The NO x can be reduced through pre-injection with small amount fuel; this prevents a long period of ignition delay and therefore leads to a lower peak pressure; for the latter, EGR is always an effective way to reduce NO x emission.
Due to the induction of exhaust gas, the global in-cylinder temperature is reduced, avoiding the thermal conditions favoured by NO x formation. Ladommatos et al. Biodiesel is the most promising fuel in the near future as an alternative to fossil diesel. Despite of its advantages, it still has some disadvantages such as source for massive feedstock, relatively poor low-temperature properties, increase in NO x emissions, etc.
These issues should be sorted out before biodiesel is applied into diesel engines in a large scale. Therefore, in-depth studies on the application of biodiesel into diesel engines are necessary. The research on alternative feedstocks is also an important area and the second-generation biodiesel is more promising made from algae and the genetic modification is a potential way to solve this problem of source of massive feedstock.
The low-temperature fuel properties can be improved by additives or the production routine. In addition, diesel engines should also be optimised in order to achieve the optimal performance and emissions. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3. Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications. Edited by Zhen Fang. We are IntechOpen, the world's leading publisher of Open Access books.
Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Introduction 1. Table 1. Biodiesel Among the alternatives for fossil diesel, biodiesel has been widely investigated due to its renewability, comparable properties to fossil diesel and the reduction in main emission products. History Vegetable oil has been used in diesel engine long time ago.
Production process There are several ways used to produce FAME through vegetable oil, pyrolysis, cracking and transesterification. Biodiesel standards Due to the difference in the feedstock and manufacturing process, the FAME products may vary very much.
Table 2. Biodiesel Standards. Security of supply Another reason for the search of alternative fuel is the energy security. Table 3. Fuel composition Due to the various feedstocks for biodiesel, the fuel composition varies in a wide range.
Viscosity Viscosity is a measure of resistance to flow of a liquid due to internal friction and it is one of the most important parameters in evaluate the fuel quality. Cetane number CN CN is used to evaluate fuel ignition quality determined by the time between start of injection and start of combustion.
Low-temperature property Diesel engines may encounter the start-up and performance problems at low temperatures. Generally, the low-temperature properties can be improved by following methods: Blending with fossil diesel blending with additives Crystallization fractionation by decreasing the saturated alkyl ester content in the biodiesel.
Employing branched esters. Fuel spray characteristics Injection spray is the process that fuel is injected from nozzle, and it is associated with following fuel atomisation, interaction with surrounding gas, mixture formation and combustion. Near-field spray characteristics In the near-field of nozzle, the spray is dominated by the injection dynamics while the spray is affected by the ambient conditions in the far field.
Macroscopic spray characteristics Normally, biodiesel shows a longer penetration and narrower spray angle than fossil fuel due to the higher viscosity, surface tension and density. Sauter Mean diameter SMD SMD is one of the parameters to evaluate fuel atomisation quality and represents the ratio of total droplet volume to surface area.
Wear Performance and Durance In diesel engines, the engine parts are lubricated by the fuel itself. Engine Output performance The adaptability of biodiesel in diesel engines has been well studied from low blend ratio to neat biodiesel. Combustion characteristics In diesel engines, combustion is to release energy contained in fuel, then impart work on piston, and power the engine. Emissions 3. Regulated emissions A number of studies on the engine emissions of engines powered by biodiesel or blends have been carried out.
There are several main reasons have been suggested: Advanced injection timing Oxygen content in biodiesel Double bond Radiative heat transfer Higher adiabatic flame temperature An advanced injection timing due to the higher bulk modulus of biodiesel in pump-in-line injection system leads to the earlier start of combustion, resulting in higher in-cylinder temperature, which can increase NO x emission [ 29 , 2 ].
Unregulated emissions For other unregulated emissions from an engine fuelled with biodiesel, polycyclic aromatic hydrocarbon PAH and nitro PAH compounds are substantially reduced, as well as the lower levels of some toxic and reactive HC species [ 26 ]. Engine emission optimisation Two popular methods have been used to reduce the engine out emission for biodiesel-fuelled engines: injection strategy and EGR.
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Euro 2. Euro 3. Euro 4. Euro 5. Euro 6 future. Austrian Standard C Feb. Australian Bio-diesel Standard. Euro Standard EN Flash point. Total sulphur. Cetane number. Sulfated ash content. Water content. Total contamination. Neutralisation value. Biodiesel also reduces tailpipe emissions, including the amount of soot and "air toxics" released into the atmosphere.
Unlike petroleum diesel, which contains sulfur and carcinogenic benzene, two components the state emissions boards and EPA regulate, biodiesel is nontoxic and biodegradable. Because of its lower emissions and the national drive to reduce reliance on petroleum, biodiesel is the U. It is used by all four branches of the U. It is often used on farms, in manufacturing equipment, and in the construction industry.
Because the demand for biodiesel is growing, producers will be able to increase production, making biodiesel more widely available for consumers. Using biodiesel fuel in diesel engines helps further reduce emissions and reduces the country's dependence on foreign oil. Moreover, vehicles can run on biodiesel without needing any modifications.
One of the greatest concerns over using biodiesel fuel has been regarding its quality and long-term effects on diesel vehicles. However, to address these concerns, the National Biodiesel Board worked with car and engine manufacturers , regulators, and the biodiesel industry to create national standards for pure biodiesel and blends.
The other major concern is how fueling stations treat biodiesel compared to other fuels. Because it's made using vegetable-based products, it must be stored at the correct temperature. If it's left for too long in a warm storage tank, it can grow mold.
Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. Although light-, medium-, and heavy-duty diesel vehicles are not technically alternative fuel vehicles, almost all are capable of running on biodiesel blends.
B20 and lower-level blends can be used in many diesel vehicles without any engine modification. Biodiesel raises the cetane number of the fuel and improves fuel lubricity.
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