A diesel engine exhaust treatment system and method integrating coaxial dual-layer electrodes

Abstract

The application discloses a diesel engine tail gas treatment system and method integrated with coaxial double-layer electrodes, and belongs to the technical field of tail gas treatment. The system comprises a plasma reaction unit and a metal honeycomb electric heater which are arranged in series along the exhaust flow direction in the same outer shell and are installed downstream of an engine tail gas pipe and upstream of a diesel engine oxidation catalyst. A temperature sensor is arranged at the inlet of the diesel engine oxidation catalyst and is used for feeding back the inlet temperature of the diesel engine oxidation catalyst to a controller in real time. The application can purify and heat the tail gas in the cold start stage of the diesel engine in situ, and realizes the continuous coverage of the purification function of the diesel engine oxidation catalyst before and after the ignition through a three-stage control method.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, and more specifically to a diesel engine exhaust gas treatment system and treatment method with integrated coaxial double-layer electrodes. Background Technology

[0002] Diesel engines are widely used in commercial vehicles, construction machinery, ships, agricultural machinery, and generator sets due to their high thermal efficiency, high torque, and relatively low carbon dioxide emissions for the same power output. However, diesel combustion inevitably produces four main pollutants: particulate matter (PM), nitrogen oxides (NOx), and particulate matter (PM2.5). x Pollutants include carbon monoxide (CO) and hydrocarbons (HC). These pollutants can cause photochemical smog, acid rain, and haze, seriously endangering the ecological environment and human health.

[0003] Current mainstream diesel engine aftertreatment systems typically employ a combination of a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a selective catalytic reduction (SCR), used for oxidizing CO / HC, capturing particulate matter, and reducing NO, respectively. x The system achieves efficient emission control once it reaches operating temperature, but each unit is sensitive to exhaust temperature: DOC typically enters its effective catalytic range at approximately 180–250°C. During the cold start phase of a diesel engine (the initial 0–500 seconds after starting from a cooled state), the exhaust temperature is lower than the ignition temperature of DOC (approximately 200–300°C), preventing timely activation of DOC and leading to the emission of HC, CO, and NO. x Large quantities of four pollutants—HC, PM, and CO—are directly released into the atmosphere. Emissions during the cold start phase account for a significant portion of the total emissions throughout the test cycle, with HC and CO emissions being particularly prominent.

[0004] Therefore, how to provide a compact exhaust gas treatment system and method that can purify exhaust gas during the cold start phase is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a diesel engine exhaust gas treatment system and method with integrated coaxial double-layer electrodes. The system integrates a plasma reaction unit and a metal honeycomb electric heater (EH) in the same housing, and is connected in series between the engine exhaust pipe and the original oxidation catalyst of the diesel engine as a pre-exhaust gas treatment device, thereby improving the efficiency of exhaust gas purification.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a diesel engine exhaust gas treatment system with integrated coaxial double-layer electrodes, the system being installed between the diesel engine exhaust pipe and the diesel engine oxidation catalyst, comprising: The outer casing contains a plasma reaction unit and a metal honeycomb electric heater arranged in series along the exhaust flow direction. A reactor support plate, disposed within the outer casing, is used to fix the dielectric barrier discharge (DBD) reactor and the metal honeycomb electric heater. The dielectric barrier discharge reactor is used to purify and heat exhaust pollutants in situ before the diesel engine oxidation catalyst is ignited. Metal honeycomb electric heaters are used for resistance heating of exhaust gas; A temperature sensor is installed at the inlet of the diesel engine oxidation catalyst to provide real-time feedback of the inlet temperature of the diesel engine oxidation catalyst to the controller. The power supply module has a built-in dual power supply, one of which is connected to the dielectric barrier discharge reactor, and the other is connected to the metal honeycomb electric heater. The controller is used to control the discharge of the power supply module based on the vehicle ignition signal and the inlet temperature feedback from the temperature sensor.

[0007] Preferably, the dielectric barrier discharge reactor comprises: The outer tube wall uses corundum ceramic tube as the medium barrier layer; The inner high-voltage rod electrode is located on the central axis of the corundum ceramic tube and is connected to the power supply module through a high-voltage terminal. The outer grounding wire mesh electrode is in close contact with the outer surface of the corundum ceramic tube and is grounded through the grounding terminal; An annular discharge gap is formed between the inner high-voltage rod electrode and the inner wall of the corundum ceramic tube, and the discharge gap is filled with a perovskite catalyst. An end-face insulating ceramic support plate is used to fix the inner high-voltage rod electrode and the outer grounding wire mesh electrode to maintain concentricity, and to insulate the inner high-voltage rod electrode from the outer shell.

[0008] Preferably, the metal honeycomb electric heater is composed of a metal honeycomb formed by alternating winding of Fe-Cr-Al corrugated foil and flat foil, with the honeycomb channel direction arranged along the exhaust gas flow direction; the two ends of the metal honeycomb electric heater are respectively led out to connect to the power supply module; the metal honeycomb electric heater and the diesel engine oxidation catalyst are directly bonded together by annular retaining rings or high-temperature brazing.

[0009] Preferably, the power supply module includes: A high-voltage AC power supply is connected to the plasma reaction unit via a first solid-state relay. A low-voltage PWM modulated DC power supply is connected to a metal honeycomb electric heater via a second solid-state relay. The controller controls the high-voltage AC power supply to power the dielectric barrier discharge reactor by controlling the opening and closing timing of the first solid-state relay, and controls the low-voltage PWM modulated DC power supply to power the metal honeycomb electric heater by controlling the opening and closing timing of the second solid-state relay.

[0010] Preferably, the controller is configured as follows: Using the inlet temperature as the feedback quantity and the output duty cycle of the low-voltage PWM modulated DC power supply as the control quantity, the cold start process is divided into three stages for control: Phase A: After the vehicle ignition signal is triggered, the first solid-state relay and the second solid-state relay are closed, and the low-voltage PWM modulated DC power supply is controlled to output the maximum duty cycle, so that the metal honeycomb electric heater works at the rated power until the inlet temperature first reaches the ignition temperature threshold. Phase B: When the inlet temperature first reaches the ignition temperature threshold, the controller switches to proportional closed-loop control to maintain the inlet temperature within the set temperature range; Phase C: When the preset termination time is reached, the controller disconnects the second solid-state relay, and the low-voltage PWM modulated DC power supply stops outputting; the first solid-state relay remains closed, allowing the dielectric barrier discharge reactor to continue operating.

[0011] On the other hand, the present invention provides a diesel engine exhaust gas treatment method with integrated coaxial double-layer electrodes, comprising: During the cold start of the diesel engine, the controller simultaneously controls the first and second solid-state relays to close, so that the high-voltage AC power supply supplies power to the dielectric barrier discharge reactor and the low-voltage PWM modulated DC power supply supplies power to the metal honeycomb electric heater; the non-thermal plasma in the dielectric barrier discharge reactor works in synergy with the perovskite catalyst to purify the exhaust gas pollutants in situ, while the metal honeycomb electric heater resistance heats the exhaust gas to raise its temperature. A temperature sensor monitors the inlet temperature of the diesel engine oxidation catalyst in real time and feeds it back to the controller. The controller uses the inlet temperature as the feedback quantity and the output duty cycle of the low-voltage PWM modulated DC power supply as the control quantity to divide the cold start process into three stages for control: Phase A: After the vehicle ignition signal is triggered, the controller controls the low-voltage PWM modulated DC power supply to output the maximum duty cycle, so that the metal honeycomb electric heater works at the rated power until the inlet temperature first reaches the ignition temperature threshold. Phase B: When the inlet temperature first reaches the ignition temperature threshold, the controller switches to proportional closed-loop control to maintain the inlet temperature within the set temperature range; Phase C: When the preset termination time is reached, the controller disconnects the second solid-state relay, and the low-voltage PWM modulated DC power supply stops outputting; the first solid-state relay remains closed, allowing the dielectric barrier discharge reactor to continue operating.

[0012] As can be seen from the above technical solution, compared with the prior art, this invention discloses a diesel engine exhaust gas treatment system and method integrating coaxial double-layer electrodes. The plasma reaction unit and the metal honeycomb electric heater are integrated into the same housing, significantly shortening the overall length compared to the scheme where the plasma reaction unit and the metal honeycomb electric heater are arranged as independent components; the total number of parts is also reduced accordingly, and the assembly process is simplified. Simultaneously, this invention utilizes the metal honeycomb electric heater to rapidly increase the exhaust temperature during the cold start phase of the diesel engine, promoting early DOC activation; combined with the highly active particles generated by dielectric barrier discharge plasma, it synergistically oxidizes pollutants, improving the purification efficiency of pollutants such as HC, CO, and particulate matter during the cold start phase. Furthermore, by controlling the output power of the electric heater through PWM, the system energy consumption is reduced while ensuring rapid heating, improving the operating efficiency and reliability of the exhaust gas treatment system. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the overall layout of the electric heating exhaust gas purification system of the present invention in the diesel engine exhaust gas aftertreatment system.

[0015] Figure 2 This is a longitudinal sectional view of the electrically heated exhaust gas purification system of the present invention.

[0016] Figure 3 This is a detailed structural diagram of a single dielectric barrier discharge reactor.

[0017] Figure 4 This is a schematic diagram of a metal honeycomb electric heater.

[0018] Figure 5 This is a circuit block diagram of the power supply module of the present invention.

[0019] Figure 6 This is a timing diagram of a three-segment PWM control law.

[0020] The components include: 1. Exhaust pipe; 2. Diesel engine exhaust gas processor with integrated coaxial double-layer electrodes; 3. Diesel engine oxidation catalyst; 4. Diesel particulate filter; 5. Selective catalytic reduction device; 6. Temperature sensor; 7. Controller; 8. Housing; 2-1 Intake pipe; 2-2 Intake flange; 2-3 Left reactor support plate; 2-4 Dielectric barrier discharge reactor; 2-5 Inner high-voltage rod electrode; 2-6 Right reactor support plate; 2-7 High-voltage terminal block; 2-8 Metal honeycomb electric heater; 2-9 Metal honeycomb electric heater terminal block; 2-10 Outlet... 2-11 Gas flange; 2-12 Outer grounding wire mesh electrode; 2-13 Perovskite catalyst; 2-14 Discharge gas gap; 2-15 DBD grounding terminal; 2-16 Corundum ceramic tube; 2-8-1 Metal honeycomb carrier; 2-8-2 Honeycomb channel formed by alternating winding of corrugated foil and flat foil; 2-8-3 Wiring terminal (positive); 2-8-4 Grounding terminal; 9-1 High-voltage AC power supply; 9-2 First solid-state relay K1; 9-3 Low-voltage PWM modulated DC power supply; 9-4 Second solid-state relay K2. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: This embodiment of the invention provides an electrically heated exhaust gas purifier 2 that integrates a DBD reactor and a metal honeycomb electric heater within the same housing, such as... Figures 1-4 As shown, it includes: like Figure 1 and Figure 2 As shown, the outer casing 8 contains N parallel DBD reactors and metal honeycomb electric heaters. The entire outer casing 8 is made of stainless steel, and the inner wall is lined with a high-temperature resistant insulating layer (such as alumina fiber felt) to reduce heat loss and prevent the casing from becoming electrified. N = 16–24, preferably N = 20. Figure 2 Only three are shown in the longitudinal section.

[0023] The reactor support plate is used to fix the DBD reactor and the metal honeycomb electric heater. The reactor support plates at both ends are made of high-temperature resistant insulating ceramic material and have N circular through holes for installing and fixing N DBD reactors. The right reactor support plate also serves as the mechanical support for the air inlet end face of the metal honeycomb electric heater. The heated exhaust gas enters the DOC directly from the outlet.

[0024] The DBD reactor is used to purify and heat exhaust pollutants in situ before the diesel engine oxidation catalyst 3 is ignited. Metal honeycomb electric heaters are used for resistance heating of exhaust gas; Temperature sensor 6 is installed at the inlet of the diesel engine oxidation catalyst 3 to provide real-time feedback of the inlet temperature of the diesel engine oxidation catalyst 3 to the controller 7; The power supply module has a built-in dual power supply, one of which is connected to the DBD reactor and the other is connected to the metal honeycomb electric heater. The controller 7 is used to control the discharge of the power supply module based on the vehicle ignition signal and the inlet temperature feedback from the temperature sensor 6.

[0025] Furthermore, each of the aforementioned dielectric barrier discharge reactors employs a coaxial double-layer electrode structure 2-4, such as... Figure 3 As shown, it specifically includes: The reactor comprises an outer shell, an inner high-voltage rod electrode, and an outer wire mesh grounding electrode. The outer shell of the dielectric barrier discharge reactor is made of corundum ceramic tube, serving as a dielectric barrier layer; the inner high-voltage rod electrode is arranged along the axis of the ceramic tube and is kept coaxial with the ceramic tube by support structures at both ends; the outer wire mesh electrode covers the outer wall of the ceramic tube and is grounded.

[0026] In one embodiment, the outer diameter of the corundum ceramic tube can be 6-12 mm, the inner diameter can be 4-10 mm, and the length can be 100-300 mm; preferably, the outer diameter is about 8 mm, the inner diameter is about 6 mm, and the length is about 160 mm.

[0027] The outer grounding wire mesh electrode 2-12 is a stainless steel wire mesh or nickel wire mesh laid close to the outer surface of the corundum ceramic tube, serving as the grounding electrode for DBD discharge.

[0028] The perovskite catalyst 2-13 is filled in the annular space between the inner high-voltage rod electrode 2-5 and the corundum ceramic tube. It is in the form of spherical or cylindrical particles with an equivalent particle size of about 0.5 to 2 mm, preferably about 0.8 to 1.5 mm, and a volume filling rate of about 20% to 40%, preferably about 25% to 35%. The preferred material is La0.8Ce0.2Fe0.3Co0.7O3 perovskite catalyst.

[0029] The discharge gap 2-14 is an annular space between the inner high-voltage rod electrode 2-5 and the inner wall of the corundum ceramic tube (partially filled with perovskite catalyst). The single-sided gas discharge gap is about 1-5 mm, preferably about 1-3 mm.

[0030] DBD high-voltage terminal 2-7 is located at one end of the reactor. The inner high-voltage rod electrode 2-5 is led out to the outside of the outer shell 8 through the feed insulator and connected to the high-voltage AC power supply 9-1 (output voltage of about 5 to 25 kV, preferably 10 to 20 kV; frequency of about 1 to 50 kHz, preferably 5 to 20 kHz).

[0031] An end-face insulating ceramic support plate fixes the inner electrode and keeps it precisely concentric with the outer electrode, while simultaneously insulating and isolating the inner electrode from the outer casing 8.

[0032] The DBD grounding terminal is led out from the outer grounding wire mesh through the outer casing 8 to the external grounding.

[0033] Furthermore, the dielectric barrier discharge reactor is connected to the engine exhaust pipe 1 via the intake pipe 2-1; and to the diesel engine oxidation catalyst 3 via the exhaust pipe 2-11, and is connected via a flange.

[0034] Furthermore, the structural and assembly relationship of the Fe-Cr-Al metal honeycomb electric heater 2-8 is as follows: Figure 4 As shown. The metal honeycomb electric heater is cylindrical or flat cylindrical in shape, and its interior is composed of a metal honeycomb made of alternating Fe-Cr-Al (typical composition Fe-20Cr-5Al) corrugated foil and flat foil, with the honeycomb channels oriented along the exhaust gas direction. Positive and negative electrode rings are brazed to both ends of the metal honeycomb, respectively. Current flows axially through the metal foil from one electrode ring through the honeycomb and then out from the other electrode ring, generating resistance heating on the foil itself. Furthermore, the metal honeycomb is insulated from the outer casing 8 by an annular mica sheet or alumina ceramic sleeve. Terminals 2-9 are led out from both ends of the metal honeycomb electric heater and connected to an external low-voltage PWM modulated DC power supply 9-3 through the outer casing 8 via feedthrough insulators. The typical dimensions of the metal honeycomb core of the metal honeycomb electric heater are an outer diameter of about 80 to 150 mm, a length of about 20 to 80 mm, a channel density of about 100 to 300 cpsi (cells per square inch), a cold resistance of about 0.5 to 1.0 Ω, and a corresponding power absorption of about 500 to 1500 W when matched with a 24V vehicle power supply.

[0035] Furthermore, the power supply module circuit of the present invention is as follows: Figure 5 As shown, it consists of the following components: High-voltage AC power supply 9-1, with an output voltage of approximately 5-25kV (preferably 10-20kV) and a frequency of approximately 1-50kHz (preferably 5-20kHz) AC high voltage.

[0036] The first solid-state relay K1 9-2 is connected in series on the high-voltage AC power supply 9-1 branch. It is closed by the controller 7 at the moment of cold start and remains closed throughout the entire purification process to control the opening and closing of DBD discharge.

[0037] Low-voltage PWM modulated DC power supply 9-3, which uses the vehicle-mounted 24V storage battery as the energy source, outputs 24V DC pulses with adjustable duty cycle via PWM controller 7, with a rated output power of approximately 500 to 1500W (preferably 700 to 1000W; in this embodiment, it is approximately 800W, corresponding to a full-duty-cycle current of approximately 30A).

[0038] Second solid-state relay K2 9-4, connected in series on the branch of the low-voltage PWM modulated DC power supply 9-3, is closed by the controller 7 at the cold start initiation moment, and is disconnected when a preset termination moment (approximately 100 to 300 seconds, which is approximately 180 seconds in this embodiment) is reached, so as to control the on and off of heating of the metal honeycomb electric heater.

[0039] In the dielectric barrier discharge reactor, the inner-layer high-voltage rod electrode 2-5 is connected to the high-voltage AC power supply 9-1 via K1; the outer-layer grounded wire mesh electrode 2-12 is connected to the ground of the outer casing.

[0040] For the metal honeycomb electric heater, electrodes at both ends are connected to the 24V DC PWM power supply via K2. There is no any electrical connection between the metal honeycomb electric heater and the DBD, and the two electrical circuits are completely isolated.

[0041] The controller 7, with a built-in three-section PWM control law, takes the DOC inlet temperature Tg(t) as the feedback quantity to respectively control the opening and closing timings of K1 and K2 and the PWM output duty cycle.

[0042] In the second embodiment, the control method of the present invention takes the DOC inlet temperature Tg(t) as the feedback quantity and the duty cycle D(t) of the low-voltage PWM modulated DC power supply 9-3 as the control quantity, divides the cold start process into three stages, and the control sequence is as Figure 6 shown. The controller 7 is configured to: take the inlet temperature as the feedback quantity and the output duty cycle of the low-voltage PWM modulated DC power supply 9-3 as the control quantity, and divide the cold start process into three stages for control: Stage A (rapid temperature rise section, 0≤t<t1) At the moment t=0 triggered by the vehicle ignition signal, the controller 7 closes K1 and K2 simultaneously: once closed, K1 remains continuously closed throughout the entire cold start process, so that the dielectric barrier discharge reactor generates NTP all the time; after K2 is closed, the controller 7 outputs the maximum PWM duty cycle D=1.0, so that the metal honeycomb electric heater continuously works at the rated power until the DOC inlet temperature reaches the light-off temperature threshold T_LOF (approximately 250 to 350°C) for the first time, and the corresponding moment is denoted as t1: D(t)=1.0, 0≤t<t1 (until Tg reaches T_LOF).

[0043] Stage B (temperature maintenance section, t1≤t<t2)

[0044] Once Tg exceeds T_LOF, controller 7 switches to proportional closed-loop control to stabilize the DOC inlet temperature near the setpoint T_set (T_set is about 10-30°C higher than T_LOF). D(t) = sat[0,1]{Kp·[T_set-Tg(t)]}, Kp is approximately 0.02~0.1℃^-1 (approximately 0.05℃^-1 in this embodiment), D∈[0,1] Stage C (Electrical heating termination stage, t≥t2) When t reaches the preset termination time t2 (approximately 100-300 seconds), controller 7 disconnects the second solid-state relay K2 9-4, and the PWM power supply stops outputting. D(t) = 0, t ≥ t² During stage C, the enthalpy of the exhaust gas during normal engine operation (approximately on the order of 1–3 kW) is sufficient to maintain the DOC at the operating temperature. The first solid-state relay K1 9-2 remains closed at all times, and the DBD discharge continues to operate throughout the entire cold start process.

[0045] The working principle of the exhaust gas treatment system provided by this invention is as follows (described according to the cold start sequence, and the values ​​of each key parameter and their basis are shown in Table 1): t=0: Cold start After the vehicle ignition signal is triggered, controller 7 simultaneously closes K1 and K2. A stable discharge is rapidly established in the dielectric barrier discharge reactor, generating low-temperature plasma; at the same time, the metal honeycomb electric heater begins to heat the exhaust gas at its rated power. The two processes are physically carried out by two independent sets of electrodes, spatially located in the upstream DBD section and the downstream metal honeycomb electric heater section of the device, respectively, without interfering with each other.

[0046] t∈(0,t_lightoff]: First stage – NTP-dominated purification

[0047] At this stage, the downstream DOC has not yet ignited (the DOC inlet temperature has not reached T_LOF), and there is no significant thermal catalytic ability. The dielectric barrier discharge reactor designed in this invention utilizes NTP and perovskite catalyst for in-situ purification.

[0048] Meanwhile, the metal honeycomb electric heater continuously injects heat into the exhaust gas. The hot gas flow passes through the zero transition section and directly enters the DOC end face. The DOC inlet temperature monotonically rises from the ambient temperature to T_LOF. This temperature rise time t_lightoff is the duration of the first stage.

[0049] t=t_lightoff: DOC ignition

[0050] Under PWM duty cycle D=1.0 (rated power heating) conditions, the time for the DOC inlet temperature to first reach T_LOF is approximately 150–200 seconds. At this point, the DOC has acquired thermal catalytic capability.

[0051] t∈(t_lightoff,t2]: Temperature maintenance transition segment

[0052] Controller 7 switches from full-power control to proportional closed-loop control, maintaining the DOC inlet temperature around T_set (within approximately ±10℃).

[0053] t≥t2: Second stage – DOC-dominated purification

[0054] Controller 7 disconnects K2, stopping the metal honeycomb electric heater; at this point, the exhaust enthalpy (approximately 1-3 kW) generated during normal engine operation is sufficient to maintain the DOC operating temperature. K1 remains closed, and DBD discharge continues, but its role has shifted from "dominant purification" to "auxiliary enhancement." This stage continues until the engine stops or the next cold start cycle.

[0055] Table 1. Values ​​of key parameters and their basis.

[0056] Compared with the prior art, the present invention can bring the following significant technical effects: (1) Compact structure and small assembly space: Since the DBD reactor and the metal honeycomb electric heater are integrated into the same shell, the overall length of the machine is significantly shorter than the scheme of arranging the DBD reactor and the metal honeycomb electric heater as independent components; the total number of parts is also reduced accordingly, and the assembly process is simplified.

[0057] (2) Significantly shortens the DOC ignition time: The comparative test results of the examples show that at an ambient temperature of about 25°C, it takes about 450 to 500 seconds for the DOC inlet temperature to reach about 300°C without electric heating; the present invention only takes about 150 to 200 seconds at a rated power of about 800W, shortening it by more than 60%; when the rated power is increased to about 1000W, it is further shortened to about 120 to 150 seconds.

[0058] (3) Significantly reduced cumulative emissions during cold starts: Cumulative HC emissions during cold starts (0-300 seconds): approximately 3.5g without EH; approximately 2.0g at approximately 800W, with an HC reduction rate of approximately 40%; approximately 1.8g at approximately 1000W, with an HC reduction rate of approximately 50%. Cumulative CO emissions show a similar pattern, with a reduction rate of approximately 40% at approximately 800W and approximately 50% at approximately 1000W. Cumulative NOx emissions are also reduced by approximately 15% to 20% due to earlier SCR activation and an increased NO→NO2 ratio.

[0059] (4) Controllable exhaust back pressure increment with minimal impact on engine performance: In an example with 20 DBD reactors in parallel, each approximately 160 mm long and with a catalyst filling rate of approximately 30%, the DBD section pressure drop is estimated to be approximately 1–2 kPa according to the Ergun equation; the pressure drop of the metal honeycomb electric heater section (Fe-Cr-Al 200 cpsi, 40 mm long) is estimated to be approximately 0.3–1 kPa according to the classical honeycomb resistance formula; the total back pressure of the entire unit (excluding downstream DOC / DPF / SCR) is estimated to be approximately 1.5–3 kPa.

[0060] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A diesel engine exhaust gas treatment system integrating coaxial double-layer electrodes, the system being installed between the diesel engine exhaust pipe and the diesel engine oxidation catalyst, characterized in that, include: outer shell; A plasma reaction unit is disposed within the outer shell and includes at least one dielectric barrier discharge reactor. When multiple dielectric barrier discharge reactors are provided, the multiple dielectric barrier discharge reactors are arranged in parallel along the exhaust flow direction. A metal honeycomb electric heater is disposed within the outer casing and located downstream of the plasma reaction unit; A reactor support plate, disposed within the outer shell, is used to fix the dielectric barrier discharge reactor and the metal honeycomb electric heater; A temperature sensor is installed at the inlet of the diesel engine oxidation catalyst to provide real-time feedback of the inlet temperature of the diesel engine oxidation catalyst to the controller. The power supply module has a built-in dual power supply, one of which is connected to the plasma reaction unit and the other is connected to the metal honeycomb electric heater. The controller is used to control the discharge of the power supply module based on the diesel engine oxidation catalyst inlet temperature feedback from the vehicle ignition signal and temperature sensor.

2. The diesel engine exhaust gas treatment system with integrated coaxial double-layer electrodes according to claim 1, characterized in that, The outer wall tube of the dielectric barrier discharge reactor is made of corundum ceramic tube as a dielectric barrier layer. The inner high-voltage rod electrode is located on the central axis of the corundum ceramic tube and is connected to the power supply module through a high-voltage terminal. The outer grounding wire mesh electrode is closely attached to the outer surface of the corundum ceramic tube and grounded through the grounding terminal; An annular discharge gap is located between the inner high-voltage rod electrode and the inner wall of the corundum ceramic tube, and at least part of the annular discharge gap is filled with a perovskite-type catalyst. The end-face insulating ceramic support plate is located at both ends of the dielectric barrier discharge reactor and is used to fix the dielectric barrier discharge reactor. An integrated coaxial double-layer electrode diesel engine exhaust gas treatment system according to claim 1, characterized in that it comprises: The metal honeycomb electric heater includes a metal honeycomb substrate; The metal honeycomb substrate is composed of a metal honeycomb formed by alternating winding of Fe-Cr-Al corrugated foil and Fe-Cr-Al flat foil, with the honeycomb channel direction arranged along the exhaust gas flow direction; The metal honeycomb substrate is provided with two wiring terminals that are connected to the power supply module; The outer shell of the metal honeycomb electric heater is directly bonded to the outer shell of the diesel engine oxidation catalyst by means of an annular retaining ring or high-temperature brazing.

3. The diesel engine exhaust gas treatment system with integrated coaxial double-layer electrodes according to claim 1, characterized in that, The power supply module includes: A high-voltage AC power supply is connected to a dielectric barrier discharge reactor via a first solid-state relay. A low-voltage PWM modulated DC power supply is connected to a metal honeycomb electric heater via a second solid-state relay. The controller controls the high-voltage AC power supply to power the dielectric barrier discharge reactor by controlling the opening and closing timing of the first solid-state relay, and controls the low-voltage PWM modulated DC power supply to power the metal honeycomb electric heater by controlling the opening and closing timing of the second solid-state relay.

4. A diesel engine exhaust gas treatment system integrating coaxial double-layer electrodes according to claim 4, characterized in that, The controller is configured to: Using the inlet temperature of the diesel engine oxidation catalyst as the feedback quantity and the output duty cycle of the low-voltage PWM modulated DC power supply as the control quantity, the cold start process is divided into three stages for control: Phase A: After the vehicle ignition signal is triggered, the first solid-state relay and the second solid-state relay are controlled to close simultaneously, and the low-voltage PWM modulated DC power supply is controlled to output the maximum duty cycle, so that the dielectric barrier discharge reactor is put into operation and the metal honeycomb electric heater operates at rated power until the inlet temperature first reaches the ignition temperature threshold. Phase B: When the inlet temperature first reaches the ignition temperature threshold, the controller keeps the first solid-state relay closed and switches the low-voltage PWM modulated DC power supply to proportional closed-loop control to maintain the inlet temperature within the set temperature range. Phase C: When the preset termination time is reached, the controller disconnects the second solid-state relay, and the low-voltage PWM modulated DC power supply stops outputting; the first solid-state relay remains closed, allowing the dielectric barrier discharge reactor to continue operating.

5. A method for treating diesel engine exhaust gas with integrated coaxial double-layer electrodes, characterized in that, include: During the cold start of the diesel engine, the controller simultaneously controls the first and second solid-state relays to close, so that the high-voltage AC power supply supplies power to the dielectric barrier discharge reactor and the low-voltage PWM modulated DC power supply supplies power to the metal honeycomb electric heater; the non-thermal plasma in the dielectric barrier discharge reactor works in synergy with the perovskite catalyst to purify the exhaust gas pollutants in situ, while the metal honeycomb electric heater resistance heats the exhaust gas to raise its temperature. A temperature sensor monitors the inlet temperature of the diesel engine oxidation catalyst in real time and feeds it back to the controller. The controller uses the inlet temperature as the feedback quantity and the output duty cycle of the low-voltage PWM modulated DC power supply as the control quantity to divide the cold start process into three stages for control: Phase A: After the vehicle ignition signal is triggered, the controller controls the low-voltage PWM modulated DC power supply to output the maximum duty cycle, so that the metal honeycomb electric heater works at the rated power until the inlet temperature first reaches the ignition temperature threshold. Phase B: When the inlet temperature first reaches the ignition temperature threshold, the controller switches to proportional closed-loop control to maintain the inlet temperature within the set temperature range; Phase C: When the preset termination time is reached, the controller disconnects the second solid-state relay, and the low-voltage PWM modulated DC power supply stops outputting; the first solid-state relay remains closed, allowing the dielectric barrier discharge reactor to continue operating.

Images