A diesel engine aftertreatment structure to improve NOx conversion efficiency under low-temperature conditions

Abstract

This utility model relates to a diesel engine aftertreatment structure for improving NOx conversion efficiency under low-temperature conditions, belonging to the field of engine emission control technology. The system, arranged sequentially along the exhaust gas flow direction, includes a DOC (Discharge Oxide), a mixer, a urea injector, an SCR (Self-Catalyst Reduction) system, and a DPF (Discharge Power Filter). The SCR system internally houses a heating device, an SCR catalyst, a NOx sensor, and a controller. The heating device, located at the front end of the SCR catalyst, heats the catalyst to promote soot oxidation when the carbon load is high. The NOx sensor monitors the NOx concentration at the SCR outlet in real time, and the controller intelligently controls the start and stop of the heating device based on sensor feedback signals. This structure optimizes the operating environment of the SCR device in the aftertreatment system, effectively improving NOx conversion efficiency under low-temperature conditions, and is particularly suitable for meeting the requirements of the next stage of emission regulations.

Description

Technical Field

[0001] This utility model belongs to the field of diesel engine exhaust aftertreatment technology, specifically relating to a diesel engine aftertreatment structure that improves NOx conversion efficiency under low-temperature conditions. Background Technology

[0002] Traditional diesel engine aftertreatment systems generally employ a DOC+DPF+SCR structure. However, in actual operation, the SCR unit is usually located at the later stage of the system. After the exhaust gas passes through the DOC and DPF, the temperature decreases, leading to insufficient catalytic activity of the SCR under cold start or low-temperature conditions, and incomplete pyrolysis of urea. This easily causes a decrease in SCR efficiency, seriously affecting emission compliance and system stability. To meet the stringent NOx limits of the next stage of emission regulations, it is urgent to optimize the aftertreatment structure to improve the SCR activity at low temperatures. Utility Model Content

[0003] The purpose of this invention is to provide a diesel engine aftertreatment structure that improves NOx conversion efficiency under low-temperature conditions. By rationally adjusting the arrangement sequence of the catalytic unit and introducing heating and control devices, the NOx conversion rate is improved under low-temperature conditions to meet the NOx emission limits under low-temperature cold start conditions in the next stage of emission regulations.

[0004] To achieve the above objectives, the present invention provides a diesel engine aftertreatment structure for improving NOx conversion efficiency under low-temperature conditions, comprising a DOC, a mixer, a urea injector, an SCR system, and a DPF arranged sequentially along the exhaust gas flow direction.

[0005] The diesel engine aftertreatment structure for improving NOx conversion efficiency under low-temperature conditions is characterized in that the SCR system includes a heating device, a controller, an SCR catalyst, and a NOx sensor.

[0006] The diesel engine aftertreatment structure for improving NOx conversion efficiency under low-temperature conditions is characterized in that the SCR system is located after the DOC and before the DPF.

[0007] The diesel engine aftertreatment structure for improving NOx conversion efficiency under low-temperature conditions is characterized in that a heating device is provided at the front end of the SCR catalyst to heat the SCR catalyst when the carbon loading is too high, thereby promoting carbon soot oxidation.

[0008] The diesel engine aftertreatment structure for improving NOx conversion efficiency under low-temperature conditions is characterized by further including a NOx sensor for detecting the NOx concentration at the outlet of the SCR catalyst, and a controller connected to the heating device, wherein the controller controls the start and stop of the heating device according to the detection signal of the sensor. Attached Figure Description

[0009] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention.

[0010] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the diesel engine aftertreatment system of this utility model.

[0012] Figure 2 This is a schematic diagram of the structure of the diesel engine aftertreatment SCR system of this utility model.

[0013] Reference numerals: 1-DOC; 2-Mixer; 3-Urea nozzle; 4-SCR system; 5-DPF;

[0014] 41-Heating device; 42-Controller; 43-SCR catalyst; 44-NOx sensor. Detailed Implementation

[0015] To provide a clearer understanding of the technical features, objectives, and effects of this utility model, the specific embodiments of this utility model are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the device or component referred to must have a specific orientation; therefore, they should not be construed as limitations on this utility model.

[0016] In the following description, specific details such as particular system structures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the present invention. However, those skilled in the art will understand that the present invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0017] like Figure 1As shown, the present invention provides a diesel engine aftertreatment structure for improving NOx conversion efficiency under low-temperature conditions, comprising DOC1, mixer 2, urea nozzle 3, SCR system 4 and DPF5 arranged sequentially along the exhaust gas flow direction.

[0018] The SCR system 4 is positioned after DOC 1 and before DPF 5 to improve the low-temperature conversion rate of nitrogen oxides. Figure 2 As shown, the SCR system 4 further includes a heating device 41, a controller 42, an SCR catalyst 43, and a NOx sensor 44. Wherein:

[0019] The heating device 41 is arranged at the front end of the SCR catalyst 43 and is used to increase the catalyst temperature by external heating when the carbon loading of the SCR catalyst is too high, thereby promoting carbon soot oxidation.

[0020] NOx sensor 44 is installed at the outlet end of SCR catalyst 43 to detect the concentration of nitrogen oxides in exhaust gas in real time.

[0021] The controller 42 is connected to the NOx sensor 44 and the heating device 41, and controls the start and stop of the heating device 41 according to the NOx concentration change trend.

[0022] Through this structural design, this invention can effectively improve the reaction activity of the SCR system under cold start or low-temperature conditions, reduce NOx emissions, and meet more stringent regulatory requirements. Simultaneously, the linkage mechanism between the heating device and the sensor prevents the SCR catalyst from experiencing increased carbon loading or performance degradation due to prolonged low-temperature operation, thus improving system reliability and durability.

[0023] It should be noted that the heating device 41 can be implemented in various forms such as an electric heater or a hot air recirculation heating module, and the controller 42 can be an ECU or a dedicated processing unit. The specific structure can be adjusted and optimized according to actual application requirements.

[0024] In summary, this invention improves the reaction activity of the SCR system under low-temperature conditions by adjusting the arrangement of the DPF and SCR, arranging a heating device in front of the SCR catalyst, and introducing a NOx concentration monitoring and control strategy. This effectively addresses the challenges of nitrogen oxide emission control under typical operating conditions such as cold start and low-speed urban environments.

[0025] It is understood that the above embodiments only illustrate preferred embodiments of the present utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present utility model patent. It should be noted that for those skilled in the art, the above technical features can be freely combined, and several modifications and improvements can be made without departing from the concept of the present utility model, all of which fall within the protection scope of the present utility model. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present utility model should fall within the coverage of the claims of the present utility model.

Claims

1. A diesel engine aftertreatment structure for improving NOx conversion efficiency at low temperature operating conditions, characterized by, It includes DOC (1), mixer (2), urea nozzle (3), SCR system (4) and DPF (5) arranged sequentially along the exhaust flow direction.

2. The diesel engine aftertreatment structure of claim 1, wherein, The SCR system (4) includes a heating device (41) disposed at the front end of the SCR catalyst (43), a controller (42) connected to the heating device, the SCR catalyst (43) and a NOx sensor (44) disposed at its outlet end.

3. The diesel engine aftertreatment structure of claim 1, wherein, The SCR system (4) is located between the DOC (1) and the DPF (5).

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