Gas inlet channel liquid ammonia injection and waste gas circulation heat recovery system and method

Abstract

The invention discloses a gas inlet channel liquid ammonia injection and waste gas circulation heat recovery system and method, and relates to the technical field of multi-fuel engine systems.The gas inlet channel liquid ammonia injection and waste gas circulation heat recovery system comprises a liquid ammonia storage tank, a liquid ammonia pressure stabilizing supply system, a liquid ammonia nozzle, a mixing heat exchanger, a waste gas recirculation system and a controller; the controller is used for calculating the liquid ammonia injection amount required in real time according to the real-time working condition information of the engine, controlling the liquid ammonia nozzle to work in real time, and calculating the real-time required heat for gasifying the liquid ammonia and heating the liquid ammonia to the set temperature according to the liquid ammonia injection amount required in real time; the real-time needed waste gas amount is calculated according to the real-time needed heat of liquid ammonia gasification and temperature rising to the set temperature, and the controller controls the waste gas recirculation system in real time according to the real-time needed waste gas amount to enable the needed waste gas to flow back to the mixing heat exchanger. The system stability of the engine can be improved, the efficiency of the engine is improved, and pollutant emission is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-fuel engine systems, and particularly to an intake port liquid ammonia injection and exhaust gas recirculation heat recovery system and method. Background Art

[0002] When ammonia is used as an engine fuel, there are problems such as difficult ignition, high ignition energy, long combustion duration, slow flame propagation speed, and high emissions of unburned ammonia and nitrogen oxides. Among the many technical routes of multi-fuel engines, injecting gaseous ammonia into the intake port is currently the simplest technical route, but its fuel supply system is complex and requires a large-volume gasification tank and a constant pressure and constant temperature control system. And in some working conditions, the liquefaction of ammonia is inevitable, which easily causes faults and failures of the injection system. Summary of the Invention

[0003] The purpose of the present invention is to provide an intake port liquid ammonia injection and exhaust gas recirculation heat recovery system and method to solve the above problems existing in the prior art, improve the stability of the engine system, improve the engine efficiency, and reduce pollutant emissions.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides an intake port liquid ammonia injection and exhaust gas recirculation heat recovery system, including: a liquid ammonia storage tank, a liquid ammonia constant pressure supply system, a liquid ammonia nozzle, a mixing heat exchanger, an exhaust gas recirculation system, and a controller. The liquid ammonia storage tank is used to store liquid ammonia; the liquid ammonia constant pressure supply system is connected to the liquid ammonia storage tank and regulates the pressure of the liquid ammonia discharged from the liquid ammonia storage tank to the set pressure; the liquid ammonia nozzle is connected to the liquid ammonia constant pressure supply system and injects the liquid ammonia at the set pressure into the mixing heat exchanger; the mixing heat exchanger provides a space for mixing liquid ammonia, exhaust gas, and air; the exhaust gas recirculation system is used to return the exhaust gas generated by the engine to the mixing heat exchanger; the controller calculates the real-time required liquid ammonia injection amount according to the real-time working condition information of the engine and controls the operation of the liquid ammonia nozzle in real time. The controller calculates the real-time required heat for liquid ammonia gasification and heating to the set temperature according to the real-time required liquid ammonia injection amount, calculates the real-time required exhaust gas amount according to the real-time required heat for liquid ammonia gasification and heating to the set temperature, and the controller controls the exhaust gas recirculation system to return the required amount of exhaust gas to the mixing heat exchanger in real time according to the real-time required exhaust gas amount.

[0006] Preferably, the liquid ammonia constant pressure supply system includes a liquid ammonia transfer oil pump, a liquid ammonia constant pressure tank, a liquid ammonia low-pressure pump, and a liquid ammonia medium-pressure pump connected in sequence through pipelines, and the liquid ammonia medium-pressure pump is connected to the liquid ammonia nozzle.

[0007] Preferably, the liquid ammonia pressure stabilizing supply system further includes a reflux heat exchanger. The oil return port of the liquid ammonia medium-pressure pump is communicated with the inlet of the heat medium channel of the reflux heat exchanger. The outlet of the heat medium channel of the reflux heat exchanger is communicated with the liquid ammonia pressure stabilizing tank. The liquid ammonia pressure stabilizing tank is communicated with the liquid ammonia storage tank through a pipeline provided with a pressure stabilizing regulating valve.

[0008] Preferably, the exhaust gas recirculation system includes a main reflux pipeline, a first branch reflux pipeline, and a second branch reflux pipeline. One end of the main reflux pipeline is communicated with the exhaust gas outlet of the engine, and the other end is communicated with one end of the first branch reflux pipeline and one end of the second branch reflux pipeline. The other end of the first branch reflux pipeline is communicated with the mixing heat exchanger, and the other end of the second branch reflux pipeline is communicated with the downstream intake air duct of the mixing heat exchanger. An exhaust gas main valve is provided on the main reflux pipeline, an exhaust gas mixing regulating valve is provided on the first branch reflux pipeline, and an exhaust gas direct-through regulating valve is provided on the second branch reflux pipeline. The controller adjusts and determines the total exhaust gas recirculation flow according to the engine working condition and the real-time combustion strategy, and then adjusts the opening degree of the exhaust gas main valve according to the total exhaust gas recirculation flow. The controller controls the opening degrees of the exhaust gas mixing regulating valve and the exhaust gas direct-through regulating valve in real time according to the real-time required exhaust gas volume to return the required amount of exhaust gas to the mixing heat exchanger.

[0009] Preferably, an electric auxiliary heating device is provided on the downstream intake air duct of the mixing heat exchanger. Under cold engine and low load working conditions, the controller controls the electric auxiliary heating device to heat the mixed gas in the downstream intake air duct of the mixing heat exchanger to ensure that the gasification of liquid ammonia and the temperature of the intake air duct meet the requirements of the preset engine working conditions.

[0010] Preferably, a liquid ammonia flowmeter is provided on the pipeline between the liquid ammonia storage tank and the liquid ammonia oil transfer pump; a liquid ammonia pressure and temperature measuring instrument is provided on the pipeline between the liquid ammonia low-pressure pump and the liquid ammonia medium-pressure pump.

[0011] The present invention also provides a method for liquid ammonia injection into the intake air duct and heat recovery of exhaust gas recirculation, including:

[0012] Calculating the real-time required liquid ammonia injection volume according to the real-time engine working condition information and controlling the liquid ammonia nozzle to work in real time;

[0013] Calculating the real-time required heat for liquid ammonia gasification and heating to the set temperature according to the real-time required liquid ammonia injection volume;

[0014] Calculating the real-time required exhaust gas volume according to the real-time required heat for liquid ammonia gasification and heating;

[0015] Controlling the exhaust gas recirculation system to return the required amount of exhaust gas to the mixing heat exchanger in real time according to the real-time required exhaust gas volume.

[0016] Preferably, the total exhaust gas recirculation flow rate is adjusted and determined according to the real-time working conditions of the engine and the real-time combustion strategy.

[0017] Preferably, the heat required for the gasification and temperature rise of liquid ammonia in real time is calculated by the following formula:

[0018]

[0019] In the formula, Q total is the total heat exchange; Q liquid is the heat exchange for the temperature rise of liquid ammonia spray; Q vap is the gasification heat; Q gas is the heat exchange for the temperature rise of ammonia gas; W a is the mass flow rate of liquid ammonia; c p,l is the specific heat capacity of liquid ammonia; T b is the boiling point of liquid ammonia under the set pressure; T l,1 is the initial temperature of liquid ammonia spray; r a is the latent heat of vaporization of ammonia under the set pressure; c p,g is the specific heat capacity of ammonia gas; T g,2 is the final temperature of ammonia gas.

[0020] Preferably, under cold engine and low load conditions, the electric auxiliary heating device is controlled to heat the mixture gas in the downstream intake passage of the mixing heat exchanger to ensure that the gasification of liquid ammonia and the temperature of the intake passage meet the requirements of the preset working conditions of the engine;

[0021] Obtain the actual flow rate of the liquid ammonia nozzle, and control the opening degree of the liquid ammonia nozzle according to the actual flow rate and the required liquid ammonia injection amount so that the actual flow rate is the same as the required liquid ammonia injection amount.

[0022] The present invention has achieved the following technical effects compared with the prior art:

[0023] The present invention proposes to inject medium-pressure liquid ammonia into the mixing heat exchanger, and through the exhaust gas recirculation system, it can ensure the gasification heat demand of ammonia gas while realizing the injection of liquid ammonia. After being fully mixed with air, it enters the cylinder for combustion work. The exhaust gas recirculation system uses the tail gas heat to heat the direct-injected liquid ammonia, promoting the full mixing of ammonia, air and part of the tail gas, which helps to enhance the reaction activity atmosphere in the engine cylinder, improve the ignition performance of ammonia, and thus improve the engine efficiency and reduce pollutant emissions.

[0024] The present invention realizes the applicability of liquid ammonia injection under cold start and various working conditions through the cooperation of exhaust gas reflux and an electric auxiliary heating device.

[0025] The present invention adjusts the injection pulse width of the liquid ammonia nozzle according to the engine working conditions to realize the quantitative injection supply of liquid ammonia, and performs real-time feedback through calculating or measuring the actual flow rate of liquid ammonia to achieve closed-loop control, which has high responsiveness and variable working condition applicability. Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 FIG. is a schematic structural diagram of an intake air duct liquid ammonia injection and exhaust gas recirculation heat recovery system and an engine provided by an embodiment of the present invention;

[0028] In the figure: 1 - liquid ammonia storage tank; 2 - liquid tank heater; 3 - pressure stabilizing pipe regulating valve; 4 - evacuation safety valve; 5 - liquid ammonia reflux pump; 6 - reflux heat exchanger; 7 - reflux safety valve; 8 - liquid ammonia flowmeter; 9 - liquid ammonia oil transfer pump; 10 - liquid ammonia pressure stabilizing tank; 11 - liquid ammonia low-pressure pump; 12 - liquid ammonia pressure and temperature measuring gauge; 13 - liquid ammonia medium-pressure pump; 14 - liquid ammonia nozzle; 15 - mixing heat exchanger; 16 - electric auxiliary heating device; 17 - engine; 18 - exhaust gas main valve; 19 - exhaust gas heat exchanger; 20 - exhaust gas direct-through regulating valve; 21 - exhaust gas mixing regulating valve. Detailed Embodiments

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0031] The fuel supply system of the existing gaseous injection of liquid ammonia technology route in the intake duct is complex, and it is prone to space shortage problems in practical applications. The gasification of liquid ammonia in fuel supply needs to be completed before the injection system, and due to nozzle limitations, gas-liquid two-phase is usually not acceptable, so the temperature and pressure control requirements for the gasification device are relatively high. Since the ammonia injection system usually also requires an ammonia injection pressure of 5-8 bar, the temperature control system in this technology route needs to be always on to ensure that ammonia remains gaseous under special engine conditions (such as startup), which has great limitations in the actual equipment application process. On the other hand, since the ammonia demand of the engine varies under different working conditions, the temperature control responsiveness of the supply system is required to be high. When the flow rate is large, the ammonia temperature is likely to decrease, and when the flow rate is small, the ammonia pressure is likely to be too high. Both situations may cause ammonia liquefaction or the injection system unable to accurately control the injection volume, resulting in system failure.

[0032] The following combines Figure 1 , to describe the embodiments of the present invention.

[0033] The present invention provides an intake duct liquid ammonia injection and exhaust gas recirculation heat recovery system, which is applicable to multi-fuel engines, such as ammonia-diesel dual-fuel engines. It includes: a liquid ammonia storage tank 1, a liquid ammonia constant-pressure supply system, a liquid ammonia nozzle 14, a mixing heat exchanger 15, an exhaust gas recirculation system, and a controller. The liquid ammonia storage tank 1 is used to store liquid ammonia; the liquid ammonia constant-pressure supply system is connected to the liquid ammonia storage tank 1 and regulates the pressure of the liquid ammonia discharged from the liquid ammonia storage tank 1 to the set pressure; the liquid ammonia nozzle 14 is connected to the liquid ammonia constant-pressure supply system and injects the liquid ammonia at the set pressure into the mixing heat exchanger 15; the mixing heat exchanger 15 provides a space for mixing liquid ammonia, exhaust gas, and air; the exhaust gas recirculation system is used to return the exhaust gas generated by the engine 17 to the mixing heat exchanger 15; the controller calculates the real-time required liquid ammonia injection volume according to the real-time working condition information of the engine 17 and controls the operation of the liquid ammonia nozzle 14 in real time. The controller calculates the real-time required heat for liquid ammonia gasification and heating to the set temperature according to the real-time required liquid ammonia injection volume, calculates the real-time required exhaust gas volume according to the real-time required heat for liquid ammonia gasification and heating to the set temperature, and the controller controls the exhaust gas recirculation system to return the required amount of exhaust gas to the mixing heat exchanger 15 in real time according to the real-time required exhaust gas volume.

[0034] The present invention proposes to inject medium-pressure liquid ammonia into the mixing heat exchanger 15, and through the exhaust gas recirculation system, it can realize the liquid ammonia injection while ensuring the gasification heat demand of ammonia, and after being fully mixed with air, it enters the cylinder for combustion and work. The exhaust gas recirculation system uses the heat of the exhaust gas to heat the direct-injected liquid ammonia, promotes the full mixing of ammonia, air and part of the exhaust gas, helps to improve the reactive atmosphere in the cylinder of the engine 17, improves the ammonia ignition performance, and then improves the efficiency of the engine 17 and reduces pollutant emissions. In addition, the solution provided by the present invention avoids large-scale gasification devices and avoids the problem of insufficient space in practical applications.

[0035] In some embodiments, the liquid ammonia pressure-stabilizing supply system includes a liquid ammonia oil pump 9, a liquid ammonia pressure-stabilizing tank 10, a liquid ammonia low-pressure pump 11, and a liquid ammonia medium-pressure pump 13, which are sequentially connected through pipelines, and the liquid ammonia medium-pressure pump 13 is connected to the liquid ammonia nozzle 14. The pressure range of the liquid ammonia output by the liquid ammonia low-pressure pump 11 is usually 10 to 15 bar, and the pressure range of the liquid ammonia output by the liquid ammonia medium-pressure pump 13 is usually greater than 15 bar.

[0036] In this embodiment, the liquid ammonia pressure regulating tank 10 uses gravity to ensure that the gaseous ammonia can always be at the top of the liquid ammonia pressure regulating tank 10, and the subsequent liquid outlet is at the bottom of the liquid ammonia pressure regulating tank 10 to ensure the liquid phase supply of ammonia. At the same time, the liquid ammonia pressure regulating tank 10 has a buffer safety function. When the pressure in the tank is higher than the preset value of the emptying safety valve under unexpected working conditions, the pressure regulating tank pressure can be reduced by exhausting the top, and the engine 17 is shut down to check the fault. The supply pressure of liquid ammonia can be controlled to above 10 bar by the liquid ammonia pressure regulating tank 10 to ensure that ammonia exists in liquid form at most ambient temperatures, and at the same time, the initial pressure is provided for the subsequent fuel supply. The two-stage pumping can reduce the pumping pressure difference between the low-pressure pump and the medium-pressure pump. It can be understood that multi-stage pumping is used to increase the injection pressure of liquid ammonia. This method is used to take into account the corrosiveness and gasification of liquid ammonia. If one-stage pumping is used, gasification may occur under variable working conditions (i.e., when the liquid ammonia flow rate changes greatly), causing the pump to fail. Multi-stage pumping helps to reduce the pumping pressure difference of each stage and improve the stability of the whole system.

[0037] In this embodiment, the liquid ammonia pressure-stabilizing supply system first ensures the stable operation of the liquid ammonia nozzle 14 through a multi-stage booster pump, and at the same time, the liquid ammonia pressure-stabilizing tank 10 is set in the middle to ensure the ammonia supply pressure while removing the gas, so as to ensure the single-phase supply of liquid in the liquid ammonia pressure-stabilizing supply system. Then, the liquid ammonia is injected into the intake duct through the pulse width calibration and pressure control of the liquid ammonia nozzle 14. The liquid ammonia is directly injected into the mixing heat exchanger 15, and while mixing with the intake air, it is heated by the heat from the exhaust gas recirculation, ensuring gasification while achieving homogeneous mixing of the intake air through the mixing of the three fluids, and then enters the engine 17 system for combustion and work. Figure 1 In the figure, the right side of the mixing heat exchanger 15 is the air inlet.

[0038] In some embodiments, the liquid ammonia pressure stabilizing supply system further includes a reflux heat exchanger 6. The oil return port of the liquid ammonia medium-pressure pump 13 is communicated with the inlet of the heat medium channel of the reflux heat exchanger 6. The outlet of the heat medium channel of the reflux heat exchanger 6 is communicated with the liquid ammonia pressure stabilizing tank 10. The liquid ammonia pressure stabilizing tank 10 is communicated with the liquid ammonia storage tank 1 through a pipeline provided with a pressure stabilizing regulating valve.

[0039] This embodiment recovers the heat of the refluxed liquid ammonia, avoiding heat loss.

[0040] In some embodiments, the exhaust gas recirculation system includes a main reflux pipeline, a first branch reflux pipeline, and a second branch reflux pipeline. One end of the main reflux pipeline is communicated with the exhaust gas outlet of the engine 17, and the other end is communicated with one end of the first branch reflux pipeline and one end of the second branch reflux pipeline. The other end of the first branch reflux pipeline is communicated with the mixing heat exchanger 15, and the other end of the second branch reflux pipeline is communicated with the intake air duct downstream of the mixing heat exchanger 15. An exhaust gas main valve 18 is provided on the main reflux pipeline, an exhaust gas mixing regulating valve 21 is provided on the first branch reflux pipeline, and an exhaust gas direct-through regulating valve 20 is provided on the second branch reflux pipeline. The controller adjusts and determines the total exhaust gas recirculation flow according to the engine 17 operating conditions and the real-time combustion strategy, and then adjusts the opening degree of the exhaust gas main valve 18 according to the total exhaust gas recirculation flow. The controller controls the opening degrees of the exhaust gas mixing regulating valve 21 and the exhaust gas direct-through regulating valve 20 in real time according to the real-time required exhaust gas volume to return the required amount of exhaust gas to the mixing heat exchanger 15.

[0041] In this embodiment, the exhaust gas recirculation system divides the total exhaust gas recirculation flow into two paths. One path is introduced into the mixing heat exchanger 15 to heat and gasify the liquid ammonia spray and raise the temperature, and the other path is directly introduced into the intake air duct downstream of the mixing heat exchanger 15. The intake air duct downstream of the mixing heat exchanger 15 is directly communicated with the intake port of the engine 17. This embodiment can make the exhaust gas return flow meet the standard and avoid potential safety hazards caused by excessive exhaust gas flow in the mixing heat exchanger 15.

[0042] In some embodiments, an electric auxiliary heating device 16 is provided on the intake air duct downstream of the mixing heat exchanger 15. Under cold engine and low load conditions, the controller controls the electric auxiliary heating device 16 to heat the mixed gas in the intake air duct downstream of the mixing heat exchanger 15 to ensure that the gasification of the liquid ammonia and the temperature of the intake air duct meet the requirements of the preset engine 17 operating conditions.

[0043] The embodiment of the present invention realizes the applicability of liquid ammonia injection under cold start and multiple operating conditions through exhaust gas reflux in cooperation with the electric auxiliary heating device 16.

[0044] In some embodiments, a liquid ammonia flowmeter 8 is provided on the pipeline between the liquid ammonia storage tank 1 and the liquid ammonia transfer pump 9; a liquid ammonia pressure and temperature gauge 12 is provided on the pipeline between the liquid ammonia low-pressure pump 11 and the liquid ammonia medium-pressure pump 13.

[0045] In this embodiment, the controller calculates the actual injection volume of the liquid ammonia nozzle 14 based on the liquid ammonia pressure and temperature measured by the liquid ammonia pressure and temperature gauge 12 and the operating state of the liquid ammonia medium-pressure pump 13, and controls the opening degree of the liquid ammonia nozzle 14 by comparing the actual injection volume of the liquid ammonia nozzle 14 and the required liquid ammonia injection volume so that the actual injection volume is equal to the required liquid ammonia injection volume.

[0046] The present invention adjusts the injection pulse width of the liquid ammonia nozzle 14 according to the operating conditions of the engine 17 to achieve quantitative injection supply of liquid ammonia, and performs real-time feedback through calculating or measuring the actual liquid ammonia flow rate to achieve closed-loop control, having high responsiveness and applicability to variable operating conditions. Specifically, the present invention obtains the engine operating conditions by communicating with the diesel control.

[0047] In some embodiments, the liquid ammonia pressure stabilizing supply system further includes a pressure stabilizing pipe regulating valve 3, an evacuation safety valve 4, a liquid ammonia return pump 5, a return safety valve 7, and a liquid ammonia flowmeter 8.

[0048] The present invention also provides a method for liquid ammonia injection in the intake duct and waste gas recirculation heat recovery, including:

[0049] Calculating the real-time required liquid ammonia injection volume according to the real-time operating condition information of the engine 17 and controlling the operation of the liquid ammonia nozzle 14 in real time;

[0050] Calculating the real-time required heat for liquid ammonia gasification and heating to the set temperature according to the real-time required liquid ammonia injection volume; specifically, the real-time heat required for liquid ammonia spray gasification and heating to the specified temperature can be obtained through calculation and database query;

[0051] Calculating the real-time required waste gas volume according to the real-time required heat for liquid ammonia gasification and heating; specifically, the required waste gas flow rate in the hybrid heat exchanger 15 can be determined by looking up a table according to the heat required for liquid ammonia spray gasification and heating and the temperature data at the exhaust port of the engine 17 tail gas.

[0052] Controlling the exhaust gas recirculation system in real time to return the required amount of exhaust gas to the hybrid heat exchanger 15 according to the real-time required exhaust gas volume.

[0053] The method for injecting liquid ammonia into the intake duct and recovering heat from exhaust gas recirculation provided by the embodiments of the present invention can abandon the existing large-scale gasification devices, and realize the liquid-phase supply and injection of ammonia through the pressure regulation of the liquid ammonia constant-pressure supply system. Moreover, the heat in the exhaust gas is used to gasify and heat the injected liquid ammonia spray, and at the same time, the exhaust gas can improve the in-cylinder combustion model, enhance the combustion efficiency, and thus improve the efficiency of the entire engine 17.

[0054] In some embodiments, the total exhaust gas recirculation flow rate is adjusted and determined according to the real-time working conditions and real-time combustion strategy of the engine 17.

[0055] In this embodiment, the method for determining the total exhaust gas recirculation flow rate belongs to conventional technology. Specifically, the exhaust gas recirculation flow rate should be determined according to parameters such as the engine speed, load, ammonia energy ratio, diesel injection working conditions, etc.

[0056] In some embodiments, the heat required for liquid ammonia gasification and temperature rise in real time is calculated by the following formula:

[0057]

[0058] In the formula, Q total is the total heat exchange; Q liquid is the heat exchange for the temperature rise of the liquid ammonia spray; Q vap is the gasification heat; Q gas is the heat exchange for the temperature rise of ammonia gas; W a is the mass flow rate of liquid ammonia; c p,l is the specific heat capacity of liquid ammonia; T b is the boiling point of liquid ammonia under the set pressure; T l,1 is the initial temperature of the liquid ammonia spray; r a is the latent heat of vaporization of ammonia under the set pressure; c p,g is the specific heat capacity of ammonia gas; T g,2 is the final temperature of ammonia gas.

[0059] It can be seen from this that the total heat exchange includes the heat exchange for the temperature rise of the liquid ammonia spray, the gasification heat, and the heat exchange for the temperature rise of ammonia gas.

[0060] In some embodiments, in the cold engine and low-load working conditions, the electric auxiliary heating device 16 is controlled to heat the mixed gas in the downstream intake duct of the mixing heat exchanger 15 to ensure that the gasification of liquid ammonia and the temperature of the intake duct meet the requirements of the preset working conditions of the engine 17.

[0061] The embodiments of the present invention realize the applicability of liquid ammonia injection under cold start and various working conditions through exhaust gas reflux in cooperation with the electric auxiliary heating device 16.

[0062] In some embodiments, the actual flow rate of the liquid ammonia nozzle 14 is obtained, and the opening degree of the liquid ammonia nozzle 14 is controlled according to the actual flow rate and the required liquid ammonia injection amount so that the actual flow rate is the same as the required liquid ammonia injection amount.

[0063] In this embodiment, the controller calculates the actual injection volume of the liquid ammonia nozzle 14 based on the liquid ammonia pressure and temperature measured by the liquid ammonia pressure and temperature gauge 12 and the working state of the liquid ammonia medium-pressure pump 13, and controls the opening degree of the liquid ammonia nozzle 14 by comparing the actual injection volume of the liquid ammonia nozzle 14 and the required liquid ammonia injection volume so that the actual injection volume is equal to the required liquid ammonia injection volume.

[0064] The present invention adjusts the injection pulse width of the liquid ammonia nozzle 14 according to the working conditions of the engine 17 to achieve quantitative injection supply of liquid ammonia, and performs real-time feedback through calculating or measuring the actual flow rate of liquid ammonia to achieve closed-loop control, having high responsiveness and applicability to variable working conditions.

[0065] Specific examples are applied in the present invention to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An intake duct liquid ammonia injection and exhaust gas circulation heat recovery system, characterized in that: include: Liquid ammonia storage tank, used to store liquid ammonia; a liquid ammonia pressure-stabilizing supply system, which is connected to the liquid ammonia storage tank and regulates the pressure of the liquid ammonia discharged from the liquid ammonia storage tank to a set pressure; A liquid ammonia nozzle, connected to the liquid ammonia pressure-stabilizing supply system and spraying liquid ammonia at a set pressure into the mixing heat exchanger; A mixing heat exchanger provides a space for mixing liquid ammonia, exhaust gas and air; An exhaust gas recirculation system, used for returning the exhaust gas generated by the engine to the mixing heat exchanger; A controller is provided, wherein the controller calculates the real-time required liquid ammonia injection amount according to the real-time operating condition information of the engine and controls the operation of the liquid ammonia nozzle in real time, the controller calculates the real-time required heat for liquid ammonia gasification and heating to a set temperature according to the real-time required liquid ammonia injection amount, calculates the real-time required exhaust gas amount according to the real-time required heat for liquid ammonia gasification and heating to a set temperature, and the controller controls the exhaust gas recirculation system in real time according to the real-time required exhaust gas amount to reflux the required amount of exhaust gas to the mixing heat exchanger.

2. The intake duct liquid ammonia injection and exhaust gas circulation heat recovery system according to claim 1 is characterized in that: The liquid ammonia pressure-stabilizing supply system comprises a liquid ammonia oil pump, a liquid ammonia pressure-stabilizing tank, a liquid ammonia low-pressure pump and a liquid ammonia medium-pressure pump which are sequentially connected through pipelines, and the liquid ammonia medium-pressure pump is connected to the liquid ammonia nozzle.

3. The intake duct liquid ammonia injection and exhaust gas circulation heat recovery system according to claim 2 is characterized in that: The liquid ammonia pressure-stabilizing supply system also includes a reflux heat exchanger, the return oil port of the liquid ammonia medium-pressure pump is connected to the heat medium channel inlet of the reflux heat exchanger, the heat medium channel outlet of the reflux heat exchanger is connected to the liquid ammonia pressure-stabilizing tank, and the liquid ammonia pressure-stabilizing tank is connected to the liquid ammonia storage tank through a pipeline provided with a pressure-stabilizing regulating valve.

4. The intake duct liquid ammonia injection and exhaust gas circulation heat recovery system according to claim 1, characterized in that: The exhaust gas recirculation system includes a main return line, a first branch return line and a second branch return line. One end of the main return line is connected to the exhaust port of the engine, and the other end is connected to one end of the first branch return line and one end of the second branch return line. The other end of the first branch return line is connected to the mixing heat exchanger, and the other end of the second branch return line is connected to the downstream intake duct of the mixing heat exchanger. An exhaust gas main valve is arranged on the main return line, an exhaust gas mixing regulating valve is arranged on the first branch return line, and an exhaust gas direct-through regulating valve is arranged on the second branch return line. The controller determines the total exhaust gas recirculation flow rate according to the engine operating conditions and the real-time combustion strategy, and then adjusts the opening of the exhaust gas main valve according to the total exhaust gas recirculation flow rate. The controller controls the opening of the exhaust gas mixing regulating valve and the exhaust gas direct-through regulating valve in real time according to the real-time required exhaust gas volume to return the required amount of exhaust gas to the mixing heat exchanger.

5. The intake duct liquid ammonia injection and exhaust gas circulation heat recovery system according to claim 1, characterized in that: An electric auxiliary heating device is provided on the downstream intake duct of the mixing heat exchanger. Under cold engine and low load conditions, the controller controls the electric auxiliary heating device to heat the mixed gas in the downstream intake duct of the mixing heat exchanger to ensure the gasification of liquid ammonia and the temperature of the intake duct meets the preset operating conditions of the engine.

6. The intake duct liquid ammonia injection and exhaust gas circulation heat recovery system according to claim 2 is characterized in that: A liquid ammonia flowmeter is provided on the pipeline between the liquid ammonia storage tank and the liquid ammonia oil transfer pump; a liquid ammonia pressure and temperature measuring meter is provided on the pipeline between the liquid ammonia low-pressure pump and the liquid ammonia medium-pressure pump.

7. A method for liquid ammonia injection in the intake duct and heat recovery from exhaust gas circulation, characterized in that: include: Calculate the required liquid ammonia injection amount in real time according to the real-time engine working condition information and control the operation of the liquid ammonia nozzle in real time; Calculate the heat required for liquid ammonia gasification and heating to the set temperature based on the real-time required liquid ammonia injection amount; Calculate the real-time required waste gas volume based on the real-time heat required for liquid ammonia gasification and temperature rise; The exhaust gas recirculation system is controlled in real time according to the real required exhaust gas volume to return the required amount of exhaust gas to the mixing heat exchanger.

8. The method for liquid ammonia injection in the intake duct and heat recovery from exhaust gas circulation according to claim 7 is characterized in that: The total exhaust gas recirculation flow rate is determined according to the real-time engine operating conditions and the real-time combustion strategy adjustment.

9. The method for liquid ammonia injection in the intake duct and heat recovery from exhaust gas circulation according to claim 7, characterized in that: The heat required for liquid ammonia gasification and temperature rise in real time is calculated by the following formula: Where Q total is the total heat exchange; Q liquid Q is the heat exchange rate of liquid ammonia spray temperature rise; vap is the heat of vaporization; Q gas W is the heat exchange rate of ammonia temperature rise; a is the mass flow rate of liquid ammonia; c p,l is the specific heat capacity of liquid ammonia; T b is the boiling point of liquid ammonia at the set pressure; T l,1 is the initial temperature of liquid ammonia spray; r a is the latent heat of ammonia vaporization at the set pressure; c p,g is the specific heat capacity of ammonia; T g,2 is the final temperature of ammonia.

10. The method for liquid ammonia injection in the intake duct and heat recovery from exhaust gas circulation according to claim 7, characterized in that: Under cold engine and low load conditions, the electric auxiliary heating device is controlled to heat the mixed gas in the intake duct downstream of the mixing heat exchanger to ensure the gasification of liquid ammonia and the temperature of the intake duct meets the preset engine operating condition requirements; The actual flow rate of the liquid ammonia nozzle is obtained, and the opening of the liquid ammonia nozzle is controlled according to the actual flow rate and the required liquid ammonia injection amount so that the actual flow rate is the same as the required liquid ammonia injection amount.

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