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Trapping diesel particulates is effective in reducing both the number and the mass of fine particulate emissions from diesel engines, but unless the accumulated soot can be burned out or regenerated periodically, the vehicle to which the trap is fitted will cease to function after a relatively short time. A programme of work with soot traps using a low treat rate iron-strontium organo-metallic fuel additive to assist and secure regeneration has been carried out. As part of this programme, an advanced specification diesel engine passenger car equipped with a diesel particulate filter (DPF), was operated on roads in the UK for approximately 18 months, during which time the vehicle covered over 50,000 km After completion of 50,000 km on roads, the vehicle was operated on a chassis dynamometer to increase the distance covered with a DPF more rapidly to a final total of 80,000 km.

With growing concern over greenhouse gases there is increasing emphasis on reducing CO2 emissions. Despite engine efficiency improvements plus increased dieselisation of the fleet, increasing vehicle numbers results in increasing CO2 emissions. To reverse this trend the fuel source must be changed to renewable fuels which are CO2 neutral. A common route towards this goal is to substitute diesel fuel with esterified seed oils, collectively known as Fatty Acid Methyl Esters. However a fundamental change to the fuel chemistry produces new challenges in ensuring compatibility between fuel and engine performance/durability. This paper discusses the global situation and shows how fuel additives can overcome the challenges presented by the use of biodiesel.

The atomisation characteristics of DI diesel engine fuel injection nozzles have been the subject of intensive study over the last decade. Much of this work has been related to clean, single hole nozzles spraying into quiescent air, at either ambient conditions or elevated pressures and temperatures. Experience shows that fuel injector nozzles may foul very rapidly in field service, and that this might have a significant effect on the performance of the engine particularly with regard to emissions. The build up of material on the injector nozzle can be controlled by the addition of suitable fuel additives. This paper describes test procedures developed to assess deposit build up and to indicate the efficacy of keep clean additives. The paper then goes on to describe high speed photographic techniques for studying the fuel spray characteristics of clean and fouled injectors in a firing engine.

The fuel injection equipment (FIE) has always been paramount to the performance of the Diesel engine. Increasingly stringent emissions regulations have dictated that the FIE becomes more precise and sophisticated. The latest generation FIE is therefore less tolerant to deposit formation than its less finely engineered predecessors. However, the latest emissions regulations make it increasingly difficult for engine manufacturers to comply without the use of exhaust aftertreatment. This aftertreatment often relies on catalytic processes that can be impaired by non-CHON (carbon, hydrogen, oxygen and nitrogen) components within the fuel. Fuel producers have therefore also been obliged to make major changes to try and ensure that with the latest technology engines and aftertreatment systems the fuel is still fit for purpose. However, there has recently been a significant increase in the incidence of reported problems due to deposit build-up within vehicle fuel systems.

Diesel fuel distilled from crude oil should contain no greater than trace amounts of sodium. However, fuel specifications do not include sodium; there is a limit of five parts per million for the amount of sodium plus potassium in fatty acid methyl esters (FAME) used as biodiesel. Sodium compounds are often used as the catalyst for the esterification process for producing FAME and sodium hydroxide is now commonly used in the refining process to produce ultra-low sulphur diesel (ULSD) fuel from crude oil. Good housekeeping should ensure that sodium is not present in the finished fuel. A finished fuel should not only be free of sodium but should also contain a diesel fuel additive package to ensures the fuel meets the quality standards introduced to provide reliable operation, along with the longevity of the fuel supply infrastructure and the diesel engines that ultimately burn this fuel.

A diesel particulate filter (DPF) is a crucial weapon in the fight to control the downsides traditionally associated with diesel engined vehicles. The DPF not only produces the benefits required from an environmental standpoint but also has the consumer benefit of eliminating the visible black smoke associated with diesel engines. Thus DPFs have now become a reality, both for series production vehicles and as a retrofit application. Inevitably there are a number of alternative types of DPF and alternative techniques are used for ensuring they continue to function in an acceptable manner. Due to the complexity of the diesel combustion process and the emissions produced it is only to be expected that a device intended primarily to control one parameter would have some effect on other parameters. This paper looks at some different DPF technologies and how they effect emissions, with the emphasis on particulate emissions and the speciation of oxides of nitrogen.

Transport Refrigeration Units (TRU) powered by small diesel engines emit high PM and cause locally high PM levels. The concomitant health risks spurred efforts to devise a cost-effective curtailment of these emissions. Diesel particulate filters (DPF) of ceramic honeycomb construction very efficiently trap PM emissions, even ultrafines in the lung penetrating size range of below 300 nm. A fuel borne catalyst (FBC) can facilitate trap regeneration, by lowering the exhaust temperature requirements, but cannot alone guarantee reliable regeneration under all operating conditions of the TRU. A Swiss development team together with industrial partners therefore developed a fully automatic active regeneration system for the California Air Resources Board.

Continuing research into the effect of vehicle emissions is driving legislation, which is increasingly being enacted to encourage the retrofitting of emissions control devices. Of particular concern are emissions of diesel particulate matter and nitrogen oxides. More recently the adverse effects of nitrogen dioxide in particular, have been highlighted. A programme of work is underway in Santiago to demonstrate the suitability of retrofitting diesel particulate filters (DPF) to urban buses. This paper presents data, including regulated and unregulated emissions, from a bus fitted with a DPF that relies on a fuel borne catalyst (FBC) to facilitate regeneration of the DPF.

Traditionally, diesel fuel injection equipment (FIE) has frequently relied on the diesel fuel to lubricate the moving parts. When ultra low sulphur diesel fuel was first introduced into some European markets in the early 1980's it rapidly became apparent that the process of removing the sulphur also removed other components that had bestowed the lubricating properties of the diesel fuel. Diesel fuel pump failures became prevalent. The fuel additive industry responded quickly and diesel fuel lubricity additives were introduced to the market. The fuel, additive and FIE industries expended much time and effort to develop test methods and standards to try and ensure this problem was not repeated. Despite this, there have recently been reports of fuel reaching the end user with lubricating performance below the accepted standards.

Recent developments in diesel engines and fuel injection equipment combined with the change to ULSD and bio-blends have resulted in increased reports regarding deposits within injectors and filters. A review of known fuel degradation mechanisms and other relevant chemistries suggests the effects of high pressure and high shear environments should be examined as the most probable causes of increasing deposit formation. Existing fuel quality tests do not correlate with reported fouling propensity. Analytical studies have shown that there are only subtle chemical changes for the materials within the standard diesel boiling range. The implications for further scientific study are discussed.

Exhaust emissions legislation for diesel engines generally limits only the mass of emitted particulate matter. This limitation reflects the concerns and measurement technology at the time the legislation was drafted. However, evolving diesel particulate filter (DPF) systems offer the potential for reductions in the mass and more importantly, the number of particles emitted from diesel exhausts. Particulate filters require frequent cleaning or regeneration of accumulated soot, if the engine is to continue to operate satisfactorily. Exothermic reactions during regeneration can lead to severe thermal gradients in the filter system resulting in damage. Fuel additives have been evaluated to show significant reductions in light off temperature which allow frequent small regeneration events to occur, under mild operating conditions.

Work was carried out on three passenger cars and a light truck. The test vehicles were chosen to cover a range of engine technologies. Different DPF technologies were also employed. The programme showed that an improved fuel additive based on the combination of iron and strontium compounds would allow all four vehicles to be successfully operated under a wide range of conditions. The three passenger cars were driven over the road for considerable distances. Regeneration of the DPF was successfully achieved under normal operating conditions in all the vehicles without recourse to use of additional heaters, fuel injection or other technique to assist regeneration. Fuel additive treat rate was low, suggesting that long-term operation without significant ash accumulation in the DPF could be achieved.

One of the most promising ways to insure the periodic regeneration of a particulate trap, consists of additising the fuel with organo-metallic compounds. The present paper deals with a novel alkali product, able to promote natural regenerations, for exhaust temperatures as low as 200 °C, and treatment rates as low as 5 ppm metal. Tests have been carried out on a soot reactor and on an engine bench, with various trap locations in the exhaust, showing that the regeneration occurrence depends on temperature, soot mass loaded inside the porous structure and engine conditions. A complete trap cleaning still needs gas temperatures up to 400 °C, which can be encountered for high load conditions of the engine.

Current developments in fuels and emissions regulations are resulting in an increasingly severe operating environment for diesel fuel injection systems. The formation of deposits within the holes or on the outside of the injector nozzle can affect the overall system performance. The rate of deposit formation is affected by a number of parameters, including operating conditions and fuel composition. For the work reported here an accelerated test procedure was developed to evaluate the relative importance of some of these parameters in a high pressure common rail fuel injection system. The resulting methodology produced measurable deposits in a custom-made injector nozzle on a single-cylinder engine. The results indicate that fuels containing 30%v/v and 100% Fatty Acid Methyl Ester (FAME) that does not meet EN 14214 produced more deposit than an EN590 petroleum diesel fuel.

The need to meet the US 2007 emissions legislation has necessitated a change in Diesel engine technology, particularly to the fuel injection equipment (FIE). At the same time as these engine technology changes, legislation has dictated a reduction in fuel sulphur levels and there has also been increased use of fatty acid methyl esters (FAME) or biodiesel as a fuel blending component. The combination of changes to the engine and the fuel has apparently led to a sharp rise in the number of reports of field problems resulting from deposits within the FIE. The problem is usually manifested as a significant loss of power or the engine failing to start. These symptoms are often due to deposits to be found within the fuel injectors or to severe fouling of the fuel filter. The characteristics of the deposits found within different parts of the fuel system can be noticeably different.

Recent developments in diesel engines and fuel injection equipment together with the move to ULSD and bio-blends have seen an increase in reports regarding deposits in both injectors and filters. Historically deposits have been generated from a number of sources: bio-contamination, both aerobic and non-aerobic, water contamination, lube oil adulteration, additives, dirt, metals in fuel, and biodiesel degradation. These may be ascribed to “poor housekeeping,” incorrect additivation, deliberate adulteration or some combination. However the recently observed deposits differ from these. The deposits are described and indicate possible precursor molecules that support proposed mechanisms and their ability to form filter deposits.

Interest has been growing in many countries in the potential use of diesel particulate filters (DPF). This type of after treatment technology has been shown to make very significant reductions in both the mass of particulate emitted in diesel exhaust gas, and also in the number of fine particulates, which have been linked in recent years with concerns for human health. Work carried out during a development programme investigating the capability of fuel soluble metallic additives to assist DPF regeneration, indicated superior performance from a novel combination of metals in fuel soluble form. Earlier work showed that a fuel soluble combination of organo-metallic additives based on sodium and strontium gave very effective regeneration characteristics, and was capable of burning out carbon at temperatures from about 160°C.

Diesel particulate filter (DPF) technology is becoming increasingly established as a practical method for control of particulate emissions from diesel engines. In the year 2000, production vehicles with DPF systems, using metallic fuel additive to assist regeneration, became available in Europe. These early examples of first generation DPF technology are forerunners of more advanced systems likely to be needed by many light-duty vehicles to meet Euro IV emissions legislation scheduled for 2005. Aspects requiring attention in second generation DPF systems are a compromise between regeneration kinetics and ash accumulation. The DPF regeneration event is activated by fuel injection, either late in the combustion cycle (late injection), or after normal combustion (post injection), leading to increased fuel consumption. Therefore for optimum fuel economy, the duration of regeneration and/or the soot ignition temperature must be minimised.

In the quest for improved fuel efficiency and reduced CO2 emissions, motor manufacturers are increasingly turning to the High Speed Direct Injection (HSDI) diesel engine for passenger car use. To achieve acceptable levels of noise and emissions at low loads two stage injection is being utilised. Such injection systems are prone to nozzle coking due to the small fuel metering holes, low opening pressures and low fuel flow rates under part load operation. This coking leads to a rapid deterioration of emissions performance. This paper describes work done to investigate conditions leading to this phenomena and the possible mechanisms involved.

For many years now, epidemiologists have been highlighting the potential damage to health and the associated cost, caused by diesel particulate emissions. There is still debate concerning the crucial characteristics of these particles, however many authorities have concluded that it is their duty to legislate the reduction of such emissions. The most common approach is to legislate that all new vehicles should meet ever stricter emissions limits. This puts the onus and the cost on the engine manufacturers. The emissions limits in developing countries are inevitably less stringent than those in the developed world, this gives the indigenous manufacturers the opportunity to compete and develop. However, vehicle replacement intervals dictate that the effect of legislation controlling new vehicles takes many years to propagate throughout the existent vehicle fleet.