Reduce NOx Emissions Research Articles

Synergistic approaches to NOx reduction: Fuel innovations and engine modifications in biomass waste-fueled CI engines

Achieving low nitric oxide emissions in biomass fuel combustion remains a challenge. This study aims at enhancement of NOx reduction by employing a sequence of strategies to arrive at the optimal combination of techniques. This work explores the role of nano particle emulsion, change in profile of combustion chamber geometry, exhaust gas recirculation rates and contribution of selective catalytic reduction (SCR) in the combustion and emission phenomena of CI engine. Cerium oxide and zinc oxide nanoparticles are added in emulsion form at 50 ppm and 100 ppm dosage to grapeseed oil biodiesel. Furthermore, combustion chamber geometry is modified to shallow depth and toroidal shape and tested with ZnO 100 nano blend of grapeseed oil biodiesel (GSBD). EGR at 5 %, 10 %, 15 % and 20 % rates are included in the toroidal shape after concluding that profile as the best performing geometry. A customized model of SCR is implemented to the above combination of ZnO fuel blend, toroidal combustion chamber geometry and 5 % EGR to further reduce NOx emission. SCR device is fabricated with suitable flow and injection parameters with dual type mixers to enhance its NOx conversion efficiency. Overall, this research work gives useful insights for development of NOx reduction strategies in biomass fuel combustion in CI engines. A comprehensive reduction of NOx from 9.3 g/kWh to 2.05 g/kWh is noticed at the end of cumulative set of experiments.

Lateral Swirl Combustion System Development of Dual Fuel Diesel Engine Piston to Improve Efficiency and Reduce NOx Emission: a Brief Review

Lateral Swirl Combustion System Development of Dual Fuel Diesel Engine Piston to Improve Efficiency and Reduce NOx Emission: a Brief Review

Effect of pre-injection strategy on the reduction of exhaust emissions from n-pentanol/biodiesel engine

N-pentanol can be used as an additive component of biodiesel to achieve NOx and soot emission reductions while improving the low-temperature fluidity of biodiesel. This paper investigates the mechanism of pre-injection strategies (pre-main injection interval and pre-injection ratio) on the emission characteristics of n-pentanol/biodiesel engines. It extends the study to investigate the effect pattern of pre-injection strategies on formaldehyde emissions. The results show that the emission characteristics of the n-pentanol/biodiesel engine can be effectively improved by using a pre-injection strategy compared to a single injection. With the pre-main injection interval increase, the in-cylinder combustion stability was improved, and the generation of NOx and soot was effectively suppressed. Compared to a single injection, a pre-main injection interval of 15 °CA resulted in a 15.38 % decrease in CA50 and an 18.32 % increase in IMEP. Meanwhile, the increase of the pre-main spray interval broke the trade-off relationship between NOx and soot, and when the main pre-spray interval was increased from 15 °CA to 30 °CA, Soot and NOx generation were reduced by 27.46 % and 21.30 %, respectively. As the proportion of pre-injection increases, the center of gravity of combustion is shifted forward, the combustion exotherm is more concentrated, and the soot emission is significantly reduced. When the percentage of pre-spray was increased from 0 % to 20 %, CA50 decreased by 19.23 %, IMEP increased by 1.32 %, and soot generation decreased by 61.02 %. When the proportion of pre-spray was increased from 15 % to 20 %, CH2O emissions were reduced by 14.81 %.

Optimization of NOX emissions of a CRDI DIESEL engine using CMA-ES method

Engine calibration is the tuning of embedded parameters in the engine control unit (ECU) software to improve vehicle characteristics and meet legal requirements. Due to the stricter emission limits and rising customer expectations, current ECU software may include variables up to 30,000, which require very much time for engine calibration development. For this reason, automotive manufacturers continuously develop mathematical-based optimization methods to find optimum operating conditions for the engines. This study aimed to develop an online optimization algorithm to conduct automated dynamometer tests in the calibration development process. A modified covariance matrix adaptation (CMA) algorithm, which is an evolutionary strategy (ES) method belonging to meta-heuristic optimization, was integrated with an automation system for online calibration optimization. Some CMA method parameters such as step size and damping factor were initially revised to achieve the method to function efficiently in online engine calibration. Optimization was conducted at three different operating points of a 2-liter common rail direct injection (CRDI) diesel engine, where NOx emission mainly impacts the New European Driving Cycle (NEDC) results. The main injection timing, rail pressure, pilot injection quantity and timing, manifold pressure, and mass air flow were controlled in the optimization process. Optimization targets were determined according to the NOx-PM Pareto curve for each operating point. Covariance matrix adaptation was used to generate Pareto curves. Sixty-five measurements were taken for each operating point in the optimization process. Once optimization targets were determined, optimization occurred at each operating point. A total NOx emission reduction of 3.8% was obtained in the NEDC test, while fuel consumption and PM remained almost the same at steady-state operating points. The modified CMA-ES algorithm is expected to be an efficient method for online calibration optimization.

SCR + ASC systems control by backward induction with adaptive grid and different disturbance scenarios

The purpose of this study is to enhance control strategies for selective catalytic reduction (SCR) and ammonia slip catalyst (ASC) systems, aiming to effectively reduce NOx emissions from automotive engines during realistic driving cycles. Despite the effectiveness of these after-treatment systems (ATS), their dynamic and non-linear characteristics present significant challenges in achieving precise control. Therefore, this research proposes a hybrid approach that combines backward induction (BI) as the primary optimization technique with model predictive control (MPC) framework for real-time application. The article introduces a reduced-state control-oriented model of the SCR + ASC system, which is embedded into the BI algorithm to calculate optimal control actions within a finite horizon. Additionally, it is proposed an alternative approach for adapting the grid of model states within the BI algorithm, effectively reducing the computational cost. This adjustment enables the algorithm to operate in real-time with near-optimal results, as confirmed by experimental validation. Lastly, the study explores how different degrees of knowledge regarding system disturbances impact the strategy’s performance, examining three distinct scenarios: constant prediction horizon, probabilistic description, and full knowledge of the prediction horizon.

Biodiesel production from eggshells derived bio-nano CaO catalyst–Microemulsion fuel blends for up-gradation of biodiesel

The utilization of bio-oil derived from biomass presents a promising alternative to fossil fuels, though it faces challenges when directly applied in diesel engines. Microemulsification has emerged as a viable strategy to enhance bio-oil properties, facilitating its use in hybrid fuels. This study explores the microemulsification of Jatropha bio-oil with ethanol, aided by a surfactant, to formulate a hybrid liquid fuel. Additionally, a bio-nano CaO heterogeneous catalyst synthesized from eggshells is employed to catalyse the production of Jatropha biodiesel from the microemulsified fuel using microwave irradiation. The catalyst is characterized through UV–Vis, XRD, and SEM analysis. The investigation reveals a significant reduction in CO, CO2, and NOX emissions with the utilization of microemulsion-based biodiesel blends. Various blends of conventional diesel, Jatropha biodiesel, and ethanol are prepared with different ethanol concentrations (5, 10, and 20 wt%). Engine performance parameters, including fuel consumption, NOX emission, and brake specific fuel consumption, are analyzed. Results indicate that the conventional diesel/Jatropha biodiesel/ethanol (10 wt%) blend exhibits superior performance compared to conventional diesel, Jatropha biodiesel, and other blends.The fuel consumption of the conventional diesel/Jatropha biodiesel/ethanol (10 wt%) blend is measured at 554.6 g/h, surpassing that of conventional diesel and other biodiesel blends. The presence of water (0.14 %) in the blend reduces the heating value, consequently increasing the energy requirement. CO and CO2 emissions for the conventional diesel/Jatropha biodiesel/ethanol (10 wt%) blend are notably lower compared to conventional C-18 hydrocarbons and various biodiesel blends. These findings accentuate the efficacy of the microemulsion process in enhancing fuel characteristics and reducing emissions. Further investigations could explore optimizing the emulsifying agents and their impact on engine performance and emission characteristics, contributing to the advancement of sustainable fuel technologies.

Ammonia energy fraction effect on the combustion and reduced NOX emission of ammonia/diesel dual fuel

With stringent regulations of internal combustion engine on reducing CO2 emission, ammonia has been used as an alternative fuel. Investigating how engine-related performance is affected by partial ammonia replacement of diesel fuel is essential for understanding the combustion. Therefore, in this study, a three-dimensional numerical simulation model is developed for the burning of two fuels of diesel and ammonia based on relevant parameters (i.e., compression ratio, load, ammonia energy fraction, etc.) in a lab-made diesel engine. The consequences of load and compression proportion on combustion and pollutant emissions are investigated for ammonia energy fractions between 50% and 90%. When the ammonia portion rises, the increased ammonia equivalent ratio causes ammonia to move away from the dilute combustion boundary and accelerates the combustion rate of ammonia. An increase in compression ratio significantly increases the specified thermal performance and combustion efficacy. When the compression ratio is 16, as the ammonia energy fractions increases, due to the increase in the proportion of ammonia, that is, the proportion of nitrogen atoms increases, more NOx is generated during the combustion process. When the ammonia substitution rate is 90%, as the compression ratio increases, the cylinder pressure and temperature increase. The combustion efficiency of ammonia increases, generating more NOx and NOx emissions can reach 0.66 mg/m3. At a compression ratio of 18, the NOx emissions can reach 1.59 mg/m3. However, under medium and low load conditions, as the ammonia fraction increases, the total energy of fuel decreases, and the combustion efficiency of ammonia decreases, resulting in a decrease in the heat released during combustion and a decrease in NOx emissions. When the ammonia substitution rate is 90% and the load is 25%, NOx emissions reach 0.1 mg/m3. This research provides theoretical suggestions for the profitable and use ammonia fuel in internal combustion engines in a clean manner.

A numerical investigation on the effect of altering compression ratio, injection timing, and injection duration on the performance of a diesel engine fuelled with diesel-biodiesel-butanol blend

Abstract Using renewable fuels for diesel engines can reduce both air pollution and dependence on fossil fuels. A computer simulation was constructed to predict the performance, combustion characteristics, and NOx emission of a diesel engine fuelled with diesel-biodiesel-butanol blends. The simulation was validated by comparing the modeling results against experimental data and a good agreement between the results was found. The fuels used for the validation were diesel (B0), biodiesel (B100), diesel-biodiesel blend (B50), and two diesel-biodiesel-butanol blends with 45% diesel-45% biodiesel-10% butanol (Bu10), and 40% diesel-40% biodiesel-20% butanol (Bu20) by volume. Experimental results showed that the addition of butanol reduced NOx emissions but deteriorated the engine performance. The aim of the current work was the numerical optimization of the different parameters to enhance the engine performance while using butanol to decrease NOx emissions. The engine compression ratio (CR) varied from 14 to 24, in increments of 2. Fuel injection timing (IT) was retarded from 30° before top dead center (bTDC) to 5° bTDC in increments of 5o. Also, the fuel injection duration (IDur) was extended from 20° to 50° in increments of 10°. Results showed that the increase in CR improved engine performance for the two investigated fuels, Bu10 and Bu20. The maximum engine brake power (BP), thermal efficiency (BTE), and minimum brake-specific fuel consumption (BSFC) of 1.46 kW, 32.3%, and 0.273 kg/kWh respectively, were obtained when the Bu10 fuel was injected at the optimum conditions of 24 CR, 15°bTDC IT, and 40° injection duration (IDur). Under these optimum conditions, the BP, BTE, and BSFC improved by 3% to 3.5% for Bu10 and Bu20 fuel blends compared to the base engine conditions of CR of 22, 30° IDur, and 10° bTDC IT. The heat release rate during the premixed phase increased when the IT was advanced, while the mixing-controlled combustion phase was enhanced when the IT was retarded. NOx emissions increased with increasing the CR, while both the increase in IDur at constant IT and the retard of IT decreased engine NOx emissions. At the optimum conditions, the NOx emissions for Bu10 and Bu20 were further decreased by 2.2% and 0.9% respectively compared to the experimental results at base engine conditions. Retarding the injection timing from 15° bTDC to 5° bTDC at a CR of 24 and IDur of 40° caused the NOx emissions for Bu10 and Bu20 to decrease by 16%. When the injection duration was increased from 20° to 50° at a CR of 24 and an IT of 15°bTDC, the NOx emissions for Bu10 and Bu20 decreased by 12.3% and 11.8% respectively. The addition of butanol to the diesel-biodiesel blend at optimum conditions showed results comparable to pure diesel, with a decrease in NOx emissions.

Background-Oriented Schlieren For The Detection Of Thermoacoustic Oscillations In Flames

Thermoacoustic oscillations are well known to combustion engineers. They are not only a cause of concern, but also give hope to be able to operate aircraft engines with hydrogen, due to flame stabilization and significant reduction of NOx emissions when thermoacoustically excited. The aim of this work is to investigate the potential of using a heterodyne background-oriented schlieren (HBOS) technique to detect thermoacoustic oscillations in the density field of an acoustically excited flame. It also seeks to address the issue of accuracy due to the small amplitude of thermoacoustic oscillations compared to turbulent density fluctuations in a flame. The experiment uses an unconfined swirl-stabilized methane flame and investigates thermoacoustic oscillations at about 3.4 kW power at ambient conditions excited by a siren at 225 Hz. The HBOS technique recently presented by the authors uses a carrier fringe system in background-oriented schlieren recordings, with subsequent analysis using evaluation techniques known from holographic interferometry. These fast algorithms reduce turbulence noise by phase averaging a large number of images. To derive local data from the line-of-sight projections, an inverse Abel transform is applied. Laser interferometric vibrometry is used to calibrate to the observed oscillations. A comparison with data from chemiluminescence is also presented to better demonstrate the application of this efficient technique to the detection of heat release oscillations. Future tasks in this project will deal with full-scale test benches and machine learning tools to address the limited observations in them.

Bottom-up assessment of air quality management strategies in Vijayawada, India: Emissions inventory, atmospheric capacity, and policy scenarios

A bottom-up approach evaluates air quality management strategies in Vijayawada, India, a rapidly urbanizing city facing declining air quality. Detailed emission inventories and dispersion modeling assess pollutant concentrations (PM10, PM2.5, SO2, NOx) under various policy scenarios for 2025 and 2030. Business-as-usual (BAU) scenarios reveal the inadequacy of current regulations for PM, SO2, and NOx control. While BS-VI standards effectively reduced NOx emissions from vehicles, overall trends indicate a diminishing atmospheric capacity to assimilate pollutants. Alternative scenarios (ALTs) incorporating sector-specific controls project emission reductions (12–15 % PM10, 19–24 % PM2.5, 24–48 % SO2, 19–32 % NOx) and are expected to maintain pollutant levels below national ambient air quality standards. This integrated approach offers valuable insights for policymakers to develop sustainable air quality strategies aligned with SDGs. The study emphasises the need to consider potential trade-offs between environmental benefits and resource demands, such as increased electricity demand for electric vehicles (SDG 7) and land use competition from urban greening (SDG 11). This study aids in identifying strategies that maximise environmental benefits while minimising trade-offs, fostering sustainable urban development. The research's novelty lies in its integration of scenario-based analysis with atmospheric capacity evaluation, providing a robust framework for air quality management in rapidly urbanising regions.

Comparative Analysis Of Cycle-To-Cycle Variabilities And Combustion Development In An Optical Spark-Ignition Engine Fueled By Pure Hydrogen And Propane: Insights From Chemiluminescence and PI

Hydrogen, derived from renewable sources and devoid of carbon emissions, is a pivotal energy carrier for the future. Representing a viable substitute for fossil fuels in internal combustion engines (ICEs), contemporary studies advocate using very-lean and ultra-lean hydrogen-air mixtures, with a fuel-air equivalence ratio below 0.5, as a potent strategy to reduce NOx emissions in hydrogen-fueled ICEs. An experimental setup with an optical spark-ignition engine was devised to investigate the primary factors influencing cycle-to-cycle variations in H2ICEs by optimizing mixture homogeneity and focusing the study on flame interaction with in-cylinder aerodynamics. Simultaneous in-cylinder pressure, chemiluminescence, and PIV analyses were performed to characterize and compare the behaviors of ultra-lean hydrogen-air and propane-air flames, assessing flame development and cyclic variation features. Results indicate that the flame development of hydrogen and propane is significantly different. Propane exhibited increased in-cylinder pressure trace variability at lean and rich flammability limits with a high flame development difference between fast and slow cycles. In contrast, hydrogen-air mixtures under various equivalence ratios (from very-lean to ultra-lean) presented much more stable in-cylinder pressures. Furthermore, fast propane flames were mainly advected to the cylinder's symmetrical axes, while fast hydrogen flames started further away from the spark plug. Horizontal and vertical PIV measurements showed a single structure flow field over the studied conditions with mainly intensity variations over the measured cycles. Fast flames were associated with more intense tumble motion. The differences between fast and slow flames for hydrogen are attributed to the early flame development. However, after initial differences in flame development over several crank angles, there are similarities in all cycles, suggesting that the low variability in in-cylinder pressures is mostly due to the robustness of hydrogen flame ignition and its independence from in-cylinder flow small variations at the early development phase.

Experimental study on combustion characteristics of a 40 MW pulverized coal boiler based on a new low NOx burner with preheating function

In this study, a novel low NOx burner is proposed and tested on a 40 MW pilot pulverized coal combustion system, aiming to experimentally investigate the impact of preheating temperature, air ratio distribution, and thermal power on furnace combustion characteristics. The experimental results demonstrate that the pulverized coal could be preheated stably above 700 °C in the designed burner. Furthermore, an increase in preheating temperature from 500 °C to 750 °C corresponds to a proportional rise in the total volume fraction of combustible pyrolysis gases released from pulverized coal, ranging from 18.34 % to 22.85 %. Consequently, the release and combustion of pyrolysis gases effectively improve the combustion characteristics within the boiler furnace and lead to reduced NOx emissions at the furnace outlet. When the thermal power is increased from 22.5 MW to 37.5 MW, the NOx emissions at the furnace output range from 46.8 mg/Nm3 to 98.3 mg/Nm3 (at 9 % O2). Under a specific thermal power of 25MWth, the boiler furnace output NOx emissions are reduced to 47.9 mg/Nm3 (@9 % O2) without any additional NOx reduction equipment. These findings offer valuable insights for advancing cleaner and more efficient low-NOx pulverized coal combustion technology.

Effect of air distribution mode on jet flame and emission characteristics of high temperature gas-solid mixed fuel

The characteristics of the flame can not only intuitively reflect the flow, mixing and reaction processes of fuel and oxidant, but also provide detailed information on combustion efficiency and stability. The present study aims to delve into the jet flame characteristics and emission properties of high-temperature gas-solid mixed fuel. A comprehensive series of experiments were conducted on a custom-designed test platform. During the experiments, variations in both the position (h3 = 200, 600, 1000 mm) and velocity (v3 = 67, 138, 223 m/s) of the tertiary air were introduced. The study focused on analyzing the flame lift-off distance, the correlation coefficient of the flame root, the normalized root mean square temperature distribution within the flame body area, and the NOx emission characteristics across various air distribution scenarios. The experimental findings reveal that alterations in the position of tertiary air exert a greater influence on the flame lift-off distance than variations in its velocity. Furthermore, temporal fluctuations in the correlation coefficient of the flame root and the normalized root mean square temperature distribution within the flame body region serve as effective indicators of flame stability. Notably, an increase in both the tertiary air position and velocity leads to a notable reduction in NOx emissions. Additionally, through a quantitative analysis of flame stability, temperature distribution uniformity, and NOx emission characteristics, this study establishes a correlation between flame characteristics and pollutant emission profiles. This correlation offers a more comprehensive understanding of the combustion process involved in high-temperature gas-solid mixed fuel.

Enhanced NOx reduction on CePO4 catalysts: Cu-loading, phosphotungstic acid, and insights from In-situ DRIFTs and DFT

This study investigates the effects of varying Cu/Ce doping ratios on the NH3-SCR denitrification efficiency using Cu-HPW/CePO4 catalysts, where CePO4 serves as the support and copper-doped phosphotungstic acid (HPW) acts as the active phase. The NH3-SCR reaction mechanism was studied by In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (In-situ DRIFTs) and Density Functional Theory (DFT). In-situ DRIFTs were employed to delve into the intricacies of adsorption and transformation dynamics at the surface sites of catalysts. This approach furnished a robust theoretical foundation aimed at augmenting the efficacy of low-temperature denitrification catalysts. DFT calculations were used to systematically investigate the reaction pathways, intermediates, transition states, and energy barriers over the HPW structure model to complete the NH3-SCR reaction. Empirical evidence suggests that modifying the catalysts with copper substantially enhances their denitrification efficacy and extends their operational temperature spectrum. A notable initial increase in denitrification efficiency was observed with increasing levels of copper modification, followed by a decline. Within the HPW-O15H site, the NH3-SCR reaction advances through both the E-R and L-H mechanisms, encompassing processes such as NH3 adsorption, intermediate formation and transformation, and product release.

Hydrogen Use in a Dual-Fuel Compression Ignition Engine with Alternative Biofuels

Recent progress has been made towards decarbonisation of transport, which accounts for one quarter of global carbon dioxide emissions. For the short to medium term, new European Union (EU) and national energy and climate plans agree on a strategy based on the combination of increasing shares of electric vehicles with the promotion of sustainable fuels, especially if produced from residual feedstock and routes with low or zero net carbon emission. Hydrogen stands out among these fuels for its unique properties. This work analyses the potential of using hydrogen in a dual-fuel, compression ignition (CI) engine running with three diesel-like fuels (conventional fossil diesel, advanced biodiesel (BD) and hydrotreated vegetable oil (HVO)) and different hydrogen energy substitution ratios. The results were confronted with conventional diesel operation, revealing that dual-fuel combustion with hydrogen demands higher exhaust gas recirculation (EGR) rates and more advance combustion, leading to a remarked reduction of NOx emission at the expense of a penalty in energy consumption due mainly to unburnt hydrogen and wall heat losses. Unreacted hydrogen was ameliorated at high load. At low load, the use of BD dual combustion permitted higher hydrogen substitution ratios and higher efficiencies than diesel and HVO.

The Suitability of the Three-way Catalyst for Hydrogen Fuelled Engines

This experimental study investigates the palladium/rhodium based three-way catalyst (TWC) in a hydrogen-gasoline dual-fuel spark ignition (SI) engine under stoichiometric and lean conditions. The work focused on lean-burn engine operating conditions with the aim of reducing nitrogen oxides (NOx) emissions during the combustion process, where the TWC is not effective, while improving the thermal efficiency of the engine. Under these lean-burn engine conditions, the combustion promoting properties of hydrogen allowed for maintained engine combustion stability as determined by the cycle-to-cycle variation (COVimep) values even up to ultra lean conditions (λ= 2.0). It was found that by reducing the combustion temperature through the application of lean conditions, engine-out NOx emissions could be reduced or even eliminated, while under these conditions the TWC was effective in reducing engine-out carbon-based gaseous emissions.

Role of analytical methods in verifying biodiesel upgrades: Emphasis on nanoparticle and acetone integration for enhanced performance, combustion, and emissions

AbstractThis study aims to address critical challenges such as global warming and energy sustainability by targeting the reduction of high NOx emissions in diesel engines. The effects of acetone (AC) and magnesium oxide (MgO) nanoparticles (NPs) as additives in improving the physicochemical properties of biodiesel derived from renewable, nonedible Pistacia terebinthus oil, which is abundant in Turkey and has a high free fatty acid (FFA) content of 5.8%, were investigated. Due to the high FFA content, a two‐step (esterification followed by transesterification [TR]) method was used for biodiesel production. Additionally, a quantitative analysis of biodiesel obtained by both single (TR) and two‐step methods was performed to address a gap in the literature. The addition of AC and MgO NPs to B20 (80% diesel fuel and 20% biodiesel) fuel resulted in reductions in the rate of pressure rise, instantaneous energy release, cylinder pressure, mean gas temperature, and cumulative heat release rate. However, brake‐specific fuel consumption increased, and brake thermal efficiency decreased. Emissions analyses showed a reduction in CO emissions by 6.65% with AC and 2.10% with AC + MgO, and a reduction in NOx emissions by 41.64% with AC and 46.03% with AC + MgO. However, hydrocarbon emissions increased by 26.48%. The study highlights the synergistic benefits of AC and MgO additives in biodiesel, presenting a viable strategy for improving the environmental and performance metrics of biodiesel blends. It provides new insights into alternative fuel formulations.

Exergy, energy, performance, and combustion analysis for biodiesel NOx reduction using new blends with alcohol, nanoparticle, and essential oil

Biodiesel is considered one of the alternative replacements to fossil fuels. However, the major challenge associated with its application in diesel engines is the higher level of NOx emissions. Fuel modification technologies, where biodiesel is blended with various additives and fuels, have emerged as a distinguished method in recent years to improve engine performance and reduce NOx. The study aims to reduce NOx emissions by fuel modification techniques. Five blends were prepared using Tucuma biodiesel along with ethanol, carbon nanotubes, and eucalyptus oil. The prepared blends were deployed to a test bed engine at rated speed and by varying loads to investigate performance, emission, and combustion characteristics. The results revealed that ethanol-blended fuels such as DE10 and TB10E10 had reduced the NOx emissions by 51.37% and 9%, respectively, at lower loads compared to diesel. Although the nanoparticle blend exhibited increased NOx emissions compared to diesel, it demonstrated reductions of 4.1%, 4.56%, 7.2%, and 3.1% at loads of 25%, 50%, 75%, and 100%, respectively, compared to TB10. The study highlights various tradeoffs observed between operating conditions and engine parameters for the blends, as detailed in this research. The study found that blends TB10E10 and TB10E10CNT20 exhibit improved performance close to that of diesel and reduced NOx and CO emissions compared to that of diesel and TB10. The study recommends further exploring the impact of injection rates with ethanol-blended fuels as they showed longer ignition delays since advancing the injection can create better combustion with ethanol blends.

Effect of burner structural parameters on combustion characteristics and NOx emission of natural gas

The low-nitrogen combustion of natural gas has always been a crucial topic in environmental protection. Currently, small and medium-sized industries use straight-through pipelines as their burner nozzles. This design results in poor heat diffusion capacity after mixed combustion and a long time of temperature diffusion, leading to low combustion efficiency and high NOx emissions. To address this issue, a new type of natural gas low-nitrogen burner with a multi-port diffusion nozzle was developed. The burner’s structure was optimized through a combined approach of experiment and numerical simulation. The optimal structural parameters for the burner are a 40° swirl angle and 8 swirl blades, as indicated by the numerical simulation research results. The designed multi-port diffusion nozzle is matched with the appropriate swirl angle and number of blades to promote natural gas diffusion, forming an annular space region flames and a stable flame shape with a height of 0.64 m. After optimization, the average concentration of NOx at the outlet of the combustion chamber decreased from 61.5 ppm to 20.81 ppm. A natural gas low-nitrogen combustion experimental system was designed and constructed based on simulation results. The experimental results were analyzed in terms of flame structure characteristics, temperature distribution, and NOx emissions. The results indicate that the trend in temperature change is consistent with the simulation process. The NOx concentration at the outlet of the combustion chamber was measured by the flue gas analyzer to be 34.1 ppm, which was 5.3 ppm lower than the NOx concentration calculated by numerical simulation. The new burner exhibited better flame stability and a 12.6 % reduction in NOx emissions compared with a traditional straight-through pipeline burner of the same size. The designed natural gas low-nitrogen burner appears to be a suitable device for reducing NOx emissions in small and medium-sized industries.

Experimental investigation of NOx emission control using carbon nanotube additives and EGR configuration on CRDI engine fueled with ternary fuel

This study aims to investigate the impact of the combined effects of carbon nanotubes and exhaust gas recirculation (EGR) of a common rail direct injection (CRDI) engine fueled with ternary fuels. Three rates of EGR (0%, 10%, and 20%) were used at a standard injection timing of 23° before Top Dead Centre (bTDC). This study involves substituting diesel with biofuels, reducing oxides of nitrogen and soot emissions by 30–40%. The experimental investigation involves the exploration of combustion, exhaust emissions, and performance parameters for a single-cylinder CRDI engine using ternary fuels, which consist of diesel, biodiesel, and bioethanol by volume %. At full load with 20% EGR, the experimental analysis indicated a 2% decrease in BTE, a 3.33% increase in BSFC, and a 3.16% increase in BSEC across the blends in performance. In terms of combustion analysis, results show a 5.25 bar in-cylinder pressure drop, 4.14% reduction in HRR, and 12.62% drop in MGT. However, in terms of emissions, 20% EGR yielded the most favorable results, showing a 62.94% reduction in NOx emissions across all blends, albeit accompanied by a 13.89% increase in hydrocarbons (HCs) and 5% rise in carbon monoxide at full load. The 20% EGR rate effectively minimized NOx emissions while slightly impacting HC and CO emissions.