CN1299924A - Oxygen-rich combustion method for engine - Google Patents

Abstract

The oxygen-rich combustion method for engine is characterized by adding an air separation method and its oxygen-making technology in air admission link of existent engine and raising oxygen concentration of air sucked by engine to form the invented oxygen-rich combustion method. It can raise power of engine, reduce fuel consumption and exhaust contamination and carbon deposit of engine.

Description

Oxygen-enriched combustion method for engine

In modern society, the wide application of a large number of engines causes serious pollution to the atmospheric environment. The main reason is that the existing engine has a contradiction between the fuel economy and the dynamic performance during operation. The fuel economy needs to be ensured, but the power is insufficient, the power performance needs to be improved, but the combustion is not complete, the fuel economy is reduced, the exhaust pollution is increased, and the environment is polluted.

The oxygen-enriched combustion method for engine is a method of oxygen-enriched combustion by adopting air separation method oxygen-producing technology to make engine suck oxygen-enriched gas (its oxygen content is greater than natural air, the same is said below) from air.

The engine is supplied with rich oxygen, so that fuel in the engine is completely combusted in an oxygen-rich state and the power performance is improved. The power per liter of the engine can be improved, and the oil consumption rate is reduced. The contradiction between the fuel economy and the dynamic performance of the traditional engine is fundamentally solved, and the dynamic performance and the fuel economy are simultaneously improved. The engine has the advantages of enhancing dynamic property, reducing the volume and weight of the engine under unit displacement, promoting complete combustion, saving energy, reducing carbon deposit of the engine to prolong the service life, reducing exhaust pollution of the engine and protecting the environment.

The engine manufactured (or modified) by the engine oxygen enrichment combustion method can be called an oxygen enrichment engine (the same applies below).

1. Problems in the prior art of engines

The existing engines generate power by mixing and burning oxygen absorbed in natural air and fuel (gasoline, diesel oil, gas and the like). However, due to the influence of factors such as working condition change, altitude and the like, the power performance and the fuel economy of the conventional engine are in contradiction.

Taking a gasoline engine as an example, whether a combustible mixture of air and gasoline sucked in during the operation of the engine can be completely combusted depends on the weight ratio (concentration) of the gasoline to the air in the mixture. Generally, a gas in which 15 kg of air is mixed with 1 kg of gasoline is called a standard mixture. In theory, the mixture that ensures rapid and complete combustion of gasoline is the standard mixture. In fact, due to the influence of various factors such as uneven mixed gas and residual waste gas in a cylinder, the mixed gas capable of being completely combusted is slightly leaner than the standard mixed gas, can be rapidly combusted, and the mixed gas capable of enabling the engine to obtain the maximum power is richer than the standard mixed gas.

The concentration of the mixture can also be expressed by an air excess factor α:theoretically, the value of α for a standard mixture is 1. in practice, to achieve complete combustion of gasoline, the fuel concentration in the mixture is reduced to ensure adequate air mixing with the gasoline, α should be greater than 1, but the engine is under-powered. for different engines, the value of α for the lowest fuel consumption is 1.05-1.15. if the engine is to burn rapidly and achieve the maximum output, the mixture should be richer, i.e., more fuel is added to burn off the oxygen in the intake air, but fuel economy is reduced. for different engines, the value of α for the maximum output is 0.85-0.95.

The engine has different requirements for the concentration of the mixed gas under five different working conditions, the α value is 0.9-1.11 only under medium load, the combustion is relatively complete, the α value is 0.2-0.6 at start, 0.6-0.8 at idle, 0.8-0.9 at full load, and more oil injection is forced to the mixing chamber during acceleration to thicken the mixed gas and ensure the power required by acceleration, the α value is less than 1 under the last four conditions, the combustion of the engine is incomplete, and the fuel waste and the environmental pollution are caused.

α, too large or too small of a value, i.e. too lean ortoo rich of the mixture, will cause the dynamic performance or economy of the engine to deteriorate.

Although many technical measures such as automatic adjustment of intake air temperature, electronic control of gasoline injection, improvement of structure of an carburetor, and application of a stratified charge combustion method have been adopted in the existing engine manufacturing technology to improve thermal efficiency and fuel economy at a partial load, the problems have not been fundamentally solved.

Reference material: 1. basic theory of energy saving for automobile and its application

Frontier glaring civil traffic publishing agency

2. First edition engine for solving automobile problems

People's traffic publishing agency

2. Oxygen-enriched engine and its characteristics

The invention aims to solve the contradiction of mutual restriction between fuel economy and dynamic performance of the existing engine, promote complete combustion and increase power, improve the fuel economy and the dynamic performance simultaneously, and achieve the multiple purposes of saving energy, reducing the emission of CO and CH in tail gas, protecting the environment and the like.

2.1 oxygen-enriched Engine principle

Any internal combustion engine relies on the chemical energy of combustion of fuel and oxygen in the intake air to produce work. Clearly, the more fuel, the greater the work produced. Increasing the supply of fuel is technically easy, but at the same time increasing the amount of oxygen is not easy. Since, air contains 21% of oxygen and 79% of nitrogen. The air sucked by the engine is constant, and the oxygen quantity sucked by the engine is also constant. The oxygen enrichment combustion method of the engine aims to solve the oxygen enrichment problem.

Fig. 1 is a schematic diagram of a gasoline engine (only one cylinder is shown) modified into an oxygen-enriched engine. In the figure: 1 is an air filter, 2 is a supporting steel mesh, 3 is an oxygen-enriched film, 4 is filter paper, 5 is a carburetor, 6 is a cylinder piston, 7 is a cylinder, and 8 is a connecting rod.

The oxygen-enriched engine can be formed only by adding a layer of plate-type oxygen-enriched film between a steel mesh and filter paper in an air filter (dry paper filter) of the existing engine. The oxygen-enriched membrane is a novel organic polymer film, is a microporous material like filter paper, and air can pass through micropores under the action of pressure difference. Except that the oxygen-rich membrane is permselective for the gas passing through, oxygen molecules pass more readily, and oxygen-rich gas is formed. The plate-type oxygen-enriched membrane can make the oxygen-enriched concentration of the passing gas reach 28%, and other types of oxygen-enriched membranes can be higher.

Fig. 1 shows that when the engine cylinder inhales, natural air is firstly inhaled into an air filter, becomes pure air through filter paper and then becomes oxygen-enriched gas through an oxygen-enriched membrane. The oxygen-enriched gas is mixed with gasoline by a carburetor to form oxygen-enriched mixed gas to be sucked into a cylinder of the engine. The oxygen in the mixed gas is rich to a certain degree, so that the engine can still be completely combusted under the condition of richer mixed gas, and the optimal power can be obtained. Both power and fuel economy will be improved. If the fuel supply is increased correspondingly with the increase of the oxygen-rich quantity, the specific power (power per unit displacement) of the engine will be increased and the fuel consumption will be reduced (see section 2.3 for details).

That is, the oxygen-enriched engine is to add an air separation oxygen generation technology (such as an oxygen-enriched membrane shown in fig. 1) in an air intake link of the existing engine, so that the gas sucked by the engine can be enriched with oxygen, and the engine becomes the oxygen-enriched engine. Except for the air inlet part, the principle of the rest parts is the same as that of the existing engine. This is the main technical feature of oxygen-enriched engines.

It is the same as the prior art, all depend on the chemical energy of fuel combustion to do work, and the difference lies in the combustion condition:

the prior art is as follows: fuel + air (or compressed air);

oxygen-enriched engine: fuel + oxygen-enriched gas.

2.2 comparative analysis of oxygen-enriched Engine versus existing Engine Combustion

Still taking the gasoline engine as an example, further analysis is as follows:

the chemical equation for complete combustion of gasoline is:

the molecular weight of gasoline is 114 and the molecular weight of oxygen is 32. The equation in weight units can be written as:

theoretically, when both gasoline and oxygen can be completely combusted, the proportion of oxygen to gasoline is as follows:

400∶114=3.51∶1

and because 4.35 kilograms of air contains 1 kilogram of oxygen, when oxygen and gasoline can be completely combusted, the theoretical mixing ratio of the air and the gasoline is as follows: $\frac{400\×4.35}{114}=\frac{1740}{114}=15.26:1$

thus, it is common to say that the "theoretical mixing ratio" (by weight) of air to gasoline is about 15: 1.

For the existing engine, when the concentration of the mixture is the theoretical mixing ratio (15: 1), namely the oxygen-oil ratio is 3.51: 1, each gasoline molecule can find corresponding number of oxygen molecules to combine with the gasoline molecule, the gasoline molecule can be completely combusted, and the maximum power can be generated. However, the gasoline is not completely combusted due to the influence of the uneven mixing and the residual exhaust gas in the cylinder, which results in waste. To complete combustion, the concentration of the mixture is reduced; to obtain larger power, the concentration of the mixed gas must be increased, and the excessive gasoline is supplied to burn out the sucked oxygen, so that the gasoline waste is serious.

The oxygen-enriched engine can be operated at the gas-oil mixing ratio of 15: 1(α =1), the oxygen-oil ratio is greater than 3.51: 1.

Therefore, when power is increased, the oxygen-enriched engine is the same as the existing engine, and the concentration of the mixed gas is increased (α is less than 1). The difference is that the existing engine can only burn out the sucked oxygen after increasing the concentration of the gasoline, and a part of the gasoline is wasted, while the oxygen-enriched engine can completely burn most of the gasoline and convert the gasoline into power because the sucked gashas rich oxygen, so that the power performance is very easy to improve, and the oxygen-enriched engine runs when the concentration of the mixed gas is lighter (α is more than 1).

The method only increases the oxygen-rich amount of the intake gas without changing the structure and parameters of the engine, is suitable for the reconstruction of the engine in use, and improves the fuel economy and the dynamic property of the engine.

Analysis result ① for the engine which has been put into use, the scheme shown in fig. 1 can be adopted to ensure that the engine sucks a proper amount of oxygen rich gas, and the engine operates in a working condition range with a small theoretical mixing ratio, so that high dynamic property and fuel economy can be obtained simultaneously.

2.3 characteristics of oxygen-enriched engines

This section focuses on the relationship between fuel economy, dynamics, and displacement of oxygen-rich engine.

FIG. 2(b) shows a cylinder of a conventional gasoline engine, which is filled with normal air (containing 21% oxygen) and a gas-oil mixture ratio of 15: 1 (oxygen-oil ratio of 3.51: 1). Its power is the rated power Ne.

FIG. 2(a) shows the situation where the oxygen-enriched gas with oxygen-enriched concentration of 42% is sucked into the same cylinder (2 times higher than the oxygen content of normal air), and the injection amount of gasoline is also increased by 2 times, that is, the air-oil mixture ratio is 15: 2 (oxygen-oil ratio is 3.51: 1).

In both cases, the cylinder volume is equal and the concentration ratio of oxygen to gasoline is equalEqual, i.e. the combustion economy should be the same. However, in the case of diagram (a), the fuel amount is 2 times that of diagram (b), and therefore the power thereof is 2 times that of diagram (b), i.e., 2 Ne. It can be seen that the power of the oxygen-enriched engine can be linearly increased in proportion to the oxygen-enriched concentration thereof. Can be formulated as: $\mathrm{Nf}=\frac{k}{21\%}\mathrm{Ne}......\left(1\right)$

wherein: nf-the power of the oxygen-enriched engine,

k-oxygen-rich concentration (%) of the inhaled gas,

ne-the rated power of the existing engine,

21% -oxygen content of normal air. The power of the existing engine is as follows: $\mathrm{Ne}=\frac{\mathrm{PeiVhn}}{225t}......\left(2\right)$

wherein: pe-mean effective pressure of cylinder

i-number of cylinders

Vh-single cylinder working volume

n-engine speed

t-stroke number if neglecting the factor that the Pe of the oxygen-enriched engine will be improved compared with the Pe of the existing engine, then: $\mathrm{Nf}=\frac{\mathrm{KPeiVhn}}{47.25t}......\left(3\right)$

the formula (3) is the power formula of the oxygen-enriched engine. The relationship among the dynamic property, the fuel economy and the engine displacement of the oxygen-enriched engine can be obtained by analyzing the oxygen-enriched engine:

①, the power per liter (power under unit displacement) of the oxygen-enriched engine is in proportion to the oxygen-enriched concentration K of the sucked gas, namely, the parameters of the oxygen-enriched engine and the prior engine such as iVh, Pe, N, t and the like are equal, the fuel economy is the same (the mixture gas concentration is correspondingly increased along with the increase of the oxygen-enriched concentration, and the mixture ratio of oxygen and oil is kept to be 3.51: 1), the power Nf of the engine is increased along with the increase of the oxygen-enriched concentration K of the oxygen-enriched engine (when the K is more than 21 percent), namely, the power per liter is increased, otherwise, if the oxygen-enriched concentration K is reduced (when the K is less than 21 percent), the power Nf of the engine is lower than the oxygen-enriched Ne, which is equivalent to the conditions of high altitude and high altitude areas, and when the K =21 percent.

②, the displacement (iVh) of the oxygen-enriched engine is inversely proportional to the oxygen-enriched concentration of the sucked gas, namely the oxygen-enriched engine is equal to Pe, N and t of the existing engine, the fuel economy is the same (the mixing ratio of oxygen andoil is 3.51: 1), and the power of the oxygen-enriched engine is equal to the power of the existing engine (N = Ne), the displacement (iVh) of the engine can be reduced along with the increase of the oxygen-enriched concentration K.

③, if pe, N, t, iVh and N of the oxygen-enriched engine and the existing engine are equal, the oxygen-enriched concentration K is increased to promote complete combustion, the fuel economy of the engine is improved very easily, thereby reducing the emission of CO and CH in the tail gas of the engine and reducing the carbon deposit of the engine.

The three points are the relationship between the power performance, the fuel economy and the engine displacement of the oxygen-enriched engine. Also belongs to the important technical characteristics of the oxygen-enriched engine.

The analysis conclusion ② shows that the oxygen-enriched engine can improve the power per liter and reduce the fuel consumption rate, can select higher oxygen-enriched concentration (the highest oxygen-enriched concentration can reach 40-55 percent in the prior art) according to the requirements of different purposes (or the power property, or the economy property, or the volume and the weight of the engine are reduced by the emphasis, or the three are mutually considered), reasonably select the indexes of the power, the working volume, the fuel economy, the manufacturing cost and the like of the engine, and can produce the ideal oxygen-enriched engine suitable for different purposes.

3. Performance index analysis of oxygen-enriched engines

The performance indexes of the oxygen-enriched engine and the exhaust gas turbocharging diesel engine are compared in the section, and the performance indexes of the oxygen-enriched engine are analyzed.

In the prior art, in order to solve the contradiction between the restriction of the dynamic property and the fuel economy of the diesel engine, the air inlet quantity of a cylinder of the diesel engine is increased by increasing the air inlet pressure of the diesel engine, and the oil injection quantity is correspondingly increased, so that the output power of the diesel engine can be increased and the fuel economy can be improved under the condition that the structure of the diesel engine is not changed. A commonly used supercharger is an exhaust gas turbocharger.

The ratio of the outlet pressure Pk of the supercharger to the inlet pressure Po is called the boost ratio. The pressure ratio is divided into three types, namely low pressure (less than 1,4), medium pressure (1.4-2.0) and high pressure (more than 2.0). The middle and high pressure superchargers with the pressure increasing ratio of more than 1.8 adopt intercoolers to reduce the temperature of the outlet air.

The case where the pressure increase ratio was 2.0 was subjected to calculation analysis. From the gaseous equation: $\frac{\mathrm{PkVk}}{\mathrm{Tk}}=\frac{\mathrm{PoVo}}{\mathrm{To}}$ wherein: pk, Vk, Tk are the pressure of the gas on the outlet side of the supercharger

Force, volume, temperature.

Po, Vo and To are respectively the pressure, volume and temperature of the gas at the inlet side of the supercharger.

Suppose that: the inlet temperature and the outlet temperature are equal due to the function of the intercooler, namely: to = Tk. The pressurization process is an isothermal process. Then:

Pk Vk = Po Vo $\frac{\mathrm{Vo}}{\mathrm{Vk}}=\frac{\mathrm{Pk}}{\mathrm{Po}}=2.0$

then: vo =2Vk

That is, when the supercharging pressure ratio is 2.0, the intake air amount of the diesel engine is increased by 2 times, and the total amount of oxygen in the intake air is also increased by 2 times.

If the non-supercharged oxygen-enriched diesel engine is changed into the oxygen-enriched diesel engine, the oxygen-enriched concentration of the intake air reaches 2 times of the oxygen content of the normal air (oxygen-enriched 42 percent), and the diesel engine has the same performance index with the diesel engine with high supercharging ratio (2.0).

According to the existing data (from the first edition engine of automobile question answering) published by people's traffic publishing company: 6135Q type non-supercharged diesel engine and supercharged diesel engineThe performance parameters of the 12V135Q diesel engine are listed in the following table:

diesel engine type	Supercharging situation	Power per liter (horsepower/liter)	Specific fuel consumption (kilogram/horsepower-hour)
6135Q	Non-supercharging	13.33	6.8
12V135Q	Pressure boost	16.70	4.0
Supercharging effect		The improvement is 25.3 percent	The reduction is 41.2 percent

After supercharging, the specific power of the diesel engine is increased by 25.3%, and the fuel consumption per horsepower is reduced by 41.2%. Both power and fuel economy are greatly improved.

If the oxygen-enriched concentration of the non-supercharged 6135Q diesel engine reaches about 28 percent (estimated from the fact that the oxygen-enriched concentration is not equal), the same performance index as that of the supercharged 12V135Q diesel engine can be achieved. If the oxygen-enriched concentration is further improved, the performance index of the oxygen-enriched air is higher.

In addition, supercharging techniques are difficult to use for engines that use lower flash points for fuel, such as gasoline engines. Because the supercharging technology increases the intake air quantity by increasing the intake pressure, the pressure and temperature will be further increased in the compression stroke of the cylinder after the intake pressure is increased. Gasoline auto-ignites before ignition and knocking occurs. The engine such as gasoline engine with lower flash point fuel is rarely supercharged under the influence of knocking factor. Even if the pressure is adopted, the specific pressure value is low, and the improvement on the dynamic property and the economical efficiency is not great. And the oxygen enrichment engine improves the dynamic property and the economical efficiency by improving the oxygen enrichment concentration of the air inlet. Therefore, the oxygen-enriched engine is a technical scheme with great potential undoubtedly for improving the dynamic property and the economical efficiency of gasoline engines and other engines using fuels with lower flash points.

Conclusion ③ oxygen-enriched engine has excellent performance index, it will become a great trend of technical progress in engine manufacturing industry.

4. Principle method for manufacturing oxygen-enriched engine

As already described in section 2.1, the oxygen-enriched engine can become an oxygen-enriched engine only by adopting an air separation oxygen generation technology (additionally arranging an oxygen-enriched membrane) on an air inlet part of the existing engine. Otherwise, the rest of the principle is the same as that of the existing engine. Therefore, the key point is the application of the technology for preparing oxygen by the air separation method.

The modern air separation oxygen preparation technology comprises the following steps: low temperature method, pressure swing adsorption method and membrane separation method. These three methods can be used in oxygen-enriched engines. The membrane separation method is the most recent oxygen production method with the simplest method and the most economical use (the gas production amount is less than 15000 standard cubic meters per hour), and the application emphasis is to be placed on the membrane separation method. The other two methods are not discussed.

The membrane separation method oxygen-making technology is the latest oxygen-making technology. The research and development center of the chemical and physical research institute of the Chinese academy, the large connective membrane engineering, is specially engaged in the research and development of membrane products. The oxygen-enriched membranes which have matured at present are: a plate-type oxygen-enriched membrane (the oxygen-enriched concentration can reach 28% as shown in figure 1), a roll-type oxygen-enriched membrane (the oxygen-enriched concentration can reach 28% as shown in figure 3), and a hollow fiber membrane (the oxygen-enriched concentration can reach 40-55% as shown in figure 4).

Still taking a gasoline engine as an example, the principle method is described.

4.1 principle method 1 (suction type)

The oxygen-enriched membrane is arranged in an air filter of an engine (shown in figure 1). Section 2.1 has already been described and will not be repeated here. This method is suitable for engines with smaller displacement. The technical key point is that the plate-type membrane is very thin, the supporting problem (such as a supporting steel mesh in figure 1) needs to be solved in application, and the area of the membrane needed is large. The method has the advantage of simplicity.

4.2 principle method 2 (Press-in type)

In fig. 5: 1 is an air filter, 2 is an air pump, 3 is a membrane component, 4 is a carburetor, 5 is an engine intake manifold and 6 is an exhaust manifold.

In the figure, a membrane module (a roll-type membrane or a hollow fiber membrane module) is added in an air suction pipeline of the existing gasoline engine, and an air pump is added to form a press-in type oxygen-enriched engine. Under the action of the pumping force of the air pump, the air firstly passes through the air filter to become pure air, and is pressurized by the air pump and then is fed to the membrane component. The air passes through the membrane component under the action of pressure difference to separate oxygen-enriched gas, and the oxygen-enriched gas is formed into oxygen-enriched mixed gas by means of carburetor and then is fed into engine to make combustion. The method is suitable for the oxygen-enriched engine with larger engine displacement and higher oxygen-enriched concentration.

The specific parameters of the two methods are determined according to the engine displacement and the performance requirement of the membrane assembly.

5. The oxygen-enriched engine has the advantages and disadvantages that:

① the oxygen-enriched engine can solve the contradiction between the dynamic property and the fuel economy of the existing engine, and greatly improve the fuel economy and the dynamic property at the same time.

②, because the oxygen-enriched engine can burn the fuel completely under all working conditions, it can save energy, reduce carbon deposit in the engine, reduce the discharge of CO and CH in the tail gas of the engine and protect the environment.

③, when the fuel economy and power performance of the oxygen-enriched engine are the same, and the strength of the material and the heat dissipation performance are allowed, the higher the oxygen-enriched concentration of the intake gas is, the more the volume and the weight of the intake gas per unit power can be reduced (the power per liter is increased) compared with the fuel economy of the existing engine.

④ the oxygen-enriched engine can also solve the problems of poor fuel economy and serious insufficient power of the existing engines in high altitude and high altitude areas.

⑤, the disadvantage is that the excessive oxygen and nitrogen are decomposed and combined at high temperature due to sufficient oxygen supply, so that NO in the tail gas is easy to be generated_XThe content of (c) increases.

6. And (3) ending:

the oxygen-enriched engine can be produced by adopting an engine oxygen-enriched combustion method and adopting an air separation method oxygen production technology in an air inlet link, not only can the engine which is put into use at present be reformed, but also parameters and indexes of the engine, such as power, discharge capacity, oxygen enrichment capacity, fuel economy, manufacturing cost and the like, can be selected in different combinations according to different requirements on the power property, the fuel economy, the volume and the weight of the engine as shown in an analysis conclusion ②, so that the oxygen-enriched engines with different performances can be produced.

The present invention relates to an oxygen-enriched combustion method for engine, which is a new combination of air separation oxygen-making technology and existent engine manufacturing technology. By the new combination, a new technical effect is produced. Thus, the present invention is a method invention.

Reference material:

1. the membrane method oxygen-enriched combustion-supporting system is provided by the film development center of the institute of chemical and physical research in the academy of sciences.

2. Oxygen generation technology is published by Lei chemical treatise metallurgy industry publishing company.

Claims (1)

1. In the field of engine manufacturing industry, the contradiction between the dynamic property and the fuel economy of the existing engine is mutually restricted, so that the engine has small power per liter, high oil consumption and large exhaust pollution. The oxygen-enriched combustion method for engine is characterized by that in the air-intake link of existent engine an air separation method is added to make the gas sucked into the engine richen in oxygen so as to promote complete combustion.

   The method is characterized in that: the oxygen preparation technology by air separation method is combined with the existing engine manufacturing technology, so that the engine can suck oxygen-enriched gas and perform oxygen-enriched combustion. The power per liter of the engine can be improved, the oil consumption rate can be reduced, and the exhaust pollution can be reduced. The relationship between the power (Nf) of an oxygen-enriched engine, the mean effective pressure of cylinders (Pe), the displacement of the engine (iVb), the number of cylinders (i), the number of strokes (t), the oxygen-enriched concentration (K), and the fuel economy may be formulated as: $\mathrm{Nf}=\frac{\mathrm{KPeiVhn}}{47.25t}$

   the method for oxygen-enriched combustion by using the air separation oxygen production technology to make the engine suck oxygen-enriched air (the oxygen content of the sucked air is higher than that of the air) is claimed.

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