GB1560118A - Pressure reducing valve - Google Patents

Description

(54) A PRESSURE REDUCING VALVE (71) We, REGEL & MESSTECHNIK GmbH REGLERUND ANLAGENBAU FUR GAS-DRUCKREGELUNG, a Joint Stock Company organised under the laws of Germany (Fed. Rep.) of Osterholzstrasse 45, 3500 Kassel-Bettenhausen, Germany (Fed. Rep.) do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The invention relates to a pressure reducing valve.

During expansion of gaseous media in known regulating valves, especially in the case of an over critical pressure drop, a free jet at high speed passes from the vena contracta (cross section of throttle) into the outlet chamber of the valve. A breakdown of this free jet can be expIained by the Prandtl theory of turbulent mixing. According to this, in the outlet chamber, as a result of the high speed drop with respect to the surrounding gas, so-called shock waves are formed and areas of turbulence of varying magnitude are detached from the border regions of the free jet core. The turbulance areas themselves break down into ever smaller units owing to the high speed differences and to encountering adjacent areas of turbulence and installations and housing walls, until the smallest have been completely dissipated by molecular friction. Due to the series of these compression shocks and due to the uncontrolled breakdown of the areas of turbulence, compressional vibrations occur which produce the so-called jet noise and are the main source of noises occurring at the time of gas expansion and which are often quite considerable.

It is known to counteract this process by gradual expansion. Attempts are thus made to provide sub-critical expansion in each stage. In practice this occurs partly due to the fact that the pressure reduction valve is followed by a throttle arrangement which consists of perforated sheets for example. Such an arrangement is illustrated in the VDI Richtlinie 2567 "Schallschutz durch Schall dämpfer" (association of German engineers guide line 2567 "sound proofing by sound absorbers").

However, the use of such a method only provides acceptable results if the operating conditions, such as inlet pressure, outlet pressure and throughflow remain constant within relatively narrow limits. Therefore, the afore-described method can only be used to a limited extent for the changing operating conditions of gas pressure control technology. In addition, the first gas expansion stage remains in the housing outlet. The mixing of the free jet thus provided in the housing outlet may thus cause considerable noise. It is therefore obvious to place the elements for sound reduction directly at the cross section of expansion, as was proposed in several German Patent Specifications, for example 1 063 432 and 1 600 927. For this, it is not possible to avoid constructing completely new valve housings, at considerable expense.

Now in order to achieve an effective noise reduction in the case of conventional valve constructions, in a technically simple and relatively inexpensive manner, the flow chamber on the outlet side of a control member housing is completely or at least partly filled with elements which owing to their particular geometric shape and due to a suitable selection of material promote the mixing of the free jet, i.e. the dissipation of the flow energy, to a considerable extent and thus restrict it to an essentially smaller region inside the outlet chamber. The compressional vibrations connected with the turbulent mixing of the free jet can thus no longer have a direct effect on the walls of the housing or in appliances with a straight passage, on the walls of the subsequent conduits. It is thus obvious to achieve a substantial reduc tion of the sound-producing vibrations due to this. At the same time, noise-producing twisting movements, cavity vibrations and flow separation of the gas jet inside the valve housing are eliminated by the filling bodies.

A method of this type, incorporating a labyrinthine flow region formed from loose material, directly after the valve seat, is already known from German Patent Specification 1 067 653 According to the present invention there is provided a pressure reducing valve comprising a valve body defining an inlet passage, an outlet passage and an opening therebetween controlled by a valve element, and a mixing zone immediately downstream of said opening and defined by perforated inlet and outlet portions serving to contain a plurality of filling elements creating a labyrinthine flow region, the outlet portion approximating in its total free flow cross sectional area to the cross sectional area of the adjacent section of the outlet passage.

Preferably, the controlled opening and the perforated inlet portion have respective free flow cross sectional areas such that with maximum throughflow the pressure drop is apportioned approximately equally therebetween.

Preferably, the flow space between the controlled opening and the perforated inlet portion is so designed that a speed distribution having the lowest possible speed changes is achieved over the flow path.

The perforated inlet portion and/or the perforated outlet portion may comprise a plurality of spaced walls. In this case the walls preferably have staggered perforations therein.

The filling elements are preferably shaped to afford low flow resistance, and may be made of resilient material.

The provision of a perforated outlet portion approximating in its total free flow cross sectional area to the cross sectional area of the adjacent section of the outlet passage, provides advantages in contrast to the method previously proposed in that the transition of the stabilized gas jet from the filling body space to the free flow cross section of the subsequent conduit takes place without substantial speed changes. If a reduction in a cross section were necessary in this case - German Patent Specification 1 067 653 expressly mentions a retaining device for the filling bodies, whose free flow cross sectional area is greater than one sixth, appropriately one quarter of the surface area - this could once more lead to the formation of free jets, which could give rise to the production of considerable noise as a result of the turbulent mixing in the uncontrolled space of the subsequent conduit.

Three embodiments of the invention are illustrated in the drawings: Fig 1. is a longitudinal section through a gas pressure regulator with a chamber formed from a one-part perforated body forming the boundary of the chamber containing the filling bodies, Fig 2. is a longitudinal section through a gas pressure regulator with two independent perforated bodies forming boundaries of the chamber containing the filling bodies and finally, Fig 3. is a further longitudinal section through a gas pressure regulator with two adjacent yet independent perforated bodies forming boundaries of the chamber containing the filling bodies.

The gaseous medium enters the housing 1 of the pressure regulator under pressure at Pe and leaves the latter at Pa. It thus arrives in the outlet flow space 3 by way of the valve controlled cross section 2 defined by a onepiece perforated body 4, arranged inside which are a plurality of filling bodies 5. In Fig 1, the perforated body 4 has an inner perforated surface 4a adjacent the valve cone and of complementary shape and an outer perforated surface 4b adjacent the flow space 3 at the outlet side. The perforated surfaces 4a, 4b may be constructed with either one or several layers, depending on the respective requirements of applications. If they are constructed with several layers, the perforations in the surfaces of each layer are offset with respect to each other. In addition, further combinations are possible such that the perforated surface 4a on the inlet side is constructed with one layer and the perforated surface 4b on the outlet side is constructed with several layers (or vice versa).

Further demands are made of the construction of the perforated body 4 for achieving optimum efficiency of the latter. In the case of maximum throughflow of the medium, the perforated surface 4a at the inlet side must distribute a given pressure ratio in approximately equal parts to the controlled valve cross section 2 of the apparatus and to itself. In this case, the flow space 3a between the valve controlled cross section 2 and the perforated body surface 4a at the inlet side is so designed that a speed distribution having the lowest possible speed changes is achieved over the flow path.

A further essential pre-requisite for reducing the production of noise and/or vibrations, consists in that the total free flow cross sectional area of the perforated surface 4b at the outlet side is at least approximately equal to that of the conduit 6 located thereafter.

For the construction or arrangement of the gas pressure regulator according to Fig 2, the same pre-requisites are valid in principle, as are given above in relation to Fig 1. In place of a single perforated body with two perforated surfaces, the solution according to Fig 2 comprises two spatially separated perforated bodies 4, of similar shape. In this solution, in order to be able to adapt the total free flow cross section and area of the perforated body 4b at the outlet side to the free flow cross sectional area of the subsequent conduit 6, it has proved advantageous to construct the perforated body 4b in the manner of a cone or funnel. The attachment of this cone or funnel-shaped perforated body 4b takes place in the simplest manner, in that its flange 4c is inserted in a corresponding recess la and is secured at the time of attaching the pipe flange 6a.

Fig. 3 shows a gas pressure regulator with an axial passage, in which the solution corresponds to that of Fig 2 and is based on virtually, the same principle: inserted centrally in the space behind the valve controlled cross section 2 is a conical perforated body 4a, whose bent flange 4d simultaneously serves for spacing the further perforated body 4b along the longitudinal axis of the valve.

In this embodiment, in order to adapt the total free flow cross sectional area of the perforated surface 4b at the outlet side at least approximately to that of the subsequent pipe 6, the perforated body is slightly dished.

Particularly suitable as filling bodies 5 are those which, on the one hand owing to their geometric shape - large surface area with turbulence ribs in a small volume - considerably promote the dissipation of flow energy and have a sound reducing effect, but on the other hand, due to their resilient nature, largely prevent vibrations from the region of the free jet breakdown from being transmitted to the walls of the housing by way of so-called sound bridges.

WHAT WE CLAIM IS 1. A pressure reducing valve comprising a valve body defining an inlet passage, an outlet passage and an opening therebetween controlled by a valve element, and a mixing zone immediately downstream of said opening and defined by perforated inlet and outlet portions serving to contain a plurality of filling elements creating a labyrinthine flow region, the outlet portion approximating in its total free flow cross sectional area to the cross sectional area of the adjacent section of the outlet passage.

2. A valve as claimed in claim 1, wherein the controlled opening and the per forated inlet portion have respective free flow cross sectional areas such that with maximum throughflow the pressure drop is apportioned approximately equally there between.

3. A valve as claimed in claim 2, wherein the flow space between the control led opening and the perforated inlet portion is so designed that a speed distribution hav ing the lowest possible speed changes is achieved over the flow path.

4. A valve as claimed in any one of claims 1 to 3, wherein the perforated inlet portion and/or the perforated outlet portion comprise a plurality of spaced walls.

5. A valve as claimed in claim 4, wherein the walls have staggered perforations therein.

6. A valve as claimed in any one of the preceding claims, wherein the filling elements are shaped to afford low flow resistance.

7. A valve as claimed in any one of the preceding claims, wherein the filling elements are made of resilient material.

8. A pressure reducing valve illustrated in Figure 1 or Figure 2 or Figure 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. bodies 4, of similar shape. In this solution, in order to be able to adapt the total free flow cross section and area of the perforated body 4b at the outlet side to the free flow cross sectional area of the subsequent conduit 6, it has proved advantageous to construct the perforated body 4b in the manner of a cone or funnel. The attachment of this cone or funnel-shaped perforated body 4b takes place in the simplest manner, in that its flange 4c is inserted in a corresponding recess la and is secured at the time of attaching the pipe flange 6a. Fig. 3 shows a gas pressure regulator with an axial passage, in which the solution corresponds to that of Fig 2 and is based on virtually, the same principle: inserted centrally in the space behind the valve controlled cross section 2 is a conical perforated body 4a, whose bent flange 4d simultaneously serves for spacing the further perforated body 4b along the longitudinal axis of the valve. In this embodiment, in order to adapt the total free flow cross sectional area of the perforated surface 4b at the outlet side at least approximately to that of the subsequent pipe 6, the perforated body is slightly dished. Particularly suitable as filling bodies 5 are those which, on the one hand owing to their geometric shape - large surface area with turbulence ribs in a small volume - considerably promote the dissipation of flow energy and have a sound reducing effect, but on the other hand, due to their resilient nature, largely prevent vibrations from the region of the free jet breakdown from being transmitted to the walls of the housing by way of so-called sound bridges. WHAT WE CLAIM IS

1. A pressure reducing valve comprising a valve body defining an inlet passage, an outlet passage and an opening therebetween controlled by a valve element, and a mixing zone immediately downstream of said opening and defined by perforated inlet and outlet portions serving to contain a plurality of filling elements creating a labyrinthine flow region, the outlet portion approximating in its total free flow cross sectional area to the cross sectional area of the adjacent section of the outlet passage.

2. A valve as claimed in claim 1, wherein the controlled opening and the per forated inlet portion have respective free flow cross sectional areas such that with maximum throughflow the pressure drop is apportioned approximately equally there between.

3. A valve as claimed in claim 2, wherein the flow space between the control led opening and the perforated inlet portion is so designed that a speed distribution hav ing the lowest possible speed changes is achieved over the flow path.

4. A valve as claimed in any one of claims 1 to 3, wherein the perforated inlet portion and/or the perforated outlet portion comprise a plurality of spaced walls.

5. A valve as claimed in claim 4, wherein the walls have staggered perforations therein.

6. A valve as claimed in any one of the preceding claims, wherein the filling elements are shaped to afford low flow resistance.

7. A valve as claimed in any one of the preceding claims, wherein the filling elements are made of resilient material.

8. A pressure reducing valve illustrated in Figure 1 or Figure 2 or Figure 3 of the accompanying drawings.