bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conceptual Design of the Electric Pumps for the High-Performance Engine of a European Lunar Lander
Authors: Danieli Piero , Masi Massimo , Tridello Riccardo , Pessana Mario , Barato Francesco , Chiesa Alessandro 
Published: September 2023

Abstract
This work deals with the design of a high-speed pump to pressurize the fuel and oxidizer of a rocket engine to be installed in a European lunar lander, being developing by NAMMO UK under ESA funding. The use of pumps (Pump-Fed engines) instead of high-pressure branches (Pressure-Fed engines) is dictated by the need of minimizing the weight of the propellant and the pressuring tanks. Electric pumps are very precise in terms of operation control; however, it is necessary they reach a high efficiency in order to minimise the overall dimensions and weight of the batteries that power them. The goal of the present work is to demonstrate that in this specific application, partial-emission pumps can be a valid alternative to the classic centrifugal pumps allowing similar hydraulic performance, easier manufacturability and, mostly, noticeably higher resistance against cavitation. These advantages can certainly make the partial-emission type of pumps competitive especially in case of demanding operating conditions such as those of small rocket engines, characterized by high heads, small flow rates and high rotation speeds. To this purpose, one centrifugal and one PE pump were optimally designed imposing the same design-point operating conditions as required by the project’s application. The two designs were implemented in the computational fluid dynamic software Star CCM+ via 360-degree 3D models and their performance at design point operation were then compared. Results demonstrated that the partial-emission pump allows achieving a cavitation resistance 37% higher than well-designed FE pumps without suffering any efficiency penalisation.
Tuning of Generalized K-Omega Turbulence Model by Using Adjoint Optimization and Machine Learning for Gas Turbine Combustor Applications
Authors: Klavaris George , Xu Min , Patwardhan Saurabh , Verma Ishan , Orsino Stefano , Nakod Pravin 
Published: September 2023

Abstract
For swirl-stabilized gas turbine combustors, turbulence modelling is generally undertaken using Scale-Resolved Simulations (SRS) methods such as Large Eddy Simulations (LES). However, LES is expensive due to large mesh sizes and small time-step size required to estimate the correct large-scale turbulence motion generated within the combustor domain. While Reynolds Averaged Navier Stokes (RANS) models are computationally very efficient in predicting qualitative behaviour, such models lack fidelity to predict complex flow characteristics such as swirl accurately. In previous studies with commercial Computational Fluid Dynamics (CFD) code, the Generalized k-omega (GEKO) based RANS model has been used for simulation of turbulent flows. The free-coefficients of the GEKO model are tuned to predict the characteristics of potential flow undergoing separation. In this paper, LES predictions are used as baseline results which are used to generate a sensitivity field by using an Adjoint solver. Machine learning (ML) via Neural Network (NN) Training is utilized to create a correlation between suitable turbulent flow features and optimal GEKO parameters, aiding the trained model’s generalization. This allows computationally faster simulations of swirling flow with optimized GEKO model compared to LES. In this paper, an industrial configuration named as the DLR PRECCINSTA burner has been used considering a cold non-reacting flow. The computations are performed with LES, and the results match the experiments for directional velocities at different sections within the combustor. The LES solution is used to train the GEKO sensitivity by using an Adjoint solver. The objective function defined in this work is based on the linear combination of difference in velocity components, and a Neural Network is trained to obtain an optimized GEKO model. The results with optimized GEKO agree qualitatively and quantitatively with LES and experiments. The generalization of the NN model is tested on different flow conditions, including a range of Reynolds numbers as well as a reacting flow scenario. The results are showing significant improvements over the baseline solution as compared to the experiment. An optimized workflow is established, which can be used in future studies concerning different geometries with similar flow fields.
The Influence of Different Total Pressure Profile Inlet Distributions on the Performance of a Turbine Vane Frame With Splitter Vanes
Authors: Pramstrahler Simon , Klemm Christian , Peters Andreas , Patinios Marios , García De Albéniz Mikel Lucas , Heitmeir Franz , Marn Andreas 
Published: September 2023

Abstract
A turbine vane frame (TVF) is a component located in between the high-pressure and the low-pressure turbine of future aeroengines. It combines the aerodynamic purposes of a turbine center frame (TCF) and the stator vane row of the first low-pressure turbine stage in one component. Further, it is also used to house structural components and instrumentation, and to guide oil pipes and wires to the inner part of the engine. With the usage of a TVF, the size and weight of the engine can be reduced, and therefore, its efficiency increased. Combined with other technologies, this can help to reach the goals and roadmap demanded by the Strategic Research and Innovation Agenda (SRIA) to reduce the CO2 emissions per passenger kilometer compared to the year 2000 by 75% in the year 2050.
From an aerodynamic point of view, a TVF is a complex component with multiple problematic areas where flow detachments can occur. The TVF investigated in the present paper shows a small separation at the shroud endwall in experimental research. By choosing the right turbulence model, this separation can be reproduced with CFD simulations. However, the separation was very susceptible to different inlet boundary conditions like the total pressure profile distribution and the turbulence intensity. The present paper investigates the influences of multiple inlet total pressure distributions on the secondary flows, boundary layers and the flow field in general in the turbine vane frame. Further, it deals with the impact of the changes in the flow field on the performance of the turbine vane frame. Depending on the design and the operating point of aerodynamic components upstream of the TVF, the total pressure profiles can vary in a significant way. Different concentrations of the total pressure provoke different distributions of the losses in the TVF and therefore impact the performance of the component. Also, different shapes of the total pressure profile at the endwalls affect the boundary layers and therefore impact the secondary flows in the TVF.
In the present paper, two key characteristics describing a simple total pressure profile are investigated: The boundary layer thickness and the skewness of the profile. The description of the effects of those profiles on the TVF can help the design engineers to improve the design of a TVF and upstream components to increase efficiency. A key aspect of the paper is to describe the physical mechanisms of secondary flow and losses in the TVF and if and how separations affect the performance of the TVF.
The Manufacturing and Experimental Validation of a Nickel Superalloy Double-Wall, Effusion Test Specimen
Authors: Murray Alexander V. , Ireland Peter T. , Green Nick R. , Wickins Michael , Hood Richard , Telisinghe Janendra 
Published: September 2023

Abstract
With the hot stage of a modern aeroengine operating with combustor firing temperatures well beyond the melting point of the nickel superalloys from which the turbine blades are manufactured, developments to the methods of cooling of these components are required to advance performance. Double-wall, effusion systems exhibit a quasi-transpiration like cooling effect with recent work demonstrating their exceptional cooling performance. Such systems are characterised by two walls, one with impingement holes and the other with film cooling holes, that are mechanically and thermally connected via pedestals. However, manufacturing such geometries from single crystal nickel superalloys remains a significant barrier to entry into service.
This paper presents a method of manufacturing double-wall effusion specimens from a nickel superalloy commonly used in modern commercial high pressure turbine components. The method maintains the mechanical integrity associated with nickel superalloys. Details of the method are presented alongside x-ray and GOM laser scan data of a flat-plate test article that demonstrates the success of the manufacturing process. Aerothermal testing of the specimen in a bespoke recirculating wind-tunnel facility was undertaken in which the overall cooling effectiveness of the system is obtained. The results reaffirm the excellent cooling performance of double-wall, effusion systems and further validate the manufacturing methodology as a method by which to realise enhanced cooling effectiveness in service.
Improved Prediction of Secondary-Flow Behaviour Through a Novel Turbulence Model Extension for Rotational Effects
Authors: Mimic Dajan , Herbst Florian 
Published: September 2023

Abstract
In this paper, we present a model extension, which enhances the sensitivity two-equation linear eddy-viscosity turbulence models to an altered turbulence production and decay in rotational flow regions. In order to achieve this, the respective production terms of the turbulent kinetic energy and turbulent dissipation rate of the k-ω shear-stress transport (SST) turbulence model are modified using a rotation-sensitive detection term based on the von Kármán length scale.
Design of a Linear Compressor Cascade for Influence Coefficient Method Flutter Testing
Authors: Gambel Julian , Peitsch Dieter , Schneider Sabine 
Published: September 2023

Abstract
A linear cascade module was designed for flutter testing of combined plunge-pitch mode shapes over a range of different stagger and inflow angles in an established low-speed wind tunnel. The iterative approach to the aerodynamic cascade design described in this paper, involved the investigation of multiple layout options and design parameters. It led to a cascade configuration with 13 blades and adjustable diffusershaped bypass ducts on both ends of the cascade. RANS simulations show that this design is capable of replicating on its central 9 blades the steady-state and unsteady aerodynamics of an infinite cascade over a wide range of inflow angles, indicating that the finite cascade is suitable for experimental investigations of aeroelastic parameters.
Aeroelastic simulations of the finite cascade design and a cyclic reference cascade yielded surprising results regarding a beneficial effect of angle of attack on flutter stability that was observed over most of the considered parameter range. This appears to conflict with common aeroelastic understanding and prompts further investigation and experimental validation.
Secondary Flow Control of Turbomachinery Blades Using Vortex Generators
Authors: Putzu Roberto , Ghisu Tiziano , Shahpar Shahrokh 
Published: September 2023

Abstract
Secondary flow control is becoming increasingly important to improve the performance of highly-loaded axial fans and compressors, especially when considering multi-row interactions, where the main passage vortex can significantly reduce the life of downstream components. In this regard, vortex generators (VGs) are investigated to assess their potential to influence the secondary flow in an axial compressor, by increasing the mixing of the main flow with the low-momentum fluid of the boundary-layer. They can also be used to produce a strong vortex that is convected downstream in the desired direction to reduce the main passage vortex strength. They can be capable of reducing viscous effects at the hub and consequently contract the blade passage vortex, thereby mitigating the vorticity production and its effects on downstream components. Despite VGs having been studied extensively especially in external aerodynamics, there is still a lack of studies on their full potential to reduce secondary flows in axial fans and compressors. This work presents a novel way of using vortex generators to reduce secondary flows in the hub region of an axial compressor. The Rolls-Royce in-house CFD suite, with its overset (chimera) mesh capability, is used to generate high-quality multiblock structured meshes rapidly for complex configurations. A parametric analysis using several geometric factors is presented, together with a comparison of using different objective functions to select the optimal VG configuration from a DOE population. A detailed analysis of the effects on pressure loss and secondary flows is reported, paving the way for an automatic optimization of these devices.
Multi-Fidelity Heat Transfer Analysis of Shrouded High-Pressure Turbine Rotor Blades
Authors: Carta Mario , Ghisu Tiziano , Shahpar Shahrokh 
Published: September 2023

Abstract
CFD simulation is frequently used in the field of analysis, design, and optimization of complex geometries such as the film-cooled turbine blades of a modern jet engine. As increasingly higher turbine entry temperatures are being sought for, computational analyses need to be able to provide high-fidelity predictions of the metal temperatures and the heat transfer coefficient on these critical components. To increase the fidelity of the flow simulation, key physical aspects that characterize the operation of these components can be included in the model, particularly the fluid-solid thermal exchange, and the rotor-stator unsteady interaction. These effects that can impact the model’s prediction capabilities are investigated in the present paper. The geometry under study is constituted by a fully-featured high-pressure turbine one-and-a-half stage of a modern commercial jet engine. Rolls-Royce’s in-house software is used to carry out the 3D Reynolds-Averaged Navier-Stokes flow simulations. To enhance the fidelity in terms of fluid-solid thermal interaction, steady-state Conjugate Heat Transfer (CHT) simulations are conducted. The CHT results are then compared to experimental data from a thermal paint test. Phase-lag simulations are run in adiabatic-wall conditions to assess the impact of the stator-rotor interaction on the near-wall gas temperatures.
Computational Assessment of Labyrinth Seal Parametric Variation on Leakage Prediction Using Modified Direct Analytical Model in Transient and Steady Operation
Authors: Ertuğral Gürkan , Uçar Dündar 
Published: September 2023

Abstract
Labyrinth seals are vital for leakage control of gas turbine engines. Over the years, several analytical models have been developed to estimate leakage flow amounts through the labyrinth seals for different seal geometries and operating conditions. This paper presents and covers a modified direct analytical model based on the Vermes equation with updated flow coefficients to accurately calculate the leakage flow rate of straight-through labyrinth seals in a steady and transient operation. A design of experiment study has been performed to derive flow coefficients by changing operating conditions and geometric parameters of labyrinth seals in a commercial one-dimensional compressible flow solver Altair Flow Simulator and a computational fluid dynamics tool ANSYS Fluent. The kinetic energy carry-over coefficient and clearance factor are identified as the most critical factors for flow coefficients. The modified analytical model was validated with several labyrinth seal test cases of Stocker and Wittig et al. Numerical experiments have been performed to enhance the capability of both coefficients and models. The modified analytical model shows good agreement with test cases and predicts the seal leakage flow amount with 95% accuracy for the straight-through labyrinth seals.
Integrated Aero-Mechanical Design and Experimental Validation for Next Generation Compressors for Energy Transition
Authors: Toni Lorenzo , Guglielmo Alberto , Grimaldi Angelo , Cangioli Francesco , Biliotti Davide , Belardini Elisabetta , Meazzini Giulia , Miris Lorenzo 
Published: September 2023

Abstract
Meeting Paris Agreement climate goals and the global warming target of 1.5°C by 2050, requires energy sector to accelerate the path to energy transition to finally achieve net zero emissions. Turbomachinery, and centrifugal compressors in particular, will play a crucial role in this scenario and will be fundamental to turn a necessary, ethical and ambitious goal into an actionable one.
New generations of very efficient centrifugal compressor stages are needed to meet the requirements of low emission compression systems; in order to extend applicability of these high efficiency centrifugal compressor to as many applications as possible, peripheral speed needs to be increased beyond the current limits.
New design philosophies must be followed both for aerodynamics and mechanical designs and the typical limitations in terms of peripheral speed are to be overcome, even when standard alloys are used. Moreover, the more compact the configuration is, the stronger the blade row interactions are, with consequently higher fluid-structure coupling, which is mainly due to the unsteady interactions between structural mode shapes and stationary row wakes and potential fields; in addition to this, the high operating speed leads also to increased static stresses.
This paper then focuses on the aerodynamic and mechanical design challenges of a high-speed centrifugal compressor stage, designed for energy transition applications: numerical outcomes will be compared against experimental results, showing an excellent predictive capability. A full aeromechanical analysis and a dedicated experimental campaign have been carried out as well and the good data match in terms of vibratory response level and aerodynamic damping will be presented and discussed.
These achievements are key technology enablers for different energy transition applications and can be directly used for hydrogen compression systems designs.
Preliminary Wear Investigations With Pressure Actuated Leaf Seals for Superheated Steam Turbine Application
Authors: Wittenberg Andreas , Rühle Tobias , Greving Johannes , Wichern Florian , Friedrichs Jens 
Published: September 2023

Abstract
Pressure Actuated Leaf Seals (PALS) are a promising technology for modern load-follow operation of power plants and turbines. Their strength lies in their radial adaptivity, which enables a significantly smaller radial gap height than conventional labyrinth seals.
In this paper, which is a continuation of ISUAAAT16-022 from 2022, the operating behavior with compressed air and shaft rotation up to 3,000 rpm is investigated, including an analysis of the wear caused by frictional contact between the shaft and the seal leaves. This includes both concentric and eccentric contact behavior. The test seal with a nominal diameter of 300 mm is designed in such a way that it can be used in a similar design in subsequent industry-related superheated steam tests. In addition to the seal performance before, during and after the wear-in process, the frictional torques, temperatures in the flow and on the shaft-contacting leaves as well as the material removal on leaves and shaft running surface are analyzed.
The results show a basically robust operating behavior of the seal with moderate performance deterioration, which can be directly attributed to the increase in the clear gap. However, the shaft wear is higher than for other contact seals, so that further investigations are necessary before use in practice is feasible.
Review of Technologies Used in Gas Journal Bearing Test Rigs
Authors: Rimpel Aaron , Shakil Ali , Kerr Thomas , Lipham Robert 
Published: September 2023

Abstract
Foil bearings are the most prevalent gas bearing technology in use today. Foil gas bearing technology development requires a two-fold approach of analytical and experimental research. Analytical simulation can be used to better understand the underlying physical principles in detail, though this is not trivial due to complex interactions of structural, thermal, and fluid dynamics effects. Targeted experimental testing may then be used to validate the models. However, in practice, foil gas bearings have relied on simplified analytical tools, experience, and empirical approaches to validate and heuristically tune new bearing designs. Static load test rigs have been used to quantify steady-state performance like drag torque and load capacity as well as transient performance like lift-off speed and start/stop wear. Dynamic load test rigs have primarily been used to characterize the stiffness and damping coefficients of the bearings. This paper reviews test rigs employed over the last several decades, focusing on static and dynamic rigs for foil gas journal bearings. Technologies and considerations for the necessary test rig functions are covered: drive system, rig topology, static load mechanism, torque measurement, dynamic excitation and response measurement, and means to test in various gas conditions. A primary goal of this paper is to serve as a reference to future researchers embarking on a new gas journal bearing test rig design who wish to understand the state-of-the-art in this area.
Flight-Path Optimization for a Hybrid-Electric Aircraft
Authors: Papadopoulos Konstantinos I. , Nasoulis Christos P. , Gkoutzamanis Vasilis G. , Kalfas Anestis I. 
Published: September 2023

Abstract
This study aims to illustrate a sequence that optimizes the flight-path trajectory for a hybrid-electric propulsion system at mission level, in addition to identifying the respective optimum power management strategy. An in-house framework for hybrid-electric propulsion system modeling is utilized. A hybrid-electric commuter aircraft serves as a virtual test-bench. Vectorized calculations, decision variable count and optimization algorithms are considered for reducing the computational time of the framework. Performance improvements are evaluated for the aircraft’s design mission profile. Total energy consumption is set as the objective function. Emphasis lies on minimizing the average value and standard deviation of the energy consumption and timeframe metrics. The best performing application decreases computational time by two orders of magnitude, while retaining equal accuracy and consistency as the original model. It is employed for creating a dataset for training an artificial neural network against random mission patterns. The trained network is integrated into a surrogate model. The latter part of the analysis evaluates optimized mission profile characteristics with respect to energy consumption, against a benchmark flight-path. The combined optimization process decreases the multi-hour-scale timeframe by two orders of magnitude to a 3-minute sequence. Using the novel framework, a 12% average energy consumption benefit is calculated for short, medium and long regional missions, against equivalent benchmark profiles.