Search Results (50)

This study investigates the combustion behavior of H₂–CH₄ mixtures with oxygen-enriched air, achieved through injecting ozone (O₃) into the air intake of the burner fan. The motivation for this approach lies in the high reactivity of hydrogen compared to methane, with the aim of promoting a more favorable oxidizing environment for overall combustion. The research combines theoretical analysis with experimental validation using a diffusion-type burner operating at a fuel flow rate of 1.2 Nm³/h. For this flow rate, the ozone injection led to an equivalent O₂ concentration of approximately 21.7%. At this enrichment level, flame temperature was calculated to increase by 70–90 °C. The burner was specifically designed for the diffusion combustion of H₂–CH₄ mixtures and features three fuel injection nozzles, each surrounded by five air inlets. Experiments employed premixed H₂-CH₄ gas cylinders (Linde) with hydrogen concentrations of 20% and 30%, respectively. The results confirmed slight combustion intensification due to elevated oxygen concentration, with no issues related to flame stability or pulsations observed. Core flame temperature and flue gas emissions, including CO₂, were measured. The results support the further development of this combustion technology by increasing the allowable oxygen concentration limit. Full article

Ammonia (NH₃) and hydrogen (H₂) are considered promising fuels for the power sector’s decarbonization. Their combustion is capable of producing energy with zero direct CO₂ emissions, and ammonia can act as a stable energy H₂ carrier. This study numerically investigates the design and implementation of staged combustion of a mixture of NH₃/H₂ by means of CFD simulations. The investigation employed the single-phase flow RANS governing equations and the eddy dissipation concept (EDC) combustion model, with the incorporation of a detailed kinetic mechanism. The combustion chamber operates under the RQL (rich–quench–lean) combustion regime. The first stage operates under rich conditions, firing mixtures of ammonia in air, enriched by hydrogen (H₂) to enhance combustion properties in a swirl and bluff-body stabilized burner. The secondary stage injects additional air and hydrogen to mitigate unburnt ammonia and NO_x emissions. Simulations of the first stage were performed for a thermal input ranging from 4 kW to 8 kW and flames with an equivalence ratio of 1.2. In the second stage, additional hydrogen is injected with a thermal input of either 1 kW or 2 KW, and air is added to adjust the global equivalence ratio to 0.6. Full article

We investigated experimentally the influence of flow conditions and electrode position on a diffusion H₂–air flame subjected to an external electric field. We determined the minimum impurity level required to observe changes in flame properties with applied voltage. Flame OH chemiluminescence signals were recorded using a UV-sensitive CCD array as a function of voltage (+10 to −10 kV) applied to a stainless-steel ring electrode placed around the burner nozzle. Changes in chemiluminescence signals are reported as a function of electrode height above the burner, airflow, and fuel composition. Significant changes in OH* distributions were observed for voltages below −5 kV. Under optimum conditions, the height of the chemiluminescence flame decreased by up to 67% at the maximum applied voltage. The flame transitioned from a teardrop shape to a flat, open-tip flame at a voltage corresponding to an inflection point in the flame height–voltage profiles. Increasing the airflow rate shifted the inflection point to more negative values until almost suppressing the effect of the electric field on the flame structure. This study reveals that carbon impurities in hydrogen fuel as low as 10 ppm are sufficient to observe significant effects from external electric fields without changing the underlying neutral chemistry. We also determine the set of parameters that control the amplitude of the structural change. Full article

Biogas, derived from human waste or industrial byproducts, is considered one of the most environmentally acceptable fuels. However, such fuels often exhibit relatively low efficiency, making it essential to develop technologies that facilitate their effective combustion. This article investigates the combustion of biogas with the addition of hydrogen at varying degrees of flow swirling. For this purpose, a burner was used in which methane, hydrogen and CO₂ were mixed in a mixer. The studies revealed that increasing the proportion of hydrogen in biogas leads to an average 15% rise in the NO_x concentration. Additionally, an increase in the degree of swirling has a positive effect on NO_x generation. On the other hand, a higher proportion of hydrogen reduces the concentration of CO in the exhaust gases. The presence of ballast gases, such as CO₂, generally results in relatively low NO_x levels when combined with a high swirling number. The analysis of combustion products for CO₂ indicates a 14% increase in CO₂ proportion. The highest concentrations of CO₂ were observed in biogas with the highest CO₂ ballast content. In terms of reducing NO_x and CO, SW = 1.3 is the most successful. On the other hand, this angle leads to an increase in the CO₂ concentration. Full article

Enhancing the combustion efficiency and flame stability in conventional systems is essential for reducing carbon emissions and advancing sustainable energy solutions. In this context, electrohydrodynamic plasma actuators offer a promising active control method for modifying and regulating flame characteristics. This study presents a numerical investigation into the effects of a ring-type plasma actuator positioned on the co-flow air side of a non-premixed turbulent methane/air combustion system—an approach not previously reported in the literature. The ring-type plasma actuator was designed by placing electrodes along the perimeter of the small diameter wall of the air duct. The impact of the plasma actuator on the reacting flow field within the burner was analyzed, with a focus on its influence on the flow dynamics and flame structure. The results, visualized through velocity and temperature contours, as well as flow streamlines, provide insight into the actuator’s effect on flame behavior. Two operating modes of the plasma actuators were evaluated: co-flow mode, where the aerodynamic effect of the plasma actuators was directed downstream; and counter-flow mode, where the effects were directed upstream. The findings indicate that the co-flow actuation positively reduces the flame height and enhances the flame anchoring at the root, whereas counter-flow actuation slightly weakens the flame root. Numerical simulations further revealed that co-flow actuation marginally increases the energy release by approximately 0.13%, while counter-flow actuation reduces the energy release by around 7.8%. Full article

High-alkali Zhundong coal presents significant challenges for power generation, due to its propensity for fouling and slagging. This study investigates a retrofit of a 300 MW tangentially fired boiler with the integration of a slag-tap chamber to improve combustion performance. Computational fluid dynamics (CFD) simulations are employed to examine the influence of this modification on combustion dynamics and the effects of Zhundong coal blending ratios on heat and mass transfer. The results demonstrate that the retrofit facilitates stable airflow recirculation, optimizing combustion efficiency with a peak temperature of 2080 K in the combustion chamber. The flue gas temperature decreases to approximately 1650 K upon exit, which can be attributed to the slag catcher cooling. The integration of the liquid slagging chamber significantly mitigates slag formation, while enhancing oxygen and CO₂ distribution throughout the furnace. As the blending ratio of Zhundong coal increases, oxygen concentrations rise in the bottom burner region, indicating improved air–fuel mixing. With a 30% Zhundong coal ratio, the combustion chamber temperature increases by 3%, and flow velocity in the upper and middle furnace sections decreases by 15%, leading to enhanced combustion intensity. This retrofit demonstrates substantial improvements in combustion stability, slagging control, and the efficient utilization of high-alkali coal. Full article

The aim of this research is to investigate the environmental emission effects and combustion properties of burning different types of FAME biodiesel fuels in an industrial oil burner. These burner heads are used in many areas of industry for heating various boilers and tube furnaces. The fuels used, the area of use, the emission norm values, and the climatic conditions are key factors in this investigation. In this research, two plant-based oils are examined, the properties of which have been compared to standard commercial heating oil. The raw material of the two tested bio-based components was rapeseed. The main gas emission parameters CO, THC, CO₂, O₂, HC, water content, and consumption data were measured. The measurements were performed in an AVL engine brake platform infrastructure, where gas emissions were measured with an AVL AMA i60 FTIR emission gas analyzer, fuel consumption was meticulously gauged using a fuel flow meter, fuel temperature was monitored using an AVL 745 fuel temperature conditioning system, and air consumption was measured with an AVL Flowsonix intake air flow meter. The measurement results showed that both tested biofuels can be burned stably in industrial oil burners, have favorable properties in terms of ignition and flame extinction tendencies, and there is no significant difference in emission parameters compared to standard fuel oil. Full article

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. Full article

The existing natural gas transportation pipelines can withstand a hydrogen content of 0 to 50%, but further research is still needed on the pathways of NO and CO production under moderate or intense low oxygen dilution (MILD) combustion within this range of hydrogen blending. In this paper, we present a computational fluid dynamics (CFD) simulation of hydrogen-doped jet flame combustion in a jet in a hot coflow (JHC) burner. We conducted an in-depth study of the mechanisms by which NO and CO are produced at different locations within hydrogen-doped flames. Additionally, we established a chemical reaction network (CRN) model specifically for the JHC burner and calculated the detailed influence of hydrogen content on the mechanisms of NO and CO formation. The findings indicate that an increase in hydrogen content leads to an expansion of the main NO production region and a contraction of the main NO consumption region within the jet flame. This phenomenon is accompanied by a decline in the sub-reaction rates associated with both the prompt route and NO-reburning pathway via CH_i=0–3 radicals, alongside an increase in N₂O and thermal NO production rates. Consequently, this results in an overall enhancement of NO production and a reduction in NO consumption. In the context of MILD combustion, CO production primarily arises from the reduction of CO₂ through the reaction CH₂(S) + CO₂ ⇔ CO + CH₂O, the introduction of hydrogen into the system exerts an inhibitory effect on this reduction reaction while simultaneously enhancing the CO oxidation reaction, OH + CO ⇔ H + CO₂, this dual influence ultimately results in a reduction of CO production. Full article

The study aims to address the need for cleaner and more efficient combustion technologies in the context of global energy demand and sustainability goals. It focuses on microflame techniques to enhance the performance of gas turbines and water heating boilers. This research investigated, for the first time, the operation of a micromodular burner for hot water boilers and a microflame burner for gas turbines, based on patented inventions. Methods for assessing efficiency included analyzing heat flows, fuel conversion rates to thermal energy, and emission analysis. Using high-precision measuring equipment, such as TESTO 350-XL, thermocouples, flow meters, and others, optimal operating modes were determined for the gas turbine combustion chamber and hot water boiler. This resulted in achieving high efficiency and reducing harmful emission levels (NO_x < 15 ppm, CO < 140 ppm). Theoretical calculations were compared with experimental data, confirming the reliability of the results obtained. Full article

Experimental measurements and modeling have been performed in the chimney of a biomass boiler to study the gaseous and particulate matter (PM) emissions during the combustion of wood pellets. A 10 kW boiler with an underfeed burner is equipped with different sensors located in the chimney (anemometer, thermocouples). The PM emissions were measured in the chimney through the engine exhaust particle sizer (EEPS) technique. Moreover, the gaseous emissions (CO₂, CO, total hydrocarbons THC, O₂) were obtained through infrared (IR) spectroscopy and flame ionization detector (FID). The emissions were recorded during the steady phase of the boiler and averaged over several tests. Four locations were investigated in the chimney to evaluate the evolution of the particle size and the potential deposition on the surface. The experimental results were compared with a CFD model with particle transportation. The modeling of turbulent flow in the chimney is based on a Reynolds-averaged Navier–Stokes (RANS) approach with turbulent viscosity closure. To account for flow anisotropy, the $\overline{v^2}-f$ turbulence model was selected for this study. The effect of turbulent fluctuations on the discrete phase is considered by the discrete random walk (DRW) turbulent dispersion model. The results obtained provide access to the topology of the carrier phase flow as well as the complete distribution of the particle field within the chimney enclosure. Advanced measurement of pollutant emissions and modeling of the PM transportation are developed for the first time in a domestic biomass boiler operating in real conditions. Experimental results demonstrate several relevant information. The CO and THC emissions show a similar evolution versus time. The PM granulometric distribution measured along the chimney highlights the particle agglomeration phenomena. Moreover, the CFD model and experimental results give similar results in terms of flow characteristics and PM granulometry. Full article

As industrial modernization advances rapidly, the need for energy becomes increasingly urgent. This paper aims to enhance the current burner design by optimizing the combustion calorific value, minimizing pollutant emissions, and validating the accuracy of the burner model using experimental data from previous studies. The enhanced porous medium burner model is used to investigate the burner’s combustion and pollutant emission characteristics at various flow rates, equivalence ratios, combustion orifice sizes, and porosity of porous media. In comparison with the previous model, the combustion traits during ethylene combustion and the emission properties of pollutants under various operational circumstances have been enhanced with the enhanced porous medium burner model. The maximum temperature of ethylene combustion in the enhanced model is 174 k higher than that before the improvement, and the CO emissions are reduced by 31.9%. It is believed that the findings will serve as a guide for the practical implementation of porous media combustion devices. Full article

In the modern world, issues related to the use of alternative fuels are becoming increasingly pressing. These fuels offer the potential to achieve significantly improved environmental and technological performance. Currently, among such fuels, biodiesel, ammonia, LPG, and hydrogen are considered the most promising options. LPG and hydrogen exhibit a high Lower Heating Value (LHV) and have a relatively low environmental impact. This article investigates the combustion of hydrogen-LPG mixtures in a diffusion burner. The main parameters under study include the proportion of hydrogen in the fuel, equivalence ratio, and vane angle. The analyzed parameters encompass NOx and CO concentrations. The studies have demonstrated that the addition of hydrogen can reduce greenhouse gas emissions, as the combustion product is clean water. The primary focus of this research is the examination of combustion processes involving flow swirl systems and alternative fuels and their mixtures. The studies indicate that flame stabilization is significantly influenced by several factors. The first factor is the amount of hydrogen added to the fuel mixture. The second factor is the degree of mixing between the fuel and oxidizer, along with hydrogen. Lastly, the equivalence ratio plays a crucial role. As the studies have shown, the maximum stabilization for a speed of 5 m/s is achieved at an angle of 60° and a hydrogen fraction of 40%, resulting in φ_LBO = 0.9. This represents an 8.0% improvement in stabilization compared to the baseline mode, primarily due to the substantial proportion of hydrogen. An analysis of flame photographs reveals that as the twist angle increases, a recirculation zone becomes more apparent. Increasing the blade angle and incorporating hydrogen leads to a reduction in CO concentrations in the exhaust gases. The analysis indicates that increasing the hydrogen proportion to 50%, compared to the absence of hydrogen, results in a 30% decrease in CO concentration. In our case, for the option φ = 0.3 and blade angles of 60°, the reduction in CO concentration was 28.5%. From the authors’ perspective, the most optimal vane angle is 45°, along with a hydrogen fraction of 30–40%. With these parameters, it was possible to achieve concentrations of NOx = 17–25 ppm, φ_LBO = 0.66, and CO = 130–122 ppm. Full article

Thermochemical processes utilizing biomass demonstrate promising prospects for the generation of syngas. In this work, a gasification process employing combination of an indigenous low-grade coal with two distinct biomass sources, namely rice husk (RH) and wood sawdust (WS), was explored. The gasification of the selected feedstock was performed using a double-staged multi-opposite burner (MOB) gasifier. A 3D computational fluid dynamics (CFD) model was employed to analyze the effect of kinetic and diffusion rates on the overall gasification performance of an entrained flow biomass gasifier. DPM was employed to track the particles’ trajectory, while the gas phase was treated as the continuous phase, and its behavior was predicted using a standard k-epsilon turbulent model. To calculate both the homogeneous and heterogeneous reaction rates, the finite rate/eddy dissipation model was implemented. The findings indicate that the char conversion efficiency exceeded 95% across all instances. Among the different reaction schemes, scheme E (which involved complete volatile and char combustion reactions) produced better results in comparison with published results, with less than 1% error. Hence, scheme E was validated and utilized for the rest of the simulated cases. The feeding rate has an inverse effect on the overall performance of the gasifier. An increase in feed rate decreases the CO and H₂ composition in syngas. The maximum CO value was observed to be 57.59% at a 1.0 O/C ratio with a 0.005 kg/s feed rate, and the maximum H₂ value was observed to be 16.58% in the same conditions for Lakhra coal samples. In summary, Lakhra coal exhibited better performance than other biomass samples due to its better fixed carbon and volatiles in its composition. Full article

Future aviation concepts should be both CO₂-neutral and without other emissions. One approach to reaching both targets is based on sustainably produced synthetic liquid fuels, which may allow very clean, lean premixed prevaporized (LPP) combustion. For that, fuels are needed with much longer ignition delay times and a lower flashback propensity than current jet fuels. We describe an experimental setup to investigate the flashback stability of liquid fuels in a multi-fuel burner. In this work, the measurement procedure and the determination of the experimentally obtained accuracy are in focus with regard to prevaporized and preheated iso-propanol/air flames in an equivalence ratio range of 0.85 to 1.05 involving three preheating levels (573, 673, and 773 K). As the determination of the accurate unburnt gas temperature just ahead of the flame is of strong importance for flashback but not directly possible, a model is implemented to determine it from the measurable quantities. Even with this indirect method, and also regarding the hysteresis of the experimental preheating temperature, it is found that the relevant quantities, namely, measured temperatures, mass flows, and values derived from them, can be determined with accuracy in the range below 1.7%. Full article