Until now, we have considered the so-called primary energy carriers, but there is also a secondary energy carrier - hydrogen, the combustion of which produces water, which led to the widespread concept of hydrogen as an environmentally friendly fuel. In reality, the situation is much more complicated. By itself, hydrogen is indeed relatively clean from an environmental standpoint. True, it should be borne in mind that when hydrogen is used as a fuel for cars, a very high temperature develops in the engine cylinders, at which nitrogen from the air begins to oxidize, and therefore there is no a large number of nitrogen oxides.
The main environmental problems arise even during the production of hydrogen - after all, there is no pure hydrogen on Earth, it must be synthesized from water or hydrocarbons. Hence it follows that in order to implement a beautiful and tempting idea called "hydrogen energy", hydrogen should be obtained, that is, energy should be expended. Moreover, to obtain it in an economically justified way, so that the cost of the energy equivalent of this energy carrier is commensurate with the cost of traditional energy carriers and the energy carrier that was used to produce hydrogen.
First and the main task hydrogen energy is declared as a replacement for oil, natural gas and coal with hydrogen. But today the world does not know the technology that meets all the requirements of this global task. All methods of hydrogen production known today are far from perfect: firstly, they are energy-consuming, and secondly, the production of hydrogen from hydrocarbons is accompanied by the release of a huge amount of carbon dioxide and other toxic substances. And if now the contribution of carbon dioxide to the increase in the concentration of greenhouse gases in the atmosphere is still relatively small and causes only concern, then the transition to hydrogen fuel, which will be obtained, for example, from methane, will lead to an increase in carbon dioxide emissions dozens of times.
Obtaining hydrogen by electrolysis of water using traditional energy sources, of course, has to be rejected, since as a result, slightly more energy will be expended than obtained by burning hydrogen. Therefore, intensive research is underway to develop materials that break down water when exposed to sunlight. In parallel, work is underway to create semiconductor solar cells for converting solar energy into electricity, which is then used for electrolysis of water. The prospects for these studies are still unclear, but if successful, it will focus on the creation of a new industry with all the ensuing consequences. Environmental problems in hydrogen energy will also arise in the development of materials for pipeline transport of hydrogen - it is explosive, has a high diffusion mobility (it easily seeps through conventional structural materials), which means that new generation materials and technologies will be required that are unlikely to be environmentally friendly.
The problem of hydrogen storage is still far from being solved. The US Department of Energy has formulated the requirements for a material that accumulates hydrogen: it must contain at least 5.5% hydrogen by mass at room temperature, the sorption-desorption process of hydrogen must be reversible at temperatures no higher than 120 ° C, the system must be safe and keep working condition for at least 5000 discharge-charging cycles. Today there is not a single material that even approximately meets these requirements. Sorbents, the absorption of which hydrogen is based on physical adsorption, are not able, due to the nature of the phenomenon, to approach these requirements, since for them a relatively high adsorbate content is achievable only at low temperatures (77 K). On the contrary, for metal hydrides and intermetallic compounds with a high hydrogen content, high temperatures are required for its release and binding. It not only complicates technical solutions in the implementation of the task, but also sharply increases the danger of using the system as a whole.
Again, one can hope that over time the problem of storing and accumulating hydrogen will be solved, but one cannot count on the complete environmental safety of the developed industrial technologies.
The scientific and technical problems of hydrogen energy, apparently, will be overcome, although this will take, according to various forecasts, from 10 to 50 years, but environmental difficulties will remain in any case. Therefore, there is no need to talk about the ecological purity of hydrogen energy - hydrogen energy is not environmentally friendly.
"Electric vehicles- environmentally friendly transport ".
Another extremely tenacious myth is associated with electric vehicles: the transition of road transport to electric traction will supposedly ensure the purity of the atmosphere. First, let's try to figure out what will happen if today a significant part of car engines internal combustion replace with electric motors. As you know, electric motors do not emit any emissions into the atmosphere and, moreover, have a high efficiency - over 90%. Unfortunately, at present, the only source of energy for car electric motors is batteries. They need to be constantly charged and, therefore, use the energy generated by the existing power plants. But about 80% of electricity is generated by thermal power plants (Table 1) that use oil, gas or coal as fuel, which are environmentally dirty fuels. This means that engine emissions will be replaced by approximately the same volume of emissions from power plants, i.e., there will be a transfer environmental issues from one area to another.
For many years, researchers have been struggling to find an alternative to gasoline as the main type of fuel for vehicles. It makes no sense to list environmental and resource reasons - only the lazy does not speak about the toxicity of exhaust gases. Scientists find a solution to the problem in the most, at times, unusual types of fuel. Recycle has selected the most interesting ideas that challenge the fuel hegemony of gasoline.
Biodiesel with vegetable oils
Biodiesel is a type of biofuel based on vegetable oils, which is used both in pure form and as various mixtures with diesel fuel. The idea of using vegetable oil as a fuel belongs to Rudolf Diesel, who in 1895 created the first diesel engine to run on vegetable oil.
As a rule, rapeseed, sunflower and soybean oils are used to produce biodiesel. Of course, vegetable oils themselves are not poured into the gas tank as fuel. Vegetable oil contains fats - esters fatty acids with glycerin. In the process of obtaining "biosolyara", glycerin ethers destroy and replace glycerin (it is released as a by-product) with simpler alcohols - methanol and, less often, ethanol. This becomes a component of biodiesel.
In many European countries, as well as in the United States, Japan and Brazil, biodiesel has already become a good alternative to regular gasoline. For example, in Germany, rapeseed methyl ester is sold at more than 800 filling stations. In July 2010, 245 biodiesel plants with a total capacity of 22 million tons were operating in the EU countries. Analysts at Oil World predict that by 2020 the share of biodiesel in the structure of consumed motor fuel in Brazil, Europe, China and India will be 20%.
Biodiesel is an environmentally friendly fuel for transport: in comparison with conventional diesel fuel, it contains almost no sulfur and, at the same time, is almost completely biodegradable. In soil or water, microorganisms recycle 99% of biodiesel in 28 days - this minimizes the degree of pollution of rivers and lakes.
Compressed air
Models of pneumatic vehicles - machines that run on compressed air - have already been released by several companies. Peugeot engineers at one time made a splash in the automotive industry, announcing the creation of a hybrid in which compressed air energy is added to the internal combustion engine. French engineers hoped that such a development would help small cars to reduce fuel consumption to 3 liters per 100 km. Peugeot experts claim that in a city a pneumatic hybrid can run on compressed air up to 80% of the time without creating a single milligram of harmful emissions.
The principle of operation of the "air vehicle" is quite simple: the car is driven not by the gasoline mixture that burns in the engine cylinders, but by a powerful flow of air from the cylinder (the pressure in the cylinder is about 300 atmospheres). The pneumatic motor converts the energy of the compressed air into the rotation of the axle shafts.
Unfortunately, machines entirely on compressed air or air-hybrids are created mainly in scanty batches - to work in specific conditions and in limited space (for example, at production sites that require the maximum level fire safety). Although there are some models for "standard" buyers.
Engineair's eco-friendly Gator micro-truck is Australia's first compressed air vehicle to enter actual commercial use. He can already be seen on the streets of Melbourne. Carrying capacity - 500 kg, volume of air cylinders - 105 liters. The mileage of a truck at one gas station is 16 km.
Waste products
What progress has reached - some cars do not need gasoline for the engine to work, but human waste entering the sewage system. Such a miracle of the car industry was created in the UK. A car was rolled out onto the streets of Bristol, which uses methane from human excrement as fuel. The prototypical model is the Volkswagen Beetle, and the manufacturer of the VW Bio-Bug with innovative fuel is GENeco. Installed on a Volkswagen convertible, a feces-processing engine made it possible to drive 15 thousand kilometers.
GENeco's invention was quickly called a breakthrough in the introduction of energy-saving technologies and environmentally friendly fuels. To the layman, the idea seems surreal, so it is worth explaining: of course, already reprocessed fuel is loaded into the car - in the form of ready-to-use methane, obtained in advance from waste.
At the same time, the VW Bio-Bug engine uses two types of fuel at the same time: the car starts from gasoline, but as soon as the engine warms up and the car picks up a certain speed, the supply of human gastric gas processed at the GENeco factories is turned on. Consumers may not even notice the difference. However, the main marketing problem remains - a negative human perception of the raw materials from which biogas is obtained.
Solar panels
The production of solar-powered cars is perhaps the most developed area of the automotive industry focused on the use of eco-fuels. Solar powered cars are being built all over the world and in a wide variety of variations. Back in 1982, inventor Hans Tolstrup in the Quiet Achiever solar vehicle crossed Australia from west to east (albeit at a speed of only 20 km per hour).
In September 2014, Stella was unable to cover the route from Los Angeles to San Francisco, which is 560 km. The solar car, developed by a group from the Dutch University of Eindhoven, is equipped with panels that collect solar energy and a 60-kilogram battery pack with a capacity of six kilowatt-hours. Stella has an average speed of 70 km per hour. In the absence of sunlight, the battery reserve is sufficient for 600 km. In October 2014, students from Eindhoven took part in their miracle car in the World Solar Challenge, a 3000 km rally across Australia for solar-powered cars.
The fastest solar-powered electric car on this moment is Sunswift, created by a team of students from the Australian University of New South Wales. On tests in August 2014, this solar car covered 500 kilometers on a single battery charge at an average speed of 100 kilometers per hour, which is amazing for such a vehicle.
Culinary waste biodiesel
In 2011, the Ministry Agriculture The United States has worked with the National Renewable Energy Laboratory to research alternative fuels. One of the surprising results was the conclusion that the use of biodiesel fuel based on raw materials of animal origin is promising. Biodiesel from residual fats is not yet a very advanced technology, but it is already being used in Asian countries.
Every year in Japan, after the preparation of the national dish, tempura, about 400,000 tons of used cooking oil are left behind. Previously, it was processed into animal feed, fertilizer and soap, but in the early 1990s, the thrifty Japanese found another use for it, setting up on its basis the production of vegetable diesel fuel.
Compared to gasoline, this non-standard type of gas station emits less sulfur oxide - the main cause of acid rain - and reduces other toxic exhaust emissions by two-thirds. To make the new fuel more popular, its manufacturers have come up with an interesting scheme. Anyone who sends ten batches of plastic bottles with used cooking oil to the RTD plant is allocated 3.3 square meters of forest in one of the Japanese prefectures.
Technology in such a volume has not yet reached Russia, but in vain: the annual amount of waste from the Russian food industry is 14 million tons, which in terms of its energy potential is equivalent to 7 million tons of oil. In Russia, waste fired on biodiesel would cover the need for transport by 10 percent.
Liquid hydrogen
Liquid hydrogen has long been considered one of the main fuels that can challenge gasoline and diesel. Hydrogen-fueled vehicles are not uncommon, but due to many factors, they have not gained widespread popularity. Although in recent times the new wave of concern about green technologies has brought the idea of a hydrogen engine to new supporters.
Several large manufacturers at once have in their lineup machines with a hydrogen engine. One of the most famous examples- BMW Hydrogen 7, a vehicle with an internal combustion engine that can run on both gasoline and liquid hydrogen. BMW Hydrogen 7 has a 74 liter petrol tank and a storage tank for 8 kg of liquid hydrogen.
Thus, the car can use both types of fuel during one trip: switching from one type of fuel to another is automatic, with hydrogen being preferred. The same engine type is used, for example, in the Aston Martin Rapide S hydrogen-petrol hybrid car. It can run on both types of fuel, and the switching between them is carried out by an intelligent system for optimizing consumption and emissions. harmful substances in atmosphere.
Other auto giants such as Mazda, Nissan and Toyota are also going to develop hydrogen fuel. It is believed that liquid hydrogen is environmentally friendly, since it does not emit any pollutants when it burns in an environment of pure oxygen.
Green algae
Algae fuel is an exotic way to generate energy for a car. First of all, the USA and Japan began to consider algae as a biofuel.
Japan does not have a large reserve of fertile land for the cultivation of rapeseed or sorghum (which are used in other countries to obtain biofuels from vegetable oils). But the Land of the Rising Sun extracts a huge amount of green algae. Previously, they were used for food, but now they are used as a basis for refueling for modern cars. Not so long ago, in the Japanese city of Fujisawa, a DeuSEL passenger bus from Isuzu appeared on the streets, which runs on fuel, part of which is derived from algae. Euglena green became one of the main elements.
Algae supplements now account for only a few percent of the total mass fuel in transport tanks, but in the future, the Asian manufacturer promises to develop an engine that will use the biocomponent at 100 percent.
In the US, algae-based biofuels are also closely tied to the issue. Propel filling station chain in Northern California has started selling Soladiesel biodiesel to all comers. Fuel is obtained from algae by fermentation and subsequent release of hydrocarbons. Biofuel inventors promise a 20% reduction in carbon dioxide emissions and a marked reduction in toxicity in other respects.
The Moscow government decided to entrust the functions of distributing ecological fuels and energy sources in the city's automobile transport to certain automobile enterprises. , which is not much different from gasoline, is less practical than alternative fuels.
The enterprises carried out work on already experimental models of cars, which are adapted to the use of compressed natural gas, that is, methane.
Half of all the vehicles in the company's fleet operate on alternative fuels.
Up to this point, in the cities of Russia, such a technique had never been used, the experience that is being actively acquired now allows you to get those necessary knowledge, which will create conditions for the expansion and implementation of innovations in all regions of the country.
In the recent 1960s, almost all highly developed countries had an energy sector that depended on oil. Western countries won for a set of cheap oil exports, a barrel cost them about $ 5. Which resulted in quite high. Thirteen years later, the organization of Arab oil exporting countries imposed an embargo on the import of oil into the United States of America, this happened due to the fact that in Israel's war with Syria and Egypt, North America supported Israel. After this incident, those countries that called themselves highly developed, came to the conclusion that the current economic plans are no longer effective, it is urgent to develop new ones, taking into account completely different types of fuel. The weakest point was the transport industry, which used hydrocarbon fuels.
Another reason for the search for an alternative to oil was that its production became more and more expensive every year, and its reserves in the bowels of the earth were consumed at a very high rate, and could disappear altogether in about 50 years.
The most interesting thing is that the gas engine is not at all a novelty of our time, since it was invented back in the very distant 19th century, by an engineer from France, Lenoir, it worked, of course, on gas. These days, when using alternative fuels in cars, it is gas that is most often used.
It should not be confused with household gas, because when refueling a car, gas stations use special propane-butane components, this is liquefied petroleum gas. Its use is cheaper and more environmentally friendly than gasoline. Refueling of cars is carried out on special complexes for refueling with alternative types of fuel.
The best fuel for vehicles.
Natural gas, methane, is something that bypasses both gasoline and petroleum gas in terms of characteristics. They are usually refueled by those who want to travel twice the distance for the same money.
Does not provoke carbon deposits, engine oil does not undergo changes. Much less damage to pistons and cylinders, good engine performance. No carbon deposits, engine oil does not dilute. Less wear on pistons and cylinders, improves engine life. Oil coke, plus soot, oxidizes the oil, significantly reducing lubricating properties.
There are very few specialized points where you can refuel without any problems. There is a network of gas stations. There are a lot of places where you can refuel.
It does not require any processing, it is suitable for use in its original form. A mixture that requires specific proportions for the seasons. Oil refineries are required.
Delivery is carried out by gas transportation routes. They are brought by special tractors. As well as propane-butane, it is delivered to filling stations in tanks.
The explored deposits should be enough for mankind for about 200 years. Since gas is produced from oil, it will last for about 50 years. Produced from oil, reserves of no more than 50 years.
Quite cheap and requires little investment. It has average price... Unstable cost, in the sense that it only grows every year.
Expensive equipment, very few specialists in the Russian Federation for installation and production, as well as for the repair of installations. Not cheap equipment cost. No additional hardware needed.
There is no possibility of methane theft at gas stations or from car tanks. Cannot be stolen from gas stations. Easily resellable.
Almost does not change its properties with decreasing temperature. Properties drop with decreasing temperature Small changes in properties if temperature drops.
Has the highest safety class 4. Not very safe, as it has only the 2nd class of safety. Stable security, 3rd grade.
The conclusion suggests itself that methane has only three drawbacks when compared with other fuel forks. Problems with specialists are easy to solve, and the high cost of equipment still pays off over time, for a set of the same savings. Methane is a fuel that has the most best performance among other types of fuels.
Today, methane can be used in almost all cars, but in the 1990s, it was thought to be used for trucks and buses. It was placed in special steel cylinders that could withstand a pressure of 200 atmospheres. But the weight of the tank of 100 kilograms scared off motorists, so few people transferred their "beast" to this fuel. Now just like any other fuel.
Today, steel cylinders have been replaced by less durable composite alloys, reliability has become a victim of lightness, that is, the lower weight of the cylinder. Cylinders, like steel, can withstand pressure and high temperatures. The explosiveness is overestimated, methane is capable of igniting only when the temperature reaches 600 degrees, while gasoline is at 250, not to mention its vapors, which are enough and 170 degrees.
Application in European countries
The widespread use is increasing in huge strides. Now there are 10 million aerated machines. Russia is the leader in supplies gas fuel, in the western market.
Modern factories are necessarily engaged in the development and production of one or two models of gas-cylinder cars Audi, Honda, Toyota and others. They all begin to establish the production of cars.
Energy benefits have been evaluated different countries, with different economic environments. Cars capable of using gas fuel can be found from the United States to Asia. In Russia, there are very few factory gas-fired vehicles, most often you can find gasoline analogues converted for gas.
Cars with alternative fuels such as gas are well produced in countries such as Germany and the Czech Republic. This is due to the fact that the first has an excellent refueling infrastructure, in the second, they plan to replace 10% of the fuel with more economical analogues. The country in which gas-fueled vehicles are already widely used is Italy. More than 779 thousand GBA, wheeling the vastness of this country.
Automobile transport as a source of environmental pollution. Reasons for the formation of toxic components in the exhaust gases of an internal combustion engine
V last years in connection with the growth of the traffic density of cars in cities, the pollution of the atmosphere with the products of combustion of engines has sharply increased. The exhaust gases of internal combustion engines (ICE) consist mainly of harmless fuel combustion products - carbon dioxide and water vapor. However, in relatively small quantities they contain substances with toxic and carcinogenic effects. These are carbon monoxide, hydrocarbons of various chemical compositions, nitrogen oxides, which are formed mainly at high temperatures and pressures.
During the combustion of hydrocarbon fuel, toxic substances are formed, associated with the combustion conditions, the composition and state of the mixture. In engines with positive ignition, the concentration of carbon monoxide reaches large values due to the lack of oxygen for complete oxidation of the fuel when they operate on a fuel-rich mixture.
When driving in the city and on roads with a variable slope and frequently changing speeds with a gear engaged and an open throttle valve, the engines have to operate in forced idle mode for about 1/3 of the travel time. At forced idle, the engine does not give up, but, on the contrary, absorbs the energy accumulated by the car. At the same time, fuel is consumed irrationally, the enhanced absorption of which leads to the greatest release of toxic gases CO and CH into the atmosphere.
Automotive exhaust gases are a mixture of approximately 200 substances. They contain hydrocarbons - unburned or incompletely burned fuel components, the proportion of which increases sharply if the engine is running at low revs or at the moment of speed increase at the start, i.e. during congestion and at the red traffic light. It is at this moment, when the accelerator is pressed, that the most unburned particles are emitted: about 10 times more than when the engine is operating in normal mode. Unburned gases also include ordinary carbon monoxide, which is formed in varying amounts everywhere where something is burned. The exhaust gases of an engine running on normal gasoline and in normal operation contain an average of 2.7% carbon monoxide. With a decrease in speed, this share increases to 3.9%, and at low speed, up to 6.9%.
The main operational factors affecting the level of harmful emissions of engines are the factors characterizing the condition of the parts of the cylinder-piston group (CPG). Increased wear of CPG parts and deviations from their correct geometric shape are the reason for an increase in the concentration of toxic components in the exhaust gases (OG) and crankcase gases (CG).
The basic part of the CPG, on which the performance and environmental friendliness of the engine depends, is the cylinder, since the tightness of the combustion chamber depends on the sealing ability of the ring in conjunction with the cylinder. The growth rate of the gaps between the rings and piston grooves mainly depends on the technical condition of the cylinders and piston rings. Thus, control and adjustment of the gap between the ring and the cylinder during operation is a significant reserve for reducing the amount of harmful impurities in the exhaust and CG by improving the combustion conditions and reducing the amount of oil remaining in the piston space.
The toxic emissions of the internal combustion engine are exhaust and blow-by gases. With them, about 40% of toxic impurities from the total emission enter the atmosphere. The content of hydrocarbons in the exhaust gases depends on the technical condition and engine settings and at idle it ranges from 100 to 5000% or more. With a total small amount of crankcase gases equal to 2-10% of exhaust gases in the total atmospheric pollution, the proportion of crankcase gases is about 10% in slightly worn engines and grows to 40% when an engine is operated with a worn-out cylinder-piston group, because the concentration of hydrocarbons in crankcase gases is 15-10 times higher than in engine exhaust. The number of KG, as well as their chemical composition depend on the state of the parts of the CPG that seal the combustion chamber. The penetration of gases from the cylinder to the crankcase and vice versa depends on the size of the gaps between the rubbing parts of the CPG. At the same time, the proportion of hydrocarbons with carcinogenic properties increases due to increased oil burnout and increased consumption of crankcase gases through a closed crankcase ventilation system.
By the time the engine reaches its wear limit, emissions increase by an average of 50%. On the example of accelerated tests carried out at NAMI, it was found that engine wear increases emissions of hydrocarbon exhaust gases by 10 times. The main mass of engines with increased exhaust gas smoke is accounted for by engines that have passed overhaul.
The degree of decompaction of the combustion chamber depends on the wear of the CPG parts, the deviation of their macrogeometry from the correct geometric shape. With an increase in the leaks in the combustion chamber, an increase in CO and CH and a decrease in CO2 as a result of deteriorating fuel combustion conditions occur. In addition to a decrease in the quality of the organization of the working process, the gaps between the ring and the cylinder, as well as the gaps between the ring and the piston groove, lead to an increase in the amount of oil that has got into the piston space, to an increase in the deviation from the specified dynamics of heat release during combustion, and, consequently, to an increase the total mass of toxic emissions. Oil makes up 30-40% of exhaust gas solids.
The basic part of the CPG is the cylinder, on which the economic and environmental feasibility of operating the engine depends. The wear of the cylinder liners has a pronounced oval shape, the major axis of which is located in the swinging plane of the connecting rod. The reason for the formation of ovality of the cylinders is mainly the increased load of the pistons on the liners precisely in the rocking plane of the connecting rods. The ovality of the cylinders is also affected by the imperfection of the cylinder block assembly technology. Changing the macrogeometry of the cylinders (ovality and taper) after assembling the engine also leads to a deterioration in the adhesion of the piston rings to the cylinder bore. It is known that when installing sleeves into blocks different brands Internal combustion engine, the ovality in the cylinders increases by 2-3 times.
It is very important to note that the nature of the distortion of the macrogeometry of cylinder liners after assembly and during operation is the same for most designs of cylinder blocks with “wet liners”. The major axis of the oval of the cylinder formed during assembly, in the stop zone of the upper compression ring at the top dead center of the piston, has the same direction as the major axis of the oval formed during operation. This nature of the deformation of the cylinders is explained by the greater deformation of the block in the places between the bores for the liners.
Reducing the ovality of the cylinders helps to reduce the wear rate of the rings and piston grooves, which generally improves the performance of the piston rings and improves the sealing of the combustion chamber. It is known that replacing the oil scraper rings after the end of their service life to some extent restores the average level of engine toxicity. Undoubtedly, if, when replacing the rings, the ovality of the cylinders is adjusted to the level of the limiting value for the manufacture of new liners, then the effect will be much greater.
The development of new methods of mixing and dissolution and a mathematical description of the effect of the corresponding additives and additives in petroleum fuels will significantly reduce the time for developing new compositions of alternative fuels and predicting their physicochemical properties, which will make it possible to improve the engine workflow when using new alternative fuels.
Analysis of domestic and foreign literature showed that the development of the transition to new types of fuel will go through three main stages. At the first stage, standard petroleum fuels, alcohols, additives of hydrogen and hydrogen-containing fuels, gas fuels and their various combinations will be used, which will solve the problem of partial saving of petroleum fuel. The second stage will be based on the production of synthetic fuels, like petroleum, produced from coal, oil shale, etc. At this stage, the problems of long-term supply of the existing engine fleet with new types of fuel will be solved. The final, third stage will be characterized by a transition to new types of energy carriers and power plants (operation of engines on hydrogen, use of atomic energy).
The conversion of internal combustion engines to hydrogen and hydrogen-containing fuel is a complex socio-economic process, which will require a major restructuring of a number of industries, therefore, at the first stage, the most acceptable option is to operate diesel engines with additives of hydrogen-containing fuels. Extremely limited information in the literature on the features of combustion of hydrocarbon fuel with the addition of hydrogen and ammonia in diesel engines does not allow an unambiguous answer to the question of the effect of hydrogen-containing fuels on the performance of a diesel engine.
Also, the question of the use in diesel engines of synthetic liquid fuel(SLT) produced from coal. Various literature data do not allow to give an unambiguous assessment of the effect of SLF on the working process, due to the fact that its physicochemical properties are highly dependent on the feedstock and processing technology.
The most likely source of motor fuel can be alcohols, but their extremely poor motor properties should be taken into account if they are used in diesel engines. The used methods of using alcohol fuels require additional design complexity (installation of carburetors, spark plugs or a second fuel system), or higher fuel prices (use of additives that increase the cetane number). The most optimal in this situation is the method of using solutions of ethanol or methanol with diesel fuel in diesel engines.
Impact research different types alternative fuels were carried out for several types of high-speed diesels with different ways mixture formation, so it was necessary to obtain as much full information on the progress of fuel supply, combustion, soot formation, toxicity, etc. Therefore, a PC-based automated system for registering and processing information was developed and implemented. For this complex, a software package was developed, including a program for collecting information from various sensors during tests, a program for processing the obtained data for analyzing the indicator diagram, results of optical indication, fuel supply and calculation of mode parameters.
For the simultaneous supply of a cyclic portion of diesel fuel and gas into the cylinder, the author developed a special dual-fuel nozzle, which was supplemented by a separate line, consisting of a gas supply connection and channels in the nozzle and sprayer housing. In the channel of the nozzle body check valve pressed against the seat by a spring. A cylindrical insert with a screw thread on the surface is pressed into the nozzle channel, which forms a mixing and accumulating chamber connected to the sub-needle cavity of the nozzle spray.
On the basis of the developed nozzle, a diesel fuel system was manufactured, which makes it possible to supply various types of gaseous additives to the fuel.
It is most effective to consider the features of the workflow when using alternative fuels, having information on the spatial distribution of the soot concentration and temperature fields. Today, there is mainly a two-dimensional representation of the temperature-concentration inhomogeneity in a diesel cylinder. As a result, the task was set experimental research spatial distribution of temperature and soot concentration fields. We used original experimental equipment to determine the mass concentration of soot, based on optical indication of cylinders, and software-implemented methods for determining temperature fields.
Calculated studies of the solubility of gas (hydrogen, ammonia, etc.) were based on the following assumptions: firstly, the dissolution process takes place in the mixing-accumulating chamber and the nozzle atomizer; secondly, dissolution proceeds in accordance with the surface renewal model, i.e. the fuel-gas contact surface is updated with a frequency equal to the frequency of fluctuations in the fuel pressure in the injection pipeline high pressure.
One of the ways to overcome the difficulties of preparing mixtures of diesel fuel with alternative ones is the use of the third component - a joint solvent of diesel fuel and alcohol. The joint solvent must have the properties of diesel fuel and alcohol, i.e. its molecule must have both polar properties and an aliphatic component for the formation of bonds with hydrocarbons.
Attempts to use hydrogen as a fuel for internal combustion engines have been known for a long time. So, for example, in the twenties, they studied the option of using hydrogen as an additive to the main fuel for internal combustion engines of airships, which made it possible to increase their flight range.
The use of hydrogen as a fuel for internal combustion engines is a complex problem that includes a wide range of issues:
Possibility of converting modern engines to hydrogen;
Study of the working process of engines when running on hydrogen;
Definition optimal ways regulation of the working process ensuring minimum toxicity and maximum fuel efficiency;
Development of a fuel supply system that ensures the organization of an efficient working process in the internal combustion engine cylinders;
Development of efficient methods for storing hydrogen on board vehicles;
Ensuring the environmental efficiency of using hydrogen for internal combustion engines;
Providing the ability to refuel and accumulate hydrogen for engines.
The solution of these issues has a variant level, however, the general state of research on this problem can be considered as a real basis for the practical application of hydrogen. This is confirmed by practical tests, studies of variant engines operating on hydrogen. For example, Mazda relies on a hydrogen-powered rotary piston engine.
Research in this area is distinguished by a wide range of options for using hydrogen for engines of external and internal mixture formation, using hydrogen as an additive, partially replacing the fuel with hydrogen, and engine operation only on hydrogen.
An extensive list of studies determines the need for their systematization and critical analysis. The use of hydrogen is known in engines fueled by conventional petroleum fuels and in combination with alternative fuels. So, for example, with alcohols (ethyl, methyl) or with natural gas... It is possible to use hydrogen in combination with synthetic fuels, fuel oils and other fuels.
Research in this area is known for both gasoline and diesel engines, as well as other types of engines. Some authors of works on this topic believe that hydrogen is an inevitability and it is necessary to better prepare for meeting this inevitability.
A distinctive feature of hydrogen is its high energy performance, unique kinetic characteristics, environmental friendliness and an almost unlimited raw material base. In terms of mass energy intensity, hydrogen surpasses traditional hydrocarbon fuels by 2.5-3 times, alcohols - 5-6 times, ammonia - 7 times.
The qualitative influence on the working process of the internal combustion engine of hydrogen is determined, first of all, by its properties. It has a higher diffusion capacity, faster combustion rate, wider flammability limits. The ignition energy of hydrogen is an order of magnitude less than that of hydrocarbon fuels. The real working cycle determines a higher degree of perfection of the internal combustion engine workflow, the best indicators of efficiency and toxicity.
To adapt the existing designs of piston internal combustion engines, gasoline and diesel engines to operate on hydrogen as the main fuel, certain changes are required, first of all, in the design of the fuel supply system. It is known that the use of external mixture formation leads to a decrease in the filling of the engine with a fresh oxidizer, and hence to a decrease in power by up to 40%, due to the low density and high volatility of hydrogen. When using internal mixture formation, the picture changes, the energy intensity of the charge of a hydrogen diesel engine can increase up to 12%, or it can be provided at a level corresponding to the operation of a diesel engine on traditional hydrocarbon diesel fuel. The peculiarities of the organization of the working process of a hydrogen engine are determined by the properties of the hydrogen-air mixture, namely: the limits of ignition, the temperature and energy of ignition, the speed of propagation of the flame front, the distance of extinguishing the flame.
In almost all known studies of the working process of a hydrogen engine, a difficult-to-control ignition of a hydrogen-air mixture is noted. The effects on premature ignition by injecting water into the intake manifold or by injecting "cold" hydrogen have been investigated with positive results.
Residual gases and combustion chamber hot spots intensify the premature ignition of the hydrogen-air mixture. This circumstance requires additional measures to prevent uncontrolled ignition. At the same time, low ignition energy in a wide range of the excess air ratio allows the use of existing systems ignition when converting engines to hydrogen.
Self-ignition of the hydrogen-air mixture in the engine cylinder does not occur at a compression ratio corresponding to diesel engines. For self-ignition of this mixture, it is necessary to provide a temperature of the end of compression of at least 1023K. Possibly, the ignition of the air mixture from a pilot portion of hydrocarbon fuel, due to an increase in the temperature of the end of compression by using pressurization or heating at the air charge inlet.
Hydrogen as a fuel for diesel engines is characterized by a high speed of propagation of the flame front. This speed can exceed 200 m / s and cause a pressure wave to travel in the combustion chamber at a speed of more than 600 m / s. The high combustion rate of hydrogen-air mixtures, on the one hand, should have a positive effect on increasing the efficiency of the working process, on the other hand, this predetermines high values of the maximum pressure and temperature of the cycle, and a higher rigidity of the working process of a hydrogen engine. An increase in the maximum cycle pressure leads to a decrease in the engine's service life, and an increase in the maximum temperature leads to an intensive formation of nitrogen oxides. It is possible to reduce the maximum pressure due to derating of the engine or combustion of hydrogen as it is fed into the cylinder at the stroke of the working stroke. Reducing the emission of nitrogen oxides to a negligible level is possible by depleting the working mixture or by using water supplied to the inlet pipeline. So, at a> 1.8, the emission of nitrogen oxides is practically absent. When water is supplied by weight 8 times more than hydrogen, the emission of nitrogen oxides is reduced by 8 ... 10 times.
CNG is permitted directly in urban areas of residential and public buildings. Moreover, in many countries it is allowed to refuel vehicles with natural gas in underground garages. 1.6. Manufacture of gas equipment for cars. Nowadays, Italy has taken over the fame of the world's best manufacturer of autogas equipment. And now in the world market it is in the greatest demand ...
The model, designated "H2R", has a top speed of over 300 km / h. A new direction in hydrogen-fueled propulsion based on the use of the Stirling engine seems promising. This engine until the end of the XX century. It was not widely used in motor transport due to its more complex structure compared to an internal combustion engine, higher material consumption and cost. ...
About environmental hazardAll hydrocarbon fuels are known to be more or less environmentally hazardous. Liquid rocket fuels are the most environmentally hazardous, while coal is the least environmentally hazardous. The environmental hazard of hydrocarbon fuels is due to the release of toxic and poisonous chemical substances, compounds and elements that are hazardous environmental pollutants.
Environmentally hazardous components are released from fuel during storage, transportation and pumping. At these stages of fuel use, in addition to gaseous hydrocarbons (for example, ethane and methane), fuel pollutants can be represented by the fuel itself, hydrocarbon-polluted waters, fuel sludge, coal dust, and others. These pollutants enter the environment through leaks, leaks, spills, accidents, etc.
In the process of direct combustion of fuel, new environmentally hazardous gaseous, liquid and solid pollutants are formed, which are derivatives of chemical elements, compounds and substances contained both in the composition of the initial fuel and in the composition atmospheric air entering the combustion. Chemical elements, compounds and substances of fuel and air interact with each other and, having undergone certain thermal transformations, are released into the environment as part of combustion products.
What is environmental cleanliness of fuel
For fuel as a product of social labor, environmental cleanliness is a complex complex property that manifests itself during storage, transportation, pumping and directly in the combustion process.
The property of the fuel "ecological cleanliness", according to the authors, should be understood as such a state of the fuel, in which at all stages of its life cycle it does not have or has the minimum acceptable negative impact on the environment and does not pose a threat to the life and existence of people, fauna and flora.
This property of fuel is complex and complex because under certain conditions of use, for example, during storage, transportation and pumping, some pollutants enter the environment, while other pollutants are formed and emitted during fuel combustion. In this connection, the ecological cleanliness of the fuel should be conventionally considered as two interrelated components: before and during combustion, with the latter component being more significant.
Let's see GOSTs and TU
Currently, the Russian Federation has a large number of GOSTs and TUs for hydrocarbon gases, oil fuel and coal. It should be recalled that GOST is a state regulatory document for products that is mandatory for all enterprises in the country. GOSTs were created for all sectoral industrial enterprises, bringing their technical base and technological equipment, and, consequently, the quality of products, to the same level.
Since 2000, instead of new state standards specifications are issued. Unlike GOST, technical conditions are a regulatory document for products for one or several enterprises, developed taking into account their technical base and technological equipment... Since the base and equipment are different even at single-profile enterprises, the technical conditions for one and the same product, and hence its quality, are different.
An analysis of regulatory documents that determine the quality of hydrocarbon fuels shows that none of them contains information about such a fuel property as "environmental cleanliness", and therefore its numerical value (ie, an indicator) is not standardized either. In fairness, it should be stated that certain indirect indicators by which one can judge the ecological cleanliness of the fuel used, in these regulatory documents are still present. So, for hydrocarbon fuels, the chemical composition of the combustible part is indicated, and the content of harmful impurities and mineral inclusions in them is normalized. At present, the content of hydrogen sulfide (H 2 S) and nitrogen (N 2) is standardized for gas fuel; for liquid petroleum fuels - sulfur (S 2), carbon (C), vanadium (V), acids and alkalis, in addition, for gasoline - manganese (Mn) and lead (Pb), and for coals - harmful components in the mineral part ...
Obviously, the existing GOSTs and TUs need to be adjusted taking into account the actual environmental situation, the deterioration of which is facilitated by a steady increase in the consumption of hydrocarbon fuel, and, consequently, an increase in the amount of harmful emissions.
What does the octane number have to do with it?
It is known that in the Russian Federation, from January 2009, the Federal Law is to enter into force, which will oblige citizens who own cars with carburetor and injection engines to use gasoline with an octane rating of at least 95 (AI-95). This law of the Russian Federation is widely promoted in the media and our citizens form the opinion that AI-95 gasoline is more environmentally friendly vehicle fuel than AI-80 or AI-92 gasoline used today.
It should be noted that the octane number of motor gasoline is only a quantitative characteristic of resistance to detonation (spontaneous explosion) of fuels used in internal combustion engines. The octane number is standardized for light hydrocarbon fuels with a boiling point from +300 ° C to +230 0 ° C, which are gasolines. A similar indicator for medium hydrocarbon (diesel and motor) fuels with a boiling point of +2500 ° C to +360 0 ° C is the cetane number, which reflects the ability of this type of fuel to self-ignite.
The octane and cetane numbers of light fuels characterize only the method of flame propagation (explosive or uniformly continuous) during the combustion chain reaction, and not the mechanism or quality of this process. In this connection, the indicators of the octane number of gasolines and the cetane number diesel fuels cannot be used for an objective assessment of the ecological purity of these types of hydrocarbon fuels.
Perhaps this mistake was made by the developers of this Federal Law due to the absence of consultants - specialists in fuel preparation and fuel use.
How to assess environmental friendliness
The content of individual impurities and mineral inclusions of hydrocarbon fuel, reflected by their numerical values in the current regulatory documents, cannot fully characterize the ecological cleanliness of the fuel. However, for a preliminary assessment of the ecological cleanliness of the fuel, it is possible to use the numerical values of the indicators of chemical elements contained in the combustible part of the fuel. If the fuel has a higher content of hydrogen (Н 2) or bound oxygen (О 2) is present in the composition of its combustible part, for example, as in biofuel, then this fuel is more environmentally friendly. An objective assessment of the ecological purity of a particular type of fuel can be carried out only on the basis of the results of qualitative and quantitative analyzes of flue (exhaust) gases during its combustion, as well as analysis of the ash part of the fuel after its combustion. In terms of their importance, of course, the results of analyzes of flue, exhaust and other gases generated during fuel combustion are of paramount importance, since they have the greatest negative impact on the environment and affect large areas.
Obviously, for an objective assessment of such an important property of fuel as ecological cleanliness, it is necessary to develop a criterion, that is, a rule according to which this indicator changes. According to the authors, this criterion should be an additive convolution of the most environmentally hazardous components, for example CO, CO 2, H 2 S, NO x, N 2, S 2, S x O y, C x H y, soot, etc. ., the quantitative ranking of which in the combustion products of a particular fuel can be reflected by the numerical value of the significance coefficient corresponding to the share of each component in the composition flue gas... The presented criterion is objective, since it quantitatively reflects the mechanism of formation of harmful emissions through the quality of the chain reaction of combustion. The numerical value of the indicator of the ecological cleanliness of the fuel should be in the range from 0 to 1.0, while the fuel is environmentally friendly when the indicator is close to 0, and environmentally hazardous, respectively, to 1.0.
What is abroad
In the countries of Western Europe, North America and Japan, environmental problems associated, among other things, with the use of hydrocarbon fuels, began to be solved from the beginning of the 60s of the last century. At the initial stage, they tried to achieve an improvement in the ecological situation exclusively through the implementation of administrative measures. Namely, the introduction and tightening of environmental legislation, the introduction and increase of fines for pollution natural environment, limiting the number and regulating the operating time of pollution sources, including vehicles, prohibiting the use of certain products, etc., etc. However, an attempt to solve environmental problems solely by administrative measures failed.
And only 30 years later, in the mid-1990s, the above complex measures, including the modernization of the technological base of oil refineries and the improvement of automobile engines and their fuel systems, were implemented, after which the fuel market of economically developed countries entered the market as a commercial fuel high-octane gasoline. Despite the positive trends in the qualitative improvement of the natural environment in the developed countries of the world, the problem of pollution, including the products of combustion of hydrocarbon fuels, has not been completely eliminated today and requires its further solution.
Instead of conclusions
According to the authors, more environmentally friendly products of social labor should be cheaper than their less environmentally friendly counterparts. This fully applies to all types of hydrocarbon fuels. The state is obliged to take on part of the costs associated with improving the ecological cleanliness of fuel, since the use of environmentally hazardous fuels causes enormous damage to flora, fauna and the health of citizens through violation of the quality of their natural habitat. Otherwise, the state will have to bear additional costs for environmental protection measures and health care, significantly exceeding the profit from the sale of environmentally friendly fuels.
