Anti-Unstart Control for TBCC Engine Mode Transition

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

High-Mach aerospace vehicles face challenges in maintaining efficient operation during transitions between gas turbine and scramjet engine modes, particularly due to the risk of engine unstart, which can lead to catastrophic conditions caused by abrupt changes in air flowrate and terminal shock position.

Innovation Solution

A turbine-based combined cycle propulsion system with an anti-unstart control system that includes a processor and actuator to adjust the position of a variable guide vane and exhaust nozzles based on the terminal shock position, allowing for apportioned air distribution between engines and maintaining stable operation by reducing air flow to the gas turbine engine while increasing it to the scramjet engine.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If air flowrate to the gas turbine engine is rapidly reduced during mode transition, then the scramjet engine can receive sufficient air for supersonic operation, but the terminal shock position becomes unstable and engine unstart may occur

Engineering Contradiction:

Improveair flowrate transition speedVSAvoidengine operation stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The guide vane is adjusted in advance during the transition process to pre-position the terminal shock before rapid air flowrate reduction occurs. This preliminary positioning prevents shock instability and unstart conditions that would otherwise occur during the rapid transition from gas turbine to scramjet mode.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The guide vane acts as an intermediary control element between the air flowrate reduction and the terminal shock position. By adjusting the guide vane, the system mediates the transition process to maintain shock stability while allowing the required air flowrate changes for mode transition.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the guide vane position is adjusted to maintain terminal shock stability, then engine unstart is prevented, but the air flow distribution between engines may be suboptimal

Engineering Contradiction:

Improveterminal shock stabilityVSAvoidair flow distribution efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The guide vane position is dynamically adjusted throughout the transition process rather than held fixed. The control system continuously modifies the guide vane angle to maintain optimal terminal shock position while accommodating changing air flow requirements, ensuring both stability and efficiency during the transition.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control system uses feedback from terminal shock position sensors to continuously adjust the guide vane position. This closed-loop control ensures that the guide vane maintains the optimal position for both shock stability and air flow distribution efficiency during the transition process.

Inventive Principle:

Principle #23Feedback

3Reliability

If multiple control elements (guide vane, exhaust nozzles) are coordinated for anti-unstart control, then engine operation stability is maintained during transition, but the system complexity increases

Engineering Contradiction:

Improveengine operation stabilityVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The control of the guide vane and exhaust nozzles is merged into a single coordinated control system managed by one or more control computers. This integration allows simultaneous adjustment of multiple elements based on terminal shock position feedback, maintaining stability while managing complexity through unified control logic.

Inventive Principle:

Principle #5Merging (Combining)

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 prevents engine unstart by dynamically adjusting air flow distribution, ensuring stable operation across a range of supersonic and hypersonic speeds, reducing the risk of damage and improving operational efficiency.

Implementation Method 1

a variable guide vane arranged between the at least two fan stages and adapted for adjustable positioning to direct an amount of the apportioned air of the gas turbine engine to the third stream

Methodology Applied

Scientific EffectFluid flow direction control:

Implementation Method 2

The anti-unstart control system may determine the desired position of the guide vane based on a position of terminal shock along the flow passageway during operation above sonic speeds to prevent unstart

Methodology Applied

Scientific EffectShock wave detection: Shock Wave

Implementation Method 3

a primary exhaust nozzle positionable between retracted and extended positions to adjust the area of exhaust flow

Methodology Applied

Scientific EffectExhaust flow control: De Laval Nozzle

Data Source

PatentUS11512667B2Anti-unstart for combined cycle high mach vehicles

Publication Date: 2022.11.29 ROLLS ROYCE NORTH AMERICAN TECHNOLOGIES INC

AI summary

Vehicles, such as aircraft, may include turbine-based combined cycle power plants (TBCC) for power to achieve high-mach speeds. An anti-unstart configuration provides control for transitioning between the amount of air directed to either engine during operation of gas turbine engine and scramjet engines, to avoid unstart during operation above sonic speeds.