DE2808999A1 - Multiple stage regulation valve for fluids - has given mathematical relationships at choke point cross sections - Google Patents

Abstract

The multi-stage regulation valve is for fluids and has a delay section and acceleration section (choke point) per stage. The flow cross-sections (e1, e11, eN) of the acceleration section can be varied by a common operating element (15) and increase in the flow direction so that the valve of a operating parameter K for all stages is equal for each stage is given by a formula of the form K=1-R 1/N where R is the ratio (Pa-Pd), Pa is the stage inlet pressure and PD is the vapour pressure. For all stages (I, II, N), the quotient of the volumes (VI, VII.. VN) of the delay section and the smallest cross-section face (e1, e11, eN) at the acceleration section is constant.

Description

Applicant: GüLDE REGELARMATUREN KG

6700 Ludwigshafen-Oggersheim

Multi-stage control valve

The invention relates to a multi-stage control valve for liquids with a delay section and a Acceleration section (throttle point) per stage, the flow cross-sections of the acceleration sections through the common actuating member can be changed for all stages of the number N and which flow cross-sections increase in the flow direction in such a way that the value of an operating parameter K is the same or approximately the same for all N levels and is derived from the formula for each level

■ '■ (

determined, where mean:

p- = vapor pressure of the liquid in bar

ρ = stage inlet pressure in bar
^e /

p_ = stage outlet pressure in bar

according to patent .... (patent application P 26 11 179.5)

The expansion of liquids from the inlet pressure ρ to the lower outlet pressure p_ basically consists of

that in an acceleration section (cross-sectional constriction)

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2608999

an acceleration to a high flow velocity and in a downstream deceleration section (cross-sectional expansion) there is a delay to a lower flow rate. Control valves with only one such "expansion stage" is referred to as single-stage; if one arranges several such stages one after the other, one speaks of "multi-stage control valves".

When the vapor pressure p _d of the liquid between the lowest pressure p, in the acceleration section and the outlet pressure p _A is, as occur when the narrowest flow cross section e steam bubbles condense again because of the pressure increase in the delay section V.

The steam bubbles collapse, causing violent pressure surges and loud, crackling noises arise. This process is known as cavitation. The intensity cavitation depends on the level of pressure recovery ρ - p, and on the operating data ρ, ρ and ρ. the Operational data are expediently combined to form an operational parameter K according to the following equation:

^p e ^p a (based on a level or

a single-stage valve) ^p e ~ ^p d

The pressure recovery p ₌ - p, in the valve can also be identified with a parameter, the so-called valve parameter D. This parameter D is determined according to a method that is described by the inventor in an article in the journal Archive for technical measuring (ATM) (Issue 2/76 V 53-9, L. 481, pages 51 - 54 "Sound level calculations for controlled systems Part One").

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The greater the quotient

Pressure recovery ρ - ρ,

a id

accelerating pressure difference "e" b

is, the smaller the numerical value of D. For example, a single-stage control valve usually has a parameter D - 0.4. The intensity of the cavitation results from the comparison of K with D. If KCD, then the cavitation is weak, whereas with K? D has strong cavitation.

In order to reduce the intensity of the cavitation, it is advantageous to work in two or more relaxation stages I, II to throttle N. The higher the number of stages is normally chosen, the weaker the cavitation "

In the subject of the main application, however, with a relatively small number of levels, a sufficiently low number is obtained Cavitation intensity is achieved by the flow cross-sections of the acceleration sections in the direction of flow increase and the dimensioning is carried out in such a way that K is constant for all levels. According to the above explanations, K ^ D be, i.e., K / D <1. In order to obtain the smallest possible K / D value for all stages, it is necessary to define valve parameters To strive for D, which are as large as possible for all stages and - since K = constant - as possible for all stages are the same size, d = h. D = constant.

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Realizing these findings does not present any difficulties when the delay lines are in their Cross-section and length are so large that there is a uniform acceleration path up to the following acceleration path Can form flow. However, such a valve would be very large and expensive. With the subject of the main application

/that
is already provided, the lengths of the delay sections

increase in the direction of flow according to the additional regulation,

that the quotient of the narrowest flow cross-section and the distance to the next stage is essentially is constant. On the basis of the features already mentioned (increasing flow cross-sections in the direction of flow, K = const.) The last-mentioned regulation leads in comparison to a known multi-stage control valve (FR - PS 1 057 107) with the shape of a fir tree-like actuator and cross-sections of the acceleration sections (throttling points) increasing in the direction of flow, leading to a weaker cavitation, but does not take sufficient account of the parameter D.

The invention is based on the multi-stage control valve The type described at the beginning, the task of the delay lines to be as small as possible while keeping the D-values of the levels as high as possible and as constant as possible. The solution to this The object is that according to the invention for all stages the quotient of the volume of the deceleration section and the smallest cross-sectional area of the acceleration section is constant.

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With a control valve of this size with a small total volume, the cavitation is surprisingly weak.

There are two options for the design:

Are the cross-sectional areas of the delay sections the same size for all stages, their lengths are allowed to increase in the direction of flow Measure according to the invention results in the respective length from the product of a quotient which is constant for all stages is to be determined from the length and the smallest cross-section with the smallest cross-section of the affected step.

If the lengths of the delay sections are the same for all stages, their cross-sectional areas are left in the direction of flow increase, with the result of the first-mentioned measure according to the invention that the respective cross-sectional area is the product of a quotient that is constant for all stages is to be determined from the cross-sectional area and the smallest cross-section with the smallest cross-section of the step concerned.

Finally, you can also use the cross-sectional areas and the Allow lengths to increase while observing the first-mentioned measure.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing. Show it:

1 shows a four-stage control valve with the delay sections and lengths increasing in the direction of flow 2 shows a four-stage control valve with cross-sections of the delay sections that increase in the direction of flow.

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The four-stage control valve in the exemplary embodiment (stages I to IV) has a housing 10 with inlet and outlet nozzles 11 and 12 for the liquid (FIGS. 1, 2). The direction of flow is indicated by arrows 13, 14. In the housing, an actuating member 15 is guided with valve cones 16 of different bevels 17, which interact with their cone area with openings 18 lying one behind the other in the flow direction of the same cross section in the intermediate base 19 of the housing 10. Their depth of immersion in the openings 18 is different, so that increasing narrowest flow cross-sections e_ in the direction of flow. <e- ^ / ⁶ X ₁₁ ζ ^e _{IV are} formed. The quotient of the respective volume V of the delay section and the smallest cross section e is constant. The narrowest cross-sections e ^. to e _IV are indicated by dashed lines in FIG. Instead of the bevels 17, other embodiments of the cross-sectional design are of course possible.

If the cross-sectional areas A of the delay sections with the volumes V ₁ , V ₁₁ , V _113. , V _{IV are the} same in all stages I to IV (A = constant), their lengths L ₁ , L ₁₁ / L, L _{IV are in} accordance with V / e = AL / e = constant, ie to be carried out according to L / e = constant (Fig. 1).

If the lengths L of the delay lines are the same for all stages I to IV (L = constant), their cross-sectional areas A_, A ₁₁ , A ₁₁₁ , A _{IV are} according to V / e = AL / e = constant, ie according to A / e = to be carried out constantly (Fig. 2) . In addition, the increase in volume can also be achieved in that the cross-sectional area A and length L increase from step to step according to AL / e = constant (not shown).

In any case, for a certain liquid with the vapor pressure p _d, the steps are optimally matched to the operating conditions that are usually fixed for a valve insert.

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The measures:

a) Enlargement of the opening widths or Flow cross-sections in the direction of flow,

b) Enlargement of the cross-sectional areas and / or lengths of the delay sections after Condition V / e = constant,

can also be implemented with stacking disks or "stress-relieving disks" through which flow radially from the inside to the outside according to the earlier patent application P 21 28 697 1 with a corresponding design (not shown).

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Claims (3)

2808399 Patent attorney
DiDl.-PhyS. HANS KLOSE D-68OO Mannheim 1.16. Feb. 78 Expectations; 11J Multi-stage control valve for liquids with a delay s section and an acceleration section (throttle point) per stage, the flow cross-sections (e_, e, -,. .., e ") of the acceleration section through the for all stages (I, II,. .., N) common actuator (15) can be changed and increase in the direction of flow in such a way that that the value of an operating parameter K for all stages (I, II, ..., N) is the same or approximately the same and is for each level (I, II, ... N) from the formula - P, determined, where mean: p, = vapor pressure of the liquid in bar ρ = stage inlet pressure in bar
p_ = stage outlet pressure in bar Cl according to patent .... (patent application P 26 11 179.5), characterized in that for all stages (I, II, ... N) the quotient of the volume (V ₁ , V ₁₁ , ..., V _n ) of the deceleration section and the smallest cross-sectional area (e-, e _IT , ..., e _N ) of the acceleration section is constant. ORiGiNAL INSPECTED 909837/0048 2. Multi-stage control valve according to claim 1, characterized in that with a constant cross-sectional area (A) for all delay sections the lengths (L, L ₁₁ / ··· / ^ _n ) of the same are increasingly dimensioned in the flow direction (Fig. 1). 3. Multi-stage control valve according to claim 1, characterized in that with the same lengths (L) for all delay sections, the cross-sectional areas (A ₁ , A ^ ₁ , ..., A ^) of the same are increasingly dimensioned in the direction of flow (Fig. 2) . 909837/0048