bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combustion Diagnostics and Emissions Measurements of a Novel Low NOx Burner for Industrial Gas Turbine Operated With CO2 Diluted Methane/Air Mixtures
Authors: Babazzi G. , Galeotti S. , Picchi A. , Becchi R. , Cerutti M. , Andreini A. 
Published: September 2023

Abstract
While the employment of Exhaust Gas Recirculation (EGR) is a well-established technique in Internal Combustion Engines to limit NOx emissions, its adoption in Gas Turbine engines hasn’t yet found a practical application due to its expensive and complex installation that doesn’t justify the emissions reduction when compared to already established DLN combustion technologies. EGR becomes an interesting option in GT engines considering the possibility of increasing the CO2 content of the exhaust gases to improve the efficiency of Carbon Capture and Storage (CCS) units. However, the decrease in oxygen content of the combustion air is extremely challenging in terms of combustion stability and therefore of engine operability.
In the present work, a low NOx burner was studied at ambient pressure in a reactive single burner test rig. The burner was fed with methane and characterised in terms of emissions and stability limits at different operating conditions. In addition, the flame position and shape were studied through OH* chemiluminescence imaging together with the flow field thanks to PIV measurements. The effects of CO2 addition on the flame were then investigated at different EGR increasing levels, highlighting the impact of the oxygen content on the combustion reaction intensity. Variations in emissions and burner stability limits in terms of maximum sustainable CO2 content were also studied, to detail the burner operating window. Data have been thoroughly analysed to gather information on the burner behaviour to support the design of new technical solutions capable of ensuring both proper flame stability and low CO and NOx emissions.
Optical Based Emission Monitoring Systems for Combustion Turbine SCR Process Control and CEM Applications
Authors: Himes Richard 
Published: September 2023

Abstract
In parallel with the trend of increasing gas generation, regulatory scrutiny of utility gas turbine emissions is projected to increase as utilities operate their gas turbine fleets dynamically in response to the variability of wind and solar generation resources. While SCR systems have historically provided significant incremental NOx control capability beyond dry low NOx combustor emission levels, associated ammonia injection process control systems are still reliant on extractive based sampling approaches, with up to several minute response time delays. These response time delays in ammonia injection control can lead to time periods of over, or under injection of SCR ammonia during load cycling. In-situ, optical based monitoring systems have the potential to improve SCR process control time response, while also reducing lifecycle operating and maintenance costs associated with NOx/diluent monitoring systems used for SCR process control.
The current paper assesses the accuracy associated with several in-situ optical monitors applied on the stack of a gas turbine combined cycle unit. Moreover, the demonstration explores novel optical monitor configurations for multi-specie measurements that could ultimately reduce the number of measurement paths required for typical continuous emission monitoring (CEM) purposes (e.g., NO, NO2, CO, NH3, CO2, O2 and H2O).
In regard to potential CEM applications, the current paper also examines in-situ optical monitor calibration approaches required under the current CEM regulatory framework, associated issues and measurement configurations that could potentially comply with current CEM quality assurance requirements.
Increased Productivity for Film Cooling Simulations Using Solution-Based Mesh Adaption
Authors: Norman Adam , Arguinzoni Carlo , Pons David , Zori Laith 
Published: September 2023

Abstract
High-pressure turbine blades in a gas turbine experience extreme thermal stress due to the high-temperature flow coming from the combustion chamber. To minimize thermal fatigue and increase durability, the blades can be cooled with an internal and external cooling system. These systems consist of intricate passages that feed a large number of small holes, creating a film on the blade surface. Hole parameters such as the location, pattern, size, and shape must be determined to maximize the cooling effectiveness requiring a large number of design variations.
In the design phase, numerical tools, such as CFD, are employed to quickly simulate design variations and reduce the overall product design phase timeline. The generation of a high-quality mesh for complex blade cooling geometries can be extremely cumbersome and time-consuming. Additionally, knowing precisely where the hot streaks will occur, a priori, is difficult if not impossible. As a consequence, a general over-refinement of the mesh in non-key areas can occur to ensure the flow is properly resolved. This requires extended timelines to mesh and solve cases with large cell counts.
In this work, a methodology is presented that avoids the issue of mesh over-refinement without sacrificing the solution’s accuracy. Solution-based mesh adaption is employed to dynamically add mesh refinement to capture the necessary physics for film cooling simulations. Initially, the methodology is verified on a single-hole configuration cooling a flat plate. This adaption framework is then applied to a standard gas turbine vane to demonstrate the flexibility of the solution-based adaption for any film-cooled geometry. These two cases are compared to mesh-independent solutions to show a reduced time to the solution while maintaining solution accuracy.
Experimental Investigation on Microsecond Pulsed Plasma Supported Biogas Combustion
Authors: Ghabi Ahlem , Boushaki Toufik , Escot Bocanegra Pablo , Robert Eric 
Published: September 2023

Abstract
This paper evaluates the effect of a microsecond pulsed plasma (MPP) on the stabilization and emission characteristics of non-premixed biogas/air flames with various CO2 contents. The MPP is generated by a unique DC-pulsed power generator providing high voltage (HV) pulses over a wide range of pulse repetition frequencies. The burner configuration is made up of two concentric tubes in which a swirler is placed inside the annular part, ensuring the oxidizer’s rotation. The central tube delivers the fuel through an injector placed close to the burner exit. Electrical diagnostics, including voltage, were performed. OH* chemiluminescence measurements were done to describe the structure and stability of the flame. Results showed that plasma generated by microsecond HV pulses can improve flame stability. In this regard, the distribution of key active species in the burner was studied via optical emission spectroscopy (OES). The results revealed that the pulsed plasma generates chemically active species such as excited N2*, CH*, OH* molecules, and H* and O* atoms, thereby improving flame stability. The dependence of the emitted species intensities on plasma parameters was investigated in detail. It is demonstrated that MPP can drastically enhance the dynamic flame stability of swirling non-premixed biogas flames, especially at lean operating conditions. In addition, NOx and CO emissions were studied over a wide range of pulse repetition frequencies. It is seen that the pulsed plasma increases NOx emission slightly and significantly reduces CO concentration in the flue gases.
Reynolds Number Calibration Coefficient for Multi-Hole Pneumatic Probes
Authors: Bachner Johannes , Pahs Andreas 
Published: September 2023

Abstract
The calibration of an additively manufactured cone-shaped five-hole probe is presented for subsonic and transonic flow. The probe has a thermocouple and an additional base pressure hole for transonic measurements. The Reynolds number is varied independently of the Mach number by adjusting the pressure level in a closed test section in three steps. Overall, a Reynolds number range from 3,000 to 20,000 is covered. A significant Reynolds number effect is observed for the pressure coefficients. More than 1,100 test points not contained in the calibration data are evaluated and measurement deviations calculated. The points are distributed over six pressure levels and four Mach numbers. Measurement deviations increase with increasing Reynolds number differences between the calibration and the test points. The Mach number measurement in transonic flow using the base pressure hole is particularly sensitive to the Reynolds number. The root mean square error of the Mach number increases by up to factor of 15 if Reynolds number similarity is not maintained. This demonstrates the importance of Reynolds number similarity when calibrating probes with a base pressure hole. The effect on the flow angles is relatively low with the exception of the radial flow angle in transonic flow. Here, the Reynolds number effect reaches a maximum of 1 deg. A calibration coefficient is proposed that decreases measurement deviations by allowing interpolation between calibration data at different Reynolds numbers and can easily be introduced to most evaluation schemes.
Development and Validation of an Accurate, Minimal-Input Mean-Line Method for the Off-Design Performance Prediction of an Axial Compressor Stage, Using a Compressor-Diffuser Analogy
Authors: Barlin Daniel , Fuls Wim 
Published: September 2023

Abstract
The analysis and performance prediction of gas turbines benefits greatly from the use of one-dimensional mean line modelling, as it can provide reasonably accurate results while requiring fewer geometric inputs and significantly lower computational expenses when compared to higher order methods such as CFD. However, even mean line codes may be limited by the amount of geometric and operational data available, often restricted by Original Equipment Manufacturers for proprietary reasons. This often results in a greater number of assumptions and tuning factors required in order to achieve accurate results. This paper documents the progress in development of a one-dimensional modelling method which requires minimal geometric inputs and tuning factors for analysing the performance of a transonic axial compressor stage, for use in a gas turbine. The minimal input model is achieved through an analogous modelling methodology, whereby the stage’s rotor and stator rows are modelled as simple diffusers with flow areas approximately equal to those in the compressor stage. A design point calibration operation is performed to estimate all diffuser flow path areas using a set of industry-knowledge-based assumptions, and blade angles are estimated using widely adopted correlations from open literature. The estimated geometries are then used as inputs for an off-design numerical model. An area correction factor calibration is required to better match the pressure ratio performance map. The model was validated against four well documented NASA axial compressor stages with good agreement. The modelling methodology presented an efficient means of predicting compressor stage pressure ratio performance with acceptable accuracy while requiring minimal inputs. Further work is still required to improve the loss characteristics such that the work and efficiency prediction accuracy is improved.
Effect of Fuel Reactivity and Operating Conditions on Flame Anchoring in the Premixing Zone of a Swirl Stabilized Gas Turbine Combustor
Authors: Tartsch Simon , Flebbe Saskia , Marques de Sousa Ponte Germano J. , Sattelmayer Thomas 
Published: September 2023

Abstract
Flashback with subsequent flame anchoring (FA) is an inherent risk of lean premixed gas turbine combustors operated with highly reactive fuel. The present study has been performed to characterize flame stabilization in the premixing zone of a lean premixed swirl stabilized burner and to identify critical combustion characteristics. An optically accessible burner was used for experimental investigations under atmospheric pressure and elevated preheat temperatures. The air mass flow rate, global equivalence ratio and preheat temperature were systematically varied to identify critical operating parameters. Hydrogen-natural gas mixtures with hydrogen mass fractions from 15 to 100 % were studied to evaluate the impact of fuel reactivity. The air-fuel mixture was ignited with a focused single laser pulse to trigger FA in the premixing zone during steady operation. High speed imaging with OH*-chemiluminescence were applied to observe flame characteristics and evaluate flame anchoring propensity. Flame anchoring limits (FAL) are reported in terms of the minimum global equivalence ratio at which the flame was blown out of the premixing zone within a critical time period. A comparison of characteristic time scales at FAL shows that the main impact during flame anchoring is given by the fuel reactivity and to some ex tent by preheat temperature. A Damköhler criterion is derived from the FAL that allows prediction of FA propensity based on operating conditions and 1-D reacting simulations.
Influence of Turbulence Modeling on the Simulation of Miniaturized Levitating Centrifugal Pumps for Cardiac Assistance
Authors: Gil Antonio , García-Tíscar Jorge , Quintero Pedro , Mares Andrea 
Published: September 2023

Abstract
Due to the limited availability of compatible heart donors, one of the most promising treatments for patients suffering from cardiac insufficiency is Mechanical Circulatory Support using Left Ventricular Assist Devices (LVAD). The main device in the market, HeartMate3, is a low size centrifugal pump incorporating a magnetic levitation system. This device assists the ventricle in generating the needed pressure head to provide the required cardiac output of blood flow through the circulatory system. However, the blood within an LVAD experiences a wide range of non-physiological phenomena such as high shear stresses and device-induced turbulence. Although there are multiple references approaching the behavior of these devices both experimentally and numerically, hardly any of them has analyzed the influence of turbulence modeling on the quantification of performance variables. Furthermore, the performance of LVAD must be evaluated through all possible working conditions. Therefore, the current work presents a set of Unsteady Reynolds-Averaged Navier Stokes and Large Eddy Simulations of the HeartMate3 operating under various conditions. Both the hemodynamic performance and the hemocompatibility of the device are considered. In addition, a 0D Windkessel model is imposed at the outlet to account for the resistance and compliance of the vascular system downstream of the device.
Experimental Investigation of High Frequency Flame Response on Injector Coupling in a Perfectly Premixed Multi-Jet Combustor
Authors: Rosenkranz Jan-Andre , Sattelmayer Thomas 
Published: September 2023

Abstract
High frequency injector-coupled thermoacoustic instabilities are a major threat to multi-jet combustors in rocket and gas turbine engines. The complex three-dimensional acoustic coupling between the combustion chamber and injector acoustics cause local fluctuations in heat release. In turn, multiple thermoacoustic feedback mechanisms close the thermoacoustic loop and serve as a source of the thermoacoustic instability. Except for the flame deformation and flame displacement mechanism, the underlying feedback mechanisms for high frequency instabilities are to a large extent unknown. The paper at hand gives new insights into the injector-coupled convective driving mechanisms that are present in multi-jet combustors at perfectly premixed conditions. The forced flame response to the first transverse combustor mode is investigated for two distinct injector tube lengths: one with an axial acoustic velocity node and one with a velocity anti-node coupling at the injector-combustor interface. Phase locked OH* images reveal convectively transported coherent vortex structures as the main source of the flame response. The origin of the flame response can be linked to the axial acoustic velocity at the injector-combustor interface using numerical simulations. Both configurations show a positive Rayleigh Integral and a clear oscillation of the heat release fluctuations in-phase with the acoustic pressure fluctuations over the full period. In similarity to time delay models in low frequency thermoacoustics, a wave number model is proposed to estimate the local flame response due to feed flow modulations and validated with the experimental results.
Effects of the Seal Wire on the Nonlinear Dynamics of the Aircraft Engine Turbine Blades
Authors: Tüfekci Mertol , El Haddad Fadi , Salles Loïc , Setchfield Richard , Renson Ludovic 
Published: September 2023

Abstract
Complicated systems made of multiple components are known to be difficult to model, considering their solutions can change dramatically even with the slightest variations in conditions. Aircraft engines contain such complicated systems, and some components in aircraft engines’ turbines can cause significant changes in the system’s overall response. Hence, this study is focused on investigating the behaviour of a turbine blade of an aircraft engine and the effects of the contact between the blade and the seal wire on the dynamics of the blade-disc system. The investigation is performed via various numerical simulations in time and frequency-domains. One sector of the bladed disc is modelled using the finite element method with the lock plate and the seal wire imposing cyclic symmetry boundary conditions in the static, modal, and frequency-domain forced response analyses. In time-domain analyses, the cyclic symmetry is replaced with simplified displacement restricting boundary conditions. The time-domain analysis contains steady-state forced responses of the system. The results show that contact with the seal wire is not a major source of nonlinearity and damping. The contacts with the lock plate contribute more to the vibration damping than the seal wire. However, compared to the contacts at the root of the blade, both components remain less significant with regard to frictional damping and nonlinearity.
A New Concept for Improving the Efficiency of Gas Turbines for Power Plant Operation
Authors: Sunkler Rupert , Stalder Jean-Pierre 
Published: September 2023

Abstract
A method for enhancing the efficiency and power output of gas turbines is presented here. The concept relies on increasing the machine’s pressure ratio without modification to the existing baseline Brayton cycle by adding independent topping gas generators in parallel. The mass flow through the compressors of the topping gas generators is higher than the baseline cycle. This additional mass flow is bled off from the topping compressors to do work through an external air expander. The conditions in the baseline cycle turbine remain unaffected.
These topping gas generators are envisioned as being installed in place of the existing combustor(s), acting as high-pressure compressor and turbine, with the original GT compressor and turbine acting as their low-pressure counterparts. The air mass flow after the low-pressure compressor is divided into several parallel partial flows, which are fed to the gas generators. The gas generators consist of a compressor (in most cases a 1-stage centrifugal compressor will suffice), combustion chamber and turbine. They are, as a matter of fact, dimensionally small high-speed gas turbines that are free-running, like turbochargers or like the HP-section of aero engines.
The concept can be applied to both new gas turbine designs and retrofits, resulting in increased power output and thermal efficiency. The paper describes the concept and presents sample calculations with various gas turbine types, indicating the possible achievable benefits under various assumptions.
GPU-Accelerated High-Fidelity Rotating Detonation Engine Simulations Using an Extended Flamelet Progress Variable Approach
Authors: Shunn L. , Ham F. , Elasrag H. A. , Hoke J. , Schumaker S. Alexander 
Published: September 2023

Abstract
A fast approach is introduced to aid the evaluation and design of rotating detonation engines (RDEs) using large eddy simulation (LES). The new approach implements an extended flamelet progress variable model in the GPU-accelerated charLES CFD solver from Cascade Technologies. In the extended flamelet approach, tabulated reaction rates from unstretched laminar premixed flames are parameterized and scaled to describe the high-pressure detonation conditions in RDEs. The reaction rate scaling parameters are trained using Zeldovich-von Neumann-Döring (ZND) detonation solutions over a wide range of operating conditions. Sensitivity analysis is performed to assess the impact of the regression algorithm and best-fit scaling parameters on the reconstructed reaction rates. The method is applied to LES of the AFRL 6-inch rotating detonation engine with non-premixed injection of hydrogen in air. The GPU-resident charLES solver demonstrates speedup of almost two orders of magnitude compared to conventional CPU-based solvers and achieves turnaround of high-fidelity RDE simulations in less than one day on modest GPU resources — a critical threshold to enable the use of LES within a design cycle. The combination of reduced-order flamelet modeling and efficient GPU acceleration makes the overall approach a viable candidate for design exploration and optimization of practical RDEs.
Complete Engine Soak-Back Using Coupled Lattice-Boltzmann and Nodal Network Simulations
Authors: Popescu Stefan , Burkia Alessandro , Mech Thomas , Zapata Alexandre , Combébias Sebastien 
Published: September 2023

Abstract
Numerical methodologies have been developed for a number of years, in order to predict engine soak-back in earlier design stages. This current paper is the second phase of a methodology development using coupled lattice-Boltzmann and nodal network simulations for the prediction of soak-back of a helicopter engine and its engine bay. The previous phase of the study (see GT2020-16096) focused on the engine bay, simulated with lattice-Boltzmann methods, whereas the core flow was simply modeled with imposed Heat Transfer Coefficients (HTC) and temperatures. Conduction and radiation within the solid parts are solved by a thermal solver, coupled with the CFD solver calculating convective heat transfers.
The current phase presented here extends the previous methodology by increasing the complexity of the core flow modeling. Two additional numerical approaches are considered: (1) a full simulation of the engine core flows and engine bay using lattice-Boltzmann simulations, and (2) a coupled methodology between lattice-Boltzmann simulations (for the engine bay) and 3D nodal network (for the core flows).
On one side, this study compares numerical predictions to tests data when available. On the other side, the numerical methodologies are compared using more detailed flow analysis and solid temperature evolutions, together with simulation turnaround times. All methodologies show promising results that could improve current industrial development processes.