bluuebunny/crossref_metadata_2025 huggingface dataset:
An Advanced Single-Stage Turbine Facility for Investigating Non-Axisymmetric Contoured Endwalls in the Presence of Purge Flow
Authors: Jones Robin R. , Pountney Oliver J. , Cleton Bjorn L. , Wood Liam E. , Schreiner B. Deneys J. , Figueiredo A. J. Carvalho , Scobie James A. , Cleaver David J. , Lock Gary D. , Sangan Carl M.
Published: November 2019

In modern gas turbines, endwall contouring (EWC) is employed to modify the static pressure field downstream of the vanes and minimise the growth of secondary flow structures developed in the blade passage. Purge flow (or egress) from the upstream rim-seal interferes with the mainstream flow, adding to the loss generated in the rotor. Despite this, EWC is typically designed without consideration of mainstream-egress interactions. The performance gains offered by EWC can be reduced, or in the limit eliminated, when purge air is considered. In addition, EWC can result in a reduction in sealing effectiveness across the rim seal. Consequently, industry is pursuing a combined design approach that encompasses the rim-seal, seal-clearance profile and EWC on the rotor endwall.

This paper presents the design of, and preliminary results from a new single-stage axial turbine facility developed to investigate the fundamental fluid dynamics of egress-mainstream flow interactions. To the authors’ knowledge this is the only test facility in the world capable of investigating the interaction effects between cavity flows, rim seals and EWC. The design of optical measurement capabilities for future studies, employing volumetric velocimetry and planar laser induced fluorescence are also presented. The fluid-dynamically scaled rig operates at benign pressures and temperatures suited to these techniques and is modular. The facility enables expedient interchange of EWC (integrated into the rotor bling), blade-fillet and rim-seals geometries.

The measurements presented in this paper include: gas concentration effectiveness and swirl measurements on the stator wall and in the wheel-space core; pressure distributions around the nozzle guide vanes at three different spanwise locations; pitchwise static pressure distributions downstream of the nozzle guide vane at four axial locations on the stator platform.
A Novel Methodology for Detecting Foreign Object Damage on Compressor Blading
Authors: Voigt Paul , Voigt Matthias , Mailach Ronald , Münzinger Daniel , Abu-Taa Kimon , Lange Alexander
Published: November 2019

Foreign Object Damage (FOD) to compressor airfoils is a common problem in operating aircraft engines that occurs when objects or debris are sucked into the engines. Especially small surface defects or impact damage (100μm – 300μm depth) can be problematic, as it only becomes noticeable during engine maintenance process, but can have a strong influence on the fatigue strength and service life of individual airfoils.

Usually the blade and vane inspection during maintenance is carried out by visual examinations. The inspection findings are individually assessed and as a result the airfoils are accepted, repaired or replaced. This manual inspection process has a significant optimization potential by the means of automatization. This paper presents a novel methodology to automatically detect FOD on compressor airfoils. For the investigation and validation, numerous used compressor blades and vanes were digitized on site with a high precision optical 3D scanning system.

A first approach is based on a machine learning algorithm. The idea is the surface segmentation of the digitized airfoil into typical affected areas such as the leading edge (LE), trailing edge (TE), pressure side (PS) or suction side (SS), wherein irregularities during the segmentation can be an indication for FOD. For a second approach, the surface curvature of the airfoil is considered. Locally limited regions with high curvature and concave shapes are sought as an indication for FOD. The required parameters position and depth associated to the individual FOD are calculated in both approaches. The results of both approaches are compared to each other and are validated against the results of a commercial software tool, which uses the approach of digital stoning to create surface defect maps. Furthermore, the results are verified by manually examining the airfoil scans.

In the case of relatively small FOD, both approaches generate meaningful results. In terms of larger damages and deformations, both approaches have difficulties detecting it. This problem can be compensated by parametrization of the scanned airfoils with a section based approach using NACA like profile parameters. Unusual changes of specific airfoil parameters (e.g. stagger angle and chord length) over the airfoils height can indicate large FOD or deformation.
Tailored Fuel Treatment Enables Optimizing the Operation of Heavy-Fueled Gas Turbines
Authors: Vierling Matthieu , Moliere Michel , Aboujaib Maher , Sokolov Dmitry , Catrin Sven , Glaser Paul , Denolle Richard , Marikkar Nuhuman , Tharindu Jayath , Egodawatta Kithsiri , Montagne Pierre
Published: November 2019

The combustion of heavy fuel oil (HFO) in gas turbines (GT) generates some operational constraints and expenses which are too often accepted fatalistically.

A first development has addressed the technical challenge caused by the deposition of ash on the hot parts of the turbines. Indeed, the combustion of HFO significantly increases the volume of ash as one must treat the fuel with a “vanadium inhibitor” that acts as an ash modifier preventing hot corrosion by vanadium. This fouling effect is the most serious drawback of HFO operation as it progressively shrinks the performances and reduces the availability of the machines. To tackle this issue, a genuine bimetallic vanadium inhibitor has been developed and field tested step by step between 2015 and 2018.

The last step that took place at Yugadanavi in March-April 2018 has allowed validating a ready-to-use version of this bimetallic inhibitor product. Upon the completion of this program, the rate of power degradation during HFO operation has been halved and the GT availability significantly increased while the emission of particulates has been substantially reduced.

As a further improvement effort, the teams have tested in the field the effect of changing the temperature of the HFO on its viscosity and monitored the impact induced on the quality of fuel atomization that underlies namely the level of particulate emissions. This second program devoted to the optimization of HFO heating, has enabled defining a rational minimum temperature of the fuel which establishes a fair compromise between atomization effectiveness and thermal energy consumption.

This paper summarizes the main outcome of this multi-year collaborative test program.
LES-Conjugate Heat Transfer Analysis of a Ribbed Cooling Passage Using the Immersed Boundary Method
Authors: Oh Tae Kyung , Tafti Danesh , Nagendra Krishnamurthy
Published: November 2019

The present study focuses on evaluating fully-coupled conjugate heat transfer simulation in a ribbed cooling passage with a fully developed flow assumption using LES with the immersed boundary method (IBM-LES-CHT). The IBM-LES and the IBM-CHT frameworks are validated prior to the main simulations by simulating purely convective heat transfer in the ribbed duct, and a laminar boundary layer flow over a 2D flat plate with heat conduction, respectively. For the main conjugate simulations, a ribbed duct geometry with a blockage ratio of 0.3 is simulated at a bulk Reynolds number of 10,000 with a conjugate boundary condition applied to the rib surface. The nominal Biot number is kept at 1, which is similar to the comparative experiment. As a means to overcome a large time scale disparity between the fluid and the solid regions, the use of a high artificial solid thermal diffusivity is compared to the physical diffusivity. It is shown that while the diffusivity impacts the instantaneous fluctuations in temperature, heat transfer and Nusselt numbers, it has an insignificantly small effect on the mean Nusselt number. Comparison between IBM-LES-CHT and iso-flux heat transfer simulations shows that the iso-flux case predicts higher local Nusselt numbers at the back face of the rib. Furthermore, the local Nusselt number augmentation ratio (EF) predicted by IBM-LES-CHT is compared to experiment and another LES conjugate simulation. Even though there is a mismatch between IBM-LES-CHT predictions and other two studies at the front face of the rib, the area-averaged EF compares reasonably well in other regions between IBM-LES-CHT prediction and the comparative studies.
The Effect of the Corner Recirculation Zone on Separated Stratified Swirling Flames and Combustion Instabilities
Authors: Song Heng , Han Xiao , Lin Yuzhen , Zhang Chi , Hui Xin , Wang Xinyao , Sung Chih-Jen
Published: November 2019

The present work investigates effects of the corner recirculation zone (CRZ) on flame macrostructures and combustion instabilities in the Beihang Axial Swirler Independently Stratified (BASIS) burner, a double-swirled full-scale burner characterized by separated stratified swirling flames at atmospheric pressure supplied with methane/air mixture. Three different macrostructures are observed, i.e. a lifted L-flame, a double-conical S-flame and a single conical V-flame as the stratification ratio (SR, the ratio of the inner stream equivalence ratio to the outer stream equivalence ratio) varies from 0.25 to 2.50 at a fixed total equivalence ratio of 0.6. It is found that the penetration of the flame into the corner recirculation zone leads to a sudden increase of acoustic oscillation. Rayleigh index maps confirm the driving effect of the CRZ region on combustion instabilities for the 0.25 ≤ SR ≤ 1.75 cases. When the corner recirculation zone is removed by the use of segmented confinements, similar flame macrostructures arise in the same SR range. More interestingly, the combustion instability is suppressed under all stratification ratios. A parametric experiment is also performed to confirm the generality of above findings, including three types of the segmented confinement, two premixednesses of the outer flame and a wider range of operating conditions. The suppressive effect is outstanding in all segmented confinements. The present study reveals the effect of the corner recirculation zone on combustion instabilities and demonstrates a potential method for passive control.
High Power Steam Turbine Lifetime Increase by Means of Front End Seal Arrangement and Start-Up Heating Conditions Improvement
Authors: Moroz Leonid , Kochurov Roman , Bakhmutska Julija , Goloshchapov Vladimir
Published: November 2019

Use of high power steam turbines in maneuver regimes by power plants became a widely-distributed practice in chase of short-term economic benefits. At the same time, these actions resulted in much higher levels of lifetime consumption for turbines which are not designed for high numbers of start-ups.

The purpose of the present study is to improve operational flexibility for 325 MW steam turbine through design modifications.

For the accurate simulation of rotor thermo-structural state and lifetime, an improved methodology was developed. The approach allows engineers to account for the steam film condensation process and the steam flow physics for regions with the anticipated high-stress levels at front-end seal zone, and the influence of the inter-casing space steam film condensation on the flow parameters in the front-end seals chambers.

Based on the simulation results for the 325 MW supercritical steam turbine HP rotor, the design changes of the front-end seal arrangement and heating conditions modification during the pre-warming phase are proposed. The results show that the proposed changes make it possible to provide a more uniform heating and lower thermo-stress level for the high-pressure cylinder rotor at the front-end seal region during the pre-warming phase, which results in an increased allowable number of turbine start-ups.

The influence of heating conditions on thermo-stresses and low cycle fatigue lifetime for the baseline and modified designs as well as modeling details for transient thermo-structural analysis have been discussed.
Efficient Design Investigation of a Turbofan in Distorted Inlet Conditions
Authors: Godard Benjamin , De Jaeghere Edouard , Gourdain Nicolas
Published: November 2019

Designing a turbofan to operate in distorted inlet conditions is an issue of growing interest. In such conditions however, fan design can be computationally challenging. Indeed, subject to neither axi-symmetrical nor periodic inlet conditions, computations must be carried out throughout the whole circumferential domain i.e. 360°. Besides, the classical CFD approach implies the use of URANS computations so as to capture the distortion transfer across the fan stage. Eventually, computations are too onerous to be used in design loops. In this context, this paper presents a methodology to effectively assess a fan blade design domain in distorted conditions. This methodology is based on a body-force source term approach formulated in order to accurately recreate deviations, loads and losses across the fan stage. It notably enables to gain two orders in terms of restitution time and thus the possibility to use optimization tools. The design domain of this study is based on variations of profile chord, blade leading and trailing edges angles applied at two different relative heights. A Latin Hypercube Sampling (LHS) associated with a meta-model based on Radial Basis Functions (RBF) enables to assess the impact of geometric variations on performance and operability. Although this study emphasizes that some modeling improvements are still necessary, it also demonstrates the potential of the body-force methodology to conduct fan design when subject to inlet distortion.
Laminar Flame Speed Experiments of Alternative Liquid Fuels
Authors: Keesee Charles L. , Guo Bing , Petersen Eric L.
Published: November 2019

New laminar flame speed experiments have been collected for multiple alternative liquid fuels. Understanding the combustion characteristics of these synthetic fuels is an important step in developing new chemical kinetics mechanisms that can be applied to real fuels. Included in this study are two synthetic Jet fuels: Syntroleum S-8 and Shell GTL. The precise composition of these fuels is known to change from sample to sample. Since these are low vapor pressure fuels, there are additional uncertainties in their introduction into gas-phase mixtures, leading to uncertainty in the mixture equivalence ratio. An in-situ laser absorption technique was implemented to verify the procedure for filling the vessel and to minimize and quantify the uncertainty in the experimental equivalence ratio. The diagnostic utilized a 3.39-μm HeNe laser in conjunction with Beer’s Law. The resulting spherically expanding flame experiments were conducted over a range of equivalence ratios from φ = 0.7 to φ = 1.5 at initial conditions of 1 atm and 403 K in the high-temperature, high-pressure constant-volume vessel at Texas A&M University. The experimental results show that both fuels have similar flame speeds with a peak value just under 60 cm/s. However, it is shown that when comparing the results from different data sets for these real fuels, equivalence ratio is not necessarily the best parameter to use. Fuel mole fraction may be a better parameter to use as it is independent of the average fuel molecule or fuel surrogate used to calculate equivalence ratio in these real fuel/air mixtures.
A New Structural Bump Foil Model With Application From Start-Up to Full Operating Conditions
Authors: Arghir Mihai , Benchekroun Omar
Published: November 2019

The paper presents a new structural bump foil model that can handle all operating conditions from start-up to full speed. The model is based on a non-linear contact algorithm with friction and gaps. The top foil is modeled as a curved beam while bump foil uses a coupled truss model.

The model considers the gaps between the bump foil and the bearing casing, between the bump foil and the top foil and between the rotor and the top foil. Thus, any numerical interference between the rotor and the top foil is avoided. A mixed lubrication model is used for the thin film pressures. Following this algorithm, contact pressures appear if the film thickness is less than three times the equivalent roughness of the rotor and of the top foil. Fluid pressures are calculated from numerical solutions of Reynolds equation while contact pressures, if present, are calculated with the model of Greenwood and Williamson.

The model is validated by comparisons with the experimental results obtained for start-up operating conditions of a first generation foil bearing of 38.1 mm diameter with static loads of 10 N to 50 N. Theoretical predictions of the start-up torque and take-off speed compare well with experimental results. It is also shown how manufacturing bump height errors can explain the differences between theoretical and experimental predictions.

Further validations are presented for the same bearing operating at high speeds (30, 45 and 55 krpm) and heavy static loads (up to 200 N). The calculated minimum film thickness and attitude angle are compared with experimental data from the literature.
Modeling and Control of a Supercritical CO2 Water Cooler in an Indirect-Fired 10MWe Recompression Brayton Cycle Near Critical Conditions
Authors: Liese Eric , Mahapatra Priyadarshi , Jiang Yuan
Published: November 2019

A one-dimensional design and dynamic model of a microtube heat exchanger is presented for cooling supercritical CO2 to near critical conditions (35°C and ∼90 bar) with water. A control strategy is designed and implemented to achieve a desired hot-side CO2 outlet temperature, while the cooling-water exit temperature is monitored (ideally kept below 50°C). The control responses during drastic process changes at the boundaries such as sCO2 inlet flow/pressure and cooling water inlet temperature are presented.
Effect of APS Flash Bond Coatings on Furnace Cycle Lifetime of Disks and Rods
Authors: Pint Bruce A. , Lance Michael J. , Haynes J. Allen , Gildersleeve Edward J. , Sampath Sanjay
Published: November 2019

Air plasma sprayed (APS) flash coatings on high velocity oxygen fuel (HVOF) bond coatings are well known to extend the lifetime of thermal barrier coatings. Recent work compared flash coatings of NiCoCrAlY and NiCoCrAlYHfSi applied to both rods and disk substrates of alloy 247. For rod specimens, 100-h cycles were used at 1100°C in wet air. Both flash coatings significantly improved the lifetime compared to HVOF-only and VPS-only MCrAlY bond coatings with no statistical difference between the two flash coatings. For disk specimens tested in 1-h cycles at 1100°C in wet air, the NiCoCrAlY flash coating significantly outperformed an HVOF-only NiCoCrAlYHfSi bond coating and a NiCoCrAlYHfSi flash coating. The flash coatings formed a mixed oxide-metal zone that appeared to inhibit crack formation and extend lifetime. In addition to the flash coating increasing the bond coating roughness, the underlying HVOF layer acted as a source of Al for this intermixed zone and prevented the oxide from penetrating deeper into the bond coating. The lower Y+Hf level in the Y-only flash coating appeared to minimize oxidation in the flash layer, thereby increasing the benefit compared to a NiCoCrAlYHfSi flash coating.
Multi-Disciplinary Design Optimization of a Horizontal Micro Kaplan Hydro Turbine
Authors: Amano Ryoichi S. , Abbas Ahmad I. , Qandil Mohammad D. , Al-Haddad Muhannad R.
Published: November 2019

This study investigates a performance-based design optimization for a Kaplan hydro turbine at a maximum water head of 2.6 m (8.5 ft), micro-sized horizontal Kaplan turbine with 7.6 cm (3.0 in) diameter that is featured fixed blades to attain the optimum performance for such type and size of hydro turbines. Optimization process includes solving design problems and enhance design development by applying a multi-disciplinary design optimization (MDO) technique. Varying the geometrical parameters of the turbine, i.e., dimensions, number of blades, blade wrap angles, and different rotational speeds (500–3000 RPM) are the relevant proposed disciplines of this study.

An in-house code is used for optimizing the geometrical parameters of the turbine. A numerical solution that utilizes computational fluid dynamics (CFD) for a 3D, turbulent, transient unsteady and swirl flow is developed using STAR-CCM+ software in conjunction with an experimental setup of a lab-sized closed-loop water system for validation. The performance of the turbine is predicted by evaluating the power output (in watts), mesh independency analysis is also presented for CFD results validation.

Two multi-simulation matrices were solved by using the high-performance computing (HPC) cluster of the University of Wisconsin-Milwaukee. First matrix includes different number of the blades (3, 4, 5, 6, and 7 blades) over six different rotational speeds (500, 1000, 1500, 2000, 2500, and 3000), while the second matrix includes 121 possible combinations of blade wrap angles starting at 60°-60° (hub-shroud) angle to 110°-110° angle with 5° increment alternated at both sides, the hub and the shroud.
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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Development of High Efficiency 5MW Class Gas Turbine the Kawasaki M5A
Authors: Ishihara Shinya , Terauchi Koji , Ikeguchi Takuya , Ryu Masanori
Published: November 2019

Kawasaki Heavy Industries (KHI) launched the M5A gas turbine with a rated output of 4.7MW and 32.6% of thermal efficiency at ISO operating conditions. This gas turbine was designed for combined heat and power application (CHP) with dry low emission (DLE) and the features are that it is compact and light-weight. It also has high efficiency (highest in class), suitable exhaust temperature for steam production and achieved the lowest level of exhaust emissions by using proven DLE technologies originating from other recent KHI gas turbines. The design philosophy was successfully applied to be based on previous reliable gas turbine structure and materials as well as using the state-of-the-art technology about aerodynamics and the cooling. The in-house verification tests have been conducted since 2016 to confirm design targets for performance, emissions, durability and operability. This paper describes the development process of M5A and includes technical features and validation test results.