bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and Numerical Investigation of Forced Ventilation Loss in Gas Turbine Package
Authors: Asti Antonio , Crugnola Federico , De Leo Elena , Lucherini Gabriele , Minotti Stefano , Singh Rajnish Kumar 
Published: September 2023

Abstract
Whenever a gas turbine is installed inside an acoustic enclosure, a ventilation system is required to cool down the package and dilute any accidental gas leakage. Due to the possible presence of gas, all items installed inside the enclosure shall be suitable and hence certified as per hazardous area requirements to prevent them from being source of ignition. For this reason, the correct operation of the ventilation system is essential to meet the certification limits and consequently to safely run the gas turbine train. A malfunction of this system can result in a reduction or a complete loss of ventilation flow in the worst case. In this event, an emergency shut down of the gas turbine train is triggered by the control system after a short transient operating condition. A robust design of a gas turbine package shall also consider such transient condition of ventilation loss to encompass all possible operating scenarios and to verify that each item stays within the certification limits during this time frame. Furthermore, each item, including the engine itself, must not fail and remain ready for the next restart.
Since ventilation fans are usually driven by AC power motors, AC power loss is the most common cause of ventilation loss. For this reason, Baker Hughes performed an experimental test on a full scale package of a Nova LT family turbine. The real scenario occurring in situ in case of AC loss was exactly replicated and several measurements were acquired with dedicated instrumentation installed inside the package. The purpose of this test was to check the thermal field inside the gas turbine enclosure and the amount of natural convection flow which is generated by the “chimney/stack effect”, in order to verify that the certification limits were not exceeded during the transient event of ventilation loss.
Additionally, the natural convection flow inside the GT internal path (intake, engine and exhaust) was also measured to better understand the contribution given by this flow in terms of heat removal from the engine casing. Measurements confirmed that the combined effect of both flows was sufficient to guarantee an adequate ventilation cooling of the package without impacting the package design. Moreover, the naturally established flow was sufficient also to avoid any possible rotor lock in, so that the engine stays ready for restart as soon as normal conditions are restored.
From the numerical point of view, a CFD model was built and run replicating the same transient scenario. The model was then fine-tuned and validated using the experimental data. In this way, having a reliable predictive method, it was also possible to simulate the natural convective flow and its related thermal field when modifications are introduced in the ventilation ducts design, as well as for gas turbine models that are different from the tested one.
Dynamic Performance of Liquid Smooth Annular Seal Operating in the Transition Regime
Authors: Hyun Seung-Hyeop , Delgado Adolfo 
Published: September 2023

Abstract
This paper presents the experimental leakage and rotordynamic performance for a liquid smooth annular operating in the transition regime. The test conditions include pressure differentials up to 64 bars with 1∼2 bar increments for 6 rotor speeds (2.5, 3.8, 5, 7.5, 8.8, and 10 krpm) as well as non-rotating rotor case under zero pre-swirl condition. The rotordynamic coefficients for all the test conditions are obtained by pseudo-random excitation of the seal at multiple subsynchronous frequencies. By considering the transition Reynolds number (1000 &lt; Re &lt; 3000) and Taylor Number (Ta) vs Axial Reynolds Number (Rez), the variations in the direct stiffness coefficients (K) can be found to be an indirect indicator of the flow regime transition boundaries. The direct stiffness K resulting from the Lomakin and hydrodynamic effects significantly drops until Rez reaches approximately 1500. For higher Rez, K increases mainly due to hydrodynamic effects. When K drops, the cross-coupled stiffness k, the direct damping C and the cross-coupled virtual mass m increase while the cross-coupled damping c and virtual mass M decrease. None of predictions based on either laminar or turbulent flow show the variations in rotordynamic coefficients obtained from experimental results. The leakage is not highly influenced by rotor speeds for low speed cases crossing laminar boundary as ΔP increases, however, results for higher speeds in the superlaminar region show reduced leakage rates.
Aeroacoustic Scaling of Axial Low-Pressure Fans With Leading Edge Serrations
Authors: Balde Nina Maimuna , Biedermann Till M. , Kameier Frank , Pohlmann Tobias 
Published: September 2023

Abstract
Previous as well as ongoing studies have shown that bioinspired modifications of the leading edge of axial fans, so-called leading edge serrations, have beneficial effects on sound radiation in rotating systems such as a broadband noise reduction. The objective of this study is to elaborate on the comparability of two geometrically similar low-pressure axial fans that differ in fan diameters. For this purpose, a fan design based on the geometric characteristics of an existing fan, which had been tested in previous studies, was developed with and without leading edge serrations at a scale of 1:3. Extensive experiments were carried out to gather detailed data on the aerodynamic and aeroacoustic performance of the specimen. Similarity laws and non-dimensional parameters are used to investigate whether a transferability comparison of the aerodynamic and aeroacoustic experimental results of these geometrically similar axial fans is possible. The latter also includes an analysis of the spectral range. The results prove that it is possible to derive a comparability of the aerodynamic parameter of the flow coefficient and thus of the flow rate of the fans. Furthermore, a correlation between the noise reduction potential of the two models can be established through spectral Strouhal number normalization. The proposed aerodynamic and aeroacoustic coherences ensure transferability from the model fan to an upscaled fan and thus allow generalized statements to accurately transfer the aeroacoustic potential of leading edge serrations for different geometrically similar fan applications.
Hot Section Thermal Imaging Technology Development: Lessons and Implications for Engine Focused Transient Measurement Techniques
Authors: Anthony Richard J. , Haldeman Charles W. 
Published: September 2023

Abstract
This paper describes non-proprietary rotating high-pressure turbine (HPT) blade thermal imaging results taken in a transient, full-scale, short-duration turbine blowdown facility as part of a larger instrumentation development program for operational aeroengine applications. While thermal imaging of stationary parts is routine, and several institutions use thermal imaging in turbine rig operations, the leap to capture HPT rotor blade transients inside operational aeroengines entail unique challenges. This paper describes an approach that inverts the traditional development path with early exposure to the real engine environment first, followed by turbine rig testing in the AFRL Turbine Research Facility (TRF) for cost-effective system improvement and enhancement between engine tests. Due to the TRF’s transient, short duration, and relatively low temperature operation, results show it is ideal for testing extreme limits of temporal, thermal, and spatial resolution needed for capturing fast engine transients. This demonstrated a new role for the TRF later in the development cycle; specifically, improving instrumentation hardware and software for engine use, while continuing its role as a design validation rig for turbomachinery research and development. Since the first thermal imaging of full speed rotating HPT blades in an operational aeroengine in 2008, the “inverted” instrumentation development path described in this paper provides lessons for future gas turbine sensing developments supporting integrated prognostic health monitoring, digital twin/digital thread, and fleet sustainment.
Experimental Investigation of Combustion Instabilities in a Laboratory-Scale, Multi-Can Gas Turbine Combustor
Authors: Beita Jadeed , Talibi Midhat , Rocha Nuno , Ezenwajiaku Chinonso , Sadasivuni Suresh , Balachandran Ramanarayanan 
Published: September 2023

Abstract
Can and can-annular (can-type) combustors are widely employed in stationary gas turbines. While majority of combustion instability research so far has focused on single can combustors, studying combustion dynamics in multi-can configurations holds more practical relevance. In can-type combustors, the annular gap between the transition ducts and first stage nozzles, known as the ‘cross-talk’ region, promotes strong can-to-can acoustic interactions. In this study, coupled interactions between neighbouring cans are experimentally investigated in a laboratory-scale, atmospheric, two-can combustor rig. Results demonstrate that an out-of-phase longitudinal mode, characterised by pressure anti-nodes in the cans and a pressure node in the cross-talk area, is preferentially excited in the multi-can combustor. Investigation into the effects of combustor flow rate and cross-talk geometry on the can-to-can dynamics revealed an increase in the amplitude of the limit cycle oscillations with mass flow rate, cross-talk volume and cross-talk exit area reduction. However, these factors exerted a weak influence on the frequency of the oscillations and did not impact the mode shape of the resonant can-to-can mode. These findings would help better understand the complex dynamical interactions that occur in multi-can systems towards model validation and tool development, while highlighting the significance of factoring in thermoacoustic aspects in the design of the combustor-turbine interface.
Co-Firing of Hydrogen and Natural Gas in a Practical DLN Combustor Model
Authors: Zhao Rang , Igie Uyioghosa , Abbott David , Wiranegara Raditya Yudha 
Published: September 2023

Abstract
To reduce carbon dioxide emissions, the combustion of natural gas-hydrogen blends in a lean premix gas turbine combustor has been investigated. Previous studies have mostly investigated the fuel blends at relatively low pressure (up to 5 bar) with relatively low hydrogen concentrations (up to 50vol%) on lab-scale or generic burner configurations. However, the influence of higher pressure and higher hydrogen content (over 50vol%) has not been widely studied, particularly on a practical industry-scale lean premixed burner as presented in this study. Such an operation is more challenging as it increases the turbulent flame speed gradient, which is an important factor in determining the likelihood of boundary layer flashback. A preliminary RANS-based Computational Fluid Dynamics (CFD) study has been conducted using ANSYS Fluent 2021R1, employing the Realizable K-Epsilon turbulence model and the Flamelet-Generated Manifold (FGM) combustion model. The combustor consists of a diffusion pilot and premixed main fuel nozzles. Methane-hydrogen blends of up to 90vol% hydrogen were investigated at a fixed fuel energy input. 100vol% methane at 15 bar pressure was taken as the baseline reference case. To investigate the flame characteristics, contour plots of OH mass fraction, equivalence ratios and temperatures (at different planes) are presented.
This study shows that the expected reduction in the flame length with increasing hydrogen concentration occurs up to 40vol%. Significantly different flame shapes (as indicated by OH contours) were seen at higher hydrogen content. For this model, the flashback occurred at 90vol% H2 as indicated by a premature development of the flame within the nozzle of the main fuel burner. NOx emissions are shown to progressively rise with increasing hydrogen content up to 60vol% but reduce as the hydrogen content increases to 70vol%. The decrease appears to be related to an improvement in the quality of fuel-air mixing. It is important to note that the apparent rate of increase in NOx with increasing hydrogen is dependent on the reporting approach used. When reporting conventionally (parts per million by volume corrected to 15% O2 on a dry basis) the increase is significantly greater than when reporting on a mass per fuel energy input basis (gram per Joule). Reporting in the conventional manner disadvantages hydrogen because of the impact of oxygen consumption and water production on the corrections.
Novel Architectures for Transcritical CO2 Refrigeration Cycle Using Rotary Pressure Exchanger
Authors: Sarawate Neelesh , Thatte Azam , Samudrala Omprakash 
Published: September 2023

Abstract
This paper highlights utilization of a rotary gas pressure exchanger (PX G) to increase efficiency of CO2 refrigeration systems using CO2, which is a natural, low global warming (GWP) refrigerant. PX G uses the high-pressure discharge of the condenser/gas cooler as a motive fluid to compress the low-pressure flash gas with minimal external energy input, thus reducing the power consumption of the main compressor. PX G simultaneously expands the high-pressure supercritical/liquid CO2 into a two-phase CO2 ready for heat absorption, thus also emulating the functionality of a typical high-pressure expansion valve.
Several new architectures using PX G are presented to increase the coefficient of performance (COP, i.e. efficiency) of such refrigeration cycles. Because of inherent small pressure losses in PX G, as well as in the gas cooler circuit and piping, two additional low differential pressure auxiliary lift devices are added to help achieve optimal volumetric flow rate through PX G. To avoid the need for auxiliary high-pressure lift devices, additional architectures explore utilizing a secondary gas cooler operating at a reduced pressure compared to the primary gas cooler. Another architecture repurposes the existing low temperature compressor to supply the low-pressure inlet of PX G, thus further eliminating auxiliary low-pressure lift devices.
This paper also describes the modeling method to solve the system of simultaneous energy balance and mass balance equations governing the cycle integrated with PX G. Mass flow constraints based on PX G’s internal physics and density ratio between low-pressure and high-pressure streams entering PX G are also put in place. Various performance metrics such as overall system COP, work done by MT and LT compressors, liquid content after expansion through PX G, flash gas production, and superheat control are analyzed for a wide range of ambient temperatures, evaporator duty, and load split between MT to LT evaporators. This paper further investigates the optimization of key system parameters such as gas cooler pressure and receiver pressure.
Turning Region Heat Transfer in Five, Stationary and Rotating, Multi-Pass Channels With Various Aspect Ratios
Authors: Chen I-Lun , Wright Lesley M. , Han Je-Chin 
Published: September 2023

Abstract
This work summarizes studies that experimentally investigated the effect of rotation on heat transfer in the 180-deg tip and hub turns of cooling channels with various aspect ratios (ARs). The studied AR ranges from 1:4 to 4:1, which is the typical range within turbine blades. In addition to the smooth surface case (baseline case), the cases with 45-deg angled ribs and turning vanes are also included in this work. For several designs, the effect of channel orientation with respect to the angle of rotation is also investigated. This work covers a wide range of Reynolds and buoyancy numbers. The rib turbulators are found to have higher heat transfer enhancement and larger disturbance on the flow impingement on the tip and hub walls in channels with a wider aspect ratio. The rotational effect is reduced by the presence of ribs and turning vanes, and it is also reduced in the blade-shaped channels with the angled rotation feature. The tip wall heat transfer is increased by rotation due to the pumping effect from the centrifugal force; however, the hub wall heat transfer is reduced. The effect of rotation is most prominent in the first pass of the channels and is gradually mitigated in the following pass after the turns. This work provides stationary and rotational heat transfer coefficients in the tip and hub turning regions in blades, and heat transfer correlations for a variety of cooling channel designs are generated, which is of benefit to the gas turbine community.
A Free Streamline Model for Fully Separated Turbomachine Flows
Authors: Prasad Dilip 
Published: September 2023

Abstract
This paper describes the use of the free streamline approach to determine flows in fully separated cascades, and to thereby provide a rational basis for estimating the performance of axial turbomachinery at severely off-design conditions. On the assumption of two-dimensional, incompressible flow, the free streamlines that bound the separated region are determined using the hodograph method, in which the methods of complex analysis are used to define a tractable numerical problem. The resulting jet-wake flow profile at cascade exit is then presumed to undergo mixing at constant-area, from which performance parameters for the cascade can be determined. The proposed method is verified by comparison against flat plate cascade solutions and by checks against momentum conservation. Validation of the free streamline approach is carried out by comparison against several cascade configurations for which experimental data and simulation results are available. In general, the predictions based upon the present theoretical model are found to be good, especially for negative incidences such as those that occur in the compressor section of an engine operating at sub-idle conditions. This suggests that the present approach can be used in the estimation of turbomachinery performance maps far from the design point, especially during early design phases.
Development of a 300 MWe Utility Scale Oxy-Fuel sCO2 Turbine
Authors: Moore J. Jeffrey , Neveu Josh , Bensmiller Jason , Replogle Cole , Lin Jianliang , Fetvedt Jeremy , Cormier Ian , Kapat Jayanta , Fernandez Erik , Paniagua Guillermo 
Published: September 2023

Abstract
A 300 MWe direct-fired supercritical carbon dioxide (sCO2) oxy-fuel turbine is being developed that will burn natural gas-fired, coal syngas and even hydrogen mixtures capable of 1,150°C turbine inlet temperature at 300 bar. This design will significantly improve the state-of-the-art for thermal efficiency and results in a high-pressure stream of CO2 with 98%+ carbon capture, making the power plant near emission-free and more efficient than Natural Gas Combined Cycle (NGCC) plants with carbon capture. This power plant will be capable of burning coal through gasification and cleanup of the synthesis gas (syngas). sCO2 power cycles are a transformational technology for the energy industry, providing higher efficiency heat source energy conversion for conventional and alternative energy sources. Oxy-fuel sCO2 cycles take these advantages even further, utilizing higher firing temperatures, improved efficiency, and simpler carbon capture strategies. This turbine will require cooled turbine nozzles and blades as well as advanced thermal management systems to accommodate these high temperatures. The cooled blade heat transfer correlations required new test programs at higher Reynolds number than air-breathing gas turbines for impingement, serpentine, and pin-fin regions. Novel blade optimization was performed to maximize aerodynamic efficiency, while minimizing cooling flows. A turbine layout was generated utilizing individual combustor cans with cooled liners feeding into a 6-stage axial flow turbine with cooled stator nozzles and turbine blades. The case design and thermal management preliminary design will be described. Experimental heat transfer and material testing will be presented as well. Finally material test results both with and without thermal barrier coatings at 780°C will be presented.
Coarse Droplet Measurement at the Last Stage Stator Exit of a Four-Stage Scaled Steam Turbine Using an Optical Backscatter Probe
Authors: Sasao Yasuhiro , Senoo Shigeki , Bosdas Ilias , Kalfas Anestis 
Published: September 2023

Abstract
Size and velocity distributions in polydisperse coarse droplets are important to estimate and reduce erosion damage and wetness losses in wet steam turbines. Diameters and velocities of coarse droplets are measured by an optical backscatter probe downstream of the last stage stator in a four-stage model steam turbine at the rated condition.
The droplet diameters distribute in the range from 30 to 90 micrometers. The Sauter mean droplet diameter is about 57 micrometers and the maximum droplet diameter is 88 micrometers. The corresponding Weber numbers are 11.4 and 17.6 respectively in the Sauter mean and maximum diameters. The Weber numbers are generally consistent with calculated values by both Kelvin-Helmholtz and Rayleigh-Taylor instability models. The mass flow rate and number of the coarse droplets is larger in the wake region from the stator, because the coarse droplets might be mainly generated by atomization of water films and rivulets on the stator. The larger droplets in diameter over 60 micrometers tend to axially deflect from steam flows. The Sauter mean diameters are slightly larger downstream from suction surface of the stator. The droplet velocities distribute in the range up to 40 m/s. The smaller droplets have the higher velocities as expected. Mean velocities are also consistent with predictions by the instability models. The measured number density distributions of coarse droplet diameters and velocities with the spatial resolution could improve the accuracy in models for blade erosion and wetness loss from models based on mean or maximum droplet diameter.