bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Unsteady Boundary Conditions on Simulations of Prefilming Airblast Atomisation
Authors: Wetherell Jack R. J. , Garmory Andrew 
Published: September 2023

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.