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The different types of fuel oils |
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What are the different types of fuel? It is only necessary to think of the different types of vehicles: cars, trucks, and planes.
For land-based vehicles, two main types of motor are in use: the petrol engine and the diesel engine. They are quite old now, since they were invented in the 19 th century. Both work on the same principle: that of explosion. They are internal combustion engines. A mixture of air and fuel introduced into a cylinder catches fire and produces combustion gases. These gases move a piston in the cylinder. The energy of the piston moving linearly is converted by a crankshaft into a rotating movement that takes the drive to the vehicle wheels. So what is the main difference between the two types of motor? The ignition of the air/fuel mixture in a petrol engine is caused by external means, by an electric spark provided by the spark plugs. Ignition in diesel engines on the other hand is automatic: the high temperatures and pressures in the cylinder are sufficient to cause spontaneous ignition.
The first explosion motor (1806) worked with hydrogen and the very first diesel motor (1892) with coal powder! Things have changed a lot since then. Petrol engines work on 95- or 98-octane petrol and diesel engines, as their name implies, use diesel fuel. Both 95- and 98-octane petrol is lead-free; a major advance as far as environmental protection is concerned. Until the end of the 20 th century, the best anti-knocking agent known for petrol was tetraethyl lead, (C2H5) 4 – Pb. However a major problem gradually came to light: enormous quantities of lead oxide, a very toxic metal, were being discharged into the atmosphere! Petroleum company research scientists and refiners have been able to adapt to the new environmental requirements, producing lead-free petrol by using other anti-knocking molecules without danger for the environment and compatible with modern engines. The figures 95 and 98 stand for two octane indices, which measure the anti-knocking capacities of a fuel. The closer the octane index to 100, the better it is. |
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| Cross-section of an internal combustion engine. |
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Today the majority of cars use petrol, but diesel cars are becoming more and more common: the fuel is less expensive, consumption is lower, and performance is very close to that of petrol engines. 43% of the total fleet of light private vehicles in France use diesel engines (compared to 33% in 1999, and 60% forecast in 2010). For all vehicles taken together, the diesel engine market will be four times that for petrol by 2010. Other automobile fuels exist but for the moment are little used.
Enormous progress has been made from the point of view of consumption and thus of energy savings. A small car uses approximately 5 l for every 100 km and a big car 10 l for the same distance, that is almost half that of 40 years ago. Formula 1 cars on the other hand have remained very greedy: almost 100 l for 100km! That is the price to be paid for this extraordinary “test bed”, which enables savings at the end of the day in production series of vehicles. Heavy goods vehicles and diesel locomotives both work on diesel fuel.
Fuel for planes is of two types: kerosene (very close to diesel) for large turbine and turbo jet commercial aircraft and aviation petrol (avgas) for light planes with piston engines. Aviation petrol necessitates a very high-octane index (maximum index 100). It is leaded petrol, one of the last to be still in use.
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