Diesel and methanol dual-fuel engine lean-burn system combined with heat and power combined supply circulating system and energy comprehensive utilization method

Abstract

The invention relates to a diesel methanol dual-fuel engine lean-burn system combined with a heat and power combined supply circulating system and an energy comprehensive utilization method, and the diesel methanol dual-fuel engine lean-burn system comprises a pre-combustion chamber, a dual-fuel injector system, a methanol injection system, an exhaust back pressure adjusting system, the heat and power combined supply circulating system and the like. The fuel injection precision control of the engine is realized through a dual-fuel injector system and a methanol injection system, two working modes of a pure diesel oil combustion mode and a dual-fuel combustion mode are realized, and lean combustion of the engine is realized by adopting an exhaust backpressure adjusting system and micro-injection ignition of a pre-combustion chamber. A combined heat and power supply circulating system is adopted to meet the electric energy and heat energy requirements of the system, and meanwhile engine combustion pollutant emission is reduced. And the economical efficiency, the dynamic property and the environmental protection property of the system under the full-working-condition operation condition are improved.

Description

Technical Field

[0001] This invention relates to the field of combustion system technology, and in particular to a lean combustion system for a diesel-methanol dual-fuel engine that combines a thermoelectric combined cycle system and a method for comprehensive energy utilization. Background Technology

[0002] To reduce NOx, SOx, and particulate matter emissions, finding suitable clean and low-carbon fuels and reducing pollutant emissions has become one of the industry's development directions for diesel-fueled marine engines. Methanol fuel has the characteristics of high oxygen content, good atomization effect, and no sulfur oxide emissions during combustion. It also has multiple synthesis routes, low cost, and easy storage, making it very suitable as a clean energy alternative fuel for engines. However, methanol fuel has problems such as high latent heat of vaporization, low cetane number, and unconventional emissions, which limit the widespread application of methanol fuel engines. Summary of the Invention

[0003] To address the shortcomings of existing production technologies, this applicant provides a lean combustion system for a diesel-methanol dual-fuel engine that combines a combined heat and power cycle and an energy utilization method. This system allows for two operating modes: pure diesel combustion and dual-fuel combustion, tailored to the engine's operating conditions. By adjusting exhaust back pressure and employing micro-injection ignition technology in the pre-combustion chamber, the high latent heat of methanol vaporization is avoided, achieving lean combustion. A single common rail dual injector system and a methanol injection system improve fuel injection precision control. The combined heat and power cycle comprehensively meets the system's electrical and thermal energy needs while avoiding pollutant emissions caused by incomplete methanol combustion, achieving efficient and clean combustion and leveraging the low pollution and economic advantages of methanol fuel.

[0004] The technical solution adopted in this invention is as follows:

[0005] A lean combustion system for a diesel-methanol dual-fuel engine combined with a heat and power cycle system includes a combustion module. The main combustion chamber is located in the middle of the combustion module. Three channels are arranged above the main combustion chamber. The middle channel forms a pre-combustion chamber. Methanol injectors and diesel injectors are installed in the channels on both sides of the pre-combustion chamber, respectively. An air intake duct and an exhaust duct are respectively arranged at both ends above the main combustion chamber. The exhaust duct is connected to a boiler. A boiler oil supply pipeline is arranged at the bottom of the boiler. A boiler combustion chamber is arranged inside the boiler. A boiler exhaust gas discharge channel is arranged at the top of the boiler. A superheater is arranged inside the boiler combustion chamber. The superheater is connected to a steam turbine unit via a superheated steam pipe. The steam turbine unit is connected to the system's electrical equipment via a generator. The steam turbine unit is also connected to a parallel condenser heat exchanger a and a condenser heat exchanger b. Condenser heat exchanger a returns to the superheater via condensate pump a, and condenser heat exchanger b returns to the superheater via condensate pump b. At the same time, condenser heat exchanger a and condenser heat exchanger b are connected to the system's heat-using equipment via pipelines.

[0006] Its further technical solution lies in:

[0007] The methanol injector is connected to the high-pressure methanol fuel rail via a pipeline.

[0008] A methanol return tank is installed on the pipeline.

[0009] Injector a and injector b are respectively installed on the top of the pre-combustion chamber and the top of the diesel injector. Both injector a and injector b are connected to the high-pressure diesel fuel rail.

[0010] The diesel high-pressure fuel rail is also connected to the diesel return tank via a branch pipeline, which is connected to injector a and injector b.

[0011] A back pressure regulating valve and a tail gas control valve are installed on the connecting pipe between the exhaust duct and the boiler.

[0012] An exhaust gas discharge channel is provided at the exhaust gas control valve.

[0013] The pre-combustion chamber has a circular structure.

[0014] Both the methanol injector and the diesel injector are installed at an angle, and the methanol injector and the diesel injector are arranged symmetrically.

[0015] A method for comprehensive energy utilization of a lean-burn system in a diesel-methanol dual-fuel engine combining a cogeneration cycle system, employing two operating modes:

[0016] First, in pure diesel combustion mode:

[0017] The high-temperature exhaust gas remaining in the pre-combustion chamber mixes with the gas vortex in the main combustion chamber to form a flammable mixture. Injector a injects a small amount of diesel fuel before the top dead center of the compression stroke, igniting the flammable mixture in the pre-combustion chamber. The turbulent flame ignites the mixture in the main combustion chamber, indirectly controlling the engine combustion timing. Injector b starts injecting before the top dead center of the compression stroke and earlier than the injection time of injector a. The turbulent flame ignites the mixture in the main combustion chamber, achieving lean combustion in the engine and meeting the power requirements of the engine under different loads in pure diesel mode.

[0018] Secondly, in dual-fuel combustion mode:

[0019] The dual-fuel combustion mode operates only during the high-load phase of the engine. Injector a, injector b, and the methanol injector work together. The injection start point of methanol fuel gradually advances as the engine load increases, and the injection end point is before the top dead center of the compression stroke. During the compression process, the lean air-fuel mixture in the cylinder forms a flammable mixture with the residual high-temperature exhaust gas inside the pre-combustion chamber. Injector a injects a small amount of diesel fuel before the top dead center of the compression stroke to ignite the flammable mixture, indirectly achieving precise control of combustion timing. The jet ignition in the pre-combustion chamber can shorten the ignition delay period and the combustion duration, effectively improving thermal efficiency and reducing NOx emissions.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention features a compact and rational structure, and is easy to operate. It achieves precise control of engine fuel injection through a dual-injector system and a methanol injection system, enabling two operating modes: pure diesel combustion and dual-fuel combustion. Simultaneously, it employs an exhaust back pressure regulation system and pre-combustion chamber micro-injection ignition to achieve lean combustion in the engine. A combined heat and power cycle system simultaneously meets the system's electrical and thermal energy needs while reducing engine combustion pollutant emissions. This improves the system's economy, power, and environmental friendliness under all operating conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention.

[0023] Figure 2 This is a partial structural schematic diagram (I) of the present invention.

[0024] Figure 3 This is a partial structural schematic diagram (II) of the present invention.

[0025] Figure 4 This is a partial structural schematic diagram (III) of the present invention.

[0026] Figure 5 This invention relates to the working state of the fuel injector and the opening degree of the back pressure regulating valve in the pure diesel combustion mode.

[0027] Figure 6This invention relates to the working state of the fuel injector and the opening degree of the back pressure regulating valve under the dual-fuel combustion mode.

[0028] The components are as follows: 1. Diesel high-pressure fuel rail; 2. Diesel return tank; 3. Injector a; 4. Pre-combustion chamber; 5. Injector b; 6. Exhaust duct; 7. Tail gas discharge passage; 8. Superheater; 9. Boiler exhaust gas discharge passage; 10. Superheated steam pipe; 11. Steam turbine unit with steam removal; 12. Generator; 13. System electrical equipment; 14. Methanol return tank; 15. Methanol high-pressure fuel rail; 16. Intake duct; 17. Methanol injector; 18. Back pressure regulating valve; 19. Tail gas control valve; 20. Boiler oil supply pipeline; 21. Boiler combustion chamber; 22. Condensate pump a; 23. Condensate pump b; 24. Condensate heat exchanger a; 25. Condensate heat exchanger b; 26. System heat equipment; 27. Main combustion chamber; 28. Diesel injector. Detailed Implementation

[0029] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0030] like Figures 1-6 As shown, the lean combustion system of the diesel-methanol dual-fuel engine combined with a cogeneration cycle system in this embodiment includes a combustion module. The main combustion chamber 27 is located in the middle of the combustion module. Three channels are arranged above the main combustion chamber 27. The middle channel forms a pre-combustion chamber 4. Methanol injectors 17 and diesel injectors 28 are respectively installed in the channels on both sides of the pre-combustion chamber 4. An intake duct 16 and an exhaust duct 6 are respectively arranged at both ends above the main combustion chamber 27. The exhaust duct 6 is connected to the boiler. A boiler oil supply pipeline 20 is arranged at the bottom of the boiler. A boiler combustion chamber 21 is arranged inside the boiler. A boiler waste gas duct is arranged at the top of the boiler. The boiler combustion chamber 21 is equipped with a superheater 8 through the exhaust channel 9. The superheater 8 is connected to a steam turbine unit 11 via a superheated steam pipe 10. The steam turbine unit 11 is connected to the system electrical equipment 13 via a generator 12. The steam turbine unit 11 is also connected to a condensing heat exchanger a24 and a condensing heat exchanger b25 in parallel. The condensing heat exchanger a24 returns to the superheater 8 via a condensate pump a22, and the condensing heat exchanger b25 returns to the superheater 8 via a condensate pump b23. At the same time, the condensing heat exchanger a24 and the condensing heat exchanger b25 are connected to the system heat equipment 26 via pipelines.

[0031] The methanol injector 17 is connected to the methanol high-pressure oil rail 15 via a pipeline.

[0032] A methanol return tank 14 is installed on the pipeline.

[0033] Injector a3 and injector b5 are respectively installed on the top of the pre-combustion chamber 4 and the top of the diesel injector 28. Injector a3 and injector b5 are both connected to the diesel high-pressure rail 1.

[0034] The diesel high-pressure fuel rail 1 is also connected to the diesel return tank 2 via a branch line, which is connected to injector a3 and injector b5.

[0035] A back pressure regulating valve 18 and a tail gas control valve 19 are installed on the connecting pipe between the exhaust duct 6 and the boiler.

[0036] An exhaust gas discharge channel 7 is provided at the exhaust gas control valve 19.

[0037] The pre-combustion chamber 4 has a circular structure.

[0038] Both methanol injector 17 and diesel injector 28 are installed at an angle, and are arranged symmetrically.

[0039] The specific structure and function of the lean combustion system of a diesel-methanol dual-fuel engine combining a thermoelectric combined cycle system described in this invention are as follows:

[0040] It mainly includes injector a3, injector b5, methanol injector 17, pre-combustion chamber 4, back pressure regulating valve 18, and exhaust gas control valve 19.

[0041] The combined heat and power cycle system includes a boiler, a steam turbine unit 11 with steam withdrawal, a generator 12, a condensing heat exchanger a24, a condensing heat exchanger b25, a condensing water pump a22, and a condensing water pump b23. The steam turbine unit 11 with steam withdrawal introduces some high-quality steam into the condensing heat exchanger a24, thus meeting the system's thermal and electrical energy requirements.

[0042] The combustion method is as follows: The diesel / methanol dual-fuel engine can operate in two modes: pure diesel combustion mode and dual-fuel combustion mode. At the same time, it adopts a pre-combustion chamber 4-turbojet ignition method and an exhaust back pressure regulation system to reduce the impact of the large latent heat of methanol fuel vaporization on the system combustion, so as to achieve lean combustion of the engine. The fuel injection of the control system is optimized through a dual injector system and a methanol injection system to ensure stable combustion of the system. The cogeneration cycle system is used to meet the system's electrical and thermal energy requirements at the same time, while avoiding pollutant emissions caused by incomplete combustion of methanol, so as to give full play to the advantages of the diesel / methanol dual-fuel engine.

[0043] The combined heat and power (CHP) cycle system includes a boiler, a steam turbine unit 11 with steam removal, condensing heat exchangers a24 and b25, condensate pumps a22 and b23, and a generator 12. The CHP cycle system simultaneously provides electrical and thermal energy. Exhaust gas from the engine mixes thoroughly with fresh air and is then fully combusted in the boiler combustion chamber 21. This prevents the release of toxic gases from incomplete combustion of methanol fuel into the atmosphere. The system's circulating water is heated to superheated steam by the boiler, which is then used to generate electricity through the steam turbine unit 11 to meet the system's electricity needs. Simultaneously, based on thermal energy requirements, a portion of the high-quality superheated steam is introduced into the condensing heat exchanger a24 through the superheated steam pipe 10, providing sufficient heat to the heat-using equipment and achieving efficient energy utilization of the system.

[0044] The cylinder exhaust back pressure regulation system is mainly controlled by the back pressure regulating valve 18. By adjusting the back pressure regulating valve 18, the amount of high-temperature exhaust gas retained in the cylinder is changed, affecting the active molecules of combustion in the cylinder, realizing lean combustion of the system, reducing the impact of the high latent heat of methanol vaporization on the initial combustion temperature of the system in dual-fuel combustion mode, and enhancing the atomization effect of methanol fuel. The opening angle of the back pressure regulating valve 18 is [A*XR]℃A. As mentioned above, A is the maximum opening degree of the back pressure regulating valve 18, which is 0 degrees when it is fully open, X is the ratio of actual output power to rated power, and R is the adjustment coefficient of the back pressure regulating valve 18. The values ​​of A and R in the formula are adjusted according to the engine characteristics. At the same time, combined with the engine operating conditions and boiler status, the exhaust gas emission path is adjusted by the exhaust gas control valve 19. When the engine is working in non-high load pure diesel mode and dual-fuel combustion mode, the engine combustion exhaust gas is fully mixed with fresh air and enters the boiler, where it is fully burned in the boiler combustion chamber 21 to prevent the emission of toxic exhaust gas. The superheated working fluid generated by combustion provides thermoelectric services to the system through the steam turbine.

[0045] By comprehensively adjusting the working states of injector a3, injector b5, and methanol injector 17, the proportion, concentration, and mode of fuel during combustion are achieved. Injector a3 ignites the pre-combustion chamber 4, forming a turbulent flame that can indirectly control the combustion timing of the main combustion chamber 27. At the same time, the exhaust back pressure regulation system reduces the influence of the latent heat of fuel vaporization. Combined with the high-temperature flame injected from the pre-combustion chamber 4, this facilitates lean combustion of fuel in the main combustion chamber 27, thus achieving stable control of lean combustion in the diesel / methanol dual-fuel engine.

[0046] The diesel / methanol dual-fuel engine of this invention can achieve two operating modes: pure diesel combustion mode and dual-fuel combustion mode. The specific implementation scheme is as follows:

[0047] (I) In pure diesel combustion mode: The high-temperature exhaust gas remaining in the pre-combustion chamber 4 mixes with the gas vortex in the main combustion chamber 27 to form a flammable mixture. Injector a3 injects a small amount of diesel fuel before the compression top dead center, igniting the flammable mixture in the pre-combustion chamber 4. The turbulent flame ignites the mixture in the main combustion chamber 27, indirectly controlling the engine combustion timing. Injector b5 starts injecting before the compression top dead center and earlier than the injection time of injector a3. The turbulent flame ignites the mixture in the main combustion chamber 27, achieving lean combustion in the engine. The diesel injection quantity is adjusted by the diesel high-pressure fuel rail 1 to meet the engine's power requirements under different loads in pure diesel mode.

[0048] (II) In dual-fuel combustion mode: Dual-fuel combustion mode only operates during the high-load phase of the engine. Injector a3, injector b5, and methanol injector 17 work together. The injection start point of methanol fuel gradually advances as the engine load increases, and the injection end point is before the top dead center of compression. During compression, the lean air-fuel mixture in the cylinder forms a flammable mixture with the residual high-temperature exhaust gas inside the pre-combustion chamber 4. Injector a3 injects a small amount of diesel fuel before the top dead center of compression to ignite the flammable mixture, indirectly achieving precise control of combustion timing. Jet ignition in the pre-combustion chamber 4 can shorten the ignition delay period and combustion duration, effectively improving thermal efficiency and reducing NOx emissions.

[0049] Based on the operating conditions of the diesel-methanol dual-fuel engine, two working modes are adopted: pure diesel combustion mode and dual-fuel combustion mode. By adjusting the exhaust back pressure and using the 4-micro-injection ignition technology in the pre-combustion chamber, the high latent heat of vaporization of methanol fuel is avoided, achieving lean combustion in the engine. Through a single common rail dual injector system and a methanol injection system, the precision control of engine fuel injection is improved. A combined heat and power cycle system is adopted to comprehensively meet the system's electrical and thermal energy needs, while avoiding pollutant emissions caused by incomplete combustion of methanol, achieving efficient and clean combustion, and leveraging the advantages of methanol fuel such as low pollution and high economy.

[0050] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A diesel methanol dual fuel engine lean burn system combined with a thermoelectric cogeneration cycle system, characterized in that: The combustion module comprises a main combustion chamber (27) in the middle, three channels are arranged above the main combustion chamber (27), the middle channel forms a pre-chamber (4), a methanol injector (17) and a diesel injector (28) are arranged in the channels on both sides of the pre-chamber (4), and an air inlet (16) and an exhaust passage (6) are arranged at the two ends above the main combustion chamber (27), the exhaust passage (6) is connected with a boiler, the boiler is provided with a boiler oil supply pipeline (20) at the bottom, a boiler combustion chamber (21) is arranged in the boiler, the boiler is provided with a boiler exhaust gas discharge passage (9) at the top, the boiler combustion chamber (21) is provided with a superheater (8) inside, the superheater (8) is connected with a superheated steam pipe (10) connected with a extraction steam turbine unit (11), the extraction steam turbine unit (11) is connected with a system electric device (13) through a generator (12), and the extraction steam turbine unit (11) is also connected with a parallel-connected condensing heat exchanger a (24) and a condensing heat exchanger b (25), the condensing heat exchanger a (24) returns to the superheater (8) through a condensing water pump a (22), the condensing heat exchanger b (25) returns to the superheater (8) through a condensing water pump b (23), and meanwhile, the condensing heat exchanger a (24) and the condensing heat exchanger b (25) are connected with a system heat device (26) through pipelines.

2. A diesel methanol dual fuel engine lean burn system combined with a thermoelectric cogeneration system according to claim 1, characterized in that: The methanol injector (17) is connected with a methanol high-pressure oil rail (15) through a pipeline.

3. The diesel methanol dual fuel engine lean burn system combined with a thermoelectric cogeneration system according to claim 2, characterized in that: A methanol oil return tank (14) is arranged on the pipeline.

4. The diesel methanol dual fuel engine lean burn system combined with a thermoelectric cogeneration system according to claim 1, characterized in that: The top of the pre-chamber (4) and the top of the diesel injector (28) are respectively provided with an oil injector a (3) and an oil injector b (5), and the oil injector a (3) and the oil injector b (5) are connected with a diesel high-pressure oil rail (1).

5. A diesel methanol dual fuel engine lean burn system integrated with a thermoelectric cogeneration cycle system as claimed in claim 4, wherein: The diesel high-pressure oil rail (1) is also connected with a diesel oil return tank (2) through a branch pipeline, and the branch pipeline communicates with the oil injector a (3) and the oil injector b (5).

6. A diesel methanol dual fuel engine lean burn system integrated with a thermoelectric cogeneration cycle system as claimed in claim 1, wherein: A back pressure regulating valve (18) and a tail gas control valve (19) are arranged on the connecting pipe between the exhaust passage (6) and the boiler.

7. A diesel-methanol dual fuel engine lean burn system integrated with a thermoelectric cogeneration cycle system as claimed in claim 6, characterized in that: The tail gas control valve (19) is provided with a tail gas discharge passage (7).

8. The diesel methanol dual fuel engine lean burn system combined with a thermoelectric cogeneration system according to claim 1, characterized in that: The pre-chamber (4) has a circular structure.

9. The diesel methanol dual fuel engine lean burn system combined with a thermoelectric cogeneration system according to claim 1, characterized in that: The methanol injector (17) and the diesel injector (28) are both arranged in an inclined manner, and the methanol injector (17) and the diesel injector (28) are arranged symmetrically.

10. The energy comprehensive utilization method of combining the diesel methanol dual-fuel engine lean burn system of claim 1 with the heat and power combined cycle system, characterized in that: Two modes are adopted: one is a pure diesel combustion mode: The high-temperature exhaust gas remaining in the pre-chamber (4) is mixed with the gas vortex in the main combustion chamber (27) to form flammable mixed gas, a small amount of diesel is injected by the oil injector a (3) before the compression top dead center, the flammable mixed gas in the pre-chamber (4) is ignited, the turbulent flame ignites the mixed gas in the main combustion chamber (27), the engine combustion timing is indirectly controlled, the injection start point of the oil injector b (5) is before the compression top dead center and is earlier than the injection time of the oil injector a (3), the turbulent flame ignites the mixed gas in the main combustion chamber (27), the engine lean combustion is realized, and the power demand of the engine under different loads in the pure diesel mode is met; two is a dual-fuel combustion mode: Dual fuel combustion mode only works in high load stage of engine, injector a (3), injector b (5), methanol injector (17) work together, the injection start point of methanol fuel gradually advances with the increase of engine load, and the injection end point is before the compression top dead center; In-cylinder lean mixture forms flammable mixture with the residual high temperature exhaust gas in the pre-chamber (4) during compression process, and a small amount of diesel is injected by injector a (3) before the compression top dead center to ignite the flammable mixture, which indirectly realizes the precise control of combustion timing; The jet ignition of the pre-chamber (4) can shorten the ignition delay period and combustion duration, effectively improve the thermal efficiency and reduce the NOx emission.

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