CN1298969C - Apparatus for supplying reducing agent to hydroxide catalyzing transforming device of internal combustion engine - Google Patents

Abstract

The utility model relates to a reducing agent supply device for a nitrogen oxide catalytic converter of an internal combustion engine, which belongs to the control technology of automobile tail gas emission. The invention includes a reductant injector, a reductant storage tank, a delivery pump, a gas storage tank, a gas control valve and an electronic controller; the reductant injector is composed of an injector body, a solenoid valve nozzle, a mixing tube with a porous nozzle, Equipped with coolant inlet, outlet and compressed air inlet. The characteristics of the present invention are: the reducing agent is mixed with the compressed air in the mixing tube, sprayed into the exhaust pipe through the porous nozzle, and evenly spread on the surface of the catalyst, which improves the effective utilization rate of the reducing agent; and the reducing agent nozzle is not directly Installed on the exhaust pipe, avoiding the high temperature of the exhaust pipe, coupled with the cooling of compressed air and coolant, can improve the reliability and service life of the supply device. The electronic controller can perform transient control on the reducing agent flow, so it can meet the needs of changing working conditions during the operation of the internal combustion engine, and is a practical reducing agent supply device.

Description

A reducing agent supply device for a nitrogen oxide catalytic converter of an internal combustion engine

technical field

The invention relates to a reducing agent supply device for a nitrogen oxide catalytic converter of an internal combustion engine, which belongs to the control of exhaust emission of automobiles

technology field.

Background technique

The exhaust of internal combustion engines contains pollutants such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx). Aftertreatment technologies such as catalytic converters are often used to convert them into harmless components such as carbon dioxide (CO ₂ ), water (H ₂ O) and nitrogen (N ₂ ). The process of converting CO and HC into CO ₂ and H ₂ O is an oxidation reaction, and the process of converting NOx into N ₂ is a reduction reaction. Conventional gasoline engines can control the air-fuel ratio to work near the stoichiometric ratio. CO, HC and NOx in the exhaust are oxidants and reductants for each other. Under the action of the three-way catalyst (TWC), the conversion efficiency of CO, HC and NOx is very high. Can meet stringent emission regulations. However, diesel engines or lean-burn gasoline engines work under lean air-fuel ratios. Due to the presence of more oxygen in the exhaust gas, that is, an oxygen-enriched environment, CO and HC are easily converted by mature oxidation catalysts, while NOx The reduction reaction is difficult to carry out. At present, the post-treatment technology of NOx in an oxygen-enriched environment is under research and development, and there is no practical product yet. In the research, people found that if reducing substances such as hydrocarbon fuel, urea, ethanol, etc. are added to the exhaust upstream of the NOx catalytic converter, the conversion efficiency of NOx can be improved. This method is called Selective Catalytic Reduction (SCR).

With the tightening of automobile emission regulations, the post-treatment of catalytic conversion of lean NOx is inevitable. Research on the practical use of the reducing agent supply device is also intensified. Patent EP 1331 373 discloses a "reductant supply system" (ReductantSupply System), which aims at the situation that the reductant nozzle directly inserted into the exhaust pipe is easily blocked by the high temperature of the exhaust gas, and proposes a method of adding fuel before the nozzle is about to be blocked. A way to spray some reducing agent to keep the nozzles clear. In this method, because the nozzle is directly inserted into the high-temperature exhaust gas, it is easy to coke. Although more reductants can be sprayed to avoid clogging, high temperature will reduce the service life of the nozzles, and more reductants will increase the cost and increase the cost of reductants. The storage capacity is not conducive to the use on transport vehicles.

The paper SAE 952489 "Development of Test Methods for Lean-NOx Catalyst Evaluation" published by Johnson Matthey Company in the United Kingdom introduces the test method and device for supplying reducing agent to lean NOx catalytic converter in laboratory research. The device is used to inject reducing agent (diesel) into the exhaust pipe, that is, the diesel oil flows into the gear pump through a solenoid valve switch, and the diesel oil flowing through the gear pump is mixed with compressed air in the nozzle and enters the exhaust pipe. The reductant flow of the device is controlled by a gear pump, the nozzle is only for mixing, and the gear pump can only perform steady-state control of the reductant flow, and cannot perform transient control, so it is not suitable for the variable working conditions of the internal combustion engine. Reductant injection volume requirements.

Contents of the invention

The object of the present invention is to provide a practical device for supplying reducing agent to a lean NOx catalytic converter of an internal combustion engine for a selective catalytic reduction system. The device can not only effectively prevent the nozzle from being blocked due to high-temperature coking of the reducing agent, but also fully atomize and evenly distribute the reducing agent in the exhaust pipe, and can perform timing and quantitative transient control of the reducing agent flow rate, thereby improving the efficiency of the injection device. The service life of the catalytic converter, the conversion efficiency of the catalytic converter and the effective utilization rate of the reducing agent.

The purpose of the present invention is achieved through the following technical solutions: a reducing agent supply device for nitrogen oxide catalytic converters of internal combustion engines, characterized in that: the device includes a reducing agent injector fixed on the exhaust pipe of the internal combustion engine, reducing agent storage tank and delivery pump, compressed air storage tank and gas control valve, and an electronic controller used to control the reducing agent supply device; the reducing agent injector includes the injector body, the solenoid valve nozzle installed in the body, A guide ring connected to the outlet of the nozzle and a mixing tube with a multi-hole nozzle, the mixing tube extends into the exhaust pipe; the injector body is respectively provided with a cooling liquid inlet, a cooling liquid outlet and a compressed air inlet; The reducing agent storage tank and delivery pump are connected to the inlet of the solenoid valve nozzle in the injector through pipelines, and the compressed air storage tank and gas control valve are connected to the compressed air inlet through pipelines; the electronic The controller is respectively connected with the solenoid valve nozzle, the gas control valve and the internal combustion engine through the control circuit.

Compared with the prior art, the reducing agent supply device proposed by the present invention has the following characteristics and outstanding effects: ①The liquid reducing agent is not directly sprayed into the exhaust pipe, but first enters the mixing pipe, where it is mixed with compressed air , After atomization, it is sprayed into the exhaust pipe through the porous nozzle of the mixing tube; in this way, the atomization and scattering of the reducing agent can make the reducing agent spread more widely on the surface of the catalyst, and improve the effective utilization rate of the reducing agent. ②The reducing agent nozzle is not directly installed on the exhaust pipe, which can avoid the influence of the high temperature of the exhaust pipe, coupled with the cooling of compressed air and cooling liquid, it can effectively improve the service life and reliability of the reducing agent supply device sex. ③ The mixture of reducing agent and air is sprayed into the exhaust pipe through the porous nozzle at the head of the mixing tube, so that the reducing agent is evenly distributed in the exhaust gas; the compressed air passes through the guide ring to generate swirl, which promotes the accelerated mixing of reducing agent and compressed air , Compressed air also prevents nozzle clogging. ④The solenoid valve nozzle can control the instantaneous injection amount of reducing agent quantitatively and regularly by pulse current, which is suitable for the requirement of reducing agent injection amount under variable working conditions during the operation of the internal combustion engine. ⑤The compressed air control valve is a valve that can change the size of the air channel to control the air flow. It can be opened and closed simultaneously with the reducing agent nozzle valve, or it can be opened separately when the nozzle is closed. When it is opened separately, the compressed air is only used for cooling nozzle. 6. The present invention adopts an electronic controller to control the entire reductant supply device, and the electronic controller can set the supply time and supply amount of the reductant and compressed air in advance according to the operating conditions of the engine, so that it can adapt to the changing working conditions of the internal combustion engine during the operation of the reducing agent. Dosage injection volume requirements.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the reducing agent supply device provided by the present invention.

Fig. 2 is a schematic structural diagram of a reducing agent injector.

Fig. 3 is a schematic structural diagram of an embodiment of a guide ring.

Fig. 4 is a schematic structural view of an embodiment of a mixing tube with a multi-hole nozzle.

Detailed ways

The specific structure, working process and best implementation mode of the present invention will be further described below in conjunction with the accompanying drawings.

The reductant supply device mainly includes a reductant injector 3, a reductant storage tank 6 and a delivery pump 7, a compressed air storage tank 8, a gas control valve 9, and an electronic controller 5 for controlling the reductant supply device; The injector 3 is attached to the exhaust pipe 2 and supplies the reducing agent to the catalytic converter 4 . The reductant storage tank 6 and delivery pump 7 are connected to the injector 3 through pipelines; the compressed air storage tank 8 and the gas control valve 9 are connected to the injector 3 through pipelines; the electronic controller 5 is connected to the reductant through control lines The injector 3, the gas control valve 9 and the internal combustion engine 1 are connected (as shown in FIG. 1 ).

Fig. 2 is a schematic diagram of the structure of the original agent injector. The reducing agent injector 3 includes an injector body 22, a solenoid valve nozzle 15 installed in the body, a guide ring 17 connected to the nozzle outlet 19, and a mixing tube 18 with a multi-hole nozzle 20, the mixing tube extends into into the exhaust pipe 2; the injector body is provided with a cooling liquid inlet 10, a cooling liquid outlet 11 and a compressed air inlet 16 respectively. On the guide ring 17 between the outlet of the solenoid valve nozzle and the mixing tube, there are at least two tangential or spiral ventilation grooves 21 .

The working process of the supply device is as follows: the delivery pump 7 feeds the reducing agent in liquid state from the storage tank 6 into the injector 3 at a certain pressure, and then sprays it out from the outlet 19 of the solenoid valve nozzle 15 . At the same time, compressed air of a certain pressure enters the injector 3 from the air storage tank 8 through the gas control valve 9, and mixes with the reducing agent ejected from the nozzle outlet 19 in the mixing pipe 18 to form a mixed gas. The mixed gas is sprayed into the exhaust pipe 2 from the mixing pipe 18 through the multi-hole nozzle 20 in an atomized state, and then spreads to the surface of the NOx catalyst in the catalytic converter 4 along with the exhaust gas from the engine. In order to prevent the high temperature of the exhaust pipe 2 from affecting the normal operation of the injector 3, the cooling liquid of the internal combustion engine cooling system or an additional cooling system (not shown in Figure 1) enters the injector cavity 13 from the cooling liquid inlet 10, and the injector is cooled Cool, and then flow back to the cooling system from outlet 11.

The electronic controller 5 is connected with the electric control interface 23 on the electromagnetic valve nozzle 15 through the control circuit, and the electromagnetic valve nozzle can control the instantaneous injection amount of the reducing agent quantitatively with the pulse current, so as to adjust the injection amount of the reducing agent to adapt to the changing working conditions during the operation of the internal combustion engine. requirements. The electronic controller sends instructions to the solenoid valve nozzle with pulse current to control the opening and closing of the solenoid valve, and then control the supply timing and quantity of the reducing agent. The reducing agent enters the solenoid valve nozzle 15 from the reducing agent inlet 24 , sprays out from the nozzle outlet 19 , and enters the mixing tube 18 . At the same time, the compressed air from the gas control valve 9 enters the injector body 22 from the compressed air inlet 16, guides along the air passage 14 to around the nozzle outlet 19, and then passes through the ventilation groove 21 on the guide ring 17 to compress The air forms a swirling flow, mixes with the reducing agent ejected from the nozzle outlet 19, forms a mixed gas in the mixing pipe 18, and finally sprays into the exhaust pipe 2 through the multi-hole nozzle 20. The guide ring 17 is a cylindrical annular part, its outer cylindrical surface is connected with the outer circle of the nozzle outlet 19 , and its inner cylindrical surface is connected with the inner cavity of the mixing tube 18 . At least two tangential ventilation grooves or spiral ventilation grooves 21 are provided on the guide ring. The inlet of the tank communicates with the compressed air inlet 16 through the air channel 14 , and the outlet of the tank communicates with the inner cavity of the mixing tube 18 . The compressed air outside the guide ring forms a swirl flow in the inner cylindrical surface after flowing through the vent groove, and flows into the mixing tube 18 . Figure 3 is a specific embodiment of the guide ring. According to the shape and characteristics of the injected reducing agent, the ventilation grooves on the guide ring can be made into various shapes, so that the air flow forms swirling flows of different intensities, and the reducing agent Better atomization.

The mixing tube 18 is an important part of the injector 3. The multi-hole nozzle is provided with at least two nozzle holes; the position and orientation of the outlet will affect the effective utilization rate of the reducing agent. Generally, the orientation of the outlet of the mixing tube in the exhaust pipe It should be in the same direction or reverse direction or at an angle to the flow direction of the exhaust in the exhaust pipe; the multi-hole nozzle should be located in the middle of the exhaust pipe or on the wall of the exhaust pipe or any position in between, and its specific position and orientation should be based on the location of the exhaust pipe. The shape of the tube and the spray are set. The porous nozzle 20 at the mouth of the mixing tube 18 is fastened to the mixing tube by welding or mechanical means, and the nozzle holes on the nozzle can be made into various shapes so that the aerosol reducing agent is sprayed out along the axial direction of the outlet of the mixing tube Or scatter around the nozzle, etc. Fig. 4 is a schematic structural view of an embodiment of a mixing tube with a multi-hole nozzle. The above-mentioned compressed air entering the injector 3 not only atomizes and disperses the reducing agent, but also cools the nozzle 15 so that the nozzle will not be blocked due to high-temperature coking of the reducing agent. The timing and amount of compressed air input into the injector are controlled by the gas control valve 9 . The gas control valve 9 is a valve that can change the size of the air passage area and change the flow rate of compressed air with a certain pressure. Its valve stem can be driven by an electromagnetic coil or a stepping motor. This control valve is also controlled by the electronic controller 5, which can be opened and closed simultaneously with the nozzle electromagnetic valve 15, and can also be opened separately when the nozzle is closed. When switched on alone, compressed air is only used to cool the nozzles. The compressed air inlet 16, the coolant inlet 10, and the coolant outlet 11 can be connected to the injector 3 by means of connection methods such as rubber hoses or steel pipes commonly used in internal combustion engines or automobiles.

Solenoid valve nozzle 15 is mounted on injector body 22 together with deflector ring 17 using the pressure plate commonly used in fuel nozzles of internal combustion engines or other connection methods; reductant mixing pipe 18 and porous nozzle 20 extend into the exhaust pipe and are welded or mechanically The way is fastened with the injector body 22. The whole injector part is installed on the exhaust pipe 2 of the internal combustion engine by means of mechanical connections such as threads or flanges.

The reducing agent supply device is controlled by an electronic controller 5 . The electronic controller is based on the signals of the speed, load (throttle opening), coolant temperature, intake air flow, exhaust temperature, exhaust composition and other signals input from various sensors of the internal combustion engine, combined with various stored data, after analysis and calculation, Use electrical signals to send action commands to actuators such as reducing agent nozzles and gas control valves to control the input timing and quantity of reducing agent and compressed air.

Claims (2)

1. reducer feeding device that is used for internal-combustion engine nitrogen oxide catalytic converter, this device comprises the reducing agent injector (3) that is fixed on the internal-combustion engine vent-pipe, reducing agent storage tank (6) and transfer pump (7), compressed air storage tank (8) and gas control valve (9) and the electronic controller (5) that is used for controlling reducer feeding device, it is characterized in that: described reducing agent injector comprises ejector body (22), be installed in intrinsic solenoid valve nozzle (15), the mixing tube (18) of guide ring (17) that links to each other with this jet expansion (19) and band porous nozzle (20), this mixing tube extend in the outlet pipe (2); On described ejector body, be respectively equipped with cooling liquid inlet (10) and cooling liquid outlet (11) and compressed air inlet (16); At least be provided with two tangential vent slots or spiral vent slot (21) on the outlet of described solenoid valve nozzle and the guide ring between the mixing tube (17), the import of this groove is connected with described compressed air inlet (16) by air passageways (14), and the outlet of this groove communicates with the inner chamber of described mixing tube (18).

2. according to the described reducer feeding device of claim 1, it is characterized in that: the ejiction opening of the mixing tube (18) of described band porous nozzle (20) in outlet pipe towards with outlet pipe in exhaust flow direction in the same way or reverse or be an angle; Porous nozzle (20) is positioned at middle part or tube wall or arbitrary position therebetween of outlet pipe.

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