The modern diesel engine is an efficient device with high efficiency. If earlier diesel engines were installed on agricultural machinery (tractors, combines, etc.), at present they are equipped with ordinary city cars. Of course, some people associate diesel with black smoke from the exhaust pipe. For some time it was, but now the exhaust system has been modernized, and there are practically no such unpleasant consequences. Let's look at two-stroke diesels and their features.
Some general information
The key feature of the diesel engine is its increased efficiency. This is due largely to fuel, which is 15% more efficient. If we look at the fuel at the molecular level, here we see a long chain of carbons. Due to this, the output efficiency of diesel fuel is slightly higher than that of gasoline.
The principle of operation of a classic dieselThe motor consists in converting the reciprocating movements of the crank mechanism (KShM) into mechanical work. The key difference from an internal combustion engine running on gasoline lies in the way the fuel-air mixture is prepared and ignited.
In a diesel engine, the mixture is formed directly in the combustion chamber. Accordingly, at maximum pressure, the mixture ignites. Whether this is good or bad, we will figure it out a little later, but now let's look at the most interesting.
Two-stroke diesel engine
This type of motor currently has little distribution, like a rotary piston engine. It consists of a gas turbine, which is necessary for converting thermal energy into mechanical energy, and a supercharger. The principle of operation of the latter is to increase power by increasing pressure. As a result, fuel consumption is reduced.
The cylinders in the engine are opposite each other in a horizontal position. Actually, why are two-stroke engines so named? This is due to the fact that the cylinders work in just one revolution of the crankshaft. That is, it turns out two cycles.
The duty cycle of a two-stroke diesel is as follows. When the piston descends to its lowest point, the cylinder is filled with air. At a certain point in time, the exhaust valve opens and gases exit through it. At the same time, air enters the cylinders through the lower windows.
The principle of operation of a two-stroke diesel engine
Noticeablethe fact that in such internal combustion engines two types of purge are used: window and valve-slot. When cylinder windows are used for intake and exhaust, this is a window system. If the outlet is adjusted through a special valve in the cylinder, and the inlet through the windows, then the valve-slot system. This method of purging and cleaning is the most optimal. This is due to the fact that not all the air remains in the cylinder. Some of it goes beyond the motor. The so-called once-through cleaning system ensures optimal removal of combustion products from the cylinders.
A two-stroke diesel engine can run for quite a long time. This is due to less mechanical action inside the cylinder. So the piston starts its movement from bottom dead center. At this time, the intake valve and windows are closed. Therefore, the compression process begins. The nozzle is located at top dead center. The fuel is ignited by hot air. When the piston moves down, the combustion product expands.
Valve slot purge
A significant increase in engine efficiency can only be achieved when air flows along the axis of the cylinder. If on the first two-stroke motors an annular purge was used, which did not give the proper result, then only valve-slot was used in the future. Thanks to this system, it was possible to minimize the volume of non-blown areas in the cylinder. The system allowed the exhaust valve to close a little earlier. This approach significantly reduced the loss of fresh charge and improved boost. Today, valve-slotted purge is used on ships and militarytechnique.
Two-stroke Advantages
The first such engine was introduced to the world at the same time as the classic diesel 4-stroke ICE. Relatively recently, 2-stroke gasoline engines have appeared. The key feature is the low weight. Here we can talk about a weight reduction of 40-50% compared to a classic diesel engine with a turbine. Quite an important characteristic for a modern car, when developers are trying to reduce the weight of the car as much as possible.
Another advantage is that the two-stroke diesel engine is somewhat simpler than its counterpart. Fewer parts make maintenance somewhat easier and cheaper. Although the latter can be argued, because not everyone has encountered this type of motor. Such a power unit can be reconstructed and repaired with a minimum number of tools. In fact, this is a simplified version of the internal combustion engine. In addition, the presence of a supercharger allows you to significantly save fuel. Approximately 40-50% of diesel fuel is saved due to the two-stroke design. Of course, all motors have their pros and cons. In some cases, disadvantages are more important, as they limit widespread use.
On weaknesses
Again, if you list all the shortcomings in a list, then a rotary internal combustion engine will come to mind. The fact is that here it is worth highlighting the following disadvantages:
- high maintenance cost;
- lack of spare parts;
- high price for the engine.
The first point is due to the lack of workshops where they are ready to take on the repair of a two-stroke diesel engine. This is quite natural and logical, because not many manufacturers mass-produce similar motors, even fewer install them on cars. At a regular service station, such a power unit, if they do, will be expensive.
But usually the third minus occurs immediately - there are no necessary spare parts. More precisely, they are, but only under the order. You can wait for them for a month or more. If in large cities it will be possible to repair such an internal combustion engine and find spare parts, then in the outback this is unlikely to be done. These are the pros and cons of this diesel. Well, now let's look at a few more important details.
A little about the lubrication system
As we have already figured out, this diesel has its strengths and weaknesses. An extremely important detail is the lubrication system. It is responsible for the efficient operation of rubbing parts and their cooling, washing off carbon deposits. Everyone has long known that for these purposes, engine oil recommended by the manufacturer is used. In our case, everything is exactly the same.
I would like to say a few words about the consumption of lubricating fluid. Don't expect savings here. This is due to the addition of lubricant directly to the fuel to ensure the normal operation of rubbing parts. It is quite logical that it will be consumed very quickly, and it will need to be replenished regularly. Moreover, a slight oil starvation can destroy two-stroke diesel engines very quickly. At leastat least an order of magnitude earlier than conventional gasoline internal combustion engines. Therefore, the lubrication system is rather weak than strong, and this should not be forgotten.
On environmental friendliness
In recent years, engineers have been constantly trying to reduce the amount of harmful substances emitted by the exhaust system into the atmosphere. The issue of ecology is quite acute. If environmental standards have long been introduced in European countries, then in Russia everything is much worse. As for diesel engines in general, they have been using special particulate filters and low-ash oils for quite a long time, which significantly reduce harmful emissions into the atmosphere.
In our case, it was said that the oil burns in the chamber. This is already a big disadvantage from an environmental point of view. In addition, part of the fuel-air mixture does not ignite and breaks out. All this, along with the exhaust system, causes serious damage to the atmosphere. Therefore, two-stroke diesel engines are most appropriate to use in military equipment and aviation.
Aviation diesel
These types of motors are widely used in flight technology. Most often used on light aircraft. High power with small dimensions - became the determining factors when choosing power units for aircraft. In addition, the presence of pressurization and the lack of ignition played only for the better. The operation of the internal combustion engine stops with the supply of a fuel-air mixture.
It is worth noting that a two-stroke marine diesel engine is not afraid of a droptemperatures. Moreover, often a big frost is an additional cooling of the internal combustion engine, which is very good. All this, along with the use of relatively inexpensive fuel, makes this diesel extremely popular. True, distribution is limited by the complexity of installing and maintaining the compressor. In addition, lubricant must be added to the fuel, and this is also not cheap. In general, this is an excellent option for aviation, due to the above factors.
Increased thermal load
We reviewed the key features of this motor. For example, now you know how much the engine weighs and what are its strengths and weaknesses. But I would like to consider a few more design features of the power unit. In particular, we will talk about the cooling system. The fact is that a two-stroke diesel engine is more heat-loaded than a 4-stroke one. This is due to the increased frequency of the piston. It turns out that the temperature in the chamber increases significantly. Efficient cooling is required to reduce it. If we are talking about aviation, then everything is clear. High speeds and oncoming air flows do their job. The same applies to operation in severe frosts, when low ambient temperatures are only a plus.
In other cases, liquid cooling is required. Usually this is a classical system. The only thing worth paying attention to is the serviceability of all systems. Overheating, even momentarily, can cause jamming or other problems. In any case, the possibility of such an outcome is necessaryexclude.
Diesel resource
The planned resource of this motor deserves special attention. The fact is that the diesel engine itself is less viable than the gasoline power unit. This is due to the use of a kind of fuel. It leaves carbon deposits in the combustion chamber and injectors. All this significantly reduces the service life. As for two-stroke diesel engines, much depends on operating conditions and timely maintenance. If the oil is changed on time, and the engine does not overheat, then 200,000 kilometers can work. For armored vehicles, the resource is much less and amounts to about 100,000 kilometers.
Important details
Modern two-stroke diesel is characterized by an advanced fuel system. The motor runs quietly and smoothly. But it was not always so. The mechanical injection pump had its own characteristics. In particular, a separate line went to each nozzle. Although this approach had weaknesses, it was famous for its reliability and high maintainability. Later, injection pumps were improved and became much more complicated. The Common Rail system appeared. In the fuel rail of such a plan, a pressure of about 2 thousand kilograms per centimeter squared was maintained. Injectors have become more sensitive to fuel quality. Bad fuel led to their rapid failure.
Summarize
In general, two-stroke diesels will develop and improve. As well as rotary piston internal combustion engines, they are considered unfinished. However, in the near futurethey will occupy their niche in the automotive industry. Already today they are used in aviation and on large industrial and military ships. This is a reliable and relatively unpretentious motor that, with proper maintenance, will work properly. At the same time, he is not without problems. For example, the issue of cooling and lubrication is acute. Even more important is the issue of ecology. A complex filtration system is needed to achieve environmental standards. For this simple reason, mass production, the use of such motors on all types of cars is difficult and not yet possible. But improving the exhaust gas treatment system can solve this problem and lead to the fact that two-stroke engines will be widely used.
