Ammonia water injection device for reducing NOx emission of natural gas engine and control method
By designing an ammonia injection device and ECU-controlled ammonia injection in a natural gas engine, the problem of thermal NOx emissions from natural gas engines is solved through coordinated cooling and reduction reactions, achieving more efficient NOx emission reduction and engine stability.
Patent Information
- Application Number
- CN202511531793.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-24
- Publication Date
- 2025-11-21
AI Technical Summary
Existing technologies are insufficient to effectively reduce thermal NOx emissions from natural gas engines while maintaining engine operational stability and structural integrity. Single water injection or reducing agent injection schemes have inherent limitations.
Design an ammonia injection device, including an ammonia injection system and an electronic control unit (ECU). By synchronously injecting tiny droplets of inorganic ammonia into the cylinder of a natural gas engine, the ECU dynamically adjusts the injection quantity and timing to achieve in-cylinder cooling and SNCR reaction, thereby synergistically reducing NOx emissions.
It achieves more thorough NOx emission reduction, avoids wet wall and corrosion problems, reduces retrofit costs, adapts to different operating conditions, and protects engine reliability and economy.
Smart Images
Figure CN120990775A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of exhaust pollution control of natural gas engines, and particularly relates to an ammonia water injection device for reducing NOx emissions of a natural gas engine and a control method. BACKGROUND
[0002] In recent years, nitrogen oxides (NOx) have become the most important of all known atmospheric pollutants. With the continuous growth of the number of vehicles, the influence of engine emissions on air quality is becoming more and more significant. Natural gas, as a clean energy, has been widely used in China, and is currently used as fuel for internal combustion engines. Natural gas is widely used as a clean fuel for internal combustion engines because it produces almost no sulfur dioxide and dust during combustion, but the formation of a local high-temperature environment during natural gas combustion leads to the generation of a large amount of thermal NOx. Thermal NOx accounts for the highest proportion of the composition of NOx emissions from natural gas engines, and has become a core obstacle for natural gas engines to meet stringent emission regulations.
[0003] To reduce NOx emissions, various technical solutions have been developed in the industry. Among them, the selective non-catalytic reduction technology (SNCR) is one of the mainstream paths, which refers to the injection of a reducing agent into the flue gas to reduce nitrogen oxides to harmless nitrogen and water in the temperature range suitable for the reaction without the use of a catalyst. Since this process does not use a catalyst, the reducing agent must be added at high temperatures. After the reducing agent is injected into the furnace at a temperature of about 850-1100°C, it rapidly thermally decomposes into NH3, which reacts with NOx in the flue gas to produce N2 and water. Using ammonia as a reducing agent, the main chemical reaction equations for reducing NOx in the temperature range of 850-1100°C are as follows:
[0004] 4NH3 + 4NO + O2 → 4N2 + 6H2O
[0005] 4NH3 + 2NO + 2O2 → 3N2 + 6H2O
[0006] 8NH3 + 6NO2 → 7N2 + 12H2O
[0007] Meanwhile, water injection technology is also applied to NOx control of internal combustion engines, which is originally derived from aero-engines and gradually introduced into the field of passenger vehicle internal combustion engines since the 1980s, and mainly includes intake port water injection (PWI) and direct in-cylinder water injection (DWI), wherein DWI is further divided into oil-water separation direct injection and oil-water mixed direct injection. However, the existing water injection technology has obvious defects: the PWI is prone to water droplet evaporation in advance and wet wall phenomenon, resulting in poor in-cylinder cooling effect and large water consumption; the DWI system has a complex structure, water injection can cause corrosion to components such as pistons and combustion chamber walls, and can also cause engine oil emulsification problem, which seriously affects the reliability and service life of the engine.
[0008] In addition, the existing technology mainly depends on a single path of “cooling” or “reduction reaction” to control NOx, and it is difficult to balance the emission reduction effect and engine operation stability, and no technical solution of “cooling + reduction” synergy is formed, which cannot efficiently solve the core problem of high proportion of thermal type NOx of natural gas engines. Under this background, there is an urgent need for a NOx emission reduction technology that can combine the advantages of cooling and reduction, adapt to the characteristics of natural gas engines, and has no additional damage risk. SUMMARY
[0009] The technical problem to be solved by the present application is to provide an ammonia water injection device and control method for reducing NOx emission of a natural gas engine, and to reduce the generation and emission of NOx of the natural gas engine.
[0010] The technical problem to be solved by the present application is solved by the following technical solutions:
[0011] An ammonia water injection device for reducing NOx emission of a natural gas engine, comprising an ammonia water injection system adapted to the natural gas engine, the ammonia water injection system works with a natural gas injection system of the natural gas engine, and the ammonia water injection system comprises:
[0012] A liquid storage device, which is a water tank containing inorganic ammonia water;
[0013] A conveying device, which is a water rail, one end of the water rail is in communication with the water tank, the water rail extends along the direction of the engine cylinder bank and is provided with branch interfaces corresponding to each cylinder;
[0014] An injection device, which is a small-diameter ammonia water nozzle with multiple holes, the number of which corresponds to the number of engine cylinders, and the input end of each ammonia water nozzle is in sealed connection with the branch interface of the water rail, and the output end extends to the inside of the cylinder through the engine cylinder head;
[0015] A control unit, which is an electronic controller unit (ECU), and the ECU is electrically connected with the ammonia water nozzle and the natural gas nozzle in the natural gas injection system, respectively;
[0016] The ammonia water nozzle is matched with the position of the natural gas nozzle in the cylinder, and can spray the inorganic ammonia water in the form of tiny droplets into the engine cylinder synchronously with the spraying action of the natural gas nozzle.
[0017] Preferably, in the above technical solution, the pipeline between the water rail and the kettle, the branch interface of the water rail and the connection of the input end of the ammonia water nozzle are all provided with an ammonia corrosion-resistant sealing structure to prevent ammonia water leakage.
[0018] Preferably, in the above technical solution, the kettle is arranged outside the engine body, and a valve for controlling the outflow of inorganic ammonia water is arranged at the liquid outlet of the kettle.
[0019] Preferably, in the above technical solution, the ECU can receive the spraying signal of the natural gas nozzle and trigger the synchronous spraying action of the ammonia water nozzle according to the signal.
[0020] A control method based on an ammonia water spraying device for reducing the NOx emission of a natural gas engine, comprising the following steps:
[0021] S1, after the engine is started, the ECU acquires the engine operating parameters and the spraying signal of the natural gas spraying system in real time;
[0022] S2, the ECU determines the spraying amount and spraying timing of the ammonia water according to the acquired parameters and signals;
[0023] S3, the ECU controls the ammonia water nozzle and the natural gas nozzle to spray inorganic ammonia water into the cylinder synchronously;
[0024] S4, the inorganic ammonia water is evaporated and cooled in the cylinder, and reacts with NOx to generate nitrogen and water at 850-1100 DEG C.
[0025] Preferably, in the above technical solution, the operating parameters include engine speed, load and cylinder temperature.
[0026] Preferably, in the above technical solution, in step (2), the ammonia water injection amount is adjusted in real time by an electronic controller unit (ECU), the spraying amount is reduced under low load conditions, and the spraying amount is increased under high load conditions, so that the best denitration effect can be achieved under different conditions, and the influence of excessive or insufficient ammonia water on the normal operation of the engine is avoided.
[0027] Preferably, in the above technical solution, the ammonia gas generated by the evaporation of ammonia water only reacts with NOx in the combustion products through SNCR reaction, and does not react with other components in the cylinder to affect the performance of the engine.
[0028] The above technical solution of the present application has the following beneficial effects:
[0029] (1) NOx emission reduction is more thorough: ammonia water evaporation not only reduces the cylinder temperature and reduces the thermal NOx generation, but also converts the remaining NOx into harmless substances through SNCR reaction, which is better than single technology in emission reduction effect.
[0030] (2) Protect engine reliability: no water droplets wet wall, oil emulsification problem, avoid component corrosion, solve the pain point of existing DWI technology damage engine.
[0031] (3) Easy to adapt to landing: only add water jug, water rail, nozzle, no need to modify the original structure of the engine, easy to install, low modification cost.
[0032] (4) Strong working condition adaptability: ECU dynamically adjusts the ammonia water injection amount and timing, which can match different engine operating conditions, and takes into account the emission reduction effect and economy. BRIEF DESCRIPTION OF DRAWINGS
[0033] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application.
[0034] Figure 1 The connection diagram for the water rail and nozzle arrangement.
[0035] 1- water rail, 2- ammonia water nozzle, 3- engine cylinder, 4- gas rail, 5- natural gas nozzle. DETAILED DESCRIPTION
[0036] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement, numerical expressions and values of the components and steps set forth in these embodiments do not limit the scope of the present application unless otherwise specifically stated.
[0037] 1、 The ammonia water injection device for reducing NOx emission of natural gas engine of the present application is mainly composed of an ammonia water injection system and a control unit:
[0038] (1) Ammonia water injection system:
[0039] Liquid storage component: a water jug (not shown) capable of containing inorganic ammonia water is used, which is arranged outside the engine body, and the liquid outlet is provided with a valve (not shown) for controlling the outflow of ammonia water.
[0040] Conveying component: including water rail 1, one end of water rail 1 is connected with the liquid outlet of water jug through pipeline, and the connection between pipeline and water rail 1, water jug adopts sealing structure to prevent ammonia water leakage. The water rail 1 extends along the arrangement direction of the engine cylinder 3, and its length is matched with the number of engine cylinders 3.
[0041] Spraying component: a plurality of small-diameter ammonia water nozzles 2, the number of which is the same as the number of cylinders 3 of the engine. The input end of each ammonia water nozzle 2 is connected to the corresponding interface on the water rail 1, and the output end of the ammonia water nozzle 2 extends through the cylinder cover of the engine to the inside of the cylinder 3, realizing in-cylinder direct injection of ammonia water.
[0042] (2) Control unit:
[0043] The control unit (not shown) is an electronic controller unit (ECU) that is electrically connected to the ammonia water nozzles 2 and the natural gas nozzles 5 of the natural gas injection system of the natural gas engine, can receive the injection signal of the natural gas injection system, and control the injection action of the ammonia water nozzles. The natural gas nozzles 5 are connected to the natural gas tank through the natural gas rail 4.
[0044] 2. Working process:
[0045] Working principle: When the natural gas engine injects natural gas, a plurality of small-diameter ammonia water nozzles 2 are used to synchronously inject ammonium water in the form of tiny droplets, so that the droplets can evaporate faster and more completely during the combustion process. During the injection of ammonia water by the ammonia water nozzles 2, the ECU is used to accurately control the injection amount of ammonia water to achieve the best denitration effect. After the ammonia water evaporates, the cylinder temperature decreases, and the amount of thermal NOx generated decreases. When the cylinder temperature reaches the temperature range of the SNCR reaction, the NOx in the combustion products reacts with the ammonia in the gas mixture after the evaporation of the ammonia water, thereby reducing the generation of NOx. In the SNCR reaction, the reducing agent only reacts with NOx in the flue gas, so compared with direct water injection, ammonia water injection can more greatly reduce the generation of NOx. This scheme uses ammonia water to reduce the generation of thermal NOx, and uses ammonia to react with NOx in the combustion products, thereby reducing the generation and emission of NOx from two aspects, which has good reference significance for practical application.
[0046] The specific ammonia water injection control method is as follows:
[0047] (1) When the natural gas engine starts, the ECU starts to work, and real-time engine operating parameters are obtained, including engine speed, load, cylinder temperature, etc., while receiving the injection signal sent by the natural gas injection system.
[0048] (2) The ECU determines the optimal injection amount and injection timing of ammonia water according to the obtained operating parameters and injection signal through internal calculation.
[0049] (3) While the natural gas nozzles 5 of the natural gas injection system inject natural gas into the cylinder 3, the ECU controls the ammonia water nozzles to inject tiny droplet-shaped inorganic ammonia water into the cylinder 3 according to the determined injection amount and injection timing.
[0050] (4) The inorganic ammonia water injected into the cylinder evaporates rapidly, absorbs heat, and reduces the temperature in the cylinder, thereby reducing the generation of thermal NOx.
[0051] (5) When the temperature in the cylinder is in the selective non-catalytic reduction (SNCR) reaction temperature range of 850-1100℃, the ammonia gas generated by the evaporation of ammonia water chemically reacts with the NOx generated in the combustion process, reducing NOx to nitrogen and water, further reducing NOx emissions.
[0052] 3. Adjustment under different working conditions
[0053] The ECU can dynamically adjust the injection amount of ammonia water according to different operating conditions of the engine:
[0054] When the engine is in a low load condition, the ECU controls to reduce the injection amount of ammonia water to adapt to lower combustion temperature and less NOx generation.
[0055] When the engine is in a high load condition, the temperature in the cylinder is high and the amount of NOx generated is large, and the ECU will correspondingly increase the injection amount of ammonia water to ensure good emission reduction effect.
[0056] Through the above embodiments, the generation and emission of NOx of the natural gas engine can be effectively reduced, while avoiding additional damage to the engine, and the device structure is simple and easy to adapt and install on existing engines.
[0057] Although the present application has been disclosed as above with examples, it is not intended to limit the present application, and any person skilled in the art can make various selections and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application is defined by the claims and their equivalent forms.
Claims
1. An ammonia injection device for reducing NOx emissions from natural gas engines, characterized in that, This includes an ammonia injection system adapted for a natural gas engine, wherein the ammonia injection system works in conjunction with the natural gas injection system of the natural gas engine, and the ammonia injection system includes: A liquid storage device, which is a kettle for containing inorganic ammonia water; The conveying device is a water rail (1), one end of which is connected to a water bottle. The water rail (1) extends along the direction of the engine cylinder (3) and has branch interfaces corresponding to each cylinder (3). The injection device is a multi-hole small-diameter ammonia water nozzle (2), the number of which corresponds one-to-one with the number of engine cylinders (3). The input end of each ammonia water nozzle (2) is sealed and connected to the branch interface of the water rail (1), and the output end extends through the engine cylinder head to the inside of the cylinder. The control unit is an electronic controller unit (ECU), which is electrically connected to the ammonia nozzle (2) and the natural gas nozzle (5) in the natural gas injection system. The ammonia nozzle (2) is adapted to the position of the natural gas nozzle (5) in the cylinder, and can spray tiny droplets of inorganic ammonia into the engine cylinder (3) synchronously with the injection action of the natural gas nozzle (5).
2. The apparatus according to claim 1, characterized in that, The pipeline between the water rail (1) and the kettle, as well as the connection between the branch interface of the water rail and the ammonia water nozzle input end, are all equipped with ammonia corrosion resistant sealing structures to prevent ammonia water leakage.
3. The apparatus according to claim 1, characterized in that, The water tank is located outside the engine block, and a valve is provided at the outlet of the water tank to control the flow of inorganic ammonia water.
4. The apparatus according to claim 1, characterized in that, The ECU can receive the injection signal from the natural gas nozzle (5) and trigger the synchronous injection action of the ammonia nozzle (2) according to the signal.
5. A control method for an ammonia injection device for reducing NOx emissions from a natural gas engine based on any one of claims 1-4, characterized in that, Includes the following steps: S1. After the engine starts, the ECU acquires the engine operating parameters and the injection signals of the natural gas injection system in real time. S2 and ECU determine the injection volume and timing of ammonia water based on the acquired parameters and signals; S3, ECU controls the ammonia nozzle and the natural gas nozzle to synchronously inject inorganic ammonia into the cylinder; S4. Inorganic ammonia evaporates and cools down inside the cylinder, while reacting with NOx at 850℃-1100℃ to produce nitrogen and water.
6. The control method according to claim 5, characterized in that, The operating parameters include engine speed, load, and cylinder temperature.
7. The control method according to claim 5, characterized in that, In step (2), the ammonia injection volume is adjusted in real time by the ECU. The injection volume is reduced under low load conditions and increased under high load conditions to ensure that the best denitrification effect can be achieved under different conditions, while avoiding excessive or insufficient ammonia affecting the normal operation of the engine.
8. The control method according to claim 5, characterized in that, The ammonia gas produced by the evaporation of ammonia water only undergoes an SNCR reaction with NOx in the combustion products, and does not undergo side reactions with other components in the cylinder that affect engine performance.