JP4225556B2 - Regenerative cooling system for combined cycle engine - Google Patents

Description

  The present invention relates to a regenerative cooling system for a combined cycle engine, and more particularly to a regenerative cooling system for a combined cycle engine capable of supplying fuel as a coolant optimal for flight conditions.

It operates as an ejector jet engine at the flight speed of Mach 3 from takeoff, operates as a ramjet engine at flight speeds of Mach 3 to 6, and operates as a scramjet engine at flight speeds of Mach 6 and higher. A multistage combined cycle engine is known (see, for example, Non-Patent Document 1). In such a single-stage combined cycle engine, a single engine covers a wide range of flight speeds from takeoff speed to earth orbit speed, so the aerodynamic heating amount for the engine constantly fluctuates according to the flight speed. Become. In particular, due to severe aerodynamic heating at high speed, these combined cycle engines employ a regenerative cooling mechanism that uses hydrogen as a fuel as a coolant.
In the regenerative cooling mechanism using hydrogen, hydrogen itself is heated from the engine wall and the nozzle wall while the engine wall and the nozzle wall are cooled by flowing through the inside of the engine wall and the nozzle wall. It is mixed with air and used for combustion. The amount of heat received from the engine wall or the like of hydrogen is proportional to the heat receiving area of the flow path through which hydrogen flows and the mass flow rate of hydrogen.

"Engine Research", Japan Aerospace Exploration Agency [online], [October 3, 2005 search], Internet <URL: http://www.ista.jaxa.jp/aet/engine/engine-k02 .html>

As described above, the amount of aerodynamic heating with respect to the engine constantly fluctuates in accordance with the flight speed, so that the amount of heat received by the hydrogen as the coolant from the engine wall also fluctuates constantly. For this reason, the temperature of hydrogen fluctuates, and the density of hydrogen fluctuates accordingly. As a result, the mass flow rate of the fuel fluctuates. For example, when the amount of heat received from an engine wall or the like increases, the temperature of hydrogen rises, and the density of hydrogen decreases accordingly, resulting in a problem that the mass flow rate of hydrogen decreases. As described above, when the mass flow rate of hydrogen is reduced, not only the cooling performance is lowered, but also the fuel provided for combustion is reduced, so that the thrust of the engine is also lowered. By the way, in order to prevent such a decrease in the mass flow rate of the fuel due to the variation in the amount of heat received, it is conceivable to design the regeneration cooling mechanism in advance according to the high amount of heat received.
However, when the amount of heat received is low, the temperature of hydrogen does not rise, so the density of hydrogen increases, the mass flow rate of hydrogen increases, and more hydrogen flows than necessary for cooling. As a result, the engine is supercooled and excess hydrogen is supplied to the combustion as fuel, which may cause a problem that the fuel consumption rate deteriorates. In particular, when the fuel is hydrogen, it is used in a liquid state at a very low temperature, and therefore the density changes drastically and the influence on the mass flow rate is very large.
Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide a regenerative cooling system for a combined cycle engine that can supply fuel as a coolant optimal for flight conditions. .

In order to achieve the above object, the regenerative cooling system for a combined cycle engine according to claim 1 is a regenerative cooling system for a combined cycle engine in which low-temperature fuel is introduced into the combustion chamber after receiving heat through the inside of the engine wall. The fuel supply line through which the fuel flows is designed so that a fuel having a predetermined mass flow rate flows under a condition that the predicted heat quantity transferred from the engine wall to the fuel supply line wall is maximized, and the fuel supply line A temperature adjusting means for increasing the temperature of the fuel flowing through the line is provided.
In general, the mass flow rate m [kg / s] of the fluid is C, the flow coefficient of the pipe, A, the cross-sectional area of the flow path, ρ, the fluid density, and the inlet pressure of the flow path (for example, pump discharge pressure). ) And the outlet pressure (for example, the pressure in the combustion chamber) is ΔP, m = C × A × (2 × ρ × ΔP) ^1/2 . If this equation is rearranged using empirical equations, the mass flow rate is ultimately largely dependent on the shape of the flow path, the fluid density ρ, and the differential pressure. Of these, only the density ρ of the fluid depends on the temperature of the fluid. That is, when the temperature of the fluid decreases, the density ρ increases → the mass flow rate m increases, and conversely, when the temperature of the fluid increases, the density ρ decreases → the mass flow rate m decreases.
Therefore, in the regenerative cooling system for the combined cycle engine according to claim 1, the fuel supply line is designed in advance so that fuel of a predetermined mass flow rate flows under a condition where the amount of heat received from the engine wall is high. Is low, the density ρ increases and the mass flow rate increases, but by increasing the temperature of the fuel by the temperature adjusting means, the density ρ is decreased to suppress an increase in the mass flow rate and a predetermined mass. Allow the flow of fuel to flow. In addition, when a heat receiving amount is high, a predetermined mass flow rate flows, so that no particular problem occurs. On the other hand, if the fuel supply line is designed in advance so that a fuel with a predetermined mass flow rate flows under a condition where the heat receiving amount is low, the density ρ decreases and the mass flow rate of the fuel decreases when the heat receiving amount is high. In order to prevent this, it is necessary to increase the density ρ by increasing the temperature of the fuel, or to increase the cross-sectional area A of the flow path, or to increase the differential pressure ΔP. After all, it is more realistic to design the fuel supply line in advance under conditions where the amount of heat received is high, and if the amount of heat received is low, it is more realistic to increase the temperature of the fuel and decrease the density ρ to decrease the mass flow rate. is there.

In the regenerative cooling system for the combined cycle engine according to claim 2, the temperature adjusting means is a heater.
In the regenerative cooling system for the combined cycle engine according to the second aspect, by using the heater as the temperature adjusting means, the temperature of the fuel can be suitably raised when the amount of heat received is low.

4. The regenerative cooling system for a combined cycle engine according to claim 3, wherein the temperature adjusting means returns a part of the heated fuel while pressurizing part of the heated fuel to the upstream side, and mixes the returned fuel with the low-temperature fuel. Provided with means.
In the regenerative cooling system for the combined cycle engine according to claim 3, since the temperature of the fuel that has cooled the engine is received from the engine and the temperature is rising, the fuel that has been heated is returned to the upstream side while being pressurized upstream. By mixing with the fuel, the temperature of the fuel can be raised and the density of the fuel can be lowered. Further, since the returned fuel recovers thermal energy from the engine and is reused, the thermal efficiency of the entire engine is improved.

In the regenerative cooling system for the combined cycle engine according to claim 4, the feedback means includes a flow rate adjusting means for controlling the flow rate of the returning fuel.
In the regenerative cooling system for the combined cycle engine according to claim 4, the mixing ratio between the low temperature fuel and the high temperature fuel can be suitably changed by the flow rate adjusting means for controlling the flow rate of the fuel. The fuel temperature can be set to an arbitrary value.

  According to the regenerative cooling system for a combined cycle engine of the present invention, the fuel supply line is designed in advance so that fuel with a predetermined mass flow rate flows under the condition that the amount of heat received from the engine wall or the like is high. For example, even if the flight conditions change and the amount of heat received decreases, by increasing the temperature of the fuel by the temperature adjusting means, the density is decreased and the increase in the mass flow rate of the fuel is suppressed, and the predetermined mass flow rate is reduced. The fuel can be controlled to flow. In particular, when the temperature adjusting means is a heater, the temperature of the fuel can be suitably increased. In addition, when the temperature adjusting means is a feedback means that returns the fuel that has cooled the engine while pressurizing it upstream and mixes it with the low-temperature fuel, the returned fuel is reused after recovering thermal energy from the engine. Therefore, the thermal efficiency of the entire engine is improved. Further, when the feedback means includes means for controlling the flow rate of the returned fuel, the temperature of the fuel can be set to an arbitrary value by suitably changing the mixing ratio of the low temperature fuel and the heated fuel. Will be able to.

  Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is an explanatory view of the main configuration of a regenerative cooling system 100 for a combined cycle engine according to an embodiment of the present invention.
This combined cycle engine regenerative cooling system 100 includes a fuel tank 1 that stores fuel at a cryogenic temperature, a fuel supply line 2 that transfers fuel to the combined cycle engine CE described below, a first pump 3 that pumps fuel, a fuel A heat exchanger 4 that transfers heat between the engine and the combined cycle engine wall, a turbine 5 that drives the first pump and the second pump, and a turbine drive line 6 that transfers fuel for driving the turbine 5. A buffer tank 7 that collects the fuel that has driven the turbine 5 and the fuel that has undergone heat exchange, a first flow rate adjustment valve 8 that regulates the flow rate of the fuel flowing through the fuel supply line 2, and fuel that has undergone heat exchange A return line 9 for returning a part of the fuel to the upstream side, a second flow rate adjusting valve 10 for adjusting the flow rate of the fuel flowing through the return line 9, and a second pump 11 for pumping the fuel in the return line 9 Constituted by and a mixer 12 for exchanging heat with mixing and the fuel heated and cold fuel.

  For example, liquid hydrogen is used as the fuel. Liquid hydrogen is stored in the fuel tank 1 at an extremely low temperature of −253 ° C., for example.

The fuel supply line 2 is designed so that hydrogen of a predetermined mass flow rate m flows when the amount of heat received from the combined cycle engine CE in the heat exchanger 4 is maximized. As an example, first, routing from the fuel tank 1 to the first injector I1 and the second injector I2 of the engine in the piping to be used is performed. Next, using the physical property values such as the density ρ and viscosity μ of hydrogen at the temperature at which the amount of heat received is maximum, the flow velocity v and the Reynolds number Re when the mass flow rate m flows are obtained, and the flow of the pipe The road resistance coefficient _CR is obtained. Then, by using the flow path resistance coefficient C _R of the pipe, determine the pressure loss ΔP when hydrogen flows through the fuel supply line 2. Next, the design is performed by selecting the first pump 3 having a head that can compensate the pressure loss ΔP and flow a predetermined mass flow rate m.
However, when the fuel supply line 2 is designed as described above, when the amount of heat received is not maximized, the hydrogen temperature becomes lower than the predicted value, and as a result, the hydrogen density becomes higher than the predicted value. Conversely the flow velocity v of hydrogen through a pipe is smaller than the predicted value and, as a result, flow path resistance coefficient C _R of the pipe is reduced apparently than the predicted value, than the results as the mass flow rate m is the design value Will increase.
Accordingly, a part of the hydrogen that has received heat from the combined cycle engine CE in the heat exchanger 4 and raised in temperature is returned to the upstream mixer 12 through the feedback line 9 while being pressurized by the second pump 11 and mixed with low-temperature hydrogen. As a result, the temperature of hydrogen flowing through the fuel supply line 2 can be raised, and as a result, the density of hydrogen can be lowered and the increase in the mass flow rate m can be suppressed.

  Further, the mass flow rate of hydrogen flowing through the feedback line 9 can be changed by the second flow rate adjusting valve 10. As a result, the mixing ratio of the low temperature hydrogen and the heated hydrogen can be changed in the mixer 12, and the temperature of the hydrogen flowing through the fuel supply line 2 can be set to an arbitrary value.

An example of the engine to which the regenerative cooling system 100 is applied is a combined cycle engine CE. This combined cycle engine CE is not equipped with a compressor and turbine, and at the flight speed from takeoff to Mach 3, while taking in air from the air intake AI using the ejector effect of the jet exhausted from the rocket engine RE, A shock wave is generated downstream of the rocket engine RE to compress the sucked air, fuel is injected from the second injector into the compressed air and burned in the main combustion chamber CH, and the combustion gas is discharged to an external nozzle (see FIG. Thrust is generated by exhausting from (not shown).
On the other hand, at the flight speeds of Mach 3 to 6, the combustion in the rocket engine RE is suppressed, the air is compressed using the ram pressure, and similarly the fuel is mixed with the compressed air and burned to generate thrust. Yes.
On the other hand, at the flight speeds of Mach 6 to 10, air is not compressed so much but introduced into the main combustion chamber CH at supersonic speed and burned while mixing the fuel to generate thrust.

Next, the operation of the regeneration cooling system 100 will be described.
First, liquid hydrogen stored in the fuel tank 1 at an extremely low temperature, for example, −253 ° C., is introduced into the heat exchanger 4 through the fuel supply line 2 when the first pump 3 rotates. Most of the introduced hydrogen is introduced into the buffer tank 7 after recovering thermal energy from the combustion chamber wall and the main combustion chamber wall of the rocket engine RE in the heat exchanger 4, but a part of the temperature rises. The hydrogen is branched and flows through the turbine drive line 6. The hydrogen flowing in the turbine drive line 6 is introduced into the buffer tank 7 after driving the turbine 5. In the buffer tank 7, the hydrogen flowing through the fuel supply line 2 and the hydrogen flowing through the turbine drive line 6 merge, and then most of the hydrogen is transferred to the first injector I 1 and the second injector I 2, and the rocket engine While being mixed with air in the RE and the main combustion chamber CH, it is used for combustion, but a part flows through the return line 9 and is introduced into the mixer 12 while being pressurized by the second pump 11. The returned hydrogen is mixed with the low-temperature hydrogen flowing through the fuel tank 1 to increase the temperature of the hydrogen flowing through the fuel supply line 2 while performing heat exchange. Thereby, for example, even when the amount of heat received by the hydrogen as the coolant from the combustion chamber wall, nozzle wall, main combustion chamber wall, and external nozzle wall of the rocket engine RE is small, the mass flow rate of hydrogen increases. Can be suppressed.

  According to the above regenerative cooling system 100, the flight condition can be controlled by designing the fuel supply line 2 in advance so that fuel of a predetermined mass flow rate flows under the condition that the amount of heat received from the engine wall or the like is high. Even if the amount of heat received is low, a part of the hydrogen heated by cooling the combined cycle engine CE is returned to the mixer 12 while being pressurized by the second pump 11 via the feedback line 9. By mixing with low-temperature hydrogen, the density of hydrogen can be reduced and an increase in the mass flow rate of hydrogen can be suppressed. In particular, the heated hydrogen that is returned is used again after recovering thermal energy from the engine, so that the thermal efficiency of the entire engine is improved. Further, by controlling the flow rate of the heated hydrogen that is returned by the second flow rate adjusting valve 10, it is possible to suitably change the mixing ratio of the low temperature hydrogen and the heated hydrogen, and as a result, the fuel supply The temperature of hydrogen flowing through the line 2 can be set to an arbitrary value.

FIG. 2 is an explanatory view of the main configuration of a regenerative cooling system 200 for a combined cycle engine according to another embodiment of the present invention.
The combined cycle engine regeneration cooling system 200 includes a fuel tank 1 for storing fuel at a cryogenic temperature, a fuel supply line 2 for transferring fuel to the combined cycle engine CE described below, a first pump 3 for pumping fuel, and a fuel. The heat exchanger 4 that transfers heat between the engine and the combined cycle engine wall, the turbine 5 that drives the first pump, the turbine drive line 6 that transfers the fuel that drives the turbine 5, and the turbine 5 A buffer tank 7 for collecting the fuel, a first flow rate adjusting valve 8 for adjusting the flow rate of the fuel flowing through the fuel supply line 2, and a heater 13 as a temperature adjusting means for heating the hydrogen flowing through the fuel supply line 2. Configured.
In the regenerative cooling system 100, a part of the hydrogen that has flowed out of the heat exchanger 4 and returned to the upstream side is returned to the upstream side by the return line 9, whereby the temperature of the hydrogen flowing through the fuel supply line 2 is increased to increase the mass flow rate of hydrogen. However, in this regeneration cooling system 200, the hydrogen flowing through the fuel supply line 2 is directly heated by the heater 13 to raise the liquid temperature, thereby lowering the hydrogen density to reduce the mass flow rate of hydrogen. It is decided to suppress the increase. This eliminates the need for the feedback line 9, the second flow rate adjustment valve 10, the second pump 11, the mixer 12, and the like, and simplifies the system.

  The regenerative cooling system for the combined cycle engine of the present invention is not limited to the combined cycle engine, but can be applied to a rocket engine or a jet engine using a coolant with a large density change.

It is principal part structure explanatory drawing which shows the regenerative cooling system of the combined cycle engine which concerns on one Embodiment of this invention. It is principal part structure explanatory drawing which shows the regenerative cooling system of the combined cycle engine which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Fuel supply line 3 1st pump 4 Heat exchanger 5 Turbine 6 Turbine drive line 7 Buffer tank 8 1st flow regulating valve 9 Return line 10 2nd flow regulating valve 11 2nd pump 12 Mixer 13 Heater 100, 200 Regenerative cooling system for combined cycle engine

Claims (4)

A regenerative cooling system for a combined cycle engine, in which low-temperature fuel is introduced into the combustion chamber after receiving heat through the inside of the engine wall,
Fuel supply line which the fuel flows, the transfer heat predicted heat from engine walls to the fuel supply line wall is designed to flow the fuel in a given mass flow rate Te conditions odors becomes maximum and, the fuel supply line Regeneration of a combined cycle engine comprising temperature adjusting means for raising the temperature of flowing fuel, and when the amount of heat actually transferred from the engine wall is low, the temperature of the fuel is raised by the temperature adjusting means. Cooling system.   The regenerative cooling system for a combined cycle engine according to claim 1, wherein the temperature adjusting means is a heater. 3. The composite according to claim 1, wherein the temperature adjusting unit includes a feedback unit that returns a part of the heated fuel while pressurizing the fuel to the fuel supply line , and mixes the returned fuel with a low-temperature fuel. Regenerative cooling system for cycle engines.   The regenerative cooling system for a combined cycle engine according to claim 3, wherein the feedback means includes a flow rate adjusting means for controlling a flow rate of the returning fuel.

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