Real Driving Emissions Research Articles

The real driving emission characteristics of light-duty diesel vehicle at various altitudes

High altitude shows a great influence on vehicle emissions because of lower pressure and shortage of oxygen concentrations. In addition, type approval test of light duty vehicle is usually carried out below the elevation of 1000 m. In order to address the effect of high altitude on vehicle emissions, real driving emission (RDE) test procedure has been introduced in China VI emission regulation. Thus, the effects of altitude on the emissions from a China IV certificated light-duty diesel vehicle under real road driving conditions were investigated in this work. Research results show that CO emissions increased with the elevated altitude. At the altitude of 2990 m, the CO emissions increased by 209% in comparison with that of near sea level in whole test cycle. At specific test modes, CO emissions follow the sequence of urban > rural > motorway. Both PN and NOx emissions also rose with altitude while NOx emissions at 2990 m showed a decreasing tendency. In addition, different tendency between high altitudes and relative low altitudes was observed under specific test modes, which was probably related to the function of after-treatment device.

Testing and evaluating real driving emissions with PEMS

Testing of real driving emissions (RDE) with portable emission measuring system (PEMS) in an appropriate road circuit became an obligatory element of new type approval of passenger cars since September 2017. In several projects the Laboratory for Exhaust Emissions Control (AFHB) of the Berne University of Applied Sciences (BFH) performed comparisons on passenger cars with different PEMS’s on chassis dynamometer and on road, considering the quality and the correlations of results. Particle number measuring systems (PN PEMS) were also included in the tests. The present paper informs about influences of E85 on RDE on two flex-fuel-vehicles, discusses some aspects of different ways of evaluation with different programs, shows comparison of different types of PN PEMS and represents the effects of simulation of slope on the chassis dynamometer.

Particle number measurements in the European legislation and future JRC activities

The solid particle number method was introduced in the European Union (EU) light-duty legislation for diesel vehicles to ensure the installation of the best-available technology for particles (i.e., wall-flow diesel particulate filters) without the uncertainties of the volatile nucleation mode and without the need of large investment for purchasing the equipment. Later it was extended to gasoline vehicles with direct injection engines, heavy-duty engines (both compression ignition and positive ignitions) and non-road mobile machinery engines. Real Driving Emissions (RDE) testing on the road with Portable Emissions Measurement Systems (PEMS) for particle number (and NOx) during type approval and in-service conformity testing was recently (in 2017) introduced for light-duty vehicles, and is under discussion for heavy-duty vehicles in-service conformity testing. This paper will summarize the existing legislation regarding solid particle number and discuss the on-going activities at EU level. The main focus at the moment is on improving the calibration procedures, and extending the lower detection size below 23 nm with inter-laboratory exercises. In parallel, discussions are on-going to introduce testing at low ambient temperature, regeneration emissions in the light-duty regulation, a particle limit for other technologies such as gasoline port-fuel injection vehicles, and the feasibility of particle measurements to L-category vehicles (mopeds, motorcycles, tricycles and minicars). A short overview of periodical technical inspection investigations and the situation regarding non-exhaust traffic related sources with special focus on brakes and tyres will be described.

Framework for the assessment of PEMS (Portable Emissions Measurement Systems) uncertainty

European regulation 2016/427 (the first package of the so-called Real-Driving Emissions (RDE) regulation) introduced on-road testing with Portable Emissions Measurement Systems (PEMS) to complement the chassis dynamometer laboratory (Type I) test for the type approval of light-duty vehicles in the European Union since September 2017. The Not-To-Exceed (NTE) limit for a pollutant is the Type I test limit multiplied by a conformity factor that includes a margin for the additional measurement uncertainty of PEMS relative to standard laboratory equipment. The variability of measured results related to RDE trip design, vehicle operating conditions, and data evaluation remain outside of the uncertainty margin. The margins have to be reviewed annually (recital 10 of regulation 2016/646). This paper lays out the framework used for the first review of the NOx margin, which is also applicable to future margin reviews. Based on experimental data received from the stakeholders of the RDE technical working group in 2017, two NOx margin scenarios of 0.24–0.43 were calculated, accounting for different assumptions of possible zero drift behaviour of the PEMS during the tests. The reduced uncertainty margin compared to the one foreseen for 2020 (0.5) reflects the technical improvement of PEMS over the past few years.

Efficient Solution of Washcoat Diffusion-Reaction Problem for Real-Time Simulations

As countries around the globe adapt more stringent emissions standards set by Real Driving Emissions (RDE) legislation, mathematical models are becoming ever more widely used as plant models for devising vehicle control strategies. It is important for the model to run on Hardware-in-Loop (HIL) and engine control unit (ECU) systems which have significantly less computational power and memory than modern personal computers. Washcoat diffusion limitations play a very important role in the efficient design of a catalytic converter. Numerical solution of aftertreatment models that include diffusion-reaction equations in the washcoat are computationally demanding. There are several simplified approaches proposed in the literature for the solution of diffusion-reaction equations in the washcoat to avoid the computational demand of the full numerical solution. In this paper, we use the recently proposed asymptotic solution and compare the results with that of the full numerical solution for the following aftertreatment reactor models with both single- and dual-layer washcoat configurations for the practical range of operating conditions; three-way catalyst (TWC), diesel oxidation catalyst (DOC), Selective Catalytic Reduction (SCR), and ammonia slip catalyst (ASC). These reactor models are constructed using published kinetic mechanisms and represent the global kinetics mechanisms (including non-linear reaction orders and inhibition functions) commonly used in the aftertreatment modeling community. We also discuss the importance of adaptive mesh, quasi-steady state assumption, and occurrence of concentration jumps in the simulation of aftertreatment reactors.

Supervisory Control for Real-Driving Emission Compliance of Heavy-Duty Vehicles

This paper presents an economic nonlinear MPC based strategy for integrated control of the engine and the exhaust aftertreatment system (EATS) of a heavy-duty powertrain. The objectives of this control strategy are to improve the fuel economy while fulfilling real-driving emission legislation based on work-based-window, as stipulated in the Euro VI emission legislation for heavy-duty vehicles. The strategy is evaluated using a high-fidelity simulation platform including a validated GT-POWER model of a 13 L turbo compound diesel engine and a first principles model of an EATS. Simulation results show that the strategy always fulfills the real-driving emission legislation.

Development of Portable Emission Measurement System for Particle Number and Application to Real Driving Emission Measurement

Development of Portable Emission Measurement System for Particle Number and Application to Real Driving Emission Measurement

Diesel and Spark Ignition Engines Emissions and After-Treatment Control: Research and Advancements

One of the major risks mankind has encountered during recent years is, without a doubt, the anthropogenic contribution to environmental pollution [...]

Assessment of real driving emissions via portable emission measurement system

The European Commission approved a so-called Real Driving Emission (RDE) test in response to the criticisms to the current driving cycle used at chassis dyno for homologation purpose (NEDC): it is considered outdated and misleading since air pollutants in real driving conditions are considerably higher than the certification thresholds. So, what’s at stake is the air quality which degraded continuously despite the ever-increasing severity of the regulations during the last almost three decades. Thus, from September 2017, the RDE test will become part of the type approval process for all cars sold in Europe. As its name points out, it will include “real world driving” using a portable emissions measurement system (PEMS). The paper presents the RDE features (PEMS mounting, testing environment, boundary conditions, driving dynamics) and presents a case study on the influence of the driving style upon the tail-pipe emissions under the RDE testing. The results presented in the paper issued from the existing cooperation on this topic between University of Pitesti and Renault Technologie Roumanie

A Combined Experimental and Computational Fluid Dynamics Investigation of Particulate Matter Emissions from a Wall-Guided Gasoline Direct Injection Engine

The latest generation of high-efficiency gasoline direct injection (GDI) engines continues to be a significant source of dangerous ultra-fine particulate matter (PM) emissions. The forthcoming advent in the 2017–2020 timeframe of the real driving emission (RDE) standards affords little time for the identification of viable solutions. The present research work aims to contribute towards a much-needed improved understanding of the process of PM formation in theoretically-homogeneous stoichiometric spark-ignition combustion. Experimental measurements of engine-out PM have been taken from a wall-guided GDI engine operated at part-load; through parallel computational fluid dynamics (CFD) simulations of the test-engine, the process of mixture preparation was investigated. About 80% of the total particle number is emitted on average in the 5–50 nm range, with the vast majority being below the regulated lower limit of 23 nm. The results suggest that both improved charge homogeneity and lower peak combustion temperature contribute to lower particle number density (PNDen) and larger particle size, as engine speed and load increase. The effect of engine load is stronger and results from greater injection pressure through better fuel droplet atomisation. Increases in pre-combustion homogeneity of 6% are associated with one order of magnitude reductions of PNDen. A simplified two-equation functional model was developed, which returns satisfactory qualitative predictions of PNDen as a function of basic engine control variables.

Analysis of the Influence of Outdoor Temperature in Vehicle Cold-Start Operation Following EU Real Driving Emission Test Procedure

Analysis of the Influence of Outdoor Temperature in Vehicle Cold-Start Operation Following EU Real Driving Emission Test Procedure

RDE-based assessment of a factory bi-fuel CNG/gasoline light-duty vehicle

On-road exhaust emissions of a Euro 5 factory bi-fuel CNG/gasoline light-duty vehicle equipped with the TWC were assessed considering the Real Driving Emissions (RDE) guidelines. The vehicle was equipped with a Portable Emission Measurement System (PEMS) that enabled the measurement of THC, CO, NOx, CO2, and CH4. With respect to the characteristics of the vehicle, the appropriate Worldwide Harmonized Light-Duty Vehicle Test Cycles (WLTC) were selected and based on the requirements of the RDE legislation a suitable route was conceived. In addition to the moderate RDE-based route, an extended RDE-based route was also determined. The vehicle was driven along each defined route twice, once with each individual fuel option and with a fully warm vehicle.RDE routes feature a multitude of new driving patterns that are significantly different to those encountered in the NEDC. However, as these driving patterns can greatly influence the cumulative emissions an insight in to local time trace phenomena is crucial to understand, reason and to possibly reduce the cumulative emissions. Original contributions of this paper comprise analyses of the RDE-LDV local time resolved driving emissions phenomena of a CNG-powered vehicle that are benchmarked against the ones measured under the use of gasoline in the same vehicle and under similar operating conditions to reason emission trends through driving patterns and powertrain parameters and exposing the strong cold-start independent interference of CO and N2O infrared absorption bands in the non-dispersive infrared (NDIR) analyzer. The paper provides experimental evidence on this interference, which significantly influences on the readings of CO emissions. The paper further provides hypotheses why CO and N2O interference is more pronounced when using CNG in LDVs and supports these hypotheses by PEMS tests.The study reveals that the vehicle's NOx real-world emission values of both conceived RDE-based routes when using both fuels are within Euro 5 and type-approval limits. Additionally, the THC and the NMHC emissions of both RDE-based routes using both fuels are within the Euro 5 limits indicating reasonable CH4 emissions. Notable increases above the type-approval and Euro 5 limits appeared in the CO emissions profile when using gasoline, while the CO2 emissions profile expectedly also exceeded the type-approval specifications.

Definition of wind blowers for vehicles testing at chassis-dyno facilities using a CFD approach

The need to increase measurement accuracy of fuel consumption and pollutant emissions in vehicles is forcing the market to develop chassis-dyno test cells that reproduce on-road conditions realistically.Air-cooling is key to vehicle performance. It is therefore critical that the design of a test cell guarantees realistic cooling of all vehicle components, as important errors in fuel consumption and emissions measurements may otherwise arise. In a test-room, a blower placed in front of the vehicle supplies the cooling air. While there are some guidelines in the literature for the selection of fans required for emissions measurements for standard driving cycles, the information for designing the air supply system for specific tests in other areas is scarce.New Real Driving Emissions (RDE) legislation will force manufacturers to perform on-road measurements of pollutants. This represents a significant challenge due to the variability of conditions coming from non-controlled parameters. In order to optimize vehicles, different tests are performed in cells equipped with a chassis-dyno where the on-road flow field around the vehicle is reproduced as closely as possible.This work provides some guidelines for the definition of the airflow supply system of chassis-dyno facilities for vehicle optimization tests, based on a CFD analysis of the flow characteristics around the vehicle. By comparison with the solution obtained for a vehicle in real road driving conditions, the exit section of the blower and the distance between the blower exit and the car that best reproduce realistic on-road flow conditions in a test room are determined.

Reduction of engine emissions via a real-time engine combustion control with an egr rate estimation model

Vehicle emissions regulations are becoming increasingly severe and remain a principal issue for vehicle manufacturers. Since, WLTP (Worldwide harmonized Light vehicles Test Procedures) and RDE (real driving emission) regulations have been recently introduced, the engine operating conditions have been rapidly changed during the emission tests. Significantly more emissions are emitted during transient operation conditions compared to those at steady state operation conditions. For a diesel engine, combustion control is one of the most effective approaches to reduce engine exhaust emissions, particularly during the transient operation. The concern of this paper is about reducing emissions using a closed loop combustion control system which includes a EGR rate estimation model. The combustion control system calculates the angular position where 50 % of the injected fuel mass is burned (MFB50) using in-cylinder pressure for every cycle. In addition, the fuel injection timing is changed to make current MFB50 follow the target values. The EGR rate can be estimated by using trapped air mass and in-cylinder pressure when the intake valves are closed. When the EGR rate is different from the normal steady conditions, the target of MFB50 and the fuel injection timing are changed. The accuracy of the model is verified through engine tests, as well as the effect of combustion control. The peaks in NO level was decreased during transient conditions after adoption of the EGR model-based closed loop combustion control system.

Impact of driving style and road grade on gaseous exhaust emissions of passenger vehicles measured by a Portable Emission Measurement System (PEMS)

Motivated by the upcoming Euro-6c regulation including Real Driving Emissions (RDE), the present study addresses the impact of different driving styles and route characteristics on on-road exhaust emissions. Gaseous emissions of two Diesel test vehicles (Euro-5 and Euro-6) were measured using a Portable Emission Measurement System (PEMS) on an RDE compliant test route.The driving parameters relative positive acceleration (RPA), mean positive acceleration (MPA) and v∗apos95 allowed a favorable classification of different driving styles. The comparison of driving parameters for normal PEMS trips with reference data obtained from the World harmonized Light-duty Test Cycle (WLTC) and from Field Operational Tests (FOT) indicated a good representation of normal driving. Severe driving led to elevated CO2 and NOx emissions as compared to normal trips while CO and HC did not allow a distinct classification of different driving styles.Route characteristics of four different routes were investigated applying the parameter cumulated altitude gain using Google Elevation data. The distance specific NOx emissions were in the same range for trips with comparable driving dynamics on routes with similar cumulated altitude gain. Based on repetitive measurements the road grade was calculated within 100m segments. CO2 and NOx emissions measured by a PEMS showed a linear increase with road grade. Larger emissions at higher road grades could be explained by more frequent high engine load points. In this study cumulated altitude gain and road grade were directly correlated to emissions measured by the PEMS and the step from 0 to 5% road grade led to a CO2 increase of 65–81% and a NOx increase of 85–115%.

Implementation of Portable Emissions Measurement Systems (PEMS) for the Real-driving Emissions (RDE) Regulation in Europe.

Vehicles are tested in controlled and relatively narrow laboratory conditions to determine their official emission values and reference fuel consumption. However, on the road, ambient and driving conditions can vary over a wide range, sometimes causing emissions to be higher than those measured in the laboratory. For this reason, the European Commission has developed a complementary Real-Driving Emissions (RDE) test procedure using the Portable Emissions Measurement Systems (PEMS) to verify gaseous pollutant and particle number emissions during a wide range of normal operating conditions on the road. This paper presents the newly-adopted RDE test procedure, differentiating six steps: 1) vehicle selection, 2) vehicle preparation, 3) trip design, 4) trip execution, 5) trip verification, and 6) calculation of emissions. Of these steps, vehicle preparation and trip execution are described in greater detail. Examples of trip verification and the calculations of emissions are given.

Implementation of Portable Emissions Measurement Systems (PEMS) for the Real-driving Emissions (RDE) Regulation in Europe

Vehicles are tested in controlled and relatively narrow laboratory conditions to determine their official emission values and reference fuel consumption. However, on the road, ambient and driving conditions can vary over a wide range, sometimes causing emissions to be higher than those measured in the laboratory. For this reason, the European Commission has developed a complementary Real-Driving Emissions (RDE) test procedure using the Portable Emissions Measurement Systems (PEMS) to verify gaseous pollutant and particle number emissions during a wide range of normal operating conditions on the road. This paper presents the newly-adopted RDE test procedure, differentiating six steps: 1) vehicle selection, 2) vehicle preparation, 3) trip design, 4) trip execution, 5) trip verification, and 6) calculation of emissions. Of these steps, vehicle preparation and trip execution are described in greater detail. Examples of trip verification and the calculations of emissions are given.

Real-driving emissions of circulating Spanish car fleet in 2015 using RSD Technology

In this paper we present the results corresponding to on-road traffic emissions measurements obtained during two field campaigns developed in the Madrid region (Spain) during 2014 and 2015 in the framework of the CORETRA project. The experimental strategy was based on the use of a RSD 4600 remote sensor in interurban roads. These measurements have produced a global database of >190,000 vehicles with their associated emission data (NO/CO2, HC/CO2 and CO/CO2), which can be considered representative of the current Spanish circulating fleet. The results of M1 vehicles were analysed according to their distribution by Euro Standard and engine model. One of the relevant findings is that, despite the progressive introduction of increasingly stringent standards, no NO emission reduction is observed for diesel vehicles with time, although this behavior shows significative differences among brands and engine models.We have also investigated the presence of “high emitter” (HE) vehicles in the Spanish M1 circulating fleet and most of the HE detected corresponded to diesel vehicles with very high NO/CO2 values. With these results at hand, we strongly propose the future incorporation of the “high emitter vehicle” definition into the European environmental legislation, as well as the establishment of specific strategies in each country/region in order to identify these anomalous vehicles. Identification and repair of HE vehicles within the European circulating fleets, although are not easy tasks, should be considered very important for the improvement of air quality in the EU. The use of non-intrusive optical technologies (i.e. RSD) is an excellent option to provide instantaneous real emission data of each individual vehicle without disturbing traffic and for on-road fleet monitoring. In summary, it is a good strategy to obtain valuable information about the long term surveillance of real vehicle emission trends, specially after the introduction of new standard.

Remarks about Real Driving Emissions tests for passenger cars

New test procedures for determining exhaust emission from passenger vehicles will be introduced in 2017. For several years, the European Commission has been developing new procedures, which aim is to perform tests in road conditions. The purpose is to determine the real values of emissions, which are not always reflected by the level of emissions obtained in the laboratory. Proper and accurate procedures for determining emissions in real traffic conditions (RDE – Real Driving Emission) have not yet been approved (as opposed to Heavy Duty Vehicles for which such conditions already exist), but there are proposals that are currently being analyzed by major research centers in Europe. There are many differences between those proposals such as determining road emission or research methodology related to emission measurement of hydrocarbons. The work compares the results of emissions measured in road tests using the latest legislative proposals related to passenger cars. The results are shown in relation to the used measurement method: classic method of determining exhaust emission; uses all measurement data determining the mass of harmful compounds and distance travelled during the test; method of averaging the measuring windows (MAW – moving average windows), also in the literature called EMROAD method, which determines the measurement windows (on the basis of carbon dioxide emissions from the WLTC test) and on its basis determines the road emission in RDE test; generalized method of instantaneous power (Power Binning), known in the literature as CLEAR – Classification of Emissions from Automobiles in Real driving, determines road emissions on the basis of generalized instantaneous power during the RDE test.

Development of the methodology of exhaust emissions measurement under RDE (Real Driving Emissions) conditions for non-road mobile machinery (NRMM) vehicles

The paper analyzes the exhaust emissions from farm vehicles based on research performed under field conditions (RDE) according to the NTE procedure. This analysis has shown that it is hard to meet the NTE requirements under field conditions (engine operation in the NTE zone for at least 30 seconds). Due to a very high variability of the engine conditions, the share of a valid number of NTE windows in the field test is small throughout the entire test. For this reason, a modification of the measurement and exhaust emissions calculation methodology has been proposed for farm vehicles of the NRMM group. A test has been developed composed of the following phases: trip to the operation site (paved roads) and field operations (including u-turns and maneuvering). The range of the operation time share in individual test phases has been determined. A change in the method of calculating the real exhaust emissions has also been implemented in relation to the NTE procedure.