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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 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.

Hybrid technology has the potential to enable dramatic reductions in greenhouse gases (GHG), such as the California goal of reducing GHG by 80 percent from 1990 levels by 2050. As a result it is expected that hybrid systems will occupy a growing proportion of the market. However, introducing a hybrid system in a vehicle may adversely affect the performance of the engine OBD system in monitoring malfunctions impacting pollutant emissions. For example, a hybrid system that reduces time of the engine in idle or deceleration overrun conditions could make a well-performing engine OBD system noncompliant, by reducing in-use frequency of some OBD monitors below acceptable levels. In this presentation, Ricardo will present a process for evaluating the impact that a hybrid system which has been optimised to minimise GHG emission over a specified drive-cycle will have on the effectiveness of engine OBD monitors.

A system for stratifying recycled exhaust gas (EGR) to substantially increase dilution tolerance has been applied to a port injected four-valve gasoline engine. This system, known as Combustion Control through Vortex Stratification (CCVS), has shown greatly improved fuel consumption at a stoichiometric air/fuel ratio. Both burnrate (10-90% burn angle) and HC emissions are almost completely insensitive to EGR up to best economy EGR rate. Cycle to cycle combustion variation is also excellent with a coefficient of variation of IMEP of less than 2% at best economy EGR rate. This paper describes a research programme aimed at gaining a better understanding of the in-cylinder processes in this combustion system.

An investigation into the application of electronically controlled solenoid activated high pressure in-cylinder gasoline injection systems has been carried out in both conventional and novel four-valve four-stroke pent-roof chamber single-cylinder engines. Air motion requirements were studied and their effects on port design and layout were assessed. Alternative injector types, locations and spray characteristics were investigated. Transient and steady-state comparisons of the engines were made under both normal and cold running conditions. The outlook for the use of in-cylinder injection technology compatible with ULEV emissions requirements is discussed in the light of the results obtained.

A system for stratifying recycled exhaust gas (EGR) in order to substantially increase dilution tolerance has been applied to a single cylinder manifold injected pent-roof four-valve gasoline engine. This system has been given the generic name Combustion Control by Vortex Stratification (CCVS). Preliminary research has shown that greatly improved fuel consumption is achievable at stoichiometric conditions compared to a conventional version of the same engine whilst retaining ULEV NOx levels. Simultaneously the combustion system has shown inherently low HC emissions compared to homogeneous EGR engines. A production viable variable air motion system has also been assessed which increases the effectiveness of the stratification whilst allowing full load refinement and retaining high performance.

Speciated hydrocarbon emissions were measured at steady-state conditions in pre- and post-catalyst exhaust from a modern multi-valve fuel-injected and closed-loop controlled European gasoline engine tested on toluene, isooctane and diisobutylene. Unburned fuel contributed 70-80% of the total engine-out hydrocarbon emissions on toluene, but only 24% and <10% on isooctane and diisobutylene respectively except at idle where values were 71% and 47% respectively. Emissions from both of the aliphatic fuels were dominated by photochemically-reactive olefins such as isobutene and propene, plus ethyne, methane and formaldehyde. With the exception of ethyne, emissions of these compounds were much less from toluene. Even at rich conditions, most hydrocarbons were catalytically controlled to some extent, but the catalyst efficiency was dependant upon hydrocarbon composition.

Seven hydrocarbons were determined continuously in gasoline engine exhaust over the US FTP cycle using Fourier Transform Infra Red Spectroscopy (FTIR). Three of the hydrocarbons were also determined using Chemical Ionisation-Mass Spectrometry (CI-MS). Tests with and without a three way catalyst illustrated the strong dependence of catalyst performance on the composition of the hydrocarbons emitted. For example, the FTIR indicated that over a cold start FTP cycle, the catalyst took 98 seconds to achieve a 50% conversion rate for ethyne, 183 seconds for ethene and 229 seconds for ethane. The work indicates that FTIR in particular is an appropriate technique for the monitoring of exhaust catalyst performance.

To gain a better understanding of the exhaust emissions impact of olefins in a low aromatic, full boiling range gasoline, an evaluation of the before and after catalyst emissions of three highly olefinic refinery streams and three highly paraffinic refinery streams, blended 50/50 in motor alkylate, was conducted using a 3.1 L GM engine. The test fuels were also selected to consider the effects of volatility in addition to olefin concentration. The fuels were evaluated under three steady state engine operating conditions. The results of the tests indicate essentially only small differences in the before and after catalyst total hydrocarbons (THC) between the pairs of highly olefinic streams and the highly paraffinic streams at relatively the same volatility level, for two of the test conditions (2400RPM-light and moderate/heavy loads. The ozone forming potentials (OFP) for these fuels, across all three speed and load conditions, also show relatively small differences.

A brief study has been undertaken with exhaust gas recirculation (EGR) applied to a prototype low emission, heavy duty, direct injection (DI) diesel engine aimed at evaluating the potential for low nitrogen oxide (NOx) emissions. By virtue of the very low smoke levels achieved with the prototype engine, EGR can be applied at full load for substantial reductions in NOx down to c. 2.5 g/kWh (1.9 g/hph) over the European R-49 13-Mode test. These results were achieved with competitive particulates and fuel consumption and without recourse to engine de-rating. Compliance with the NOx emissions proposed for the year 2000 Japanese market was also demonstrated. These results are summarised in this paper and justify the need for a major research programme aimed at demonstrating the full potential of using EGR to develop a fuel efficient, low emission truck engine concept for the 1990's and beyond.

Natural gas has been the subject of growing interest as a low emissions alternative to conventional automotive engine fuels. The development of a control system for a very low emissions heavy-duty natural gas engine is described. The engine is intended for city bus applications, with emissions targets set well within US 1994 levels. The engine uses a stoichiometric air-fuel mixture with exhaust gas recirculation and a three-way catalyst. The control system was implemented on a prototype hardware architecture designed to facilitate algorithm development. The control system software was constructed from a number of fundamental modules. Good steady-state and transient air-fuel ratio control was particularly important for maintaining optimum catalyst efficiency and hence minimum emissions. To achieve this, the air-fuel ratio control system used solenoid gas injectors and lambda feedback.