FR2678751A1 - ELECTRONICALLY CONTROLLED FLUID PRESSURE REGULATOR AND THERMALLY CONTROLLED VALVE, PARTICULARLY FOR FLUIDS FOR SUPPLYING SPACE ENGINES. - Google Patents

Abstract

The regulator comprises, to reduce the pressure of a fluid: - a thermally controlled valve (12) comprising: a shutter formed by a valve (17) and a seat (19) movable so as to define between them a passage (24) of variable section; an expandable element (16), cooperating with the shutter so that its expansion or retraction modifies the relative position of the valve and the seat and, correspondingly, the section of the passage; and means (20) for controlled heating of the expandable element, - means for measuring the downstream pressure, and - control means, receiving a pressure signal delivering a control signal controlling the heating means. Very advantageously, the shutter member is devoid of elastic return means and the heating means are split (20, 20 ') and controlled separately.

Description

Fluid pressure regulator with electronic control,
and thermally controlled valve, especially for
space engine supply fluids
The invention relates to an electronically controlled fluid pressure regulator, as well as a thermally controlled valve usable in particular for such a regulator.

 It is in particular intended for the fluid supply circuits of space engines, taking into account the very severe environmental and reliability constraints of such an application, for which the invention proves to be perfectly suitable.

 The object of a pressure regulator is to reduce the high pressure of a fluid, for example that prevailing in a tank, to a low pressure - constant or variable, as the case may be - compatible with the member of use. An example, of course in no way limiting, is the supply thereof to ion-propelled engines of space vehicles, in particular orbital control motors, motors which must be supplied with a pressure of the order of 2 bars by a gas stored under pressure. of the order of 100 bars in a tank.

 The pressure regulators proposed until now for this type of spatial application were based on two distinct concepts, namely digital electronic regulators, and mechanical regulators.

 A digital electronic regulator, the principle of which is illustrated diagrammatically in FIG. 1, essentially comprises, downstream of a high pressure fluid inlet 1, a filter 2 followed by a choke or calibrated orifice 3 introducing into the fluid circuit a loss of charge inducing a lowering of the fluid pressure.

Downstream of this throttle 3 is disposed a primary flow control valve 4 ensuring, by an all or nothing control appropriately sequenced, a modulation of the fluid flow.

The throttle valve 3 is designed so as to reduce the flow rate sufficiently so that the valve opening time is long compared to the valve response time, a condition necessary for proper servo-control of the regulator.

 This primary valve 4 is made redundant by adding a second valve 5, open during normal operation, ensuring safety against a refusal to close valve 4.

 Security against a refusal to open the primary valve 4 is obtained by splitting elements 2 to 5 into identical elements 2 'to 5', arranged between them in series, the assembly being arranged in parallel on the series of elements 2 to 5.

 The outputs of the two valves 5 and 5 'are connected together and lead to an accumulator balloon 6 making it possible to absorb the flow spurts and delivering by an output 7 the fluid under controlled low pressure. The control of the primary valve 4 (or of the secondary valves 5, 4 'and 5') is controlled by the measurement of the low pressure, carried out by a low pressure sensor 8, preferably doubly redundant (sensors 8 'and 8 " ) acting on a control electronics 9 controlling the different valves 4, 5, 4 'and 5'.

 The control electronics 9 ensures the on-off switching of the valve 4 as a function of a predetermined low pressure setpoint level, and actuates the secondary valves 5, 4 ′ and 5 ′ in the event that the output pressure exceeds a alert level indicative of a refusal to close the primary valve 4, or falls below a minimum level indicative of a refusal to open the primary valve 4.

 This first concept of regulator, although it is sufficiently precise and reliable and that it provides good protection against malfunctions of the primary valve, is nevertheless of relatively complex structure taking into account the multiplicity of components, which considerably limits its possibilities of use in space applications, where it is essential to have simple structures, to be reliable and light.

 The second concept is that of the mechanical regulator, illustrated diagrammatically in FIG. 2, which essentially comprises, downstream of the inlet 1 and of the filter 2 and upstream of the storage tank 6 and of the low pressure outlet 7, a regulating member 10 operating purely mechanical, generally a two-stage regulator taking into account the required regulation precision and the high ratio between inlet pressure and outlet pressure. A cut-off valve 11 is provided upstream of the regulator 10, made redundant by adding in parallel a second identical valve 11 ′ which provides security against refusals to open the valve 11.

 This second valve concept, due to the essentially mechanical nature of the regulation control, has poorer precision and poorer regulation fidelity. However, given its robust and compact nature, it is used in most of the space applications requiring such regulation.

 One of the aims of the invention is to propose a new type of regulator, of electronic type and therefore derived from the first concept mentioned above, but which is of much simpler design, while presenting at least equal performance and the same degree of safety. against refusals to open or close the primary valve.

 It will also be seen that the regulator of the invention does not operate in digital all-or-nothing mode like the prior regulators, but in analog mode, which provides a much finer modulation of the pressure to be regulated.

 The invention also relates, as a new industrial product, to the valve of the particular type fitted to the regulator, considered independently of this regulator.

 Essentially, the invention uses the advantages of a type of valve in itself known, but modified according to the aims sought, the thermally controlled valve or ETV (Electro-Thermally operated Valve), which is a valve, comprising very few moving parts, where the opening and closing of the valve flap are controlled by thermal expansion or retraction of an expandable element. Such a known ETV valve is for example described in US-A-3,211,414 ; in the valve described by this patent, the valve is biased against its seat by a spring positively applying pressure allowing a sealed closure; a stop system makes it possible to overcome the closing pressure of the valve with a relatively low expansion force in order to cause the opening of the valve. When closing, the presence of the spring guarantees an acceptable closing time for this type of valve.

It will be seen in particular that the invention provides the following advantages:
very high reliability, despite a long service life,
simplicity of structure,
low cost (both direct and indirect),
low mass,
low need for electrical power supply,
- long service life, in number of cycles,
low sensitivity to particulate contamination, therefore low
risk of blocking as a result,
- excellent regulation characteristic (low overshoot
on both sides of the setpoint level, very high stability
loop), and
- ease of testing.

 More specifically, the invention relates to an electronically controlled fluid pressure regulator, comprising a fluid inlet, a fluid outlet and means for controlled reduction of the pressure of this fluid between the inlet and the outlet, in particular for fluids for space engines.

 Characteristically of the invention, the means for controlling the pressure of the fluid in a controlled manner comprise: a thermally controlled valve comprising, housed in a valve body a shutter member formed by a movable valve and valve seat one with respect to the other so as to define between them a passage of variable section between an open position, corresponding to a maximum section of the passage, and a closed position, corresponding to a minimum section of the passage, a expandable element, cooperating with the shutter member so that the expansion or retraction of this element under the effect of temperature modifies the relative position of the valve and of the seat and, correspondingly, the section of the passage, and of the heating means controlled of the expandable element; means for measuring the pressure downstream of the valve, and control means, receiving as input a pressure signal delivered by the measuring means and outputting, as a function of this input signal, a signal servo controlling the heating means.

 Very advantageously, the shutter member is essentially devoid of elastic return means, the maximum section of the passage is chosen so as to ensure said controlled reduction of the pressure of the fluid, the latter then being operated directly by the shutter member, and the controlled heating means of the expandable element are split and controlled separately.

 The invention also covers, as a new industrial product, a thermally controlled valve, in particular for fluids supplying space engines, which comprises, housed in a valve body: a shutter member formed by a valve and '' a valve seat movable with respect to each other so as to define between them a passage of variable cross section between an open position, corresponding to a maximum cross section of the passage, and a closed position, corresponding to a minimum section of the passage, this shutter member being essentially devoid of elastic return means; an expandable element, cooperating with the shutter member so that the expansion or retraction of this element under the effect of temperature modifies the relative position of the valve and of the seat and, correspondingly, the section of the passage; and means for controlled heating of the expandable element.

0
We will now describe an embodiment of the invention, with reference to the accompanying drawings.

 Figure 1, above, shows the diagram of an electronic regulator of the conventional type.

 Figure 2, above, shows the block diagram of a mechanical regulator of the conventional type.

 FIG. 3 illustrates a valve according to the invention, of the normally closed type, in the rest position.

 Figure 4 illustrates the valve of Figure 3 in the active position.

 Figures 5 and 6 are equivalent to Figures 3 and 4, for a normally open type valve.

 FIG. 7 shows the block diagram of a regulator according to the invention, produced around the valves of FIGS. 3 and 5.

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Figure 3 shows the general diagram of a valve according to the invention, of the normally closed type (normally closed means a closed valve when no energy is applied to it from the outside, this valve opening under the effect of an energy application - and vice versa, for a normally open type valve).

 The valve 12 essentially comprises, inside a cylindrical housing 13 traversed by the fluid whose pressure is to be regulated, a transverse disc 14 provided with wide perforations 15 and supporting the end of an axial rod 16 carrying, its other end (free end) a valve 17 for closing the valve.

This valve 17 is for example provided with concentric circular reliefs 18 whose summits come to bear, in the closed position, on a valve seat 19. The material of the rod 16 is an expandable material so that, by heating, the rise in temperature material comes to expand the rod 16 and release the valve 17 from the seat 19, thus allowing a gradual opening of the valve.

 This heating of the rod 16 is carried out by an electrical resistance 20 regularly wound around the rod over the major part of the length of the latter. For safety, this winding is made redundant, the switching from one to the other winding 20 or 20 'being effected by a switch 21 upon detection of a malfunction. The selected winding 20 or 20 ′ is connected to an electric current source 22 by closing a switch 23, selectively controlled when it is desired to open the valve.

 More precisely, the valve is activated when the interrupter 23 is closed, which supplies the winding 20 or 20 ′ and establishes the desired temperature level within the expandable rod 16. The increase in temperature of the latter releases the valve 17 of the seat 19, revealing an annular gap 24 through which the fluid will be able to pass (Figure 4).

 Very advantageously, the gap 24 is dimensioned so as to introduce into the fluid circuit a pressure drop sufficient to directly achieve the desired pressure reduction, without it being necessary to provide a specific throttling to perform this function, as in the prior art. The cross section of the fluid passage in the open position depends both on the expansion of the rod 16 (parameter which can possibly be modulated by varying the supply of electrical heating energy) and on the diameter of the valve 17, parameter on which depends the valve surface facing the seat 19.

 In the case of the invention, if, for example, an aluminum rod 50 mm long and 3 mm in diameter is provided, an increase in temperature of 40 "C. makes it possible to achieve, with a valve diameter of 10 mm, at an annular gap of approximately 1 mm2 (the exact value being a function of the properties of the sealing material used and the closing pressure required), a value which is quite sufficient for the applications envisaged.

 On closing, the opening of the switch 23 isolates the winding and the rod 16 cools quickly - and this is all the more rapid since, on the one hand, the rod is located, due to its axial position. , surrounded by the moving fluid and that, on the other hand, it is in thermal contact with the disc 14 and the valve 17, these elements therefore participating in the cooling of the rod -, which causes the valve to gradually close.

 It will be noted, and this is an important aspect of the invention, that this valve is devoid of any return spring, unlike the thermally controlled valves known from the prior art, which always provided for such a return spring to guarantee an acceptable closing time.

 For an electrical power supply of 2 W, the opening valve of the order of 1 s and a closing time of the order of 5 s are obtained with the valve of the invention, values which are entirely compatible. with the space applications envisaged above, with a thermal conductivity of the rod-carrying disc 14 optimized to a value of approximately 50 mW / K.

 it is possibly possible, always without providing any return spring, to obtain shorter response times by modifying the values of the various parameters; it will be noted however that it then becomes necessary to provide a power supply of significantly higher power, imposing a stricter thermal control of the overall behavior.

 Figures 5 and 6 are homologous to Figures 3 and 4, for a valve of the normally open type. In these figures, the same reference numerals designate homologous elements, and it can be seen that the only essential difference is that, in the case of FIGS. 5 and 6, the valve 17 is located upstream of the seat 19, so that the expansion of the rod 16, instead of moving the valve 17 away from the seat 19, on the contrary, brings it closer to the latter.

 FIG. 7 is a diagram of a regulator according to the invention, using a primary control valve 12 of the same type as that illustrated in FIG. 3, that is to say a thermal control valve without return spring. We find in Figure 7 the same elements 1 (high pressure inlet), 2 (filter), 6 (storage tank), 7 (low pressure outlet), 8, 8 ', 8 "(low pressure sensors) and 9 (electronics control) than in the device of Figure 1, with comparable functions.

 It will be noted, first of all, that the absence of a mechanical return spring eliminates the risk of refusal to open for mechanical reasons, a risk which, in conventional regulators such as those illustrated in FIG. 1, must be covered by a complete doubling of the regulation chain (redundant elements 2 ', 3', 4 'and 5' of the figurel).

 The only risk of refusal to open would result, in the regulator of the invention, from a malfunction of the heating coil 20. However, the presence of a double coil 20, 20 'very simply and very effectively provides security. against such refusal to open.

 The only redundancy which is necessary is a redundancy of protection against a refusal to close the primary valve 12, protection which can be ensured by providing downstream of this a secondary valve 25, similar but of the type normally open.

 Finally, since the orifice between seat and valve can be controlled with precision, it is no longer necessary to provide a separate calibrated throttle or orifice (component 3 of FIG. 1), which further simplifies assembly.

 Another advantage of the new configuration according to the invention is that, in the event of a power supply failure, the primary valve 12 returns by itself to the closed position, thus introducing intrinsic safety against this risk without use of no additional elements.

 With regard to the control of the valves 12 and 25 by the control electronics 9, this control can be ensured by control stages controlled in either digital (all or nothing) or analog mode, with in this case a continuous variation, gradual cross-section of the passage between valve and seat which, through the pressure drop introduced, controls the reduction in pressure.

Claims (1)

CLAIMS I. An electronically controlled fluid pressure regulator comprising a fluid inlet (1), a fluid outlet (7) and means for controlled reduction of the pressure of this fluid between the inlet and the outlet, in particular for fluids supplying space engines, characterized in that the means for reducing the fluid pressure in a controlled manner comprise: - a thermally controlled valve (12;  25) including, accommodated  in a valve body (13):  a shutter member formed by a valve (17) and a seat  valve (19) movable relative to each other so as to  define between them a passage (24) of variable section between  an open position, corresponding to a maximum section  male passage, and a closed position, corresponding  at a minimum section of the passage,  an expandable element (16), cooperating with the obturating member  so that the expansion or retraction of this element  under the effect of temperature changes the relative position  tive of the valve and seat and, correspondingly, the section of the  passage, and  means (20) for controlled heating of the dilata element  corn,  - means (8, 8 ', 8 ") for measuring the pressure downstream of the valve, and  - Control means (9), receiving as input a pressure signal delivered by the measuring means and outputting, as a function of this input signal, a control signal controlling the heating means.  2. The pressure regulator of claim I, wherein the shutter member is essentially devoid of elastic return means.  3. The pressure regulator of claim 1, wherein the maximum section of the passage is chosen so as to ensure said controlled reduction of the pressure of the fluid, the latter then being operated directly by the shutter member.  4. The pressure regulator of claim 1, wherein the controlled heating means of the expandable element are split (20, 20 ') and controlled separately.  5. A thermally controlled valve (12; 25), in particular for fluids supplying space engines,  characterized in that it comprises, housed in a valve body (13):  - a shutter member formed by a valve (17) and a seat  valve (19) movable relative to each other so as to  define between them a passage (24) of variable section between a  open position, corresponding to a maximum section  passage, and a closed position, corresponding to a  minimum passage section,  this shutter member being essentially devoid of mo  elastic booster yen,  - an expandable element (16), cooperating with the shutter member  so that the expansion or retraction of this element  under the effect of temperature changes the relative position of the  valve and seat and, correspondingly, the section of the passage, and  - Means (20) for controlled heating of the expandable element.  6. The valve of claim 5, in which the maximum section of the passage is chosen so as to ensure a controlled reduction of the pressure of the fluid.  7. The valve of claim 5, wherein the controlled heating means of the expandable element are split and controllable separately.