A flow equalization and drag reduction structure for the hot secondary air duct at the outlet of a four-compartment air preheater

Abstract

This invention provides a flow equalization and resistance reduction structure for the hot secondary air duct at the outlet of a four-compartment air preheater. This structure optimizes the hot secondary air duct at the outlet of the four-compartment air preheater, achieving flow equalization and resistance reduction, thereby reducing the power consumption of the blower. It includes a hot secondary air distribution duct I and a hot secondary air distribution duct II, as well as a hot secondary air mixing duct that mixes the secondary air output from hot secondary air distribution duct I and hot secondary air distribution duct II to form mixed air. A first guide plate group is arranged at the turning points within hot secondary air distribution duct I, hot secondary air distribution duct II, and the hot secondary air mixing duct. A second guide plate group is arranged at the outlet of hot secondary air distribution duct II. The air inlet area of ​​the hot secondary air mixing duct is divided into two duct spaces by the second guide plate group. The secondary air output from hot secondary air distribution duct I and hot secondary air distribution duct II is guided by the first guide plate group to the corresponding two duct spaces, and then output to the hot secondary air mixing duct for mixing.

Description

Technical Field

[0001] This invention relates to the field of air duct technology for coal-fired power units, specifically to a flow equalization and resistance reduction structure for the hot secondary air duct at the outlet of a four-compartment air preheater. Background Technology

[0002] To ensure heat exchange efficiency, the size of air preheaters increases with the increase in unit capacity. However, for traditional three-compartment air preheaters, the increased size leads to a greater deviation in the flue gas outlet temperature, with some areas experiencing temperatures below the flue gas acid dew point, thus affecting the safe operation of the unit. Four-compartment air preheaters (hereinafter referred to as air preheaters) are increasingly favored by large-capacity units due to their advantages such as low air leakage rate, high flue gas side heat exchange efficiency, good uniformity of exhaust gas temperature distribution, and low resistance on both the primary air side and the flue gas side. However, existing four-compartment air preheaters, due to the arrangement of two secondary air compartments, have increased secondary air leakage rate and resistance. The structure of the hot secondary air duct at the outlet of the four-compartment air preheater is as follows... Figure 1 As shown, after exiting the four-compartment air preheater, the two secondary air streams pass through hot secondary air distribution duct I1 and hot secondary air distribution duct II2 respectively. The two streams mix before entering the main hot secondary air duct 3. However, due to the presence of multiple bends, mixing ducts, and variable diameter ducts in the hot secondary air duct at the outlet of the four-compartment air preheater, the duct structure is more complex than that of the three-compartment air preheater, further increasing the resistance of the secondary air system. This can lead to problems such as low blower output and high blower power consumption in some units. Furthermore, since the four-compartment air preheater structure is less commonly used in units, there are currently no reports on the flow equalization and resistance reduction of the hot secondary air duct at the outlet of the four-compartment air preheater. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a flow equalization and resistance reduction structure for the hot secondary air duct at the outlet of a four-compartment air preheater. This structure optimizes the hot secondary air duct at the outlet of the four-compartment air preheater, achieving flow equalization and resistance reduction, thereby reducing the power consumption of the blower.

[0004] The technical solution of this invention is as follows:

[0005] A flow equalization and resistance reduction structure for the outlet hot secondary air duct of a four-compartment air preheater includes a hot secondary air distribution duct I and a hot secondary air distribution duct II connected to the four-compartment air preheater, and a hot secondary air mixing duct for mixing the secondary air output from the hot secondary air distribution duct I and the hot secondary air distribution duct II to form mixed air. The structure is characterized in that: a first guide plate group is arranged at the turning points in the hot secondary air distribution duct I, the hot secondary air distribution duct II, and the hot secondary air mixing duct; a second guide plate group is arranged at the outlet in the hot secondary air distribution duct II; and the air inlet area of ​​the hot secondary air mixing duct is divided into two duct spaces by the second guide plate group. The secondary air output from the hot secondary air distribution duct I and the hot secondary air distribution duct II is guided by the first guide plate group to the corresponding two duct spaces, and then output to the hot secondary air mixing duct for mixing.

[0006] Its further features are:

[0007] The first guide vane group includes at least two first guide vanes, and the second guide vane group includes at least two second guide vanes. The first guide vanes and the second guide vanes are arranged in parallel along the airflow direction; and the first guide vanes and the second guide vanes are arranged at equal intervals.

[0008] Both the first and second guide vanes are arc-shaped plates with an arc angle of 30° to 80°.

[0009] The corner located at the airflow inflection point of the secondary hot air distribution duct II is an arc-shaped structure, and the arc of the corner is the same as the arc of the second guide plate, and is set parallel to the second guide plate;

[0010] The two air duct spaces are a first air duct space and a second air duct space. The second guide plate group is arranged in the second air duct space and the second air duct space is evenly divided by a plurality of second guide plates.

[0011] The first guide vane group includes three first guide vanes, and the second guide vane group includes three second guide vanes. The width of the air inlet area of ​​the hot secondary air mixing duct is L, and the widths of the first duct space and the second duct space are both L. The air outlet of the second air duct space is evenly divided into sections with a width of [missing information] by the second guide vane assembly. The three primary airflow channels;

[0012] The outlet width of the hot secondary air mixing duct and the outlet width of the hot secondary air distribution duct II are both W. The outlet of the hot secondary air mixing duct is evenly divided into sections with a width of W by the first guide plate assembly. The four second airflow channels; the air inlets of the second airflow channels are evenly divided into sections with a width of [missing information] by the second guide plate assembly. The three third airflow channels;

[0013] The turning points of both the hot secondary air distribution duct I and the hot secondary air distribution duct II are formed by the first guide plate assembly, each having a secondary air inlet and a secondary air outlet. The width of the secondary air inlet is L, and it is evenly divided by the first guide plate assembly into sections with a width of L. The four fourth airflow channels; the width of the secondary air outlet is H, and it is evenly divided into channels with a width of H by the first guide plate group. The four fifth airflow channels.

[0014] The beneficial effects of this invention are that a first guide plate group is arranged at the turning point in the hot secondary air distribution duct I, the hot secondary air distribution duct II, and the hot secondary air mixing duct, and a second guide plate group is arranged at the outlet in the hot secondary air distribution duct II. Furthermore, the secondary air output from the hot secondary air distribution duct I and the hot secondary air distribution duct II is then output to the hot secondary air mixing duct through the two duct spaces respectively, which further optimizes the duct structure and enables uniform gas flow distribution in the duct. This reduces the resistance of the hot secondary air duct at the outlet of the four-compartment air preheater and reduces the power consumption of the blower. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the existing four-compartment air preheater outlet hot secondary air duct structure;

[0016] Figure 2 This is a schematic diagram of the assembled three-dimensional structure of the present invention;

[0017] Figure 3 yes Figure 2 Enlarged structural diagram at point A in the diagram;

[0018] Figure 4 This is a top view of the structure in this invention;

[0019] Figure 5 This is a side view of the structure in this invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings.

[0021] like Figures 2-5As shown, the present invention discloses a flow equalization and resistance reduction structure for the hot secondary air duct at the outlet of a four-compartment air preheater. This structure includes a hot secondary air distribution duct I1 and a hot secondary air distribution duct II2 connected to the four-compartment air preheater (not shown in the figure), and a hot secondary air mixing duct 4 that mixes the secondary air output from the hot secondary air distribution ducts I1 and II2 to form a mixed airflow. A first guide plate assembly is arranged at the turning points within the hot secondary air distribution ducts I1, II2, and 4. A second guide plate assembly is arranged at the outlet of the hot secondary air distribution duct II2. The air inlet area of ​​the hot secondary air mixing duct 4 is divided into two duct spaces by the second guide plate assembly. The secondary air output from the hot secondary air distribution ducts I1 and II2 is guided by the first guide plate assembly to the corresponding two duct spaces, and then output to the hot secondary air mixing duct 4 for mixing.

[0022] The first guide vane group includes at least two first guide vanes 5, and the second guide vane group includes at least two second guide vanes 6. The first guide vanes 5 and the second guide vanes 6 are arranged parallel to each other along the airflow direction. The first guide vanes 5 and the second guide vanes 6 are also equidistant. The first guide vanes 5 and the second guide vanes 6 are both arc-shaped plates with an arc of 30° to 80°. The corner 7 located at the airflow inflection point of the hot secondary air distribution duct II2 is an arc-shaped structure, and the arc of the corner 7 is the same as that of the second guide vanes 6 and is set parallel to the second guide vanes 6. The two air duct spaces are the first air duct space 8 and the second air duct space 9. The second guide vane group is arranged in the second air duct space 9 and the second air duct space 9 is evenly divided by several second guide vanes 6.

[0023] The first guide vane group includes three first guide vanes 5, the second guide vane group includes three second guide vanes 6, the width of the air inlet area of ​​the hot secondary air mixing duct 4 is L, and the widths of the first duct space 8 and the second duct space 9 are both L. The air outlet of the second air duct space 9 is evenly divided into sections with a width of [missing information] by the second guide vane assembly. The three first airflow channels 10 occupy half of the air inlet area of ​​the hot secondary air mixing channel 4. The secondary air output from the hot secondary air distribution channel I1 flows from the first airflow space 8, thereby avoiding the collision between the secondary air output from the hot secondary air distribution channel I1 and the hot secondary air distribution channel II2.

[0024] The outlet width of the hot secondary air mixing duct 4 and the outlet width of the hot secondary air distribution duct II 2 are both W. The outlet of the hot secondary air mixing duct 4 is evenly divided into sections with a width of W by the first guide plate group. The four second airflow channels 11; the air inlets of the second airflow space 9 are evenly divided into sections with a width of through the second guide plate group. 12. The three third airflow channels.

[0025] At the turning points of hot secondary air distribution duct I1 and hot secondary air distribution duct II2, a secondary air inlet 15 and a secondary air outlet 16 are formed by a first guide vane assembly. The width of the secondary air inlet 15 is L, and it is evenly divided into sections with a width of L by the first guide vane assembly. The four fourth airflow channels 13; the secondary air outlet 16 has a width of H, and is evenly divided into sections with a width of H by the first guide vane group. 4 fifth airflow channels 14.

[0026] In this embodiment of the invention, the widths L, W, and H are all different values, which means that the diameter of the air duct is not the same. Air duct sections with the same or different diameters can also be set according to the actual situation.

[0027] The working process of this invention is as follows: the four-compartment air preheater is connected to hot secondary air distribution duct I1 and hot secondary air distribution duct II2, and the gas width is... The four fourth airflow channels 13 flow in, and then through a width of Gas exiting from the four fifth airflow channels 14 in the hot secondary air distribution channel I1 enters the first airflow channel space 8, and gas exiting from the fifth airflow channel 14 in the hot secondary air distribution channel II2 first enters a space with a width of The airflow then enters the second airflow space 9 through one of the three third airflow channels 12, that is, through a space with a width of The gas flowing out of the three first airflow channels 10, the gas flowing out of the first airflow channel space 8 and the second airflow channel space 9 enters the hot secondary air mixing channel 4 and mixes, then passes through a channel with a width of The gas flows out through the four second air passages 11 and is sent into the secondary air box 17, which is then connected to the burner (not shown in the figure).

[0028] The present invention has the following advantages:

[0029] 1. A set of first guide vanes is designed at the turning points in hot secondary air distribution duct I1 and hot secondary air distribution duct II2, which can improve the uniformity of the flow field at the turning points in hot secondary air distribution duct I1 and hot secondary air distribution duct II2 and reduce resistance.

[0030] 2. A set of first guide vanes is designed at the turning point in the hot secondary air mixing duct 4, which can be used to improve the uniformity of the flow field at the turning point in the hot secondary air mixing duct 4 and reduce resistance.

[0031] 3. A second guide plate assembly is arranged at the outlet of the hot secondary air distribution duct II2. The air inlet area of ​​the hot secondary air mixing duct 4 is divided into two identical first air duct space 8 and second air duct space 9 by the second guide plate assembly. The secondary air output from the hot secondary air distribution duct I1 and the hot secondary air distribution duct II2 is output to the hot secondary air mixing duct 4 through the first air duct space 8 and the second air duct space 9 respectively, thus avoiding the collision between the secondary air output from the hot secondary air distribution duct I1 and the hot secondary air distribution duct II2.

[0032] 4. The corner 7 located at the airflow bend of the secondary hot air distribution duct II2 is an arc-shaped structure, which can smooth the airflow at the corner 7 and reduce resistance.

[0033] In summary, by optimizing the flow distribution structure in the hot secondary air distribution duct I1, hot secondary air distribution duct II2, and hot secondary air mixing duct 4, it is possible to reduce the resistance of the hot secondary air duct at the outlet of the four-compartment air preheater and reduce the power consumption of the blower.

[0034] Taking a 600MW four-compartment air preheater unit in a power plant as an example, through CFD numerical simulation, the total resistance from the air preheater outlet to the burner outlet is 1188Pa, of which the resistance from the air preheater outlet to section 4 of the hot secondary air mixing duct is 607Pa, the resistance from section 4 of the hot secondary air mixing duct to the secondary air box is 207Pa, and the resistance from the secondary air box to the burner outlet is 374Pa.

[0035] According to the technical solution of the present invention, after the optimization of the duct structure, the uniformity of the flow field distribution of the entire duct is greatly improved and the resistance is significantly reduced. The resistance of the entire duct after optimization is 898Pa, which is 290Pa lower than that of the existing duct, and the resistance reduction effect is very obvious.

[0036] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A flow equalization and resistance reduction structure for the hot secondary air duct at the outlet of a four-compartment air preheater, comprising a hot secondary air distribution duct I and a hot secondary air distribution duct II connected to the four-compartment air preheater, and a hot secondary air mixing duct for mixing the secondary air output from the hot secondary air distribution duct I and the hot secondary air distribution duct II to form mixed air, characterized in that: A first guide plate group is arranged at the turning point in the hot secondary air distribution duct I, hot secondary air distribution duct II, and hot secondary air mixing duct. A second guide plate group is arranged at the outlet in the hot secondary air distribution duct II. The air inlet area of ​​the hot secondary air mixing duct is divided into two duct spaces by the second guide plate group. The secondary air output from the hot secondary air distribution duct I and hot secondary air distribution duct II is guided by the first guide plate group to the corresponding two duct spaces, and then output to the hot secondary air mixing duct for mixing. The first guide vane group includes at least two first guide vanes, and the second guide vane group includes at least two second guide vanes. The first guide vanes and the second guide vanes are arranged in parallel along the airflow direction; and the first guide vanes and the second guide vanes are arranged at equal intervals. The two air duct spaces are a first air duct space and a second air duct space. The second guide plate group is arranged in the second air duct space and the second air duct space is evenly divided by a plurality of second guide plates. The first guide vane group includes three first guide vanes, and the second guide vane group includes three second guide vanes. The width of the air inlet area of ​​the hot secondary air mixing duct is L, and the widths of the first duct space and the second duct space are both L. The air outlet of the second air duct space is evenly divided into sections with a width of [missing information] by the second guide plate assembly. The three primary airflow channels; The outlet width of the hot secondary air mixing duct and the outlet width of the hot secondary air distribution duct II are both W. The outlet of the hot secondary air mixing duct is evenly divided into sections with a width of W by the first guide plate assembly. The four second airflow channels; the air inlets of the second airflow channels are evenly divided into sections with a width of [missing information] by the second guide plate assembly. The three third airflow channels; The turning points of both the hot secondary air distribution duct I and the hot secondary air distribution duct II are formed by the first guide plate assembly, each having a secondary air inlet and a secondary air outlet. The width of the secondary air inlet is L, and it is evenly divided by the first guide plate assembly into sections with a width of L. The four fourth airflow channels; the width of the secondary air outlet is H, and it is evenly divided into channels with a width of H by the first guide plate group. The four fifth airflow channels.

2. The flow equalization and resistance reduction structure of the hot secondary air duct at the outlet of a four-compartment air preheater according to claim 1, characterized in that: Both the first and second guide vanes are arc-shaped plates with an arc angle of 30° to 80°.

3. The flow equalization and resistance reduction structure of the hot secondary air duct at the outlet of a four-compartment air preheater according to claim 1, characterized in that: The corner located at the airflow inflection point of the secondary hot air distribution duct II is an arc-shaped structure, and the arc of the corner is the same as the arc of the second guide plate, and is set parallel to the second guide plate.

Images