Abstract:
Supply of a liquid component in a combustion chamber of a rocket engine is controlled by a feed valve provided with an obturator mobile between a pen position and a closed position of at least one supply pipe, which has an inlet that communicates with a tank for containing the liquid component and an outlet that communicates with the combustion chamber; the displacement of the obturator from its closed position to its open position being triggered by a pressurized fluid supplied to the outlet of the supply pipe.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Italian Patent Application No. TV2009A 000238 filed Dec. 23, 2009, the entire disclosure of which is herein incorporated by reference. 
         [0002]    The present invention relates to a rocket engine. 
         [0003]    The present invention finds particularly advantageous application in a hybrid-propulsion rocket engine used, preferably though not necessarily, in launching a remote-control aircraft, to which the ensuing treatment will make explicit reference without, however, this implying any loss of generality. 
       BACKGROUND OF THE INVENTION 
       [0004]    In the sector of hybrid-propulsion rocket engines, it is known to provide a rocket engine of the type comprising: a combustion chamber for combustion of a fuel, in the case in point a fuel in the solid state, with a comburent, in the case in point an oxidant in the liquid state; a nozzle for discharge of the products of combustion from the combustion chamber; a tank for containing the liquid oxidant; and a feed valve to control the supply of the liquid oxidant from the container tank to the combustion chamber. 
         [0005]    Generally, the feed valve comprises a valve body, at least one supply pipe made in the valve body for communicating with the container tank and with the combustion chamber, an obturator mounted in the supply pipe, and an actuator device to move the obturator between a position of opening and a position of closing of the supply pipe itself. 
         [0006]    Since the obturator must be displaced between its open and closed positions in a relatively short time interval and, hence, at a relatively high actuation rate, the actuator device must be shaped for generating a relatively high actuation power and is, hence, relatively cumbersome, heavy, and costly. 
         [0007]    From what has been set forth above, it follows that, on account of the presence of the device for actuating the obturator, known rocket engines of the type described above are relatively complex, cumbersome, heavy, and costly. 
       SUMMARY OF THE INVENTION 
       [0008]    The aim of the present invention is to provide a rocket engine that will be free from the drawbacks described above and that will be simple and inexpensive to produce. 
         [0009]    According to the present invention a rocket engine is provided as claimed in the attached Claims. 
         [0010]    The present invention moreover regards a method for controlling combustion of a rocket engine. 
         [0011]    According to the present invention, a method for controlling combustion of a rocket engine is provided as claimed in the attached Claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will now be described with reference to the annexed drawings, which illustrate a non-limiting example of embodiment thereof and in which: 
           [0013]      FIG. 1  is a schematic view of a preferred embodiment of the rocket engine of the present invention; 
           [0014]      FIG. 2  is a schematic longitudinal section, with parts removed for reasons of clarity, of a first detail of the rocket engine of  FIG. 1 ; and 
           [0015]      FIGS. 3   a ,  3   b , and  3   c  are three schematic longitudinal sections, with parts removed for reasons of clarity, of a second detail of the rocket engine of  FIG. 1  illustrated in three different operating positions. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    With reference to  FIGS. 1 and 2 , designated as a whole by  1  is a hybrid-propulsion rocket engine comprising a combustion chamber  2  of a substantially cylindrical shape, which has a longitudinal axis  3 , houses inside it a fuel in the solid state (known and not illustrated), is axially limited, at one free end thereof, by a exhaust nozzle  4  able to discharge of the products of combustion into the atmosphere, and is axially limited, at its free end opposite to the exhaust nozzle  4 , by an injection head  5 . 
         [0017]    The nozzle  4  has a convergent inlet portion  6  and a divergent outlet portion  7 , and is closed, in an initial starting configuration thereof, by a closing disk  8 , which has a substantially circular shape, is mounted in an intermediate point of the nozzle  4  in a direction orthogonal to the axis  3 , and is shaped so as to break when the pressure in the chamber  2  is at least equal to a given threshold value as will be will be described in what follows. Breakage of the disk  8  enables the combustion products to exit from the chamber  2  and the rocket engine  1  to generate the thrust required. 
         [0018]    The head  5  is limited by a side wall  9  substantially shaped like a truncated cone, is provided with a plurality of pyrogenic primers  10  mounted through the wall  9  so as to project within the chamber  2 , and is axially limited by an injection plate  11 , which is substantially orthogonal to the axis  3 , and has a plurality of holes  12  made through the plate  11  parallel to the axis  3  itself. 
         [0019]    According to what is illustrated in  FIGS. 1 and 3 , the chamber  2  is connected to a tank  13  for containing a pressurized oxidant in the liquid state via the interposition of a feed valve  14  comprising a tubular valve body  15 , which is substantially bell-shaped and is limited by a side wall  16 , which is fixed to the head  5  so that it shares the axis  3 , and is shaped so as to define a substantially frusto-conical intake chamber  17  facing the plate  11  and a sliding cylinder  18  set on the opposite side of the plate  11  with respect to the chamber  17  itself. 
         [0020]    The cylinder  18  has a restricted portion  19  and a widened portion  20 , arranged in succession with respect to one another starting from the chamber  17 , and communicates with the tank  13  via a plurality of supply pipes  21 , which are made through the valve body  15 , are distributed about the axis  3 , face the portion  19 , and are connected with the tank  13  itself. 
         [0021]    The cylinder  18  is slidably engaged by a slide valve  22 , which is substantially bell-shaped with concavity opposite to that of the valve body  15 , is provided with a plurality of annular gaskets  23  mounted on the outer surface of the slide valve  22  sharing the axis  3 , and has an annular end flange  24  projecting radially outwards from the outer surface of the slide valve  22  itself. 
         [0022]    The slide valve  22  is displaced, and normally held, in a closed position ( FIG. 3   a ), in which the pipes  21  are closed and hydraulically separated in a fluid-tight way from the chamber  17  via the gaskets  23 , by a spring  25  mounted between the valve body  15  and the slide valve  22  so that it is coaxial the axis  3  in order to exert on a first side of the slide valve  22  an axial thrust oriented parallel to the axis  3  and in the direction of the chamber  17 . 
         [0023]    The slide valve  22  is stopped in its closed position by engagement of the flange  24  with an annular end stop shoulder  26  defined between the portions  19  and  20 . 
         [0024]    In use, ignition of the pyrogenic primer  10  generates within the combustion chamber  2  a pressurized hot flow of gas, which enters the intake chamber  17  through the holes  12  of the injection plate  11 , has a pressure lower than the pressure of failure of the closing disk  8 , and thus determines an increase in the pressure within the chambers  2  and  17 , and generates on a second side of the slide valve  22  opposite to the aforesaid first side an axial thrust opposite to the thrust of the spring  25 . 
         [0025]    When the thrust exerted on the slide valve  22  by the pressurized gas present in the chamber  17  exceeds the thrust exerted on the slide valve  22  itself by the spring  25 , the slide valve  22  is moved against the action of the spring  25  from its closed position into a position of partial opening of the supply pipes  21  ( FIG. 3   b ). 
         [0026]    Since the pressure of the liquid oxidant contained in the tank  13  is higher than the pressure of the flow of gas generated by ignition of the pyrogenic primers  10 , the partial opening of the pipes  21  enables supply of the liquid oxidant from the tank  13  into the chamber  17  and, hence, movement of the slide valve  22  from its position of partial opening into a position of total opening of the pipes  21  themselves ( FIG. 3   c ). 
         [0027]    In connection with what has been set forth above, it should be pointed out that the pressure of the liquid oxidant contained in the tank  13  is approximately ten times higher than the pressure of the flow of gas generated by ignition of the pyrogenic primers  10  and that the slide valve  22  is hence moved from its closing position into its position of partial opening in a time interval longer than the time interval in which the slide valve  22  is moved from its position of partial opening into its position of total opening. 
         [0028]    Following upon complete opening of the pipes  21 , the liquid oxidant is first supplied into the chamber  17  through the total section of passage of the pipes  21 , is then supplied into the combustion chamber  2  through the holes  12  of the injection plate  11 , and finally reacts chemically with the solid fuel contained in the chamber  2  itself. 
         [0029]    The products of combustion generated by the chemical reaction between the solid fuel and the liquid oxidant have a pressure higher than the pressure of failure of the disk  8 . They thus determine failure of the disk  8 , and are discharged outside the chamber  2  through the nozzle  4  so as to generate the thrust required of the rocket engine  1 . 
         [0030]    Following upon progressive emptying of the tank  13  and consequent reduction of the pressure in the chamber  17  to a value equal to a first given threshold value, the thrust exerted on the slide valve  22  by the liquid oxidant present in the chamber  17  is lower than the thrust exerted on the slide valve  22  by the spring  25 , and the slide valve  22  is axially displaced starting from its position of total opening so as to close the pipes  21  progressively. 
         [0031]    When the total section of passage of the liquid oxidant from the pipes  21  into the cylinder  18  is substantially equal to the total section of passage of the holes  12  of the plate  11  and the pressure in the chamber  17  is substantially equal to a second threshold value lower than the aforesaid first threshold value, the amount of oxidant liquid supplied into the chamber  17  through the pipes  21  is unable to oppose the thrust exerted on the slide valve  22  by the spring  25 . 
         [0032]    For values of pressure in the chamber  17  lower than the aforesaid second threshold value, the behaviour of the slide valve  22  is degenerative and each reduction in pressure in the chamber  17  entails each time a further reduction in the total section of passage of the liquid oxidant from the pipes  21  into the cylinder  18  and, hence, a further reduction of the pressure in the chamber  17  until the valve  14  closes completely. 
         [0033]    In connection with what has been set forth above, it should be pointed out that the pressure in the chamber  17  decreases from the first threshold value to the second threshold value in a time interval longer than the time interval in which the slide valve  22  completes closing of the valve  14  starting from the second threshold value. 
         [0034]    Since the valve  14  is actuated by combining the action of the pyrogenic primers  10  with the action of the liquid oxidant supplied by the tank  13  into the chamber  17  and the slide valve  22  is displaced between its opened and closed positions without resorting to a driving motor, the rocket engine  1  is relatively simple, inexpensive, and light. 
         [0035]    In addition, the conformation and modes of opening of the valve  14  enable rapid supply of a large amount of liquid oxidant from the tank  13  into the combustion chamber  2 , rapid increase in the pressure in the chamber  2 , and rapid generation of a high thrust through the exhaust nozzle  4 . 
         [0036]    Obviously, according to variants not illustrated, the feed valve  14  can be used for controlling supply of a fuel in the liquid state into the combustion chamber of a hybrid-propulsion rocket engine with comburent in the solid state and for controlling supply of a fuel in the liquid state and of a comburent in the liquid state into the combustion chamber of a liquid-propulsion rocket engine.