Recuperator burner with counter-current twin-fluid induction recuperator

Abstract

The recuperator (1) has a dual-fluid system (2,3) with separate flow passages for conducting dual fluids, each of which includes at least one flow passage (4,5) open on both sides, which enter and leave through the intake input and exhaust output (6,7;8,9) at opposite ends of the burner inlet (10) and the burner outlet (11), one of the fluids consisting of the combustion air to be preheated and the other consisting of the burner exhaust gases. The recuperator (1) houses the dual-fluid system (2,3) in a one-piece heat transfer housing (12) whose jacket-like outer wall (14) forms a fluid reservoir (13) with the burner inlet (10) and the input (6) and output (8) attached integrally thereto.

Description

[Technical Field]

[0001] The present invention relates to an improvement to a recuperator burner with counter-flowing twin fluids as set forth in the preamble of claim 1. [Background technology]

[0002] The efficiency of a recuperator burner is increased by exchanging heat between the burner feed gas stream and the burner exhaust gas stream. A recuperator is used for this purpose, exchanging heat between the feed gas stream and the burner exhaust gas stream. Recuperators can be made from different materials, particularly metal and ceramic materials. In particular, metal materials are used in the low and medium temperature ranges, and ceramic materials are used in the high temperature ranges. By using a combination of materials, the individual parts of the recuperator can be optimized to exhibit good heat transfer.

[0003] A recuperator for a recuperative burner made of ceramic material is known from US Pat. No. 5,623,799. The recuperator includes an inner tube, an outer tube, and a heat-transfer intermediate tube. The intermediate tube divides the annular space between the inner and outer tubes into two concentric, essentially ring-shaped passages. Combustion air to be preheated flows through the inner passage, and exhaust gases from the burner flow through the outer passage.

[0004] Compared to steel recuperators, ceramic recuperators have the distinct advantage of high heat resistance. However, this advantage comes at the expense of significantly reduced efficiency, as the ceramic tubes are constructed as smooth or corrugated tubes with limited heat transfer surface. To improve recuperator efficiency, it is known to increase the heat transfer surface area. To achieve this, the walls of the intermediate tubes are curved outward to form outward protrusions and inward to form inward protrusions at numerous points distributed along their length and circumference.

[0005] The protrusions greatly expand the heat transfer surface of the intermediate tube, resulting in a highly efficient recuperator. The inverted protrusions create depressions that force the gas to alternately compress and expand along the flow path, creating a linear flow path with a series of contracting and expanding sections along the length of the intermediate tube. This results in uniform flow conditions along the length of the recuperator and prevents the formation of boundary layers. This results in flow conditions that bring the recuperator's efficiency closer to that of a fractured steel recuperator. The entire recuperator is constructed from silicon-impregnated silicon carbide (SiSiC).

[0006] A recuperator burner with a ceramic recuperator is known from US Pat. No. 5,623,999, which has pleats extending in the longitudinal direction of the recuperator to increase the heat exchange surface. The pleats are gradually curved, in particular wavy, and are intended to ensure a large heat exchange surface. Optimum heat transfer is achieved by designing the shape and number of the pleats. The recuperator is advantageously made of silicon carbide ceramic and is advantageously manufactured as a slip casting part.

[0007] Patent Document 3 also discloses a ceramic recuperator for a recuperator burner, also consisting of a tube section. The tubes of this recuperator have a combustion chamber at the end and are used to separate the outgoing combustion gas from the incoming combustion air and exchange heat between them. Radial serrations formed on the recuperator increase the recuperator's surface area and enhance heat transfer from the combustion gas to the combustion air. The serrations repeatedly disrupt the flow boundary layers on both the exterior and interior of the recuperator, greatly increasing heat transfer compared to a smooth surface. The ceramic combustion chamber held in the recuperator can be manufactured using silicon carbide. When the recuperator tube section is integrally formed with the combustion chamber at the end, a simple and robust design results. The combustion chamber walls are smooth. The combustion chamber can be formed on the recuperator during manufacturing using a slip casting process without any further effort. Silicon carbide ceramic is particularly suitable as a ceramic material for recuperators because it has suitable heat resistance and heat conductivity.

[0008] Known ceramic recuperators are therefore based on tubes with complexly shaped surfaces to increase the heat exchange surface. The surfaces of these structures tend to be rounded, especially when the recuperator is made of ceramic. Furthermore, they are not possible to manufacture cost-effectively with high precision. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] German Patent Publication No. 19616288 [Patent Document 2] European Patent No. 1486728 [Patent Document 3] German Patent No. 19541922 Second Publication Specification Summary of the Invention [Problem to be solved by the invention]

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a recuperator burner with a counter-flow twin-fluid induction recuperator that maintains good heat transfer while at the same time being capable of being manufactured in a cost-effective manner. [Means for solving the problem]

[0011] This object is achieved by a series of inventive features set forth in claim 1. According to the features of the invention set forth in claim 1, a recuperator is provided, in which a two-fluid system (hereinafter referred to as a "dual-fluid system") for dual fluids flowing in opposite directions is housed in a single heat transfer housing. According to the invention, the heat transfer housing has a fluid reservoir at its end, connected to the burner inlet, which integrally connects the inlet for preheated combustion air and the outlet for exhaust gas. Due to the shape of the heat transfer housing with the fluid reservoir, the outer wall of the heat transfer housing is defined at the burner inlet as a kind of vessel wall enclosing the internal space. Two flow paths (hereinafter referred to as "dual flow paths") can be configured in this internal space for the inflow or outflow of two fluids (hereinafter referred to as "dual fluids").

[0012] Since the fluid reservoir is formed by the material extension of the heat transfer housing, which forms the only external boundary area, the internal structure of the main body through which the dual flow passages penetrate can terminate like the bottom of the reservoir, or can protrude into the reservoir by an extension of the heat exchanger. In this way, improved heat exchange characteristics can be achieved by integrating the inlet and outlet necks of the flowing fluid. The problem of discontinuity caused by the connection point between the inlet and outlet is avoided. This increases wear resistance and provides more options for improving the integration of the recuperator into the recuperator burner.

[0013] Advantageously, a single spatial shape can be selected for the heat transfer housing in order to integrate a dual-fluid system provided for guiding dual fluids flowing in opposite directions, so that a dual-flow path extending in the longitudinal direction of the recuperator can be formed, thus developing, for example, a serpentine dual-flow field.

[0014] Additive manufacturing can be used to construct heat exchanger structures with cellular structures having triply periodic minimal surfaces (TPMS), such as gyroids, double gyroids, gyroids with rectangular, cylindrical, or spherical cellular structures. The flow rates of the two fluids can be optimized by selecting the cellular structure. The flow lengths of each of the two fluids can be increased by the present invention without significant contraction or expansion, as is the case with conventional techniques.

[0015] The recuperator according to the present invention can be manufactured from metal and / or ceramic materials. The cold / low temperature combustion air or fresh air can flow more effectively into the recuperator through the fluid reservoir, both from the viewpoint of fluid technology and improving heat exchange efficiency. The space in the heat transfer housing can be used to create a fluid field inside the heat transfer housing.

[0016] The dual flow passages provided in the heat transfer housing can be cut / opened at one end of the burner inlet, especially if several passages are advantageously arranged in the longitudinal direction of the recuperator, so that an almost simultaneous inflow of dual fluids is possible through said inlets. [Effects of the Invention]

[0017] It has been surprisingly found that the present invention not only improves the heat transfer characteristics by increasing the area of ​​the heat transfer surface, but also improves the fluid conditions in each of the dual flow paths. The improved fluid conditions in each of the dual flow paths are particularly important. The integral connection configuration results in an additional heat exchange surface being available, which is a function-enhancing connection, especially for the combustion air intake at the burner inlet. Therefore, the present invention also allows for an increase in the area of ​​the heat transfer surface.

[0018] Particularly advantageously, the heat exchanger body has a gyroid structure, which is a special design of a triple periodic minimal surface (TPMS). The gyroid structure can, for example, divide the heat exchanger space into a dual-fluid system, i.e., dual-flow paths running in the longitudinal direction of the recuperator without intersecting each other. Additional flow paths for at least one of the third and fourth fluids can be integrated into the heat transfer housing, particularly in combination with the gyroid structure. The dual-flow paths can also be divided into partial dual-flow paths, which can also produce a cooperative effect in the fluid reservoir of the main flow section.

[0019] The advantageous all-ceramic design of the recuperator with intake air input, exhaust output, and combustion chamber, i.e., integrating all relevant components of the recuperator burner, further minimizes the connection interfaces. The effect of the solution of the present invention is to improve the efficiency of the recuperator due to the beneficial material properties (e.g., high heat transfer rate) and material transformation characteristics of 3D printable reaction-bonded silicon carbide (RBSiC).

[0020] Low maintenance costs are achieved by eliminating the use of iron and copper materials, which are conventionally intended for use in recuperators. Preferably, achieving a monolithic (all-ceramic) recuperator by designing the individual regions as a single unit is achieved by using 3D technology suitable for reaction-bonded silicon carbide materials. [Brief explanation of the drawings]

[0021] [Figure 1]1 shows a partially cutaway perspective view of a recuperative burner with a ceramic recuperator according to a first embodiment; [Figure 2] 2 shows a longitudinal section of the recuperative burner shown in FIG. 1; [Figure 3] 1 shows a cross section of a recuperative burner according to FIG. [Figure 4] Based on FIG. 1, a longitudinal element is shown which is added to the recuperative burner. [Figure 5] FIG. 10 is a partial cross-sectional perspective view of a recuperator without a jacket pipe in a recuperative burner according to a second embodiment. [Figure 6] 6 shows a longitudinal section of the recuperator shown in FIG. 5. [Figure 7] FIG. 10 is a partial cross-sectional perspective view of a recuperator without a jacket pipe in a recuperative burner according to a third embodiment. [Figure 8] 10 shows a cross section of a recuperator in a recuperative burner according to a fourth embodiment. [Figure 9] FIG. 10 is a partial cross-sectional perspective view of a recuperator without a jet tube in a recuperative burner according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Further embodiments of the invention and their advantages can be seen from the following description and the dependent claims. The invention is explained in more detail below with reference to the attached drawings. The invention, as explained in detail below, relates to a recuperative burner which can be divided into three areas, independent of the corresponding functional areas, namely a burner inlet connection area, a recuperator area and a flame outlet area with a burner outlet.

[0023] 1 to 4 show a recuperator burner according to a first embodiment, which includes a recuperator 1, which can be made of, for example, a metallic material and / or a ceramic material. The recuperator 1 has separate fluid systems 2 and 3, each having at least one flow path 4 and 5 opening on both sides for guiding dual fluids flowing in opposite directions. The at least two fluids (dual fluids) can enter and exit via intake inputs 6 and 7, and exhaust outputs 8 and 9 at opposite ends of the burner inlet 10 and burner outlet 11, respectively.

[0024] One of the twin fluids in the opposite directions consists of combustion air to be preheated, and the other of the twin fluids consists of exhaust gas from the burner. In the embodiment of Figures 1 to 4, the combustion air to be preheated flows through flow path 5, and the exhaust gas flows through flow path 4, which is sealed by the adjacent recuperator jacket 20 and opens to the outside. A heat transfer housing 12 is provided as the recuperator 1, which is made in one piece and houses the fluid systems 2 and 3, respectively, and whose jacket-shaped outer wall 14 forms a fluid reservoir 13 at the burner inlet 10, which has the input 6 and output 8 attached in one piece.

[0025] 2, the input 6 for the combustion air to be heated or fresh air can be positioned to at least partially axially overlap the heat transfer housing 12 so that the combustion air to be preheated can enter the input 6 directly from the side. The fluid reservoir 13 comprises an outer wall 14 that tapers relative to the heat transfer housing 12, thereby forming a spherical extension 15 of the heat transfer housing 12. The spherical extension 15 can have a shoulder 16 that connects together the necks 17 and 18 for the input 6 for the combustion air to be preheated and the output 8 for the exhaust gases from the burner.

[0026] In order to fluidically separate and guide the counter-flowing dual fluids to the input 6 and the output 8, the fluid reservoir 13 defines an internal space surrounding at least one inlet wall 19. The at least one inlet wall 19 can be configured as a lateral surface of a body of revolution, as shown in the embodiment based on Fig. 5. In the at least one inlet wall 19, a spatial separation system 21 can be inserted into the fluid reservoir 13 in order to transfer at least one flow path to the input 6 or the output 8, as shown in Fig. 7. Preferably, the at least one inlet wall 19 can be configured integrally with the heat transfer housing 12.

[0027] 1 to 4, the flow paths 4 and 5 of the fluid systems 2 and 3, respectively, are divided into a plurality of partial dual flow paths for guiding dual fluids in opposite directions. The partial flow paths of at least one of the flow paths 4 and 5 can be fluidly connected via the flow path wall openings 22. At least one of the flow paths 4 and 5 has a number of aligned pipe sections, each of which is made of minimal curved surface elements and is connected in series.

[0028] The minimal surface elements are preferably composed of triply periodic minimal surfaces. The cellular structure resulting from the triply periodic minimal surfaces can be rectangular, cylindrical, or spherical. The first embodiment shown in Figures 1 to 4 has a rectangular cellular structure. Figure 8 shows an embodiment in which the cellular structure is cylindrical. The recuperative burner 1 further includes, for example, a combustion gas connection piece 23 for a combustion tube passing through the heat transfer housing 12, so that the combustion gas can be delivered to the burner outlet 11. Instead of a combustion tube, the combustion gas passage from the combustion gas connection piece 23 to the heat transfer housing 12 can also be molded integrally.

[0029] As shown in Figure 9, at least one of the third and fourth fluid systems, each having at least one flow path opening on both sides for at least one of the third and fourth fluids, can be integrated into the heat transfer housing. At least one of the inlet and / or outlet connection pieces 24 can be integrally formed in the fluid reservoir for at least one of the third and / or fourth fluid systems.

[0030] 1-4 show that the heat transfer housing 12 can have an internal body structure 25 through which air can flow, and the internal body structure 25 can be positioned to extend into the fluid reservoir 13, so that the combustion air to be preheated can enter the internal body structure 25 directly from the side. Acute or obtuse flow angles can be formed in the region of the input 6 as well as the output 8.

[0031] As the embodiment according to Figures 1 to 4 shows, the input 6 and the output 8 can be arranged opposite each other, for example in the recuperator 1. A second embodiment according to Figures 5 and 6 shows the components connecting the input 6 and the output 8 arranged at an angle to each other.

[0032] 7 shows a third embodiment with corresponding connection elements for the input 6 and output 8 and a spatial separation system 21 in the fluid reservoir 13, as previously described. The all-ceramic recuperator 1 is preferably monolithic. The ceramic preferably consists of silicon-impregnated silicon carbide. Non-oxide and / or oxide ceramic materials are particularly preferred, in particular silicon-impregnated reaction-bonded silicon carbide (RBSiC), silicon-impregnated reaction-bonded silicon carbide / boron carbide (RBSiC / B4C), silicon-impregnated silicon carbide (RBSiC), nitride-bonded silicon carbide (NSiC), pressureless sintered silicon carbide (SSiC), recrystallized silicon carbide (RSiC), aluminum oxide, silicate-bonded silicon carbide, and zirconium oxide. [Explanation of symbols]

[0033] 1... recuperator, 2, 3... dual fluid system, 4, 5... flow path, 6... input (intake input), 8... output (exhaust output), 10... burner inlet, 11... burner outlet, 12... heat transfer housing, 13... fluid reservoir, 14... outer wall, 15... spherical extension, 16... shoulder, 17... neck, 19... inlet wall 20... recuperator jacket, 21... space separation system, 22... flow path wall opening, 23... combustion gas connection part, 24... connection part, 25... main body internal structure part

Claims

1. A recuperative burner consisting of three areas: a burner inlet, a recuperator connected to the burner inlet, and a burner outlet connected to the recuperator, wherein the recuperator is a heat transfer housing integrally formed with a jacket-shaped outer wall portion; a dual-fluid system housed in the heat transfer housing and configured to induce dual-fluids composed of fluids flowing in opposite directions and separated from each other; Equipped with one fluid of the dual-fluid system comprises combustion air to be preheated, flowing through the heat transfer housing from one intake input located at the burner inlet to one exhaust output located at the burner outlet; the other fluid constituting at least a part of the dual-fluid system flows through the heat transfer housing from the other intake input disposed at the burner outlet to the other exhaust output disposed at the burner inlet so as to be comprised of exhaust gas from the recuperative burner; A recuperative burner characterized in that at the burner inlet, the jacket-like outer wall portion of the heat transfer housing forms a fluid reservoir including the one intake input and the other exhaust output that are integrally attached.

2. 2. The recuperator burner of claim 1, wherein the fluid reservoir comprises an outer wall portion having tapered walls forming a spherical extension in the heat transfer housing with a shoulder for connecting together one neck for the one intake input and the other neck for the other exhaust output.

3. 3. The recuperator burner according to claim 1, wherein the internal space of the fluid reservoir surrounds at least one inlet wall for fluidically separating and guiding the dual fluids to the one intake input and the other exhaust output.

4. 4. The recuperator burner of claim 3, wherein said at least one inlet wall is configured as a side of a three-dimensional geometric body of revolution.

5. 5. The recuperator burner according to claim 4, wherein the at least one inlet wall inserts a plate-shaped spatial separation system into the fluid reservoir to separate the flow path of the one fluid from the flow path of the other fluid flowing toward the other exhaust output, so as to distinguish between the flow path of the one fluid flowing from the one intake input and the flow path of the other fluid flowing toward the other exhaust output.

6. 6. The recuperative burner according to claim 3, wherein the at least one inlet wall is integral with the heat transfer housing.

7. The recuperator burner according to any one of claims 1 to 6, characterized in that at least one of the flow paths constituting the dual-fluid system is divided into a plurality of partial dual-fluid flow paths for guiding the dual-fluids.

8. A recuperator burner as described in Claim 7, characterized in that the partial dual flow paths can be fluidly connected by flow path wall openings.

9. A recuperative burner described in any one of claims 1 to 8, characterized in that the heat transfer housing has a gyroid structure.

10. A recuperator burner as described in Claim 9, characterized in that the minimal curved surface elements that make up the cell structure of the gyroid structure are composed of triple periodic minimal curved surfaces.

11. The recuperator burner according to claim 10, wherein the cell structure resulting from the triple periodic minimal curved surface is a rectangular solid, a cylindrical or a spherical shape.

12. A recuperative burner as described in any one of claims 1 to 11, further comprising a third fluid system opening on both sides of the flow path of the third fluid, or a fourth fluid system opening on both sides of the flow path of the fourth fluid, wherein the third or fourth fluid system is integrated into the heat transfer housing.

13. 13. A recuperator burner according to claim 12, wherein at least one of an inlet and / or outlet connection for at least one of the third and / or fourth fluid systems is integrally attached to the fluid reservoir.

14. A recuperative burner as described in any one of claims 1 to 13, characterized in that the heat transfer housing is arranged so that a main body internal structure, into which the combustion air can flow, extends into the fluid reservoir, and the preheated combustion air can flow directly into the main body internal structure from the side.

15. A recuperator burner as described in Claim 14, characterized in that the flow of combustion air flowing into one of the intake inputs can form an acute or obtuse inflow angle in the area of ​​the one of the intake inputs.

16. A recuperator burner as claimed in any one of claims 1 to 15, characterized in that the one intake input and the other exhaust output are arranged opposite each other on the recuperator in a straight line alignment.

17. A recuperative burner as described in any one of claims 1 to 16, characterized in that a combustion tube is introduced at the burner inlet so that it extends through the heat transfer housing and opens toward the combustion chamber.

18. 18. A recuperator burner according to any one of claims 1 to 17, wherein the heat transfer housing is made of ceramic or metal or both materials.

19. 19. The recuperator burner according to claim 1, wherein the recuperator is designed as an integrated ceramic recuperator made entirely of ceramic.

20. 20. The recuperator burner of claim 18 or 19, wherein the ceramic is made from at least one of a non-oxide and an oxide ceramic material including silicon-impregnated reaction-bonded silicon carbide (RBSiC), silicon-impregnated reaction-bonded silicon carbide / boron carbide (RBSiC / B4C), silicon-impregnated silicon carbide (RBSiC), nitride-bonded silicon carbide (NSiC), pressureless sintered silicon carbide (SSiC), recrystallized silicon carbide (RSiC), aluminum oxide, silicate-bonded silicon carbide, and zirconium oxide.

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