JPS5849755B2 - duct equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized in that when a fluid flows from a duct with a small cross-sectional area to a duct with a large cross-sectional area connected at an almost right angle or at an inclined angle close to a right angle, the flow is disturbed. The present invention relates to a duct device that maintains a stable flow state and allows the flow to flow into a downstream duct.

When adjusting and inspecting an aircraft jet engine, a significant noise is generated when the engine is mounted on the aircraft or during a ground test run with the engine alone.

Therefore, ground quenching equipment is used to reduce the noise transmitted to the surrounding area.

Representative examples are shown in FIGS. 1 and 2.

FIG. 1 shows a silencer for an airframe, which is operated with an engine 01 mounted on an airframe 02.

FIG. 2 shows a silencer for a single engine, and the engine 01 is mounted on a test stand 03 and operated.

Arrows in the figure indicate the direction of flow of air or exhaust gas.

The exhaust ducts are horizontal duct 04 and vertical duct 05.
is threatened by

The engine exhaust jet mixes with the air dragged by it in the horizontal duct 04, and then flows into the vertical duct 0.
It is emitted upward from 5.

At the connection between the horizontal duct 04 and the vertical duct 05, cylindrical ducts 0 and 6 with a large number of through holes are provided in order to rectify the flow flowing out into the vertical duct 05.

The cross-sectional shapes of the horizontal duct 04 and the vertical duct 05 are often circular, oval, or polygonal.

Most of the inner surface of the duct is fitted with sound-absorbing material to absorb engine noise.

If a large sound deadening ability is required, a partition 07 is provided inside the duct, and a sound absorbing material is also attached to the surface of the partition 07.

The sound absorbing material will scatter if the flow velocity inside the duct is high, so the maximum flow velocity within the duct must be kept below the allowable value determined by the method of installing the sound absorbing material.

Therefore, in order to downsize the duct in order to reduce costs, it is required that the flow direction is small, that is, the flow velocity distribution is uniform.

Furthermore, in order for the engine to operate stably and maintain a constant attitude of the aircraft, the flow within the silencer must be stable and pressure fluctuations must be small.

In a silencer for a turbojet engine with an afterburner, which is particularly noisy among aircraft jet engines, the horizontal duct has a circular cross-section and a small cross-sectional area, and the vertical duct has a rectangular cross-section and a large cross-sectional area, and the partition 07 is placed at the top. Usually, a large number of them are installed to enhance the sound deadening effect.

Conventionally used methods for converting lateral flow in horizontal ducts of small cross-sectional area to upward flow in vertical ducts of large cross-sectional area are shown in FIGS. 3 to 6.

In each figure, a shows a vertical sectional elevation view, and b shows a perspective view.

In Figure 3, the rear part of the horizontal duct }04a is gradually bent and connected to the vertical duct }05a.
There is a drawback that the overall height of 5a becomes high.

In Fig. 4, a horizontal duct 04b with a circular cross section and a vertical duct 05b with a rectangular cross section are connected so that they intersect directly at right angles, but strong vortices are formed at the corners of the connection and the flow is strongly disturbed. The flow velocity distribution in the vertical duct is not uniform.

FIG. 5 shows that in the apparatus of FIG. 4, the vertical duct}0
Although a plurality of guide vanes 07c are provided at the lower part of the guide vanes 5c, a sufficient rectifying effect cannot be obtained because the horizontal ducts 04c and the vertical ducts 05c have different cross-sectional shapes and sizes.

FIG. 6 shows a large number of through holes in the partition wall in the device shown in FIG. 4.
Cylindrical duct with 13d}06d and vertical duct}05d
It is installed at the bottom of the aircraft, and is often used in aircraft silencers.

However, if the ratio of the hole opening ratio and the total hole area to the total surface area of the cylinder is increased, the flow velocity distribution in the vertical duct will worsen, and if the hole opening ratio is decreased, the pressure loss will increase, causing pressure fluctuations throughout the silencer. This may cause various problems.

Even if a compromise between velocity distribution and pressure loss (pressure fluctuation) is attempted by modifying the diameter of the holes and the number of holes and the arrangement of the holes, sufficient effects cannot be obtained.

In view of the above-mentioned circumstances, the present invention provides that when fluid flows from a duct with a small cross-sectional area to a duct with a large cross-sectional area connected with an axis substantially perpendicular or close to the perpendicular to the duct, the flow is turbulent toward the connection part. This project proposes a duct device that allows flow to flow in a stable state without being affected by the flow, which consists of an upstream duct with a small cross-sectional area and a downstream duct with a large cross-sectional area connected at an almost right angle or at an inclined angle close to the right angle. At the connection part, a hollow cylindrical body with a large number of through holes in the partition wall is connected to the connection end opening of the upstream duct in order to uniform the flow velocity distribution of the flow flowing into the downstream duct, and the fluid flows downstream through the through holes. In a duct device configured to allow fluid to flow into a side duct, the hollow cylindrical body is constructed by arranging a plurality of hollow cylindrical units having mutually different cross-sectional areas in the longitudinal direction, and a step for fluid circulation is provided between the partition walls of each hollow cylindrical unit. A duct device is provided.

In the device of the present invention, fluid is allowed to flow out into the downstream duct not only through the through holes provided in the partition wall of each hollow cylindrical unit but also through the step, thereby allowing the fluid to flow into the downstream duct. The flow velocity distribution of the flowing fluid can be made uniform over the entire channel cross section.

In other words, most of the fluid flowing from the through hole flows slightly downstream, and if this flow is only such, it tends to be concentrated near the downstream inner wall of the downstream duct, but the fluid flowing from the step is directed upstream. This flow mixes with the flow exiting from the through hole, thereby equalizing the flow velocity distribution of the flow exiting into the vertical duct.

Furthermore, by providing the step, the pressure loss is small, and therefore there is no risk of causing pressure fluctuations within the duct system.

The number of steps, that is, the number of hollow cylindrical units and the size of the steps may be appropriately selected depending on individual conditions.

Next, one embodiment of the device of the present invention will be described based on the drawings.

7, 4a is a horizontal duct with a circular cross section and a small cross-sectional area, 5a is a vertical duct with a rectangular cross-section and a larger cross-sectional area than the horizontal duct 4;
are connected almost at right angles.

A hollow cylindrical body 8a consisting of an upstream single cylindrical body 9a and a downstream single cylindrical body 10a is provided at the junction between the horizontal duct}4a and the vertical duct}5a.

The upstream cylinder unit 9a is a horizontal duct}4a connecting end opening 15
a, and has a larger diameter than the downstream single cylinder 10a & the upstream single cylinder 9a, and these steps 11a are open to allow fluid to flow.

Numeral 12a is a connecting member that connects the upstream single cylinder 9a and the downstream single cylinder 10a, and is provided in the circumferential direction as many times as necessary for strength, but may be omitted if there is sufficient strength.

A large number of through holes 13a are provided in the partition walls of the upstream single cylinder 9a and the downstream single cylinder 10a, so that the fluid flowing through the horizontal duct 4a is uniformly transferred to the vertical duct 5a through the through holes 13a. leak.

Reference numeral 14a is a conical member provided to improve the stability of the flow, but it may be omitted depending on the case.

In such a device, the flow in the horizontal duct 4a is as follows:
At the joint with the vertical duct 5a, the upstream cylinder unit 9
It flows out to the vertical duct 5a side from a large number of through holes 13a provided in the partition wall of the single cylinder body 10a on the downstream side, and simultaneously flows out from the step 11a.

As shown in FIG. 7, most of the flow flowing out from the through hole 13a is directed slightly downstream, whereas the flow flowing out from the step 11a
The flow flowing out from the vertical duct 5a is directed slightly upstream, and by mixing these two types of flows, the flow velocity distribution within the vertical duct 5a becomes almost uniform.

In the conventional duct device shown in Fig. 6, the cylindrical duct}06
The flow coming out of the upper through hole d is biased toward the downstream inner wall of the vertical duct 05d, and the flow flowing out from the lower through hole is biased toward the upstream inner wall of the vertical duct, which has the disadvantage that the flow velocity in the center is slow. However, in this device, the water is allowed to flow out from the step 11a, so there is no such drawback.

Furthermore, in this device, the amount of outflow from the through hole 13a and the step 11a is sufficiently large and the pressure loss is small, so there is no risk of causing pressure fluctuations in the entire duct system.

In the device shown in FIG. 6, if the aperture ratio of the through holes is made small in order to make the velocity distribution in the vertical duct uniform, pressure loss increases and pressure fluctuations in the entire duct system increase.

On the other hand, in this device, since the flow is also allowed to flow out from the step 11a, the pressure loss does not increase even if the aperture ratio of the through hole is made small.

In addition, in this device, the difference in diameter between the upstream single cylinder 9a and the downstream single cylinder 10a and the single cylinder 9a, 1
By appropriately selecting the length of 0a in the longitudinal direction, the opening area of the step 11a can be set to an optimal value according to individual conditions.

FIG. 8 shows another embodiment of the device of the present invention, in which the lengths of the hollow cylinder 8b, the upstream single cylinder 9b and the downstream single cylinder 10b are shortened to create a step difference of 1 lb.
The difference is that the opening area of the comb is larger and that a through hole 13b is provided only in the upper half of the upstream cylindrical unit 9b, but the other structures are the same.

A connecting member connecting the single cylinders 9b and 10b is omitted.

The rectification effect of the device of this embodiment is the same as that of the previous embodiment, and 1
This embodiment has the advantage that the drilling work for the through hole 13b can be reduced compared to the previous embodiment.

That is, in this device, since a through hole is not provided in the lower half of the upstream cylinder unit 9b, the vertical duct }5
The flow toward the vicinity of the upstream inner wall of b disappears, but instead, the flow coming out from below the step 1 lb flows toward the upstream side and supplements this flow.

Therefore, the flow in the vertical duct is made uniform by combining the flow exiting from the upper through hole 13b and heading slightly downstream and the flow exiting from above the step 1lb and heading slightly upstream.

FIG. 9 shows yet another embodiment of the device of the present invention. In this embodiment, three cylindrical units 9c having different diameters are used.
, 12c and 10c are provided, two step portions 11c are provided, and the cylindrical units 10c and 12c are made into a slightly conical shape, and the same flow rectification effect is achieved.

Note that when the cross-sectional shape of the horizontal duct is rectangular or polygonal, the same flow rectification effect can be obtained by making the cross-sectional shape of the hollow cylindrical body provided in the vertical duct match the shape.

The cross-sectional shape of the vertical duct can also be arbitrarily selected.

The shape of the through hole formed in the partition wall of the hollow cylindrical body is not limited to a round shape, and may be, for example, a polygon or an elongated shape.

Further, the individual hollow cylinders in the above embodiments do not need to be provided concentrically with each other, but may be provided offset in the radial direction.

As described above, the duct device of the present invention prevents flow turbulence at the connection point when fluid flows from a duct with a small cross-sectional area to a duct with a large cross-sectional area that is connected at an almost right angle or at an inclination angle close to a right angle. It is designed to flow with a uniform flow velocity distribution in the cross section of the downstream duct without causing any noise.For example, when applied to a silencer during the ground test run of an aircraft jet engine, the air or exhaust gas flowing inside the silencer is It has the advantage of making the flow velocity distribution uniform, improving the noise reduction effect, and stabilizing the flow inside the silencer, keeping the aircraft's attitude constant and the engine operating stably.

[Brief explanation of the drawing]

Figures 1 and 2 are longitudinal sectional elevation views showing a conventional silencer for ground operation of an aircraft jet engine, respectively, and Figures 3 to 6 are respectively a conventional silencer at the point where a horizontal duct and a vertical duct connect. The structure is shown, of which a is a vertical elevation view,
7b is a perspective view, and FIGS. 7 to 9 are vertical sectional elevational views showing each embodiment of the device of the present invention. 4a, 4b, 4c--Horizontal duct, 5a, 5b, 5c
...Vertical duct, 8a, 8b, 8c...Hollow cylindrical body, 9a, 9b, 9c, 10a10b, 10c, 1
2 c- Single hollow cylinder, 11a, 1lb, 11c...
Step, 12a connecting member, 13a, 13b, 13c...
・Through holes, 1 5a, 15b, 15c”・Horizontal duct connection end opening.

Claims (1)

[Claims] 1. At the connection between an upstream duct with a small cross-sectional area and a downstream duct with a large cross-sectional area that is connected at an almost right angle or at an inclined angle close to a right angle, the flow velocity distribution of the flow flowing into the downstream duct is made uniform. In the duct device, a hollow cylindrical body having a large number of through holes in the partition wall is connected to the connection end opening of the upstream duct, and fluid flows out to the downstream duct through the through holes. What is claimed is: 1. A duct device comprising a plurality of hollow cylindrical units having mutually different cross-sectional areas arranged in a longitudinal direction, and a step for fluid circulation provided between the partition walls of each hollow cylindrical unit.