JPS6124892A - Fluid path - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a fluid passage having a structure that distributes the flow rate downstream of a bend, and is suitable for obtaining a constant flow distribution ratio for a given flow rate. related to fluid passages.

[Background of the invention]

In a fluid passage structured to distribute the flow rate downstream of a bend, a phenomenon occurs in which the flow distribution ratio changes depending on the magnitude of the flow rate due to the bend. The present invention has been made for the purpose of keeping the flow rate distribution ratio constant regardless of the magnitude of the flow rate, and an embodiment thereof is shown in FIG.

In Fig. 1(a), a streamline-shaped protrusion through which the fluid flow passes through the separation point lO where separation begins is fixed to the curved inner wall 2 upstream from the point where the fluid separates. . Here, a streamline is a curved line on which the tangent at each point coincides with the direction of the velocity vector at that point. Therefore, a streamline passing through the delamination point where delamination begins encompasses the delamination region. In FIG. 1), the curved inner wall 2 has the same shape as the portion of the protrusion that comes into contact with the fluid. In the embodiments shown in FIGS. 1(a) and 1(b), it is possible to avoid the separation phenomenon that occurs due to changes in the direction of the main flow, and as a result, the flow distribution on the downstream side can be controlled regardless of the magnitude of the flow rate. can be kept constant.

The phenomenon in which the flow distribution ratio changes depending on the magnitude of the flow rate is explained as follows.

When the direction of fluid flow suddenly changes, a vortex is generated due to the reverse flow in the shaded area in Figure 2, causing separation of the boundary layer.
This is because a separation region (dead water region) 1 is formed. In such a region where delamination occurs, the effective flow path area decreases due to backflow, and the flow distribution ratio changes compared to the case where delamination does not occur. When the flow velocity is small, no separation occurs, and the flow distribution ratio W of the cicada shown in Fig. 2 is reduced.
1/W2 is approximately equal to the channel area ratio of 81/82.

However, as the flow rate increases and the mainstream flow velocity exceeds a certain value and the flow reaches a turbulent region, the flow separates, and the flow rate distribution ratio W+/w2 becomes larger than the channel area ratio 81/82.

If we think about this peeling phenomenon from the perspective of pressure distribution, when the boundary layer separates, the pressure distribution on the wall surface will be significantly different from that in the case of potential flow (flow without eddies), and the difference in pressure will cause drag (pressure power) increases. Further, in the internal flow as shown in FIG. 2, a problem arises in that the pressure loss increases significantly in the process of mixing the uneven flows caused by separation.

In a fluid passage with such branched flow, there is a problem in that when separation occurs, the flow rate distribution ratio changes greatly depending on the flow rate, and pressure loss increases.

Conventionally, many ideas have been proposed and put into practical use in order to reduce or eliminate the increase in pressure loss caused by peeling.

For example, devices that manipulate the mainstream outside the boundary layer to prevent separation include guide vanes in the mainstream, wire mesh or perforated plates uniformly placed on the cross section of the flow path, and grids and slits. There is a way to put it.

These methods are advantageous if the wall friction loss due to the guide vanes, wire mesh, and perforated plate is smaller than the mixing loss due to peeling.

The following methods can be used to directly change the properties of the boundary layer without changing the mainstream state.

(1) Dripping wire (2) Portex generator (3) Suction and blowing from the slit 4) Cooling or heating the wall surface However, these devices have some of the drawbacks shown below.

(1) Complex structure (2) Insufficient structural strength in high flow velocity field (3) Pump,
A separate power source such as a blower or heater is required.Also, if all of these conventional examples are applied to the fluid passages that divide the flow, the design is delicate and not necessarily necessary to keep the IN and sensitive distribution ratio constant regardless of the size of the flow rate. It is not an easy method to try,
Even in cases where this is not the case, there are problems with workability, cost, etc., and it may not be possible to apply the method to actual fluid passages with branched flows.

Furthermore, in a conventional embodiment similar to the present invention, as shown in FIG. There is one in which a streamlined guide vane is provided in a branch pipe extending on both sides from a portion constituting the section. (Unexamined Japanese Patent Publication No. 58-39
993 Publication) The above conventional example has the effect of controlling the flow to the left and right branch pipes without fluctuation by the guide vane, but the target fluid passage is limited to the T-shaped branch pipe, and the fluid passage targeted by the present invention, That is, the structure and purpose are different from a fluid passage in which a branch point is located downstream of a bend where the main flow direction changes.

[Object of the invention] The object of the present invention was proposed in view of the above points, and
A fluid passage with a bending part that changes the direction of the main flow and a structure in which the flow rate is distributed downstream of this bending part, so that a constant flow distribution ratio can be obtained regardless of the flow rate, and the fluid has low pressure loss. The purpose is to provide a passage, −
! It is an object of the present invention to provide a highly practical fluid passageway that is easier to design and manufacture than the above-mentioned conventional techniques, does not require a separate power source.

[Summary of the invention]

In order to achieve the above object, in the fluid passage of the present invention, the space between the streamline passing through the separation point where the fluid flow starts to separate due to a change in the main flow direction and the flow path wall facing the separation area. By blocking the flow of fluid into the area upstream of the position where the fluid is divided, the flow distribution ratio does not change even if the flow rate changes, and the flow rate distribution is adjusted to the current flow area ratio. be determined.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 4 shows a flow velocity vector diagram in a fluid passage having a structure in which the flow is completely distributed downstream of the bend.

FIG. 1 shows an embodiment of the present invention for the fluid passageway of FIG. 4. FIG. 1(a) shows a projection in the shape of a streamline that passes through the separation point lO where the flow begins to separate, and is fixed to the curved inner wall 2 upstream of the position where the fluid separates. In FIG. 1 Φ), the curved inner wall 2 has the same shape as the part of the protrusion that comes into contact with the fluid.

Next, the operation of the present invention will be explained with reference to FIGS. 1 and 4.

FIGS. 4(a) and 4(b) Vi correspond to the case where no peeling occurs and the case where peeling occurs, respectively. In (a), the flow is in a laminar flow state and the flow rate distribution ratio Wl /W2 is approximately equal to the channel area ratio St /s2. On the other hand, in Φ), the flow is in a turbulent region and the flow rate to one branch channel decreases due to the separation region near the inner wall 2, resulting in a flow rate distribution ratio W.

/W2 is larger than the channel area ratio. Figure 1 (a
), no peeling occurs due to the presence of the protrusions, and the flow rate distribution ratio Wl/W2 becomes approximately equal to the channel area ratio. This is because the upstream side of the protrusion is smoothly connected to the internal boundary wall 2, so peeling is less likely to occur at this position. In addition, on the downstream side of the protrusion, the protrusion has a streamlined shape, so it has a convex shape, and the boundary layer is separated due to the so-called Coanda effect, in which the jet adheres along the convex wall surface. 9. Prevents peeling.

The shape of the protrusion must be determined through experiments or numerical analysis. In internal flow, the larger the flow rate, the larger the separation area, except in cases where instability such as pulsation occurs. Therefore, the shape of the protrusion 7 in FIG. 1(a) and the inner wall 2 in FIG. 1(b) may be in the shape of streamlines that form the peeling region at the maximum flow rate. By doing this, it is possible to obtain a uniform flow rate determined by the channel area ratio without causing peeling even at a flow rate below the maximum flow rate.

FIG. 5 shows a cooling water conduit for a condenser used in nuclear power plants, thermal power plants, etc., as an example of a fluid passage structured to distribute the flow rate downstream of a bend. The cooling water flows in from point A, changes its flow direction at point B, is divided by the partition plate 8, flows along the partition plate, and reaches 0.
At the point, the water is sucked up by the water pump and guided to the condenser. As shown in FIG. 6, when a separation region occurs due to bending of the fluid passage, the distribution ratio W+ /Wt of the flow rate flowing along the partition plate is the flow passage area ratio S.

/Sz may be significantly different. In this case, fluid motion occurs in the water absorption pump 9. In addition, the flow distribution ratio is 1,0
If it deviates significantly from the position, the rotating blade of the pot will be damaged.5
Tability occurs.

Figure 7 shows the results of numerical analysis of the flow from the inlet through the bend to the partition plate. The flow characteristics are determined by the density P1 of the fluid, the viscosity μ, the representative length De of the flow path, and the Reynolds number Re expressed by the flow velocity V.

pDe'V Re=- μ In this calculation example, the Reynolds number is 106, the flow belongs to the turbulent flow region, and as seen in Figure 7, a separation region l is formed on the downstream side of the bend. .

For this purpose, the area ratio of the branch flow path at the tip of the partition plate is S, /
Although s, is l'''C, the flow distribution ratio is Wl
/W2 = 65/35, which means that the flow rates flowing through the two branch channels are significantly different. For this reason, conventionally, in such a water conduit, a method has been adopted in which the installation angle of the partition plate tip 11 is changed to reduce the area of the branch channel with a larger flow rate. However, in this case, since the heating region varies depending on the magnitude of the flow rate of the water conduit, it is difficult to maintain the heat distribution ratio k constant regardless of the magnitude of the weight.

FIG. 8(a), Φ) shows an embodiment of the present invention for the water conduit. Figure 8(a) shows the space region between the streamline passing through the separation point where the fluid flow begins to separate due to a change in the main flow direction and the channel wall facing the separation heat region, and where the fluid branches. A structure is installed in the area upstream from the location where the In FIG. 8), the shape of the inner flow path wall on the downstream side of the curve 9 is shaped like a streamline passing through the separation point.

FIG. 9 shows the results of numerical analysis of the flow for the embodiment shown in FIG. The Reynolds number is 106, which is the same as in the numerical analysis example shown in FIG. In this case, since no exfoliation region occurs, the flow rate distribution ratio W+/Wt=52/48 for the flow path area ratio 8 I/S2=1. Uniform flow distribution ratio w determined based on flow path area ratio,
/wt = 1, the flow rate distribution ratio can be kept within a variation range of ±2-. Further, at a flow rate lower than this, the fluctuation width of the flow rate distribution ratio becomes smaller, so the flow rate distribution ratio approaches the flow path area ratio.

Furthermore, in this embodiment, the pressure difference between the inlet 4 and the outlets 5 and 6 is 1 compared to the case of the shape shown in FIG.
Since it decreases by around 0%, it becomes possible to reduce the capacity of the water suction pump.

〔Effect of the invention〕

As explained above, according to the present invention, in a fluid passage configured such that the flow of fluid along a wall changes direction along the wall and is divided into streams on the downstream side, the flow of fluid changes due to a change in the main flow direction. Prevents fluid from flowing into the space between the streamline passing through the separation point where the flow begins to separate and the channel wall facing the separation heat area, and upstream from the point where the fluid separates. do. Thereby, it is possible to obtain a uniform flow rate distribution ratio for any given flow rate without creating a heating region. Further, according to the present invention, it is possible to provide a practical small fluid passageway that is easier to design and manufacture than the prior art, and does not require a separate power source.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a fluid passage that branches off on the downstream side of a bend according to the present invention, and Fig. 2 is a diagram showing the direction of flow and the heat exchange area of the fluid passage that branches on the downstream side of a bend. , 3rd
The figure shows a T-shaped branch pipe with a streamlined kite vane inside the pipe, Figure 4 shows the fluid passage and flow velocity vector that separates the flow downstream of the bend, and Figure 5 shows the flow velocity vector of the condenser. An explanatory diagram of the cooling water conduit. Figure 6 is a diagram showing the heating area of the condenser's cooling water conduit. Figure 7 is a flow velocity vector diagram of the condenser's cooling water conduit and numerical analysis. , FIG. 8 is an explanatory diagram of the cooling water conduit of the condenser according to the present invention, and FIG. 9 is a diagram showing the cooling water conduit of the condenser according to the present invention and a flow velocity vector obtained by numerical analysis. l...Filming heat area, 2...Inner wall of downstream part of bend,
3... Outer wall of the downstream part of the bend, 4... Inlet, 5,
6... Outlet, 7... Projection, 8... Partition plate, 9
. . . Water suction pump, lO . . . Separation point where the flow starts to separate, 11 . . . Partition plate tip, 12 . . . Guide vane.

Claims (1)

[Claims] 1. In a fluid passage configured such that the flow of fluid along a wall changes its direction along the wall and then branches on the downstream side, the flow of fluid is separated due to a change in the direction of the main stream. The fluid is prevented from flowing into the space between the streamline passing through the separation point where the flow starts and the channel wall facing the separation area, and upstream from the point where the fluid separates. fluid passage. 2. The fluid passage according to claim 1, characterized in that a structure for preventing fluid from flowing into the separation region is installed. 3. The fluid passage according to claim 1, wherein the flow path wall facing the separation area has a shape of a streamline passing through the separation point.