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Renewable fuels have an important role to create sustainable energy systems. In this paper the focus is on biodiesel, which is produced from vegetable oils or animal fats. Today biodiesel is mostly used as a drop-in fuel, mixed into conventional diesel fuels to reduce their environmental impact. Low quality drop-in fuel can lead to deposits throughout the fuel systems of heavy duty vehicles. In a previous study fuel filters from the field were collected and analyzed with the objective to determine the main components responsible for fuel filter plugging. The identified compounds were constituents of soft particles. In the current study, the focus was on metal carboxylates since these have been found to be one of the components of the soft particles and associated with other engine malfunctions as well. Hence the measurement of metal carboxylates in the fuel is important for future studies regarding the fuel’s effect on engines.

Non-petroleum based liquid fuels are essential for reducing oil dependence and greenhouse gas generation. Increased substitution of alcohol fuel for petroleum based fuels could be achieved by 1) use in high efficiency spark ignition engines that are employed for heavy duty as well as light duty operation and 2) use of methanol as well as ethanol. Methanol is the liquid fuel that is most efficiently produced from thermo-chemical gasification of coal, natural gas, waste or biomass. Ethanol can also be produced by this process but at lower efficiency and higher cost. Coal derived methanol is in limited initial use as a transportation fuel in China. Methanol could potentially be produced from natural gas at an economically competitive fuel costs, and with essentially the same greenhouse gas impact as gasoline. Waste derived methanol could also be an affordable low carbon fuel.

Research conducted at the Supercritical (SC) facility of MIT's Energy Laboratory provided visual confirmation of a single phase, homogeneous water/fuel mixture near the critical temperature and pressure of water. Equal volumes of water and diesel fuel were observed to be completely miscible, and high temperature polymerization of fuel molecules was not found. This is believed to be the first observation of a solution of diesel fuel and water. This mixture was subsequently burned under atmospheric spray conditions with very low NOx, smoke, CO, and HC. The results suggested that in-cylinder combustion in a compression ignition engine was warranted. Tests were conducted in a single cylinder, air-cooled, naturally aspirated, 3.5 horsepower Yanmar diesel engine. The compressibility of this new fuel composition necessitated a modified injector to provide smooth operation.

Long-haul and other heavy-duty trucks, presently almost entirely powered by diesel fuel, face challenges meeting worldwide needs for greatly reducing nitrogen oxide (NOx) emissions. Dual-fuel gasoline-alcohol engines could potentially provide a means to cost-effectively meet this need at large scale in the relatively near term. They could also provide reductions in greenhouse gas emissions. These spark ignition (SI) flexible fuel engines can provide operation over a wide fuel range from mainly gasoline use to 100% alcohol use. The alcohol can be ethanol or methanol. Use of stoichiometric operation and a three-way catalytic converter can reduce NOx by around 90% relative to emissions from diesel engines with state of the art exhaust treatment.

Renewable fuels are essential in the field of heavy duty transportation if we are to reach a fossil-free society in the foreseeable future. However renewable diesel fuels based on fatty acid methyl ester (FAME) might face problems with degradation and with cold flow properties. From the perspective of an engine, this may cause problems in the fuel injection system, such as fuel filter clogging and injector deposits. These phenomena, especially fuel filter clogging, can be connected to gel-like soft particles, which could originate from degradation products as well as from byproducts created during biodiesel refining. In this study, soft particles from the degradation of bio-based diesel fuel were examined. The tested fuels included hydrogenated vegetable oils (HVO), rapeseed methyl ester (RME) and 10% blend of rapeseed methyl ester with standard diesel (B10).

The global demand for decreased emission from engines and increased efficiency drives manufactures to develop more advanced fuel injection systems. Today's compression-ignited engines use common rail systems with high injection pressures and fuel injector nozzles with small orifice diameters. These systems are highly sensitive to small changes in orifice diameters since these could lead to deteriorations in spray characteristics, thus reducing engine performance and increasing emissions. Phenomena that could create problems include nozzle fouling caused by metal carboxylates or biofuels. The problems increase with extended use of biofuels. This paper reports on an experimental study of nozzle hole fouling performed on a single-cylinder engine. The aim was to identify if the solubility of the fuel has an effect on deposit build-up and, thus, the reduction in fuelling with associated torque loss, and if there is a probability of regenerating the contaminated injectors.

The formation of deposits in the fuel systems of heavy-duty engines, using drop-in fuels, has been reported in recent years. Drop-in fuels are of interest because they allow higher levels of alternative fuels to be blended with conventional fuels that are compatible with today’s engines. The precipitation of insolubles in the drop-in fuel can lead to clogging of fuel filters and internal injector deposits, resulting in increased fuel consumption and engine drivability problems. The possible mechanisms for the formation of the deposits in the fuel system are not yet fully understood. Several explanations such as operating conditions, fuel quality and contamination have been reported. To investigate injector deposit formation, several screening laboratory test methods have been developed to avoid the use of more costly and complex engine testing.

Heavy-duty transportation accounts for significant part of the greenhouse gas emissions. Currently the most common powertrain for long-haul trucks is compression-ignited engines. In order to reduce the greenhouse gas emissions of these engines, renewable fuels, such as biodiesel can be used. Today biodiesel is used as a drop-in fuel, however when biodiesel is mixed with conventional diesel, soft particles may form. Soft particles have been identified as a mixture of insoluble impurities and degradation products in the fuel. These soft particles can lead to deposits in the injection and fuel filtration system, leading to reduced engine performance. In this paper, zinc-neodecanoate and soft particles from the degradation of biodiesel is studied. In both cases, the emphasis is on soap type contaminants. Zinc-neodecanoate has shown to lead to nozzle fouling, while soft particles from degradation of biodiesel have been found in diesel fuel filters.

One way to reduce carbon dioxide emissions from the current heavy-duty vehicles fleet is to replace fossil fuel with renewable fuel. This can be done by blending so-called drop-in fuels into the standard diesel fuel. However, problems such as insoluble impurities may arise when the fuels are mixed. These precipitates, known as soft particles, can cause deposits in the fuel system, e.g., injectors and fuel filters, reducing the engine´s performance. The most used drop-in fuel today is biodiesel which, is blended with different concentrations. To better understand how soft particles are formed in the vehicle´s fuel system, the degradation of biodiesel blends in the engine has been investigated. This study explores biodiesel blends´ degradation process by comparing the incoming fuel with the return fuel from a modern diesel engine to investigate how the fuel is affected by this process. The engine was run using different blends of biodiesel fuel.