CN1318817C - Heat regenerator of original surface for gas turbine - Google Patents

Abstract

The invention relates to a regenerator of a micro gas turbine, in particular to a raw surface heat exchanger used to improve the thermal efficiency of the gas turbine, which can improve the compactness and service life of the regenerator. The gas inlet and outlet channels are installed at the lower right and upper left corners of the main body of the regenerator. High-pressure air flows into the main body of the regenerator from the air inlet channel, flows out from the air outlet channel, and forms an air inlet through the left and right frames of the welded heat exchange plate. Outlet, the gas inlet and outlet are formed by welding the upper and lower frames of the heat exchange plate at intervals. The gas flows into the main body of the regenerator from the gas inlet and flows out from the gas outlet on the other side. The center of the heat exchange plate forms a parallelogram heat exchange corrugation The plate is located in the triangular stepping area on the left and right sides of the heat exchange corrugated sheet. The stepping area is used to place the deflector, and the heat exchange plate has a frame strip for welding and sealing. The improved corrugated plate is used to make the difference of the fluid velocity on both sides is not large, and the heat exchange effect of the media on both sides is the best, and the heat exchange effect is improved.

Description

A gas turbine primary surface regenerator

technical field

The invention relates to a recuperator of a micro gas turbine, in particular to a raw surface heat exchanger used to improve the thermal efficiency of the gas turbine.

Background technique

Regenerators are used in micro gas turbines to effectively use the waste heat of the gas at the outlet of the turbine to heat the high-pressure air at the outlet of the compressor, thereby improving the thermal efficiency of the device. Generally, a plate heat exchanger composed of parallel thin plates is used. In order to enhance heat transfer and increase the rigidity of the plate, corrugations are pressed on the plate, and the two adjacent corrugated plates are separated by a designed sealing strip to form a Channels, cold and hot fluids flow in each channel at intervals. A split type regenerator of the prior art is now described with the help of accompanying drawing 1 .

Fig. 1 (a), (b) shows the structure diagram of the split type regenerator in the prior art, wherein the air from the compressor flows into the regenerator 1 from the circular channel 6 at the lower left along 9, and flows through the center inclined The corrugated heat exchange channel at a certain angle is heated, and flows out from the upper right circular channel 7 into the combustion chamber. The gas enters the regenerator from one side 10 of the regenerator, exchanges heat with the air, and flows out from the other side 10 after being cooled. The corrugation directions of the two heat exchange plates 2 and 3 forming a heat exchange channel form a certain angle, and the two heat exchange plates of the air side heat exchange channel are sealed with two "L"-shaped sealing strips 19 to allow air to enter, The outlet forms air inlet and outlet passages 4 and 5 like this; the upper and lower edges of the two heat exchange plates are sealed with straight sealing strips 20 to form a gas side heat exchange passage, and the two sides form gas inlet and outlet passages respectively. It can be seen from the figure that this prior art regenerator includes a corrugated sheet welded as a whole, and two upper and lower circular air inlet and outlet channels.

The corrugated plate in the prior art uses the CC (Cross Corrugated) surface with the same corrugation size and the improved CC surface, which are two kinds of enhanced heat exchange surfaces. When the fluid flows in the channels formed on these surfaces, there are two The secondary flow can change the direction of the primary flow. The fluid flow channels on both sides formed by the former surface are the same, and the cross-sectional areas of the flow channels are also the same.

However, the current regenerator has the following problems:

The CC corrugated surface and the improved CC surface are used in the split regenerator. From the perspective of the enhanced heat transfer mechanism, the heat transfer can be enhanced by using the secondary flow and continuously changing the flow direction of the fluid in the mainstream direction. Taking the air side as an example, After the air enters the regenerator from the circular channel, there are two forms of primary flow and secondary flow. It first enters the inlet and outlet triangular area 8 as shown in Figure 1(a), and then enters the core part of the heat exchange plate in parallel. In the quadrilateral area, since the channel of the heat exchange plate has a certain inclination angle, the closer to the top of the triangular area 8, the greater the flow resistance and the lower the flow velocity, resulting in serious uneven distribution of fluid flow, especially this structure makes it difficult for part of the fluid to reach the triangular area At the top, it is difficult for air to flow through the top area of the regenerator to exchange heat with the gas, that is to say, there is a "dead zone" at the top of the regenerator with this structure that air is difficult to reach. This situation not only causes uneven heat transfer and a significant drop in heat transfer efficiency, but also affects the life of the regenerator.

This regenerator with a corrugated surface improves the corrugation of the triangular area 8 of each heat exchange plate. The corrugation height of the triangular area of the heat exchange plate is lower than the corrugation height of the parallelogram area of the core part, so that the two heat exchange plates 2 and 3 are not in contact with each other in the triangular area. Although the use of this surface in the triangular area can play a certain role in diversion, it will greatly reduce the heat exchange area of the regenerator and reduce the heat exchange efficiency.

In addition, when this regenerator structure forms a heat exchange channel, the two heat exchange plates 2 and 3 are staggered to form a certain angle in the flow direction. The larger the cross angle, the stronger the longitudinal flow of the fluid and the better the heat exchange performance. , but at the same time the pressure loss is also greater. Especially for the air side, the gas turbine system relies on increasing the pressure and temperature of the air to perform external work, and if the pressure loss in the regenerator is too large, it will be very detrimental to the efficiency of the entire gas turbine. In fact, pressure loss is an important factor affecting the efficiency of the regenerator. In addition, as the pressure loss increases, the regenerator is prone to fouling and blockage.

For the regenerator with CC surface, the cross-sectional area of the gas side and the air side flow channel are equal, which means that when the volume flow on both sides is similar, the heat transfer effect is better, but if the volume flow difference on both sides is large, such as in a micro gas turbine The volume flow rate difference between the gas and the air on both sides is more than three times, the flow velocity difference is relatively large, and the heat transfer effect is obviously reduced.

For the improved CC surface in the prior art, only the corrugated shape of this surface has been improved, and the ratio of the cross-sectional area of the flow channels on both sides of the air and gas formed on this surface has not been determined, and how to improve this surface has not been determined. Only in this way can the heat exchange effect of the media on both sides of the regenerator be the best.

Contents of the invention

The purpose of the present invention is to provide a gas turbine regenerator structure that can make both hot and cold fluids flow in a more reasonable form, so as to improve the heat exchange efficiency of the regenerator, and greatly improve the compactness and the service life of the regenerator. surface regenerator.

In order to achieve the above object, the present invention provides an original surface regenerator with deflectors, which includes a regenerator body, and gas inlet and outlet channels are installed at the lower right corner and upper left corner of the regenerator body, and the regenerator body is composed of A number of heat exchange plates are welded. High-pressure air flows into the main body of the regenerator from the air inlet channel, flows out from the air outlet channel, and forms an air inlet and outlet by welding the left and right frames of the heat exchange plate at intervals. The gas inlet and outlet are formed by the upper and lower frames. The gas flows into the main body of the regenerator from the gas inlet, and flows out from the gas outlet on the other side. The improvement is that the heat exchange plate is composed of three parts: the center is a parallelogram heat exchange The corrugated sheet is located in the triangular flattened area on the left and right sides of the heat exchange corrugated sheet. There are frame strips around the heat exchange plate for welding and sealing, and the flattened area is used to place the deflector.

For the diversion area of the regenerator, in addition to fully realizing the function of making the fluid evenly enter the corrugated heat exchange area, since the area of the diversion part accounts for a considerable proportion of the entire heat exchange area, for a compact high-efficiency regenerator, we zone for enhanced heat transfer. In the present invention, we can use CC corrugated sheet, straight fin or sawtooth fin structure to make the flow diversion sufficient, reduce the pressure drop, increase the heat transfer area, and effectively improve the heat transfer efficiency. In addition, The heat exchange plate using the deflector has a simple process, which makes the structure of the regenerator more compact.

In the present invention, the selection of the intersection angle of the corrugation direction of two adjacent heat exchange plates considers the best match between heat exchange performance and pressure loss, and is selected as 60°. After the fluid enters the heat exchange channel, a secondary flow is generated, which not only obtains a higher The heat exchange efficiency is high, and the pressure loss is not too high. The whole structure is light in weight and compact, which improves the service life of the regenerator.

The heat exchange plate of the present invention is improved by using MCC (Modified Cross Corrugated, improved staggered herringbone corrugation) corrugated plate, that is, the air and gas flow cross-sectional areas are not equal, and are determined according to the pressure recovery coefficient and volume flow rate on both sides of the air and gas, so that The flow rate of the fluid on both sides is not much different, and the heat exchange effect of the medium on both sides is the best.

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. Other objects and advantages of the invention may also be realized herein.

Description of drawings

Fig. 1 (a) is the overall structure schematic diagram of prior art original surface regenerator;

Fig. 1 (b) is the schematic structural diagram of the heat exchange plate of the original surface regenerator in the prior art;

Fig. 2 (a) is the overall structure schematic diagram of the original surface regenerator with deflector of the present invention;

Fig. 2 (b) is the structural representation of heat exchange plate of the present invention;

Fig. 3 (a) is the partial core decomposition diagram of the original surface regenerator with deflector and seal of the present invention;

Fig. 3 (b) is the sectional view along A-A in Fig. 3 (a);

Fig. 3 (c) is the sectional view along B-B in Fig. 3 (a);

Fig. 4 (a) is the structural representation of the CC corrugated sheet used in the air side deflector of the present invention;

Fig. 4 (b) is the structural representation of the CC corrugated sheet used in the gas side deflector of the present invention;

Fig. 5 (a) is a schematic structural view of the air side deflector adopting straight fins of the present invention;

Fig. 5 (b) is a schematic structural view of the gas side deflector adopting straight fins of the present invention;

Fig. 6 (a) is a structural schematic diagram of the air side deflector adopting zigzag fins of the present invention;

Fig. 6(b) is a schematic diagram of the structure of the gas-side guide vane adopting zigzag fins according to the present invention.

Detailed ways

Accompanying drawing is the specific embodiment of the present invention.

Below in conjunction with accompanying drawing, the specific content of the present invention is described in further detail:

Referring to Figure 2(a), the original surface regenerator is composed of a main body 1 welded with air inlet and outlet circular passages 6, 7, the main body 1 is formed by welding together a plurality of heat exchange plates 2, 3, and the heat exchange plates Air inlets and outlets 4 and 5 are formed during welding, and circular passages 6 and 7 outside the air inlets and outlets are respectively parallel to the air inlet 4 and air outlet 5, and are respectively welded at two opposite corners of the regenerator, and the air is shown along 9 The gas flows into the port 4 in the direction of flow, enters the heat exchange corrugated area 12 through the deflector 11, and then leads out of the main body 1 along the other side of the deflector 11, flows out of the regenerator along the air outlet 5, and the gas flows from the side of the regenerator along the 10 shown Enter the main body 1 in the same direction and flow out along the other side 10.

When forming an air-side heat exchange channel, the air inlet and outlet 4, 5 are not sealed, and a series of parallel air inlet and outlet 4, 5 will be formed, and the corresponding air inlet and outlet 4, 5 will be welded on the air inlet and outlet 4, 5 respectively. The gas inlet and outlet passages 6,7, when the gas inlet and outlet passages 6,7 are welded on the main body 1, the cross section is a circle with a circular segment cut off, and the chord length of the circular segment is equal to the width of the air inlet and outlet 4,5 respectively coincide, and the gas inlet and outlet passages 6, 7 can also be selected circular, rectangular, elliptical and so on.

Referring to Fig. 2(b), the heat exchange plates 2 and 3 are divided into two parts: the heat exchange corrugated sheets 12 and 13 with a parallelogram in the center, and the triangles on the left and right sides of the heat exchange corrugated sheets 12 and 13 on the heat exchange plate. The treading area 14 is used to place the deflector 11 in the treading area 14.

The regenerator is welded together through the sealing strip on the frame strip, and is supported by the contact between the crest and the trough of the intermediate heat exchange corrugated plate.

Referring to Figure 3(a), frames are reserved around the heat exchange corrugated plate 2, and two adjacent frames respectively form two “L” shaped frame strips 19, which are located on two opposite corners of the heat exchange plate 2, When the heat exchange plates 2 and 3 are welded to form air passages, the "L"-shaped sealing strips are welded along the frame strips 19 to form the heat exchange plates 2 and 3, and the unsealed sections serve as air inlets and outlets 4 and 5 respectively. The inlet and outlet 4,5 extend into the triangular CC deflector 11, the height of the CC corrugated sheet will match the height of the air inlet and outlet 4,5, and 4,5 will maintain their respective dimensions during welding. For the welding of the main body 1 of the regenerator, it is only necessary to carry out the sealing of the frame, and the deflector placed in the triangular stepping area only needs to be fixed by spot welding.

In addition, frame strips 20 are left on the upper and lower parts of the heat exchange corrugated plate 3, and the straight sealing strips weld the heat exchange plates 3 and 2 along the frame strips 20 to form a gas heat exchange channel, thereby obtaining the gas inlet 17 on the side frame and another Gas outlet 18 on the side frame. Trapezoidal CC deflectors 11 are respectively placed along the gas inlet and outlet 17 and 18 . CC corrugated fins 11 are placed in the diversion area, and the direction is consistent with the direction of the fluid entering and exiting the regenerator, and the diversion fins on the two heat exchange plates form an included angle of 90°.

To process and manufacture a regenerator, it is very important to have as high a surface density as possible (that is, the heat exchange area per unit volume), and it is required to increase the disturbance in the best medium flow mode as much as possible, so as to strengthen the heat exchange, in order to achieve For this purpose, it is important to choose the structural type of the heat exchange plate.

Referring to Fig. 3(b), (c), air and gas flow channels 15 and 16 are formed at intervals between the corrugated plates 2 and 3 respectively, and the core part of the heat exchange plate 2 is a parallelogram-shaped corrugated plate 12, and the corrugated plate The waveform on 12 is composed of crests 25 and troughs 26. Similarly, the core part of the heat exchange plate 3 is a parallelogram corrugated plate 13, and the waveform on the corrugated plate 13 is composed of crests 23 and troughs 24. The troughs 26 of the corrugated sheet 12 meet the crests 23 of the corrugated sheet 13 when an air channel 15 is formed. In contrast, a gas channel 16 is formed when the crest 25 on the corrugated plate 12 meets the trough 24 on the corrugated plate 13 . The crest 25 on the corrugated plate 12 has the same size as the inscribed circle 21 of the trough 24 on the corrugated plate 13 , and the trough 26 on the corrugated plate 12 has the same size as the inscribed circle 22 of the crest 23 on the corrugated plate 13 . In this way, by adjusting the ratio of the radii of the inscribed circles 21 and 22, different ratios of the area of the air passage section 15 to the area of the gas passage section 16 can be obtained. The ratio of the radius of the inscribed circle 22 of the wave trough 26 of the heat exchange plate 2 to the radius of the inscribed circle 21 of the wave crest 25 is the pressure ratio of air and gas. The radius ratio of the inscribed circle 21 is the pressure ratio of air and gas. When two or more heat exchange plates are welded, the crests and troughs extend along the flow channel, and the fluid flows between the crests and troughs. The flow channel formed by the crests and troughs determines the characteristics of the medium flow.

In another example, in order to obtain a suitable pressure drop distribution, the corrugated plates may have different patterns in order to obtain different types of flow channels when assembling the heat exchange plates. As shown in Fig. 3 (b), the trough 26 of the corrugated plate 12 of the core part on the heat exchange plate 2 and the trough 24 of the corrugated plate 13 of the core part on the heat exchange plate 3 get different depths respectively, which can also adjust the air, The cross-sectional area of the gas channel.

The trough 26 of the heat exchange plate 2 and the peak 23 of the heat exchange plate 3 meet to form an air-side heat exchange channel, and the air heat exchange channel 15 is staggered by a certain angle between the trough 26 of the heat exchange plate 2 and the peak 23 of the heat exchange plate 3 form. The trough 26 of the heat exchange plate 2 and the wave crest 23 of the heat exchange plate 3 intersect to have a contact point, and when the heat exchange plates are welded together, the strength of the regenerator is enhanced. The intersection angle between the trough 26 and the peak 23 is 45°-75°, and the optimum angle is 60°.

The heat exchange channel on the gas side of the regenerator is formed by the connection between the crest 25 of the heat exchange plate 2 and the trough 24 of the heat exchange plate 3 . The crests 25 of the heat exchange plate 2 and the troughs 24 of the heat exchange plate 3 are interlaced at a certain angle to form a gas flow channel 16 . The crests 25 of the heat exchange plate 2 have the same height as the troughs 24 of the heat exchange plate 3 . During welding, a sealing strip with an appropriate thickness is used to make the crest 25 and the trough 24 have a contact point. This avoids deformation of the flow channels 15 , 16 on both sides due to the higher pressure when the air flows in the other flow channel 15 .

A gas heat exchange channel is formed by welding the sealing strip, thereby obtaining a gas inlet 17 on one side frame and a gas outlet 18 on the other side frame. Because the mass flow rate of air and gas are not much different, and the gas is discharged from the turbine after work, its pressure is only slightly higher than the atmospheric pressure, and the air pressure can reach 3-6bar after being compressed by the compressor. Here we Take 3.8bar, so the density of air is higher than that of gas. In order to make the flow velocity on both sides not much different, the cross-sectional area of gas inlet and outlet is larger than that of air inlet and outlet.

In addition, another embodiment of the present invention is that the air outlet 5 is larger than the air inlet 4. For a micro gas turbine with a power of 100kW, the air outlet 5 is 16% wider than the air inlet 4, that is, the air outlet triangle is larger than the air inlet. The area of the triangle is larger. This is because with the flow of air, the temperature of the air increases, the pressure decreases, the density decreases, and the flow velocity increases. In order to make the difference between the flow velocity of the air inlet and outlet fluid is not large, the outlet size of the air is increased.

The very important function of the deflector 11 is to make the medium flow evenly in the heat exchange plate, and the pressure loss should be as small as possible, so as to ensure the maximum work done by the high-pressure air in the turbine. We use a straight channel for the deflector, the pressure loss is small, and the flow direction of the medium in the deflector is consistent with the flow direction of the respective inlet and outlet. When the two media flow in from their respective inlets, the path of each fluid flowing through the entire heat exchange channel is the same, that is, the pressure drop is the same, which avoids uneven fluid flow in the channel.

Referring to Figure 4(a) and (b), the diversion area adopts the CC corrugated surface, and the heat exchange fins are punched into a certain waveform on the surface. The surface heat transfer coefficient is high, and it has a considerable influence on the comprehensive performance of heat transfer resistance. Superiority.

Referring to Figure 5(a) and (b), straight fins are used in the diversion area, which has a small flow resistance coefficient and high bearing strength.

Referring to Figure 6(a) and (b), the diversion area adopts zigzag fins, which can be regarded as the straight fins used in the prior art are cut into many short pieces, which are formed by staggering each other at certain intervals. intermittent fins. The fins can effectively disturb the gas, promote the turbulence of the fluid, and destroy the boundary layer, thereby effectively improving the heat exchange efficiency. Practice shows that under the same pressure loss conditions, its heat transfer coefficient is more than 30% higher than that of straight fins. Due to the high heat exchange efficiency of such fins, the regenerator can be further compacted.

In the original surface regenerator with deflector provided by the present invention, the heat exchange plate is composed of three parts: the heat exchange corrugated sheet with a parallelogram in the center, and the triangular ones on the left and right sides of each heat exchange plate for placing the deflector The leveling area of the board is surrounded by frame strips for welding and sealing. When processing the heat exchange plate, there are only stamped corrugations in the central parallelogram area, and the left and right sides of the heat exchange plate are reserved triangular flat areas. Since the corrugated curves formed by stamping are very small, the average equivalent diameter of the air and gas side channels is only 1.5mm Therefore, the folds at the boundary line between the corrugated area and the flat area are small, and the influence on the fluid flow resistance is negligible. Then, place the processed deflector into the flat plate area, and only need to fix it by spot welding. The deflectors are placed in accordance with the respective inlet and outlet directions of air and gas, and the deflectors on the two heat exchange plates form an included angle of 90°. Using this corrugated plate regenerator with deflectors, the function of the deflectors is very obvious, which can evenly distribute the gas on both sides to the core of the heat exchange plate for heat exchange. For each fluid they flow through The path of the entire heat exchange channel is the same, that is, the pressure drop is the same, which avoids the so-called "short circuit" phenomenon caused by uneven flow. In addition, the pressure drop of the fluid flow in the diversion area is very small, which fully realizes the function of making the fluid evenly enter the corrugated heat exchange area.

Claims (6)

1. A gas turbine original surface regenerator, comprising a regenerator main body (1), installing gas inlet and outlet passages (6, 7) at the lower right corner and upper left corner of the regenerator main body (1), and the regenerator main body ( 1) It is welded by a number of heat exchange plates (2, 3), high-pressure air flows into the regenerator body (1) from the air inlet channel (6), flows out from the air outlet channel (7), and exchanges heat through interval welding The left and right frames of the plate (2) form air inlets and outlets (4, 5), and the gas inlets and outlets (17, 18) are formed by welding the upper and lower frames of the heat exchange plate (3) at intervals, and the gas is fed from the gas inlet (17 ) flows into the main body (1) of the regenerator, and flows out from the gas outlet (18) on the other side. It is characterized in that the heat exchange plate (2, 3) is composed of three parts: the heat exchange corrugated sheet (12 ), the triangular step-down area (14) located on the left and right sides of the heat-exchange corrugated sheet (12) of the heat-exchange plate, with frame strips (19, 20) for welding and sealing left on the periphery, wherein the step-down area (14 ) is used to place the deflector (11), the ratio of the radius of the inscribed circle of the trough (26) of the heat exchange plate (2) to the radius of the inscribed circle of the crest (25) is the pressure ratio of air and gas, and the heat exchange plate ( 3) The ratio of the radius of the inscribed circle of the crest (23) to the radius of the inscribed circle of the trough (24) is the pressure ratio of air to gas. 2. The gas turbine original surface regenerator according to claim 1, characterized in that, the step-down area (14) is a smooth flat plate. 3. The gas turbine original surface regenerator according to claim 1, characterized in that, the deflector (11) is placed into the step-down area along the direction in which air and gas enter and exit the regenerator body (1) respectively (14), the deflectors (11) on the two heat exchange plates (2,3) are at an angle of 90 °. 4. The original surface regenerator of gas turbine according to claim 1 or 3, characterized in that, the guide fins (11) adopt staggered herringbone corrugated CC corrugated sheets or straight fins or zigzag fins. 5. The original surface regenerator of gas turbine according to claim 1 or 3, characterized in that, the guide vane (11) is a zigzag fin, and the zigzag fin is cut from a straight fin Intermittent fins formed at a certain interval staggered from each other. 6. The gas turbine original surface regenerator according to claim 1, characterized in that, when the heat exchange plates (2, 3) are connected into heat exchange channels, the heat exchange corrugations on the heat exchange plates (2) The trough (26) of the sheet (12) and the crest (23) of the heat exchange corrugated sheet (13) on the heat exchange plate (3) are staggered by 45°-75° in the corrugation direction, and the two heat exchange plates (2, 3) The corrugated sheets (12, 13) are point contacts.

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