bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerodynamic Design and Performance Analysis of a Vaneless Counter-Rotating Fan and Compressor
Authors: Ren Xinyu , Shen Yuxin , Zhang Tao , Li Jiabin , Ji Lucheng
Published: August 2024

The vaneless counter-rotating fan/compressor can effectively reduce the axial length and gyro torque of the engine. However, the absence of the stators can lead to a frequently changing incidence angle at the downstream, which deteriorates the offdesign performance. Moreover, this characteristic deteriorates with the increase of the tangential velocity at the blade tip. In this paper, taking advantage of the low circumferential speed at the root of the fan blade of the small-sized turbofan engine, the fan and compressor were designed as a counter-rotation scheme without a stator.

Firstly, the performance of the vaneless counter-rotating fan/compressor are analyzed through the velocity triangle. Then, an one-dimensional design program for the vaneless counter-rotating fan/compressor is developed to optimize the design parameters. Finally, a small size vaneless counter-rotating fan/compressor is designed with its design point efficiency of 85.1% and pressure ratio of 3.16. Results show that the relative inlet flow angle towards the downstream rotors varies less than that in conventional compressors, while the incoming flow velocity would increase by 1.5 to 3 times compared to conventional ones. Thus, the hub ratio and speed ratio of a counter-rotating fan/compressor have a sensitively effect on its efficiency and stall margin. Moreover, a reduction in speed ratio could improve the efficiency and stall margin of the counter-rotating fan/compressor, and the speed ratio should be set as a compromise value under the design restrictions.
Multi-Fidelity Aeromechanical Design Framework for High Flow Speed Multistage Axial Compressors
Authors: Nigro Rémy , Baert Lieven , Nyssen Florence , de Cazenove Jean , Dominique Joachim , Lepot Ingrid , Veglio Monica , Princivalle Rémy
Published: August 2024

The development of novel engine architectures is vital in achieving the aviation sector’s net-zero carbon emission target by 2050. With today’s digital decade providing support for an accelerated technology maturation, the challenge for turbomachinery design remains to significantly push the limits of current performance within an ambitious development lead time. In this context, it is essential to adopt a design framework where the predictive models or simulations employed target a sufficiently reliable performance assessment. These models must be tailored to the dynamics of an evolving industrial design process, and therefore continuously balance required design flexibility, robust evaluation, appropriate fidelity (i.e. the level of detail and accuracy they provide), and resulting evaluation time.

This paper discusses a framework for designing axial compressors and its application to the aeromechanical optimisation of a high-speed compressor rotor. The design environment integrates geometry parametrisation, a modular evaluation with different levels of fidelity for the aerodynamic and structural models, and surrogate-based optimisation (SBO) capabilities. It is shown how the combination of a modular sequencing of the different models and the acceleration enabled by high-performance computing (HPC) and machine learning allows for a more advanced preliminary design. A significant gain in isentropic efficiency is attained while satisfying all structural constraints. At the same time, it is demonstrated that the framework is compatible with the characteristics of the preliminary design phase: both in its ability to adapt to cycle and design changes as well as regarding the turnaround time of the optimisation itself.
Numerical and Experimental Aeromechanic Study in High Frequency Domain of Hydrogen Compressor
Authors: Shanmugam Venkatachalam Ravi , Ganiger Manjush , Toni Lorenzo , Guglielmo Alberto , Biliotti Davide , Miris Lorenzo
Published: August 2024

Hydrogen economy is no more a futuristic need, rather it is the need of the hour to combat climate change. However, the scale, accessibility and price of the clean fuel are the main challenges to be overcome for its widespread adaptation. In order to accelerate the journey towards net-zero, the compression, storage and transportation of hydrogen are going to be critical to balance the supply and demand scenarios, and to ensure hydrogen enters new energy markets like refueling stations, green ammonia production and power generation, apart from the existing markets like fertilizer industry.

Hydrogen being the lighter and low-density gas, its compression with traditional technologies such as centrifugal and reciprocating compressors demand new design philosophies to meet the new energy market’s needs. New generations of high efficient centrifugal compressor stages are needed to meet such requirements, including a new target for the peripheral speed that has to be increased beyond the current limits to reach a high head rise per stage.

This paper presents numerical and experimental aeromechanic studies on high peripheral speed impellers for hydrogen centrifugal compressors. High frequency mode shapes that are typical for these applications were excited at low peripheral speed using an innovative approach. Under similitude condition, the experimental studies were carried out at Authors’ internal test facility, revealing that even at low speed, the higher frequency domain, like hydrogen compression one, can be properly excited.

Steady state and transient numerical simulations were carried out, considering a complete stage composed by the upstream return channel, the impeller, the diffuser, and the downstream return channel. The results were then compared against the experimental outcomes, obtaining a successful validation that will be widely discussed in the paper.
Blade Designs for Improved Multi-Phase Performance in sCO2 Compressors: Part I - Design and Numerical Evaluation at Application Relevant Conditions
Authors: Hosangadi Ashvin , Weathers Timothy , Cepero Antonio , Cooper Paul , Fernandez Erik , Kapat Jayanta
Published: August 2024

Design changes to improve the performance of MWe scale sCO2 compressors by delaying the onset of phase change at the leading edge have been evaluated. The design changes involve modifications to the leading edge suction surface of the blade and are referred to as a biased wedge blade. Simulations were performed with the CRUNCH CFD® software tool that has been matured to accurately model near critical real fluid effects in sCO2. Simulations in a stationary cascade compared well with test data and confirm that the biased wedge design reduces the velocity acceleration on the suction surface. Numerical parametric studies at higher velocities in the range of inlet tip speed for MWe scale compressors indicate that the biased wedge design can suppress the onset of phase change in this regime and preserve single phase supercritical flow. These designs can potentially be retrofitted into existing compressor models since this design change is agnostic to the specifics of the design paradigm.
The Effects of Casing Profile on the Aerodynamics of Integrated Intermediate Turbine Ducts
Authors: Hou Jiangdong , Duan Xiaozhi , Kang Ziyu , Yi Yu , Zhou Chao
Published: August 2024

To reduce the engine’s length and weight, the concept of integrated intermediate turbine duct (IITD) is proposed, in which the first row of the low-pressure turbine vanes are replaced by the turning struts in ITD. The effects of the casing profile on the flow features and loss mechanism in the IITD are investigated by experimental, numerical and theoretical methods. In the baseline case, the casing passage vortex at the exit of the IITD is featured with two branches, which is caused by the entrainment effect of the suction side leg of horseshoe vortex near casing. By making the casing profile upstream of the leading edge more downward convex, the thickness of the casing boundary layer can be reduced, and the horseshoe vortex is weakened. The structure of the exit casing secondary flow is thus more complete. In the IITD with higher mean rise angle, the entrainment effect has the ability to reduce the low-momentum fluid and suppress the separation on the suction surface. A method of controlling the casing secondary flow is proposed accordingly. To analyze the loss mechanism, the loss is broken down into the parts generated by mean vortex and turbulence theoretically. The casing boundary layer acceleration can lead to larger velocity gradient and loss caused by mean vortex. While the turbulent dissipation will be reduced on the other hand. Large turbulent dissipation can also be generated when the mixing between the casing secondary flow and wake is enhanced.
Optimal Control Allocation for Distributed Electric Propulsion in a Series/Parallel Partial Hybrid Powertrain
Authors: Litt Jonathan S.
Published: August 2024

The SUbsonic Single Aft eNgine (SUSAN) Electrofan is a NASA concept transport aircraft representative of technology anticipated for a 2040 entry-into-service date. The powertrain consists of a single thrust-producing geared turbofan engine with generators driving a series/parallel partial hybrid power/propulsion system. The architecture includes 16 underwing contrarotating fans, eight on each side. The distributed fans can be used by the flight control system to augment or replace the rudder function. This paper sets up the optimal control problem of setpoint determination for individual wingfans in the distributed propulsion system, accounting for electrical string efficiencies, saturations, and failures. The solution minimizes power consumption while maintaining thrust and torque on the airframe for maneuvering. Additionally, thrust that would have been lost due to temporary fan speed or power saturation is optimally redistributed to maintain overall desired thrust and torque on the aircraft. A simulation of a coordinated turn utilizing the distributed electric propulsion for yaw rate control in a multiple wingfan failure scenario demonstrates the robustness of the powertrain design to failures and helps define its limitations.
Synergetic and Performance Characteristics of a High-Speed Pre-Cooled Propulsion Concept
Authors: Chatzistefanou Athanasios , Tsentis Spyros , Kalfas Anestis
Published: August 2024

Pre-cooled air-breathing cycles are promising candidates to power future high-speed flight as well as Single-Stage-To-Orbit vehicles, due to their increased efficiency over contemporary propulsion systems and launch vehicles. These concepts usually feature complex interactions in the synergy of their thermodynamic cycles, which are not yet well understood, especially at off-design conditions. In this study, a performance model for a pre-cooled, hybrid, air-breathing, rocket-cycle engine is developed for its air-breathing mode of operation. One-dimensional thermodynamic modeling is employed within a component-level approach, to evaluate the performance and operation of the cycle under investigation in the range of 1.35 ≤ M∞ ≤ 5 and conditions of up to 26 kilometers altitude. The model is validated quantitatively and qualitatively for both design and off-design conditions. The specific impulse Isp and specific thrust Fspec, as predicted by the model, agree within less than 5% for the design-point conditions at M∞ = 5. At off-design conditions, the model captures the trend of Isp and agrees within less than 1% with respect to the data for the maximum value of Isp. The maximum gross thrust Fgross point is predicted correctly at M∞ = 4. The fundamental operating principles and synergetic characteristics of the engine at design and off-design conditions are investigated and reported. Parametric analyses quantify the influence of the engine’s parameters on the leading performance metrics. A model which does not feature a bypass duct is created and compared for the same inflow conditions and mission profile. It is found that the engine without the bypass duct exhibits reduced specific impulse which can be up to 32% lower at off-design conditions. In addition, the corresponding fuel mass flow rate to achieve the same mission is increased by a factor of 1.5. It is demonstrated that the overall trend of engine efficiency cannot be properly captured without modeling of the bypass duct, especially at the region of M∞ < 3.5, where the ramjet-like operation is critical. This highlights the importance of the bypass, which is typically neglected in the modeling of such high-speed, combined-cycle systems.
Thermohydraulic Performance and Flow Structures of Diamond Pyramid Arrays
Authors: Corbett Thomas M. , Thole Karen A.
Published: August 2024

Surface features are a common heat transfer enhancement method used in a myriad of applications including gas turbines and heat exchangers. One such style of surface features is diamond pyramids, which offer significant heat transfer augmentation for moderate increases in overall pressure losses. This study investigated a suite of additively manufactured pyramids in a variety of sizes and arrangements at relevant scale contained in test coupons. Designs were printed with low surface roughness relative to typical additive components (Ra < 5μm), and pyramids were printed within 100 μm of the design intent. Experimental and computational results indicate that the pressure penalty and heat transfer increased as the pyramids increased in size with aligned pyramids on both channel walls having higher values than staggered pyramids. It was found that implementing the pyramids onto a rough surface had a lesser impact on the friction factor than implementing on a smooth surface, but that the relative increase in heat transfer was the same regardless of the roughness of the endwall. The greatest enhancement to local heat transfer and pressure loss was offset from the location of minimum flow area due to local acceleration around the wake regions. The vortices formed in the wake of the pyramid structures enhanced the endwall heat transfer and shear stress. The performance of the pyramids investigated in this study follows a similar trend to prior studies investigating smooth rib geometries, though certain rib designs had higher heat transfer at lower pressure losses.
Considerations for Hydrogen Fueled Aerospace Gas Turbine Combustion Sub-System Design
Authors: Clemen Carsten , Ravikanti Murthy , La Bianca Nicholas , Eggels Ruud , Wurm Benno , Young Kenneth
Published: August 2024

As part of its commitment to the decarbonization of the aviation sector and the UN Race to Zero global campaign, Rolls-Royce is actively developing hydrogen combustion gas turbine engine technology capable of powering a range of aircraft from 2035 onwards. These innovative technologies are undergoing integration and validation through a demonstrator project, which involves the modification of a Pearl15 engine for ground testing with gaseous and liquid hydrogen.

The design of an aerospace combustor needs to satisfy conventional requirements such as cost, weight, aero-thermal performance, and lifespan. However, the introduction of hydrogen as the primary fuel introduces additional challenges, including potential novel failure modes, operability considerations and pollutant emissions.

The NOx emissions resulting from hydrogen combustion are currently the subject of extensive research and are considered, to be one of the key considerations which will ultimately influence the design of the optimum hydrogen combustion sub-system for aerospace applications.

This paper describes the development of the first prototype combustion technology at Rolls-Royce. Innovative fuel injection concepts were investigated to enable operation with 100% hydrogen on the Pearl 15 combustor architecture which is to serve as the test vehicle for ground demonstration in the Clean Aviation Project “CAVENDISH”. The paper details the process which began with prototype development and validation on a single sector atmospheric test rig to map the design space and understand sensitivities. This allowed the selection of four leading configurations based on NOx emissions, flame stability (measured using optical methods), ignition and weak extinction performance.

The four configurations were then tested in a single sector, intermediate pressure rig testing at engine-representative low power conditions. This testing aimed at identifying challenges related to flame stability and combustor temperature distribution, thereby mitigating risks associated with engine combustor testing. Finally, tests were undertaken in a full annular, high pressure combustion rig at engine-representative maximum takeoff conditions.

Aerothermal performance, as measured by NOx emissions, weak extinction and exit temperature traverse, demonstrated promising comparisons to kerosene-based fuel. These results demonstrate that a retrofittable combustion solution is credible and realistic for a minimum viable hydrogen gas turbine product.
Determination of Vibration Properties and Reliable Frequency Estimation for Synchronous Vibrations Through Improved Blade-Tip-Timing Techniques Without a Once-per-Revolution Sensor
Authors: Sasakaros Marios , Mann Luca , Schafferus Markus , Wirsum Manfred
Published: August 2024

Synchronous vibrations, which are caused by periodic excitations, can have a severe impact on the service life of impellers. Blade-Tip-Timing (BTT) is a promising technique for monitoring synchronous vibrations due to its non-intrusive nature and ability to monitor all blades at once. BTT generally employs an Once-per-Revolution (OPR) sensor that is mounted on the shaft for blade identification and deflection calculation. Nevertheless, OPR sensors can be unreliable as they may be affected by shaft vibrations and their implementation can be restricted by space constraints. Moreover, the low number of BTT sensors typically leads to under-sampled deflection signals, which consequently hinders the estimation of the vibration frequencies due to aliasing problems. For this reason, BTT is commonly accompanied by strain gauge measurements on some blades.

In this paper improved BTT techniques are presented, which enable the determination of vibration properties of synchronous vibrations without the need for an OPR sensor and ensure a reliable frequency assessment. Specifically, the blades are identified by unique characteristics resulting from manufacturing tolerances while the blade deflections are calculated through a novel method, which relies on the impeller’s circumferential position. Subsequently, by employing approaches based on Non-Uniform Fast Fourier Transform the vibration frequency is accurately estimated. Finally, the vibration properties are determined using regression models. The proposed BTT techniques are validated through comparison with a commercial BTT system as well as SG measurements using experimental data acquired from a turbocharger test bench. The proposed methods eliminate the need for an OPR sensor and parallel strain gauge measurements.
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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Creep Lifetime Prediction of Alloy 617 Using Black Box Machine Learning Approach
Authors: Hossain Md Abir , Stewart Calvin M.
Published: August 2024

This study explored the application of black box machine learning (ML) to build high throughput models that predict the creep response of Ni-based Alloy 617. Black Box ML refers to highly complex machine learning algorithms that generate outputs from inputs without an interpretable internal process. The rapid implementation of suitable heat of alloys into targeted service is impeded by the extended qualification process involving chemistry-processing-structure-performance assessment. The ASME B&PV Code III outlines the requirement of 10,000 hours of creep testing before each heat can be qualified for service and 30,000 hours for heats that exhibit metastable phases. There is a critical need to shorten the development-to-deployment timeline for heats of an alloy at specific applications. Recent advancement in ML offers the ability to identify correlations in data which is difficult to elucidate by other approaches. To that end, black box ML is employed to expedite the HEAT qualification of Alloy 617 and predict performance from HEAT chemistry out to an unprecedented timescale.

In this study, creep data for Ni-based alloy 617 — a solid solution strengthened material is gathered from a wide range of data sources. The alloy chemistry, phases, precipitates, and microstructural features are analyzed to obtain the key strengthening mechanism. Service conditions, mechanical properties, chemistry, and chemical ratios are provided as potential input features. The Pearson Correlation Coefficient with a 95% confidence bound is employed for input feature screening where poorly correlated inputs are eliminated to speed up the ML process and prevent under- and/or over-fitting of predictions. In the ML algorithm, the selected input features are regarded as predictors, and rupture is regarded as the response. An algorithm evaluation is performed where 20 ML algorithms are trained with the training set. The 3-layered Neural Network (NN) was observed to be the best algorithm for the given data based on statistical rationale. The NN accurately predicts rupture across a range of isotherms and data sources. The interpolative and extrapolative predictions are in compliance with ECCC V5 guidelines. A post-audit validation exhibits neither under- nor over-fitting and confirms the applicability of NN algorithms to unseen data. The black box ML provides a pathway to predict the performance directly from chemistry and opens avenues to rapid heat qualification.
Application of CFRP Sleeve to Increase Efficiency of Air Compressor for Fuel Cell Electric Vehicle
Authors: Lee Changha , Lee Jongsung , Yang Hyunsup , Lim Jeong Kyu , Ko Young Yoon , Park Jeong Hee , Dong Seung-jin
Published: August 2024

This paper presents the analysis and experimental results of the application of a composite material (CFRP) sleeve to the rotor for enhancing motor efficiency measurements in the highspeed motor of an oil-free air compressor for fuel-cell electric vehicles (FCEVs). Carbon Fiber Reinforced Plastic (CFRP) applies two or more types of materials for better properties: high strength and lower density. The predicted motor loss at the maximum speed of the oil-free air compressor compared the sleeve performance of each sleeve between Inconel718 and CFRP. The eddy current loss of the CFRP sleeve rotor decreased by 90% compared with that of the previously developed rotor. Rotordynamics model predictions of the two types of sleeves manufactured benchmark the test data. The 1st bending natural frequencies of the CFRP sleeve rotor decreased by 15% against the Inconel718 sleeve rotor. In addition, this study compares the analyses of 2D and 3D models. The results show that the CFRP has low isotropy compared Inconel718 sleeve rotor. This trend is the same as that observed in the experiments. The CFRP sleeve was made by the prepreg of T300-class carbon yarn and epoxy resin, which are commonly used, and was molded using autoclave equipment. It satisfies a 1.5 mm thickness through 8Ply rolling. A series of rotor impact tests were conducted to compare the 1st bending natural frequencies of the previously developed sleeve rotors; Inconel718 and CFRP sleeves. The impact test showed that the CFRP sleeve rotor exhibited different 1st bending natural frequencies depending on the high-temperature and room-temperature conditions, and the range of change was larger than the Inconel718 sleeve rotor. The impact test results at room temperature showed a 25% decrease compared to the Inconel718 sleeve rotor. A previously mass-produced compressor was used in this experiment. Our performance evaluation equipment measured the performance and efficiency of the test compressor. A series of compressor performance and saturation tests at 80k and 90k RPM indicate that the CFRP sleeve results in an efficiency increase of 2% and an 8% decrease in the operating temperature. However, the CFRP sleeve rotor needs to be further improved to increase the operation speed (up to 90kRPM) of the high-speed motor of the oil-free air compressor.
Advancements in Wall Film Thickness Measurement Under High Pressure and High Temperature Conditions for Gas Turbine Applications
Authors: Yin Zhiyao , Lammel Oliver , Lückerath Rainer , Ax Holger , Poulios Dennis
Published: August 2024

In pursuit of quantitative measurements of liquid wall film thickness under high-pressure and -temperature conditions, a novel image processing approach in combination with a standard laser-shadowgraphy setup was developed and demonstrated for the first time at the high-pressure combustion test rig (HBKS). The wall-film extraction technique was validated against a laser triangulation sensor under laboratory conditions for film thicknesses in the range of 100–800 μm. It was then applied to detailed shadow images of liquid fuels (kerosene and light heating oil) and water spray impingement onto a long metal plate in a jet-in-crossflow configuration at 10 bar. After reaching a maximum thickness of about 680 μm, the kerosene film diminished completely prior to reaching the end of the metal plate. In comparison, the water film exhibited a delayed onset on the metal plate but grew steadily and persisted at a thickness of above 600 μm. Injection of kerosene emulsified with water at a 1:1 mass ratio also resulted in a persisting liquid film until the end of the metal plate. In the latter two cases, substantial quantity of liquid exited the spray chamber in the form of film and spray particles.