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Principle of operation of a diesel engine

Principle of operation of a diesel engine



The diesel engine came after the invention of the gasoline engine. Nicholas Auguste Otto invented and patented the gasoline engine in 1876. His invention used the four-stroke combustion principle, also known as the "Otto cycle," on which most automobile engines still operate today. In the early days, gasoline engines were inefficient, and other major modes of transportation, such as the steam engine, also performed poorly. Only about 10% of the fuel used in these types of engines was actually used to drive the vehicle. The rest of the fuel simply produced useless heat.


In 1878, Rudolf Diesel spent most of his time developing the "combustion engine" and invented a more efficient engine. By 1892, Diesel had patented what we now call the diesel engine.


For decades, the diesel engine was known for its black smoke, odor, and noise. Although the technology was widely adopted in Europe, most drivers in the U.S. did not recognize it. Although diesel engines became cleaner, quieter, and even more efficient in the 21st century, diesel-fueled vehicles suffered an even bigger setback in public opinion due to the 2014 Volkswagen diesel scandal. Despite this, diesel is regaining some ground due to its time-tested efficiency.


Diesel engines vs. gasoline engines

Diesel engines have long been a popular choice for vehicles due to their efficiency and power. Similar to gasoline engines, they are internal combustion engines that convert chemical energy in the fuel into mechanical energy. This mechanical energy is then used to move the vehicle forward.


 One of the key components of a diesel engine is the piston, which moves up and down in the cylinder. As the piston moves upward, it compresses the air inside the cylinder, raising its temperature. At the same time, fuel is injected into the cylinder at high pressure. The combination of high temperature and pressure causes the fuel to spontaneously ignite without the need for a spark plug like in a gasoline engine.


 Ignition of the fuel creates a rapid expansion of hot gases, pushing the piston back into the cylinder. This linear motion is transmitted to the crankshaft, which converts it into rotational motion. The rotational motion is then transferred to the vehicle's wheels, propelling the vehicle forward.


 One of the advantages of diesel engines is their efficiency. Due to their high compression ratio and lack of spark plugs, diesel engines are able to extract more energy from the fuel than gasoline engines. This results in better fuel economy and lower CO2 emissions.


 Diesel engines are also known for their torque. Torque is the twisting force applied to the crankshaft, and diesel engines generally produce more torque than gasoline engines. This makes diesel engines particularly suitable for heavy-duty vehicles such as trucks and SUVs, as well as for towing purposes.


 Diesel engines do have some disadvantages, however. They tend to produce more nitrogen oxides and particulate matter than gasoline engines, which contribute to air pollution. This is why diesel engines are subject to strict emissions regulations in many countries.


 In recent years, there has been growing interest in alternative fuel options for vehicles, including electric and hybrid vehicles. These technologies promise higher efficiency and lower emissions. However, diesel engines remain popular in many industries and applications, especially in areas with limited availability of charging infrastructure.


 To sum up, diesel engines and gasoline engines are similar to internal combustion engines that convert chemical energy in fuel into mechanical energy. The up-and-down motion of the piston creates the rotational motion needed to move the vehicle's wheels forward. Despite higher emissions compared to gasoline engines, diesel engines remain a popular choice due to their efficiency and torque, especially in heavy-duty applications.

In theory, diesel engines and gasoline engines are very similar. They are both internal combustion engines designed to convert the chemical energy available in the fuel into mechanical energy. This mechanical energy moves a piston up and down in the cylinder, which is connected to the crankshaft. The up and down motion of the piston (called linear motion) creates the rotational motion needed to move the wheels of the car forward.


Both diesel and gasoline engines convert fuel into mechanical energy through a series of explosions or combustion. The main difference between a diesel engine and a gasoline engine is the way these explosions occur. In a gasoline engine, the fuel is mixed with air and enters the combustion chamber, where it is compressed by a piston to a point where it is ignited by a spark from a spark plug. However, in a diesel engine, the air is first compressed to a certain level, and then the fuel is injected into the combustion chamber. When the air is compressed to a high pressure, it becomes hot enough to ignite the fuel.


Diesel engines use the same four-stroke combustion cycle as gasoline engines. The four strokes are:

1) Intake Stroke: The intake valve opens to allow air to enter and the piston moves downward.


2) Compression stroke: the piston moves up and compresses the air.


3) Combustion Stroke: When the piston reaches the top, fuel is injected and ignited at just the right moment, forcing the piston back down.


4) Exhaust stroke: The piston returns to the top and pushes the exhaust gases from the combustion out the exhaust valve.


A diesel engine does not have a spark plug to ignite the air-fuel exchange. Instead, it injects fuel directly into the combustion chamber (direct injection). It is the heat of the compressed air that ignites the fuel in a diesel engine.


A major difference between a diesel engine and a gasoline engine is the injection process. Gasoline engines use a combination of inlet injection (injection of fuel prior to the intake stroke) and direct fuel injection. Intake jetting is used at lower engine speeds because it has a more stable mixture of air and fuel. Direct injection is used at higher speeds to provide more power and less chance of detonation. Diesel engines use only direct fuel injection - diesel fuel is injected directly into the cylinders.

The fuel injector on a diesel engine is its most complex component and remains at the center of diesel engine research - it may be located in different places in different engines. The injector must be able to withstand the high temperatures and pressures in the cylinder and must deliver the fuel in the form of a fine mist. Circulating the fuel mist through the cylinders so that it is evenly distributed is also a problem, so some diesel engines use special intake valves, pr-combustion chambers, or other devices to rotate the air in the combustion chamber or otherwise improve the ignition and combustion process. (Continued next week)



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