NOx Emission Factors Research Articles

Environmental benefit analysis of “road-to-rail” policy in China based on a railway tunnel measurement

The substitution of long-distance road transportation by railways, so-called the “road-to-rail” policy, is one of the major national regulatory policies for atmospheric pollution mitigation in China. However, owing to the lack of real-world diesel locomotive emission measurements, the environmental benefits of the “road-to-rail” policy have not been well evaluated. In this study, emissions from 245 in-use line-haul diesel locomotives (including three types of DF4, HX3, and HX5) were measured under real-world conditions via a railway tunnel observation conducted in Beijing on September 7–13, 2017. The fuel-specific and distance-specific emission factors (EFs) of NOx, CO, SO2, and BC were determined by using the carbon balance and mass conservation methods, respectively. The measured EFs of NOx and CO for the HX series locomotives were 41% and 30% higher than the Tire 2 emission standard limits respectively. Based on the two sets of EFs and corresponding activity levels, total locomotive emissions of NOx and CO in China in 2018 were approximately 17.36–19.23 × 104 t and 4.76–5.69 × 104 t respectively. Scenario analysis based on the fuel life cycle shows that all “road-to-rail” scenarios reduce the total energy consumption and pollutant emissions in the short term. For the scenario maintaining the current proportion (20%) of diesel locomotives, the “road-to-rail” policy may reduce NOx and BC emissions by 7.03–70.33 × 104 t/year and 0.10–1.02 × 104 t/year respectively. Considering the upgradation of emission standards with heavy-duty diesel vehicles, the air quality improvement benefit of the “road-to-rail” policy may only be sustained for 2–3 years and 8 years respectively, under the full diesel locomotive scenario and the current diesel locomotive scenario. We highlight the necessity of a more careful and accurate estimation of “road-to-rail” policy environmental benefits to obtain better air quality and the greatest health benefits.

Effects of driving behavior on real-world emissions of particulate matter, gaseous pollutants and particle-bound PAHs for diesel trucks

This study employed a portable emissions measurement system to investigate the effects of vehicle attributes, driving behavior, and road grade on real-world emissions of particulate matter (PM), regulated gaseous pollutants, and particle-bound polycyclic aromatic hydrocarbons (PAHs) for old-model diesel trucks (model year 1995–2006, 6.7–35.0 metric ton) with little to no tailpipe emission control. The rated power of engines was a major determinant of the distance-specific emission factors of PM, particle-bound PAHs, and most gaseous pollutants. However, the engine size was unrelated to the total hydrocarbon emission factor and the benzo[a]pyrene equivalent (BaPeq) emission factor of PAHs. Aggressive (AG) and normal (NR) driving behaviors were quantitatively defined with a relative positive acceleration. The emission factors of PM, CO2, and THC were significantly different (p < 0.05) between the AG and NR driving modes. AG driving caused an average increase in emissions of PM, CO2, NOx, and particle-bound PAHs by 122%, 56%, 15%, and 128%, respectively, compared to the respective emissions under the NR mode. The BaPeq emission factor of PAHs in the AG mode was more than 10 times that in the NR mode. The road gradient (ranging from −9.3% to 9.0% over the test route) had significant impacts on the emissions of PM, CO2, and NOx. PM, CO2, and NOx emission factors increased by 109%, 168%, and 160%, respectively, in the >6% grade bin and decreased by 95%, 91%, and 90%, respectively, in the equivalent negative-grade bin, implying that the decrease in emissions on negative road slopes may not compensate for the increase in emissions on the equivalent positive road slopes despite the road slope being compensated. The findings of this study will be valuable for developing air quality management strategies and furthering scientific knowledge on the complex interplay of different variables that affect real-world emissions of on-road vehicles.

Variability in real-world emissions and fuel consumption by diesel construction vehicles and policy implications

Strategically reducing the emission of non-road mobile source especially diesel construction vehicle (DCV) has a large potential in improving air quality and has attracted much scientific and public attention in recent years around the world. In this study, we explored real-world fuel consumption rate and gaseous emissions factors for multiple pollutants of three typical DCVs in China. The sampling campaign considered the operation mode, cumulative operation hour, emission standard stage and engine power. Results show that the accumulated fuel consumption per hour of vehicle weight for working, load-free moving and idling modes was 0.3, 0.2 and 0.1 kg/h·tons, respectively. The fuel-based NOx emission factor exhibited a bimodal distribution at 27 and 41 g/kg. The fuel-based emission factors for volatile organic compounds (VOCs) were in the range of 0.8 to 2.6 g/kg, where alkene and alkane were the dominant components (>80%), i.e., ethylene, acetylene, propylene, and isobutane. We observed that the ratio of toluene and benzene concentration (T/B) (1.4 ± 1.3) differed from other key emission sources and may be used as the specific indicator of DCV emission exhaust. Our estimates suggest that in 2017 the fuel consumption and NOx emissions of DCV emission accounted for 22–28% of non-road mobile sources in China; NOX emissions were 2.7 times higher than those in 2006, and it is forecasted that NOx emissions would reduce by 23% between 2017 and 2025 with the implementation of stage IV and the strict supervision policy. The comprehensive dataset on DCV emissions will either guide the government to establish precise and effective policies to regulate the non-road mobile source or significantly improve our understanding of source apportionment of atmospheric NOx and VOCs, both of which are key precursors of haze and ozone pollution.

Grid impact of non-residential distributed solar energy and reduced air emissions: Empirical evidence from individual-consumer-level smart meter data

Most existing assessments of the energy saving and environmental benefits from distributed solar panels assume that the entire amount of electricity generated by distributed solar panels goes to replace the same amount of electricity needed from the electric grid. However, such an assumption can overestimate the actual environmental benefits because it incorrectly ignores the existence of rebound effects – increases in energy service usage. We provide the first empirical evidence of the grid impact of non-residential distributed solar energy and the associated reduced air emissions. Using consumer-level high frequency electricity consumption and solar panel installation data from Arizona, United States, we estimate the actual hourly reduction in electricity needed from the grid of commercial and industrial consumers through an econometric analysis. We show that this reduction is much smaller than the actual solar electricity generation. We also show that business distributed solar consumers create a further challenge to the utilities by not reducing their monthly maximum demand in July and August. Lastly, we calculate the benefit of reduced air emissions by multiplying the measured hourly reduction in electricity purchased from the grid by the marginal emission factors of CO2, SO2, NOx, and particulate matter. We estimate that the annual benefit of reduced air emissions from an average-size business distributed panel system is $1147.

In-use emissions and usage trend of pellet heating stoves in rural Yangxin, Shandong Province

The use of coal in Chinese households for winter heating emits harmful pollutants that severely affect indoor air quality and climate. Therefore, China has made efforts to transition into clean heating using improved heating stoves and biomass pellets. Although the economic and policy implications of such demonstration projects have been extensively investigated, little has been done to understand the real-world performance and adoption trends of such stoves. This study measured in-use emissions from nine different pellet stoves used for heating among 52 rural households in Yangxin, Shandong Province. The temperature of the stove chimney of 21 households was monitored and 56 households were surveyed to explore the stove use trend. The particulate and gaseous emission concentrations for most of the stoves exceeded the limits specified in the Chinese national standard. The measured fuel energy-based emission factors (mean±standard deviation) for CO2, CO, NOx, and PM2.5 were 103±3, 1.41±1.19, 0.336±0.237, and 0.146±0.108g/MJ, respectively. Between January to February, the average daily heating duration was 8.71h, and the sustained use of heating stoves was seen among over 85% of the households. On average, the households used their heating stoves for 3.28 months and the estimated annual pellets consumption for a household was 2.7 tons. Besides inherent variabilities associated with user habits, the stove's design-related shortcomings and low-grade pellets hindered the performance and effectiveness of pellet stoves. This study provides insights into opportunities and challenges for the promotion of cleaner fuels and heating technologies. Furthermore, it will provide information on emissions from rural residential sources to build the emission inventory and inform policymaking for successful stove promotion programs.

Quantifying Environmental Benefits of Ridesplitting based on Observed Data from Ridesourcing Services

The increasing emissions from the transportation sector pose substantial hazards to the environment and human health around the world. With the rapid development of information and communication technologies, ridesplitting, a form of ridesourcing service accessed via smartphone applications, enables passengers with similar origins and destinations to be matched to the same driver and share the ride. This is regarded as a promising travel mode that could mitigate air pollution. However, because of a lack of quantitative analysis, the environmental benefits of ridesplitting have not been rigorously justified. As vast amounts of observed data of ridesourcing have become increasingly available, this study quantifies the environmental benefits of ridesplitting based on the global positioning system (GPS) trajectory and trip order datasets of DiDi Chuxing in Chengdu, China. First, the saved distances of ridesplitting are calculated by analyzing the travel distances of both ridesplitting trips and the corresponding trips under non-ridesplitting conditions. Then, the emission factors of CO, NOx, and HC are estimated by a localized MOVES model. Combining the saved distances and emission factors, the emission reductions from each ridesplitting trip can be calculated. The results show that ridesplitting can decrease the travel distance by 22% on average compared with non-ridesplitting. As a consequence, the average emission reductions per ridesplitting trip are 10.601 g of CO, 0.691 g of NOx, and 1.424 g of HC, respectively. This study provides a better understanding of the environmental benefits of ridesplitting and theoretical guidance for the government’s decision-making in green transport planning.

Developing On-Road NOx Emission Factors for Euro 6b Light-Duty Diesel Trucks in Korean Driving Conditions

This study aimed to develop on-road NOx emission factors for Euro 6b light-duty diesel trucks (LDDTs) in Korea. On-road NOx emissions were measured using portable emissions measurement systems and compared with those measured using the Korean Driving Cycle (KDC), the conventional laboratory test used to develop emission factors. To ensure the representativeness of the LDDTs emission factors, five vehicles of three models were driven along two real driving routes for total traveled mileage of 2280 km. On-road NOx levels were 2.1 to 6.9 times higher on average than those measured using the KDC because the latter does not cover the wide variability in vehicle speed and relative positive acceleration, common in real driving conditions. The lean-NOx trap was found to have disappointingly low NOx reduction efficiency in on-road driving. The on-road NOx emission factors by vehicle speeds developed in this study were comparable to the COPERT 4 factors.

Does California’s EMFAC2017 vehicle emissions model underpredict California light-duty gasoline vehicle NO x emissions?

ABSTRACT On-road remote sensing measurements of light and medium-duty gasoline vehicles collected within California’s South Coast Air Basin since 1999 generally fall within the range of observed summer ambient molar NO x /CO measurements collected during morning rush hours. Compared with ambient and on-road emissions, the California Air Resources Board EMFAC model underpredicts 2018 gasoline vehicle NO x emission factors by more than a factor of 2.6. Contributing to these differences is that vehicles older than model year 2006 have NO x emission deterioration rates that are up to four times higher on-road than predicted by the EMFAC model. A fuel-based inventory using the 2018 on-road gasoline emission factors for CO and NOx results in total CO emissions similar to the basin inventory but NOx emissions that are 74% higher than the inventory. The higher NO x emission estimates from on-road gasoline vehicle measurements make their contribution to the inventory slightly larger than heavy-duty diesel vehicles. We have found LEV I (1994–2003) gasoline vehicles are a major source of these on-road emissions and that significant NOx reductions in the South Coast Air Basin are being overlooked by not targeting the high emitters for removal. Implications: A comparison of ambient and on-road vehicle molar NOx/CO ratios collected in California’s South Coast Air Basin with those predicted by California’s EMFAC2017 vehicle emissions model shows that the model significantly underpredicts NOx emission factors for gasoline vehicles. This results in a 74% underestimate of the contribution of gasoline vehicles to the basin’s NOx inventory, with the contribution from gasoline vehicles comparable to that from heavy-duty diesel trucks. This likely means that current projections for future NOx emission reductions from mobile sources in the basin will not be realized unless additional NOx reductions are obtained from older gasoline vehicles.

Study on the real-world emissions of rural vehicles on different road types.

To better understand the real-world emissions of rural vehicles (RVs) in China, 8 China II RVs and 18 China III RVs were tested on a provincial road, rural road and farm road using a portable emissions measurement system. The results are illustrated in contour maps of the speed, acceleration and emission rates and show that CO, HC, NOx and PM emissions differ for the three road types; however, the peak emission points all occur on the provincial road. The average CO, HC, NOx and PM emission factors based on distance for the China II RVs are 9.21, 4.05, 1.68 and 2.58 times higher, respectively, than those of the China III RVs. However, the average NOx emission factors of the China II and III RVs are 2.21 and 1.65 times higher than the corresponding recommended values of national emission inventory guideline, resulting in underestimation of overall RVs' emissions. Distance-based emission factors of four pollutants ranked from high to low are farm road>rural road>provincial road. In contrast to the average emission factors of the China II RVs on the three road types, those of the China III RVs are significantly less in terms of distance and fuel consumption. The results of other researchers differ from those in this study: the CO emission factor of the China II RVs is 2.12 times higher than that of the China II light-duty diesel vehicles (LDDVs). The PM emission factor of the China III RVs is 2.67 times higher than that of the China III LDDVs. The NOx emission factors of the China II and III RVs are similar to those of the corresponding China II and III LDDVs. Our research increases the understanding of real-world emissions of RVs and can act as great references for policy makers developing RV emission baselines.

ASSESSMENT OF STREET AIR POLLUTION THROUGH OSPM MODEL IN LAHORE, PAKISTAN

Traffic emissions are one of the main contributors in worsening the air quality of developing countries like Pakistan. The current research work is an effort to find out emission factor of different classes of vehicles as well as to model the certain air pollutants level on five different main streets of Lahore, Pakistan. The Town Hall air quality monitoring station at Mall road is taken as background station. The data of street configuration, background urban air pollution, meteorological conditions, diurnal traffic count and emission factor of vehicles was calculated to model the street air pollution. Operational Street Pollution Model (OSPM) was used to model the street pollutants. PM2.5 levels exceed National Environmental Quality Standards (NEQS) during all months of calendar year, while SO2 and NO2 exceed NEQS during entrance of heavy traffic at night in the city. Diesel vehicles have high SO2, NOx, PM2.5 and PM10 emission factors; while gasoline vehicles have high CO emission factors. Industrial region has relatively high level of SO2 emissions; while roadside have relatively high level of CO emissions. A significant correlation (rvalue > 0.5) was observed between modeled and observed results for all the streets for the NOx, SO2 and CO levels, except for NOx level at Gulberg (r-value= 0.42). The better modeling results have been observed for those streets which are relatively polluted spots and are close to the background station.

Effects of passenger load, road grade, and congestion level on real-world fuel consumption and emissions from compressed natural gas and diesel urban buses

This study investigated the effects of passenger load, road grade, and congestion level on the fuel consumption and emissions from a Euro VI compressed natural gas (CNG) urban bus and a Euro V diesel urban bus. Testing was performed under real-traffic conditions in Madrid, Spain, using a portable emission measurement system (PEMS). The PEMS data also were combined with the vehicle specific power (VSP) methodology to analyse the differences between the performance of the two types of buses and develop an energy-based emission model. Between the empty and 4000 kg passenger load cases, the fuel consumption and CO2 emissions for the diesel bus showed a significant increase by approximately 25%. With an increase in the road grade, and congestion level, the fuel consumption and CO2 emissions of both types of buses increased, by 6–55%. Unlike in the case of the diesel bus, the NOx emissions of the CNG bus decreased by 40–50% as the level of road grade and congestion increased. At intervals of VSP ≥ 2 kW/t, NOx emission rates for the CNG bus were approximately 60% lower than those of the diesel bus. Finally, the proposed VSP-based model estimated the fuel consumption and the CO2 and NOx emission factors with relative total errors of less than 13%.

Emission factor development for light-duty vehicles based on real-world emissions using emission map-based simulation.

Transport emission factors describe pollutant emissions of vehicles by relating with vehicle activities such as traveled distance. Accurate emission factors are essential for estimating transport emission and making better decision to address air pollution and climate change. In this paper, map-based simulations were used to develop emission factors of CO2, NOx and CO based on real-world emissions, as were measured with a Portable Emission Measurement System (PEMS). Vehicle dynamic-based simulation model were used to calculated emission factors using the emission maps as input data, which were developed from real-world emissions. We developed emission factors by fuel type, emission regulation, aftertreatment system and engine displacement. Among various factors, the introduction of Real Driving Emission (RDE) regulation had the greatest influence on the emission factor. For diesel LDVs, NOx and CO emission factors of the Euro 6 d-temp vehicles, which have been applied RDE regulation for the first time, were lower than those of the Euro 5 and Euro 6b/c vehicles. However, the CO2 emission factors of the Euro 6 d-temp was higher than those of the Euro 5 and Euro 6b/c vehicles. In addition to calculating emission factors, the proposed methodology provides an improved process that simulate vehicle emissions based on real-world emissions.

Model for leisure boat activities and emissions – implementation for the Baltic Sea

Abstract. The activities and emissions from leisure boats in the Baltic Sea have been modeled in a comprehensive approach for the first time, using a new simulation model leisure Boat Emissions and Activities siMulator (BEAM). The model utilizes survey data to characterize the national leisure boat fleets. Leisure boats have been categorized based on their size, use and engine specifications, and for these subcategories emission factors for NOx, PM2.5, CO, non-methane volatile organic compounds (NMVOCs), and releases of copper (Cu) and zinc (Zn) from antifouling paints have been estimated according to literature values. The modeling approach also considers the temporal and spatial distribution of leisure boat activities, which are applied to each simulated leisure boat separately. According to our results the CO and NMVOC emissions from leisure boats, as well as Cu and Zn released from antifouling paints, are significant when compared against the emissions originating from registered commercial shipping in the Baltic Sea. CO emissions equal 70 % of the registered shipping emissions and NMVOC emissions equal 160 % when compared against the modeled results in the Baltic Sea in 2014. Modeled NOx and PM2.5 from the leisure boats are less significant compared to the registered shipping emissions. The emissions from leisure boats are concentrated in the summer months of June, July and August and are released in the vicinity of inhabited coastal areas. Given the large emission estimates for leisure boats, this commonly overlooked source of emissions should be further investigated in greater detail.

Experimental study on the influence of the nitrogen concentration in the oxidizer on [formula omitted] and CO emissions during the oxy-fuel combustion of natural gas

In this research, the influence of the nitrogen concentration in the oxidizer, oxygen/fuel equivalence ratio and temperature of the combustion chamber on the combustion characteristics of a natural gas fired oxy-fuel jet burner was observed. The thermal input of the fuel was 600 kW and the nitrogen concentration in the oxidizer was varied between 0 and 15 vol.-%, wherein either the maximum combustion chamber temperature or the thermal output were held constant.It was observed that in case of a constant combustion temperature, even small volume fractions of nitrogen in the oxidizer resulted in non-negligible reductions in the thermal output. Furthermore, the experimental results showed that an increase in the nitrogen concentration from 0 to 15 vol.-% caused an approximately eight-fold increase in the NOx emissions and a considerable decrease in the CO emissions. The impact of the oxygen/fuel equivalence ratio on the NOx emissions was negligibly small up to a nitrogen concentration of 2 vol.-%. A reduction of the oxygen/fuel equivalence ratio to near stoichiometric levels resulted in NOx emission factors below 52 mg/kWh. The influence of the oxygen/fuel equivalence ratio on the NOx emissions was significantly more pronounced with an increasing amount of nitrogen present in the oxidizer.

Pollutant concentration measurement and emission factor analysis of highway tunnel with mainly HGVs in mountainous area

In recent years, with the rapid growth of traffic flow in highway tunnels, the in-tunnel environmental pollution problem has aroused widespread concern in China. Previous studies mainly focused on the emission factors in tunnels dominated by passenger cars (PCs) and light commercial vehicles (LCVs). However, this study concentrated on the characteristics of traffic flow dominated by heavy-goods vehicles (HGVs), environmental monitoring and assessment in highway tunnels in mountainous areas. To explore the emission characteristics of vehicle pollutants in highway tunnels in such regions, a field measurement was conducted in Qinling No. 3 Tunnel in China, focusing on the traffic volume, air velocity, and pollutant concentration. Measurement results show that the average daily traffic volume in Qinling No. 3 Tunnel is 22,218 pcu/d, with the HGVs comprising more than 65%. The average air velocity in case tunnel reaches 5.09 m/s. The average concentrations of NH3, SO2, CO, and NOx in the tunnel are 4.54 ppm, 0.06 ppm, 6.22 ppm, and 4.39 ppm, respectively. The single vehicle emission rates of measured pollutants are calculated based on collected data, among which, the emission factor of NOx is the largest (average: 9.37 g/(km·veh)), while that of SO2 is the lowest (0.09 g/(km·veh)). The results show that the dilution of NO2 in the tunnel should be considered in the ventilation design of highway tunnels.

Inventory and Distribution Characteristics of China's Thermal Power Emissions Under Ultra-Low Reconstruction

This study updates a bottom-up high-resolution emission inventory and estimates the concentrations, emission factors, emissions, and performance values of China's power plants, based on the data from continuous emission monitoring systems and environmental statistics in 2018. The results show that the ultra-low emission policy has significant effects: the average concentrations of SO2, NOx, and PM in thermal power plants were 37.57, 56.71, and 7.41 mg ·m-3, respectively in 2018, which were 58.71%, 43.12%, and 60.79% lower than those in 2015. The average emission factors of SO2, NOx, and PM from coal-fired units in China were 0.3, 0.48, and 0.06 g ·kg-1, respectively, which were 55.2%, 36.84%, and 62.5% lower than those in 2015. The total emissions of SO2, NOx, PM, and PM2.5in thermal power plants were 721.4, 1183.8, 149.0, and 135.9 kt ·a-1, respectively, down by 41.32%, 19.29%, 48.12%, and 40.39% from 2015.

On-road performance and emission characteristics of CNG-gasoline bi-fuel taxis/private cars at the roadside environment

The real-world emission factors (EFs) and emission performance of bi-fuel (CNG/GAS) vehicles have been seriously investigated by the emission scientists and urban planners. In the present study, we propose an almost new practical methodology and perform on-road experiments on 60 bi-fuel vehicles to discuss the impacts of vehicle speed, fuel type, usage, and accumulated mileage on the CO, HC, and NOx EFs. 80% and 20% of the tested vehicles were private cars (PCs) and taxis (TXs), respectively. TXs and PCs are compared together based on their emission performances, emission characteristics, vehicular specific power (VSP) distributions, and type of fuel. The results show that in the entire cases except for GAS-PCs, CO EFs increased with vehicle speed. Although CNG vehicles show less HC EFs, they produce higher NOx mileage-based EFs compared to gasoline ones. NOx mileage-based EFs decrease with vehicle accumulated mileage, whereas the opposite trend was observed for the CO and HC EFs. Burning CNG rather than gasoline decreases 70% and 42% of CO, and 70% and 85% of HC mileage-based EFs in PCs and TXs, respectively. The influence of burning CNG on NOx emission of TXs seems to be insignificant, but NOx was more emitted by a factor of 1.7 in CNG PCs. Accumulated mileage has a destructive effect on combustion quality, especially in CNG vehicles. The factors of usage and accumulated mileage could considerably develop the VSP distribution and fuel consumption rate of GAS vehicles, while they have no detectable impact on that of CNG vehicles.

The effect of particle size on the pollution reduction potential of a South African coal-derived low-smoke fuel

The coal combustion in cast-iron stoves leads to health hazards and air pollution. In this study the CO, SO2, NOx, PM and VOC emission concentrations were measured whilst combusting four fuel particle sizes (15, 20, 30, and 40 mm) as well as a composite of the sizes (all pre-devolatilized at a temperature of 550 °C) in a cast-iron stove. The results were compared to their raw coal analogues to evaluate the emission performance of each fuel type. Emission factors for NOx and SO2 were found to depend on the fuel nitrogen and sulphur contents in the coal and the combustion conditions used during pyrolysis. The PM, SO2 and VOC emissions show a strong dependence on the ash percentage and volatile matter yields, which both increased with increasing particle size. In addition, the PM, SO2 and VOC missions were found to only depend on particle size on a mechanistic level. The VOCs and PM emission factors are inversely correlated with particle size. The results from this study offer insight into the combustion environment in the Falkirk Union No 7 cast-iron stove as well as how this environment applies to low smoke fuels. The work contributes to the emission and performance inventories from South African domestic coal combustion in this stove used in informal settlements.

Analysis of vehicle CO and NOx road emissions test based on PEMS

ABSTRACT To provide a corresponding preparation and foundation for the implementation and testing of China 6, as well as provide a strong reference for the formulation of China automotive test cycle (CATC) in the future, portable emission measurement system (PEMS) was applied to carry out CO and NOx emissions test on conventional roads for a light-duty gasoline vehicle (Toyota Levin) and a heavy-duty diesel vehicle (KING LONG bus) in Nanjing. The results showed that the CO emission rate of the Toyota car was mainly determined by the speed. As the vehicle speed increased, the CO emission rate increased rapidly while it was below 0.035 g/s. The CO emission rate of KING LONG bus accelerated with the increase of the vehicle speed at the lower speed and began to decrease when the speed reached 60 km/h. In terms of NOx emission rate, as the vehicle speed increased, the NOx emission rates of both vehicles increased. The CO and NOx emission factors of the two models showed similar patterns, both of which decreased significantly as the vehicle speed increased. Compared with the corresponding emission limits, the CO emission of both vehicles was higher, especially for light vehicle, and it was more than 3 times the limit. The NOx emission of both vehicles met the corresponding emission standards. The CO and NOx emission rates of light vehicles were positively correlated with specific power of vehicle (VSP). When VSP was less than 16, the two pollutants emission rate variation with VSP of heavy vehicle showed the same trend, while it was different when VSP was more than 16.

Real-road Emission and Fuel Economy of Buses using Different Fuel

The real-road emission and the fuel economy of 2 China-VI buses and 2 China-III buses using different fuel are tested using portable emission measurement system. The results show that, compared with Beijing VI diesel buses, China VI buses using B5 biodiesel is 33.1% lower in CO specific emission, 15.6% higher in NOx specific emission, and 13.1% lower in PN specific emission. The CO emission factors of the four buses using B5 biodiesel decrease by 29.5% averagely compared with Beijing VI diesel buses, while the NOx emission factors increase by 12.7% and PN emission factors decrease by 9.1%; the CO2 emission factors increase by 11.3% and thus the fuel consumption per 100km increase by 11.51% which is calculated using carbon-balance method considering the impact by fuel density. The fuel economy difference is high. More research on the impact on fuel economy by fuel heat value or other physical and chemical parameters is necessary in the future.