JPS6249094A - Decompression device - 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] [Industrial application field] The present invention relates to a gas decompression device.

[Conventional technology and its problems]

Although pressure reducing valves are known as devices for reducing the pressure of gas, commonly used pressure reducing valves often do not take into account flow at a pressure ratio higher than the critical pressure ratio, that is, at supersonic speed. In particular, with pilot-operated pressure reducing valves, flow rate adjustment is handled by the area of the boat, and although it is not impossible to reduce pressure above the critical pressure ratio, the structure is complex, and the amount of pressure reduction that can be achieved with the valve itself is limited. Its effect is also unclear.

On the other hand, as a special pressure reducing valve for noise countermeasures, it has a double structure and has a small structure (the outside is covered with a cage with many holes).
Some systems use this cage as a muffler to achieve a pressure reduction effect, while others have many branch pipes branching off from the main pipe and reduce the pressure by the pressure loss of these branch pipes.

However, for pressure reducing devices using such valves, it is difficult to manufacture large-diameter ones due to the fact that the valve body is cast, the flow inside the valve is complicated, and other reasons, and it is difficult to manufacture large-diameter devices that can handle large volumes of gas at once. To decompress) & shi.

On the other hand, a pressure reduction technique using a perforated plate 1 as shown in FIG. 8 is also known, but in this case, the straight line 1k of the perforated plate 1 is usually subsonic. 2 in the figure shows a shock wave, but if it is used in a state where the pressure reduction ratio is supersonically fast immediately after blowing out and the pressure reduction ratio is higher than the critical pressure ratio, vibrations will occur. This is because depressurization above the critical pressure ratio is carried out by shock waves, and these shock waves change very sensitively due to changes in front pressure and interfere with each other.

Also, it is possible to consider a method of arranging a plurality of perforated plates 1 in multiple stages with intervals, but this would allow for supersonic flow on the -Jz flow side and subsonic flow on the downstream side, or vice versa. occurs,
It is difficult to choke the upstream and downstream perforated plates at the same time, and the pressure in the intermediate pressure area between the perforated plates tends to change due to unstable interference of shock waves, and vibration is more likely to occur than with a single perforated plate. .

An object of the present invention is to provide a pressure reducing device which eliminates the disadvantages of the conventional example, has a simple structure, does not require advanced manufacturing technology, and can reliably reduce the pressure of a large volume of gas without vibration or noise. It is in.

Means to Solve the Problems] In order to achieve the above object, the present invention provides orifices at the inlet and outlet of the pressure reducing tube, thereby sealing the shock wave within the pressure reducing tube.

[Effect]

According to the present invention, shock waves are stably generated only within the pressure reducing pipe, and a pressure reduction effect greater than the critical pressure ratio can be reliably obtained with this shock wave.Moreover, noise and vibration are also prevented because the shock waves do not go outside. In addition, by arranging a large number of such pressure reducing pipes in parallel, it is possible to reduce the pressure of a large volume of gas.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

First, the principle of the present invention will be explained with reference to FIG. 6.
In the figure, numeral 3 is a pressure reducing pipe, and an inlet orifice 4 is provided at its inlet, and an outlet orifice 5 is provided at its outlet. 6 in the diagram
, 7 indicate piping that communicates before and after the pressure reducing pipe 3.

In this way, the high-pressure gas is choked when passing through the inlet orifice 4 from the pipe 6, expands at supersonic speed within the pressure reducing pipe 3, and enters a supersonic state. Shock wave 2 is then generated and transitions to subsonic speed. The gas then flows through the pipe 3, passes through the outlet orifice 5, flows out into the pipe 7, and mixes with the outside air.

In this case, the conditions for the gas passing through the inlet orifice 4 to become supersonic are that the pressure ratio before and after the orifice 4 is greater than or equal to the critical pressure ratio, and that the flow path area expands after being contracted. With such a high pressure ratio, the static pressure in the part undergoing supersonic expansion becomes very low, while the surrounding pressure is high, such as atmospheric pressure, so a pressure imbalance occurs, and in an attempt to fill this gap, a shock wave 2 is generated. occurs.

For example, FIG. 9 shows the state of shock wave generation when only the inlet orifice 4 is provided in a straight pipe and the pressure ratio is large.
The case where the pressure ratio is reduced is shown in FIGS. 10 and 11. The f
The Ji shock waves 2 include an oblique shock wave 2a, a vertical shock wave 2b,
There is a pseudo shock wave 2C. This also depends on the ratio Pa/P of the pressure Pa on the inlet side and the pressure P on the outlet side, and unless this is considerably large, the oblique shock wave 2a and pseudo shock wave 2C as described above will not occur. Note that the part indicated by [stock] is the throat 23.

By the way, the wake of the pseudo shock wave 2C1 or the vertical shock wave 2b is always subsonic, that is, the pseudo shock wave 2c,
Alternatively, the part up to the vertical shock wave 2b becomes a supersonic part, and the pressure is reduced behind it. As for the oblique shock wave 2a, this is mainly caused by friction loss due to supersonic flow, and there is almost no pressure reduction due to the oblique shock wave. In addition, the overall pressure reduction of the pseudo shock wave 2C is approximately the same as the amount that can be reduced by one of the complete vertical shock waves 2b, or at most 10%.
It is a slight increase. Therefore, even if oblique shock waves and pseudo shock waves exist, the oblique shock wave 2a is ignored, and the friction loss of supersonic flow and the large number of pseudo shock waves! It can be designed by calculation in which the β wave is replaced with one vertical shock wave 2, and is applicable to the present invention.

In addition, the positions where the vertical shock wave 2b and the pseudo fili shock wave 2c are generated are very unstable, and due to changes in the pressure ratio, the barrel shock state shown in FIG. 6 changes from the state shown in FIGS. Although it is not, it changes to a state where a shock wave blows through.

Therefore, in the present invention, a state of the barrel shock 8 is obtained in which the generation position of the shock wave 2 can be easily determined.

On the other hand, regarding the effect of the exit orifice 5, if there is no effect at all and depressurization is performed at a large pressure ratio, the pseudo shock wave 2
There is a risk that the 0 etc. will not remain in the tube 3 but will blow through, and the pressure reduction in the tube 3 will not be achieved.

Furthermore, even if the diameter of the exit orifice 5 is too large, the effect of the blowout will cause pseudo shock waves 20 etc. to be generated outside the pipe 3.
Although the pressure can be reduced to some extent in the pressure reducing tube 3, it is insufficient, and since the shock waves are outside the tube, there is a risk that noise and weak vibrations will be generated.

On the other hand, if the diameter of the outlet II orifice 5 is narrowed too much, the outlet orifice 5 will be choked, and the outlet orifice 5 will be choked on the outflow side as well as the inlet orifice 4 as shown in FIGS.
The supersonic expansion part shown in the figure occurs, and the pressure reducing effect as a pressure reducing tube cannot be obtained.

The case where the orifice has a thin blade has been described above, but if the orifice plate is made thick, a larger reduction in pressure becomes possible. The flow state at this time is as shown in FIG. 12, where the fluid chokes at the inlet of the thick plate orifice 24 and becomes supersonic inside the orifice. The thickness of the orifice plate is appropriate, i.e.
If the plate thickness is about 10 times or less than the orifice diameter di,
It becomes choked or supersonic at the orifice exit and expands supersonically in the vacuum tube, resulting in the same flow situation as in the case of a thin-bladed orifice. The pressure ratio Po/P at this time is Po/P=P
a /P1xp1 /P, which is the pressure ratio that can be reduced with a thin-blade orifice? A pressure reduction ratio greater than 1/P by Po/Px becomes possible. Next, if the thickness of the thick orifice plate 24 is made thicker than necessary, a shock wave is generated within the orifice plate as shown in Fig. 13, and a subsonic flow with high pressure occurs at the outlet of the orifice plate, resulting in a depressurization. The pressure inside the pipe cannot be reduced, and a barrel shock occurs at the outlet of the pressure reducing pipe to reduce the chamber pressure. In this case, the pressure reduction capacity in the pressure reduction tube including the orifice plate is usually about 1.3 to 3 at the pressure ratio P o / P 2, although it depends on the length of the orifice plate, pressure reduction tube, etc. I can't.

Therefore, in the present invention, all shock waves are designed to be contained within the pressure reducing pipe 3 within the inlet orifice 4 and the outlet orifice 5. Containment of such shock waves is achieved through the entrance orifice 4.
This is achieved by providing an exit orifice 5 with a diameter that correlates with the length of the decompression pipe 3 following By appropriately selecting the cross-sectional area of the tube 3 and the surface area ratio of the inlet orifice 4, the barrel shock 8 and Matsuha disk 9 can be easily installed, thereby making it possible to shorten the required length of the tube 3. be.

In such a design, the front and rear pressures Po/PO of the pressure reducing pipe 3
If o is determined, the relationship di/D between the diameter di of the inlet orifice 4 and the diameter of the pipe 3 is determined from this value, and when the length of the pressure reducing pipe 3 is determined, the diameter de of the outlet orifice 50 is determined.

These are determined by a certain calculation method, and a chart in the case where the gas to be depressurized is air and a thin-blade orifice is used is shown in FIG.

To show how to use it, if the pressure ratio (reduction ratio) Po/P■, pressure reduction pipe diameter, and pressure reduction pipe length 6or6/D are known, for example, given Po /Pw-406/D = 19, this chart From di/D = 0.20de/D
= 0.88 is obtained, and the shape of the pressure reducing pipe is determined.

On the other hand, if Po/PoQ, D, di are known,
For example Po/Poo-=50 di/D=0
．． 183, in Fig. 7 di/D
= 0.175 and di7'D = 0.20 to find the line di/D = 0.183. When finding the intersection of this line P o / P -50, e /
D = 30 de/D = 0.895 is determined, and the tube shape is determined.

In addition, when using a thick orifice plate, actually reduce the pressure.
By multiplying the desired pressure ratio by 0.8 and setting the value as PO/P■, the shape of the pressure reducing pipe can be determined using the same method.

Next, a specific embodiment of the present invention using the pressure reducing tube 3 based on the principle described above will be described.

FIG. 1 is a longitudinal sectional side view showing one embodiment of the present invention.
A plurality of these were arranged in parallel inside the main body shell 10, and the front and rear thereof were supported by tubes Fj and 1L12. Further, an orifice plate 13 is provided to form an inlet orifice 4 and an outlet orifice 5 at the front ends and f&6N of the large number of pressure reducing pipes 3.
14. These orifice plates 13 and 14 are a single plate with a circular hole approximately the same diameter as the main body 10, and in particular, the orifice plate 13 is a thick plate to form a tunnel-shaped entrance orifice 4. I decided to do so. In this way, if the orifices 4 and 5 of each pressure reducing tube 3 are formed in common with one plate, the manufacturing effort is greatly reduced, and the inlet orifice 4 is strong enough to withstand a large pressure difference. Things can be formed. In addition, the entrance.

The outlet orifice plate 13.14 is similar to the tube plate 11.12;
It may be fixed with a flange.

Pipes 6.7 having the same diameter as the main body shell 10 are provided before and after these orifice plates 13.14, and in particular, the lower rear flow pipe 7 has a fitting flange 15 attached to its front end. It is slidably fitted into the In the figure, 16 is an elastic packing interposed between the main body 10 and the flange 15 pipe, 17 is a stop plate fixed to the outer periphery of the main body 10, and the stop plate 17 and the fitting flange 15 on the piping 7 side are The fixed position can be adjusted and connected by a bolt nut 18. By adjusting the bolt nut 18 of the α bag in the figure? /) is the amount of elongation obtained.

In this way, the gas from the piping 6 is depressurized by each pressure reducing pipe 3 in the main body shell 10 and flows out to the piping 7. The required number of pressure reducing pipes 3 is determined by the following.

Moreover, when the temperature of the gas is high, the pressure reducing tube 3 itself may also increase in temperature and expand. The connection means using the bolt/nut 18 is used to make adjustments in such cases.

3 and 4 show a second embodiment of the present invention, in which a partition plate 19 movable along the orifice plate 13 is provided on the front upstream side of the orifice plate 13 on the inlet side. The flow rate passing through the pressure reducing pipe 3 can be controlled. This partition plate 19 is arranged with a packing 21 interposed between the orifice plate 13 and a flange 20 on the outside thereof.

FIG. 5 shows a third embodiment of the present invention, in which an orifice 22 is further provided upstream of the pressure reducing device of the present invention shown in the first or second embodiment. In this way, a greater pressure reduction can be achieved through the orifice 22.

〔Effect of the invention〕

As described above, the pressure reducing device of the present invention uses a simple tube structure, can be manufactured at low cost without requiring advanced molding technology, and can reduce pressure below the critical pressure ratio without vibration and with low vibration. This can be achieved reliably with no noise, and a large volume of gas can be decompressed by using the required number of single decompression tubes.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view showing a first embodiment of the pressure reducing device of the present invention, FIG. 2 is an enlarged longitudinal sectional side view of the main parts of the same, and FIG.
FIG. 4 is a longitudinal cross-sectional side view of the main part showing the embodiment, and FIG.
A view taken along line A, FIG. 5 is a partially cutaway side view showing the third embodiment, FIG. 6 is an explanatory diagram showing the principle of the device of the present invention, and FIG. 7 is a diagram showing the correlation between orifice diameter and pipe length. , FIG. 8 is a longitudinal sectional side view showing a conventional example, and FIGS. 9 to 13 are explanatory diagrams showing gas flows when only inlet orifices of various shapes are provided. 1... Porous plate 2... Shock wave 2a... Oblique shock wave 2b... Vertical shock wave 2c... Pseudo shock wave 3... Decompression tube 4... Inlet orifice 5...
・Exit orifice 6.7...Piping 8...Barrel shock 9...Matsuha disk 10...Main body barrel lL12...Tube plate 13.14...Orifice plate 15...Fitting flange 16 ...Packskin 17...Stopping plate 18...Bolt nut 1
9... Partition plate 20... Flange 21...
・Patsukin 22...Orifice applicant
Kobe Steel, Ltd. Figure 2 Figure 3 Figure 4; 2] Figure 5 8 5 1Q 7 Figure 6 Figure 7 Retsue 4za R/D

Claims (4)

[Claims] (1) A decompression device characterized by providing orifices at the inlet and outlet of the decompression tube, thereby sealing shock waves within the decompression tube. (2) A decompression device characterized by a plurality of decompression tubes each provided with an inlet orifice and an outlet orifice arranged in parallel inside the main body. (3) The pressure reducing device according to claims 1 and 2, characterized in that the orifice plate forming the inlet orifice is a thick plate, and the pressure is reduced by both the orifice plate and the pressure reducing pipe. (4) Each inlet orifice of the parallel decompression tubes is formed using a single orifice plate, and a partition plate movable along the orifice plate is provided. and the pressure reducing device according to item 3.