bluuebunny/crossref_metadata_2025_split huggingface dataset:
Entry Region Heat Transfer Augmentation With Pins, Fins, and Turbulators in Circular Channels
Authors: Lundburg Evan , Lynch Stephen , Lyall Michael 
Published: August 2024

Abstract
Entry region heat transfer is known to provide significantly higher heat transfer than fully developed conditions. Utilizing entry region heat transfer would provide an additional heat sink at the inlet of an aircraft engine before the fan, but requires further investigation of the convective heat transfer augmentation and downstream boundary layer impacts. The addition of near wall heat transfer augmentation features only in the entry region at high Reynolds numbers is uncommon. Thus, heat transfer enhancement comparing small features in the entrance region of a circular channel and the effect on the downstream boundary layer has not been investigated. This study investigates three heat transfer augmentation features: pins, fins, and turbulators, mounted on the wall at the inlet of a circular channel. Two boundary layer probes, one mounted immediately after the augmentation features and one located three diameters downstream of the features are used to evaluate the growth of the boundary layer due to the features. The convective heat transfer is evaluated using a constant heat flux surface with surface temperature measurements using infrared thermography. All features are evaluated at Reynolds numbers ranging from 1.0*105 to 5.0*105. Each type of geometry is capable of producing augmented heat transfer relative to a smooth entry region, with the maximum overall heat transfer coefficient augmentation of 2.8 compared to a smooth entry region. Fin arrays produced the lowest average total pressure losses, doubling the losses compared to a smooth channel. Overall, the fin arrays also provided the highest overall heat transfer coefficient performance with minimal total pressure boundary layer losses, but also exhibit a sensitivity to Reynolds number.
A Coupling Model of Ice Crystal Icing in a Three-Stage Compressor
Authors: Zheng Haoran , Cheng Xianda , Dong Wei 
Published: August 2024

Abstract
The occurrence of engine power loss due to ice crystal accretion has been recorded since 1990s. Ice crystals at high altitudes can pose a threat to aircraft engine compression, including the degradation of compressor performance, engine rollback, compressor surge and flame out. The ice crystal accretion is attributed to ice crystals partially melting and sticking on the static components of the compression system. An ice crystal icing model in a whole three-stage compressor, consisting of the flowfield simulation module, the ice crystal tracking in three dimensions and phase change, and interactions of particle and surface. The performance of the compressor is simulated by S2 relative stream surface with a circumferential average, providing the flowfield condition for ice crystal simulation. The particle trace of ice crystals with different sizes and initial positions at the inlet are obtained by Lagrangian method. Ice crystals will bounce, fragment or stick when impacting the blade surface. The ice crystals simulation module is coupled with the compressor performance module by the heat transfer between air and particles. The possible icing position can be predicted by the model and the influence of ice crystals on the flowfield is also discussed in this research. Heat transfer to ice crystals has effects of decreasing the pressure ratio and the outlet temperature on the compressor performance.
Gas Turbine Gas-Path Fault Diagnosis Based on Decision Fusion of Model-Based and Data-Driven Methods
Authors: Cheng Xianda , Zheng Haoran , Dong Wei 
Published: August 2024

Abstract
Model-based methods (MBMs) and data-driven methods (DDMs) are currently the primary approaches for gas turbine (GT) gas-path fault diagnosis. However, the accuracy of model-based methods can be decreased due to the mismatch between the real engine and model, while data-driven methods struggle to handle untrained fault types. To solve this problem, this study proposes a fusion framework based on the Bayesian network (BN) for decision fusion of model-based and data-driven methods, aiming to enhance the reliability of the gas-path fault diagnosis system. Firstly, a health parameter estimation system is constructed using the component-level model (CLM) of the GT and the unscented Kalman filter (UKF). This system is then combined with a fault identification system based on the fuzzy inference approach to form a model-based diagnostic system. Subsequently, a data-driven diagnostic system is developed using historical operational data and the artificial neural networks. Next, the BN is adopted for decision fusion of diagnostic results. A new BN parameter calculation methodology is proposed based on the characteristics of MBMs and DDMs. The resultant Bayesian network can effectively fuse two different diagnostic methods. Finally, the fusion diagnostic results are compared with those obtained from the individual diagnostic systems. The results indicate that decision fusion method effectively overcomes the limitations of individual diagnostic systems and enhances the scope of health state identification, leading to improved overall performance in GT gas-path fault diagnosis. This research has significant importance for the performance monitoring and maintenance of GTs.
Air Jets to Modulate Flow in a Nozzle Vane Passage Within a Linear Cascade
Authors: Ferguson Tyson , Mohr Jim , Heitland Greg , Burnes Dan , Martel Matos Alberto 
Published: August 2024

Abstract
In gas turbines, it is difficult to effectively incorporate variable geometry within the pressurized hot section of the engine. To avoid using complex mechanical linkages that may wear and leak, an approach using pneumatic actuation with air jets can be deployed eliminating the need for any internal moving parts. An application for an internal pneumatic actuator was conceived and studied. After initial conceptual assessment and CFD analysis of air jets within a turbine nozzle vane passage, a linear cascade rig was assembled to validate and demonstrate the modulation of flow capacity within a nozzle vane passage using the jet flow. This paper will explain the concept, reflect on the supportive analysis demonstrating feasibility, and will show test results from the linear cascade rig. The additive manufactured test section, method, and instrumentation is described including the various configurations evaluated. Data show that flow capacity can be altered with the injection of air at high momentum flux ratios upstream of the throat plane. Incurred pressure losses are sufficiently small to favor integration in engine for cycle thermal efficiency increases at part load operation. Parameters investigated include total pressure losses, flow reduction, flow angle and momentum flux ratio. Geometry variations assessed included hole positioning relative to nozzle throat, injection hole designs. Airfoil geometry was representative of a center section of a low-pressure turbine. Also included is the detailed normalized data analysis and conclusions.
Tool Wear Prediction in Broaching Based on Tool Geometry
Authors: Zachert Christoph , Meurer Markus , Bergs Thomas 
Published: August 2024

Abstract
The aircraft engine is a safety-critical part of an aircraft. Constructive modifications resulting in ecological and economic improvements of the engine lead to necessary changes in manufacturing processes. The turbine discs in the low-pressure section are made of temperature resistant nickel-based superalloys. For the connection of the turbine blades with the disc, fir-tree slots are machined by broaching. The broaching process achieves high geometrical accuracy as well as process reliable rim zone properties. Alternative manufacturing processes such as milling or wire electrical discharge machining are still the subject of research in many applications and do not yet achieve the required process reliability.
Especially in finishing operations, tool geometry is complex. In previous research work, the local rake angle and, as a result, the acting cutting force were determined analytically and empirically. Based on these results, the relationship between tool geometry, cutting force, and tool wear will be investigated in this work to enable a cutting length dependent prediction of tool wear. The aim of this work is a model-based prediction of tool wear for a given cutting length and a previously unknown tool geometry. For this purpose, a method was developed to predict tool wear using empirical test data as well as internal machine data. With the results of this work, it is not only possible to identify critical points on newly developed broaching tools by maxima of the cutting force, but also to predict wear locally, depending on the cutting length. Thus, tools can be optimized, and efficiency of the broaching process is increased.
CFD Analysis of Inlet Flow Region in a Centrifugal Compressor
Authors: Sudheer Meera , Dhinne Giridhar Kumar , Hoch Greg 
Published: August 2024

Abstract
The inlet region of a typical multi-stage centrifugal compressor for oil and gas applications consists of an inlet flange/nozzle, splitter vanes, and inlet guide vanes (IGVs). Recent findings of an existing legacy multi-stage centrifugal compressor, which had been recently revamped, indicated a lower flow capacity than what is expected. Further testing of the compressor revealed a potential scope for improvement in flow capacity. After performing stage-by-stage analysis, it was determined that an improvement in the design of the inlet region could enhance the performance. The inlet region plays a crucial role in guiding the flow towards the impeller, ideally distributing the flow uniformly with minimal loss. Flow distortions may occur in any inlet, the extent of which may differ depending on its design and can further lead to poor performance characteristics of the compressor. This paper will describe the work completed to reduce the flow losses and distortions in the inlet region by performing Computational Fluid Dynamics (CFD) analysis with the help of a simulation software. A parametric study was carried out to optimize the flow characteristics in the inlet region, where it was observed that rotating the IGV angles by a certain amount, loss coefficient and pressure distortions are reduced. The results obtained and lessons learned can be used for enhancing the performance and improving existing correlations when designing future compressors.
Shear-Driven Hydrogen-Air Mixing in OP16 DLE Combustor: A Comparative Study Between URANS and LES
Authors: Donepudi Teja , Pecnik Rene , Peeters Jurriaan W. R. , Klein Sikke , Bouten Thijs , Axelsson Lars-Uno 
Published: August 2024

Abstract
This paper presents numerical predictions of the flow field in the swirl-stabilized OP16 DLE combustor using hydrogen as a fuel. Computational Fluid Dynamics (CFD) simulations employing unsteady Reynolds-Averaged Navier-Stokes (URANS) and Wall Modelled Large Eddy Simulations (WMLES) are performed without including reaction mechanisms. The objective is to gain insights into scalar mixing predictions of the two approaches when hydrogen and air undergo shear-driven turbulent mixing. Accurate scalar mixing predictions are crucial in the combustors’ design process to assess the uniformity of fuel-air mixing as localized regions of high fuel concentrations can lead to increased NOx emissions and to identify locations with a propensity for Boundary Layer Flashback (BLF). Results are compared and analyzed in terms of time-averaged equivalence ratio, unmixedness and Turbulent Kinetic Energy (TKE) profiles. TKE predictions are lower in URANS, leading to significantly lower fuel-air mixing levels than WMLES, indicating differences in their predictions of shear-layer interactions in the mixing region and the swirl section of the combustor.
Design and Analysis of a Liftfan for eVTOL Aircraft
Authors: Hine Rory D. , Cousins Dominic R. , Maden Leo , Walker Samuel J. , Atkins Nicholas R. , Grimshaw Samuel D. , Taylor James V. 
Published: August 2024

Abstract
Ducted liftfans can provide greater hovering efficiency to eVTOL aircraft than open propellers of an equal disk area. The goal of liftfan design is to minimise length in order to limit the weight added by propulsors and the drag incurred during forward flight. The increased complexity of liftfans over open propellers poses three challenges which are addressed in this paper.
First, instead of a single row propeller, the liftfan consists of a complete stage which must be designed as a whole. The preliminary and 3D design variables of the rotor row and splittered-diffuser stator row are optimised together using 3D CFD to maximise the hovering figure of merit, a non-dimensional measure of power consumption. The resulting prototype liftfan design is validated through experimental testing.
Second, unlike an open propeller, a liftfan rotor is enclosed within a complete nacelle. To be viable, it must perform effectively during edge-on forward flight, as well as in pure hover. A low-order model is developed to investigate the maximum range for different fan designs with varying diffuser area ratios and forward flight tilt angles. Design selections are validated using full annulus 3D CFD and experimental wind tunnel tests.
Third, as the electric motor of a liftfan is mounted within the hub, fan-driven active cooling is necessary to prevent overheating. The stagnation pressure losses incurred by cooling airflow must be minimised without impeding heat transfer. Low-order models are developed to predict motor heat transfer and loss and to guide the design of a mixed-flow cooling fan. The addition of forward sweep and adoption of a high blade count are found to reduce cooling fan loss, confirmed through 3D CFD simulations and experimental testing.
Efficient Modelling of Blade Cooling Using a Hybrid 1D-3D Approach
Authors: Kainz Marc , Britz Vincent , Du Toit Bennie , Morales Juan Carlos 
Published: August 2024

Abstract
The first turbine stages downstream of the combustor are subjected to extreme high temperatures. Simulating the flow and heat transfer in and around the blades is therefore crucial for optimizing cooling and achieving the highest possible engine efficiencies.
The blade cooling optimization process requires iteration on many parameters. Due to the disparity in the geometrical length scale between the blade itself, the internal cooling channel structures, and the cooling holes, meshing and solving the cooling flow inside a turbine blade using a full 3D CFD model is very time-consuming and costly.
1D CFD codes allow for detailed and efficient modelling of the internal cooling flow in the conceptual design stage. The effort involved and the computational cost are orders of magnitude less than for a fully resolved 3D internal flow CFD simulation. In contrast, the main passage flow simulation is still well suited to a 3D CFD model.
The current work describes the coupling of a 1D flow and heat transfer network model to account for the internal cooling structures with a 3D CFD model for the main passage flow on a typical gas turbine vane geometry. The so-called injection region model was used to model the film cooling flow injection at the vane surface without having to resolve each hole patch by the surface mesh itself.
The paper presents a validation of the injection region model, and it compares the results of the different modelling approaches, including the hybrid 1D-3D model.
The 1D network model is able to predict accurate film cooling inflow conditions for the 3D CFD simulation. The results of the injection region model show good agreement with that of the fully resolved 3D simulation. Therefore, it has the potential to speed-up the film cooling simulations in the early design phase.
Numerical Investigation of Flow Structure and Pressure Drop Prediction for Radial Inflow Between Co-Rotating Discs With Negative Effective Inlet Swirl Ratio
Authors: Xu Yang , Ding Shuiting , Liu Peng , Zhao Yu , Qiu Tian 
Published: August 2024

Abstract
This paper presents a numerical simulation of the flow structure of radial inflow between co-rotating discs with a negative ceff (effective inlet swirl ratio), which may occur in a vortex reducer equipped with deswirl nozzles. When the value of ceff approaches zero, asymmetric flow structure is observed in the cavity, possibly as a result of the “Coanda effect”. Besides this, the flow structure inside the disc cavity at ceff &lt; 0 can be divided into a source region, a sink region, an interior core region, and two Ekman layers, which is identical to the situation when 0 &lt; ceff ≤ 1. However, there exist two distinct patterns: the stagnation point on the disc and on the peripheral. According to a theoretical analysis, ceff = −1/8 is used to distinguish between these two patterns.
Based on flow structure partitioning, a theoretical model for predicting the swirl ratio (V¯) radial distribution and pressure drop in a disc cavity with ceff &lt; 0 was established. The model employs the turbulent boundary layer integral method, and von Karman’s assumption of velocity profile and wall shear stress for a free disc. The calculation results of the swirl ratio in the cavity are in good agreement with the CFD results except when the negative ceff approaches zero because of the deviation of the radial velocity profile from the “1/7” power law. Since the pressure drop in the cavity approaches zero at the same time when the negative ceff approaches zero, the absolute error of the theoretical model in predicting pressure drop is not significant and does not affect its practical application, which has been verified through comparison with public experimental results.
Attention-Based Model With Component Embedding for Aero-Engine Performance Estimation
Authors: Liang Yufeng , Xiao Hong , Song Shuo , You Rui 
Published: August 2024

Abstract
Prognostics and Health Management (PHM) technology plays a vital role in the condition-based maintenance of aeroengines. Real-time models that monitor and estimate aeroengine performance are essential in this domain. The precision, stability, and interpretability of models are paramount for aeroengine research. However, both conventional data-driven models and physics-based models grounded on the component characteristic exhibit areas that can be further refined and improved. Therefore, this study presents a novel approach to improve predictive precision by incorporating engine domain knowledge into performance estimation models. We introduce a component embedding technique that effectively captures the concealed interdependencies among parameters in the corresponding component. The features are mapped to a high-dimensional space, characterizing the different engine components separately. Furthermore, we present a pioneering model for aero-engine performance estimation based on the attention mechanism. The attention-based model implements an encoder-decoder architecture. The multiple stacked encoders are responsible for capturing crucial engine performance information at different scales. The decoder utilizes the feature map generated by the encoders to produce an accurate prediction. Experimental results on the historical operating data of turbofan engines demonstrate that our proposed model outperforms conventional models in exhaust gas temperature (EGT) estimation in both normal and degraded conditions. Naturally, the presented model can also be utilized for the estimation of other performance parameters, thus providing support for the optimization of maintenance schedules.
HFTsim: A Component Library for High-Frequency Gas Turbine Engine Performance Simulations
Authors: Güllü Emrah , Aran Gökhan 
Published: August 2024

Abstract
HFTsim is a gas turbine engine component library for high-frequency pre and post-stall transient performance simulations. Standard component models are extended using gas dynamic equations for duct and volume elements. This extension allows us to model the temporary accumulation of mass, momentum, and energy within the components, which is important for high-frequency transients. Gas dynamic equations, together with dynamic equations for spool inertia, delays, and heat soakage, are integrated using the implicit Euler method. HFTsim has a flexible structure to allow the formation of any gas turbine engine configuration. The accuracy and stability of the gas dynamic equations set are first checked by a simple 1-D plenum-duct system, using data from CFD computations. This data includes cases with sinusoidal boundary condition transients of different frequencies. Then, the Rolls-Royce Viper engine, a single-spool turbojet engine, is modeled using HFTsim, and its pre and post-stall behavior is validated using the literature data. Shaft-breakage simulations of the Viper engine are conducted to showcase the application of the developed methodology. Surge provides passive protection during an HP-spool breakage by reducing turbine airflow and causing an eventual combustor blowout. Terminal speeds can also be reduced by detecting the breakage and cutting the fuel. These two strategies are compared and it is concluded that the selection of the strategy depends on compressor recovery, combustor stability, and heat-soakage characteristics.
Development of a Toroidal Jet-Stirred Reactor for Lean Blowoff and Emissions Studies of Ammonia-Hydrogen Mixtures
Authors: Zamora David , Ahmed Marzuqa , Barrios Cadenas Guillermo , Maia Amanda , Garai Priyankar , Bobi Shahzad , Rahman Ramees K. , Urso Justin , Vasu Subith S. 
Published: August 2024

Abstract
The present paper describes the design of a toroidal jet-stirred reactor (TJSR) for lean blowoff and emissions studies of ammonia-hydrogen mixtures at atmospheric pressure, with provisions for high-pressure testing in the future. The TJSR is a kind of well-stirred reactor experiment that has been used by other researchers for understanding the combustion characteristics of fuels. It consists of a ceramic torus, jet ring, casing, and exhaust pipe. Chemkin-Pro was used to approximate the flow rate through and the temperature inside the ceramic torus. The jet ring was made from Inconel 625; its design is a tradeoff between having sufficient wall thickness for storing pressure while minimizing the length of the nozzles. Thermomechanical simulations were conducted in Ansys Mechanical to determine the stresses and expansion of the reactor at operating conditions. ASME codes were used to design the exhaust pipe and flanges. Laser absorption spectroscopy will be used to measure the chemical species in the exhaust, so optical ports were designed to fit in the exhaust pipe’s flanges. Passages were designed in the optical ports for cooling the windows. Future work will consist of testing the reactor at atmospheric pressures and then modifying it to fit in a pressure vessel for high pressure.