CN114658572A - Method for cooling recirculated exhaust gas of LNG engine - Google Patents
Method for cooling recirculated exhaust gas of LNG engine Download PDFInfo
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- CN114658572A CN114658572A CN202210294421.4A CN202210294421A CN114658572A CN 114658572 A CN114658572 A CN 114658572A CN 202210294421 A CN202210294421 A CN 202210294421A CN 114658572 A CN114658572 A CN 114658572A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
- F02M26/23—Layout, e.g. schematics
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60H—ARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
- B60H1/00—Heating, cooling or ventilating [HVAC] devices
- B60H1/32—Cooling devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
- F02D41/0077—Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
- F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
- F02M21/0203—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels characterised by the type of gaseous fuel
- F02M21/0215—Mixtures of gaseous fuels; Natural gas; Biogas; Mine gas; Landfill gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
- F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
- F02M21/06—Apparatus for de-liquefying, e.g. by heating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
- F02M26/29—Constructional details of the coolers, e.g. pipes, plates, ribs, insulation or materials
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60H—ARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
- B60H1/00—Heating, cooling or ventilating [HVAC] devices
- B60H1/32—Cooling devices
- B60H2001/3286—Constructional features
- B60H2001/3289—Additional cooling source
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Combustion & Propulsion (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Exhaust-Gas Circulating Devices (AREA)
Abstract
The invention discloses a method for cooling recirculated waste gas of an LNG engine, which is based on a waste gas cooling device and comprises an LNG gas storage tank, a waste gas cooling heat exchanger, an EGR (exhaust gas recirculation) electric control valve, a cold energy recovery heat exchanger, a water cooling heat exchanger, an air heat exchanger, a three-way valve at the outlet of a storage tank and a three-way valve at the front of a waste cooler, realizes the cooling of the recirculated waste gas by recovering and utilizing LNG cold energy and improving the structure of an EGR system, solves the problems of high inlet temperature and low charging efficiency caused by the recirculation of the waste gas,can improve the dynamic property of the engine to achieve the national NOxEmission standard; the waste gas cooling heat exchanger adopts shell-and-tube heat exchange, and has compact structure; the cold and hot fluid performs countercurrent heat exchange, so that the heat exchange efficiency is high; the expansion joint is arranged on the shell, so that the problem of thermal expansion of the fluid with large temperature difference is effectively solved; the method can be flexibly adjusted according to seasons, and can be suitable for the requirements of cold energy recycling and recirculated waste gas cooling in different seasons by utilizing the three-way valve to switch the LNG flow.
Description
Technical Field
The present invention relates to the purification technology of harmful engine emissions, and more particularly to a method for effectively reducing NO of an enginexA device and method for using the cold energy of fuel LNG used by LNG buses for cooling recirculated exhaust gas during the discharge of the used exhaust gas recirculation technology.
Background
With the implementation of the national six-emission standard, the emission of harmful gases of automobiles faces more strict limits, wherein NOxThe emission limit is also greatly reduced relative to the national five standard. The Exhaust Gas Recirculation (EGR) technology is that the NO of the current automobile engine is reducedxAn acknowledged effective method for harmful emissions is to introduce part of the recirculated exhaust gas into the cylinder, which can effectively lower the highest combustion temperature and reduce NOxThe amount of production of (c). However, since the introduction of a certain amount of recirculated exhaust gas easily causes a decrease in the amount of fresh air, a decrease in the combustion speed, and an increase in the amounts of HC and CO produced; as analyzed by li xinghu's "car environmental pollution and control strategy" (chemical industry press, 2019.8), the EGR system of modern cars is often equipped with a cooling system in order to gradually cool the exhaust gas entering the EGR system from the exhaust pipe in the EGR line, increase the amount of fresh air in the cylinder, and facilitate complete combustion of the mixture. However, the cooling system generally adopts an air cooling method, and has the problems of relatively complex system structure and low heat exchange efficiency of a gas-gas heat exchange method. As a low-pollution environment-friendly automobile suitable for urban operation, a bus using LNG as a fuel has been widely used. Because the low-temperature liquid fuel LNG can be used by the engine only by heating and gasifying, if the cold energy released in the heating process is recovered, the low-temperature liquid fuel LNG can be used as a refrigerating air conditioner in a bus compartment in summer and also can be used as a refrigerant of an LNG refrigerated vehicle, and has a good energy-saving effect. At present, the LNG temperature rise and heat exchange method adopts a refrigerant to recover cold energy and then is used for a refrigeration air conditioner, for example, the 'LNG automobile fuel system and air conditioner cold energy utilization' of gold tref, and after the cold energy is recovered by the heat exchange of the refrigerant and LNG, the refrigerant is supplied to a carriage through an air heat exchanger and a refrigeration fan. Also, for example, patent application No. 201310462726.2 "a method for refrigerating an LNG refrigerator car and a refrigerator car thereof" also uses LNG in the refrigerator carThe method essentially recycles LNG fuel used by an LNG automobile engine to release cold energy for refrigerating in a carriage during heating and gasification, and does not consider other recycling ways of the cold energy.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a device for recycling LNG cold energy and cooling recirculated waste gas, aiming at utilizing the LNG cold energy to reduce NO in the prior artxThe EGR system structure arranged for emission is improved, the problems of high intake temperature, reduced fresh charge and reduced charging efficiency caused by the fact that exhaust gas enters the cylinder in a recirculating manner of the engine are solved, the dynamic property of the engine is improved, and the engine can reach the aim of NOxHigher emission limit standards.
In order to achieve the purpose, the technical scheme of the invention is as follows:
1. a method for cooling the recirculated exhaust gas of an LNG engine is based on a device for cooling the recirculated exhaust gas of the LNG engine, and comprises an LNG gas storage tank, an exhaust gas cooling heat exchanger, an EGR (exhaust gas recirculation) electric control valve, a cold energy recovery heat exchanger, a water cooling heat exchanger, an air heat exchanger, a three-way valve at the outlet of the storage tank, a three-way valve at the front of a waste cooler, an engine and a recirculated exhaust gas inlet pipe; the heat absorption side fluid inlet of the cold energy recovery heat exchanger is connected with the LNG gas storage tank through a three-way valve at the outlet of the storage tank, and the outlet of the cold energy recovery heat exchanger is connected with the heat absorption side fluid inlet of the waste gas cooling heat exchanger through a three-way valve at the front of the waste gas cooler; the heat absorption side of the waste gas cooling heat exchanger is LNG fluid, and the heat release side fluid is recirculated waste gas; the recirculated waste gas comes from an engine exhaust pipe and is connected with a waste gas cooling heat exchanger through an EGR (exhaust gas recirculation) electric control valve, and a heat release side fluid outlet is connected with the front section of an air inlet pipe through a recirculated waste gas introducing pipe; the fluid outlet at the heat absorption side of the waste gas cooling heat exchanger is also connected with the rear section (close to the inlet valve) of the air inlet pipe; the EGR outlet is connected with an EGR electric control valve, the EGR electric control valve is connected with the exhaust gas cooling heat exchanger, and the EGR electric control valve is controlled by an engine ECU.
Furthermore, a shell-and-tube heat exchanger structure is adopted in the waste gas cooling heat exchanger, round heat exchange tubes which are uniformly arranged at equal intervals are fixed on fixed tube plates positioned at two ends of a heat exchanger shell, LNG flow channels are arranged in the tubes of the round heat exchange tubes, a space formed between the outer wall of each heat exchange tube and the waste gas cooling heat exchanger shell is a recirculating waste gas flow channel, the heat exchanger shell is cylindrical, and an expansion joint is arranged in the middle of the heat exchanger shell. LNG fluid at the heat absorption side flows in from an inlet at the lower part of the left side of the waste gas cooling heat exchanger and flows out from an outlet at the upper part of the right side of the waste gas cooling heat exchanger; the recirculated waste gas of the heat release side enters from the inlet at the upper part of the right side of the waste gas cooling heat exchanger, passes through the waste gas flow channel and flows out from the outlet at the lower part of the left side of the waste gas cooling heat exchanger.
Furthermore, a water inlet of the water cooling heat exchanger is connected with an outlet of engine cooling water through a cooling water control valve and a cooling water inlet pipe, and a water outlet of the water cooling heat exchanger is connected with an inlet of the engine cooling water through a cooling water outlet pipe.
Furthermore, a heat release side fluid inlet of the cold energy recovery heat exchanger is connected with the circulating water pump, and an outlet of the cold energy recovery heat exchanger is connected with the air heat exchanger.
2. The invention relates to a method and a device for cooling recirculated exhaust gas of an LNG engine, which recycles a large amount of cold energy released in the processes of heating and gasifying LNG from a very low temperature storage state and cooling the recirculated exhaust gas, and the method comprises the following steps:
(1) in summer, when a refrigeration air conditioner needs to be provided in the bus carriage, LNG in the gas storage tank enters the cold energy recovery heat exchanger through the three-way valve at the outlet of the storage tank, and cold energy released by heat absorption, temperature rise and gasification is recovered by cold medium fluid at the heat release side; refrigerant fluid at the heat release side circularly flows through the air heat exchanger, low-temperature air is sent into the carriage by using the blower, cold energy is recovered in the process and released, and a low-temperature air-conditioning environment required by refrigeration in summer in the bus is maintained;
(2) LNG flows out of the cold energy recovery heat exchanger, enters the waste gas cooling heat exchanger through the three-way valve in front of the waste cooler, exchanges heat with the recirculated waste gas from the exhaust outlet pipe of the engine, the LNG is further heated, the recirculated waste gas is cooled, and the temperature is reduced to some extent so as toThe purposes of increasing the air charging efficiency of the engine, improving the dynamic property of the engine and reducing NO are achievedxThe purpose of the production amount;
(3) the EGR electric control valve is controlled by an engine ECU (electronic control Unit), the ECU can send out opening and closing or any opening instructions to the EGR electric control valve according to sensor signals such as the opening degree of a throttle valve, the rotating speed of an engine and the like, so that the accurate control of the amount of the recirculated exhaust gas is realized, and the reduction of NO can be obtained by combining the cooling of the recirculated exhaust gasxThe best effect of the amount of production.
(4) When in winter or in seasons needing no refrigeration energy in the bus compartment, the LNG flowing out of the gas storage tank is switched to flow, enters the water cooling heat exchanger through the three-way valve at the outlet of the gas storage tank, exchanges heat with cooling water from the engine, is heated and gasified, and flows out of the water cooling heat exchanger and enters the waste gas cooling heat exchanger through the three-way valve in front of the waste cooler, so that the recirculated waste gas from the exhaust pipe is cooled, the temperature of the recirculated waste gas is reduced, and the function of reducing the temperature of the recirculated waste gas is still achieved.
3. The beneficial effects are that:
compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:
(1) the waste gas cooling heat exchanger provided by the invention has the advantages that through the heat exchange between LNG and the recirculated waste gas from the exhaust pipe of the engine, the temperature of the cooled waste gas is reduced, the mixing temperature of the recirculated waste gas and fresh air can be reduced, the charging efficiency and the engine power are improved, and the highest combustion temperature and NO can be reducedxThe amount of production of (c). Tests show that when the temperature of the recirculated waste gas is reduced by 40 ℃, compared with the condition that the recirculated waste gas is not cooled, the power of the engine can be improved by 3 to 4 percent, and NO isxThe emission can be reduced by about 5 percent, the effect is better in summer with high environmental temperature, and the engine can be ensured to reach NOxThe national emission limit standard of (1);
(2) the waste gas cooling heat exchanger adopts a shell-and-tube heat exchanger and has the characteristics of compact structure and reliable operation; because the temperature difference between the cold fluid and the hot fluid is large, and the countercurrent heat exchange is adopted, the heat exchange efficiency and the cooling effect on the waste gas are far higher than those of a heat exchange mode adopting air cooling; the expansion joint is arranged on the shell of the heat exchanger shell, so that the problem of thermal expansion caused by large temperature difference between the LNG fluid and the waste gas is effectively solved;
(3) according to the invention, a large amount of cold energy released in the processes of heating and gasifying the LNG from the extremely low temperature storage state is recovered and comprehensively utilized, so that the energy requirement for refrigeration and air conditioning in the carriage of the bus is effectively met, the comprehensive utilization rate of energy is obviously improved, and the running cost of the LNG bus is reduced;
(4) the invention is suitable for energy utilization requirements in different seasons and is convenient to adjust. According to whether the bus has a cooling demand or not, the flow of the LNG can be switched through a three-way regulating valve configured by the system; when cold supply is needed in the bus compartment in summer, LNG flows through the cold energy recovery heat exchanger, and the recovered cold energy is supplied to the air conditioner for refrigeration; when the carriage does not need to be cooled, the LNG flows through the water cooling heat exchanger.
Drawings
Fig. 1 is a schematic structural diagram of a method and an apparatus for cooling recirculated exhaust gas of an LNG engine according to the present invention.
Fig. 2 is a schematic view of the internal structure of the exhaust gas cooling heat exchanger according to the present invention.
The reference numerals in the figures denote:
1 LNG gas holder 2 fan controller 3 hair-dryer 4 air heat exchanger 5 circulating water pump
6 cold energy recovery heat exchanger 7 water cooling heat exchanger 8 waste cooler front three-way valve 9 EGR export
10 EGR (exhaust gas recirculation) electronic control valve 11, exhaust gas cooling heat exchanger 12, fresh air 13, air inlet pipe 14 engine
15 exhaust pipe 16 cooling water control valve 17 cooling water inlet pipe 18 cooling water outlet pipe
19-expansion joint of exhaust gas flow passage 22 of recirculating exhaust gas inlet pipe 21 of three-way valve 20 at outlet of storage tank
23 round heat exchange tube 24 heat exchanger shell
Detailed Description
The technical scheme of the invention is further explained in detail with reference to the attached drawings. These drawings are simplified schematic views illustrating only the basic structure of the present invention in a schematic manner, and thus show only the constitution related to the present invention.
The invention relates to a method for cooling recirculated exhaust gas of an LNG engine, which recycles a large amount of cold energy released in the processes of heating and gasifying LNG from a very low temperature storage state and solves the problem that the recirculated exhaust gas needs to be cooled. The method is based on a device for cooling the recirculating exhaust gas of an LNG engine, and comprises an LNG gas storage tank 1, an exhaust gas cooling heat exchanger 11, an EGR (exhaust gas recirculation) electric control valve 10, a cold energy recovery heat exchanger 6, a water cooling heat exchanger 7, an air heat exchanger 4, a storage tank outlet three-way valve 19, a waste cooler front three-way valve 8, an engine 14 and a recirculating exhaust gas inlet pipe 20; the heat absorption side fluid inlet of the cold energy recovery heat exchanger 6 is connected with the LNG storage tank 1 through a storage tank outlet three-way valve 19, and the outlet of the cold energy recovery heat exchanger is connected with the heat absorption side fluid inlet of the waste gas cooling heat exchanger 11 through a waste cooler front three-way valve 8; the heat absorption side of the waste gas cooling heat exchanger is LNG fluid, and the heat release side fluid exchanging heat with the LNG fluid is recirculated waste gas; the recirculated exhaust gas comes from an engine exhaust pipe, an EGR outlet 9 is connected with an EGR electric control valve 10, the EGR electric control valve 10 is connected with an exhaust gas cooling heat exchanger 11, and a heat release side fluid outlet is connected with the front section of an air inlet pipe 13 through a recirculated exhaust gas introducing pipe 20; the EGR outlet 9 is connected with an EGR electric control valve 10 which is also connected with an exhaust gas cooling heat exchanger 11, and the EGR electric control valve is controlled by an engine ECU (electronic control Unit); the recirculated exhaust gas flows through the exhaust gas cooling heat exchanger 11 to exchange heat with the LNG fluid on the other side, in the process, the exhaust gas is cooled, and the cooled exhaust gas flows into the engine intake pipe through the recirculated exhaust gas introduction pipe 20 and then is mixed with the fresh air 12; the fluid outlet on the heat absorption side of the exhaust gas cooling heat exchanger is connected with the rear section (close to the inlet valve) of the air inlet pipe 13 and supplies LNG fuel required by the work of the engine.
The LNG flowing out of the LNG storage tank 1 has two flow paths, is regulated by a storage tank outlet three-way valve 19, and can respectively flow into the cold energy recovery heat exchanger 6 or the water cooling heat exchanger 7; if LNG flows into the cold energy recovery heat exchanger 6, the LNG enters the waste gas cooling heat exchanger 11 through the waste cooler front three-way valve 8 after cold energy recovery.
Further, the heat-releasing side fluid (in this embodiment, ethylene glycol is used as the refrigerant fluid for absorbing the LNG cold energy) of the cold energy recovery heat exchanger 6 has an inlet connected to the circulating water pump 5, and an outlet connected to the air heat exchanger 4; when cold load needs to be supplied in a bus compartment in summer, LNG flowing out of the LNG storage tank 1 enters the cold energy recovery heat exchanger 6 through the storage tank outlet three-way valve 19, and cold energy released in the processes of heat absorption, temperature rise and gasification is recovered by cold medium fluid at the heat release side; refrigerant fluid at the heat release side circularly flows through the air heat exchanger 4, low-temperature air is fed into the carriage by using the blower 3, and LNG cold energy recovered by the cold energy recovery heat exchanger 6 is released, so that a comfortable air-conditioning environment required in the bus carriage in summer is maintained; the blower controller 2 controls the operation and the wind speed of the blower 3 to maintain an appropriate air conditioning temperature in the vehicle compartment.
Further, a shell-and-tube heat exchanger structure is adopted in the waste gas cooling heat exchanger 11, the round heat exchange tubes 23 which are uniformly arranged at equal intervals are fixed on the fixed tube plates at two ends of the heat exchanger shell, LNG flow channels are arranged in the tubes of the round heat exchange tubes 23, a space formed between the outer wall of each heat exchange tube and the waste gas cooling heat exchanger shell is a waste gas flow channel 21, the heat exchanger shell 24 is cylindrical, and an expansion joint 22 is arranged in the middle of the heat exchanger shell. LNG fluid at the heat absorption side flows in from an inlet at the lower part of the left side of the waste gas cooling heat exchanger, absorbs heat while flowing in each circular heat exchange tube, and flows out from an outlet at the upper part of the right side after being collected at the right end of the waste gas cooling heat exchanger; the recirculated waste gas of heat release side gets into from the upper portion entry in right side of waste gas cooling heat exchanger, when flowing through the waste gas flow path, and with the LNG fluid heat transfer in the heat transfer pipe and cool off, flow out from the left side lower part export of waste gas cooling heat exchanger after the cooling. The heat exchange process of the two fluids in the waste gas cooling heat exchanger is countercurrent heat exchange, so that the heat exchange efficiency is improved.
Further, the water inlet of the water cooling heat exchanger is connected with the outlet of the engine cooling water through a cooling water control valve 16 and a cooling water inlet pipe 17, and the water outlet of the water cooling heat exchanger is connected with the inlet of the engine cooling water through a cooling water outlet pipe 18. When the cooling energy is not needed to be supplied in winter or in seasons when the bus compartment does not need to be supplied with cooling energy, the LNG flowing path flowing out of the LNG storage tank 1 is switched, enters the water cooling heat exchanger 7 through the storage tank outlet three-way valve 19, exchanges heat with cooling water from the engine, is continuously heated and gasified in the water cooling heat exchanger, then flows out of the water cooling heat exchanger 7, and enters the waste gas cooling heat exchanger 11 through the waste cooler front three-way valve 8, so that the recirculated waste gas from the exhaust pipe 15 is cooled and the temperature is reduced, and the effect of reducing the temperature of the recirculated waste gas is also kept.
Further, the heat release side fluid inlet of the cold energy recovery heat exchanger 6 is connected to the circulating water pump 5, and the outlet thereof is connected to the air heat exchanger 4.
The above embodiments are only a part of the embodiments of the present invention, and not all of them. Other embodiments, which can be derived by one of ordinary skill in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Claims (1)
1. A method for cooling the recirculating exhaust gas of an LNG engine is based on a device for cooling the recirculating exhaust gas of the LNG engine, and comprises an LNG air storage tank (1), an exhaust gas cooling heat exchanger (11), an EGR electric control valve (10), a cold energy recovery heat exchanger (6), a water cooling heat exchanger (7), an air heat exchanger (4), a storage tank outlet three-way valve (19), a waste cooler front three-way valve (8), an engine (14) and a recirculating exhaust gas inlet pipe (20); the LNG cold energy recovery heat exchanger is characterized in that a heat absorption side fluid inlet of the cold energy recovery heat exchanger (6) is connected with the LNG storage tank (1) through a storage tank outlet three-way valve (19), and an outlet of the LNG storage tank is connected with a heat absorption side fluid inlet of the waste gas cooling heat exchanger (11) through a waste cooler front three-way valve (8); the heat absorption side of the waste gas cooling heat exchanger is LNG fluid, and the heat release side fluid is recirculated waste gas; the recirculated exhaust gas comes from an engine exhaust pipe (15), and a heat release side fluid outlet is connected with the front section of the air inlet pipe through a recirculated exhaust gas introducing pipe (20); a fluid outlet at the heat absorption side of the waste gas cooling heat exchanger (11) is also connected with the rear section (close to an inlet valve) of the air inlet pipe; the EGR outlet (9) is connected with an EGR electric control valve (10), the EGR electric control valve (10) is connected with an exhaust gas cooling heat exchanger (11), and the EGR electric control valve (10) is controlled by an engine ECU (electronic control Unit); the waste gas cooling heat exchanger (11) is internally of a shell-and-tube heat exchanger structure, round heat exchange tubes (23) which are uniformly arranged at equal intervals are fixed on fixed tube plates positioned at two ends of a heat exchanger shell, LNG flow channels are arranged in the tubes of the round heat exchange tubes, a space formed between the outer wall of each heat exchange tube and the waste gas cooling heat exchanger shell is a waste gas flow channel (21), the heat exchanger shell is cylindrical, and the middle part of the heat exchanger shell is provided with an expansion joint (22); LNG fluid at the heat absorption side flows in from an inlet at the lower part of the left side of the waste gas cooling heat exchanger (11) and flows out from an outlet at the upper part of the right side of the waste gas cooling heat exchanger; the recirculated waste gas at the heat release side enters from an inlet at the upper part of the right side of the waste gas cooling heat exchanger, passes through a waste gas flowing channel and flows out from an outlet at the lower part of the left side of the waste gas cooling heat exchanger; a water inlet of the water cooling heat exchanger (7) is connected with an outlet of engine cooling water through a cooling water control valve (16) and a cooling water inlet pipe (17), and a water outlet of the water cooling heat exchanger is connected with an inlet of the engine cooling water through a cooling water outlet pipe (18); the method for cooling the engine recirculating exhaust gases comprises the following steps:
(1) in summer, when refrigeration air-conditioning needs to be provided in the bus carriage, LNG in the gas storage tank enters the cold energy recovery heat exchanger (6) through the three-way valve (19) at the outlet of the storage tank, and cold energy released by heat absorption, temperature rise and gasification is recovered by cold medium fluid at the heat release side; refrigerant fluid at the heat release side circularly flows through the air heat exchanger (4), low-temperature air is sent into the carriage by using the blower (3), cold energy is recovered in the process and released, and a low-temperature air-conditioning environment required by refrigeration in summer in the bus is maintained;
(2) LNG flows out of the cold energy recovery heat exchanger (6), enters the waste gas cooling heat exchanger (11) through the waste cooler front three-way valve (8) and exchanges heat with the recirculated waste gas from the engine exhaust pipe (15), the LNG is further heated, the recirculated waste gas is cooled, the temperature is reduced, the inflation efficiency of the engine is increased, the dynamic property of the engine is improved, and NO is reducedxThe purpose of the production amount;
(3) the EGR electric control valve (10) is controlled by the engine ECU, the ECU can send out opening, closing or any opening instructions to the EGR electric control valve according to sensor signals such as the opening of a throttle valve, the rotating speed of the engine and the like, the accurate control of the amount of the recirculated exhaust gas is realized, and the NO reduction can be achieved by combining the cooling of the recirculated exhaust gasxOptimal effect of production amount;
(4) when the cooling energy is not needed to be supplied in winter or in seasons when the bus compartment does not need to be supplied with cooling energy, the LNG flowing out of the gas storage tank is switched to flow into the water cooling heat exchanger (7) through the three-way valve (19) at the outlet of the gas storage tank, exchanges heat with cooling water from the engine, is heated and gasified, and flows out of the water cooling heat exchanger (7) and also enters the waste gas cooling heat exchanger (11) through the three-way valve (8) in front of the waste cooler, so that the recirculated waste gas from the exhaust pipe is cooled, the temperature is reduced, and the function of reducing the temperature of the recirculated waste gas is still achieved.
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| CN202210294421.4A CN114658572A (en) | 2022-03-19 | 2022-03-19 | Method for cooling recirculated exhaust gas of LNG engine |
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| CN202210294421.4A CN114658572A (en) | 2022-03-19 | 2022-03-19 | Method for cooling recirculated exhaust gas of LNG engine |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140202149A1 (en) * | 2011-08-22 | 2014-07-24 | International Engine Intellectual Property Company Llc | Waste Heat Recovery System for Controlling EGR Outlet Temperature |
| CN204436572U (en) * | 2015-01-22 | 2015-07-01 | 潍柴西港新能源动力有限公司 | A kind of natural gas engine low pressure EGR system |
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| US20140202149A1 (en) * | 2011-08-22 | 2014-07-24 | International Engine Intellectual Property Company Llc | Waste Heat Recovery System for Controlling EGR Outlet Temperature |
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| CN110985246A (en) * | 2019-12-11 | 2020-04-10 | 潍柴动力股份有限公司 | Natural gas engine and EGR (exhaust gas recirculation) secondary cooling device thereof |
| CN113212109A (en) * | 2021-05-18 | 2021-08-06 | 扬州工业职业技术学院 | LNG bus supercharged engine cold energy recovery method and device |
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