Flow control system for a rocket engine with parallel fuel passage network

A flow control system (22) includes a fuel passage network (34) that has first (36) and second (38) network portions that are in a parallel flow arrangement with each other. A fueldraulic device (40) is located in the first network portion. Operation of the fueldraulic device varies flow through the first network portion. A flow restriction orifice (42) is located in the fuel passage network and is arranged in series with, and upstream of, the fueldraulic device. The flow restriction orifice is operable to generate a pressure differential that varies responsive to the flow through the first network portion. A flow control valve (44) is located in the second network portion. The flow control valve is operable responsive to the pressure differential across the flow restriction orifice to control flow through the second network portion.

BACKGROUND

Liquid propulsion rocket engines may include a thrust vector control actuator to vector engine thrust. The thrust vector control actuator is powered hydraulically by fuel (i.e., fueldraulic) tapped from a fuel supply to a main combustion chamber. The fuel that hydraulically powers the thrust vector control actuator is then conveyed back into the main fuel supply. Thus, operation of the thrust vector control actuator changes the fuel flow in the main fuel supply to the main combustion chamber, which in turn can alter the fuel/oxidizer mixing ratio in the main combustion chamber or require controls and hardware to adjust oxidizer flow.

SUMMARY

A flow control system according to an example of the present disclosure includes a fuel passage network that has first and second network portions that are in a parallel flow arrangement with each other. A fueldraulic device is located in the first network portion. Operation of the fueldraulic device varies flow through the first network portion. A flow restriction orifice is located in the fuel passage network. The flow restriction orifice is arranged in series with, and upstream of, the fueldraulic device. The flow restriction orifice is operable to generate a pressure differential that varies responsive to the flow through the first network portion. There is a flow control valve located in the second network portion. The flow control valve is operable responsive to the pressure differential across the flow restriction orifice to control flow through the second network portion.

In a further embodiment of any of the foregoing embodiments, the fueldraulic device is a thrust control valve.

In a further embodiment of any of the foregoing embodiments, the flow control valve includes a pressure port that opens to the fuel passage network upstream of the flow restriction orifice. The pressure port operatively connects the fuel passage network with a valve member of the flow control valve.

In a further embodiment of any of the foregoing embodiments, the second network portion includes a bypass passage, and the valve member is moveable in the bypass passage via the pressure port and the pressure differential to control flow through the bypass passage.

In a further embodiment of any of the foregoing embodiments, the flow control valve is biased to an open position permitting flow through the second network portion.

In a further embodiment of any of the foregoing embodiments, the flow control valve includes a bias member, a valve member, and a power piston.

In a further embodiment of any of the foregoing embodiments, the flow control valve includes a pressure port that opens to the fuel passage network upstream of the flow restriction orifice. The pressure port operatively connects the fuel passage network with the power piston.

In a further embodiment of any of the foregoing embodiments, the fuel passage network includes a common passage downstream of the first and second network portions, at which the first and second network portions merge.

The flow control system as recited in claim8, further comprising a pump having a pump inlet connected with the common passage.

The flow control system as recited in claim9, further comprising a combustion chamber and a fuel supply passage that connects a pump outlet of the pump with the combustion chamber.

In a further embodiment of any of the foregoing embodiments, the fuel passage network includes a tap passage off of the fuel supply passage. The tap passage is connected with the first and second network portions.

In a further embodiment of any of the foregoing embodiments, the tap passage includes a pressure regulator.

In a further embodiment of any of the foregoing embodiments, the fuel passage network includes at least one pressure balance passage that operatively connects a bias member cavity of the flow control valve with a location in the fuel passage network between the flow restriction orifice and the fueldraulic device.

A rocket engine according to an example of the present disclosure includes a combustion chamber, a pump that has a pump inlet and a pump outlet, a supply passage connecting the pump outlet with the combustion chamber, and a fuel passage network. The fuel passage network has first and second network portions that are in a parallel flow arrangement with each other, and a tap passage off of the supply passage. The tap passage is connected with the first and second network portions. A common passage is downstream of the first and second network portions, at which the first and second network portions merge. The common passage connects to the pump inlet. There is a fueldraulic thrust control valve actuator located in the first network portion. Operation of the fueldraulic thrust control valve actuator varies flow through the first network portion. The flow restriction orifice is arranged in series with, and upstream of, the fueldraulic thrust control valve actuator. The flow restriction orifice is operable to generate a pressure differential that varies responsive to the flow through the first network portion. There is a flow control valve located in the second network portion. The flow control valve is operably responsive to the pressure differential across the flow restriction orifice to control flow through the second network portion.

In a further embodiment of any of the foregoing embodiments, the fuel passage network is operable to provide constant flow from the tap passage to the common passage independent of variation in flow through the fueldraulic thrust control valve actuator in the first network portion.

DETAILED DESCRIPTION

FIG. 1schematically illustrates an example rocket engine20, such as a liquid propulsion rocket engine, that includes a flow control system22. As will be described, the flow control system22permits operation of a fueldraulic device while reducing or eliminating fluctuations in fuel flow to a combustor.

As shown, the rocket engine20includes a combustion chamber24and a pump26that has a pump inlet26aand a pump outlet26b.A fuel supply passage28connects the pump outlet26bwith the combustion chamber24. The combustion chamber24is also connected with an oxidizer source passage30, which receives oxidizer from an oxidizer supply source (not shown). The pump inlet26ais connected with fuel source passage32, which receives fuel from a fuel supply source (not shown). As can be appreciated, the rocket engine20may include additional components related to the operation thereof, which are generally known and thus not described herein.

The flow control system22includes a fuel passage network34. The fuel passage network34includes a first network portion36and a second network portion38. The first and second network portions36/38are in a parallel flow arrangement with each other. For example, as used herein, a parallel flow arrangement is an arrangement that provides more than one path through the fuel passage network34.

The flow control system22further includes a fueldraulic device40that is located in the first network portion36. For example, operation of the fueldraulic device40(a fueldraulic load) varies flow of fuel through the first network portion36. In one example, the fueldraulic device40is a thrust vector control actuator that is operable to gimbal the engine. When the thrust vector control actuator is operated, fuel flows through the first network portion36. When the thrust vector control actuator is fully dormant, there is no flow or less flow through the first network portion36. There may also be intermediate levels of operation of the thrust vector control actuator and thus intermediate levels of fuel flow through the first network portion36.

The flow control system22further includes a flow restriction orifice42that is located in the fuel passage network34in series with, and upstream of, the fueldraulic device40. The flow restriction orifice42is an orifice that is narrower in cross-sectional size than the cross-sectional size of the fuel passage network34upstream and downstream of the flow restriction orifice42. The flow restriction orifice42, which may also be considered a sensing orifice, is operable to generate a pressure differential (ΔP) that varies responsive to the flow through the first network portion36.

The pressure differential (ΔP) is the difference in fuel pressure between a location upstream of the flow restriction orifice42and a location downstream of the flow restriction orifice42. Typically, these locations will be immediately upstream and downstream of the flow restriction orifice42. For example, when fuel passes through the flow restriction orifice42, the fuel is restricted by the flow restriction orifice42. As the fuel converges and passes through the flow restriction orifice42, fuel flow velocity increases and the pressure decreases such that there is the pressure differential ΔP across the flow restriction orifice42. The pressure differential ΔP varies in proportion to mass flow of fuel through the flow restriction orifice42.

The flow control system22also includes a flow control valve44that is located in the second network portion38. The flow control valve44in the illustrated example includes a valve member46and a bias member48, such as a spring, that is situated in a bias member cavity50. The bias member48serves to bias the valve member46to an open position with regard to flow through the second network portion38. For example, the second network portion38includes a bypass passage52, and the valve member46(e.g., a spool) is movable in the bypass passage52to control fuel flow there through.

The flow control valve44further includes a pressure port54that opens to the fuel passage network34upstream of the flow restriction orifice42. The pressure port54operatively connects the fuel passage network34with the valve member46. As shown, the fuel passage network34also includes at least one pressure balance passage56that operatively connects the bias member cavity50of the flow control valve44with a location in the fuel passage network34that is between the flow restriction orifice42and the fueldraulic device40.

The first and second network portions36/38merge at a common passage58. The common passage58connects the first and second network portions36/38to the pump inlet26a.The fuel passage network34includes a tap passage60off of the fuel supply passage28. Although the tap passage60in this example is off of the fuel supply passage28, the tap passage60, and thus the flow control system22, could be located off of another portion of the fuel supply passage28or elsewhere in a fuel supply system.

The fuel passage network34, in combination with the pump26and the fuel supply passage28, forms a fuel circuit loop that bypasses fuel flow to the combustion chamber24. The tap passage60is connected with the first and second network portions36/38. In this example, the tap passage60includes a pressure regulator62that serves to provide constant pressure fuel into the fuel passage network34from the fuel supply passage28. Thus, in operation, the pump26moves fuel through the fuel supply passage28. A portion of the fuel from the fuel supply passage28flows to the combustion chamber24and another portion of the fuel is “bled” into the fuel passage network34via the tap passage60. The fuel that flows into the fuel passage network34is circulated back to the pump26at pump inlet26avia the common passage58.

The flow control system22permits fuel to flow, when needed, to the fueldraulic device40without altering the fuel flow in the fuel supply passage28to the combustion chamber24. When there is less flow or no flow needed to the fueldraulic device40, fuel can instead flow through the second network portion38. Thus, variation in fuel flow to the fueldraulic device40does not alter the total, constant flow through the flow control system22or flow through the fuel supply passage28to the combustion chamber24.

In this regard, there are at least two functional states in which fuel flows through the flow control system22. In a first state the fueldraulic device40is inactive, i.e., is dormant, and there is low flow or no flow of fuel through the first network portion36. In the first state, most or all of the fuel instead flows through the second network portion38.

In the second state the fueldraulic device40is active and thus creates a demand for fuel flow in the first network portion36. In the second state, most or all of the fuel may flow through the first network portion36and fueldraulic device40, and less fuel or no fuel flows through the second network portion38. The total fuel flow through the flow control system22is constant though, regardless of which state. There may also be intermediate levels of operation of the fueldraulic device40and thus intermediate levels of fuel flow through the first network portion36.

The bias member48of the flow control valve44generally biases the valve member46to an open position such that fuel can, by default, flow through the bypass passage52into the common passage58when the fueldraulic device40is inactive. The position of the valve member46is subject to the pressure differential ΔP across the flow restriction orifice42though. As an example, when most or all of the fuel flows through the flow restriction orifice42, into the fueldraulic device40, and through to the common passage58to the pump inlet26a,the pressure differential ΔP is high.

When most or all of the fuel flows through the second network portion38, there is little or no fuel flow through the first network portion36(because the fueldraulic device40is inactive), and the pressure differential ΔP is zero or is at least below a pressure threshold that is high enough to actuate the valve member46against the bias member48. In this case, because the valve member46is biased to an open position, fuel can bypass the first network portion36and flow through the second network portion38to the common passage58and pump26.

When there is a demand for fuel flow into the first network portion36because of operation of the fueldraulic device40, the pressure differential ΔP across the flow restriction orifice42increases. The pressure differential ΔP causes an increase in pressure near the pressure port54while generally decreasing the pressure behind the valve member46in the bias member cavity50by way of the pressure balance passage56. The increase in pressure at the pressure port54serves to actuate the valve member46against the bias force of the bias member48to close or partially close the bypass passage52. In this case, less flow or no flow is permitted through the bypass passage52while flow is permitted through the first network portion36and fueldraulic device40. Since the pressure port54is downstream of the pressure regulator62, there are no fuel flow variations in the fuel passage network34, other than the pressure differential ΔP, acting on the valve member46.

As can be appreciated, the position of the valve member46depends on the pressure differential ΔP and bias force of the bias member48. That is, at intermediate pressure differentials ΔP the valve member46may partially close to permit partial flow of fuel through the bypass passage52and partial flow of fuel though the fueldraulic device40. Thus, the flow through the first network portion36is inversely proportional to the flow through the second network portion38such that, ultimately, the flow to the common passage58is constant.

The size of the valve member46and the size of the bias member48can be tailored with regard to the size of the flow restriction orifice42such that the flow control valve44operates within the actual range of pressure differentials produced by the flow restriction orifice42. The range of pressure differentials may be from zero or near zero (when there is no flow through the first network portion36because the fueldraulic device40is inactive) to a maximum pressure differential (when there is full flow through the first network portion36because the fueldraulic device40is fully open). Additionally, the flow control valve44may be tailored to desirably proportion the flow between the first and second network portions36/38. For example, the flow control valve44acts within a linear spring response range of the bias member48such that the flow is linearly proportioned between the first and second network portions36/38. Moreover, the flow control valve44operates passively, without reliance on electronic control signals, in response to the pressure differential ΔP. Therefore, there is no need for complicated control schemes and electronic circuitry.

The fuel flow through the flow control system22for operating the fueldraulic device40may be a relatively small percentage of the (main) pump26discharge flow. The effect of fuel flow fluctuation on fuel/oxidizer mixing ratio may be less in the illustrated configuration than if the fuel flow through the flow control system22was taken off a boost pump to a pre-burner or gas generator. A boost pump may be configured to provide the additional constant fuel flow. Since a boost pump discharge pressure is relatively high (compared to a main pump discharge pressure) at a typical throttled engine power level (e.g., 40%), the size of the actuator for thrust vector control may be reduced in comparison to running it from a lower main pump discharge pressure. By utilizing a constant fuel flow, engine thrust or mixture ratio would not be affected by thrust vector control actuator motion. Moreover, accurate engine thrust or mixture ratio may be scheduled via fuel valves of a pre-burner, gas generator or main combustor based on throttle valve position.

FIG. 2illustrates another example of the rocket engine20and a flow control system122. The flow control system122is similar to the flow control system22except that the flow control valve144includes a power piston170. The power piston170is coaxially located adjacent the valve member46, but is not physically connected with the valve member46. The power piston170is operatively connected with the pressure port54such that the pressure differential ΔP acts on the power piston170. In this regard, the effective area of the power piston170upon which the pressure differential ΔP acts can be tailored to act on the valve member46against the bias force provided by the bias member48. For instance, the size of the power piston170is tailored such that under a maximum fuel flow through the first network portion36to the fueldraulic device40, the differential pressure ΔP across the flow control orifice42will be sufficient to move the valve member46to the fully closed position. With such a configuration, if the maximum differential pressure ΔP would otherwise be insufficient to act on the valve member46alone against the bias member48, the power piston170in essence increases the actuating force from the differential pressure ΔP in order to operate the valve member46.