JP2615413B2 - Combined cycle rocket engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocket engine, and more particularly to an improvement in a reusable rocket engine using liquid oxygen and liquid hydrogen as a propellant.

[0002]

2. Description of the Related Art In launching a rocket, at first, it is important that the thrust is large even if the specific thrust is somewhat low. This is because at first, the heavy aircraft must overcome the gravity and be quickly lifted, but after the ascent, the speed of the lighter aircraft is increased.

The expansion area ratio (ε) of the nozzle of a booster rocket engine fired from the ground is usually as high as possible without causing separation of the nozzle flow above the ground (atmospheric pressure = 1 atmosphere) (separation limit nozzle expansion). Area ratio: εcr). This is the nozzle expansion area ratio (ε) for the same engine
Is higher, the higher the specific thrust can be obtained.

[0004] Fig. 2 shows, by broken lines, how the usable εcr increases by increasing the combustion pressure, and also shows a gas generator cycle (hereinafter referred to as a GG cycle) and an expander cycle (hereinafter referred to as "GG cycle") when the nozzle is used. , EX cycle) are indicated by solid lines. That is, the broken line indicates εcr which can be realized by the combustion pressure on the horizontal axis, the solid line GG indicates the specific thrust in the GG cycle at that time, and the solid line EX indicates EX when the nozzle is used and the combustion pressure is 3.5 MPa.
Shows the specific thrust of the cycle. The higher the combustion pressure (Pc), the greater the εcr. However, in the GG cycle, if Pc is increased, the loss due to the increase in the flow rate of the turbine driving gas increases, and the specific thrust hardly increases. In the EX cycle, the achievable combustion pressure is low (about 4 MPa or less), and it is difficult to obtain a large thrust required for launching. The conventional rocket engine employs either the GG cycle or the EX cycle depending on its structure, so that it has been difficult to use the propellant most efficiently.

[0005]

SUMMARY OF THE INVENTION The present invention realizes securing of thrust at launch and increase of specific thrust after ascending with a single engine without changing the nozzle expansion area ratio (ε) or the combination of propellants. It is to try to make it.

[0006]

SUMMARY OF THE INVENTION A combined cycle rocket engine according to the present invention is a booster rocket engine using liquid oxygen and liquid hydrogen as a propellant, wherein both a gas generator cycle and an expander cycle are used as a propellant supply cycle. By using the gas generator cycle at the beginning (at launch), and then using the expander cycle (after ascending), the characteristics of the GG cycle and the EX cycle can be utilized to achieve performances that cannot be realized by a single unit. It is characterized by being realized by an engine. More specifically, the engine supplies a circuit to supply these propellants from the liquid oxygen and liquid hydrogen tanks to the main combustion chamber of the engine by a pump, and supplies a part of these propellants to the turbine driving gas generator from the pump. After driving the turbine, the generated gas is discharged from the auxiliary nozzle, and the main combustion chamber and the nozzle are cooled by the liquid hydrogen sent out by the pump, and then the turbine is driven.
A circuit for supplying to the main combustion chamber is provided, and the GG cycle and the EX cycle are switched by a valve disposed in each circuit.

[0007]

As described above, the GG cycle is used at the time of launch, and then the GG cycle is performed when switching to the EX cycle is performed.
By using a nozzle having a high εcr which can be used on the ground due to the high combustion pressure of the cycle and taking over in the EX cycle after ascending, a high specific thrust can be obtained, and the engine efficiency as a whole can be improved. For studying the performance of the combined cycle rocket engine of the present invention, engine specifications as shown in Table 1 are assumed.

[Table 1]

FIG. 3 shows the relationship between the switching time of the engine cycle and the burn-off speed in the engine based on the above assumptions, with the tank volume being 348 m ³ , the structure + payload being 40 tons, and the maximum acceleration being 3 G.
Shown in In both cases where the nozzle expansion area ratio is 40, the first engine in which the combined engine performing the mode switching of the present invention has a higher burn-out speed than the case where all the propellant is consumed only in the GG cycle (right end point). It can be seen that there is a mode propellant consumption rate (optimal mode switching time).
In the illustrated example, if the burn-off speed is constant, the payload increases by about 1 ton.

[0009]

FIG. 1 shows an example of the configuration of a combined cycle rocket engine according to the present invention. In the GG cycle used at the time of launch, liquid oxygen LOX and liquid hydrogen LH ₂ as propellants are sent out by the pump 12 and supplied to the main combustion chamber 9 via the valves 2 and 1,7. Pump 1
Some of LOX and LH ₂ from 2, is supplied through the valve 3, 4 to the turbine drive gas generator 13, the generated gas drives the pump driving turbine 11, the injection from the auxiliary nozzle 10 through the valve 8 Is done. At this time, valves 5, 6
Is closed. As described above, when the consumption of the propellant reaches a predetermined amount, the cycle is switched to the EX cycle. The switching is performed by closing the valves 3, 4, and 8, and switching the valve to the EX cycle.
6 is performed. By switching this valve, the entire amount of LOX is directly supplied to the main combustion chamber 9,
On the other hand, the LH ₂ cools and evaporates the main combustion chamber and the nozzle, drives the turbine 11 via the valve 5, and is then supplied to the main combustion chamber 9 via the valve 6. At this time, the valve 7 serves as a bypass for the flow to the turbine 11 and is used for adjusting the flow rate to the turbine.

[0010]

The reusable rocket engine is required to have a long service life and high reliability. Although the combined cycle engine of the present invention has a launch performance that is lower than that of an engine using a two-stage combustion cycle, the system maximum pressure is the same as the GG cycle, which is lower than that of the two-stage combustion cycle, and the performance is higher than that of the GG cycle alone. . In addition, both the GG cycle and the EX cycle are well-established technologies, and can provide a highly reliable system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a combined cycle engine of the present invention.

FIG. 2 is a graph showing a change in specific thrust according to a combustion cycle and a combustion pressure.

FIG. 3 is a graph showing the relationship between engine cycle mode switching and burn-off speed.

[Explanation of symbols]

1,2,3,4,5,6,7,8 Valve 9
Main combustion chamber and nozzle 10 Auxiliary nozzle 11 Pump drive turbine
12 pump 13 gas generator LOX liquid oxygen
LH ₂ liquid hydrogen

Claims (2)

(57) [Claims] 1. A booster rocket engine using liquid oxygen and liquid hydrogen as a propellant, which is provided with both a gas generator cycle and an expander cycle as a propellant supply cycle, and initially uses the gas generator cycle, Combined cycle rocket engine using expander cycle 2. A circuit for supplying these propellants from a liquid oxygen and liquid hydrogen tank to a main combustion chamber of an engine by a pump, and a part of these propellants from a pump to a turbine driving gas generator for generation. After driving the gas turbine, the circuit for discharging the gas from the auxiliary nozzle, and cooling the main combustion chamber and the nozzle with the liquid hydrogen pumped out, then driving the turbine,
A combined cycle rocket engine comprising a circuit for supplying to the main combustion chamber, and switching between the gas generator cycle and the expander cycle by a valve disposed in each circuit.