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The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing. Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions. As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.

Octane appetite of modern engines has changed as engine designs have evolved to meet performance, emissions, fuel economy and other demands. The octane appetite of seven modern vehicles was studied in accordance with the octane index equation OI=RON-KS, where K is an operating condition specific constant and S is the fuel sensitivity (RONMON). Engines with a displacement of 2.0L and below and different combinations of boosting, fuel injection, and compression ratios were tested using a decorrelated RONMON matrix of eight fuels. Power and acceleration performance were used to determine the K values for corresponding operating points. Previous studies have shown that vehicles manufactured up to 20 years ago mostly exhibited negative K values and the fuels with higher RON and higher sensitivity tended to perform better.

In a modern diesel engine, a high fuel injection pressure is achieved by a common-rail system. Therefore, it is important to understand the effects of fuel properties on engine performances because a diesel fuel could deteriorate inside an injector at such severe conditions. The test methods so far basically use the fuel with pro-fouling agent to form deposit on injector. In this study, a novel test procedure was developed to evaluate the effect of the use of the fuel with and without zinc contaminant on injector performance. With Zn doped European specification B7 fuel (7% biodiesel) as a reference, the test result showed that an engine torque decreased almost lineally over time, and the overall torque drop was 9% after 300 hours. The investigation of the dismantled injector after the test revealed that the deposit was not formed on the sliding parts of the injector, but on the nozzle hole surface.

There is an increasing recognition of injector deposit (ID) formation in fuel injection equipment as direct injection spark ignition (DISI) engine technologies advance to meet increasingly stringent emission legislation and fuel economy requirements. While it is known that the phenomena of ID in DISI engines can be influenced by changes in fuel composition, including increasing usage of aliphatic alcohols and additive chemistries to enhance fuel performance, there is however still a great deal of uncertainty regarding the physical and chemical structure of these deposits, and the mechanisms of deposit formation. In this study, a mechanical cracking sample preparation technique was developed to assess the deposits across DISI injectors fuelled with gasoline and blends of 85% ethanol (E85).

Synthetic fuels are expected to play an important role for future mobility, because they can be introduced seamlessly alongside conventional fuels without the need for new infrastructure. Thus, understanding the interaction of GTL fuels with modern engines, and aftertreatment systems, is important. The current study investigates potential benefits of GTL fuel in respect of diesel particulate filters (DPF). Experiments were conducted on a Euro 4 TDI engine, comparing the DPF response to two different fuels, normal diesel and GTL fuel. The investigation focused on the accumulation and regeneration behavior of the DPF. Results indicated that GTL fuel reduced particulate formation to such an extent that the regeneration cycle was significantly elongated, by ∼70% compared with conventional diesel. Thus, the engine could operate for this increased time before the DPF reached maximum load and regeneration was needed.

The regeneration of a Diesel Particulate Filter (DPF) is dependent on both the amount and type of soot present on the filter. The objective of this work is to understand how the fuel can affect this ease with which soot can be oxidized. This soot was produced in a two-cylinder four-stroke direct-injection diesel engine, operated with a matrix of fuels with varying aromatic and sulphur level. Their oxidation behaviour in different environments was determined by Temperature Programmed Oxidation in TGA and a six-flow reactor. Transmission electron microscopy was used to examine the soot morphology. Oxidation with only O2 shows oxidation temperatures strongly dependent on the fuel type. Soot oxidation in the presence of NO and a Pt-catalyst results in a lower oxidation temperature. SO2 has an inhibiting effect leading to higher soot oxidation temperature.

This paper presents an overview of the results on light duty vehicles collected in the “PARTICULATES” project which aimed at the characterization of exhaust particle emissions from road vehicles. A novel measurement protocol, developed to promote the production of nucleation mode particles over transient cycles, has been successfully employed in several labs to evaluate a wide range of particulate properties with a range of light duty vehicles and fuels. The measured properties included particle number, with focus separately on nucleation mode and solid particles, particle active surface and total mass. The vehicle sample consisted of 22 cars, including conventional diesels, particle filter equipped diesels, port fuel injected and direct injection spark ignition cars. Four diesel and three gasoline fuels were used, mainly differentiated with respect to their sulfur content which was ranging from 300 to below 10 mg/kg.

A field problem associated with flakes of combustion chamber deposits getting trapped on the exhaust valve seat and causing starting problems has appeared recently. Four fuels have been tested in three different car models using a deposit flaking road test procedure. For each piston top, flaking can be characterised using T1 and T2, the mean deposit thickness on the piston crown before and after flaking respectively. A new measure of deposit flaking, ΔT, the mean of (T1-T2) averaged over all cylinders has been introduced and its variance established for the standard test using one of the models. ΔT quantifies the actual amount of deposits that have flaked and is likely to be a more relevant indicator of flaking for startability problems than Rw, the mean of the ratio of T2 to T1, used in previous work. Deposit flaking is directly related to an increase in valve leakage rates and startability problems.

There is increasing concern that small flakes of combustion chamber deposits (CCD) can break lose and get trapped between the exhaust valve and the seat resulting in difficulties in starting, rough running and increase in hydrocarbon emissions. In this paper we describe experimental observations which might explain how this flaking of CCD occurs and the factors that might be important in the phenomenon. The experiments include thirty one engine tests as well as tests done in a laboratory rig and show that some CCD flake when they are exposed to water; indeed water is far more effective in bringing this about than gasoline or other organic solvents. The hydrophilicity of the deposit surface which determines the penetration of water and the inherent susceptibility of the relevant deposit layer to inter-act with water are both important. Consequently there are large differences between deposits produced by different fuels and additives in terms of their susceptibility to flake.

Fuel volatility and vehicle characteristics have long been recognised as important parameters influencing the exhaust emissions and the driveability of gasoline vehicles. Limits on volatility are specified in a number of world-wide / national fuel specifications and, in addition, many Oil Companies monitor driveability performance to ensure customer satisfaction. However, the relationship between driveability and exhaust emissions is relatively little explored. A study was carried out to simultaneously measure driveability and exhaust emissions in a fleet of 10 European gasoline vehicles. The vehicles were all equipped with three-way catalysts and single or multi-point fuel injection. The test procedure and driving cycle used were based on the European Cold Weather Driveability test method.