dillon Samuel , Mercier Renaud , Fiorina Benoît
Published: September 2023

With air traffic expected to grow 5% annually until the year 2030, alternative fuels such as hydrogen are being investigated in order to tackle the current environmental crisis. Due to safety concerns, future hydrogen combustion chambers will require new designs of injection systems and are expected to operate under multi-mode combustion regimes. From a Large-Eddy-Simulation (LES) perspective, a prerequisite for the shift towards new hydrogen combustion chamber technologies is a robust turbulent combustion model capable of functioning in non-premixed conditions. Turbulent combustion modeling using flame front filtering is a well-developed strategy in premixed combustion (Filtered-TAbulated Chemistry for Large-Eddy-Simulation - F-TACLES). This approach has been extended to non-premixed flames however, it suffers from high flame filter size sensitivity. Moreover, thin hydrogen flame fronts will result in lower resolution on the LES grid, potentially amplifying this issue. In order to address the feasibility of the non-premixed F-TACLES model applied to hydrogen fuel, simple 1-D and 2-D laminar counterflow diffusion flames are computed. The model is then tested on the 3-D Sandia hydrogen jet flame with a Reynolds number of 10000. Simulations and a-priori tests show that tabulated sub-grid-scale correction terms are stiff and can result in nonphysical results, however the model is capable of correctly reproducing non-premixed flame structures for small filter sizes.
A Numerical Analysis of Cross-Flow Reinforced Impingement Cooling With a U-Shaped Flow-Guide on the Hole Plate
Authors: Brakmann Robin G. , Brose Nina , Carvalho Francisco , Chargui Safae , Guarino Roberto
Published: September 2023

Impingement cooling offers an efficient usage of cooling air in order to obtain high heat transfer rates. In this study a U-shaped turbulator is installed downstream of the jet hole. This arrangement uses the cross-flow to reinforce the jet by guiding it into the adjacent jet and thus increasing its effective jet Reynolds number. Compared to a smooth channel configuration, the Nusselt number on the target can be increased by 5–16% without a significant change in the pressure loss. This is a purely aerodynamic effect and is not caused by increasing the area of the heat exchanging surface. The geometry represents a generic impingement cooling configuration with a row of nine inline impingement jets. All jets are influenced by a self-induced cross-flow. The jet-to-plate spacing as well as jet pitch are set to 5D and the curved U-shape ribs are installed downstream of the jet on the hole plate. The RANS simulations are performed with the SST turbulence model. The effects of different jet-to-plate spacing, jet Reynolds number as well as rib height, position and shape are investigated numerically. The effectiveness of the U-shaped turbulator is discussed in combination with additional turbulators (from the literature). This paper concludes with a recommended set of rib and impingement parameters for the usage of the U-shaped turbulator in gas turbine cooling designs. A discussion of the manufacturability by Selective Laser Melting is included.
Analysis on Nonlinear Vibrations of Mistuned Blades With Frictional Under-Platform Dampers Considering Asynchronous Excitation Force
Authors: Umehara Ryuichi , Akaki Tomohiro , Onozato Naoki , Kitada Hiroki
Published: September 2023

Turbine blades are used under increasingly severe conditions to increase the thermal efficiency of the gas turbines in operation. Friction dampers reduce vibration responses of the blades and improve the power plant reliability. One of the representative friction dampers is the under-platform damper designed to generate friction between two blade platforms and a damper pin. The under-platform damper has been widely adopted in gas turbines. It is important to predict the characteristics of vibration for turbine blades with the dampers analytically on design phase. Thus, a lot of analytical methods have been intensively proposed. However, it is very difficult to obtain analytical results showing high consistency with actual phenomena, which depend on mistuned blades with nonlinear friction dampers and on complicated excitation force included asynchronous random force. The authors indicated necessity of consideration of the two effects, i.e., synchronous harmonic excitation force and asynchronous random excitation force, in the past paper. Although some papers are specific to frictional vibration analysis on mistuned blades, there are no papers considering the effect of asynchronous excitation force. This paper presents the analytical method dealing with nonlinear vibrations of mistuned blades with under-platform dampers on actual condition considering asynchronous excitation force. The analytical results show good agreement with amplitude of vibration and variation of frequency response curves under the mistuned condition. It is suggested that analytical models should take into consideration of variation in the blade properties and asynchronous excitation force to obtain reproducible analytical results on the actual variation of each blade response.
Roughness Investigations on In-Service High-Pressure Compressor Blades – Part II: Roughness Parameterization and CFD-Based Modelling of its Impact on Turbulent Flows
Authors: Vasilopoulos Ilias , Adami Paolo , Voigt Matthias , Meyer Marcus , Mailach Ronald
Published: September 2023

The two-part publication deals with roughness investigations on in-service high-pressure compressor (HPC) blades, both in terms of measurements and simulations. In this paper (Part II), first, stripe measurements of surface roughness coming from the suction side of the blades are conducted, using a highly accurate Alicona measuring device (see Part I for details of the measurement approach). Then, these roughness distributions are used to construct the walls of zero-pressure-gradient, fully turbulent channel flow simulations. Body-fitted unstructured grids of up to 80M nodes are generated, on which wall-resolved LES as well as RANS simulations with the k-ω SST turbulence model are performed. The CFD setup is first validated on a smooth channel reference case against LES and DNS data from the relevant literature. In addition, the impact of Reynolds number on several rough channel flow simulations is explored, using two different setups at Reτ = 540 and Reτ = 880. Finally, after an identification of the most important roughness parameters (given the relatively limited database at hand), a new roughness function model is proposed, which would allow the prediction of the flow over a rough surface without the need of geometrically resolving the roughness scales.
Spatial Temperature and Water Molar Concentration Measurements Using Thermal and Electrostrictive LIGS During Operation of a Swirl Burner at Pressure
Authors: Weller Lee , Shah Priyav , Giles Anthony , De Domenico Francesca , Morris Steve , Williams Benjamin A. O. , Hochgreb Simone
Published: September 2023

Laser-Induced Grating Spectroscopy (LIGS) was applied in a high-pressure combustion facility. Instantaneous (sub-μs), spatially resolved (within 5 mm) measurements of temperature and molar fractions of water were obtained using thermal and electrostrictive LIGS signals. Temperatures up to 1800 K and water molar fractions between 0.01 and 0.12 were measured. A new analytic approach was developed to extract temperature from the frequencies of the measured signal within the flame brush region, where mixtures contain both burnt and unburnt gases. Mean product temperatures are shown to be 8% lower than the adiabatic temperatures for the nominal equivalence ratio, and 14% higher than measurements made with a thermocouple, uncorrected for radiation losses. This work represents the first application of LIGS to a high-pressure, turbulent swirling flame, opening up the potential for future uses in other real world applications. Challenges associated with the deployment of the technique are described, as are potential measures to overcome these difficulties.
Concurrent Design and Operation Optimization of a Multi-Generation Energy System by Using a SMO-MILP Hybrid Algorithm
Authors: Castorino Giulia Anna Maria , Losi Enzo , Manservigi Lucrezia , Pinelli Michele , Spina Pier Ruggero , Venturini Mauro
Published: September 2023

Multi-generation energy systems, which include both fossil fuel technologies and renewable energy systems, are recognized as key players towards more sustainable energy production. To this aim, this paper proposes a methodology for the concurrent design and operation optimization of a multi-generation energy system by considering both life cycle energy consumption and economic aspects. The multi-generation energy system considered in this paper comprises renewable energy systems (photovoltaic panels, solar thermal collectors), heat pumps, fossil fuel energy systems (combined heat and power systems, gas boilers, absorption and compression chillers), and thermal storage systems.

The design optimization problem is solved by means of a surrogate modeling approach, while the operation optimization problem is addressed by means of mixed-integer linear programming and by considering the minimization of fossil cumulative energy demand or total cost. A clustering approach is employed to simulate the yearly electrical, thermal and cooling energy demand by using selected representative days. The variability of natural gas and electricity price in year 2019 and 2022 is also investigated.

The validity of the suggested approach is demonstrated by using the Campus of the University of Parma (Italy) as the case study. The proposed methodology provides an effective and flexible framework for the optimal design and operation of multi-generation energy systems, with a reduced computational time thanks to the clustering approach which allows the identification of a low number of representative days that simulate actual energy demand. The energy saving that can be achieved by means of the methodology developed in this paper can be up to 53%.
Predicting Transitional and Turbulent Flow Around a Turbine Blade With a Physics-Informed Neural Network
Authors: Hanrahan Sean K. , Kozul Melissa , Sandberg Richard D.
Published: September 2023

Despite the demonstrated usefulness of RANS for many industrially-relevant problems, it can be challenging to accurately simulate certain flow features with the method. Due to the Reynolds-averaging process, the Reynolds-averaged Navier-Stokes equations require a turbulence model to close the equations, and the simple physical arguments and approximations used in many turbulence models can cause erroneous results when applied to flows featuring separation or strong pressure gradients. Physics-informed neural networks (PINNs) offer a way to model aerodynamic problems without explicitly requiring a closure. The network can use sparse training data and the unclosed RANS equations to reconstruct the flow without a turbulence model. In this work, PINNs are applied to two problems of relevance in the tubomachinery community, a variable area channel known as the periodic hills, and the T106C low-pressure turbine blade with two different levels of inlet turbulent intensity. These turbulent flows feature shear layers, separation bubbles, as well as favourable and adverse-pressure-gradients. We demonstrate that PINNs are capable of modelling wall-bounded quantities such as Cf and Cp in such complex flows, capturing sensitive features such as the change in separation length when the turbulent inlet conditions are altered. Excellent predictions of wake mixing are also achieved with sparse training data required. Based on these results, future potential work should focus on reconstructing the wake loss region of a linear cascade with sparse experimental data.
Wall Resolved Large-Eddy Simulations of High-Speed Low-Pressure Turbine Cascades
Authors: Tene Hedje Patrick , Bechane Yacine , Lavagnoli Sergio , Bricteux Laurent
Published: September 2023

The current energy challenges in the field of aircraft propulsion demands a better understanding of turbine flows. The complexity of the flows and the geometrical configurations at play limit the feasibility of experimental investigations in this field. Building predictive numerical methods to capture accurately the flow physics is thus important, even if it still constitutes a challenge.

This paper focuses on numerical simulations of high-speed low-pressure turbine blades (HS-LPT), a major component in the framework of high-efficiency geared turbofan engine designs. In this framework, Wall Resolved Large-Eddy Simulations (WRLES) of flows in HS-LPT transonic cascades are performed, using a high order Finite Volume Method (FVM). The Explicit Compressible Solver (ECS) of the massively parallel code “YALES2” is used here. The study focuses on two different cases of low-pressure turbine cascades. First, the well-known T106-C cascade benchmark is studied in order to assess the YALES2 solver for compressible turbomachinery flows. The predictions matches fairly well with those of other numerical codes in the literature and experiments. The second test case investigated is the “SPLEEN” cascade, a next-generation high-speed low-pressure turbine cascade developed by Safran aircraft engines and the von Karman institute for fluid dynamics as a part of a large scale collaborative project. The aim here is to assess the solver for transonic flows, in terms of prediction of the SS separation bubble, the separation-induced laminar-turbulent transition and the wake deficit, using a very detailed experimental database. The results are thus compared with high-fidelity experimental data. This paper shows that the method presented here is able to provide predictive results that can be further used to help in the design LPT blades.
The Effect of Methane-Ammonia and Methane-Hydrogen Blends on Ignition and Light-Around in an Annular Combustor
Authors: Kwah Yi Hao , Wiseman Samuel , Dawson James R.
Published: September 2023

The use of hydrogen and ammonia in gas turbines, either alone or blended with natural gas, poses various technical challenges for combustion systems, including ignition. Depending on the fuel composition, the laminar flame speed and the ratio of unburned to burned gas density (dilatation ratio) of hydrogen and ammonia flames can be well outside the range seen in natural gas flames. Previous studies in annular combustion chambers have provided evidence of the importance of these properties in determining the ignition dynamics including light around times. So far, these studies have mostly considered hydrocarbon fuels, have been limited to only a few runs, and have not yet systematically investigated variations in the dilatation ratio and the flame speed but rather have considered them as a lumped parameter. To investigate these effects in more detail, experiments characterizing the light around times were carried out on an atmospheric annular combustor in which the dilatation ratio and the laminar flame speed was independently varied. This was achieved by varying the equivalence ratio and employing a variety of different hydrocarbon fuels (ethylene, propane, methane) and fuel blends of methane-ammonia and methane-hydrogen. Light around times were evaluated from global chemiluminescence measurements obtained using an azimuthal array of photomultipliers placed round the combustor chamber as well as high speed imaging. To improve statistical certainty, more than 3000 ignition and light-around times were measured with 30 repetitions obtained for each operating condition. To provide some insight into the light around dynamics in specific cases, 900 of the 3000 sets included high-speed OH* chemiluminescence images. Light around times for premixed pure hydrocarbon flames showed a similar dependence on SL as reported in previous studies. For the range of ammonia fuel blends investigated, an increase in laminar flame speed leads to a predictable increase in the flame propagation speed, as in the case of hydrocarbon fuel. Furthermore, collapse of this dependence for all blends could be achieved when corrected for an effective Lewis number, noting that all Lewis numbers for these blends were above unity. However, for hydrogen fuel blends, a decrease in dilatation ratio was found to decrease the light-around time counter to existing experimental results on the ignition of hydrocarbon fuels for which we currently do not have an explanation.
Towards the Multifidelity Optimization of H2-Air Injector for Aircraft Propulsion
Authors: Farjon Philippe , Bertier Nicolas , Dubreuil Sylvain , Morio Jérôme
Published: September 2023

The use of hydrogen as a fuel is one of the most promising way to reduce the climate impact of civil aviation but it requires the development of wholly new injectors in the engine’s combustion chamber. Thanks to the increase in available computing power, new methodologies such as surrogate-based optimization, relying heavily on Computational Fluid Dynamics (CFD) along with automated optimization procedures, can be used to design these injectors. One important point is that 3D geometrical models and high-fidelity numerical approaches are often mandatory to capture key features of the multi-species, turbulent reactive flow through the combustion chamber. However, an optimization process only based on these approaches would be much too expensive. The multifidelity surrogate-based approach is a promising alternative and consists in using CFD simulations with various fidelities. However, its effectiveness depends on the correlation between the different levels of fidelity. The final, long run, goal of this work is the multifidelity optimization of H2-air injector for aircraft. In this paper, we focus on the very first steps of this work with the methodology presentation and a comparison of low (2D RANS) and intermediate (3D RANS) fidelities, which shows a fairly well agreement. Then, preliminary results of comparisons between intermediate and high (LES) fidelities, which highlight the need to improve modeling of RANS simulations, are discussed.
Computation of Isolated Periodic Solutions for Forced Response Blade-Tip/Casing Contact Problems
Authors: Vadcard Thibaut , Thouverez Fabrice , Batailly Alain
Published: September 2023

This article introduces a numerical procedure dedicated to the identification of isolated branches of solutions for nonlinear mechanical systems. It is here applied to a fan blade subject to rubbing interactions and harmonic forcing. Both contact, which is initiated by means of the harmonic forcing, and dry friction are accounted for. The presented procedure relies on the computation of the system’s nonlinear normal modes and their analysis through the application of an energy principle derived from the Melnikov function. The dynamic Lagrangian frequency-time strategy associated with the harmonic balance method (DLFT-HBM) is used to predict the blade’s dynamics response as well as to compute the autonomous nonlinear normal modes. The open industrial fan blade NASA rotor 67 is employed in order to avoid confidentiality issues and to promote the reproducibility of the presented results. Previous publications have underlined the complexity of NASA rotor 67’s dynamics response as it undergoes structural contacts, thus making it an ideal benchmark blade when searching for isolated solutions. The application of the presented procedure considering a varying amplitude of the harmonic forcing allows to predict isolated branches of solutions featuring nonlinear resonances. With the use of the Melnikov energy principle, nonlinear modal interactions are shown to be responsible for the separation of branches of solutions from the main response curve. In the end, the application of the presented procedure on an industrial blade model with contact interactions demonstrates it is both industry-ready and applicable to highly nonlinear mechanical systems.
Hydrogen Co-Firing Demonstration at New York Power Authority Brentwood Site: GE LM6000 Gas Turbine
Authors: Steele Robert C. , Martz Thomas D. , Ettlinger Alan , Zandes Timothy , Alexander Michael J. , Hockman Brian K. , Goldmeer Jeffrey
Published: September 2023

The New York Power Authority (NYPA), EPRI, and General Electric (GE) developed and executed a pilot project focused on hydrogen-fueled power generation. As part of the Low-Carbon Resources Initiative (LCRI), the companies jointly conducted a hydrogen blending project at NYPA’s Brentwood Power Station. This collaborative effort demonstrated the burning of a hydrogen-natural gas blend on an LM6000 gas turbine (GT) to identify the resulting impact on combustion emissions (CO2, NOx, CO) and GT operation. The GT was operated on hydrogen blends ranging from 5 to 44% by volume. The successful test represents the first utility-scale hydrogen blending project in the state of New York, which is mandating a zero-emission electricity sector by 2040 and calling for an orderly and just transition to clean energy for a economy-wide carbon neutrality through the Climate Leadership and Community Protection Act.
Exploring the Effects of Pin-Fins in a Gas Turbine Blade Internal Cooling Channel
Authors: Nourin Farah Nazifa , Amano Ryoichi S.
Published: September 2023

The narrow cooling passage of the internal section of the turbine blades is one of the complicated zones of the gas turbine system. It confronts a high temperature. Pin-fins are an excellent structure to insert in this section to ensure effective cooling. It accomplishes a higher heat transfer coefficient. Pin-fins are also implemented as a mechanical structure to bridge the thin metallic pressure surface and suction surface. However, the pressure drop is significantly higher in the case of pin-fin cooling, which can lower the thermal performance of the cooling channel. The optimization of pin-fin design is important to find the optimal pressure drop. The present study considers two different pin-fin designs, i.e., partial spherical and dome with different arrays of pin-fins. The experimental and computational investigation was conducted with rotation numbers ranging from Ro = 0 to Ro = 0.13. The experimental study was conducted with Reynolds (Re) numbers ranging from 9,000 to 50,000. A computational study was conducted with the Large Eddy Simulation (LES) technique. The final judgment was completed based on the cooling channel’s heat transfer coefficient, friction factor, and thermal performance. The cooling channel with dome-shaped pin-fins with an array of 14 × 2 pin-fins showed a better thermal performance than other cooling channels.
Development of a Hydrogen Micro Gas Turbine Combustor: Atmospheric Pressure Testing
Authors: Tanneberger Tom , Mundstock Johannes , Rex Christoph , Rösch Sebastian , Paschereit Christian Oliver
Published: September 2023

The vision of a carbon-neutral world, implies the shift from fossil to clean fuels for combustion-driven processes and machines like gas turbines. Green hydrogen is a promising alternative to substitute natural gas and other fossil fuels.

In the H2mGT project, funded by the German BMWK, a micro gas turbine (mGT) burner with 100% hydrogen firing is developed and validated. The project is a collaboration between TUB and the manufacturer Euro-K GmbH. The project consists of three phases: 1. Atmospheric pressure tests with a fused silica combustion chamber; 2. Atmospheric pressure tests with counterflow-cooled steel combustion chamber and secondary air injection; 3. Validation of the burner in the micro gas turbine at elevated pressure levels. This paper will present the results of Phase 1.

The hydrogen burner is based on a swirl-stabilized burner of TUB and was scaled to match the requirements of the mGT with its 130 kW thermal power. The burner design features multiple geometrical parameters to enable the optimization of the flame towards low NOx emissions. Therefore, a variable swirl intensity, additional axial momentum of air in the mixing tube, a movable center-body and different fuel injection locations are implemented. Phase 1 investigates the parameter space in terms of flame stability, operational range and parameter impact on flame shape and emissions. Therefore, temperature, pressure, and emission measurements as well as OH* imaging are carried out. It is found that the flame can be operated over a large range of equivalence ratios and preheating temperatures up to 500 °C for many parameter settings. However, at some geometries flashback into the mixing tube is triggered. As expected, the NOx emissions are mainly influenced by the equivalence ratio, the fuel distribution, and the swirl intensity. Single digit emissions are reached up to an equivalence ratio of 0.4 at atmospheric pressure conditions. Furthermore, at low air mass flow, the burner can be operated at 100 % natural gas or 100 % hydrogen without any geometry changes. The fuel switch, thereby, does not change the NOx emissions significantly if reasonable normalization is used.