Patent Publication Number: US-2022220926-A1

Title: Jet nozzle equipped with a thermally regulated ring

Description:
TECHNICAL FIELD 
     The present invention relates to a rocket engine nozzle comprising a combustion chamber and a divergent formed of a cone-shaped wall, the divergent being connected to the downstream end of the combustion chamber by a flange or a ring. 
     Prior art 
     Document WO 2018/002523 discloses a nozzle comprising a combustion chamber made of metallic material having a downstream end and a divergent made of composite material formed of a cone-shaped wall and whose upstream end of the divergent made of composite material is connected to the downstream end of the combustion chamber by an annular flange made of metallic material. The downstream end of the combustion chamber is provided with a cooling circuit for reducing the temperature in the area of the combustion chamber where the axial fixation with the divergent is made. 
     However, the solution consisting in providing the downstream end of the combustion chamber with a cooling circuit complicates the production of the combustion chamber as well as the geometry of the annular flange for fixing the divergent to the chamber. 
     Furthermore, while the cooling circuit integrated into the combustion chamber allows effectively regulating the temperature of said chamber, it does not allow cooling the elements present in the vicinity of the downstream end of the chamber such as the annular flange. However, the annular flange is exposed to very high temperatures due to its proximity to the divergent. Consequently, the annular flange must be capable of withstanding high temperatures, which involves the use of expensive materials. 
     DISCLOSURE OF THE INVENTION 
     The aim of the invention is to propose a solution for nozzles having more efficient thermal regulation at the connecting part between the combustion chamber and the divergent. 
     This aim is achieved thanks to a nozzle having a longitudinal axis comprising a combustion chamber having a downstream end and a divergent formed of a cone-shaped wall extending between an upstream end and a downstream end, the upstream end of the divergent being connected to the downstream end of the combustion chamber by an intermediate ring comprising an upstream flange fixed on the downstream end of the combustion chamber and a downstream flange connected to the upstream end of the divergent, characterized in that the intermediate ring comprises at least one inner channel present between the upstream and downstream flanges of the intermediate ring and in that a material able to take heat from the ring is present in the inner channel. 
     By cooling the connection between the combustion chamber and the divergent directly at the intermediate ring, the latter is protected from the heat emitted by the divergent, which improves the reliability of the connection between the combustion chamber and the divergent. It is thus possible to envisage a use of the nozzle with high combustion temperatures while being able to use relatively inexpensive materials for the production of the intermediate ring. In addition, this cooling solution simplifies the geometry of the combustion chamber at its downstream end allowing envisaging a connection with different types of divergents. 
     According to one particular aspect of the nozzle according to the invention, a heat transfer fluid circulates in said at least one inner channel of the intermediate ring. The ring and the connection made thereby are cooled by means of a cooling circuit independent of that of the combustion chamber. The flow rate and the nature of the heat transfer fluid can therefore be chosen in order to obtain the best thermal regulation. This independent cooling circuit can further be used after shutdown of the rocket engine to mitigate the heating effects due to the phenomenon called “heat soak back” which corresponds to the heating after operation of some elements by others having a high thermal inertia. 
     According to one particular characteristic, the inner channel(s) of the intermediate ring have a geometry able to create swirls in the heat transfer fluid. This allows increasing the heat exchanges and consequently the cooling of the ring and surrounding portions. 
     According to another particular aspect of the nozzle according to the invention, a phase change material is present in said at least one inner channel of the intermediate ring. In this case, the thermal transfer (cooling) is made by latent heat, the phase change material being able to store the energy by a simple change of state while maintaining a temperature constant. The ring and the connection made thereby are maintained at acceptable temperature levels and independently of the cooling circuit of the combustion chamber. The properties of the phase change material can be defined based on the only need for cooling at the intermediate ring. The cooling made by the phase change material can further be used after shutdown of the rocket engine to mitigate the heating effects due to the phenomenon called “heat soak back” which corresponds to the heating after operation of some elements by others having a high thermal inertia. 
     According to another particular aspect of the nozzle of the invention, the downstream flange of the intermediate ring is fixed to the upstream end of the divergent by clamping members. 
     According to yet another aspect of the nozzle of the invention, the downstream flange of the intermediate ring includes support lugs, said lugs cooperating with one or more shoulders present on the upstream end of the divergent. The heat exchange surfaces between the divergent and the ring are thus limited by minimizing the contact surface between these two elements. 
     According to one particular characteristic of this connecting mode, the intermediate ring comprises, on its face opposite the wall of the divergent, bosses spaced from each other along a circumferential direction. This facilitates the radial centering of the divergent on the intermediate ring. 
     The divergent can be in particular made of metallic material or of composite material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a nozzle according to one embodiment of the invention, 
         FIG. 2  is a schematic sectional view showing the connection between the combustion chamber and the divergent of the nozzle of  FIG. 1 , 
         FIG. 3  is a schematic view of a nozzle according to another embodiment of the invention, 
         FIG. 4  is a schematic perspective view showing the intermediate ring of the nozzle of  FIG. 3 , 
         FIG. 5  is a schematic sectional view showing the connection between the combustion chamber and the divergent of the nozzle of  FIG. 4 , 
         FIG. 6  is another schematic sectional view showing the connection between the combustion chamber and the divergent of the nozzle of  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIGS. 1 and 2  illustrate a rocket engine nozzle  100  in accordance with one embodiment of the invention. The nozzle  10  of longitudinal axis ZZ′ comprises a combustion chamber made of metallic material  110  having a downstream end  111  and a divergent  120  formed of a cone-shaped wall  121  extending between an upstream end  122  and a downstream end  123 , the upstream end  122  of the divergent  120  being connected to the downstream end  111  of the combustion chamber  110 . The combustion chamber  110  further comprises a cooling circuit allowing circulating a coolant on the wall of the chamber (not represented in  FIGS. 1 and 2 ) as it is the case in particular of a combustion chamber called regeneration combustion chamber. 
     In accordance with the invention, the nozzle  100  further comprises an intermediate ring  130  which ensures the connection between the combustion chamber  110  and the divergent  120 . The intermediate ring  130  comprises an upstream flange  131  which extends along a radial direction DR perpendicular to the longitudinal axis ZZ′ and which cooperates with a fixing flange  112  extending along the radial direction at the downstream end  111  of the combustion chamber  110 . The upstream flange  131  of the intermediate ring  130  is fixed to the fixing flange  112  of the combustion chamber by a plurality of clamping members  140  each comprising a fixing screw  141  and a nut  142 , each fixing screw  141  passing through an orifice  1120  present on the fixing flange  112  and an orifice  1310  present on the upstream flange  131 . 
     The intermediate ring  130  comprises a downstream flange  132  which is fixed to the upstream end  122  of the divergent  120  by a plurality of clamping members  150  each comprising a fixing screw  151  and a nut  152 , each fixing screw  151  passing through an orifice  1320  present on the downstream flange  132  and an orifice  1220  present on the upstream end  122  of the divergent  120 . 
     In accordance with the invention, the intermediate ring  130  further comprises an inner channel  133  present between the upstream flange  131  and the downstream flange  132 . In the example described here, the inner channel extends annularly and forms a circulation circuit for a heat transfer fluid  160  which circulates in the channel  133  between an inlet and an outlet (not represented in  FIGS. 1 and 2 ). A pumping and heat exchanger system (not represented in  FIGS. 1 and 2 ) independent of the one used for the cooling circuit of the combustion chamber is connected between the inlet and the outlet of the inner channel in order to ensure the continuous circulation of the heat transfer fluid and the thermoregulation of the intermediate ring  130 . The thermal regulation of the intermediate ring and of the elements thermally in contact therewith is thus made by a cooling device independent of that of the combustion chamber. The flow rate and the nature of the heat transfer fluid can therefore be chosen in order to obtain the best thermal regulation. This independent cooling circuit can further be used after shutdown of the rocket engine to mitigate the heating effects due to the phenomenon called “heat soak back” which corresponds to the heating after operation of some elements by others having a high thermal inertia. 
     According to one particular characteristic, the inner channel  133  has a geometry able to create swirls allowing increasing the heat exchanges and, consequently, the cooling of the ring and of the surrounding portions. 
     The heat, particularly convective, exchanges can further be improved by structuring the inner surface  133   a  of the channel  133 , for example by forming therein porosities or open cavities on said inner surface. This structuring can be obtained by producing the intermediate ring by additive manufacturing. 
     According to one variant of embodiment, the inner channel  133  of the intermediate ring is filled with a phase change material instead of the heat transfer fluid. In this case, the inner channel is no longer connected to a pumping and heat exchanger system, because the phase change material is statically present in the inner channel. At least one fill/drain valve (not represented in  FIGS. 1 and 2 ) is provided instead of the inlet and outlet of the inner channel. In this case, the thermal transfer (cooling) is made by latent heat, the phase change material being able to store the energy by simple change of state while maintaining a temperature constant. The ring and the connection made thereby are cooled independently of the cooling circuit of the combustion chamber. The properties of the phase change material can be defined based only on the need for cooling at the intermediate ring. The cooling made by the phase change material can further be used after shutdown of the rocket engine to mitigate the heating effects due to the phenomenon called “heat soak back” which corresponds to the heating after operation of some elements by others having a high thermal inertia. 
     The phase change material can in particular be paraffin or water. 
       FIGS. 3 to 6  illustrate another embodiment of a nozzle according to the invention which differs from the nozzle  100  described above, in particular at the connection between the intermediate ring and the divergent. More specifically, in  FIG. 3 , the nozzle  200  of longitudinal axis ZZ′ comprises a combustion chamber made of metallic material  210  having a downstream end  211  and a divergent  220  formed of a cone-shaped wall  221  extending between an upstream end  222  and a downstream end  223 , the upstream end  222  of the divergent  220  being connected to the downstream end  211  of the combustion chamber  210 . The combustion chamber  210  further comprises a cooling circuit for circulating a coolant on the wall of the chamber (not represented in  FIGS. 3 to 6 ). 
     The nozzle  200  further comprises an intermediate ring  230  which ensures the connection between the combustion chamber  210  and the divergent  220 . The intermediate ring  230  comprises an upstream flange  231  which extends along a radial direction DR perpendicular to the longitudinal axis ZZ′ and which cooperates with a fixing flange  212  extending along the radial direction at the downstream end  211  of the combustion chamber  210 . The upstream flange  231  of the intermediate ring  230  is fixed to the fixing flange  212  of the chamber combustion by a plurality of clamping members  240  each comprising a fixing screw  241 . Each fixing screw  241  passes through an orifice  2310  present on the upstream flange  231  and is screwed into a threaded bore  2120  present on the fixing flange  212 . 
     In the example described here, the downstream flange of the intermediate ring  230  consists of the support lugs  232  spaced from each other along a circumferential direction D C . The support lugs  232  extend from the inner face  230   a  of the ring  230  opposite the wall  221  of the divergent  220  along the radial direction DR. The support lugs  232  cooperate with an annular shoulder  224  present on the wall  221  of the divergent at its upstream end  222 . Once the intermediate ring  230  is fixed on the combustion chamber  210  and the support lugs  232  are in contact with the shoulder  224 , the proximal portion  220   a  of the divergent  220  is held bearing on the distal portion  210   b  of the combustion chamber  210  thus ensuring continuity between the inner surfaces of the combustion chamber and of the divergent. 
     In the example described here, the intermediate ring  230  comprises, on its inner face  230   a  opposite the wall  221  of the divergent  220 , bosses  238  spaced from each other along the circumferential direction D C . This facilitates the radial centering of the divergent on the intermediate ring. 
     In accordance with the invention, the intermediate ring  230  further comprises an inner channel  233  present between the upstream flange  231  and the downstream flange  232 . In the example described here, the inner channel extends annularly and forms a circulation circuit for a heat transfer fluid  260  which circulates in the channel  233  between an inlet  234 ,  236  and an outlet  235 ,  237  ( FIG. 4 ). A pumping and heat exchanger system (not represented in  FIGS. 3 to 6 ) independent of the one used for the cooling circuit of the combustion chamber is connected between the inlet and the outlet of the inner channel in order to ensure the continuous circulation of the heat transfer fluid and the thermoregulation of the intermediate ring  230 . The thermal regulation of the intermediate ring and of the elements thermally in contact therewith is thus made by a cooling device independent of that of the combustion chamber. The flow rate and the nature of the heat transfer fluid can therefore be chosen in order to obtain the best thermal regulation. This independent cooling circuit can further be used after shutdown of the rocket engine to mitigate the heating effects due to the phenomenon called “heat soak back” which corresponds to the heating after operation of some elements by others having a high thermal inertia. 
     According to one particular characteristic, the inner channel  233  has a geometry able to create swirls allowing increasing the heat exchanges and, consequently, the cooling of the ring and of the surrounding portions. 
     The heat, particularly convective, exchanges can further be improved by structuring the inner surface  233   a  of the channel  133 , for example by forming therein porosities or open cavities on said inner surface. This structuring can be obtained by producing the intermediate ring by additive manufacturing. 
     According to one variant of embodiment, the inner channel  233  of the intermediate ring is filled with a phase change material instead of the heat transfer fluid. In this case, the inner channel is no longer connected to a pumping and heat exchanger system, because the phase change material is statically present in the inner channel. At least one fill/drain valve (not represented in  FIGS. 3 to 6 ) is provided instead of the inlet  234 ,  236  and of the outlet  235 ,  237  of the inner channel  233 . In this case, the thermal transfer (cooling) is made by latent heat, the phase change material being able to store the energy by simple change of state while maintaining a temperature constant. The ring and the connection made thereby are cooled independently of the cooling circuit of the combustion chamber. The properties of the phase change material can be defined based on the only need for cooling at the intermediate ring. The cooling made by the phase change material can further be used after shutdown of the rocket engine to mitigate the heating effects due to the phenomenon called “heat soak back” which corresponds to the heating after operation of some elements by others having a high thermal inertia. 
     In the example described here, the intermediate ring  233  is formed of two half-rings  2331  and  2332  each comprising respectively an inlet  234 ,  236  and an outlet  235 ,  237  for the circulation of the heat transfer fluid. The inlets  234 ,  236  and the outlets  235 ,  237  being replaced by fill/drain valves in case of use of a phase change material instead of a heat transfer fluid. 
     Furthermore, in the example described here, the support lugs  232  are spaced from each other by material interruption between the lugs. However, the lugs  232  can also be produced with a continuous ring present protruding from the inner surface  230   a  of the intermediate ring  233 . Likewise, the shoulder  224  is continuous in the present example. According to one variant of embodiment, the shoulder could be discontinuous in order to form a plurality of shoulders spaced from each other around the upstream end of the divergent. 
     The divergent of the nozzle of the invention can be made of metallic material or of composite material. The divergent can be particularly made of ceramic matrix composite (CMC) material which, in a known manner, is a material formed of a carbon or ceramic fiber reinforcement densified by an at least partially ceramic matrix, such as one of the following CMC composite materials: 
     carbon-carbon/silicon carbide (C/C—SiC) corresponding to a material formed of a carbon fiber reinforcement and densified by a matrix comprising a carbon phase and a silicon carbide phase, 
     carbon-silicon carbide (C/SiC) which is a material formed of a carbon fiber reinforcement densified by a silicon carbide matrix, silicon carbide-silicon carbide (SiC/SiC) corresponding to a material formed of a silicon carbide fiber reinforcement densified by a silicon carbide matrix, 
     oxide/oxide type CMC material corresponding to a material formed of a refractory oxide fiber reinforcement, for example fibers based on alumina Al 2 O 3 , densified by a refractory oxide matrix. 
     The divergent may also be made of a carbon/carbon (C/C) composite material which, in a known manner, is a material formed of a carbon fiber reinforcement densified by a carbon matrix and which may be possibly provided with a coating such as for example a ceramic deposit (example SiC). 
     Thanks to the thermo-regulated intermediate ring of the invention, it is possible to envisage higher operating temperatures for the nozzle as well as the use of materials having maximum use temperatures lower than the temperatures seen by the divergent such as Inconel® type alloys. The thermal regulation of the intermediate ring further allows reducing the temperature gradient between the divergent and the cooled combustion chamber.