Cold and hot primary air mixed flow structure and system

Abstract

The utility model discloses a cold and hot primary air mixed flow structure and system. The mixed flow structure comprises an elbow connected with a hot air outlet pipeline and a straight head connected with a cold air duct, wherein the elbow comprises a bent pipe section and linear pipe sections located at the two ends of the bent pipe section, the first linear pipe section is connected with the hot air outlet pipeline, the other linear pipe section is connected with a downstream pipeline, one end of the straight head is connected with the cold air outlet pipeline, and the other end of the straight head is connected with the cold air outlet pipeline. And the other end of the second straight pipe section penetrates through the elbow towards the direction of the second straight pipe section and is completely positioned in the elbow. One section of the straight head is arranged in the elbow in a penetrating manner, so that the airflow direction at a cold air and hot air mixing position is parallel to the greatest extent, the disturbance of a flow field at a primary air mixing position is reduced, the uniformity of a downstream speed field and a temperature field is improved, the measurement condition is improved, and the accuracy of air quantity measurement is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of air supply systems of thermal power plants, and in particular relates to a cold and hot primary air mixed flow structure and system. Background Art

[0002] In the primary air system of a thermal power plant, the hot primary air duct in front of the coal mill delivers mixed air to the coal mill, where the coal is ground and dried during the conveying process, and qualified coal powder is delivered to the furnace. The mixed air is usually a mixture of high-temperature hot primary air sent from the air preheater outlet and pressurized cold air drawn from the cold primary air of the primary fan outlet connecting air duct. The primary air temperature is controlled by adjusting the cold and hot air volumes. After the cold and hot primary air are mixed in the primary air mixing structure, a measuring point is usually set downstream to measure the primary air flow through a flow measurement control system.

[0003] In recent decades, thermal power stations have been developing rapidly towards large-scale, high-parameter, and supercritical characteristics. As the capacity of the main engine continues to increase, the cross-sectional dimensions of the flue and air ducts have also increased, while the plant and layout have been continuously optimized.

[0004] However, due to the limited space at the coal mill inlet and the compact air duct layout, the straight pipe section length requirements of the air volume measurement device are usually not met. In addition, the conventional primary air mixed flow structure, due to its own internal structural shortcomings, easily causes great disturbances at the primary air mixing point and turbulent flow field, making it impossible to measure the accurate and true primary air flow. The damper opening and air volume measurement value are difficult to linearly respond, and ultimately, accurate feedback adjustment cannot be achieved.

[0005] At the same time, when the disturbance of the flow field at the mixing point of cold and hot primary air is very severe, the noise at the inlet of the coal mill will also increase. Due to the obstruction of the internal structure and the impact of cold and hot air flow, the local resistance of the air duct is significantly increased, thereby increasing the energy consumption of the fan. Utility Model Content

[0006] The purpose of the utility model is to overcome the defects of the existing technology and provide a cold and hot primary air mixing flow structure and system, in which a section of the straight head is inserted into the elbow to make the airflow directions at the mixing point of the cold air and the hot air as parallel as possible, reduce the disturbance of the flow field at the mixing point of the primary air, improve the uniformity of the downstream velocity field and temperature field, improve the measurement conditions, and improve the accuracy of air volume measurement.

[0007] The purpose of this utility model is achieved through the following technical solutions:

[0008] A cold and hot primary air mixed flow structure, comprising an elbow connected to the hot air outlet pipe and a straight head connected to the cold air duct;

[0009] The elbow comprises a curved pipe section and straight pipe sections at both ends of the curved pipe section, wherein the first straight pipe section is connected with the hot air outlet pipeline, and the second straight pipe section is connected with the downstream pipeline, one end of the straight head is connected with the cold air outlet pipeline, and the other end penetrates through the elbow and is completely located in the elbow and faces the direction of the second straight pipe section.

[0010] In one embodiment, the end of the straight head is located in the curved pipe section and the first straight pipe section of the elbow.

[0011] In one embodiment, the center line of the second straight pipe section and the center line of the straight head are located on the same straight line.

[0012] In one embodiment, the intersection of the center line of the straight head and the side wall of the elbow is a first intersection, the intersection of the straight head and the first straight pipe section is a second intersection, and the distance between the first intersection and the second intersection is less than the minimum distance between the end surface of the first straight pipe section and the first intersection.

[0013] In one embodiment, the end of the straight head penetrating into the elbow has an inclined cutting surface.

[0014] In one embodiment, the distance between any point on the cutting surface and the side wall of the elbow in the axial direction of the straight head is not less than 5 mm.

[0015] The utility model also provides a cold and hot primary air mixing system, including the above -mentioned cold and hot primary air mixing structure.

[0016] In one embodiment, the coal mill is further connected with the downstream pipeline, and the flow measuring device is arranged on the downstream pipeline.

[0017] In one embodiment, the second straight pipe section is connected with the downstream pipeline, and the center line of the downstream pipeline and the center line of the second straight pipe section are located on the same straight line.

[0018] The utility model has the advantages that:

[0019] (1) the end of the straight head is penetrated into the elbow and faces the direction of the second straight pipeline, so that the airflow direction at the mixing position of the cold air and the hot air is parallel as much as possible, the disturbance of the flow field at the primary air mixing position is reduced, the uniformity of the downstream velocity field and the temperature field is improved, the measurement condition is improved, and the accuracy of the air volume measurement is improved.

[0020] (2) the center line of the second straight pipe section and the center line of the straight head are located on the same straight line, and the flow field uniformity of the cold and hot air mixing is further improved.

[0021] (3) One end of the straight head passing through the elbow has an inclined cross section, which improves the obstruction of the straight head outputting cold primary air to the hot primary air and reduces the interference with the flow field.

[0022] (4) The mixed flow system provided can improve the measurement conditions and increase the accuracy of air volume measurement. The mixed air volume flow and damper opening can achieve a linear response, thus achieving more accurate feedback regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be described in more detail below based on embodiments with reference to the accompanying drawings.

[0024] in:

[0025] Figure 1 Shows a schematic diagram of the mixed flow structure of the present utility model;

[0026] Figure 2 A schematic diagram of a mixed flow system of the present invention is shown;

[0027] In the drawings, like reference numerals are used for like parts, but the drawings are not necessarily true to scale.

[0028] Reference numerals:

[0029] 1-elbow, 2-straight end, 3-hot air outlet pipe, 4-downstream pipe, 5-coal mill, 6-flow measuring device, 101-first straight pipe section, 102-curved pipe section, 103-second straight pipe section, 201-inclined surface. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings.

[0031] The utility model provides a cold and hot primary air mixed flow structure, such as Figure 1 As shown, it includes an elbow 1 connected to the hot air outlet pipe 3 and a straight head 2 connected to the cold air duct;

[0032] The elbow 1 includes a curved pipe section 102 and straight pipe sections at both ends of the curved pipe section 102. The first straight pipe section 101 is connected to the hot air outlet pipe 3, and the other is a second straight pipe section 103 connected to the downstream pipe 4. One end of the straight pipe 2 is connected to the cold air outlet pipe, and the other end passes through the elbow 1 in the direction of the second straight pipe section 103 and is completely located inside the elbow 1.

[0033] It should be noted that thermal power stations are developing rapidly in the direction of large-scale development. With the continuous increase in the capacity of the main engine, the cross-sectional dimensions of the flue and the air duct are also increasing. However, due to the limited space of the coal mill inlet and the relatively compact arrangement of the air duct, it is usually impossible to meet the requirements of the air volume measurement device for the straight pipe section length. In addition, the conventional primary air mixed flow structure is prone to cause great disturbances at the primary air mixing point and turbulent flow field due to the shortcomings of its own internal structure. It is impossible to measure the accurate and true primary air flow rate. The opening of the damper is difficult to respond linearly to the air volume measurement value, and ultimately accurate feedback adjustment cannot be achieved. In this In the embodiment, the straight pipe sections at both ends of the curved pipe section can be divided according to the flow direction of the medium. For example, the hot air inflow side is the first direct pipe section 101, and the other end is the second direct pipe section 103 connected to the downstream pipe 4. The other end of the straight head 2 connected to the cold air outlet pipe is passed through the second straight pipe section 103 toward the elbow 1, thereby reducing the footprint of the mixed flow structure and making the airflow directions at the mixing point of the cold air and the hot air as parallel as possible, reducing the disturbance of the flow field at the primary air mixing point, and improving the uniformity of the downstream velocity field and temperature field, thereby improving the measurement conditions and the accuracy of the air volume measurement.

[0034] Among them, the elbow 1 can be a shrimp elbow or a welded elbow. The diameters of the first straight pipe section 101 and the second straight pipe section 103 of the elbow 1 are the same and larger than the diameter of the straight head 2, and the diameter of the curved pipe section 102 of the elbow 1 is 1 to 1.5 times the diameter of the first straight pipe section 101 of the elbow 1 to adapt to different environmental requirements and facilitate the straight head 2 to be completely located in the elbow 1;

[0035] Furthermore, if Figure 1 As shown, the end of the straight head 2 is located in both the curved pipe section 102 of the elbow 1 and the first straight pipe section 101, further reducing the disturbance of the flow field at the primary air mixing flow;

[0036] In one embodiment, Figure 1 As shown, the center line of the second straight pipe section 103 and the center line of the straight head 2 are located on the same straight line. In this embodiment, the center line of the straight head 2 is completely aligned with the center line of the second straight pipe section 103, further reducing the directional disturbance of the cold air and the hot air;

[0037] In one embodiment, the intersection of the center line of the straight head 2 and the side wall of the elbow 1 is the first intersection, and the intersection of the straight head 2 and the first straight pipe segment 101 is the second intersection. The distance between the first intersection and the second intersection is less than the minimum distance between the end face of the first straight pipe segment 101 and the first intersection. Figure 1 As shown, b is greater than c, and the length of the first straight pipe segment 101 is controlled to avoid that when the center line of the straight head 2 and the center line of the second straight pipe segment 103 are on the same straight line, there is a structure in which part of the straight head 2 is located outside the elbow 1, which affects the disturbance of the flow field;

[0038] In one embodiment, Figure 1 As shown, one end of the straight head 2 passing through the elbow 1 has an inclined section. Figure 1 The angle β is greater than 30° and less than 90°, so that the inclined surface 201 extends along the curved pipe section 102 of the elbow 1, minimizing the blocking effect on hot air, reducing energy consumption and noise;

[0039] In one embodiment, the distance between any point on the cross section and the side wall of the elbow 1 along the axis of the straight head 2 is not less than 5 mm, that is, while reducing the blocking effect on hot air, it ensures that the part where the straight head 2 enters the elbow 1 has sufficient strength to prevent the device from being damaged by mixed flow;

[0040] In one embodiment, the present invention also provides a cold and hot primary air mixed flow system, such as Figure 2 As shown, the cold and hot primary air mixed flow structure mentioned above also includes a coal mill 5 connected to the downstream pipeline 4. The downstream pipeline 4 is provided with a flow measuring device 6, that is, the mixed air is measured by the flow measuring device 6 of the downstream pipeline 4. Under the action of the cold and hot primary air mixed flow structure, the uniformity of the velocity field and temperature field of the downstream pipeline 4 is ensured, the measurement conditions are improved, the accuracy of the air volume measurement is improved, the linear response of the mixed air volume flow and the damper opening is achieved, more accurate feedback regulation is achieved, and the drying effect of the coal grinding and transportation process in the coal mill 5 is improved;

[0041] Furthermore, the second straight pipe section 103 is connected to the downstream pipe 4, and the center line of the downstream pipe 4 and the center line of the second straight pipe section 103 are located on the same straight line. That is, in this mixed flow system, the center line of the downstream pipe 4 and the center line of the second straight pipe section 103 are located on the same straight line, which further improves the accuracy of feedback regulation.

[0042] In the description of the present invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "back", "inside", "outside", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0043] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A cold and hot primary air mixed flow structure, characterized in that: It includes an elbow connected to the hot air outlet pipe and a straight head connected to the cold air duct; Among them, the elbow includes a curved pipe section and straight pipe sections located at both ends of the curved pipe section, wherein the first straight pipe section is connected to the hot air outlet pipe, and the other is a second straight pipe section connected to the downstream pipe. One end of the straight head is connected to the cold air outlet pipe, and the other end passes through the elbow in the direction of the second straight pipe section and is completely located inside the elbow.

2. The cold and hot primary air mixed flow structure according to claim 1, characterized in that: The end of the straight head is located in both the curved pipe section of the elbow and the first straight pipe section.

3. The cold and hot primary air mixed flow structure according to claim 1, characterized in that: The center line of the second straight pipe segment and the center line of the straight head are located on the same straight line.

4. The cold and hot primary air mixed flow structure according to claim 3, characterized in that: The intersection of the center line of the straight head and the side wall of the elbow is the first intersection, and the intersection of the straight head and the first straight pipe segment is the second intersection. The distance between the first intersection and the second intersection is less than the minimum distance between the end face of the first straight pipe segment and the first intersection.

5. The cold and hot primary air mixed flow structure according to claim 1, characterized in that: One end of the straight head passing through the elbow has an inclined section.

6. The cold and hot primary air mixed flow structure according to claim 5, characterized in that: The distance between any point on the section and the side wall of the elbow along the axis of the straight head is not less than 5 mm.

7. A cold and hot primary air mixed flow system, characterized in that: It includes the cold and hot primary air mixed flow structure described in any one of claims 1 to 6.

8. The cold and hot primary air mixed flow system according to claim 7, characterized in that: It also includes a coal mill connected to the downstream pipeline, and a flow measuring device is provided on the downstream pipeline.

9. The cold and hot primary air mixed flow system according to claim 7, characterized in that: The second straight pipe segment is connected to the downstream pipeline, and the center line of the downstream pipeline and the center line of the second straight pipe segment are located on the same straight line.

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