Combustion Systems Research Articles

Evaluation of combustion system for organically bound tritium analysis using dried fish samples.

The combustion process of the organically bound tritium (OBT) analysis method is difficult and requires sophisticated techniques. For ease, safety, and reproducibility a semi-automatic combustion system was developed. An arbitrary combustion program that prevents sudden ignition was devised and combustion tests were conducted. Analytical test runs were conducted using fish standard samples to confirm the validity of the developed system. The test values were compared with values obtained with another analysis method, and the recovery rate of the combustion water was evaluated. The results confirmed that the analytical values obtained with this combustion system were equivalent to those obtained with another analytical method and were valid for OBT analysis.

Modeling two-phase gas-solid flow in axisymmetric diffusers using cut cell technique: an Eulerian-Eulerian approach

AbstractAxisymmetric diffusers find wide applications in various industrial processes, including combustion systems, pneumatic conveying, and fluidized bed reactors. Understanding and accurately modeling the behavior of two-phase flows in these devices are critical for optimizing their performance and efficiency. Various aspects of the two-phase gas-solid flow, including particle-particle and particle-wall interactions, interphase momentum transfer, and phase segregation, are investigated. Our currently developed technique, which uses a cut-cell technique, is an established new method to handle the inclined wall of an axisymmetric diffuser. The near-wall cells are treated as five faces for the new grid; one is the inclined wall. This helps treat the boundary condition at the wall in an accurate physical way. The code FORTRAN, developed in-house, was used to solve the axisymmetric diffuser using a cut-cell technique. The results of this study will provide valuable insights into the behavior of gas-solid two-phase flows in axisymmetric diffuser. A parametric study of the impact of particles diameters ($100,\ 200,\ \text{and} \ 300\mu m$ 100 , 200 , and 300 μ m ), the solid volume loading ratios $(0.005,\ 0.008,\ 0.01)$ ( 0.005 , 0.008 , 0.01 ) , and cant angle $(4.5^{\circ},\ 7^{\circ},\ 9.5^{\circ}) $ ( 4.5 ∘ , 7 ∘ , 9.5 ∘ ) effect of axisymmetric diffuser on the local skin friction, pressure, velocity, turbulent kinetic energy, and separation zone.

Advanced image processing techniques for multi-level characterization of significant flame features in carbon-neutral combustion

This research presents an advanced image processing framework designed for the multi-level characterization of significant flame features in carbon-neutral combustion systems. The study introduces an optimized neural network based on a brainstorming algorithm and an enhanced support vector machine (SVM) algorithm, which utilizes an improved particle swarm optimization (PSO) technique. The framework is capable of accurately processing complex flame image data, achieving flame classification accuracy rates of up to 100 %. The proposed system combines detailed analysis of flame brightness, texture, and morphological features, contributing to the comprehensive monitoring of combustion states. Additionally, the paper describes the design of a clean burner that promotes the full combustion of zero-carbon gases. The integration of this burner with the advanced monitoring system significantly enhances safety and efficiency in industrial applications. This work addresses the challenges associated with the transition to renewable gases and provides a robust solution for maintaining stable and efficient combustion processes.

Numerical modeling and parameter optimization of the combustion chamber in a tower-type zinc refining furnace

With the implementation of “coal-to-gas” projects, the tower-type zinc refining furnace (TZRF) has encountered a mismatch between high-calorific value fuel and the primary combustion system. To address this issue, this study conducted a full-scale modeling of the combustion and heat transfer processes in the TZRF combustion chamber using computational fluid dynamics. An in-depth analysis and condition diagnosis of the TZRF were performed, elucidating the key causes of deteriorating furnace conditions, reduced efficiency, and decreased production capacity following fuel replacement. This study shows that the flow ratios of gas outlets are unevenly distributed, leading to poor mixing of natural gas and air, resulting in an uneven temperature field in the TZRF. A low-temperature zone is clearly observed below the second-layer burner, where significant accumulation of natural gas fails to combust completely. Although tilting the first-layer burner upward slightly enhances the overall heat transfer performance of the tray, it detrimentally affects the overall combustion of natural gas in the TZRF. The deployment of third-layer air outlets substantially eliminates low-temperature zones, expands the range of high-temperature zones, and significantly improves the furnace condition. The optimal flow ratio of the third-layer air outlets is 29.57%.

Laminar burning characteristics of ammonia and hydrogen blends at elevated initial pressures up to 2.5 MPa

Ammonia is a highly promising alternative fuel, and blending it with hydrogen can mitigate its poor combustion performance. However, the combustion mechanism of ammonia-hydrogen mixtures requires further validation through measurements of laminar burning velocity, particularly under high-pressure conditions relevant to practical combustors. Experimental data at high initial pressures (>1.0 MPa) are notably scarce. In this study, experiments were conducted using an outwardly propagating spherical flame in a high-pressure, high-temperature, constant-volume combustion chamber to determine the laminar burning velocities of ammonia-hydrogen blends at elevated initial pressures. The effects of different equivalence ratios (0.6 ∼ 1.4), volumetric hydrogen ratios (0.1 ∼ 0.6), and initial pressures (0.1 ∼ 2.5 MPa) were evaluated. Chemical kinetics of ammonia and hydrogen combustion was investigated at high pressures. The experimental results were compared with the simulation results under a wide range of conditions using several existing mechanisms to evaluate their applicability. The results show that the laminar burning velocity increases first and then decreases as the equivalence ratio (ϕ) increases and reaches a maximum value around ϕ of 1.1. The laminar burning velocity increases non-linearly with the volumetric hydrogen ratio, with more pronounced acceleration at higher hydrogen ratios. In contrast, the laminar burning velocity decreases non-linearly with the increasing initial pressure, and this reduction becomes progressively slower as the initial pressure rises. The predictive performance of the mechanisms by Okafor et al. and Gotama et al. is relatively satisfactory under certain conditions, but further optimization based on experimental data is necessary. Additionally, reaction pathway analysis of ammonia-hydrogen combustion indicates that introducing hydrogen increases the concentration of active radicals such as OH, O, and H, thereby enhancing ammonia combustion. Sensitivity analysis of the laminar burning velocity identified the critical elementary reactions across varying pressures, providing strong support for optimizing ammonia-hydrogen chemical kinetics models and developing simulation models for practical combustion systems.

Surrogate modeling of multi-dimensional premixed and non-premixed combustion using pseudo-time stepping physics-informed neural networks

Physics-informed neural networks (PINNs) have emerged as a promising alternative to conventional computational fluid dynamics (CFD) approaches for solving and modeling multi-dimensional flow fields. They offer instant inference speed and cost-effectiveness without the need for training datasets. However, compared to common data-driven methods, purely learning the physical constraints of partial differential equations and boundary conditions is much more challenging and prone to convergence issues leading to incorrect local optima. This training robustness issue significantly increases the difficulty of fine-tuning PINNs and limits their widespread adoption. In this work, we present improvements to the prior field-resolving surrogate modeling framework for combustion systems based on PINNs. First, inspired by the time-stepping schemes used in CFD numerical methods, we introduce a pseudo-time stepping loss aggregation algorithm to enhance the convergence robustness of the PINNs training process. This new pseudo-time stepping PINNs (PTS-PINNs) method is then tested in non-reactive convection–diffusion problem, and the results demonstrated its good convergence capability for multi-species transport problems. Second, the effectiveness of the PTS-PINNs method was verified in the case of methane–air premixed combustion, and the results show that the L2 norm relative error of all variables can be reduced within 5%. Finally, we also extend the capability of the PTS-PINNs method to address a more complex methane–air non-premixed combustion problem. The results indicate that the PTS-PINNs method can still achieve commendable accuracy by reducing the relative error to within 10%. Overall, the PTS-PINNs method demonstrates the ability to rapidly and accurately identify the convergence direction of the model, surpassing traditional PINNs methods in this regard.

Future Technological Directions for Hydrogen Internal Combustion Engines in Transport Applications

The paper discusses some of the requirements, drivers, and resulting technological paths for manufacturers to develop hydrogen combustion engines for use in two types of market application – on-road heavy- and light-duty. One of the main requirements is legislative certainty, and this has now been afforded – at least in the major market of Europe – by the European Union's recent adoption into law of tailpipe emissions limits specifically designed to encourage the uptake of hydrogen engines in heavy-duty vehicles, giving manufacturers the confidence they need to invest in productionized solutions to offer to customers.It then discusses combustion systems and boosting systems for the two market types, emphasizing that heavy-duty vehicles need best efficiency throughout their operating map while light-duty ones, since they are rarely operated at full load, will mainly primarily need efficiency in the part-load region. This difference will likely cause a divergence in solutions, with heavy-duty engines running very lean everywhere and light-duty ones likely operating at the stoichiometric air-fuel ratio, at least for most of the map. The impacts of the strategies on engine systems and vehicle integration are discussed.It is postulated that due to reasons of preignition avoidance and efficiency hydrogen engines will rapidly adopt direct injection and that the long-term heavy-duty types will migrate towards the typical current spark-ignition-type cylinder head architecture where tumble, rather than swirl, will ultimately be needed for air motion in the cylinder for these reasons. They may also adopt active pre-chamber technology to ignite extremely lean mixtures for maximum efficiency and minimum emissions of oxides of nitrogen.It is suggested that light-duty engines will evolve less from their current gasoline architectural norm since they already contain all of the necessary fundamentals for hydrogen combustion. However, since part-load efficiency will be important, some new strategies may become desirable. Developing dual-fuel light-duty engines could accelerate their uptake as the heavy-duty market simultaneously accelerates the creation of the fuel supply infrastructure.The likely technological evolution suggests that variable valve trains, and specifically cam profile switching technology, would be extremely useful for all types of hydrogen engine, especially since they are readily available in different gasoline engines now. New operating strategies afforded by variable valve trains would benefit both heavy- and light-duty engines, and these strategies will become more sophisticated. There will therefore likely be a convergence of technologies for the two markets, albeit with some key differences maintained due to their vehicle applications and their differing operation in the field.

Convective heat transfer parameters in the film cooling with thermal radiation

Thermal radiation is a large contributor to the total heat transfer of combustion systems so that it cannot be neglected, with the improvement of gas temperature and infrared stealth requirements. This paper deeply investigated the convective parameters in film cooling with thermal radiation through theoretical analysis and numerical simulation. A method to obtain the convective driving temperature under radiation was proposed and demonstrated. Research found that the film cooling effectiveness with radiation should be expressed by the mixing temperature rather than the adiabatic wall temperature. Although heat transfer and mass transfer under radiation cannot be theoretically analogized due to the radiant source term in the energy equation, the concentration cooling effectiveness without and with radiation remains approximately the same. The numerical results indicate that although conjugate coupling plays a crucial role in determining convective and radiative heat fluxes, the coupling of radiation and convective parameters is very weak. Radiation has little influence on the film cooling effectiveness (η) and the convective heat transfer coefficient (hf). Convective parameters can be decoupled from radiation with negligible loss of accuracy. This allows the non-radiation convective parameters η and hf to be directly used for calculating the convective heat flux under radiation, with relative deviations of less than 5%.

Computational Prediction of Co-firing with Various Biomass Waste Using Turbulent Non-Premixed Combustion

Co-firing in coal power plants has limitations because the existing combustion systems are designed to provide optimal performance only with coal. Therefore, investigating the combustion aspects of co-firing by mixing coal with biomass before applying it to existing coal power plants is necessary. To address this, a new numerical model was developed to predict the co-firing behavior of coal with various types of biomass waste, specifically focusing on temperature and pollutant behavior. This study developed a co-firing model in a Drop Tube Furnace (DTF) using a composition of 25% Wood Chips (WC), 25% Solid Recovered Fuel (SRF), 25% Empty Fruit Bunch Fibers (EFFR), and 25% Rice Husk (RH). A structured grid arrangement and the Probability Density Function (PDF) were utilized to depict the relationship between chemical combustion and turbulence. The distributions of temperature and mass fractions of pollutants along the furnace axis were predicted. The highest temperature was observed with 25% EFFR, attributed to its highest volatile matter content. The simulation predicted that 25% RH would be the lowest SO2 emitter. However, it also showed a slight increase in NO and CO levels due to the increased oxygen content when coal was mixed with biomass. The simulation with 25% EFFR predicted a decrease in CO2 emissions compared to other biomass types. The results of this parametric investigation could support the implementation of biomass co-firing technology in existing coal-fired power plants.

Combined control of PM and NOx emissions from small-scale combustions by electrostatic precipitation

Electrostatic precipitators (ESPs) have demonstrated promise in reducing particulate matter (PM) emissions, but their potential for simultaneously reducing NOx in small-scale combustion systems remains largely unexplored. This study examines the potential of ESP with DC corona discharge of negative polarity to reduce both PM and NOx emissions from small-scale combustion. A chemical kinetic model is first developed to predict NOx removal in the ESP. The model accounts for the non-uniform electric field distribution and inhomogeneity of non-thermal plasma in chemical kinetic while remaining simple enough for practical engineering applications. This allows for the optimisation of ESP parameters during the initial design phase. Using this model, the ESP was developed and applied with different energisation regimes to control emissions from a 15 kW pellet combustion heating unit. The initial concentrations for PM and NOx were 48 mg/m3 and 305 mg/m3, respectively (0 °C, 101.3 kPa; at reference O2 = 10 %vol.). The efficiency of the ESP was both theoretically and experimentally determined for various operational regimes at voltages ranging from 6.8 to 11 kV. At 11 kV, the ESP demonstrated a PM removal efficiency of 99.99 % and a NOx removal efficiency of 38 %, achieving compliance with Ecodesign Directive limits. The model's predictions showed reasonable agreement with experimental data, with a slight miscalculation for both particle precipitation and NOx removal. These findings have significant implications for the design and operation of ESPs in small-scale biomass combustion systems, offering a foundation for optimising these devices for combined NOx and particulate matter control.

Effect of dilution and Lewis number of the fuel in the fuel-air mixture on the heat flux during flame wall interaction (FWI)

Most combustion systems where flame is bounded by walls encounter Flame-wall interactions (FWI). Heat losses during FWI are in the magnitude of MW/m2 leading to concern about inefficiency, and thermal stresses. Hence, FWI is a topic of significant interest. With the goals of climate change pushing us toward renewable fuels with least carbon emissions, it is imperative to understand the FWI of renewable fuels like hydrogen-air mixture. In this study, FWI in a head-on-quenching configuration is carried out in a constant volume chamber. High-speed surface temperature measurement is carried out to compute instantaneous wall heat flux. Adding inert diluents to methane-air mixtures, the effect of dilution on the peak of heat flux during FWI is studied. Dilution affects the peak of heat flux predominantly by changing the adiabatic flame power of the fuel-air mixture. Furthermore, a large variation in flame power is carried out by changing the dilution fraction in the methane-air mixture to quantify its effect. It is found that the peak of heat flux and non-dimensional heat flux follows a nonlinear decrease with an increase in flame power. Knowing this effect, FWI of three different fuels, that is, methane, hydrogen, and a mixture of acetylene and hydrogen, having different Lewis numbers ( Le) of fuel in a fuel-oxidizer mixture are studied at equivalent flame power. This comparison shows that FWI of hydrogen-air mixtures in HOQ configuration have a lower peak of heat flux compared to other fuels which may be due to the preferential diffusion of hydrogen-air mixture.

Assessing thermoacoustic quality in combustion systems using the stability quality factor S

Thermoacoustic instability poses a significant challenge in the development of combustion appliances, where the lack of specific information on upstream and downstream acoustic terminations during the research and development phase is common. This knowledge gap often necessitates extensive trial-and-error approaches, emphasizing the need for a reliable indicator to assess thermoacoustic quality in advance. Traditionally, a burner and its associated flame are characterized as an acoustically active two-port block, coupled with passive acoustic terminations upstream and downstream. In this paper, we investigate the application of the direct conservative stability criterion in the frequency domain to introduce a suitable indicator, termed the [Formula: see text] factor, as a figure-of-merit for thermoacoustic quality. We explore various scenarios that may arise during the research and development phase of thermoacoustically stable combustion systems. Additionally, we address the limitations associated with using Monte Carlo simulations to determine the probability of instability as a potential figure-of-merit. Our findings highlight potential misinterpretations and misrepresentations when employing the Monte Carlo approach to evaluate and compare the thermoacoustic quality of different burners and flames. Finally, the applicability of the [Formula: see text] factor is demonstrated and experimentally validated in the lab-scale thermoacoustic system to rank two different burners at the same thermal power.

Solid-to-gas phase transition kinetics of diverse potassium occurrence forms during biomass pellet combustion: Time-resolved detection and multi-step modeling

The solid-to-gas phase transition of potassium during biomass combustion significantly impacts ash-related issues in bioenergy systems, affecting operational efficiency and equipment longevity. However, the specific mechanisms and kinetics of this transition process remain inadequately understood. This work investigates the time-resolved transition of solid-phase potassium to the gas phase during the combustion of rice husk and wheat straw pellets, combining experimental measurements with theoretical modeling. Tunable diode laser absorption spectroscopy (TDLAS) was employed to measure atomic potassium concentrations 15 mm above burning pellets tray, where gas-phase equilibrium is approached. Key combustion characteristics including thermogravimetric profiles, spectral radiation, and temperature were simultaneously monitored. A novel multi-step model was developed to describe the transition of different forms of solid-phase potassium (organic, exchangeable, and inorganic) to the gas phase. This model integrates TDLAS measurements, observed combustion characteristics, and biomass physicochemical properties. Thermodynamic equilibrium calculations were used to estimate the atomic potassium fraction from total gaseous potassium. The results showed that the solid-to-gas phase transition of organic potassium synchronizes with volatiles release. In contrast, the maximum emission rates of inorganic and exchangeable potassium occurred at the onset of char combustion. The developed model agrees well with the online detection experiments and were further validated by offline ICP analysis of residual ash. While not directly simulating gas-solid interface reactions near the particle surface, this work lays groundwork for future multi-scale modeling of particle-laden flows and reactor-scale phenomena in biomass combustion systems.

Optimization of combustion chamber geometry for a two-stroke spark-ignited direct-injection opposed-piston rod-less aviation kerosene engine

Spark-ignited direct-injection opposed-piston rod-less kerosene engines are highly suitable for small and medium-size unmanned aerial vehicles (UAVs) because of the high power-to-weight ratio, self-balancing ability, and safety of such engines. The design and optimization of combustion systems are crucial for power, fuel economy, and knock control. To meet the increasing demand for UAV power systems and fill the research void in this area, reported here for the first time are the design and optimization of a swirl-wall-guided combustion system including the spray pattern and pit structure on the top surface of the piston, with the dynamic, fuel economy, and knock intensity as the evaluation indicators. The results indicate that the spray pattern mainly affects the fuel escape rate and inhomogeneity. After it is injected into the pit, the fuel is guided to the combustion chamber by the steering role of the guide arc. If the spray drop point is located away from the pit, it leads to increased fuel escape rate and inhomogeneity. The turbulent kinetic energy in the spark-plug zone decreases as the pit diameter decreases, fluctuating by 48 %, while the average value remains relatively constant. The distribution is influenced primarily by the enveloping effect of the pit structure on the airflow. Under low-speed conditions, as the pit diameter decreases, the ignition delay period increases and then decreases, and the combustion duration decreases monotonically. The fluctuation of indicated power is relatively small (2.64 %), and the fuel escape rate decreases monotonically, resulting in the same variation pattern of indicated specific fuel consumption (ISFC). When the pit diameter is 43 mm, the fuel escape rate and ISFC reach their lowest values. Knock combustion near the wall is influenced mainly by two factors: the temperature rise rate and the flame propagation speed. The temperature rise rate increases significantly with decreasing pit diameter. When the pit diameter is less than 50 mm, knock combustion begins to occur. Under high-speed equivalent combustion conditions, as the pit diameter decreases, the indicated power changes by 5.21 %, and the ISFC decreases monotonically.

Numerical study of a chemical looping combustion system: Effects of fuel type and particle size distributions on the operating performance

Chemical looping combustion (CLC) using biomass offers a promising pathway for achieving negative carbon emissions. However, the different properties of coal and biomass affect reaction performance, which has not been fully explored in the CLC system. Additionally, the effects of particle size distributions (PSDs) of solid fuels and oxygen carriers (OCs) are inadequately addressed. In this study, a 3D reactive model using the computational particle fluid dynamics (CPFD) method is developed to investigate the effects of PSDs of both solid fuels and oxygen carriers on operating performance with coal and biomass as fuels. Results indicate that the average residence time in FR of coal and biomass particles is 0.86 s and 0.68 s, respectively, but biomass outperforms coal in reaction efficiency. For coal-fueled CLC, the average residence time is 0.46 s for coal particles with diameters of 100–200 μm, whereas it reaches 0.86 s for coal diameters of 300–700 μm. However, the reaction performance is better with smaller coal sizes due to char gasification being the rate-limiting step. In comparison, for biomass-fueled CLC, the reaction efficiency remains consistent across various particle sizes under the specified conditions due to the rapid release of volatile components and the low content of char. Additionally, it is found that the OC conversion ratio is mainly determined by their residence time in the zones with relatively higher concentrations of the combustible gas in FR. Employing OCs with overly wide PSDs such as 300–800 μm can compromise the material seal above the AR, increase the risk of gas leakage and decrease the separation efficiency of the inertial separator.

The Research of Diesel Engine Assembly Consistency Influence NOx Emission Based on Uniform Design Method

ABSTRACT Diesel engines need to meet the higher emission requirement according to the Euro VI emission standards, and changes in the assembly tolerance of diesel engines will affect the consistency of nitrogen oxides(NOx) emissions. To study the influence of assembly tolerance on NOx emission, a heavy diesel engine was used as the research prototype. The combustion model of the diesel engine was simulated by the Converge software and calibrated with the bench test data. Because the combustion system parameters have a significant impact on emissions, a three-factor eleven-level uniform design is arranged with three parameters, including compression ratio, fuel injection nozzle extension height and injection advance angle. The regression analysis method is used to obtain the relationship between the parameters and NOx emissions. The R2 test value of the regression equation is 0.916 and the F test value is 43.5, which shows that the results of the analysis are very effective. Then the single factor test method is applied to analyze the varying laws of compression ratio, nozzle extension height and fuel injection advance angle on NOx emissions, and the results reveal the inherent law similar to the regression equation. According to the Euro VI emission standards and the law of diesel engine emission performance consistency, the tolerance variation range of the key dimensions of the assembly parameters is obtained.

Prediction of the Flame Characteristics of an Industrial Gas Turbine Operated With CO2-Diluted Air Through a High-Fidelity Numerical Analysis: A Comparison Between Flamelet Generated Manifolds and Artificially Thickened Flame

Abstract In light of the global commitment to decarbonize industrial processes, carbon capture and storage (CCS) plays a pivotal role in mitigating greenhouse gas emissions from gas turbine (GT) power generation processes. Achieving an efficient GT–CCS coupling requires the employment of high percentages of exhaust gas recirculation (EGR) to maximize the CO2 content at the CCS inlet. Nevertheless, such operating conditions pose critical challenges for conventional combustion systems due to reduced oxygen levels associated with higher EGR, limiting engine operability. To address this challenge, the development of innovative technical solutions is essential to extend the combustor operational capabilities at high EGR rates. For this goal, a significant number of computational fluid dynamics (CFD) simulations are required to identify the flame stability limits across various EGR levels and burner designs. It is imperative, in this context, to minimize computational costs while maintaining high accuracy. In this work, a comprehensive comparative study of an extended version of the flamelet generated manifolds (FGM) and the artificially thickened flame (ATF) model is performed through a large eddy simulation (LES)-based CFD analysis. The investigation is performed within the context of an industrial lean-premixed burner manufactured by Baker Hughes, operating with natural gas and CO2-diluted air at atmospheric pressure. While the extended-FGM has been previously presented by the authors in a study on the same test rig under standard air conditions, the current work aims to extend its application to critical oxygen-depleted conditions, where near-blowout phenomena such as flame liftoff and length elongation may become significantly pronounced. Numerical validation is carried out through a direct comparison of the computed averaged heat release, representing the flame topology, with detailed OH* chemiluminescence images from a test campaign conducted by the technology for high temperature (THT) Lab of the University of Florence. The experimental data will serve as the primary benchmark for assessing the models’ effectiveness in capturing the main dynamics of such critical operating conditions. Furthermore, potential disparities in both thermal and flow fields at the burner exit region between the two models will be discussed.

The Effect of Heterogeneous Natural Gas–Hydrogen Input Into F-Class Gas Turbine Combustor As a Combustion Optimization Method

Abstract The global push to combat climate change by transitioning to clean power generation is accelerating. One promising avenue involves using hydrogen in place of natural gas in gas turbine-based power plants. While the development of new hydrogen combustors shows potential, advancements in operational technologies are needed to ensure higher hydrogen cofiring with existing combustion systems. In our study, we propose a novel approach called heterogeneous natural gas–hydrogen input: varying hydrogen content between different nozzle groups in gas turbine combustors. Using a full-scale combustor of an F-class gas turbine model, we experimentally investigated the impact of heterogeneous hydrogen concentrations at the center and outer nozzles on combustion dynamics and emissions, comparing these with homogeneous fuel supply cases of 100% natural gas and natural gas–hydrogen mixtures. While hydrogen cofiring did not change the maximum amplitude of combustion dynamic pressure across the total frequency range, peak amplitudes in the 125–245 Hz domain were linearly proportional to the hydrogen cofiring ratio, with a 41.2% increase at 30% cofiring identified as a possible limiting factor. Our findings revealed a significant correlation between NOx emissions and combustion stability under varying levels of heterogeneity. Higher heterogeneity with intensive hydrogen input into the center nozzle improved cofiring performance, reducing the peak amplitude in the limiting frequency domain by 22% for a 25% cofiring ratio, potentially extending the critical hydrogen cofiring ratio. Implementing heterogeneous natural gas-hydrogen inputs emerges as a promising method to enhance combustion stability and enable effective hydrogen cofiring.

Surface in situ Co-Mn modification over LaMnO3 perovskite with enhanced activity for ethane combustion

Catalytic combustion is one of effective ways to remove short-chain alkanes. In this study, we elaborately designed a novel catalyst of in situ Co-Mn decorated LaMnO3 perovskite for ethane catalytic combustion, in which extra Mn and Co species were introduced via acidic KMnO4 and Co(NO3)2 solution precipitation method. The addition of Mn and Co could not only slightly etch LaMnO3, thereby increasing specific surface area and redox property, but also generate new active phase CoMn2O4, thus accelerating reaction. Among all the as-prepared catalysts, CMO/LMO-0.5 exhibited admirable ethane removal efficiency with a T90 of 365 °C, a reaction rate of 0.46 mmol·g−1·h−1, a TOF value of 0.64 mmol·g−1·h−1, and excellent hydrothermal stability and reusability. Moreover, according to in situ DRIFTS, a possible pathway was proposed. This work can rationalize an alternative approach to develop an active catalyst for short-chain alkanes catalytic combustion or other catalytic systems.

Control of Liquid Hydrocarbon Combustion Parameters in Burners with Superheated Steam Supply

A numerical simulation of reacting mixture flow in a full-scale combustion chamber of a prototype burner with a fuel-sprayed jet of superheated steam and a controlled excess air ratio was performed based on a verified model. The influence of steam jets on the combustion parameters of the created prototype device was analyzed based on the results, and a comparison with data from various atmospheric burners, including evaporative and spray types, direct-flow and vortex types, and those with natural and forced (regulated) air supply, was made. Various schemes for supplying steam to burner devices were discussed. It was shown that the relative steam consumption is a parameter for controlling the emission of toxic combustion products, such as NOx and CO, for all designs. A high burner performance is achieved when superheated steam is supplied at more than 250 °C with a relative steam flow rate of >0.6. The design features of the burner systems and operational parameters that ensure high thermal and environmental efficiency when burning various types of fuel and waste are identified.