bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acoustic Scattering Behaviour of an Aero Engine Injector: Numerical Investigation Using Compressible CFD and CAA
Authors: Alanyalıoğlu Çetin , Reinhardt Hanna , Fischer André , Lahiri Claus , Hasse Christian 
Published: October 2022

Abstract
During development of modern lean burn aero engine combustors, prediction and characterization of injector thermoacoustic response plays an important role. The SCARLET (SCaled Acoustic Rig for Low Emission Technologies) test rig fulfills this need by providing acoustically defined upstream and downstream conditions under realistic operating conditions to characterize the acoustic response of full-scale injectors in a single sector setup. This work presents results from the complementary numerical analysis campaign that aims to reproduce the acoustic scattering behaviour as measured in the SCARLET rig. As a first step, non-reacting flow simulations were performed using fully compressible CFD simulations and the CAA (computational aero acoustics) method to compute upstream and downstream acoustic fields. The results obtained are then post-processed based on a multi-microphone method to yield the acoustic scattering matrix, which follows the employed experimental post-processing strategy. Results obtained from both methods show satisfactory agreement with measurements. Geometrical simplifications and their implications on scattering behaviour are investigated to achieve a trade-off between accuracy and geometrical complexity. Both methods are compared in terms of their inherent advantages and disadvantages. Limitations associated with employed models and possible improvements are discussed.
Numerical Prediction of Surface Roughness Effect on the Performance of Internal Channels
Authors: Sandeep  , Manoharan Mahendran , Kuchana Vinayender , Liu Jong 
Published: October 2022

Abstract
Additive Manufacturing (AM) in turbine technology enables the manufacture of complex and detailed shapes such as optimized cooling channel designs. However, the AM components are usually produced with high surface roughness. The ability to predict the pressure loss and heat transfer during the AM components’ design phase gives the designer an extra edge to arrive at a better design. In this paper, numerical prediction for the effect of roughness on pressure loss (friction factor) and heat transfer (Nusselt number) for flow in the internal channel is discussed. Numerical simulations were performed using the commercial computational fluid dynamics (CFD) tool by ‘Siemens Star-CCM+’. Initially, the best practices for the CFD process were arrived at by comparing the CFD results with the theoretical correlations for a fully developed channel flow. Further, these best practices were invoked to validate the two test cases from the open literature. From the first test case, three test coupons with the lowest, intermediate, and the highest level of roughness were selected for the validation. From the second test case, in-line and stagger configurations were selected for validation. To reduce the simulation time, modeling the full channel domain as a single channel was explored. The single-channel results were found to be matching well with the full channel results at the two Reynold’s numbers simulated. For all the cases, the friction factor predictions are close to the theoretical and test data, whereas the Nusselt number predictions show a consistent trend with the theoretical data but over-predicts when compared to the test data.
DMD Analysis of Radial Turbomachinery
Authors: Ludewig Alexander , Brenner Gunther , Skinder Kathrin 
Published: October 2022

Abstract
In the design of turbomachinery, the avoidance of flow-induced vibrations offers optimisation potential with regard to noise reduction and the extension of the service life of a machine. To achieve this, damage-relevant should be analyzed in the development phase using methods such as forced response or flutter calculations. A forced response analysis requires the specification of flow-induced excitations in the spectral range, which can be obtained from a temporal numerical simulation using FFT. Since the FFT depends on the time span and therefore only reproduces discrete frequencies, only rotational frequencies and their integer harmonics can be determined from a single rotational period. To work around this, a Dynamic Mode Decomposition (DMD) is applied to analyse the flow field in a high performance centrifugal fan obtained from simulation and measurement data. DMD is a model order reduction method based on singular value decomposition. It extracts modes and eigenvalues of a nonlinear, dynamic system. DMD is considered an ideal combination of proper orthogonal decomposition in space and Fourier transform in time. The numerical data were generated with a CFD calculation based on the unsteady Reynolds-averaged Navier-Stokes equations together with the k-ω SST turbulence model. As a result of this study, it can be shown that the DMD agrees exactly with the analysis of the FFT based on transient local pressure sensors. For the two-dimensional pressure field, however, the DMD deviates significantly from the FFT in the amplitudes for higher-frequency excitations, partly showing better agreement with the measurements of the pressure sensors.
Inverse Design of a Centrifugal Fan for High Flow Rate Operating at Low Noise Level
Authors: Singh Vijender , Baraiya Nikhil A. , Banerjee Jyotirmay 
Published: October 2022

Abstract
Centrifugal blowers are commonly used for heating and ventilation applications. Centrifugal fan is a kind of fluid machinery for energy conversion used in industrial engineering with huge energy consumption. The impeller is the core component of a centrifugal fan, and the performance of the impeller determines the performance of the fan. High-pressure blowers present the problem of high noise with low efficiency coupled with large dimensions.
The centrifugal fan is designed to provide 600 cfm of outflow with a static pressure rise exceeding 2.5kPa at all times at design rpm of 30000 with noise level restrictions up to 80 dB levels operated by a 2kW power input. Inverse design approach has been followed to generate the dimensions and blade profiles. Variable area distribution volute with circular cross-section has been developed, providing pressure recovery and reducing the flow separation. This provides better stall characteristics and increases the overall total to total efficiency of the stage. High rpm operating range provides the opportunity for reducing the overall size with increased noise.
Representation of Components Characteristics Under Performance Degradation of Gas Turbine Engine
Authors: Jiang Zhen , Wang Xi , Yang Shubo , Liu Jiashuai , Chen Huairong 
Published: October 2022

Abstract
The current self-tuning performance model can only reflect the components degradation under operating state, while not non-operating states. Aiming at this disadvantage, this paper studies the representation of components characteristic drift for the purpose of obtaining one that suitable for full operating conditions. Firstly, the real component characteristics regarding the measurement data of engine are calculated by gas path analysis, and the drift of component characteristics is determined by analyzing how original characteristic maps are shifted. Secondly, the relationship between component characteristic drift and operating condition is established. In the relationship, the operating condition is represented by feature parameters, which describe the feature of operating condition. The number of dimension of feature parameters (n) are determined as 0, 1, and 2 respectively. Finally, with the assistance of the relationship generated, component deterioration models are constructed and employed in a self-tuning model framework. By applying the characteristic drift obtained from the component deterioration models to the original characteristic maps, the framework can mirror the degradation of engine’s performance. Comparing the output of framework with reference data, results show that the deviation in the test range is no more than 0.86% when n = 2, while the maximum deviation of n = 0 and n = 1 are 1.92% and 2.51%. It is illustrated that the difference of component characteristic drift within operating envelope can be represented by corrected rational speed and inlet pressure of fan, which will help to realize the performance modeling under the concept of “digital twin”.
Advancement of Electrical Resistance Towards Monitoring Crack Growth in SiC Based Composites at Elevated Temperatures
Authors: El Rassi Joseph , Morscher Gregory N. 
Published: October 2022

Abstract
Electrical resistance has been used to detect in situ changes to SiC based material as damage occurs. Damage in the composite, typically in the form of matrix cracking, increases the resistance due to the local constrain of current flow. Efforts have been ongoing to quantify the effects of increasing potential drop with crack growth in a pre-preg SiC-based composite. Two variations of the pre-preg SiC-based composite were studied: one with a single layer of SiC monofilaments with carbon core (1 fiber/mm) inserted in the center of the composite and extending through the length of the composite and the other possessed three layers of monofilaments, one layer in the center of the composite and the other two layers near both surfaces of the composite. It was found that the high conductive Si phase varied considerably for the different variations of composites and dominated the current flow rather than C. Tension-tension fatigue tests were conducted at 815 °C in a static furnace for both composite systems, electrical resistance was monitored during the test along with acoustic emission. A ply level electric circuit was constructed, and ply resistivity at temperature was obtained based on the Si content in each ply. The function of the electric circuit was to interpret the change in resistance obtained during the fatigue testing of the MI material with the morphology of transverse crack growth. Microscopy and energy dispersive spectroscopy were conducted to better understand the crack morphology.
A Study on Fundamental Combustion Properties of Trimethyl Orthoformate: Experiments and Modeling
Authors: Ngũgĩ John Mbũrũ , Richter Sandra , Braun-Unkhoff Marina , Naumann Clemens , Riedel Uwe 
Published: October 2022

Abstract
Trimethyl orthoformate (TMOF: HC(OCH3)3) has recently been examined as a viable biofuel. TMOF is a branched isomer of oxymethylene ether-2 (OME2) that, due to its high oxygen content and lack of direct carbon-carbon bonds, considerably reduces the formation of soot particles. To meet the challenges of a more flexible and sustainable power generation, a detailed understanding of its combustion properties is essential for its safe and efficient utilization, neat or in blends. In this work, two fundamental combustion properties of TMOF were studied: (i) Auto-ignition of TMOF / synthetic air mixtures (φ = 1.0; diluted 1:5 with N2) using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) Laminar burning velocities of TMOF / air mixtures using the cone angle method at ambient and elevated pressures of 3 and 6 bar. Furthermore, the impact of TMOF addition to a gasoline surrogate (PRF90) on ignition delay times was studied using the shock tube method at φ = 1.0, 1:5 dilution with N2, T = 900–2000 K, and at 4 bar. The experimental data sets have been compared with predictions of the in-house chemical kinetic reaction mechanism (DLR Concise mechanism) developed for interpreting the high-temperature combustion of a broad spectrum of different hydrocarbon fuels as well as oxygenated fuels, including TMOF. The results demonstrate that the ignition delay times of TMOF and OME2 are nearly identical for all pressures studied in the moderate-to high-temperature region. The results obtained for the blend indicate that ignition delay times of the TMOF / PRF90 blend are shorter than those of the primary reference fuel 90 (PRF90) at 4 bar. In the lean-to stoichiometric region, the results obtained for laminar burning velocities of TMOF and OME2 are similar. However, in the fuel-rich domain (φ &gt; 1.0), laminar burning velocities for TMOF are noticeably lower, indicating a decreased reactivity. The model predictions based on the in-house model reveal a good agreement compared to the measured data within the experimental uncertainty ranges. In addition, sensitivity analyses regarding ignition delay times and laminar flame speeds were performed to better understand TMOF oxidation.
Performance Improvement of Heat Exchangers Used in a Hybrid Electric Aircraft
Authors: Rasimarzabadi Faezeh , Crain Alexander , Canteenwalla Pervez , Zdunich Patrick , Gibney Evan 
Published: October 2022

Abstract
Thermal management system analysis of a kW scale hybrid electric aircraft developed at the National Research Council of Canada (NRC) has been provided with the aim of assessing the cooling capacity and improving the efficiency. For the electric propulsion system of the aircraft, a series cooling loop has been designed that comprises a heat exchanger (radiator) and two pumps. As coolant travels through the motor and controller, it accumulates heat, then the heat is dissipated from the coolant passing through the radiator. From the calculated parameters for different demonstration flight phases of the aircraft, it is concluded that the current radiator design is limited by the air side resistance. This air thermal resistance comprises over 76% of the total thermal resistance in all flight phases. Therefore, a large frontal area to meet cooling needs is required. The potential of different methods for cooling improvement of the radiator were investigated and a new concept was suggested for heat transfer enhancement which is a passive enhancing method by applying different micro-fin roughness on the fins or coolant tubes of a radiator.
Numerical Prediction of Long Term Droplet Erosion and Washing Efficiency of an Axial Compressors Through the Use of a Discrete Mesh Morphing Approach
Authors: Agati Giuliano , Borello Domenico , Di Gruttola Francesca , Simone Domenico , Rispoli Franco , Castorrini Alessio , Gabriele Serena , Venturini Paolo 
Published: October 2022

Abstract
Online water washing represents an operation strategy commonly used to reduce compressor performance deterioration due to blade fouling. Since this kind of washing is applied when the machine operates close to full load conditions, injected droplets are strongly accelerated and consequently impact the rotor blades at high velocity, thus inducing undesirable phenomena like erosion. Here we present a novel technique to study long-term water droplets erosion by also considering the geometry modification caused by droplets impacts. Two-phase unsteady numerical simulations were carried out, considering the injection of water droplets and their transport across the fluid flow in the first part of a real compressor, which is modelled in the region extending from the inlet to the rotor blades of the first stage. Simulations are performed on the whole machine to account for the asymmetric distribution of the spray injectors, the machine struts, IGV and rotor blades. The k-ε realizable turbulence model with standard wall functions was adopted and coupled with the discrete-phase model to track injected droplets motion. Droplets-wall interaction is modelled following the Stanton-Rutland approach aiming at detecting the effect of droplet impact (deposit, rebound, splashing), depending on the impact conditions. Moreover, a semi-empirical erosion model developed by the authors was implemented in ANSYS Fluent through a User Defined Function (UDF) to evaluate the erosion induced by the droplets injection. Material removal due to erosion is converted into nodal mesh displacement that is used by a secondary UDF to implement mesh morphing. The mesh modification is applied at discrete steps to reduce the computational load. This technique is adopted to account for the blade geometry modification due to water droplet erosion leading to performance losses. Moreover, an estimation of the compressor operating life before maintenance operations is given and the water washing efficiency during the whole life of the machine is evaluated by means of proper indices. At the end of the simulation workflow erosion phenomena are observed on all the compressor regions, especially in the rotor where erosion peaks are reached at the hub of the leading edge. The rotor blades wet surface was found to remain almost constant around the 50% during compressor operating life. Erosive phenomena were proved to evolve non linearly with time indicating the necessity to account for the mesh modification for an accurate prediction of the long-time process.
Experimental Study on Combustion of Methane / Ammonia Blends for Gas Turbine Application
Authors: Ditaranto Mario , Saanum Inge , Larfeldt Jenny 
Published: October 2022

Abstract
Hydrogen from renewables or reformed natural gas with CO2 Capture and Storage (CCS) can be used as fuel to achieve CO2 free power production. Because of the challenges related to transport and storage of H2, NH3 has been proposed as a hydrogen carrier as it can be stored in liquid form at moderate pressures and temperatures. NH3 can be used as a fuel directly, but the low reactivity and flame speed in air makes combustion stability challenging in conventional gas turbine combustors. As no solutions are commercially available today, a transitional approach is to only replace part of the fuel with NH3 to limit the change in the combustion properties, although this only partly decarbonizes the fuel. This study investigates combustion of CH4/NH3 blends with air in a downscaled Dry Low Emission (DLE) burner at pressures up to 6 bar and thermal power up to 100 kW. The effects of equivalence ratio and NH3/CH4 mixture ratio on the emissions of NOx, CO, CH4, HCN, N2O, and NH3 are studied at different pressures and power. Even small amounts of NH3 introduction in the fuel results in unacceptable high NOx emissions in a conventional combustor and the flame stability limits the maximum NH3 content in the fuel. However, by using a two-stage combustion strategy with a rich primary zone, NOx emissions down to ca. 100 ppm could be achieved with a NH3 content up to 100%, provided the thermal intensity of the combustor is severely reduced.
Turbulence Model Impact on Predicting Precursors to Surge Flow Instabilities in a Turbocharger Compressor
Authors: Trigell E. , Mihaescu M. 
Published: October 2022

Abstract
Turbocharger compressor simulations can improve the development of compressors with broad operating ranges and improved noise signatures. At low mass flow rates aerodynamic instabilities, known as rotating stall and surge, limit the operating range of the compressor. However, the triggering factors for these instabilities are currently unknown. High quality numerical methods are therefore needed to capture instabilities and to simulate reliable performance maps. The aim of this study is to improve the understanding of the chosen numerical approach going from design to off-design operating conditions. It is shown that flow structures are under-predicted using URANS k-ω SST and that a LES WALE method better captures the flow structures in the blade region. Further, the level of fluctuations in different parts of the compressor is presented. By increasing the predictive quality of the numerical simulations, the need for empirical calibration can be reduced and turbocharger matching can be improved.
Innovative Expanders for Supercritical Carbon Dioxide Cycles
Authors: Perri Alessandro , Renuke Avinash , Traverso Alberto 
Published: October 2022

Abstract
Supercritical carbon dioxide plants are attracting strong interest, particularly for distributed power generation, thanks to the high-power density, allowing high compactness and efficiencies due to the particular features of the fluid conditions near the critical point. In the present work, the feasibility of innovative turboexpanders is evaluated for the first European demonstrator of MW size, coupling small volumetric flows with technological simplicity, typical of these types of plants. In particular, the possibility of replacing conventional turbines with bladeless expanders is studied, proposing a design in line with those achievable by small radial and axial turbomachines. The bladeless expanders consist of flat parallel disks mounted on a shaft, separated by spacers to maintain small gaps between them. The laminar flow inside the rotor makes it highly efficient: however, rotor-stator interaction losses reduce the overall performance. Such bladeless expanders maintain high interest for their capability to tackle low volumetric flows, their relatively simple design and ease of manufacturability.
The design case presented in this paper is the feasibility study of a single modular bladeless expander using the existing conventional design (axial and radial stages) as the reference design. 3D numerical analysis is carried out using commercial computational fluid dynamic software. The results show ∼55% total static efficiency of the bladeless expander at 37000 rpm for approximately 1.25MW output power. The impact on performance at different nozzle throat cross-sections and rotor disks diameter has been discussed. The overall performance of the expander is presented by evaluating the losses and improvement strategies that are discussed.
Validation and Assessment of a Numerical Methodology for Turbulent Liquid Fuel Jets in High-Speed Crossflow
Authors: Zghal Malika , Sun Xiaoxiao , Gauthier Pierre , Sethi Vishal 
Published: October 2022

Abstract
For lean combustion technology, sufficient mixing between fuel and air helps to move away from stoichiometric combustion, the flame temperature of which enormously promotes the production of harmful pollutants. Good fuel-air mixing is also essential to avoid fuel-rich pockets, where unburnt hydrocarbon and soot are likely to be produced. For low emissions gas turbines using liquid fuels, such as diesel, jet in crossflow is one the approaches to achieve efficient liquid jet breakup and evaporation as well as superior mixing characteristics.
In order to develop low emissions fuel spray technologies that use transverse jets, it is important that the current numerical tools have the ability to accurately predict the jet breakup, both primary and secondary, evaporation mechanisms, to properly assess the performance of an injector design. However, because the numerical tools often use model constants that are calibrated with experimental data mostly only applicable to a specific range of operating conditions, a particular test fluid or injection method, it is very challenging to assess the accuracy of the predicted results without further experimental validation. To the author’s best knowledge, the breakup mechanism and the predictive capabilities of the breakup models used to guide the design of novel injectors for fuel transverse jets at elevated pressure and high-speed turbulent crossflow have not been reported in full detail.
Thus, the main focus of this study is to compare and assess the capabilities of the breakup models used in state-of-the-art CFD, including a stochastic approach that relies less on experimental model constants, to predict the spray characteristics of turbulent jets in crossflow at different pressures, gas Weber numbers and momentum flux ratios that are more representative of gas turbine applications. This study will be conducted by using Simcenter STAR-CCM+.
The simulated results will be compared to experimental data to validate and calibrate the breakup models through a parametric and sensitivity study.