Variable Bypass Valve for Aircraft Precooler Weight Reduction
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Solution Overview
Problem
Modern turbofan engines with high bypass ratios produce less compressed air for aircraft environmental control systems, leading to increased fuel consumption and the weight of precooler systems, which is undesirable due to rising fuel costs and the need for more efficient engines.
Innovation Solution
A gas turbine engine compressor bleed air supply system with a variable bypass valve that allows for the bypassing of compressor bleed air around an air-to-air heat exchanger, enabling selective use of low or high pressure bleed air sources and optimizing fan air usage to reduce the load on the precooler.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger precooler is used to handle one engine out conditions, then reliability is improved, but weight increases
Solution Approach 1:
The patent applies a variable bypass valve that dynamically adjusts the amount of bleed air bypassing the precooler based on operating conditions. During normal operation, more air flows through the precooler for cooling, while during one-engine-out conditions, the bypass valve opens to allow more air to bypass the precooler, reducing its required size while maintaining reliability across all operating scenarios.
Solution Approach 2:
The system changes the flow parameters of bleed air by using a variable bypass valve to adjust the proportion of air going through the precooler versus bypassing it. This parameter adjustment allows the precooler to be sized for normal operating conditions rather than extreme one-engine-out conditions, reducing weight while maintaining adequate cooling capability.
2Power
If more compressed air is used for ECS, then cooling capability is improved, but fuel consumption increases
Solution Approach 1:
The patent applies partial action by using a variable bypass valve to control the exact amount of bleed air needed for ECS cooling. Instead of providing maximum cooling capability continuously, the system adjusts the bypass valve to allow only the necessary amount of air through the precooler, reducing excess air consumption and associated fuel burn while maintaining adequate cooling when needed.
Solution Approach 2:
The patent converts the potential harm of having excess bleed air available into a benefit by using the bypass valve to control and optimize air flow. The bypass capability, which could be seen as waste, is actually used to precisely control the amount of air going to the precooler, improving fuel efficiency while maintaining cooling capability when required.
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 reduces the amount of compressed air used and the weight of the precooler, improving fuel efficiency and reducing the size and weight of the environmental control system while maintaining necessary air flow and temperature conditions for the aircraft cabin.
Implementation Method 1
The precooler includes an air-to-air heat exchanger in fluid communication with a source of cooling air and operable for cooling the compressor bleed air
Data Source
AI summary
A precooler for cooling compressor bleed air for an environmental control system includes a heat exchanger in fluid communication with a source of cooling air and operable for cooling the bleed air. A variable bypass valve between a bleed air source and environmental control system is operable for bypassing at least a portion of the compressor bleed air around the heat exchanger. The cooling air may be a portion of fan air modulated by a variable fan air valve. The bleed air source may be selectable between the low pressure bleed air source and a high pressure bleed air source. One method includes flowing the compressor bleed air from a single low pressure source only and increasing thrust sufficiently to meet a minimum level of pressure of the bleed air during one engine out aircraft operating condition during approach or loitering.