Bleed Air Temperature Control via Ram Air Flap Dynamics
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Solution Overview
Problem
Existing bleed air systems for aircraft engines face challenges in efficiently controlling the temperature of bled air, particularly in minimizing drag and achieving optimal aerodynamic performance while maintaining effective cooling, as they often rely on simple ejector devices or air-to-air coolers that do not adapt well to varying engine types and cooling demands.
Innovation Solution
A bleed air system incorporating a ram air duct with a flap and ejectors, controlled by sensors and actuators, which adjusts the inlet section and ejector pressure to dynamically manage cooling flow, utilizing a PID algorithm for precise temperature control and minimizing drag, suitable for a wide range of engines including turboprop and turbofan engines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ram air duct is used to cool bleed air, then cooling effectiveness is improved, but drag increases
Solution Approach 1:
The patent implements a movable flap in the ram air duct that can dynamically adjust the inlet cross-sectional area based on cooling demands. The flap is controlled by an actuator to modify the inlet section between a first position (maximum cooling) and a second position (minimum drag), allowing the system to adapt to varying thermal conditions while minimizing aerodynamic penalty when full cooling is not required
Solution Approach 2:
The system changes the physical parameter of the ram air duct inlet area by moving the flap between different positions. This parameter adjustment allows optimization of the trade-off between cooling effectiveness (requiring larger inlet area) and drag reduction (requiring smaller inlet area), enabling the system to operate at optimal efficiency points under different flight conditions
2Temperature
If ejector devices are used to control cooling flow, then temperature control is improved, but device complexity increases
Solution Approach 1:
The ejector devices are powered by bled air from the engine itself, creating a self-service system where the engine's own compressed air is used to drive the cooling mechanism. This eliminates the need for external power sources or additional complex actuation systems, reducing overall device complexity while maintaining effective temperature control capability
Solution Approach 2:
The control system uses feedback from temperature sensors and pressure sensors to automatically adjust the ejector valve opening and flap position. The control means processes sensor inputs and commands actuators to maintain optimal temperature, creating a closed-loop system that improves temperature control precision without requiring complex manual intervention
3Quantity of substance
If the inlet section of ram air duct is maximized for cooling, then cooling capacity is improved, but aerodynamic performance deteriorates
Solution Approach 1:
The movable flap enables dynamic adjustment of the inlet section area, allowing the system to maximize cooling air flow when thermal demands are high and minimize inlet area when cooling requirements are low. This dynamic adaptation resolves the contradiction by matching the inlet size to actual cooling needs rather than maintaining a fixed large opening
Solution Approach 2:
The ram air duct with movable flap serves multiple functions: it provides cooling air flow when needed while maintaining aerodynamic efficiency when cooling is not required. The single structure adapts to different operational modes, functioning as both a cooling inlet and an aerodynamic surface, thereby resolving the contradiction between cooling capacity and drag
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
This solution provides efficient temperature control with improved dynamic response and reduced drag, ensuring optimal aerodynamic performance and adaptability across different engine types, enhancing the system's ability to manage cooling demands effectively.
Implementation Method 1
The hot bled air is usually cooled by a heat exchanger, which uses ambient air to reduce the temperature of the bled air
Implementation Method 2
at least one ejector placed in the ram air duct downstream the precooler adapted to generate an induced cooling flow in the ram air duct
Data Source
Figure 1~3
AI summary
The invention provides a bleed air system (1) of an engine and a method for controlling the temperature of a bleed air flow in said bleed air system. The method comprising the steps of: sensing a duct temperature in the bleed air duct (2) downstream the pre-cooler (4), sensing an ejector pressure in an ejector valve, measuring the flap position, establishing a target value in terms of temperature variation, setting the operation of the bleed air system in either a first mode where the control means actuate on the actuator, or in a second mode, where the control means actuate on the ejector valve, calculating a new target value, which in the event the bleed air system is operating in the first mode, the new target value is a target flap position and in the event the bleed air system is operating in the first mode, the new target value is a target ejector pressure, and actuating either on the actuator or on the ejector valve so that the flap or the ejectors acquires the new target value.