Assisted Engine Start Bleed System for Gas Turbines
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Solution Overview
Problem
Gas turbine engines face challenges in starting up due to the lack of power in the turbine section, requiring bleed valves to reduce the load on the compressor section, but existing systems are inefficient in managing air flow during this process.
Innovation Solution
A system that includes a bleed air duct of larger diameter than the pressurized air duct, with strategically positioned entrance points along the compressor sections and a controller to manage airflow, facilitating a stable sub-idle initial condition during engine starting by inducing a higher rate of bleed flow from the mid-stage of the high pressure compressor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bleed valves are used to reduce compressor load during start-up, then the compressor can be driven more easily, but the system becomes more complex and air flow management becomes less efficient
Solution Approach 1:
The bleed air duct is divided into multiple sections with different diameters - a larger diameter section for high flow capacity and a smaller diameter pressurized air duct for targeted pressure control. This segmentation allows the system to achieve effective bleed flow while maintaining simpler valve control mechanisms.
Solution Approach 2:
The patent introduces a dimensional change by using a larger diameter bleed air duct compared to the pressurized air duct. This dimensional difference creates a natural flow distribution mechanism that reduces the need for complex valve arrangements and control systems.
2Productivity
If multiple bleed valves are used to optimize air flow, then start efficiency improves, but the mechanical complexity and pressure losses increase
Solution Approach 1:
The patent applies local quality by positioning specific entrance points at strategic locations within the compressor - one upstream of the low pressure compressor and another downstream of the high pressure compressor. This localized approach optimizes bleed flow at critical points without requiring multiple valves throughout the entire system, thereby reducing pressure losses.
Solution Approach 2:
The patent extracts and utilizes pressurized air from a specific location downstream of the high pressure compressor to provide additional driving force for bleed flow. This extracted pressurized air is introduced into the bleed air duct to enhance the bleed effect without requiring additional bleed valves, thus improving start efficiency while minimizing mechanical complexity.
3Stability of the object's composition
If pressurized air is added to enhance bleed flow, then start stability improves, but the system complexity increases
Solution Approach 1:
The patent merges the bleed air flow from the compressor with pressurized air from a separate source into a common bleed air duct. This combination creates a more stable and robust bleed flow that ensures reliable start performance. The merging is achieved through a unified duct system with strategically positioned entrance points, avoiding the need for separate complex control systems for each air source.
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
Enables a faster and more stable engine start by reducing pressure in the compressor section and optimizing air flow, particularly effective for high pressure ratio compressors, while minimizing mechanical complexity and pressure losses.
Implementation Method 1
A vortex tube may be included in the pressurized air duct downstream of the pressurized air valve to provide cooled air to an anti-ice unit.
Implementation Method 2
inducing a higher rate of bleed flow from the mid-stage of the high pressure compressor
Data Source
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AI summary
A system for bleeding air from a core flow path of a gas turbine engine includes a bleed valve (102) in a bleed air duct (104) configured to receive bleed air from a first entrance point (112) to the core flow path (C) into the bleed air duct (104); a pressurized air valve (106) in a pressurized air duct (108) configured to receive pressurized air from a second entrance point (114) to the core flow path (C), the pressurized air at a pressure greater than that received into the first entrance point (112); an eductor outlet (126) from the pressurized air duct (108) located in the bleed air duct (104); and a control system (110) operable to control operation of the bleed valve (102) and the pressurized air valve (106).