US3252480A - Cascade valves - Google Patents

Description

May 24, 1966 Filed March 21, 1963 W. ODENDAHL ETAL CASCADE VALVES 2 Sheets-Sheet l lnvenforzs W/L HELM ODE/VDAHL WERNER 5A TTENFELD y 1966 w. ODENDAHL ETAL. 3,252,480

CASCADE VALVES Filed March 21, 1963 2 Sheets-Sheet 2 Fig. 3

W/LHELM ODENDAHL WERNER 5/ 1 TTENFELD la /mmvg mw United States Patent Office 3,252,489 Patented May 24, 1966 3,252,480 CASCADE VALVES Wilhelm Odendahl, Lebrechstr. 25, Gummersbach, Germany, and Werner Battenfeld, Lindenstrasse 8, Meincrzhagen, Germany Filed Mar. 21, 1963, Ser. No. 267,051

Claims priority, application Germany, Mar. 23, 1962,

A 39,784 8 Claims. (Cl. 137-6253) The'present invention relates to a multi-stage cascade throttle valve for decompressing fluids, particularly liquids, being under very high pressure.

The principle of the invention consists in the provision of a plurality of decompression stages with means to conduct the fluid through the stages so that the impulse vector is reduced upon each decompression in each of the various stages.

Multi-sta'ge throttle valves are known per se. Such a known multi-stage simple valve seat control valve is provided with a closing element and is also provided with several control stages extending along the entire height of the valve stem. The closing element arranged before the first part of the control path, has a cylindrical stern which is guided in a piston-like manner along the entire control path in the connecting parts disposed between the recesses that are spaced along the valve stem. These recesses form decompression chambers. The stem has throttle notches extending in axial direction. The cross sectional area for free flow of the throttle grooves increases with the stroke and thus in the direction of flow so that they act in a manner similar to Venturi tubes. Assuming that only 75% of the pressure is being restored, the pressure drop in each stage will be four times as great in the region of the narrowest cross-section as the pressure drop of the entire stage. In each stage therefore, a considerable pressure minimum is passed which results in cavitationat least in the last stage. On account of the forcibly occurring pressure drop, the flow velocity becomes twice as high at the narrowest point as it would be without such pressure build-up. As a result of the throttle grooves extending axially, the flow is applied always to the same areas of the ducts independently of the stroke. The individual jets always hit the same parts of the walls in the decompression chambers thus forming stagnation points. In the case where water of elevated temperatures which is fully freed from salt is to be decompressed, this will lead to theformation of local elements with respective corrosion.

Undesirable corrosion and erosion will occur, especially when locally considerably difierent solution concentrations appear, and when very low pressures prevail at individual parts of the walls, because concentrations and pressures appear with their logarithms in the equations of the voltage potentials so that upon approaching zero the electrode potential will approach infinity. If cascade valves are used for discharge of the minimum quantity from maximum pressure feed pumps in feed water tanks and if the feed water is fully freed from salt, then considerable corrosion occurs actually only in the last stage of decompression.

A single seat valve is known having a large cone-shaped plunger, which plunger is partially provided with intersecting throttle notches thus causing the throttled current i to flow in a zigzag line. The impulse vector is nullified at the intersection of the notches. In view of the fact that this does not take place in a decompression chamber, there is very much wear, which can even be more than in a standard control valve having a valve stem' and decompression chambers.

There are also known condensate discharges comprising several decompression stages which are either inserted in plates or formed by valve stems control bulges. The latter are constructed in such a manner that upon axial displacement of the valve stem the annular throttling cross-sections are modified by the same factor, and the narrowest cross-sections of the various stages are adjusted for equal steam velocities. Such devices are therefore suitable only for steam-water separation but not for decreasing of pressure and for blocking, for example, feed water.

There is also known a multi-stage valve which has a valve member guided in the throttle openings by means of four ribs each, and which has a cylindrical extension in front of the valve seat, which extension has near the locking or closing position such a strong throttling elfect on the flow that the seat areas are relieved to a great extent. The impulse is nullified after each point of decompression in a decompression chamber but the walls of the casing are vertically hit so that this valve arrangement is unsuitable for reducing high pressures.

In a further known valve, a cylindrical throttle cone and a respective throttle wall of the casing is roughened by finely threading. The fluid current does not pass through the threads but in axial direction through a ring slot provided for this purpose. The thread of the wall of the casing is cut to such a degree that it will be able to arrest the ring-shaped stream flowing oif axially behind the valve cone.

In still another known valve, the valve seat is staged so that near the locking position there will be present a cascade system nullifying the impulse without however rotating the current. There is furthermore known a valve which consists of a number of shutters arranged in series, the bores of which form a conical surface matching the valve cone. Upon operation of the valve, the cone at the shutters releases annular openings which are approximately of the same size. Decompression is thus caused by the abrupt enlargement behind the various shutters. In this manner, that part of the pressure which corresponds to the jet impulse is always recuperated, the conditions thus being similar to those of Venturi channels.

Known valves are thus unsuitable for decreasing high pressures, particularly for the decompression of feed water which is fully freed from salt.

One object of the present invention is the provision of a decompression valve in which the flow of fluid is conducted in such a manner that the walls come in contact with the fluid are approached only tangentially.

It is another object of the invention to maintain in decompression chambers a turbulent flow so as to obtain an even formation of boundary layers.

It is a further object of the invention to provide throttle ribs on one side of decompression channels which produce a stronger secondary current thus providing a pressure drop which extends over a greater length of the channel.

The disadvantage of the known valves are overcome in the cascade valve according to the invention by providing a cylindrical valve stem which is guided at the throttle region and which has throttling channels which spiral unidirectionally Within one and the same throttling stage. The channels may have variable cross sections which terminate and discharge into rotationally symmetrical decompression chambers. The direction of spirals of the throttle channels in each of the several throttling stages is alternated from stage to stage.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects, and features of the invention, and further objects-and features and advantages thercof will be better understood from the following description taken in connection with the accompanying drawing in which:

FIGURE 1 is a longitudinal sectional view showing a cascade valve according to a preferred embodiment of the invention;

FIGURE 2 is a development of a stem portion with carved in channels of one throttling stage; and

FIGURE 3 illustrates an enlarged cross section through a channel with adjacent guiding land.

Proceeding now to the detailed description of the drawing, there is shown a valve housing 5 receiving a valve stem 1 in a bore having in its lower portion a lining 4 defining a its upper end a valve seat 3 upon which rests conical valve surface 2 of stem 1. The drawing shows this valve in valve-closed position. The upper end of the valve stem 1 extends through a packing bush and protrudes upwardly from housing 5. A lever 7 is linked to this upper and protruding valve stem portion for actuation of the valve stem.

The lower part of valve stem 1 is snugly received but with clearance, in cylindrical guiding lands 8 integral with the lining 4. In between adjacent guiding lands 8 there are defined rotationally symmetrical decompression chambers 9, and there is a discharge chamber below the lowest guiding land. Along the stem there are thus alternating guiding members and decompression chambers.

The valve stem 1 is provided with a plurality of spiral throttling grooves or channels 11 generally being in the range of chambers 9 and 10. Each channel basically follows a section of 'a helix. Each such channel 11 has, in the drawing, an upper end 11a which is also in the upper portion of a decompression chamber 9 when the valve stem is in the illustrated closing position. The particular cross section and width of channels 11 depends upon the desired control characteristics relative to the valve stem displacement upon lifting thereof.

Also, the pitch of the channels is determined by these aforementioned characteristics. Still considering valve closing position, the channels 11 have terminal ends 116 at the lower end (in axial direction) of the respective decompression chamber.

The channels 11 at the discharge chamber 10 have a configuration just as if they were at a decompression chamber. The direction of spiral of the channels 11 alternates in axial direction from one decompression chamber to the next.

Reference numeral 12 designates the inlet or feed pipe and the fluid may enter therethrough into a valve entrance chamber 13 above seat 3.

Upon slightly lifting valve stem 1 by means of lever 7, some fluid will flow to exit region 14 which is a residual or leakage current along lands 8. This provision protects valve surfaces 2-3.

Upon further opening of the valve, i.e. upon further lifting of valve stem 1, the entrance ends 11a of the several channels 11 recede from the respective lands 8 and the entrance end of each channel appears at the lower part of the next upper decompression chamber and defines a passageway between chamber 13 and exit region 14. The spiral of the throttling channels 11 results in a decompressing action which is totally different from the decompression produced by straight channels, since a force field of centrifugal forces is set up as determined by the flow speed and the channel. curvature.

In the range of guiding lands 8, the channels are in fact covered producing relatively high speeds of the fluid due to the relative decrease of the cross section available for fluid flow. The overall state of flow is determined by and corresponds to the total energy level of the fluid.

At the entrance ends 110 of the respective throttling channels 11 there is a small cross section available for flow and thus the speed is relatively high resulting in a corresponding strong centrifugal force. This, in turn, reduces the amount of energy available for the corresponding high speed so that the centrifugal force actually has a speed reducing effect (total energy to remain constant).

The enlarged portions of the channels 11 are adjacent to and are covered by the respective guiding lands 8 and thus do not increase the pressure (as is the case in straight channels), but there results, instead an energy reduction corresponding to the reduction of centrifugal force; the centrifugal force is, of course, directly proportional to the square of the fluid speed. The enlargement of the cross section of channels 11 measured from their entrance ends 11a surprisingly produces a pressure reduction not merely at the narrowest channel cross section, but along the entire channel portion covered by a land 8. This avoids and eliminates the energy concentration observed in known valves, and hence the wear and tear due to jet action is avoided.

Thus, in comparison, straight throttling channels produce excessive speeds at strong local energy concentration and energy density peaks in the range of the narrowest cross section due to the Venturi effect; the spiral throttling channels 11 of the invention, on the other hand, produce surprisingly exactly the opposite effect which is of high advantage because it reduces undesired local energy concentration.

New tests with diffusers in general have shown that curved diffuser structures have a very poor efiiciency when in case of an elliptic cross section the long axis extends in the plane of curvature. Hence, in accordance with a further feature of the invention, it is suggested to have the throttling channels 11 deep and narrow. At least at the entrance portion, the channel is deeper than it is Wide. The poorer the diffuser effect is, the smaller will be any undesired load pressure drop increase. The undesired pressure drop increase is, of course, dynamically speaking, the cause of the excessive flow speeds at the known valves.

Proceeding now with the description of the inventive valve and its operation, fluid, after passing through a respective throttling channel 11 covered by a land 8 then enters a decompression chamber 9 and an eddy is set up in this chamber 9 fed with energy from the fluid current and its energy content. Accordingly, flow energy is passed on to the walls of chamber 9 by friction. The conditions in the boundary layer are similar throughout a chamber 9 so that no electrical potential field is being set up producing corrosion. Particularly no stagnation points are set up. Any jet not only wears on the valve by corrosion but also by way of direct impacts and friction erodes the valve. Naturally any wall surface transversely subjected to a jet wears and under this impact a jet passing along a wall surface wears it out by friction.

There are, unfortunately, no materials known which offer complete resistance against such impact wear as well as against friction wear, since such material should be viscous, expansible and very hard, all at the same time. The invention now provides for an arrangement in which the walls of the chambers 9 are only subjected to friction wear so that the material can be very hard indeed while viscosity and expansibility can more or less be disregarded. Additionally, this has the advantage that no electrochemical potential differences are found as are usually set up when different types of material are being used for the valve structure. Thus, one of the prime sources of corrosion in the valve is avoided.

From the decompression chamber which the fluid first enters, the fluid enters the throttling channels 11 of the next throttling stage. One can see from the drawing that the sense and orientation of winding of these channels is opposite to that of the first set of channels 11 (first stage). Due to this reversal of the winding sense, the entire residual jet impulse produced by decompression remains inside of decompression chamber 9 because the impulse is a vector. Since the sense of winding changes from the stage to stage of throttling, all of the jet impulses remain in the respective decompression chambers. Thus, each throttling stage works on its own partial pressure drop without positive pressure feed back and gain. According, the fluid flow speed and wear and tear are low throughout the passage.

Taking the valve structure as a whole, upon lifting of stem 1 and of plate 2 from seat 3, fluid enters from entrance chamber 13 the entrance ends 11a of the uppermost set of channels 11; the fluid then passes under the first upper land .8, along channels 11 and enters the first uppermost decompression chamber 9. This constitutes passage through the first throttling stage.

The fluid then enters the channels 11 pertaining to the second set of throttling channels having their respective entrance ends 11a projecting at the lower portion of the uppermost decompression chamber 9. The fiuidpasses through this second set of channels 11, below the second land 8, and enters the second decompression chamber. This constitutes throttling by the second stage of the cascade, etc. Depending upon the degree of clearance between stem and mantles, the entrance ends 11a of the respective channels might not necessarily project into the respective-next, upper decompression chamber.

The last (lowest) throttling stage has as its cooperating decompression space the exit or discharge chamber 10 with exit region 14 to be connected to an outlet pipe line (not shown). The fluid of course is being discharged with an angular momentum forming a spiral. Hence, cavitation bubbles can be drawn in at the center portion of the stream which bubbles can collapse further along in the outlet pipe line.

If a pipe portion with sharp curvature is connected to exit region 14-, one has to place an eddy remover and destroyer in such pipe so as to prevent destruction of the inner wall portion by eddies.

FIGURE 2 illustrates a development of the throttling channels 1 1 having in their upper portion a smaller pitch than in their lower portion. The overall pitch is nowhere more than 45. Due to the smaller pitch at the channel leading from entrance end 1'1a the channels 11 remain covered by guiding lands 8 over a long path so that in the range nearcomplete valve closing a very high control sensitivity is being obtained.

FIGURE 3 illustrates at enlarged scale, the cross section of a particularly shaped throttling channel 11. There are provided lateral ribs 15 placed in and transversely across the flow path but only at one side in the channel. These ribs prevent creation of centrifigu'al forces in the immediate vicinity of each rib. The channel portion not having such rib is of course subjected to the centrifugal force determined by flow speed and radius of curvature of the winding channel. Hence, there is produced a strong secondary current flow due to the differences of the flow conditions all across channel 11.

In the tree portion of channel 11 (no ribs) the fluid follows a path radially outwardly along arrow 16 while in the ribbed portion the flow pattern is as shown by arrow 17. One can compare these conditions with a central channel pump but there is the difference that the instant ribs 15 are stationary with the flow resulting from a pressure gradient while such pump has a moving conveyer wheel. In both cases, however, there is superimposed upon the main stream a secondary flow path which instantly increases the throttling elfect of each and any channel 11. Also, this secondary flow path pattern distributes the throttling effect along the entire covered area of each channel 11.

It is not necessary at all that the channels 11 in all the stages are similarly shaped. Nor do the diameters of the guiding lands, such as 8, have to be similar among themselves. Hence, it is possible to'completely elminate 6 valveseat 3 and valve surface 2. is used, it can be placed anywhere in the flow or channel path, for example in between two cascade stages or even below the lowest cascade stage.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be covered by the following claims.

What is claimed is:

1. A cascade valve comprising; a housing having a cylindrical bore and fluid entrance and exit chambers communicating therewith, means forming a plurality of axially separated guiding lands in between said chambers inside of said bore; a valve stem in said bore having portions snugly received by but clearing said lands, means also defining decompression chambers between said bore and said stem, said decompression chambers being axially spaced and respectively separated vby said guiding lands; and means in said stern defining a plurality of throttling channels winding around the stem axis as helix sections with substantially the entire length of any channel being opposite a decompression chamber when said valve is in closed position, the channels opposite the same decompression chamber having similar sense of winding.

2. A cascade valve comprising; a housing having a cylindrical bore and fluid entrance and exit chambers communicating therewith, means forming a plurality of axially separated guiding lands in the bore between said chambers; a valve stem in said bore having portions snugly received by but clearing said lands, said means also defining decompression chambers between said bore and said stern, said decompression chambers being axially spaced and respectively separated by said guiding lands; and means in said stem defining a plurality of throttlingchannels winding around the stern axis as helix sections with substantially the entire length of each channel being opposite a decompression chamber when said valve is in closed position, those channels opposite adjacent decompression chambers having respectively oppositely orientated direction of winding.

3. A cascade valve comprising; a housing having a cylindrical bore and fluid entrance and exit chambers communicating therewith, means forming a plurality of axially separated guiding lands between said chambers along the bore wall; a valve stem in said bore having portions snugly received by but clearing said lands, said means also defining decompression chambers between said bore and said stem, said decompression chambers being axially spaced and respectively separated by said guiding lands; and means in said stem defining a plurality of throttling channels winding around the stem axis as helix sections at a pitch angle smaller than 45, substantially the entire length of each channel being disposed within a single decompression chamber when said valve is in closed position, all of the channels so disposed within the same decompression chamber having a similar sense of winding.

4. A cascade valve comprising; a housing having a cylindrical bore and fluid entrance and exit chambers communicating therewith, means forming a plurality of axially separating giuding lands between said chambers along the said here; a valve stem in said bore having portions snugly received by but clearing said lands, said means also defining decompression chambers between said bore and said stem, said decompression chambers being axially spaced and respectively separated by said guiding lands; and means in said stem defining a plurality of throttling channels win-ding around the stern as helix sections with substantially the entire length of each channel being disposed within a single decompression chamber when said valve is in closed position, all of the channels so disposed within the same decompression chamber having a similar sense of winding, each said channel in at least the entrance region thereof, having a depth greater than the width thereof.

If a shut-off valve stage 5. A cascade valve comprising; a housing having a cylindrical bore and fluid entrance and exit chambers communicating with said bore, means forming a plurality of axially separated guiding lands between said chamhere along said bore; a valve stem in said bore having portions snugly received by but clearing said lands, said means also defining decompression chambers between said bore and said stem, said decompression chambers being axially spaced and respectively separated by said guiding lands; and means in said stem defining a plurality of throttling channels winding around the stem axis as helix sections, the pitch angle of each channel being smallest in the region of the entrance end thereof, substantially the full length of each channel being disposed within a single decompression chamber when said valve is in closed position, all of the channels so located within the same decompression chamber having a similar sense of winding.

6. A cascade valve comprising; a housing having a cylindrical bore and fluid entrance and exit chambers comunicating with said bore, means forming a plurality of axially separated guiding lands along said bore; a valve stem in said bore having portions snugly received by but clearing said lands, said means also defining dccompression chambers between said bore and said stern, said decompression chambers being axially spaced and respectively separated by said guiding lands; means in said stem defining a plurality of throttling channels Winding around the stem axis as helix sections with substantially the full length of each channel being disposed within a single decompression chamber when said valve is in closed position, all of the channels so disposed within the same decompression chamber having similar sense of winding; and laterally extending ribs in at least some of said channels.

7. A cascade valve comprising; a housing having a cylindrical bore and fluid entrance and exit chambers communicating with said bore, a valve seat in said housing at said entrance chamber, means forming a plurality of axially separated guiding lands between said chambers along said bore; a valve stem in said bore having portions snugly received by but clearing said lands, said means also defining decompression chambers between said bore and said stem, said decompression chambers being axially spaced and respectively separated by said guiding lands; means on said stem for cooperating with said valve seat and defining therewith valve open and valve closed positions; and means in said stern defining a plurality of throttling channels winding around the stem axis as helix sections with substantially the full length of each channel being disposed within a single decompression chamber when said valve is in closed position, the channels so disposed within the same decompression chamber having similar sense of winding.

3. A cascade valve comprising; a housing having a cylindrical bore and fluid entrance and exit chambers communicating with said bore; a valve stem in said bore defining together therewith a plurality of axially separated rotationally symmetrical decompression chambers, axially adjacently positioned decompression chambers being separated by guiding lands formed in said bore and snugly receiving but clearing adjacent valve stem portions; and means in said stem defining a plurality of throttling channels winding around the stem axis as helix sections with substantially the full length of any channel being disposed within a single decompression chamber when said valve is in closed position, all of the channels so disposed in the same decompression chamber having similar sense of Winding.

No references cited.

M. CARY NELSON, Primary Examiner.

L. KAMPSCHROR, Assistant Examiner.

Claims (1)

1. A CASCADE VALVE COMPRISING; A HOUSING HAVING A CYLINDRICAL BORE AND FLUID ENTRANCE AND EXIT CHAMBERS COMMUNICATING THEREWITH, MEANS FORMING A PLURALITY OF AXIALLY SEPARATED GUIDING LANDS IN BETWEEN SAID CHAMBERS INSIDE OF SAID BORE; A VALVE STEM IN SAID BORE HAVING PORTIONS SNUGLY RECEIVED BY BUT CLEARING SAID LANDS, MEANS ALSO DEFINING DECOMPRESSION CHAMBERS BETWEEN SAID BORE AND SAID STEM, SAID DECOMPRESSION CHAMBERS BEING AXIALLY SPACED AND RESPECTIVELY SEPARATED BY SAID GUIDING LANDS; AND MEANS IN SAID STEM DEFINING A PLURALITY OF THROTTLING CHANNELS WINDING AROUND THE STEM AXIS AS HELIX SECTIONS WITH SUBSTANTIALLY THE ENTIRE LENGTH OF ANY CHANNEL BEING OPPOSITE A DECOMPRESSION CHAMBER WHEN SAID VALVE IS IN CLOSED POSITION, THE CHANNELS OPPOSITE THE SAME DECOMPRESSION CHAMBER HAVING SIMILAR SENSE OF WINDING.

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