Active Shock Train Control in Scramjet Isolators
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Solution Overview
Problem
Scramjet engines face challenges in controlling shock train length, which can lead to unstart events, especially at hypersonic conditions, causing loss of vehicle control and requiring significant isolator length margins that increase engine size, weight, and drag.
Innovation Solution
A system that includes sensors to detect pressure changes and a processor to determine shock train position, coupled with a shock train fuel injector to modulate fuel flow and control back pressure, allowing for active control of the shock train within the isolator to prevent unstart.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the isolator length is increased to prevent unstart events, then the reliability is improved, but the weight and drag increase
Solution Approach 1:
The patent applies active flow control to dynamically adjust the shock train position within the isolator. By using actuators to modify the flow field in real-time, the system can prevent unstart events with a shorter isolator than would be required for passive designs. This dynamic control allows the isolator to maintain reliability while reducing its length, weight, and drag.
Solution Approach 2:
The system employs feedback control mechanisms that monitor shock train position and adjust flow control actuators accordingly. This closed-loop control enables the isolator to actively respond to changing flight conditions, maintaining shock train containment with reduced margin requirements compared to passive designs, thereby reducing isolator length while preserving unstart prevention capability.
2Reliability
If the isolator length is increased to constrain shock train, then the reliability is improved, but the engine size increases
Solution Approach 1:
Active flow control dynamically manages shock train position throughout the isolator, allowing shorter isolator designs to maintain shock train containment. The system adjusts flow parameters in real-time to prevent shock train propagation beyond the isolator, eliminating the need for excessive length margins required by passive designs.
Solution Approach 2:
The system changes flow parameters (such as pressure, temperature, or velocity) through active control mechanisms to influence shock train behavior. By modifying these parameters dynamically, the system can constrain the shock train within a shorter isolator length, reducing overall engine size while maintaining reliability.
3Reliability
If the isolator length is increased to prevent unstart, then the reliability is improved, but the drag increases
Solution Approach 1:
Active flow control dynamically manages the shock train to prevent unstart events within a compact isolator configuration. This reduces the isolator length required compared to passive designs, thereby reducing the drag generated by the engine while maintaining unstart prevention capability.
Solution Approach 2:
By actively modifying flow parameters through control actuators, the system can maintain shock train containment with a shorter isolator. This reduces the parasitic drag associated with a longer isolator while preserving the reliability needed to prevent unstart events.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively constrains the shock train within the isolator, reducing the need for excess length, improving engine performance, efficiency, and reducing weight by enabling timely control of shock train position, thus preventing unstart events and enhancing vehicle control.
Implementation Method 1
sensors configured to sense a pressure change generated by a shock train in the isolator
Implementation Method 2
shock train fuel injector to modulate fuel flow to the engine to control back pressure
Implementation Method 3
pre-combustion pressure rise from the inlet conditions to the backpressure imposed by heat release in the combustor. This diffusion process is accomplished through a series of normal or oblique shock waves
Data Source
AI summary
This disclosure relates to a system for actively controlling shock train in a high speed, air-breathing propulsion engine. The system includes an isolator, a sensor associated with the isolator, and a shock train fuel injector in electrical communication with the sensor. The sensor is configured to sense changes in pressure generated by a shock train in the isolator. The shock train fuel injector is in electrical communication with the sensor. The shock train fuel injector is 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.