RU2549744C2 - Operation of four-stroke ice running of hydrogen with pre-cooling of fuel mix by air cryogenic component - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to machine building, particularly, to propulsion engineering. This invention consists in that fuel mix consists of hydrogen and atmospheric air to be ore-cooled before compression by air cryogenic component to make is the fuel mix component including its liquid phase. Application of hydrogen allows ore-cooling of said mix with liquid air with increase in mix compression ratio at engine knock-free operation and to lower the mix compression. High compression ratio allows addition of extra heat produced by fed hydrogen to combustion product expansion and increase in cycle efficiency.

EFFECT: higher efficiency.

9 cl, 3 dwg

Description

The invention relates to mechanical engineering, namely engine building, in particular the organization of cycle processes and the development of fuel supply systems (mixture of fuel and oxidizer) into the combustion chamber.

The aim of the invention is to increase the efficiency of the cycle, for example, a four-stroke internal combustion engine with forced ignition of the fuel mixture in the combustion chamber, by increasing the efficiency of the constituent processes of the cycle and improving the supply system of hydrogen-containing fuel.

It is well known that the maximum efficiency of a heat-using cycle for obtaining mechanical energy can be obtained by implementing the Carnot cycle and is determined only by the temperature range between the heating and cooling sources [1] and the larger this difference, the higher the cycle efficiency.

However, the technical implementation of heat-using cycles in ICE devices does not allow to fully utilize the potential of the hydrocarbon fuel used, in which atmospheric air plays the role of an oxidizing agent.

Thus, an increase in the upper cycle temperature in adiabatic uncooled ICEs with a high-temperature combustion chamber slightly increases the engine efficiency, since the work of compression of the fresh mixture increases due to its higher temperature.

A technical solution of the cryogenic engine is known [2] in which an attempt is made to spread the temperature levels of the cycle due to the lower temperature level towards cryogenic temperatures. The disadvantage of this heat-consuming cycle is the incomplete use of the potential of the accumulated cold in a cryogenic liquid.

As a result of thermodynamic analysis of the cycles of reciprocating internal combustion engines (ICE), considered in [3], with various methods of heat input (with constant volume, constant pressure and mixed), it was shown that the main factor affecting the increase in the cycle efficiency is the degree of compression in engine. However, the use of hydrocarbon fuel in ICE does not allow to increase this indicator for an engine with spark ignition above (6-11) and for an engine operating on a diesel cycle (15-22).

In the first case, the compression ratio is limited mainly by the detonation resistance of light gasolines, and in the second, the longer burning of heavy diesel fuel due to the increased carbon content in it and its partial (not burnt) emission into the atmosphere.

The consequence of the use of hydrocarbon fuel in the implementation of the considered ICE cycles is a significant loss of heat discharged into the atmosphere by the exhaust stream. So, the temperature values of exhaust gases for ICE with spark ignition are in the region of 600 K and for ICE operating on a diesel cycle of 850 K.

In addition, in real internal combustion engines operating on hydrocarbon fuels, there is an incomplete use of heat associated with heat losses in the walls of the combustion chamber and a significant burn-out in the process of expansion of the combustion products. This in turn leads to additional mechanical energy costs for compressing a fresh portion of the fuel mixture at a higher temperature due to its heating from the hot walls of the combustion chamber.

As a result, the effective efficiency of the well-known, massively used ICEs and operating on the Otto and Diesel cycle does not exceed (33 and 40)%, respectively.

In the proposed method, there is the possibility of a significant improvement in the factors affecting the effective ICE efficiency due to the use of hydrogen as a fuel and the application of preliminary cooling of the fuel mixture by the cryogenic air component, including its injection into the combustion chamber before the compression of the fuel mixture.

The cryogenic component of air is liquid air enriched with nitrogen or oxygen.

So the use of hydrogen as fuel allows you to stably, at the right time in the cycle and for a short period of time, burn all the hydrogen in the fuel mixture and clearly regulate its combustion during the expansion of the combustion products.

In addition, the unique properties of hydrogen as a fuel [4] allow its combustion to occur in super-lean fuel mixtures. So when using air as an oxidizing agent, the minimum concentration of hydrogen with stable flammability and combustion of hydrogen is in the range (4.1-5)%, which dramatically improves the efficiency of ICE. For comparison, the maximum values of the air excess coefficients of super-lean mixtures are equal: for a gas engine - 1.25, and for a hydrogen engine - 10.

In the proposed method, one of the main factors for increasing the effective efficiency of the internal combustion engine is the preliminary cooling of the supplied hydrogen and gaseous air to the engine by the cryogenic component of the air due to their mixing and feeding the resulting cold mixture into the engine cylinder. In this case, the mixing of the cold mixture with hydrogen gas can be both external and internal. In addition, the cryogenic air component, brought directly into the cylinder of the engine before the compression process of the fuel mixture, allows you to bring the compression process closer to the isothermal process, which reduces the work of its compression.

With this method of preparing and supplying fuel (a mixture of chilled air and hydrogen), a double effect is observed:

1. The work of compression of the fuel mixture in the ICE cycle is reduced due to the reduced temperature of the working mixture before compression and the reduced temperature of the compression process. Saving mechanical energy by compressing the working fluid is a net gain and increases the mechanical energy produced by the engine.

2. There is the possibility of a sharp increase in one of the main factors affecting the efficiency of the internal combustion engine, the compression ratio during detonation-free operation of the engine. This is achieved by the fact that by lowering the temperature of the working mixture before compression in the combustion chamber and shifting the process to the isothermal side, the temperature of self-ignition of the mixture (detonation) will correspond to a higher compression ratio (or the degree of pressure increase). The application of these measures, depending on the degree of cooling of the fuel mixture by the cryogenic component of air and its partial injection directly into the cylinder, allows to increase the compression ratio by 10 or more times.

In figure 1. a block diagram of one of the devices of a power plant using hydrogen as fuel for transport or ground based and consisting of the following components:

I - ICE.

II - Metal hydride storage and supply of hydrogen.

III - Storage and supply of cryogenic air components.

IY - The device for mixing and cooling the fuel mixture.

Y - Cycle control device at the upper temperature level.

According to the block diagram, the components of the fuel mixture: hydrogen through pipeline 1 from the metal hydride system II for storing and supplying hydrogen, the cryogenic air component through pipeline 2 from block III and atmospheric air from the air intake 3 enter the device of the mixer-cooler IY, from which the cooled gas-droplet fuel mixture through pipeline 4 enters the cylinder of engine I.

The cycle control device Y at the upper temperature level is designed to conduct the expansion of combustion products close to isothermal and optimize the cycle as a whole.

The discharge of exhaust gases at the end of the cycle is carried out through pipeline 5.

Figure 2. the device of a power plant using hydrogen as fuel using one of the variants of a metal hydride system for storing and supplying hydrogen according to the patent [5] is presented. As hydride-forming material, alloys based on magnesium or titanium can be used, for example, an alloy of magnesium and nickel in various proportions, as well as with the addition of various alloying additives.

The device consists of metal hydride elements 7, compactly located in the casing of the metal hydride module 8 and connected to a hydrogen collector 9, from which hydrogen is supplied through a pipe 10 through a shut-off valve 11 to a device for increasing pressure, for example, a piston compressor or a mechanical vacuum pump 14 and then through the pipeline 16 enters the mixer-cooler 17 through an adjustable valve 15. To supply heat from the environment to the metal hydride elements 7, a fan 18 is installed. llogidridnyh elements is carried via line 12 through a check valve 13. The released heat in the metal hydride cell is discharged in the environment as by the fan 18.

The storage and supply system for the cryogenic air component is made in the form of a Dewar vessel 19, for which the cryogenic liquid is filled with a neck 20. For supplying the cryogenic air component, for example, a pumping system is used, by which, by means of a mechanical pump 21, the cryogenic liquid is piped 22, through an adjustable valve 23 enters the mixer-cooler 17.

In the mixer-cooler 17 three streams of fuel components are mixed: this is hydrogen entering through the adjustable valve 15, the cryogenic component of the air coming through the adjustable valve 23 and the air from the environment (arrow B) entering through the air inlet 24, the flow rate of which is regulated by the shutter 25. Thus, in the mixer-cooler a fuel mixture is formed of three components - hydrogen, atmospheric air and the cryogenic component of air, with which hydrogen and atmospheric air are cooled.

From the mixer-cooler 17, the fuel mixture enters the cylinder 41 of the internal combustion engine 26.

The internal combustion engine operates on a four-cycle cycle, in which there are valves 27 for the intake of the fuel mixture and valves 28 for the release of exhaust gases (arrow VG).

In the head 34 of the cylinder 41 of the internal combustion engine 26, a device 29 for controlling the process of expansion of the combustion products, which is, for example, capillary channels, is installed.

The piston 40 is mechanically connected by means of a crank mechanism 45 with a shaft 46 and a flywheel 47 of the internal combustion engine 26.

Figure 3 presents one of the variants of the device 29. The device includes a set of parallel capillary channels 35, the inlet openings of which begin on the inner surface of the head 34 of the cylinder 41, and the ends are combined into a manifold 36 with an adjustable volume. Also shown here is a variant of additional hydrogen recharge of the manifold 36 from the pipeline 16 (connection at point C) through the pipeline 39 (the pipeline 39 is not shown in FIG. 2) through an adjustable valve 38 and then through a non-return valve 37.

Additional hydrogen recharge collector 36 allows you to fine-tune the supply of heat in the cycle.

To ignite the fuel mixture, an arson device 30 is mounted in the cylinder head 34, for example, an electric spark plug.

The thermal conditions of the head 34 of the cylinder 41 and the temperature of the fuel mixture are measured with thermocouples and 32 and 31, respectively, and the pressure (vacuum) of the fuel mixture in the mixer-cooler with a pressure sensor 33.

For the operation of the device of the power plant shown in FIG. 2, it is necessary to charge metal hydride elements 7 with hydrogen and fill the Dewar vessel 19 with a cryogenic component of air.

Hydrogen filling of metal hydride elements is carried out at a gas station.

For hydrogen filling, the filling line 12 is connected to a hydrogen source, for example, to a balloon system, the shut-off valve 11 is closed, the shut-off valve 13 is opened, through which hydrogen enters the metal hydride elements 7.

The heat released in the metal hydride elements in the process of their saturation with hydrogen is discharged into the environment using the included fan 18.

At the end of the process of refueling metal hydride elements with hydrogen, the filling valve 13 is closed, the filling pipe 12 is disconnected from the filling station and the fan 18 is turned off.

The cryogenic component of the air is filled with a Dewar vessel using the standard technique for filling Dewar vessels with liquid air or nitrogen. The filling tube from the cryogenic liquid tank is introduced into the filling neck 20 and the filling process is carried out. In this case, the shutoff valve 23 of the cryogenic liquid supply is closed, and the cryogenic liquid supply pump 21 is turned off. At the end of the filling, the filling tube is removed from the Dewar vessel 19, and the neck 20 is closed.

The ratio of nitrogen and oxygen in the cryogenic component of air can be within wide limits and, in comparison with the standard composition of liquid air (21% oxygen and 79% nitrogen), the amount of nitrogen in the cryogenic component of air can be either 100% or have a composition, for example, 50 % oxygen and 50% nitrogen.

The implementation of the processes of the ICE cycle with hydrogen as fuel and with preliminary cooling of the fuel mixture by the cryogenic component of liquid air is considered on the example of a four-stroke engine.

Consider the processes of the ICE cycle in the device of the power plant, shown in Fig.2.

1. The process of preparing and supplying the fuel mixture to the engine cylinder.

The process of preparing and supplying the fuel mixture to the internal combustion engine cylinder includes mixing and cooling hydrogen and atmospheric air with a cryogenic air component in the fuel mixture mixing and cooling device 17, from where the cooled gas-droplet fuel mixture is piped 4 and valve 27 enters the engine cylinder. The movement of the piston is carried out from the highest dead center (TDC) down to the lowest dead center (BDC).

The supply of hydrogen gas from the metal hydride elements 7 to the mixing and cooling chamber 17 is carried out through pipeline 10, with the shut-off valve 11 open, by means of the switched-on reciprocating compressor or mechanical vacuum pump 14, then through the pipeline 16 and through an adjustable shut-off valve 15. Temperature stabilization of metal hydride elements 7 at the ambient temperature level is provided by the turned-on fan 18.

At the same time, hydrogenation of the tank 36 is carried out through the pipeline 39 through an adjustable valve 38 and a check valve 37.

The cryogenic component of air is supplied from the Dewar vessel 19 to the mixing and cooling chamber 17 by means of the included submersible pump 21, via a pipe 22, on the line of which an adjustable shut-off valve 23 is installed.

The amount of atmospheric air entering the mixer-cooler 17 is controlled by a shutter 25.

Using the adjustable shut-off valves 15 and 23, as well as the shutter 25, both qualitative and quantitative mixture formation of the gas-droplet fuel mixture is formed.

High-quality mixture formation prevails when the engine reaches a steady temperature when it starts. In this case, temperature sensors can be, for example, a thermocouple 31 for determining the temperature of the fuel mixture when it is supplied to the engine cylinder and a thermocouple 32 for determining the thermal state of the head 34 and the upper part of the engine cylinder 41. The pressure sensor 33 monitors the detonation-free mode of operation of the engine when it exits to the steady-state thermal mode and gives one of the signals to cover or open the shutter 25.

To fill the cylinder cavity with a metered portion of the gas-droplet fuel mixture, when the piston 40 moves downward, the valve 27 opens.

2. The process of compression of the fuel mixture.

With the transition of the BDC, the compression of the fuel mixture begins and the movement of the piston 40 occurs in the direction of the TDC.

The mechanical energy used to compress the fuel mixture by moving the piston 40 toward TDC is consumed from the energy of the untwisted flywheel on the engine shaft.

The temperature of the fuel mixture at the beginning of compression is determined by the degree of its preliminary cooling in the mixer-cooler 17 and, depending on the amount of cryogenic air component in it, can be significantly lower than the ambient temperature, for example, by 100 degrees lower.

The preliminary cooling of the fuel mixture allows one to sharply increase the degree of compression without reaching the temperature of self-ignition and the detonation process, and the presence of the droplet cryogenic component of the liquid air component allows the compression of the fuel mixture to shift towards the isothermal process and reduce its compression work.

In the process of compression of the fuel mixture, part of it enters through the capillary channels 35 into the reservoir reservoir 36, where hydrogen is already present, and there the hydrogen-rich mixture is stored for some time.

3. The process of supplying heat and expanding combustion products.

After arson of the fuel mixture in the combustion chamber when passing the position of the piston 40 near TDC, combustion products with high pressure and temperature are formed.

The process of expanding combustion products with the transfer of energy to the engine shaft consists of three stages, which are sequentially carried out when the piston 40 moves down to the BDC:

- A stage close to the isobaric process, in which the bulk of the hydrogen is burned and there is no significant decrease in the pressure and temperature of the combustion products at the end of this stage,

- A stage close to the isothermal process of expansion of the products of combustion, with the supply of heat due to the combustion of hydrogen accumulated in the device 29 (in the reservoir 36).

The device 29 for controlling the process of expansion of the products of combustion in a cycle at the upper temperature level allows additionally supplying and burning with some delay, due to the hydraulic resistance of the capillary channels, the accumulated hydrogen from the reservoir 36 of the device 29 during the expansion of the products of combustion, which allows you to adjust the temperature and pressure in end of their expansion.

For example, an excess of the cryogenic component of the air during cooling of the fuel mixture at the beginning of the compression process can lead to the appearance of negative temperatures of the exhaust gases relative to the ambient temperature, therefore it is possible to burn additional hydrogen and increase the efficiency of the cycle as a whole.

- A stage close to the adiabatic process with a further decrease in pressure and temperature, the values of which at the end of the process approach the values of pressure and ambient temperature.

4. The process of displacing combustion gases from the engine cylinder.

This is the closing process of the cycle, in which the exhaust gases are discharged into the atmosphere. For this, when the piston 40 moves from BDC upward to TDC, valve 28 opens.

When the piston reaches TDC, the cycle repeats.

Information sources

1. Technical thermodynamics. Kirillin VU.A., Sychev V.V., Sheindlin A.E. - M.: Energy, 1968.

2. UA patent No. 22721 A, 1977, Bondarenko S.I., Fenchenko V.N.

3. Car engines. V.M. Arkhangelsk, M.M. Wichert, A.N. Voinov, Yu.A. Stepanov, V.I. Trusov, M.S. Howah. Ed. M.S. Hovaha. M., A 22 "Engineering", 1977.

4. Hydrogen is the fuel of the future. Podgorny A.N., Varshavsky I.L. K., “Science. Dumka ", 1977.

5. RF patent No. 2381413 C2

Claims (9)

1. The method of operation of the internal combustion engine, the cycle of which consists of the following processes: compression of the fuel mixture based on hydrocarbon fuel; heat supply due to the combustion of fuel in the mixture and the formation of combustion products with high temperature and high pressure; expanding the combustion products and expelling the expansion energy to the engine shaft, characterized in that the fuel mixture consists of hydrogen and atmospheric air and is pre-cooled by a cryogenic component of air, which becomes a component of the fuel mixture, including its liquid phase. 2. The method according to p. 1, characterized in that the preparation and cooling of the fuel mixture, consisting of gaseous hydrogen, atmospheric air and the cryogenic component of air, is carried out in a mixer-cooler, from where the cooled mixture, including the liquid phase of the cryogenic component of air, enters the cylinder engine. 3. The method according to p. 1, characterized in that the cryogenic component of the air is liquid air enriched with nitrogen or oxygen over a wide range. 4. The method according to p. 1, characterized in that the supply of hydrogen from the metal hydride elements to the cooler-mixer and then into the cylinder of the engine is carried out using a reciprocating compressor or a mechanical vacuum pump. 5. The method according to p. 1, characterized in that the processes of hydrogen extraction from metal hydride elements use the heat of the environment using a fan system. 6. The method according to p. 1, characterized in that the supply of cryogenic air components in the cooler-mixer can be carried out by a pumping system. 7. The method according to p. 1, characterized in that in the process of compressing the fuel mixture, part of it enters through the capillary channels into the reservoir capacity and burns with some delay at the stage of expansion of the combustion products. 8. The method according to p. 1, characterized in that the device of the hydrogen collector allows for the additional supply of hydrogen into it through the feed system directly from the metal hydride elements. 9. The method according to p. 1, characterized in that the process of expanding the products of combustion with the removal of energy to the engine shaft consists of three stages, which are carried out sequentially when the piston moves down to bottom dead center: a stage close to the isobaric process, in which the main part of the hydrogen with decreasing gas pressure and temperature at the end of this stage; a stage close to the isothermal process of gas expansion, with heat supply due to combustion of hydrogen supplied from the reservoir, and a stage close to the adiabatic process with a further decrease in pressure and temperature, the values of which at the end of the process approach the values of pressure and ambient temperature.

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