US2763984A - Device for regulating the effective cross-section of a discharge-nozzle - Google Patents

Description

Pt. 25, 1956 M. KADOSCH ETAL 2,763,984

DEVICE FQR REGULATING THE EFFECTIVE CROSS-SECTION OF A DISCHARGE-NOZZLE Filed Sept. 15, .1955

INVENTORS Manual. KADoscH Raw Mom: H. MARCHRL 34 410.}, M, M rmw ATTORNEYS DEVICE FUR REGULATKNG THE EFFECTIVE CRGSELSECTHUN (ME A. DISQHARGE-NDZZLE Marcel Kadosch and Raymond H. Marchal, Paris, France, assignors to Societe Nationale dEtude et de Construction do Moteurs dAviation, Paris, France, a company of France Application September 13, 1955, Serial No. 534,119 Claims priority, application France September 17, 1954 2 Claims. (Cl. 60-35.6)

In the U. S. patent applications Ser. No. 263,666, filed December 27, 1951; Ser. Nos. 358,666, 358,667 and 358,668, filed June 1, 1953; Ser. Nos. 396,991 and 396,992, filed December 8, 1953; Ser. No. 397,112,

nit n7 rates Patent filed December 9, 1953; Ser. No. 455,852, filed September 14, 1954-; and Ser. No. 485,179, filed January 31, 1955, is described a method enabling the flow of a gaseous fluid inside a conduit to be controlled, and in particular the cross-section of passage available to the said flow, the said method consisting in directing on to the said fiow an auxiliary jet of a gas at suitable pressure, the initial speed of which has a component at right angles to the direction of the said flow.

Devices for carrying this method into eifect have also been described in the said applications for patents thereto, together with various applications of the said method, particularly in respect of the regulation of the outlet crosssection of the discharge-nozzle of a reaction-propulsion unit.

In general, the discharge-nozzles of reaction motors form convergent surfaces with a double curvature, the extremity of which is tangential to a cylinder parallel to the axis (see Fig. l of the attached drawings showing in axial cross-section the cylindrical extremity 1 of a discharge-nozzle of this kind). In this way, by suitably determining the shape of the discharge-nozzle, and in particular the various radii of curvature, reaction jets can be produced such that all the molecules are discharged in a direction truly parallel to the axis of the discharge-nozzle and at the same speed, the jet retaining a constant cross-section for some time after its discharge from the nozzle, this cross-section being identical with that of the extremity of the said discharge-nozzle.

Now there exists a further type of reaction dischargenozzle, in which the streams of gas discharge are no longer parallel but are convergent. In a discharge-nozzle of this kind, the jet reaches its minimum cross-section a short distance on the downstream side of the outlet cross-section. In order to obtain this result, it is merely necessary for the extremity of the discharge-nozzle to be tangential to a convergent cone, and very often this discharge-nozzle will have one curvature only without a point of inflection, its concavity being always turned towards the interior of the conduit. For example, the discharge-nozzle may terminate quite simply in a 45 cone. A discharge-nozzle of this kind may be termed a truncated discharge-nozzle.

In addition to the fact that a shape of this kind results in a simpler and lighter construction, it is also to be recommended because of the following feature. With such a truncated discharge-nozzle, the minimum crosssection of the jet is less than the minimum geometric cross-section of the discharge-nozzle. The relation between these two cross-scetions, which is known as the coetficient of discharge of the nozzle, is less than unity. Now this coeificient of discharge depends to some extent on the pressure on the upstream side of the dischargenozzle, and thus on the speed of operation of the reaction ice unit, and it happens that this variation in the coefiicient of discharge makes it more easy to regulate the whole machine.

With such a truncated nozzle, it is possible to control aerodynamically the passage cross-section for the motive fluid, by providing one or more auxiliary nozzles fed with pressure fluid and orientated in such a manner that the jet or jets formed by this fluid pass into the dischargenozzle in a direction roughly parallel to its axis or to its plane of symmetry, depending on the case, and with a direction of flow opposite to the mean direction of the main flow.

It is this particular combination of a truncated discharge-nozzle with one or a number of nozzles for aerodynamic control of the crosssection which forms the object of the present invention.

The description which follows below with reference to the attached drawings (which are given by Way of example only and not in any sense by way of limitation) will make it quite clear how the invention may be carried into effect, the special features which are brought out, either in the text or in the drawings, being understood to form a part of the said invention.

Fig. 1 is a view in axial cross-section of a dischargenozzle with a cylindrical extremity, and has already been referred to in the preamble to the present description.

Fig. 2 is a view in axial cross-section of a truncated discharge-nozzle provided with an application of the invention.

Fig. 3 is a detail view to a larger scale and in crosssection of the extremity of this dischargenozzle.

The discharge-nozzle 2 shown in Figs. 2 and 3, is given a shape which converges continuously towards a point located on the axis and on the downstream side of the outlet orifice. Its terminal portion 3 may be formed, for example, by a frustum of a cone having its apex on the axis A-A, and an apex angle of 45. Around the outlet orifice is formed an annular slot 41 through which a nozzle 5, also of annular form, discharges into the main conduit, the nozzle 5 communicating with an annular collector 6 which is supplied with auxiliary gas from a suitable source, for example from the air compressor of the reaction unit, through the medium of a pipe 7 which may be provided with a control valve 7a. The gas in the collector 6 should have a total pressure greater than the static pressure applied by the main jet on the wall or" the discharge nozzle in the zone of the slot i. The nozzle 5 has a form suitable for the complete expansion of this gas by causing it to penetrate into the discharge-nozzle in the form of an annular jet at high velocity. By opening the vaive 7a to a greater or less extent, the momentum of the auxiliary jet and, in consequence, its effect, can be regulated from zero up to a maximum.

In accordance with the present invention, the nozzle 5 is disposed in such a way that the jets of gas which are discharged through it when the valve 7a is opened, have a speed V1 substantially parallel to the axis A-A, or slightly oblique with respect to the said axis, and have a direction in the opposite sense to the speed of how of the main jet. Under the action of the main flow, and in particular of the streams of the main jet which follow the inturnal wall of the discharge-nozzle 23, and which are directed obliquely with respect to the speed V1, the auxiliary jet curves inward following the lines shown dotted, and passes out of the discharge-nozzle with a speed V2. It thus forms a fluid screen which has the effect of reducing the efiective cross-section of passage available in the discharge-nozzle to the main jet. In the figure, the cross-section of passage, instead of being the physical cross-section S of the outlet orifice becomes the section S1. If d represents the mass flow of the auxiliary jet, the restrictive effect is proportional, in accordance with Eulers theorem, to the vectorial difierence between the two momentum values, namely dVzdV1. It will be seen that V2 and V1 being substantially parallel and in opposite directions, this vectorial difference is a maximum and, in consequence, the rectrictive effect is also a maximum.

With a discharge-nozzle of the type shown in Fig. 1, which has a cylindrical extremity, it would be dilficult to arrange the nozzle of the auxiliary jet so that this jet would have a speed parallel to the axis, since there would then be produced wall effects which would tend to cause the auxiliary jet to adhere to this wall, thus destroying its action on the main jet. In a case of this kind, it is hardly possible to have an inclination towards the upstream side at a greater angle than 45.

On the other hand, in the case of a truncated dischargenozzle, the arrangement of a nozzle giving an auxiliary jet parallel to the axis and opposite to the main flow does not give rise to any difiiculty and enables the maxi- 4 mum constrictive efiect on the main jet to be obtained for a given energy of the auxiliary jet.

What we claim is:

1. A device for the aerodynamic control of the crosssection of a discharge-nozzle comprising a main discharge nozzle having a convergent shape, an auxiliary nozzle provided on the inner wall of said main nozzle ahead of its outlet orifice and means for feeding said auxiliary nozzle with fluid under pressure so as to form a fluid jet which escapes into said main nozzle, said auxiliary nozzle having a direction substantially parallel to the axis of the main discharge-nozzle, opening towards the upstream part of the main nozzle.

2. A device in accordance with claim 1 in which the said main discharge-nozzle has a shape which converges towards a point located on the axis on the downstream side of the outlet orifice of said nozzle, the terminal portion of said nozzle being constituted by a frustum of a cone with an apex angle of 45.

No references cited.

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