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The current European fleet of vehicles is ageing and lifetime mileages are rising proportionally. Consequently, a substantial fraction of the vehicle fleet is currently operating at mileages well beyond current durability legislation (≤ 160,000 km). Emissions inventories and models show substantial increases in emissions with increasing mileage, but knowledge of the effect of emissions control system deterioration at very high mileages is sparse. Emissions testing has been conducted on matched pairs (or more) of diesel and gasoline (and CNG) vehicles, of low and high mileage, supplementing the results with in-house data, in order to explore high mileage emission deterioration factors (DF). The study isolated, as far as possible, the effect of emissions deterioration with mileage, by using nominally identical vehicle models and controlling other variables.

The implementation of emission standards has brought significant reductions in vehicle emissions in the EU, but road transport is still a major source of air pollution. Future emission standards will aim at making road vehicles as clean as possible under a wide range of driving conditions and throughout their complete lifetime. The current paper presents the methodology followed by the Consortium for ultra LOw Vehicle Emissions (CLOVE) to support the preparation of the Euro 7 proposal. As a first step, the emission performance of the latest-technology vehicles under various driving conditions was evaluated. Towards this direction, an emissions database was developed, containing data from a wide range of tests, both within and beyond the current RDE boundaries.

Substantial advances in European road vehicle emissions have been achieved over the past 3 decades driven by strengthening revisions in emissions legislation and enabled by advances in fuel, vehicle engine and emissions control technologies. As both vehicle technology and emissions legislation in Europe continue to evolve, Concawe has conducted a study to examine the opportunities that fuels can provide to further reduce emissions from light-duty diesel passenger cars. Three European diesel cars spanning Euro 5, Euro 6b and Euro 6d-TEMP emissions certification levels have been tested over the cold-start WLTC (Worldwide harmonized Light-duty Test Cycle) with 6 fuels: an EN590-compliant B5 (petroleum diesel containing 5% biodiesel by volume), a bio-derived paraffinic diesel, a 50:50 blend of the aforementioned fuels, a low density petroleum-derived B5, a B30 and the same B30 additized with a high dose of cetane number improver.

The latest generation of internal combustion engines may emit significant levels of sub-23 nm particles. The main objective of the Horizon 2020 “DownToTen” project was to develop a robust methodology and provide policy recommendations towards the particle number (PN) emissions measurements in the sub-23 nm region. In order to achieve this target, a new portable exhaust particle sampling system (PEPS) was developed, being capable of measuring exhaust particles down to at least 10 nm under real-world conditions. The main design target was to build a system that is compatible with current PMP requirements and is characterized by minimized losses in the sub-23 nm region, high robustness against artefacts and high flexibility in terms of different PN modes investigation, i.e. non-volatile, volatile and secondary particles.

In Europe, the development and implementation of new regulatory test procedures including the chassis dynamometer (CD) based World Harmonised Light Duty Test Procedure (WLTP) and the Real Driving Emissions (RDE) procedure, has been driven by the close scrutiny that real driving emissions and fuel consumption from passenger cars have come under in recent times. This is due to a divergence between stated certification performance and measured on-road performance, and has been most pointed in the case of NOx (oxides of nitrogen) emissions from diesel cars. The RDE test is certainly more relevant than CD test cycles, but currently certification RDE cycles will not necessarily include the most extreme low speed congested or low temperature conditions which are likely to be more challenging for NOx after-treatment systems.

The market share of Gasoline Direct Injection (GDI) vehicles has been increasing, promoted by its positive contribution to the overall fleet fuel economy improvement. It has however been reported that this type of engine is emitting more ultrafine particles than the Euro 6c Particle Number (PN) limit of 6·1011 particles/km that will be introduced in Europe as of September 2017 in parallel with the Real Driving Emission (RDE) procedure. The emissions performance of a Euro 6b GDI passenger car was measured, first in the OEM build without a Gasoline Particulate Filter (GPF) and then as a demonstrator with a coated GPF in the underfloor position. Regulated emissions were measured on the European regulatory test cycles NEDC and WLTC and in real-world conditions with Portable Emissions Measurement Systems (PEMS) according to the published European RDE procedure (Commission Regulation (EU) 2016/427 and 2016/646).

The exhaust emissions of two Euro 6 diesel cars with different emissions control systems have been evaluated both on the road and over various chassis dynamometer test cycles. European emissions limits are currently set using the New European Driving Cycle (NEDC), but the European Commission is preparing additional test procedures to ensure that emissions are well controlled both in real-world use and over the legislative test cycle. The main focus of this work on ‘Real Driving Emissions’ (RDE) is on measurements using Portable Emissions Measurement Systems (PEMS) in truly representative, on-road, driving. A key focus of the test programme, undertaken as a collaboration between AECC (the Association for Emissions Control by Catalyst) and Ricardo UK, was therefore the use of PEMS systems to measure on-road emissions of both gaseous pollutants and particulate matter. This included measurement of particle number emissions with a new candidate system for this type of measurement.

An investigation has been carried out to examine the influence of up to 300 MPa injection pressure on engine performance and emissions. Experiments were performed on a 4 cylinder, 4 valve / cylinder, 4.5 liter John Deere diesel engine using the Ricardo Twin Vortex Combustion System (TVCS). The study was conducted by varying the injection pressure, Start of Injection (SOI), Variable Geometry Turbine (VGT) vane position and a wide range of EGR rates covering engine out NOx levels between 0.3 g/kWh to 2.5 g/kWh. A structured Design of Experiment approach was used to set up the experiments, develop empirical models and predict the optimum results for a range of different scenarios. Substantial fuel consumption benefits were found at the lowest NOx levels using 300 MPa injection pressure. At higher NOx levels the impact was nonexistent. In a separate investigation a Cambustion DMS-500 fast particle spectrometer, was used to sample and analyze the exhaust gas.

This paper describes the results of a series of tests on a heavy-duty truck diesel engine using conventional and low viscosity lubricants. The objectives were to explore the impact of reducing lubricant viscosity on wear, friction and fuel consumption. The radiotracing Thin Layer Activation method was used to make on-line measurements of wear at the cylinder liner, top piston ring, connecting rod small end bush and intake cam lobe. The engine was operated under a wide range of conditions (load, speed and temperature) and with lubricants of several different viscosity grades. Results indicate the relationship between lubricant viscosity and wear at four critical locations. Wear at other locations was assessed by analysis of wear metals and post test inspection. The fuel consumption was then measured on the same engine with the same lubricants. Results indicate the relationship between oil viscosity and fuel consumption under a wide range of operating conditions.

The heavy duty Particle Measurement Programme (PMP) inter-laboratory exercise consists of three parts: 1) the exploratory work to refine the measurement protocol, 2) the validation exercise where each lab will measure the emissions of a “golden” engine with two “golden” particle number systems simultaneously sampling from full and partial flow dilution systems, and 3) the round-robin where the emissions of a “reference” engine will be determined with a lab’s own particle number instrumentation. This paper presents the results of the exploratory work and describes the final protocol for testing in the validation exercise (and round robin) along with the necessary facility modifications required for compliance with the protocol. Key aspects of the protocol (e.g. filter material, flow rates at the full and partial flow systems, the pre-conditioning etc.) are explained and justified.

Four state-of-the-art >500 cc Euro 3 and one 150 cc Indian specification motorcycles were selected and evaluated over the Euro 3 and world harmonized WMTC test cycles for regulated pollutants and particles. The objectives of the work were to examine the correlation between emissions on the WMTC and Euro 3 cycles, to compare those results with previous work completed before the European WMTC limits were set, to examine particulate emissions, and to then evaluate the durability of one machine. The correlation between Euro 3 and WMTC emissions results was used to extrapolate the appropriate level of WMTC limit values from the emissions limits on the Euro 3 test cycle. These WMTC extrapolated emissions limits were in line with the previous AECC motorcycle test program conducted in 2004 on Euro 2 motorcycles and also confirmed the appropriate level of the WMTC Euro 3 limits set in European Directive 2006/72/EC amending 97/24/EC.

During a test programme on a modern heavy-duty engine, measurements were made at engine-out and tailpipe of particle number and particulate mass using the draft heavy-duty inter-laboratory correlation exercise guide prepared by the UN-ECE Particle Measurement Programme (PMP)1. In addition to the PMP measurements, the elemental carbon content of the particulate matter from this programme was analysed using thermogravimetric analysis of separate filters. The particle number measurement system proved to provide a reliable and repeatable measurement procedure. Test results over a variety of operational cycles showed a reduction in particle numbers of some 3 orders of magnitude. Particle number emissions were of similar magnitude regardless of the test cycle. Background-corrected particulate mass emissions results using the partial flow dilution method showed emissions levels below 5mg/kWh over all the transient cycles tested.

By early 2007, all major manufacturers of light-duty diesel vehicles are marketing models equipped with diesel particulate filters (DPFs). However, there is still a lack of understanding of the particles emitted when the DPF undergoes regeneration. This paper focuses on measuring particle emissions of a representative light-duty diesel vehicle equipped with DPF and employing a fuel-borne catalyst (FBC) to aid regeneration. Particulate Matter (PM) and non-volatile particle number emissions are measured throughout testing according to the Particle Measurement Programme (PMP) proposals. In addition, an Engine Exhaust Particle Sizer (EEPS) connected directly to the CVS is used to give real time size distributions of both volatile and non-volatile particles. The paper focuses on particle emissions during regenerating New European Driving Cycles (NEDCs).

An Iveco Cursor 8 heavy-duty Diesel engine (7.8L, 6 cylinder) meeting Euro III emission regulations and equipped with a catalyst based passively regenerating Diesel particulate filter (CB-DPF) system, was used to investigate the impact of lubricant formulation on exhaust emissions. Measurements of both regulated and unregulated emissions were made during ESC and ETC cycles undertaken during a strictly controlled experimental protocol. Testing was carried out using ultra low sulphur, Swedish Class 1 Diesel fuel and a range of lubricant formulations. No significant effects of lubricant composition were observed on regulated gaseous emissions. However, the number of nucleation mode particles appeared to be both drive cycle and lubricant formulation dependent. Test methodology proved to be key; with engine, exhaust and dilution tunnel preconditioning and test order a major influence on ESC particle emissions.

This programme involved the testing of two Euro II compliant diesel vehicles over the current European legislated drive cycle. The aim of the programme was to determine and compare the emissions of 100% virgin vegetable oil (VVO100) and a baseline UK marketplace Ultra Low Sulphur (ULSD) diesel fuel. A splash blend of 5% rapeseed methyl ester in ULSD (RME5) was also evaluated. Results of tests on RME5 showed that generally the effects on emissions compared to ULSD were small for regulated and most unregulated emissions. There was some evidence of a PM10 benefit for RME5 fuel. VVO100 showed large increases in HC (up to 250%) and CO emissions in both vehicles, as well as increases in polycyclic aromatic hydrocarbons (PAH), compared to ULSD. Effects on NOx and particulate were vehicle - specific.

The impact of lubricant sulphur and phosphorus levels on the formation of nucleation mode particles was explored in a light duty diesel vehicle operating over the New European Drive Cycle (NEDC). All measurements were undertaken using a Scanning Mobility Particle Sizer (SMPS), sampling from a conventional Constant Volume Sampler (CVS) system. Rigorous sampling system and vehicle conditioning procedures were applied to eliminate oil carry-over and nanoparticle artifact formation. An initial vehicle selection process was undertaken on vehicles representing three fuel injection strategies, namely; distributor pump, common rail and unit injector. The vehicles met Euro III specifications and were all equipped with oxidation catalysts. Idle and low load stability were key requirements, since these conditions are the most significant in terms of their propensity to generate nucleation mode particles.

This paper describes a practical approach used within the UK contribution to the UNECE PMP study in adopting some of the recommendations stated in the draft 2007 regulations for the measurement of particulate mass emissions from heavy-duty diesel engines in the US. This approach was named “2007PM” but the intention was to align rather than fully comply with the draft requirements for the US. In the PMP test work, four main changes were made to the standard European method of particulate emissions measurement (SPM). These were adopted as the 2007PM method. These were the application of a cyclone pre-classifier to 2007PM - with a 50% cut-size at 2.5μm, the use of a single 47mm filter rather than primary and back-up filters, close control of the filter face temperature to 47°C +/-5°C by heating of the dilution air and an increased filter face velocity. Measurements were predominantly made from aerosols generated by engines equipped with Diesel Particulate Filters (DPFs).

The DETR/SMMT/CONCAWE Particulate Research Programme was designed to investigate the effects of vehicle/engine technology level, fuel specification and various operating conditions on emissions of particle mass, number and size. Results from the heavy duty part of the programme and details of the measuring protocols have already been published. This paper gives the results of the light duty study. This consisted of six vehicles and eight fuels covering gasoline, Diesel and LPG technologies. These six vehicles represented Euro II (1996) and Euro III (2000) technologies. Diesel fuels included EN590 (1996), EN590 (2000), UK ultra low sulphur Diesel (UK ULSD) and Swedish Class I Diesel, while gasoline fuels comprised EN228 (1996), EN228 (1999) and UK ultra low sulphur gasoline (UK ULSG).

The aim of this study was to investigate the changes in mass and number based heavy duty diesel engine particle emissions with respect to various test conditions, engine technologies and fuel specifications. Comparative particle size data and regulated particulate matter are presented from three heavy duty engines and three fuels. This paper describes results from the DETR/CONCAWE/SMMT Particle Research Programme. Three heavy duty diesel (HDD) engines representing Euro I, II and III technologies were tested with a range of fuels. These fuels included UK ultra low sulphur diesel (UK-ULSD), EN590 (EU2000) specification and Swedish Class I fuels. Continuing research suggests that when changes in regulated particulate mass emissions are compared to both individual mode and total cycle mass and number weighted particle size distributions there is often no significant correlation. In an attempt to provide further data in this area the following measurement methodology was adopted.

This paper describes the observed effects of parameters such as tunnel dilution ratio, test procedures and measurement methods on particle emissions. Attention is drawn to the transient behavior of nanoparticles within real legislated cycle conditions using conventional dilution systems. The aim of the paper is to communicate the limitations of widely used measurement equipment to enable a more confident interpretation of the particle size data. The paper describes the information obtained during the DETR/CONCAWE/SMMT Particle Research Programme with regard to the sampling and measurement of particles emitted from light duty vehicles and heavy duty engines. Light duty vehicles were tested on gasoline, diesel and LPG, while heavy duty engines were tested on both diesel and compressed gaseous fuels. Two Scanning Mobility Particle Sizer (SMPS) instruments were employed in order to cover a measurement range from a lower limit of ∼7nm up to ∼710nm.