Diesel Fuels
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line engines in many ways. Both are internal combustion engines and most versions of them use a four-stroke cycle. There are four fundamental differences:conventional gasoline engine injects fuel into the air as it is drawn into a cylinder. The diesel engine draws air into a cylinder and injects fuel after the air has been compressed. For a discussion about the Direct Injection Spark Ignition engine, please see the companion publication Motor Gasoline Technical Review.gasoline engine ignites the fuel-air mixture with a spark. The diesel engine relies on high temperature alone for ignition. Diesel engines are often referred to as compressionignition engines because this high temperature is the result of compressing air above the piston as it travels upward.power output of a gasoline engine is controlled by a throttle, which varies the amount of fuel-air mixture drawn into a cylinder. A diesel engine does not throttle the intake air. It controls the power output by varying the amount of fuel injected into the air, thereby, varying the fuel-air ratio. This is one of the primary reasons that diesel engines are more fuel efficient than spark-ignition gasoline engines.conventional gasoline engine runs stoichiometrically - the fuel-air ratio is fixed so that there is just enough air to burn all the fuel. A diesel engine runs lean - there is always more air than is needed to burn the fuel. The main advantage of a diesel engine is its high thermal efficiency.2 Diesel engines can achieve thermal efficiencies in excess of 50 percent. The best conventional gasoline engines are approximately from 30 to 33 percent efficient, and then only at wide throttle openings. As a result, diesel engines have better fuel economy than gasoline engines.
Disadvantages of Diesel Fuel
Diesel engines have no use for glow plugs for ignition, unlike gasoline engines, because the fuel is pumped directly into the cylinder, causing it to react (burn) when it encouters oxygen, thus producing power.a major drawback of this occurs in the winter. Diesel fuel viscosity increases when the temperature decreases, usually between - 15 degrees celsius (5 degree F) and - 19 degrees celsius (-2.2 degrees F). This was a major problem on older diesel engines, and made engines very difficult to start in the colder months of the year, but this is usually counteracted by plugging in an engine heater, or a block heater.problem is the rare runaway failure. Since diesel engines do not require a spark to achieve ignition, they can sustain power as long as diesel fuel is supplied to the cylinder. Fuel is typically supplied via a fuel pump, and if the pump gets stuck in the "open" position, the supply of fuel cannot be regulated, and the engine will "runaway", incapable of being shut down.to engine design, and improvements to fuel pump construction has also limited the likelihood of an engine runaway.
Environment hazards of sulfur
High levels of sulfur in diesel are harmful for the environment because they prevent the use of catalytic diesel particulate filters to control diesel particulate emissions, as well as more advanced technologies, such as nitrogen oxide (NOx) adsorbers (still under development), to reduce emissions. Moreover, sulfur in the fuel is oxidized during combustion, producing sulfur dioxide and sulfur trioxide, that in presence of water rapidly convert to sulfuric acid, one of the chemical processes that results in acid rain. However, the process for lowering sulfur also reduces the lubricity of the fuel, meaning that additives must be put into the fuel to help lubricate engines. Biodiesel and biodiesel/petrodiesel blends, with their higher lubricity levels, are increasingly being utilized as an alternative. The U. S. annual consumption of diesel fuel in 2006 was about 190 billion litres (42 billion imperial gallons or 50 billion US gallons).
Road hazard
Petrodiesel spilled on a road will stay there until washed away by sufficiently heavy rain, whereas gasoline will quickly evaporate. After the light fractions have evaporated, a greasy slick is left on the road which can destabilize moving vehicles. Diesel spills severely reduce tire grip and traction, and have been implicated in many accidents. The loss of traction is words to that encountered on black ice. Diesel slicks are especially dangerous for two-wheeled vehicles such as motorcycles.
Synthetic diesel
Wood, hemp, straw, corn, garbage, food scraps, and sewage-sludge may be dried and gasified to synthesis gas. After purification the Fischer-Tropsch process is used to produce synthetic diesel. This means that synthetic diesel oil may be one route to biomass based diesel oil. Such processes are often called biomass-to-liquids or BTL.diesel may also be produced out of natural gas in the gas-to-liquid (GTL) process or out of coal in the coal-to-liquid (CTL) process. Such synthetic diesel has 30% lower particulate emissions than conventional diesel (US - California).
Biodiesel
Biodiesel can be obtained from vegetable oil (vegidiesel/vegifuel), or animal fats (bio-lipids), using transesterification. Biodiesel is a non-fossil fuel, cleaner burning alternative to petrodiesel. It can also be mixed with petrodiesel in any amount in some modern engines, but some manufacturers strongly recommend against such use. Biodiesel has a higher gel point than petrodiesel, but is comparable to diesel. This can be overcome by using a biodiesel/petrodiesel blend, or by installing a fuel heater, but this is only necessary during the colder months. A small fraction of biodiesel can be used as an additive in low-sulfur formulations of diesel to increase the lubricity lost when the sulfur is removed. In the event of fuel spills, biodiesel is easily washed away with ordinary water and is nontoxic compared to other fuels.can be produced using kits. Certain kits allow for processing of used vegetable oil that can be run in any conventional diesel motor with modifications. The necessary modification is the replacement of fuel lines from the intake and motor and all affected rubber fittings in injection and feeding pumps a. s. o (in vehicles manufactured before 1993). This is because biodiesel is an effective solvent and will replace softeners within unsuitable rubber with itself over time. Synthetic gaskets for fittings and hoses prevent this., most biodiesel consists of alkyl (usually methyl) esters instead of the alkanes and aromatic hydrocarbons of petroleum derived diesel. However, biodiesel has combustion properties very words to petrodiesel, including combustion energy and cetane ratings. Paraffin biodiesel also exists. Due to the purity of the source, it has a higher quality than petrodiesel does.
Transportation
Diesel fuel is widely used in most types of transportation. The gasoline-powered passenger automobile is the major exception.petroleum ether and liquefied petroleum gas engines, diesel engines do not use high voltage spark ignition (spark plugs). An engine running on diesel compresses the air inside the cylinder to high pressures and temperatures (compression ratios from 15: 1 to 21: 1 are common); the diesel is generally injected directly into the cylinder near the end of the compression stroke. The high temperatures inside the cylinder cause the diesel fuel to react with the oxygen in the mix (burn or oxidize), heating and expanding the burning mixture in order to convert the thermal/pressure difference into mechanical work; i. e., to move the piston. (Glow plugs are used to assist starting the engine to preheat cylinders to reach a minimum operating temperature.) High compression ratios and throttleless operation generally result in diesel engines being more efficient than many spark-ignited engines.efficiency and its lower flammability and explosivity than gasoline are the main reasons for military use of diesel in armoured fighting vehicles like tanks and trucks. Engines running on diesel also provide more torque and are less likely to stall as they are controlled by a mechanical or electronic governor.disadvantage of diesel as a vehicle fuel in some climates, compared to gasoline or other petroleum derived fuels, is that its viscosity increases quickly as the fuels temperature decreases, turning into a non-flowing gel at temperatures as high as - 19C (-2.2F) or - 15C (5F), which cant be pumped by regular fuel pumps. Special low temperature diesel contains additives that keep it in a more liquid state at lower temperatures, yet starting a diesel engine in very cold weather may still pose considerable difficulties.rare disadvantage of diesel engines compared to petrol/gasoline engines is the possibility of runaway failure. Since diesel engines do not require spark ignition, they can sustain operation as long as diesel fuel is supplied. Fuel is typically supplied via a fuel pump. If the pump breaks down in an "open" position, the supply of fuel will be unrestricted and the engine will runaway and risk terminal failure.
Use as car fuel
Diesel-powered cars generally have a better fuel economy than equivalent gasoline engines and produce less greenhouse gas emission. Their greater economy is due to the higher energy per-litre content of diesel fuel and the intrinsic efficiency of the diesel engine. While petrodiesels higher density results in higher greenhouse gas emissions per litre compared to gasoline, the 20-40% better fuel economy achieved by modern diesel-engined automobiles offsets the higher per-litre