Since they were created, diesel engines have been used primarily in the industrial field and in heavy vehicles. This has been due to outstanding characteristics of this kind of engine, including hardness and low consumption.
Although gasoline and diesel engines are used for similar tasks, the latter is preferred when more power is needed. Examples of this are the engines to mobilize locomotives, ships, high capacity generators or cargo vehicles.
The origin of the diesel engine dates back to 1893, in the hands of a worker at a truck company called Rudolf Diesel and from whom it derives its name. This engine followed the same four-stroke cycles as gasoline. The idea was that it had a more efficient thermal efficiency, using alternative volatile fuel.
Once Bosch created the first injector pump for diesel engines in 1927, the goal had been achieved: Develop an internal combustion engine that had a much lower consumption. In addition, it was cheaper, had a higher compression value and could work between 700 and 900 ° C.
What are diesel engines?
Diesel engines are thermal machines that work by alternative internal combustion. Combustion is the product of the auto-ignition that the fuel suffers due to the high-temperature levels generated by the high compression ratio it possesses. The cycle that it fulfills for its operation is known as the Diesel cycle.
It varies with respect to a gasoline engine in the type of fuel it uses, namely gas-oil, diesel or heavy oils, petroleum products. You can also use natural olives, such as sunflowers. In fact, the fuel that was initially used to put the diesel engine to work was peanut oil.
Diesel engine parts
A diesel engine that operates four times has basically the same components as the gasoline engine. Among the elements that make it up are The segments, the engine block, the cylinder head, the crankshaft, the steering wheel, the pistons, the camshaft, and the crankcase. On the other hand, the parts mentioned below are common in both engines (except for preheating nozzles and spark plugs ), but may have a variable design and performance. These are the injection pump, mechanical or electrical; pipelines, injectors (mechanical, electro-hydraulic or piezoelectric); the transfer pump, the nozzles, and the glow plugs.
In the diesel engines, the spark plugs are not found because the explosion is achieved by compression and not by a spark. As these engines have more compression than gasoline, their elements must be robust and resistant to withstand the pressures. Sometimes they can present elements that are also called spark plugs, but they are simple heaters added to the air compression, they do not produce any spark.
- Segments: These are circular and self-tensioned pieces that are placed in the piston grooves. They serve as a mobile hermetic lock between the crankcase and the combustion chamber. They prevent oil leaks when it passes into the combustion chamber while leaving a thin layer of lubricating oil on the walls of the jacket.
- Engine block: It is a structure where the rest of the pieces are placed, such as Crankshaft, camshaft, among others. It has an opening where the cylinders, valve pushrods, antifreeze lines, camshafts and bed support bearings are placed. It also has some holes in the top where the head gaskets are held.
- Cylinder head: It is the piece that closes each cylinder at the top. They are supported for other components such as seesaws, valves, injectors, etc.
- Crankshaft: They are a set of small cranks, one for each piston. Your job is to convert the linear movement into a rotating movement. It is located on the main bearings of the engine block.
- Pistons: These are structures that move from top to bottom, being fundamental elements of the engine. They have 2 to 4 segments. The upper segment is compression and the lower one is greased.
- Camshaft: It is the rotating shaft that is responsible for moving some cams and allows to distribute of the synchronized movement in the engine.
- Crankcase: Also known as a sump, it is the component that closes the engine block and where most of the oil is housed. Surround the crankshaft mainly.
- Injection pump: Device that raises the fuel pressure in the injection system to a high level. When injected, it enters the chamber sprayed to produce spontaneous inflammation. It also distributes the fuel to the cylinders in the proper order of operation.
- Transfer pump: It is the one that constantly feeds the injection pump, using a specific pressure.
- Nozzles: They are responsible for introducing the pulverized diesel into the combustion chamber. They are made up of a piston/cylinder assembly. Towards the end of the cylinder, it has a super fine hole through which the fuel is expelled at high pressure.
- Glow plugs: It is an element that is used to help the diesel engine to start. Some of these engines, in cold conditions, have difficulty starting. Glow plugs direct heat to the block around the cylinders.
How do diesel engines work?
The operation of a diesel engine is the same as that of any internal thermal combustion engine. It presents self-ignition due to the high temperatures offered by the compression of the air inside the cylinder. They vary in relation to those of gasoline by not requiring a spark to ignite. The glow plugs climbing the chamber temperature improve cold start and the heat is used to reach the optimum temperature.
The four-time cycle in diesel engines
- Admission: In the first time of operation the filling of air occurs. The intake valve remains open as the piston goes down to its bottom dead center. The entry of the total amount of air is always allowed, regardless of the load condition. The cooler it is, the lower the density and the more it will enter, causing the combustion to increase.
- Compression: The inlet valve is closed once the piston reaches its lower dead center and begins to rise to the upper one while contracting the air inside the cylinder. The ratio is approximately 18: 1 and at this time the temperature rises significantly.
- Combustion: Shortly before the piston reaches the top dead center, an injector atomizes the fuel into the chamber. The fuel ignites immediately when it comes into contact with the hot air. As you can see, the spark produced by the spark plug is not needed, with the heat that it transmits is sufficient.
- Exhaust: The high temperature generates pressure, pushing the piston down hard. Some of the energy produced here is then used to return to the bottom dead center. The burned gases are expelled, allowing the cycle to start as a result of inertia.
Advantages of the diesel engine
The fuel used for the operation of diesel engines (diesel or gas-oil) has always been considered cheaper and more efficient than gasoline. However, when talking about prices, it should not be overlooked that the vehicles that use these engines are more expensive at the time of purchase and also expensive to maintain.
Even so, and despite the degree of pollution, always greater with diesel engines, more technologies have been developed around them than in the case of gasoline. That is why they have more output and their sales have increased to the point of overcoming them.
It is advisable to purchase a diesel motor vehicle when you plan to travel many kilometers. In this way, the difference in fuel consumption will compensate, in addition to being more durable and have less wear when they circulate at a few revolutions. The most important advantages of using a diesel engine are summarized below.
- Durability and long life: This is the most important of the advantages of diesel-powered engines. As the combustion process is by air compression, this means that they have less wear on the parts and withstand more mileage, comparing them with gasoline.
- Reliability: Since its inception at the end of the 19th century, the diesel engine has been adopted by heavy and hard-working machines. His career in this area has given him fame, making him reliable, especially for his simplicity: Does not require spark plugs, cables, distributor, rotors, etc. The principle of operation has been maintained and it’s few but resistant parts, compared to those of a gasoline engine, make it more reliable in front of the user.
- Economy: Another great advantage is that this kind of engine is capable of rolling up to double the distance of the gasoline engine, consuming the same amount of fuel. The reason is that diesel is denser than gasoline and consequently saves up to 30% of consumption.
- Drag capacity: The diesel engine generates less mechanical torque, known as torque, because of the low revolutions it produces. As a result, there is an increase in the effectiveness and ability to load or drag.
Disadvantages of diesel engines
Although the diesel engine is very reliable and its use implies fewer fuel costs, there are some disadvantages that must be assessed.
- Price: Since historic times the diesel engine is much more expensive compared to gasoline. Although this expense can be balanced with fuel savings, the difference in the initial cost remains considerable.
- Maintenance: This type of engine needs more frequent periodic care than any other type. If regular maintenance is not done, they become very polluting.
- Weight: A diesel engine is much heavier than gasoline, but this aspect is not given as much relevance due to the weight/power ratio of these vehicles.
- Speed: They are less fast engines, although current technological advances have made these generate speeds similar to those that use gasoline.
- Repairs: There is less chance of exchanging parts for technology, durability, and frequency of maintenance. Even so, in case of changes and repairs, labor is more expensive, as are parts and spare parts.
- Noise: Despite the progress made in this kind of engine, these continue to be noisier than gasoline engines.