RU2756713C1 - Recuperative burner block - Google Patents

Abstract

FIELD: energy.

SUBSTANCE: invention relates to the field of energy. The recuperative-burner block contains a burner and a recuperator with an air supply unit, which includes a flow swirl generator with a tangential air supply pipe, forward and reverse annular air ducts connected through a swirler, serially connected to the flow swirl generator and separated by a partition, while the return duct is connected to to the air manifold connected to the burner, a cylindrical heat-transferring wall, a smoke channel with radiation and convective stages, the latter containing a perforated pipe plugged from the rear end. The inlet part of the perforated pipe is made in the form of an inner quarter of a torus, on the outer surface of which there are protrusions, and on the inner surface of the cylindrical heat-transferring wall there is an annular flow divider.

EFFECT: invention makes it possible to increase the final temperature of the heated air and to increase the thermal efficiency of the proposed device.

1 cl, 5 dwg

Description

The invention relates to recuperative devices for heating gas furnaces and can be used for high-temperature heating of air used for fuel combustion in heating and thermal furnaces.

Known recuperative-burner unit containing a burner and a recuperator, placed close to each other in the masonry of the furnace, where the air supply unit containing a swirl generator with a tangentially installed branch pipe is connected in series to the direct (internal) and return (external) air annular channels, separated by a cylindrical a partition, and the smoke channel, located coaxially with the annular air channels and separated from the inner straight channel by a cylindrical heat-transferring wall, contains a radiation and convective stage, the latter containing a perforated pipe plugged from one end (E.N. Saburov, Cyclonic heating devices with intensified convective heat exchange / Arch. State Technical University - Arkhangelsk: North - Western book publishing house, 1995. - 341 p.) - analogue.

The disadvantage of this recuperative-burner unit is its low thermal efficiency.

The closest in technical essence to the proposed invention is a recuperative-burner unit having a burner and a recuperator, with a unit supplying air to the recuperator, containing a swirl generator with a tangential air supply pipe, forward and reverse annular air ducts connected in series to the swirl generator and separated by a partition , while the return channel is connected to the air manifold connected to the burner, the smoke channel located coaxially with the annular air channels, and the cylindrical heat transfer wall, the latter is located between the smoke and return air channels, the direct and return channels are connected through a swirler, and the partition separating them made in the form of a truncated cone expanding in the direction of the inlet of the smoke channel (RF patent for invention No. 2682214, IPC F23L 15/04 (2006.1) from 11.07.2018. Publ. 03/15/2019 Bul. No. 8) - prototype.

The disadvantage of this recuperative-burner unit is its low thermal efficiency due to the fact that in the front part of the convective stage there is a weak intensity of heat transfer from flue gases to the heat-transferring cylindrical wall.

The objective of the invention is to increase the thermal efficiency of the recuperative-burner unit.

To achieve this, in a recuperative-burner block, which has a burner and a recuperator, with an air supply to the recuperator, a unit containing a swirl generator with a tangential air supply branch pipe connected through a swirler of forward and reverse annular air ducts connected in series to the swirl generator and separated by a partition, at the return channel is connected to an air manifold connected to the burner, a cylindrical heat-transfer wall, a smoke channel with radiation and convective stages, the latter containing a perforated pipe plugged from the rear end, the inlet part of which is made in the form of an inner quarter of a torus, and on its outer surface are installed protrusions, annular flow divider located on the inner surface of the cylindrical heat transfer wall.

FIG. 1 shows a recuperative burner block, longitudinal section; in fig. 2 - callout A in figure 1; in fig. 3 - section b-b in figure 1; in fig. 4 - section B-B in figure 1; in fig. 5 shows graphs characterizing the sequential effect of various structural elements on the change in the heat transfer coefficient along the length of the part of the heat transfer cylindrical wall located at the beginning of the convective stage, in the directions of the flue gas flow: line 20 - for the convective stage of the prototype design, line 21 - for the convective stage, the inlet part of which is made in the form of an inner quarter of a torus, line 22 is for a convective stage, the inlet part of which is made in the form of an inner quarter of a torus, and projections are installed on its outer surface, line 23 is for a convective stage, the inlet part of which is made in the form of an inner quarter torus, with protrusions on its surface, and an annular flow divider is located on the inner surface of the heat-transferring wall.

FIG. 5 the following designations are used: α is the heat transfer coefficient for the cases of the convective stage in the proposed design options; z is the longitudinal coordinate measured from the beginning of the convective stage in the direction of the flue gas flow.

The recuperative-burner unit includes a burner 1 and a recuperator 2, with an air supply unit to the recuperator, containing a flow swirl generator 3 with an air supply pipe 4 located tangentially with respect to the inner surface of the flow swirl generator 3, to which direct 5 and return 6 are connected in series annular air channels connected through a swirler 7 and separated by a partition 8, and the return channel 6 is connected from the opposite side to the air manifold 9 connected to the burner 1, and the smoke channel, located coaxially with the annular air channels 5 and 6, has a cylindrical heat transfer wall 10 , radiation 11 and convective 12 stages, while the latter contains a perforated pipe 13 plugged from the rear end, forming an annular channel 14 with a heat transfer wall 10, and the front end of the perforated pipe 15 is made in the form of an inner quarter of a torus, with protrusions 16 on its surface, and on the inner surface On the heat transfer wall 10, there is an annular flow divider 17, which separates the front part of the annular channel 14 and forms a set of vortex chambers 18.

The recuperative-burner block operates as follows.

The air inlet to the recuperator through the pipe 4 the inner surface tangentially swirling generator 3, is twisted, extends straight annular air channel 5 and is heated from its inner surface - separating air baffle channels 8. After that, the air is turned through 180 ^0, is twisted in the swirler through 7 and the return annular channel 6 and the air collector 9 are directed to the burner 1. In this case, the air in the channel 6 is heated from the cylindrical heat-transfer wall 10 and the partition 8. Through the inlet 19, the waste products of combustion with high temperature enter the radiation stage 11 of the smoke channel, and then with a lower temperature to the convective stage 12. In the radiation stage 11, the flue gases transfer heat to the heat-transferring cylindrical wall 10 mainly due to radiation, and in the convective stage 12 - due to convection from the swirling stream of flue gases supplied to the vortex chambers 18 through the first row of holes and their jet outflow from the remaining rows of the perforated pipe 13 onto the cylindrical heat transfer wall 10. The cooled flue gases are removed from the convective stage through the annular channel 14. The heat transfer wall transfers part of the heat received from the flue gases by radiation to the partition 8 separating the air channels and heats it ...

In accordance with the graph 20 shown in Fig. 5, when the flue gases enter the perforated pipe 13 of the prototype design, an extended separation zone is formed from its input edge, the pressure in which is lower than in the annular channel 14. This leads to the formation of a return flow from the annular channel 14 back to the perforated pipe 13 through the first row of holes. There is a stagnant zone in the annular channel 14 opposite the first row of holes, and the intensity of heat transfer to the cylindrical heat transfer wall 10 in this area is the lowest.

When the inlet part of the perforated pipe is made in the form of an inner quarter of the torus, a smooth entrance of flue gases into the perforated pipe is observed, the flow separation zone is eliminated, the pressure of flue gases in the perforated pipe increases near the first row of holes, there is a jet outflow of gases from the perforated pipe into the annular channel 14 and the coefficient heat transfer on the cylindrical heat transfer wall 10 opposite the first row of holes increases 3 ... 3.5 times (line 21).

Installation of protrusions 16 in front of the holes of the first row reduces the kinetic energy of the flue gas flow at the first row of holes, thereby increasing its pressure behind the protrusions, improving the flow of flue gases through the first row of holes, increasing the flow rate of the jets onto the cylindrical heat transfer wall 10. The heat transfer coefficient on it the surface in the area of impact of the first row of jets increases in comparison with the prototype from 3.5 to 10 times (line 22).

When installed on the inner surface of a cylindrical heat transfer wall in the convective stage of the annular flow divider separating the front part of the annular channel 14, a set of vortex chambers 18 is formed. Swirling of flue gases leads to additional intensification of heat transfer on the surface. As a result, in comparison with the prototype, the heat transfer coefficient increases here from 5.5 to 13 times (line 23).

The presented results were obtained by the authors during numerical modeling of aerodynamics and heat transfer in a convective stage of a recuperative-burner unit with a thermal power of 140 kW in a three-dimensional formulation using the ANSYS Fluent 15.0 software package. Testing of the calculation methodology was carried out according to experimental data obtained with a jet flow of a coolant in a modular recuperator (E.N. Saburov, S.I.Ostashev, A.N. Orekhov, Yu.L. Leukhin, models of jet modular recuperator // Promyshlennaya energetika. 1988. No. 6. - P. 33–37). Comparison of calculations and experiments showed their good agreement.

When the inlet part of the perforated pipe is made in the form of an inner quarter of a torus and smooth protrusions are installed in front of the holes of the first row, the flow of flue gases through the first row of holes is improved, the speed of the jets flowing onto the cylindrical heat-transfer wall increases. Installation of an annular flow divider on the inner surface of the last in the convective stage, separates the front part of the annular smoke channel and forms a set of vortex chambers in which the flue gas flow swirls. An increase in the flow rate of the flue gas jets, as well as the swirling of the flow, lead to a significant intensification of heat transfer on the cylindrical heat transfer surface. All of the above measures will ensure an increase in the heat transfer coefficient from flue gases to the heated air, a higher final temperature of the heated air and will lead to an increase in the thermal efficiency of the proposed device.

Claims (1)

A recuperative-burner block containing a burner and a recuperator with an air supply unit, including a swirling flow generator with a tangential air supply branch pipe, direct and reverse annular air channels connected through a swirler, serially connected to the swirling flow generator and separated by a partition, while the return channel is connected to the air manifold connected to the burner, a cylindrical heat-transfer wall, a smoke channel with radiation and convective stages, the latter containing a perforated pipe plugged from the rear end, characterized in that the inlet part of the perforated pipe is made in the form of an inner quarter of a torus, on the outer surface of which there are installed protrusions, and an annular flow divider is located on the inner surface of the cylindrical heat-transfer wall.

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