RU2496995C2 - Compression ignition ice and method of its operation - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: proposed engine comprises working cylinder, intake system, discharge system and fuel feed system and incorporates singlet oxygen generator arranged in intake line to enrich air fed in working cylinder with singlet oxygen molecules. Solid-stage laser emitting 762.3-762.4 nm-long waves is used as said laser radiation source, or singlet oxygen generator with chamber with inlet and outlet. Said chamber feature mirror sinner surface to reflect laser radiation and diffuse it. Proposed method consists in feeding air and fuel in engine cylinder and enriching the air with singlet oxygen at inlet, making fuel-air mix of preset composition, igniting said mix in said cylinder, expanding combustion products and discharging them from said cylinder. Note here that air oxygen molecules fed in inlet line are excited to singlet state $$O_2(b^1{\Sigma }_g^{+})$$

and O₂(alΔg). Amount of singlet oxygen in state O₂(alΔg) is set to 1-4% or oxygen content in air fed in intake line.

EFFECT: simplified design, lower material input.

5 cl, 1 dwg

Description

The invention relates to mechanical engineering, namely to engine building and is intended to intensify the combustion processes of air-fuel mixtures and to reduce the toxicity of exhaust gases.

The problem of creating an effective internal combustion engine (ICE) is inextricably linked with the need to ensure minimal emission of air-fuel products ^: mixtures into the surrounding atmosphere. In this case, it is essential that low-emission combustion should be provided without reducing the thermodynamic efficiency of the cycle and reducing the specific power.

Various methods of intensifying combustion are known.

There is, for example, a method for intensifying combustion of a fuel-air mixture, namely, that a working mixture in a combustion chamber is activated by means of a pulse-periodic nanosecond high-voltage discharge having certain characteristics: amplitude, rise time of the leading edge of the pulse and duration of the high voltage pulse (RF patent No. 23333381 IPC F02M 27/04, published on 09/10/2008). The activation of the working mixture in the combustion chamber of an internal combustion engine provides a decrease in the ignition temperature, an increase in the intensity of chemical reactions and, as a result, an increase in efficiency and a significant decrease in the emission of harmful substances, in particular nitrogen oxides, into the atmosphere. According to the model experiment, the decrease in the ignition temperature is 200-250 K.

The disadvantage of this method is the need for the formation of a high voltage discharge (up to 250 kV) directly in the combustion chamber of the engine, the high energy intensity of the method, and the need to ensure high-quality insulation of high voltage arresters. In addition, it is known that with increasing gas density the effectiveness of the plasma-chemical effect of a high-voltage discharge is noticeably reduced, therefore, this method will be of limited use in piston ICEs with an increased compression ratio.

A well-known modern technology of ignition and combustion of fuel-lean mixtures, which allows to reduce the emission of carbon oxides (CO) and nitrogen oxides (NO, NO ₂ ) in ICE to a very low level without the use of catalytic converters in the exhaust channels of ICE. This technology includes volumetric self-ignition of a homogeneous air-fuel mixture during rapid compression and is implemented in an engine called HCCI (homogeneous charge compression ignition). In some sources, an engine that implements this method is called CAI (Control Auto-Ignition).

Theoretically, HCCI or CAI is a process in which a highly diluted (by air or recirculated exhaust gas) homogeneous mixture spontaneously self-ignites simultaneously in the entire volume of the combustion chamber due to compression of the charge by the piston to a temperature of about 1100K and very quickly burns out volumetrically. It should be noted that in order to achieve autoignition temperature, as a rule, an additional source of thermal energy is required.

Also known is an engine selected as the closest analogue that implements a method of working with compression ignition of a homogeneous air-fuel mixture (US patent, No. 7900600, NKI 123 / 406.55, publ. 08.03.2011). The engine contains a working cylinder with intake and exhaust pipelines, an ignition system, a gas distribution system with adjustable phases for opening and closing valves and a control system with sensors for engine operating parameters. Moreover, the inlet pipe is additionally equipped with a device for heating the intake air and the bypass channel.

A well-known drawback of HCCI engines is unstable engine operation at idle and maximum revolutions, uncontrolled detonation of mixture residues and uneven distribution of air-fuel charge in the combustion chamber, which together significantly reduces engine power and limits the range of operating modes.

In the known engine at maximum loads and idle, to maintain the torque of the engine shaft and the rhythm of its operation include a spark ignition system, i.e. transfer the engine to work on the Otto cycle with ignition of the air-fuel mixture from an electric spark. In this case, there is a need to enrich the air-fuel mixture, the cycle temperature increases, which leads to an increase in the concentration of pollutants in the exhaust gases of the engine.

Another disadvantage of the known engine is the need to heat the intake air. Heated air at the inlet reduces the filling of the cylinder and reduces the thermodynamic efficiency of the engine cycle as a whole.

To ensure the minimum required temperature Tc = 1100K at the end of the compression stroke, it is necessary to heat the air at the inlet to 200 ° C (see table 1).

Table 1 Intake air heater, ° C So Compression ratio, ε Amount of polytropic compression, n ₁ Tc, K Gas engine 0 293 10 1.37 687 fifty 343 10 1.37 804 one hundred 393 10 1.37 921 150 443 10 1.37 1038 200 493 10 1.37 1156 Diesel 0 293 twenty 1.37 888 fifty 343 twenty 1.37 1039 one hundred 393 twenty 1.37 1191 150 443 twenty 1.37 1342 200 493 twenty 1.37 1494 Diesel 0 293 fifteen 1.37 798 fifty 343 fifteen 1.37 934 one hundred 393 fifteen 1.37 1070 150 443 fifteen 1.37 1207 200 493 fifteen 1.37 1343

The temperature Tc of the end of the compression stroke was calculated for an atmospheric engine at different compression ratios and an ambient temperature of 20 ° C.

The objective of the invention is to expand the range of operating modes of an engine with compression ignition by increasing the stability of ignition of the air-fuel mixture in the engine cylinder.

Another objective of the invention is the need to ensure environmental safety of fuel combustion products, taking into account the fact that low-temperature combustion of a rich hydrocarbon-air mixture leads to incomplete oxidation of carbon, the formation of carbon monoxide and soot, on the other hand, high-temperature combustion gives high concentrations of NOx.

The technical result is to simplify the design of the engine and reduce its material consumption, which is achieved by increasing the thermodynamic parameters of the cycle and expanding the range of operating modes of the engine, as well as reducing the toxicity of exhaust gases.

The present invention is based on the fact that increasing the stability of ignition of the air-fuel mixture in the engine cylinder can be achieved by enriching the inlet air with active particles, which reduces the time of induction and the implementation of volumetric ignition of the air-fuel charge at a lower initial temperature.

The tasks are solved in that the piston engine with compression ignition, containing a working cylinder, an intake system, an exhaust system and a fuel supply system, is equipped with a singlet oxygen generator located in the intake pipe with the possibility of enriching the air supplied to the working cylinder by singlet oxygen molecules.

In this case, the singlet oxygen generator is performed in the form of a laser radiation source and a camera with input and output, and the inner surface of the camera is made mirrored with the possibility of reflection and diffusion scattering of laser radiation. And the source of laser radiation is performed in the form of a solid-state laser emitting waves with a length of 762.3 to 762.4 nanometers.

и O₂(a¹Δ_g).The problem is also solved by the fact that they carry out a method of operating a piston engine with compression ignition, which consists in supplying air and fuel to the inlet pipe, forming a predetermined composition of the air-fuel mixture in the inlet pipe, letting it into the engine cylinder, compressing, igniting the air-fuel charge from compression, expanding the combustion products and releasing them from the engine cylinder, in which according to the invention, the oxygen molecules of the air supplied to the intake manifold are excited into a single est conditions $$O_2(b^{\mathrm{one}}{\sum }_g^{+})$$

and O ₂ (a ¹ Δ _g ).

The amount of singlet oxygen in the O ₂ state (a ¹ Δ _g ) is set in an amount from 1 to 4 percent of the oxygen content in the air supplied to the inlet pipe.

Currently, it is known that electronically excited molecules and atoms react much faster than unexcited ones. Therefore, the excitation of reacting molecules makes it possible to accelerate the formation of active radicals, carriers of the chain mechanism, in the reactions of chain initiation and propagation, and, as a result, to intensify combustion.

с последующим переходом молекул кислорода в состояние O₂(a¹Δ_g).Saturation of intake air with singlet oxygen intensifies the occurrence of a chain oxidation reaction in the combustion chamber of the engine. To produce singlet oxygen in the O ₂ state (a ¹ Δ _g ), it is preferable to use a laser generating radiation with a wavelength of 762.35 ± 0.05 nm, which resonantly excites O ₂ molecules from the ground state to an electronically excited state $$b^{\mathrm{one}}{\sum }_g^{+}$$

followed by the transition of oxygen molecules to the O ₂ state (a ¹ Δ _g ).

с образованием синглетного кислорода состояния O₂(a¹Δ_g) детально описана в работе «Световой котел-генератор синглетного кислорода O₂(a¹Δ_g)» H.И. Липатов, А.С. Бирюков, Э.С. Гулямова // Квантовая электроника 2008. Т.38. №13, C.1179-1182 и согласована с экспериментальными данными.Kinetics of the formation of electronically excited state oxygen molecules $$b^{\mathrm{one}}{\sum }_g^{+}$$

with the formation of singlet oxygen, the O ₂ state (a ¹ Δ _g ) is described in detail in the work “Light boiler-generator of singlet oxygen O ₂ (a ¹ Δ _g )” H.I. Lipatov, A.S. Biryukov, E.S. Gulyamova // Quantum Electronics 2008.V.38. No. 13, C.1179-1182 and is consistent with experimental data.

эффективно сокращает время индукции и температуру воспламенения.The effect of singlet oxygen on the intensity of pre-flame reactions is shown in the work "Comprehensive analysis of the ignition and combustion of hydrogen-air and methane-air mixtures when exposed to resonant laser radiation" A.M. Old Man, P.S. Kuleshov, H.S. Titova // in the book. “Nonequilibrium physicochemical processes in gas flows and new principles of combustion organization”, ed. AM Old Man, M .: TORUS PRESS 2011, p. 603-634. In the indicated work, based on numerical simulation, it was shown that for methane-air mixtures, laser-induced excitation of O ₂ molecules by radiation with λ = 762.346 nm to the state $$b^{\mathrm{one}}{\sum }_g^{+}$$

effectively reduces induction time and flash point.

The present invention is illustrated by the following detailed description of the design and operation of the engine with reference to the illustration shown in FIG. 1, which shows a diagram of a compression ignition piston engine equipped with a singlet oxygen generator.

A compression ignition piston engine consists of a working cylinder 1 in which a piston 2 is placed to form a combustion chamber 3. The piston 2 through the connecting rod 4 is connected to the crankshaft 5. In the head of the engine block, valves 6 of the gas distribution system are located. The engine is equipped with an exhaust pipe 7 and an intake pipe 11.

In the inlet pipe 11 there is a node 8 for forming an air-fuel mixture with a device 9 for measuring and regulating air flow. Fuel 10 enters the input of the mixture-forming device of the air-fuel mixture forming unit 8. The node 8 may contain a carburetor, or a nozzle with electromagnetic control.

Also, a singlet oxygen generator is located in the inlet pipe 11, which provides saturation of the intake air with 12 molecules of excited oxygen in the O ₂ state (a ¹ Δ _g ).

The singlet oxygen generator is made in the form of a chamber 14 with an internal mirror surface 13. In the hole in the wall of the chamber 14, an output part of the optical fiber 15 is fixed, the input part of which is connected to a solid-state Nd: YAG laser 16 equipped with an Al ₂ O ₃ Ti ³⁺ crystal.

The engine operates as follows.

в электронное состояние $$O_2(b^1{\sum }_g^{+},V",J",K")$$

с колебательными квантовыми числами V'=V"=0 и вращательными квантовыми числами J'=9, J”=8 и K'=K”=8. Из электронно-возбужденного состояния $$b^1{\sum }_g^{+}$$

большая часть молекул кислорода переходит в более устойчивое возбужденное состояние O₂(a¹Δ_g).The formation of molecules of excited oxygen in the O ₂ state (a1Δg) occurs in the singlet oxygen generator. The radiation from a solid-state Nd: YAG laser 16 with an Al ₂ O ₃ Ti ³⁺ crystal with a wavelength of λ = 762.346 nm is supplied through the optical fiber 15 to the chamber 14. Since the inner surface 13 of the chamber 14 is made mirror-like, after several reflections, due to diffusion scattering of laser radiation in the volume of the chamber 14 forms a homogeneous isotropic light field. Also, air 12 is supplied to the chamber 14. Laser radiation with a wavelength of 762.346 nm ensures the excitation of molecular oxygen, and the molecule is transferred from the ground state $$O_2({\mathrm{<figure-callout\; id="3"\; label="X"\; filenames="00000011.png"\; state="\{\{state\}\}">X</figure-callout>}}^3{\sum }_g^{-},V\text{'}\text{'},J\text{'}\text{'},K\text{'}\text{'})$$

into electronic state $$O_2(b^{\mathrm{one}}{\sum }_g^{+},V",J",K")$$

with vibrational quantum numbers V '= V "= 0 and rotational quantum numbers J' = 9, J” = 8 and K '= K ”= 8. From an electronically excited state $$b^{\mathrm{one}}{\sum }_g^{+}$$

most of the oxygen molecules go into a more stable excited state of O ₂ (a ¹ Δ _g ).

Air 12 enters the intake manifold 11. Passing through the singlet oxygen generator, it is saturated with molecules of excited oxygen in the O ₂ state (a ¹ Δ _g ). Fuel 10 enters the input of the mixture-forming device of the air-fuel mixture forming unit 8. Next, in node 8, a fuel-air mixture of the required composition is formed, which at the intake stroke enters the combustion chamber 3. The fuel-air charge is compressed in the cylinder 1 of the engine and at the end of the compression stroke, the temperature of the mixture in the combustion chamber 3 rises to the limit of self-ignition, and the chain process of fuel oxidation begins. After reaching a sufficient concentration of active oxidation centers, volume ignition and rapid combustion of the air-fuel charge in the full volume of the combustion chamber 3 occurs. Combustion occurs in the region of top dead center, with almost constant volume.

The following are expansion and release processes. The engine cycle is repeated.

и O₂(a¹Δ_g) в топливовоздушном заряде создает условия для сокращения времени индукции и обеспечения объемного воспламенения топливовоздушного заряда в камере 3 сгорания при более низкой начальной температуре. Понижение предела воспламенения обеспечивает расширение диапазона рабочих режимов двигателя, а изменение концентрации синглетного кислорода в смеси за счет регулирования мощности лазерного излучения позволит предотвратить неустойчивую работу двигателя.The presence of singlet oxygen molecules $$O_2(b^{\mathrm{one}}{\sum }_g^{+})$$

and O ₂ (a ¹ Δ _g ) in the air-fuel charge creates conditions for reducing the induction time and providing volume ignition of the air-fuel charge in the combustion chamber 3 at a lower initial temperature. Lowering the ignition limit provides an extension of the range of engine operating modes, and a change in the concentration of singlet oxygen in the mixture by controlling the power of the laser radiation will prevent unstable engine operation.

Lowering the ignition limit, in addition, allows to reduce the compression ratio of the engine, because for self-ignition of the air-fuel mixture containing singlet oxygen, a lower temperature is required at the end of the compression stroke. Due to the decrease in the degree of compression of the gas, the pressure in the cylinder of the engine decreases, and, therefore, its material consumption decreases and the engine resource increases.

The calculations showed that the presence of singlet oxygen in the mixture and a decrease in the degree of compression can reduce the emission of NO _x with the exhaust gases of the engine. Table 2 shows the concentration of nitric oxide NO _x formed in the cylinder 1 of the engine, with different contents of O ₂ (a ¹ Δ _g ) in the air-fuel mixture. The calculations were carried out with the composition and quantity of the air-fuel mixture entering the engine cylinder at a constant speed and the condition of maintaining a given level of power developed by the engine

Thus, saturation of air at the engine inlet with singlet oxygen molecules reduces the induction time and favorably affects the process of volume ignition of the air-fuel charge. Moreover, the presence of active centers of fuel oxidation in the form of singlet oxygen O ₂ (a ¹ Δ _g ) allows one to intensify the occurrence of the chain oxidation reaction in the combustion chamber of the engine and lower the temperature of the onset of self-ignition. The presence of singlet oxygen in the intake air eliminates the need for additional air heating at the inlet, which allows to increase the filling of the cylinder and increase engine power.

Table 2. Compression ratio 8, necessary to provide a given power, and the molar fraction of NO in the exhaust gases of an HCCI engine, depending on the concentration of singlet oxygen in the inlet pipe.

O ₂ (a ¹ Δ _g ) / O ₂ ,% ε Mole fraction of NO, ppm 0 16.5 53 one 14.0 47 2 12.95 32 four 11.65 28

An increase in engine power is also achieved by intensifying the combustion process and reducing the total duration of combustion of the air-fuel charge. In the absence of the need for more power, it is possible to reduce the working volume of the cylinder or reduce the compression ratio, which ultimately will reduce the material consumption of the engine as a whole. The implementation of intensive combustion of a depleted fuel-air mixture at a lower temperature will also reduce the emission of toxic substances with engine exhaust gases, which together creates significant environmental and technical and economic effects.

Claims (3)

1. A piston engine with compression ignition, comprising a working cylinder, an intake system, an exhaust system and a fuel supply system, characterized in that the engine is equipped with a singlet oxygen generator located in the inlet pipe so as to saturate the unheated air introduced into the working cylinder with singlet oxygen molecules in the amount of up to 4% of the oxygen content in the air supplied to the inlet pipe. 2. The method of operation of a piston engine with compression ignition, characterized in that the fuel and unheated air are supplied to the inlet pipe, the oxygen molecules of the air supplied to the inlet pipe are excited to singlet states $$O_2(b^{\mathrm{one}}{\Sigma }_g^{+})$$

and O ₂ (a1Δg), form a fuel-air mixture of a given composition in the inlet pipe, let it into the engine cylinder, compress and ignite the air-fuel charge from compression, expand the combustion products and release them from the engine cylinder. 3. The method according to claim 2, characterized in that the amount of singlet oxygen in the O ₂ state (a1Δg) is set in an amount from 1 to 4% of the oxygen content in the air supplied to the inlet pipe.

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