Nitrogen-free combustion system and combustion control method thereof

Abstract

This disclosure relates to a nitrogen-free combustion system and its combustion control method. The nitrogen-free combustion system includes: an intake mechanism suitable for accommodating a mixture of combustion-supporting fuel and / or reformed gas formed by the cracking of liquid fuel; an internal combustion engine connected to the exhaust end of the intake mechanism, suitable for accommodating the combustion of liquid fuel and / or reformed gas and performing work externally; and a cracking mechanism including: a cracker having a hot side and a cold side, configured to use the exhaust gas of the internal combustion engine passing through the hot side of the cracker as a heat source, causing the liquid fuel passing through the cold side of the cracker to crack into reformed gas and return to the intake mechanism; wherein, the internal combustion engine, in response to the ratio of liquid fuel and reformed gas to be burned, has an initial combustion state in which work is performed entirely by the combustion of liquid fuel, a reformed combustion state in which work is performed entirely by the combustion of reformed gas, and a mixed combustion state in which work is performed by the combustion of a mixture of liquid fuel and reformed gas.

Description

Technical Field

[0001] This disclosure relates to the field of nitrogen-free fuel combustion, specifically to a nitrogen-free combustion system and its combustion control method. Background Technology

[0002] Fuel storage typically refers to generating electricity from renewable energy sources and producing H2 through water electrolysis, followed by the synthesis of gaseous or liquid energy storage fuels from the captured CO2 or N2 via catalytic reactions. Compared to directly producing and storing H2, synthesizing hydrocarbon fuels from CO2 is more suitable for long-term, cross-seasonal, low-cost, and large-scale energy storage.

[0003] Nitrogen-free combustion is essentially a carbon capture, storage, and utilization (CCUS) technology, a novel combustion-based carbon capture technology with the potential to achieve low-cost CO2 recovery from the exhaust gases of internal combustion engines burning energy storage fuels. The fuel burns in an environment of oxygen and carbon dioxide, with a portion of the flue gas returned to the system for recycling. A major advantage of nitrogen-free combustion is that the flue gas is primarily composed of carbon dioxide and water vapor, thus the energy consumption for carbon dioxide separation is close to zero. However, nitrogen-free combustion in internal combustion engines with carbon dioxide dilution suffers from a bottleneck problem: low thermal efficiency, with nearly 50% of the energy being emitted through the exhaust gases.

[0004] Therefore, how to provide a method that can effectively recover waste heat from exhaust gases and improve the overall efficiency of nitrogen-free combustion systems in internal combustion engines has become an urgent technical problem to be solved. Summary of the Invention

[0005] To address at least one technical problem in the prior art and other aspects, this disclosure provides a nitrogen-free combustion system and its combustion control method. The system utilizes the exhaust gas from the internal combustion engine to preheat the pyrolysis unit, and adjusts the ratio of reformed gas and liquid fuel generated within the pyrolysis unit to enable the internal combustion engine to operate in multiple combustion states, thereby improving the overall efficiency of the nitrogen-free combustion system.

[0006] One aspect of this disclosure provides a nitrogen-free combustion system, comprising: an intake mechanism adapted to accommodate a mixture of combustion gas and / or reformed gas formed by the cracking of liquid fuel; an internal combustion engine connected to the exhaust end of the intake mechanism, adapted to accommodate the combustion of liquid fuel and / or reformed gas and to perform work externally; and a cracking mechanism comprising: a cracker having a hot side and a cold side, configured to use the exhaust gas of the internal combustion engine passing through the hot side of the cracker as a heat source, causing the liquid fuel passing through the cold side of the cracker to crack into reformed gas and return to the intake mechanism; wherein, the internal combustion engine, in response to the ratio of liquid fuel and reformed gas to be burned, has an initial combustion state in which work is performed entirely by the combustion of liquid fuel, a reformed combustion state in which work is performed entirely by the combustion of reformed gas, and a mixed combustion state in which work is performed by the combustion of a mixture of liquid fuel and reformed gas.

[0007] According to embodiments of this disclosure, the aforementioned nitrogen-free combustion system further includes a fuel supply mechanism, the output end of which is connected to an internal combustion engine and a pyrolysis unit respectively, and is configured to adjustably supply liquid fuel to the internal combustion engine and / or the pyrolysis unit.

[0008] According to embodiments of this disclosure, the aforementioned nitrogen-free combustion system further includes a control mechanism configured to connect the fuel supply mechanism to the pyrolyzer in response to the inlet temperature of the cold side of the pyrolyzer, and to connect the pyrolyzer and the internal combustion engine in response to the pressure of the reformed gas, so as to adjust the internal combustion engine from the initial combustion state to the mixed combustion state.

[0009] According to embodiments of the present disclosure, the control mechanism is further configured to cut off the fuel supply mechanism from the internal combustion engine in response to the oxygen-fuel ratio of the internal combustion engine, so as to adjust the internal combustion engine from a mixed combustion state to a reformed combustion state.

[0010] According to embodiments of this disclosure, the aforementioned nitrogen-free combustion system further includes a pressure stabilizing mechanism disposed between the exhaust end of the pyrolyzer on the cold side and the intake end of the intake mechanism, which is suitable for stabilizing the pressure of the reformed gas entering the intake mechanism.

[0011] According to embodiments of this disclosure, the aforementioned nitrogen-free combustion system further includes an exhaust mechanism disposed between the exhaust end of the internal combustion engine and the intake end of the hot side of the pyrolyzer, which is adapted to guide the exhaust gas of the internal combustion engine into the pyrolyzer and adjust the intake volume of the exhaust gas of the internal combustion engine entering the pyrolyzer.

[0012] According to embodiments of this disclosure, the aforementioned nitrogen-free combustion system further includes a separation mechanism connected to the exhaust end of the exhaust mechanism and / or the exhaust end of the hot side of the pyrolyzer, which is suitable for separating at least a portion of the water and carbon dioxide gas-liquid from the exhaust gas of the internal combustion engine.

[0013] According to embodiments of this disclosure, at least a portion of the carbon dioxide separated from the exhaust gas of an internal combustion engine is configured to flow back into the intake mechanism.

[0014] According to embodiments of this disclosure, the intake mechanism includes: a mixer, the exhaust end of which is connected to the intake end of an internal combustion engine; a first gas source adapted to input a first gas into the mixer; and a second gas source adapted to input a second gas into the mixer to mix with the first gas to form combustion-supporting gas.

[0015] Another aspect of this disclosure provides a combustion control method for a nitrogen-free combustion system, comprising: burning liquid fuel in an internal combustion engine to perform work, thereby putting the internal combustion engine in an initial combustion state, and preheating a pyrolysis unit with exhaust gas generated by the internal combustion engine; once the cold side of the pyrolysis unit reaches the pyrolysis temperature of the liquid fuel, allowing the liquid fuel to enter the pyrolysis unit for pyrolysis to form reformed gas; and adjusting the ratio of liquid fuel and reformed gas entering the internal combustion engine for combustion, thereby adjusting the internal combustion engine to a mixed combustion state or a reformed combustion state.

[0016] According to the nitrogen-free combustion system provided in this disclosure, by connecting the internal combustion engine to the hot side of the pyrolysis unit, the waste heat from the exhaust gas discharged from the internal combustion engine is used to heat the cold side of the pyrolysis unit. The liquid fuel on the cold side of the pyrolysis unit absorbs heat and undergoes evaporation and cracking to generate reformed gas with a higher calorific value than the liquid fuel, thereby achieving waste heat recovery from the exhaust gas. The reformed gas formed on the cold side of the pyrolysis unit is then returned to the intake mechanism and further transported to the internal combustion engine, where it begins to participate in combustion. Based on the change in the ratio of liquid fuel to reformed gas, the internal combustion engine sequentially experiences an initial combustion state where work is entirely generated by the combustion of the liquid fuel, a mixed combustion state where work is generated by the combined combustion of the liquid fuel and the reformed gas, and a reformed combustion state where work is generated entirely by the combustion of the reformed gas. Since the reformed gas has a higher calorific value than the liquid fuel and a higher flame propagation speed, the intervention of the reformed gas can improve the thermodynamic cycle efficiency of the fuel, thereby improving the overall efficiency of the nitrogen-free combustion system of the internal combustion engine. Attached Figure Description

[0017] Figure 1 This is a block diagram of a nitrogen-free combustion system according to an illustrative embodiment of the present disclosure; and

[0018] Figure 2 This is a flowchart of a combustion control method according to an illustrative embodiment of the present disclosure.

[0019] Figure Labels

[0020] 1. Fuel supply organization;

[0021] 11. Fuel tank;

[0022] 12. Fuel pump;

[0023] 13. First nozzle;

[0024] 14. Second nozzle;

[0025] 2. Control mechanism;

[0026] 3. Pyrolysis mechanism;

[0027] 31. Cracking unit;

[0028] 32. Filter;

[0029] 33. Temperature sensor;

[0030] 4. Voltage stabilizing mechanism;

[0031] 41. Voltage stabilizer box;

[0032] 42. Pressure sensor;

[0033] 43. Third nozzle;

[0034] 5. Separation mechanism;

[0035] 51. Condenser;

[0036] 52. Water storage tank;

[0037] 53. Carbon dioxide storage tank;

[0038] 6. Air intake mechanism;

[0039] 61. First valve body;

[0040] 62. Second valve body;

[0041] 63. Oxygen storage tank;

[0042] 64. Mixer;

[0043] 65. Throttle position sensor;

[0044] 7. Internal combustion engine;

[0045] 71. Speed ​​sensor;

[0046] 8. Exhaust system; and

[0047] 81. Oxygen sensor. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0050] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0051] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0052] The low thermal efficiency of nitrogen-free combustion in internal combustion engines under carbon dioxide dilution is a bottleneck issue, with nearly 50% of the energy being emitted through exhaust gases. Effectively recovering waste heat from exhaust gases and improving the overall efficiency of nitrogen-free combustion systems in internal combustion engines are crucial problems that need to be addressed for the large-scale application of fuel storage.

[0053] In view of the above, embodiments of this disclosure provide a nitrogen-free combustion system and a combustion control method thereof based on the same inventive concept.

[0054] Figure 1 This is a block diagram of a nitrogen-free combustion system according to an illustrative embodiment of the present disclosure.

[0055] According to the nitrogen-free combustion system disclosed herein, such as Figure 1 As shown, the system includes an intake mechanism 6, an internal combustion engine 7, and a pyrolysis mechanism 3. The intake mechanism 6 is suitable for accommodating a mixture of combustion gases and / or reformed gas formed from the pyrolysis of liquid fuel. The internal combustion engine 7 is connected to the exhaust end of the intake mechanism 6 and is suitable for accommodating the combustion of liquid fuel and / or reformed gas, and for performing work. The pyrolysis mechanism 3 includes a pyrolyzer 31. The pyrolyzer 31 has a hot side and a cold side, and is configured to use the exhaust gas from the internal combustion engine 7 passing through the hot side of the pyrolyzer 31 as a heat source, causing the liquid fuel passing through the cold side of the pyrolyzer 31 to be pyrolyzed to form reformed gas, which then flows back to the intake mechanism 6. The internal combustion engine 7, in response to the ratio of liquid fuel to reformed gas in combustion, has an initial combustion state where work is entirely performed by the combustion of liquid fuel, a reformed combustion state where work is entirely performed by the combustion of reformed gas, and a mixed combustion state where work is performed by the combustion of a mixture of liquid fuel and reformed gas.

[0056] In this implementation, by connecting the internal combustion engine 7 to the hot side of the pyrolysis unit 31, the waste heat from the exhaust gas from the internal combustion engine is used to heat the cold side of the pyrolysis unit 31. The liquid fuel on the cold side of the pyrolysis unit absorbs the heat and undergoes high-temperature pyrolysis to generate reformed gas with a higher calorific value, thereby achieving the recovery of waste heat from the exhaust gas. Furthermore, by returning the reformed gas generated on the cold side of the pyrolysis unit to the intake mechanism 6 and further conveying it to the internal combustion engine 7, the reformed gas begins to participate in combustion and work. Based on the change in the ratio of liquid fuel to reformed gas, the internal combustion engine 7 successively experiences the initial combustion state where work is done entirely by the combustion of the liquid fuel, the mixed combustion state where work is done by the mixed combustion of the liquid fuel and the reformed gas, and the reformed combustion state where work is done entirely by the combustion of the reformed gas. Since the calorific value of the reformed gas is higher than that of the liquid fuel and it has a higher flame propagation speed, the intervention of the reformed gas can improve the thermodynamic cycle efficiency of the fuel, thereby improving the overall efficiency of the nitrogen-free combustion system of the internal combustion engine.

[0057] In one illustrative embodiment, the liquid fuel includes, but is not limited to, at least one of methanol, ethanol, polyoxymethylene dimethyl ether (PODE), dimethyl ether (DME), methoxyethyl ether (OME), and other nitrogen-free liquid energy storage fuels. The reformed gas generated in the cracker 31 is primarily composed of H2 and CO.

[0058] According to embodiments of this disclosure, such as Figure 1 As shown, the intake mechanism 6 includes a mixer 64, a first gas source, and a second gas source. The exhaust end of the mixer 64 is connected to the intake end of the internal combustion engine 7. The first gas source is used to input a first gas into the mixer 64. The second gas source is used to input a second gas into the mixer 64 to mix with the first gas to form combustion-supporting gas.

[0059] In one illustrative embodiment, the first gas includes, but is not limited to, CO2, and the corresponding first gas source includes, but is not limited to, a carbon dioxide storage tank storing gaseous or liquid CO2. Further, the second gas includes, but is not limited to, O2, and the corresponding second gas source includes, but is not limited to, an oxygen storage tank storing gaseous or liquid O2. Based on the above embodiments, the combustion-supporting gas is a mixture of CO2 and O2.

[0060] In this implementation, when reformed gas (H2 and CO) participates in combustion to do work, the calorific value of reformed gas (H2 and CO) is higher than that of liquid fuel, and it has a higher flame propagation speed. With the intervention of reformed gas, the influence of CO2 dilution gas on flame propagation speed in the nitrogen-free combustion system can be largely eliminated. Moreover, the specific heat ratio of H2 to CO is comparable to that of nitrogen, which is significantly higher than that of CO2. Therefore, the thermodynamic cycle efficiency of the fuel can be improved, thereby improving the overall efficiency of the nitrogen-free combustion system of the internal combustion engine.

[0061] Furthermore, O2 and the energy storage fuel undergo equivalence combustion, with no N2 involved in the combustion process. The high-temperature exhaust gas contains CO2 and H2O. After the waste heat of the exhaust gas is utilized by a heat exchanger, H2O and CO2 are easily separated and collected without energy consumption. The captured CO2 can be reintroduced into the cylinder for oxygen-enriched combustion. Excess CO2 can be used to produce energy storage fuel through a renewable energy system for long-term storage. H2O can be recycled by electrolyzing water using renewable energy to produce H2 and O2, achieving recycling. This ensures that the system's operating cycle is carbon neutral and produces no NOx (nitrogen oxides) emissions.

[0062] In one illustrative embodiment, such as Figure 1 As shown, the air intake mechanism 6 also includes a first valve body 61, a second valve body 62, and an oxygen storage tank 63. The first valve body 61 is located at the first air source (i.e., Figure 1 The carbon dioxide storage tank 53 shown is located between the mixer 64 and the mixer, and is suitable for supplying a first gas source (i.e., CO2) to the mixer through the opening and closing of the first valve body 61; the second valve body 62 is located between the second gas source (i.e., CO2) and the mixer 64. Figure 1 The oxygen storage tank 63 shown is located between the oxygen storage tank 63 and the mixer 64, and is used to input a second gas source into the mixer 64.

[0063] In one illustrative embodiment, the O2 in the oxygen storage tank 63 can be derived from the electrolysis of water by renewable energy sources (wind power, solar power, etc.), thus eliminating the need for an air separation device, resulting in no additional output power loss and no additional investment in the system, thereby reducing costs.

[0064] According to embodiments of this disclosure, a fuel supply mechanism 1 is also included. The output end of the fuel supply mechanism 1 is connected to the internal combustion engine 7 and the pyrolyzer 31, respectively, and is configured to adjustably supply liquid fuel to the internal combustion engine 7 and / or the pyrolyzer 31.

[0065] In one illustrative embodiment, such as Figure 1 As shown, the fuel supply mechanism 1 includes a fuel tank 11, a fuel pump 12, a first nozzle 13, and a second nozzle 14. The fuel pump 12 is connected to the output end of the fuel tank 11 and is used to provide power for supplying liquid fuel to the fuel tank. The first nozzle 13 is located between the fuel pump 12 and the internal combustion engine 7, through which fuel is adjustablely injected into the internal combustion engine 7. The second nozzle 14 is located between the fuel pump 12 and the pyrolysis unit 31, and is used to adjustably inject fuel into the pyrolysis unit 31.

[0066] According to embodiments of this disclosure, such as Figure 1 As shown, it also includes a control mechanism 2, which is configured to connect the fuel supply mechanism 1 to the pyrolyzer 31 in response to the inlet temperature of the cold side of the pyrolyzer 31, and to connect the pyrolyzer 31 and the internal combustion engine 7 in response to the pressure of the reformed gas, so as to adjust the internal combustion engine 7 from the initial combustion state to the mixed combustion state.

[0067] According to embodiments of the present disclosure, the control mechanism 2 is further configured to cut off the fuel supply mechanism 1 from the internal combustion engine 7 in response to the oxygen-fuel ratio of the internal combustion engine 7, so as to adjust the internal combustion engine 7 from a mixed combustion state to a reformed combustion state.

[0068] In one illustrative embodiment, the control mechanism 2 includes, but is not limited to, employing an electronic control unit (i.e., an ECU).

[0069] In one illustrative embodiment, such as Figure 1 As shown, the pyrolysis mechanism 3 also includes a temperature sensor 33 disposed inside the pyrolyzer 31. Specifically, the temperature sensor 33 is communicatively connected to the control mechanism 2. The temperature sensor 33 is used to collect the temperature signal of the inlet temperature on the cold side of the pyrolyzer and transmit the temperature signal to the control mechanism 2. The control mechanism 2 is also communicatively connected to the second nozzle 14, and in response to the temperature signal from the temperature sensor 33, it can control the second nozzle 14 to inject liquid fuel into the pyrolyzer.

[0070] For example, when the pyrolyzer inlet temperature reaches a preset temperature T0, the control mechanism 2 controls the second nozzle 14 to inject liquid fuel into the pyrolyzer 31, and the liquid fuel begins to evaporate and crack in the pyrolyzer 31 to generate reformed gas. The preset temperature T0 is not limited to values ​​obtained through experience and / or calculation, and can be characterized as the temperature suitable for evaporating and cracking the liquid fuel.

[0071] According to embodiments of this disclosure, such as Figure 1 As shown, it also includes a pressure stabilizing mechanism 4 located between the exhaust end of the pyrolyzer 31 and the intake end of the intake mechanism 6 on the cold side, which is suitable for stabilizing the pressure of the reformed gas entering the intake mechanism 6.

[0072] In one illustrative embodiment, such as Figure 1 As shown, the pressure stabilizing mechanism 4 includes a pressure stabilizing tank 41. The pressure stabilizing tank 41 is connected to the pyrolyzer 31 through a filter 32 and is used to store the reformed gas filtered from the filter 32 and to stabilize the pressure of the reformed gas.

[0073] In this implementation, the pressure stabilizing box 41 can buffer, reduce or eliminate fluctuating airflow after it enters the box, so as to ensure the pressure of the reforming gas entering the internal combustion engine 7 is stable.

[0074] In one illustrative embodiment, such as Figure 1As shown, the pressure stabilizing mechanism 4 also includes an internal pressure sensor 42 and a third nozzle 43 disposed in the pressure stabilizing tank 41. The pressure sensor 42 is communicatively connected to the control mechanism 2 and is used to monitor the pressure inside the pressure stabilizing tank and transmit the pressure signal back to the control mechanism 2. The third nozzle 43 is located between the pressure stabilizing tank and the mixer 64 and is communicatively connected to the control mechanism 2. In response to the pressure signal from the pressure sensor 42, the control mechanism 2 can control the third nozzle 43 to inject reformed gas into the mixer 64 and adjust the injection amount of liquid fuel injected by the second nozzle 14 into the pyrolysis unit 31.

[0075] For example, when the pressure in the pressure stabilizing tank 41 reaches the set value P0, the control mechanism 2 controls the third nozzle 43 to open and inject reformed gas into the mixer 64. After the reformed gas and the combustion improver are mixed in the mixer 64, they are delivered to the internal combustion engine and mixed with liquid fuel for combustion to perform work. The internal combustion engine changes from a combustion state in which only fuel participates in combustion to a mixed combustion state in which reformed gas and liquid fuel are mixed and burned. The preset pressure value P0 mentioned above is not limited to values ​​obtained through experience and / or calculations, to ensure that the supplied reformed gas can be burned in an oxygen-rich manner in the internal combustion engine 7.

[0076] In addition, the control mechanism 2 can also respond to the pressure signal of the pressure sensor 42 and adjust the amount of liquid fuel injected into the cracker 31 by the second nozzle 14 in real time to ensure the pressure of the reformer pressurizer is stable.

[0077] In one illustrative embodiment, the reformed gas includes, but is not limited to, multi-point injection through the intake manifold via a third nozzle 43, so that the reformed gas is fully mixed with O2 and CO2 in the mixer before entering the internal combustion engine 7.

[0078] In one illustrative embodiment, the pyrolysis unit 31 includes, but is not limited to, a spiral tube heat exchanger, not shown in the figure. Specifically, the pyrolysis unit 31 includes a shell and a spiral tube, with the space between the shell and the spiral tube serving as the hot side of the pyrolysis unit, and the tube side of the spiral tube serving as the cold side. Exhaust gas inlets and outlets are provided at both ends of the shell, suitable for introducing internal combustion engine exhaust gas from the exhaust gas inlets and discharging it from the exhaust gas outlets. The spiral tube is of metal structure, axially arranged within the shell cavity, and its inner wall is coated with a catalyst. The spiral tube inlet is connected to a second nozzle 14 for injecting liquid fuel, wherein the direction of the liquid fuel inlet is opposite to the direction of the exhaust gas inlet, thus ensuring that the reformed gas after pyrolysis flows in the opposite direction to the exhaust gas flow. After entering the spiral tube, the liquid fuel rapidly heats up and vaporizes through heat exchange with the tube wall, then enters the catalyst tube coated with the catalyst for catalytic pyrolysis, ultimately outputting reformed gas from the spiral tube outlet.

[0079] In this implementation, the spiral tube design maximizes turbulence and increases heat exchange efficiency. The reformed gas flows in the opposite direction to the exhaust gas, ensuring a higher pyrolysis temperature and better pyrolysis effect.

[0080] According to embodiments of this disclosure, such as Figure 1 As shown, it also includes an exhaust mechanism 8 disposed between the exhaust end of the internal combustion engine 7 and the intake end of the hot side of the pyrolyzer 31, which is suitable for guiding the exhaust gas of the internal combustion engine 7 into the pyrolyzer 31 and adjusting the intake volume of the exhaust gas of the internal combustion engine 7 entering the pyrolyzer 31.

[0081] In this implementation, the temperature of the pyrolyzer is adjusted by controlling the intake air volume of the exhaust gas into the internal combustion engine, ensuring that the pyrolyzer is within the range of optimal pyrolysis rate. Here, "optimal" refers to the preferred temperature at which liquid fuel can be pyrolyzed, obtained through experimentation or calculation, and does not necessarily mean that the liquid fuel can be completely pyrolyzed to form reformed gas at that temperature.

[0082] According to embodiments of this disclosure, such as Figure 1 As shown, it also includes a separation mechanism 5 connected to the exhaust end of the exhaust mechanism 8 and / or the exhaust end of the hot side of the pyrolyzer 31, which is suitable for separating at least a portion of the water and carbon dioxide gas-liquid from the exhaust gas of the internal combustion engine 7.

[0083] In one illustrative embodiment, such as Figure 1 As shown, the exhaust mechanism 8 also includes a bypass valve 82 for connecting the output end of the exhaust mechanism 8 and the input end of the separation mechanism 5, and simultaneously communicating with the control mechanism 2. The control mechanism 2 adjusts the intake volume of the exhaust gas from the internal combustion engine 7 entering the pyrolysis unit 31 in response to the temperature signal from the temperature sensor 33.

[0084] For example, when the exhaust temperature is greater than the preset temperature T2, the control mechanism 2 controls the opening of the bypass valve 82. At this time, some of the high-temperature exhaust gas does not pass through the pyrolyzer, causing the pyrolyzer temperature to decrease. When the exhaust temperature is less than the preset temperature T1, the opening of the bypass valve 82 is reduced, causing the pyrolyzer temperature to rise. By adjusting the opening of the bypass valve 22, the pyrolyzer temperature is kept within the optimal range (T1:T2) where the pyrolysis rate is stable.

[0085] In one illustrative embodiment, such as Figure 1 As shown, the internal combustion engine 7 / exhaust system 8 also includes an oxygen sensor 81, which is disposed within the exhaust system and communicates with the control mechanism 2. This sensor monitors the oxygen-fuel ratio of the exhaust gas output from the internal combustion engine and transmits the signal to the control unit. The control mechanism 2 is also communicated with the first nozzle 13. In response to the oxygen-fuel ratio signal, the control mechanism 2 can adjust the amount of fuel injected into the internal combustion engine 7 by the first nozzle 13, and adjust the reforming gas injection pulse width of the third nozzle 43.

[0086] In one illustrative embodiment, an oxygen sensor may be positioned after the exhaust manifold to monitor the oxygen concentration in the exhaust gas after combustion in the internal combustion engine and feed it back to the control mechanism 2 (such as an ECU, i.e., an electronic control unit). Thus, if the oxygen concentration in the exhaust gas is higher than a reference value, it is determined that the air-fuel mixture for combustion in the cylinder of the internal combustion engine 7 is too lean; conversely, it is too rich, thereby adjusting the fuel injection quantity.

[0087] In this implementation, when the oxygen sensor 81 detects that the oxygen-fuel ratio has decreased, the control mechanism controls the first nozzle 13 to reduce the fuel injection quantity and controls the third nozzle 43 to increase the reforming gas injection pulse width until the first nozzle 13 completely cuts off the fuel injection quantity, and the engine enters the full reforming mode.

[0088] In one illustrative embodiment, such as Figure 1 As shown, the intake mechanism also includes a throttle position sensor 65, which is communicatively connected to the control mechanism. The internal combustion engine 7 also includes a speed sensor 71, which is communicatively connected to the control mechanism.

[0089] In this implementation, when the internal combustion engine is in full reforming mode, the control mechanism 2 responds to the electrical signals from the valve position sensor 65 and the speed sensor 71, and adjusts the injection quantity of reforming gas from the third nozzle 43 in real time to ensure that the internal combustion engine operates under near stoichiometric oxygen-fuel ratio conditions.

[0090] In one illustrative embodiment, such as Figure 1 As shown, the separation mechanism 5 includes a condenser 51, a water storage tank and a carbon dioxide storage tank 53. The input end of the condenser is connected to the output end of the reformed gas hot end, and the output end of the condenser is connected to the water storage tank 52 and the carbon dioxide storage tank 53 respectively, which is suitable for separating the exhaust gas.

[0091] According to embodiments of this disclosure, at least a portion of the carbon dioxide separated from the exhaust gas of the internal combustion engine is configured to flow back into the intake mechanism 6.

[0092] According to embodiments of this disclosure, such as Figure 2 As shown, the combustion control method of a nitrogen-free combustion system includes, but is not limited to, the following steps:

[0093] Step S110: The liquid fuel is burned in the internal combustion engine 7 to perform work, so that the internal combustion engine 7 is in the initial combustion state, and the exhaust gas generated by the internal combustion engine 7 is used to preheat the pyrolysis unit 31.

[0094] Step S120: When the cold side of the pyrolyzer 31 reaches the pyrolysis temperature of the liquid fuel, the liquid fuel is introduced into the pyrolyzer 31 for pyrolysis to form reformed gas.

[0095] Step S130: Adjust the ratio of liquid fuel and reformed gas entering the internal combustion engine 7 for combustion, so that the internal combustion engine 7 is adjusted to a mixed combustion state or a reformed combustion state.

[0096] In this implementation, the internal combustion engine can operate in three states: initial combustion, mixed combustion, and reformed combustion. The waste heat from the engine exhaust is used to crack the liquid fuel, generating reformed gas with a higher calorific value, effectively recovering the waste heat. Once the reformed gas begins to contribute to combustion, its high calorific value and higher flame propagation speed significantly reduce the impact of CO2 dilution gas on the flame propagation speed in the oxygen-enriched combustion system. This improves the thermodynamic cycle efficiency and enhances the overall efficiency of the nitrogen-free combustion system.

[0097] In one illustrative embodiment, such as Figure 1 As shown, in the initial combustion state, the internal combustion engine only performs work by mixing and burning the liquid fuel and the oxidizer, and the resulting exhaust gas is sent to the pyrolysis unit for preheating. In this mode, the pyrolysis unit, the second nozzle, the third nozzle, and the pressure stabilizing box are all inactive.

[0098] As the exhaust gas temperature gradually increases, when the pyrolyzer temperature reaches the preset temperature T0, the second nozzle opens to inject fuel into the pyrolyzer, the preheating pyrolyzer starts to operate, and a high-temperature pyrolysis reaction occurs to generate reformed gas, which is then transported to the pressure stabilizing box for pressure stabilization.

[0099] When the pressure in the pressure stabilizing box reaches the set value P0, the third nozzle 43 opens, inputting reformed gas into the internal combustion engine. The internal combustion engine then performs work by mixing and burning liquid fuel, reformed gas, and combustion-supporting gas, and enters a mixed combustion state.

[0100] When the reforming gas begins to intervene, the engine oxygen sensor 81 detects that the oxygen-fuel ratio has decreased. At this time, the controller controls the first nozzle 13 to reduce the fuel injection quantity and controls the third nozzle to increase the reforming gas injection pulse width until the first nozzle 13 completely cuts off the fuel injection quantity, and the internal combustion engine enters the reforming combustion state.

[0101] In one illustrative embodiment, under reforming combustion conditions, the control mechanism can adjust the intake air volume of the pyrolysis tail gas in real time according to the temperature of the pyrolysis unit. For example, when the pyrolysis unit temperature is greater than T2, the control mechanism reduces the intake air volume of the tail gas entering the pyrolysis unit, thereby lowering the pyrolysis unit temperature. When the pyrolysis unit temperature is less than T2, the control mechanism increases the intake air volume of the tail gas entering the pyrolysis unit, thereby raising the pyrolysis unit temperature. This ensures that the pyrolysis unit operates stably within its optimal temperature range.

[0102] To make the technical solution and advantages of the present invention clearer, the present invention will be further described below in conjunction with specific embodiments.

[0103] In one illustrative embodiment, methanol is used as a liquid fuel. The methanol is cracked into hydrogen-rich reformed gas through a cracking mechanism, so that part of the exhaust gas energy is converted into the chemical energy of the fuel, which improves the fuel grade. At the same time, the flame propagation speed of hydrogen-rich reformed gas is faster and the specific heat ratio is higher than that of methanol combustion, which can effectively improve the engine thermal efficiency.

[0104] Table 1 Low calorific value of several fuels

[0105] fuel Low calorific value (MJ / kg) Liquid methanol 19.68 Methanol vapor (573K) 21.31 Methanol is completely cracked into reformate. 23.94

[0106] The reaction equation for the methanol cracking reaction is as follows (1):

[0107] CH3OH + 90.7kJ → CO + 2H2 (Equation 1)

[0108] In fact, methanol cracking is completed in two stages: liquid methanol evaporates into methanol vapor, and methanol vapor cracks.

[0109] (1) Evaporation of methanol: When liquid methanol is heated and evaporated into methanol vapor, its energy increases by about 8.3%;

[0110] (2) Cracking of methanol vapor: The complete cracking of methanol vapor into H2+CO increases its energy by about 13.3% compared to liquid methanol;

[0111] Combining the effects of the two reactions, the calorific value of methanol completely cracked into reformed gas is about 21.6% higher than that of liquid methanol.

[0112] In internal combustion engines, methanol is typically decomposed using exhaust heat at low temperatures, where anhydrous methanol is broken down into H2 and CO at a relatively low reaction temperature (around 300°C). A Pd-based catalyst with a coated honeycomb structure is selected. Pd-based catalysts do not suffer from high-temperature deactivation, have a wider catalytic temperature range, and exhibit higher selectivity for hydrogen. Considering the impact of temperature on the activity of the Pd catalyst and the pyrolyzer start-up time during engine cold starts, T0 is set at 300°C.

[0113] In this embodiment, the following reaction occurs:

[0114] Methanol cracking: CH3OH + 90.7kJ → CO + 2H2 (Equation 1)

[0115] Oxygen-enriched combustion of methanol: 2CH3OH + 3O2 → 2CO2 + 4H2O Equation (2)

[0116] Oxygen-enriched combustion of reformed gas: 2CO + 4H2 + 3O2 → 2CO2 + 4H2O Equation (3)

[0117] Internal combustion engines operate in three states: initial combustion, mixed combustion, and reforming combustion. In-cylinder combustion occurs under near-stoichiometric conditions.

[0118] (1) In the single methanol fuel mode (i.e., initial combustion state), the engine starts and preheats, and the exhaust temperature of the internal combustion engine gradually increases, raising the temperature of the connected waste heat pyrolysis unit through the waste heat of the exhaust gas. In this mode, an oxygen-rich combustion reaction of methanol with O2 / CO2 occurs in the cylinder. The combustion products are only H2O and CO2, which are separated without energy consumption after condensation by the waste heat exchanger. Part of the separated CO2 re-enters the engine to participate in combustion, and the remainder can be used to prepare energy storage fuel for renewable energy systems.

[0119] (2) When the inlet temperature of the pyrolyzer reaches the set value T0, the control mechanism controls the second nozzle 14 to start injecting methanol into the pyrolyzer 31. Methanol enters the pyrolyzer 31 and undergoes a pyrolysis reaction to generate reformed gas (H2:CO=2:1). The generated reformed gas is transported to the pressure stabilizing tank 41 connected to the pyrolyzer 31 until the pressure of the reformed gas pressure stabilizing tank 41 reaches the set value P0. Then, the third nozzle 43 opens, and the reformed gas begins to enter the cylinder for combustion. At this time, the engine enters a mixed combustion state. In this mode, methanol, reformed gas, and oxygen-enriched combustion of O2 / CO2 occur in the internal combustion engine.

[0120] (3) Due to the intervention of reformed gas, the engine oxygen sensor 81 detects a decrease in the oxygen-fuel ratio. At this time, the control mechanism controls the first nozzle 13 to reduce the fuel injection quantity and controls the third nozzle 43 to further increase the injection pulse width until the first nozzle 13 completely cuts off the fuel injection quantity, and the internal combustion engine enters the reformed combustion state. In this mode, oxygen-rich combustion of reformed gas and O2 / CO2 occurs in the engine cylinder. Since the pyrolyzer fully recovers the waste heat of the engine exhaust gas and catalytically cracks the fuel into reformed gas (H2:CO=2:1), it increases the calorific value of the fuel. At the same time, the flame propagation speed of the reformed gas (H2:CO=2:1) ​​is higher, which can largely eliminate the influence of CO2 dilution gas on the flame propagation speed of the oxygen-rich combustion system. Moreover, the specific heat ratio of H2 to CO is comparable to that of nitrogen and significantly higher than that of CO2, thus improving the thermodynamic cycle efficiency.

[0121] In another illustrative embodiment, ethanol is used as the liquid fuel, and a non-metallic Co-based catalyst with high activity and selectivity is selected. The internal combustion engine operates in three states: initial combustion, mixed combustion, and reformed combustion. In the single ethanol fuel mode, startup and preheating are completed, and the exhaust temperature of the internal combustion engine's exhaust system gradually increases, using waste heat to raise the temperature of the connected pyrolyzer. When the inlet temperature on the cold side of the pyrolyzer reaches the set value T0, the control mechanism's second nozzle 14 begins to inject aqueous ethanol into the pyrolyzer 31. The ethanol enters the reformer and undergoes a reforming reaction. The generated reformed gas is transported to the pressure stabilizing tank 41 connected to the pyrolyzer 31 until the pressure in the reformed gas pressure stabilizing tank 41 reaches the set value P0. Then, the third nozzle 43 opens, and the reformed gas begins to enter the cylinder for combustion. At this time, the engine enters a mixed combustion state. The engine oxygen sensor 81 detects a decrease in the oxygen-fuel ratio. The control mechanism then controls the first nozzle 13 to reduce the fuel injection quantity and controls the third nozzle 43 to further increase the injection pulse width until the first nozzle 13 completely cuts off the fuel injection quantity, and the engine enters the reformed combustion state. Throughout the entire process, the internal combustion engine undergoes an oxygen-rich combustion reaction between fuel and O2 / CO2. The combustion products are only H2O and CO2, which are separated by a separation mechanism without requiring energy. Part of the separated CO2 re-enters the internal combustion engine for combustion, while the remainder can be used to produce energy storage fuel for renewable energy systems.

[0122] In another illustrative embodiment, polyoxymethylene dimethyl ether (PODE) is used as a liquid fuel, which can effectively reduce diesel emissions. Its molecular structure has no C-C bonds, and it possesses a high cetane number, low corrosivity, and high oxygen content. Its physical properties, such as density, viscosity, melting and boiling points, are similar to diesel fuel, and it can be directly applied to existing diesel engines (i.e., the internal combustion engine of this disclosure). PODE combined with a novel combustion method has the potential to achieve efficient and clean combustion in engines. By controlling the reforming boundary conditions, the composition of the reforming products can be controlled, thereby increasing the efficiency potential of the reforming products. The internal combustion engine operates in three states: initial combustion, mixed combustion, and reforming combustion. Start-up and preheating are completed in a single PODE fuel mode, and the exhaust temperature of the engine exhaust pipe (i.e., the internal combustion engine and exhaust system of this disclosure) gradually increases, using waste heat from the exhaust gas to raise the temperature of the connected pyrolyzer. High-temperature anaerobic pyrolysis is employed. Once the pyrolysis inlet temperature reaches the set value T0, the control mechanism's second nozzle 14 begins injecting PODE into the pyrolysis unit 31. The PODE enters the reformer and undergoes a reforming reaction. The generated reformed gas is transported to a pressure stabilizing tank 41 connected to the pyrolysis unit 31 until the pressure in the reformed gas pressure stabilizing tank 41 reaches the set value P0. At this point, the third nozzle 43 opens, and the reformed gas begins to enter the cylinder for combustion. The engine enters a mixed-fuel state. The engine oxygen sensor 81 detects a decrease in the oxygen-fuel ratio. The control mechanism then controls the first nozzle 13 to reduce the fuel injection quantity and controls the third nozzle 43 to further increase the injection pulse width until the first nozzle 13 completely cuts off the fuel injection quantity, and the engine enters a reformed combustion state. Throughout the entire process, the internal combustion engine undergoes an oxygen-rich combustion reaction between fuel and O2 / CO2. The combustion products are only H2O and CO2, which are separated by a separation mechanism without energy consumption. A portion of the separated CO2 re-enters the internal combustion engine for combustion, while the remainder can be used to prepare energy storage fuel for renewable energy systems.

[0123] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A nitrogen-free combustion system, characterized in that, It includes an intake mechanism (6), an internal combustion engine (7), a pyrolysis mechanism (3), a separation mechanism (5), and an exhaust mechanism (8); The air intake mechanism (6) is suitable for accommodating a mixture of combustion gas and / or reformed gas formed by the cracking of liquid fuel. The air intake mechanism includes a mixer (64), a first gas source and a second gas source. The exhaust end of the mixer (64) is connected to the intake end of the internal combustion engine (7); The first gas source is adapted to input a first gas into the mixer (64); as well as The second gas source is adapted to input a second gas into the mixer (64) to mix with the first gas to form the combustion-supporting gas, wherein the first gas includes carbon dioxide and the second gas includes oxygen; The internal combustion engine (7) is connected to the exhaust end of the intake mechanism (6) and is suitable for accommodating the combustion of the liquid fuel and / or the reformed gas and performing work on the outside. The pyrolysis mechanism (3) includes a pyrolyzer (31); The pyrolysis unit (31) has a hot side and a cold side, and is configured to use the exhaust gas of the internal combustion engine (7) passing through the hot side of the pyrolysis unit (31) as a heat source to cause the liquid fuel passing through the cold side of the pyrolysis unit (31) to be cracked to form the reformed gas and flow back to the intake mechanism (6). The separation mechanism (5) is connected to the exhaust end of the separation mechanism (5) and the exhaust mechanism (8) and / or the exhaust end of the hot side of the pyrolyzer (31). The separation mechanism (5) includes a condenser (51), a water tank and a carbon dioxide tank (53). The input end of the condenser is connected to the output end of the reforming hot end. The output end of the condenser is connected to the water tank (52) and the carbon dioxide tank (53) respectively. It is suitable for separating at least a portion of the water and carbon dioxide gas-liquid from the exhaust gas of the internal combustion engine (7). At least a portion of the carbon dioxide separated from the exhaust gas of the internal combustion engine (7) is configured to flow back into the intake mechanism (6). The internal combustion engine (7) has, in response to the ratio of the liquid fuel and the reformed gas being burned, an initial combustion state in which work is done entirely by the combustion of the liquid fuel, a reformed combustion state in which work is done entirely by the combustion of the reformed gas, and a mixed combustion state in which work is done by the mixed combustion of the liquid fuel and the reformed gas.

2. The system according to claim 1, characterized in that, It also includes a fuel supply mechanism (1), the output of which is connected to the internal combustion engine (7) and the pyrolyzer (31) respectively, and is configured to adjustably supply the liquid fuel to the internal combustion engine (7) and / or the pyrolyzer (31).

3. The system according to claim 2, characterized in that, It also includes a control mechanism (2) configured to connect the fuel supply mechanism (1) to the pyrolyzer (31) in response to the inlet temperature of the cold side of the pyrolyzer (31), and to connect the pyrolyzer (31) and the internal combustion engine (7) in response to the pressure of the reformed gas, so that the internal combustion engine (7) is adjusted from the initial combustion state to the mixed combustion state.

4. The system according to claim 3, characterized in that, The control mechanism (2) is also configured to disconnect the fuel supply mechanism (1) from the internal combustion engine (7) in response to the oxygen-fuel ratio of the internal combustion engine (7), so that the internal combustion engine (7) is adjusted from the mixed combustion state to the reformed combustion state.

5. The system according to any one of claims 1 to 4, characterized in that, It also includes a pressure stabilizing mechanism (4) disposed between the exhaust end of the cold side of the pyrolyzer (31) and the intake end of the intake mechanism (6), which is suitable for stabilizing the pressure of the reformed gas entering the intake mechanism (6).

6. The system according to any one of claims 1 to 4, characterized in that, It also includes an exhaust mechanism (8) disposed between the exhaust end of the internal combustion engine (7) and the intake end of the hot side of the pyrolyzer (31), which is adapted to guide the exhaust gas of the internal combustion engine (7) into the pyrolyzer (31) and adjust the intake volume of the exhaust gas of the internal combustion engine (7) entering the pyrolyzer (31).

7. A combustion control method based on the nitrogen-free combustion system according to any one of claims 1 to 6, comprising: The liquid fuel is burned in the internal combustion engine (7) to do work, so that the internal combustion engine (7) is in the initial combustion state, and the exhaust gas generated by the internal combustion engine (7) preheats the pyrolysis unit (31); When the cold side of the pyrolyzer (31) reaches the pyrolysis temperature of the liquid fuel, the liquid fuel is allowed to enter the pyrolyzer (31) for pyrolysis to form reformed gas. as well as Adjust the ratio of the liquid fuel and the reformed gas entering the internal combustion engine (7) to adjust the internal combustion engine (7) to a mixed combustion state or a reformed combustion state.

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