bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Design Validation of a Swirl-Stabilized Burner With Fluidically Variable Swirl Number
Authors: Eck Mattias E. G. , zur Nedden Philipp , von Saldern Jakob G. R. , Peisdersky Christoph , Orchini Alessandro , Paschereit Christian Oliver 
Published: August 2024

Abstract
Swirling flows are commonly used for flame stabilization in gas turbine combustors, which are hence equipped with suitable swirler units. In these units the air rotation, quantified by the swirl number, is fixed through the geometry and represents a parameter significantly affecting flame stability and dynamics. The possibility of a continuous swirl variation, on the other hand, would be advantageous for the assessment and control of thermoacoustic instabilities. This is especially true for fuel-flexible applications, for which different swirl numbers are needed to stabilize flames arising from the combustion of different fuels. Most swirl-varying systems rely on mechanical adjustments. In this work, instead, a novel swirl-stabilized burner is investigated experimentally, which is based exclusively on fluidic actuation. For the experimental assessment of the resulting flow field, the axial and azimuthal velocity components are determined through Laser Doppler Anemometry (LDA) measurements. The measurements are performed in a volume downstream of the burner’s mixing tube. The data is processed and computed into swirl-numbers in order to quantify the degree of swirl as a function of the fluidic actuation. The characteristics of two different burner geometries are investigated, with and without a central cone within the swirler, respectively. The configuration with the cone is found to generate higher swirl over the investigated operational range. For this configuration, the technically relevant operating range is determined in which the swirl number can be continuously set from zero to around 0.9. Our experimental results show that fluidic actuation is a viable way to continuously change the swirl number, and that the achievable swirl range is quantitatively comparable to that of state-of-the-art swirl-stabilized burners.
Bayesian Data Assimilation in Cold Flow Experiments on an Industrial Thermoacoustic Rig
Authors: Zheng Jingquan , Fischer André , Lahiri Claus , Yoko Matthew , Juniper Matthew 
Published: August 2024

Abstract
We assimilate experimental data from non-reacting flow in the SCARLET (SCaled Acoustic Rig for Low Emission Technologies) test rig using physics-based Bayesian inference. We model the complex geometry of the combustor with a qualitatively-accurate 1D low order network model. At the first level of Bayesian inference, we assimilate experimental data to optimize the parameter values by minimizing the negative log posterior probability of the parameters of each model, given the prior assumptions and the data. At the second level of inference, we find the best model by comparing the marginal likelihoods of candidate models. We apply Laplace’s method accelerated with first and second order adjoint methods to assimilate data efficiently. The first order adjoint is used for rapid data assimilation and optimization. The first and second order adjoints are used for inverse uncertainty quantification. We propose six candidate models for the burner and select the model with most evidence given the data. This produces an improved physical model of the rig, with known uncertainties.
Rotor Rubbing Fault Diagnosis Method Based on Deep Learning
Authors: Tao Zhenyu , Wu Yafeng , Chong Zezhong , Li Jin 
Published: August 2024

Abstract
During aero-engine production and design, optimizing engine performance frequently involves minimizing the gap between dynamic and static rotors, thereby elevating the likelihood of friction. Rubbing amplifies equipment vibration and, in severe instances, jeopardizes the entire shaft system, rendering it incapable of normal operation and incurring substantial economic losses. This paper presents a diagnostic method for identifying engine rotor rubbing faults using wavelet time-frequency images with a deep convolutional autoencoder neural network. The method converts original vibration signals into two-dimensional time-frequency images via wavelet decomposition, serving as input for a deep neural network. Leveraging the autoencoder’s characteristics with minimal dimensionality reduction parameters and the convolutional network’s robust feature extraction capability for two-dimensional data, the network is trained to extract crucial image features. Subsequently, these features undergo classification an d diagnosis of faults by training a Softmax classifier. An experimental system was established to validate the method’s feasibility, simulating fault phenomena such as misalignment, looseness, cracks, and rubbing by adjusting the fixing degree of the rotor system support seat. Test data are collected using the data acquisition system, which also preprocesses the raw data by introducing noise and conducting wavelet transforms. Subsequently, the data undergo transformation into time-frequency images, serving as inputs to the autoencoder neural network for extracting essential features. These features are inputted into this classification convolutional network, enabling fault diagnosis. The results could demonstrate the validity of the deep convolutional autoencoder neural network for detecting engine rotor rubbing faults.
A Validated Unsteady Turbofan Engine Performance Simulation Using Pseudo Bond Graph Approach
Authors: Goeing Jan , Lück Sebastian , Friedrichs Jens 
Published: August 2024

Abstract
In this paper, the unsteady performance of a turbofan engine is illustrated and modelled using the Pseudo Bond Graph approach. The Pseudo Bond Graph method allows multiphysical and interdisciplinary systems to be described analytically and comprehensibly across disciplines. In this study, a high bypass ratio turbofan engine is modelled using a Pseudo Bond Graph model that can be adapted for hybrid electric propulsion systems. The development of the model is followed by a full-scale test run of the in-house V2500-A1 turbofan engine. The highly instrumented turbofan engine enables the time-resolved recording of performance-specific variables, thus facilitating the validation of the numerical model. Slam acceleration and deceleration are performed to analyse the unsteady performance. It is shown that the Pseudo Bond Graph model is able to predict the dynamics of the turbofan engine. High deviations are explained by the incomplete modelling of the control system.
Analysis of Flow Fields in a Steam Turbine Control Valve With One Chamber
Authors: Slama Vaclav , Rudas Bartolomej 
Published: August 2024

Abstract
A flow field inside steam turbine control valves can be very variable from subsonic to transonic and with or without a flow detachment. It depends on changeable operating conditions and a valve geometry. Understanding phenomena that appear in valves helps predict and reduce pressure losses, enhancing the valve design. It also ensures safe operation and a reasonable price. The primary motivation of this paper is to provide a detailed view of different flow fields at various operating conditions. For this reason, a control valve with one chamber is analyzed using numerical simulations. It is a part of the most often used valve assembly for different steam turbines with outputs from about 10 to 1000 MW. The numerical simulations were carried out using a package of ANSYS software tools. The settings and models are based on the previous comprehensive studies, where a validation using measurements on the model was performed. Eight different valve cone lifts were computed, ranging from fully closed to fully opened valves. For each valve cone lift, about twelve different pressure ratios were defined. As a result, a complete flow characteristic of the valve was created. Based on this, the most typical cases with different flow fields are shown. At first, the position of the sonic line is analyzed. It was found that it has a direct connection with the flow contraction coefficient, which is introduced and described in detail. It is also connected with the strong field non-uniformity under the valve cone. Second, the length of the backflow region under the valve cone and in the diffuser is described and analyzed. All in all, this paper complements the previous papers about valves for steam turbines, which have already been presented at ASME Turbo Expo, created by the research and development team from the Doosan Skoda Power Company and the Institute of Thermomechanics of the Czech Academy of Sciences.
Inferring Flame Transfer Functions of Turbulent Conical Flames From Pressure Measurements
Authors: Yoko Matthew , Juniper Matthew P. 
Published: August 2024

Abstract
We use approximate Bayesian inference, accelerated by adjoint methods, to construct a quantitatively accurate model of the thermoacoustic behaviour of a turbulent conical flame in a duct. We first perform a series of automated experiments to generate a data set. The data consists of time series pressure measurements from which we extract (i) the eigenvalue, whose real part is the growth rate and imaginary part is the angular frequency, and (ii) the pressure eigenmode measured at several axial locations. We assimilate the data into a thermoacoustic network model to infer the unknown model parameters. We begin this process by rigorously characterizing the acoustics of the cold rig. We then introduce a series of different flames and infer their flame transfer functions with quantified uncertainty bounds. The flame transfer function is obtained with the flames in situ, so it accounts for any confinement or heat loss effects. The inference process uses only pressure measurements, so the technique is suitable for complex combustors where optical access is not available, provided the eigenvalue or eigenmode of oscillations can be measured. We validate the method by comparing the inferred fluctuating heat release rate against direct measurements. We find that the inferred quantities compare well with the direct measurements, but the uncertainty bounds can be large if the experimental error is large.
Analysis of Pre-Stall Pressure Disturbances in an Axial Compressor
Authors: Hernley Valerie , Kang Jeongseek , Montgomery Matthew , Jemcov Aleksandar , Morris Scott C. 
Published: August 2024

Abstract
Pre-stall rotating pressure disturbances were observed at off-design conditions in an axial compressor. The temporal and spectral characteristics of the rotating disturbances were studied at different mass flow rates along a part-speed, partially-closed inlet guide vane (IGV) compressor characteristic. Specifically, unsteady casing pressure measurements were analyzed at several steady operating points. The auto-spectral density (ASD) of the pressure measurements was characterized by a broadband local maximum with distinct peaks superimposed, each corresponding to a different circumferential wavenumber, consistent with observations in the literature of pre-stall rotating disturbances, or “rotating instabilities.” Using the wavenumber-dependent ASD, each peak’s amplitude, center frequency, and local width were characterized as a function of circumferential wavenumber for four distinct operating points. Additionally, temporal analysis of the pressure signals indicated that the rotating disturbances were compact in space and time. A Morlet wavelet model was developed to understand how physical parameters such as the disturbance size, frequency-of-occurrence, and circumferential propagation speed affected the wavenumber-dependent ASD. The model informed the characterization of physical flow features from statistics of the casing pressure measurements.
Innovative H2-O2 Burner Utilizing Water-Cooled Combustion for Superheated Steam Generation
Authors: Sanders Dennis , Eichhorn Lars , Siwczak Niklas , Scharf Roland , Dinkelacker Friedrich , Oehlert Karsten 
Published: August 2024

Abstract
This paper presents a novel burner designed specifically for the combustion of hydrogen in conjunction with oxygen. The combustion of hydrogen and oxygen poses significant technical challenges due to the exceptionally high combustion temperatures and rapid flame propagation speeds involved. In this innovative burner design, a precise amount of liquid water is introduced into the oxygen stream within the burner, forming a finely atomized water spray. This water-oxygen mixture then reacts with the hydrogen in the combustion chamber to generate water vapor. One of the key advantages of this approach is the effective reduction of the adiabatic flame temperature by incorporating water directly into the flame. This serves to mitigate the extreme temperatures characteristic of hydrogen-oxygen combustion scenarios. Moreover, the utilization of liquid water capitalizes on its enthalpy of vaporization, further enhancing the cooling effect. This strategic incorporation of water not only optimizes cooling efficiency but also minimizes volume usage, maximizing the cooling impact per unit volume. Measurements utilizing planar laser-diagnostical techniques were conducted to analyze the OH concentration and droplet distribution alongside parallel computational fluid dynamics (CFD) simulations. These investigations aimed to assess the efficacy of the proposed concept and the burner stability. The findings revealed distinct zones characterized by substantial droplet presence but low OH radical concentrations, suggesting effective reactivity reduction within these zones. Two burner configurations were scrutinized, one devoid of swirl and another incorporating swirl. The results underscored a notable improvement in flame stability with the swirl-enhanced burner configuration, indicating the advantageous impact of swirl on burner performance.
Data-Driven Radial Compressor Design Space Mapping
Authors: Brind James 
Published: August 2024

Abstract
Estimates of turbomachinery performance trends inform system-level compromises during preliminary design. Existing empirical correlations for efficiency use limited experimental data, while analytical loss models require calibration to yield predictive results. From a set of 3708 radial compressor computations, this paper maps efficiency as a function of mean-line aerodynamics, and determines the governing loss mechanisms. An open-source turbomachinery design code creates annulus and blade geometry, then runs a Reynolds-average Navier-Stokes simulation for compressors sampled from the mean-line design space. Polynomial surface fits yield a continuous eight-dimensional representation of the design space for analysis, predicting efficiency with a root-mean-square error of 1.2% points.
The results show a balance between surface dissipation in boundary layers and mixing losses due to casing separations sets optimum values for inlet Mach number, hub-to-tip ratio, de Haller number, and backsweep angle. Surface dissipation drives the effect of flow coefficient, with high surface areas at low values, and high velocities at high values. Compact compressor designs are achieved by increasing inlet Mach number, reducing hub-to-tip ratio, and minimising the radial loading coefficient — all of which reduce efficiency approaching design space boundaries.
An interactive web-based tool makes the results available to practising engineers, demonstrating large ensembles of automated designs and simulations as a higher-fidelity replacement for legacy empirical correlations in preliminary design.
Experimental and Analytical Stability Investigation of High Speed Rotors Supported on Novel Internally Skewed Journal Bearings in a 60000 RPM Test Rig
Authors: El-Shafei Aly , Ibrahim Mohamed S. , Dimitri Antoine S. 
Published: August 2024

Abstract
This paper presents the experimental and analytical stability investigation of high speed rotors supported on novel internally skewed journal bearings in a 60000 RPM test rig. The stability of turbocharger rotors has been widely investigated. Some expensive solutions for the stability of turbocharger rotors have been proposed, however this paper provides a simple bearing design with a skewed journal bearing that can be easily and simply applied to turbocharger rotors.
In this paper the analytical model of the skewed journal bearings is first developed. Then the numerical analysis and the experimental stability results are provided for a 60000 rpm turbocharger test rig with a simple journal bearing, a floating ring bearing, and a skewed journal bearing. The skewed journal bearing showed superior stability characteristics both numerically and experimentally. In fact the test rig was stable with the skewed journal bearing up to the maximum speed of the test rig of 60000 rpm.
The shaft centerline position in the bearings is also presented, as well as the power loss in the skewed journal bearings, thus providing a complete analysis of these internally skewed journal bearings. Design considerations are also discussed at the end of the paper.
Effect of Flow Distortions on Pin Fins in the Entry Region of Circular Channels
Authors: Lundburg Evan , Lynch Stephen , Lyall Michael 
Published: August 2024

Abstract
Utilizing heat transfer augmentation features at the inlet of aircraft engines as an additional heat sink requires further understanding of entry region heat transfer and flow field interactions. The effect of asymmetric flow fields or distortions on entry region heat transfer has not been studied. Typically, distortion screens are attached to the inlet of an engine to simulate non-ideal flow that occurs in flight. Because the addition of augmentation features will create a near-wall distortion that can impact downstream aircraft components, comparing entry region features to standard distortion screens can provide insight on the performance impact to aircraft engines. This study investigates the effect of inlet distortion screens on pin fin entry region heat transfer, in order to understand if flow field disturbances disrupt the benefits of augmented entry region heat transfer. In addition, the superposition of the distortion caused by pin fin features onto a screen distorted smooth entry region is also tested. Three distortion screens are investigated with pin fin arrays: tip, hub and an asymmetric aircraft distortion, each based on SAE standard designs. Reynolds numbers ranging from 1.5*105 to 3.50*105 are investigated. From this study, inlet heat transfer augmentation due to pin fins is not significantly impacted by inlet distortion flowfields. This is due to the near wall boundary layer impact of augmentation features overshadowing the effect of distortion. Due to the insensitivity of the near wall boundary layer for pin fin arrays with distortions, superimposing the smooth entry region distorted flow with the non-distorted pin fin array flow provides an adequate estimate of the flow field of the pin fin array with a distorted inlet.
Design and Commissioning of the IRIS: A Setup for Aircraft Vapour Compression Cycle-Based Environmental Control System Testing
Authors: Ascione Federica , Head Adam Joseph , Colonna Piero , De Servi Carlo Maria 
Published: August 2024

Abstract
The aircraft Environmental Control System (ECS) is the main consumer of non-propulsive energy, accounting for 3% of the total energy consumption among all the aircraft subsystems. The ECS efficiency can be improved by recurring to an electrically-driven Vapour Compression Cycle (VCC) system for cabin cooling. This work documents the detailed design and the commissioning of a novel experimental test rig, called Inverse organic Rankine cycle Integrated System (IRIS). The setup has been conceived for testing the performance of VCC systems and some of their components for aircraft ECS applications in different operating conditions, and for validating the numerical models developed for systems and components simulations. The facility implements a single-stage compression refrigeration cycle with two test sections: a volumetric compressor testing setup and an air-cooled condenser test bed. The evaporator is heated by a glycol-water mixture, warmed up in an independent loop. The design working fluid is R-1233zd(E). The successful commissioning of the facility is documented by discussing the data recorded during steady-state operation at the design operating point, together with the operation of the setup during start-up and shut-down procedures. The system cooling capacity is equal to 17.88 ± 0.8 kW, which is slightly higher than the design value of 15.5 kW. The difference has a positive effect on the system efficiency, which is 4% higher than the one calculated at design.
QCSEE — Design and Test Contributions to the Rise Open Fan Program
Authors: Wadia Aspi , Schilling Jan , Solomon William , Steinmetz Gregory , Mollmann Daniel 
Published: August 2024

Abstract
After the successful introduction of commercial turbofan engines with medium bypass ratios, NASA’s Lewis Research Center spearheaded an aircraft propulsion development program in the early 1970’s called “Quiet Clean Short-Haul Experimental Engine” commonly referred to as QCSEE. In addition to the goal of doubling the bypass ratio relative to early production turbofan engines, QCSEE led in pioneering (a) reversible-pitch composite fan blades, (b) a high bypass ratio geared fan/turbine, (c) extensive use of composites, (d) noise reduction technologies, and (e) digital electronic controls. This paper reports on the design, fabrication and testing of two propulsion systems for QCSEE by GE Aviation under contract from NASA in the mid-1970’s. The first design was an Under-the-Wing (UTW) engine, which incorporated a reduction gearbox to drive the low-speed fan with variable pitch to further improve fan efficiency along with elimination of the thrust reverser. The variable pitch fan was used for modulating forward as well as reverse thrust. This design utilized a low-pressure ratio fan (lower tip speed) at take-off and a bypass ratio of 12. The other design entitled as the Over-the-Wing (OTW) engine also used a reduction gearbox to drive a low-speed fixed pitch fan. The OTW engine configuration had a slightly higher fan pressure ratio (higher tip speed) at take-off and a bypass ratio of 10. The design and testing of these fans for the QCSEE program are presented. Key design features of the composite fan blade and the variable pitch mechanism are presented. The QCSEE design was based on a lightweight, high-speed, power turbine driving a slower speed, quiet fan that required a compatible, compact, lightweight, high-power-capability, main reduction gear. Performance results of two reduction gears designed, fabricated, and rig-tested are summarized. A summary of the development of the composite frame and nacelle is presented. Limited highlights of the digital engine control are shown. Finally, overall engine aerodynamic, acoustic, and mechanical test performance are reported in this article. The impact of each of these key QCSEE technologies to existing GE/CFM products, and their contribution to CFM’s current RISE Open Fan technology program will be discussed.