Page 1 of 17 Type Paper Number Here Soot Investigation on Fish Oil Spray Combustion in a Constant Volume Cell M. Malin, V. Krivopolianskii, B.M. Rygh, V. Aesoy, E. Pedersen Copyright © 2014 SAE International Abstract Maritime environmental regulations stipulate lower emissions from the shipping industry. To cope with these rules, improving the combustion processes, make use of cleaner alternative fuels and implement exhaust gas cleaning systems is necessary. Alternative fuels, like fish oil, have a potential to reduce soot formation during the combustion process and will be deeply investigated in this paper. For this purpose, two different types of fish oil and their blends with marine gas oil (MGO) have been tested in a constant volume pre-combustion cell (CVPC). The CVPC laboratory was built in collaboration between MARINTEK and NTNU. To generate similar injection condition in the combustion cell as in an internal combustion engine, the CVPC is heated using a chemical heating process. The CVPC is used as a fundamental investigation tool for studying the fuel injection system for large engine applications. Parameters that were studied include the combustion, spray development, fuel evaporation process and ignition delay. The general experimental setup of the test facility is described and the optical methods applied are explained for the investigation of fish oil. The aim is to study soot intensity and spray development and to compare the results to pure low-sulphur MGO as a reference fuel. The results conclude that the combustion and ignition properties of fish oil are very similar to marine gas oil and this makes it applicable as an alternative fuel for power generation in the maritime industry. The tests also showed a significant decrease in soot formation for the two fish oils. Introduction As the earth’s population and peoples standard of living increases, the global society is faced with an increasing energy demand. Fossil fuels have been a reliable source of energy in the past and will continue to be an important energy source in the future. However, fossil energy sources are finite and new energy sources must be investigated to ensure energy security in the future. Biologically derived fuels have the advantage of being produced from organic material and are hence renewable. Biofuels are also carbon neutral and their use will prevent further build-up of carbon dioxide in the atmosphere. The marine industry is in these days facing stricter emission regulations and the introduction of new and expansion of existing emission controlled areas means that the industry will be needing cleaner fuels. As cleaner more refined petroleum products are expensive, biofuels can be an economically viable alternative. Biofuel shows positive effects on greenhouse gas (GHG) emissions, but based on the production pathway the magnitude of savings are varying. A Well-To-Wheel (WTW) analysis conducted by the European Environment Agency in 2006 [1] shows GHG emission savings in the range of 50% - 90% and an analysis done by the European Commission in 2011 [2] conclude with savings in the range of 40% - 70%. Studies on emission characteristics from the combustion of biodiesel are well documented and there seems to be an established consensus of the positive and negative impact biofuels have on emission characteristics. The main difference in chemical structure between biodiesel and petroleum diesel are the fuel bound oxygen found in the ester group of the biodiesel. This oxygen is believed to be the main reason for differences in emission characteristics. Increased oxygen content promotes the mixing process leading to a cleaner, more complete, combustion, which reduces the emissions of unburned hydrocarbons [3]. More oxygen also facilitates oxidation of carbon to carbon monoxide and further to carbon dioxide. This decreases the emissions of soot and carbon monoxide. The soot emissions are further decreased by the biofuels lack of aromatics, which is believed to be the origin of polycyclic aromatic hydrocarbons, also causing soot emissions [4]. In addition, emissions of sulphur oxides are eliminated due to the biofuels lack of sulphur. However, emissions of nitrogen oxides are believed to increase [5], [6], [7] and the heating value is reduced. This is also contributed to the increased oxygen content. The increased oxygen content improves the combustion process leading to a higher combustion temperature, which facilitates the oxidation of nitrogen. The oxygen also occupies volume otherwise used by hydrocarbons and these results in the biofuels lower energy content compared to petroleum diesel. Two different biofuels and their blends (in sum six fuels) based on fish waste are tested in this study. One is an unprocessed crude fish oil (CFO) produced from category two aquatic products. Category two aquatic products is farmed fish that has died or been killed for other reasons than human consumption. The main problem with this fuel is the high viscosity and low volatility compared to petroleum diesel [8]. For these reasons, the other biofuel is processed through transesterification of fish oil to produce a biofuel with similar viscosity and volatility as petroleum diesel. Fatty acid oils contain triglycerides, which are esters that consist of one glycerol molecule and three fatty acid molecules. In the transesterification process, the oil is reacted