Method of combustion speed control through stoichiometric stratification for internal combustion engine using hydrogen fuel

Abstract

The present invention relates to a method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel. By controlling the combustion speed, thermal efficiency can be improved by reducing heat transfer losses, heat transfer losses can be reduced and effective power can be generated by improving the initial combustion speed including the flame development period, and nitrogen oxide emissions can be reduced by lowering the overall average temperature of the combustion chamber.

Description

Technology Field

[0001] The present invention relates to a method for controlling combustion speed in an internal combustion engine using hydrogen fuel by stratifying the equivalence ratio within the combustion chamber according to the region. Background Technology

[0003] Internal combustion engines using hydrocarbon fuels are used in various fields such as automobiles, ships, power generation, and aerospace, but exhaust gases containing carbon oxides generated during the combustion of hydrocarbon fuels are a cause of serious environmental problems such as air pollution, global warming, and acid rain.

[0004] Unlike hydrocarbon fuels, hydrogen fuel does not emit exhaust gases containing carbon oxides during combustion, making it a key energy source for achieving carbon neutrality. While hydrogen fuel is generally used primarily in fuel cells based on electrochemical reactions, it is also a suitable fuel for reciprocating internal combustion engines (RECs) that rely on thermochemical reactions similar to combustion.

[0005] Reciprocating internal combustion engines may utilize a port fuel injection (PFI) method, which injects fuel into a port supplying air to the combustion chamber, and / or a direct injection (DI) method, which injects fuel directly into the combustion chamber.

[0006] Internal combustion engines using hydrogen fuel via port injection operate at relatively lower pressures than direct injection systems, offering the advantages of lower technical difficulty and higher combustion and thermal efficiency. However, they have the drawbacks of a relatively higher likelihood of abnormal combustion phenomena such as backfire, pre-ignition, and knocking, and a relative decrease in engine output due to the inevitable reduction in fresh air intake caused by the volume of hydrogen fuel.

[0007] Meanwhile, internal combustion engines using hydrogen fuel with a direct injection method have the advantage of a lower risk of backfire and pre-ignition compared to port injection methods. However, since hydrogen must be injected at an injection pressure higher than the internal pressure of the combustion chamber, there is a relatively high risk of hydrogen fuel leakage in the hydrogen fuel system, and there is a problem where combustion and thermal efficiency are reduced due to a decrease in the pre-mixing rate of hydrogen and air within the combustion chamber.

[0008] Engines based on stratified combustion using a direct injection method that uses conventional gasoline as fuel directly inject gasoline fuel into the combustion chamber, causing the equivalence ratio within the combustion chamber to vary depending on the region. However, due to the narrow combustibility range of gasoline fuel (volume ratio 1 to 6%, equivalence ratio approximately 0.7 to 1.5) and the slow maximum flame point velocity (within approximately 0.4 m / s), the purpose is to improve ignition stability by forming a rich mixture region near the spark plug rather than controlling the combustion speed. Additionally, since gasoline has the characteristic that the laminar flame velocity decreases when the mixture is rich or lean starting from an equivalence ratio of approximately 1.1, there is no advantage in improving the combustion speed due to stratification.

[0009] In contrast, hydrogen fuel has the advantage of increasing combustion speed as it forms a rich mixture with an equivalence ratio of approximately 1.8. Additionally, since hydrogen requires only 0.02 mJ compared to gasoline, which has a minimum ignition energy of approximately 0.24 mJ based on stoichiometric air-fuel ratio, there is no need to form a rich mixture near the igniter for stable ignition. Therefore, unlike conventional gasoline direct injection stratified combustion, hydrogen stratified combustion has the advantage of being operable in both cases: a Rich to Lean case where the center near the spark plug is rich and the periphery near the combustion chamber walls is lean, and a Lean to Rich case where the center near the spark plug is lean and the periphery near the combustion chamber walls is rich. The problem to be solved

[0011] The problem that the present invention aims to solve is to provide a method for controlling the combustion speed by stratifying the equivalence ratio within the combustion chamber according to the region in order to improve combustion efficiency and reduce harmful exhaust gases in an internal combustion engine using hydrogen fuel.

[0012] However, the problems that the present invention aims to solve are not limited to the problems mentioned above, and include problems that, even if not mentioned above, can be easily derived or clearly understood by a person skilled in the art from the description below. means of solving the problem

[0014] According to one aspect of the present invention, a method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel, comprising a port injection injector and a direct injection injector, is provided, comprising: a step of port injecting hydrogen fuel after the intake valve is closed; and a step of directly injecting hydrogen fuel into the combustion chamber after the bottom dead center has passed. Effects of the invention

[0016] The method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel according to the present invention can improve thermal efficiency by reducing heat transfer losses through controlling combustion speed, effectively reduce heat transfer losses and generate power by improving the initial combustion speed including the flame development period, and reduce the emission of nitrogen oxides, which are high-temperature combustion products, by lowering the average temperature of the entire combustion chamber.

[0017] The effects of the present invention are not limited to the effects described above, and even if not described, effects that are obvious to a person skilled in the art from the present specification are included. Brief explanation of the drawing

[0019] FIG. 1 is a schematic diagram of an internal combustion engine using hydrogen fuel including a port injection injector and a direct injection injector according to the present invention. Figure 2 is a graph showing the direct injection timing of stratification from the lean to rich region and stratification from the rich to lean region within the combustion chamber. Figure 3 illustrates an exemplary stratification in an internal combustion engine using hydrogen fuel, including a port injection injector and a direct injection injector, in which the periphery of the combustion chamber is a lean region and the center of the combustion chamber is a rich region. Figure 4 illustrates an exemplary stratification in an internal combustion engine using hydrogen fuel, including a port injection injector and a direct injection injector, in which the periphery of the combustion chamber is a rich region and the center of the combustion chamber is a lean region. Specific details for implementing the invention

[0020] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0021] Throughout this specification, "A and / or B" means "A and B, or A or B".

[0022] Throughout this specification, "Top dead center (TDC)" refers to the point where the piston of an internal combustion engine is located at the top of the cylinder.

[0023] Throughout this specification, "Bottom dead center (BDC)" refers to the point where the piston of an internal combustion engine is located at the lowest point inside the cylinder.

[0024] Throughout the entire specification, "equivalence ratio" refers to the ratio of the actual air-fuel ratio to the theoretical air-fuel ratio, wherein the theoretical air-fuel ratio is the ratio of the minimum mass of air required to completely combust the fuel input relative to the mass of the fuel input. Accordingly, if the equivalence ratio is 1 or greater, it refers to a fuel-rich mixture, and if the equivalence ratio is less than 1, it refers to a fuel-lean mixture.

[0025] The technical configuration and contents of the present invention will be described in detail below with reference to the attached drawings.

[0026] FIG. 1 is a schematic diagram of an internal combustion engine using hydrogen fuel including a port injection injector and a direct injection injector according to the present invention.

[0027] The internal combustion engine (100) using hydrogen fuel according to the present invention may be an electric ignition type reciprocating internal combustion engine and may include a port injection injector (10), a direct injection injector (20), a combustion chamber (30), a spark plug (40), an intake valve (50), an exhaust valve (60), a piston (70), and a crankshaft (80). In addition, the internal combustion engine (100) using hydrogen fuel according to the present invention may not have intake throttling.

[0028] The above port injection injector (10) has an injector tip located at a port that supplies air and fuel to the combustion chamber, so hydrogen fuel is injected into the port to indirectly supply fuel into the combustion chamber (30).

[0029] The above direct injection injector (20) supplies fuel by directly injecting hydrogen fuel into the combustion chamber (30) because the injector tip is located inside the combustion chamber (30).

[0030] The spark plug (40) is located inside the combustion chamber (30) and ignites the hydrogen fuel supplied inside the combustion chamber (30) to cause combustion (explosion), and the combustion of the hydrogen fuel causes the piston (60) and crankshaft (70) to move.

[0031] The method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel according to the present invention utilizes an internal combustion engine using hydrogen fuel comprising two injectors, namely a port injection injector and a direct injection injector, thereby enabling more effective control of the fuel injection ratio and timing compared to using only a single indirect injection injector (or direct injection injector), and facilitating the formation of equivalence ratio stratification within the combustion chamber.

[0032] One embodiment of the present invention provides a method for controlling the combustion speed of an internal combustion engine using hydrogen fuel through equivalence ratio stratification, comprising a port injection injector and a direct injection injector, the method comprising: a step of port injecting hydrogen fuel after the intake valve is closed; and a step of directly injecting hydrogen fuel into the combustion chamber after the bottom dead center has passed.

[0033] According to one embodiment of the present invention, after the step of port-injecting hydrogen fuel after the intake valve is closed, the intake valve may be opened and hydrogen fuel supplied into the combustion chamber.

[0034] Figure 2 is a graph showing the timing of direct injection from the lean to rich region and from the rich to lean region.

[0035] According to one embodiment (Rich to Lean) of the present invention, the step of directly injecting hydrogen fuel into the combustion chamber after the bottom dead center may involve directly injecting hydrogen fuel into the combustion chamber intermittently twice within a 90-degree crank angle after the bottom dead center to form a stratification in which the periphery of the combustion chamber is a lean region and the center of the combustion chamber is a rich region (Lean to Rich). Here, the lean region and the rich region may be distinguished based on the periphery of the spark plug (40). In the two direct injections, the duration of each injection may be the same or different. By adjusting the timing of the direct injections to form a stratification in which the periphery of the combustion chamber is a lean region and the center of the combustion chamber is a rich region, the combustion speed can be controlled to improve thermal efficiency by reducing heat transfer losses.

[0036] According to another embodiment (Rich to Lean) of the present invention, the step of directly injecting hydrogen fuel into the combustion chamber after the bottom dead center may involve directly injecting hydrogen fuel into the combustion chamber once within a 90 crank angle after the bottom dead center, and then directly injecting hydrogen fuel into the combustion chamber once within a 90 crank angle before the top dead center to form a stratification in which the periphery of the combustion chamber is a rich region and the center of the combustion chamber is a lean region (Rich to Lean). Here, the lean region and the rich region may be distinguished based on the periphery of the spark plug (40). In the two direct injections, the duration of each injection may be the same or different. By adjusting the timing of the direct injections to form a stratification in which the periphery of the combustion chamber is a rich region and the center of the combustion chamber is a lean region, heat transfer loss can be reduced and effective power can be generated by improving the initial combustion speed, including the flame development period.

[0037] According to one embodiment of the present invention, the port-injected hydrogen fuel may be 60% to 80% of the total hydrogen fuel injected during one cycle. Specifically, the port-injected hydrogen fuel may be 60% to 80%, 60% to 75%, or 65% to 75% of the total hydrogen fuel injected. By controlling the port-injected hydrogen fuel within the aforementioned range, stratification from a lean to rich region and stratification from a rich to lean region can be easily formed within the combustion chamber. In addition, the injection duration of the directly injected hydrogen can be appropriately varied to achieve effective stratification.

[0038] According to one embodiment of the present invention, the hydrogen equivalent ratio of the entire combustion chamber may be less than 1. The flammability range of hydrogen fuel has a lower flammable limit (LFM) and a higher flammable limit (HFM) wider than that of conventional hydrocarbon fuel. Therefore, by adjusting the hydrogen equivalent ratio of the entire combustion chamber to less than 1, stratification from a lean region to a rich region and stratification from a rich region to a lean region can be easily formed within the combustion chamber.

[0039] According to another embodiment of the present invention, the hydrogen equivalent ratio of the rich region may be 1 or more and 2 or less. When gasoline fuel is rich or lean starting from an equivalent ratio of about 1.1, the laminar flame velocity decreases, whereas when hydrogen fuel forms a mixture rich up to an equivalent ratio of 1.8, the combustion speed improves. Therefore, by adjusting the hydrogen equivalent ratio of the rich region to 1 or more and 2 or less, the combustion speed can be improved.

[0040] According to one embodiment of the present invention, the hydrogen equivalent ratio of the lean region may be less than 1. By adjusting the hydrogen equivalent ratio of the lean region to less than 1, stratification from the lean region to the rich region and stratification from the rich region to the lean region can be easily formed within the combustion chamber.

[0042] Although the present invention has been described above by limited embodiments, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs. Explanation of the symbols

[0044] 100: Internal combustion engine using hydrogen fuel 10 : Port injection injector 20 : Direct injection injector 30 : Combustion chamber 40 : Spark plug 50 : Intake valve 60 : Exhaust valve 70 : Piston 80 : Crankshaft

Claims

Claim 1 A method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel, comprising a port injection injector and a direct injection injector, comprising: a step of port injecting hydrogen fuel after the intake valve is closed; and a step of directly injecting hydrogen fuel into the combustion chamber after the bottom dead center has passed; wherein the step of directly injecting hydrogen fuel into the combustion chamber after the bottom dead center has passed is characterized by intermittently directly injecting hydrogen fuel into the combustion chamber twice within a 90-degree crank angle after the bottom dead center has passed, thereby stratifying the periphery of the combustion chamber into a lean region and the center of the combustion chamber into a rich region (Lean to Rich). Claim 2 delete Claim 3 A method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel, comprising a port injection injector and a direct injection injector, comprising: a step of port injecting hydrogen fuel after the intake valve is closed; and a step of directly injecting hydrogen fuel into the combustion chamber after the bottom dead center has passed; wherein the step of directly injecting hydrogen fuel into the combustion chamber after the bottom dead center has passed is characterized by directly injecting hydrogen fuel into the combustion chamber once within a 90-degree crank angle after the bottom dead center has passed, and then directly injecting hydrogen fuel into the combustion chamber once within a 90-degree crank angle before the top dead center has passed, thereby stratifying the periphery of the combustion chamber into a rich region and the center of the combustion chamber into a lean region (Rich to Lean). Claim 4 A method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel, wherein, in claim 1 or 3, the port-injected hydrogen fuel constitutes 60% to 80% of the total injected hydrogen fuel. Claim 5 A method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel, wherein, in claim 1 or 3, the hydrogen equivalence ratio of the entire combustion chamber is less than 1. Claim 6 A method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel, wherein, in claim 1 or 3, the hydrogen equivalence ratio of the rich region is 1 or more and 2 or less. Claim 7 A method for controlling combustion speed through equivalence ratio stratification of an internal combustion engine using hydrogen fuel, wherein, in claim 1 or 3, the hydrogen equivalence ratio of the lean region is less than 1.

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