Active control of scramjet isolator shock systems

1. A system for actively controlling shock train in a high speed, air-breathing propulsion engine, the system comprising:

an isolator;

a sensor disposed in the isolator, the sensor configured to sense a pressure change generated by a shock train in the isolator;

a shock train fuel injector;

a processor operatively coupled to the sensor; and

a memory, with instructions stored thereon, the instructions, when executed by the processor, cause the system to:

sense, by the sensor, the pressure change to establish a sensed pressure change;

determine a position of the shock train relative to the isolator based on the sensed pressure change to establish a shock train position; and

communicate with the shock train fuel injector based on the shock train position to enable the shock train fuel injector to modulate fuel flow to the engine to control back pressure produced by the engine to limit unstart.

2. The system of claim 1 , wherein the instructions when executed by the processor further cause the system to:

convert the determined shock train position to a position identification, wherein the position identification includes a leading-edge shock location position; and

control the leading edge-shock train location position by a feedback controller, wherein the feedback controller is configured to control the shock train fuel injector, which in turn controls the back pressure produced by the engine.

3. The system of claim 1 , wherein the processor has a feedback controller.

4. The system of claim 1 , wherein the sensor includes a pressure transducer.

5. The system of claim 1 , wherein the shock train fuel injector includes:

a direct injector inlet configured to receive fuel from a fuel source;

a direct injector configured to supply the fuel to the engine; and

a fast-acting direct injector valve configured to modulate the flow of the fuel to control back pressure produced by the engine.

6. The system of claim 5 , wherein the system further includes a pulse width modulation (PWM) power amplifier configured to control fuel flow to the engine by providing current to the fast-acting direct injector valve.

7. The system of claim 2 , wherein controlling the leading edge-shock train location position includes:

determining when to actuate the shock train fuel injector based on the position identification; and

causing the shock train fuel injector to modulate the fuel flow when a determination to actuate the shock train fuel injector is communicated by the feedback controller to the shock train fuel injector.

8. The system of claim 5 , wherein the fast-acting direct injector valve is disposed on an end face of the direct injector.

9. The system of claim 2 , wherein the feedback controller minimizes a difference between a desired leading-edge shock location and an actual shock location.

10. The system of claim 1 , wherein the system is configured to move the position of the shock train relative to the isolator in about 10 milliseconds or less.

11. The system of claim 1 , wherein a ratio of a response time of the system to a response time of the engine may be as low as about 1:5 and as high as about 1:10.

12. The system of claim 2 , wherein the shock train fuel injector is disposed in electrical communication with the feedback controller.

13. A system for actively controlling shock train in a high speed, air-breathing propulsion engine, the system comprising:

an isolator;

a sensor associated with the isolator, the sensor configured to sense changes in pressure generated by a shock train in the isolator; and

a shock train fuel injector in electrical communication with the sensor, the shock train fuel injector configured to modulate fuel flow to the engine to control back pressure produced by the engine in response to predetermined pressure changes in the shock train.

14. The system of claim 13 , further comprising a feedback controller in electrical communication with the sensor and the shock train fuel injector.

15. The system of claim 13 , wherein the sensor includes a pressure transducer.

16. The system of claim 13 , wherein the shock train fuel injector includes:

a direct injector inlet configured to receive fuel from a fuel source;

a direct injector configured to supply the fuel to the engine; and

a fast-acting direct injector valve configured to modulate the flow of the fuel to control back pressure produced by the engine.

17. The system of claim 16 , wherein the system further includes a pulse width modulation (PWM) power amplifier that provides current to the fast-acting direct injector valve.

18. A method for actively controlling a shock train in a high speed, air-breathing propulsion engine, the method comprising:

determining, by a sensor, a change in pressure in an isolator of the scramjet engine system;

determining a location of a leading-edge of a shock train in the isolator based on the change in pressure in the isolator determined by the sensor; and

actuating a shock train fuel injector in electrical communication with the sensor to modulate fuel flow in a scramjet engine of the scramjet engine system based on the location of the leading-edge of the shock train in the isolator to control back pressure produced by the scramjet engine system.

19. The method of claim 18 , wherein the method further includes:

controlling the location of the leading edge of the shock train by a feedback controller in electrical communication with the sensor.

20. The method of claim 17 , wherein the steps of determining, by the sensor, the change in pressure in the isolator, determining the location of a leading-edge of the shock train in the isolator, and actuating the shock train fuel injector are effectuated within about 10 milliseconds or less.