Thrust nozzle with double contour and smooth transition

Abstract

A thrust nozzle, in particular thrust nozzle for a rocket engine, with a convergent wall section, a throat section and a divergent wall section. The divergent wall section has a first region adjacent to the throat section, the wall contour of which region corresponds to a truncated ideal nozzle, and the divergent wall section has a second region facing away from the throat section, which region has a wall contour deviating from the first region.

Claims

1. A thrust nozzle comprising: a convergent wall section downstream of a combustion chamber of a rocket engine, a throat section and a divergent wall section, wherein the divergent wall section has a first region adjacent to the throat section, wherein the wall contour of the first region corresponds to a truncated ideal nozzle, and the divergent wall section has a second region facing away from the throat section, wherein the second region has a wall contour deviating from the wall contour of first region, wherein a transition from the wall contour of the first region to the wall contour of the second region is continuous, wherein a contour angle corresponding to a tangential angle to the wall, at a last point of the wall contour of the first region, corresponds to the contour angle at a first point of the wall contour of the second region, wherein the contour angle of the divergent wall section, seen in longitudinal section through the thrust nozzle, runs continuously on the transition from the first region to the second region such that the contour angle at a last point of the wall contour in the first region and the contour angle at a first point of the wall contour in the second region are the same, and wherein the second region of the divergent wall section is paraboloid-shaped.

2. A rocket engine with a thrust nozzle comprising: a convergent wall section downstream of a combustion chamber of the rocket engine, a throat section and a divergent wall section, wherein the divergent wall section has a first region adjacent to the throat section, wherein the wall contour of the first region corresponds to a truncated ideal nozzle, and the divergent wall section has a second region facing away from the throat section, wherein the second region has a wall contour deviating from the wall contour of first region, wherein a transition from the wall contour of the first region to the wall contour of the second region is continuous, wherein a contour angle corresponding to a tangential angle to the wall, at a last point of the wall contour of the first region, corresponds to the contour angle at a first point of the wall contour of the second region, wherein the contour angle of the divergent wall section, seen in longitudinal section through the thrust nozzle, runs continuously on the transition from the first region to the second region such that the contour angle at a last point of the wall contour in the first region and the contour angle at a first point of the wall contour in the second region are the same, and wherein the second region of the divergent wall section is paraboloid-shaped.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a thrust nozzle according to the invention;

(2) FIG. 1A shows the section A from FIG. 1;

(3) FIG. 2 shows a previously known ideal nozzle;

(4) FIG. 3 shows the contour of a first exemplary thrust nozzle according to the invention in comparison with a TOP thrust nozzle;

(5) FIG. 4 shows the contour of a second exemplary thrust nozzle according to the invention in comparison with a TOP thrust nozzle; and

(6) FIG. 5 shows the contour of the two exemplary thrust nozzles according to the invention as shown in FIGS. 3 and 4 in comparison with a TOP thrust nozzle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) A thrust nozzle S according to the invention is shown in longitudinal section in FIG. 1, wherein the nozzle wall is drawn only as a contour line and permits no conclusion as to the design configuration of the nozzle wall (material construction, cooling ducts, etc.). The construction of nozzle walls, especially of rocket thrust nozzles, is sufficiently known and is not an object of the present invention.

(8) The nozzle has a convergent wall section 1, a throat section 2 and a divergent wall section 3. The narrowest cross section of the nozzle is located in the throat section 2 in the cross-sectional plane E1 at the narrowest diameter of the throat section 2. The passage of flow through the nozzle is in the direction of the flow arrow P from the nozzle section with the convergent wall section 1 through the nozzle throat to the nozzle section with the divergent wall section 3. A combustion chamber situated ahead of the nozzle section with the convergent wall section 1 in a rocket engine is not shown in FIG. 1, but is sufficiently known to the person skilled in the art.

(9) As already described in connection with the prior art in FIG. 2, the wall contour 20 in the throat section 2 is executed as a circular arc. Connected to this circular arc of the wall contour 20 of the throat section 2 in a downstream direction, thus towards the divergent wall section 3, is a first region 30 of the divergent wall section 3, the wall contour 31 of whichas already described in connection with FIG. 2is formed as a truncated ideal nozzle (TIC nozzle). The transition from the circular-arc-shaped wall contour 20 of the throat section 2 to the wall contour 31 of the first region 30 formed as a truncated TIC nozzle is defined by a first transition point 34, through which a first transition cross-sectional plane E3 runs.

(10) The transition from the circular-arc-shaped wall contour 20 of the throat section 2 to the wall contour 31 of the first region 30 is realized continuously; this means that the tangential angle (in the longitudinal sectional plane shown in FIG. 1) at the last point of the circular-arc-shaped wall contour 20 of the throat section 2 corresponds to the tangential angle at the first point of the wall contour 31 of the first region 30.

(11) The first region 30 with the contour of a truncated ideal nozzle extends in the direction of the nozzle longitudinal axis 101, but not over the full length of a TIC nozzle as shown in FIG. 2 and described in connection with FIG. 2, but only over a portion of the length of an ideal nozzle close to the throat. The axial length L1 of the first region 30 is determined according to a design specification, which is described further below.

(12) Adjoining the first region 30 of the divergent wall section 3 at the end of the first region 30 facing away from the throat section 2 is a second region 32 of the divergent wall section 3, which has a wall contour 33 deviating from the first region 30 and thus also from an ideal TIC nozzle. The transition between the wall contour 31 of the first region 30 and the wall contour 33 of the second region 32 of the divergent wall section 3 is realized at a second transition point 35, through which a second transition cross-sectional plane E4 runs.

(13) The transition from the wall contour 31 of the first region 30 to the wall contour 33 of the second region 32 is continuous. This means that the contour angle , that is the tangential angle (in the longitudinal sectional plane shown in FIG. 1) to the wall at the last point of the wall contour 31 of the first region corresponds to the contour angle at the first point of the wall contour 33 of the second region 32, as is to be seen in the enlarged representation in FIG. 1A.

(14) In the example of FIG. 1, the wall contour 33 of the second region 32 is formed as a quadratic parabola. This second region 32 configured in a paraboloid shape of the divergent wall section 3 extends in the direction of the nozzle longitudinal axis 101 over a length L2 as far as the outlet plane E2. The position of this outlet plane E2 is determined by the predetermined overall length L of the nozzle, measured from the plane E1 to the plane E2.

(15) The design of such a combined TICTOP thrust nozzle according to the invention and, in particular, the determination of the second transition point 35 with the second transition cross-sectional plane E4 is described below.

(16) In the design process of a thrust nozzle, the nozzle throat cross section, the nozzle length and the nozzle outlet diameter are normally preset. The start and end point of the nozzle according to the invention are thus fixed. Thus three parameters remain as free parameters in the design process, namely:

(17) 1. The first free parameter is the design Mach number of the ideal nozzle. The greater the design Mach number, the more divergent (at the same axial length L1) is the first region 30 formed as a truncated ideal nozzle, i.e., the greater the divergence angle at the first transition point 34 between the circular-arc-shaped wall contour 20 of the throat section 2 and the wall contour 31 of the first region 30, thus the truncated ideal nozzle. Due to this the greater the contour angle is also at the second transition point 35 between the wall contour 31 of the first region 30 and the wall contour 33 of the paraboloid-shaped second region 32 of the divergent wall section 3.

(18) 2. The second free parameter is the axial length L1 of the thrust nozzle S in the first region 30, thus of the truncated ideal nozzle used, and thus the axial position of the second transition point 35.

(19) 3. The third free parameter is the divergence angle of the paraboloid-shaped wall contour 33 of the second region 32 at the open outlet end of the thrust nozzle, thus in the area of the outlet plane E2. The nozzle end pressure can be varied by this value. The smaller the divergence angle is at a constant nozzle length L, the higher the nozzle end pressure.

(20) The starting point (second transition point 35) and the starting angle (contour angle ) of the paraboloid-shaped second region 32 of the divergent wall section 3 are determined here by the end point and the end angle of the truncated ideal nozzle, thus of the first region 30. This point is the second transition point 35. In principle it would also be possible to permit a small angle change outwards at the second transition point 35. This would add another degree of freedom for the design. However, the further the nozzle is opened at the second transition point 35, thus the greater the change in the contour angle at this point, the greater the risk that a shock is induced in the further progression of the paraboloid-shaped second region 32 that would nullify the advantages of the contouring method described.

(21) The end point of the paraboloid-shaped second region 32 is normally predetermined in the design process on account of the predetermined nozzle length L and the predetermined opening cross section of the nozzle in the outlet plane E2.

(22) Upstream of the second transition point 35, a wall contour of a truncated ideal nozzle should necessarily be chosen up to the first transition point 34, because only this guarantees shock-free operation. Downstream of the second transition point 35, a wall contour must be selected which contains the three fixed design parameters, namely the starting point, the starting angle and the end point of the wall contour and in which the third free parameter (divergence angle ) can be varied. This doesn't necessarily have to be an oblique parabola of the second degree, but this is an obvious choice. Alternatively, the wall of the second region 32 could also be described by a higher-order curve when seen in cross section.

(23) The thrust nozzle according to the invention shown in FIG. 1 thus combines the advantages of an ideal nozzle (TIC nozzle) with the advantages of a TOP nozzle with paraboloid wall contour and can therefore be described as a TICTOP nozzle.

(24) FIGS. 3 and 4 illustrate the contour of two examples of the combined TICTOP thrust nozzle according to the invention compared to the TOP thrust nozzle with the same exit point. The dashed lines correspond to the contour (31, 33) y as a function of the length-coordinate x of the respective thrust nozzle, while the solid lines correspond to the first derivative dy/dx of the curve. The transition between the TIC and the parabolic nozzle section can be identified in the first derivative, since the first derivative shows a kink at the transition point from the TIC to the parabolic nozzle section. This transition is surrounded by the circle 110.

(25) FIG. 5 illustrates the contour of the TOP thrust nozzle in comparison with the two examples of the TICTOP thrust nozzle of FIGS. 3 and 4. As becomes apparent from FIGS. 3 to 5, the TICTOP thrust nozzle is provided with a contour (31, 33) line in the transition region between the first and the second region (30, 32) that lies well below the contour line of the TOP thrust nozzle, while upstream and downstream of the transition point, the contour line (31, 33) of the TICTOP thrust nozzles converges against the contour line of the TOP thrust nozzle.

(26) Reference signs in the description and the drawings serve only for a better understanding of the invention and are not intended to limit the protective scope.

(27) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

LIST OF REFERENCE SIGNS

(28) 1 Convergent wall section 2 Throat section 3 Divergent wall section 20 Wall contour of the throat section 30 First region 31 Wall contour of the first region 32 Second region 33 Wall contour of the second region 34 First transition point 35 Second transition point 100 Rotationally symmetrical nozzle 101 Nozzle longitudinal axis 102 Nozzle throat 103 Wall 104 Circular arc 105 Point 106 Expansion wave propagation line 107 Expansion wave reflection propagation line 108 Section of the wall contour 109 Wall end point 110 Circle indication the transition from TIC to TOP Contour angle Divergence angle E.sub.1 Cross-sectional plane at the narrowest throat diameter E.sub.2 Outlet plane E.sub.3 Transition cross-sectional plane E.sub.4 Second transition cross-sectional plane K Kernel region L Overall length of nozzle L.sub.1 Axial length of the first region L.sub.2 Axial length of the second region P Flow arrow S Thrust nozzle