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As the world market develops for biodiesel fuels, it is likely that a wider variety of biodiesels will become available, both locally and globally, and require engines to operate on a wider variety of fuels than experienced today. At the same time, tighter emissions regulations and a drive for improved fuel economy have focused interest on advanced combustion modes such as HCCI or PCCI, which are known to be more sensitive to fuel properties. This research covers two series of biodiesel fuels. In the first, B20 blends of natural methyl esters derived from palm, coconut, rape, soy, and mustard were evaluated at light load in an HCCI research engine to determine combustion and performance characteristics. These fuels showed performance differences between the biodiesels and the base #2 ULSD fuel, but did not allow separation of chemical effects due to the small number of fuels and correlation of various properties.

The influence of various diesel fuel properties on the steady state emissions and performance of a Cummins light-duty (ISB) engine modified for single cylinder operation has been studied at the mid-load “cruise” operating condition. Designed experiments involving independent manipulation of both fuel properties and engine control parameters have been used to build statistical engine response models. The models were then applied to optimize for the minimum fuel consumption subject to specific constraints on emissions and mechanical limits and also to estimate the optimum engine control parameter settings and fuel properties. The study reveals that under the high EGR, diffusion-burn dominated conditions encountered during the experiments, NOx is impacted by cetane number and the distillation characteristics. Lower T50 (mid-distillation temperature) resulted in simultaneous reductions in both NOx and smoke, and higher cetane number provided an additional small NOx benefit.

Fuel additives are used in diesel fuel for various reasons. For example, poor lubricity of some low sulfur and ultra low sulfur fuels necessitate the addition of lubricity additives to maintain acceptable protection of fuel system components. However, with today's high pressure fuel systems and lubricant oil recycling practices, some lubricant mixing with the fuel is unavoidable. As a result, an increase in fuel filter plugging was reported when lubricant components are present in the fuel. This paper shows filter plugging resulted from the interaction of basic lubricant additives with acidic fuel additives. Attempts to reduce the plugging by supplemental fuel additives were technically successful, but not economically feasible. The linkage between filter plugging and additive interactions is demonstrated in this paper. Part II of this series will explore the mechanisms of the additive interactions, and other causes for filter plugging.

Sulfur containing species as well as other polar molecules provide lubricity and thermal stability to diesel fuels. During the refining process to produce low and ultra-low sulfur diesel fuels, these components are removed. As a result, fuel additives such as lubricity agents and antioxidant may be added to protect fuel stability and prevent fuel pump wear. Some lubricity additives, such as dimer acids, resulted in fuel filter plugging. The plugging mechanism was related to the capability of aliphatic acids to form agglomeration by interactions with the overbased detergents, delivered into the fuel as oil contaminants. Other sources of acids, derived from thermal degradation, can lead to the same problem. In this study, individual lubricant additives were mixed in the fuel to form single- and dual-component systems. Levels of compatibility and amounts of interaction products were evaluated for individual solutions.

Sulfur poisoning from engine fuel and lube is one of the most recognizable degradation mechanisms of a NOx adsorber catalyst system for diesel emission reduction. Even with the availability of 15 ppm sulfur diesel fuel, NOx adsorber will be deactivated without an effective sulfur management. Two general pathways are currently being explored for sulfur management: (1) the use of a disposable SOx trap that can be replaced or rejuvenated offline periodically, and (2) the use of diesel fuel injection in the exhaust and high temperature de-sulfation approach to remove the sulfur poisons to recover the NOx trapping efficiency. The major concern of the de-sulfation process is the many prolonged high temperature rich cycles that catalyst will encounter during its useful life. It is shown that NOx adsorber catalyst suffers some loss of its trapping capacity upon high temperature lean-rich exposure.

Diesel engines are far more efficient than gasoline engines of comparable size, and emit less greenhouse gases that have been implicated in global warming. In 2000, the US EPA proposed very stringent emissions standards to be introduced in 2007 along with low sulfur (< 15 ppm) diesel fuel. The California Air Resource Board (CARB) has also established the principle that future diesel fueled vehicles should meet the same low emissions standards as gasoline fueled vehicles and the EPA followed suit with its Tier II emissions regulation. Achieving such low emissions cannot be done through engine development and fuel reformulation alone, and requires application of NOx and particulate matter (PM) aftertreatment control devices. There is a widespread consensus that NOx adsorbers and particulate filter are required in order for diesel engines to meet the 2007 emissions regulations for NOx and PM. In this paper, the key exhaust characteristics from an advanced diesel engine are reviewed.

Tests of ultra-low sulfur diesel blended with soy-biodiesel at 5% and 20% were conducted using a 2002 model year Cummins ISB engine (with exhaust gas recirculation) that had been retrofitted with a passively regenerated catalyzed diesel particulate filter (DPF). Results show that on average, the DPF balance point temperature (BPT) is 45°C and 112°C lower for B20 blends and neat biodiesel, respectively, than for 2007 certification diesel fuel. Biodiesel causes a measurable increase in regeneration rate at a fixed steady-state condition, even at the 5% blending level. The data show no significant differences in NOx emissions for these fuels at the steady-state regeneration conditions, suggesting that differences in soot reactivity are responsible for the observed differences in BPT and regeneration rate.