Simultaneous Reduction Of NOx Research Articles

Application End Evaluation of Electrostatic Precipitation for Control PM and NOx Emissions from Small-Scale Combustions

Electrostatic precipitators (ESPs) have shown promise in reducing particulate matter (PM) emissions, but their potential for simultaneous NOx reduction in small-scale combustion systems remains underexplored. This study focuses on using non-thermal plasma generated in a corona discharge to reduce PM and NOx emissions from small-scale combustion. ESP was specifically designed for a commercially available 15 kW boiler with wood pellet combustion and used with both positive and negative discharge polarity to control emissions without any chemical additives. ESP performance was evaluated across a range of specific input energies (SIE) in terms of particle mass and number concentrations and NOx concentrations obtained by continuous gas analysis. ESP ensured the reduction in PM concentrations from 48 mg/m3 to the magnitude of PM content in the ambient air. The highest precipitation efficiency was observed for particles in the 20–200 nm range. Concurrently, NOx emissions were reduced by up to 78%, from 178 mg/m3 to 39 mg/m3. These results were achieved at specific input energies of 36 for positive and 48 J/L for negative corona, which is significantly lower than those reported for many existing separate PM and NOx control systems. This study demonstrates the potential of ESPs as a compact, energy-efficient solution for simultaneous PM and NOx removal in small-scale combustion systems, offering promising implications for improving air pollution control technologies for small-scale combustion systems.

Ammonium Chloride Powder Feeding for the Simultaneous Reduction of NOx and Oxidation of Hg0 in the SCR Process

Ammonium Chloride Powder Feeding for the Simultaneous Reduction of NOx and Oxidation of Hg⁰ in the SCR Process

Techno-economic and environmental feasibility study of MILD combustion in domestic utility boilers under partial load operation

This paper aims to achieve the benefits of MILD combustion, such as enhanced thermal efficiency with simultaneous NOx reduction in existing conventional domestic hot water utility boilers which encounter partial heat loads. For this purpose, a system based on waste heat recovery and flue gas recirculation (FGR) is introduced to perform techno-economic and environmental studies under continuous fluctuations of heat load demand in a typical building at various climate conditions. Technical investigations on several types of utility boilers revealed that MILD combustion could be implemented only in modulation boilers, which can serve combustion stability requirements in turndown conditions due to partial load demands. Up to 6 % fuel saving, which aligns with a commensurate decrease in CO2 emissions and a minimum 75 % reduction in NOx emissions, is foreseeable by manipulating optimal FGR for each specific boiler in various climate conditions. Finally, economic investigation demonstrated that the payback period for the proposed revamped system is less than one year for most climates.

Elucidating the role and enhancement mechanisms of CH4 on the coupling abatement of N2O & NO over Fe-SSZ-13 catalysts

CH4 + NH3 + NOx + N2O coupling system was proposed for high-effective simultaneous catalytic reduction of both NO and N2O from flue gas generated by nitric or adipic acid industries. The Fe-SSZ-13 catalyst performed both elegant activity for NOx and N2O at 400–600 °C. Based on experimental studies, the active Fe species were illustrated and the transforming of Fe species during the N2O decomposition (deN2O) and selective catalytic reduction (SCR) processes was clarified. It found that deN2O could cause the main active sites of [Fe-O2-Fe]2+ transform to [Fe-O-Fe]2+ and consequently inhibited the NH3-SCR process over the Fe-SSZ-13 catalyst. Meanwhile, the αO* generated via N2O decomposition would strengthen NO oxidation to NO2, which is advantageous to NH3-SCR. More importantly, the functions of CH4 for deN2O and NH3-SCR were also investigated. CH4 could work as reductant to convert N2O over the Fe-SSZ-13. CH4 could also facilitate the reduction of NO; however, NH3 has stronger activity to NO than that of CH4. And CH4 was easily oxidized by O2 rather than N2O or NO, which significantly limit the CH4-SCR for N2O with present of O2. At the same time, CH4 can also accelerate αO* consumption that somehow enhance deN2O efficiency. Moreover, the consumption of αO* by CH4 prevent the transforming of [Fe-O2-Fe]2+ to [Fe-O-Fe]2+, and CH4 play an important role on turnover rates of [Fe-O2-Fe]2+ and [Fe-O-Fe]2+ active sites, guaranteeing both satisfactory purifying efficiency for NO and N2O. This work reveals the positive promoting effect of CH4 on simultaneous reduction of NOx and N2O, and proposes a potential catalyst for implementation.

Measurement report: Source apportionment and environmental impacts of volatile organic compounds (VOCs) in Lhasa, a highland city in China

Abstract. Hypoxia and adverse health outcomes might be affected by O3 pollution in the highland city of Lhasa. NOx emissions can amplify the role of volatile organic compounds (VOCs) in the secondary production of O3 under the conditions of high ultraviolet (UV) radiation levels and unfavourable dispersion patterns in the Lhasa River valley. Here, online C2–C11 VOC measurements, accompanied by other parameters concerning the O3 chemical budget, were first obtained and employed to identify the key VOC species and key sources of VOCs in terms of the loss rate against OH radicals (LOH), ozone formation potential (OFP), secondary organic aerosol potential (SOAP), and toxicity. Oxygenated VOCs (OVOCs) not only were the most abundant VOCs but also dominated LOH, OFP, and toxicity. Isoprene and anthropogenic VOCs were further identified as precursors of these OVOCs. Aromatics accounted for 5 % of the total VOCs (TVOCs) but contributed 88 % to the SOAP and 10 % to the toxicity. As the primary oxidative intermediates of aromatics were not well characterized by our measurements, the environmental impact of aromatics could be underestimated by our data. Source appointment and ternary analysis of benzene, toluene, and ethylbenzene confirmed the combined contribution of traffic emissions, solvent usage, and biomass burning. This suggests that O3 precursors are mainly from sources associated with residents' lives, except for solvent usage emissions which contribute to aromatics. Preliminary comparisons between source spectrums of transport sector emissions with positive matrix factorization (PMF)-decomposed ones and our measured ones suggest that vehicle emission patterns of VOCs at high altitude generally follow the ground-level impression. More quantitative data are required to further confirm this point though. Emission reduction strategy analysis for O3 pollution control highlighted multiple benefits of the simultaneous reduction in NOx originating from diesel vehicle emissions, biomass burning, and background sources (possibly dominated by incense burning). The notable biogenic emission contribution to the OFP was also first confirmed in our study, and this highlights the side effects of the government's pursuit of a greener city.

Effects of reformed exhaust gas recirculation (REGR) of ethanol-gasoline fuel blends on the combustion and emissions of gasoline direct injection (GDI) engine

Transportation is one of fast-growing sources of greenhouse gas emission worldwide. Road transport accounts as the main cause of HC, CO, NOX, CO2, and PM emissions. Ethanol blended fuel could improve engine performance and reduce both gaseous and PM emissions. Meanwhile, reformed exhaust gas recirculation (REGR) is introduced to achieve simultaneous reduction of NOX and PM from gasoline engines. In this work, the effect of REGR on combustion characteristics, and emissions of the gasoline direct injection (GDI) engine fuelled with ethanol-gasoline fuel blends (E10 and E20) was investigated. The H2 and CO mixture were used as a simulated REGR charge which was fed to the GDI engine’s intake manifold. The H2/CO ratio was determined via modelling of ethanol-gasoline fuel blend reforming based on equilibrium analysis. Moreover, the characteristics of PM emission (e.g. size distribution, primary particle size, morphology) were explored using TEM imaging. The results revealed that REGR could simultaneously improve both the engine thermal efficiency and engine-out emissions. A total number of PM particles and average primary particle size were reduced and compared with baseline (no-EGR) condition. An insight from this investigation can be used for designing control strategies to reduce the negative impact of internal combustion engine usage on human health and environment.

CFD analysis of combustion and emission characteristics of biodiesel under conventional and late-injection based premixed combustion conditions

The simultaneous reduction in NOx and smoke emissions can be achieved with biodiesel under a late-injection based low temperature combustion (LTC) strategy. However, this occurs at the expense of a substantial increase in unburned hydrocarbon (HC) and carbon monoxide (CO) emissions. It is worthwhile to understand the reasons behind the formation of these emissions, emphasizing comparison with conventional combustion, which is known to result in significantly low HC and CO emission levels, particularly with oxygenated biodiesel fuel. The present investigation attempts to examine the same with 3D CFD simulation. Experimental data were obtained from a light-duty diesel engine using biodiesel from non-edible Karanja oil. The unmodified engine with OEM low-pressure mechanical fuel injection system was utilized for conventional combustion operation. It is replaced with a modified common rail injection system for a late-injection-based LTC mode of operation. By combining retarded high-pressure injection with EGR, sufficient premixing was sustained to enable late injection-based premixed combustion (LI LTC). The combustion simulation was performed using CONVERGE CFD tool, utilizing a two-component surrogate of methyl butanoate (MB) and n-dodecane to represent biodiesel. A reduced chemical kinetic mechanism, developed and validated in an earlier investigation on biodiesel combustion, was utilized in the current study. The mechanism was solved using the SAGE Detailed CHEMKIN solver in CONVERGE. Validation was conducted at two engine operating conditions defining low and high loads for both combustion modes. The cylinder pressure and heat release rates were predicted with a maximum error of 1.5 and 13%, respectively. The validated CFD tool was employed to compare and analyze the equivalence ratio, in-cylinder gas temperatures, and HC and CO contours between conventional and LI LTC modes. Under LTC mode, the cylinder pressure and heat release rates were predicted with a maximum error of 10 and 15%, respectively. The comparison revealed fuel-rich regions concentrated near the bowl in conventional combustion, while the fuel was spread throughout the combustion chamber in LI LTC mode with over-rich and over-lean regions near the cylinder wall. The cylinder temperature is significantly higher for conventional combustion than LI LTC mode. The O and OH radical concentrations are higher for conventional combustion, corroborating with lower CO emissions, as they aid in CO oxidation. Fuel-rich regions contribute to increased CO emissions, whereas over-lean regions at a low-temperature result in high HC emissions, exhibited by the emission contours. Possible countermeasures to reduce high HC and CO emissions in LI LTC mode include maintaining higher coolant temperatures to enable HC and CO oxidation in the near-wall regions and fuel injection system modification to alter the air–fuel mixing.

Monohydric aliphatic alcohols as liquid fuels for using in internal combustion engines: A review

The environmental and air pollution brought about by the increasing energy consumption has increased the interest in the use of renewable energy sources in the transportation sector, where internal combustion engines are used, which is responsible for a large part of the exhaust emissions. Alcohol fuels have been evaluated as renewable energy sources for utilising in internal combustion engines and they are reported to have lowering exhaust emissions and costs. This study analyses four monohydric aliphatic alcohol fuels (methanol, ethanol, propanol and butanol) by reviewing the available literature to represent their applicability as an alternative fuel in internal combustion engines. In the study, researches on the directly use of acetone–butanol–ethanol and isopropanol–butanol–ethanol as alcohol fuel were also examined because the production of butanol by acetone–butanol–ethanol and isopropanol–butanol–ethanol distillation is costly, and isopropanol–butanol–ethanol is more preferred due to the corrosive feature of acetone. The higher fuel consumption of alcohol fuels than fossil fuels was the most common result, with reductions in NOxand smoke emissions except for isopropanol–butanol–ethanol, which had higher NOxemissions. It has been reported that less carbon and high oxygen content, low cetane number and high latent heat of alcohol fuels are responsible for the above results. The increase in thermal efficiency with the use of acetone–butanol–ethanol and isopropanol–butanol–ethanol in contrast to other alcohol fuels was a notable result. A comparison among the alcohol fuels showed that methanol was more effective than ethanol in reducing CO, unburned HC and smoke emissions while isopropanol–butanol–ethanol demonstrated high NOxemissions. A simultaneous reduction of NOxand Smoke emissions, which was commonly reported for most of alcohol fuels, makes a significant contribution to the development of internal combustion engines. This study gains importance in terms of comparing the individual effects of the use of alcohol fuels on exhaust emissions and better understanding the current status of these fuels.

Parametric investigation on the performance-emissions trade-off and knocking occurrence of dual fuel engines using CFD

Dual fuel (DF) engines have been an attractive alternative of traditional diesel engines for reducing both the environmental impact and operating cost. The major challenge of DF engine design is to deal with the performance-emissions trade-off via operating settings optimisation. This study aims at parametrically investigating the engine settings optimisation for a simultaneous reduction of NOx emissions and brake specific fuel consumption (BSFC) of marine DF engines while avoiding knocking accurrence by using a computational fluid dynamics (CFD) model. The model is developed in the CONVERGE software and validated by employing the measured in-cylinder pressure and emissions. Subsequently, the model is used to parametrically investigate the engine operating settings (pilot injection timing, equivalence ratio and natural gas mass) that allow simultaneous reduction of NOx and BSFC emissions at three engine operating conditions (1800 r/min, 1629 r/min and 1457 r/min). Result shows that the optimal solution at 1800 r/min and 1629 r/min operation conditions can be achieved by controlling the pilot injection timing, equivalence ratio variation and NG mass variation within –5 to –7.5 °CA, –5% to +5 % and 0 % to +20 %, respectively. For the 1457 r/min operation condition, the appropriate ranges of pilot injection timing and the equivalence ratio variation are the same with those at 1800 r/min and 1629 r/min, whilst the NG mass variation range should be between –10 % and +10 %. The derived results in this study are expected to support the combustion analysis and enhancement of marine DF engines during the design phase, whilst the derived optimal solution is expected to provide guidelines of DF engine management for reducing operating cost and environmental footprint.

SIMULTANEOUS REDUCTION OF NOX AND SMOKE EMISSIONS IN GASOLINE-ETHANOL BLENDED RCCI ENGINE WITH BIOGAS AS A TERNARY FUEL

SIMULTANEOUS REDUCTION OF NOX AND SMOKE EMISSIONS IN GASOLINE-ETHANOL BLENDED RCCI ENGINE WITH BIOGAS AS A TERNARY FUEL

Experimental investigation and multi-objective optimization of boiler-recuperator systems to reach MILD combustion characteristics

The article aims to achieve the benefits of MILD combustion in a conventional hot water utility boiler by performing a simple revamping and generalizing results to the industrial utility boilers. For this purpose, experimental and numerical investigations were performed on preheating and diluting of combustion air using a recuperator and a flue gas recirculation (FGR) line in a pilot-scale boiler equipped with a conventional premixed burner. Experimental results of maximum preheating and optimal dilution led to increased thermal efficiency and simultaneous NOx reduction in the pilot-scale boiler, which are characteristics of MILD combustion. Thermodynamic modeling and optimization were conducted to determine the optimum air dilution for different industrial utility boilers equipped with various recuperators. Multi-objective optimization provides a set of optimal solutions for fuel flow rate, excess air and FGR to improve system efficiency and reduce NOx emission. It was found that the optimal FGR decreases with increasing boiler efficiency. For instance, in a system equipped with 50 % recuperator effectiveness, the optimal FGR reduces from 0.6 to 0.24 when boiler efficiency increases from 60 % to 90 %, respectively. These optimal FGRs ensure that the system efficiency is maximized while reducing NOx emissions to less than 30 ppm. The novelty of present study is investigating wide range of FGRs for various boiler-recuperator systems and demonstrating that maximum possible preheating together with optimum FGR can provide advantages of MILD combustion to any conventional utility boilers.

Improvement of NOx and CO Reduction Performance at Low Temperature of H2-SCR Catalyst

The purpose of this study is to improve the simultaneous reduction of NOX and CO, harmful gases emitted from internal combustion engines, at low temperatures using a Pt/TiO2 H2-SCR catalyst. A better NOX/CO reduction performance was observed upon loading 2 wt% of the additive catalyst CeO2 on the main catalyst Pt because the oxygen storage capacity improved. In the presence of CO, the water gas reaction was promoted, resulting in the NOX conversion rate by the 0.5Pt−2CeO2/TiO2 SCR catalyst of 42 % at 75 °C and 70 % at 100 °C; this was a 15 ∼ 20 % higher NOX conversion as compared to without CO at low temperatures. The NOX reduction performance by the 0.5Pt−2CeO2−2ZrO2/TiO2 SCR catalyst was the highest at temperatures below 100 °C. At an appropriate amount of the additive catalyst ZrO2, the reaction rate improved because the acid point of the catalyst surface and the intensity of adsorption are adjusted. The optimum reduction temperature for NOX/CO reduction performance by the H2-SCR catalyst was 400 °C. Our results also indicate that the Pt species has a significant impact.

Experimental investigation on effects of equivalence ratio on combustion with knock, performance, and emission characteristics of dimethyl ether fueled CRDI compression ignition engine under homogeneous charge compression ignition mode

This study deals with the effects of different equivalence ratios on combustion with a knock, performance, emissions of a DME fueled automotive CI engine under HCCI mode. The conventional common rail direct injection (CRDI) CI engine was modified to run with DME fuel (manifold injection) under HCCI mode. The experiments were conducted on the engine at different equivalence ratios at a constant speed of 1400 rpm. Two stages of combustion (low-temperature reaction (LTR) region and high-temperature reaction (HTR) region) were observed under HCCI mode. The LTR region occurs at the temperature range from 700 to 750 K. In contrast, the HTR region was at a temperature beyond 1000 K. The cyclic variations with the coefficient of variation (COV) of maximum in-cylinder pressure, indicated mean effective pressure with knock peak pressure and knocking intensity (KI) were analyzed for assessment of combustion stability. Based on the knocking intensity, the optimum equivalence ratio with controlled auto-ignition (CAI) was found as 0.55, with peak in-cylinder pressure of 70.87 bar and peak in-cylinder temperature of 1815 K. The COV for all the parameters and KI found below the limit value (COVlimit − 5% and knocklimit − 5 MW/m2) till 0.55 equivalence ratio and beyond the equivalence ratio, the knock occurred resulting in uncontrolled auto-ignition (UAI). Ultra-Low NOx (10–15 ppm) and zero smoke emissions with a considerable reduction in CO and HC emissions were observed at a higher equivalence ratio from DME fueled HCCI mode. However, CO and HC emissions were higher at lower equivalence ratio. This study shows that the simultaneous reduction of NOx and smoke emissions could be achieved in a DME fueled HCCI engine.

Simultaneous reduction of NOx emission and SOx emission aided by improved efficiency of a Once-Through Benson Type Coal Boiler

With significant contributions in global emissions of air pollutants, sustainable practices for coal-fired power generation are fundamental to mitigate global climate change, besides ensuring compliance to the local authorities, which is as critical as climate issues. Despite the importance of these issues, some gaps exist in the literature to develop practices capable of fostering emissions reduction of NOx and SOx. In this sense, the present study aimed to present a comprehensive approach to NOx emission and SOx emission reduction through improved efficiency of a once-through Benson type coal boiler in a coal-fired power plant. In improving efficiency, NOx and SOx emissions were strongly influenced by O2 concentration, coal mass flow, air/fuel ratio and coal calorific value. The optimum conditions that resulted in simultaneous reduction of NOx and SOx emissions were achieved when the O2 concentration was 3.28 vol% with the coal mass flow of 281 tonnes/hr. The results further suggested that NOx concentration was reduced by a large margin when the air/fuel ratio changed from the lean side to the rich side. The findings of this study help to establish benchmarks relating to a comprehensive assessment of SOx and NOx emissions reduction.

Effects of Injection Rate Shape on Performance and Emissions of a Diesel Engine Fuelled by Diesel and Biodiesel B20

The combustion process in diesel engines is controlled by the injection rate shape. The stricter emission regulations requiring simultaneous reduction of nitrogen oxides and particulate matter imposes intense research and development activity for achieving clean and robust combustion. This work describes the experimental investigation made for calibration of an engine model and the numerical investigation performed to assess the influences of different injection rate shapes on performances of a diesel engine fuelled with diesel and rapeseed biodiesel B20. The engine model was developed with the AVL-BOOST code using the AVL-MCC combustion mode. The model was calibrated for the reference Top-Hat injection rate shape using experimental data registered for maximum brake torque and maximum brake power speed conditions. Other injection rate shapes such as triangular, trapezoidal, and boot having the same area, start, and duration of injection were investigated in terms of combustion characteristics, performance, and pollutant emissions. The link existing between the injection characteristics and the NOx and Soot emissions highlights that, for the optimal rate of injection shape, a simultaneous reduction of NOx and Soot by 11%, respectively 4% for maximum brake torque and by 22%, respectively 7% for maximum brake power, can be obtained using biodiesel B20.

Numerical investigation on the impact of multiple injection strategies and spray included angles on combustion and emissions in a marine diesel engine

The computational fluid dynamical software AVL-FIRE code was used for investigating the impact of multiply injection strategies and spray included angles on combustion and emissions in a marine diesel engine. The fuel injection parameters of spray included angle and pilot injection timing with pilot-main injection, as well as post injection ratio and post injection duration angle with pilot-main-post injection, were all investigated and optimized. The results indicate that retarding pilot injection timing with pilot-main injection declines high temperature region, resulting in a notable reduction in NOx emissions. Since fuel evaporation and burn are hampered by long spray penetration due to low temperature and pressure with pilot injection, a suitable spray included angle are used to offer more efficient air-fuel mixing process. A wider spray included angle simultaneously reduces soot emission and indicated specific fuel consumption (ISFC). Post injection fuel exerts impact on combustion process by causing a great disturbance to flow field during post combustion. Increasing post injection ratio from 4% to 10% at a small post injection duration angle great emission performance is achieved by simultaneous reduction in NOx and soot emissions while only using a slight consumption of ISFC. To summarize, the defeat of traditional NOx-soot trade-off occurs as both NOx and soot emissions are decreased with optimized multiple injection strategy and spray included angle. Particularly, there are respectively four cases with pilot-main injection and two cases with pilot-main-post injection, that achieve simultaneous reduction in NOx emissions, soot emission, and ISFC, compared to the prototype.

Emission and performance characteristics of CRDI diesel engine using Quadruple injection strategy with different pilots and post injection timing

Multiple injections in association with suitable (High/heavy) exhaust gas recirculation (EGR) is a promising technique to achieve low temperature combustion (LTC) regime in modern CRDI (common rail direct injection) diesel engine. This helps for simultaneous reduction of NOx and Soot to meet the stringent emission norms without penalizing the fuel efficiency and overcome the drawbacks of EGR-LTC. There are limited insights available which discuss about the potentiality of latest Quadruple injection (early-pilot-main-post/after; epMa) strategy in combination with high EGR and different injection timing over triple injections (pilot-main-after; pMa) at wide operating conditions. This paper deals with the study on the effect of Quadruple injection (epMa) startegy on performance, emissions and noise with different Pilot injection timing and post injection dwell combinations (8 Nos) on a CRDI diesel engine with high EGR and fixed main injection schedule at 4 operating loads and 5 speeds. The study shows that Quadruple injection strategy with retarded early and advanced pilot (early 35° and pilot 19°CA BTDC) and advanced post injection dwell timing 1100 ms is superior in providing optimum results in emissions (NOx, PM, THC, CO) and combustion noise (CN)[1.55–2 dBA @Rig level and 0.7 dBA @ Vehicle level Pass by Noise (PBN)]. This gives the best results in brake specific fuel consumption (BSFC)[0.2 to 1.31%], Torque and brake thermal efficiency (BTE) performance w.r.t other combinations and base triple injections (pMa). In contrary, the quadruple injection strategy having advanced double pilots with delayed post injection dwell (early-39°, Pilot-19°CA BTDC and DtA 1300 ms); shows the best CN reduction. Best smoke results found with the combination of retarded pilots and advanced post injection dwell. This study shows the importance of injection timing specially the twin pilots (early, pilot) along with post injection dwell. Furthermore, it indicates the potentiality of newest Quadruple injection strategy over triple injection.

A relative assessment of emulsification and water injection methods to mitigate higher oxides of nitrogen emissions from biodiesel fueled light-duty diesel engine

In-cylinder emission control strategies based on fuel modifications have gained considerable interest in diesel engine applications because of the potential to simultaneously reduce the oxides of nitrogen (NOx) and soot emissions. There is a renewed interest to replace diesel with carbon-neutral biodiesel to mitigate global warming potential from the transport sector. Further, the bi-directional NOx-soot trade-off problem in conventional diesel combustion has been reduced to a unidirectional higher NOx problem with biodiesel. The efficacy of utilizing emulsification and water injection methods to mitigate the higher NOx emissions with biodiesel is investigated in the present work. The water to biodiesel ratio for the emulsion and injection methods was kept similar at 3%, 6%, and 9% by mass of fuel. Experiments were conducted in a light-duty diesel engine at rated speed, varying load conditions with neat biodiesel, biodiesel-water emulsion, and biodiesel water injection. Biodiesel-water emulsions prepared using a combination of non-ionic surfactants, Span 80 and Tween 80, were stable for over four months. The average droplet size measured using the Dynamic Light Scattering (DLS) technique was 305 nm, 334 nm and 443 nm with 3%, 6% and 9% emulsion, respectively. The intake manifold was modified to include a low-pressure port fuel injector (PFI) to enable water injection. The pulse width of the PFI injector was controlled using a National Instruments PFI module to vary the injected water mass per cycle. The results obtained with biodiesel-water emulsion and biodiesel water injection were compared with neat biodiesel as a reference fuel. The ignition delay time increased, and the peak pressure was reduced with biodiesel-water emulsion. The combustion duration was reduced with emulsion indicating faster burning characteristics. The engine brake thermal efficiency increased with emulsion with a maximum increase of 6%, and there was a 10% reduction in the brake-specific fuel consumption. Both emulsion and water injection result in a simultaneous decrease in NOx and smoke emissions. The drop is significant with emulsion, with a maximum reduction of 40% and 34% in the NOx and smoke emissions, respectively. Overall, the present study shows that biodiesel-water emulsion has a higher potential to achieve a simultaneous reduction in NOx and smoke emissions with better engine performance.

Effects of isopropanol-butanol-ethanol (IBE) on combustion characteristics of a RCCI engine fueled by biodiesel fuel

The reactivity controlled compression ignition (RCCI) strategy using fuels with different reactivity’s has attracted attention due to its high thermal efficiency as well as very low NOx and PM emissions in comparison to conventional combustion. As previous studies have shown that the type and amount of low reactivity fuel have a significant contribution to the in-cylinder reactivity, thus RCCI combustion, in this study, Iso-Propanol-Butanol-Ethanol (IBE), which has comparable characteristics to n-butanol and ethanol, is employed as low reactivity fuel (LRF) in a RCCI engine fueled by petroleum based EN590 fuel and commercial biodiesel. The IBE mixture was in volumetric ratios of 3:6:1 as in the fermentation process of butanol, that is to say; 30% Iso-Propanol, 60% Butanol and 10% Ethanol. In each experimental condition, keeping the total energy of the fuel supplied to the engine in conventional combustion mode for each cycle as constant, the premixed ratio (Rp) in case RCCI combustion was applied as 0%, 15%, 30%, 45% and 60% (the amount of LRF in energy basis) over this energy amount. The effect of premixed ratio of IBE on combustion characteristics were investigated in a single-cylinder RCCI engine under different loads with using both petroleum diesel and biodiesel as high-reactivity fuels (HRF), respectively. According to experimental results, a higher in-cylinder pressure was measured by using diesel in both conventional and RCCI mode compared to the use of biodiesel. Considering the peak in-cylinder pressure and rate of heat release, the premixed ratio (Rp) of up to 45% was found as optimum for all loads while it was up to 30%Rp for the NOx emissions. In addition, the biodiesel-fueled RCCI engine produced the lowest smoke opacity in all loads and it gradually decreased by up to 97% with the application of the RCCI strategy. Furthermore, the results showed that a simultaneous reduction in NOx and smoke opacity could be obtained under 60% load and up to 30% Rp with a marginal increase in unburned HC emissions.

Influence of air staging strategies on flue gas sensible heat losses and gaseous emissions of a wood pellet boiler: An experimental study

An effective air staging strategy is of great importance for achieving low emissions and sensible heat losses through flue gas extraction. In cases where a commercially available system needs to be optimised, often the only viable measure is the modification of process parameters. In this work, the aim is to (1) Discover a combination of the most suitable process parameters based on a multi-criteria decision-making method and (2) To unveil relevant correlations between the two process parameters under study (PA/SA ratio and excess air), emissions and combustion temperatures. A modified commercial small-scale hot water wood pellet boiler was installed into a laboratory heating system. Nine different cases have been addressed within a parametric study, differing in the PA/SA ratio and overall excess air. Emissions, temperatures inside the combustion chamber and the flow rate of air entering the combustion chamber were measured. A low PA/SA ratio of 0.53 (54.7% reduction from factory settings), combined with a low O2 concentration in the flue gases of 5.26% (39.8% reduction from factory settings), and the elimination of infiltration air resulted in a simultaneous reduction of NOx and CO emissions by 14.4% and 93.9% respectively and a flue gas sensible heat loss reduction of 31.6%.