bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Additive Manufacturing on Internal Cooling Channels With Varying Diameters and Build Directions
Authors: Wildgoose Alexander J. , Thole Karen A. , Sanders Paul , Wang Lieke 
Published: January 2021

Abstract
The use of additive manufacturing (AM) processes, such as direct metal laser sintering, provides the design freedom required to incorporate complex cooling schemes in gas turbine components. Additively manufactured turbine components have a range of cooling feature sizes and, because of the inherent three-dimensionality, a wide range of build angles. Previous studies have shown that AM build directions influence internal channel surface roughness that, in turn, augment heat transfer and pressure loss. This study investigates the impact of additive manufacturing on channel feature size and build direction relative to tolerance, surface roughness, pressure losses, and convective cooling. Multiple AM coupons were built from Inconel 718 consisting of channels with different diameters and a variety of build directions. An experimental rig was used to measure pressure drop to calculate friction factor and was used to impose a constant surface temperature boundary condition to collect Nusselt number over a range of Reynolds numbers. Significant variations in surface roughness and geometric deviations from the design intent were observed for distinct build directions and channel sizes. These differences led to notable impacts in friction factor and Nusselt number augmentations, which were a strong function of build angle.
Forced Response Variation of a Compressor Utilizing Blade Tip Timing, Strain Gages, and As-Manufactured Finite Element Models
Authors: Gillaugh Daniel L. , Janczewski Timothy J. , Kaszynski Alexander A. , Brown Jeffrey M. , Beck Joseph A. , Nessler Chase 
Published: January 2021

Abstract
The dynamic response of turbine engine components varies widely due to manufacturing deviations in the blades known as mistuning. This dynamic variation is investigated using a single stage compressor experimentally using both blade tip timing (BTT) and strain gage (SG) measurements and using as-manufactured finite element models (AMMs) on a 1st bend mode. Operational BTT and SG safety limits were generated using both averaged and AMM models via Goodman material properties. The predicted individual blade stress/deflection (S/D) ratios and strain gage ratios for this mode will be compared to the average finite element counterparts. Additionally, the correlation between BTT and SG’s will be presented. This correlation will be performed using two approaches: blade maximum stress comparisons and measured response compared to the sensors safety limits. It will be shown that accounting for geometry with AMMs produce more accurate strain gage to BTT correlation compared to average models. An experimental model updating procedure is developed to increase the strain gage to BTT correlation by optimizing the location the BTT optical spot probes measure on the blade chord. Implementing this procedure using as-manufactured models are able to improve strain gage to BTT correlation.
Transonic Relief in Fans and Compressors
Authors: Lefas Demetrios , Miller Robert J. 
Published: January 2021

Abstract
Every supersonic fan or compressor blade row has a streamtube, the ‘sonic streamtube’, which operates with a blade relative inlet Mach number of one. A key parameter in the design of the ‘sonic streamtube’ is the area ratio between the blade throat area and upstream passage area, Athroat/Ainlet. In this paper, it is shown that one unique value exists for this area ratio. If the area ratio differs, even slightly, from this unique value then the blade either chokes or has its suction surface boundary layer separated due to a strong shock. It is therefore surprising that in practice designers have relatively little problem designing blade sections with an inlet relative Mach number close to unity. This paper shows that this occurs due to a physical mechanism known as ‘transonic relief’. If a designer makes a mistake, and designs a blade with a ‘sonic streamtube’ which has the wrong area ratio, then ‘transonic relief’, will self-adjust the spanwise streamtube height automatically moving it towards the unique optimal area ratio, correcting for the designer’s error. Furthermore, as the blade incidence changes, the spanwise streamtube height self-adjusts, moving the area ratio towards its unique optimal value. Without ‘transonic relief’, supersonic and transonic fan and compressor design would be impossible. The paper develops a simple model which allows ‘transonic relief’ to be decoupled from other mechanisms, and to be systematically studied. The physical mechanism on which it is based is thus determined and its implications for blade design and manufacturing discussed.
Design Framework for Optimized Multifunctional Coatings
Authors: Moazami Nima , Abdi Frank , Morscher Gregory N. , Godines Cody , Zawada Larry , Jefferson George , Ahmed Jalees 
Published: January 2021

Abstract
An ICME (Integrated Computational Material Engineering) and lifing model/method is developed for optimizing multifunctional coatings Atmospheric Plasma Spray (APS) process of metallic TBC (Thermal Barrier Coating) system. Optimized TBC performance was achieved by minimizing thermal conductivity and residual stresses/strains during APS utilizing multiphysics-based multi-objective topology optimization methodology, and virtual design of experiment (DOE), surrogate meta modeling methodology. Thermal conductivity and residual strains were minimized 41% and 27%, respectively, for APS 8YSZ TBC with MCrAlY bond over Waspaloy substrate considering as variables yttria (mol.%), number of layers, total thickness, substrate initial temperature, and coating initial temperature.
Durability and Damage Tolerance (D&DT) analysis of Metallic bonded TBC dogbone specimen was performed using Multi-Scale Progressive Failure Analysis (MS-PFA). The objective was to determine the Remaining Useful Life (RUL) of Metal/TBC (8YSZ, Bond, Inconel-718) system under Low Cycle Fatigue (LCF) in-service loading at 900°C. The multi-scale multi-layer TBC modeling considered Thermal Growth Oxidation (TGO) in bond coat, and recession of top coat. Prediction was validated by Rig testing; TGO measurement Progressive damage analysis revealed that failure is due to tension and out of plane shear, delamination growth due to when recession penetrates bond. The results showed that predicted fatigue life compared well to experimental observations.
Simulation Driven Design Workflow for Aircraft Gearbox
Authors: Park Youn , Gasevski Dragi , Springer Marlow , Stanic Milos , Kulkarni Viraj , Marjadi Dhiren 
Published: January 2021

Abstract
The aerospace industry is driven more than ever to reduce time and cost of developing aircrafts while reducing weight without compromising performance. This challenge cascades down to design of aircraft engines, where manufacturers are striving to deliver engines with higher fuel efficiency and power per unit weight. The challenge cascades down further to aerospace systems such as gearboxes. The focus of this paper is to addresses this challenge through application of model-based systems engineering and a design workflow based on simulation and optimization.
A typical gearbox design starts with system level performance requirements such as power requirements, speed, torques and operating conditions. The goal is to design a minimum weight, manufacturable gearbox in the shortest possible time that meets the performance requirements. In this paper, authors present a design workflow developed for meeting this goal.
The efficiency of the workflow presented here comes from the use of advanced simulation technologies, seamless integration of the workflow tasks, and modern and intuitive user experience.
The proposed workflow focuses on design of housing and lubrication. This workflow is demonstrated on an aircraft engine accessories gearbox. Gear and bearing design are currently out of the scope of this paper and can be addressed in future work.
Demonstrating a fully detailed workflow on a real-life gearbox housing with all the physics covered here would require many man-months of work and is outside the scope of authors’ IRAD funding. Instead, authors have presented a proof of concept of the workflow while providing key statistics to support the value and feasibility of the workflow.
Experimental Study of Full Coverage Film Cooling Effectiveness for a Turbine Blade With Compound Shaped Holes
Authors: Zhang Shuai-qi , Liu Cun-liang , Guo Qi-ling , Liang Da-peng , Zhang Fan 
Published: January 2021

Abstract
The film coverage of a turbine blade surface is determined by all the film cooling structures. The direct study of full coverage film cooling is relatively rare, especially for related research on turbine blades. In this paper, the pressure-sensitive paint (PSP) measurement technique is used to carry out experiments under different turbulence intensities and mass flux ratios, and the distribution of the film cooling effectiveness on the entire surface is studied in detail. In this study, a basic turbine blade and an improved turbine blade are investigated. The film cooling hole position distribution on the improved blade is the same as that on the basic blade, but the film cooling hole shape on the suction surface and the pressure surface is changed from cylindrical holes to laid-back fan-shaped holes. Both blades have 5 rows of cylindrical holes at the leading edge and 4 rows of film cooling holes on the suction surface and the pressure surface. The leading edge, suction surface, and pressure surface have their own coolant inlet cavities. This kind of design is not only close to the actual working conditions in a flow distribution but also conveniently eliminates the mutual interference caused by the uneven flow distribution between the pressure surface and the suction surface to facilitate the independent analysis of the pressure surface and the suction surface.
In this paper, the film cooling effectiveness of two kinds of turbine blades under different turbulence intensities and mass flux ratios is studied. The results show that the average cooling effectiveness of the improved blade is much better than that of the basic blade. The laid-back fan-shaped hole rows improve the cooling effectiveness of the suction surface by 60% to 100% and 50% to 120% on the pressure surface. The increase in turbulence intensity will reduce the cooling effectiveness of the blade surface; however, the effect of the turbulence intensity becomes weaker with an increase in the mass flux ratio. Compared with the multiple rows of cylindrical holes, the cooling effectiveness of the laid-back fan-shaped holes is more affected by the turbulence intensity under the small mass flux ratio.
Effect of Matching Parameters Between Rotor and Diffuser on the Flow Loss Characteristic in an Axial Turbine
Authors: Wang Xing , Zhu Yangli , Li Wen , Zhang Xuehui , Chen Haisheng 
Published: January 2021

Abstract
Diffuser is a key component affecting the aerodynamic performance of an axial turbine significantly. However, there is little research on the matching parameters between a rotor and a diffuser. In present study, effect of matching parameters which are normalized axial clearance (ACLR‘) and normalized radial size deviation (RDev‘) between rotor and diffuser on the aerodynamic performance and flow loss characteristic of a typical diffuser is revealed. A validated Computational Fluid Dynamic (CFD) model which couples the cavity between the rotor and diffuser is also proposed. The results illustrate that the isentropic efficiency is decreased with the increase of ACLR‘ and RDev‘. The RDev‘ presents a larger influence on isentropic efficiency. When ACLR‘ is increased from 0.21 to 0.43, the isentropic efficiency is only decreased by 0.3%, while the isentropic efficiency reduction of 0.65% is achieved when RDev‘ is increased from 0.091 to 0.192. A “leakage flow”, which is a result of the egress and ingress of the fluid near diffuser-cavity interface, is formed. It presents limited effect on the main flow in the diffuser when ACLR’ is only included and the flow loss near the guide cone surface is increased slightly. However, obvious back flow caused by the “leakage flow” is observed near the diffuser-cavity interface, when RDev’ is included. A flow separation is thus formed downstream and the flow loss in the diffuser is thus increased. The efficiency reduction caused by actual matching parameters (ACLR‘ with 0.21 and RDev‘ with 0.091) is increased with the decrease of expansion ratio. It can be more than 1.26% when the expansion ratio is less than 2.0. An isentropic efficiency reduction of 0.65% is found when different tip clearance are further adopted, and the mixture loss between tip leakage flow and back cavity flow can be neglected. In summary, matching parameters, especially for radial deviation, should be minimized reasonably in further optimization.
Experimental Study on Internal Flow Field of a High-Speed Centrifugal Compressor at Different Altitudes
Authors: Yu Xinghang , Ma Hongwei , Shi Lei , Zhao Lianpeng 
Published: January 2021

Abstract
The alteration of altitude will affect the stability of centrifugal compressors. In this paper, the pressure field on the casing wall of a high-speed centrifugal compressor at two different altitudes (h = 0m and h = 4500m) was investigated by using 15 high-response pressure sensors. The operating condition of the centrifugal compressor ranged from choke condition to developed stall condition. The results show that the interaction of the shock wave and splitter-blade tip leakage flow occurs at 70% chord region near the choke condition, and the loss is more severe at the high altitudes. At the near-stall condition, the unstable disturbance at the low altitude is caused by the collapse of the horseshoe vortex, and the unstable disturbance at the high altitude is dominated by advanced breakdown of the main-blade tip leakage vortex. At the developed-stall condition, the stall mechanisms at the two altitudes are different, both of which are closely related to the main-blade tip leakage flow. With the decrease of flow rate, the unsteady disturbance caused by the volute tongue moves upstream from the diffuser to the impeller inlet. At the same time, the unsteady disturbance propagates along the opposite direction of the rotational direction in the partial impeller passage at the low altitude case. However, the circumferential propagation characteristics at the high altitudes case are not obvious.
Numerical Simulation of Reacting Flows Around a Bluff-Body Flame Stabilizer With Lattice Boltzmann Method
Authors: Zhang Zhihong , Li Zhiqiang , Wu Yunke 
Published: January 2021

Abstract
A 2-dimensional lattice Boltzmann model for combustion phenomena is presented. Mathematically, the model is composed of a standard lattice Boltzmann distribution function to recover the hydrodynamic model which describe the density and flow velocity and two distribution functions to recover the governing equation of temperature and chemical reaction process. The temperature could be described by solving an advection-diffusion equation with a simpler lattice. The actual combustion processes are very complicated. In this work, we consider the simple combustion processes with the assumption that the reaction process is irreversible and described by an empirical equation. The evolution of chemical process is described by another passive scalar convection-diffusion equation. The chemical energy released in the progress of combustion is dynamically coupled into the system by adding a chemical term to the temperature distribution function. The model is verified and validated via well-known benchmark tests. In this paper, the case of vortex street arising from the flow around the circular cylinder at Re = 100, 150 and 200, is taken to examine the validation of the numerical simulation. The Strouhal numbers achieved in the numerical simulation match well with the theoretical values. We also simulate a flame at constant pressure to validate the model, the temperature and concentration distributions is consistent with the laminar premixed combustion theory. The objective of the present work is to investigate the effect of Reynolds number on the stability of the flame behind the bluff-body. For the circular cylinder flame stabilizers, the effect of different inlet speeds on flame stability was investigated.
Averaging for High Fidelity Modelling: Towards Large Eddy Simulations in Multi-Passage Multi-Row Configurations
Authors: He L. 
Published: January 2021

Abstract
A major challenge in high-fidelity turbomachinery flow computations is the need for high resolution in a very large domain of multiple blade-passages and multiple blade-rows. Scale-resolving turbulent solutions are prohibitively costly. The question is, what will it take to get high-fidelity solutions if we are only after time-mean flows for aerothermal performance?
A novel two-scale approach is adopted to address the issue by coupling between a local fine-mesh domain in a singlepassage and a global coarse-mesh multi-passage domain. This is achieved by harnessing the extra product terms generated when averaging a nonlinear process in time, as well as in space. As such a space-time averaging is purposely utilized in either a direct mode or an inverse one in the two domains respectively. The source terms in a compact form (one scalar for one equation) can be conveniently obtained and used to enable the interaction between the single-passage fine-mesh and the multipassage coarse-mesh solutions. The converged solution for this two-scale coupled system should meet two seemingly conflicting requirements: an otherwise poorly conditioned local fine-mesh domain is now subject to a right environment/flow conditions, and an otherwise poorly resolved global coarse-mesh domain is now effectively subject to high resolution. In this paper, the concepts, the formulations of the framework methodology and the implementation methods will be described. The validity and feasibility of the approach for efficient scale-resolving high-fidelity turbomachinery flow simulations will be illustrated by several computational examples of practical interest.
Uncertainty Based Optimization Strategy for the Gappy-POD Multi-Fidelity Method
Authors: Poethke Bernhard , Völker Stefan , Vogeler Konrad 
Published: January 2021

Abstract
In the surrogate model-based optimization of turbine airfoils, often only the prediction values for objective and constraints are employed, without considering uncertainties in the prediction. This is also the case for multi-fidelity optimization strategies based on e.g. the Gappy-POD approach, in which results from analyses of different fidelities are incorporated. However, the consideration of uncertainties in global optimization has the advantage that a balanced coverage of the design space between unexplored regions and regions close to the current optimum takes place. This means that on the one hand regions are covered in which so far only a few sample points are present and thus a high degree of uncertainty exists (global exploration), and on the other hand regions with promising objective and constraint values are investigated (local exploitation).
The genuine new contribution in this work is the quantification of the uncertainty of the multi-fidelity Gappy-POD method and an adapted optimization strategy based on it. The uncertainty quantification is based on the error of linear fitting of low-fidelity values to the POD basis and subsequent forward propagation to the high-fidelity values. The uncertainty quantification is validated for random airfoil designs in a design of experiment.
Based on this, a global optimization strategy for constrained problems is presented, which is based on the well-known Efficient Global Optimization (EGO) strategy and the Feasible Expected Improvement criterion. This means that Kriging models are created for both the objective and the constraint values depending on the design variables that consider both the predictions and the uncertainties. This approach offers the advantage that existing and widely used programs or libraries can be used for multi-fidelity optimization that support the (single-fidelity) EGO algorithm.
Finally, the method is demonstrated for an industrial test case. A comparison between a single-fidelity optimization and a multi-fidelity optimization is made, each with the EGO strategy. A coupling of 2D/3D simulations is used for multi-fidelity analyses. The proposed method achieves faster feasible members in the optimization, resulting in faster turn-around compared to the single-fidelity strategy.
Experimental Investigation in Turbocharger Compressors During Surge Operation
Authors: Marelli Silvia , Misley Anna , Ferrando Marco 
Published: January 2021

Abstract
Flow instabilities in centrifugal compressors are one of the most limiting factors to the performance of the system where the compressor is installed (i.e., internal combustion engines, fuel cell, etc.). A better understanding of the surge phenomenon allows to properly set-up the operative region of the turbomachine in order to avoid a decrease in performance and to prevent the risk of damage. Actually, the instability phenomenon of surge can seriously damage the compressor for vibrations and temperature stress. To avoid damage to the compressor, the maximum boost pressure is generally limited with a by-pass system, reducing the mass flow rate provided by the machine.
The results of a broad experimental investigation performed at the turbocharger test bench of the University of Genoa are reported to deeply analyze the behavior of a small centrifugal compressor. A specific circuit adaptable in volume and length is used to study the effect of different configurations on steady compressor performance with special reference to the unstable operation. Measurements of instantaneous pressure and mass flow rate signals are performed in different sections located upstream and downstream the turbomachine. The difficulties related to measurement of instantaneous fluid-dynamics parameters in the turbocharging circuit and data post-processing are highlighted under unsteady flow conditions occurring in surge operation.
The effect of the compressor operating conditions (i.e., turbocharger rotational speed) and the circuit geometry is studied during the transition from steady to unsteady operation. In particular, the hysteresis loops surrounding the steady state map are reported highlighting filling and emptying and wave action phenomena, also in the region of zero mass flow and in the case of reverse flow condition. All measured quantities presented in this paper are the time synchronous averages of a large number of consecutive cycles in deep surge operation.
The aim of the paper is to extensively analyze the compressor behavior in unstable operating conditions in order to improve simulation models such as a physics-based compressor model previously developed by the Authors.