Patent Publication Number: US-2020300197-A1

Title: Casing for a propellant feed turbopump for a rocket engine

Description:
FIELD OF THE INVENTION 
     The invention relates to a casing of a propellant feed turbopump for a rocket engine, to a rocket engine propellant feed turbopump including such a casing, and to a rocket engine fitted with such a turbopump. 
     BACKGROUND 
     In general, prior to starting a rocket engine propellant feed turbopump, it needs to be cooled down. Cooling down is in operation during which all or part of the turbopump casing is taken to a predetermined temperature, generally by cooling it, so that the turbopump is in its required operating conditions. 
     Known circuits for cooling rocket engine propellant feed turbopumps are generally complex and present fluid flow connections with the pumping circuit of the turbopump for feeding propulsion propellant to the rocket engine combustion chamber, such that using such circuits for cooling purposes is often difficult. Furthermore, for manifest safety reasons, the cooling fluid used for cooling down is always identical to the propulsion propellant in order to avoid any risk of explosion. This imposes several constraints that it would be desirable to avoid. There therefore exists a need in this sense. 
     SUMMARY OF THE INVENTION 
     The present disclosure relates to a casing of a propellant feed turbopump for a rocket engine. 
     An embodiment provides a casing of a propellant feed turbopump for a rocket engine, the casing including a cooling circuit, wherein the cooling circuit is formed at least in part in a wall of said casing. 
     It can be understood that the casing of the turbopump may be formed as a single-piece part, or else as a plurality of distinct pieces that once assembled together form the complete casing of the turbopump. 
     It can also be understood that the turbopump presents a pumping circuit for pumping propellant to the combustion chamber of the rocket engine for propulsion purposes (i.e. the propulsion propellant), a drive circuit in which there flows a propellant for driving the turbine of the turbopump in rotation (i.e. a drive propellant), and a cooling circuit. It can also be understood that the pumping circuit, the drive circuit, and the cooling circuit do not present any fluid duct in common, and are therefore mutually independent. The pumping circuit, the drive circuit, and the cooling circuit are thus in fluid flow isolation from one another. In other words, the cooling circuit is a circuit dedicated solely to cooling and that is used only for cooling. 
     It can also be understood that the cooling circuit for cooling the turbopump presents ducts that are integrated in at least one wall of the casing of the turbopump. In other words, the cooling circuit includes at least one duct extending in the thickness of a wall of the casing. This makes it possible to improve the cooling of the casing, while also providing complete separation between the cooling circuit and both the pumping circuit and also the turbopump drive circuit. 
     Having a cooling circuit that is distinct from the pumping circuit makes it possible to be unaffected by the constraints associated with having a fluid for cooling purposes (i.e. the cooling fluid) and then a propulsion propellant (i.e. a propellant that is to be injected into the combustion chamber for propulsion purposes) both flowing in succession in ducts that are common. 
     Finally, the independence between the pumping circuit, the drive circuit, and the cooling circuit makes it possible to cool the turbopump with a propellant that is different from the propellant that is to flow in the pumping circuit and the propellant that is to flow in the drive circuit. This is made possible only because the cooling circuit is distinct, and thus presents no fluid duct in common with the pumping circuit or with the drive circuit. Specifically, if the circuits were not distinct, it would be particularly dangerous to cause two different propellants to flow in succession one after the other in a common duct since that would present a risk of explosion by reaction between the two propellants. It is thus possible to select a cooling fluid, e.g. a propellant, for cooling the turbopump independently of the natures of the propellant(s) flowing in the pumping circuit and in the drive circuit of the turbopump. It should be observed that the propulsion propellant is not necessarily identical to the drive propellant. 
     In some embodiments, the cooling circuit extends at least in part in a wall of a pump inlet portion of the turbopump. 
     It can thus be understood that the casing includes a portion that forms an inlet for the pumping circuit. Since the cooling circuit presents a duct in a wall of this inlet portion, it is possible to cool this portion in very effective manner, which portion is the first to come into contact with the propulsion propellant. This serves to avoid this inlet portion suffering from thermal shocks when starting the turbopump, and also to avoid unwanted heating of the propulsion propellant that could lead to said propellant vaporizing in part, which would run the risk of cavitation within the turbopump. 
     In some embodiments, the cooling circuit extends at least in part in a wall of a volute portion of the turbopump. 
     It can be understood that the casing comprises a portion that forms a volute, with the pumping circuit passing through the volute. Since the cooling circuit presents a duct in a wall of this volute portion, it is possible to cool this portion in a very effective manner, which portion comes into contact with a large volume of propulsion propellant. This serves to avoid the volute portion being subjected to thermal shocks when starting the turbopump, and also to avoid unwanted heating of the propulsion propellant that could lead to said propellant vaporizing in part, which would run the risk of cavitation within the turbopump. 
     In some embodiments, the cooling circuit extends at least in part in a wall of a portion configured to receive a bearing. 
     It can be understood that the casing includes a portion in which a bearing is located, e.g. a bearing supporting the rotor of the turbopump. Since the cooling circuit presents a duct in a wall of this portion, it is possible to cool this portion in very effective manner, which portion needs to have its temperature controlled very accurately in order to ensure good operating conditions for the bearing. 
     In some embodiments, the cooling circuit includes a duct outside the walls of said casing. 
     It can be understood that such ducts are not provided in the thickness of a wall of the casing. By way of example, such a duct makes it possible to connect together the ducts formed in the walls of different portions of the casing. This makes it possible to avoid mechanically weakening the casing by generating too many zones having ducts formed in a wall of the casing, and to avoid cooling portions of the casing of the turbopump that do not need to be cooled. 
     The present disclosure also provides a propellant feed turbopump for a rocket engine, the turbopump including a casing according to any of the embodiments described in the present disclosure. 
     The present disclosure also provides a rocket engine including a rocket engine propellant feed turbopump according to any of the embodiments described in the present disclosure. 
     The present disclosure also provides a method of fabricating a casing of a propellant feed turbopump for a rocket engine according to any of the embodiments described in the present disclosure and comprising at least one step of additive manufacturing. 
     It should be recalled that additive manufacturing is a method of manufacturing by adding material, by stacking successive layers. 
     Such a method of manufacture is particularly well adapted to manufacturing complex parts, such as the turbopump casing of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention and its advantages can be better understood on reading the following detailed description of various embodiments of the invention given as nonlimiting examples. The description makes reference to the accompanying sheets of figures, in which: 
         FIG. 1  shows a space vehicle fitted with a rocket engine; 
         FIG. 2A  is a half-view in section of the turbopump of the  FIG. 1  space vehicle rocket engine; 
         FIG. 2B  is a diagram showing the layout of the turbopump cooling circuit; and 
         FIG. 3  is a diagram showing an example of a complete circuit for cooling the  FIG. 2A  turbopump within the space vehicle. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a space vehicle  100  having a rocket engine  50  fed from a propellant tank  60 .  FIG. 2A  is a half-view in section parallel to the axial direction X of a turbopump  10  for feeding propellant to the rocket engine  50 . 
     The propellant feed turbopump  10  comprises various internal elements drawn in fine lines, and in particular a rotor  12  having a shaft  12   a , an inducer  15 , an impeller  12   b , and a turbine wheel  12   c . The rotor  12  is supported to rotate within the turbopump  10  by bearings  14   a  and  14   b . The axis of rotation of the rotor  12  defines the axial direction X of the turbopump  10 . Below, and unless mentioned to the contrary, the radial direction R is a direction perpendicular to the axis X. The azimuth direction corresponds to the direction describing a ring around the axial direction. The axial, radial, and azimuth directions correspond respectively to the directions defined by the height, the radius, and the angle in a cylindrical coordinate system. 
     The enclosure of the turbopump  10  is defined by the casing  20 , drawn in bold lines. In this example, the casing  20  comprises three distinct elements, namely a pump inlet casing  20   a , an intermediate casing  20   b , and a turbine outlet casing  20   c . Together, these inlet, intermediate, and outlet casings form the casing  20 . 
     Bold arrows represent the flow of propulsion propellant, i.e. the propellant that is pumped by the turbopump  10  in order to be sent to the combustion chamber  50   a  of the rocket engine  50 . 
     The propulsion propellant enters into the turbopump  10  via the pump inlet casing  20   a , passes via the inducer  15 , and then via the impeller  12   b , which sucks in the propellant and discharges it into the volute  22  formed by a portion of the intermediate casing  20   b . The propellant pressurized in this way flows from the volute  22  via a tangential outlet, not shown. These passages form the pumping circuit  11   a.    
     The pressurized propellant is then taken to the combustion chamber  50   a  (see  FIG. 1 ). 
     The flow of propellant for driving the turbine  12   c  is also represented by bold arrows. The drive propellant which may be in various forms, themselves known to the person skilled in the art (e.g. after being heated or after being burnt in full or in part), is introduced via an inlet (not shown) into the “turbine upstream cavity”  23  formed by a portion of the intermediate casing  20   b , then flows through the turbine  12   c , thereby driving the rotor  12  in rotation, and subsequently reaches the exhaust cavity  24  as defined by the turbine outlet casing  20   c  so as to be discharged from the pump  10  via an outlet (not shown). These passages form of the drive circuit  11   b  for driving the turbine  12   c.    
     It can be considered that the pumping circuit  11   a  and the drive circuit  11   b  of the turbine  12   c  form a main circuit  11  in which the “main” propellants of the turbopump flow. The pumping circuit  11   a  forms part of the feed circuit for feeding the combustion chamber  50   a . The drive circuit  11   b  does not form part of the feed circuit (i.e. the circuit for feeding propellant to the combustion chamber). It should be observed that the propulsion propellant and the drive propellant are generally, but not necessarily, different. The turbopump presents means (not shown) that are themselves known for providing isolation between the pumping circuit and the drive circuit. 
     With reference to  FIGS. 2A and 2B , there follows a description of the cooling circuit  30  for cooling the casing  20  of the turbopump  10 . The casing  20  presents a plurality of walls having ducts formed therein. In this example, each of these ducts forms a portion of the cooling circuit  30 . 
     The pump inlet casing  20   a , which forms a pump inlet portion of the turbopump  10 , presents an annular duct  30   a  formed in its wall and extending in the axial direction X. Thus, the duct  30   a  presents a shape that is generally helical about the axis X. 
     The intermediate casing  20   b , which forms in particular a volute  22  or a volute portion of the turbopump  10 , presents an annular duct  30   b  formed in its wall and extending both in the axial direction X and in the radial direction R. Thus, the duct  30   b  presents a shape that is generally helical and of varying radius about the axis X. 
     The intermediate casing  20   b  likewise presents two portions  20   ba  and  20   bb  respectively configured to receive the bearings  14   a  and  14   b . These portions present respective annular ducts  30   c  and  30   d  formed in their walls, which ducts extend both in the axial direction X and also in the radial direction R. Thus, each of the ducts  30   c  and  30   d  presents a shape that is generally helical and of varying radius about the axis X. 
     The ducts  30   a  and  30   b  are connected together by an intermediate duct  30   ab  formed in the walls of the pump inlet casing  20   a  and of the intermediate casing  20   b . The ducts  30   b  and  30   c  are also connected together by an intermediate duct  30   bc  formed in the wall of the intermediate casing  20   b . Finally, the ducts  30   c  and  30   d  are connected together by a duct  30   cd  that is outside the wall of the intermediate casing  20   b . The ducts  30   a ,  30   ab ,  30   b ,  30   bc ,  30   c ,  30   cd , and  30   d  form of the cooling circuit  30  for cooling the turbopump  10 , and more particularly for cooling the casing  20  of the turbopump  10 . 
       FIG. 2B  shows a diagrammatic view of the cooling circuit  30  within the casing  20  of the turbopump  10 . The flow direction of the cooling fluid within the circuit  30  is indicated by arrows. It should be observed that the inlet and the outlet of the circuit  30  are represented in symbolic manner by discontinuous lines for illustrative and instructional purposes. In like manner, it is possible to envisage any other shape for the ducts of the cooling circuit  30 , and the example shown in  FIGS. 2A and 2B  is illustrative rather than limiting. Naturally, it is also possible to envisage providing ducts of the cooling circuit  30  in any other portions of the casing  20  of the turbopump  10 . 
     With reference to  FIG. 3 , there follows a description of an example of a complete cooling circuit  80  for the turbopump  10  within the space vehicle  100 . Naturally, the complete cooling circuit  80  includes the cooling circuit  30  that forms part of the turbopump  10 . 
     The complete cooling circuit  80  comprises a propellant tank  82  containing a propellant that is used as a cooling fluid for cooling the turbopump  10 . It should be observed that the propellant tank  82  could be a tank that is configured to receive only a propellant for use in cooling the turbopump  10  (as shown in  FIG. 3 —the tank  60  and the tank  82  then being tanks that are distinct), or else a tank that also serves for feeding the pumping circuit of the turbopump with propulsion propellant (variant not shown). Under such circumstances, the tank  82  and the tank  60  coincide and form a single tank  82 , this tank  82  then being the only element that is common to the feed circuit (i.e. the circuit dedicated to feeding the propulsion propellant) and to the complete cooling circuit  80 , which nevertheless remain distinct and independent of each other. For example, the two circuits are kept independent by on/off valves, check valves, or any other device known to the person skilled in the art. 
     A motor-driven pump  84  sends the propellant from the tank  82  to a propellant feed pipe  86  taking the propellant to the circuit  30  of the turbopump  10 . This pipe  86  has a valve  86   a  for isolating the circuit  30  from the tank  82 . 
     A return pipe  88  serves to take the propellant that has flowed through the circuit  30  and return it back to the tank  82 . The pipe  88  is fitted with a valve  88   a  so as to enable the tank  82  to be isolated from the circuit  30 . 
     The propellant feed pipe  86  and the return pipe  88  have respective branch circuits  86   b  and  88   b , respectively forming an inlet branch circuit and an outlet branch circuit, so as to enable the circuit  80  to communicate with the outside of the space vehicle  100 . By means of these branch circuits, it is possible for example to cause a cooling fluid to flow in the circuit  80  while the space vehicle is on the ground, so as to conserve the propellant contained in the tank  82  for additional cooling performed in flight. 
     Furthermore, the return pipe  88  has a discharge nozzle  88   c  that is isolated from the pipe  88  by a valve  88   cc . Thus, it is possible to purge the circuit  80  by opening the valve  88   cc  in order to discharge all of the fluid contained in the circuit  80  to outside the space vehicle  100 . 
     By means of the complete cooling circuit  80 , it is thus possible to cool the turbopump  10  while the space vehicle  100  is on the ground via the branch circuits  86   b  and  88   b , with the valves  86   a  and  88   a  being closed, or else in independent manner, whether in flight or on the ground, by using the propellant contained in the tank  82  (the branch circuits  86   b  and  88   b  naturally then being shut off). In order to purge the circuit  80 , the valves  86   a  and  88   a  are closed (unless it is desired also to purge the tank  82 ), and the valve  88   cc  of the discharge nozzle  88   c  is opened. While it is being used, it is also possible to discharge the cooling propellant progressively via the nozzle  88   c , in which case the valves  86   a  and  88   cc  are opened, while the valve  88   a  is closed. 
     Naturally, in a variant, the complete cooling circuit  80  does not have a branch circuit to the outside. In another variant, the complete cooling circuit  80  does not have a tank  82 , but only has branch circuits to the outside. In yet another variant, the return pipe  88  leads directly into the discharge nozzle  88   c  and is not connected to the tank  82  (the propellant feed pipe  86  being connected to the tank  82  and/or to the branch circuit  86   b ). Furthermore, the discharge nozzle is optional. 
     Although the present invention is described with reference to specific embodiments, it is clear that modifications and changes may be made to those embodiments without going beyond the general ambit of the invention as defined by the claims. In particular, individual characteristics of the various embodiments that are illustrated and/or mentioned may be combined in additional embodiments. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive.