Higher Nitrogen Oxides Research Articles

Multi-objective optimization of micro co-generation spark-ignition engine fueled by biogas with various CH4 / CO2 content based on GA-ANN and decision-making approaches

After the advances in biogas upgrading techniques, the optimization of power and heat generation engines fueled by biogas with varying compositions has become a necessity. Therefore, the aim of the present study is to investigate the necessity of upgrading biogas, mainly CO2 removal, in order to generate power and to determine the optimal operating parameters of a spark-ignition (SI) engine fueled by upgraded biogas. Thus, we propose to couple the artificial neural network technique, multi-objective optimization concept and decision-making approaches in order to improve the performance of a stationary SI engine and to reduce its nitrogen oxides (NOx) emissions while keeping the level of biogas upgrading as low as possible. The brake power (BP), brake thermal efficiency (BTE), and NOx emissions of a SI engine were predicted by using artificial neural network models. The spark ignition timing (IT), biogas CH4 concentration, and throttle valve opening (TVO) were taken as independent variables. The artificial neural network models were trained by using the genetic algorithm (GA) to achieve the best weights and biases. The data used to train and test the ANN models came from experimental tests carried out at constant engine speed (1500 rpm) and air-fuel ratio (λ = 1.4). In the optimization part, the BP, BTE, NOx emissions, and CH4 concentration were all taken as objective functions in order to achieve better performance while lowering NOx emissions and biogas upgrading level. In addition, the optimum operational parameters were obtained by using decision-making approaches. The final optimal point, for the best compromise between high engine performance and low NOx emissions, shows that there is no need to enhance biogas upgrading (lowering CO2 content) in order to generate power and heat. As a result, a SI engine under full load fueled by cleaned raw biogas is the best option.

Chemical Production of Oxygenated Volatile Organic Compounds Strongly Enhances Boundary-Layer Oxidation Chemistry and Ozone Production.

Photolysis of oxygenated volatile organic compounds (OVOCs) produces a primary source of free radicals, including OH and inorganic and organic peroxy radicals (HO2 and RO2), consequently increasing photochemical ozone production. The amplification of radical cycling through OVOC photolysis provides an important positive feedback mechanism to accelerate ozone production. The large production of OVOCs near the surface helps promote photochemistry in the whole boundary layer. This amplifier effect is most significant in regions with high nitrogen oxides (NOx) and VOC concentrations such as Wangdu, China. Using a 1-D model with comprehensive observations at Wangdu and the Master Chemical Mechanism (MCM), we find that OVOC photolysis is the largest free-radical source in the boundary layer (46%). The condensed chemistry mechanism we used severely underestimates the OVOC amplifier effect in the boundary layer, resulting in a lower ozone production rate sensitivity to NOx emissions. Due to this underestimation, the model-simulated threshold NOx emission value, below which ozone production decreases with NOx emission decrease, is biased low by 24%. The underestimated OVOC amplifier effect in a condensed mechanism implies a low bias in the current 3-D model-estimated efficacy of NOx emission reduction on controlling ozone in polluted urban and suburban regions of China.

Distinct impacts of humidity profiles on physical properties and secondary formation of aerosols in Shanghai

As a key component in the atmosphere, the increase in water vapor content can aggravate air pollution by promoting hygroscopic growth and secondary formation of aerosols. In this study, water vapor mixing ratio (WVMR) profiles retrieved from Raman lidar at night in Shanghai were used to evaluate the accuracy of a maintained microwave radiometer (MWR) and reanalysis datasets (ERA5 from ECMWF and MERRA-2 from NASA). The relative humidity (RH) profiles from radiosonde and reanalysis datasets were used to explore the influence of humidity vertical distributions on aerosol physical properties and secondary formation. There was a large WVMR difference between MWR and Raman lidar, with a mean bias (MB) and a root mean square error (RMSE) being 2.47 g/kg and 3.29 g/kg, respectively. However, the WVMR from ERA5 and MERRA-2 showed excellent agreement (correlation coefficients were both 0.94, N = 11288 and 3619, respectively) with that from Raman lidar and high accuracy especially MERRA-2, which are more suitable for meteorological and climatic applications than MWR. It was found that RH had a significant effect on the vertical distribution of aerosol extinction coefficient (AEC). Aerosol hygroscopic growth caused by high RH resulted in an obvious enhancement of AEC at 355 nm below 610 m in summer. As a good indicator for determining contribution of aerosol secondary formation, large ratios of PM2.5 to CO (PM2.5/CO > 0.08) corresponded to high nitrogen oxidation ratios (NOR), sulfur oxidation ratios (SOR), and also high RH below 800 m during nighttime in winter, suggesting that RH and its vertical distribution played an important role in the aerosol secondary formation. The RH was high in the vertical direction when nitrate and sulfate mainly come from the secondary formation (NOR >0.1 or SOR >0.1), and in contrast to nitrate, the secondary formation for sulfates tended to depend on higher RH (>70%), which indicated that more stringent measures for nitrogen oxides emission reduction should be implemented in Shanghai to reduce the pollution of secondary aerosols in the future.

Effect and mechanism of combustion enhancement and emission reduction for non-premixed pure ammonia combustion based on fuel preheating

Ammonia (NH3) is a hydrogen-rich carrier with high energy density and is a carbon-free energy source. NH3 is a new carbon-free alternative fuel with great attraction and prospect. NH3 is restricted to large-scale industrial application because of its low reactivity and high nitrogen oxide (NOx) emissions in combustion. This research evaluated non-premixed pure NH3 combustion enhancement method and emission law based on fuel preheating. An NH3 preheating device, non-premixed burner, flue gas analysis, and temperature measurement system were designed and constructed. Combustion characteristics of NH3 preheating were investigated under different preheating temperatures and NH3 flow rates. NH3 flame images were captured by a CCD camera. The temperature distributions of the NH3 flames were reconstructed by deflection tomography technology. In addition, the composition concentrations of flue gas were obtained by a multi-component gas analyzer. The influence of preheating temperature on flame characteristics, combustion temperature field, and pollutant emission were analyzed. A numerical simulation was performed under the same experimental conditions. The effects of NH3 preheating on flame and emission characteristics were analyzed by sensitivity analysis and reaction path analysis. The mechanisms of the combustion enhancement and emission reduction for preheating NH3 non-premixed combustion were explained. Results showed that stable non-premixed pure NH3 flame was generated at different experimental flow rates when the NH3 preheating temperature was higher than 593 K. The brightness, color, and structure of the flame varied significantly with increasing preheating temperature. Furthermore, the concentration of NOx decreased obviously, and the concentration of unburned NH3 was extremely low. The chemical reaction rate was tremendously promoted with increasing preheating temperature, and the reaction pathway of N radical was extremely related to nitric oxide (NO) production and consumption.

High atmospheric wet nitrogen deposition and major sources in two cities of Yangtze River Delta: Combustion-related NH3 and non-fossil fuel NOx

High ammonia (NH3) and nitrogen oxide (NOx) emissions are related to serious air pollution in urban areas and the negative impacts of excessive reactive nitrogen (N) deposition on many ecosystems. However, whether there is a relationship between N deposition rates and their sources with urbanization or not remains unclear in many areas. Here, we investigated the deposition rates of ammonium (NH4+), nitrate (NO3−), dissolved organic N, and water-insoluble particular N from July 2017 to June 2018 at two urban and two suburban sites in the Yangtze River Delta (YRD). The δ15N values of precipitation NH4+ and NO3− were measured, and major sources were analyzed using a Bayesian isotope mixing model. Wet N deposition rates were higher in Yangzhou (developing city, 20.3–22.7 kg N ha−1 yr−1) than those in Nanjing (developed city, 19.4–20.5 kg N ha−1 yr−1), and were higher at urban sites (20.4–22.5 kg N ha−1 yr−1) than those at suburban sites (18.7–20.3 kg N ha−1 yr−1). δ15N values of precipitation NH4+ increased with an increase in precipitation pH because ambient acidity affects the equilibrium isotope fractionation between NH3 and NH4+ and wet scavenging coefficients of NH3 and particulate NH4+. For NH4+, combustion-related NH3 sources (62%–65% with 5.5–6.4 kg N ha−1 yr−1, including coal combustion, vehicle exhaust, and biomass burning) contributed more than volatilization NH3 sources (35%–38% with 2.9–3.9 kg N ha−1 yr−1, including fertilizer application and waste volatilization). For NO3−, non-fossil fuel NOx sources (50%–63% with 3.4–4.1 kg N ha−1 yr−1, including biomass burning and microbial N cycle) were comparable to fossil fuel NOx sources (37%–50% with 2.4–3.4 kg N ha−1 yr−1, including coal combustion and vehicle exhaust). This study evidenced high N deposition rates and the importance of combustion-related NH3 emissions and non-fossil fuel NOx emissions in city areas of the YRD.

Influence of syngas composition on combustion and emissions in a homogeneous charge compression ignition engine

Homogeneous charge compression ignition (HCCI) is a promising combustion concept that can simultaneously achieve high efficiency and low nitrogen oxides (NOx) emissions. Synthesis-gas (syngas)-fueled HCCI engines can be adapted for a wide range of fuel compositions. The aim of this study was to investigate the combustion and emissions of an HCCI engine with various syngas compositions. The baseline syngas contained 30% H2, 25% CO, and 45% CO2 by volume, which provided a low heating value (LHV) of 6.08 MJ/Nm3. The fuel composition varied from hydrogen-rich to lean. It was found that syngas with an LHV of 3.34 MJ/Nm3 could be auto-ignited by implementing intake boosting with sufficient intake heating. The intake temperature required to achieve autoignition was reduced at higher loads. The start of combustion temperature mainly relied on the intake temperature and fueling rate, regardless of the fuel composition. A higher H2 content in the fuel facilitated fast burning with good combustion stability, even under lean conditions. It was revealed that a higher CO fraction deteriorated the combustion stability on the lean side with slow burning. The gross indicated thermal efficiency (ITEg) increased with an increase in the LHV of the syngas, with an ITEg of 38.1% realized at a low load of 0.3 MPa for the base fuel, while maintaining engine stability. The combustion efficiency was greater than 90% for the fuels examined at a higher fuel rate. The NOx emissions were very low because of the ultra-lean, diluted charge used for HCCI combustion.

Prenatal exposure to near-roadway air pollution and autism spectrum disorders in children

BACKGROUND AND AIM: Previous studies have reported associations between {in-utero} exposure to regional air pollution and autism spectrum disorders (ASD). {In-utero} nitrogen oxide (NOx) exposure has been linked to adverse neurodevelopment in animals and cardiovascular conditions in humans, but few studies have investigated pregnancy exposure to near-roadway air pollution (NRAP) and ASD risk. METHODS: This retrospective birth cohort included 311,617 mother-child pairs of singletons born between 2001-2014 at Kaiser Permanente Southern California (KPSC) hospitals. Maternal and child data were extracted from KPSC electronic medical records. Children were followed until: clinical diagnosis of ASD, non-KPSC membership, death, or December 31, 2019, whichever came first. Exposure to the complex NRAP mixture during pregnancy was estimated by monthly California line-source dispersion models (CALINE4) for both near-roadway (freeway; non-freeway) and total NOx, using maternal addresses during pregnancy. Cox proportional-hazard models were used to estimate hazard ratios (HR) of ASD associated with NRAP during pregnancy, adjusted for covariates. Nonfreeway NRAP was analyzed using quintile distribution due to nonlinear associations with ASD. RESULTS:A total of 6,291 children (5,114 boys, 1,177 girls) were diagnosed with ASD. Prenatal exposure to total NRAP was associated with ASD diagnosis [HR (95% CI): 1.03 (1.00,1.06) per 10 ppb increase in NOx]. Nonfreeway NRAP was associated with ASD diagnosis; however, freeway NRAP was not. The HR (95% CI) comparing the highest quintile of nonfreeway NRAP exposure (3.8 ppb NOx) to the lowest quintile (0.89 ppb) or to the lower 4 quintiles (≤3.8 ppb) were 1.20 (1.08, 1.33) and 1.20 (1.13, 1.27) respectively. The HR (95% CI) associated with high nonfreeway NOx (3.8 vs ≤3.8 ppb) were significant in boys [1.20 (1.10, 1.26)] and girls [1.23 (1.06,1.39)], and robust to adjustment for PM2.5. CONCLUSIONS:Prenatal exposure to near-roadway air pollution, particularly from nonfreeway sources, may be associated with ASD risk in boys and girls KEYWORDS: oxides of nitrogen, neurodevelopmental, children's environmental health

The Roles of N, S, and O in Molecular Absorption Features of Brown Carbon in PM2.5 in a Typical Semi‐Arid Megacity in Northwestern China

AbstractBrown Carbon (BrC) absorbs light in wavelength of 300–400 nm, and BrC molecule (BrCM) is a fundamental component responsible for aerosol radiative forcing. In this study, Fourier‐transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) coupled with electrospray ionization (ESI) was used to determine methanol extracted BrCM in PM2.5 collected in Xi'an, China. The absorption of individual BrCM was quantified through partial least square regression (PLSR) method. Results showed that 77.5% and 91.8% of winter and summer BrCMs were weak absorptive. The top BrCMs were responsible for 60.4% and 84.6%, respectively, of the absorbances in summer and winter. The nitrogen (N)‐containing organic molecules were identified to be critical components of light‐absorbing matters in both of the two seasons, outlining the significance of N chromogenesis in BrC. The top BrCMs were more closely related to ‐(O)NO2 that originated from NO2 engaged reactions in winter, and to ‐NH that formed in NH3 reactions in summer. Sulfur (S)‐containing functional groups were not chromophoric while sulfur dioxide (SO2) triggered N‐containing and S‐free BrCM formations under high nitrogen oxides (NOx) concentration levels and relative humidity (RH) in winter. Hypochromicity of oxygen (O) in BrC was discovered because of the photobleaching of oxidation and weak light‐absorbing of highly oxidized molecules.

Emissions from homogeneous charge compression ignition (HCCI) engine using different fuels: a review.

The main objective of this paper is to review the emission characteristics of homogeneous charge compression ignition (HCCI) engines using different fuels and additives. Additionally, the impacts of various operating conditions on HCCI engine emissions are also analyzed. There is a demand faced by the engine and car manufacturers for high fuel efficiency and low emission from both consumers and the government. HCCI is an alternative internal combustion technology that is more efficient and cleaner than traditional combustion techniques. In this engine, fuel and oxidiser (typically air) are entirely mixed and compressed to the point of auto-ignition. It is a new combustion concept that provides high efficiency and resolves high nitrogen oxide (NOx) and particulate matter (PM) emissions simultaneously. Conventional diesel engine emits NOx around 2000-2500 ppm which is a primary concern; however, when diesel is used in HCCI engine, it reduces NOx to only 70-400 ppm. Furthermore, natural gas cannot be used as fuel in the conventional engine but can be used in HCCI engine. It helps reduce NOx emission even below 10 ppm. This paper reviews several works done by researchers on HCCI engines to reduce their emissions and benefit future research.

Study of the Combustion Process of a Homogeneous Charge Compression Ignition (HCCI) Engine and a Partially Premixed Combustion (PPC) Mode of a Compression Ignition Engine Using Natural Gas as an Alternative Fuel

In order to investigate a viable approach to achieving high efficiencies and low nitrogen oxide (NOX) emissions, this paper presents the application of a homogeneous charge compression ignition (HCCI) engine and the partially premixed combustion (PPC) mode applied to a heavy diesel engine. The effect of carbon dioxide (CO2) fraction on combustion parameters was analyzed and discussed in detail. For this purpose, on the one hand, ANSYS CHEMKIN-Pro software was used to perform simulations of a closed homogeneous reactor under conditions relevant to HCCI engines, and on the other hand, ANSYS-Fluent software was used by adding a CO2 fraction varying from 20% to 58% to methane fuel to study 2D flow simulation by applying a PPC combustion mode to predict the distribution of various output parameters such as in-cylinder temperature, in-cylinder pressure and emissions. In comparison with the two presented models, it was found that the HCCI engine showed a lower NOX level than the PPC mode and this was due to the lower in-cylinder temperature in the HCCI engine.

Nitrogen Oxides (NOx) in the Arctic Troposphere at Ny-Ålesund (Svalbard Islands): Effects of Anthropogenic Pollution Sources

Atmospheric measurements of nitrogen oxides (NOx = NO + NO2), ozone (O3) and other constituents were carried out during three field campaigns (29 March–30 April 2010, 1–26 April 2011, 18 May–8 October 2015) at Ny-Ålesund. The study focused on the variability of important O3 precursors, such as NOx, in the Arctic troposphere, and on the impact from anthropogenic sources on their measured concentrations: higher NO and NO2 levels were mostly associated with the lowest wind speeds and northern directions, indicating local pollution. Long-range transported sources from Russia and Europe were also identified with an occurrence of high NOx levels. Several ozone depletion events were observed and associated to winds blowing from the north-west direction (Arctic Ocean). Most of these events were connected to the lower NO and NO2 concentrations. Measurements of halogen and low molecular weight carbonyl compounds in 2010 and 2011, respectively, showed variable effects during the ozone depletion events. Other data, such as high time-resolved radon progeny measurements, were used in 2015 to identify source tracking and transport of air masses, local effects and atmospheric stability dynamics that could influence the NOx concentrations at Ny-Ålesund.

Fabrication of molten nitrate/nitrite dual-phase four-channel hollow fiber membranes for nitrogen oxides separation

Molten salt-ceramic dual-phase membranes have great prospects in the selective separation of nitrogen oxides. A gas-tight KNO3–Ba0.5Sr0·5Co0·8Fe0·2O3-δ (KNO3-BSCF) four-channel hollow fiber membrane was developed in this study. A wide operating temperature window of 350–500 °C with high nitrogen oxides permeance was achieved. The maximum nitrogen oxides permeance reached 9.2 × 10−9 mol m−2 s−1 Pa−1 under the condition of 1% NO2, 1% CO2 and 20% O2 at 500 °C. The presence of nitrogen oxides was able to suppress the reaction of BSCF oxide with CO2 to form carbonates. Insights on the transport mechanism of nitrogen oxides transport were provided and the existence of nitrite route for nitrogen oxides transport was firstly demonstrated by experiments. An 1800 h long-term nitrogen oxides permeation was running on the KNO3-BSCF hollow fiber membrane while the permeance increased by a factor of ~40 (5.2 × 10−10 mol m−2 s−1 Pa−1 to 2.2 × 10−8 mol m−2 s−1 Pa−1 at 450 °C) due to the partial decomposition of nitrate into nitrite. This nitrite route was also verified in KNO3/KNO2-BSCF hollow fiber membrane constructed by preloading 30 wt% nitrite in molten salt.

A Review of Photocatalytic Materials for Urban NOx Remediation

NOx is a pervasive pollutant in urban environments. This review assesses the current state of the art of photocatalytic oxidation materials, designed for the abatement of nitrogen oxides (NOx) in the urban environment, and typically, but not exclusively based on titanium dioxide (TiO2). Field trials with existing commercial materials, such as paints, asphalt and concrete, in a range of environments including street canyons, car parks, tunnels, highways and open streets, are considered in-depth. Lab studies containing the most recent developments in the photocatalytic materials are also summarised, as well as studies investigating the impact of physical parameters on their efficiency. It is concluded that this technology may be useful as a part of the measures used to lower urban air pollution levels, yielding ∼2% NOx removal in the immediate area around the surface, for optimised TiO2, in some cases, but is not capable of the reported high NOx removal efficiencies >20% in outdoor urban environments, and can in some cases lower air quality by releasing hazardous by-products. However, research into new material is ongoing. The reason for the mixed results in the studies reviewed, and massive range of removal efficiencies reported (from negligible and up to >80%) is mainly the large range of testing practices used. Before deployment in individual environments site-specific testing should be performed, and new standards for lab and field testing should be developed. The longevity of the materials and their potential for producing hazardous by-products should also be considered.

Influence of plasma-assisted ignition on flame propagation and performance in a spark-ignition engine

Lean-burn is an attractive concept for reasons of high thermal efficiency and low nitrogen oxide (NOx) emissions, however, successful implementation in spark-ignition (SI) engines turned out to be challenging because of misfire or partial burn caused by attenuated flame propagation. In order to overcome this issue, microwave-assisted plasma ignition system (MAPIS) has been applied in combustion systems. The MAPIS consists of a conventional ignition coil, a non-resistor spark plug, a mixing unit, a waveguide, and a magnetron (2.45GHz, 3kW). A series of experiments was carried out to understand discharge characteristics and to validate its performance in a constant volume vessel as well as in a single-cylinder spark-ignition engine. The fundamental investigation based on optical emission spectroscopy and flame imaging showed that the ejection of the microwave was beneficial to produce more reactive species such as OH and O radicals thanks to higher electron temperature than conventional spark ignition. The lean limit was able to be extended up to an equivalence ratio of 0.5 based on a larger initial flame kernel size with MAPIS in the vessel test. Meanwhile, in the engine test, combustion stability was noticeably improved showing smaller cycle-to-cycle fluctuations in in-cylinder pressure. Improvement in fuel efficiency up to 6% could be achieved by stable operation under fuel-lean conditions. In terms of emissions, MAPIS was advantageous to reduce carbon monoxide (CO) emissions by promoting more complete combustion.

Insight into ozone profile climatology over northeast China from aircraft measurement and numerical simulation

Tropospheric ozone is a major pollutant that can harm human health, animals and plants. With a rapid development in Northeast China, ozone pollution has become an increasingly serious environmental challenge. To study the ozone distribution and the potential sources of ozone precursors in Northeast China, we analyzed vertical ozone profiles from the In-service Aircraft for a Global Observing System (IAGOS) in 2012–2014 and provided the climatological vertical structure of tropospheric ozone over Shenyang. The tropospheric ozone generally presents high in hot months, mainly due to the combined effects of the strong solar radiation and high volatile organic compounds emission in summer. While in cold months, the ozone is low because of weak solar radiation and high nitrogen oxides emission. Besides, a low-ozone center exists within lower troposphere in August, which is mainly caused by the East Asian summer monsoon prevailing in summer. To analyze the sources of ozone, typical ozone pollution episodes were studied and the results revealed the different pathways for the enhancement of ozone pollution in Shenyang: regional transport of anthropogenic emissions from North China Plain (NCP), long-range transport from Siberian biomass burning and local photochemical production. Modeling results show that the largest contribution to the surface ozone in Northeast China is local anthropogenic emissions (exceed 90%); the regional transport of NCP anthropogenic emissions contribute more to the pollutants around 2 km, and account for more than 50% pollutants during highly ozone polluted days; through long-range transport, Siberian biomass burning in the spring also have a nonnegligible effect on the near-ground ozone in Northeast China. Overall, this study provides tropospheric ozone climatology and its source attribution in Northeast China, and highlight the great importance of regional transport of anthropogenic and biomass burning emissions in ozone pollution.

Influence of Ammonia and Relative Humidity on the Formation and Composition of Secondary Brown Carbon from Oxidation of 1-Methylnaphthalene and Longifolene

Improved understanding of the optical properties of secondary organic aerosol (SOA) particles is needed to better predict their climate impacts. Here, SOA was produced by reacting 1-methylnaphthalene or longifolene with hydroxyl radicals (OH) under variable ammonia (NH3), nitrogen oxide (NOx), and relative humidity (RH) conditions. In the presence of NH3 and NOx, longifolene-derived aerosols had relatively high single scattering albedo (SSA) values and low absorption coefficients at 375 nm independent of RH, suggesting that the longifolene SOA is mostly scattering. In 1-methylnaphthalene experiments, the resulting SSA and SOA mass absorption coefficient (MACorg) values suggest the formation of light-absorbing SOA, and the addition of high NOx and high NH3 enhanced the SOA absorption. Under intermediate-NOx dry conditions, the MACorg values increased from 0.13 m2 g–1 in NH3-free conditions to 0.28 m2 g–1 in high-NH3 conditions. Under high-NH3 conditions, the MACorg value further increased to 0.36 m2 g–1 with an increase in RH. Under dry high-NOx conditions, the MACorg value increased from 0.42 to 0.67 m2 g–1 with the addition of NH3, while with elevated RH, the MACorg value reached 0.70 m2 g–1. The time series of MACorg showed increasing trends only in the presence of NH3. Composition analysis of SOA suggests that organonitrates, nitroorganics, and other nitrogen-containing organic compounds (NOCs) are potential chromophores in the 1-methylnaphthalene SOA. Significant formation of NOCs was observed in the presence of high-NOx and NH3 and was enhanced under elevated RH.

INVESTIGATION ON THE AIR-GAS CHARACTERISTICS OF AIR-HYDROGEN MIXER DESIGNED FOR DUAL FUEL – ENGINES

High smoke emissions, nitrogen oxide and particulate matter typically produced by diesel engines. Diminishing the exhausted emissions without doing any significant changes in their mechanical configuration is a challenging subject. Thus, adding hydrogen to the traditional fuel would be the best practical choice to ameliorate diesel engines performance and reduce emissions. The air hydrogen mixer is an essential part of converting the diesel engine to work under dual fuel mode (hydrogen-diesel) without any engine modification. In this study, the Air-hydrogen mixer is developed to get a homogenous mixture for hydrogen with air and a stoichiometric air-fuel ratio according to the speed of the engine. The mixer depends on the balance between the force exerted on the head surface of the valve and the opposite forces (the spring and friction forces) and its relation to decrease and increase the fuel inlet. Computational fluid dynamics (CFD) analysis software was utilised to study the hydrogen and airflow behaviour inside the mixer, established by 3.2 L engine. The Air-hydrogen mixer is examined with different speeds of engine1000, 2000, 3000 and 4000 RPM. Results showed air-hydrogen mixture was homogenous in the mixer. Furthermore, the stoichiometric air-fuel ratio was achieved according to the speed of the engine, the developed mixer of the AIR-Hydrogen mixing process provides high mixing homogeneity and engines with stoichiometric air-fuel ratios, which subsequently contributes to the high levels of efficiency in engine operation. In summary, the current study intends to reduce the emissions of gases and offer a wide range of new alternative fuels usage. While the performance of the diesel engine with the new air-hydrogen mixer needs to be tested practically.

Performance and ecological parameters of a diesel engine fueled with diesel and plastic pyrolyzed oil (PPO) at variable working parameters

Plastics are one of the major pollutants to the environment. An investigation is carried out in converting low density polyethylene (LDPE) to oil by pyrolysis method with the aid of catalyst for the use in internal combustion engines. Experiments were conducted at different speeds (1200, 1500 and 1800 rpm) and variable loads (low, medium and full) with constant compression ratio engine to evaluate the performance and ecological parameters. Plastic pyrolyzed oil (PPO) is blended with diesel fuel in 20:80 volume proportion to get D80PO20 blended mixture which is employed in engine in order to assess its characteristics. Encouraging outcomes have been obtained as cylinder pressure in combustion is of same order as that of diesel fueled engine. The results showed that increasing engine speeds resulted in higher cylinder pressure and brake thermal efficiency. Also, high nitrogen oxide (NOX) and low brake specific energy consumption (BSFC) has been identified. Lower smoke (BSN) and NOX emissions are noticed from engine tail pipe with D80PO20 blended mixture.

Numerical analysis of the performance and NOx emission of a diesel engine fueled with algae biofuel-diesel blends

ABSTRACT Researchers are looking for alternative energy sources, and biofuel from algae has a significant contribution as an alternative renewable fuel. This paper aims to evaluate fundamental running parameters (heat release rate, peak pressure, specific fuel consumption, and brake torque) and estimates the factors influencing nitrogen oxides (NOx) formation for algae biofuel-diesel blends (A-diesel). The analyses were done using a thermodynamic model and simulated with Diesel-RK and ANSYS. The numerical results of Diesel-RK and ANSYS were validated with experimental in-cylinder pressure data, and also compared with existing literature where needed. Injection timing, engine speed, and inlet temperature were selected as variables for developing the model. The engine speeds were chosen from 1400 rpm to 2500 rpm, and the injection timings were varied from 30° Before Top Dead Center (BTDC) to 20° After Top Dead Center (ATDC). Three algae biofuel blends such as 5% Algae-oil and 95% diesel (A5), 10% Algae-oil, and 90% diesel (A10), 15% Algae-oil and 85% diesel (A15), and pure diesel were considered as fuels for the analysis. The numerical findings indicate that higher inlet temperature, in-cylinder combustion temperature, and advanced injection timing are the main reasons for higher NOx formation during combustion. Among all the four fuels, algae bio-fuel blends showed lower NOx formations than conventional diesel fuel, and also, the engine performance was satisfactory. These two developed numerical models will also help researchers investigate various fundamental parameters of a diesel engine using blended fuels.

INVESTIGATION ON DIESEL ENGINE FUELLED BY MAHUA BIODIESEL

The primary objective of this study is to discover the effects of injection timing on performance, emission and combustion characteristics effect of advanced and retarded injection timing of the engine fuelled with mahua oil biodiesel blends. The engine performance, combustion and emission characteristics of the mahua oil biodiesel blends (B20, B40, B60, B80and B100) are investigated in this experimentation without any modification of the diesel engine. At this advanced pressure t
 he efficiency of engine by means of CO, Unburned HC gases and smoke emissions with higher oxides of nitrogen was observed compared to diesel. The obtained results are compared with a neat diesel and mahua oil biodiesel blends are shown through the graphs. From this study, identifies optimum fuel blend of this work. Thus, the combustion of duration is similar in all variance in pressure. This research paved a way to bio-diesel in mahua oil mixture and draws best outcome in emission less and to maintain eco-friendly environment.