Enhance Combustion Efficiency Research Articles

Effect of rear blunt body structure and inlet conditions on the flow and combustion characteristics of an advanced vortex combustor for a gas turbine

The rear blunt body plays a crucial role in the total performance of an advanced vortex combustor. This paper presents a numerical simulation study on the flow and combustion characteristics of an advanced vortex combustor fueled by liquid aviation kerosene under atmospheric pressure conditions, with inlet velocities of 0–100 m/s and inlet temperatures of 300–800 K. Different structural and aerodynamic parameters, including cavity length, rear blunt body height, rear blunt body width and inlet conditions are studied to determine the variation trends of the velocity field, total pressure recovery coefficient, fuel concentration field, combustion efficiency, outlet temperature distribution and pollutant emissions. The results indicate that the presence of the rear blunt body facilitates the formation of a dual vortex structure within the cavity, leading to an increased total pressure recovery coefficient, an improved fuel concentration distribution, an enhanced combustion efficiency, and a more uniform outlet temperature distribution. At an inlet velocity of 100 m/s, the total pressure recovery coefficient increases from 97.01 % to 97.29 %. However, as the cavity length, the rear blunt body height and width increase, the total pressure recovery coefficient and the CO emission increases, and the combustion efficiency, outlet temperature distribution and NO emission decrease to different degrees. In addition, an increase in inlet temperature enhances the fuel concentration distribution, leading to improved combustion efficiency, better outlet temperature distribution, and an increase in NO emission. Additionally, it results in a reduction in CO emission. As the inlet temperature increases from 500 K to 800 K, the combustion efficiency increases from 86.57 % to 92.81 %, representing a growth rate of 7.21 %. In summary, when the cavity length is 24 mm, the rear blunt body height is 24 mm, the rear blunt body width is 5 mm, and the inlet temperature is 800 K, the overall combustion performance of the advanced vortex combustor is optimal, which is conducive to providing an important theoretical basis for the design and optimization of advanced vortex combustors.

Enhancement of Aeroengine Combustion Chamber Air Cooling Holes Design for Emission Reduction and Pattern Factor Control

The results of a comprehensive numerical analysis of temperature uniformity and NOx and CO emission predictions in an aeroengine annular combustor liner, conducted by geometrical modifications through design changes in primary cooling air, including effusion cooling holes, are shown in the paper. A total of five geometric configurations were studied using computational fluid dynamics (CFD) simulations in ANSYS CFX. The adopted combustion model was sort of a combination of the finite-rate (i.e., chemistry, chemical processes) and eddy dissipation model (FRC/EDM). Further, the combustion of liquid kerosene (C10H22) with air, subsequent to the evaporation of fuel droplets, was simulated, and the Rosin-Rammler droplet size distribution was used in spray modeling for accurate depiction of fuel atomization. Both thermal and prompt formation mechanisms of NOx were considered, while k-ε model for turbulence was adapted to capture the nature of emission. An annular combustion chamber of realistic dimensions with a double radial air swirler was modelled in 3D CAD to undertake this study for good, tangible results. Built contour plots allowed to analyze the temperature distribution and NOx concentration along the axis from the center of the injector. Charts on the pattern factor, temperature, and NOx and CO concentrations at the outlet of the combustor served as performance metrics. The simulation was implemented with a two-step chemical kinetics scheme for kerosene combustion with the P1 radiation model, which would give an accurate thermal radiation prediction. One of the major objectives of this research is to compare the CFD results at the combustor outlet with gas dynamic and thermodynamic calculations that have been carried out using AxStream software at the Department of Aeroengine Design, Kharkiv Aviation Institute. It is important to emphasize that the mean deviation of gas dynamic results obtained from AxStream and CFD simulation results was found to be insignificant, hence the CFD approach has been validated. The results testify that redesigning the combustor liner, especially in the design related to primary and effusion cooling holes, drastically reduced NOx and CO emissions. Also, these design modifications have helped in reducing or improving temperature uniformity at the combustor outlet, either way enhancing combustion efficiency and performance.

Evaluation of Operability and Exhaust Emissions of Common Rail Direct Injection Engine using Biodiesel Blends in Moderate Cold Environment

Malaysia has restricted the use of biodiesel blends to B7 in the highlands due to challenges related to cold flow operability, while B10 and B20 are used in the lowlands. This study evaluated the performance and emissions of a light-duty, 4-cylinder Euro III turbocharged common rail direct injection diesel vehicle using palm biodiesel blends (B10, B20, and B30) at speeds of 60, 80, and 100 km/h under simulated cold temperatures of 10, 15, and 20°C in a controlled cold chamber. The combustion of B10 and B20 in the diesel engine showed enhancements in power and torque of 3.9% and 4.6%, respectively, compared to Euro 2M (B7) diesel. These improvements are likely the result of the synergistic effects of the enriched oxygen levels in biodiesel and the increased density of cold air, which enhance combustion efficiency. CO2 emissions decreased by 1.5%, 4.3%, and 11.2% with the use of B10, B20, and B30 fuels, respectively. NOx emissions decreased as biodiesel content increased at 10 and 15°C; however, the emissions increased by 17.6% and 38.2% for B20 and B30, respectively, in comparison to B10 at 20°C. B20 demonstrated good engine performance and emissions at 15°C, with improvements of 1.3% in power and 3.7% in torque, which compensated for a 3.2% increase in fuel consumption, and there were reductions of 8.9% in NOx emissions and 0.9% in CO2 emissions compared to B7 diesel. Palm biodiesel blends ranging from 7 wt.% to 20 wt.% are capable of withstanding the moderate cold ambient temperatures of the highlands without compromising engine operation.

Image Processing Technique for Enhanced Combustion Efficiency of Wood Pellets

The combustion efficiency of wood pellets is partly affected by their average length. The ISO 17829 standard defines the methodology for assessing the average length of sample pellets, but the method does not always lead to representative data. Furthermore, a standard analysis is time-consuming as it requires manual measurement of the pellets using a caliper. This paper, whilst evaluating the effect of pellet length on combustion efficiency, proposes a pending-patented dimensional image processing method (DIP) for assessing pellet length. DIP allows the dimensional data of grouped and stacked pellets to be obtained by exploiting the shadows produced by pellets when exposed to a light source, assuming that different-sized pellets produce different shadows. Thus, the proposed method allows for the extraction of dimensional information from non-distinct objects, overcoming the reliance of classical image processing methods on object distance for effective segmentation. Combustion tests, carried out using pellets varying only in length, confirmed the influence of length on combustion efficiency. Shorter pellets, compared to longer ones, significantly reduced CO emissions by up to 94% (mg/MJ). However, they exhibited a higher fuel mass consumption rate (kg/h), with an increase of up to 22.8% compared to the longest sample. In addition, longer pellets produced fewer but larger shadows than shorter ones. Further studies are needed to correlate the number and size of shadows with samples’ average length so that DIP could be implemented in stoves and programmed to communicate with the control unit and automatically optimize the setting in order to improve combustion efficiency.

Effects of Heat Transfer on Combustion Characteristics in a Cylindrical Vortex Combustor

A vortex flows in micro/meso scale combustors for small-scale power generation play a crucial role in enhancing combustion efficiency and stability. They enhance mixing between fuel and air, promoting better combustion and help stabilize flames by maintaining consistent fuel-air ratios. The temperature are significantly impacts the reactant temperature due to heat conduction wall in Cylindrical Vortex Combustor (CVC). This phenomenon, known as preheating, occurs as the wall transfers heat to the reactants. ANSYS Fluent software is used for conducted a numerical investigation on a CVC. The combustor was characterized by a prescribed mass flow rate of 40 mg/s and an equivalence ratio (j) ranging from 0.5 to 1.5. Our analysis aimed to understand the combustion behavior within this confined geometry, considering factors such as heat loss and temperature behavior. The numerical findings indicate that elevated equivalence ratios correlate with the highest flame temperature in micro-combustion. Specifically, at an equivalence ratio of j=0.5, the flame temperature remains consistently low compared to the higher value of j=1.5. However, when accounting for wall temperature effects, the maximum flame temperature occurs at an equivalence ratio of j=1.3. The heat dissipation region is quite limited, especially at low equivalence ratio. In summary, heat transfer in cylindrical vortex combustors (CVC) contribute to reliable and efficient power generation, making them essential for portable energy systems.

Seebeck coefficient and thermal properties of graphene oxide doped calcium cobalt copper oxide nanoceramics

In this study, graphene oxide undoped and doped Ca3Co3.8Cu0.2Ox nanoceramic materials were produced using the sol–gel method. After achieving gelation of the mixtures produced via this method, calcination was carried out to remove organic structures. The nanoceramic powders obtained from calcination were compressed as pellets, which were sintered to ensure the fusion of the structures. Graphene oxide undoped and doped pellets were characterized, and the Seebeck coefficient and thermal conductivity as a function of temperature were determined for these samples using a physical properties measurement system device. Upon examining the characterizations, it was generally observed that the crystallite sizes decreased with the addition of graphene oxide, which was consistent with the XRD and SEM results. When the peaks in the FTIR results were compared with the compound bond structures in the XRD results, they were found to be compatible in both samples. Additionally, when the EDX and mapping results were examined, the elements were found to be consistent with the XRD, FTIR and TGA results. TGA analysis demonstrated that graphene oxide doping shifted decomposition temperatures and enhanced combustion efficiency by reducing carbon content. BET results demonstrated that graphene oxide doping significantly increased the surface area and alters the pore structure. In the Seebeck coefficient results, the addition of graphene oxide provided a 1.3-fold advantage at room temperature, and a 10-fold advantage in thermal conductivity was observed with the addition of graphene oxide.

Experimental Investigation on Combustion Characteristics of LHR and Conventional Engines Using Tobacco and Cotton Seed Methyl Ester Blend

This study presents an experimental investigation into the combustion characteristics of Tobacco Seed Oil Methyl Ester (TSOME), Cotton Seed Oil Methyl Ester (CSOME) and its blend (TCOME) as alternatives fuel in both conventional and Low Heat Rejection (LHR) engines. The LHR engine, integrating thermal barrier Ni90 insert is inserted on piston crown to enhance combustion efficiency by reducing heat loss. The work focuses on comparing key combustion parameters such as in-cylinder pressure and heat release rate (HRR) for TSOME, CSOME and its blend in both engines across varying load conditions. The experimental results indicate that both biodiesel fuels and its blend demonstrate good combustion characteristics near to conventional diesel. The LHR engine with blend outperformed compare to the conventional engine of higher peak pressures and heat releasing rate compared to CSOME and TSOME. Peak inside cylinder pressure and heat releasing rate occurred for both engines at 80% of load, for LHR engine peak pressure is 10% high and similarly heat releasing rate is 13% high compare to conventional engine. The present work suggests that the combination of LHR engine with blend of TSOME and CSOME offer a viable solution for improving engine combustion efficiency while reducing consumption of conventional fuels.

Gold nanocatalysts supported on Mono-/Mixed oxides for efficient synthesis of methyl methacrylate

Developing sustainable methods for producing methyl methacrylate (MMA) has gained strategic importance for industrial applications and as a promising oxygenated fuel additive to enhance combustion efficiency and reduce emissions. This dual-purpose approach addresses both industrial needs and the growing demand for cleaner fuel solutions. Our study focuses on synthesizing gold nanoparticles (AuNPs) supported by alumina (Al2O3), cerium oxide (CeO2), and Al2O3/CeO2 combination by deposition–-precipitation method, aiming to advance far-reaching MMA synthesis through direct oxidative esterification (DOE) of methacrolein (MAL) with methanol. The research explores the relationship between catalyst structure and activity, particularly investigating the impact of AuNPs doping on Al2O3, CeO2, and Al2O3/CeO2 and the mechanism that promotes selective oxidation. The intimate interaction between CeO2 and Al2O3 and adequate doping of AuNPs with Al2O3/CeO2 is beneficial in enhancing catalytic activity and facilitating selective oxidation. Notably, Au/Al2O3/CeO2 demonstrated significantly higher catalytic activity compared to Au/Al2O3 and Au/CeO2 catalysts, achieving 98% MAL conversion and 95% MMA selectivity. The reaction yield, in particular, strongly correlated with surface and active oxygen species around AuNPs. This highly efficient catalytic process provides a green route for MMA production and enables its application as a sustainable fuel additive, contributing to improved engine performance and reduced environmental impact. The optimized catalyst system presents a viable pathway for both industrial chemical production and sustainable energy applications, addressing crucial environmental and energy challenges simultaneously.

Effect of Nozzle Type on Combustion Characteristics of Ammonium Dinitramide-Based Energetic Propellant

The present study explores the influence of diverse nozzle geometries on the combustion characteristics of ADN-based energetic propellants. The pressure contour maps reveal a rapid initial increase in the average pressure of ADN-based propellants across the three different nozzles. Subsequently, the pressure tapers off gradually as time elapses. Notably, during the crucial initial period of 0–5 μs, the straight nozzle exhibited the most significant pressure surge at 30.2%, substantially outperforming the divergent (6.67%) and combined nozzles (15.5%). The combustion product variation curves indicate that the contents of reactants ADN and CH3OH underwent a steep decline, whereas the product N2O displayed a biphasic behavior, initially rising and subsequently declining. In contrast, the CO2 concentration remained on a steady ascent throughout the entire combustion process, which concluded within 10 μs. Our findings suggest that the straight nozzle facilitated the more expeditious generation of high-temperature and high-pressure combustion gases for ADN-based propellants, expediting reaction kinetics and enhancing combustion efficiency. This is attributed to the reduced intermittent interactions between the nozzle wall and shock waves, which are encountered in the divergent and combined nozzles. In conclusion, the superior combustion characteristics of ADN-based propellants in the straight nozzle, compared to the divergent and combined nozzles, underscore its potential in informing the design of advanced propulsion systems and guiding the development of innovative energetic propellants.

Combustion performance of an evaporative flameholder under subsonic-supersonic mixing inflow

The combustion process in rocket-assisted subsonic ramjet engines represents a key advancement in integrated aerospace propulsion, particularly for embedded rocket-based systems. These engines offer the potential to improve combustion performance at altitudes of 25–35 km. However, the significant temperature and velocity differentials between the rocket jet and the subsonic ramjet flow restrict heat and mass transfer. Investigating the relationship between combustion performance and inlet parameters under subsonic-supersonic mixing conditions offers a promising approach to enhancing thrust performance. This study introduces subsonic and supersonic airflow mixing via a flat-plate shear layer in a rectangular channel, with an evaporative flameholder placed centrally to assess combustion. Results reveal that combustion efficiency decreases as the equivalence ratio exceeds 0.2, while the static temperature ratio has minimal impact on efficiency but strongly influences the maximum flame stabilization limit. As the temperature ratio increases from 1.30 to 1.80, the flame limit narrows from 1.656 to 0.237. Higher pressure ratios initially enhance combustion efficiency and flame coverage but eventually cause a decrease. The flame limit broadens from 0.900 to 1.626 as the pressure ratio increases from 1.12 to 1.50. While Mach number changes have little effect on efficiency, the flame limit exhibits an initial rise followed by a drop. Novel findings include an asymmetrical flame pattern and a “Z” shaped outlet temperature distribution, contributing to optimized combustion strategies for combined-cycle engines.

Enhancing Combustion Efficiency: Utilizing Graphene Oxide Nanofluids as Fuel Additives with Tomato Oil Methyl Ester in CI Engines

The research aims to conduct a thorough examination of the combustion, injection, performance, and emission characteristics of a diesel engine below different engine loads, as well as the synthesis of graphene oxide (GO) nano fuels and their utilization in combination with Tomato Oil methyl ester (TOME) and diesel fuel blend. The graphene oxide, plays a vital role in the pre-mixed combustion phase of diesel engines. Addition of graphene oxide nano fuels enhances the high-pressure combustion stage, resulting in increased maximum pressure and heat release rate. TOME (B20GO75) and TOME (B20GO100) exhibit comparable heat release rate to diesel due to improved fuel characteristics and quicker ignition delay duration. While TOME (B20) shows a slight decrease in (BTE) compared to diesel, the addition of graphene oxide improves BTE, with TOME (B20GO50) displaying the highest BTE at full load, indicating enhanced combustion efficiency. Moreover, graphene oxide addition leads to a reduction in carbon monoxide (CO) and hydrocarbon (HC) emissions, with emissions decreasing as the concentration of graphene oxide increases. However, NoX emissions initially decrease with TOME (B20) compared to diesel but increase with higher graphene oxide concentration. Smoke emissions increase with TOME (B20) but decrease with higher graphene oxide dosages. Overall, the incorporation of graphene oxide nano fuels into Tomato Oil methyl ester blends demonstrates potential for improving engine performance and reducing emissions.

Investigation the Thermal Behavior of Lemon and Orange Peels Composite Fuel Diesel

Background: The aim of this research is to investigate the thermal behavior of a composite fuel prepared by mixing diesel fuel with citrus peel powder in the presence of activators and combustion accelerators. The study focused on utilizing abundant citrus waste, such as lemon and orange peels, as sustainable bioresources to reduce environmental pollution and optimize fuel efficiency. The research explored the thermal properties of the composite fuel and compared it with pure diesel through combustion experiments conducted at atmospheric pressure and combustion pressure in the engine. Methods: The study set the limits of the investigation to various proportions of lemon and orange peel powder mixed with diesel, ranging from 5% to 15% by mass of the total fuel composite. Two catalysts, sodium hydroxide (NaOH) and sulfuric acid (H2SO4), along with calcium oxide (CaO) powder were incorporated into the mixtures as activators to enhance combustion efficiency. The composite fuel characterization included thermogravimetric analysis (TGA) and thermographmetric station experiments to observe the combustion processes and assess the thermal behavior of the composite fuel. Results: The results revealed four distinct phases of combustion during the burning time of 60 seconds: volatile combustion, liquid combustion, combustion of solid materials, and the interaction of active substances with combustion residues. Using activators and catalysts significantly enhanced combustion efficiency and minimized the amount of residue produced during the process, resulting in thermal behavior that is more similar to that of pure diesel. Lemon peel powder with activators demonstrates better thermal behavior compared to orange peel powder. Conclusions: Based on the findings, some recommendations are proposed for further development such as the optimization of activator ratios, exploration of different proportions of lemon and orange peel powder, and investigation of other catalysts. Real-world engine performance tests and emission profile analysis can validate the thermal behavior results obtained from combustion experiments.

To Study the Effects of Microemulsion Based Hybrid Biofuel on Emission Characteristics of CI Engine: A Short Review

AbstractMicroemulsion based fuels (MBF) have gained significant attention in recent years due to their potential to enhance combustion efficiency, reduce emissions, and improve overall engine performance. This research paper enlightens the effects of physiochemical properties on the emission characteristics of CI engine. The microemulsions are formulated using surfactants, co‐surfactants, water or alcohols, and fuel components. The effects of density, viscosity, calorific value, cold flow properties, and cetane number along with the stability and the multi‐component characteristics of (MBF) has been taken into consideration to examine its effects on Emission characteristics such as nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), particulate matter (PM), and unburned hydrocarbons (UHC). Microemulsion‐based fuels lower emissions of NOx and PM, recognized to the more complete combustion. The review highlights various studies that have investigated the benefits of microemulsion fuels, including reduced emissions of different pollutants and thus reduce the adverse effect on environment.In conclusion, microemulsion‐based fuels show likely physiochemical properties, as well as favorable emission characteristics, with reduced NOx, SOx, CO, PM, and UHC emissions. This study highlights the potential of microemulsion‐based fuels as environment friendly alternatives, flagging the way for further research.

Unraveling the Nanosheet Zeolite-Catalyzed Combustion of Aluminum Nanoparticles-Doped exo-Tetrahydrodicyclopentadiene (JP-10) Energetic Fuel.

Nanosheet MFI zeolites (Zeolite Socony Mobil, five) have grown in popularity in cracking catalysis considering their tunability in porous topologies, acidic sites, and sheet thickness, thus allowing them to selectively adsorb molecules of specific sizes, shapes, and polarities, resulting in improved cracking performance for a specific fuel. Five different MFI zeolites in the form of a mesoporous nanosheet structure with a controlled concentration of acidic sites denoted as NSMFI(y), where y is Si/Al ratio, have been synthesized. The effects of the relative acidity content of these NSMFI(y) samples on the zeolite-catalyzed combustion of aluminum nanoparticles (AlNPs)-aided exo-tetrahydrodicyclopentadiene (JP-10) mixed energetic fuel droplets levitated in an oxygen-argon atmosphere were investigated using time-resolved imaging (optical and thermal infrared) and spectroscopic techniques (UV-vis and FTIR). The addition of 1.0 wt % of NSMFI(y) zeolites to AlNPs-JP-10 fluid fuel results in critically reduced ignition delays (9 ± 2 ms), elevated ignition temperatures (2800 ± 170 K), and prolonged burning times (60 ± 10 ms) with an enhanced combustion efficiency. The NSMFI(y) zeolites, which possess high acidity and significant mesoporosity, play a crucial role in improving the combustion efficiency by effectively catalyzing the chemical activation of JP-10 and prolonging the burning of the igniting droplet. The NSMFI (60) variant with the highest acidic site content achieved a maximum combustion efficiency of 80 ± 6%. A comprehensive catalytic combustion mechanism has been elucidated based on the detected reactive intermediates such as hydroxyl radical (OH) and aluminum monoxide (AlO). These findings will help to critically advance the development of next-generation, sustainable, and innovative mixed nanofluid fuels.

Insight into HTPB pyrolysis mechanism under high-temperature: A reactive molecular dynamics study

Hydroxyl-terminated polybutadiene (HTPB) is widely utilized in solid and hybrid rocket propellants due to its mechanical properties and combustion performance. Insight into its pyrolysis process is key to enhancing combustion efficiency in rocket engines. This study employs ReaxFF molecular dynamics (MD) simulations to explore the pyrolysis mechanism of HTPB under extreme conditions, with temperatures ranging from 1000 K to 2000 K. The results identify the primary degradation products and elucidate their formation mechanisms. The simulation reveals that C-C bond cleavage at polymerization sites is the initial step, followed by the formation of linear oligomers and butadiene. Subsequent reactions, including hydrogenation and dehydrogenation, lead to the generation of smaller molecular species. The kinetic analysis confirms that HTPB pyrolysis follows first-order reaction kinetics, with an activation energy of 8.12 kcal/mol. The findings are compared with existing experimental data, highlighting the influence of thermal environments on pyrolysis mechanisms and product distributions.

Investigation of Al-Li particle ignition dynamics with different Li content

Promoting the ignition of aluminum powder is considered an effective method to inhibit the agglomeration of aluminum powder in propellants and enhance combustion efficiency. This study utilizes laser ignition technology and high-speed photography to investigate the ignition and combustion processes of single aluminum particles and aluminum-lithium alloy particles. The focus is on comparing the effects of the diameter of micron-sized metal particles and the lithium content in aluminum-lithium alloy particles on the ignition and combustion processes of metal particles. The results show that the ignition delay time is directly proportional to the diameter of the metal particles and inversely proportional to the lithium content. For the aluminum-lithium alloy particle with a lithium content of 3.5 %, even if the diameter is close to 300 μm, the ignition delay time is only 125.5 ms, which is much smaller than that of the pure aluminum particle with a diameter of 208 μm. Compared to aluminum particles and aluminum-lithium alloy particles, there is basically no difference between the two during the combustion stage. However, in the ignition stage, aluminum-lithium alloy particles sequentially exhibit a red gas-phase flame corresponding to lithium and a yellow gas-phase flame corresponding to aluminum. This indicates that during the ignition process of aluminum-lithium alloy particles, lithium first reacts with the oxidative atmosphere and releases heat, providing a heat source for the subsequent ignition of aluminum particles. This also explains why the ignition delay time of metal particles is inversely proportional to the lithium content. An ignition model for aluminum particles in a multi-component atmosphere is established, which further considers the chemical reactions between lithium and oxidative gases, making the model applicable to aluminum-lithium alloy particles. This ignition model effectively describes the impact of particle diameter and lithium content on the ignition process of metal particles. The model is further verified, and the results show that the calculated ignition delay is in good agreement with the experimental data. Overall, this study provides deeper experimental and theoretical insights into the ignition and combustion processes of aluminum-lithium alloys, and the findings can guide the application of aluminum-lithium alloys in propellants.

Effect of Piston Geometry on Performance Characteristics of VCR Engine with and without EGR when Fueled with Blends of Methyl Ester

The growing population and exhaustion of fossil fuels necessitate our search for new sources of energy. The study for this research encompasses an amalgamation of interest in alternative fuels, advanced engine technology such as variable compression ratio VCR, engine component modification, and a methodical approach to testing for assessing the effects on key performance of the engine. A 3.5 kW compression ignition (CI) engine was fueled with blends of behada, chicken fat, and turmeric oil methyl ester. Engine operating parameters, such as the compression ratio (CR), rate of exhaust gas recirculation (EGR), and piston top geometry, are optimized to maximize engine performance. CI engine was modified by changing the piston head (square and tangential groove top) for methyl ester diesel blend operations. In the study, diesel fuel is designated as B00 and methyl ester as B20. The influence of compression ratio (CR16 and CR18) with exhaust gas re-circulation (EGR 0% and EGR 10%) was evaluated. The key performance indicators: brake thermal efficiency (BTE), brake-specific energy consumption (BSEC), brake-specific fuel consumption (BSFC), air-to-fuel ratio (AFR), and exhaust gas temperature (EGT) are investigated. Results indicate that an increase in BTE accompanies an increase in load, suggesting enhanced thermal efficiency with increased power output. The consequence of VCR is also investigated, and it is determined that a higher CR results in a higher BTE due to an increase in compression pressure and temperature, thereby enhancing combustion. Due to the re-combustion of unburned hydrocarbons with the addition of EGR at a 10% rate, BTE increases further. Utilizing a piston geometry with tangential grooves and methyl ester blends also contributes to increased BTE. BSEC increases with increasing load, with an important rise observed when operating at maximum capacity. However,at CR 18, BSEC decreases as a result of enhanced combustion efficiency. EGR has different effects on BSEC depending on the geometry of the piston and the kind of fuel used. Enhanced air-fuel blending and re-combustion of unburned hydrocarbons reduce the BSEC of the engine. The tangential groove top piston operates with 10% EGR. Similar to BSEC, BSFC decreases with increasing CR and improves with the use of a piston with a tangential groove and 10% EGR operation. AFR decreases as the consumption of fuel increases to meet the power demand, and higher CR values result in a lower AFR. EGT rises with load, and CR18 has a lower EGT than CR16 as a result of a higher compressing temperature and pressure. 10% EGR operation reduces EGT by decreasing the concentration of oxygen in the combustible area.

Experimental investigation of performance, emission, and combustion characteristics of a diesel engine using blends of waste cooking oil-ethanol biodiesel with MWCNT nanoparticles

In this study, blends of 5 % and 10 % ethanol with waste cooking oil biodiesel are mixed with Multi-Walled Carbon Nanotubes (MWCNT) at a concentration of 30 ppm. MWCNTs, known for their high surface area and unique properties, are added to potentially enhance combustion efficiency and reduce emissions. These blends are then tested in a diesel engine to evaluate their performance, emission and combustion characteristics using Design of experiment technique. After conducting various experiments and analyses, the blend of 20 % biodiesel, 10 % ethanol, and 30 ppm MWCNT was identified as the most optimal due to its favorable engine characteristics. Brake Thermal Efficiency (BTE) was increased from 3.1 % to 3.4 % with the addition of MWCNTs, indicating enhanced fuel efficiency. Moreover, average Fuel Consumption is decreased from 2.2 % to 2.5 %, suggesting improved fuel utilization. Using MWCNT 30 ppm in B20 ethanol blends (MWCNT 30 ppm B20+E10) resulted in 35 % reduction in nitrogen oxide (NOx) emissions, 37 % reduction in CO emissions and 39 % reduction in HC emissions. Hence MWCNTs demonstrated effectiveness in mitigating harmful exhaust emissions The optimized values for all parameters fall within acceptable ranges, indicated successful optimization using Response surface methodology. Additionally, statistical analysis reveals that the machine learning- XGBoost model outperformed all other advanced machine learning models across all tested metrics, including MSE, MAE, and R-square.

Experimental research on wide load operation characteristics of circulating fluidized bed under the action of high-temperature activated gas-solid binary fuels

The circulating fluidized bed (CFB) units, with their robust combustion stability under low load conditions, are poised to play a significant role in future deep peak shaving of power grids. However, issues such as NOx emissions exceedance arise when the CFB unit operates for deep peak shaving. To mitigate these problems, this paper innovatively proposes a CFB coal blended with the high-temperature activated gas-solid binary fuel combustion mode to reduce the NOx emissions of the CFB across a wide load range. The wide load operation characteristics of the CFB under the action of high-temperature activated gas-solid binary fuel were initially examined on a 2 MW experimental platform. A comparison between the conventional combustion mode and the CFB coal blended with high-temperature activated gas-solid binary fuel combustion mode revealed that the latter improved the uniformity of temperature distribution within the CFB across a wide load range, particularly at lower loads. Furthermore, the CFB coal blended with high-temperature activated gas-solid binary fuel significantly reduced the original NOx emissions, decreasing from 136.9 mg/m3, 37.5 mg/m3, and 38.8 mg/m3 to 92.0 mg/m3, 24.7 mg/m3 and 20.6 mg/m3 at 100 %, 50 %, and 30 % load respectively, thereby achieving ultralow original NOx emissions during deep peak shaving operations. However, there is room for improvement in enhancing combustion efficiency using this combustion mode.

The influence of exhaust gas recirculation on combustion and emission characteristics of ammonia-diesel dual-fuel engines: Heat capacity, dilution and chemical effects

As the greenhouse effect intensifies, ammonia is garnering increasing attention as a carbon-free fuel. In the transport sector, ammonia-diesel dual-fuel (ADDF) engines are regarded as an effective means of reducing carbon emissions. The objective of this study is to investigate the combustion and emission optimization of an ADDF engine under high load conditions. To this end, an experimental optimization study of different start of diesel injection timing (SODI) and exhaust gas recirculation (EGR) rates was conducted at a load of 18 bar and an ammonia energy ratio of 80 %. The mechanism of heat capacity, dilution, and chemical effects of EGR was also revealed by numerical simulation based on the separated variables method. It was demonstrated that advancing SODI is effective in enhancing combustion efficiency. However, this approach is limited by the upper limit of in-cylinder pressure and results in higher nitrogen oxides (NOx) emissions, which can be mitigated by the EGR. The heat capacity effect of EGR increases the specific heat capacity and decreases the average temperature. The suppression of the combustion process leads to a reduction in thermal and fuel NOx, but an increase in nitrous oxide (N2O) emissions. The dilution effect of EGR results in insufficient oxygen, which decreases the heat release rate and combustion efficiency. Additionally, the NOx and N2O are significantly reduced. The chemical effect of EGR affects reactive groups and unburned components that accelerate heat release rate and increase accumulated heat release, resulting in significantly higher NOx. The comprehensive effect of EGR results in a decrease in N2O emissions and a significant reduction in thermal and fuel NOx. The EGR and further optimization of SODI enabled the ADDF engine to achieve a gross indicated thermal efficiency of 48.5 % with a load of 18 bar and an ammonia energy ratio of 80 %. In addition, NO emissions were reduced by 32.8 percent and greenhouse gas emissions by 63.3 percent.