Variable Area Bypass Nozzle for Gas Turbine Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Small gas turbine engines face challenges in maintaining stable operation during off-design conditions, particularly due to back pressure issues, which existing designs fail to address effectively.
Innovation Solution
A small gas turbine engine with a single spool and a fan incorporating a variable area bypass nozzle and a twin stream impeller, where the variable area bypass nozzle is controlled by a sliding valve and actuator to adjust flow area, and a static guide vane is used to manage pressure ratios, reducing structural loads and enhancing operational flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed area bypass nozzle is used in a single spool gas turbine engine, then the structure is simple, but the engine cannot maintain stable operation during off-design conditions due to back pressure issues
Solution Approach 1:
The bypass nozzle is designed with a variable area configuration that can dynamically adjust its opening area. The nozzle includes a movable portion that shifts between different positions (e.g., first position for minimum area, second position for maximum area) to optimize bypass flow according to operating conditions, thereby maintaining stable operation across the entire operating range while preventing back pressure issues.
2Adaptability or versatility
If a twin stream impeller is used to manage pressure ratios, then operational flexibility and thrust development are improved, but the impeller design becomes more complex
Solution Approach 1:
The impeller is divided into two distinct stream channels: an inner stream and an outer stream. The inner stream handles core flow with higher pressure ratio requirements, while the outer stream manages bypass flow. This segmentation allows each stream to be optimized independently for its specific function, providing operational flexibility across different operating conditions while maintaining manageable design complexity through modular construction.
3Reliability
If the bypass nozzle area is increased to reduce back pressure, then stable operation during off-design conditions is achieved, but the thrust development may be reduced
Solution Approach 1:
The variable area bypass nozzle allows dynamic adjustment of the bypass flow area based on operating conditions. During off-design conditions with high back pressure, the nozzle opens to maximum area to stabilize operation. During design-point operation, the nozzle can be positioned at minimum area to optimize thrust development. This dynamic control enables the system to optimize performance for each operating regime independently.
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 solution enables stable operation during off-design conditions by adjusting the bypass nozzle area and utilizing a twin stream impeller to manage pressure ratios, reducing structural loads and improving thrust development while maintaining efficient bypass pressure ratios.
Implementation Method 1
a sliding valve 21 mounted on a turbine exhaust case 22 where the valve is positioned with an actuator 23 mounted on the exhaust nozzle 24
Implementation Method 2
a fan with a variable area bypass nozzle... a twin stream impeller 32
Implementation Method 3
a static fan exit guide vane row 33 is positioned downstream of the rotating fan stage 31
Implementation Method 4
The actuator may be hydraulic and can use fuel as the actuator hydraulic liquid
Data Source
AI summary
A gas turbine engine for a small aircraft such as a UAV having a bypass flow with a variable area bypass nozzle located at an outlet of the bypass channel, the nozzle having one position with a maximum flow area and a second position with a minimal flow area. The compressor is a twin stream compressor with an inner flow path for compressed air to the combustor and an outer flow path for the bypass channel. A fan stage can be used in front of the compressor.