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Abstract: The use of numerical models for estimating fuel consumption and emission of HC, CO, NO x and CO2 of gasoline vehicles, under urban driving conditions, is examined. Three models were selected for evaluation: EcoGest, CMEM and ADVISOR. The models were used to simulate a sample of 14 urban trips for two 1999 Ford Taurus vehicles. Trip statistics were monitored on-board of the passenger vehicles across a variety of traffic conditions, using a portable emissions measurement device (PEMS). A key conclusion is that the tested models can be used with relatively high confidence to predict fuel consumption and CO2 emissions. However, results must be viewed with greater caution when it comes to predictions for other pollutants. [Copyright &y& Elsevier]

• On-road fuel use and emission with PEMS. • On-road data used to build fuel and emission maps. • Experimental on-road data used for numerical analysis. • Numerical analysis of current fuel use and emission mitigation technologies. • Analysis within the framework of Real Driving Emission regulation. This work includes an original approach that combines on-road experimental fuel use and emission maps and a numerical analysis to assess the impacts of fuel efficiency and NO x emission reduction technologies on a light-duty passenger vehicle. The solutions analyzed include Stop/Start, vehicle mass reduction up to 100 kg, drag coefficient reduction, as well as SCR and Lean NO x Trap systems. For this purpose, a reference EURO 6 diesel vehicle was monitored under real-world driving conditions with a PEMS and the experimental data obtained allowed building engine maps of fuel use and NO x emission to be used on AVL Cruise software. The results obtained with Cruise were firstly validated with the experimental data (with errors up to 10,6% on fuel and 17,5% on NOx) and then the solutions implemented were tested individually and simulated on 48 real-world driving cycles. The results pointed to Stop/Start, mass reduction of 100 kg and SCR as the most effective solutions in reducing fuel consumption and NO x emission up to 14,6% and 57,5%, respectively, depending on driving context. The combination of these technologies was tested and the results showed maximum fuel savings of 17% on urban context and a maximum reduction of 58% on NO x on combined driving cycles. Despite all the efforts, real-world driving presents NO x emissions not yet compliant with standards, indicating the need for new strategies in order to face the environmental challenges. [ABSTRACT FROM AUTHOR]

Discrepancies between real-world use of vehicles and certification cycles are a known issue. This paper presents an analysis of vehicle fuel consumption and pollutant emissions of the European certification cycle (NEDC) and the proposed worldwide harmonized light vehicles test procedure (WLTP) Class 3 cycle using data collected on-road. Sixteen light duty vehicles equipped with different propulsion technologies (spark-ignition engine, compression-ignition engine, parallel hybrid and full hybrid) were monitored using a portable emission measurement system under real-world driving conditions. The on-road data obtained, combined with the Vehicle Specific Power (VSP) methodology, was used to recreate the dynamic conditions of the NEDC and WLTP Class 3 cycle. Individual vehicle certification values of fuel consumption, CO 2 , HC and NO x emissions were compared with test cycle estimates based on road measurements. The fuel consumption calculated from on-road data is, on average, 23.9% and 16.3% higher than certification values for the recreated NEDC and WLTP Class 3 cycle, respectively. Estimated HC emissions are lower in gasoline and hybrid vehicles than certification values. Diesel vehicles present higher estimated NO x emissions compared to current certification values (322% and 326% higher for NO x and 244% and 247% higher for HC + NO x for NEDC and WLTP Class 3 cycle, respectively). [ABSTRACT FROM AUTHOR]

Abstract: We examine the strategies of modifying drive behavior adopted by two bus companies operating in the Lisbon Metropolitan Area to minimize fuel consumption and associated CO2 emissions. Rodoviária de Lisboa uses a commercial tool for monitoring buses during regular work, with data collected based on events representing undesired behavior that was subsequently used as the basis for classroom training of drivers. Barraqueiro Transportes adopted a vehicle monitoring system capable of processing information during operation giving real time driver feedback on energy, comfort and safety indicators. Both systems produced fuel economies, although to differing degrees. [Copyright &y& Elsevier]

Abstract: The conversion efficiency of a catalytic converter, mounted on a vehicle equipped with a 2.8l spark ignition engine, was evaluated under steady state operating conditions. The inlet and outlet chemical species concentration, temperature and air fuel ratio (A/F) were measured as a function of the brake mean effective pressure (BMEP) and engine speed (rpm). Oil temperature, coolant temperature, brake power and spark advance were also monitored. In parallel, a mathematical model for the catalytic converter has been developed. The main inputs of the model are the temperature, flow rate, chemical species mass flow and local A/F ratio as measured at the catalyst inlet section. The main conclusions are: (i) the exhaust gas and substrate wall temperatures at the catalyst outlet increase with BMEP and rpm; (ii) the HC conversion efficiency increases with the value of BMEP up to a maximum beyond which it decreases; (iii) the CO conversion efficiencies typically increase with BMEP; (iv) the NO x conversion efficiency remains nearly constant regardless of BMEP and rpm; (v) except for idle, the NO x conversion efficiency is typically the highest, followed in turn by the CO and HC conversion efficiencies; (vi) conversion efficiencies are lower for idle conditions, which can be a problem under traffic conditions where idle is a common situation; (vii) regardless of rpm and load, for the same flow rate the conversion efficiency is about the same; (viii) the model predictions slightly over estimate the exhaust gas temperature data at the catalyst outlet section with the observed differences decreasing with BMEP and engine speed; (ix) in general, the model predictions of the conversion efficiencies are satisfactory. [Copyright &y& Elsevier]

Abstract: Currently, oil based fuels are the primary energy source of road transport. The growing need for oil independence and CO2 mitigation has lead to the increasing importance of alternative fuel usage. CO2 is produced not only as the fuel is used in the vehicle (tank-to-wheel contribution), but also upstream, from the fuel extraction to the refueling station (well-to-tank contribution), and the life cycle of the fuel production (well-to-wheel contribution) must be considered in order to analyse the global impact of the fuel utilization. A road vehicle tank-to-wheel analysis tool that may be integrated with well-to-tank models was developed in the present study. The integration in a demonstration case study allowed to perform a life cycle assessment concerning the utilization of diesel and natural gas fuels in a specific network line of a bus transit company operating in the city of Porto, Portugal. [Copyright &y& Elsevier]

A method to perform the energy characterization of a vehicle according to the specific power required while driving was developed using public vehicle certification data. Using a portable emission measurement system, fuel consumption was quantified in a second-by-second basis under on-road conditions for 19 vehicles (spark-ignition, compression-ignition and hybrids). This data allowed building generic curves of fuel consumption as a function of the specific power, according to Vehicle Specific Power methodology. Comparing on-road measurements and the model estimates, a R 2 higher than 0.9 for conventional and hybrid vehicles was obtained regarding modal fuel consumption. Comparing the fuel consumption measured on the drive cycles performed by each vehicle and the correspondent estimates, an absolute deviation of 9.2% ± 9.2% was found for conventional vehicles and 4.7% ± 1.8% for hybrids vehicles. This methodology was validated and applied to estimate the energy impacts of the best-selling vehicles in Portugal for different driving cycles. This prompt method, that does not require vehicle monitoring, can estimate curves of fuel consumption in g/s, as a function of specific power, which allows quantifying the absolute fuel use for any driving cycle. [ABSTRACT FROM AUTHOR]

Abstract: NO x emission standards are becoming stringiest over the world especially for heavy-duty vehicles. To comply with current and future regulations some vehicle manufacturers are adopting exhaust aftertreatment systems known as Selective Catalytic Reduction (SCR). The catalysts are based on Vanadium (Va) and the reductant agent based on ammonia. However, Va is listed on the California Proposition 65 List as potentially causing cancer and alternatives are being studied. This paper presents a model based on neural networks that integrated with a road vehicle simulator allows to estimate NO x emission factors for different powertrain configurations, along different driving conditions, and covering commercial, zeolite and mordenite alternatives as the base monolith for SCR. The research included the experimental study of copper based and iron based zeolites (ZSM5 and Cuban natural mordenite). The response of NO x conversion efficiency was monitored in a laboratory for varying space velocity, oxygen, sulfur, water, NO x and SO2 emulating the conditions of a Diesel engine exhaust along a trip. The experimental data was used for training neural networks and obtaining a mathematical correlation between the outputs and inputs of the SCR system. The developed correlation was integrated with ADVISOR road vehicle simulator to obtain NO x emission factors and to test each SCR system installed on light-duty and heavy-duty vehicles for standardized driving cycles and real measured driving cycles. Despite having lower NO x conversion efficiencies than the CATCO in the ETC/ESC and NEDC cycles, FeZSM5 maintain the Euro regulation level. Therefore FeZSM5 can be a possible candidate as far as pollutants regulation is considered. [Copyright &y& Elsevier]

The effect of aggregation on soot radiative properties in the infrared region of the spectrum is numerically investigated using Rayleigh–Debye–Gans theory for fractal aggregates (RDG-FA). In order to use the RDG-FA theory for a wide range of aggregate sizes and wavelengths, the predicted phase functions, scattering and absorption coefficients are compared with a more accurate theory, the integral equation formulation for scattering—IEFS. The importance of scattering when compared with absorption is investigated, as well as the effect of aggregation on the phase function shape and on the scattering cross section. It is concluded that in the case of small aggregates formed with small primary particles the scattering coefficient is negligible compared with the absorption coefficient, and scattering and aggregation of primary particles can be ignored. Thus, the Rayleigh approximation can be used leading to isotropic scattering. In the case of large aggregates constituted by large primary particles, aggregation becomes important and the scattering cross section is of the same order of magnitude of the absorption cross section. Moreover, the phase function becomes highly peaked in the forward direction. Therefore, the Rayleigh and the equivalent volume Mie sphere approximations are not valid, and the RDG-FA method emerges as a good compromise between accuracy and simplicity of application. However, radiative transfer calculations between two infinite, parallel, black walls show that scattering may always be neglected in the calculation of total radiative heat source and heat fluxes to the walls. The minor influence of scattering on the accuracy of the predictions is explained by the shift between the spectral region where scattering is important and the region where the spectral radiative heat source is large. [Copyright &y& Elsevier]