bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two-Phase Cryogenic Expander for Nitrogen Rejection and Cooling Process in Natural Gas Applications
Authors: Karakas Enver S. , Stasenko David 
Published: September 2023

Abstract
A typical refinery process of natural gas requires cyclic cooling (liquefaction) and vaporization of the fluid in stages to separate and remove certain impurities, primarily nitrogen, from the ‘raw’ gas.
Natural gas from underground sources often has nitrogen contamination due either to its natural occurrence or from previous nitrogen injection to enhance recovery of the natural gas. Nitrogen content must be limited or reduced by a nitrogen rejection process in order to meet the heating value requirement for the natural gas. This process is fundamentally a refrigeration cycle, within which the process pressure must be reduced; traditionally via a throttling process with a Joule-Thomson valve. Replacing the Joule-Thomson valve with a two-phase flashing expander can improve the overall efficiency of this refrigeration process with enhanced cooling, and electrical power co-generation.
This paper considers prior art, and reviews the current design considerations and technical challenges for a two-phase expander to be used in the Nitrogen Rejection process. Hydraulic and aerodynamic components of such two phase expanders are reviewed, and their operational characteristics are studied in this paper. Thermodynamic analyses of cooling and liquefaction processes are conducted to quantify the benefits of two phase expanders in terms of cooling, energy recovery and production rate. Site operational data and performance characteristics of an actual two-phase expander are reviewed to better understand two phase expansion within the expander.
Assessing Transfer Matrix Models and Measurements Using Acoustic Energy Conservation Principles
Authors: Latour Véranika , Rajendram Soundararajan Preethi , Durox Daniel , Renaud Antoine , Candel Sébastien 
Published: September 2023

Abstract
Acoustic transfer matrices are now widely used in the analysis of combustion dynamics of gas turbines. The reliability of the analysis depends on the quality of the determination of the transfer matrices of the individual acoustic elements composing the overall acoustic network of the system. These matrices are, in some simple cases, deduced analytically, using one-dimensional acoustic modeling. However, for more complex elements, such as swirlers, perforated plates or injector units, the transfer matrix has to be obtained experimentally using an impedance tube. A few models that attempt to account for the dynamics of some key elements like the injector unit are also available in the literature. There are, however, uncertainties in the experimental determination of the transfer matrix coefficients and questions raised by the modeling so that it is worth examining experimental results and assessing transfer matrix models using acoustic energy conservation principles. The general idea is to consider the acoustic power flow in the element represented by the transfer matrix T, and compare the power input to the power output. This is best accomplished by obtaining a representation in terms of a scattering matrix S, which may be deduced from the transfer matrix T. It is first shown that standard models like those corresponding to a constant area duct or to an area change comply with acoustic energy conservation. This analysis is then employed to assess the L-ζ model that has been widely used to describe injection unit dynamics. It is shown that acoustic power is dissipated in the injection element only if a certain condition is met by the modeled transfer matrix coefficient T12. The expression that is commonly used for this coefficient fulfills this condition. The power dissipation in the injector is evaluated and shown to be linked to the head loss and typical Mach number in this unit. Finally, acoustic conservation principles are used to assess transfer matrices of a family of injectors determined experimentally and check that the data is compatible with these principles.
Performance Evaluation of an Axial Compressor With Modified Blades Using Leading Edge Tubercles
Authors: Sidhu Satpreet S. , Asghar Asad , Allan William D. E. 
Published: September 2023

Abstract
The performance of a Rolls-Royce A250 gas turbine axial compressor was evaluated for four different compressor configurations employing a flow control device called leading-edge tubercles. The tubercle shape was selected based on optimization performed in a 2-D compressor cascade for the design conditions of a first stage compressor rotor blade. The A250 compressor was tested without flow control to establish its compressor map for baseline performance. Tubercle shape was manufactured onto the leading edge of each compressor blade using a technique called Sinker EDM. An operational axial compressor with tubercle-modified rotor and stator blades was tested. For the final configuration, a compressor with modified rotor blades only was tested. The fully modified compressor showed slight improvements in the pressure rise along with increased mass flow rate, with a slightly open bleed valve at the fifth stage. At high speeds, the modified compressor configurations were unable to improve performance over the baseline. However, subsequent analysis revealed encouraging affects on stability. High frequency pressure transducer results showed that in the baseline compressor, stall precursors appeared first at the first stage that then propagated downstream in the compressor. The modified compressor completely eliminated the presence of stall cell in the first stages. With flow control, the stall developed at the last stage before propagating upstream. The challenging blade modification method precluded careful finishing of tubercle edges. Degraded modified compressor performance is attributed to this. Leading-edge tubercles showed potential for their application on compressors, demonstrating slight performance improvement in some ranges of operation and the elimination of stall cells known to lead to complete compressor stall in the baseline compressor.
The Hybrid Pathway to Flexible Power Turbines: Part A, Novel Autoencoder Methods for the Automated Optimization of Thermal Probes and Fast Sparse Data Reconstruction, Enabling Real-Time Thermal Analysis
Authors: Baker Mark , Rosic Budimir 
Published: September 2023

Abstract
The global drive towards renewable energy is imposing challenging operating requirements on power turbines. Flexible load-leveling applications must accept more frequent and demanding start-stop cycles. Full transient analyses are too computationally expensive for real-time simulation across all operating regimes so monitoring relies on sparse physical measurements. Alone, these sparse data lack the fidelity for real-time prediction of a complex thermal field.
A new hybrid methodology is proposed, coupling data across a range of fidelities to bridge the limitations in the individual analyses. Combining several fidelity methods in parallel: low-order models, corrected by real-time physical measurements, are calibrated with high-fidelity simulations. The multi-faceted hybrid approach enables the real-time speed of low-order analysis at high resolution. This paper series develops the critical enabling features of the hybrid method.
Real-time cross-fidelity data transition is fundamental to the hybrid methodology. A novel neural network autoencoder method is presented, facilitating complex thermal profile reconstruction. Uncovering a compressed latent space, autoencoders leverage underlying data features for fast simulation. Coupled with a dynamic mask and top-k selection, thermal probe placement can be automatically optimized. The autoencoder method is demonstrated on a turbine casing, reconstructing over 500 hours of transient operation in real-time, whilst reducing the required number of measurements by half.
Numerical Study of the Effect of Fuel Heating Value Change on Combustion for Siemens Energy Dry Low Emission Combustor
Authors: McManus Liam , Sadasivuni Suresh , Liu Kexin , Munktell Erik 
Published: September 2023

Abstract
Reacting flow simulation with lower or medium calorific value fuels is a challenge with the existing combustion models and chemical mechanisms. This paper attempts for numerical validation on the effect of fuel heating value or Wobbe Index (WI) of fuel on combustion performance for an industrial gas turbine Dry Low Emissions (DLE) combustor which is an SGT-300 twin shaft system. The engine produces up to 9 MWe power which was rig tested in Lincoln at High Pressure Air Facility (HPAF) with single combustor consisting of main burner, pilot burner, combustor can and transition duct. In this paper, the Simcenter STAR-CCM+® solver is used to perform numerical simulations of the DLE combustor in the HPAF rig configuration. Large Eddy Simulations with a Flamelet Generated Manifold (FGM) combustion model and kinetic rate closure are used. The GRI-MECH 3.0 chemical mechanism is used to generate flamelet manifolds for each configuration of varied calorific value. Change in fuel heating value was achieved through diluting natural gas with CO2 and CO2 volume concentration varied from 22.7% to 32.1% which resulted in WI from 30 MJ/m3 to 25 MJ/m3. Flame structure and combustion dynamics signatures were investigated in detail at ISO full load engine condition for these fuels and compared with UK natural gas. Results from numerical study were compared with those from HPAF test.
An Optimal CFD Strategy for Intake in Crosswind Conditions
Authors: Chennuru Venkata Y. T. , Zhao Fanzhou , Vahdati Mehdi 
Published: September 2023

Abstract
Crosswind can reduce the operability of an aeroengine significantly at static or near static operating conditions. CFD predictions of the flow at crosswind conditions will play an important part in future designs, however, accurate numerical predictions of the flow within the intake remain challenging even for simulations of cases with intake only. The main objective of this paper is to demonstrate the importance of numerical setup and to determine an optimal computational model for crosswind investigations that can be used by other researchers. By considering the flow to be inherently unsteady, the influence of inlet and exit boundary conditions, and grid sensitivity is studied by using URANS simulations. Numerical predictions of the time-averaged intake pressure recovery (IPR) and the motion of the vortex on the ground are compared against the existing experimental data. The results show that for an intake under crosswind, the ground vortex that forms under the intake and the in-duct separation, when present, exhibit unsteady behaviour that become stronger as the crosswind velocity is increased. The steady-state simulation is only representative at lower crosswinds. The intake flow separation and ground vortex predictions are influenced by the inlet boundary layer profiles. Moreover, acoustic reflection was observed at the intake exit boundary which propagates upstream, creating artificial unsteady frequencies in IPR. The reflection is generated from the use of uniform boundary conditions at the intake exit and is not dissipated in the grid due to the long wavelength; this can be mitigated by using a choked nozzle at the intake exit. Acoustic reflection was also observed at the far-field exit boundary. These reflections are caused from interaction of trailing vortex and far-field boundary.
Modeling, Analysis, and Control of the Power and Temperature Dynamics of a Heavy-Duty Gas Turbine
Authors: Müller Eric Andre 
Published: September 2023

Abstract
Operational flexibility of a gas turbine power plant crucially depends on an accurate feedforward control of the prime mover. Since the power & temperature dynamics of a gas turbine are characterized by a non-minimum phase transmission zero, the associated feedforward control problem cannot be solved through system inversion, as the resulting controller would be unstable. In this article, a model-based feedforward controller that overcomes the problem of the non-minimum phase transmission zero is derived based on a validated model of Ansaldo Energia’s GT36 gas turbine. The controller is designed to follow a reference model trajectory on the power output and to enable a configurable but consistent trade-off between temperature control performance and increasingly harsh actuator commands. In a simulation case study, the functionality of the controller is verified, and the specific benefits of its design are discussed. Finally, the strong dynamic capabilities of the GT36 are demonstrated by comparing the ideal response of the linear system with measured engine data in a rapid de-loading/loading transient.
Experimental Investigation of the Effect of Bleed on the Aerodynamics of a Low-Pressure Compressor Stage in a Turbofan Engine
Authors: Spanelis Apostolos , Denman Paul A. , Mariah Ian , Walker A. Duncan 
Published: September 2023

Abstract
The compression system in modern turbofan engines is split into several stages linked by s-shaped transition ducts. Downstream of the low-pressure system, a handling bleed is often required for off-design performance and/or to extract ice/water and foreign debris prior to the air entering the high-pressure compression stages. The inclusion of this bleed and various structural vanes can introduce unwanted component interactions and compromise the aerodynamic performance of the upstream low-pressure compressor stage and downstream transition duct. This paper presents an experimental investigation of the aerodynamic performance of a compressor transition duct and bleed for a very high bypass ratio turbofan. A fully annular, low-speed test facility incorporating a 1½ stage axial compressor was used to examine the mean and unsteady flow in the last stage of a low-pressure compressor and the downstream transition duct. The transition duct incorporated load bearing struts, including a so-called King strut with twice the thickness of the regular struts. The bleed utilized a 360° annular slot located on the casing immediately downstream of the low-pressure rotor and upstream of the outlet guide vane. The results showed that the King strut, caused a similar flow distortion and redistribution in the OGV like the Regular struts, and had otherwise imposed a negligible effect on overall performance over a range of rotor flow coefficients. The addition of bleed had a more notable effect, generating an increasing outboard bias in the rotor efflux, as the flow migrated towards the offtake. At the design flow operating point, the OGV were relatively insensitive to this until the highest bleed rate (18%) where evidence of stall was observed. At a lower operating point, the change of rotor swirl and additional OGV incidence caused earlier onset of stall and a full OGV stall was observed above 10% bleed. Increasing bleed was observed to cause a gradual increase in duct loss up to the point of OGV stall when losses increased more rapidly.
Development of 5MW Hydrogen Gas Turbine Suitable for Eco-Friendly Power Plant Energy Grid
Authors: Shin Youngjun , Cho Eun-Seong , Hwang Jeongjae , Kim Minkuk 
Published: September 2023

Abstract
Doosan, the Heavy-duty gas turbine OEM manufacturer, have been successfully achieving the progress of developing hydrogen gas turbine combustor. Considering the low hydrogen production rate, the safety of hydrogen flame, and above all, the connection with green hydrogen production through eco-friendly energy generation, we started to develop a 5MW small sized gas turbine for 100% hydrogen, and we plan to gradually expand it to medium and large sizes combustors.
This paper presents the results of testing four different types of good performance nozzles, selected from among the designed hydrogen concept nozzles with the idea for anti-flashback. The nozzles were verified and updated through commercial CFD analysis, and in this study, they were tested in an actual hydrogen atmospheric pressure test. The nozzle characteristics were compared and analyzed, and the results show that all nozzles performed well under base load conditions, with low NOx emissions and no flashback. Extreme conditions were also tested to check flame stability, such as the Lean blow out and the Flashback. The study concludes that the designed nozzles show promise for use in actual Full CAN combustors, and updates will be made to improve their shortcomings.
Experimental Investigation of Additional Loss Associated With Incoming Wakes in Low-Pressure Turbine Cascades
Authors: Kodama Hidekazu , Funazaki Ken-ichi 
Published: September 2023

Abstract
The present paper aims at experimentally investigating the influence of wake-passing frequency, Reynolds number and suction surface diffusion rate on the additional loss due to incoming wakes to the profile loss in low-pressure turbine (LPT) cascades and discussing a design guide for reducing the additional loss. Using a moving-bar mechanism, the unsteady effects of incoming wakes were measured in a low-speed linear turbine cascade facility. The wake-passing frequency was varied by adjusting the moving-bar speed. The different airfoils with different surface velocity distributions were tested to examine the effect of suction surface diffusion rate. For each test case in an unsteady flow condition, the additional loss due to incoming wakes was derived by subtracting the profile loss from the measured total pressure loss across the cascade. Here the profile loss was estimated by using the friction drag force, which was calculated by the measured surface velocity distribution, and the pressure drag force, which was calculated by the measured surface pressure distribution and the predicted base pressure. The resultant additional loss includes all kinds of losses associated with incoming wakes, such as mixing loss of incoming wakes enhanced in the blade passage and unsteady interaction loss between incoming wakes and surface boundary layers. It was demonstrated that, in an unsteady flow condition, a substantial performance improvement was obtained in the entire Reynolds number range by applying the surface velocity distribution with no laminar separation to a low solidity blade row.
Partially Premixed Hydrogen-Methane Flame Simulations at Relevant Gas Turbine Conditions With a Thickened Flame Model Enhancement
Authors: Meloni Roberto , Orsino Stefano , Ansari Naseem , Yadav Rakesh , Bessette Didier , Castellani Simone , Nassini Pier Carlo , Andreini Antonio , Boxx Isaac 
Published: September 2023

Abstract
The prediction of the behavior of stratified flames involving the hydrogen will represent a crucial task for the improvement of the Gas Turbine (GT) combustors performance in the next years. The Computational Fluid Dynamic (CFD) models usually employed to help the design definition need major revisions and improvements to provide reliable insights in this context.
In this paper, an enhancement of the standard Thickened Flame Model (TFM) will be introduced trying to adapt the transport equation source term of each species to the combustion regime, the latter identified by the local flame index value. Being the TFM mainly devoted to describing a perfectly premixed flame, its mathematical formulation needs be redefined when also the diffusive regime has to be accounted for. The proposed approach will be validated against detailed measurements executed on a Jet in Cross Flow (JICF) fed with two moderate volumetric contents of H2 in blend with CH4. The selected operating conditions are relevant for the transfer of the methodology to real GT applications in terms of both temperature and pressure of the oxidizer.
In particular, the ability of the model to predict the anchoring of the flame close to the fuel injection location only in the case of high H2 content (as highlighted by the experiments) will be investigated. Analogously, the correlation between the strain rate and the thermal field leading to a different flame anchoring mechanism of the jet when a low H2 mixture is considered will be addressed as well. The numerical findings in terms of flame position and morphology will be compared with the PLIF acquisition while the flow field will be characterized through the PIV measurements.
The Prediction of Condensation Characteristics of Supercritical Carbon Dioxide in the Laval Nozzle During Supersonic Flow
Authors: Huang Zhe , Shen Xin , Chen Laijie , Ouyang Hua , Du Zhaohui 
Published: September 2023

Abstract
The non-equilibrium condensation and nucleation process contribute to enormous challenges to accurately predict the condensation behaviors in rotating machines. Considering the similarity of flow, the analysis of the condensation characteristics in the Laval nozzle is the basis for the study in the compressor. In this paper, an Eulerian-Eulerian Source term (EES) numerical model is developed to investigate non-equilibrium condensation features in supersonic compressible flow in nozzle. High precision real gas property table is introduced to calculate the thermophysical properties of CO2 in nozzle. The difference of droplet distribution and liquid fraction between EES model and homogeneous equilibrium (HEM) model is discussed. The relationships between inlet parameters, condensation site and nucleation rates are also analyzed. The numerical analysis result shows that although the prediction deviation of EES model and HEM model at outlet temperature and pressure is less than 3%, the liquid mass fraction at the outlet of HEM model is 12% larger than that of EES model. Shock wave of supersonic flow causes the forward movement of condensation site in HEM model, indicating that HEM model might overestimate condensation characteristics and aerodynamic effects in the nozzle. Decreasing the inlet pressure and increasing the inlet temperature delay the occurrence of condensation and reduce the liquid mass fraction, but could also bring about the increase of the droplet average radius at the outlet. These results provide valuable suggestions in the analysis of non-equilibrium condensation characteristics of supersonic flow and the design of compressor inlet conditions.
Time-Frequency Analysis of the Synchronous Response of Rotor Components: A Guideline for the Parameters’ Choice
Authors: Carassale Luigi 
Published: September 2023

Abstract
The measured synchronous response of rotor components may be analyzed with two objectives. On the one hand, the estimation of the response amplitude is necessary for structural calculations such as the assessment of the low-cycle fatigue safety margin. On the other hand, it is used for system identification purpose with particular interest for damping. Both these tasks can be carried out efficiently and accurately using the time-frequency analysis based on the continuous wavelet transform. A major issue that limits a wide use of this tool is the lack of criteria to guide the analysist to a proper choice of the parameters involved in the wavelet transform. This paper discusses this problem from a theoretical and practical point of view and provides a criterion valid for the analysis of the response during resonance crossings.