Diesel engine: structure, principle of operation, advantages

The diesel engine (diesel) is a piston internal combustion engine, the principle of operation of which is based on the self-ignition of fuel under the influence of hot compressed air. If you can’t get the engine repaired, or if you don’t think it makes sense, recycle the machine: https://towingandscrapcarremoval.ca/scrap-car-removal-newmarket.

Operating principle of the diesel engine

The operating principle of the diesel engine is based on the compression ignition of fuel, which enters the combustion chamber and mixes with the hot air mass. The diesel operating process depends solely on the inhomogeneity of the FAM (fuel-air mixture). The fuel-air mixture in this type of engine is fed separately.

At the beginning the air is supplied, which in the process of compression is heated to high temperatures (about 800 degrees Celsius), then the fuel is fed into the combustion chamber under high pressure (10-30 MPa), after which it selfignites.

The process of fuel ignition is always accompanied by high levels of vibration and noise, so diesel engines are noisier in comparison with gasoline counterparts.

This principle of operation of diesel allows the use of more affordable and cheap (until recently 🙂 ) types of fuel, reducing the level of costs for its maintenance and refueling.

Diesels can have either 2 or 4 working cycles (intake, compression, stroke and exhaust). Most vehicles are equipped with 4-stroke diesel engines. 

Types of Diesel Engines

Diesel engines can be divided into three types based on combustion chamber design:

With a divided combustion chamber. In these devices, the fuel is not fed to the main combustion chamber, but to an additional, so-called vortex chamber, which is located in the cylinder head and is connected to the cylinder by a channel. When the air mass enters the swirl chamber, it is compressed as much as possible, thereby improving the ignition process of the fuel. The auto-ignition process begins in the vortex chamber, then proceeds to the main combustion chamber.

With undivided combustion chamber. In these diesel engines, the combustion chamber is located in the piston, and the fuel is fed into the space above the piston. Undivided combustion chambers on the one hand allow saving fuel consumption, and on the other hand – raising the noise level of the engine.

Pre-combustion chamber engines. Such diesel engines are equipped with an inserted pre-chamber, which is connected to the cylinder by thin channels. The shape and size of the channels determine the speed of gas movement during fuel combustion, reducing noise and toxicity, and increasing engine life. 

Fuel system in a diesel engine

The basis of any diesel engine is its fuel system. The main task of the fuel system is the timely supply of the required amount of fuel mixture at a given working pressure.

Diesel engine fuel system

The important elements of the fuel system in a diesel engine are:

high pressure fuel pump (HPP);

fuel filter;


fuel pump

The pump is responsible for supplying fuel to the injectors according to the set parameters (depending on RPM, operating position of the regulator lever and turbocharger pressure). Two types of fuel pumps can be used in modern diesel engines – in-line (plunger) and distribution pumps.

Fuel filter

The filter is an important part of a diesel engine. The fuel filter is selected strictly according to the type of the engine. It has the function of filtering out and removing the water from the fuel, and any extra air from the fuel system.


Nozzles are no less important elements of the fuel system in a diesel. Timely delivery of the fuel mixture into the combustion chamber is only possible if the fuel pump and injectors work together. Two types of injectors are used in diesels – multihole and font distributor. The nozzle distributor determines the shape of the flare, ensuring a more efficient self-ignition process.

Cold start and turbocharging of a diesel engine

Cold start is responsible for the preheating mechanism. This is provided by electric heating elements – glow plugs, which the combustion chamber is equipped with. When starting the engine, the glow plugs reach a temperature of 900 degrees, heating the air mass that enters the combustion chamber. Power is removed from the glow plug 15 seconds after the engine starts. Pre-start heating systems ensure that the engine starts safely, even in low atmospheric temperatures.

The turbocharger is responsible for increasing the power and efficiency of the diesel engine. It supplies more air for a more efficient combustion process and increases the operating power of the engine. A special turbocharger is used to provide the necessary supercharging pressure for the air mixture in all operating conditions of the engine.

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