bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on Vibration Response Characteristics of Mistuned Bladed Disk Expressed by Vibratory Stress
Authors: Kaneko Yasutomu , Watanabe Toshio , Furukawa Tatsuya , Washio Saiji 
Published: November 2019

Abstract
Although bladed disks of turbomachinery are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of individual blades on a disk differ slightly owing to manufacturing tolerance, deviation of material properties, wear during operation, etc. These small variations break cyclic symmetry and split eigenvalue pairs. Actual bladed disks with small variations are called mistuned systems. Many researchers have studied mistuning and the main conclusion is that while mistuning has an undesirable effect on forced response, it has a beneficial effect on blade flutter. Although mistuning phenomena have been studied since the 1980s, studies on forced response are mostly related to increase in the resonant amplitude due to harmonic excitation force. In addition, because few papers have treated the amplification factor expressed in terms of vibratory stress, the mistuning phenomena of bladed disks expressed in terms of vibratory stress are not fully understood. In this study, the mistuning effect expressed in terms of vibratory stress is examined using the reduced-order model SNM (Subset of Nominal Modes) without any assumptions. By comparing the amplification factor expressed in terms of displacement response with that expressed in terms of vibratory stress response, including synthesized stress (von Mises stress and principal stress), the mistuning phenomena expressed in terms of vibratory stress are clarified. The effect of bladed disk structure on amplification factor is examined in detail as well.
Numerical Study on Flow and Heat Transfer Characteristics of Pin-Fins With Different Shapes
Authors: Jin Wei , Jia Ning , Wu Junmei , Lei Jiang , Liu Lin 
Published: November 2019

Abstract
Equipping pin-fins in the blade trailing edge is an significant method for enhancing heat transfer. In order to obtain a geometry of pin-fins with good heat transfer effect and small friction factor, six pin-fins (circular, elliptic, oblong, teardrop, lancet and NACA) are selected. The flow and heat transfer features of the rectangular channel with the staggered pin-fins were numerically studied through FLUENT software. The channels with different pin-fins have the same relative spanwise pitch (S/D = 2.5) and streamwise pitch (X/D = 2.5), and the range of Reynolds number is 5×103 to 3×104. The applicability and accuracy of five turbulence models (Standard k-ε, Realizable k-ε, RNG k-ε, Standard k-ω and SST k-ω) are checked by comparing the numerically predicted results with the experimental from literature. It is found that the Realizable k-ε model is better at capturing the microstructure of flow field and has higher precision in predicting the averaged Nusselt number on the heated surface. For the six pin-fins, the leading edge is surrounded by a “U-shaped” strong heat exchange zone, but the vortex systems in the trailing edge are different from each other. Compared to the circular pin-fin, the oblong pin-fin has the best heat transfer enhancement effect, but the friction factor of channel is also larger. While the NACA pin-fin has the lowest friction factor, and the heat transfer effect is second only to the oblong. NACA pin-fin may be applied in blade trailing edge cooling by further optimizing the relative position of the pin-fins in the channel.
Effect of the Double-Slot Injection on the Leakage Flow Control in a Honeycomb-Tip Turbine Cascade
Authors: Wang Yabo , Song Yanping , Yu Jianyang , Chen Fu 
Published: November 2019

Abstract
The effect of five arrangements of the double-slot injections on the leakage flow control is studied in a honeycomb-tip turbine cascade numerically. The honeycomb tip is covered with 67 intact honeycomb cavities, since the uneven tip is wearable and the cavity vortex could realize the aerodynamic sealing for the leakage flow. Then in the present study, a pair of injection slots is arranged blow each cavity, aiming to enhance the leakage flow suppression by modifying the cavity vortex. According to the orientation of the two slots, five designs of the double-slot injections are proposed. In detail, the two slots are opposite to each other or keep tangential to the original cavity vortex roughly. The three dimensional calculations were completed by using Reynolds-averaged Navier-Stokes (RANS) method and the k-ω turbulence model in the commercial software ANSYS CFX. The estimation of these tip designs is mainly according to the tip leakage mass flow rate and the total pressure loss. Firstly, the injection structures induced by the slots can be divided into X- and T-types inside the cavity. The results show that the T-type structure is more effective in reducing the tip leakage mass flow rate, with the maximum reduction up to 48.2%. Then the effect on the flow field inside the gap and the secondary flow in the upper passage is analyzed. Compared with the flat tip, the span-wise position of the tip leakage vortex core drops within the cascade and the range of the affected loss region expands. At the cascade exit, the tip leakage vortex moves toward the passage vortex near the casing, while the latter’s core rises. The position changes of the secondary vortices eventually determine the total pressure loss contour downstream the cascade. Finally, the injection total pressure and the upper casing motion are investigated. Interestingly, the injection intensity (mass flow rate) increases with the injection total pressure but this value decreases as the casing speed increases. The tip leakage mass flow rate decreases linearly as increasing the injection total pressure or the casing speed. Yet the averaged total pressure loss downstream the cascade increases with the injection total pressure but appears a nonlinear distribution against the casing speed.
Experimental Analysis of an Ultra Compact Combustor Powered Turbine Engine
Authors: Bohan Brian T. , Polanka Marc D. 
Published: November 2019

Abstract
The innovative Ultra Compact Combustor (UCC) is an alternative to traditional turbine engine combustors and has been shown to reduce the combustor volume and offer potential improvements in combustion efficiency. Prior UCC configurations featured a circumferential combustion cavity positioned around the outside diameter (OD) of the engine. This configuration would be difficult to implement in a vehicle with a small, fixed diameter and had difficulty migrating the hot combustion products at the OD radially inward across an axial core flow to present a uniform temperature distribution to the first turbine stage. The present study experimentally tested a new UCC configuration that featured a circumferential cavity that exhausted axially into a dilution zone positioned just upstream of the nozzle guide vanes. The combustor was sized as a replacement burner for the JetCat P90 RXi small-scale turbine engine and fit inside the engine casing. This combustor configuration achieved a 33% length reduction compared to the stock JetCat combustor and achieved comparable engine performance across a limited operating range. Self-sustaining engine operation was achieved with a rotating compressor and turbine making this study the first to achieve operation of a UCC powered turbine engine.
Development and Initial Testing of a Radial Wave Engine
Authors: Akbari Pejman , Tait Christopher J. , Polanka Marc D. , Sell Brian C. 
Published: November 2019

Abstract
Smaller combustion chambers, as well as pressure gain combustion processes, are desired in terms of reducing the space, weight, lowering engine manufacturing costs, and increasing the efficiency and specific power of gas turbine engines. In this paper, a compact single rotor disk pressure gain combustor engine is introduced with interesting merits compared with existing turbine engine designs. The engine introduced as the Radial Wave Engine (RWE) features purely radial-flow resulting in a compact and light weight design with only two moving parts. The core of the engine is a spinning radial combustor in which constant volume combustion occurs using stationary inlet and exit end walls resembling a valved-combustor. Power output is generated via a radial-outflow turbine forming a purely disk-shape engine. The proposed engine is a hybrid engine concept, midways between piston and turbine engines with improvements to other counterpart designs. This paper discusses the engine background, operating principles, instrumentation, high-speed video recording, and initial testing of a prototype proof-of-concept demonstrator. This study is the first step towards a new pressure gain combustion configuration which has not designed or tested before.
Sensitivity and Forced Response Analysis of Anisotropy-Mistuned Bladed Disks With Nonlinear Contact Interfaces
Authors: Koscso Adam , Petrov E. P. 
Published: November 2019

Abstract
A new method has been developed for the analysis of nonlinear forced response of bladed disks mistuned by blade anisotropy scatter and for the forced response sensitivity to blade material anisotropy orientations. The approach allows for the calculation of bladed disks with nonlinear friction contact interfaces using the multi-harmonic balance method. The method uses efficient high-accuracy model reduction method for the minimization of the computational effort while providing required accuracy.
The capabilities of the developed methods are validated and demonstrated using a two-blade model. A thorough study of the influence of the material anisotropy mistuning and its sensitivity on the characteristics of the forced response is carried out using finite element modes of anisotropy mistuned realistic bladed disk with nonlinear friction joints of blade roots and shroud contacts. The dependency of the nonlinear forced response on excitation level and contact pressure values has been carried out for anisotropy mistuned bladed disks.
Effect of Compressor Inlet Condition on Supercritical Carbon Dioxide Compressor Performance
Authors: Chen Haoxiang , Zhuge Weilin , Zhang Yangjun , Liu Hongdan 
Published: November 2019

Abstract
Supercritical carbon dioxide (S-CO2) Brayton power cycle has attracted a lot of attention around the world in energy conversion field. It takes advantage of the high density of CO2 near the critical point while maintaining low viscosity to reduce compressor power and achieve high cycle efficiency. However, as CO2 approaches to its critical point, the thermodynamic properties of CO2 vary dramatically with small changes in temperature or pressure. As a result, the density of the working fluid varies significantly at the compressor inlet in the practical cycle if operating near the critical point, especially for small-scale cycles and air-cooled cycles, which leads to compressors operating out of the flow range, even being damaged. Concerns of large density variations at the inlet of the compressor result in S-CO2 compressor designers selecting compressor inlet conditions away from the critical point, thereby increasing compressor power. In this paper, a criterion to choose inlet pressure and inlet temperature of compressors as the design inlet condition is proposed, which is guaranteeing ±50% change in inlet specific volume within ±3 °C variation in inlet temperature. By the criterion, 8 MPa and 34.7 °C is selected as the design inlet condition. According to design requirements of the cycle, a S-CO2 centrifugal compressor is designed through 1-D design methodology. Based on the two-zone model, the effects of compressor inlet condition including inlet pressure and inlet temperature on the compressor performance are analyzed in detail. In practical operation, the compressor inlet condition is varied. Thus, an accurate prediction of compressor performance under different inlet conditions is necessary. The traditional correction method is not suitable for S-CO2 compressor. Dimensionless specific enthalpy rise is used to correct pressure ratio by the real gas table. And the S-CO2 compressor performance can be predicted correctly under different inlet conditions.
Non-Axisymmetric Flows and Rotordynamic Forces in an Eccentric Shrouded Centrifugal Compressor: Part 2 — Analysis
Authors: Song Jieun , Song Seung Jin 
Published: November 2019

Abstract
An integrated analytical model to predict non-axisymmetric flow fields and rotordynamic forces in a shrouded centrifugal compressor has been newly developed and validated. The model is composed of coupled, conservation law-based, bulk-flow sub-models, and the model takes into account the flow coupling among the blades, labyrinth seals, and shroud cavity. Thus, the model predicts the entire flow field in the shrouded compressor when given compressor geometry, operating conditions, and eccentricity. When compared against the experimental data from Part 1, the new model accurately predicts the evolution of the pressure perturbations along the shroud and labyrinth seal cavities as well as the corresponding rotordynamic stiffness coefficients. For the test compressor, the cross stiffness rotordynamic excitation is positive — the contribution of the shroud is the highest; the contribution of the seals is less than but on the same order of magnitude as that of the shroud; and contribution of impeller blades is insignificant. For accurate flow and rotordynamic force predictions, it is critical to model the coupling among the components (e.g., impeller, shroud, labyrinth seal, etc.) which determines the non-axisymmetric boundary conditions for the components. The new model also enables insight into the physical mechanism for pressure perturbation development. The labyrinth seal pressure distribution becomes non-axisymmetric to satisfy mass conservation in the seal cavity, and this non-axisymmetry, in turn, serves as the influential boundary condition for the pressure distribution in the shroud cavity.
Investigation of Stall Process in a Centrifugal Compressor With a Volute Under Transonic Conditions
Authors: Yang Ce , Wang Wenli , Zhang Hanzhi , Li Yanzhao , Tong Ding , Yang Changmao , Yi Weilin 
Published: November 2019

Abstract
In a centrifugal compressor with a volute, the internal flow field is circumferentially nonuniform owing to the asymmetric structure of the volute. Currently, the mechanisms by which the volute influences the stall inception circumferential position and the stall process in a transonic centrifugal compressor are not clear. In this study, the stall process in the centrifugal compressor with a volute is investigated under transonic inlet conditions. Obtained by experimental and simulation results, the static pressure distributions around the casing wall are compared with each other. Thereafter, an unsteady simulation is conducted on the stall process under transonic inlet conditions. By analyzing the stall cell evolution pattern at the impeller inlet, the stall process can be divided into three stages: stall onset, stall development, and stall maturation. The spike-type stall inceptions occur twice at the tip in the circumferential 135° position of the impeller inlet. This circumferential position is also the affected position of the high static pressure region induced by the volute tongue. Because of the circumferentially nonuniform flow field, there is a stall cell decay zone and a stall cell formation/growth zone at the impeller inlet. For the compressor under study, the approximate circumferential range of 135° to 270° is the decay zone, and the circumferential range of 270° to 360° is the formation/growth zone. The stall inception cannot occur in the decay zone. However, the stall cells can pass through the decay zone when the stall cell size is large enough. The first stall inception cannot propagate circumferentially, while the second one can. The propagation speed of stall cells in the circumferential direction is at approximately 70% of the rotational speed of impeller.
Progress in Burner Design Using Additive Manufacturing With a Monolithic Approach and Added Features
Authors: Moosbrugger Vanessa , Giuliani Fabrice , Paulitsch Nina , Andracher Lukas 
Published: November 2019

Abstract
Additive manufacturing (AM) is a promising technology for producing better burners. Achieving better energy efficiency on a system level (CO2 emissions) and lower NOx, particulate emissions and CO, as directed by the International Civil Aviation Organisation (ICAO) standards, is a priority for all aircraft and aircraft engine manufacturers. At the current state-of-the-art, technologies like Powder Bed Fusion (PBF) offer a certain freedom of design one can make good use of. Instead of starting from an established conventional burner design and improve it using AM, the proposed approach in this paper is to define from scratch a design that maximises the potential benefits of AM towards a better burner. However, there are a few playing rules one must be aware of. The design, manufacturing and testing of a staged premixed burner with separate injection ramp was done as the follow-up of paper GT2018-75165 where new swirler shapes had been assessed. For this paper a monolithic, profiled burner design for premixed injection was tested for low-emission combustion. Additional features were included and assessed. Separately, regarding the fuel injection system a new design of a fuel ramp disconnected from the burner is proposed in a first approach, which combines the injection and pre-heating of the fuel. It serves as a fuel splitter (burning fuel / bypassed flow), as a miniature heat exchanger and as a multipoint injection ramp. A merging of the monolithic burner and the injection ramp is planned at a later stage. The fuel injection system using AM parts is assessed separately from the burner in a first approach. It suggests some novel technical solutions regarding 3D printed burner designs. Early combustion experiments are described and supported with function tests using a carefully selected instrumentation.
Impact of Turbine Center Frame Wakes on Downstream Rows in Heavy Duty Low Pressure Turbine
Authors: Biagiotti Sara , Bellucci Juri , Marconcini Michele , Arnone Andrea , Baldi Gino , Ignesti Mirko , Michelassi Vittorio , Tapinassi Libero 
Published: November 2019

Abstract
In this work, the effects of Turbine Center Frame (TCF) wakes on the aeromechanical behavior of the downstream Low Pressure Turbine (LPT) blades are numerically investigated and compared with experimental data. A small industrial gas turbine has been selected as a test case, composed of a TCF followed by the two low pressure stages and a Turbine Rear Frame (TRF) before the exhaust plenum. Full annulus unsteady computations of the whole low-pressure module have been performed. Two operating conditions, full (100%) and partial (50%) load, have been investigated with the aim of highlighting the impact of TCF wakes convection and diffusion through the downstream rows. Attention was paid to the harmonic content of rotors’ blades. From an aerodynamic point of view, the results show a slower decay of the wakes through the downstream rows in off-design conditions as compared to the design point. The wakes generated by the struts at partial load persist throughout the domain outlet, while they are chopped and circumferentially transported by the rotors motion. This is due to the strong incidence variation at which the TCF works, which induces the growth of wide regions of separated flow on the rear part of the struts. Nevertheless, the analysis of the rotors’ frequency spectrum reveals that moving from design to off-design conditions, the effect of the TCF does not change significantly, thanks to the filtering action of the first LPT stage movable Nozzle Guide Vane (NGV). From unsteady calculations the harmonic contribution of all turbine components has been extracted, highlighting the effect of statoric parts on the last LPT blade. Anyhow the TCF harmonic content remains the most relevant from an aeromechanic point of view as per experimental evidence, and it is considered for a Forced Response Analysis (FRA) on the last LPT blade itself. Finally, aerodynamic and aeromechanic predictions have been compared with the experimental data to validate the numerical approach. In the last part of this paper some general design solutions, that can help mitigation of the TCF wakes impact, are discussed.
Efficient Robust Design for Thermoacoustic Instability Analysis: A Gaussian Process Approach
Authors: Guo Shuai , Silva Camilo F. , Polifke Wolfgang 
Published: November 2019

Abstract
In the preliminary phase of analysing the thermoacoustic characteristics of a gas turbine combustor, implementing robust design principles is essential to minimize detrimental variations of its thermoacoustic performance under various sources of uncertainties. In the current study, we systematically explore different aspects of robust design in thermoacoustic instability analysis, including risk analysis, control design and inverse tolerance design. We simultaneously take into account multiple thermoacoustic modes and uncertainty sources from both the flame and acoustic boundary parameters. In addition, we introduce the concept of a “risk diagram” based on specific statistical descriptions of the underlying uncertain parameters, which allows practitioners to conveniently visualize the distribution of the modal instability risk over the entire parameter space. Throughout the present study, a machine learning method called “Gaussian Process” (GP) modeling approach is employed to efficiently tackle the challenge posed by the large parameter variational ranges, various statistical descriptions of the parameters as well as the multifaceted nature of robust design analysis. For each of the investigated robust design tasks, we propose an efficient solution strategy and benchmark the accuracy of the results delivered by GP models. We demonstrate that GP models can be flexibly adjusted to various tasks while only requiring one-time training. Their adaptability and efficiency make this modeling approach very appealing for industrial practices.
Numerical Investigation of Cut-Corner in Recess Vaned Casing Treatment
Authors: Chen Xiangyi , Chu Wuli , Zhang Haoguang , Luo Bo 
Published: November 2019

Abstract
This paper studies the effects of cut-corner in the recess vaned casing treatment (RVCT) on the performance of a low-speed axial fan. The solid casing fan and fans with corner-cut RVCT have been simulated respectively. The numerical simulation shows that the introduction of the RVCT and the modification of RVCT cut-corner size bring about obvious changes in fan performance. The RVCT establishes a connection between the RVCT channel and the main flow, contributing to the extra flow circulation in the tip region and resulting in an efficiency penalty for each RVCT configuration. The cut-corner is not necessarily beneficial to the improvement of the stable operating range. With the increase of cut-corner size at the rear wall of RVCT, the improvement of stall margin firstly demonstrates a drop to −8.82% before jumping to over 60%. RVCTs with different cut-corner sizes play different roles in the flow interaction between RVCT channel and main flow, and the stall margin poses a positive relationship with the mass flow passing through RVCT. The size of the cut-corner is responsible for the flow field in RVCT. The RVCT with small cut-corner size functions as a larger blade tip clearance and results in a smaller stall margin than the solid casing fan. Therefore, the size of the cut-corner in RVCT should be large enough to dredge the flow blockage in the tip region and delay the origin of stall.