Enhance Combustion Efficiency Research Articles

Experimental Investigation on the Effect of Heating Oil and Tyre Pyrolysis Oil Combustion in an Evaporative Combustion Chamber

This research aims to delve into the intricacies of combustion processes, specifically focusing on heating oil and a blend of heating oil with Tire Pyrolysis Oil (TPO) in a self-developed evaporative combustion chamber featuring steam injection. The primary objective is to scrutinize the impact of steam injection on the combustion dynamics. Conducting a series of tests, the investigation involved the meticulous manipulation of stoichiometric ratios while introducing ambient air through gravity fuel flow. Subsequent iterations of these tests incorporated the introduction of steam into the ambient air stream. The examination encompassed the combustion of both heating oil and the TPO blend within the combustion chamber. The evaluation criteria comprised an in-depth analysis of flame characteristics, temperature distribution within the combustion chamber, and the quantification of emissions such as particulate matter (PM), nitrogen oxides (NOx), carbon dioxide (CO2), carbon monoxide (CO), and water vapor (H2O). Throughout the experimentation phase, commercially available diesel fuel served as the primary fuel source. To facilitate the tests, the combustion chamber under scrutiny was seamlessly integrated into an AVL engine test bench system. Essential parameters, including fuel consumption, were meticulously gauged using an AVL 735 fuel flow meter, while fuel temperature was monitored using the AVL 745 fuel temperature conditioning system. The intake air, a crucial element in the combustion process, was quantified with precision using an AVL Flowsonix sensor. Emission measurements were conducted meticulously using state-of-the-art equipment, with gaseous emissions analyzed using an AVL FTIR AMA i60 exhaust gas analyzer. Simultaneously, soot emissions were quantified through employment of an AVL Micro Soot sensor. This comprehensive approach not only delves into the fundamental aspects of combustion but also extends its reach to the exploration of innovative techniques, such as steam injection, to enhance combustion efficiency and reduce emissions. The integration of advanced measurement tools ensures a robust and thorough analysis of the combustion process and its environmental implications.

Machine learning-based design of target property-oriented fuels using explainable artificial intelligence

This study presents a machine learning (ML) and explainable artificial intelligence (XAI) integrated framework to guide the experimental investigation of engine combustion toward the most promising fuel compositions. Specifically, the experimental study evaluated nine diesel fuels with differing levels of paraffin, cycloparaffins, and aromatics in a heavy-duty engine, providing key data for subsequent model development. Building on this data, we introduce a multidimensional neural network methodology for feature optimization and performance assessment, incorporating 31 distinct features including engine variables, fuel properties, and components. The methodology innovatively integrates tree-based models with shapley additive explanations (SHAP) for detailed feature importance ranking. Features are sequentially added to subsets based on their importance for multilayer perceptron (MLP) model training, allowing for precise regression performance metrics for each subset. The comprehensive assessment of these best subsets revealed robust regression capabilities, with coefficient of determination (R2) values ranging from 0.9918 to 0.9999, and both root mean square error (RMSE) and mean absolute percentage error (MAPE) maintained below 0.4974 and 0.1388, respectively. Through SHAP and partial dependence plots (PDP), it was demonstrated that optimizing diesel fuel compositions by increasing paraffin levels, reducing aromatics, and moderately increasing cycloparaffins can significantly enhance combustion efficiency and reduce emissions.

Combustion and emission of diesel/PODE/gasoline blended fuel in a diesel engine that meet the China VI emission standards

The present study examined the impact of blending polyoxymethylene dimethyl ethers (PODE) and gasoline with diesel on combustion and emission characteristics in an engine compliant with China VI emission standards. The effects on cylinder pressure, combustion duration, and emissions (CO, THC, PN, and NOx) by blending 20 % PODE into diesel and adjusting the gasoline content (0 %, 5 %, and 10 %) were analyzed. The results showed that the cylinder pressures and the combustion duration were reduced with the addition of PODE, compared to the cases of the pure diesel. Moreover, it was found that PODE contributed to reducing the emissions of CO, THC, and PN, and but increasing NOx emissions. Compared to the cases of PODE and diesel blended fuel, the effect of the addition of gasoline on the cylinder pressures and combustion duration presented a minor increasing tendency, and the lower proportion of gasoline blending was found to effectively curb NOx formation. Specifically, blending 5 % gasoline with a 20 % PODE and diesel mixtures resulted in a 4.01 % reduction in NOx emissions. Based on the results of the present study, it can be concluded that 5 % gasoline and 20 % PODE blend in diesel can enhance combustion efficiency and heat release rate and also can achieve a balanced reduction in NOx emissions. The present study provides valuable insights for the development of energy-saving and emission reduction technologies for diesel engines, highlighting the potential of optimized fuel blends to improve combustion and emissions control.

Study on Hydrocarbon Fuel Ignition Characterization Based on Optimized BP Neural Network

The investigation of the ignition delay of hydrocarbon fuel is highly valuable for enhancing combustion efficiency, optimizing fuel thermal efficiency, and mitigating pollutant emissions. This paper has developed a BP-MRPSO neural network model for studying hydrocarbon fuel ignition and clarified the novelty of this model compared to the traditional BP and ANN models from the literature. The model integrates the particle swarm optimization (PSO) algorithm with MapReduce-based parallel processing technology. This integration improves the prediction accuracy and processing efficiency of the model. Compared to the traditional BP model, the BP-MRPSO model can increase the average correlation coefficient, from 0.9745 to 0.9896. The R2 value for predicting fire characteristics using this model can exceed 90%. Meanwhile, when the two hidden layers of both the BP and BP-MRPSO models consist of 9 and 8 neurons, respectively, the accuracy of the BP-MRPSO model is increased by 38.89% compared to the BP model. This proved that the new BP-MRPSO model has the capacity to handle large datasets while achieving great precision and efficiency. The findings could provide a new perspective for examining the properties of fuel ignition, which is expected to contribute to the development and assessment of aviation fuel ignition characteristics in the future.

Gear-Shaped High-g Combustion Chamber for Micro Turbojet Engine Applications.

Enhancing combustion efficiency and optimizing the thrust-to-weight ratio are critical technical challenges encountered in the development, application, and growth of micro turbojet engines. The high-centrifugal (high-g) combustion chamber, as an innovative combustion chamber system, has the capability to replace the primary combustion chamber of the traditional turbojet engine, reducing the length of the combustion chamber while maintaining engine performance. Previous studies on the structure of the high-g combustor (HGC) have shown problems such as uneven temperature distribution of the turbojet rotor. To improve the feasibility of HGC integration into micro turbojet engines, this study conducts relevant experiments on a 120 N thrust engine. Subsequently, the results of these experiments were used to analyze the structural design of HGC through a simulation approach. Including six main configurations, the first four structural designs focused on establishing a suitable highly centrifugal environment to stabilize and improve the combustion performance, which was successfully achieved by designing the outer ring gear-shaped inlet with four different angles. Subsequent structural designs were based around improving the uniformity of the temperature distribution at the combustion chamber outlet. The final design of the HGC combustion efficiency is not much different from the original combustion chamber, and it can shorten the axial length of the combustion chamber by nearly 30%. The design of the air inlet holes and the baffle plate effectively improves the temperature uniformity at the outlet of the combustion chamber. Moreover, without changing the combustion chamber material, the corresponding engine weight can be reduced by about 10.7%, and the engine thrust-to-weight ratio can be improved by up to 12% with the same thrust, which provides design ideas for further lightweight applications.

Performance analysis and optimization of thermal barrier coated piston diesel engine fuelled with biodiesel using RSM

The current research investigates diesel and simarouba biodiesel blends (10%, 20%, & 30% by volume) in conventional and Low Heat Rejection (LHR) diesel engines, each rated at 4.4 kW. While optimization techniques like Response Surface Method and Taguchi have been extensively studied, the impact of LHR and optimization on LHR engine performance and emissions is rarely explored. Converting the conventional engine to LHR involved applying 300 μm of stabilized zirconia to the piston crown to enhance combustion efficiency. Performance and emissions were analyzed at rated injection pressure (200 bar) and timing (23° before top dead center - btdc). Experiments were continued on LHR engine by varying injection timings (advancing - 26°btdc and retarding - 20°btdc). Advanced injection timing showed significant improvement in performance of Low heat rejection engine. MINITAB statistical tool is used to optimize engine performance using Response Surface Method. The 20% blend showed improved performance in both engines. The optimum values for Low heat rejection engine responses are 26.8%, 0.32 kg/kW-h, 0.018%, 59.59 ppm, and 1419.03 ppm for brake thermal efficiency, brake specific fuel consumption, carbon monoxide, and unburnt hydrocarbons, respectively. Confirmation experiments aligned well with model predictions, indicating the potential of LHR engines to enhance thermal efficiency and reduce emissions.

Formulation effect on combustion and agglomeration characteristics in nitramine solid propellants

The formulation fundamentally determines the combustion characteristics and agglomeration behavior of propellants. This study compared the effects of four factors on the combustion, agglomeration, and combustion efficiency of nitramine solid propellants: the aluminum size, the ammonium perchlorate size, the nitramine size, and the mass ratio of ammonium perchlorate to nitramine. The comparison was conducted through a series of experimental methods including burning rate tests, collection of the condensed-phase combustion products, chemical titration, and physicochemical analysis. In terms of burning rate, reducing the particle sizes of aluminum powder and ammonium perchlorate, increasing the nitramine size, and increasing the mass ratio of ammonium perchlorate to nitramine all effectively enhance the burning rate. The influence of these four factors on burning rate, in descending order of impact, is: the mass ratio of ammonium perchlorate to nitramine > the ammonium perchlorate size > the aluminum size > the nitramine size. Regarding agglomeration and combustion efficiency, increasing the particle sizes of aluminum and nitramine, increasing the mass ratio of ammonium perchlorate to nitramine, and decreasing the ammonium perchlorate size can effectively inhibit agglomeration and enhance combustion efficiency. Among these, the ammonium perchlorate size has the greatest effect on enhancing the combustion efficiency, potentially increasing it by 16%. The nitramine size has the weakest impact on combustion efficiency, with a potential increase of 5.5%. The experimental results of this study can provide references for a deeper understanding of the combustion mechanisms of nitramine solid propellants, the establishment of combustion models, and the realization of formula optimization.

A computational study of a laminar methane–air flame assisted by nanosecond repetitively pulsed discharges

Nanosecond repetitively pulsed (NRP) discharges have been considered a promising technique for enhancing combustion efficiency and control. For successful implementation, it is necessary to understand the complex plasma–combustion interactions involving chemical, thermal, and hydrodynamic pathways. This paper aims to investigate the mechanisms enhancing a laminar methane–air flame assisted by NRP discharges by high fidelity simulations of the jet-wall burner employed in a previous experimental study. A phenomenological plasma model is used to represent the plasma energy deposition in two channels: (1) the ultrafast heating and dissociation of O2 resulting from the relaxation of electronically excited N2 , and (2) slow gas heating stemming from the relaxation of N2 vibrational states. The flame displacement, key radical distribution and flame response under plasma actuation are compared with experimental results in good agreement. The computational model allows a systematic investigation of the dominant physical mechanism by isolating different pathways. It is found that the kinetic effect from atomic O production dominates the flame dynamics, while the thermal effect plays a minor role. Hydrodynamic perturbations arising from weak shock wave propagation appear to be sensitive to burner geometry and is found to be less significant in the case under study.

A comprehensive investigation on the internal flow and outflow characteristics of GDI elliptical divergent nozzles

The substantial demand for enhanced combustion efficiency and achieving near-zero emissions in GDI engines has spurred the introduction of a novel approach employing elliptical divergent nozzle spray technology. This innovative method, which marries the elliptical shape with a divergent nozzle, not only elevates downstream atomization quality but also mitigates nozzle tip wetting. Nevertheless, there exists a dearth of documented research regarding the internal flow and outflow characteristics related to the atomization potential of elliptical divergent nozzles. Numerical investigations have been carried out to scrutinize alterations in the three-dimensional cavitation morphology, the dispersion of turbulent vortex structures, and the nozzle exit flow parameters across a range of cavitation number conditions for both circular and elliptical divergent nozzles. The research findings demonstrate that the cavitation intensity of the elliptical divergent nozzle consistently surpasses that of the circular divergent nozzle. Also, the elliptical divergent nozzle consistently exhibits a greater number of turbulent vortex structures compared to the circular divergent nozzle across all cavitation number conditions. Additionally, as the cavitation number decreases, the difference in turbulence vorticity magnitude between the exits of the circular and elliptical divergent nozzles gradually increases. Furthermore, the elliptical diverging orifices are more susceptible to cavitation compared to their circular counterparts. The elliptical divergent nozzle outperforms the circular nozzle with a substantial 24.6% increase in exit velocity, especially at a cavitation number of 1.016.

Enhancing Combustion Efficiency and Emission Reduction in Single Cylinder CI Engines: A Study on Waste Dairy Scum Methyl Ester Biodiesel Blends with Aluminium Oxide Nanoparticles

Enhancing Combustion Efficiency and Emission Reduction in Single Cylinder CI Engines: A Study on Waste Dairy Scum Methyl Ester Biodiesel Blends with Aluminium Oxide Nanoparticles

Gasification Burner Performance Test Using Bio-Coal Fuel

Fuel for high-energy solid fuel combustion systems must meet abundant availability, affordability, and environmental friendliness criteria, particularly having low greenhouse gas emissions. One type of fuel that meets these criteria is bio-coal. Gasification burners employ staged combustion techniques that enhance combustion efficiency and reduce the formation of harmful substances, making them more environmentally friendly. This article discusses the performance testing of gasification burners using bio-coal as fuel, with variable primary air flow rates of 25, 30, 35, 40, and 50 m3/hour and biomass percentages in the bio-coal of 25%, 50%, and 75% by weight. The parameters observed are burner capacity, temperature, and CO2 gas emission factor. The experimental results show that increasing the air flow rate from 25 to 35 m3/hour significantly increases burner capacity and temperature, while further increasing the primary air flow rate to 50 m3/hour results in a gradual increase in burner capacity. The experiments also indicate that increasing the biomass percentage in the bio-coal slightly increases burner capacity and temperature due to the similar calorific values of palm pellet and coal used. The gasification burner technology developed by BBP Tekmira has proven to operate effectively within a capacity range of 8 to 20 kg/hour for bio-coal fuel with biomass percentages ranging from 25% to 75% by weight, producing burner temperatures between 805 and 933 degrees Celsius. Using bio-coal for gasification burners has also been shown to reduce greenhouse gas emissions when the biomass percentage in bio-coal exceeds 64%.

Carbon neutrality with ammonia: An analysis of its feasibility as a fuel for diesel engines fuelled with spirulina microalgae and oxygenated additives

Ammonia has emerged as a promising gaseous fuel for replacing conventional fossil fuels and achieving carbon neutrality. This research explores the viability of using ammonia as a fuel in compression ignition diesel engines operating in dual-fuel mode. The study investigates the performance and emission characteristics of diesel engines fueled with ammonia, microalgae-based biodiesel, and their combinations, with the addition of Fe2O3 nanoparticles to enhance combustion efficiency. A series of experiments were conducted using various blends of ammonia, biodiesel, and nanoparticles in a single-cylinder engine. The objective was to assess the impact of ammonia and biodiesel on thermal efficiency and carbon-based emissions. Comparative analysis revealed that ammonia-based fuels exhibited higher brake thermal efficiency and lower carbon emissions compared to traditional diesel fuel. The combination of ammonia, biodiesel, and nanoparticles resulted in an 8.5% increase in thermal efficiency compared to diesel fuel. However, the fuel consumption increased by 18% due to the lower energy density and higher viscosity of the biodiesel blends. Furthermore, the study examined the emissions profile of the tested fuels. The use of ammonia and nanoparticles led to significant reductions in carbon monoxide, hydrocarbon, and smoke emissions. However, there was a slight increase in nitrogen oxides and carbon dioxide emissions, regardless of engine loading conditions. It was observed that the emission of NOx was influenced by combustion delay and autoignition temperature. To mitigate NOx emissions, optimizing the combustion delay and avoiding premixed combustion phases are crucial. Based on the findings, the study concludes that ammonia has the potential to serve as a viable substitute for diesel fuel in engines. Ammonia-based fuels exhibit higher brake thermal efficiency and lower carbon emissions. Future research should focus on optimizing combustion parameters to minimize NOx emissions, thereby facilitating the widespread adoption of ammonia in diesel engines and contributing to the decarbonization of the transportation sector.

Experimental investigation on a novel external-mixing prefilming atomizer for advanced aircraft engines

As a crucial component of aircraft engine combustors, the external-mixing prefilming atomizer exhibits significant advantages in enhancing combustion efficiency and reducing pollutant emissions. However, the intricate relationship between spray characteristics, droplet breakup mechanisms, flow fields, and geometric parameters of the external-mixing prefilming atomizer remains poorly understood. This paper presents a novel external-mixing prefilming atomizer, aiming to address this knowledge gap. Additionally, particle image velocimetry (PIV), high-speed Schlieren photography, and particle image analysis (PIA) measuring systems were employed to gain insights into the spray characteristics and droplet breakup mechanism of the external-mixing prefilming atomizer under various swirl flow fields. The obtained results reveal the formation of two distinct regions, namely a low-density area and a high-density area. Notably, the number of droplets in the low-density area, located within 0–2 cm from the central axis, is significantly lower compared to the high-density area situated further away from the central axis. The breakup of droplets in the low-density region is primarily attributed to the inner swirl airflow, while the outer swirl airflow induces droplet breakup in the high-density region. As the Reynolds number of the incoming flow increases, the air-liquid ratio (ALR) and Weber number also increase, thereby enhancing the fuel breakup effect. The Schlieren results reveal a two-stage spray development process. The initial stage is characterized by the dominant momentum of the dense spray, with the spray tip penetration (STP) exhibiting a relatively slow increase. The aerodynamic force of airflow plays a crucial role in governing the breakup and transport of droplets, leading to a linear variation of STP over time. As the swirl number increases, there is an enhanced momentum exchange between droplets and airflow, resulting in accelerated spray penetration and droplet breakup.

Impact of medium-pressure direct injection in a spark-ignition engine fueled by hydrogen

In the automotive sector, hydrogen is being increasingly explored as an alternative fuel to replace conventional carbon-based fuels. Its combustion characteristics make it well-suited for adaptation to internal combustion engines. The wide flammability range of hydrogen allows for higher dilution conditions, resulting in enhanced combustion efficiency. When combined with lean combustion strategies, hydrogen significantly reduces environmental impact, virtually eliminating carbon dioxide and nitrogen oxide emissions while maintaining high thermal efficiency. This paper aims to assess the potential of using an outwardly opening poppet valve hydrogen direct injection (DI) system in a small engine for light-duty applications. To achieve this, a comparison of performance, emission levels, and combustion parameters is conducted on a single-cylinder spark-ignition (SI) research engine fueled by hydrogen, using both port fuel injection (PFI) and this new direct injection system. Two different engine loads are measured at multiple air dilution and injection timing conditions. The results demonstrate notable efficiency improvements, ranging from 0.6% to 1.1% when transitioning from PFI to DI. Accurate control of injection timing is essential for achieving optimal performance and low emissions. Delaying the start of injection results in a 7.6% reduction in compression work at low load and a 3.9% reduction at high load. This results in a 3.1-3.2% improvement in ISFC in both load conditions considered.

The thermal behavior during the co-combustion of bituminous coal and oil palm trunk hydrochars

ABSTRACT Utilizing oil palm trunk (OPT) residue as a co-fuel in coal-fired plants offers an environmentally favorable solution to agricultural waste disposal and fossil fuel combustion impacts. This study investigates the potential of hydrochar from OPT (HTC-OPT) as a coal-like solid fuel for co-combustion. The combustion characteristics of coal, HTC-OPT, and their blends (10–50% HTC-OPT) were analyzed via thermogravimetric analysis with heating rates ranging from 10 to 30°C/min. The Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models were employed to explore co-combustion interactions and kinetic parameters. Results reveal enhanced combustion efficiency with HTC-OPT addition to coal. Higher HTC-OPT ratios correlate with increased maximum combustion rates, ignition and comprehensive combustibility indices, and decreased ignition and burnout temperatures. Additionally, blended fuels exhibit a proportionally synergistic co-combustion interaction. Both KAS and FWO models indicate similar trends in activation energies, with the lowest values (49.94 kJ/mol for KAS and 60.90 kJ/mol for FWO) at a 10% HTC-OPT ratio.

Unstable combustion behavior of syngas/air mixture with different components in a narrow gap disk reactor

In this paper, the combustion behavior of the syngas/air mixture in a narrow gap disk reactor were explored. Besides, the influence of the hydrogen volume fraction and the mixture equivalence ratio in syngas on the property of propagating flames were investigated in the narrow gap disk reactor under the gap thicknesses of 8 mm, 6 mm, 4 mm, 3 mm, and 2 mm, respectively. The focus was placed on the behavior of the flame propagation under the gap thickness of 2 mm. The research results demonstrated that the increase of the hydrogen volume fraction from 5 % to 30 % exerted a significant impact on the flame propagation velocity (FPV) and the pressure in the tube. Moreover, the equivalence ratio of this mixture could markedly affect both the propagation characteristics and morphology of flames. Strong flame instabilities accompanied by pressure oscillations were observed in the reactor at a 2 mm gap thickness during the later stages of flame propagation. Notably, there were significant differences in unstable combustion behavior between different syngas components. Moreover, the combined action of heat losses and compression waves leads to significant flame instability. The insights gained from this study have practical implications in various production applications. For example, optimizing hydrogen volume fraction and mixture equivalence ratios can enhance combustion efficiency and reduce pressure fluctuations in industrial reactors, leading to improved energy utilization and reduced environmental emissions.

The impacts of nanoscale silica particle additives on fuel atomisation and droplet size in the internal combustion engines: A review

The combustion process in compression ignition (CI) engines is complex and affects their efficiency and emission levels. Internal combustion engines (ICE) are being studied to find better ways to burn fuel and produce less pollution to meet the growing demand for these qualities. However, one intriguing avenue is the utilisation of nanoparticle additives, such as silica nanoparticles, to enhance fuel atomisation and droplet size. This study aimed to comprehensively review the impact of silica nanoparticle additives on fuel atomisation and droplet size in internal combustion engines. This review explores the researchers' underlying mechanisms and experimental techniques to determine nanoparticle fuel additives' overall impact on engine performance. The results achieved from the literature study indicated that incorporating these nanoparticles (following the engine design and fuel formulations) can enhance combustion efficiency and reduce exhaust emissions, thereby contributing to developing more sustainable transportation and power production systems.

Analysis of pulse combustion processes and thermodynamic cycles in pulse combustors

This study explores the dynamic behavior of pulsating combustors during stable operation, examining pressure characteristics, flame dynamics, and thermodynamic cycles. Through analysis of pressure signal derivatives and high-speed photography, it unveils a distinctive counterclockwise thermodynamic cycle in these combustors, diverging from prior research. Crucial points in the combustion process, including zero-pressure points, valve timings, and flame ignition dynamics, were successfully identified. The research introduces a novel clockwise thermal cycle diagram based on ignition events and valve operations, providing real-time insights into combustion processes. Key findings include the identification of critical combustion process points, immediate flame ignition upon valve opening, and the introduction of an innovative thermal cycle diagram. The study's comprehensive approach, integrating pressure analysis, flame dynamics, and derivative curves, offers profound insights into the dynamics of pulsating combustors, furthering our understanding and providing avenues for optimization. Our comprehensive approach enhances the understanding of pulsating combustor dynamics and provides valuable insights for system improvement. The unconventional thermodynamic cycle underscores the novelty of our work. These findings are pivotal for enhancing combustion efficiency and reducing emissions, emphasizing the significance of further research and development in this field.

Positional effect of vortex generators on the combustion efficiency of the micro combustor fuelled with hydrogen/air mixture

The focus of this study is to explore the effect of vortex generator placement in a planar hydrogen combustor. The optimization of vortex generator placement is crucial for improving combustion efficiency and reducing pollutant emissions in the exhaust by achieving higher combustion. A numerical simulation model was developed using ANSYS- Reynolds-averaged Navier Stokes to examine the effect of vortex generators. Vortex generators were placed at four different locations away from the inlet at distances of 0.25 m, 0.30 m, 0.40 m, and 0.60 m such as 0.25S, 0.3S, 0.4S, and 0.6S models, respectively. Parameters such as combustion temperature, mass fraction of H2, mass fraction of H2O, turbulence intensity, and heat of reactions (HOR) were determined. The flow was assumed to be turbulent and steady, with hydrogen and air used as the fuel mixture. Hydrogen was released from the nozzle at a pressure of 300 bar and the velocity of air was 10 m/s. The strategic placement of vortex generators near the air inlet has been shown to have a significant impact on combustion temperatures and mixing, resulting in notable improvements in H2O formation and peak HOR. Furthermore, the utilization of vortex generators has been observed to enhance velocity magnitude and HOR, with the 0.25S model demonstrating the highest HOR values. 0.25S model also exhibited elevated temperatures and turbulent kinetic energy, indicating its potential for achieving optimal combustion efficiency. However, it is crucial to optimize the design and placement of vortex generators to mitigate disturbances in fuel spray patterns and attain the desired performance levels. Overall, these findings strongly suggest that vortex generators represent a promising technology for enhancing combustion efficiency and reducing emissions in planar combustors.

NOx and SO2 emission of oxygen carrier aided combustion in fluidized bed

Oxygen carrier aided combustion (OCAC) has been established as an innovative concept for improving fuel combustion in fluidized bed (FB) combustors. OCAC uses the particles of oxygen carrier (OC) to partly or completely replace the inert bed materials within the FB, which can make the oxygen distribution in the combustor more uniform and subsequently enhance combustion efficiency. However, the fundamental study on SO2 and NOx emissions during the OCAC is still not sufficient and controversial. In this work, the OCAC of coal and petroleum coke has been evaluated under different operating conditions on a lab-scale FB combustor with a special focus on the SO2 and NOx emissions. The conversion ratios of volatile-N (XV-N) and char-N (XC-N) have been quantitatively decoupled, and the influence of operating parameters on XC-N and XV-N has been revealed. Results showed that the OCAC concept has significantly reduced CO emission, enhanced NOx emission, and increased nitrogen conversion (XN). However, the NOx emission decreased by reducing the ilmenite ore proportion in the bed materials. This was attributed to the presence of ilmenite ore, which reduced the reducing regions and weakened the NOx reduction. Under OCAC operation, the XV-N increased significantly with the increase of O2 concentration and primary air ratio (A); and the variation of A shows a most decisive effect on XV-N. However, the XC-N was insensitive to the change of O2 concentration and A, when the XC-N was in the range of 31.01–34.89 % for all OCAC operations. The significant reduction of the SO2 emission during OCAC is mainly due to the employment of the ilmenite ore as bed materials that not only can absorb S element, but also lead to more uniform distribution of both oxygen and bed temperature, thereby improving the self-desulfurization of ash and reducing the sulfate decomposition.