JP6094556B2 - Highly active substance addition equipment - Google Patents

Description

  The present invention relates to a highly active substance addition apparatus for adding a reducing agent used for NOx reduction.

  2. Description of the Related Art Conventionally, a technique for purifying NOx (nitrogen oxide) contained in exhaust gas of an internal combustion engine by reacting with a reducing agent on a catalyst is known. In Patent Document 1, a highly active substance addition is performed in which a liquid reducing agent atomized by static electricity is reformed by passing between discharge electrodes, and the reformed reducing agent is added to the upstream side of the catalyst. An apparatus is disclosed.

JP 2009-162173 A

  However, in the conventional highly active substance addition apparatus, the configuration when atomizing the reducing agent is relatively complicated, and the reducing agent that has vaporized may condense and adhere to, for example, an air passage or an electrode. is there. When such adhesion occurs, the timing at which the adhering reducing agent vaporizes cannot be controlled as intended. Therefore, when the reformed reducing agent is added to the upstream side of the catalyst, it cannot be added at a desired timing.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly active substance addition device that easily and sufficiently vaporizes the reducing agent and further suppresses the attachment of the reducing agent. There is to do.

  The invention disclosed herein employs the following technical means to achieve the above object. Note that the reference numerals in parentheses described in the claims and in this section indicate a corresponding relationship with specific means described in the embodiments described later as one aspect, and limit the technical scope of the invention. Not what you want.

One of the disclosed inventions is a highly active substance adding device. This highly active substance addition device is provided in a combustion system in which an NOx purification device (15) for purifying NOx contained in exhaust gas of an internal combustion engine (10) on a reduction catalyst is provided in an exhaust passage (10ex). It is assumed that a reducing agent is added to the upstream side of the reduction catalyst. Then, heating means ( 34A, 34B) for heating the supplied liquid hydrocarbon and cracking so as to reduce the carbon number of the hydrocarbon is provided, and the heating means heats the liquid hydrocarbon. vaporizing heated surface for vaporizing (343,342A), and the vaporized hydrocarbons further heated while chromatic cracking heated surface cracking (344,342B), heating elements for heating the vaporizing heating surface (341A) and said heating elements for heating the cracking heating surface (341B) possess separately, the cracked hydrocarbon by the heating means, by partial oxidation, and generating a reformed reducing agent as a highly active substance .

  According to the present invention, the boiling point of the hydrocarbon is lowered by cracking after the supplied hydrocarbon is vaporized. Therefore, the supplied hydrocarbons are sufficiently vaporized, and are prevented from condensing and adhering to the passages and electrodes. Therefore, it is possible to relatively easily suppress the problem that the modified reducing agent cannot be added at a desired timing when it is added to the exhaust passage.

The schematic diagram which shows the combustion system to which the highly active substance addition apparatus which concerns on 1st Embodiment of this invention, and its apparatus are applied. The schematic diagram which shows the detail of a heating means in 1st Embodiment. The figure explaining film | membrane boiling which arises on the heating surface of a heating means in 1st Embodiment. The schematic diagram explaining the mechanism in which reformed HC is generated in a 1st embodiment. The schematic diagram explaining the mechanism by which ozone is produced | generated in 1st Embodiment. The figure which shows typically the cross-section of a discharge reactor in 1st Embodiment. The flowchart which shows the procedure of the control which switches ozone production | generation and reformed HC production | generation in 1st Embodiment. The flowchart which shows the procedure which controls fuel supply amount and heater temperature in 1st Embodiment. The schematic diagram which shows the detail of a heating means in 2nd Embodiment of this invention. The schematic diagram which shows the detail of a heating means in 3rd Embodiment of this invention. The schematic diagram which shows the detail of a heating means in 4th Embodiment of this invention. The schematic diagram which shows the detail of a heating means in 5th Embodiment of this invention. The figure explaining the effect by suppressing film boiling. The schematic diagram which shows the combustion system to which the highly active substance addition apparatus which concerns on 6th Embodiment of this invention, and its apparatus are applied.

  Hereinafter, a plurality of modes for carrying out the invention will be described with reference to the drawings. In each embodiment, portions corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals and redundant description may be omitted. In each embodiment, when only a part of the configuration is described, the other configurations described above can be applied to other portions of the configuration.

(First embodiment)
The combustion system shown in FIG. 1 includes an internal combustion engine 10, a supercharger 11, a particulate collection device (DPF 14), a NOx purification device 15, a reducing agent purification device (DOC 16), and a highly active substance addition device, which will be described in detail below. . The combustion system is mounted on a vehicle, and the vehicle travels using the output of the internal combustion engine 10 as a drive source. The internal combustion engine 10 is a compression self-ignition diesel engine, and light oil is used as a fuel for combustion.

  The supercharger 11 includes a turbine 11a, a rotating shaft 11b, and a compressor 11c. The turbine 11a is disposed in the exhaust passage 10ex of the internal combustion engine 10 and rotates by the kinetic energy of the exhaust. The rotating shaft 11b couples the impellers of the turbine 11a and the compressor 11c to transmit the rotational force of the turbine 11a to the compressor 11c. The compressor 11c is disposed in the intake passage 10in of the internal combustion engine 10, compresses the intake air, and supercharges the internal combustion engine 10.

  A cooler 12 for cooling the intake air compressed by the compressor 11c is disposed on the downstream side of the compressor 11c in the intake passage 10in. The compressed intake air cooled by the cooler 12 is adjusted in flow rate by a throttle valve 13 and then distributed to a plurality of combustion chambers of the internal combustion engine 10 by an intake manifold.

  In the exhaust passage 10ex, on the downstream side of the turbine 11a, a DPF 14 (Diesel Particulate Filter), a NOx purification device 15, and a DOC 16 (Diesel Oxidation Catalyst) are arranged in this order. The DPF 14 collects fine particles contained in the exhaust. A supply pipe 24 of a highly active substance addition device is connected to the exhaust passage 10ex on the downstream side of the DPF 14 and the upstream side of the NOx purification device 15. The reforming / reducing agent generated by the highly active substance adding device is added from the supply pipe 24 to the exhaust passage 10ex. The reforming / reducing agent is obtained by partially oxidizing a hydrocarbon (fuel) used as the reducing agent to reform it into a partially oxidized hydrocarbon, which will be described in detail later with reference to FIG.

The NOx purification device 15 includes a honeycomb-shaped carrier 15b that carries a reduction catalyst, and a housing 15a that houses the carrier 15b. The NOx purifying device 15 purifies NOx contained in the exhaust by reacting NOx in the exhaust with the reforming reducing agent on the reduction catalyst and reducing it to N ₂ . The exhaust gas contains O ₂ in addition to NOx, but the reforming / reducing agent reacts selectively with NOx in the presence of O ₂ .

  A reduction catalyst having a function of adsorbing NOx is used. Specifically, when the catalyst temperature is lower than the activation temperature at which the reduction reaction is possible, the reduction catalyst exhibits a function of adsorbing NOx in the exhaust. When the catalyst temperature is equal to or higher than the activation temperature, the adsorbed NOx is reduced by the reforming reducing agent and released from the reduction catalyst. For example, the NOx purification device 15 having a NOx adsorption function is provided by a reduction catalyst made of silver alumina supported on the carrier 15b.

  The DOC 16 is configured by accommodating a carrier carrying an oxidation catalyst in a housing. The DOC 16 oxidizes the reducing agent that has not been used for NOx reduction on the reduction catalyst and has flowed out of the NOx purification device 15 on the oxidation catalyst. This prevents the reducing agent from being released into the atmosphere from the outlet of the exhaust passage 10ex. Note that the activation temperature of the oxidation catalyst (eg, 200 ° C.) is lower than the activation temperature of the reduction catalyst (eg, 250 ° C.).

  Next, a highly active substance adding device that generates a reforming and reducing agent and adds it to the exhaust passage 10ex from the supply pipe 24 will be described. The highly active substance addition apparatus includes a discharge reactor 20, an air pump 31, a fuel injection valve 33, and an electric heater 34, which will be described in detail below. The discharge reactor 20 includes a plurality of pairs of a pair of electrodes 21 that have a ground voltage and a high voltage. Each electrode 21 has a flat plate shape and is disposed so as to face each other in parallel. The voltage application to the electrode 21 is controlled by a microcomputer (microcomputer 81) included in the electronic control unit (ECU 80).

  A mixing case 30 that forms a mixing chamber 30 a is attached to the upstream side of the discharge reactor 20. The air blown by the air pump 31 flows into the mixing chamber 30a through the blow pipe 32. The air pump 31 is driven by an electric motor, and the electric motor is controlled by the microcomputer 81. The air blown by the air pump 31 is a normal temperature and normal pressure atmosphere existing around the highly active substance adding device. Since air contains oxygen molecules, it can be said that the air pump 31 supplies oxygen-containing gas to the mixing chamber 30a. Hereinafter, such a gas containing at least oxygen is simply referred to as oxygen gas. The air pump 31 provides “oxygen supply means” for supplying oxygen gas to the discharge reactor 20.

  The liquid fuel in the fuel tank 33t is supplied to the fuel injection valve 33 by the pump 33p and injected from the injection hole of the fuel injection valve 33 into the mixing chamber 30a. The fuel in the fuel tank 33t is also used as the fuel for combustion described above, and the fuel used for combustion of the internal combustion engine 10 and the fuel used as the reducing agent are shared. The fuel injection valve 33 is structured to open by an electromagnetic force generated by an electromagnetic solenoid, and the energization of the electromagnetic solenoid is controlled by the microcomputer 81. The fuel injection valve 33 provides “hydrocarbon injection means” for supplying hydrocarbons to the electric heater 34 by injecting fuel.

  The fuel pressure-fed to the fuel injection valve 33 by the pump 33p is injected from the injection hole of the fuel injection valve 33 and decompressed to be supplied to the electric heater 34 in the atomized state. That is, the fuel injection valve 33 also provides “atomization means” for atomizing the liquid fuel and supplying it to the electric heater 34. For example, the fuel injection valve 33 injects the liquid fuel with a particle size of 60 μm or less.

  A vaporizing case 35 is connected to the mixing case 30 by a fuel supply pipe 35a. A fuel injection valve 33 and an electric heater 34 are attached to the vaporizing case 35. As shown in FIG. 2, the electric heater 34 includes a heating element 341 that generates heat when energized, and a protective member 342 that covers the heating element 341 and protects it from the outside. A portion of the protective member 342 in the electric heater 34 is disposed in the vaporizing chamber 35 b in the vaporizing case 35. The fuel injection valve 33 injects liquid fuel into the vaporizing chamber 35b. The injected particulate liquid fuel is heated by the electric heater 34.

  The surface of the protection member 342 functions as a heating surface that heats the fuel. The protection member 342 has a rod shape extending in the vertical direction, and a lower portion of the heating surface functions as a vaporization heating surface 343 that heats and vaporizes the injected liquid fuel. The upper part of the heating surface functions as a cracking heating surface 344 described below. The cracking heating surface 344 further heats the fuel vaporized by the vaporization heating surface 343 and decomposes it into hydrocarbons having a small number of carbon atoms. Such cracking is called cracking, and the cracked fuel has a low boiling point.

  It can be said that the vaporization heating surface 343 and the cracking heating surface 344 share the same heat source (heating element 341). The microcomputer 81 controls the energization state of the heat generator 341. For example, the microcomputer 81 controls the heating element 341 so that the fuel is heated to a temperature at which light oil is cracked (350 ° C. to 500 ° C.), whereby the liquid fuel is vaporized and cracked in the mixing chamber 30a. Further, since the cracking possible temperature is higher than the vaporization temperature, the vaporization heating surface 343 inevitably becomes equal to or higher than the vaporization temperature by controlling the heating element 341 to be equal to or higher than the cracking possible temperature.

  As shown in FIG. 3, when the amount of liquid fuel injected into the vaporization case 35 per unit time is larger than the amount of vaporization vaporized per unit time, the liquid fuel is stored in the vaporization case 35. It becomes. In this case, the vaporizing case 35 provides a storage tank that temporarily stores the injected liquid fuel until it is vaporized. The symbol L in the figure indicates the liquid level of the fuel accumulated in the vaporizing case 35. The gaseous fuel evaporated from the liquid level L is further heated and cracked by the cracking heating surface 344 located above the liquid level L.

  The fuel injection valve 33 is disposed so as to spray liquid fuel toward the vaporization heating surface 343. Further, the fuel injection valve 33 is disposed so as to be inclined with respect to the rod-shaped protection member 342 extending in the vertical direction so as to spray liquid fuel from the upper side of the vaporization heating surface 343. In a state where liquid fuel is accumulated in the vaporizing case 35, the fuel injected from the fuel injection valve 33 is sprayed onto the liquid level L.

  In the mixing chamber 30a, the fuel vaporized and cracked by the electric heater 34 and the air containing the oxygen gas supplied by the air pump 31 are mixed. The air-fuel mixture flows through the interelectrode passage 21 a between the electrodes 21 of the discharge reactor 20 and is added to the exhaust passage 10 ex through the supply pipe 24. The discharge reactor 20 oxidizes fuel (hydrocarbon) contained in the air-fuel mixture to generate a reforming reducing agent as a highly active substance. Hereinafter, the production reaction will be described with reference to FIG.

  First, as indicated by reference numeral (1) in FIG. 4, the electrons emitted from the electrode 21 collide with oxygen gas (oxygen molecules) contained in the air-fuel mixture. Then, the oxygen molecules are ionized and become active oxygen (see symbol (2)). Next, the active oxygen reacts with the gaseous fuel (hydrocarbon) contained in the air-fuel mixture to partially oxidize the hydrocarbon (see symbol (3)). Thereby, the reforming / reducing agent in a state where the hydrocarbons are partially oxidized is generated (see reference numeral (4)). Specific examples of the reforming / reducing agent include partial oxides in a state in which a part of the hydrocarbon is oxidized to a hydroxy group (OH) or an aldehyde group (CHO).

  Further, the discharge reactor 20 actively generates ozone as shown in FIG. 5 in a state where the fuel injection by the fuel injection valve 33 is stopped and no fuel flows. That is, first, electrons emitted from the electrode 21 collide with oxygen gas (oxygen molecules) blown by the air pump 31 (see reference numeral (1)). Then, the oxygen molecules are ionized and become active oxygen (see symbol (2)). Then, the active oxygen is oxidized by reacting with the oxygen molecules that are blown (see symbol (5)).

  In short, if a voltage is applied to the electrode 21 to activate the air pump 31, the discharge reactor 20 turns oxygen gas into a plasma state by glow discharge and ionizes oxygen molecules into active oxygen. If the fuel is injected in this state, the discharge reactor 20 partially oxidizes the fuel with active oxygen to generate a reforming and reducing agent. On the other hand, if the fuel injection is stopped, the discharge reactor 20 generates ozone as a highly active substance from the oxygen gas by active oxygen. The generated reforming / reducing agent or ozone flows out from the interelectrode passage 21 a between the electrodes 21 by the blowing pressure of the air pump 31, and is added to the exhaust passage 10 ex through the supply pipe 24.

  The discharge reactor 20 includes a housing 22 that forms a flow passage 22a therein, and an electrode 21 is disposed in the flow passage 22a (see FIG. 1). Hereinafter, the arrangement state of the electrodes 21 in the housing 22 will be described in detail with reference to FIG. As illustrated, the electrode 21 includes an insulating substrate 21b, a metal plate 21c, and an insulating protective film 21d. The insulating substrate 21b is made of ceramic and holds the metal plate 21c. When a high voltage is applied to the metal plate 21c, discharge occurs in the flow passage 22a. The insulating protective film 21d covers the surface of the metal plate 21c from the interelectrode passage 21a side so that the metal plate 21c is not exposed to the interelectrode passage 21a.

  The plurality of electrodes 21 are stacked and arranged via spacers 23. Thereby, the flat electrode 21 is arrange | positioned so that it may mutually oppose in parallel. The pair of electrodes 21 is kept at a predetermined interval by the spacer 23, and an interelectrode passage 21 a is formed between the electrodes 21. The discharge reactor 20 includes a plurality of pairs of electrodes 21. As described with reference to FIGS. 4 and 5, the reforming / reducing agent and ozone are generated between the electrodes 21.

  The microcomputer 81 provided in the ECU 80 includes a storage device that stores a program and a central processing unit that executes arithmetic processing according to the stored program. The ECU 80 controls the operation of the internal combustion engine 10 based on detection values of various sensors. Specific examples of the various sensors include an accelerator pedal sensor 91, an engine speed sensor 92, a throttle opening sensor 93, an intake pressure sensor 94, an intake air amount sensor 95, an exhaust temperature sensor 96, and the like.

  The accelerator pedal sensor 91 detects a user's accelerator pedal depression amount. The engine rotation speed sensor 92 detects the rotation speed of the output shaft 10 a of the internal combustion engine 10. The throttle opening sensor 93 detects the opening of the throttle valve 13. The intake pressure sensor 94 detects the pressure on the downstream side of the throttle valve 13 in the intake passage 10in. The intake air amount sensor 95 detects the mass flow rate of intake air.

  In general, the ECU 80 controls the injection amount and injection timing of combustion fuel injected from a fuel injection valve (not shown) according to the rotation speed of the output shaft 10a and the load of the internal combustion engine 10. Further, the ECU 80 controls the operation of the highly active substance adding device based on the exhaust temperature detected by the exhaust temperature sensor 96. That is, the microcomputer 81 performs control so that the generation of the reforming / reducing agent and the generation of ozone are switched by repeatedly executing the program of the procedure shown in FIGS. 7 and 8 at a predetermined period. These programs are triggered by the ignition switch being turned on as a trigger, and are always executed during the operation period of the internal combustion engine 10.

  First, in step S10 in FIG. 7, the microcomputer 81 operates the air pump 31. In subsequent step S <b> 11, a voltage is applied to the electrode 21 to discharge in the discharge reactor 20. In subsequent step S12, it is determined whether or not the temperature of the reduction catalyst (NOx catalyst temperature) of the NOx purification device 15 is lower than the activation temperature. The NOx catalyst temperature is estimated from the exhaust temperature detected by the exhaust temperature sensor 96. Here, the activation temperature of the reduction catalyst indicates a temperature at which NOx can be reduced and purified by the reforming reducing agent.

  If it is determined that the NOx catalyst temperature is lower than the activation temperature, the ozone generation flag is set to ON in step S13. This ozone generation flag instructs to generate ozone as shown in FIG. On the other hand, if it is determined that the NOx catalyst temperature is not lower than the activation temperature, the reforming flag is set to ON in step S14. This reforming flag instructs to generate a reforming reducing agent as shown in FIG.

  Next, in step S20 of FIG. 8, it is determined whether or not the reforming flag is set to ON. If it is determined that the reforming flag is not on, energization of the electric heater 34 is stopped in the subsequent step S21, and the fuel injection valve 33 is closed so as to stop the fuel injection in step S22. The microcomputer 81 at the time of executing the process of step S22 provides “ozone generation control means”.

  On the other hand, if it is determined that the reforming flag is on, in the subsequent step S23, the amount of reforming reducing agent (necessary reducing agent amount) required by the NOx purification device 15 per unit time is calculated. The microcomputer 81 at the time of executing the process of step S23 provides “necessary amount calculation means”. Hereinafter, a specific example of calculating the necessary reducing agent amount will be described.

  First, the NOx concentration in the exhaust gas and the exhaust amount are calculated based on the operating state of the internal combustion engine 10 such as the load of the internal combustion engine 10, the rotational speed of the output shaft 10a, and the amount of fuel injected for combustion. Next, the NOx amount (NOx emission amount) in the exhaust gas is calculated based on the calculated NOx concentration and the exhaust gas amount. Next, the amount of NOx adsorbed by the NOx purification device 15 (NOx adsorption amount) is calculated based on the calculated NOx emission amount, the supplied amount of reforming / reducing agent, NOx catalyst temperature, and the like. Next, the total NOx amount is calculated by adding the current NOx emission amount to the calculated NOx adsorption amount. Next, the amount of reforming / reducing agent necessary to purify the total NOx amount is calculated as the necessary reducing agent amount.

  After calculating the required reducing agent amount in step S23 as described above, in the subsequent step S24, the target heater temperature is calculated based on the calculated required reducing agent amount. Specifically, the target heater temperature is set higher as the required amount of reducing agent is larger. However, the lower limit value of the target heater temperature is set to be equal to or higher than the crackable temperature.

  In the subsequent step S25, the power supplied to the electric heater 34 is controlled so as to reach the target heater temperature. For example, the supply power is controlled by duty-controlling the pulse width of the voltage applied to the electric heater 34. When the fuel is vaporized, the amount of heat is removed from the vaporization heating surface 343 by the latent heat of vaporization. Therefore, electric power is supplied to the electric heater 34 so as to reach the target heater temperature in consideration of the temperature decrease due to the latent vaporization heat. In the subsequent step S26, the fuel injection is performed by controlling the valve opening time of the fuel injection valve 33 so that the fuel injection amount per unit time becomes the required reducing agent amount. The microcomputer 81 when executing the process of step S26 provides “reforming control means”.

  As described above, the highly active substance adding device according to this embodiment is configured to heat the liquid fuel and reduce the carbon number of the fuel by discharging the oxygen gas by the discharge of the electrode 21 and the liquid fuel. And an electric heater 34 for cracking. Then, by supplying the fuel cracked by the electric heater 34 to the discharge reactor 20, the fuel is partially oxidized with the ionized oxygen gas to generate the reforming and reducing agent.

  Therefore, since the boiling point of the fuel is lowered by being cracked, the fuel is suppressed from being liquefied again when the vaporized fuel is cooled by oxygen gas and the temperature is lowered. That is, the gaseous fuel supplied from the fuel supply pipe 35 a can be prevented from condensing and adhering to the electrode 21. Therefore, the problem that the reforming / reducing agent is added unintentionally at a low exhaust temperature or the addition of the reforming / reducing agent is delayed, that is, the timing of adding the reforming / reducing agent to the exhaust passage 10ex as intended. It is possible to suppress a problem that the control becomes impossible.

  Further, in the present embodiment, the electric heater 34 has a vaporization heating surface 343 that heats and vaporizes the liquid fuel, and a cracking heating surface 344 that further heats and vaporizes the vaporized fuel. As described above, since the vaporization heating surface 343 for vaporization and the cracking heating surface 344 for cracking are separately provided, the thermal load on the cracking heating surface 344 can be reduced as compared with the case where the vaporization heating surface 343 is not provided.

  Furthermore, in this embodiment, the vaporization heating surface 343 and the cracking heating surface 344 share the same heat source (heating element 341), and the temperature of the heating element 341 is set to be equal to or higher than the crackable temperature. Therefore, fuel can be vaporized and cracked with the same heat source, and the heating means can be downsized.

  Here, film boiling that may occur in a portion of the vaporization heating surface 343 that is buried in the liquid fuel will be described with reference to FIG. The stored liquid fuel evaporates from the liquid level L and evaporates. However, when the liquid fuel reaches a certain temperature, nucleate boiling that vaporizes in a portion other than the liquid level L and enters a bubble state occurs. In the example shown in FIG. 3, the portion of the stored liquid fuel that is in contact with the vaporization heating surface 343 has the highest temperature, and nucleate boiling occurs first in this portion. Thereafter, when the liquid fuel is further heated, the number of bubbles increases and the bubbles are connected. Then, as shown by a one-dot chain line in the figure, a gaseous fuel film M is generated on the vaporization heating surface 343. Such a state of boiling in the form of a film is called film boiling.

  When the gaseous fuel film M is formed on the vaporization heating surface 343, the vaporization heating surface 343 is prevented from coming into contact with the liquid fuel, and heat propagation from the vaporization heating surface 343 to the liquid fuel is deteriorated. That is, if the gaseous fuel film M is not formed, the liquid fuel is heated by heat conduction from the vaporization heating surface 343. On the other hand, when the gaseous fuel film M is formed, the liquid fuel is heated by the heat radiation from the vaporization heating surface 343, so that the temperature rise of the liquid fuel is suppressed.

  On the other hand, in the present embodiment, the fuel injection valve 33 is arranged so that the liquid fuel is injected toward the vaporization heating surface 343. Therefore, the injected fuel collides with the gaseous fuel film M and the film M is destroyed. Alternatively, when the injected fuel collides with the liquid level L, the stored fuel is agitated and the membrane M is destroyed. Therefore, since it can accelerate | stimulate contacting the liquid fuel to store to the vaporization heating surface 343, it can suppress that the vaporization amount falls by generation | occurrence | production of film | membrane boiling.

  Furthermore, in the present embodiment, the electrodes 21 have a flat plate shape disposed so as to face each other, and an interelectrode passage 21 a through which oxygen gas flows is formed between the pair of electrodes 21. As described above, when the electrode 21 of the discharge reactor 20 has a parallel plate structure, the discharge can be efficiently performed in a limited area, but as a contradiction, the surface to which the fuel adheres becomes wide. Moreover, the fuel adhering to the surface tension tends to stay in the portion of the electrode 21 that forms the end of the interelectrode passage 21a. Therefore, the above-described effects such as suppression of adhesion to the electrode 21 are more effectively exhibited.

  Furthermore, in this embodiment, the discharge reactor 20 which ionizes supplied oxygen gas by discharge and makes it active oxygen, and the fuel injection valve 33 which supplies a fuel to the discharge reactor 20 are provided. And the ozone production | generation control means by FIG.8 S22 and the reforming control means by step S26 are provided by the microcomputer 81. FIG. Therefore, if fuel injection is stopped by the ozone generation control means, ozone is generated by active oxygen, and if fuel is injected by the reforming control means, the fuel is oxidized (reformed) by active oxygen and reformed and reduced. An agent is produced. Therefore, both the reforming of the reducing agent and the generation of ozone can be realized with one discharge reactor 20.

  Here, when the liquid fuel adheres to the electrode 21, when switching from the generation of the reforming / reducing agent to the generation of ozone, the adhering fuel is vaporized and the electrode is vaporized even though the fuel supply is stopped. There will be fuel in the inter-passage 21a. Then, the active oxygen generated by the discharge oxidizes the fuel to generate a reforming and reducing agent, and the amount of ozone that is generated by oxidizing oxygen molecules is reduced. On the other hand, according to this embodiment, since the fuel adhesion to the electrode 21 can be suppressed as described above, it is possible to suppress the problem that the reforming / reducing agent is generated when the ozone generation flag is on.

  Furthermore, in this embodiment, the fuel injection valve 33 which supplies the liquid fuel to the electric heater 34 in the state atomized is provided. Therefore, the time required to vaporize and crack the liquid fuel with the electric heater 34 is shortened. Therefore, the responsiveness of adding the modified reducing agent with respect to the necessary reducing agent amount can be accelerated.

  Further, in the present embodiment, the necessary reducing agent amount is calculated in step S23 of FIG. 8, and the heater temperature and the fuel injection amount are controlled according to the necessary reducing agent amount. According to this, when the amount of necessary reducing agent is large, not only the fuel injection amount can be increased, but also the heater temperature can be increased to increase the addition amount. On the other hand, when the required amount of reducing agent is small, the power consumption in the electric heater 34 can be reduced by reducing the fuel injection amount and lowering the heater temperature.

Furthermore, in this embodiment, the reduction catalyst has a function of adsorbing NOx. Therefore, when ozone generated in the discharge reactor 20 is added to the exhaust passage 10ex, NO in the exhaust is oxidized to NO ₂ and is easily adsorbed by the reduction catalyst. Therefore, the generated ozone can be used for improving NOx adsorption on the reduction catalyst.

Further, in the present embodiment, ozone is generated on the condition that the reduction catalyst is lower than the activation temperature, and the reforming reducing agent is generated on the condition that the reduction catalyst is higher than the activation temperature. Therefore, it can be avoided that the reforming reducing agent is added to the exhaust passage 10ex at a low temperature when the reduction catalyst cannot exhibit the reducing ability. And, at the low temperature, ozone is added to the exhaust passage 10ex to oxidize NO to NO ₂ and improve NOx adsorption, so that NOx can be prevented from flowing out of the NOx purification device 15 without being purified at low temperatures. Further, although ozone is more likely to be thermally decomposed as the temperature is higher, in the present embodiment, ozone is added to the exhaust passage 10ex when the temperature is low, and is not added except when the temperature is low. Therefore, the possibility that the added ozone is thermally decomposed by exhaust heat can be reduced.

(Second Embodiment)
In this embodiment shown in FIG. 9, mesh members 345 and 346 are attached to the vaporization heating surface 343 and the cracking heating surface 344, respectively. The mesh member 345 attached to the vaporization heating surface 343 functions to attract the liquid fuel accumulated in the vaporization case 35 by the capillary phenomenon and adhere to the vaporization heating surface 343, thereby providing a “capillary member”. According to this, since the liquid fuel is forcibly attached to the vaporization heating surface 343, the formation of the film M shown in FIG. 3 is suppressed. Therefore, it can suppress that the vaporization amount falls by generation | occurrence | production of film | membrane boiling.

  The mesh member 346 attached to the cracking heating surface 344 functions to increase the area for heating the vaporized fuel and provides a “heating area expanding member”. According to this, since the mesh member 346 heated by the cracking heating surface 344 heats the gaseous fuel, the gaseous fuel is heated by both the cracking heating surface 344 and the mesh member 346. This can be said that the mesh member 346 increases the contact area between the cracking heating surface 344 and the gaseous fuel. Therefore, it is promoted that the gaseous fuel is heated by the cracking heating surface 344, and the cracking of the gaseous fuel is promoted.

(Third embodiment)
In the embodiment shown in FIGS. 2 and 9, the electric heater 34 is installed in a direction in which the heating surface extends in the vertical direction. On the other hand, in this embodiment shown in FIG. 10, the electric heater 34 is installed in the direction in which the heating surface extends in the left-right direction. The fuel injection valve 33 and the electric heater 34 are arranged so that the liquid fuel injected from the fuel injection valve 33 directly adheres to the vaporization heating surface 343 and does not directly adhere to the cracking heating surface 344.

(Fourth embodiment)
In the embodiment shown in FIGS. 2, 9, and 10, the vaporization heating surface 343 and the cracking heating surface 344 share the same heat source (heating element 341). On the other hand, in this embodiment shown in FIG. 11, the first electric heater 34A for vaporization heating and the second electric heater 34B for cracking heating are provided separately.

  Each of the electric heaters 34A and 34B includes heating elements 341A and 341B, and protection members 342A and 342B that cover the heating elements 341A and 341B and are insulated and protected from the outside. The surface of the protection member 342A functions as a heating surface for vaporization heating, and the surface of the protection member 342B functions as a heating surface for cracking heating. A first case 351 to which the fuel injection valve 33 and the first electric heater 34A are attached and a second case 352 to which the second electric heater 34B is attached are connected by a communication pipe 353.

  In the first space 351a in the first case 351, the injected liquid fuel is heated and vaporized by the first electric heater 34A. The vaporized fuel flows into the second space 352a in the second case 352 through the communication pipe 353, and is heated and cracked by the second electric heater 34B. The cracked gaseous fuel flows into the mixing chamber 30a through the fuel supply pipe 35a.

(Fifth embodiment)
In the embodiment shown in FIGS. 2, 9, 10, and 11, liquid fuel is injected from the injection hole of the fuel injection valve 33 to be atomized. On the other hand, in this embodiment shown in FIG. 12, the fuel injection valve 33 is replaced with an electromagnetic valve 33A. When the microcomputer 81 controls the electromagnetic valve 33A to open, the fuel supplied from the pump 33p flows out from the electromagnetic valve 33A to the vaporizing case 35 without being atomized, and is temporarily stored in the vaporizing case 35. The Thereafter, the stored liquid fuel is heated by the vaporization heating surface 343 and evaporated from the liquid surface L, and then further heated by the cracking heating surface 344 and cracked.

  However, according to the valve system according to the present embodiment using the electromagnetic valve 33A, the above-described film boiling cannot be sufficiently suppressed unlike the injector system using the fuel injection valve 33. FIG. 13 shows the test results showing the effect of suppressing the film boiling by the injector method. In FIG. 13, reference numeral L1 shows the injector method and reference character L2 shows the valve method. In this test, the heater temperature at the boiling point Ta is further increased, and the relationship between the amount of vaporization per unit time and the heater temperature is measured when the temperature is increased to a temperature Tb or higher at which cracking is possible. Yes.

  As shown in the figure, the vaporization amount similarly increases in both the injector method and the valve method until the heater temperature rises from the boiling point Ta and reaches a certain temperature. However, in the case of the valve method, when the heater temperature reaches a certain temperature, film boiling occurs and the amount of vaporization decreases rapidly. On the other hand, in the case of the injector system, even if the heater temperature is increased beyond the temperature Tb at which cracking is possible, film boiling does not occur immediately and the amount of vaporization increases. Therefore, if the injector system is employed to suppress the occurrence of film boiling, film boiling does not occur even if the heater temperature is controlled to a temperature Tb at which cracking is possible.

(Sixth embodiment)
In the first embodiment, the discharge reactor 20 is installed downstream of the electric heater 34 in the air flow. On the other hand, in this embodiment, as shown in FIG. 14, the discharge reactor 20 is installed upstream of the electric heater 34 in the air flow. The air blown by the air pump 31 first flows into the discharge reactor 20. When discharging is performed between the electrodes 21 of the discharge reactor 20, ozone is generated from oxygen in the air. The ozone thus generated is supplied to the supply pipe 24 together with air.

  The structures of the discharge reactor 20, the vaporization case 35, the fuel injection valve 33, and the electric heater 34 according to the present embodiment are the same as those in the first embodiment. And also about the control content of the fuel injection valve 33 and the electric heater 34, this embodiment is the same as the said 1st Embodiment. Therefore, the liquid fuel injected from the fuel injection valve 33 is vaporized and cracked in the vaporization chamber 35b.

  In the first embodiment, the cracked gaseous fuel is supplied to the discharge reactor 20, and the fuel is partially oxidized inside the discharge reactor 20 to be reformed. On the other hand, in the present embodiment, the fuel is partially oxidized mainly in the supply pipe 24. That is, the fuel that has been vaporized and cracked in the vaporizing chamber 35b flows out of the fuel supply pipe 35a, is mixed in the supply pipe 24 with the air blown by the air pump 31, and is partially oxidized by oxygen contained in this air ( Modified). The fuel (reducing agent) thus reformed is added to the exhaust passage 10ex through the supply pipe 24. The air blown by the air pump 31 contains ozone generated by the discharge reactor 20, and this ozone promotes the partial oxidation reaction.

  As described above, the present embodiment also includes the electric heater 34 (heating means) that heats the supplied liquid hydrocarbon and cracks it so as to reduce the carbon number of the hydrocarbon. The heating means has a vaporization heating surface 343 for heating and vaporizing liquid hydrocarbons, and a cracking heating surface 344 for further heating and cracking the vaporized hydrocarbons. And a reforming reducing agent is produced | generated as a highly active substance from the hydrocarbon cracked by the heating means.

  Therefore, since the boiling point of the fuel is lowered by being cracked, the fuel is suppressed from being liquefied again when the vaporized fuel is cooled by the air blown from the air pump 31 and the temperature is lowered. That is, it is possible to suppress the gaseous fuel supplied from the fuel supply pipe 35 a from condensing and adhering to the inner wall surface of the supply pipe 24. Therefore, it is possible to suppress a problem that the fuel adhering in this way is added to the exhaust passage 10ex at a time contrary to the intention.

(Other embodiments)
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made as illustrated below. Not only combinations of parts that clearly show that combinations are possible in each embodiment, but also combinations of the embodiments even if they are not explicitly stated unless there is a problem with the combination. Is also possible.

  In controlling the fuel injection amount in step S26 of FIG. 8, it is desirable to control the injection amount so that the cracking heating surface 344 is not buried. According to this, it is possible to suppress the fuel vaporized in the vaporization case 35 from flowing out from the fuel supply pipe 35a without being cracked.

  In the embodiment shown in FIG. 1, the electric heater 34 is employed as a heating means for heating and vaporizing liquid hydrocarbons, but a heat exchanger using waste heat of the internal combustion engine 10 is employed as the heating means. Also good. In the embodiment shown in FIG. 1, the liquid fuel is supplied from the fuel injection valve 33 to the mixing chamber 30a. However, the liquid fuel is heated and vaporized outside the mixing chamber 30a, and the gaseous fuel is mixed into the mixing chamber 30a. You may make it supply to 30a.

  In the embodiment shown in FIG. 1, the discharge reactor 20 is installed so that the plate-like electrode 21 is in a horizontal orientation in a vehicle-mounted state. On the other hand, the liquid fuel attached to the electrode 21 may be easily dropped by gravity by installing the plate-shaped electrode 21 so that the plate surface is inclined with respect to the horizontal direction. Moreover, you may install so that the plate | board surface of the plate-shaped electrode 21 may become the direction parallel to the up-down direction.

  In the embodiment shown in FIG. 1, the fuel injection valve 33 is employed as the atomizing means for atomizing liquid hydrocarbons and supplying them to the heating means. On the other hand, a vibrating device that vibrates the liquid fuel and makes it atomize by bringing the liquid fuel into contact with a vibration plate that vibrates at a high frequency such as ultrasonic waves may be employed as the atomizing means.

  In the embodiment shown in FIG. 1, an air pump 31 that blows air is used as oxygen supply means for supplying oxygen gas to the discharge reactor 20. On the other hand, a part of the intake air of the internal combustion engine 10 may be branched and allowed to flow into the discharge reactor 20. In this case, in the intake passage 10in located on the downstream side of the compressor 11c, the intake air may be branched from the upstream portion of the cooler 12, or the intake air may be branched from the downstream portion of the cooler 12.

  Further, a mode in which the high-temperature intake air before being cooled by the cooler 12 is branched from the upstream portion of the cooler 12 and a mode in which the low-temperature intake air after being cooled by the cooler 12 from the downstream portion of the cooler 12 are branched. You may make it switch. In this case, it is desirable to suppress the destruction of the generated ozone by the heat of the intake air by setting a mode in which the low-temperature intake air is branched when ozone is generated. In addition, it is desirable to suppress the cooling of the fuel heated by the electric heater 34 by the intake air in the mixing chamber 30a by setting the mode in which the high temperature intake air is branched when the reforming / reducing agent is generated.

  In the case of a complete stop in which both the generation of ozone and the generation of the reforming reducing agent are stopped, the discharge by the discharge reactor 20 may be stopped to suppress wasteful power consumption. Specific examples of the case of complete stop include a case where the NOx catalyst temperature is lower than the activation temperature and the NOx adsorption amount is saturated, or the NOx catalyst temperature exceeds the reducible range and becomes high. There are cases. In the case of the complete stop, power consumption may be reduced by stopping the operation of the air pump 31 and stopping the supply of oxygen gas.

  In the above embodiment shown in FIG. 1, a reduction catalyst that physically captures (that is, adsorbs) NOx is employed. However, the combustion system employs a reduction catalyst that traps (that is, stores) NOx by chemical bonding. Alternatively, a highly active substance addition apparatus may be applied.

  When the internal combustion engine 10 is burned in a state leaner than the stoichiometric air-fuel ratio, the highly active substance addition device is applied to a combustion system in which the NOx purification device 15 adsorbs NOx and reduces NOx in other than lean combustion. May be. In this case, ozone may be generated at the time of lean combustion, and a reforming reducing agent may be generated at times other than lean combustion. As a specific example of the catalyst that captures NOx during lean combustion in this way, an occlusion reduction catalyst using platinum and barium supported on a carrier can be cited.

The highly active substance addition device may be applied to a combustion system in which the NOx purification device 15 that does not have an adsorption or storage function is employed. In this case, ozone generated in the discharge reactor 20 may be used for regeneration of the DPF 14. That is, by adding ozone upstream of the DPF 14, NO in the exhaust is oxidized to NO ₂ and flows into the DPF 14. Then, the carbon component of the fine particles collected and deposited by the DPF 14 reacts with NO ₂ and is oxidized. Thereby, the fine particles deposited on the DPF 14 are removed, and the DPF 14 is regenerated.

  In the first embodiment, the NOx catalyst temperature used in step S <b> 12 of FIG. 7 is estimated from the exhaust temperature detected by the exhaust temperature sensor 96. On the other hand, a temperature sensor may be attached to the NOx purification device 15 to directly measure the NOx catalyst temperature. Alternatively, the NOx catalyst temperature may be estimated based on the rotation speed of the output shaft 10a, the load of the internal combustion engine 10, and the like.

  In the embodiment shown in FIG. 1, the discharge reactor 20 is configured by arranging flat-plate electrodes 21 so as to face each other in parallel. On the other hand, the discharge reactor may be constituted by a needle-like electrode protruding in a needle shape and an annular electrode surrounding the needle-like electrode in an annular shape.

  In the embodiment shown in FIG. 1, a highly active substance addition device is applied to a combustion system mounted on a vehicle. On the other hand, a highly active substance addition device may be applied to a stationary combustion system. In the embodiment shown in FIG. 1, a highly active substance addition device is applied to a compression self-ignition diesel engine, and light oil used as a fuel for combustion is used as a reducing agent. On the other hand, gasoline used as a fuel for combustion may be used as a reducing agent by applying a highly active substance addition device to an ignition ignition type gasoline engine.

  In the embodiment shown in FIG. 14, the highly active substance addition apparatus includes the discharge reactor 20, but the present invention is not limited to the apparatus including the discharge reactor 20, and the apparatus that eliminates the discharge reactor 20 may be used. Applicable. In this case, although the partial oxidation reaction cannot be promoted by ozone, the cracked gaseous fuel can be partially oxidized (reformed) by oxygen in the air, and the reformed fuel can be added to the exhaust passage 10ex. it can.

  In the embodiment shown in FIG. 14, the gaseous fuel cracked in the vaporization case 35 and the ozone generated in the discharge reactor 20 are mixed in the supply pipe 24. That is, it can be said that the gaseous fuel supply path and the ozone supply path are connected in parallel to the supply pipe 24. On the other hand, ozone may be supplied to the vaporizing case 35, and gaseous fuel and ozone may be mixed in the vaporizing case 35 and then blown to the supply pipe 24. That is, the ozone supply path, the gaseous fuel supply path, and the supply pipe 24 may be connected in series while the discharge reactor 20 is installed on the upstream side of the vaporization case 35.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 10ex ... Exhaust passage, 15 ... NOx purification apparatus, 20 ... Discharge reactor, 21 ... Electrode, 22a ... Flow passage, 34, 34A, 34B ... Electric heater (heating means).

Claims (8)

A NOx purification device (15) for purifying NOx contained in the exhaust gas of the internal combustion engine (10) on the reduction catalyst is provided in a combustion system provided in the exhaust passage (10ex), and upstream of the reduction catalyst in the exhaust passage. In a highly active substance addition device that adds a highly active substance to the side,
Heating means ( 34A, 34B) for heating the supplied liquid hydrocarbon and cracking it to reduce the carbon number of the hydrocarbon;
It said heating means, vaporizing heating surface to heat vaporizing hydrocarbons of the liquid (343,342A), and the vaporized hydrocarbons further heated while chromatic cracking heated surface cracking (344,342B), the heating element for heating the vaporizing heating surface (341A) and the heating element for heating the cracking heating surface (341B) possess separately,
The highly active substance addition apparatus characterized by producing | generating the reforming | reducing reducing agent as said highly active substance by partially oxidizing the hydrocarbon cracked by the said heating means. It has an electrode (21) for generating ozone by discharge, and further comprises a discharge reactor (20) arranged upstream of the heating means so as to supply the generated ozone to the heating means. Item 2. The highly active substance addition device according to Item 1. A discharge reactor (20) which forms a flow passage (22a) through which oxygen gas containing at least oxygen flows and has an electrode (21) disposed in the flow passage and ionizes the oxygen gas by discharging the electrode. )
By supplying the cracked hydrocarbon to the flow path, the hydrocarbon is oxidized with oxygen gas ionized by the discharge reactor to generate a reforming and reducing agent as the highly active substance. The highly active substance adding device according to claim 1. The electrodes have a flat plate shape arranged to face each other,
The highly active substance addition apparatus according to claim 3 , wherein an interelectrode passage (21a) through which the oxygen gas flows is formed between the pair of electrodes. Ozone generation control means (S22) for controlling the generation of ozone from the oxygen gas ionized by the discharge reactor by stopping the supply of hydrocarbons to the heating means;
Reform control means (S26) for controlling to oxidize hydrocarbons with oxygen gas ionized by the discharge reactor to produce the reforming reductant by supplying hydrocarbons to the heating means. When,
The highly active substance addition apparatus according to claim 3 or 4 , characterized by comprising: The highly active substance addition device according to any one of claims 1 to 5 , further comprising hydrocarbon injection means (33) for injecting the liquid hydrocarbon toward the vaporization heating surface. Wherein the vaporization heating surface, any one of claims 1-6, characterized in that it said capillary member to adhere to the vaporization heating surface (345) is mounted attracted by the hydrocarbon capillary action of the liquid The highly active substance addition apparatus described in 1. The highly active substance addition device according to any one of claims 1 to 7 , wherein a mesh-like mesh member (346) is attached to the cracking heating surface.

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