Fuel Combustion Efficiency Research Articles

Numerical Simulation of CO Generation and Combustion Efficiency in Sintering Process: Effect of Solid Fuel Particle Size

For sintering pot productive process with various fuel particle size distributions, a transient numerical simulation sintering model based on the computational fluid dynamics approach is developed using Fluent 2021R1. The model combines chemical reaction, mass and heat transfer, Euler–Euler model, and fluid flow in porous media. In this study, CO is employed as the combustion's intermediate product, which is further oxidized by secondary combustion in the high‐temperature zone. Through calculations, the solid fuel combustion behavior of the sintering is explained collectively with the changing bed temperature, CO emission, and solid fuel combustion efficiency of the process under various fuel particle size distribution. In the sintering process, the fuel particle size distribution is crucial for lowering CO emissions and increasing combustion efficiency. The combustion efficiency shows a tendency of increasing initially before decreasing with the reduction of solid fuel particle size, while CO emissions show a trend of reducing first and then increasing. It is advantageous to lower the CO emission in the sintering process, and the combustion efficiency of the sintering process is greatly boosted by 5.13% when the proportion of solid fuel with 5 mm particle size decreases and the proportion of solid fuel with 3 mm particle size increases.

Study on the combustion characteristics and reaction mechanism of aluminum/alcohol-based nanofluid fuel

Enhancing the volumetric energy density of fuels is a crucial approach in the exploration of efficient energy sources. As a commonly used high-energy additive, Aluminum nanoparticles (Al NPs) holds broad application prospects. This study delves into the effects of Al NPs on the combustion characteristics of methanol and ethanol fuels through in-depth analysis of single droplet combustion and spray combustion experiments involving alcohol-based nanofluid fuels. The experiments revealed that adding Al NPs significantly enhances fuel combustion efficiency, shortening both the combustion life and ignition delay time. Spray combustion tests demonstrated that adding 2 wt% Al NPs increased the maximum and average flame propagation speeds of ethanol fuel spray by 48.93 % and 47.94 %, respectively, while the maximum explosion pressure rose from 0.66MPa to 0.83MPa, with a reduced time to reach peak explosion pressure by 106ms. Based on the SEM and XRD characterization results of the combustion residues and the analysis of flame morphology, a physical model of the alcohol-based nanofluid fuel spray combustion flame was established. Numerical simulations of the gas-phase kinetics model showed that the generation rates of radicals such as H, O, and OH were significantly increased with the addition of Al NPs, intensifying the combustion reaction. The findings provide a theoretical basis for future fuel design and combustion performance optimization.

Observed decade-long improvement of combustion efficiency in the Yangtze River Delta region in China

The ΔCO/ΔCO2 ratio is a good indicator of the combustion efficiency of carbon-containing fuels, and can be useful to assess the combustion efficiency on a regional scale. In this study, we analyzed in-situ observations of CO2 and CO concentrations from 2011 to 2021 at the Station for Observing Regional Processes of the Earth System (SORPES), in the Yangtze River Delta (YRD) region of eastern China, and calculated the ΔCO/ΔCO2 ratio to investigate the combustion efficiency in the YRD region. Furthermore, we used a Lagrangian particle dispersion model WRF-FLEXPART to evaluate the contribution of each emission sources to the observed ΔCO/ΔCO2 ratio. We found that the observed ΔCO/ΔCO2 ratio showed a persistent decreasing trend of 1.0 ppb/ppm per year and decreased ∼47.9% during this period, illustrating an evident improvement in the combustion efficiency in the YRD region. The improvement of the combustion efficiency is a result of China’s Air Pollution Prevention and Control Action Plan announced in 2013. However, the decrease of ΔCO/ΔCO2 ratio slowed down from 1.3 ppb ppm−1 per year during 2011–2016 to 0.6 ppb ppm−1 per year during 2017–2021. The simulation results reveal that the slowdown of the decrease in the ΔCO/ΔCO2 ratios can be explained by the slowing improvement of combustion efficiency in steel source in the industry sector. Our results verify the effectiveness of emission reduction efforts in the YRD region and highlight the necessity of long-term observations of CO2 and CO.

Effect of O2/n-C5H12 Ratio on Oxygenates Production from Plasma N-pentane Partial Oxidation

Objective: Non-thermal plasma is a promising method for producing clean fuels. This work provides a deeper understanding of the impact of O2/n-C5H12 ratio on the partial oxidation of n-pentane from both physical and chemical perspectives. Moreover, this work offers insight into improving fuel combustion efficiency and technical support for the preparation of clean fuels. Methods: An experimental system based on dielectric barrier discharge plasma was established. The discharge characteristics and product generation status of n-pentane partial oxidation were measured by changing the concentration of oxygen and n-pentane to evaluate different O2/n-C5H12 ratios. Results: Research on discharge characteristics showed that the O2/n-C5H12 ratio did not affect the discharge mode, and typical Lissajous shapes were present at different ratios. Changing the O2/n-C5H12 ratio affected the oxygen concentration, average electron energy or electron density, and background temperature. As the O2/n-C5H12 ratio increased, the conversion of the n-pentane partial oxidation reaction increased. However, changing the O2/n-C5H12 ratio did not affect the type of generated products. The oxygenates exhibited a volcano curve, and an O2/n-C5H12 ratio of 1.00 achieved the highest selectivity of 35.1%. As the O2/n-C5H12 ratio continued to increase, the selectivity of oxygenates decreased and the selectivity of CO2 increased. This was potentially due to a shift from partial oxidation toward complete oxidation, which led to the generation of secondary pollutants. Thus, higher O2/n-C5H12 ratios were not conducive to clean fuel production and environmental friendliness. Conclusion: In the partial oxidation of n-pentane, the highest clean fuel production rate was achieved when the O2/n-C5H12 ratio was 1.00. When this ratio exceeded 1.00, the reaction shifted toward complete oxidation, producing secondary pollutants. This study provides ideas for improving fuel combustion efficiency and technical support for the preparation of clean fuels.

Research on Boiler Energy Saving Technology Based on Internet of Things Data

This paper proposes a heat demand prediction model that analyzes the heat behavior of heat users, and analyzes the heat behavior data of heat users through a clustering algorithm to predict their heat demand. This paper is based on the supply-demand balance strategy to reduce the heat loss during the transmission of heat medium, and then improve the energy-saving efficiency of the boiler. The traditional boiler energy-saving and consumption reduction method is to optimize the boiler combustion parameters, improve the fuel combustion efficiency and waste heat recovery technology through the Internet of Things and big data technology. The method of balancing the heat-using end with the load of the boiler at low usage frequency is seldom considered. Therefore, this paper predicts the heat demand of the heat-using end by analyzing its thermal behavior, and balances the heat demand and boiler heat supply under the condition of meeting the heat demand. Finally, through simulation experiments, the validity of the model is verified, and the trend and data can be well predicted in the short-term heat demand prediction.

Combustion Efficiency of Carbon-neutral Fuel using Micro-Combustor Designed for Aerospace Applications

Recent advancements in the field of micro combustor research are growing for achieving high-performance systems in micro power generation and microelectromechanical devices. To mitigate the hazardous emissions from carbon fuels, as an alternative, zero-carbon-free fuels ammonia, and hydrogen are being explored in micro combustion processes. The distinctive feature of a micro combustor lies in its significantly higher area to volume ratio in comparison with traditional combustion systems, leading to accelerated combustion reaction rates. However, the small size of micro combustors poses a challenge in achieving efficient mixing of highly reactive fuels like hydrogen and ammonia with oxidizers. The unique properties of micro combustors can lead to differences in the combustion behavior of hydrogen and ammonia compared to larger-scale combustion systems. Hence, examining the performance of carbon-free fuels in micro combustors is crucial for the advancement of clean energy combustion systems. A numerical investigation on a Y-shaped micro-combustor was carried out to identify the aspects of non-premixed combustion of ammonia/air and hydrogen/air. The findings reveal that in the case of hydrogen combustion, stable flames were reached, even at low equivalence ratios. Therefore, the distinct combustion properties of hydrogen and ammonia result in varying NOx emissions, with hydrogen generally leading to higher NOx levels due to its higher flame temperature and increased thermal NOx production.

Role of cavity in a Mach 8 axisymmetric scramjet combustor: Flame stabilization vs combustion enhancement

The cavity-assisted scramjet has been proven to be the most promising propulsion system for air-breathing hypersonic vehicles. In this paper, numerical simulations of a Mach 8 axisymmetric scramjet combustor are conducted and validated to investigate the effect of the cavity. The results indicate that the combustion state undergoes significant changes as the combustion heat release increases. Detailed analysis reveals that the role of the cavity in flame stabilization and combustion enhancement also changes with combustion heat release. Under weak heat release conditions, the high-speed environment results in reduced combustion efficiency, and the primary role of the cavity is to stabilize the flame. Increasing the cavity size does not yield significant gains but could bring redundant mass. As heat release intensifies, the combustion enhancement effect of the cavity becomes more prominent. The presence of the cavity dramatically improves fuel combustion efficiency. The distribution of supersonic and subsonic combustion modes, as well as that of premixed and diffusion combustion modes, is also affected by cavity size and combustion heat release. In the engineering development of scramjets, it is suggested that the design of the cavity flameholder should involve careful consideration of combustion heat release.

Ignition and thermal decomposition of solid organic fuel: The influence of activation, deactivation, and composite formation

The article discusses research on the thermal decomposition and ignition of coal, pine sawdust, and composite fuels derived from them. Through simultaneous thermal analysis, it was observed that the combustion process occurs in two primary stages. In the first stage, gaseous products are released and burned, while in the second stage, carbon produced in the first stage undergoes oxidation. The study also revealed the impact of mechanical activation and deactivation of ground fuel. Interestingly, the properties of coal and sawdust in the composite fuel formation are not simply additive. When the composite contains more carbon, there is a shift in the maximum decomposition rates towards higher temperatures in the first stage. Additionally, there is a decrease in decomposition magnitude during the first stage and an increase during the second stage. Moreover, it was found that the combustion temperatures of the composite fuel and mixture are higher than those of sawdust alone. Furthermore, the composite fuel exhibits superior burning characteristics as compared to the mixture. It ignites earlier, and the combustion zone shifts towards the center, resulting in enhanced fuel combustion efficiency.

A ReaxFF and DFT study of effect and mechanism of an electric field on JP-10 fuel pyrolysis

To investigate the sustainable use of electric fields in improving aviation fuel combustion efficiency, a ReaxFF molecular dynamics simulation was conducted using exo-TCD (exo-tetrahydrocyclopentadiene) as the major component of JP-10 fuel. The study aimed to investigate the pyrolysis efficiency and the mechanism of electric field modulation at different temperatures. It elucidates that the pyrolysis reaction activation energy and molecular motion are the key factors affected by the co-effect of temperature and electric field. A filed strength of 10−5 V/Å was shown to increase both the reaction barriers and the probability of collision for JP-10 molecule pyrolysis, which promotes a higher reaction rate in weak electric fields with high-temperature pyrolysis. The DFT calculation was used to analyze the electronic structure and reaction potential of the JP-10 molecule under the electric field, which further discloses the effect mechanism of electric field on the pyrolysis reaction pathway. This study provides a detailed explanation of combined effects of temperature and electric field effect on aviation fuel pyrolysis to enable effective combustion of aviation fuels.

Humic-like Substances (HULIS) in Ship Engine Emissions: Molecular Composition Effected by Fuel Type, Engine Mode, and Wet Scrubber Usage.

Humic-like substances (HULIS), known for their substantial impact on the atmosphere, are identified in marine diesel engine emissions obtained from five different fuels at two engine loads simulating real world scenarios as well as the application of wet sulfur scrubbers. The HULIS chemical composition is characterized by electrospray ionization (ESI) ultrahigh resolution mass spectrometry and shown to contain partially oxidized alkylated polycyclic aromatic compounds as well as partially oxidized aliphatic compounds, both including abundant nitrogen- and sulfur-containing species, and clearly different to HULIS emitted from biomass burning. Fuel properties such as sulfur content and aromaticity as well as the fuel combustion efficiency and engine mode are reflected in the observed HULIS composition. When the marine diesel engine is operated below the optimum engine settings, e.g., during maneuvering in harbors, HULIS-C emission factors are increased (262-893 mg kg-1), and a higher number of HULIS with a shift toward lower degree of oxidation and higher aromaticity is detected. Additionally, more aromatic and aliphatic CHOS compounds in HULIS were detected, especially for high-sulfur fuel combustion. The application of wet sulfur scrubbers decreased the HULIS-C emission factors by 4-49% but also led to the formation of new HULIS compounds. Overall, our results suggest the consideration of marine diesel engines as a relevant regional source of HULIS emissions.

Research on the Impact of Supplying the Air-Cooled D21A1 Engine with RME B100 Biodiesel on Its Operating Parameters

It is known that the use of alternative fuels leads to changes in the operating parameters of internal combustion engines, and the nature of the changes in most cases is not known. Therefore, the question of researching the main operating indicators of the internal combustion engine supplied with RME B100 biodiesel fuel is important, and the results will help to eliminate or reduce negative factors that can lead to the deterioration of the operational and technical indicators of the internal combustion engine. The purpose of the research was to develop an experimental research facility using appropriate equipment and to study the main operational and technical parameters of the air-cooled D21A1 diesel engine on RME B100 biodiesel fuel. To reach the goal, the following tasks were formulated: the development of a test facility and research on the main technical and operational performance indicators of the D21A1 diesel engine on RME B100 biodiesel fuel. The authors’ previous research results were applied in the setting of the D21A1 test engine in the process of RME B100 biodiesel research; namely, to achieve maximum fuel combustion efficiency, the injection moment was increased by 6°. The results ensured the maximum efficiency of using RME B100 biodiesel in engines without making changes to the design of the latter. System analysis and the comparison method were used during the research. In the process of using RME B100 biodiesel fuel on the air-cooled D21A1 engine, we found a decrease in engine torque of 6.5%; a decrease in effective power of 6.7%; a growth in specific effective fuel consumption of up to 22.3%; and an increase in hourly fuel consumption of 14.1%. This is because the use of RME B100 fuel requires changes in the engine design that improve the mixture formation process.

Combustion optimization of a hydrogen free-piston engine with high-energy ignition

With the advantages of simple structure, high power density, and better fuel adaptability, the hydrogen FPE is one of the ideal onboard power devices for new energy vehicles in the future. The combustion system is essential for forming the in-cylinder mixture and the stable operation of the engine. This paper compares combustion, injection, and performance at different ignition energy using high-energy ignition methods and applying computational fluid dynamics simulations. In order to further optimize the combustion system, the influence of ignition timing was discussed. The results show that with the increase of ignition energy, the flame kernel size increases continuously, the speed of flame propagation increases, and the mixture participating in combustion increases simultaneously. When the ignition energy reaches 300 mJ, the fuel combustion efficiency rises to 90.22%, and the indicated thermal efficiency rises to 32.76%. Finally, a comparison was made with a gasoline FPE; the hydrogen FPE in this paper reduces the NO emission value to less than 20 ppm without any after-treatment device, while no other pollutants are generated. The performance stability of pure hydrogen combustion under FPE is preliminarily revealed.

Application of a clean fuel produced by electrolysis in iron ore sintering process: Brown gas injection to assist sintering

Using a clean fuel produced by electrolysis named Brown gas to assist sintering in the iron ore sintering process was proposed to reduce coke consumption and carbon emissions. The effect of additional injection of Brown gas on the combustion characteristics and the quality of the sintered ore were explored. An optimal fuel ratio was investigated by gradually reducing the coke ratio based on Brown gas injection. The experimental results show that additional injection of Brown gas improves the thermal mode of the sintering bed, improves fuel combustion efficiency, prolongs the duration time of melting temperature, and the sintered ore yield and shatter strength first increases and then decreases, reaching the maximum value at an injection concentration of 2%. Based on a Brown gas injection concentration of 2%, the coke ratio can be reduced from 4.5% to 4% without affecting the quality of the sintered ore. As the coke ratio further decreases to 3.5%, the quality of the sintered ore deteriorates even if the Brown gas injection concentration increases to 3%. Based on a 2% Brown gas injection, the consumption of coke can be reduced by 11.1%, and the carbon emissions during the sintering process can be reduced by 11.1%.

Study of the characteristics and combustion efficiency of liquid kerosene/oxygen-enriched air rotating detonation wave with different modes

In a liquid kerosene rotating detonation engine (RDE), detonation waves often exhibit different propagation modes. The propagation characteristics with different modes are worthy of further study. To further investigate the propagation characteristics, a series of experiments was conducted, and the flow field characteristics under different modes were comparatively studied using high-speed photography and pressure sensors. The modal features and mode change trends obtained in the experiments were simulated using numerical methods. Based on this, the combustion efficiencies of the different modes were quantitatively characterized. The results showed that with increasing propellant mass flux, the detonation wave gradually changes from the two-counter wave mode to the single-wave mode, and the interim mode is a hybrid mode. Compared with the two-counter wave mode, the velocity deficit of a single wave is smaller, and the reaction zone is more compact. Numerical simulations show that a higher proportion of fuel is consumed by more violent chemical reactions in the single-wave mode; that is, the combustion efficiency in the single-wave mode is higher than that in the two-wave mode. The results provide a reference for further understanding the liquid fuel detonation phenomenon and improving fuel combustion efficiency.

Effect of ammonia injection stages and segregation degrees on the characteristics of iron ore sintering process

To reduce solid fuel consumption and carbon emissions during iron ore sintering, ammonia injection-assisted sintering was proposed, and its feasibility was verified through sinter pot experiments. The effects of ammonia injection stages and segregation degrees on the sintering characteristics were investigated based on the uneven heat distribution in the sintering bed. The results show that ammonia injection improves fuel combustion efficiency, sinter bed temperature and melting quantity index. The sinter ore strength and yield were improved, and the effect of injecting ammonia in the early sintering stage was more significant. When the ammonia injection segregation degree is 0.042 %/min, the sinter ore yield and tumbler index increase from 61.93% and 49.4% to 68.85% and 58.8%, respectively, the average fuel combustion efficiency increases from 89.02% to 92.30%. When the segregation degree increases from 0 to 0.125 %/min, the standard deviation of the uniformity coefficient of the high-temperature index first decreases and then increases, reaching the minimum value when the segregation degree is 0.042 %/min. A segregation degree of 0.042 %/min can achieve the most uniform heat distribution in the sintering bed and the best sinter ore quality, which provides a reference for applying ammonia injection-assisted sintering in industrial production.

Real-world emission characteristics and inventory of volatile organic compounds originating from construction and agricultural machinery

Volatile organic compound (VOC) emissions originating from nonroad mobile sources constitute an important but uncertain source of secondary organic aerosols (SOAs) and ozone (O3). In this study, we investigated the emission factors (EFs) of 120 individual VOC species for 40 machines via gas chromatography–mass spectrometry/flame ionization detection and high-performance liquid chromatography. The results showed that the diesel-based VOC EF for the tested machines was 4.18 ± 2.55 (average ± standard deviation) g/kg fuel, dominated by alkanes (38.20 % ± 18.08 %) and oxygenated VOCs (OVOCs; 30.94 % ± 15.71 %). The machine type, rated power, emission standards, and operating conditions affected the emissions of VOCs and their components, and this effect maybe mostly depends on the fuel combustion efficiency. The VOC species were primarily distributed in the C1–C2 and C4–C6 (based on the carbon number) and B4–B6 (based on the saturated vapor concentration) intervals. Furthermore, the estimated formation potential (FP) values of SOAs and O3 from VOCs were 21.02 ± 15.57 mg/kg fuel and 15.96 ± 11.87 g/kg fuel, respectively. VOC control based on the SOA formation potential (SOAFP) and ozone formation potential (OFP) could be more effective in the mitigation of fine particulate matter (PM2.5) and O3 pollution because the top 5 species ranked by percentage contribution accounted for 83.09 % ± 9.59 % and 51.78 % ± 14.38 % of the estimated SOAFP and OFP, respectively. Finally, the emission estimates showed that the VOC emissions originating from construction and agricultural machinery in China (2020) reached 64.05 and 95.24 Gg, respectively. We provide species-specific VOC EFs and detailed emission characteristics to facilitate a comprehensive understanding of gas emissions originating from nonroad mobile sources and an update of emission inventories and atmospheric chemistry models.

Numerical study on the dynamic process of ramjet/scramjet mode transition in the integrated RBCC full flow path through multistage fuel injection strategies

The rocket-based combined-cycle (RBCC) engine usually completes the transition process from ramjet to scramjet mode under the Ma∞ = 5.5–6.0. The dual-mode (ramjet/scramjet) transient process is an important technology for engine operation. CFD modeling based on Reynolds average Navier-Stokes was for studying the influence of fuel injection position, high-temperature rocket jet and fuel throttling time on the combustion flow structure and transient characteristics of RBCC engine during the mode transiton . The results showed that whether RBCC engine could successfully achieve stable mode transition was mainly influenced by flame stability in the combustor. When the rocket shuts down, it was more suitable to choose the fuel injection arrangement which distributed downstream of the combustor to realize relatively smooth mode transition. The analysis shows that in the mode transition process, using the synergistic combustion-supporting effect of the cavity and the strut is beneficial to improve the fuel combustion efficiency and reduce the thrust fluctuation. Although the high temperature rocket jet with low mass flow rate cannot maintain the fuel combustion in the isolator at high Mach number, it can expand the high temperature combustion area width in the central flow of RBCC engine and increase the secondary fuel combustion efficiency. Therefore, keeping the rocket running at low mass flow rate can reduce the thrust drop caused by insufficient fuel heat release. When adopting a mode transition strategy that throttles the fuel linearly over time, the engine can go through the thrust dip more smoothly, but this correspondingly increases the time required for the internal flow field to stabilize.

Improving the Efficiency of Fuel Combustion with the Use of Various Designs of Embrasures

Currently, NOX emission requirements for thermal power plants and power equipment are being tightened. Regime and technical measures are being developed to improve the efficiency of fuel combustion in boilers. Due to the high cost of field studies, and in some cases the impossibility of conducting them, mathematical modeling tools allow one to work out technical and tactical measures. In this paper, the multidisciplinary STAR-CCM+ platform with GMU-45 type burners is used to simulate the combustion of gaseous fuel in a digital model of an energy boiler of the type TGME-464. By conducting numerical experiments, the possibility of reducing NOX emissions by using flue gas recirculation is considered, and the efficiency of burner devices is compared when using different embrasure configurations.

Intensive carbon combustion in sintering packed bed via steam spraying: An experimental study on carbon monoxide emission reduction.

Improving the combustion efficiency of solid fuels is important for reducing carbon monoxide emissions in the iron ore sintering process. In this paper, the surface steam spraying technology is introduced in the sintering process based on the auxiliary combustion effect of steam on coke, and its potential to reduce carbon monoxide emissions is demonstrated. Thermogravimetric analysis experiments of coke breeze in air and air-steam mixed atmosphere are carried out, and the results show that the introduction of steam can reduce the concentration of carbon monoxide in the exhaust gas from 183×10-6 to 78×10-6. At the same time, the mechanisms of carbon monoxide emission reduction by surface steam spraying technology are analyzed from the thermodynamic and kinetic perspectives. Then, a series of laboratory-scale sintering pot tests are carried out under no spraying operation, interval spraying operation, and continuous spraying operation. The results indicate that both interval and continuous spraying operations can reduce carbon monoxide emissions. The optimal mode of steam spraying under the present experimental conditions is continuously spraying for 13 min at a volume rate of 0.053 m3/min. Compared with no spraying, the average carbon monoxide concentration in the exhaust gas is reduced from 7565×10-6 to 6231×10-6, and total carbon monoxide emissions for per ton sinter are reduced from 13.46 m3/t to 9.51 m3/t.

Experimental study results of the front-end device with two-tier air burner as part of the gas turbine engine combustion chamber

In recent years, the gas turbine power plant has been increasingly used in various industries in Kazakhstan. The reasons for this are: thermal efficiency, simplicity of the thermal scheme and design, small mass per power unit, high maneuverability, low toxicity, and relatively simple automation of operation. This paper presents the experimental study results of a two-tier air burner as the part of the gas turbine engine combustion chamber at burning liquid fuel. ? new design of a microflame device was developed. Two-tier burner makes possible the combustion process in a number of discrete zones, i.e. microflame combustion. During the experiment, the installation angles of the blades of the external and internal registers, as well as the ratio of the coefficients of excess air in the tiers, were changed. The experimental studies of a two-tier burner confirmed the possibility to increase fuel combustion efficiency, a low degree of temperature field unevenness and to decrease NOx emission.