Feed system and a method of suppressing the pogo effect

Abstract

A feed system for feeding a rocket engine with a liquid propellant includes a feed circuit, and a device to vary a volume of gas in the feed circuit. The device is configured to cause a volume of gas in the feed circuit to vary while the rocket engine is in operation. The device to vary gas volume includes at least one variable-flow-rate gas injector to inject gas into the liquid propellant in the feed circuit. Methods of suppressing a POGO effect are also provided.

1 . A feed system for feeding a rocket engine with a liquid propellant, the system comprising:
 a feed circuit; and   a device to vary a volume of gas in the feed circuit, which device is configured to cause a volume of gas in the feed circuit to vary while the rocket engine is in operation,   wherein the device to vary gas volume comprises at least one variable flow-rate gas injector to inject gas into the liquid propellant in the feed circuit.   
     
     
         2 . A feed system according to  claim 1 , further comprising a control unit configured to control the device to vary gas volume. 
     
     
         3 . A feed system according to  claim 2 , further comprising at least one sensor connected to the control unit, and wherein the control unit is configured to control variation in the gas volume as a function of signals sensed by the at least one sensor. 
     
     
         4 . A feed system according to  claim 3 , wherein the at least one sensor comprises an accelerometer. 
     
     
         5 . A feed system according to  claim 3 , wherein the at least one sensor comprises a sensor to sense pressure of the propellant. 
     
     
         6 . A feed system according to  claim 2 , wherein the control unit is configured to control variation of the gas volume as a function of time. 
     
     
         7 . A method of suppressing a POGO effect, comprising:
 varying a volume of gas in a feed circuit of a system to feed a rocket engine with a liquid propellant while the rocket engine is in operation, to control a difference between at least one hydraulic resonant frequency of the feed circuit and at least one mechanical resonant frequency of a structure coupled to the feed circuit, wherein the gas volume is caused to vary by varying a rate at which gas is injected into the liquid propellant in the feed circuit.   
     
     
         8 . A method of suppressing the POGO effect according to  claim 7 , wherein the gas volume varies to keep the difference above a predetermined threshold. 
     
     
         9 . A method of suppressing the POGO effect according to  claim 7 , wherein the gas volume is caused to vary as a function of at least one mechanical oscillation value sensed on the structure. 
     
     
         10 . A method of suppressing the POGO effect according to  claim 9 , further comprising performing spectral analysis on at least one mechanical oscillation to determine the at least one mechanical resonant frequency of the structure. 
     
     
         11 . A method of suppressing the POGO effect according to  claim 10 , wherein a filter algorithm, or an unscented Kalman filter, is applied to at least one sensed mechanical oscillation to determine the at least one mechanical resonant frequency and/or to predict its future variation. 
     
     
         12 . A method of suppressing a POGO effect, comprising:
 performing spectral analysis on at least one mechanical oscillation to determine at least one mechanical resonant frequency of a structure coupled to a feed circuit of a system to feed a rocket engine with a liquid propellant;   varying a volume of gas in the feed circuit while the rocket engine is in operation, to control a difference between at least one hydraulic resonant frequency of the feed circuit and the at least one mechanical resonant frequency of the structure coupled to the feed circuit.   
     
     
         13 . A method of suppressing the POGO effect according to  claim 12 , wherein a filter algorithm is applied to the at least one sensed mechanical oscillation to determine the at least one mechanical resonant frequency. 
     
     
         14 . A method of suppressing the POGO effect according to  claim 12 , wherein an unscented Kalman filter is applied to the at least one sensed mechanical oscillation to determine the at least one mechanical resonant frequency and predict its future variation. 
     
     
         15 . A method of suppressing the POGO effect according to  claim 12 , wherein the gas volume varies to keep the difference above a predetermined threshold. 
     
     
         16 . A method of suppressing the POGO effect according to  claim 12 , wherein the variable gas volume is located at least in part in a hydraulic accumulator connected to a duct of the feed circuit. 
     
     
         17 . A method of suppressing the POGO effect according to  claim 12 , wherein the gas volume is caused to vary by varying a rate at which gas is injected into the propellant in the feed circuit. 
     
     
         18 . A non-transitory computer readable medium including computer executable instructions for performing a method of suppressing the POGO effect according to  claim 12 .