Automatic multi-stage control nozzle

This First Page has been artificially created and is not part of the CIPO Official Publication ’•5:

<img file="CA599028A_D0001.tif" />

The invention relates to a multi-stage control nozzle, especially for the discharge of steam condensate with the narrowest flow cross-section increasing from stage to stage, with conical expansion in every stage and with an axially movable control element. These control nozzles have the disadvantage that when they are used for the discharge of steam condensate or other boiling-hot liquids in the event of sharply decreasing or entirely ceasing access of liquid, i,e., steam condensate for example, a penetration of steam occurs, which may under certain circumstances reach inadmissibly high values if the control element under these conditions is not moved in the closing direction. In addition to suitable hand adjusting apparatuses, automatic controls for operating a control element have already been suggested, e.g. float controls which act directly or indirectly, on the control element depending on the position of the steam surface, or thermal control depending on the temperature of the liquid to be discharged e.g. by interposition of known hydraulic or pneumatic servo elements. Controls of this kind entail considerably greater costs of construction and decreased operating reliability.

These disadvantages are to be avoided in the present invention by utilizing the different intermediate pressures occuring during discharge of liquid, e.g. water, or of steam, as the case may be, in the individual nozzle stages for direct automatic control of

I the governing element. For this purpose it is suggested that in a multi-stage control nozzle of the type described above, where, for example, the governing element takes the form of a controlling mandrel, the flow through the first stage or stages - looking in the discharge direction - should be in the direction of opening of the control mandrel and that in the last stage or stages should be in the closing direction of the control mandrel. This is realized according to the invention by means of a re-routing duct disposed between two successive stages in such a way that - looking in the direction of discharge IC

<img file="CA599028A_D0002.tif" />

./ 3

<img file="CA599028A_D0003.tif" />

the flow through the stage or stages situated in front of the re-routing duct will be in the opening direction of the control mandrel and the flow through the stage or stages behind the re-routing duct will be in the closing direction of the control mandrel.

An especially simple construction is obtained if the last stage of the multi-state control nozzle is divided up into two half-stages of e.g. equal narrowest discharge cross-section, the half-stages being connected in parallel, with the flow in one halfstage being in the opening direction and that in the other half-stage in the closing direction of the control mandrel. In each case the increase of control mandrel area under pressure from stage to stage is such that when cold liquid is discharged the control mandrel moves in the opening direction, and when steam is discharged it moves in the closing direction.

To illustrate the invention three examples cf execution of the invention are represented schematically in the drawing, where Figure 1 shows a multi-stage control nozzle with a control element in the form of a mandrel, where the flow through the first two stages and one-half of the third stage is in the opening direction while that in the second half of the third stage is in the closing direction;

Figure 2 shows a multi-stage control nozzle corresponding to that of Figure 1, but where a fourth stage, again divided into two halves, is added after the third stage;

Figure 3 shows a longitudinal section through a two-stage control nozzle with a control element in the form of a plate;

Figure 4 shows a section IV-IV through the two-stage control nozzle of Figure 3.

The control nozzle represented in Figure 1 is in three stages 1,2,3',3, where the flow through stages 1 and 2 with narrowest discharge cross-sections F^ and 1® lⁿ the opening direction of control mandrel 5.

IC

/)£/·,.

ill®?,

3//5/

9/ “Mi//

- 3 599028

The third stage is divided into two half stages 3' and 3 which are connected in parallel and which have e.g. equal narrowest cross-sections F^' and F^, where the flow through F^' is in the opening direction of control mandrel 5 and that through F^ is in the closing direction.

j This is brought about by disposition of a re-routing duct 6 between narrowest flow cross-section F£ of the second-last stage 2 and narrowest flow cross-section F^ of the final half 3 of the last stage.

The expansion through the control nozzle is to take place e.g, from an initial pressure pi = 10 atm. abs. to the final pressure

-æ P4 = 1 atm. abs. with intermediate pressures p2 — 4.9 atm. abs. after the first narrowest cross-section F^ and p3 = 2.4 atm. abs. after the second narrowest cross-section Fg. This is for discharge of steam with saturation steam temperature. In this case, therefore, each stage must handle a critical pressure gradient so that in all three narrowest flow cross-sections F^, F£ and F^ (i.e, F^ = F^' + F ) the same critical steam velocity occurs. The dimensioning of the narrowest cross-sections in this example is therefore determined solely by the specific steam volume present in each at any given time. The latter is obtained from the known steam tables for the given pressure in the narrowest cross-section determined with the aid of the critical pressure ratio, and is found to be approximately 0.33 in F2, 0.66 in F, and I.32 in F . In the given example, therefore, the ratio of the 3

I flow cross-sections must be 1 î 2 : 4.

The areas f^, f^- Î2» ^an&lt;^ ^4 ^con'^t'^ro1 ^ndrel 5 which are under pressure should now be related e.g. as 1 j 2 : 4 s 15.

In that case when saturated steam flows through the nozzle the force acting on the control mandrel 5 in the opening direction is given by fj. (P2-P₂)⁺(^f2^fi)· (P2^pP⁺^^f3·^⁵ ίΡ3-Ρ₄)^=1χ5.1+2x2.5+4^1.4=5.1+5+5.6= I5.7 units of force and that in the closing direction is f^.(p₃~p₄)= ₃0 15x1.4= 21 units of force. In other words control mandrel 5 is brought with 5.3 units of force into the closed position so that an inadmissible penetration of steam is avoided.

Λ £

IC

- 4 599028

Now, if a liquid, e.g. cold water, flows through the control nozzle, then for the given ratio of narrowest cross-sections ft; F₂^! ft — 1:2:4 the pressure gradients in the stages must be related as 1 : l/4 : l/Ιό. In other words the pressure gradient in the first stage is now ?1 - P₂ = 6.8 atm., in the second stage pg - p^ = 1.7 atm. and in the third stage - p^ = 0.5 atm, for the total pressure difference:· of ρ_χ - = 10 - 1 = 9 atm. Thus lx 6.8 +2x1.7 + 4 x 0.5 - 6.8 + 3.4 +

2.0 = 12.2 units of force act on control mandrel 5 in the opening direction and 15 x 0.5 = 7.5 units of force in the closing direction. In other words control mandrel 5 is now being opened automatically with 4.7 units of force, so that the cold water can be discharged without hindrance. Now, if this water is gradually warmed, e.g. with gradual heating up of the steam plant connected ahead of it, there will then be incareasing steam formation accompanying the expansion in the control nozzle and a return motion of control mandrel 5 in the closing direction will take place.

In order to prevent any sudden complete closing of the control nozzle with increasing steam discharge, which after the subsequent pressure drop in intermediate compartments 7, 3 and especially 9 of the control nozzle is bound to result in a sudden reopening, and under certain circumstances may lead to a continuous repetition of this process, it is advisable to provide a preferably adjustably disposed stop 10 or the like by means of which the stroke of mandrel 5 is restricted in the closing direction.

Stop 10 may advantageously be adjusted, for example so that when control mandrel 5 has been moved as far as it can go in the closing direction the residual cross sections ft, ft and ft are just sufficient to discharge the steam concentrate still accumulating in the fully heated plant, without penetration of fresh steam. Under continuous operation no movement of control mandrel 5 is then necessary, so that mechanical wear and noise production are kept to a minimum.

In this way a steady, constant operation of control mandrel 5 and simultaneously an automatic deaeration and degasification of the

I'/·. :/.

/.4 0:

IC

J

X., /

9 028

- 5 steam condensate line, and hence also constant and unhindered operation of the steam condensate discharge system containing such a control nozzle, is guaranteed.

Control mandrel 5 is preferably designed as a body of rotation vrith annular flow cross-sections to F^» however other cross-sectional shapes with basically the same effect are also possible, e.g, square ox· rectangular.

Fig. 2 shows another example of execution of the invention where an additional stage has been added after stage 3’, 3 of a multi-stage control designed according to Fig. 1. This new stage is again divided into two half-stages 4^f, 4 , fhe flow through halfstage 4’ being in the opening direction of control mandrel 5 while that in half-*stage 4” is in the closing diredtion. In this nozzle an additional by-pass duct 12 is provided, connected to outlet 11 between half-stages 3&gt; and 3. By-pass duct 12 is forked in such a way that through one fork, 12/, the flow is conducted in the opening direction of control mandrel 5 and through the other fork 12 it is conducted in the closing direction of mandrel 5» The outlet from the multi-stage control nozzle is then located at 34.

There are other possible variations in the design of the multi-stage control nozzle. For instance it is possible to have a forat of the multi-staged control nozzle according to Fig, 1 where the third stage is not divided into two half stages 3*, 3*' but receives the flow as an undivided stage in the closing direction of control mandrel 5. Instead of the narrowest flow cross-section Frj* between the second stage 2 and the half-stage 3’ of the third stage in this case it is necessary to provide a seal 35 between the flow space of the first two stages and that of the third stage, a seal which does not restrict the axial motion of control mandrel 5, such as is provided in the example of Fig, 2 between the third stage 3* , 3 and the fourth stage 4’, 4*

It is also possible to imagine a design of the multi-stage control nozzle according to Fig. 2 where¹ the third stage is not di-

<td></td><td colspan="3"></td><td></td><td colspan="3"> ' ·?. ·? 7 ' . :-:,</td>

<td></td><td></td><td></td><td></td><td></td><td> .. · ' /·:</td><td></td><td></td>

<td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td> -f. ;</td><td></td><td></td><td> X/ :</td><td></td><td></td>

.//

<img file="CA599028A_D0004.tif" />

' / '

<img file="CA599028A_D0005.tif" />

vided into two halves 3', 3, but is entirely subject to flow in the closing direction of control mandrel 5, and it is also possible to imagine a design where the fourth stage is not divided into two halves 4' and 4 but in which the flow is entirely in the closing direction of mandrel 5. In this case the third stage may or may not be divided into two halves 3'&gt; 3.

Another advantageous realization of the invention in a twostage control nozzle is found in the example of Figure 3 and 4· In this example the control element is designed as a flat plate 19 with sealing surfaces lying in a plane. This plate is arranged so as to have freedom of motion in all directions inside the nozzle space formed by control nozzle body 13 and the upper part 36. However, the control element can also be designed as an arched element.

In control nozzle body 13 there is provided an inlet hole 14 through which the steam condensate or the boiling hot liquid gains access to re-routing space 15 which is designed as a swirl space. The outlet for the condensate from inlet hole 14 into swirl space 15 constitutes the first stage of the two-stage control nozzle. Symmetrical to entrance opening 14 in the body 13 of the control nozzle, outlet holes 16 and 17 are provided. The entrances to outlet holes 16 and 17 constitute the second stage of expansion. Both stages are situated In plane 18.

In the simplest case one entrance and an exit hole would suffice for controlling the steam condensate or boiling-hot liquids to be discharged. This, however, results in a symmetrical loading and consequently uneven wear of the controlling element. The invention therefore provides for one or more symmetrically arranged inlet holes 14 forming the first stage and one or more outlet holes 16, 17 arranged symmetrically with respect to the inlet holes 14 and forming the second stage.

3d The flow medium gains access to the two-stage control nozzle

IC / j·

<img file="CA599028A_D0006.tif" />

- 7 599028 through holes 32 and the outlet from the nozzle is through hole 33 which is connected on the one hand with outlet holes 16, 17 and on the other hand with the external discharge line, which is not shown in the drawing.

In order to avoid a suction effect at the inlet hole or holes 14, and a damping effect at the outlet holes 16, 17, sealing surfaces 20 which are as narrow as possible (e.g. l/2 mm.) are provided at the inlet hole 14 and wide sealing surfaces 21 which are several times as wide as surface 20 are provided at outlet holes 16, 17.

In order to avoid a steam break-through in the event of sharp reduction or complete cessation of fluid flow to the control nozzle, a condition which under certain circumstances may result in a high value loss, and in order to prevent a possible sub-pressure from arising between the inlet hole and the outlet holes, which would result in a reduced water output, the re-routing space 15 between inlet and outlet holes 14 and 16, 17 is designed as a swirl space whioh is large enough to prevent steam penetration. Holes 14, 16 and 17 are preferably designed so as to project after the fashion of valve seats. An annular swirl duct whose wall 23 on the side of inlet hole 14 is bevelled off and which is disposed around the inlet hole has also been found advantageous. In this way the flow cross-section behind the valve-seat-shaped, projecting mouth of inlet hole 14, representing the first stage of expansion, widens out gradually into re-routing space 15.

To enlarge the cold water stroke pressure equalizing holes 25 are provided between re-routing /space 15, designed as a swirl space and space 24 above plate 19. For the same purpose a reflecting recess 26 is also provided in plate 19 above the inlet hole 14.

In order to discharge the air present in the steam condensate or in boiling-hot liquids faster and more effectively and to bring down the eômpartment pressure more quickly it is advantageous to provide air escape grooves 27, 28 which cross the sealing surfaces of inlet and/or outlet holes 14, 16, 17, specifically in sealing surfaces 20, 21 at

IC

<img file="CA599028A_D0007.tif" />

A

<img file="CA599028A_D0008.tif" />

<img file="CA599028A_D0009.tif" />

&gt;ntrol nozzle body 13 and/or in the sealing surfaces corresponding to these on plate 19. In place of air escape grooves 27, 28, however, air escape holes can pierce plate 19 above the inlet and/or outlet holes 14-, 16» 17. It Is also impossible to provide, for example, air escape grooves in the sealing surfaces of inlet hole 14 and air escape holes in plate 19 above outlet holes 16, 17, and it is also possible for air escape grooves 27, 28 to be provided in the sealing surfaces of outlet holes 16, 17 while providing air escape hole in plate 19 above inlet hole 14, and it is further possible to have both air escape grooves in the sealing surfaces and at the same time air escape holes in plate 19 above the inlet and/or outlet holes 14·, 16, 17.

The closing motion of control element 19, like that of control mandrel 5» of Figure 1 and 2, should be amendable to restriction by a preferably adjustable stop 29 or the like, preferably in sueh a way that by means of the flow cross-section left open by the restriction the condensate accumulating under the normal conditions of continuous operation of a fully heated plant, will be discharged without penetration of steam. By this means the condensate accumulating during normal operation at full boiling temperature is discharged without any movement of the control element, i.e. of plate 19 in the case of the example according to Figure 3 and 4-, whereby a minimum of noise and mechanical wear is achieved.

It is advantageous to provide a by-pass duct which is amendable to regulation and/or shutting off, which can be used both for blowing out and also for rapid air exhaustion as well as varying the discharge temperature of the hot water, and which leads from interior spaces 15, 22, 24. of the multistage control nozzle to condensate discharge 33» or to the outside. A regulating and shut-off valve is used preferably as a controlling and shut-off element 31. It may be operated byhand or also by a device which works automatically, e.g. one having a thermostat for a temperature-dependent control.

In order to obtain the quickest possible exhaustion of air and water when the plant is cold, say at the start of operation, and to ensure the smallest possible steam loss when the plant is fully heated and no condensate is coming out, the thermally operated by-pass should be opened by means of by-pass duct 30 at room, temperature and olosed at steam temperature.

'&lt;·/· ‘

Z

IC yyv /7/// /'

99028

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS