For all their advantages, modern transport motors have one serious drawback, for which they still cannot be blamed. You can't because nothing in the world is perfect. In the production of energy, the presence of harmful consequences for the environment is still inescapable. Since the most common source of mechanical energy on Earth is the internal combustion engine, it is necessary to do something with the engines first of all, so that the harm due to their unusual prevalence does not outweigh the benefit.
The conflict situation is obvious. Well, where there is conflict, there is war. Silent, undeclared, but military actions aimed at providing engines with high environmental performance have been going on for more than a dozen years, and so far it cannot be said that people are winning this battle. There are more and more motors, and environmental requirements are becoming stricter. But there are not so many ways to satisfy them.
For the sake of fairness, it should be noted that humanity still has a secret weapon capable of radically solving the task of ensuring high environmental performance for motors. Back in the 60s of the last century, professor of the Leningrad Research Institute of Aviation Instrumentation V.M. Kushul proposed an engine design that creates virtually no harmful emissions. The fuel charge in this motor burns on 99%, which allows us to talk about it as a smokeless design. But for a number of reasons, including due to some unusual arrangement of this engine, so far this solution to the problem has not been particularly widespread. It is quite possible because the auto world is just waiting for Kushul's design to be called the invention of Carmel Scuderi, who distinguished himself by implementing the Soviet development of the 60s in America in 2001, and presented it to SAE engineers under the name Split-Cycle Combustion (SCC). One way or another, motorist designers all over the world continue to look for opportunities to solve the current task in their own way. And it must be said that sometimes these attempts acquire a rather interesting expression.
In 2001, Kushul's engine magically turns into an invention of the American Carmelo Scuderi.
Soot as a reason to worry
Of the recent events on this front, the proposal of a number of well-known firms to ensure high environmental safety, first of all, to modern diesel engines, stands out. The fact is that with a known advantage from the point of view of thermal efficiency, diesel is still impeccable from the point of view of harmful emissions. What is particularly unattractive in a number of indicators for this parameter in diesel engines is the high content of nitrogen oxides and such a waste of mechanical energy production as soot in the exhaust. Yes, yes, it is ordinary soot, in the form of unburned hydrocarbon residues, which, when leaving the diesel engine, take on a dangerous appearance for humans. After all, the fact is that small dust particles, less than 5 microns, are not removed from the human body. Hydrocarbon particles of this and smaller size form the soot waste from the operation of a diesel engine. And although nitrogen oxide, another diesel problem, is much more dangerous in terms of its effects on living organisms, it contributes to the growth of the risk of cancer, the primary task that motorists decided to solve was the task of eliminating soot from diesel emissions. The decision, taking everything into account, was not so simple. But having considered that if even with such a combustion organization, which ensures a reduction of soot in the exhaust, the proportion of carcinogenic nitrogen oxides in it is steadily increasing, it is better to let the engine produce more soot, which will be easier to overcome than such a dangerous product of nitrogen oxidation.
In the course of solving the problem of eliminating soot-forming solid particles in the exhaust of a diesel engine, the designers decided not to take the easy way out. Of course, the task could be solved by simply installing a replaceable particulate filter, similar to the principle by which the well-known air filter is used. However, having discovered that the soot filter of this principle of operation clogs quite quickly due to the uneven deposition of solid particles in it, the environmentally concerned auto industry decided that a trivial victory over simply uneven clogging of the replaceable soot filter would not impress the fans of diesel engines too much. And that's why a decision was made to introduce much more extravagant and exotic designs on a mass scale. And so, in full accordance with the mass perception of diesel engines as extremely high-tech products, the most diverse, but certainly impressive, systems and devices for cleaning harmful diesel emissions from soot began to appear on the market, like mushrooms after rain.
One of the first to speak in this direction was the well-known leader – the Mercedes-Benz company with its Bluetec cleaning system, based on the use of urea as a means of eliminating the harmful effects of diesel cars of the same name.
The consumption of urea (ADBlue reagent, a solution of water and ammonia), necessary for the operation of the cleaning system according to this principle, is about 100 ml per 100 km, and therefore, the prospect of high additional costs should not scare anyone. Especially since in California, for example, for the sake of clean air, people do not go to such costs. As for the rest of the world, she was less fortunate. The magic urea system may not help everyone. Because the ADBlue reagent turned out to be not so resistant to negative temperatures and freezes already at minus 11 °C.
ADBlue is a registered trademark of the product AUS 32 (aqueous urea solution, 32%). Copyright belongs to the Association of the German Automotive Industry (VDA). It is used as an additional working fluid in diesel engines with SCR technology - Selective Catalytic Neutralization.
Of course, given this circumstance, Mercedes-Benz did not stop at offering the market the Bluetec system exclusively. However, the further development of diesel engine exhaust cleaning systems was no longer so extraordinary and completely coincided with what Mercedes' competitors, who never sleep, are doing in the field of this activity. And the competitors, it must be said, did not sleep. And while Mercedes was mastering the urea system, the market was offered alternative options for particulate filter systems. Today, the market already has an idea of two types of systems of this kind: soot filter systems with the use of FAP fuel additives and without the use of DPF fuel additives.
FAP DPF is not better
The structure of the FAP and DPF systems differs radically. FAP is based on a working principle that is somewhat similar to Bluetec. The FAP system also uses liquid reagent injection into the engine exhaust manifold to clean diesel engine exhaust. The truth is that it is not at all with the purpose for which this process is implemented in Bluetec. Instead of a chemical reaction in the case of FAP, a special gel solution of diesel fuel with cerium microgranules bound in jelly-like capsules is supplied to the exhaust tract. Post-injection of this consistency is carried out at the moment when the exhaust valves of the motor are open and a flow of hot exhaust gases flows through them. During the feeding of the solution, the jelly-like capsules of the microgranules evaporate, and as a result, cerium particles fall into the soot FAP filter, which in the presence of carbon and oxygen create local combustion centers where the temperature reaches 1000°C. It is natural that with such an organization of the process, the soot qualitatively burns out in the mode that is the most merciful for the filter ceramics. Among the advantages of this type of particulate filter systems, one can probably attribute the selectivity of the process. After all, a local increase in temperature occurs precisely in those places where more soot settles. Well, the second indisputable plus is the indifference of the filter to the place of installation in the intake tract. The cleaning temperature when using the FAP filter will be achieved under all conditions, even if the filter itself is quite far from the exhaust valves that emit hot exhaust.
To implement the uninterrupted operation of the DPF soot filter, the control system involves many sensors that are not found in the gasoline engine.
1. Dashboard. 2. Electronic control unit. 3. Air flow sensor. 4. Diesel engine. 5. Temperature sensor in front of the turbocharger. 6. Turbocharger. 7. Temperature sensor before the soot filter. 8. Oxygen sensor (lambda). 9. Soot filter (DPF). 10. Pressure drop sensor on the soot filter. 11. Temperature sensor after the soot filter.
Of course, the blue dream of every designer of a particulate filter for cleaning the exhaust of diesel engines was and remains a system that allows for its effective use without the need for additional consumables, cerium contains jelly or even ammonia with water. It was in pursuit of such a dream that the designers proposed DPF soot cleaning systems. Indeed, why bother with crucibles and feed some cerium, if it is enough only to place a ceramic soot filter near the exhaust valves, and the high temperature of the exhaust gases of the engine working with a high degree of intensity will clean the soot deposits from the filter by itself, burning out the soot previously settled in this filter. Everything ingenious is simple - the designers decided in this case. And these systems were offered to the market as a product of unparalleled engineering and marketing ingenuity.
The DPF system for cleaning diesel engine exhaust from soot works quite easily. The pressure sensor in the exhaust manifold provides the engine ECU with data on the level of filter contamination. The control unit calculates the volumetric flow of exhaust gas, which is measured by the air flow meter and the exhaust gas temperature sensor to the soot filter. Separately installed on the intake manifold in front of the turbine, another temperature sensor provides data on the temperature of the exhaust gases directly at the exit from the cylinders. Based on the data received from these sensors, the engine control unit calculates the moment of additional fuel injection, the purpose of which is to increase the temperature in the area of the soot filter so that this increase ensures the burning of the soot accumulated in the filter. The system can calculate the required moment quite accurately. After all, in addition to the listed sensors, data from the oxygen sensor installed in front of the neutralizer is also taken into account. Thanks to this, the heating of the particulate filter and its regeneration proceed in an optimal mode.
The structure of the DPF particulate filter is a ceramic (silicon carbide) matrix structure enclosed in a metal housing. All cells of the matrix are parallel channels, alternately open and closed on one side (inlet and outlet), separated from each other by filter walls, on which a coating of zirconium and aluminum oxides is applied. These filtering walls perform the function of a catalyst substrate, which promotes the flow of chemical reactions, but at the same time does not form new compounds and does not change itself. Since the filter has a porous structure with alternately closed channels, the exhaust gases pass through the porous walls and soot particles in the intake valves. DPF diesel filter is a closed type filter. When exhaust gases pass through it, soot particles as small as 0.11 μm are retained. Most modern diesel cars have a particulate filter combined with an oxidation catalyst located in the front of the filter. It performs the functions of a soot filter and a catalyst at the same time.
As you can see, the DPF cleaning system, thanks to this simple and, probably, inexpensive set of measures, is quite capable of protecting the owner of a diesel car from unnecessary expenses on consumables, practically ensuring the effect of using ordinary replaceable filters. However, at the same time, you need to remember that to get the desired effect, all car systems must work flawlessly. The failure of at least one of the sensors is quite capable of causing the entire system to become expendable.
There is one more unpleasant feature. In conditions of saturation of the DPF filter on the 105-125%, the system simply does not start due to the danger of a fire caused by the clogging of the soot filter. But there are no problems if you remember the danger of such a state of affairs throughout the entire period of operation. A diesel engine with a DPF filter designed for 120,000 km. km, it will be able to honestly work out the entire resource, if the fuel is of good quality, and the owner will not deny himself the pleasure of periodically driving at least 40 km at high speed with the reduced gear engaged. It is more convenient to do this at night, when dense traffic will not interfere with long-term operation of the engine at high speeds, which provides optimal conditions for burning soot from the filter. If, for some reason, the filter was clogged to such an extent that the engine does not develop power and cannot even maintain the calculated number of idling revolutions, this does not mean that you need to urgently change the soot filter, the price of which starts at $1,000. Much, of course, depends on the mileage and operating conditions of the car. However, if everything is fine with this, then a relatively simple procedure - washing the soot filter - can help supporters of environmental protection using high-tech methods.
Melted particulate filter. This happens if a clogged filter is burnt out by driving at full throttle and during this the driver suddenly drops the gas. Too much oxygen gets into the filter, and the temperature rises uncontrollably.
Unhealthy consequences of health care
There are literally legends about the ability of the DPF soot filter to be washed with affordable even household products among those who have faced the need to replace this unit. They say that the filter can be washed even with plain water, under pressure directed into the filter against the direction of the exhaust gas flows. According to the experimenters, special success can be expected if you use a dishwashing agent that is effective in other life situations. There is an opinion, which probably no one has yet managed to verify, that this approach to solving the problem can help. Well, the experiment is, of course, a noble thing, why not try it, stocking up on a new filter from a needle in advance. In this case, you can try a lot: starting from solvent and ending with moonshine, suddenly you will be lucky. However, if you remember that carbon deposits accumulate in the filter, which, under the influence of high temperatures and pressure fluctuations, are compacted in the narrow and repeatedly looping passages of the filter, then at least out of a desire not to permanently damage a densely clogged filter, it is still better to turn to professional cleaning products. After all, in contrast to means for plumbing, this auto chemistry is primarily designed to first qualitatively loosen the soot that coked the filter passages, and only then to effectively remove the resulting loose mass, using the principle of the filter itself.
Given the increase in the number of cars in service with diesel engines equipped with DPF filters, the market offers a number of chemical cleaning agents for a clogged diesel particulate filter. There is no doubt that, for the most part, all these liquids are able to cope with the task assigned to them to one degree or another. However, it is still possible to determine a more effective product if you pay close attention to the cleaning technology recommended by the manufacturer of the product. From this point of view, Xenum DPF FLUSH (STEP 1 and STEP 2) looks attractive.
The manufacturer of this set for cleaning the filter provides such a complete set that allows cleaning without removing the filter, using the technological holes of the sensor mounting locations. At the same time, the cleaning itself is carried out in several stages, between which the regular operation of the engine and the filter regeneration system is used. STEP 1 and STEP 2 agents supplied to the exhaust system effectively loosen the soot deposit, providing the regular system with the ability to cope with the excessive amount of soot. Nothing exotic, but this is the secret of the effectiveness of the tool. Upon completion of all operations, the tool manufacturer recommends the same as the car manufacturer: at least 20 minutes of driving the car with the engine running at over 2,500 rpm. At this time, the exhaust system of the engine will finally remove the soot combustion products from the filter, which should be clearly visible from the thick smoke from the exhaust pipe. After the operation, the car is ready for further operation.
Prevention is smarter than treatment
Of course, this method of cleaning the soot filter is more troublesome than the often practiced drastic removal of it from the exhaust system of the car with parallel emulation of the work of sensors to ensure the possibility of engine operation. But still, it is worth remembering that by agreeing to such a move, the car owner unwittingly turns into a killer of the people around him, and greatly risks his own health. Whether it is worth making such sacrifices, or simply periodically using auto chemical products that allow you to solve the problem without these sacrifices - everyone decides for himself. And in the series of choices to remove the filter, replace it with a new one, or periodically refer to cleaning, everyone will choose the most optimal and reasonable solution. Moreover, the same Xenum, in addition to a means of correcting neglected cases, also offers a means of prevention, which allows you to prevent the critical filling of the particulate filter.
The Xenum IN & OUT CLEANER preventive agent, acting on the NEXGEN technology developed and patented by this company, solves the task of preventing extreme soot filter clogging by a method reminiscent of the FAP filter technology. This fuel additive contains particles of rare earth metals, which, settling in places of the greatest accumulation of soot in the filter, cause a high-temperature local reaction that ensures the burning of excess carbon. Xenum's solution in this case is interesting in that the company declares that there is no need to use gelatin capsules as a means of delivering reaction activators to places where soot accumulates. And this fuel additive works more extensively, also cleaning the intake system. The technology is interesting in that the developer demonstrates approaches that allow, according to him, to surpass the methods of well-known manufacturers.
Epilogue
In war, all means are good. Today, car manufacturers solve the task of selling their products like a military commander who, because of an instruction to take care of the health of his soldiers, forces these same soldiers to run after the advancing tanks wearing gas masks sold to them at a similar price. But no amount of health will be enough to run like that!
Nervousness due to the unpredictability of the behavior of soot filters is no better than the smoky air from car engines running without them. Both are equally unacceptable in the relationship between car manufacturers and users of this technology. And it is all the more valuable in this situation that technology developers who solve the problem at a cost level acceptable to the market come to the rescue.
It will probably continue to do so. In any case, for now the giants of the automobile industry will treat such examples of a successful solution to the problem, such as the Kushul engine, with the same amount of attention with which they treat the real problems of consumers of their products today. If the problem of ecology is so important, then it should be solved constructively, and not at the expense of creating problems for the consumer and significantly increasing the cost of operation. The consumer should not pay for environmental safety from the very beginning with technology that is claimed to be safe for him. But even if he is forced to do it, there will always be a way out. However, with all the consequences that follow for the reputation of the equipment manufacturer. In war as in war...