WO2020137750A1 - Catalytic reaction system for engine - Google Patents

Abstract

A catalytic reaction system (10) for an engine (90) is equipped with: a catalyst (11) provided in an exhaust passage (91) of the engine (90); a mixer (12) provided upstream from the catalyst (11); a sprayer device (13) for spraying a liquid reduction agent, which is a prescribed liquid, in the form of a spray toward the mixer (12); and a spray control unit (24) for controlling the spray particle size and/or the spray velocity of the sprayer device (13) in accordance with the state of exhaust air in the exhaust passage (91), which is a catalyst installation passage in which the catalyst is provided, such that atomization or gasification of the spray particles proceeds downstream from the mixer (12).

Description

Engine catalytic reaction system Cross-reference of related applications

This application is based on the patent application No. 2018-247805 filed on December 28, 2018 and the patent application No. 2019-179747 filed on September 30, 2019, and the description content here. Is used.

The present disclosure relates to a catalytic reaction system of an engine.

Conventionally, a catalytic reaction system that uses a catalyst to perform exhaust purification and fuel reforming, for example, has been known. For example, the catalyst reaction system disclosed in Patent Document 1 has a catalyst provided in an exhaust passage, a mixer having a plurality of fins radially arranged so as to form a swirl flow, and urea water directed toward the mixer. And an injector for injecting to reduce and purify nitrogen oxides in the exhaust gas.

JP, 2014-148896, A

In Patent Document 1, the spray of urea water is homogenized in the circumferential direction of the exhaust passage by the swirling flow of the mixer. However, there are cases where the spray is biased outward in the radial direction by the centrifugal force due to the swirling flow, and homogenization beyond a predetermined level cannot be expected. Therefore, it has been difficult to maintain the homogenized state of the injection product from the injector at the catalyst inlet.

The present disclosure has been made in view of the above points, and an object of the present disclosure is to provide a catalytic reaction system capable of maintaining a homogenized state of the injection product from the injection device at the catalyst inlet.

An engine catalytic reaction system of the present disclosure includes a catalyst provided in an exhaust system passage of an engine, a stirring unit provided upstream of the catalyst, an injector that injects a predetermined liquid as a spray toward the stirring unit, and a stirring unit. A spray control unit that controls one or both of the injection particle size and the injection speed of the injection device according to the exhaust state of the catalyst installation passage section where the catalyst is provided so that atomization or vaporization of the spray on the downstream side of the section proceeds. And

By performing such spray control, the centrifugal state due to the swirling flow will be suppressed in the spray state on the downstream side of the stirring section. For example, as the injection particle size becomes smaller, the total surface area of the spray becomes larger, the heat reception from the exhaust gas is promoted, and the vaporization of the spray progresses. Further, as the injection speed increases, the spray collides with the wall surface vigorously, and atomization and vaporization of the spray progress. Therefore, since the centrifugal force due to the swirling flow is sufficiently reduced, the spray is less likely to be biased outward in the radial direction, so that the homogenized state of the injection product from the injection device at the catalyst inlet can be maintained. Thereby, the catalytic reaction is suitably performed.

The above and other objects, features and advantages of the present disclosure will become more apparent by the following detailed description with reference to the accompanying drawings. The drawing is
FIG. 1 is a schematic view showing a catalytic reaction system of a first embodiment and an engine to which the catalytic reaction system is applied, FIG. 2 is a diagram showing a necessary supply amount calculation map, FIG. 3 is a diagram showing a target injection pressure calculation map, FIG. 4 is a flowchart for explaining the processing executed by the control unit, FIG. 5 is a sub-flowchart explaining the processing executed by the control unit, FIG. 6 is a schematic view showing a catalytic reaction system of the second embodiment and an engine to which the catalytic reaction system is applied, FIG. 7 is a diagram showing the relationship between the injection particle size and the injection speed together with the control range, FIG. 8 is a diagram showing the relationship between the injection particle diameter and the injection speed together with the control range, and is a diagram showing a state in which the exhaust flow rate is larger than that in the state shown in FIG. FIG. 9 is a diagram showing the relationship between the wall surface temperature and the threshold value, FIG. 10 is a diagram showing a map that stores the homogeneity of the spray with respect to the spray particle size and the spray velocity FIG. 11 is a sub-flowchart illustrating the processing executed by the control unit, FIG. 12 is a schematic diagram showing a catalytic reaction system of the third embodiment and an engine to which the catalytic reaction system is applied, FIG. 13 is a diagram showing the relationship between the required injection particle size and the valve lift amount, FIG. 14 is a diagram showing the relationship between the injection pressure and the injection speed for each valve lift amount, FIG. 15 is a diagram showing the relationship between the injection pressure and the injection particle diameter for each valve lift amount. FIG. 16 is a diagram showing the relationship between the injection particle size and the injection speed together with the control range, FIG. 17 is a diagram showing the relationship between the injection particle diameter and the injection speed together with the control range, and is a diagram showing a state in which the exhaust flow rate is larger than that in the state shown in FIG. FIG. 18 is a sub-flowchart illustrating the processing executed by the control unit, FIG. 19 is a schematic diagram showing a catalytic reaction system of the fourth embodiment and an engine to which the catalytic reaction system is applied, FIG. 20 is a diagram showing a fuel reforming amount calculation map, FIG. 21 is a schematic diagram showing a catalytic reaction system of the fifth embodiment and an engine to which the catalytic reaction system is applied, FIG. 22 is a schematic view showing the catalytic reaction system of the sixth embodiment and the engine to which the catalytic reaction system is applied, FIG. 23 is a diagram showing the relationship between the engine speed, the accelerator opening, and the required supply amount used by the control unit in another embodiment.

A plurality of embodiments of the engine catalytic reaction system will be described below with reference to the drawings. The configurations that are substantially the same between the embodiments are given the same reference numerals, and description thereof will be omitted.

[First Embodiment]
The catalytic reaction system of the first embodiment is applied to the engine 90 shown in FIG. The catalytic reaction system 10 includes a catalyst 11, a mixer 12, an injection device 13, and a control unit 14.

The catalyst 11 is provided in the middle of the exhaust passage 91 of the engine 90, and reduces and purifies a predetermined component in the exhaust. The exhaust passage 91 is an exhaust system passage through which exhaust flows, and is also a catalyst installation passage portion in which the catalyst 11 is provided. In the first embodiment, the catalyst 11 selectively reacts urea water as a reducing agent with nitrogen oxides (hereinafter, NOx) in exhaust gas to decompose NOx into nitrogen gas N ₂ or the like to render it harmless. With function. In the first embodiment, the catalytic reaction system 10 is an exhaust gas purification system.

The mixer 12 as a stirring unit is provided on the upstream side of the catalyst 11 in the exhaust passage 91, and mixes the reducing agent and the exhaust with stirring. The reducing agent is supplied to the mixer 12 in a mist state (that is, spray), a gas state, or a mixed state thereof.

The injector 13 includes a tank 16 for storing urea water, a pump 17 for pumping the urea water in the tank 16, and a urea water as a “predetermined liquid” pumped from the pump 17 as a spray in the exhaust passage 91. The injection valve 18 which injects toward 12 is provided. The injection valve 18 is provided upstream of the mixer 12 in the exhaust passage 91.

The control unit 14 is a control unit of the engine 90 as well as a control unit of the catalytic reaction system 10. The control unit 14 includes sensors such as an accelerator opening sensor 93, an engine speed sensor 94, an intake amount sensor 95, an exhaust amount sensor 96, an exhaust temperature sensor 97, a NOx concentration sensor 98, and a catalyst temperature sensor 99, and not shown. Another control unit is connected. The control unit 14 executes a program process based on the detection signal of each sensor and controls the driving of the fuel addition valve 92, the pump 17, the injection valve 18, and the like. The exhaust gas sensor 96, the exhaust gas temperature sensor 97, and the NOx concentration sensor 98 are installed immediately downstream of the engine 90, but the invention is not limited to this, and they may be installed immediately upstream of the catalyst 11.

Specifically, the control unit 14 has an information acquisition unit 21, a temperature determination unit 22, a supply amount calculation unit 23, and a spray control unit 24.

The information acquisition unit 21 acquires various information such as the exhaust flow rate, exhaust temperature, NOx concentration, and catalyst temperature of the catalyst installation passage section from the detection signals of various sensors.

The temperature determination unit 22 determines whether or not the catalyst temperature has reached the “temperature at which the NOx purification reaction occurs in the catalyst 11”. That is, it is determined whether the catalyst temperature Tc is equal to or higher than the threshold value Tx. When the catalyst temperature is not equal to or higher than the threshold value Tx, purification cannot be performed, and thus the injection device 13 does not inject the urea water.

The supply amount calculation unit 23 calculates the supply amount of urea water required for purifying NOx by the catalyst 11 (hereinafter, required supply amount) according to the operating state of the engine 90. In the first embodiment, the exhaust flow rate, the exhaust temperature, and the NOx concentration are used as the information indicating the operating state. Further, the required supply amount W of urea water is calculated based on the exhaust gas flow rate Q, the exhaust gas temperature T, and the NOx concentration C using a three-dimensional map as shown in FIG.

The spray control unit 24 can control the state of the spray supplied by the injection device 13. The spray control unit 24 controls the injection particle size and the injection speed of the injection device 13 in accordance with the exhaust state of the exhaust passage 91 so that atomization or vaporization of the spray on the downstream side of the mixer 12 proceeds. Atomization and vaporization of the spray are important for successfully mixing the spray on the swirl flow after the mixer 12. The spray control unit 24 controls the state of droplets of urea water at the time of injection in order to create an optimum state of the reducing agent (that is, high atomization or high vaporization rate) at the outlet of the mixer 12. In order to promote atomization or vaporization of the spray, it is effective to make the injection particle size of the injection device 13 relatively small and to make the injection speed of the injection device 13 relatively high.

Specifically, when vaporization due to heat received from the exhaust is dominant as a phenomenon that occurs with respect to spray, the total surface area of the spray is increased by decreasing the injection particle size, heat reception from the exhaust is promoted, and Vaporization progresses. Therefore, in this case, atomization is required as the exhaust gas temperature is lower and the exhaust gas flow rate is increased. Further, when atomization and vaporization due to collision with the wall surface are dominant as phenomena that occur with respect to the spray, the spray speed increases and the spray vigorously collides with the wall surface of the mixer 12, and atomization and vaporization of the spray progress. .. Therefore, in this case, it is necessary to increase the injection speed as the exhaust gas temperature is lower, and it is better that the injection particle diameter is to some extent. Thus, the required injection method differs depending on the phenomenon of focusing. In the first embodiment, instead of continuously ejecting the same spray as in the conventional case, by controlling the spray particle size and the spray speed according to the state of exhaust gas, the spray at the outlet of the mixer 12 is optimized and the spray at the inlet of the catalyst 11 is optimized. Maintain a homogenized state of the reducing agent.

In the first embodiment, the map as shown in FIG. 3 is used, the target injection pressure P is calculated based on the exhaust temperature T and the exhaust flow rate Q, and the injection pressure of the injection device 13 is adjusted to adjust the injection particle size and the injection. The speed is controlled at the same time. The target injection pressure P is an injection pressure that provides an injection particle size and an injection speed necessary to achieve a target value of homogeneity of the reducing agent at the catalyst inlet (hereinafter, target homogeneity). The target homogeneity corresponds to a desired homogenized state of the reducing agent in the circumferential direction and the radial direction of the exhaust passage 91.

Each functional unit 21 to 24 of the control unit 14 may be realized by hardware processing by a dedicated logic circuit, or a CPU executes a program previously stored in a memory such as a computer-readable non-transitory tangible recording medium. It may be realized by software processing by doing, or may be realized by a combination of both. Which part of each of the functional units 21 to 24 is realized by hardware processing and which part is realized by software processing can be appropriately selected. This also applies to the functional units described below.

(Process executed by the control unit)
The control unit 14 executes each process shown in FIG. The routine of FIG. 4 is repeatedly executed at a predetermined timing. Hereinafter, “S” means a step.

First, in S10, the exhaust flow rate Q, the exhaust temperature T, the NOx concentration C, and the catalyst temperature Tc are acquired from the detection signals of various sensors. After S10, the process proceeds to S20.

At S20, it is determined whether the catalyst temperature Tc is equal to or higher than the threshold value Tx. When the catalyst temperature Tc is equal to or higher than the threshold value Tx (S20: YES), the process proceeds to S30. When the catalyst temperature Tc is lower than the threshold value Tx (S20: NO), the process exits the routine of FIG.

In S30, the required supply amount W is calculated according to the information acquired in S10. After S30, the process proceeds to S40.

At S40, the subroutine for spray control shown in FIG. 5 is called and executed. When the subroutine of FIG. 5 is started, the target injection pressure P of the injector 13 is calculated based on the exhaust temperature T and the exhaust flow rate Q in S101. After S101, the process proceeds to S102.

In S102, the pump 17 is controlled so that the injection pressure of the injection device 13 becomes the target injection pressure. After S102, the process returns to the main routine of FIG.

In S50 of FIG. 3, the injection valve 18 is driven and the reducing agent is injected. After S50, the process exits the routine of FIG.

(effect)
As described above, in the first embodiment, the catalytic reaction system 10 uses the catalyst 11 provided in the exhaust passage 91 of the engine 90, the mixer 12 provided upstream of the catalyst 11, and the liquid of the reducing agent as the spray. The injection device 13 that injects toward the mixer 12, and the injection particle size and the injection speed of the injection device 13 according to the exhaust state of the exhaust passage 91 so that atomization or vaporization of the spray on the downstream side of the mixer 12 proceeds. And a spray control unit 24 for controlling.

By performing such spray control, the spray state on the downstream side of the mixer 12 becomes a state in which the centrifugal force due to the swirling flow is suppressed. For example, as the injection particle size becomes smaller, the total surface area of the spray becomes larger, the heat reception from the exhaust gas is promoted, and the vaporization of the spray progresses. Further, as the injection speed increases, the spray collides with the wall surface vigorously, and atomization and vaporization of the spray progress. Therefore, since the centrifugal force due to the swirling flow is sufficiently small, the spray is less likely to be biased outward in the radial direction, and the homogenized state of the reducing agent at the catalyst inlet can be maintained. As a result, the purifying reaction on the catalyst 11 is suitably performed.

Further, in the first embodiment, the spray control unit 24 adjusts the injection pressure of the injection device 13 to simultaneously control the injection particle size and the injection speed. Thereby, the injection particle diameter and the injection speed can be controlled relatively easily.

[Second Embodiment]
In the second embodiment, the spray control unit 34 shown in FIG. 6 switches the control range of the injection particle size and the injection speed between the first control range and the second control range according to the exhaust flow rate. As shown in FIG. 7, the first control range A1 is a control range in which the injection particle size becomes relatively large. The second control range A2 is a control range in which the injection particle size is relatively small. The first control range A1 and the second control range A2 are ranges including a combination of the injection particle diameter and the injection speed necessary to achieve the target homogeneity of the reducing agent at the catalyst inlet.

Atomization and vaporization are important in order to mix the spray well on the swirl flow after the mixer 12. In the second control range A2, vaporization by receiving heat from the exhaust is dominant as a phenomenon that occurs with respect to the spray. In other words, the smaller the injection particle size, the larger the total surface area of the spray, the heat received from the exhaust gas is promoted, and the vaporization of the spray progresses. On the other hand, in the first control range A1, as phenomena that occur with respect to spraying, atomization and vaporization due to collision with the wall surface are dominant. In other words, as the injection speed increases, the spray vigorously hits the wall surface of the mixer 12, and atomization and vaporization of the spray proceed.

The solid line Lc in FIG. 7 shows the injection particle diameter and the injection speed that change depending on the adjustment of the injection pressure of the injection device 13. In FIG. 7, the solid line Lc passes through both the first control range A1 and the second control range A2. In this case, the target homogeneity can be achieved in both the first control range A1 and the second control range A2. Since the homogenization is possible with less energy (low speed ≈ low injection pressure) when the large particle size is maintained, for example, the first control range A1 is used, and the injection speed is the highest in the first control range A1. The point p1 that is a smaller combination is adopted.

On the other hand, in FIG. 8 showing a state where the exhaust flow rate is larger than the state shown in FIG. 7, the solid line Lc passes only the second control range A2. In this case, the target homogeneity can be achieved in the second control range A2. For example, the point p2, which is the combination in which the injection speed is smallest in the second control range A2, is adopted.

In this way, if the exhaust flow rate is above the specified value, the target homogeneity cannot be achieved with a large particle size, so atomization will be performed. Hereinafter, the predetermined value will be referred to as a "threshold value Qd". The spray control unit 34 in FIG. 6 uses the second control range A2 when the exhaust gas flow rate is equal to or greater than the threshold value Qd.

The information acquisition unit 31 shown in FIG. 6 acquires the wall surface temperature Tm of the mixer 12 (measured temperature of the mixer 12) from the detection signal of the wall surface temperature sensor 19. As shown in FIG. 9, the spray control unit 34 performs correction so that the lower the wall surface temperature Tm, the smaller the threshold value Qd. In other embodiments, the estimated temperature of the mixer 12 is not limited to the measured temperature of the mixer 12, and the estimated temperature of the mixer 12 estimated from other values may be used.

The spray control unit 34 in FIG. 6 has a three-dimensional map as shown in FIG. 10 showing the homogeneity of the reducing agent at the catalyst inlet with respect to the injection particle size and the injection speed. The spray control unit 34 has a plurality of the three-dimensional maps for each of the exhaust gas flow rate, the exhaust gas temperature, and the reducing agent injection amount. The spray control unit 34 uses the above three-dimensional map to calculate a combination of the injection particle size and the injection speed that can achieve the target homogeneity, and controls the injection particle size and the injection speed. When the exhaust gas flow rate is equal to or higher than the threshold value Qd, the spray control unit 34 reduces the spray particle size as the exhaust gas flow rate increases. Further, the spray control unit 34 reduces the spray particle size as the exhaust gas temperature is lower. Further, the spray control unit 34 reduces the spray particle size as the wall surface temperature Tm is lower.

(Process executed by the control unit)
The wall surface temperature Tm of the mixer 12 is acquired from the detection signal of the wall surface temperature sensor 19 in S111 of the subroutine of FIG. 11 which is called in S40 of FIG. After S111, the process proceeds to S112.

In S112, a threshold value Qd regarding the exhaust gas flow rate is set according to the wall surface temperature Tm. After S112, the process proceeds to S113.

In S113, it is determined whether the exhaust flow rate Q is equal to or greater than the threshold value Qd. When the exhaust gas flow rate Q is equal to or greater than the threshold value Qd (S113: YES), the process proceeds to S114. When the exhaust gas flow rate Q is smaller than the threshold value Qd (S113: NO), the target can be achieved with the default injection setting, so the process exits the routine of FIG.

In S114, a three-dimensional map as shown in FIG. 10 is used, and a combination of the injection particle diameter and the injection speed that can achieve the target homogeneity is calculated. After S114, the process proceeds to S115.

In S115, the target injection pressure of the injection device 13 that satisfies the injection particle diameter and the injection speed calculated in S114 is calculated. After S115, the process proceeds to S116.

The processing content of S116 is the same as that of S102 of FIG. After S116, the process returns to the main routine of FIG.

(effect)
As described above, in the second embodiment, the spray control unit 34 sets the control range of the injection particle size and the injection speed to the first control range in which the injection particle size is relatively large and the injection particle size is relatively small. Switching between the second control range and the second control range according to the exhaust flow rate. As a result, atomization of the spray is performed by switching to the second control range when the target homogeneity cannot be achieved with the default injection setting.

Further, in the second embodiment, when the exhaust flow rate is equal to or higher than the threshold value Qd, the spray control unit 34 reduces the spray particle size as the exhaust flow rate increases. Further, the spray control unit 34 reduces the spray particle size as the exhaust gas temperature is lower. Further, the spray control unit 34 performs correction so that the threshold value Qd becomes smaller as the wall surface temperature Tm becomes lower. Further, the spray control unit 34 reduces the spray particle size as the wall surface temperature Tm is lower. In this way, the target homogeneity can be achieved by controlling the injection particle size and controlling the amount of heat received from the exhaust gas and the wall surface.

[Third Embodiment]
In the third embodiment, the spray control unit 44 shown in FIG. 12 can control the injection particle size and the injection speed of the injection device 13 independently of each other. For example, the spray control unit 44 adjusts the valve lift amount of the injection device 13 to control the injection particle size. Specifically, as shown in FIG. 13, the spray control unit 44 makes the valve lift amount relatively smaller as the required injection particle size is smaller. By reducing the valve lift amount, the lateral flow of the reducing agent inside the injection valve 18 is strengthened and the turbulence is strengthened, so that atomization is promoted. The finer the atomization, the faster the spraying speed decreases, and the penetration force of the spraying becomes smaller. Then, the spray control unit 44 calculates the injection pressure that satisfies both the required injection particle diameter and the required injection speed from the relationships shown in FIGS. 14 and 15. Note that in another embodiment, the injection particle size may be controlled by adjusting the valve lift time of the injection device 13.

The spray control unit 44 in FIG. 12 uses one of the first control range A1 and the second control range A2 that achieves the target homogeneity of the reducing agent at the catalyst inlet with lower energy. For example, as shown in FIG. 16, let us consider a case where the relationship between the injection particle diameter and the injection speed, which changes due to the adjustment of the injection pressure in accordance with the three-step change of the valve lift amount, is shown by three solid lines Lc1 to Lc3. All of the solid lines Lc1 to Lc3 pass through both the first control range A1 and the second control range A2. In this case, adopting the point p1 on the solid line Lc1 can achieve the target homogeneity with lower energy than adopting the point p2 on the Lc2 or the point p3 on the solid line Lc3.

On the other hand, in FIG. 17, the solid line Lc3 passes through both the first control range A1 and the second control range A2, while the solid lines Lc1 and Lc2 pass through only the second control range A2. In this case, when the point p3 on the solid line Lc3 is adopted, the injection speed becomes slower and the target homogeneity can be achieved with lower energy than when the point p1 on the solid line Lc1 or the point p2 on the Lc2 is adopted. is there.

In addition, when the spray control unit 44 of FIG. 12 has a plurality of combinations of the injection particle diameter and the injection speed that can achieve the target homogeneity, and the difference in the required energy between these combinations is within a predetermined value, the spray is performed. Use a combination with a smaller particle size. For example, a combination of the injection particle size and the injection speed that can achieve the target homogeneity is extracted in the presence or absence of the partial lift, that is, in each of the three-step changes of the valve lift amount, and the combination in which the spray particle size becomes smaller is adopted. .. The spray control unit 44 has a plurality of three-dimensional maps showing the homogeneity of the reducing agent with respect to the injection particle diameter and the injection speed, for each of the three valve lift amounts.

(Process executed by the control unit)
In S121 of the subroutine of FIG. 18, which is called in S40 of FIG. 4, the wall surface temperature Tm of the mixer 12 is acquired from the detection signal of the wall surface temperature sensor 19. After S121, the process proceeds to S122.

In S122, a three-dimensional map is used, and a combination of the injection particle diameter and the injection speed that can achieve the target homogeneity is extracted for each of the three-step changes in the valve lift amount. After S122, the process proceeds to S123.

In S123, the required energies are compared between the respective combinations extracted in S122, and the combination that can achieve the target homogeneity with lower energy is adopted. When the difference in required energy is within a predetermined value, a combination with a smaller atomized particle size is adopted. After S123, the process proceeds to S124.

In S124, it is determined whether or not the required injection particle diameter D is equal to or larger than the predetermined value D2. When the required injection particle diameter D is the predetermined value D2 or more (S124: YES), the process proceeds to S126. When the required injection particle diameter D is smaller than the predetermined value D2 (S124: NO), the process proceeds to S125.

In S125, the valve lift amount is changed according to the required injection particle diameter D. After S125, the process proceeds to S126.

In S126, the target injection pressure of the injection device 13 that satisfies the required injection particle size and injection speed is calculated. The same relationship is maintained for the injection cycle as well, and the one with the smaller required energy is selected. After S126, the process proceeds to S127.

In S127, the valve lift amount is controlled and the pump 17 is controlled so that the injection pressure of the injection device 13 becomes the target injection pressure. After S127, the process returns to the main routine of FIG.

(effect)
As described above, in the third embodiment, the spray control unit 44 can control the injection particle size and the injection speed of the injection device 13 independently of each other. As a result, the control range is expanded as compared to the case where the injection particle size and the injection speed are simultaneously controlled only by the injection pressure, and the target homogeneity can be achieved with lower energy.

In addition, in the third embodiment, the spray control unit 44 uses one of the first control range A1 and the second control range A2 that achieves the target homogeneity of the reducing agent at the catalyst inlet with lower energy. As a result, the target homogeneity can be achieved with lower energy.

Further, in the third embodiment, the spray control unit 44 has a plurality of combinations of the injection particle diameter and the injection velocity that can achieve the target homogeneity of the reducing agent at the catalyst inlet, and the difference in the required energy between the combinations. Is within a predetermined value, a combination with a smaller spray particle size is adopted. The smaller the amount of the atomized particles injected, the less the reducing agent that collides with the mixer 12 in the liquid state decreases, and the more difficult the deposit is formed. Therefore, the particles can be atomized within a range that the required energy allows, and the deposit can be suppressed.

Further, in the third embodiment, the spray control unit 44 controls the injection particle diameter by adjusting the valve lift amount of the injection device 13. Thereby, the injection particle diameter and the injection speed of the injection device 13 can be controlled independently of each other.

[Fourth Embodiment]
In the fourth embodiment, the catalytic reaction system 10 is applied to an engine 90 provided with an EGR system (exhaust gas recirculation system) 100 as shown in FIG. The EGR system 100 is a system for re-injecting a part of exhaust gas through an EGR passage 101 that branches from an exhaust passage 91, and uses an EGR valve 102 to adjust the amount of exhaust gas sent to the intake side.

In the fourth embodiment, the catalyst 51 and the mixer 12 are provided in the middle of the EGR passage 101, the injection device 53 injects fuel as a "predetermined liquid", and the control is performed corresponding to the above points. The unit 54 is different from the first embodiment in that the control is performed, but other configurations are the same as those in the first embodiment. The EGR passage 101 is an exhaust system passage through which exhaust gas flows, and is also a catalyst installation passage portion in which the catalyst 51 is provided. The catalyst 51 has a function of reacting fuel with exhaust heat to reform the fuel. In the fourth embodiment, the catalytic reaction system 10 is a fuel reforming system.

The information acquisition unit 61 acquires various information such as the exhaust flow rate, exhaust temperature, and catalyst temperature of the EGR passage 101, which is a catalyst installation passage, from the detection signals of various sensors. The exhaust flow rate and the exhaust temperature of the EGR passage 101 may be estimated from the operating conditions of the engine 90 and the EGR valve 102, or may be obtained from the control value of the engine control unit.

The temperature determination unit 62 determines whether or not the catalyst temperature has reached the “temperature at which the reforming reaction occurs in the catalyst 51”. That is, it is determined whether the catalyst temperature Tc is equal to or higher than the threshold value Tx. When the catalyst temperature is not equal to or higher than the threshold value Tx, reforming cannot be performed, and therefore the fuel injection by the injector 53 is not performed.

The supply amount calculation unit 63 calculates the amount of fuel that can be reformed under the current conditions (hereinafter, reformed fuel amount). In the first embodiment, the exhaust flow rate, the exhaust temperature, and the required output of the engine 90 are used as the information indicating the above conditions. A three-dimensional map as shown in FIG. 20 is used, and the reformed fuel amount W is calculated based on the exhaust flow rate Q, the exhaust temperature T, and the required output. In addition, when the fuel required for maintaining the output is insufficient by the reformed amount alone, the insufficient amount is supplied from a fuel reformer (not shown).

The spray control unit 64 controls the injection particle size and the injection speed of the injection device 53 according to the exhaust state of the EGR passage 101 so that atomization or vaporization of the spray on the downstream side of the mixer 12 proceeds. Similar to the first embodiment, these controls are performed by calculating the target injection pressure P based on the exhaust temperature T and the exhaust flow rate Q using the map shown in FIG. 3, and adjusting the injection pressure of the injection device 53. Be seen.

The control unit 54 executes the same processing as that of FIG. 4 in the first embodiment, acquires various information, calculates the fuel reforming amount W when the catalyst temperature Tc is equal to or higher than the threshold value Tx, and performs the spray control. To inject fuel.

In the fourth embodiment, the catalytic reaction system 10 performs the injection of the injection device 53 according to the exhaust state of the EGR passage 101, which is the catalyst arrangement passage portion, so that atomization or vaporization of the spray on the downstream side of the mixer 12 proceeds. A spray control unit 64 that controls the particle size and the injection speed is provided. Therefore, according to the fourth embodiment, as in the first embodiment, the homogenized state of the fuel at the catalyst inlet can be maintained, and the reforming reaction in the catalyst 11 can be suitably performed.

[Fifth Embodiment]
In the fifth embodiment, as shown in FIG. 21, the catalyst 51 and the mixer 12 are provided in the middle of the EGR passage 101, the injection device 53 injects fuel as a “predetermined liquid”, and the above-mentioned. The difference from the second embodiment is that the control unit 54 performs control corresponding to the points, but the other configurations are the same as those of the second embodiment. The information acquisition unit 71 corresponds to the information acquisition unit 31 in the second embodiment.

The spray control unit 74 adjusts the control range of the injection particle size and the injection speed according to the exhaust flow rate between a first control range in which the injection particle size is relatively large and a second control range in which the injection particle size is relatively small. Switch. Further, when the exhaust gas flow rate is equal to or higher than the threshold value Qd, the spray control unit 74 reduces the spray particle size as the exhaust gas flow rate increases. Further, the spray controller 74 reduces the spray particle size as the exhaust gas temperature is lower. Further, the spray controller 74 corrects the threshold value Qd such that the lower the wall surface temperature Tm, the smaller the threshold value Qd. Further, the spray control unit 74 reduces the spray particle size as the wall surface temperature Tm is lower. Therefore, according to the fifth embodiment, the same effect as that of the second embodiment can be obtained.

[Sixth Embodiment]
In the sixth embodiment, as shown in FIG. 22, the catalyst 51 and the mixer 12 are provided in the middle of the EGR passage 101, the injection device 53 injects fuel as a “predetermined liquid”, and The third embodiment is different from the third embodiment in that the control unit 54 controls in correspondence with the points, but the other configurations are the same as those in the third embodiment.

The spray control unit 84 can control the injection particle diameter and the injection speed of the injection device 13 independently of each other. Further, the spray control unit 84 uses one of the first control range A1 and the second control range A2 that achieves the target homogeneity of the reducing agent at the catalyst inlet with lower energy. Further, the spray control unit 84 has a plurality of combinations of the injection particle diameter and the injection speed that can achieve the target homogeneity of the reducing agent at the catalyst inlet, and the difference in required energy between these combinations is within a predetermined value. In this case, a combination having a smaller spray particle size is adopted. Further, the spray control unit 84 adjusts the valve lift amount of the injection device 13 to control the injection particle size. Therefore, according to the sixth embodiment, the same effect as the third embodiment can be obtained.

[Other Embodiments]
In other embodiments, the purification target is not limited to NOx, but may be dinitrogen monoxide N ₂ O, carbon dioxide CO _2, or the like. Further, the reducing agent is not limited to urea water, and organic substances such as hydrocarbons and alcohols that are more easily oxidized than the object to be purified, hydrogen peroxide water, and the like may be used. In other embodiments, not only the reducing agent but also a precursor of the reducing agent may be supplied.

In other embodiments, when calculating the required supply amount of the reducing agent or the fuel reforming amount, the exhaust gas flow rate may be replaced with, for example, the intake air amount or the engine speed, and the exhaust temperature may be replaced with the accelerator opening degree or the fuel injection amount. Etc. may be replaced. Further, when calculating the required supply amount of the reducing agent, a two-dimensional map as shown in FIG. 23 is used without using the NOx concentration, and the required supply amount W of the urea water is calculated based on the engine speed R and the accelerator opening A. It may be calculated. The same applies when calculating the fuel reforming amount.

In other embodiments, the exhaust state such as the exhaust flow rate and the exhaust temperature may be estimated from the engine operating condition or the like instead of being acquired from the sensor.

In other embodiments, the control may be performed using the intake air amount instead of the exhaust gas flow rate. In that case, a correction may be made so that the intake air amount is largely estimated according to the fuel injection amount. This makes it possible to add the volume increase of the fuel gas to the calculation and make it closer to the actual value.

In another embodiment, the current reducing agent temperature or fuel temperature may be measured, and the requirements for the injection particle size and the injection speed may be corrected to the large particle size side and the low speed side according to the temperature. Since the higher the temperature is, the more likely it is to vaporize, the target homogeneity can be achieved even by the above correction.

In another embodiment, the injector may have a mechanism for giving heat or an electric charge to the reducing agent or the fuel, and by giving the heat or the electric charge, the surface tension of the reducing agent or the fuel may be lowered to promote atomization. Further, in another embodiment, the injection device may have a mechanism for changing the diameter of the injection hole, and may control atomization by changing the diameter of the injection hole. Further, in another embodiment, the injection device may have a mechanism for preheating the reducing agent or the fuel, and may preheat the reducing agent or the fuel so that the reducing agent or the fuel is immediately vaporized at the time of injection to control the injection particle size. Further, in another embodiment, the injection device may have a spray angle control mechanism, and the amount of heat received from the surroundings may be controlled by adjusting the spray angle to control the injection particle size in a pseudo manner.

In another embodiment, a catalyst deterioration estimating unit is provided, and correction or request is made to lower the exhaust flow rate threshold value in order to further improve the purification rate or the reforming rate in accordance with the catalyst deterioration. Correction may be performed so that the injection particle size becomes smaller. In another embodiment, the NOx amount after the catalyst is measured by a sensor, and the larger the NOx amount, the lower the threshold value of the exhaust flow rate, or the correction such that the required injection particle size becomes smaller. You can go.

In another embodiment, considering that the heat absorption from the surroundings changes depending on the injection amount of the reducing agent or the fuel, the exhaust flow rate threshold value may be corrected to be small according to the injection amount of the reducing agent or the fuel. Good.

In another embodiment, in order to avoid lowering the injection pressure of the injection device more than necessary, the spray control may be performed within a range of a predetermined injection pressure or higher.

The control unit and the method described in the present disclosure are realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied by a computer program. May be done. Alternatively, the control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method thereof described in the present disclosure are based on a combination of a processor and a memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. It may be implemented by one or more dedicated computers configured. Further, the computer program may be stored in a computer-readable non-transition tangible recording medium as an instruction executed by a computer.

The present disclosure has been described based on the embodiments. However, the present disclosure is not limited to the embodiments and structures. The present disclosure also includes various modifications and modifications within an equivalent range. Further, various combinations and forms, and other combinations and forms including only one element, more, or less than them are also within the scope and spirit of the present disclosure.

Claims (15)

A catalyst (11, 51) provided in an exhaust system passage (91, 101) of the engine (90);
A stirrer (12) provided upstream of the catalyst;
An injection device (13, 53) for injecting a predetermined liquid as a spray toward the stirring section;
One or both of the injection particle diameter and the injection speed of the injection device are controlled according to the exhaust state of the catalyst installation passage portion in which the catalyst is installed so that atomization or vaporization of the spray on the downstream side of the stirring unit proceeds. Spray control unit (24, 34, 44, 64, 74, 84)
A catalytic reaction system for an engine. The spray control unit (34, 44) controls the control range of the injection particle size and the injection speed with respect to the first control range (A1) where the injection particle size is relatively large and the second control range where the injection particle size is relatively small. The catalytic reaction system for an engine according to claim 1, wherein the catalytic reaction system is switched between (A2) according to an exhaust flow rate of the catalyst installation passage. The engine catalytic reaction system according to claim 2, wherein the spray control unit uses the second control range when the exhaust flow rate of the catalyst installation passage is equal to or greater than a threshold value (Qd). The engine catalytic reaction system according to claim 3, wherein the spray control unit reduces the spray particle size as the exhaust flow rate increases, when the exhaust flow rate of the catalyst installation passage section is equal to or higher than the threshold value. The catalytic reaction system for the engine according to claim 3 or 4, wherein the spray control unit reduces the spray particle size as the exhaust temperature of the catalyst installation passage is lower. A temperature acquisition unit (34) for acquiring a measured temperature or an estimated temperature of the stirring unit,
The catalytic reaction system for an engine according to any one of claims 3 to 5, wherein the spray control unit performs correction so that the threshold value becomes smaller as the temperature acquired by the temperature acquisition unit becomes lower. Further comprising a temperature acquisition unit for acquiring the measured temperature or estimated temperature of the stirring unit,
The catalytic reaction system for the engine according to any one of claims 3 to 5, wherein the spray control unit reduces the spray particle size as the temperature acquired by the temperature acquisition unit decreases. The engine catalytic reaction system according to claim 2, wherein the spray control unit (44) can control the injection particle diameter and the injection speed of the injection device independently of each other. The said spray control part uses which of the said 1st control range and the said 2nd control range which achieves the target homogeneity of the injection material from the said injection device in the said catalyst inlet with lower energy. Engine catalytic reaction system. In the case where the spray control unit has a plurality of combinations of the injection particle diameter and the injection velocity that can achieve the target homogeneity of the liquid at the catalyst inlet, and the difference in required energy between the combinations is within a predetermined value. The catalytic reaction system for an engine according to claim 8 or 9, wherein a combination having a smaller atomized particle size is adopted. The engine catalytic reaction system according to any one of claims 8 to 10, wherein the spray control unit controls a valve lift time of the injection device to control an injection particle size. The catalytic reaction system for an engine according to any one of claims 8 to 10, wherein the spray control unit controls an injection particle size by adjusting a valve lift amount of the injection device. The catalytic reaction system for an engine according to any one of claims 1 to 7, wherein the spray control unit (24, 34) adjusts an injection pressure of the injection device to control an injection particle size and an injection speed at the same time. The liquid is a reducing agent or a precursor thereof,
The catalytic reaction system for an engine according to any one of claims 1 to 13, wherein the catalyst reduces and purifies a predetermined component in exhaust gas. The liquid is fuel,
The engine catalytic reaction system according to any one of claims 1 to 13, wherein the catalyst uses exhaust heat to react the fuel.

Images