Cryogenic engine. Cryogenic electric motors. The principle of operation of a cryogenic refrigeration unit

The engines are intended for use on aircrafts with cryogenic fuel, for high-speed land transport, in electric propulsion systems for sea vessels, space and general industrial cryogenic equipment for driving cryogenic pumps, "cold" axial compressors, etc.

High-temperature superconducting (HTSC) ceramic elements based on yttrium or bismuth are used as active materials for the rotor.

Main advantages

HTSC motors of various types, operating in liquid nitrogen, have a specific output power 3-4 times higher than conventional electric motors.

Since 2005, the MAI has been developing highly dynamic electric motors for drives of cryopumps for hydrogen energy and cryogenic supply systems for power cable JV cables. It has been shown experimentally that highly dynamic motors with permanent magnets and volumetric HTSC elements have an output power 1.3-1.5 times higher than conventional synchronous motors with the same cooling modes in liquid nitrogen.

In 2007 at MAI together with JSC NPO Energomash named after ak. VP Glushko "and OJSC" AKB Yakor "created and successfully tested an industrial prototype of a cryopump with an HTSC electric drive for cryogenic supply systems for power JV cables.

The development and testing of motors with a power of up to 100 kW was completed. Engines up to 500 kW are under development.

The novelty of the proposed solutions is protected by seven invention patents.

The research is carried out within the framework of joint German-Russian projects uniting MAI (Moscow), VNIINM im. A. A. Bochvara (Moscow), VEI (Moscow), ISSP RAS (settlement Chernogolovka, Moscow region), IPHT (Jena, Deutschland), Oswald Elektromeotoren GmbH (Miltenberg, Deutschland), IEMA (Stuttgart, Deutschland), IFW ( Dresden, Deutschland), as well as under the Science for Peace project between MAI and Oxford University (Great Britain).

Main technical characteristics

• Hysteresis type motors

• Reactive motors

As already mentioned, a heat engine and a refrigerator are required for the operation of a heat engine, which, by definition, must have a higher temperature. The temperature of the refrigerator is almost always the same as the temperature of the air, while the temperature of the heat source of the combustion chamber, reactor or solar collector can vary. However, a body with an ambient temperature iJ can be used in a heat source. In this case, the refrigerator should have a lower temperature, which can be obtained using cryogenic liquids, which engines are called cryogenic. There are known developments of _ mental engines operating according to the open Rankine cycle using liquid nitrogen. In fig. 3.16 shows a diagram of such a mustache - * and.

Light nitrogen is in a special cryogenic reservoir under pressure - From this reservoir, the liquid is directed to the heat exchanger, through which a certain amount of heat is supplied to the working fluid, sufficient; about evaporation. In this case, we will get already gaseous nitrogen with a pressure pt __ and the temperature Tv

in the initial position, the outlet valve of the working cylinder is closed, and the inlet is I ікріт. The cylinder receives | і kmol of evaporated nitrogen. Acting. Low gas pressure causes it to drop. This process takes place by removing heat at constant pressure (p2 = p,) and temperature (T2 = Ty) pore, until the gas fills the volume of the cylinder v2.

We have:

In the next operating position, the inlet valve closes. The high gas pressure inside the cylinder will lead to the continued movement of the piston and increase the volume until the gas pressure becomes equal to p3 and the volume occupied by it - v3. This process can occur both isothermal (T3 = Tu) with the continuation of heat supply, and adiabatically (T3< Тх) в завн! симости от типа используемого устройства. Рассмотрим более предпочтительны изотермический процесс:

Let us now consider the case of adiabatic expansion, which is much easier to carry out in real life. If there is no heat exchange during expansion, the gas temperature will change according to the following law:

Here for nitrogen y = 1.4. Expansion work

s, = R / (y - 1) = 20.8 kJDcmol K).

I / atm = Ra ™ "" 3 = ^ LT3 "

In this case, the useful work will be equal to

And s = pRT1-pRT3 + W23 = iiRT (Tl-T3) + iicv (T1-T3) = ii (Tl-T3) R -? - i. (38)

Thus, in the example discussed above, the final work obtained during expansion will be equal to 4.2 MJ / kmol, or 150 kJ / kg. Compare this figure with 5.7 MJ / kmol, or 204 kJ / kg, for the case of isothermal expansion and with the specific heat of combustion of gasoline 47 000 kJ / kg.

It is clear that the specific energy of the cryogenic working fluid can be increased -> by increasing the working pressure. However, this growth is subject to the logarithmic | the law. Thus, with an increase in pressure 10 times (up to 10 MPa), the specific energy will increase to 11.4 MJ / kmol, or only 2 times. Note that a pressure of 10 MPa corresponds to 100 atm. Building an engine for this operating pressure- a difficult technical problem: the engine will be heavy and very expensive.

Gasoline internal combustion engines have an average efficiency of less than 20%. That is, the useful work per 1 kg of the working fluid in a gasoline engine is 8000 kJ / kg or more, or almost 40 times more than in a cryogenic engine.

In the created first experimental cryogenic engines, the achieved values ​​of the specific work were less than 50 kJ / kg. In a demonstration car with this engine, 1 gallo of nitrogen was consumed per 0.3 miles. That is, it has not yet been possible to create a sufficiently practical cryogenic engine. It is possible that after appropriate modifications, the efficiency is as follows: * "engines can be significantly improved1).

Cryogenic engines for vehicles have not yet provided high mileage. The current cost of liquid nitrogen is $ 0.5 / kg, or $ 1.52 / gallon. Taking into account the achieved values ​​of the specific mileage, this means that with the same mileage, the cost of the used d - this fuel will be ten times higher than that of gasoline engines.

At the same time, a higher specific consumption of "fuel" requires a greater reserve of it. vehicle... And this, in turn, leads to a decrease in the payload that the vehicle can carry.

Approx. ed. The first and one of the few developers of a cryogenic engine is. University of Washington (USA), which created its LN2000 prototype based on the Grumman-Olson postal vehicle. An experienced 5-cylinder engine with a capacity of 15 liters was installed on the car. with., working on liquid nitrogen in an open Rankine cycle. The cryogenic engine provided a maximum vehicle speed of 35.4 km / h, and a Dewar vessel of 80 liters, which was used to store liquid nitrogen at a pressure of 24 bar, providing a cruising range of about 2 miles (3.2 km). The cryogenic car was created in the mid-90s in the course of the search for power plants for a car of the ecological category ZEV (with zero displacement), alternative to the electric drive. There are also enthusiasts in Russia trying to create an efficient cryogenic engine. However, significant successes, which speak of the efficiency and relevance of this direction for road transport, neither in Russia nor abroad, has not yet been achieved.

The only undoubted advantage of cryogenic engines is their environmental friendliness. However, the ecological harmlessness of such systems is not zero, since the production of liquid nitrogen requires expenditures of rgi, accompanied by harmful emissions. The question is whether the environmental benefits compensate for the serious disadvantages of cryogenic burners described above.

Prove that the theoretical efficiency of a Stirling engine without regeneration

where ПCamot is the efficiency of the Carnot cycle corresponding to the given temperature range; v is the number of degrees of freedom of the working fluid (gas); g - compression ratio.

What gas is better to use as a working fluid? Explain why?

In the examples, we have assumed a compression ratio of 10. What would the engine efficiency be with a compression ratio of 20? What disadvantages will gsto have at a higher compression ratio? Does it make sense to increase the compression ratio?

Draw the processes typical of the Stirling engine in diagrams and T, S for the example given in the text. What is the physical meaning of the lengths under the curves p, V - and 7 ~, V - for v and s and m osty?

Consider two cylinders A and B with pistons inside. Ra - e volumes inside the cylinders can be changed independently. The maximum h of each of these cylinders is 10 m3, the minimum volume is zero. Cylinder - they are hydraulically interconnected so that the gas at any point in the volume of the cylinders will have the same pressure. At the initial moment of time, the volume of the cylinder A is equal to 10 m3, and the volume of the cylinder B is zero. In other words, piston A will go up and piston B will go down. The adiabatic exponent of his body is y = 1.4.

Only gas (kmol) is in the system at a pressure of 0.1 MPa and a temperature of 400 K.

3. Now imagine that piston A has risen so that the volume in the cylinder is reduced to 1 m3, and the volume in the cylinder B remains unchanged. What are the m> temperature of the gas and its pressure under the condition of an adiabatic process? How is energy expended in compression?

4. Then the pistons began to move simultaneously until the volume in cylinder A became equal to zero, and in cylinder B - 1 m3. What are the pressure and the temperature of the gas in the cylinder B!

5. The next step is the transfer of heat to cylinder B so that * the volume has increased to 10 m3. The gas temperature does not> change during the process. How much heat was transferred to the gas during this process. What work did piston B do? What is the final gas pressure?

6. Now piston B begins to rise, while piston A is lowered. Gas flows from one cylinder to another. This process. " theoretically occurs without energy consumption. From cylinder A, heat is discharged into the environment, and the gas is cooled to a temperature of 400. In the final position, when cylinder A has a maximum volume, ci is considered completely complete. How much energy was released into the environment during this process?

7. What is the efficiency of a given machine, that is, what is the ratio of the amount of work done to the heat received from the heater?

8. How does this efficiency compare with the efficiency of the Carnot cycle?

9. Draw the considered processes in p, Y - and 7, ^ diagrams.

10. Get the formula for efficiency versus compression ratio. Draw a curve of efficiency versus g in the range 1< г < 100.

11. If the obtained value of efficiency turns out to be clearly overestimated (n realistic), for example, equal to 10,000, what would the actual efficiency be? Can it exceed the efficiency of the Carnot cycle? Explain your findings.

3.4. Imagine a certain machine equipped with a spark engine: internal combustion (Otto cycle). This engine uses gasoline (for pr< стоты допустим, что бензин состоит из чистого пентана), и поэтому его степе сжатия ограничена и равна девяти. Номинальный удельный расход топлива а томобиля 40 миль/галлон.

Since gasoline engines can use nol as fuel, the owner of the car decided to convert it to this type of fuel. At the same time, the step ", compression" increased to 12. Let us assume that in any case, the real effective car is approximately equal to half the theoretical efficiency. What is the specific fuel consumption of a car running on ethanol?

The lowest calorific value and density of the substances under consideration: pentane - 28.16 MJ / l, 0.626 kg / l; ethanol - 21.15 MJ / l, 0.789 kg / l.

Solve this problem twice, once for y = 1.67 and the other for y = 1.4.

3.5. Consider a cylinder with a frictionless piston. At the initial stage of the experiment, it contains 1 liter of gas (y = 1.4, c = 20 kJ / (K kmol)) at a temperature of 400 K and pressures of 105 Pa.

How much gas, in kilometers, is in the cylinder?

2 What is the product pV in this case!

GKst now the piston moves with a decrease in gas volume to 0.1 l. The compression is adiabatic.

What is the gas pressure after compression? і What is the gas temperature equal to?

J What work was done by the compressor?

1 measure isothermally supply 500 J of heat to the gas.

і What is the volume of gas after that?

What was the equal of the gagging?

Since when heat is supplied, the gas expands (the piston moves), what work does it do?

Now the gas expands adiabatically until its volume is equal to 1 liter.

What is the gas pressure after adiabatic expansion? і What is the gas temperature?

what work is done in adiabatic expansion?

Let the heat be removed from the gas isothermally until its pressure is equal to 105 Pa. In this case, the system returns to state 1.

2. What is the total work of the piston transferred to the external load? what is the total amount of heat received by the system (rejected heat is not taken into account here)?

What is the efficiency of the device?

5 What is the corresponding efficiency of the Carnot cycle?

No. Draw the processes and the whole cycle in p. K-diagram.

Let us assume that the gasoline has an octane number of 86. The octane number of ethanol is 160. Let us assume that y = 1.4.

1. How has the calorific value of 1 liter of the mixture changed in comparison with the calorific value of pure gasoline?

2. What is the octane number of the whole mixture?

Let us assume that the maximum allowable compression ratio of the fuel is r = 0.093 Og, where Og is the octane number.

3. What is the maximum compression ratio of a gasoline engine? Mixed fuel engine?

4. What is the relative efficiency of the engine?

5. What is the specific fuel consumption per unit of distance traveled when pure gasoline is used and when a fuel mixture is used?

3.7. The open-circuit piston engine runs on atmospheric air. which enters it in an amount of 23 * 10 () kmol at a temperature of 300 K and a pressure of 105 Pa. The compression ratio of the engine is 5.74.

The contraction and expansion are adiabatic. Heat is supplied isobaric, while heat is removed isothermally. 500 Jb of heat is supplied to the gas per cycle. Air has c. = 20 790 J / (K - kmol) and y = 1.4.

What is the theoretical efficiency of the engine? Compare this to the efficiency of the Karnot cycle.

Follow these steps:

calculate the initial volume of the cylinder;

determine for the process of adiabatic compression the final values ​​of V, p, T and the required work:

determine the thermodynamic parameters of the system after heat supply; calculate the perfect work in the process of expansion.

3.8. Some Stirling engines realize only half when running; its theoretical effectiveness. The engine operates in the temperature range from 1000 to 400 K. What will be the efficiency of the device in the following cases:

1. If you use an ideal heat regenerator, argon as the working medium, and the compression ratio is 10: 1.

2. Under the same conditions as in claim 1, the compression ratio is 20: 1.

3. Under the same conditions as in item 1, but without using a regenerator.

4. Under the same conditions as in item 2, but without using a regenerator.

3 9. When using rich mixtures, the efficiency of the Otto engine decreases, while when working on a lean mixture, there may be problems of ignition. The solution to this issue can be the use of engines with stratified combustion.

Consider an engine with a compression ratio of 9: 1. A rich mixture has y = 1.2, a lean mixture y = 1.6. All other things being equal, what is the ratio of ■ »the efficiency of using the lean mixture to the efficiency of using - V. 4th of the rich mixture?

3.8. Consider a spark-ignited Otto engine that has the following characteristics:

maximum cylinder volume VQ = 1 l (KN m3); compression ratio r = 9: 1; pressure at the end of the inlet p0 = 5 104 Pa; mixture temperature at the end of the inlet 70 = 400 K; the average value of the adiabatic index of the mixture is 1.4;

specific heat of the mixture (at constant volume) c = 20 kJDC - kmol).

What power is transferred to the load if the motor shaft rotates at> * 00 rpm?

Chtomnye masses: N - 1 daltons: C - 12 daltons; N - 14 Daltons: 0-16 Dal - tone. The presence of argon in the mixture can be neglected.

3.12. The highest heat of combustion of i-heptane (at 1 atm and 20 ° C) is 48.11 MJ / kg. What is the net calorific value?

3.13. 1 mole of some gas (y = 1.6, cv = 13.86 J / (K kmol) at 300 K takes 1 liter. For each step described below, determine the values ​​of p, Vu T.

Step 1 -> 2.

Adiabatic compression of gas to a volume of 0.1 l. How much energy tV12 was expended in compression?

Step 2 -> 3.

Isothermal transfer of 10 kJ of heat to the working fluid. What is external work equal to?

Step 3 -> 4.

Adiabatic gas expansion 10: 1.

Step 4 -> 1.

Isothermal heat removal with gas return to state 1. What is the removed energy equal to?

What is the overall cycle efficiency?

What is the efficiency of the corresponding Carnot cycle?

How much power will the motor have if its shaft is rotating at 5000 rpm (5000 cycles per minute)?

3.14. In the Stirling engine discussed earlier, isothermal compression occurs, followed by isochoric heat input, isothermal compression, and isochoric heat removal.

Isothermal compression is difficult to achieve, especially in high-speed engines. Therefore, we assume that the engine is performing adiabatic compression during operation. Note that the other phases of the engine in question correspond to the phases of the previously described engine. So, with isothermal heat supply, 293 J is supplied to the working fluid. That is, the "hot" cylinder after the adiabatic compression process will have a temperature of 652 K until the end of the heat supply process.

Determine the theoretical efficiency of the engine (without heat recovery) and compare it with the efficiency of the corresponding Carnot cycle.

Determine the power produced by one cylinder of a given engine, assuming that the efficiency of a real engine will be approximately 2 times less than that of an ideal engine. The engine shaft speed is 1800 rpm. Each revolution of the shaft rotation corresponds to one complete engine cycle. For calculations, take y = 1.4.

3.15. Suppose the engine is operating in a temperature range between 1000 and 500 K with the efficiency of a Carnot engine. The heat source has a power of 100 kW and a temperature of 1500 K. This heat is transferred to the working fluid of the previously described engine. Let us assume that the transfer of heat flow is carried out at a temperature gradient that reduces the temperature from 1500 to 1000 K. The efficiency of heat transfer is assumed to be 100%, that is, 100 kW power is supplied to the engine without losses.

What is the efficiency of the engine described above, operating on the Iirno cycle? What is the net power of this system (engine)?

3.16. The steam boiler supplies steam to the steam turbine. There are channels in the walls of the boiler through which steam flows. On one side, these walls are in the zone of the furnace flame. The temperature of the heated steam is 500 K, the temperature of the wall in contact with the flame is 1000 K. A heat flux of 1 kW passes through each square centimeter of the heating surface. The thermal conductivity of the metal walls of the channel X depends on the temperature as follows: X = 355 - 0.111Т (in SI). The temperature is given in Kelvin.

Calculate the wall thickness.

2 Determine the temperature at the midpoint between the inner and outer walls of the duct.

I ". The 4-stroke Otto spark ignition engine has a total volume of 2 liters and runs on methane (gross calorific value 55.6 MJ / kg). The compression heat in the engine is 10: 1. The fuel injection system uses an injection system that supplies fuel in such a way that the specified stoichiometric ratio is maintained.The adiabatic exponent of the mixture is 1.4.< температуре 350 К, так как гидравлические потери на входе можно считать небрежимо малыми.

is the power transmitted by the engine to the load if the rotation frequency of its shaft is 5000 rpm? Taking into account the peculiarities of the engine, the calculation should be made based on the lowest heat of combustion of the fuel.

18. Consider a spark ignition engine with a compression ratio of 9: 1. The gas inside the cylinder has y = 1.5.

the initial state of the working fluid has the following parameters: = I l;

I atm; Tx = 300 K.

At the end of the compression process, 10 mg of gasoline is injected, then the ignition mixture is g "I. Combustion of the fuel occurs instantly. Let us assume that the specific heat of gasoline is 45 MJ / kg.

Determine the ideal engine efficiency.

Calculate the efficiency of the corresponding Carnot cycle.

3. Prove that reducing the amount of injected fuel in one peak will bring the efficiency of the Otto cycle closer to the efficiency of the Carnot CEC.

3.19. In a diesel engine, fuel is injected into hot compressed air in the cylinder, after which the mixture ignites spontaneously. Suppose the fuel is supplied relatively slowly so that combustion of the mixture takes place at substantially constant pressure. The g compression ratio used in most diesel engines is between 16: 1 and 22: 1. In diesel engines, spontaneous ignition reliably occurs at an air temperature of at least 800 K.

Air has a ratio of the specific heat at constant pressure to the specific heat at constant volume, equal to 1.4 (y = 1.4). Start air temperature at the entrance to a cold diesel engine 300 K.

What should be the minimum compression ratio required to start the engine?

3.20. Consider a machine that uses air> i (y = 1.4) as a working medium and performs a sequential series of thermodynamic processes.At the end of each process, determine the characteristics of the state of the gas (pressure, volume and temperature), as well as the energy characteristic of each process.

In the initial state (state 1), the gas has the following characteristics рх = 105 Pa; Vx = 10-3 m3; Tx = 300 K.

1. 1st process (step I -> 2): adiabatic compression, volume reduction to 10-4 m3.

2. 2nd process (step 2 -> 3): isobaric supply of 200 J of heat.

3.3rd process (step 3 -> 4): adiabatic expansion up to V4 = 10_3m3.

Calculate all the thermal and mechanical energy that is supplied to the motor and all the mechanical energy that is removed from it. Based on this, determine the efficiency of the machine. (Hint: Be sure to consider all the processes in which energy is removed.)

3.21 In the cycle of a diesel engine, the following phases can be distinguished:

phase 1 2. Adiabatic compression of clean air from volume Vx to volume ":

phase 2 -> 3. Combustion of fuel at constant pressure with expansion from volume V2 to volume K3;

phase 3 ^ 4. Adiabatic expansion from volume V3 to volume V4; phase 4 - »1. Isochoric heat removal, in which the gas is in the initial conditions.

t cycle is similar to the Otto cycle with the only difference that combustion in Otto nickle proceeds isochoric, while in a diesel engine it is isobaric, we look at a cycle in which Fj = K) 3 m3, V2 = 50 W-6 m3, V3 = 100 10-6 m3, = 105 Pa, 7] - 300 K and for all processes we will consider y = 1.4.

Calculate the theoretical efficiency of the cycle.

Calculate the efficiency using the Diesel cycle efficiency equation obtained in Ch. 4.

Calculate efficiency by evaluating all mechanical energy (compression and expansion) and all thermal processes (heat input and removal). Be careful enough when analyzing what happens during the combustion phase (2-> 3), when combustion energy is released and some mechanical work is performed at the same time.

discounts on PP. 2 and 3 must be the same.

We all know that one of the foundations of the material life of modern mankind is the well-known minerals oil and gas. Blessed hydrocarbons are present in one way or another in every area of ​​our life, and the first thing that comes to mind of any person is fuel. These are gasoline, kerosene and natural gas used in various energy systems (including vehicle engines).

How many cars on the roads of the world and airplanes are burned in the air in their engines ... Their number is huge and just as huge is the amount of fuel that goes out, so to speak, into the pipe (and at the same time strives to contribute its considerable share to the atmosphere poisoning :-)). However, this process is not endless. Oil reserves, from which the lion's share of the world's fuel is produced (despite the fact that it is gradually losing ground to natural gas), is rapidly decreasing. It is constantly becoming more expensive and its deficit is felt more and more.

This situation has long forced researchers and scientists around the world to look for alternative sources of fuel, including for aviation. One of the directions of such activity was the development of aircraft using cryogenic fuel.

Cryogenic means " born of the cold”, And the fuel in this case is liquefied gas, which is stored at very low temperatures. The first gas that attracted the attention of developers in this regard was hydrogen. This gas has three times the calorific value of kerosene and, moreover, when it is used in an engine, water and a very small amount of nitrogen oxides are released into the atmosphere. That is, it is harmless to the atmosphere.

Airplane TU-154B-2.

In the mid-80s of the last century, the design bureau of A.N. Tupolev began to create an aircraft that uses liquid hydrogen as fuel. It was developed on the basis of the serial TU-154B using the NK-88 bypass turbojet engine. This engine was created in the engine building design bureau im. Kuznetsova(Samara), again based on a serial engine for the Tu-154 NK-8-2, and was intended to run on hydrogen or natural gas. It must be said that in this bureau, work on new topics has been carried out since 1968.

The same Tu-155 is in storage ... Unfortunately, disgusting storage :-(.

New aircraft running on cryogenic fuel received the name TU-155. However, things are not so simple. The point is, hydrogen is a dangerous fuel. It is extremely flammable and explosive. Possesses exceptional penetrating ability, and can only be stored and transported in a liquefied state at very low temperatures, close to absolute zero (-273 degrees Celsius). These features of hydrogen are a big problem.

Therefore, the TU-155 was a flying laboratory for researching and solving existing problems, and the base aircraft underwent a radical alteration during its creation. Instead of the right engine NK-8-2, a new cryogenic NK-88 was installed (the other two remained relatives :-)). At the rear of the fuselage, in the place of the passenger compartment, a special tank was placed for cryogenic fuel, liquid hydrogen, with a volume of 20 cubic meters. with enhanced screen-vacuum insulation, where hydrogen could be stored at temperatures below minus 253 degrees Celsius. It was supplied to the engines with a special turbo pump unit like on a rocket.

NK-88 engine. A massive turbo pump assembly is visible on top of the engine.

Due to the high explosion hazard, almost all electrical equipment had to be removed from the compartment with the fuel tank in order to exclude the slightest possibility of sparking, and the entire compartment was constantly purged with nitrogen or air. To control units power plant a special helium control system was created. In addition, hydrogen vapors from the tank had to be diverted away from the engines in order to avoid ignition. For this, a drainage system was made. On the plane, its branches in the aft fuselage are clearly visible (especially on the keel).

Layout diagram of TU-155. Blue - fuel tank. The front compartment contains support equipment. Cryogenic engine in red.

In general, more than 30 new aircraft systems were created and implemented. In general, the work was carried out tremendous :-). But there was also a need for ground-based, no less complex equipment that would provide refueling and storage. True, then the development of the Buran system was in full swing, on the carrier rocket of which liquid hydrogen was one of the propellants. Therefore, it was believed that everything would be supplied on an industrial basis and there would be no shortage of fuel. But, I think, everyone understands that cryogenic fuel in such a system becomes simply "gold" in terms of cost. And this means that commercial use of liquid hydrogen is hardly possible in the near future. Therefore, even then preparations were underway for the transition to another species. cryogenic fuel – liquefied natural gas(LNG).

Nevertheless, the first flight of the TU-155 on liquid hydrogen took place on April 15, 1988. Besides that, there were 4 such flights. After that, the TU-155 was modified for flights using liquefied natural gas (LNG).

Compared to hydrogen, this type of fuel is much cheaper and more accessible; moreover, it is also several times cheaper than kerosene. Its calorific value is 15% higher than that of kerosene. In addition, it also does little to pollute the atmosphere, and it can be stored at a temperature of minus 160 degrees, which is as much as 100 degrees higher than that of hydrogen. In addition, against the background of hydrogen, LNG is still less fire hazardous (although, of course, such a danger still exists) and there is sufficient experience in maintaining it in a safe state. The organization of gas supply (LNG) of airfields, in general, is also not extremely difficult. Gas pipelines are connected to almost every major airport. In general, there are enough advantages :-).

The first flights of the TU-155 already using cryogenic fuel liquefied natural gas took place in January 1989. (The video below talks about this). There were also about 90 such flights. All of them showed that fuel consumption is reduced by almost 15% in comparison with kerosene, that is, the aircraft becomes more economical and more profitable.

Now a little about the prospects ... At the end of the 90s, the main manager of Russian gas reserves, Gazprom, came up with an initiative to build at the beginning a cargo-passenger plane, and then just a passenger plane, which could run entirely on LNG. The aircraft received the name TU-156 and was created on the basis of the existing TU-155. Three new NK-89 engines were to be installed on it. These are similar to NK-88, but with two independent fuel systems: one for and the other for cryogenic fuel(LNG). This was convenient in the sense that it was far from always possible to refuel with gas, and the plane could switch from one power system to another as needed. According to the developed technology, this took only five minutes. NK-89 also had a heat exchanger in the turbine space, where the liquefied gas passed into a gaseous state and then entered the combustion chamber.

A lot of research and design work was carried out on the rearrangement of the compartments and the location of the fuel tanks. By 2000, three TU-156s were to be produced at the Samara Aviation Plant, and their certification and trial operation were to begin. But ... Unfortunately, this was not done. And the obstacles to the implementation of the plans conceived were exclusively financial.

After that, several more projects of aircraft using cryogenic fuel (LNG) were developed, such as, for example, the TU-136 with turboprop engines running on both kerosene and liquefied gas and the wide-body TU-206 with turbojet engines running on LNG. ... However, at the moment, all these projects are still projects and have remained.

Tu-136 aircraft model.

Airplane model TU-206 (TU-204K).

Time will tell how things will develop in this area of ​​aviation science and technology. While the creation of aircraft using cryogenic fuel hindered by various circumstances, both objective and subjective. Much remains to be done in the development of special aircraft systems, the development of ground infrastructure, fuel transportation and storage systems. But this topic is extremely promising (and, in my opinion, very interesting :-)). Hydrogen, with its enormous energy intensity and practically inexhaustible reserves, is the fuel of the future. We can talk about this with complete confidence. The transitional stage to this is the use of natural gas.

And this decisive step into the future has been made precisely in Russia. I am proud to say this again :-). Nowhere in the world were there and to this day there are no aircraft similar to our TU-155. I would like to quote the words of the famous American aviation engineer Karl Brever: “ The Russians have done a job in aviation commensurate with the flight of the first satellite of the Earth!»

This is the true truth! I just want these things to go in a stream (and the Russians can do it :-)), and so that this stream would be continuous, and not move in jerks, as it often happens with us ...

Dearman in partnership with scientists, leaders industrial enterprises and specialists in cryogenic equipment specializes in the development of technologies using liquefied gases. The main achievement of this research is the Dearman engine, a state-of-the-art reciprocating engine that works by expanding liquid nitrogen or liquid air to produce environmentally friendly cold and mechanical energy.

When nitrogen passes from a liquid to a gaseous state of aggregation, this gas expands 710 times. This increase in volume is used to drive the engine pistons. Dearman engines work like steam engines high pressure, but at a low boiling point of liquid nitrogen. This means that both waste heat and ambient temperature can be used as a source of thermal energy, eliminating the need for traditional fuels.

A unique feature of Dearman engines is the use of a mixture of water and glycol as a coolant. When this coolant is mixed with extremely cooled nitrogen, this liquid expands quasi-isothermally, which greatly improves engine efficiency.

It is important to note that when the Dearman engine is running, it emits only air or nitrogen, without emissions of nitrogen oxides (NOx), carbon dioxide (CO2) or particulate matter.

Dearman technology has many advantages over other low carbon technologies:

• Low capital cost and associated carbon - Dearman engines are manufactured from common materials using technologies common in the engine manufacturing industry.
• Fast filling - liquid gas can be transferred between tanks to high speeds... The modern gas industry uses systems capable of distilling more than 100 liters of liquid gas per minute.
• Large amounts of existing infrastructure - the gas industry is global in nature. Currently, there is a well-developed liquid nitrogen production facility capable of operating thousands of Dearman engines.
• The efficiency of the "fuel" production process is the liquefaction of air, a long-established process that requires only air and electricity.

• The air liquefaction facility can be used very flexibly - for example, during off-hours or during part-load times. Renewable energy sources can be used to further reduce costs.

How it works

The Dearman engine works as follows:
1.the coolant is pumped into the engine cylinders, filling almost their entire volume;

2. then cryogenic nitrogen is introduced into the cylinder, which comes into contact with the heat exchange liquid and begins to expand;

3. heat from the coolant is absorbed by the expanding gas, resulting in an almost isothermal expansion;

4. the piston moves downward, the exhaust valve opens, and the gas-liquid mixture exits the engine;

5. The coolant is recovered, heated and reused, while nitrogen or air is released to the atmosphere.

On the territory of the Gromov Flight Research Institute in Zhukovsky near Moscow, there is an airplane with an inscription on board the Tu-155. This unique machine is a flying laboratory for testing cryogenic fuel systems and engines. Work in this direction was carried out at the end of the 80s. The Tu-155 became the first aircraft in the world to use liquid hydrogen and liquefied natural gas as fuel. It has been 27 years since the first flight of this unusual machine. And now she is quietly standing among the decommissioned aircraft. Several times they wanted to cut it into metal. So what makes this plane unique?
1.

Before talking about this aircraft, it is worth explaining what cryogenic fuel is and how it differs from hydrocarbon fuel. Cryogenics is a change in the properties of various substances at extremely low temperatures. That is, cryogenic fuel means “born of the cold”. It is liquid hydrogen, which is stored and transported in a liquid state at very low temperatures. And about liquefied natural gas, which also has very low temperatures.

Compared to kerosene, liquid hydrogen has several advantages. It has three times the calorific value. That is, when burning equal masses, hydrogen releases more heat, which directly affects the economic characteristics of the power plant. In addition, when used, water and very small amounts of nitrogen oxides are released into the atmosphere. This makes the power plant environmentally friendly. However, hydrogen is a very dangerous fuel. When mixed with oxygen, it is extremely flammable and explosive. Possesses exceptional penetrating ability, and can only be stored and transported in a liquefied state at very low temperatures (-253 ° C).

These features of hydrogen are a big problem. That is why, together with liquid hydrogen, natural gas was also considered as an aviation fuel. Compared to hydrogen, it is much cheaper and more affordable. It can be stored liquefied at -160 ° C, and compared to kerosene, it has 15% higher calorific value. It is several times cheaper than kerosene, which makes it also economically viable as an aviation fuel. However, natural gas is just as flammable, albeit to a lesser extent than hydrogen. It was with these difficulties that the engineers of the Tupolev Design Bureau had to cope when creating an experimental Tu-155 aircraft.
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For the first time, aviation designers have encountered cryogenic technology. Therefore, the design went not only in the quiet of the design halls, but also in research laboratories. The designers, step by step, introduced new design solutions and technologies that ensure the creation of fundamentally new aircraft systems, a cryogenic power plant and systems that allow its safe operation.
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The flying laboratory was created on the basis of the serial Tu-154, modified for the Tu-154B standard. Board number USSR-85035. Vladimir Aleksandrovich Andreev was appointed chief designer of the Tu-155. The plane had many fundamental differences from the basic version. A cryogenic fuel tank with a volume of 17.5 m 3, together with a fuel supply system and a pressure maintenance system, constituted an experimental fuel complex located in the aft compartment of the fuselage, separated from other aircraft compartments by a buffer zone. The tank, pipelines and units of the fuel complex had a screen-vacuum insulation, providing the specified heat flow. Buffer zones protected the crew and vital aircraft compartments in the event of a leak in the hydrogen systems.
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The aircraft was equipped with an experimental turbojet bypass engine NK-88, created in Samara at the engine-building design bureau under the leadership of Academician Nikolai Dmitrievich Kuznetsov on the basis of the serial engine for Tu-154 NK-8-2. It was installed instead of the right-hand regular engine and used hydrogen or natural gas for operation. The other two engines were native and ran on kerosene. They have now been removed. But NK-88 remained in place.
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There are a number of systems for the control and monitoring of the cryogenic complex on the aircraft:

Helium system that controls the power plant units. Since the engine was running on hydrogen, it was impossible to supply electric drives to it. That is why its control system was replaced with a helium one.

Nitrogen system replacing air in compartments where cryogenic fuel leaks are possible.

Gas control system that monitors the gas environment in the aircraft compartments and warns the crew in case of hydrogen leaks long before the explosive concentration.

Vacuum control system in heat-insulating cavities.

In the cargo compartment of the forward fuselage there are round nitrogen cylinders. They are also installed in the aircraft cabin above the windows. On the floor, instead of passenger seats, helium cylinders are installed. Plus stands with instrumentation and recording equipment.

In general, more than 30 new aircraft systems were created and implemented. Among new technologies, an important place is occupied by the technological process, which ensures the cleaning of the internal cavities of pipelines and units. Because with highly efficient insulation and vacuum tightness, cleanliness is the key to the safety of your future flight.

The cockpit has undergone changes. The partition was moved deeper into the cabin, and the workplaces of the second onboard engineer were installed in the cockpit, who was responsible for the operation of the experimental engine and the test engineer, who controlled the operation of the onboard experimental systems. An emergency escape hatch was installed in the cockpit floor.

An aviation cryogenic complex was created for servicing the aircraft and performing test work. It consisted of a liquid hydrogen (or liquefied natural gas) filling system, pneumatic power supply, power supply, television monitoring, gas analysis, water irrigation in case of fire, and cryogenic fuel quality control.

At the stage of ground tests, the functioning of all experimental systems was checked, including the operation of the NK-88 engine on liquid hydrogen. The modes of refueling, maintenance of vacuum systems, modes of operation of the fuel system and the pressure maintenance system in combination with a running engine were worked out. At the same time, the preparation of the aircraft for flight, refueling of the onboard systems with helium and nitrogen was practiced.

The photo shows a long tube extending from under the fuselage to the nozzle of the central engine. This is an emergency discharge system for liquid hydrogen (natural gas). It made it possible, if necessary, to drain the cryogenic fuel onto the nozzle cut of an average standard engine. In the course of ground tests, various situations associated with the danger of an explosion and fire were worked out.

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In the process of direct preparation for the flight, liquid hydrogen was delivered by refuellers. They were connected to the aircraft through stationary cryogenic pipelines with shut-off and connecting fittings, which provided the necessary fire-prevention gaps between the aircraft, the tanker and the place where drained hydrogen gas was discharged into the atmosphere. After docking of the tankers, the quality control of liquid hydrogen was carried out using a special sampler and a gas chromatograph. In addition to the usual operations in preparing the aircraft for flight, the preparation of the experimental engine, experimental systems of the aircraft and the ground complex was carried out. Particular attention was paid to explosion and fire safety equipment, gas control systems, nitrogen control systems, vacuum control in insulating cavities, fire extinguishing systems, ventilation of the fuel complex compartment and engine nacelle. During the tests, various means of protection against an increase in the concentration of hydrogen in the compartments were tested, both with the use of a neutral medium (nitrogen), and ventilation with air from the on-board air conditioning system.

Due to the high explosion hazard, almost all electrical equipment had to be removed from the compartment with the fuel tank. This eliminated the slightest possibility of sparking, and the entire compartment was constantly purged with nitrogen or air. In addition, hydrogen vapors from the tank had to be diverted away from the engines to avoid ignition. For this, a drainage system was made. One of its elements is the first to catch the eye on the keel of the aircraft. This is the exhaust manifold fairing.
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For the first flight, the aircraft was prepared at the Zhukovskaya flight test and development base of Tupolev (ZhLiDB). Tu-155 was towed to the place where the engines were started. "I am 035, please take off." "035, cleared for takeoff." On April 15, 1988, at 5.10 pm, a Tu-155 aircraft with a liquid hydrogen engine took off from an airfield near Moscow on its maiden flight. It was piloted by a crew consisting of: first pilot - honored test pilot of the USSR Vladimir Andreevich Sevankaev, second pilot - honored test pilot of the USSR Andrei Ivanovich Talalakin, flight engineer - Anatoly Aleksandrovich Kriulin, second flight engineer - Yuri Mikhailovich Kremlev, lead test engineer - Valery Vladimirovich Arkhipov.

The flight proceeded normally. All ground services and the Tu-134 escort aircraft were monitoring its implementation. The systems that have been tested and tested on the ground have been tested in the air for the first time. The flight lasted only 21 minutes in small circles at different altitudes no higher than 600 meters. It ended a little earlier than planned, for which test engineer Valery Arkhipov had good reasons: in the nitrogen compartment, the sensors recorded the presence of nitrogen, which should have automatically appeared in case of hydrogen leaks. But, thank God, the reason was different. Nitrogen was supplied through a balloon valve, which was depressurized when the aircraft was tilting to both sides of the axis. This became clear only on earth.

Only the first step was taken towards solving the complex problems of introducing liquid hydrogen as aviation fuel. During the flight tests, flights were performed to check the operation of the power plant and aircraft systems in various flight modes and during the evolution of the aircraft. The experimental engine was started, the operation of explosion and fire safety systems was tested in the modes of creating a neutral environment and air ventilation. In June 1988, the liquid hydrogen flight test program was completed. After that, the Tu-155 was modified for flights using liquefied natural gas. The first flight using this fuel took place on January 18, 1989. The aircraft was tested by the crew consisting of: ship commander - honored test pilot of the USSR Vladimir Andreevich Sevankaev, second pilot - Valery Viktorovich Pavlov, flight engineer - Anatoly Aleksandrovich Kriulin, second flight engineer - Yuri Mikhailovich Kremlev, lead test engineer - Valery Vladimirovich Arkhipov ...

As General Designer Alexey Andreevich Tupolev said: “Today, for the first time in the world, an airplane took off, using liquefied natural gas as fuel. And we hope that this first flight of this aircraft will give us the opportunity to collect all scientific and experimental data and build an aircraft that will be able to fly passengers in the near future ”.

Tests have shown that fuel consumption is reduced by almost 15% compared to kerosene. Plus, they confirmed the possibility of safe operation of the aircraft using cryogenic fuel. During an extensive set of tests on the Tu-155, 14 world records were set, as well as several international flights from Moscow to Bratislava (Czechoslovakia), Nice (France) and Hanover (Germany) were made. The total operating time of the experimental power plant exceeded 145 hours.

At the end of the 90s, the main manager of Russian gas reserves, Gazprom, came up with an initiative to build, at the beginning, a cargo-passenger plane, and then just a passenger plane, which could completely run on liquefied natural gas. The aircraft was named Tu-156 and was created on the basis of the existing Tu-155. Three new NK-89 engines were to be installed on it, similar to the NK-88, but having two independent fuel systems: one for kerosene and the other for cryogenic fuel. A lot of research and design work was carried out on the rearrangement of the compartments and the location of the fuel tanks.

By 2000, three Tu-156s were to be produced at the Samara Aviation Plant and their certification and trial operation were to begin. Unfortunately, this was not done. And the obstacles to the implementation of the plans conceived were exclusively financial.

Probably, we can say that the Tu-155 is ahead of its time. For the first time, they used systems to which humanity will return. And the Tu-155 is worthy of being in a museum, and not among the forgotten decommissioned aircraft.

At the International Aviation and Space Salon MAKS-2015 Scientific and engineering company "NIK" and B The Aviation Legends Charity Foundation with the support of the Zhukovsky City Administration and Aviasalon OJSC presented this unique aircraft to the general public for the first time.

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