Article
Thermodynamics
Changxiao Shao, Kazuki Maeda, Matthias Ihme
Summary: This study investigates the relative importance of direct and indirect combustion noise in a realistic gas-turbine combustor. Findings show that both direct and indirect noise contribute significantly to the overall noise emission at certain operating points, with direct noise dominating at higher frequencies.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Mechanics
Animesh Jain, Andrea Giusti, Luca Magri
Summary: In this study, a low-order model is proposed to predict the impact of reacting inhomogeneities on indirect noise in nozzle flows. The physical sources of sound and their mechanisms are identified. The study shows that hydrogen inhomogeneities have a larger influence on indirect noise than methane inhomogeneities.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
Mitchell L. Passarelli, Timothy M. Wabel, Arin Cross, Krishna Venkatesan, Adam M. Steinberg
Summary: This study investigates cross-frequency coupling between different signals in a model aeronautical gas turbine combustor, with non-stationary oscillations exhibiting temporal changes in frequency and amplitude. The experimental data supports the notion of mutually coupled self-oscillators.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Acoustics
Lorenzo Pinelli, Michele Marconcini, Roberto Pacciani, Friedrich Bake, Karsten Knobloch, Paolo Gaetani, Giacomo Persico
Summary: This article presents a detailed study on the clocking effect between entropy wave spots and stator leading edges in a high pressure turbine stage. The study includes experimental campaigns and numerical simulations, and the results show good agreement between the experiments and simulations. This study also demonstrates the potential of using simulations for the design optimization of combustor/turbine coupling.
JOURNAL OF SOUND AND VIBRATION
(2022)
Article
Thermodynamics
Yongbin Ji, Bing Ge, Shusheng Zang
Summary: The cooling performance of an effusion-cooled gas turbine combustor is investigated experimentally and numerically. The study reveals that orthogonal cooling holes have higher cooling effectiveness, while backward injections can resist impingement impact and achieve the highest cooling effectiveness.
APPLIED THERMAL ENGINEERING
(2022)
Article
Thermodynamics
Wookyung Kim, Jeffrey Cohen
Summary: This study investigated the effectiveness of implementing a plasma discharge to improve combustor dynamics and flame stability. The results showed that plasma discharge can significantly reduce pressure fluctuation levels, extend lean blowout limits, but also lead to substantial incomplete combustion.
COMBUSTION SCIENCE AND TECHNOLOGY
(2021)
Article
Energy & Fuels
Pedro M. de Oliveira, Daniel Fredrich, Gianluigi De Falco, Ingrid El Helou, Andrea D'Anna, Andrea Giusti, Epaminondas Mastorakos
Summary: The ultralow emission combustor concept based on flameless oxidation demonstrates the potential for achieving clean and efficient combustion of aviation kerosene. It shows soot-free and single-digit NOx levels under atmospheric conditions, attributed to a unique combustor mixing configuration. The experimental results are supported by numerical simulations, providing further insights into mixing and air dilution effects on emissions and combustion completeness.
Article
Thermodynamics
Navin Mahto, Satyanarayanan R. Chakravarthy
Summary: This study presents the parametric design space study and optimization of a gas turbine combustor using computational fluid dynamics simulations. The combustor performance was evaluated based on various parameters, and the response surface methodology was used to analyze the effects of design variables. The exclusion of blow-off design points improved the accuracy and smoothness of the response surface predictions.
APPLIED THERMAL ENGINEERING
(2022)
Article
Thermodynamics
Changxiao Shao, Davy Brouzet, Nicholas Rock, Matthias Ihme
Summary: This study investigates the combustion noise from a realistic gas-turbine combustor using a hybrid simulation framework. The results show that the level of flow field unsteadiness is higher at take-off condition, leading to an overall increase in noise emissions. In addition, the indirect noise from compositional inhomogeneities exceeds the entropy noise.
APPLICATIONS IN ENERGY AND COMBUSTION SCIENCE
(2022)
Article
Thermodynamics
Varun Shastry, Eleonore Riber, Laurent Gicquel, Benedicte Cuenot, Virginel Bodoc
Summary: Large Eddy Simulations were conducted to compare the characteristics of traditional JetA-1 fuel and an alternative At-J fuel in the LOTAR combustor. The simulations revealed that JetA-1 fuel forms combustion regime with the possibility of droplet clusters burning individually, while At-J fuel achieves complete combustion through premixed lean reactions. The study highlights the need to develop models capable of identifying and handling combustion regimes encountered in such spray flames.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Seongpil Joo, Jongwun Choi, Min Chul Lee, Namkeun Kim
Summary: A new method for early detection of combustion instability based on spectral features shows the best performance in terms of speed, sensitivity, and accuracy compared to conventional methods. However, it may misclassify unstable flames when multi-mode combustion instability occurs, leading to the modification of spectral features for better detection.
Article
Chemistry, Physical
Zhaoxing Li, Suhui Li
Summary: This paper conducted a kinetics modeling study on the NO(x) emission characteristics of a staged rich-lean combustor cofiring NH3/H-2 mixture, revealing that the equivalence ratio in the rich-burn stage is a key factor influencing NOx emissions. Balancing NO production and unburnt NH3 in the rich-burn stage is crucial for reducing NOx emissions.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Nanoscience & Nanotechnology
Y. Gong, W. P. Jones, A. J. Marquis
Summary: In this study, Large Eddy Simulations were used to investigate indirect noises generated by compositional disturbances in a non-isotropic convergent nozzle. The simulations successfully reproduced the processes of direct and indirect noise generation, showing good agreement with experimental measurements. Different injection positions and operating conditions were explored, with findings indicating a close relationship between air mass flow rate and direct and indirect noise amplitudes.
Article
Thermodynamics
Kaiyuan Zhang, Zhiyu Li, Jun Wu, Zhigang Li, Jun Li
Summary: This study investigates the cooling performance of the combustor-turbine interface cooling system by solving the Reynolds-Averaged Navier-Stokes equations. It is found that optimizing the nozzle guide vane cooling design can significantly improve cooling effectiveness and reduce heat flux. The Marquardt cooling scheme shows better cooling performance under high mass flow ratio conditions, but the mass flow ratio has a more significant impact on the cooling effectiveness regardless of the mass flow ratio condition.
APPLIED THERMAL ENGINEERING
(2023)
Article
Thermodynamics
Yeseul Park, Minsung Choi, Dongmin Kim, Joongsung Lee, Gyungmin Choi
Summary: This study investigates the impact of fuel exceeding the allowable Wobbe index range on gas turbine system performance through thermodynamic analysis. Different fuel compositions and diluent methods have varying effects on the operability and main parameters of each component.
Article
Physics, Fluids & Plasmas
Francisco Huhn, Luca Magri
Summary: This study proposes a versatile gradient-free optimization method for chaotic acoustics, which overcomes the challenges of exponential growth of perturbations, slow convergence of solution statistics, and discontinuous variations of time-averaged acoustic energy. The method utilizes reservoir computing based on echo state networks, which accurately predicts the dynamics of chaotic acoustics and allows efficient exploration of the thermoacoustic parameter space. The findings demonstrate the effectiveness of the method in minimizing the time-averaged acoustic energy of chaotic oscillations and its potential for hands-off optimization of chaotic systems.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Thermodynamics
Luis Lopez, Andrea Giusti, Eva Gutheil, Hernan Olguin
Summary: This study investigates the rates of heat release and soot emission in counterflow flames fueled by ethanol and n-butanol. The results show that ethanol flames release more heat and less soot compared to n-butanol flames. Additionally, the fuel injection phase plays a crucial role in optimizing combustion processes.
Article
Thermodynamics
Daniel Fredrich, Andrea Giusti
Summary: This study numerically investigates the evaporation and autoignition behavior of a three-component kerosene surrogate under various operating conditions. The results show that gas temperature affects preferential evaporation and droplet composition, while pressure and dilution level have a significant impact on autoignition. Droplet preheating can be used as a design parameter to control autoignition delay time.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Efstratios M. Kritikos, Aditya Lele, Adri C. T. van Duin, Andrea Giusti
Summary: This study investigates the effect of externally applied electrostatic fields on the chemical kinetics of n-dodecane combustion at high temperatures through reactive Molecular Dynamics simulations. The results show that strong external electric fields are required to induce changes to the chemical kinetics, and the consumption rates of n-dodecane and oxygen exhibit different trends under various electrostatic field strengths. The kinetics of oxygen molecules play a primary role in determining the reaction behavior under external electrostatic fields.
COMBUSTION AND FLAME
(2022)
Article
Mechanics
Daniel Fredrich, Erik Weiand, Andrea Giusti
Summary: This study proposes the use of electrostatic fields to control the position of electrically charged fuel droplets, enhancing pre-evaporation of liquid sprays in confined spaces. Numerical simulations and a deterministic model were used to investigate the feasibility and effects of this approach. Results show that external electrostatic fields can change droplet trajectory and potentially stabilize the spray position, improving evaporation rate and mixing quality.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Thermodynamics
Epaminondas Mastorakos, Savvas Gkantonas, Georgios Efstathiou, Andrea Giusti
Summary: This article proposes a new stochastic model to simulate the propagation of fires, which combines the Lagrangian transported probability density function method for turbulent reacting flows and the cellular automata approach for forest fires. Unlike conventional cellular automata models for fires, the ignition of cells in this model is determined by a random walk that mimics turbulent convection and diffusion of hot gases and firebrands from upwind and neighboring fire fronts. The model aims to approximate the key physics while speeding up computation by using only a few terrain-related inputs and tunable parameters.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Efstratios M. Kritikos, Andrea Giusti
Summary: Reactive molecular dynamics simulations were conducted to investigate the combined effects of iron nanoparticles and external electrostatic fields on the combustion of n-dodecane. The results showed that iron nanoparticle additives significantly accelerated fuel and oxidizer consumption, demonstrating a catalytic behavior. The application of an external electrostatic field further increased the consumption rate and led to the formation of a anisotropic shell with varying chemical composition.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Chemistry, Physical
Efstratios M. Kritikos, Aditya Lele, Adri C. T. van Duin, Andrea Giusti
Summary: Reactive molecular dynamics and density functional theory are used to study the effects of external electrostatic fields on hydrocarbon reaction kinetics. The results show that the MD method is suitable for modeling electrodynamics. External electric fields can cause catalysis or inhibition of oxidation reactions, but have no effect on pyrolysis reactions. The reaction kinetics is also affected by applied external forces, and electric fields can affect the alignment of polar species. Under strong electric fields, fuel, oxidizer, and product molecules experience acceleration and reduced vibrational energy. This study improves the current methods used in MD and develops novel methodologies for modeling reacting flows under electrostatic fields.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Mechanics
Animesh Jain, Andrea Giusti, Luca Magri
Summary: In this study, a low-order model is proposed to predict the impact of reacting inhomogeneities on indirect noise in nozzle flows. The physical sources of sound and their mechanisms are identified. The study shows that hydrogen inhomogeneities have a larger influence on indirect noise than methane inhomogeneities.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Navraj S. Lalli, Li Shen, Daniele Dini, Andrea Giusti
Summary: Previous studies have shown that a magnetic field can alter the drainage in soap films containing magnetic particles. However, it is still unclear whether a magnetic field can control the rate of drainage and film stability, as well as its effect on key drainage mechanisms. This experimental study investigates the behavior of soap films containing magnetite nanoparticles, revealing that a magnetic field can have a stabilizing or destabilizing effect on magnetic soap films depending on their composition.
Article
Thermodynamics
Luigi Miniero, Khushboo Pandey, Daniel Fredrich, Sergey Shcherbanev, Ulrich Doll, Andrea Giusti, Nicolas Noiray
Summary: Increasing regulations on aviation pollutant emissions require rapid adoption of new combustion technologies. The concept of moderate or intense low-oxygen dilution (MILD) combustion has been investigated and shows promise. The MILD regime involves recirculating hot combustion products to increase reactant temperature, resulting in distributed reactions and lower flame temperatures.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Leon C. Thijs, Efstratios M. Kritikos, Andrea Giusti, Giel Ramaekers, Jeroen A. van Oijen, Philip de Goey, XiaoCheng Mi
Summary: Molecular dynamics simulations were used to study thermal and mass accommodation coefficients for the combination of iron(-oxide) and air. The obtained coefficients were applied in a point-particle Knudsen model to investigate the combustion behavior of (fine) iron particles, considering chemisorption and the Knudsen transition regime.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Jonas E. Petersen, Saaras Kapur, Savvas Gkantonas, Epaminondas Mastorakos, Andrea Giusti
Summary: A physics-based model combining cellular automata and virtual Lagrangian fire particles is developed to predict wildfire propagation and include fire extinction actions. The model is coupled with Monte Carlo Tree Search (MCTS) algorithm to optimize the allocation of fire extinction actions and has been validated with model fires and applied to realistic scenarios. The study finds that MCTS optimization outperforms human intuition for medium-scale fires and enhances human decision-making capabilities for large-scale fires with the use of convolution-based terrain re-sampling.
COMBUSTION SCIENCE AND TECHNOLOGY
(2023)
Article
Thermodynamics
Majd Sayed Ahmad, Efstratios M. M. Kritikos, Andrea Giusti
Summary: The role of nanomaterials in the consumption of hydrocarbon fuel vapor is investigated, and it is found that both aluminum and iron nanoparticles act as catalysts and enhance fuel decomposition. The presence of aluminum leads to faster particle heating and fragmentation, further enhancing the reactivity of the system.
COMBUSTION SCIENCE AND TECHNOLOGY
(2023)
Article
Engineering, Civil
Georgios Efstathiou, Savvas Gkantonas, Andrea Giusti, Epaminondas Mastorakos, C. Michael Foale, Rhonda R. Foale
Summary: A stochastic model combining cellular automata approach and random walk method was developed to simulate the Marshall fire in Colorado in December 2021. Information on burning duration and ignition delay time for firebrand emission was distilled from literature profiles of burning wooden houses. Satellite images and in-person inspection provided information on vegetation, housing structures, and model parameters. The model predicted the extent and time evolution of the fire reasonably well, and a parametric analysis identified sensitivity and areas for improvement. The low computational cost and ease of operation make the proposed framework suitable for operational decision-making and damage assessment.
FIRE SAFETY JOURNAL
(2023)