JPH0459522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an asymmetric branch pipe used for joining a spirally arranged water-cooled wall pipe and a vertically arranged water-cooled wall pipe in a boiler furnace water-cooled wall pipe structure.

BACKGROUND OF THE INVENTION This type of asymmetric branch pipe in which a two-phase flow of water and steam flows, for example, includes two vertically arranged water-cooled wall pipes 2 for one pipe of an inclined water-cooled wall pipe 1, as shown in FIG. 6a. As shown in FIG. 6b, a three-branch pipe 4 has three vertically disposed water-cooled wall pipes 2 joined to one pipe of the inclined water-cooled wall pipe, and a third branch pipe 6c
As shown in the figure, a four-branch pipe 5 in which four vertically arranged water-cooled wall pipes 2 are joined to one pipe of the inclined water-cooled wall pipe.
An example of the structure of a water-cooled wall tube furnace connected by the two-branch pipe is as shown in FIG. Since the two-phase flow is branched as shown in FIG. 8, there is a drawback that the fluid properties and flow rate between the branch pipes are non-uniform.

In the first place, in a once-through boiler, the amount of water supplied decreases almost proportionally with the boiler load, so as the load decreases, the flow rate in the furnace water-cooled wall pipes, and therefore the flow velocity, decreases to the minimum once-through load (below this load). Even in cases where canned water is recirculated by a boiler circulation pump or a boiler feed water pump, the furnace water-cooled wall tubes are arranged in a spiral to maintain the flow velocity in the tubes necessary to protect the water-cooled wall tubes. By reducing the number of parallel tubes in the furnace, on the other hand, in the upper part of the furnace where the heat load is low, the flow velocity in the pipes required to protect the water-cooled wall tubes is only a fraction of that in the lower part of the furnace (which has a spiral water-cooled wall) where the heat load is high. Therefore, in order to reduce pressure loss and improve the boiler structure, the upper part of the furnace has a vertical pipe structure in which the number of parallel tubes is several times that of the lower furnace. Since the number of pipes is different, there are two ways to connect the section: one using a header and the other using a branch pipe.The former has a complicated header, water-cooled wall tube structure, furnace wall structure, etc., so the furnace wall structure The latter method is advantageous in terms of reliability. However, this latter method also requires improvement in the following points. In other words, in the lower furnace, the water-cooled wall tubes are not vertical but are placed at a slight inclination to the horizontal (usually 15 to 30 degrees), and in the lowest once-through load region, the flow velocity in the tubes is slow and the void ratio is low. Because of the high flow rate, the two-phase flow inside the pipe is almost separated, forming a laminar or wavy flow pattern with steam flowing in the upper part of the pipe and water flowing in the bottom part of the pipe. This is noticeable in variable pressure boilers where the difference in specific gravity between steam and water is large.

In this way, the fluid at the branch pipe inlet becomes a laminar flow or a wavy flow, and the water flows at the bottom of the pipe, so the flow within the branch pipe is not necessarily uniform. flows, that is,
A vertical pipe through which steam flows and a vertical pipe through which water flows exist adjacent to each other, but in the pipe through which steam flows, the inside of the pipe becomes superheated steam due to heating of the vertical pipe section, and in the pipe through which water flows, the inside becomes saturated steam. Alternatively, it becomes a two-phase flow and a temperature difference occurs between the vertical pipes, so
It may cause damage to the furnace wall structure. As mentioned above, the method using a header has drawbacks regarding the furnace wall structure, and the method using branch pipes has the drawback that some flow imbalance tends to occur between the branch pipes.

Problems to be Solved by the Invention The present invention is to connect the water-cooled wall pipes of the lower and upper furnaces, which have different numbers of pipes, by means of branch pipes that ensure uniformity of flow between the branch pipes. .

Means for Solving the Problems This invention provides a water-cooled wall tube that is arranged at an angle to form a furnace wall, and a plurality of water-cooled wall tubes that are connected to one water-cooled wall tube and are arranged vertically. In the boiler furnace wall made of water-cooled wall tubes, a fluid stirring means is built in on the upstream side of the fluid flow from the connection part with the vertically disposed water-cooled wall tubes inside the inclined water-cooled wall tubes.

Therefore, according to the configuration of the present invention, the inlet fluid on the upstream side of the connecting portion with each of the inclined and vertically arranged pipes is stirred and homogenized, and the flow rate of each of the vertically arranged pipes is Distribution will also be equalized.

Embodiments Next, a first embodiment of the present invention will be described with reference to FIGS. 1a and 1b. In each of the embodiments described below, two vertically disposed water-cooled wall pipes 2 are connected to each other by a bifurcated pipe 3. Let us take as an example a case in which one pipe of the inclined water-cooled wall pipes 1 is connected, and a cutter 9 is locally protruded from the bottom of the branch pipe inlet side upstream of the connection part of the inclined water-cooled wall pipes. By scattering the flow of laminar or wavy water 6, it becomes a homogeneous two-phase flow and the fluid in each pipe of the vertically arranged water-cooled wall pipe is made uniform. In FIG. 2, a swirler vane 10 is installed in the inlet side pipe of the branch pipe to homogenize or annularly flow the internal fluid as in the previous embodiment, thereby homogenizing the fluid in each branch pipe. In the third embodiment shown in FIG. 3, a coiled ribbon 11 is installed in place of the swirling blade of the second embodiment, and in the fourth embodiment shown in FIG. Furthermore, in the fifth embodiment shown in FIGS. 5a and 5b, a punch 13, which is substantially similar to the punch 9 of the first embodiment, is locally protruded from the top of the pipe on the inlet side of the branch pipe. This is designed to generate a vortex flow in the wake of the steam 7 to disturb the laminar or wavy flow and to reduce the dynamic pressure at the branch pipe inlet, and each of the above-mentioned embodiments can exhibit the same effects. .

In addition, each property of the fluid state at the inlet of the branch pipe is displayed with respect to the boiler load in FIG.

Effects of the Invention As described above, the present invention incorporates a simple fluid stirring means in the lower water-cooled wall tube when connecting lower and upper water-cooled wall tubes having different numbers of configurations, thereby improving the flow of water to each upper water-cooled wall tube. Since the fluid temperature and the wall tube temperature in each tube can be made equal by equalizing the flow rate distribution, the industrial value is extremely wide and great.

[Brief explanation of the drawing]

FIG. 1a is a longitudinal sectional side view of the main part showing the first embodiment of the present invention, FIG. 1b is a sectional view taken along the line A-A in the previous figure, and FIGS. A vertical sectional side view of the main parts showing the second, third and fourth embodiments,
Fig. 5a is a vertical sectional side view of the main part showing the fifth embodiment of the present invention, Fig. 5b is a sectional view taken along the line BB in the previous figure, and Figs. 6a, 6b and 6c are respectively a bifurcated pipe, A longitudinal sectional side view of the main part showing the connection state of the inclined water-cooled wall pipes with the vertically arranged water-cooled wall pipes using three-branch pipes and four-branch pipes; FIG. 8 is a vertical cross-sectional side view of the main part showing the two-phase fluid flow state in the water-cooled wall pipe connected by a bifurcated pipe, and FIG.
FIG. 3 is a curve diagram showing various properties of the fluid state at the inlet of the branch pipe with respect to the boiler load. 1... Inclined water-cooled wall pipe, 2... Vertical water-cooled wall pipe, 3... Two-branch pipe, 4... Three-branch pipe, 5...
Four-branch pipe, 6...water, 7...steam, 8...missing number,
9...Bottom cover, 10...Swirl blade, 11...Ribbon, 12...Spiral rib or groove, 13...Top cover.

Claims (1)

[Claims] 1. In a boiler furnace wall consisting of a water-cooled wall tube arranged at an angle to form a furnace wall, and a plurality of water-cooled wall tubes connected to one water-cooled wall tube and arranged vertically, An asymmetrical branch pipe characterized in that a fluid stirring means is built in the upstream side of the fluid flow from a connecting portion with the vertically arranged water-cooled wall pipe inside the inclined water-cooled wall pipe.