bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a Dynamic Turbine Expansion Model Using a Paired Thermofluid and FEA Methodology
Authors: Ross Michael , Fuls Wim 
Published: October 2022

Abstract
With increased pressure for conventional coal-fired power plants to adopt a flexible operating principle, an increased need for computationally inexpensive thermal and structural turbine models has been observed. This paper documents the formulation of a paired thermofluid and FEA turbine modelling methodology to predict the radial and axial clearances within a 600MW candidate steam turbine during a full cold start procedure. This study formulates a method for sizing and modelling a representative turbine with limited OEM input through the implementation of the Nozzle Analogy theory for axial, multistage steam turbines. Following the development of a full turbine process model and representative 3D FEA turbine model, a successful validation of key turbine temperatures and differential expansions was carried out using real-world plant data within a high level of accuracy. The modelling methodology presented a computationally inexpensive method to predict internal turbine temperature boundaries as well as the structural behaviour of turbine components under transient loads, and proved invaluable in a thorough understanding of flexible turbine operation.
Lean Stability Limits and Exhaust Emissions of Ammonia-Methane-Air Swirl Flames at Micro Gas Turbine Relevant Pressure
Authors: Avila Cristian , Wang Guoqing , Zhu Xuren , Es-Sebbar Et-Touhami , Abdullah Marwan , Younes Mourad , Jamal Aqil , Guiberti Thibault , Roberts William L. 
Published: October 2022

Abstract
This study reports on the lean stability limits and exhaust emissions of ammonia-methane-air swirl flames with varied ammonia fuel fractions. A reduced-scale burner was manufactured, inspired by Ansaldo’s micro gas turbine AE-T100 burner, and it was installed inside a high-pressure combustion duct to operate at 4.5 bar. This pressure corresponds to that found at full-load in the actual micro gas turbine’s combustion chamber. The lean stability limits were measured by igniting the flame at an equivalence ratio of ϕ = 0.85 and then progressively decreasing the equivalence ratio until lean blowout. Emissions of CO2, NO, and N2O were recorded for different equivalence ratios and ammonia fractions. Rich flames at an equivalence ratio of ϕ = 1.20 were also considered. Results show that the equivalence ratio at lean blowout increases when the ammonia fraction increases and that all the ammonia fractions tested lead to flames more prone to lean blowout than the pure methane reference flame. The CO2 emissions are monotonically reduced by increasing the ammonia fraction, both for lean and rich flames. The NO emissions exceed many regulations limit regardless of the ammonia fraction for all lean equivalence ratios. N2O emissions are almost negligible, except for very lean equivalence ratios where the N2O mole fraction in the exhaust reaches unacceptably high values. Only rich ammonia-methane-air flames show good NO and N2O performance. Therefore, FTIR analysis was carried out to quantify the amount of the unburnt NH3 in the exhaust for these flames. Results show that unburnt NH3 concentration is invariant, around 200 ppmv, between 0.70 ≤ XNH3 ≤ 0.95. Data reported in this study provide insights for future work on combustors and after-treatment systems towards zero-emissions micro gas turbines.
Design of a Blowing Type Flow Treatment to Complement Casing Treatments for Compact High-Pressure Compressor Rear Stages
Authors: Köhler Christian P. , Kendall-Torry Christofer , Helcig Christian , Gümmer Volker 
Published: October 2022

Abstract
A common way to increase the operating range of rotor tip limited compressor configurations is the application of casing treatments (CT). However, the resulting strengthening of the rotor tip flow is accompanied by a radial re-balancing effect in the compressor’s flow path. This effect weakens the hub regions downstream of the CT. Consequently, a premature compressor stall can occur near the compressor hub. This paper presents the numerical design efforts for a hub strengthening flow treatment to leverage the potential of CTs within a compact high-pressure compressor (HPC) rear stage concept. A baseline HPC stage with large rotor tip clearances and stage loading is used as a starting point. An increase in compressor operating range substantiates within the rotor tip critical baseline HPC as axial slot CTs are applied. However, a premature stall initiation at the downstream stator hub occurs due to the radial re-balancing effect caused by the CT. Hence, a blowing-type flow treatment (FT) is introduced to delay the formation of the hub corner stall. Different geometrical variations of this FT type are tested numerically via a design of experiments (DoE). Finally, URANS simulations utilize this FT together with CTs to assess the changes in compressor operating behavior. The simulations show an enhancement of the stator operability due to a delay of the onset of the hub corner stall. By applying additional FTs, the adverse effects of the CT on the downstream stator can be partially compensated, and the potential of the HPC design can be leveraged.
Investigation of the Map Width Improvement in a Radially Reduced Diffuser Design Concept for a Centrifugal Compressor
Authors: McLaughlin Laura , Spence Stephen , Rusch Daniel , Stuart Charles , Geron Marco , So Kwok Kai , Fischer Magnus 
Published: October 2022

Abstract
Often, an improvement in performance at one operating point in a compressor/turbine operating map will lead to a reduction in performance at another area. For example, improving the efficiency of a compressor at design point (DP) may result in a reduction of efficiency at other operating points or it may result in a reduced stable operating range.
In order to reduce the compressor cost and weight, a 15% radial reduction was applied to the diffuser passage length of a high pressure ratio centrifugal compressor. The diffuser endwall was diverged to achieve an appropriate area ratio from diffuser inlet to outlet. Two different vane shapes were considered with the radially reduced diffuser passage. The first diffuser vane was a scaled version of the baseline airfoil vane shape and this was used to develop an understanding of the impact of the passage length reduction and diverging endwall. The second vane geometry was parameterized using an unconventional method derived from published literature and optimized to improve performance at DP.
Increased losses were generated through the diffuser passages of the radially reduced designs, but this was compensated for by lower losses through the volute due to more desirable flow at volute inlet. As a result, the radially reduced designs not only matched the performance of the baseline configuration, but also succeeded in achieving a marginal efficiency improvement. Furthermore, despite not being one of the goals of the optimization procedure, an extension of the stable operating range of 36% and 20% at the highest speed condition was achieved for the scaled and optimized designs, respectively. The current study focuses on understanding the physical reasons that generated this significant enhancement to the compressor operating range.
In order to acquire the desired understanding, experimental data is presented to validate the Computational Fluid Dynamics (CFD) model and a detailed numerical investigation is presented to explain the changes in the flow field within the radially reduced designs. The study focuses on low flow rate operating points, necessitating the use of an Unsteady Reynolds Averaged Navier-Stokes (URANS) approach to analyse the flow. Detailed scrutiny of the flow field revealed a secondary flow feature in the diffuser passage which resulted in higher diffuser passage losses at DP but stabilised the flow as it developed for lower mass flow rate operating points.
100-Hour Test of an Inside-Out Ceramic Turbine Rotor at Operating Conditions
Authors: Dubois P. K. , Picard B. , Gauvin-Verville A. , Méthot P. , Landry-Blais A. , Jean L.-P. , Richard S. , Plante J.-S. , Picard M. 
Published: October 2022

Abstract
Converting sub-MW turbine rotor blades to ceramics is not a trivial endeavour, but the promise of a substantial increase in turbine inlet temperature (TIT), and therefore cycle efficiency and power density, could mean wide use in upcoming, distributed power, turboelectric aircraft. The inside-out ceramic turbine (ICT) rotor configuration attempts to address this by loading ceramic blades in compression, as centrifugal force pushes them against a rotating structural composite shroud. This paper reports significant experimental progress in the development of ICT rotor technology, aimed at the development of a high-efficiency, turboelectric powerpack.
A 20-kW scale, single spool, recuperated ICT was operated with monolithic silicon nitride blades, for a total of 113 h above 1100 °C, including 13 h at the design tip speed of 400 m/s and a cumulative 100 h at 360 m/s, with no critical failure. ICT rotors sustained short excursions with TIT up to 1200 °C and tip speeds up to 430 m/s in hot conditions, and 500 m/s in ambient conditions. An ICT rotor was successfully integrated within a complete recuperated turbogenerator with a nested high speed electric motor. Results suggest that further work on an ICT turbogenerator should enable it to reach a TIT of 1275 °C, a target to achieve 45 % cycle efficiency in the sub-MW range.
Application of the Harmonic Balance Method for Large Spread Multiple Frequency Scales
Authors: Biesinger Thomas , Kölzer Maximilian , Schukmann Alexander , Roclawski Harald , Kainz Marc , Godin Philippe , Morales Juan Carlos , Zori Laith 
Published: October 2022

Abstract
This paper presents the application of the harmonic balance method to periodic turbomachinery flow problems containing multiple fundamental frequencies. It is well known that the solution convergence of a transient turbomachinery flow using classical integration methods is computationally intensive and requires the integration for multiple periods to achieve a converged periodic solution. The computational effort is even higher when multiple fundamental frequencies (vastly different time scales) are modeled since the time stepping required is limited by the higher frequency in the flow. Unlike the classical time integration methods, the multifrequency harmonic balance method is very well suited for these applications since it allows for much faster calculations than the standard time marching algorithms. In addition, to resolve all the fundamental frequencies and higher harmonics, the current implementation of the harmonic balance method allows for solutions on unequal time interval distributions of the time planes. Given a user-defined list of frequencies that govern the flow problem, this method utilizes an optimization strategy to compute the time planes. There are two simulation cases of interest: aerodynamic performance and forced response analyses, both with different accuracy requirements. The number of required frequencies is dependent on the goal of the simulation. For aerodynamic performance analysis, global quantities such efficiency, pressure ratio, etc. can be predicted with fewer fundamental frequencies than forced response analysis where accurate local flow details demand a higher number of fundamental frequencies.
The advantages of the multifrequency harmonic balance are illustrated by modeling two radial turbine configurations subjected to an inlet pulse from a reciprocating engine. Not only the expected trends such as higher-modes modeling granularity and time transient accuracy are shown, but also the calculations agree well with experimental data. The computational effort can be up to tenfold lower than the standard time-marching simulations. Machine aerodynamic performance predictions from the harmonic balance method are compared to accurate time-marching solutions and experimental data measurements. The efficiency of the computation is also discussed. The second example will compare the predicted surface excitation from the harmonic balance method vs. the time-marching solution.
History of Steam Expansion Machines Seen as Polytropic Efficiency Achievements
Authors: Wettstein Hans E. 
Published: October 2022

Abstract
Among the heat to power cycles the historically first successful technologies used cycles with steam expansion machines in its core. In the first phase as of the eighteenth century, reciprocating steam engines dominated. As of 1890 steam turbines were developed, which replaced the reciprocating steam engines until around 1930 with the exception of steam locomotives and some other niche applications. Up to now in steam cycle technology mostly the isentropic efficiency definition for expansion is used. Such numbers depend both on the dissipation and on the pressure ratio.
In history the overall pressure ratio of steam cycles has developed from low single digit values to over 3000. Thus it is interesting to consider the achievements of this technology especially for different pressure ratios with an efficiency definition, which is completely independent of the pressure ratio. Such a definition is well established in the form of the polytropic efficiency. This is the most used isentropic efficiency minus the heat recovery effect. The latter depends on the dissipated heat within the pressure drop and it grows with increasing pressure drop. The polytropic efficiency definition assumes a constant dissipation rate along the expansion change of state in contrast to the isentropic efficiency.
Predicting and Validating Spatial Distributions of Particulate Deposition in Gas Turbine Components
Authors: Gaskell Jack G. , Vadgama Nikul , Villain Florian Y. A. , Beal Simon , McGilvray Matthew , Gillespie David R. H. , Littley Benjamin 
Published: October 2022

Abstract
Cooling passages and the secondary air system of gas turbine components are prone to blockage from sand, dust and ash. The ability to model deposition accurately using CFD would allow the prediction of in-service performance degradation and the design of deposition-tolerant hardware. Predictions of deposition require accurate modelling of particle transport and wall interactions. Bounce stick models predict whether a particle will bounce, stick, or shatter upon impact and calculate rebound trajectories. Turbulent transport models allow the interaction of particles with near-wall turbulent structures to be predicted in RANS CFD solutions. This paper implements a Continuous Random Walk (CRW) transport model with a Discrete Elements Methods (DEM) based bounce stick model to predict deposition in commercial CFD software. The resulting spatial trends of deposition are compared with experimental data of particle deposition in an S-bend. The case considered is representative of the flow and metal conditions, particle size and loading distribution, and passage geometry seen in high pressure turbine blade cooling passages. Numerical predictions of deposition distribution show good qualitative agreement with experimental data. This validates the combined CRW/DEM approach for modelling the location of particulate deposition in gas turbine components. The approach is therefore suitable to assess and compare the susceptibility of components to particulate damage in industry. To the author’s knowledge, this is the first example in the open literature of experimentally-validated deposition trends in CFD. It was found that a deposit evolution and erosion model is essential to predict deposit height numerically. Particle tracking simulations without turbophoresis modelling showed significant differences in particle impact velocities and locations, justifying the use of the CRW model. The inclusion of the Magnus force produced considerable differences in quantitative and qualitative measures of deposition throughout the domain, demonstrating the importance of modelling collision-induced rotation in particle tracking. The performance of the DEM bounce stick model was favourable compared to energy-based alternatives which showed reduced accuracy in inertia-dominated regimes where multiple bounces occurred per particle. On average, eleven impacts were observed for each injected particle, reinforcing the dual importance of accurate bounce stick and turbulent transport models.
Numerical Prediction of Thermomechanical Sensitivity of the First Stage Nozzle Guide Vane With Film Cooling
Authors: Khumhaeng Siwanart , Suksa Thitapa , Laohalertchai Nutcha , Chaiprasit Benyapa , Chotroongruang Thanapat , Prapamonthon Prasert 
Published: October 2022

Abstract
Practically, a gas-turbine engine’s first-stage nozzle guide vane (NGV) must operate under extreme conditions induced by high temperatures from burned gases, causing severe damage to the vane, such as cracks or fatigue failures. As a result, the first stage NGV’s lifespan is shortened. In other words, the first stage NGV’s lifespan is determined by the vane material’s durability. Therefore, effective cooling systems and thermal barrier coating (TBC) are provided. This paper presents a numerical prediction of the thermomechanical sensitivity of the first stage NGV with film cooling under aerothermal conditions and TBC using a 3D CFD/CHT approach with a static structure model for a steady temperature analysis. Turbine inlet temperature (TIT), coolant inlet temperature (CIT), blowing ratio (BR), and TBC thickness, which are key factors for gas turbines’ performance improvement, are used as independent variables. An examination of vane cooling performance is presented in the first part, followed by a prediction of the thermomechanical sensitivity of the vane under the four variables in terms of von Mises equivalent stress and strain in the second part. The findings obtained from both parts show that the relationship between cooling performance and thermomechanical characteristics is sensitive to the influences of turbine inlet temperature (TIT), coolant inlet temperature, and TBC thickness. In addition, the findings indicate the role of the blowing ratio in thermal and mechanical sensitivity for the film-cooled vane.
Measured Leakage and Rotordynamic Force Coefficients for Two Liquid Annular Seal Configurations: Smooth-Rotor/Grooved-Stator Versus Grooved-Rotor/Smooth-Stator
Authors: Childs Dara W. , Yang Jing , San Andrés Luis , Torres Rueda Jose M. , Moreland J. Alex 
Published: October 2022

Abstract
This paper reports and compares the experimental results of leakage and dynamic force coefficients for two liquid annular pressure seals, one having a smooth-rotor/circumferentially-grooved stator (SR/GS), the other one with a circumferentially-grooved rotor/smooth-stator (GR/SS). Differing only in the grooves’ location, the GR/SS seal’s geometry and operating conditions are representative of those in electrical submersible pumps (ESPs) used for oil recovery. Supplied with an ISO VG2 oil at 46 °C, both seals have the same diameter D = 102 mm, length-to-diameter ratio L/D = 0.5, and nominal land clearance Cr = 0.203 mm. The seals have 15 circumferential grooves with groove and land lengths equal to 1.52 mm. Test variable ranges include: (a) shaft speeds (ω) ranging from 2 to 8 krpm (shaft surface speed ∼ 43 m/s), and (b) pressure differences (ΔP) from 2 to 8 bar. Upstream of the test seals, three separate pre-rotation rings generate a range of inlet circumferential velocities (entrance swirl). Under all conditions, the GR/SS seal leaks about 10% less than the SR/GS seal. For both seals, the direct stiffnesses (KXX, KYY) have low magnitudes that drop with increasing ω; in some cases, they turn negative at 6 krpm. The GR/SS seal produces cross-coupled stiffnesses (KXY, KYX) that are ∼1.5 times larger than those for the SR/GS seal. Under the same conditions, the SR/GS seal is more stabilizing as its direct damping and added mass coefficients are ∼ 20% larger than those for the GR/SS seal. Instability issues are likely to arise with either seal geometry because negative KXX and KYY drop a pump critical speed, aggravating the well-known destabilizing coefficients KXY and KYX. The whirl frequency ratio (WFR) combines the effects of the cross-coupled stiffness, direct damping and cross-coupled mass terms, thus providing a good basis for comparing two seals’ stability characteristics. Overall, the WFR magnitudes for the GR/SS seal are about three times higher than those for the SR/GS seal. Note that, irrespective of the inlet swirl condition, the GR/SS approaches a WFR ∼ 0.50 for operating shaft speeds greater than 4 krpm. At the lowest shaft speed (2 krpm), the WFR &lt;&lt; 0.5 for the low inlet pre-swirl ring, whereas WFR &gt; 0.8 for the medium and high pre-swirl rings. For the SR/GS seal, the WFR ∼ 0.2 at the highest shaft speed of 6 krpm, and not affected by the inlet pre-swirl condition. On the other hand, at the lowest shaft speed, the WFR ranges from 0.5 to 0.75 for the SR/GS seal with medium and high pre-swirl rings. At this speed, the WFR = 0 with the low inlet pre-swirl ring. Hence, to enhance the operational stability, an effective swirl brake that could drop the inlet pre-swirl ratio upstream of a seal is helpful for the GR/SS seal out to 4 krpm and for the SR/GS seal out to 6 krpm.
Experimental and Numerical Investigations of the Non-Equilibrium Condensation on the Performance and the Flow Pattern in Steam Turbine
Authors: Tabata Soichiro , Segawa Kiyoshi , Takahashi Tadashi , Aoyagi Jin 
Published: October 2022

Abstract
In this paper we present the test results of measurements in a scaled model steam turbine test operated at Mitsubishi Heavy Industries, Ltd. In order to understand the aerodynamic behavior of the low-pressure steam turbine, numerical and experimental results obtained on a five-stage scaled steam turbine module are presented.
In order to investigate the effect of non-equilibrium condensation on the performance of the low-pressure steam turbine, inlet temperature change tests were conducted, and wetness loss change was evaluated experimentally. Besides, the overall performance and the flow pattern were evaluated numerically by the commercial CFD code ANSYS CFX. The wetness loss and flow pattern change due to the non-equilibrium process was numerically evaluated by ANSYS CFX. Besides, the pressure ratio and loading distributions in low pressure turbine stage were evaluated numerically by ANSYS CFX. In a turbine stage in which the non-equilibrium condensation occurs, the pressure ratio is decreased, while the pressure ratio of the adjacent stage is increased. The flow pattern obtained by the non-equilibrium condensation modeling CFD was good agreement with that of tests data.
In order to more accurately capture the flow pattern characteristics by CFD analysis, it is necessary to consider non-equilibrium condensation modeling. Therefore, it was found that CFD is useful for understanding the flow pattern of a low-pressure steam turbine.