The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which the fuel is ignited by the increased temperature of the air in the cylinder as a result of mechanical compression; thus, the diesel engine is a so-called compression-ignition engine. This is in contrast to engines that use spark plug ignition of the air-fuel mixture, such as a gasoline engine or a gas engine.
Diesel engines work by compressing only air or air plus residual combustion gases from the exhaust. Air is introduced into the chamber during the intake stroke and compressed during the compression stroke. This increases the air temperature in the cylinder so much that atomized diesel fuel that is injected into the combustion chamber ignites.
Since the fuel is injected into the air just before combustion, the distribution of the fuel is uneven; this is called a heterogeneous air-fuel mixture. The torque produced by a diesel engine is controlled by manipulating the air-fuel ratio (λ); Instead of throttling the intake air, the diesel engine relies on a change in the amount of fuel injected, and the air-fuel ratio is usually high.
The diesel engine has the highest thermal efficiency (engine efficiency) of any practical internal or external combustion engine due to its very high expansion ratio and its inherent lean burn, which allows heat dissipation through the excess air.
A small efficiency loss is also avoided compared to non-direct injection petrol engines as there is no unburned fuel during valve overlap and therefore no fuel passes directly from intake/injection to exhaust.
Low-speed diesel engines can achieve effective efficiencies of up to 55%. The combined cycle gas turbine is an internal combustion engine that is more efficient than a diesel engine, but its mass and dimensions make it unsuitable for vehicles, watercraft, or aircraft.
Diesel vehicles are similar to gasoline vehicles because they both use internal combustion engines. One difference is that diesel engines have a compression-ignited injection system rather than the spark-ignited system used by most gasoline vehicles.
In a compression-ignited system, the diesel fuel is injected into the combustion chamber of the engine and ignited by the high temperatures achieved when the gas is compressed by the engine piston.
Unlike the emission control systems on gasoline vehicles, many diesel vehicles have additional after-treatment components that reduce particulate matter and break down dangerous nitrogen oxide (NOx) emissions into harmless nitrogen and water. Diesel is common transportation fuel, and several other fuel options use similar engine systems and components.
Animation showing the four stages of a diesel engine: intake, compression, power, and exhaust.
Like a gasoline engine, a diesel engine normally works by repeating a cycle of four stages or strokes during which the piston moves up and down twice during the cycle (in other words, the crankshaft rotates twice).
In a two-stroke diesel, the complete cycle happens with the piston moving up and down just once. Confusingly, there are really three phases in a two-stroke cycle:
Two-stroke engines are smaller and lighter than four-stroke engines and tend to be more efficient because they generate electricity once per revolution (rather than once every two revolutions like a four-stroke engine). This means they require more cooling and lubrication and are subject to higher wear.
There are three basic size groups of diesel engines based on power—small, medium, and large.
The small engines have power-output values of less than 188 kilowatts or 252 horsepower. This is the most commonly produced diesel engine type. These engines are used in automobiles, light trucks, and some agricultural and construction applications and as small stationary electrical-power generators (such as those on pleasure craft), and as mechanical drives. They are typically direct-injection, in-line, four- or six-cylinder engines. Many are turbocharged with aftercoolers.
Medium engines have power capacities ranging from 188 to 750 kilowatts, or 252 to 1,006 horsepower. The majority of these engines are used in heavy-duty trucks. They are usually a direct injection, in-line, six-cylinder turbocharged, and aftercooled engines. Some V-8 and V-12 engines also belong to this size group.
Large diesel engines have power ratings in excess of 750 kilowatts. These unique engines are used for marine, locomotive, and mechanical drive applications and for electrical power generation. In most cases, they are direct injection, turbocharged, and aftercooled systems. They may operate at as low as 500 revolutions per minute when reliability and durability are critical.
Diesel engines are commonly used as mechanical engines, power generators, and mobile drives. They find widespread use in locomotives, construction equipment, automobiles, and countless industrial applications. Their realm extends to almost all industries and can be observed on a daily basis if you were to look under the hood of everything you pass by.
Industrial diesel engines and diesel-powered generators have construction, marine, mining, hospital, forestry, telecommunications, underground, and agricultural applications, just to name a few. Power generation for prime or standby backup power is the major application of today’s diesel generators. Check out our article on the various types of engines and generators and their common applications for more examples.
The diesel engine is much more efficient and preferable as compared with gasoline engine due to the following reasons:
Diesel engine, any internal-combustion engine in which air is compressed to a sufficiently high temperature to ignite diesel fuel injected into the cylinder, where combustion and expansion actuate a piston.
As with petrol engines, diesel engines are started by being turned with an electric motor, which begins the compression-ignition cycle. When cold, however, diesel engines are difficult to start, simply because. compressing the air does not lead to a temperature that is high enough to ignite the fuel.
Petrol and diesel come from crude oil, which comes from deep underground. Crude oil is refined to make petrol (in America this is known as gasoline) or diesel. Most forms of transport use either petrol or diesel to power their engines – from lawnmowers, cars, buses, and motorbikes to large ships and airoplanes.
The major components in a diesel engine:
Conceptually, diesel engines operate by compressing air to high pressure/temperature and then injecting a small amount of fuel into this hot compressed air. The high temperature causes the small amount of highly atomized injected fuel to evaporate.
Diesel engines are sometimes called compression-ignition engines because initiation of combustion relies on air heated by compression rather than on an electric spark. In a diesel engine, fuel is introduced as the piston approaches the top dead centre of its stroke.
There are two classes of diesel engines: two-stroke and four-stroke. Most diesel engines generally use the four-stroke cycle, with some larger engines operating on the two-stroke cycle.
A diesel engine takes air, compresses it, and then injects fuel into the compressed air. The heat of the compressed air ignites the fuel spontaneously. A diesel engine does not contain a spark plug.
Diesel delivers more power at lower engine revs than their petrol equivalent. This makes diesel feel more suited to longer motorway trips because they’re not working as hard as petrol engines to produce the same performance. This also helps to make diesel cars better suited for towing.
When it comes to efficiency, diesel engines provide more efficiency by using 15-20% less fuel compared to petrol engines. The low-end torque of diesel engines provides a much better highway driving experience. However, the price of this efficiency is a higher premium compared to the petrol variant of the same car.
Diesel fuel is made from crude oil and biomass. Most of the diesel fuel produced and consumed in the United States is refined from crude oil at petroleum refineries. U.S. petroleum refineries produce an average of 11 to 12 gallons of diesel fuel from each 42-gallon (U.S.) barrel of crude oil.
Diesel engines are still more efficient than gas engines, but less so for those who are mostly engaged in city driving. Diesel cars also have more torque, which results in better fuel economy along with more impressive acceleration.
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-called compression-ignition engine (CI engine).
Diesel fuel is the common term for the distillate fuel oil sold for use in motor vehicles that use the compression ignition engine named for its inventor, German engineer Rudolf Diesel. He patented his original design in 1892. Diesel fuel is refined from crude oil and from biomass materials.
Three basic size groups. There are three basic size groups of diesel engines based on power—small, medium, and large.
A premium diesel has a higher cetane number, better lubricity, and includes detergents that provide injector-cleaning capability versus standard #2 diesel. Cetane measures a fuel’s ignition delay. Higher cetane equals a shorter delay and better ignition quality for quicker start-ups and less pollution.
Diesel fuel usually costs more. Servicing can be more expensive, although you don’t need to do it as often. Diesel cars produce a lot more NO2. Diesel engines can be slightly noisier.
When it comes to efficiency, diesel engines provide more efficiency by using 15-20% less fuel compared to petrol engines. The low-end torque of diesel engines provides a much better highway driving experience. However, the price of this efficiency is a higher premium compared to the petrol variant of the same car.
In the 1890s, Rudolf Diesel invented an efficient, compression ignition, internal combustion engine that bears his name.
Diesel had the intention of developing an internal combustion engine and worked on the idea for several years, which led to his introduction of a prototype in 1893 and the first diesel engine production model in 1897.
Gasoline rose to prominence in 1892 while diesel took a little longer with some sources pointing to 1893 when it was first used and recognized as a fuel source. So, with that in mind, gasoline was technically the first, as it gained popularity and commercial success faster than its diesel counterpart.
Rudolf Diesel’s first compression ignition engines ran on peanut oil at the World Exposition in Paris.
The first true car engine is typically credited to Karl Benz. After years of being obsessed with bicycles and technology, Benz developed what’s taken to be the first gasoline-powered automobile in 1885. The engine in question was a single-cylinder four-stroke contraption.
