Tailpipe Exhaust Research Articles

Fuel-Operated Auxiliary Heaters Are a Major Additional Source of Vehicular Particulate Emissions in Cold Regions

Fuel-operated auxiliary heaters (AHs) can be notable sources of particle emissions from vehicles. The emissions of AHs are unregulated, and the number of devices is high; therefore, they make considerable contributions to local air quality, and even the global emissions budget. Experiments for studying the emissions were performed in Finland for a total of eight selected vehicles with Original Equipment Manufacturer (OEM) AHs installed, including both diesel- and gasoline-operated heaters. We present the numerical results of particle emissions and compare the particle concentrations in the AH exhaust to values found in the tailpipe exhaust of the same vehicle. Our results show that the emissions from auxiliary heaters are typically several orders of magnitude higher than of a car exhaust when idling. This raises the question of whether the use of heaters is justified based on the goal to reduce total emissions from vehicle use; furthermore, whether fuel-operated heaters should also be applied in electric vehicles for cabin heating. More research will be needed to characterize the emissions more thoroughly to understand the air quality and climate effects from AHs, and to provide further recommendations on the use of these heaters.

Diesel Soot as a Supercapacitor Electrode Material

Diesel soot (DS) collected directly from the exhaust tailpipe of the diesel-powered vehicle was explored for its performance as an electrochemical supercapacitor electrode material. X-ray diffraction and Raman spectroscopy evidenced the existence of graphite carbon form in DS along with low amount of defects in the form of disordered graphite, amorphous carbon, ionic, and polyene impurities. The carbon (C, ∼94 at.%) and oxygen (O, ∼5 at.%) elements were identified using the X-ray photoelectron spectroscopy technique on the DS surface. The morphology of DS powder consisted of nanoparticles with nearly spherical-shaped morphology as observed under the scanning electron microscope. Further, the transmission electron microscope showed the chain type interconnectivity of DS nanoparticles. The average surface area, average pore radius, and total pore volume of DS were measured to be 88 m2 g−1, 1.62 nm, and 0.17 cc g−1, respectively. Cyclic voltammetry and galvanostatic charge-discharge studies were performed to explore the electrochemical behavior of DS slurry-coated electrode. The supercapacitor behavior of DS was studied using various aqueous and organic electrolytes. Higher values of specific capacitance (Csp) were achieved for DS in the case of aqueous electrolytes in comparison to organic electrolytes. The observed highest specific capacitance (Csp) value was 36.77 F g−1 for DS at the current density value of 0.25 A g−1 using 0.5 M H2SO4 electrolyte. DS retains nearly 78.10% of its initial capacitance even after the execution of 5000 cycles, clearly indicating the excellent durability and stability of the material. Thus, DS could be a promising supercapacitor electrode material.

Prediction of System-Level Energy Harvesting Characteristics of a Thermoelectric Generator Operating in a Diesel Engine Using Artificial Neural Networks

This study evaluated the potential of artificial neural networks (ANNs) to predict the system-level performance of a thermoelectric generator (TEG), whose performance depends on various variables including engine load, engine rotation speed, and external load resistance. Therefore, a Python code was developed to determine an optimal ANN structure by tracking the training/prediction errors of the ANN as a function of the number of hidden layers and nodes of hidden layers. The optimal ANN was trained using 484 output current (I)–load resistance (R) datasets obtained under three different engine rotation speeds and five different engine loads. The prediction accuracy of the ANN was validated by comparing 88 I–R datasets reproduced by the ANN using experimental data that were not used for training. In the validation procedure, differences of only 3.49% and 2.59% were observed in the experimental and ANN-predicted output power obtained for the 1000 rpm–0.8 MPa brake mean effective pressure (BMEP) and 1500 rpm–0.4 MPa BMEP scenarios, respectively. The exhaust gas flow characteristics were used for training and validation to predict the pumping loss caused by the installation of the TEG in the middle of the exhaust tailpipe with high accuracy. The results demonstrated that the ANN effectively reproduced datasets to fill the gaps between the discretized experimental results for all the experimental scenarios without any noticeable overfitting and underfitting. The net power gain obtained by the ANN exhibited a clear peak point for the engine rotation speed of 2000 rpm, which is difficult to obtain using experimental data.

Fuel Economy and Emissions of E85 in Passenger Cars - A Move towards Flex Fuel Vehicle

<div class="section abstract"><div class="htmlview paragraph">Many countries are developing strategies to curb the consumption of fossil fuels, and to increase the share of alternative fuels such as alcohols, natural gas, fuel cell and electricity in the energy pool in order to improve energy security and reduce atmospheric pollution. Alcohol fuels are promising one and it has been widely used in many countries as blending component for gasoline. Ethanol has a high-octane number but it has a lower calorific value than gasoline. The performance of engine may be affected with higher percentage of ethanol in gasoline due to demand for larger quantity of fuel that could not be supplied by vehicles which are tuned to run on gasoline only. In this study, a second electronic control unit (ECU) was installed in series with the existing commercial or primary ECU and an ethanol sensor was installed in the fuel line. This secondary ECU modulates the fuel injection pulse width of the primary ECU depending on ethanol concentration in the fuel. The vehicle studies were carried out using Indian automotive gasoline meeting IS:2796 specification and 85% ethanol blended gasoline (E85) in a climatically controlled chassis dynamometer lab in which test cell temperature maintained at 25±1 °C throughout the test. Modified Indian Driving Cycle tests (MIDC) and constant speed tests were carried out using E85 and commercial gasoline to investigate the fuel economy, gaseous mass emissions, particulate emission in terms number and size characteristics. Gaseous emission was reduced up to 30% with the penalty of reduction in fuel economy by approximately 30% over the MIDC. The vehicle power was maintained while using both fuels at respective constant speeds during the road load simulation cycles however an increase in fuel consumption was observed with E85. The tailpipe exhaust particle emission measurement had shown up to 50% reduction in exhaust particulate emissions with E85. This study demonstrates the potential of using higher blends of ethanol up to E85 and meeting power or speed demand at constant speeds and driving cycle tests.</div></div>

Toxicological effects of personal exposure to fine particles in adult residents of Hong Kong.

Toxicological studies have demonstrated the associations between fine particle (PM2.5) components and various cytotoxic endpoints. However, few studies have investigated the toxicological effects of source-specific PM2.5 at the individual level. To investigate the potential impact of source-specific PM2.5 on cytotoxic effects, we performed repeated personal PM2.5 monitoring of 48 adult participants in Hong Kong during the winter and summer of 2014-2015. Quartz filters were analyzed for carbonaceous aerosols and water-soluble ions in PM2.5. Teflon filters were collected to determine personal PM2.5 mass and metal concentrations. The toxicological effects of personal PM2.5 exposure-including cytotoxicity, inflammatory response, and reactive oxygen species (ROS) production-were measured using A549cells invitro. Personal PM2.5 samples collected in winter were more effective than those collected in summer at inducing cytotoxicity and the expression of proinflammation cytokine IL-6. By contrast, summer personal PM2.5 samples induced high ROS production. We performed a series of statistical analyses, Spearman correlation and a source apportionment approach with a multiple linear regression (MLR) model, to explore the sources contributing most significantly to personal PM2.5 bioreactivity. Secondary inorganic species and transition metals were discovered to be weak-to-moderately associated with cytotoxicity (rs: 0.26-0.55; p<0.01) and inflammatory response (rs: 0.26-0.44; p<0.05), respectively. Carbonaceous aerosols (i.e., organic and elemental carbon; rs: 0.23-0.27; p<0.05) and crustal material (Mg and Ca) was positively associated with ROS generation. The PMF-MLR models revealed that tailpipe exhaust and secondary sulfate contributed to ROS generation, whereas secondary nitrate was the major contributor to PM2.5 cytotoxicity and inflammation. These results improve and variate the arguments for practical policies designed to mitigate the risks posed by air pollution sources and to protect public health.

Oxidation behaviors and nanostructure of particulate matter produced from a diesel engine fueled with n-pentanol and 2-ethylhexyl nitrate additives

Experiments were performed on a high pressure common-rail diesel engine fueled with D100 (diesel fuel), DP15 (15% n-pentanol and 85% diesel, v/v), DP30 (30% n-pentanol and 70% diesel, v/v), DP30E1 (DP30 and 1000 ppm EHN) and DP30E2 (DP30 and 2000 ppm EHN), respectively. Particulates were sampled from the engine exhaust tailpipe and further analyzed with transmission electron microscope (TEM), Raman spectroscopy (RS) and thermogravimetric analysis (TGA). Results showed that an increase in soot oxidation reactivity was observed with increasing n-pentanol concentration in diesel/n-pentanol mixtures. This trend was in line with the poorer structural ordering of soot particles generated from blended fuels by both TEM and RS analyses. Regarding the impact of EHN addition to DP30 fuel, the soot oxidation reactivity decreased as the fuel was changed from DP30 to DP30E1, and then increased as the fuel was changed from DP30E1 to DP30E2. Notably, the soot from DP30 + EHN additive was easier to be oxidized than that from DP30. Similarly, the trends in soot oxidation reactivity with EHN additive can qualitatively capture the variations in soot nanostructure. The correlation between soot reactivity and nanostructure in this study was nonlinear, which infers that soot oxidation reactivity would be also influenced by other features like active surface area and surface functional group. It can be suggested that the application of DP30 would significantly affect the regeneration performance of diesel particulate filter (DPF); when the baseline fuel is DP30, the impacts of EHN additives on regeneration performance of DPF are relatively slight.

Real-world activity, fuel use, and emissions of heavy-duty compressed natural gas refuse trucks

Over 50% of new refuse truck sales have been compressed natural gas (CNG). Compared to diesel, CNG is less expensive on diesel gallon equivalent (dge) basis. This study quantifies the real-world fuel use and tailpipe exhaust emissions from three front- and three side-loader refuse trucks, each with a spark ignition CNG engine, three-way catalyst, and similar gross weight. Measurements were made at 1 Hz using a portable emissions measurement system (PEMS). Inter-cycle and inter-vehicle variability is quantified. Effect of vehicle weight was analyzed and comparisons were made with MOVES predicted cycle average emission rates. In total, about 220,000 s of data covering 490 miles of operation were recorded. The average fuel economy was 1.9 miles per dge. On average the trucks spent 53% of time in idle, which includes trash collection activity. The average speeds were 10 mph and 5 mph, for front- and side-loader trucks, respectively. Overall, compared to side-loader trucks, front-loader trucks had 55% better fuel economy and 60% lower emission rates. Compared to diesel trucks, CNG truck cycle average NOx and PM emission rates, at 1.2 g/mile and 0.006 g/mile respectively, were substantially lower while CO and HC rates, at 29 g/mile and 6 g/mile respectively, were considerably higher. Fuel use and CO2 emissions rates increased by 10% due to increase in truck weight during trash collection, while CO emissions rates increased by up to 30%. Compared to measured values, MOVES estimated cycle average fuel use and CO2 emissions were 25% lower, CO emissions are 70% lower, and NOx emissions were 200% higher. Results from this study can be used to improve solid waste life cycle and tailpipe emission factor models and, when combined with previous studies on diesel refuse trucks, evaluate the effect on fuel use and emissions from adoption of CNG refuse trucks.

Influence of exhaust gas temperature and air-fuel ratio on NOx aftertreatment performance of five large passenger cars

Exhaust aftertreatment systems are crucial to ensuring real-world NOx emission limits for motor vehicles. Operating conditions constrain the NOx reduction performance of aftertreatment devices. This study analysed real-world NOx emissions, tailpipe exhaust gas temperatures, and air-fuel ratios during cold start in a closed-loop urban route, followed by hot-start real driving emissions (RDE) tests. Five Euro-6b sport utility vehicles (SUV) were tested: two gasoline vehicles with three-way catalyst (TWC), namely, one gasoline direct injection (G-DI) and one hybrid electric vehicle (HEV); three diesel vehicles with different NOx control systems, namely, only exhaust gas recirculation (EGR), lean-burn NOx trap (LNT), and selective catalytic reduction (SCR).The only-EGR- and LNT-equipped diesel vehicles and the G-DI vehicle surpassed the NOx Euro 6 limits in all tested sections. For the same vehicles, the total RDE emission factors were 9.0, 7.4, and 5.0 times the Euro 6 limits, respectively. In contrast, the diesel vehicle with SCR had an RDE emission factor 1.0 times the limit, and the HEV exhibited very low emissions at approximately 2 mg NOx km−1. However, during the cold start phase (first 5 min), the emission levels of the SCR and HEV vehicles surpassed the Euro 6 limits by 2.7 and 1.1 times, respectively. Based on the measurements at the tailpipe, the results indicate that cold start, urban driving, and cooling conditions of aftertreatment devices can lead to a decrease in the NOx conversion efficiency of TWC and SCR systems. The air-fuel ratio was key for the NOx conversion in TWC aftertreatment. The large differences between G-DI and HEV vehicles were primarily attributed to the lean and rich operations of the G-DI and HEV engines, respectively. To comply with stringent future regulations, lean-burn engines would require diesel-like aftertreatment. SCR and hybrid vehicles would require a careful aftertreatment thermal management or heating to further exploit their potential for reducing emissions in urban areas.

Vehicular non-exhaust particulate emissions in Chinese megacities: Source profiles, real-world emission factors, and inventories

Vehicular non-exhaust emissions account for a significant share of atmospheric particulate matter (PM) pollution, but few studies have successfully quantified the contribution of non-exhaust emissions via real-world measurements. Here, we conduct a comprehensive study combining tunnel measurements, laboratory dynamometer and resuspension experiments, and chemical mass balance modeling to obtain source profiles, real-world emission factors (EFs), and inventories of vehicular non-exhaust PM emissions in Chinese megacities. The average vehicular PM2.5 and PM10 EFs measured in the four tunnels in four megacities (i.e., Beijing, Tianjin, Zhengzhou, and Qingdao) range from 8.8 to 16.0 mg km−1 veh−1 and from 37.4 to 63.9 mg km−1 veh−1, respectively. A two-step source apportionment is performed with the information of key tracers and localized profiles of each exhaust and non-exhaust source. Results show that the reconstructed PM10 emissions embody 51–64% soil and cement dust, 26–40% tailpipe exhaust, 7–9% tire wear, and 1–3% brake wear, while PM2.5 emissions are mainly composed of 59–80% tailpipe exhaust, 11–31% soil and cement dust, 4–10% tire wear, and 1–5% brake wear. Fleet composition, road gradient, and pavement roughness are essential factors in determining on-road non-exhaust emissions. Based on the EFs and the results of source apportionment, we estimate that the road dust, tire wear, and brake wear emit 8.1, 2.5, and 0.8 Gg year−1 PM2.5 in China, respectively. Our study highlights the importance of non-exhaust emissions in China, which is essential to assess their impacts on air quality, human health, and climate and formulating effective controlling measures.

Modeled and measured near-road PM2.5 concentrations: Indianapolis and Providence cases

Modeling analyses were developed to evaluate near-road PM2.5 concentrations predicted by the AERMOD dispersion modeling chain under real-world conditions, and to assess the sensitivity of modeled near-road concentrations to the choice of dispersion model (AERMOD or CAL3QHCR), meteorological data, and travel data processing approach. We evaluate PM2.5 monitoring sites near major freeways in Indianapolis, Indiana (for 2016) and Providence, Rhode Island (for 2015–2016). The modeling analyses are built upon bottom-up estimates of temporally and spatially resolved roadway PM2.5 emissions based on traffic monitoring data and local vehicle fleet emission factors. The dispersion model simulations use local meteorological data collected at or close to the near-road monitoring sites. Predictions involved a modeling chain that included travel activity data processing, emissions modeling (MOVES and AP-42), and air quality dispersion modeling. We estimated the difference between PM2.5 concentrations at the near-road monitor and at nearby urban air quality monitoring sites (the measured near-road “increment”), and compared modeled results to the measured increments. Based on monitoring data, estimates of multi-day-averaged near-road PM2.5 increments were 0.9 ± 0.6 μg/m3 at Indianapolis and 1.4 ± 0.2 μg/m3 at Providence (where the uncertainty represents the 95% confidence interval on the mean value), and were comparable to measured PM2.5 increments at these sites in the near-road literature. Modeled roadway contributions to multi-day-averaged near-road concentrations substantially exceeded measured values based on the near-road monitoring data. The average near-road PM2.5 increment modeled with AERMOD was more than 300% (factor of four) larger than the measured increment at Indianapolis, and more than 500% (factor of six) larger than the measured increment at Providence. These biases reflect cumulative uncertainty throughout the near-road PM2.5 modeling chain. The emissions modeling component may have contributed to the modeling chain biases in two ways. First, the relative contribution of modeled non-exhaust emissions (PM2.5 brake wear, tire wear, and re-suspended road dust) compared to tailpipe exhaust emissions was higher than what has been documented in several published studies. Second, other research findings indicate that the U.S. EPA MOVES2014 model may over-predict tailpipe PM2.5 exhaust. The dispersion modeling component may have also contributed to the modeling chain biases. For example, when local meteorological data were used, AERMOD results were relatively insensitive to wind direction on a daily averaged basis; as a result, modeled concentrations exceeded measured values regardless of whether the near-road monitor was upwind or downwind of the roadway. In summary, this work provides a unique evaluation of PM2.5 concentrations predicted by the near-road modeling chain, and provides valuable information to understand potential sources of uncertainty in the near-road modeling process.

Efficient Method of Moments for Simulating Atmospheric Aerosol Growth: Model Description, Verification, and Application

AbstractThe atmospheric aerosol dynamics model (AADM) has been widely used in both comprehensive air quality model systems and chemical transport modeling globally. The AADM consists of Smoluchowski's coagulation equation (SCE), whose solution undergoing Brownian coagulation in the free molecular regime is a challenge because it is inconsistent with aerosols whose size distribution cannot exactly follow the lognormal size distribution. Thus, a new method for solving the SCE without assuming lognormal size distribution is proposed and developed. The underlying principle of this method is that the hybridization of the well‐established method of moments with the assumed lognormal size distribution (log MOM) and Taylor‐series expansion method of moments (TEMOM) is implemented. This method shows excellent agreement with the sectional method (SM) which is used as reference. The accuracy of these two specific models closely approaches that of the TEMOM, but overcomes the limitation of the classical log MOM. The computational time of this scheme is considerably lower than that of the SM. The new method was successfully implemented to reveal the formation and growth of secondary particles emitted from a vehicle exhaust tailpipe. It was found that the formation of new particles only occurs in the interface region of the turbulent exhaust jet (which is very close to the tailpipe exit), whereas no new particles are formed in the mixture of the exhaust jet plume and the surrounding cold air downstream. The new method is verified as an efficient and reliable numerical scheme for studying atmospheric aerosol dynamics.

Comprehensive emission characterisation of exhaust from alternative fuelled cars

Abstract Exhaust emissions from Euro 2-6a cars using diesel, gasoline, high concentration ethanol (E85) fuel and compressed natural gas (CNG) were studied comprehensively, with a focus on results obtained at −7 °C test temperature. Higher emissions than desired were noticed in some cases, e.g. elevated methane emissions from natural gas fuelled cars, as well as methane and acetaldehyde emissions from E85 fuelled flexible fuel vehicles. Additionally, mutagenicity of PM samples and oxidative potential of semivolatile samples were observed. However, emission performance improved significantly when moving from older to newer Euro 6a cars, showing that low tailpipe exhaust emissions can be achieved when combining new car technology with CNG, E85, gasoline and diesel fuels. Furthermore, the climate impact of these technologies could reduce by using renewable counterparts of these fuels.

The Measurement of Fast Transient Emissions During Real World Driving

Some of the most challenging aspects of preparing vehicles to comply with the new RDE (Real Driving Emissions) legislation are the calibration of engines to minimize emissions during numerous short lived transients. Fast response emissions analyzers are necessary to resolve rapid transient emissions and have been deployed simultaneously in the engine-out and tailpipe exhaust gas stream of several vehicles. The methodology presented and capability of the instrumentation enables fine resolution of emissions events leading to the opportunity for fine tuning of controller performance. Data has also been logged from the vehicles' ECUs and combined with accurate GPS data. The results show that certain road lay-outs (e.g., congested junctions and speed bumps) can provoke significant tailpipe NOx emissions; often emitting very high levels near schools where traffic calming measures have been adopted for road safety. The lean excursions and insufficient rich purge during such transients are generally shown to be the cause of such emitting events.

Extracting methyl-ester from waste cooking oil for fueling a light duty diesel engine – a dual fuel approach

ABSTRACT The intention of this test is to efficiently use waste cooking oils (WCOs) that are used globally for cooking and frying purposes. In most cases, these used cooking oils (UCOs)/WCOs are disposed in an unstandardized manner that can cause soil contamination and may affect the groundwater if disposed in large quantities. Recent studies are exploring new vegetable oils that are surplus available all over the country and are especially non-edible. Most of these oils can be extracted from seeds through transesterification and can be attempted to be used for fueling engines, some of the oils are mahua oil, jatropha, lemongrass oil, mango seed oil, and so on. Alike extraction of vegetable oils from seeds, we can extract useful forms of WCOs in the same technique to make sure WCO can be used in a CI engine. Interesting outputs were witnessed when the WCO and neat diesel (ND) blends were fueled in a dual-fuel (DF) diesel engine. In a DF engine, a volatile liquid or gaseous fuel bearing higher octane value is inducted along with air through the intake manifold and compressed to a temperature less than its self-ignition point. In addition, a pilot fuel (with a higher cetane value) is injected through the conventional injection technique which initiates the combustion in the primary fuel-air mixture. Hydrogen looks very attractive for DF operation as “primary fuel”. As well the pilot fuel is WCO and neat diesel (ND) blends. WCOB was mixed with mineral diesel fuel by a volume fraction of 50% (WCOB50). In addition to this pure hydrogen was inducted into the intake along with air at the volume flow rate of 4, 6 and 8 lpm (liter per minute). Tests were conducted in a single-cylinder farming based direct injection light-duty diesel engine at several load conditions. At first, test results were correlated with ND fuel and WCOB50 fuel at all loads. WCOB50 fuel indicates a negligible reduction in brake thermal efficiency (BTE) when compared to ND fuel. Further, in this test, the influence of hydrogen induction on tailpipe exhaust emissions of a CI engine fueled with WCOB is examined.

Effect of Zirconia on Hydrothermally Synthesized Co3O4/TiO2 Catalyst for NOx Reduction from Engine Emissions

Effect of zirconia on the 6 wt.% Co3O4/TiO2 catalyst for NOx reduction is investigated in this paper. Co3O4/TiO2 catalyst was prepared by using hydrothermal method and then was promoted with zirconia by impregnation to get 8% wt. ZrO2-Co3O4/TiO2 catalyst. Catalysts were characterized by using XRD, SEM, and TGA. Catalysts real time activity was tested by coating them on stainless steel wire meshes, containing them in a mild steel shell and mounting them at the exhaust tailpipe of a 72 cm3 motorcycle engine. Zirconia promoted catalyst showed higher conversion efficiency of NOX than the simple Co3O4/TiO2 catalyst due to small crystalline size, fouling inhibition and thermal stability.

Urban Air Pollutant from Motor Vehicle Emissions in Kuala Lumpur, Malaysia

The increasing amount of motor vehicles that emit pollutants are contributing significantly to urban air pollution, be it in industrial or developing countries. This study investigates the emission of particulate matter (PM10) from exhaust and non-exhaust sources and gaseous pollutants, such as carbon monoxide (CO) and nitrogen oxide (NOx) from several different classes of motor vehicles in the tropical city of Kuala Lumpur. Air pollutants from fuel consumption were obtained from emission factors, while non-exhaust particulate matter was estimated from the United States Environmental Protection Agency (U.S. EPA) Compilation of Air Pollutant Emissions Factors (AP-42). The total PM10 emissions from all classes of motor vehicles estimated from the tail-pipe exhaust was 1,029,883 kg, while non-exhaust sources were 1,573,539 kg. Emissions of PM10 from newly registered private cars was the most dominant at 214,427 kg, followed by emissions from motorcycles at 118,582 kg in 2014. Private cars also contributed 14,605 kg of CO and 5,726 kg of NOx in 2014, compared with 9,830 kg of CO and 3,854 kg of NOx in 2010. Comparison with other Organisation for Economic Co-operation and Development (OECD) countries shows that the total emissions for PM10 and NOx were lower in Malaysia than in most countries, but the CO emissions here were higher than in Asian countries such as Japan and Korea, as well as in other European countries. Various strategies and policies should be implemented by the local authorities and government agencies to reduce emissions from the transportation sector in urban areas to improve the quality of the urban environment, human health, and the urban community.

Engine’s behavior on hydrogen addition of waste cooking oil fueled light duty diesel engine - A dual fuel approach

Foremost aim of this work is to study the influence of hydrogen induction on tail pipe exhaust emissions of a compression ignition engine fueled with waste cooking oil biodiesel (WCOB). Waste cooking oil biodiesel was mixed with mineral diesel fuel by a volume fraction of 50% (WCOB50). In addition to this pure hydrogen was inducted into the intake along with air at the volume flow rate of 2, 4 and 6 lpm. The test was conducted in a single cylinder agricultural based direct injection light duty diesel engine at various load conditions. At first, test results were correlated with neat diesel fuel and WCOB50 fuel at all loads. WCOB50 fuel indicates an insignificant reduction in BTE when compared to neat diesel fuel. Emission study revealed that WCOB50 usage moderately increases NOx emission and depreciates CO, HC and smoke opacity. However, hydrogen enrichment significantly decreased exhaust emissions such as smoke opacity, HC and CO except for NOx emission. Also, the BTE of the engine gradually improved with the increasing volume flow rate of hydrogen in the intake. At maximum power output in cylinder pressure and heat release rate were found to be higher for maximum hydrogen flow rate.

Particle number emission factors from diesel trucks at a traffic intersection: Long-term trend and relation to particle mass-based emission regulation

Abstract Particulate matter (PM) in automobile tailpipe exhaust is regulated by PM mass but not particle number (PN) in most parts of the world, including Japan, so the effect of PM mass regulations on the atmospheric PN concentration (PNC) is of interest from the point of view of whether a PNC regulation should be introduced to reduce PNCs. This study examined long-term (2004–2017) monitoring of PNCs and other pollutants at a traffic intersection and other sites in Japan. The decay rate of elemental carbon concentrations at the traffic intersection excellently matched the reductions of PM mass in tailpipe emissions from diesel trucks, indicating that the reduction in atmospheric concentrations directly reflected cleaner vehicle exhausts. Both the reduction of traffic volume and the replacement of older vehicles with newer models that comply with tighter regulations were found to reduce emissions. However, a slower reduction trend was found for exhaust-related PNCs (after excluding photochemically formed aerosols) with particle diameter Dp

Effect of varying biogas mass flow rate on performance and emission characteristics of a diesel engine fuelled with blends of n-butanol and diesel

Dwindling petroleum products and environment degradation, owing to the gases from the exhaust tailpipe of compression ignition engines, have obligated the investigators to invent some unconventional fuel. Current experimentation aimed to evaluate the combustion, performance and emission characteristics of a dual fuel engine by using blends of diesel and n-butanol as pilot fuel with biogas as primary fuel. Under dual fuel mode, biogas at different mass flow rates (0.5, 1.2 and 2.0 kg h−1) was admitted into the engine through inlet manifold and blends of n-butanol with diesel (D90/nb10 and D80/nb20) were injected as a pilot fuel to initiate the combustion. The fuel properties of the tested fuels were measured as per ASTM standards. The engine testing was carried out at constant speed of 1500 rpm and different engine loads. The experimental results depict that under dual fuel mode, brake-specific fuel consumption increased by 22.6% and brake thermal efficiency of the engine decreased by 11.9% in comparison to conventional diesel. As far as emissions are concerned, carbon monoxide and hydrocarbon emissions increased by 50.8 and 11.9%, respectively, whereas NOx and smoke opacity decreased by 19.8 and 40.9%, respectively, when compared to conventional diesel. Thus, such fuel combinations can be used in existing diesel engines for addressing long term energy needs and solving environmental associated challenges.

Source identification of personal exposure to fine particulate matter (PM2.5) among adult residents of Hong Kong

Epidemiological studies provide evidence of the harmful effects of source-specific fine particulate matter (PM2.5) on human health. Studies regarding relative contributions of multiple sources to personal exposure are limited and inconsistent. Personal exposure monitoring for PM2.5 was conducted in 48 adult subjects (ages 18‒63 years) in Hong Kong between June 2014 and March 2015. We identified seven sources of personal PM2.5 exposure using Positive Matrix Factorization (PMF). These sources included regional pollution (associated with coal combustion and biomass burning), secondary sulfate, tailpipe exhaust, secondary nitrate, crustal/road dust, and shipping emission sources. For personal PM2.5 exposure, one additional source related to individuals' activities was found: non-tailpipe pollution (characterized by Fe, Mn, Cr, Cu, Sr). We also applied principal component analysis (PCA) for PM2.5 source identification. The results revealed similar factor/component profiles using PMF and PCA, with some discrepancies in the number of factors. PCA/absolute principal component scores (PCA/APCs) coupled with a linear mixed-effects model (LMM) was applied to the same dataset for source apportionment, adjusting for temperature and relative humidity. Furthermore, stratified PCA/APCs-LMM models were applied to estimate season- and group-specific source contributions of personal PM2.5 exposure. A mixed source contributions of secondary sulfate, secondary nitrate, and regional pollution were shown (35.1–43.6%), with no seasonal or subject group differences (p > 0.05). Shipping emissions were ubiquitous, contributing 6.3–8.8% of personal PM2.5 exposure for all subjects. Tailpipe exhaust and traffic-related particles varied by season (p < 0.01) and subject group (p < 0.05). Caution should be taken when using source-specific PM2.5 as proxies for the corresponding personal exposures in epidemiological studies.